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TECHNICAL REPORTBL 28

(Revision of Special Report 211):

USE OF ULTRAVIOLET RADIATION

IN MICROBIOLOGIICAL LABORATORIES

G. BRIGGS PHILLIPSEVERETT HANEL, JR.

NOVEMBER 1960

U.S. ARMY CHEMICAL CORPSBIOLOGICAL LABORATORIES

r 'FORT DETRICK/I

U.S. ARY CHIMICAL CORPS RESEARCH AND D3VELOPMEIT CGOMANDU.S. ASKT BIOLOGICAL LABORATORIES

Fort Detrick, a•aylmad

DL Technical Report 28(Revision of Special Rmport 211)

US Of ULTRAVIOLET RADIATTON IN KICBOIlOLOGICAL LABORATORIES

G. Briggs Phillips

Everett Hanel, Jr.

Safety DivisionOOoCE 07 THE0 SAFETY DI3CTO)r

*Project 4311-05-015 November 1960

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Qualified requestors may obtain copies ofthis document from ASTIA.

This publication has been cleared for re-lease to the general public. Non DOD agenciesmay purchase this publication, order numberPB147 043, from the Library of Congress, Photo-duplication Sorviges,0 Publications Board Project,Washington 25p DeC.

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'FORIYWORD

The authors desire to recognize the guidance and encouragement givenby Dr. A. G. Wodum throughout this p)roject.

The services of Dr. Rudolph Nagy, who reviewed this report, were in-valuable. Dr. Nagy made available valuable unpublished data which wereincluded in this report and prepared several of the chapter&. Mr. RichardIt. Kruse assisted in editing the report and in preparing the LiteratureCited and Indexes.

Many others contributed in a variety of ways toward making this reportpossible. Part of Chapter XI is the work of Mr. Herbert M. Decker andMr. J. Bruce liarstad.

DIGEST

This report summarizes the results of a six-year research programwhich was established because it was desirable first to survey the litera-ture concerning the action and use of UV radiation, and second, to determineexperimentally the susceptibility of various types of microorganisms whenexposed to radiation under conditions that might be found in the infectiousdisease laboratory. Pinally it was planned to use the aseembled data as aguide in developing,, designing, and testing suitable UV installations foruse in the infectious disease laboratory. Germicidal UV radiation is usedin industry for protection of personnel and protection of the product. Itsuses in this r6port have been directed primarily toward protection of per-sonnel and test animals.

5

CONTENTS

Foreword . * . . . . . , . o . . . . . . * * . . * . * * , * * * 3

Digest . . . . . . . . . . 3

I .INTROI)UCTION .. . . . . . . . . . . . . . e o e e o a .s a e 17

II. GE(NSRAL CHARACTERI2RSTICS OF UV........ . . . . . . . 19A. H listory. . -. . . . .. . . . . .4 1 1 0 .0 19

B. Mechanism of B~iological Action . e g ... .... 22.C. Characteristics of Various Wave Lengths.&......... 24

I.I1. LAMPS W4.1CII PRODUCIE UV RADIATION . . . . . . . . . . . . ..... 27A, Ganeral. . . . . . . . . . . . . . . . . 6 . . 27B. Glass thai irr~nsndt; UV Rdiation. e a 9 a a a s s 28

1. Coming Number 9741 Glass. .0 . , . . . . . , .... . . . 282. 'Corn.ing Number 9823 Glass. ..... . . . . . . 2 . . . 93. Comrn.ing Vycor Number 7910 Glass. , . . . . . . . . . . 294. Oorning Vycor Number 7912 Glass .... . . . . . . . . 29

C. Hot Cathode Germicidal Lamps .A . . . . . . . . . . . . . 29D. Cold Cathode Germicidal Lamps.... .......... . 31E. IHigh,-Thtensity Germicidal Lamps (Slimline) . . . . . . . . . 31F. 1High-Prossure Mercury Lamps. o . . . . . . . . °. . . . . . 33G. li-xplosion-Proof Lamp Fixtures. . . . . . . . . . . .e 34H. UV Radiation from White Light Sources. . . . . . . . . . . 34

1. Incandescent Lamps . ..... .s...... . 342. Fluorescent Lamps, . . @ ° . .... . , . ,, . . 3 . 63. Survival of Bacterial Spores on Fluorescent LAIps. . . .

IV. REFLE;CTANCE OF UV RADIATION.. . . . . ..... . .... . . 39A. Literature Review, . . .#. . . . . . . . . . . . . . . . . 39H. Experimental . . . a 0 0 a 0 1 0 a 0 s . G w 0 1 1 0 0 . a 42

1. Increase in Inteonsity of Radiation by Use of•Re lo ctorg . .. . . . . . . , 6 , .* 6 , . . , 0 @ 1. . . . 422. Use or Reflectors with Cold Cathode Lamps. . . . . . . . 43,3 Alum•inum Paints. ..... , .. .. . ........ . . 444. Reoflector )esign . . . ,.455. Distribution of Radiation from a Cold Cathode Fixture. 45

V. TRANSISSIONOF UV.RADIATION . .. . . . . ... . . ... . . . 50A. Literature Review.@ 50B3. Experimental . 0 9 57

VI. HMEASURIE24ENT OF UV RADIATION. . . . . . . . . . . . . . . . . . . 59A. Units of Measurement - . . . . . . . . . . . . . . . . . 59B. Methods of Measurement . . . . . . . . . . . . . ..... . 62C. CalculatingUV Intensiti es.......... . . . . . 68

VII. OZONE• . . . . . .. :. . . . 72A. The Chemistry and"0Physics of Ozone .... .• . . 72B. Measurement o f0one e •o.. o*s# .s... •. 74C. Ozone in theiAtmosphere.s. ..... a .... . .*. . .a 81D. Toxic Limiti of Ozone. a e * • a .s@s s s * a . a. .. . . 85E. Productiohi'of Ozone by UV Lamps. . . . . . . . • . . . . 88F. Germicidal Activity of Ozone . . . . g o . • .... .• .• 90

1. Sv.rface and Air-Borne Microorganisms . .-.•• ....... 902. rficroorg,%nisms Suspended in Liquid . . . , ..... • • 923. Hedical Usos . • . . . . . . . . .. . • • . • • . , 93

G. Deodorizing Effects of Ozone . . . • . . . *. . . . . . 93

VIII. FACTORS AFFECTING THE BTOLOGICAL ACTION OF UV RADIATION. . . . 95A. Temperature. ... .... . • • • . . . . . • • • • 95. . . . . . . 5 , • • . . , . . , • , 9C Ae o Ct ue ,.id .. . .• . . . . . . . .A . . . . 6 95D. Relative Humidity.,* * .... *0 0 0 0 97

L. Literature Review. . . . . . s o . • • . • . 97"2lr -Exporimontal . . . I a • . • 1 , . . 1 0 . . , 99

a. Methods. . . . . . . . . . .. . . . .. . . 6 99be Results, a c # o a s .a . .s , s e # @ o . 100

E. Irradiation of Media . o . . . . . . . a . . . . . . , • 100F. Heat Sensitivity . . . .4 a a 0 0 a 0 a 4 a 1 .. . . . 106G. Photoreactivation.. s .# e s a s .o a s . . . . e . . 106

IX. GEI4ICIDAL IEFFECTS OF UV RADIATION . . . . . . . . . • . . 108A General. o e s o a s . . s a a s s 9 a 9 . e 108B3e Effects on Bacteria . . . ., . . . . .s a # . 110

1. Literature Review.. .. .. . . .. . . . . . . 1102. Experimental ..... . . . .. . . . . . . . . 115

a. In Water Suspension& ............. 115b. On Surfaces . . .... . . . . . . . . . . . . 117c. On Air-Borne Organism . ............ 118d. On Bacterial Spores. . o . . .. .. s . .e . . 120

C. Effects on Viruses and Bacteriophage ..... . . . . . . . 120

2. Viacteripae . . . . . . . ..... 124

a. Literature Review. ..... 4.... ... 124b. Experimental Studies on Agar Surfaces....... 125c, Experimental Studies on Air-Borne Clouds . . . . . 125

D. Effects on Fungi . .*1. .a .0. .a. .e. 129E. Toxin-Destroying Powers. . . . . . .. . .. .. 130

X. PRACTICAL USES OF ULTRAVIOLET RADIATION. . . . . 1 0 131A. Literature Reviews. .e s . , .. ... * .... .s 131

1. Toxins, Viruses, Vaccine., and Blood Plasma. . o . . . 1312. Water Sterilization.. . .. . . . . . . .. .. . . , 1333. Hospitals. . o 0 . . a . , . 1 C . .a . , . .6 0 13549 Schools. . .s . . . . . . . . . . . . . . . . . .a 1425. Miscellaneous Applications . . . . . .. . . 143

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B.* Air Locks. . . . . . . . . . .. . . . ,. .* * ** ** 1471. Air Look for FieldChang Room,.. .. * 148

a. Inactivation of Air-Borne Clouds Passing Through theUV Air Lock. . I 1 . . . . .. . . , , . , . . , . a , . 151

b. Decontamination of Surfaces. . . . . @ # s a @ * e .a,* 152c. Decontamination of Personnel Wearing Protective

Field Clothing. ... . . . ... . . ..... . 1522. Laboratory Air Lock Number I . . . . . . . . . . .... . 1533. Laboratory Air Lock Number 2 . . . . . . . . . . . . . . 1564. Laboratory Air Lock Number 3 . . . . . . . . . . . . . . 160

C. Door Barriers . .. . . . . . . . . . . . . . . .a 161D. Ultraviolet Animal CageRacks. . . . . . . . . . .... 16

1. Materials and Methods.......... . ,. . . . . . 1682. Results. 170

a. Experiment I " Artificially Pro due Aerosols. . . .. 170b. Experiment II = Secondary Aerosols . . . . . . 174

3. Discussion . . . . . . . . . . . . . . . . . . . . 176E. Ultraviolet in Incubatorsl/and Refrigerators. . . . . . 177

1. Effects of UV Radiation on Stored Cultures . . . . .a 177a. Preliminary Experiments. . . . .s s e * . . . . .6 . 177b. Quantitative Experlimente . . . . . . . . . 170c. Plates Exposed Agiir Side Up... . . . . 180d. Plates Exposed Agir Side Down. 0. .... . 181o. Conclusions. . . tW . . . . . . . . . . . 8lea

2. Effects of UV Radiation in a Walk-In Incubator . . . . . . . 183F. The UV Decontamination Chamber . . . . . . . . . . . . . . .a . 187

1. Effect of UV Radiation on Plastic Recording Discs. . . . . . 1872. Docontamination of Plastic Recording Discs . . . . . . .s 1873. Effect of UV Radiation on Paper.. . . . . .s e a. . . . . s 1904. Decontamination of Paper . . . . . . . . . . . . . . . . 190

a. Experimental Tests ................ . 190b. Conclusions....... .. . . . . . 191

,G. UV P~ass-Through Chamber for Single Sheesisof' Pape ... 1911. Materials and Methods...... . . .s . . . . . . 1912. Results. . . . . . . . . .. . . . . . . . . 193

H. UV Clothing Discard Racks. . . . . . . . . . .... . . 1961, The Discard Rack .... .. .*. . ..... . . 196

a. intensity Moasurementson . . . . . . .... . . . 196b. Results of Tests . .... .. .. . . . . . l.. 198c. Conclusions. .. . ... . . . ... .. . . . , . 196

1. Portable UVFloodlight 'o"" S.s . ' ' ' ' ' ' ' ' ' ' . 199J. Safe-T-Aire Industrial trilizr . . . . . . . . . . . 199

1. Design M . . . . . . . . . . 1992. Testing Methods . . . . .. .. ... 9 ,3. C n u s . . . . .. . . . . . . . . . . . . . . . . .Res3994. U onle aions . . V . . . . . . ..OS 203K. Ultraviolet Radiation in Ventilated Cabinets . . . . . . . . 203

L. Ultraviolet Shoe Rack...... . 203M. Ultraviolet Radiation for Direct Irradiatioof Lab;r- 'tory Rooms and in the Treatment of Moving Air. . 9. . . . 203

XI. THE TREATMENT OF MOVING AIR WITH UV RADIATION. . . . . . . . . 206A. General Observations . . . . . . . . . . . . . . a . . e 206Be Design Criteria. . . . .1 . .1 . . . . . . . ..a 207

1. Westinghouse blectric Corporation. . . . a a a 0 2072. General Electric Company . 2133. HIanovia Chemical and Manufacturing Company . . . . . 215

C. Applications . . . . . . .. . .I . . . . . . . . . . . . . 217D. Safety Requiremontsefor UV Installation. . . . . . . . . 21.9

1. Fire and Smoke Hatards . .. .. . . . . . .... a 2192. Winrng . . . . . . . . 1 ............ . . . . . .a a 220

5. Circuits and Lamup Mountings. 0 . . m ' . 8 0 0 0 6 0 a 2209. Experiments with UV Radiation in Air-Handling Systems. . . 221

i. Largo-Volume Air System.@. .a . . . . . . . . . . a 221a. Ultraviolet installation . . . . . . . . . .0 . a 221be Test Methods . . . . . . 221c., Results . ... . .. . . . . .a I a . 223d. Conclusions. . . . . . . . . . .4 0 0 6 a # 0 0 . 225

2. Room-Type Air-Conditioning Units . . . . a a 0 . 0 0 0 225a. Methods. . . . . . . .0 0 0 . .0 $ . .6 .a 6 . 225b. Results . . . . . . . . . . , 0 a 229c.* Conclusions. . . . . . .0 # a 0 0 231

3. Sterilization of Air Flows of One to Ten CubicFeet Per Minute. . a . 6 a a a 6 . 0 0 0 0 6 a . 0 . 0 231a, Description of the UV Air Steriliter a a . . . . a 232be Test Methods . . . . . . 0 . 0 a a 0 0 0 0 0 0 0 . 2,4c. Results. .a. . . . . . . . . . . . . . . . . . . 234

XII. M4AINTENANCE OF UV INSTALLATIONS.*. . . . ., .. . . . . . . . . 236A. Testing. , , 4 i t . .a , . . . . . . . . . . . . . . . 236Be Cleaning . a . a a a a a a a . a . . a . .. . . .. . * 236C. Disposal , . . 4 6 , . . . . . . . . . . . . . . . . . .a 237

XIII. EFFECTS OF UV RADIATION ON EXPOSED PERSONNEL 4 . . . . . . . . 238A. Effects on the Eyes and Skin . . . . . . . . . . . . . . 238

1. Effects on the Eyes (Blepharoconjýuntivitis) . . . . 238a. Medical Effects. . .. . . . . . . . . . . . . . a 238be Effects on Mice... . . . . . . . . . . . . . 239c. Effects on Guinea Pigs . . . . . . . . . . . . . 239d. Effects on Humans. . . . . . a a . 239e. Conclusions. . .. . . . . . 240

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2. Effects on the Skin (Erythema) . . . . . . . . . . . .a . 240a. General Radi ion Effectso.. .es....... , .a 240b. Effects on Hice. s s. . . . . . . . . .e . . . . , 244c,. Effects of 2537A . . . . . . . . . . . . . . . . . 246d. Conclusions. . . . .. . . . . . . . . . . . . . 248

B. Personnel Protection . .s . . . . . . . . . . . . . . . 2481. Eye Protection ... . . . . . . . . . . . . . . . . 2492. Skin Protection. .. . . .a . . . . . . . . . . . . 249

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . 251Author Index . .e s s s s, m s a 275Subject Index. . . . . . . . . . . . . . . . . . . . . . . , . 285

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FIGURES

1. Spectrum of Radiant Energy,. . . A . 202. Comparison or Lethal Action or UV and Absorption of UV by

Nuclear Materials,. , . . .# a .I I a 1 A .a 6 1 233. UV Output of Bactericidal Lamps Made from Various Glasses. . . . 304. Effect of Bulb Wall Temperature on the UV Output of Low

Pressure Mercury Vapor Lamps . .e ., .e . . . . . . . . .9 . . .a 325. Hoistureproof UV Fixture . .. . . . .a . .0 . .a . 356. Spectral Reflectance of Aluminum With and Without Aliak

Treatment. , . . . . . . . . . . . . . . . . . . . . . . . . . 41

7. Parabolic UV Reflector . .4.6.. . . . . .. . .. . . . . . 468. Distribution Curves for Two Rofroctor Designs.......... 479. Distribution from a Cold Cathode Lamp (782-.30) Installed in

a SB.30 Fixture. . s . s. # a v @ e # o * . . . .s . ., # s # 4910. Transmission for Various Thicknesses of Pyrex Clear

Chemical Glass No. 774 . . . . * a . a a s a 9 a a .* . .a s 5211. Spectral Transmittance of Several Clear Plastics . . , . . . . 5412. Transmission of Plexiglass . . . 1 . a . a . " 0 8 a 0 . . . o . 5513. Per Cent Transmission of 2537A for Waters of Different

0oefficients of Absorption . . .k. .. .. . . , . . . . 5 . 614. Response of' UV Phototubas . . . . . . . . . . . . 6415. Wiring Diagram.-UV Meter. . . .. . . . 9 0 a a 0 S 0 0 . 6616. Circuit Diagram oe' tht Westinghouse SM..200 UV Meter. ,. . . . 6717. Intonsity v'o Dfstance from Lamp for Slimline and Cold

Cathode lt7att Lamps . ..... . . . . .... . . . . . .. 7018. Ozone.-Absorbing Devic6 ...... , . . . . .... ..a . 7619. Electrometric Titration Vessel . . . . . . . . . . . . . .0 . 7820. Correction Curve for Ozone Estimation. . o . . . . . a . . . . . 8021. Seasonal Variation of Total Ozone in Atmosphere at

Different liatitudes. . . . . , , . . . . . . . , , , . . , . . 8222. Day.By.Day Content of Ozone in the Atmosphere at Murray Hill,

N. J., from January 1 to December 31, 1944 . . 0 . . 0 . . .9 . 8423. Per;Cent Bacteria Killod aV Various Media Hydrogen Ion

Concentrations . . . .a . .6 .a A A . 1 . a . . . o9624. Effect of' Relative llumidity on the Bactoricidal Action of

UV Radiation . ,* 4 . . . . i . . . . . . . e . a . a a a a 9825. UV Humidity Apparatus.. . . . . . . . . .. . .a # e .. e 10126. Per Cent Survival of UV Irradiated B. subtilis Spores at

Varying Relative llmidititos. . . . . . . O 0 9 9 .a 0 4 a . 10527. UV Intensity and Exposure Time Required to Give Various Values

and Survival Ratio& for Bacteria and Molds . . . . . . .*.. . 11428. Survival of So marcescens Cells in Distilled Water. Exposed

to Radiation from a iatt Germicidal Lamp . . . . . a .a a 11629. Survival of Organisms on Glass and Agar Surfaces Exposed to

UV Radiat,iov . . . . . . . . .a a a . a a a . . a 0 , a . . 11930. Concentrations of Air-Borne Bacteria in a 1890 Cubic Foot

Room Before? During? and After Irradiation for One Hour withTwo 30,Watt UV Lamps . . , . . . . . . a a a a a a a a 121

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31. Survival of T-3 Coliphage on Agar Surfaces Exposed toUV Radiation.. . . . . . . .. ... . .• . 126

32. Duke University Operating Room. 6 . . . . . , . . . . ... 13833,. Duke Univorsity Preparation Room. . I S . • • . . , . . 13934. Protective Clothing Worn at Duke University . . . . . . . 14035. Product Production with UV Radiation. .. . .. . . .a . .. . 14436. Baryaire Safe-T-Airo Equipment. . . . . . . • •. • 14637. Siovoe.Type Air Spapler, . . . • . . . • .. . . .as 149,38. UV Entrance Locke . . • . . . • . . • . .a • a . . . . . .a . 15039. UV Air Lock . . •. . • . • . • . • • • • . • • .. 15540. UV LAmp Installation at Doorway . . . . .. .• . . . 16341. Vinyl Plastic Curtain . .. ... . . . • . • a s . . . .a . 16742. UV Cage Rack . . . . . . • • , a . a . 0 a . a a . .' . • . . 16943. Typical UV Intensities Obtained on an Animal Rack Shelf -

Equipped with Two Cages ard Two UV Fixtures . . • .a • . ,. . 17144. UV Animal Cage Rack . . . . . . i,. . . . . . . . . . . 172cý. Recovery, of Air-Bo. ne Sl.n d B.',ubtilis Spores

Released from Hair of Fou~rerosol-Exposed-Guinea Pigs Housedin Solid-Sidod, Screened-Top Cages Placed on an UV Cage Rack, * 175

46. VentilatedPorsonnel Hood . . . . 17847. UV Intensities in Microwatt. per Sq Cm in an'Incbat;r•

Room. Two Cold Cathode Lamps • .a ... . . . . . 18648. UV Paper Decontamination Chambert Closed. • a • . , a . a a . . 18849. UV Paper D~econtamlnation Chamber, Opened.L • .• . 18950. UV Paper Sterilizer (Single Sheet), Exterior View • a . . . a . 19251. UV Paper Sterilizer (Single Sheet), Interior View a . . .a a . 19252. Receiving Box for UV Paper Sterilizer . • . ..• • 0 . .1 9 19453. UV Laundry Bag Holding Device . . . a a 0. . . .. . 19754. UV Clothing Discard Rack. . .a. .a . . . . . . . . .a a . .. a 19855. Portable UV Floodlight.. a . , .a .a . .a 9 . . . . .1 1 20056. UV Intensities in Hicrowatt, per Sq Cm at Various Distatss

from a Portable UV Floodlight.. . . .. . . . .* 0# 20057. UV Intonsitios in Xcrowatts per Sq Cm at Various Distances

from a Portable Safe-T-Alre Sterilizer. . . . . . a a ... a. . 20158. UV Equipped Ventilated Cabinet.* .op, a. .. . . . . . . . 20459. UV Shoo Rack. . . . . . . I P .... , o 20560. UV Installation in a Laboratory 0 0 . .. . . . . . . . . .a . 205-61. Curve to Calculate Lamp RYequirements. . . a .. . . . . . . . . 20ft62. Curves Showing VoDoW. Values. .a. . . . . . . . . . . . .0 9 21063. Correction Curve for Two or Three Banks of Laps . . . . . . , 21164. UV Output as Affected by Temperature and Air Flow . . . . . . 21265. Theoretical 99 Por Cent Disinfection of Air at 8O0F in

Nonreflectivo Ducts . 9 , 9. . . ... . . . ..a 21466. Variation of Radiation 2537A in L.the Per Hour with

Changes in Relative Humidity. .. .. .. .. . . . . . . . . . 21667, Ray Length Factors for Various Distances Between Lamps and

Ceiling, or Between Lamps and Nearest Duct Wall . . . . . . . . 218

68. Large-Volume UV Air Sterilizer.s. . . . .a . . . . . . . . . . . 222

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69. Window-Type Room Air Con2ditioner . . . . . . . . . . . 22670. Air Conditioner Test; Room....... . , . . .. . . 228"71. UV Air Conditioner 28. . . . . . , . . . . . . . . . 2272. Small Volume UV Air Sterilizer . . . . . . . 23373. UV Installation Record 2 . . . . . . . . .. .. . . 23774. -rythemal Response Curve . . . . . .* . . , , . 24175. Plastic Personnel Hood for Protootion Against UV Radiation . . . 250

S0S

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TABLES

11V VAction Spectra s.a. @.a. * v, ,*a & @a... 2211. Moat Effective Germicidal Wave Length . . . a 0. . . . . . 25I11, Characteristics of' Three Typos of UV Lumps. . . . . . . . . 33IV. Radiation from Incandescent Lumps . . . . . . . . . 36V. UV fromFluorescent Lamps . . ............ 37

V1. Recovery of I'lacillus subtilis Spore-s from BurningFluorescent IM l-i . ... . . . . . . . . . . . . .. .. . 38

VII. Reflectance of UV Radiation from Various Surfaces . . . . . 39VIII. Increase in UV Intensities Through the Use of

Aluminum Reflectors . . . ./ .,•

TX. UV Tntonsities at Various Distance froa 2.'7i-Watt CoI d 7Cathode Lump in a SB-30 Fixture.. . , , , . . , , . ../ 48

X. Relative Amounts of' Energy of Various Wave Lengths ,/-Emitted by Typica Germicidalt am' s. . . . . . . ./ps 50

XI. Transmission of 2537A UV Radiation by Different Typesof Glass. . . , . . , . . .s / , 51

X11. Per Cent' Transmission of' Five Differont UV*Wave Lengths'Through PyraxGlass. . ,.. , ., .. ,. ' . 53

XIII. Transmisilon of' 2537A Radiation Through" Various MKteriKLls . 58XV. UV Lntonsit'ios at Various D)istances from'Two 30-Watt

XV. Characteristics of Woutinghouse U Ph... bs. . . 63XVI. Factors for I•stimating Gormicidsil. ntensities at Various

Distances f'rm an UV Lump . .'. . , , , , . . .1. 7XVII. Ozone Concentration Factors ......... *...... 73

XVIII. Average Atmosphoric Ozone Concentrations.......... 83SXIX. Physiological Effects of Ozone. . . .S8

XX. Su-8 v•--•a, of UV Irradiated B. subtilis Spores at VariousRelative Ilumidities (Toet f). ..l.. . . a . , .. 0 102

XX:I. Survival of' UV Irradiated B. subtiii; Sporeas at VariousRelativo Ilumidities (Test 1). .. .- . * * * 1 * .a 103

XXII. Survival of U;V Irradiated B. subtilis Spores at VariousRelative Humidities (Test I), go. . . 104

XXiii, I l. , crowatt.Minutes per Square Centimeter (ST Valu;)Naoossary, to Reduce Colony Formation 90 Per Cent onA igar Plates . . . . . . .0 . . . . . . 2.12.

XXIV. Incident E,'nergios at 2537A Millimicrons Necessary toInhibit Colony Formation in 90 and 100 Per Cent of theTest Organisms. . . . . . . . . 112

XXV. Survival of Washed S. marcescCe in Distilled WaterExposed to Radiation from a 30-Watt Hot Cathode Lump. . . . 215

XXVI. Summary of ET Values for 90, 99 and 100 Per Cent Inacti-vation of Test Organisms in Water and on Several Dif-forent Surfacesc e . . . . . . .1 .. *.1a 117

XXVII. Reduction of Air-Borne Bacteria by UV Radiation in FourT oo . . . . . . . . . . , . . . . . . . 122

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XXVIII. UV Inactivation of B. coli in Air at Ordinary Tepiperaturesand at Relative llumTdiTre' Loes Than 40 Per Cent. . . . . . 123 W

XXIX. Relative Amounts of UV Energy Required to InactivateBacterial Spores po.. a... . 'a... ' ' 123

XXX. Inactivation of T-3 Coliphago on Agar Surfaces with UVRadiation . . . . ... . . . . . . . .. . . .. 127

XXXI. Inactivation of AirIlorne T-,,3 Coliphage with UV Radiation . 128XXXII. Inactivation of E. colt in Water in a Six.-Inch Diameter

Cylinder. . . . . . . . , .. . a. 6 * 0 0 134XXXIII. Inactivation of Air-Borno S. indict in a Field Air Lock . . 151

XXXIV. Inactivation of S. indict on SlurfCes in s Field Air Lock . 152XXXV. Decontamination of Personnel in a Field Air Lock, One to

Five Minutes' Exposure .... ..aa..... . 154XXXVI. Decontamination of Personnol in a Field Air Lock, Five to

Twenty Minutes Exposure. 1 .0.. 10 A a aquipped154

XXXVII. UV Intensities in an 81 x 41 x 10' Air Lock Equippedwith Three 30-Watt Lamps. . . . . .a . . . . . . . . . 156

XXXVIII. Bacteriological Tests of an UV Air Lock Using S. indictas the Test Organism. a P .. , A * * e a , * . .* . . . 157

XXXIX. UV Intensities in ALr Lock Number 2 . . . . . . . a * 158XL. Results of Bacteriological Tests in an UV Air Lock. .. . A 159

XLI. UV Intensities in Air Lock Number 3 , . .. # . . . o 160XLII. Results of Bacteriological Tests in an UV Air Lock. . . a . 161

XLIII. UV Intensitioo in Hicrowatta per Sq Cm at the VerticalCenter of a Door larrier.s .. . .. , *. . . . .e 162

XLIV. Bacteriological Tests of an UV Door Barrier . . . , . . . 106XLV. Passage of Artificially Produced Aerosols of S. indict

from a Cage on anUV Rack to the Room . . A a .... a 173XLVI. Passage of Artificially Produced Aerosols o.f S indiaa

from Cage to Cage on an UV Rack .... 'A-A.. ... 173XLVII. Effect of UV Radiation on Air-.Dorne So indica Released

from the flair of Guinca PIgs .. . , . A , . . . 174XLVIII. Effect of UV Radiation on Air-Borne Do subtilis Spores

Released from the flair of Guinea Pigs 1 1 1 . ., . . 174XLIX. Effectiveness of the UV Cage Rack in Reducing the Ntmer

of S. indict Cells and B. subtilis Spores Released fromWit~in"-M-eage from HaIr of Tirea Pigs., . . . . A o * . 176

L. Growth of S. indica Colonies on Agar Surfaces When thePetri Dishes Wer' Exposed Agar Side UI •to UV Radiation. . . 181

LI. Growth of S. indica Colonies on Agar-Surfaces When thePetri Dishes "TWer xposed Agar Side Down to UV Radiation. 182

LII. Reduction of Organisms by ContinuouslJVRadiation in anIncubator Room (30C). .a . .. . . , A * . . . . 184

LIII. Recovery of So indict in a Walk-In Incubator During andAfter NebuliiatýLon d the Effect of UV Radiation onRecovery. . e , .. ... . . . @ . .a .P . . . . . . . 186

LIV. Bactericidal Effectiveness of an UV Pass,.,Through Chamber., 195LV. B. subtilis Spores Recovered After Different Exposure

TerMor UV Radiation 4 o a ,o * . .... e a a * s . 202

15

LVI. S. indica Cells Recovered After Ten-Minute Exposure to

LVII. Recovery of S. indic, in an Air-Conditioning LDut (Tet 1) , , 223LVIII. Recovery of L indic in an Air-Conditioning Duct (Test 2) 224

LIX. Recovery of 3. indIc in an Air-Conditioning Duct (Test 3) . 225LX. Use of UV Irradt"=on in a Room Air Conditioner for

Removal of Bactehria,.......... 14 **,o**** 230IXI. Recovery of Organisms from Exhaust Air from Forcibly

Aerated Broth Cultures of S. indica. . . . . 0 0 9 a .o s 231LXII. Comparative Efficiency of U-a-ne T7ur UV Lamps in the

Ultraviolet Sterilizer in the Presence of Aerosols ofB3. subtilis and S. indica, .o . . . . .a * # .* o * 235

LXITI. 7or 7en 'rransmissi3no UV Through Skin . . 0. . . . . . 243LXIV. Permissib•le• Daily Exposure to UV Radiation . . . . . . . . . 248

li

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17

I. INTRODUCTION

During the past several decades an enormous amount of experimentalovideng has accumulated demonstrating the bactericidal, virucidal, andfungicidal propertios of ultraviolet (UV) radiation. For the most partthis has been. a direct result of the development of new and better typesof' artificial UV sources, As a result of these data, the germicidal prop.ertios of UV radiation are well o•stablished and accurately defined, andthe radiations aro being used in many practical instances whore the de.struction of microorganisms is required. Ultraviolet radiation is also

,-,widely used as a research tool in the fields of cytochemistry and photo.chemistry. These latter itses, as well as its employment as a mutagen fora variety of purposes, will not be discitssed in this report.

In safety programs for laboratories handling highly infectious materi.ala, UV radiation was given early consideration. It seemed probable thitthe germicidal lproportlos of radiant energy could be utiflled, in conjuno.tion with othor control measures, to reduce the number of instances inwhich laboratory workori become tnfoctod with the microorganisms vithwhich they work. It was also thought that the radiations could be used forcontrolling the common airborne or dust-borne microorganisms which harassthe bacteriologist by oontinually infiltrating sterile media and equipment.

Survey informatton prosently available on the frequercy of laboratory.acqiiired occutat.ionaL 4Llnesseas in this country oraphasizes the n-ed whichexists 'or varioun typos of' germicidal agents. The survey of Sulkin andPike (278)0 inr 1951 ,1-i•ted 1342 laboratory.acquired infections, includingdiseases such as tularomla, psittacosis, tuberculosis, Q fever, and glanders.When thQ survey was brought up to date in 1956, (301) a total of 2262 lab-oratory infections wero listed. It is believed that the reported infectionsrei)resent only a ['ract Lon of' those actually occurring because correct di.agnosis is diffLcuLf, in many instances, and there have been few attempts todiscover inapparent inf'octtons.

The evalu'ation of' many of the procedures and techniques used in infec.tious disease laboratories (237p238,6244,p288,300,3l9) and the realization ofthe hazards attending those tochniques, particularly those involving airtransmission of disoasep also suggests the need for the use of aerogenicdisinfoctants such as UV radiation.

Several facts wore noted early in the efforts to determine the utilityof UV radiation in bacteriological laboratories. Much of the quantitativeexperimental data available were of little value when attempts were made toapply the informatton to practical use. The most obvious reasons for thiswere the lack of accurate measurements of UV intensity and variations in theUV sources used, in the methods of exposure and in the types of test organ.

*aisms employed. In addition, various workers have not agreed on the effect

* All such numbers in parentheses refer to applicable literature references;see Literature Cited, page 251.

18

of relative humidity and other physical factors affecting the biological.reaction. It was evident that the radiations could be used in many differ.ent ways, and, for the most part, each use would require a specially designedinstallation. Other factors were encountered, such as the hazard of cutn.neous or ocular burns From artificial UV sources, the effect of UV radiationnn exposed equipmenz, and the effects of ozone.

The investigational program which is reported here was established be-cause it was desirable first to survey the literature concerning the actionand use, of UV radiation, and second, to determine experimentally the sus.,ceptibility of various types of microorganisms when exposed to radiationunder conditions that might be found in the infectious disease laboratory,Finally it was plannod to use the assembled data as a guide in developing,designingg and testing suitable UV installations for use in the infectiousdisease laboratory.

Germicidal UV radiation is used in industry for protection of personneland protection of the product. Its uses in this report have been directedprimarily toward protection of personnel and teat animals.

F)I

19

I1. GENERAL CHARACTERISTICS OF UV

A, HISTORY

In 1878 two EngLish sciantisti Downs and Blunt (68)p discovered that C

sunlight was bactericidalo This discovery led to the early pioneering onsunlight during the latit decade of the 19th century (13,14,69,296,297).In 1892 it was suggaotod that a splcitric region of the sun's radiation wasresponsible for bacterlidal offects (297). A Danish physicianp Nielsydberg VI'tnsont established the fact that two of the outstanding effects

of sunlight, the bactericidal action, and the production of photo-erythema,resulted from invisiblo UV radiation. Many studies followed in which in-vestigators studied sunlight to learn more about the bactericidal UV radia-tion, However, it was boon realized that the sun is a very unreliablesource of radiation because the intensity varies with the time of day, theseason of the year, and the elevation above sea level (25). .The develop.mont of artificial UV radiation sources gave great impetus to studies ofthe germicidal activity of thio radiation. The three principal types ofartificial sources in use today as listed by Ellinger (74) ares (a) thearc lampsj carbon and mercury vapor; (b) the glow lampe, mercury or hydro.gen discharge tubes; and (c) the spark lamps, such as the iron electrodewhere a discharge takes place between cold electrodes.

Radiation whether visible or invisible, ira an electromagnetic vibra-tion, It is considered to be a wave or a quantum phenomenon. These wavesare propagated at a speed of about 186,300 miles per second. Differenttypes of light are defined according to the length of the wave (Figure 1).The radiant energy is in the form of photons,: the energy per photon beinga function or the frequency of the waves (oscillations per second). As thewave length becomes smaller, the energ/yvalue of the photon increases andthe wave frequency increases, The tnergy state of UV radiation, as comparedto Wnfrared radiationo is responsible for the greater antimicrobial effect.of the former. Radiant energy is absorbed, by the organisms and used in thephoto, decomposition of many of the essenttal compounds and enlymes. Someof the infrared radiation would be absorbed; however, this would not havethe energy to rupture any chemical bonds. Monochromatic light, or radiationof one wave lonjth, 16s rarely encountered except when obtained by speciallamps or speciae prisms and filters. Consequently, it is customary to des-ignate various regions in the radiant energy spectrum according to approxi-mate maximum and minimum wave lengths.

The visible portion of the spectrum includes radiations whose wavelengths lie between about 4000 and 7700 angstrom units (4000A to 7700A).That portion generally designated as ultraviolet includes all the radia-tions from those overlapping the X rays (about 150A), to those borderingthe visible. The spectrum is further divided on an arbitrary basis whichdepends upon the use for which the radiation is intended. Wave lengthsshorter than 2000A have been called the Schumann region. The portion most

20

00

C, 21

commonly studied for bacfericidal properties extends from 2000A to 3100Aand is often called the abiotic region because these wave lengths kill or

* injure cells. Cellular destruction does not occur in the 3100A to 4000Arange to the same extent as with the shorter radiation.

It is convenient to divide the entire UV spectrum into four generalregions, based upon the tise of the radiation. These four regions cannot beaccurately defined because their effects tend to overlap the defined limit.

Rion l 4000A to 3200A . This is the region nearest the visible andprovijWis Rdiation which is used to produce fluorescent effects and photo.chemical reactions.

Region 21 3200A to 2800A - Sometimes called biologically effectiveradiiaTion.This radiation is antirachitic and aids in the production of'vitamin D. Erythema and tanning is also produced.

Region 3r 3000A to 2000A - This region comprises the radiation whichdestroys bacteria, yeasts, viruses and molds.

Region4 Below 2000A . This radiation is absorbed by the oxygen in theair Ra -converts tho kattor into ozone. Radiation below O000A will ionizeair constituents,

B MECHANISM, OF BIOLOGICAL ACTION

Early attempts to explain the mechanism of the lethal action of UVradiation have been for the most part uneatisfactorc. Bedford (23) sup-ported the theorythat organisms were killed by the action of hydrogenperoxide formed by the UV radiation. Hoers and Webster (215) claimed thatthe germicidal action of sunlight was attributable to the formation offormaldehyde. It ha•s been suggested by Voogd and Dams (294) that UV ir-radiation prevents multiplication of cells and allows normal dying tooccur "his explanation does not satisfy the known action of UV radiationagainst many dormant spores.

Voluminous publiirhed experimental work has proved that, within the 4general regions, various monochromatic wave lengths show decided tendenciestoward exerting certain desired biological phenomena more effioiently. Theso.called "action spectra" (100) relates the efficiencies which have beendetermined for certain ultraviolet effects by various wave lengths. Manydata are available concerning the absorption of UV radiation by protoplasmiccompounds. It has been found that UV radiation is more readily absorbedthan other wave lengths by substances such as albumin and nucleic acid.Attempts have been made to correlate UV absorption by protoplasmic com-pounds with germicidal action, but, as pointed out by Giese (100), no caseof perfect agreement has been found. A review of the action of UV radiation

* on protoplasmic compounds is beyond the scope of this report, but the in-rewation recorded in Table I, taken from data collected by Giese, serves toilluotrate the correlation of some of the effects.

22

TABLE I. UV ACTION SPECTRA

UV Effects Which Resemble Absorption by:

Nonconjugated proteins (albumin NucLeic acid .marumummaximum absorption about 2800A) absorpti:on about 2600A

(1) Effects on division of sea (1) Mutagenic effectsurchin eggs

(2) Immobilization of paramecia (2) Vtrucidal effects(3) Ciliary roverial & motility (3) IDatchrioldal off'o•ts(4) Encystment of Colpoda (4) Fungicidal effes(ts

Unreported studies in which aerosols of Serratia marcescens were ex.posed at 40 per cent relative humidity to wa-venihstin the region of2800A to 4100A have illustrated that the a~r borne particles below fivemicrons are more susceptible than those larger than hrve microns (159).This observation is in agreement with that ot fourdillorn et al '(34) whostated that organ'Isms in small droplet nuclei are more oas"sl"inactivatedthan those in largeparticles. However, most investigators favor thequantum.hit interpretation because of observed exponential survival curves.

Although as early as 1.914 (139) bacterial ofifectiveness was comparedwith cellular absorptionj biological action spectra using accurately de.finod monochromatic UV radiation were not ptiblished until 1928 (93). Anumber of authors have since published action spectra for a variety ofmicrobial foms incluiding bacteria (94,185), I)acteriophage"(85,88,95,327),vinises (153) and nomatode eggs (154,164).

Hollaonder (149) hai shnwn that nucleic acid absorbs most effectivelythose wave lengths that also show maximum lethal action against bacteriaand fungi (2650A). Absorption curves of typical proteins show peaks ofabsorption at those wave lengihs, which are also most damaging to pin wormeggs and to tobacco mosaic virus (below 2500A). Hollaender believed thatthe action of UV radiation near 2600A functioned through the nucleic acidconstituent of the cell and that shorter wave lengths (2250A), because oftheir lack of penetrability, affected the outoide protein layer. Ellisst al (75) have summarized graphically the results of several workers andrem0strated that the wave length of maximum absorption by nucleic acid isin the same general range as those wave lengths reported to give maximumkilling of blacteria and paramecia. These data are shown in Figure 2.

Although the exact mode of' germicidal P ,,ion of' UV energy is as yet un.-known, many of the factors involved in the action have received considerableattention. It has been c'laimed by Giese (100) that, in contrast to photo.dynamic reactions, UV radiation acts equally well in the presence or absenceof oxygen. The fundamontal reaction is thought to be photochemical, and

23

RECIPROCAL OF30,000- ENERGIES REQUIRED 13

TOKILL CO 12z GATES ;41

IIF25•000 / ' • I -- o

, DESTRUCTIVE 9X 20,000 ACTIONFOR

w PARAMECIA 8aWEINSTEIN (302)I7

wJ 10,000, THYMUS 4

' vABSORPTIB-ACTERICID L '5,000 CURVE 2 ew

(Re 1oiptma ofkilling time) II BANGAW 10)-

2 )0 2500 2800 54QQ.. 3400

Figure 2. Comparison of Lethal Action of UV andAbsorption of UV by Nuclear Materials.Ellis et al (75)

24

with bacteria the temperature coefficients obtained for the reaction havesubstantiated this theory (94). For a discussion of the photochemical andcytochemical action of UV radiation, reference is made to Radiation Biology,Vol., II, edited by Hollaender (151),

UV radiation produces its main effect upon the organism absorbing theradiation rather than by affecting the medium. A "single photon hit to kill"theory has been advanced by Lea (183) but with bacteria this has so far beendifficult to prove (135,247). According to the Bunsen.Roscoe reciprocitylaw, the amount of energy required to kill an organism is a product of theradiation intensity and time (T x t ' K). For the bactericidal action ofUV radiation? this Law iias boen proved to hold true ,veor a range of inten.sities requiring from only a few microseconds to ýseveral hours to producethe same amotint of total radiation (247). The law was found not to applywhen the time of exposure involved an appreciable part of the- fe cycle ofthe organism,

Over a wide range of temperature the resistance of bacteria to UV radia.o,tion is not affected quaLitatively, providing the temperature used has nodeleterious effects on the bacteria In question. UV radiation has beenshown to kill fungal spores oven at the temperature of liquid air (100).

Several othor'factors have been recorded by Rentschler et al (247) fromexperiments in which inoculated agar plates were exposed to/TV radiationm

(1) A sublethal exposture of bacterial cells to UV radiation retards therate at which bacterial colonies will develop.

(2) An individual organism will differ in its resistivity to UV radia.tion at different stages of its life cycle.

(3) In a given species, (dlffurnt |bactaora at the same stage of' theirlife cycle may vary in their rosi•stvity to UV radiation.

C. CHARACTERISTICS Or VARIOUS WON IP. "A1('tIIS

Good agreement has boon obtained by difforent workers concerning themost effective wave length for inactivating various microorganisms. Table1I gives the wave lengths fotind to be most efficient for a variety of organ..isms, as well as the reference source. The evidence rather conclusivelydemonstrates that the most effective range for inactivating bacteria andfor most virus strains is between 2250A and 2800A.

UV radiation shorter than 2000A is not particularly effective as agermicide. The radiation lacks the penetrating properties of the longerradiation and is absorbed to great extent by air. The germicidal propertiesof radiations longer than 2800A have been amply investigated. Hollaender(149) has shown that the intensity or exposure time necessary to kill bacte- Wria with energy of longer wave lengths than 3650A is 1,000 to lOO00 times

26

TABLE II. MOST EFFECTIVE GERiMICIDAL WAVE LENGTH

ORGANISM47 MOST EFFECTIVE REFERENCEWAVE LENGTH, A

Bacteriophage 2250 Giese (100) /

E. coli bacteriophage 2650 Zelle & Hollaender (327)E. col 2650 H Hollaender & Claus (152)

E. coi 2652 Wells (305)E. col 2650 Gates (94)E. col 2537 - 2575 Luckiesh (185)is - 2652 Wyokoff (326)Influenza A virus 2650 Giese (100)Paramecium (protozoa) 2650 Weinstein (302)

Rous' sarcoma virus 2300 Giese (100)

Salmonella tychosa 2100 - 2800 Newcoýr (223)

S. marcescens 2805 Ehrisman & Noethllng (72)

Stagh aureus 2537 Gates (94)Staoh aureus 2650 Ehrisman & Noethling (72)Tobacco mosaic virus 2250 Giees (100)Tobacco mosaic virus 2250 Hollaendor (149)

%accinia virus 2650 Giese (100)Bacteria, unidentified 2800 Cernovodeanu & Henri (44)

Bacteria, unidentified 2750 Mashimo (201)Bacteria, unidentified 2500 Bang (17)

Dacteria, unidentified 2265 - 3287 Barnard & Morgan (19)

Bacteria, unidentified 2400 - 3020 Bucholu & Von Jeney (38)

0

26

that required with radiation shorter than 3000A. Data published by Luckiesh(185) demonstrate that the effectivenoss of 2537A is about 4000 times that Wof 3660A; 10,000 times that of 4047AI 30,000 times that of 5461AI and per-hape 35,000 times that of 5780A.

Studies on the effect of the UV radiation emitted from commercial sun-lamps on aerosols of Serratia mardescons at an 1W of 40 per cent showed thatwave lengths in the range of 29t EM50Azhad approximately 10 times theor'act as wave lengths in the 3450A to 7600A range (160).

A great deal of the work on the bactericidal effects of UV radiationwas done before the advent of the low-pressure morcury vapor lamp (so-calledgermicidal lamp). The authors, Weinstein (302), Coblents and Fulton (46),Hollaender (149), Duggar (70), and Hollaender and Claus (152) used carbon,mercury, and tungsten arc lamps with water-cooled quartz jackets. The radi-ation emitted from these arcs cover a wide band and must be separated by asystem of filters or prisms before quantitative data can be collected.

With the development of the low-pressure mercury vapor lamps, which emit95per cent or their UV radiation in the resonance line of 2537A, most ofthe recent data have been reported on the basis of the quantity or energyin this wave length needed to destroy microorganisms. Wave length 2537A isestimated to possess abuut 865 per cent the relative germicidal effectivenessof wave length 2650A. However, Buttolph (151) has suggested that the factthat 2537A is 10 to 20 per cent los ,effective than the maximum effectivewave length I.s of minor importance because of the experimental errors inher-ent in determining the optimum bactericidal region. Adoption of a more orless standard ultraviolet source has greatly simplified the problem ofecor-relation of data and has greatly enlarged the practical uses to whicK-,UVradiation may be applied.

it Cited in Hollaonder.

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III. LAMPS WHICH PRODUCE UV RADIATION

A. GENERAL

During the past thirty years approximately 75 new types of UV lampshave been developed and placed on the market, These lamps vary in size,in wattage, and in the emitted spectrum. Many have been designed forspecific applications; for example, for photochemical reactions, for sun-tanning and vitamin D production, for light, for bactericidal effect orfor ozone production.

Ultraviolet lamps contain mercui'y vapor, The passage of currentthrough the vapor excites the mercury atoms to various energy states, Inmaking the transition from one state to another the atoms emit radiationof definite wave lengths. The probability of these various transitionsdepend upon the pressure of the mercury vapor, the amount and type of othergases prosent, and the electrical conditions in the discharge,

At very low mercury pressures, such as ten microns, most of the emittedradiation is a result of transition from the lowest excited state to thenormal state, This is known as resonance radiation, Radiation thus pro-duced may be absorbed by other mercury atoms and re-emitted without changein frequency. In low-pressure, mercury discharge lamps, almost all of theradiation is emitted at wave length 2537A, Increase of pressure results in'broadening of the emission lines and in an increase in the continuous back-ground radiation, At very high. pressures the radiation approaches that ofan incandescent body, In typical quartz lamps the amount of energy emittedbelow 3800A is greater than the visible energy radiated by a factor of 80to 50 per cent, depending upon the pressure of the mercury,

-Recently, a number of xenon and xenon-mercury arcs have been designed.The 'envelopes are of fused quartz and the lamps operate at 20 to 40 atmos-pheres. The lamps are primarily used as light sources, however, a con-siderable amount of energy is radiated in the UV region.

Mercury in the xenon lamp increases both the visible and the UV radia'tLon, Xenon lamps have been suggested for use as sun lamps.

Sun lamps produce UV radiation such as emitted from ths sun. TheCouncil of Physical Therapy of the American Medical Associalion (7) hasproposed that the energy below 2800A should be less than one per cent ofthe total energy of wave lengths between 2800A and 3132A and that the in-tensity should be sufficient to produce an erythema on an untanned skin inone hour or less at a distance of 24 inches.

Two general types of sun lamps are manufactured, the mercury vapor typeand the fluorescent type. The mercury lamp is located inside a reflectorbulb together with a tungsten filament coil which acts as a ballast for theinside lamp. The outer bulb removes all of the radiation below 2800A,These Rs, sun lamps can be operated directly from a normal 110-125V line.

28

The fluorescent sun lamp is made similar to a regular fluorescent lampexcept that the lamp wall is made from a glass permitting most of the radia-tion above 2800A to escape. A phosphor coating on the inside of the lapabsorbs the 2537A resonance line and produces a fluorescence band having apeak at approximately 3150A. The emission of this lamp closely simulatesthe UV radiation from the sun. Regular fluorescent ballasts and fixturesare used to operate these lamps.

Application of' the nun lamp is mainly for the formation of vitamin D inthe skin, to prevent riokets and to produce a "sun-tan". Ronge (258) hasfound that sun lamps in a schoolroom reduced absenteeism and improved thephysical fitness of the children.

The, following discussion of UV lamps will, be confined primarily to low-pressure, meric-ury vapor lamps which produce germicidal radiation. Such lam",have pressures of 0,004 to 0.02 millimeter- of' mercury as compared to high.pressure sources which may operate at 0.5 to 75 atmospheres, Low-pressurelamps ware made possible by the development of inexpensive glass capable of

/1 transmitting IIV radiation, The greatest portion (95 per cent) of theiremitted radiation ii irA the 2537A wave length band (99,312). This wave

H11 alength 16 ncar the most gerrnuiidal portion of' the spectrum for bactericidal

I/ B, GLASS THAT TRANSMITS UV RADIATION

The constituents of' ordinary glass, which are the chidf absorbents ofUV radiation, are iron and týitnium oxides. Ferrous ions absorb very littleof' the UV radiation while farric ions give high absorption (174). UVtransmitting glass shows a teir-eased radiation transparency after prolongedexposure to high intensities of' UV radiation. This phenomenon is calledsol.arization* The transmitting ability is usually, improved when the glassib heated. Davidovivh (57) in 1930 and Nordberg (226) in 1947 reviewed thestatus of' ommerelal (IV transmitting glass#

The glass commonly• u•sed for the manufacture of present day UV tubes has

characteristics as folluws3

1. Corning Number' 9741 Gl.ass

Corning n4mber 9741 glass was originally used as the envelope i'orall hot and coldc cathode, UV lamps. This glass had a number of undesirableproperties, The glass solarized rapidly and blackened, especially'whenoperated at low temperatures. When new, the lamps sometimes produce ex-cessive, amounts of ozone, At the present time number 9741 glass is usedonly in special 3,6 to 4 watt ozone producing buLbs.

29

2. Cornin.g Number 9823 Glass

This is the glass now used in the manufacture of all hot cathodelamps. The glass does not solarize or blacken as rapidly as Corning 9741glass. It does not transmit radiation below 2000A ard therefore does notproduce ozone,

3. Corning Vycor Number 7910 Glass

This glass is madks by Loaching the flux from alkali-borosilicateglass and oonsolidating by hoat thu high silica residue (211). The glassis used in the manufacture of cold cathode and Slimline type UV tubes.This glass is in some respects similar to quartz (96% silica and 4$alumina), theroforop UiV transmission properties are similar. The trans-mission of 2537A radifttion is about 80 per cent, the rate of solarizationis inegligible, and very little darkening occurs even when operated at lowtemperatures. This glass transmits less than 0. per cent of radiationbelow 2000A which produces only a negligible amount of ozone.

4, Corning Vycor Number 7912 Glass

This glass is used in the manufacture of some cold cathode andSlimline lamps. It has the same characteristics as the 7910 glass exceptthat a controlled amount, approximately 2.0 per cent, of short ozono-producing radiation is transmitted, Lamps from this glass are called"high-ozone lamps." Older quartz UV lamps transmitted fm.om 50 to 90 percent of radiation below 2200A, At the present time some quartz lamps usea Vycor or quartz jacket with an acetic acid solution to filter out radia-tion below 22OOA,

The maintenance of UV output by these glasses is shown in Figure 3.There are three types of low pressure mercury vapor lamps and one high-pres-sure lamp used for bactericidal purposes.

C. HOT CATHODE GERMICIDAL LAMPS

The operation of these lamps is similar to standard fluorescent lamps,They operate at a low voltage from a ballast or transformer and for startingrequire a device such as a glow-switch to preheat the electrodes. Argongas is used to facilitate starting. The electrodes are located in the endsof the lamp and consist of tungsten filaments coated with emission material(calcium, barium, and strontium oxides), The life of the lamp is governedby the life of the electrodes and the rate of solarization of the glass,If the lamp is turned on and off frequently its life will be shortened.Corning number 9823 glass is now used for the fabrication of the glass tube,

30

120

7910 or 7912 glass bulb

60

040060 20

Hor

Figue3 VOtu fBceiia LmsMd rmVrosGassWetnhueEeti oprto 33

31

One of the important characteristics of hot cathode lamps is the effectof tube wall temperature on the UV radiation output, Operation at lowtemperatures results in lamp blackening and low output. Also" startingthe lamp at low temperatures is sometimes unreliable and may require specialequipment. Figure 4 shows how the.tube wall temperature affects UV radia-tion output. When operating with a tube wall temperature of 320Fg the out-put is less than one tenth that of the output obtained when the wall temper-ature i, 1000P, Tho mout efficiont1 ambient tomporraturo for opotL".ton isaround 800F. Oporation in strong uir currents also shortens the life ofthis lamp and lowers the output of UV radiation.

D. COLD CATHODE GERMICIDAL LAMPS

This lamp, containing argon and neon gas, is equipped with cylindricalnickel electrodes and. is made from Corning Vycor number 7910 or 7912 glass.The lamp requires a transformer to obtain high voltages for starting andoperating, but no preheating of the electrodes is required, Thorium metalinside of the electrode increases the electron emission, The life of thelamp is governed mainly by the ability of the glass tube to transmit UVradiation. The electrodes operate "cold" and seldom wear out. The lampsmay be operated at refrigerator temperatures without excessive lamp black-ening, however with some loss of UV radiation output. Instantaneousstarting is obtained at low temperatures.

The relative UV radiation output per rated mamp watt from the coldcathode lamp is of the same order of magnitude as obtained from the hotcathode type, Two types of cold cathode lamps are commercially available;one is designed for high ozone production and the other for low ozone pro-duction, The difference is the glass used in the lamps.

E. IHIGH,.,INTNSITY GERMICIDAL LAMPS (SLIMLINE)

This lamp has characteristics in common with both the hot and coldcathode lamps, It utilizes a high starting voltage which gives instantstarting. Although the electrodes areicold when the lamp is istarted, afterthe start it operates with the electrodes hot. The life of the lamp, as inthe hot cathode type, depends mainly on the life of the electrode wh:Lch inturn depends on the frequency of starts,-,

The ou-tstanding feature of the Slimline lamp is its high output. Thelamps may be operated at four different currents (-120, 200, 300 and 420milliamperes). The UV radiation output per rated lamp watt is higher thanthat obtained with the hot cathode lamps because of the higher transmissionof the glass. The higher intensities obtained make it useful for installa-tions requiring large amounts of 2537A radiation. The ozone output is

* rated as negligible. This lamp is also available in Corning Vycor number7912 glass which emits some 1849A radiations and thus produces small amountsof ozone,

32

100

I C)Cindio 4uo je

33

Table III shows some of the charaoteristics of the three types of lampsdiscussed above,

TABLE III. CHARACTERISTICS OF THREE TYPES OF UV LAMPS

IOT CATHODE COLD CATHODE HIGH-INTINSITY

Rated watts 30 17 39

Over-all length 36" 34-3/4" 36"Tube diameter 1" 5/8" 6/8"

Operating voltage 103-108 410 130Operating current in amps .34 .050 .420

Related life hoturs 7500 17,500 7500UV intensity at 1 motor 74in microwatts per sq cm 72-80 46 120UV output in watts of 7284 5,2 13182537A

The figures listed by lamp manufacturing concerns for UV lamp outputare average values obtained from readings on many lamps (133,0320):o Theoutput of individual UY lamps is known to vary more tha4 the visible lightoutput of lightingdlamps.

F. HIGH-PRESSURK MERCURY LAMPS

For routine practical use, high-pressure lamps offer few advantages. andare useful only for special research purposes. The following sumnarisebriefly their essential charactoristicsl

(a) The efficiency of the conversion of input electrical energy tooutput radiant energy is lose than with low-pressure lamps. However, thegermicidal output per unit of high-pressure quarts lamps is generally,greater,

(b) The energy emission is -l distributed over a wide range of wavelengths (about 20), therefore, much of the UV is not in the spectral areaof maximum germicidal effectiveness*

(a) The rated life is generally shorter than with low-pressurelamps.

34

(d) As a high-pressure lamp solarizes and depreciates, the intensityof different wave lengths may decrease at variable rates.

(o) The transformer necessary to operate a high-pressure mercurylamp im generally large and expensive.

(f) Highprosure mercury lamps made of quartz produce a great dealof ozone unless enclosed in a special ultraviolet transmitting jacket.

Further information on types of high-pressure UV lamps may be found inpublications by Ellinger (74) and Meyer and Seitz (210).

G, EXPLOSION-PROOF LAMP FIXTURES

Several kinds of explosion-proof UV lamp fixtures are manufactured,These are actually -lamp fixtures equipped with explosion-resistant Vycoror quartz glass housings, Regular UV lamps are placed inside the housing.The fixtures may be used in areas which are considered hazardous because ofthe presence of flammable vapors, gases, or combustible dusts. In additionto the high initial cost of these fixtures (approximately $125.00 each) thnUV radiation output of the lamps is somewhat lowered because o'f absorptionby the Vycor glass housing. Explosion-proof lamp fixtures are manufacturedby Hanovia Chomicel Manufacturing Company and by CrousoeHinds ManufacturingCompany.

Conversion of the Westinghouse type SB-30 fixture, for cold cathodelamps# to produce a water-tight unit (not explosion-proof) can be done ata cost of about $52.00 per fixture, including the price of the fixture andlamp, Such a de eign has been accomplished on a local basis, and tests haveshown such a unii• safe to operate in areas of high humidity or where roomsare washed with liquid solutions, The converted fixture is shown in Figure5s The transformer has been placed in an aluminum box with a gasket lid.Neoprene membranes are used to produce water-tight seals at the socket con-nections at each end of the UV tube, This fixture satisfactorily resistedsprays of brlno solution without shorting or gathering moisture on criticalparts and without significant change in UV radiation output.

1I, UV RADIATION FROM WHITE LIGHT SOURCES

1, Incandescent Lamps

Most artificial sources of white light are weak sources of UV radia-tion. Photoflood lamps are probably the highest generators of incidentalUV radiation. The glass walls of ordinary incandescent type lamps will notpermit the passage of radiations ahorter than 3200A, 'Koller (174) presenteddata showing the relative amount of energy in various wave length bands pro-duced by several types of incandescent lamps (Table IV). All five lamps

It

*j�I

II

36

listed produced UV radiation in the 3200A to 3800A wave length band.Three of them produce detectable amounts in the 2800A to 3200A band.Aocording to Roller, total UV radiation of less than 3600A emitted by the1000-watt photoflood lamp (life of 10 hours) is approximately three- watts.

TABLE IV. RADIATION PRON INCANDESCENT LAMPS

Energy in various wave length bandsfsalling on a unit areaat a distance of 1 meter from the lamp. (Koller 174)

TYPE O LAMP ICRONATTS PER SQUARE CENJTIMETERlt, OF LAM4P 2800A-3200A 32ooA.380oA 800A-7600A

40,watt standard 0,08 22.•51100 watt standard 0.45 75500 watt standard 0.045 3.0 4401000 watt standard 0i28 80. 11001000 watt photoflood 1.4 25 1580

2. Fluorescent Lamps

fluorescent lamps also emit small amounts of UV radiation. Znfact, in its simplest form, the fluorescent lamp is an UV lamp whichutilimes a glass envelope coated on the inside with special fluorescentpowders or phosphors. About 60 per cent of the wattage input of a fluo-rescent lamp is used to produce radiation concentrated at 2537A wavelength. This radiation is produced inside the lamp and is used to excite s '

the phosphors which produce the white light. The over-all efficiency ofthis type of lamp in the production of light is about 10 per cent.

Although the amount is very smoll, some UV radiation is emitted byfluorescent lamps, the amount vazyTng with the type of phosphor materialused, The data shown in Table V are taken from a table by Luckiesh andTaylor (187) and show the intensity of UV radiation shorter than 3150A pro-duced by sunlight and by a fluorescent light. The foot-oandle concentra-tion of the white light is given for each sources Although direct sunlightat 6600 foot-candles contains 70 times as much UV radiation as fluorescentlight at 50 foot-candles, it is obvious that higher intensities of fluo-rescent light will be proportionally greater. For instancep another way toexpress the relationship shown by Luckiesh and Taylor would be to calculatethe microwatts per square centimeter of UV radiation produced per foot-candle of light, Fl*orescent light produces 0,010 microwatts per squarecentimeter of UV radiation shorter than 8150A for each foot-candle of light

37

by this wthod, while the same figure for direct sunlight is 0,0085. Onthis basis the UV output of fluorescent leaps per foot-candle appears to beleos than skylight with a clear blue sky, or sunlight and skylight combined,but more than direct sunlight,

TABLE V. UV FROM ILUORESCENT LAMPS(Luckiesh & Taylor 187)

Intensity of UY radiation shorter than 3150A

FOOT- MICROWATTS PER SQUARE CENTIMETERCANDLES Absolute Rlative

Direct sunlight 6600 so 70Skylight-clear blue sky 1900 117 146Sunlight and skylight 86500 173 216Direct fluorescent light 50 0.8 1

35000 white

There is no doubt that the germicidal effectiveness of the longerUV wave lengths discussed above are of a very low order, but the fact thatthese weak sources of UV radiation exist is worthy of consideration, It isobvious that unless all culture work is done entirely in the dark or unleisspecial visible light sources are used, small amounts of UT radiation fromthe usual lighting system are apt to be present in all biological labora-tories.

3, Survival of Bacterial Spores on lnuorescent Lmps

Two 15-watt daylight fluorescent lamps, mounted in receptacles, wereplaced in a ventilated cabinet@ One lamp surface was ece,'aminated with acotton swab soakel in a suspension of Bacillup subtilis var. o sporescontaining 2 x 10 spores per -illiliter, Wetr ap was ri'-ated simi-larly with a 2 x 17 spore suspension.

-Both lamps were turned on after contamination was completed and"sero" time surface samples taken, A portion of the surface of each lamp

-' was sampled at intervals of 30 minutes for a period of 11* hours and atthe end of 24 hours.

88

The control experiment was conducted in the same fashion with tJheexception that lamps remained off. On the unlit lamp oontaminated withthe 2 x 10' spores suspension, surface samples remained TNTC for 9 days onthe 2 x 107 lamp, samples were TNTC for 8 days, and.•2 colonies were, re-covered at , days, Sampling was discontinued at 9 dAys.

The'resiwlts of the tests with burning lamps are shown in Table VI.Since the temperature at the surface of4a fluorescent lamp is not sufficientto cause inactivation of bacterial spores, it is likely that the results obs-tained were dues in part, to the action of ultraviolet radiation on thespores Itf one assumes that approximately 24 hot's is required for thelethal action and that a dose of 800 microwatt minutes of 2587A is necessaryto inactivate a spore population (see page 59), it can be theorised that thetotal radiation at the surface of the lamp had a germicidal equivalent of1.8 microwatts per square centimeter of 2537A.

TABLE VI, RECOVERY OF BACILLUS SUBTLIS SPORES FROKBURNING FLUORESCENT LAMPS

SWAB CON- TIME OF SAMPLINGSITE TROL 30 min 1 hr 6 hr 6,5 hr 7Thr 11 hr 11.5 hr 24 hr

Bulb 1 0 TNTC TNTC TNTCA/ TNTCi/ TNTCW 65 15 13Bulb 2 0 TNTCJ4/ TNTCi/ 100 72 35 0 '1 1

Bulb I - Contaminated from 2 x 109 spore suspension.Bulb. - Contaminated from 2 x 107 spore suspension.TNTC - Growth confluent; no distinct colonies6TNTC/ ,... Colonies distinct but TNTC,* Surface sample of lamp prior to contaminations

39

IV. RDLETANCE OF UV RADIATION

A. LITERATURE REVIEW

All radiant energy is reflected to some extenzt from surfaces, Theamount reflected depends upon the type of surface, the wave length of theenergy, and the angle of incidences Luckiesh and Taylor (188) reportedexperiments to determine the percentage of UV energy (2587A) reflected byvarious surfaces. A specially designed reflectometer was used with aBausch and Lomb number 2800 quarts monochrosator for spectral measurementseThe authors concluded that aluminum is by far the best reflecting mediumfor 2587A UV radiations Table VII, prepared from data presented by Luckieshand Taylor, shows the per cent reflectance of 2537A energy from the varioussurfaces tested#

(. TABLE VII. REFlECTANCE OF UV RADIATION JMU VARIOUS SURFACES /(Luckiesh & Taylor 168)

NATERIAL PE CENT RULECTANCE OF 2537A

Aluminum metal, etches and brightenedAluminum metal, bright, rolled 64 PAluminum metal, foil 78Aluminum metal, Alsak treated 65Aluminum metal 9 mill 40 -60Aluminum paint 40 - 75White-coat pla tsr 40 - 60Chromium metal 45 - 55Stainless steel 20 -80Wall paper (ivory and white) 21 - 82Acoustic plaster and wallboard 10 -20Vitreous enamel 5 - 10Kalsomino white water paint 12Alabsetine white water point 10Average oil paints 5 - 10White porcelain enamel 4.7

40I

In another series of test. (185) in which nine different a2.uminum paintswere used, it was found that when painted surfaces were exposed to high in-tensity 2b37A energy the reflectance for longer wave lengtha ws increaseed12 per cent. Reflection coefficients ranging from 46 to 66 per cent wereobtained for the nine brands of aluminum paint. Several important pointsregarding reflectance of UT radiation arel

(a) Aluminum metals and aluminum paints are the best refl•ectors of uyenergy. Intensive and prolonged exposure of aluminum paint does not seemto destroy its ability to rofloot the radiation. Such a paint, h~wever,should be made- of pure aluminum flakes, and the plastic lacquer should have::high UT transmissi~on properties and stability.

(b) Stainloess steel has~ approximatel•y 50 per cent the reflectanceefficiency of aluminum, For maximum reflectance, reflectors made withstainless steel or an other metal except aluminum should be painted witha:luminum paint.

(c) Oil paints and some water-soluble paints are poor reflectors ofUT radiation, Reflectance depends upon the type of pigment in the paint;zinc oxide pilgment uuually giLves low refl~ctivity. O L;. paints usuall~y givefrom five to ten per cent reflectance and water-solublq paint from 10 to 12•per cent reflectance,

(d) White wall plaster has reflectance values on the order of 40 to60 ,per cent of 2537A,

Alnsk aluminum metal gives h igh ref:lectance values and is suitable foruse as reflectors for UT limps (Figure 6). Aluak is a trade-mark regisetredby the Aluminum Compan~y of Amnerica. The aluminum is first brightened by anelectrol•ytic method to reoveo surface impurities and then oxidised to pro-vido a thin coating of aluminum oxide to prevent weathering. rP

The average reflection coefficient of human skin for 2600A adiLntion isfour per cent (169). There is little difference between tanned and untannedskins

The amount of radiant energyr reflected from the surface of an~y trnes-parent medium, such as glaJss will vary with. the angle 1of incidence. At.normal incidence (10 to 60 degr"ees) the reflection from glass of SOSIA UVradiation is about five per cent. Per cent reflectance rises rapidl•y atangles greater than 75 degreeos,

I -

41

I'

-- - . . . . . .. ..

N N _- - _ - i C

- "" -- - - - -

'\-\ 1 '11I\ - - n

*- ' •NVJ±D3".1i3W J.N3) t3dd

42

Koller (174) gives the following reflectance values for several surfaces:

Reflection of SOOOA UV radiation from the around 0Surface Per Cent Reflection

Tres h snow 85Dry dune sand 17Sandy turf 2,5Water 5

Anderson (10) gives the following reflectivity values for 2537A radia-

tions

Surface Per Cent Reflection

Glass (brick., mirrors), 4 - 6Enaels (baked , any color and white) 5 - 10Oil paints (lead, any color and "hite) 5 - 10Oil paints (sinc, any color and white) 3 - 6

Anderson also reports that water paints and paper frequently have highreflec-tivity values. This would be true especially for very large anglesof incidences.

In the use of UY radiation for control of infectious hasards, aluminumpaint or metal should be used if a high degree of reflectanceis desired,and, oil or suitable water paints thould be used if the reflectance is to be

In connection with the use of reflectors., Buttolph( (151) has, pointed outthgt the mercury vapor in UV lamps will completely absorb 2537A radiationsentering the tube from the outside., The 2537A radiation generated in thecenter of the tube is also absorbed by the mercury vapor and re-radiated tothe atom close to the wall of the tube until it finally escapes. Therefore,to obtain-a high intensity of radiation in one direction, the bare lampsshould not be placed side by side. Placement of parallel lamps individually

,.-in front of reflectors on centers three or four times the lamp diameter wasreoommendei by Duttolph,

., EXPDIENTAL

1, Increase in Intensity of Radiation by Use of Reflectors

Tests were made to determine what practical increase in intensity ofUV radiation might be expected by the use of reflectors. Measurements weretaken before and after the installation of aluminum reflectors in a doorbarrier installation.

* Cited in Hollaender.

43

A considerable increase in intensities was obtained after the in-stallation, Table VIII shows a typical set of measurements for comparison.An increase of over 100 per cent in UV intensities was obtained by the useof five reflectors. It is evident that in soms applications the use ofaluminum reflectors will permit more efficient and economical. tilisationof the germicidal enerL,. The cost of the reflectors used in this instal-lation was approximately $2,00 each. The use of a properly designed para-bolic aluminum reflector behind an UV lmp ,will direct the radiations ofthe entire lamp in one direction, and 'by this meane intensities in thisdirection can be increased three- to five-fold,

TABLE VIII. INCIRASE IN UV INTENSITIES THIDUGH THEuss or ALUmiNU REFLnCTORS

ROADING Dh•lRS INSTALLATION lErING ArTER INSTALLATIONOF RIcToks orR EfEcTOR

del

52 10836 9226 72rs0 _75

Totals 212 409

2. Use of Reflectors with Cold Cathode Limps

Studies had previously been made of air looks and door barriers Ininstallations utililing hot cathode amp without reflectors. A series ofUT intensity measurements were made in an M OW barrier using hot cathodelamps wth reflectors, cold cathode lamps without refleotore and coldcathode-l-amps with reflectors. The object was to determine if suitable UTintensities coulbe obtained when cold cathode fixtuske (17watt) weresubstituted for the hot cathode fixtures (80-watt). Specular AlIaa alumi-num reflectors were used* tMimination of the data obtained showed the fol-lowing results:

(a) When hot cathode lamps are used with reflectores the in-tensities obtained far exceed the mini.u required for efficient operationof door barriers.

44

(b) When five cold cathode lamps without reflectors are used inplace of the five hot cathode lampes the intensRo es obtained were inadequatefor' the purposes for which the barrier is intended.

(o) When five cold cathode lamps with aluminum reflectors weresubstituted for the hot cathode lamps, the inTe-nsities were adequate.

As a result of these testsp the standard UV door barrier was de-signed to utilize five 17-watt, cold cathode UV lampes each equipped with aproperly designed Alsak aluminum reflector.

It was also evident from these tests that the cold cathode lmp wouldbe suitable for use in air looks and other installations. Higher radiationintensities can be obtained if needed by the use of Slimline lampo.

3. Aluminum Paints

The reflectance and resistance to UT radiation of two comercialbrands of alum•num paint 1ure investigated. Glidden brand paint* was com-pared to Rust-Oieum #470o The rpfecoi2nco test using 2537A UV radiationshowed that the reflecting abilities of'metal surfaces painted with bothpaints were practically the smo. Glidden paint reqflected about three percent more than did the Rust-Olous paint (about 50 1,r cent reflectance).No deterioration of either surface was evident-aftir exposure of both paintedsurfaces to UV radiation, The total radiation does would be equivalent tothat received in two years in an UV air look with intensities of 20 to S0microwatta per square centimeter. Another sample of Glidden paint was ex-posed for a period of eiqht mosths to an UV radistion, intensity of 1500microwatteper square centimeter without any indication of deteriorations

The effect of aluminum paint in increasing intensity levels by pro-viding better reflecting surfaces is illustrated by tests done on an animalcage racks

The rack had solid metal shelves located 17 inches sapart. UV lampswere mounted horizontally at eaoc end of sach shelf. The area betweenshelves rceived the benefit of sky reflected radiation from the bottom ofthe shelf above. Using calibrated lomps and moters, intensity measurementsJ• were made at various locations betwoon-the shelves when the reflecting sur-face of the cage rack shelf above was painted, first with aluminum paint,and then with a semi-gloss, oil base paint. Typical readings art shown be-low in milliwatts per square footo

C The Glidden Company, Cleveland 2, Ohio.S*Rumt-1Olum #470, Ready Mixed, Aluminum - LO, Rust-Oleum Paint Company# 4,

45

UV RADIATION REFLECTD FROM A SURFACE

Painted Aluminum Painted Semi-Gloss

30 515 .410 3

4. Reflector Design

Experiments to determine proper reflector shapes for UV lamp fix-tures have been conducted.* It was desired in these tests to design pol-ished aluminum reflectors capable of producing narrow parallel beams ofhigh intensity radiation such as would be required on UV cage racks and inUV door barriers.

Parabolic shapes are necessary to concentrate radiations from UVlamps. To obtain a narrow emission band, a parabola with as large a focallength as is practical should be employed. The center of the UV tube shouldbe placed at or slightly in front of the focal point for maximm efficiency.

For convenience small, cold cathode lamps and fixtures were used.Intensity and radiation patterns were appraised by plotting spatial distri-bution curves on polar obordinate graft paper. Spectral planes horizontaland vertical to the lampo and fixtures were plotted.

Parabolic polished aluminum reflectors for testing were constructedas shown in Figure 7 with a focal length of O/S fzh. For comparison, re-flectore of an irregular shape intonded for use on UV cage racks were alsotested, Spatial distribution curves were plotted of the bare lamp, thelamp with the irregular reflector, and the lamp with the experimental para-olic reflector. Results obtained in the vertical and horisontal plans are

shown in Figure 8d The experimental parabolio reflector produced a wideflat beam of radiations on a flux intensity in the beam at least five timesgreater than that of the bare lamps and twice that of the lamp with theirregular reflector*

Based on mthese experiments, it was recommended that parabolic shapereflectors be 'ued on all UV fixtures where it is desired to project a nari-row beam of high intensity radiation. For hot cathode lamps (one-inohdiameter) the parabola should have a focal length of 5/8 in, ch old cathodeand Slimline lamps, a 8/8-inoh focal length parabola.

5. Distribution of Radiation from a Cold Cathode Fixture

In some applications of UT radiation, such as in air lockst it is* desirable to have a uniform distribution of energy rather than a concen-

trated beams. Generally the cold cathode lamp in a Weutinghouse SB fixtureis used. The portion of the fixture under the lamp has a small V shaped

46

full scale

parabolic curve focal length 3/8"

focal point

S3 7/8"0

\, polished surfaceUV lamp 115/16"

-25/8"---

Alzak aluminum approx 1/32" thick

figure 7. Parabolic UV Reflector.

47

IdI

"H0

sfo~ftoo, @Ges*

48

piece of aluminum which acts to reflect radiation, The spectral distribu.tion is given in Figure 9. The UV output in microwatts per square centimeterat various distances is given in Table IX.

TABLE .IX, U7 INTENSITIES AT VARIOUS DISTANCES FROM A 17-WATTCOLD CATHODE LAMP IN A SB-30 OIXTURU

VERTICAL DISTANCE MICROWATTS PER SQUARE CENTIMETER120 LAMP, feet

6 17.8 17,4 17.0 15.3 13o07 13.5 13.3 13.2 12.2 .1,2a 10?7 10.7 10.6 10.4 9g4,9 8o9 8.9 8.6 8.4 7.9

10 7.0 7ol 7.0 609 60611 5.9 5.9 6.0 6.0 5.712 500 501 501 5o2 5.3X3 4.4 4-5 4.5 4.4 4.4

HORIZONTAL DISTANCE 0 2 3 4 5FRO LAMP, feet

ii

/6/

49

BARE LAMP.46 PW/cm at IM5 3

FIpe OS. Kietrlbution from a Cold Cathods:Lam ("23-O0) Installedin a 83.80 FVwure.

s0

V.TRANSNI6ilON"01 i~ RADIATION

A. LITERATURE REVIEW

The extent to'whi ch various materials permit the passage of UV radis-tion has boon reported at length in the literature, although the exaot wavelengths used have not alwayd been idourately defined. It Is important todesignate the portion of the spectrum being used when interpreting suchexperimental data., Elliot *t al (75B) refer to work done by Moms and Knappwhere the investigators fouil Eait four millimeter Mshets of Pyrex glasstransmitted 40 per cent of the erythemal UV radiation used, The orythemalrange includes those ways lengths between 2800A and 3200A. Luckiesh and'Taylor (186) demonstrated that Pyrex glass will not trazaszit-the shorterwave lengths of 2537A9 The re;Lative amounts of energy of various wavelongths omitted by low-pressure mercury discharge leamps is shown in Tabli X,

TABLE X. RELATIVE AMOUNTS OF DENERY 0F VARIOUS WAVELENGTHS EMITTED BY TYPICAL GEN1ICIDAL LAMPS

(Generall Electric-Co. 99)

WAVE LD4GTHO A RELATIVE ENEWT, A

2537 95.152652612604 .042694 6102967 0433022 60223130 1.903650 2.001650 trace -according io

type of lamp

Luckiesh (165) investigated the extent to which 2587A radiations poen.trated various types of glass, The data shown in Table XC are taken fromthis work and show the transmission abilities of 16 different kinds of glass.Table 731 shows the transmission of several wave lergths through four typesof PWex glass. Estimation of the relative bactericidal effectiveness oftwo wave lengths is included. Other data are shown in Figure 10.

61

TABLE 11. TRANSKISSION 0F 2587A UV RADIATION BY DInMENT0 TYPES Of GLASS (Luokiesh 165)

THI•ESS PER CDETTYPE F LASS - TRANSMISSION

Glass Found to Transmit 2537A

Corning Noo 97401 68

Corning No# V410. 6Corning 'No. 9730 145Corming Noe 9700 1 7Corning Corex D 1 2

Glass Found Not to Transmit 25SUA

Comning Noe 774 (Chemical Pyrex) 1Lead glass 1'Lies glass1Corning No. 772 .(Nosex)Misoellaneous Pyrex 1.05Microscope glass 0618Microscope slide 0o96quarttlite 2.02Helioglass 2.00Vitaglass 2.77Optical glass (6 types) 2Optical Is: -sea 10Window glass (50 samples) 1-7

* Glass used in the manufaoture of VV lamps0

SO0

52

0 0 0 0I0'own aI

uoj~j~luDjý4eGIIe

58

TABLE X1I. PR CENT TRANSHISSION OF FlVE DIl ENT UVWAlE LGTHS THROUGH PY1 CLASS

WAVE LENGTHSGLASS 2587A 8022A 3180A 8842A 8650A

Sheet,, 8- thick 0 21 47 79 89sheet, 4.85 - thick 0 7 80 so 89

Pebbled sheet, 8 -m thick 0 28 44 78 82Pressed eight, 5.8 - thick 0 7 29 72 so

Relative bactericidal effective-ness of wave length 100%

Plexiglass Snd other clear plastics transmit very little 2587A energy.The degree of transmittanceis a function of the thickness of the plasticas well as the type. Figures 11 And 12 (174) show the per cent transmit-tace of various wave lengths through several clear plastics.

Various substituted bensophenones are tvailable (11) which can be in-cluded in the formulation of may plastics to absorb radiatieon between2000A and 4000A and to prevent the discoloration of plasties caused by UVexposure. The newest of these is 2-hydroqW-4-mthomobe isoe'-Aeme, known asUT-B, marketed by American Cyanamid Compaq, Doud 1rook, ow Jersey.

UV radiation of 2587A and longer show high tranmissiin through dis.tilled water. Shorter wave length show Increasingly higher absorptionrates.o oller (174) gives the following table for the itrasmission of2587A ultraviolet in diestilled watero

Depth in inches 8 6 12 24Per cent transmission 92 68 76 61

Transmission is reduced by the presence of dissolved sultivalont saltsor organic matter. Generallyt iron salts and organic matter heve a greatereffect on absorption than 4o alkali salts. The transmission, tq variesexponentially with the depth of the waterw, do

tue -ad

The value a is called the absorption coefticient. The transmission ofý2587A radlatlon through water of varLou cooefficients of absorption isshown in Figure 183 Municipal waters show a considerable variation in thetransmission. Water samples from 19 large U.S, cities transmitted from

54 __

s0~ -,a d'°"....

Sr(

.!€ soo

j 4o I °30IO-10 0

90 se..

0I I

.00 300 400 500 o00 700 600 $00

Wave Length In Millimicrons

A. Methyl methocrylate, thickness 1,47 mm,R. Allyl alcohol, thicknest 3.05 mm,C, Cellulose acetate butyrote ,thlckness 0.41mm.0, Cellulose: acetate, thickness 0. 50 mm,

10090' - •so:

G!o-

'40.30-

170 -

200 300 400 5006$00 ?00 g00 t00

Wave Length In Mfll~mleron!e.

E. Cellulose nltiate thickness 0.680 mm.F. Cellulose proplonate, thickness 0.23 mm.0. Ethyl cellulose, thickness 0.79 mm,4, Polystyrene, thickness 0.45 mm,

figure 11, Spectral Tranmittance of SeveralClear Plastics. Kollr '(174)

\55

.100so-

ISO

" 60- 0.IIn

40-

240

2 Oo 3500 4500Wave Length In Angstroms

Figure 12. Transmiasion of ]Plexigdas.

56

*1090

60

Cetmtrsooae40 ueL.PrCntTamsino 53Afz aeso

Difrn oefc0t f bopin

05C

5.7

*0.86 to 45 per cent of the UV radiation passed through a test cell onefoot in depth (186). Contamination of water with small bits of filterpaper, cork, or dust can roduce XJV transmission by a large factor.. Thetransmission of distilled water can be reduced from 95 to 58 per cent bypassage through two filter paperes

Rong. (258) reviewed information on the permeability of clothing to UVradiation. Whipcord fabrics are practically impermeable to UT radiation,while cotton or milk stocking material may transmit from 18 to 40 par cent.The pore-suee or weave of the fabric ha the most effect on UT penetration.Hart (124) states that closely woven starched cloth is sufficient to stopover 99 per cent of the radiation from a bactericidal loape

3X. XPEINTDTAL

Studies have been made by the authors on the transmittance of 2537Aenergy through various materials using a 15-wattp hot cathode germicidallmp* The UV intensity at a point two inches from the outer edge of thelamp, as measured by SM-200 click meter, was 1710 microwatte par squarecentimeter.

As shown in Table XIII, only the onion skin paperl the powdered weigh.ing paper and the operating gown showed detectable transmission of thegermicidal radiations No reading wis obtained on the instiument with theother materials tested.

In general it may be concluded that most surfaces, including glass,plastios, and paper, are incapable of transmitting 258TA radiation to aqgreat extent. Laboratory glassware (soft glass or /mex) does not transmitthe 258'A band* Pure distilled water three to six inches in depth does notseriously reduce UV penetration, while municipal waters may absorb a con-siderable proportion of radiation.

00

58 0

TABLE XIII. TRANSMISSION OF 258A .RADIATION THROUGH VARIOUS MATERIALS

Intensity directed against each ateriai *1720 microwatta per squaoe centimeter

MICROWATTS PER SQMATERIAL CH PASSING THROUGH PER CNIT

MATERIAL TRANSXMISSION

Flexible vinyl plastic -2 .ill thick 0 0

Plastic •ie• of fece shield 0 0Plexiglass, t" thick 0 0Visor of plastic personnel hood 0 0Bacs of plastic personnel hood 0 0Pyrox Petri dish 0 0Glass eye - piece of Sa msk 0 0Brown wrapping paper, sheet 0 0Bond typing paper', 1 sheet 0 0Scratch paperp 1 sheet 0 0Onion skin paper, Isheot 27 1.5Powde" weighing paperp I shoot 78 402Bath towel 0. 0.Operating gown 20 102

VI. *dEASUlMDIIT OF UV RADIATION

A. UNITS OF NEASURiDENT

Just as erythemal energy is radiant energy capable of producing ery-thema, germicidal energy is capable of producing germicidal effects.Visible radiant energy, on the other hand, is capable of producing luminos.ity. These energies may be measured and expressed in terms-of erg-seconds,joules, microwatt-seconds per square centimeter (sq cm), or lumens.

In the case of erythemal producing radiation, the flux is analogous tolight or to luminous flux. Flux is energy masured according to the effeo.tiveness of equal amounts of energy of various wave lengths. Luminousflux, or brightness, is measured in foot-lmberts and the correspondingterm for use with erythemal UV is 3-viton, or microwatts per square centi-meter of effective radiation, Thus the unit of exposure is the Z-viton-second per square centimeter which Ls equivalent to ten vicrowatt-secondsper square centimeter of 296TA radiation or equivalent.

In the measurement of germicidal eoierg, the radiation emitted by the.lamps is concentrated in the spectral ivegion of 2587A which is near thenmxinum for germicidal effectiveness. ,fThe intensity of germicidal radia-tions is usually expressed in microwattes per square centimeter of 2587Arafitation and is a measurement of flux.! The total UV dose is caloulatedas the product of the fluxp the exposure surface (1 sq om), and the expo-sure timet thus giving microwatt-minutes per square centimeter. This ternrepresevts the total energy incident upon a square oentimeter of surftacand for simplicity my be designated as the 9T (intensity z tinm) value.

The following physical definitions a helpful when converting or cal-

oulating UV intensilies (180).

Ener, measurements

I erg w 1 dyne m

107 erg - 1 joule

- I watt-second

Power measUwrments

I watt 0 07 ergs per second

- 106 microwatts

1 erg per second w 10" microwatts

60

Intensity of radiant Dower (per unit area)

1 microvatt per sq on - 10 ergo per second per sq on

Exposure or dosae

2 microwatt-second - 10 ergs

1 microvattmminute - 600 ergo

Intonsity of exposure or doesae (ger unit areL)

2. icrowatt-socouid per sq cO m 10 ergs per sq cn

2 microwatt-minuto per sq c *- 600 ergs per sq cn

Wells (305) advocated the use of a survival-ratio called a "lethew. Onelethe is equivalent to the reduction in bacterial air count resulting frcmone complete air change in an occupied area. This ratio has been termed a"unit lethal exposure" by Luckiesh (285). The survival-ratio is the frac-:tion of the original concentration (PO) of bacteria per unit area or perunit volume surviving after a given exposure, With certain microorganim0sthe relationship between the exposure dose and fte survivil-ratio holds ap-proximately over a range sufficient for practical purposes. The relation-ship for air-borne bacteria exposed to UV radiations is represented by thefollowing fowrlsa

where P - initial concentration

P a concentration at time t

e - base of the natural system of logarithm (approximately 2418)

3 a intensity of gernicidal flux

t w the time

X w a constant depending on environmental conditions 'such ashumidity

When the exponent of we" is less than unit, the survLivl-ratio equals0.868 and corresponds to a survival of 36.8 per cent, or one lethe, Theestablished procedure is to plot a straight line survival curve using a log-arithmic ordinate scale. In some instances where the required accuracy isnot criticas1 the use of this system may be ,advantageoust but in general it

62.

* is better to calculate inactivation of microorganism based on the radia-tion does available to inactivate and experimental data showing the rela-tive resistivity of various air-borne forms.

The moat conven:ient iiothod to express the concentration of UV radiationis by the use of the term ET (microwatts per sq cmx time in minutes),This tends to make the experimental data presented here more easily appli-"cable for practical uso. For examplo, in one test room (375 cu ft) wo30-watt, hot cathode, UY lamps without reflectors located on the ceilingwere turned on and a series of readings taken with a meter to measure theintensities falling on various surfaces* An average value was determinedfor each surface as shown in Table XIV.

TABLE XIV. UV INTENSITIES AT VARIOUS DISTANCES MON TWO30-WATT LAMPS

DISTANCE FROM NICIOWATTS PERSURFACE CEILINGt cn SQUARE CENTIMETER

On tocp of transfer cabinets 90 85On tab10 tops 160 25On shaiih tops 210 16On floor 206 15

From thoes data one can determine that NT value for any surface levelby multiplying by the expected exposure time. 'Then with this figure andother data presented here, an estimation of the conditions necessary toobtain any degree of microbial killing can be madoe Of course, in actualpractice it is best to include a suitable safety factor.

B *METHODS OF MEASUREMENT

Because of the characteristics of the spectral output of the low-pres.sure mercury vapor UV lamp, the problem of measurement is greatly simpli-fied, Since over 95 per cent of the energy emitted from the lmps is inthe range of 2537A, a measuring device having a good sensitivity in thisregion without high selectivity of response is satisfactory f~r making ac-curate intensity measurements, In other words, practically all that is

* necessary is to compensate in some manner for the visible radiations andfor the UV radiations longer than about 9000A. Two general methods for themeasurement of energy in the region of 2587A are in common use,

62

The first method involves the use of a photocell or photronLo cell whichmeasuroes through quartz, the total UT radiation plus white lights Then bymeans of a suitable filterr suoh as a thin shoot of Pyx glass,0 radiationslonger than SOOOA can be measured and subtracted from the total, The "yrexglass transmits the energy in the 8000A region and longer but not the 2587Aeneyrg, whereas the quartz is transparent to both* The difference In thetwo regions is designated at 2537A radiation.

Such a motor doveloped by Taylor (280) consists of a light motor (phowtronio cell graduated in foot-candles) and a special attachment, The at-tachnunt employs a thin layer of fluorescent material between a sheet ofquarts and a sheet of glass. Zinc-silicate phosphor was selected as thefluorescent material because of its selective character when exposed to UVradiation of various wave lengths. The maximu sensitivity of sino-silioatephosphor occur, at 2587A (99 per cent), while radiations of 3000A and loangerproduce no fluorescent effect, In the operation of the meter a reading isfirst taken with the quarts and then with the glass side of the attachmentexposed to the UV source, The difference in the two readings is proportion-al to the intensity of the UV energy. Bach attachment is calibrated to givea factor by which the difference in the two roadings (in foot-candles) mustbe multiplied in order to obtain the intensity in microwatts per squarecentimeter, The sensitivity of the meter is such that one foot-candle onthoemeter indicates an intensity of about 40 miorowatte per square centi-motor i energy in the 2537A range, This motor is suitable only for mas-uring hbigh intensities received at a short distance from the UT• ouroe. Themeter is called the Luckiesh-Taylor Germicidal Attachennt and Is availablefrm General Electric Company

estlinghouse Electric Corp, 9manufactures a similar moter, designatedas thUs IN600 UV mter, for the purpose of measuring the intensity of UVlSamps This motor is a converted foot-oandli moter -with enclosed filterswhich is held directly against the UT aa to ýobtain the intensity. Cor-roeotion factors are supplied so that readings may be taken from all typesof UT lamps.

In Sweden, Laurell and Range (179) constructed a "filter difference"motor using a selenium barrier-layer cell with its lacquer surface removed.Activation of the cell is measured on a galvanometers A reading is-f1raI - ,made through an UT-transparent but light-absorbing UG-5 filter. A secondreading is mado using 0.20 per cent copper sulfate solution or a thin layerof cellulose seotate as an additional filter to rove bactericidal radia-tion, The difference in the two readings is a measure of the UV int•noity.

Other moters have been designed using phosphor-coated quarts and Pyroxglass cells connected to aicrommesters or galvanometers to measure the dif-ference in current generated by the two cells. The sensitivity depends uponthe selection of the phosphor cellos Calibrations we generally such thatone microampere is equal to an intensity of ton micrewatts per square centi- imoter of 2587A onergy. W

63

The second general method for measuring germicidal UV radiations in-volves the use of phototubes. '

Several types of vacuum phototubes for measuring UV intensities areavailable. These phototubes operate on the principle that a pure metal hasphotoelectr•c respanse to a definite band in the spectrums The cathodesurfaces are coated with a metal which is sensitive in the desired rangesThe phototubes are made of UY transmltting glass. Perhaps the first tubeof this tyle was devolo•oid by Koller (173) who used a cadmium-magnesiumalloy as the oathode in a Covex D bulb. The upper response of this bulbwas around 3400A.

The characteristics of four UV phototubes made by Westinghouse Corp.(310) arc shown in Table XV. Thi zirconium tube has its maximum responseat 2340A, the thorium phototube at 2550A, the tantalum tube at 2400A andthe platinum tube at 1849A, The lower limit of response (2O00A) is thesam for the first three and is deterained by the glass of the bulb, Thelimit of upper response is a function of the metal used. For measuringgermioidal radiation, the WLa-77T5 tantalum phototube is probably preferablebecause radiation longer than SDOOA will not sensitize the tube. Thismeans that the WL-775 tube is practically insensitive to ordinary sunlight,Figure 14, The manufacturer ri~oomends that phototubes be cleaned with analcohol soaked cotton pledget before use. Phototubes are presolarised atthe factory before being calibrated. Howeverexposure to high intensityradiation can cause further solarization. Phototubes must be used withelectrometers or integrating meters such as the Westinghouse SKX200,4

TAB•E XV. CHARACTZRISTICS OF WESTINGHOUSE UV PHOTOTU1E3S(Westinghouse Electric Corp. 310)

DESIGNATION WL-767 WL-773 WL-776 WL-789

Cathode surfaeo Zirconium Thorium Tantalum PlatinumMaximum response 2390A 2550A 2400A 1849AResponse range 2000A-3150A 2000A-3677A 2000A3OOOA 1700A-2100AUses Erythemal Erythemal Erythemal Ozone

Vitamin D Vitamin A BactericidalVi~iin DGeneral UV

64

IN.

x3

_ _00

1 .0 , 0 . o

stuodoei iDAI4DISH0

65

An UV meter using the WL-775 phototube was used in many of the studiesreported here# The meter was capable of accurately measuring intensitiesfrom one to 150 microwatts per square centimeter. The readings were ob-tained in milliamperes and then converted to microwatts per square centi-meter by applying the proper correction factors. This meter was standard.i.ised by the National Bureau of Standards before being used.

Another satisf'actory meter for measuring intensities of 2537A rangingfrom one to 500 miorowatts per square centimeter was designed and built forthe authors by the local engineering department. Inf'ormation for the basic

p7J design was obtained from Luckiesh (185). The moter utilizes an RCA type935 vacuum phototube employed in combination with a suitable amplificationsystem. The phototube has a low cutoff of approximately 2000A. A filteris used to zero the instrument, and an ordinary glass microscope slide isused to eliminate any reading due to luminous flux. The moeor is first ad-justed to sero with the glass slide covering the aperture. Consequently,when the microscope slide is removed, any reading on the motor will be dueto radiant energy in the region between 2000A to 2650A. This meter wasalso standardized by the National Bureau of Standards, and has proved valu.able in practical as well as experimental studies. The wiring diagran isshown in Figure 15.

A battery operated "Germicidal UV Intensity Mter" is manufactured byGeneral•kloctria Company, The portable motor utilizes a phototube and anEveready #467 battery. Intensity moasiuoments are expressed in milliwattsper squaro foot, which can be chaiged to microwatts per square centimeterby multiplying by 1,073. The metor has four sensitivity selectors and canmeasure intensities up to 100 milliwatts per square foot.

The Archer.,boed Company, Dearborn, Michigan, has developed an intensitymeter with a tantalum photocell for the measurement of low intensity germi-cidal radiation.

A motor for determining the per cent reflectance of UV radiation fromflat surfaces such as walls and ceilings has been made by General ElectricCompany (281), The meter utilizes a four-watt germicidal lamp as the radia-tion source.

An intepoating UV meter which records the energy by means of a mechani.cal counter and an audible click device is manufactured by WestinghouseElectric Corp, This meter is known as the SH-200 UV motor. The circuitdiagram of this motor is shown in Figure 16, Westinghouse Electric Corp.(311) has supplied the following descriptive information.

UV radiation on the sensitive surface of the phototube causes currentproportional to the intensity of the radiation to flow through the photo-tube and charge condenser C1 (Figure 16). When the voltage across the con-denser reaches a definite value, the condenser discharges across the triggerT and cathode K, electrodes in the relay tube WL-759. This action starts adischarge between cathode K and anode A which operates relay Ll in metercase by discharge of condenser C2#

66

0 -I __ _

Hill

RAI!

NL'N

I ,)

I'

I,

67

AOOZ

I 4I

68

The momentary closing of the relay Ll contacts operates the counter L2.As soon as condenser C2 discharged, the current through the relay tube Wbetween anode A and cathode X ceases to flow, and the circuit is in condi-tion to repeat the cycle of operations. Because of the lag in the operationof relay Ll and counter L2 the meter will not be accurate at intensitieswhich give counter clicks of more than 40 per minute. To insure accuracyof measurement and long life of the relay and counter, it is recommendedthat the phototube be placed at such a distance from the source being meas-ured that the counter on the meter will operate, at approximately 20 clicksper minute.

The characteristics of phototube ,and relay tube WL-759 varyt hence itis necessary to calibrate the SH-200 motor for each tube used. If a photo-tube or relay tube is changed, the meter should be returned to the factoryto be recalibrated with the new tube because this cannot be done conven-iently in the field.

An 54-200 meter registers one unit on the counter, or one click, for aspecific number of microwatt-seconds. Usually one click equals between 250to 300 microwatt-seconds and the meter maintains its calibration over longperiods of time if used carefully. The sensitivity of the phototube andthe c•pacity of the control condenser must be balonced to keep the numberof clicks per minute within the maximum of 40 per minute. More than 40clicks per minute may cause inaccurate readings and the counter to be tem-porarily inoperative.

The 53-200 meter can be calibrated for use with any of the UV phototubeslisted in Table XV. The WL-TT7 tantalum photocell is the photocell of choicefor use with artificial UV radiations. This meter has been found to be themost accurate of those discussed. In practice the meter is used periodicallyto standardize other meters routinely used.

C. *CALCULATING UV INTENSITIES

The method of calculating the total output of UV leaps has been suppliedby Nagy (218). The formula used iss

where V - watts of germicidal UV radiation (2587A),

X * a constant which is 9.92 for 30-inch lamps,

L an intensity measurement in 'iicrowatts per sq am at a perpendiculardistance from the lamp, which is at least five times the lengthof the lamp, and

D * that distance from the, lamp, in centimeters.

69$

For example, if the intensity, 300 centimeters from a 80,-centimeterlamp, is 10 idorowatts per square centimeters

V ,,92 x..10 x (9)2,. 86.28 x 1051o5 -105

V 8.82

For use in conjunction with the above formula, a curve such as shown inFigure 17 is conveniently used to determine average intensities at variousdistances from the source.

It is sometimes useful to calculate the UV intensity at the surface ofa lamp or at distances very close to the lamp surfaces First the total out.put must be determined* This figure may be obtained by the methodiesribedabove. Then the area of the emitting surface is calculated, remembering

- that the effective emitting length of the tube must be used rather than itsover-all length. If the area is divided into the total output, an estimateof the emission intensity per unit area of lamp surface is obtained. Forexample# the effective emitting area of 17-watt cold cathode iamps is ap-proximtesly 383 square centimeter and the total output is 5,2 watts, Thustdividing 5.2 by 383 yields 0,01361 watts per square centimeter or 13,610microwatts per square centimeter of bulb surface,

This technique can also be used to estimate intensities up to severzlinches from the lamp surfaces Thus one could calculate the intensity perunit area of a cylindrical type 10 centimeters in diameter into which a UVlamp had been centered by determining the area of the tube and dividing intothe total output,

A "factor system" is sometimes useful to estimate the approximate radia-tion intensity on surfaces at different distances from an UT lamp. The in-tensity of the lamp at one moter in microwatts per square centimeter ismultiplied by a factor for the distance selected. These factors are shownin Table XVI, They are applicable for hot and cold cathode lamps as wellas Slimline lamps. The intensity at one meter can be measured by an SH-600meter or it can be taken as the 100 hour output. Since it accounts forlamp doterir'tion and for the output at the prevailing temperature, theformer method is probably the more accurates The intensity factors inFigure 17 are applicable only for+,UV lamps with no reflectores These fac-tors provide an easy method for quickly calculating UV intensities withinfive per cent accuracy. For precise measurements, howeverp a reliablemeter should be used.

70

4 IN

(I- . - S'

In1

ii

- - -

P1-i III -IIII I I - HU

S_• I_8 . • •- -d.r1 -.~N:.N .- N j W

TABLE XVI. FACTOR FOR ESTIMATING GERMICIDAL INTISITINSAT VARIOUS DISTANCES 1lM AN UV LAMP,

DISTANCE FROM LAPN, inches INTENSITY FACTOR

2 83283 22,8

/?4 18666 12098 96

10 79412 6.4814 50,35S18 8.6

24 2,8836 102239.37 (1 motor) 1.00046 .J8160 .45260 ,256

100 .169120 4115

/

72

VII. OZONE

The role of osone in any adequate discussion of UT radiation mnt beconsidered because this gas is produced by some germicidal lamps. A reviewof a limited number, of publications available concerning ozone Lhdicatesthat controversial issues exist, It is appropriate, therefore, that thisohaster include a rather complete- discusslon of osone as it pertains to UT

Because the reports are numerous and conflcting, a certain amount ofselectivity has been necessary in the choice of reference material, Refer"once material and original studies which were supplied by Dr, Re Nagy (2190220,221) were Lnvaluable. A report and bibliography by Thorp (285,287) wasalso very helpful and. should be referred to for more complete LnformatLon.

A. THE CHMIISTIY AD PHYSICS OF OZONE

In 1782, Coavallo noted that "electrified air" exhibited a purifyringaction on decaying animal and vegetable matter* Over 50 years later, in1840 SchonbeLn showed that the compound was a form of oxygen and named Ltcone.~

Osone is a gaseous compound produced by the photochemical reaction of3 03 to 2 09, It is a powerful oxiLdLsLng agent and readily combines withmany substances. It is a deep blue liquid at .180 0 0, When osone oxLdLiesmuterials, oxgen is released. Oone is more soluble in water than is oxygen.

Som of the constants of pure osone have been listed by Hann and Manley(115).

Be?* -1120CNIP -2500Cd4 .188 1.057Vapor density at OOCgo 1gml 2,14Solubility in water at '04, 1ms/l 0.57

For concentrations of osone below 1.0 per cent, values should be ex-'pressed in term of ppa/wt, Table XVII (285) 'will be found valuable forcalculating and converting osone concentrations.

Osone can be used to hasten the drying of paints, oiles and varnishes,by rapid oxidatLon It is employed to sterilise and deordorise water,bleach organicu pLgents, and oxLdLe organic odors (221), for filteringlarge amounts of osone from breathing air, Van Atta (201) has recoindeda bed of absorbent carbon or possibly sLiLca-gel.

73

TABLE XVII. OZONE CONCENTRATION FACTORS

O°C - 760 mm1 liter of ozone weighs 2,144 p1 liter of oxygen weighs 1.429 gm1 liter of air weighs 1.293 gs

To convert:

Parts per million to per cent, divide by 10,000 (1)Parts per million by volume to parts per million by weights

in oxygen, multiply by l150 (2)in airf m*Xtiply by 194,6

NOTE: If over 10900 parts per million for accuracy convert firstto per cent and then use equations (8) or (9)s"

Milligrams per liter to parts per million by weight:in oxygen, multiply by 700 (4)in air, multi~ply by 773 (5)

NOTEs If over 10 mg/i for accuracy convert directly to per cent bymeans of equations (6) or (7).

Grams per liter (X) to weight per cent, use the following equAtions:

in oxygen (

in air,Wt per cent- (X) (10) (7)

Volume per cent (Y) to weight per. cent, use the following equations:

,in oxygen, irt per cent• *,(244 (6)142.9 1 rt.715) STr)

in air, Wt per cent - (Y) (M14@4) (0)

or(285551)).

Thorp (285)o

7'

The diffusion rate of osone into air is about 0.12 centimeter per second,The half-life of ozone at room temperatures and at relative humidities be- Wtween 54 and 88 per cent is approximately three minutes (78), Moisture andtemperature affect the rate of decomposition of ozone, The rate of decom-position is proportional to the square root of the absolute humidity* Atwofold increase in the decomposition rate would result from a relative in-crease from 20 to 90 per cent (at room tomperaturo). This is a fivefold in-creams in absolute humidity, At lower temperatures, moisture affects de-composition to a lesser degree because the absolute humidities are muchlower. Te decomposition rate oQfozono is increased by a rise in tempeo-.tureo When the temperature Is raiiiad from 70C to 8200, the equilibrium con-centration is reduced one-half (78), At a temperature of 1009C the decom-position of ooens would be neoly instantaneous (219),' The amount of ex-posed surface area also affects the rate of ozone decomposition, Ewell (78)states that the decomposition coefficient (K) of osone is approxmatoll:

0.207 .0.28

where t• - the osone half-life (three minutes)

A method for calculating the osone production of UT lamps is given on page69. Information on the physical properties have been conveniently compiledby Thorp (287)o

B. MEASUREMENT OF OZONE

For the past 97 years, the mot omeon reagent for ozone detection hasbeen potassium iodide solutionp although other reagents have been suggested(28).0

One simple test involves the use of strips of filter paper which havebeen dipped in a solution containing starch and potassium iodide (01),Upon exposure to osonom the paper will turn deep blues The test is notquantitative, and It is nonspecific in that other oxidising agents (oeg.chlorine) will produce the same reaction This crude method is sometimesused for estimating concentrations between 0.4 to 20 ppm per volume, It hasbeen used for checking osone concentrations In cold storage rooms,

In 1940, Thorp (283) reported soe improvements in the starch-Lodide.ethod of, ozonv awlysis # The comen method then in use involved passingosone containing air through a neutral solution of potassium Lodide, acidi-fyLng the solution and titrating the free iodine with a standard sodiumthiosulfate solution. Using 2 N potassium iodide solution in this maner,osone concentrations of 0.0018 milligram per cubic centimeter of solutioncould be detected, At this sensitivity, a mininum of 9.9 liters of air con-taining 0,1 ppm per weight osone had to be sampled for each cubic centimeterof potassium iodide test solution. Lowering the pH of the test solutionfailed to increase the sensitivity but introduced other errors (68).

75

Thorp (283) found that the use of a buffer solution increased the sen-sitivity of the potassium iodide solutions Five gram of aluminum chloridehexthydrate and one gram of imonium chloride made up to one liter con.stituted the stock buffer solution. Five cubic centimeters of the stockbuffer were added to each 100 cubic centimeters of potassium iodide testsolution before the test was run. The test soltuion was not acidified dur-ing the titration and, on storage, was stable for three hours in light and40 hours in the dark. Using this methodt Thorp increased the sensitivityto 0.00062 milligram of osone per cubic centimeter of potassiumJ iodide saou-tion. The titration was made with not greater than 0•01 N thiosulfait usinga 2-cubic centimeter microburet. Thorp recomnds that "an absorption tubecontaining chromic acid and a tube containing potassium permanganAte ...be provided before the potassium iodide absorption bottles" to insure thatonly pure osone reaches the test solution.

Nagy (219) investigated the accuracy of an ozone analysis method inwhich the potassium iodide was titrated (225) and another (272) employinga colorimetric analysis and found the results of some to be high by as muchas a factor of tens

In 1938, Paneth and Edgar (233) suggested a modified method of osoneanalysis with potassium iodide. This method was reported further in 1941(234) and in 1944 (105), and modified in 1946 by Crabtree (50j51).Crabtree's method has been used by Nagy at Westinghouse Electric Corp. whohas supplied a description of the method (219). Since this method appearsto be best for accurate determination of small quantities of osone,Crabtree's description is presented below.

To furnish sufficient iodine for measurement in the short time allot-ted, a large volume of air must be sampled. To insure absorption of theosone, the air to be measured is made to generate a fine spray of potassimiodide solution. In this way a large solution surface is furnished for thereaction. The apparatus is shown schematically in Figure 18.

In Figure 18, A, is a glass tube 0.375 inch La, diameter and app oxi-mately four inches long, terminating at B in a short length of caprllarytubing with a bore of one to two millimeters, Concentric within A is asmaller glass tube, C (Figure 18, a, shows this assembly on a largerscale), The end of C is first carefully heated in a blow-pipe flam untilthe bore is reduced in size so as to just admit a number 69 drill. Atthis thickened end two flats are ground off on a sheet of fine Aloxitepaper as at D in Figure 1,8 b. When in position in tube A, end D fitssnugly against the hole in capillary Pe The nozsle C may be sealed to Aat the upper end, but it is better to rely on the rubber connection at 3to hold the tubes in place, since once sealed in, C cannot be removed forcleaning in the event of,blockage.

'76

K4

L F

A-IL

- 4 (b)

F,'V

irpar. 26. Ouone-Absorbilng Device.

r1

A traps F, is two inches in diameter and tour inches long. G is annlargemesit in the exit tube 1,5 inches in diameter, containing glass wool

to trap sjTay passing 0. The trap F is connected to the side tube of A byrubber tubing or the trap may be permanently attached as shown in thefigures The rubber connector is more convenientp but the tubing used mustfirst be soaked for a long period in dilute iodine solution and thoroughlywashed, or iodine may be taken up from the reagent. H is a one-litertthree-necked Woulff's bottle in which A and F are secured by Pyrex groundjoints, A occupying the center opening with B protruding Just below theneck and tube J reaching to within 0.5 inch of the bottom of the botileoThe third neck serves for introducing and removing the reagent.

A is connected through rubber Joints and glass or plastic tube, K, torotometer, LO graduated from 0 to 1.0 cubic meters of air per hour, Theinlet to the rotometer is open to the atmosphere whose osone content is tobe determined. The outlet from G is connected to a vacuum line. After 75milliliters of reagent are introduced into H, the stopper is roplaced, andthe vacuum gradually applied. Almost the entire body of liquid will enterF9 furnishing a head of reagent at B, where the entering air resolves itinto a fine mist which fills the entire bottle. At the end of the run thevacuum is disconnected and the liquid transferred to the titration vessels"When runs longer than one hour are called fort It is necessary to add dis-tilled water at intervals to compensate lor evaporation. This is convon-iently done through the air intake. The amount of liberated iodine isdetermined by titration with &odium thiosulfate. Since the amount is sosmalp 0002 N to 04001 N solutions must be used, and since the end pointusing starch as indicator is uncertain, the electrometric method of Youlkand Dawden (86) is resorted to, in which use is made of the depolarisingeffect of iodine on a polarised electrode.

The titration vessel (Figure 19) is a 250-cubic centimeter wide-mouthedextraction flask having a hole in the side near the neck. A two-hole rub-ber stopper carries into the, flask two glass tubes into whioh a•e sealedthe two electrodes, in this 'ase stout platinum wires (0o. iiaeh thick) withcircular loops at the ends to increase the area exposed to tthe liquid.Circular loops are used because they ire roiled and not disvurbed by agita.tion of the liquid. A potential of 30 to 40 millivolts is applied to theelectrodes, This is readily obtained by connecting suitable resistors -e.|g, 30,O00 and 1,000 ohm - in series across 1,5-volt dry cell and pick-ing off the voltage across the resistor of lower values A Rubicon 8402 -H.H. with an Ayrton shunt galvanomete* is connected in series. A loessensitive type may also be sufficient.

fifteen grams of potassium iodide are dissolved in 75 milliliters ofbuffer solution (equal volu'mes of 0#026 N disodium hydrogen phosphate and0,025 N potassium dihydrogen phosphate). The solution is introduced intothe titration flasksl the electrodes are inserted and the liquid isswirled vigorously over them. Following an initial kick the galvanometerwill return to sero if no iodine is present because polarization of the

78

400

* electrodes will prevent passage of current. Presence of an oxidizingagent such as iodine removes the polarizing hydrogen from the cathode andcurrent flows* Addition of thiosulfate (through the hole in the side ofthe flask) until the iodine is removed restores the polarized state and re-turns the galvanometer deflection to zeros The reagent will usually re-quire the addition of two to five drops of 0e002 N thiosulfate to bringthis about*

After the ozone run, the iodide solution containing the iodine is placedin the titration vessel and thiosulfate is added until a barely perceptibleyellow remains, then the electrodes are inserted and thiosulfate is addeddrop by drop at intervals until no deflection is obtained, the liquid being.vigorously swirled meanwhile. The liquid is then returned through the trapto rinse the apparatus and the titration is completed, One cubic centimeterof 0,001 N thio0ulfate represents 0,0112 cubic centimeter of ozone at stand-ard temperature and pressures

A little difficulty may be encountered at first in identifying the endpoint to within one drop of thiosulfate solution at this low concentration#It will be found easier if the titration is made to a small residual do-feoction of the galvanometero

Neither the form nor dimensions of the apparatus described are critical.i'Duplicate apparatus reproduces results within - five per cent, which isgood enough at these low concentrations. Ith•as been found that reducingthe concentration of the potassium iodide solution below 20 per cent giveslow results. The system described passessbout 0.3 cubic meter of air perhour, but this can be controlled by ohanging the sixe of the air jetp CsWith a given jet there may be considerable leeway in the size of the capil-lary nozzle. The criterion is to obtain a reaction vessel filled with amist of reagent.

It is important to remember that potassium .iodide in solution is photo-chemically oxidized to iodine in the presence of light, even in neutral oralkaline solution, Therefore, titration must not be conducted in brightdaylight and, during the o.one test, the absorption apparatus must be eon-closed in a dark box.

The 0.002 N thiosulfate solution should be standardised at frequentintervals, becoause dilute solutions of thiosulfate lose strength throughoxidation. Since iodine is volatile, some will be vaporised and carriedaway in the exhausted air, therefore• a correction must be applied to theresult obtained, The per cent loss with time is shown in Figure 20,

Investigations by various workers (21,51,105,219) indicate that in themethod described very little interference due to other gases or oxidizing

* agents in the air is to be expected.

so

S100 - - - - a - -

S90 ,

so

i70

S60 "

SAMPLING TIME IN HOURS

Fipnr. 20. Correot•on Curve forOsone Estimntion.

00

SI

A simple ozone meter utilizing a rubber band and a calibrated scale hasbeen developed (87,52). When the rubber band is exposed to minute amountsof oaone, it loses its elasticity. The rate of lose of elasticity gives ameasure of the amounts of ozone in the air. An ozone concentration as lowas 0901 ppm by volume can be estimated by this method. This onone-rubberband method, however, requires careful standardization because:

(a) Ozone io not the only oxidizing gas which will attack rubber,

(b) the reaction depends upon the formulation of the rubber, and

(o) the reaction to oaone is a function of the stress placed onthe rubber band.

Other methods of analysis of osone which have been studied from time totine are:

(a) Reaction of oaone with aldehydes tfllowed by oxidation to acids,

(b) photometric methods depending on the action of ozone to createor destroy fluorescence,

(a) reaction of ozone with-potassium pemanganate sodium nttritoeand other chemicalst and

(d) optioal determination of-osone with infrared or ultravioletradiation.

"Methods for ozone determination up to the Vea 194 are convenientlyoutlined in the bibliography by Thorp (3S6).

C, OZONE IN THE ATMOSPHERE

The presence of ozone In the atmosphere was noted at least 175 yearsago. It was identified as an oxygen compound and named osone by Schonbeinin 1840. Short-wave UV radiation in the stratosphere is responsible# by,

/,photochemical action, for the formation of atmospheric alone (49)0 The-/-reaction is one of equilibrium because UV also catalyses the breakdown of

aoone to oxGen (3 02 O a 2 08), The reaction occurs at a height greaterthan 30 kilometers and requires radiation shorter than 2000A. The finalatmospheric ozone concentration depends not only upon the equilibrium retaction, but also on the presence of oxidisable matter suspended in the airand contact with surfaces to cause catalytic decomposition. The totalamount of ozone in the atmosphere is said to be equivalent to a l yer about0.21 centimeter thick at STP. Figure 21, from Crabtree and Kemp (51) gives

* the ozone variation at different latitudes. Since radiation of below wavelength 2000A is not found in the lower atosphere, ozone is produced athigh altitudes only, and is brought into the habitable zone by diffusionand convection.

82

2.50

2.00

co~• I,50 I I"• ..

28,00 ' I I I I I' I I I I IjI

-3.00

J 2.50 i 1

JAN. FEB. MAR.APR.MAY JUN. JUL AUG. SIER OCT NOV. DEC.

Figure 21. Seasonal Variation of Total Osone in Atmosphere at 6}Different Latitudes. Crabtree and Kemp (51)

68

The amount of ozone present in the air at the surface of the earth isknown to be quite variablet although precise and accurate information seento be lacking. Accurate measurements have necessarily depended upon devel-opment of adequate methods for sampling ozone (Measurement of Oonoe page74,).

It has boon stated that ozone is not present in the air of large in-dustrial cities, Thorp (285) states that this is not true and that appre-ciable amounts are present. Table XVIII shows average ozone concentrationsfound in several cities. Figure 22p reproduced from Crabtree and Kemp,(51)p shows the ozone concentrations at Murray ,l9 Now Jorsey, over aperiod of one year. The day-by-day irregularity caused by weather condi-tions is significant, Huntington (157) points out that the normal ozoneconcentration in some parts of the world frequently exceeds one ppm perweight. In discussing atmospheric ozone, Crabtroe andXKemp (51) call at-tention to the apparent influence of meteorological conditions. High osonevalues are found on windy days; low o'one is found on calm days when thewinds are predominantly from a westerly direction (in Now Jersey). Windsfrom the East give low ozone concentrations. Highest ozone values are ob-tained in late, summer, There is no difference between the ozone content ofthe air during'the day as compared with nightp weather conditions being thesame.

TABLE XVIII. AVERAGE ATMOSPHERIC OZONE CONCENTRATIONS

LOCATION AVERAGE OZONE CONCENTRATION RXIN CE

Murray Hilly N, J. 0.05 ppm/vt Crabtree & Kemp"(51) 1946

Chicago, Illinois 0.01 to 0.15 pp•.wt Thorp (65), 1950Los Angeles, Calif. 0003 to 035 ppi/wt Bartell and Tomple

(21) 1952London, England 0.02 to 0006 ppswt Stanford Research

Inst. (275) 1954Collegoe Alaska 0.059 ppr/wtDetroit? Mich. 0*026 ppm/wtLos Angeles, Calif. 0,2 to 0,4 PN/wt

,(during smog)

14DISM Aq Uog111,01 4Od UPu

0

*wnloA Aq JIV A UOHI I I 1M JOd Sl~

Reports by Stanford Research Institute (275) and, others in connectionwith the smog problem in Los Angeles county give further disoussion of at-mospheric ozone,

Summarizsitig it may be stated that ozone is present in the air near thesurface of the earth, sometimes in concentrations as high as 1.0 ppm perweight, but more often in concentrations from 0.01 to 0.35 ppm per weightor approximately 0.05 ppm per weight,

D, TOXIC LIMITS OF OZONE

Unfortunately, literature dealing with the toxic limits of ozone is ex-tremely inconsistent and rather confusing. However, a clearer understandingof the situation has been made possible in recent years as some of thelimitations of earlier work have been explained, The oft quoted introduc-tory remarks of Thorp (285) are appropriate for this discussion.

"Webster defines the word 'toxicity' as 'the degree of poisonnessO,To state the toxicity of a substanco however, does not necessarily implythat the substance is a poison inasmuch as all substances are toxic to thehuman body if taken in excess of normal human tolerance. For eaumple,ordinary table salt is beneficial in small quantities, but an excess, overa long period of time, cainproduce very harmful results. Arsenic, normallyclassed as a poison, may also be cited as another example insmuch as it isoften given in small amounts for the sake of certain beneficial reactions.The toxicity of a substance, therefore, msot be described with respect tothe maximum allowable 'dosage' per unit time. If the human body is capableof eliminating small quantities of a substance within a comparatively shortperiod of time, small dosages of the substance may be tolerated continuallyeven though it may normally be considered a poison. If, however, the bodyhas difficulty in eliminating the substance, toxic effects may result fromlong exposure to what is normally considered a non-toxic concentrationsOzone falls in the former class of compou!f4•-r whereas carbon monoxide maybe classed as an example of the latter type substances"

"Gases may also be classed as irritants or non-irritants, Irritantgases are so called because their first reaction is generally on the skin,mucous membranep or titsues of the nose and throat; whereas non-irritantgas usually requires absorption in the lungs before toxic results appearsIn general, it may be stated that the non-irritant lases are more dangerousbecause the toxic limit may be exceeded before a physical result on thehuman body is noticeable@ Boron trichloride, chlorine, dimethyl other,ethylaminen ethylene oxide, and ozone may be given as examples of variousdegrees of irritant gases.; and carbon monoxide and methyl chloride as ex-amples of non-irritant gases#"

SI

86

In order to demonstrate the many different osone concentrations whichhave been reported to have or not to have physiological effects on humansor animale, a few of the many references available have been used to com.plete Table XIX. Each authors' designation -as to effect and ozone conoen-tration is listed*

TABLE XIX. PHYSIOLOGICAL EFFECTS OF OZONE

OZONECONCDETRTION EFFECT REPORTD AUTHORS

1 pPm/vol Nontoxic to school children aue (22) 1918I to 10 ppm Death of dogs and rabbits Jordon at &l (165) 1918

15 to 20 ppm Death of test animals, 2-8 Schneockinben 8g (265) 1916hours

1.0 ppm MAC Hill 6 Aeborly (146) 1921065 ppm MAC () Henderson & Haggard (187)

1986001 pml/.vol Detect by smell Witheridge & YTalou (320)_

19390.01 ppmvol Irritating to nose and throat.004 ppm/vol AC I

50 ppm Nontoxic Hill (145) 19421 ppm no Dolla Valle (56) 19451.0 MAC Stlvrman (209) 1947

SO ppm/vt Nontoxic in short periods Thorp (•7) 195020 pmt MAC The 1171 19504 ipm/vt Nontoxic over long periods Thor" So 19501.o ppm MAC keMI $62) 19510.1 pp MAC' Van Atsa (391) 19510.1 pp no Amerioan Medioal Associ.

ation (5) 1956

MAC a Maximum, allowable concentrations

One of the most common methods for the generation of onone for medicalor experimental purposes is the use of osonluers. Thoee machines use a"brush" discharge between high potential electrodes separated by air or-oxygen# The output of the machine is influenced by the density of the our-rent, the source of oxgen (air or pure oygen) and the relative humidity(for air only)# Air is generally used as the source of oxygen for air con. aditioning and general sanitation or for odor control purposes, Cylinders W

of oxygen are usually employed by medical investigatore. Osonisers producepure ozone only when sure oxygen is utilized (221). Conditions at highvoltage, high humidityt and the use of air may result in the production ofoxides of nitrogen, even in excess of the amount of ozone produced (264).The difference between the smell of pure ozone and ozone contaminated withoxides of nitrogen was described as the difference between clover or "now-mown hay" and chlorine or ammonia (286).

As early as 1913, Von Kupffer (293) and Cnaplewski (54) mentioned theharmful effects of nitrogen oxides in ozone. However, supporting evidencewas lacking until 1941 when Thorp (284) demonstrated how the toxicity wasinfluenced by the ozone source and suggested that mixtures of nitrogenoxides and ozone were more toxic than ozone alone. Hill (145) in 1942 con-firmed this supposition by using pure ozone and repeating experiments donein 1921 (146) with mixtures of oaone and oxide of nitrogen mixtures.

Thorp (2865) reviewed the situation in 1950, evaluating the toxic limitsgiven by various investigators on the basis of the purity of the ozone used,and came to the following conclusLonst

(a) "... ow. one containing rAtrojen oxides is toxic and exposureto concentrations of over 145 parts per million by weight for long periodsof time may be considered definitely detrimental to humans.,"

(b) "Up to four parts per million (of pure ozone) may be classifiedas the 'non-symptomatLc region', i.e., a worker exposed to concentrationsin this range experiences no physical effects except odor. Several defi-nite physiological changes, however, occur in this region; namelyj a de-creased EXR and lowered pulse rates"

(c) "Ozone concentrations as high as 50 ppawt for short periods oftime have no irritating physical effect although there occurs a symptomtermed, substernal pressures"

(d) •T•enty pWwt of ozone in air is non-toxic,"

In relprd to the poisonous nature of oCone, Hill (145) statest "pureozone is •ot poisonous in any sense of the word as it breaks down in con-tact with the mucous membranes and only oxygen remains. for this reason,there are no cumulative effects and ozone may be breathed for long periodsof time without harm provided, of course, that the ildiate irritationsof strong concentrations is avoided."

Concentrations of ozone believed to be in•Jurious to man were listed bySollmsn (273) and Elford and Van do Ende (78) as follow:o

,1

CONCENTRATION OURE TNE EWICT

0004 long tin safe0.05 long tiN irritation of throat

0o8-0,5 long tin respiratory irritation1.0 affect@ 02 uee and C02

output10 U15 minutes sore throat.5-10 short time fatigue, drowsiness5-10 long time pulmonary edema,

pneumonia

At the Armour Research Foundation the following LD5O'"i were determinedfor anmauls during an exposure time of three houris

Nice and rate 20 ppn olsonoRabbits and cats 35 ppn OzoneGuinea pigl 50 ppm ozlone

In the past, it was coon practice to express the maxim allowableconoentration for omone as one p er olme (1.66 ppmwt) in air, althoughsonm felt this mount was too high 291). In spite of the lack of agreementamong workers in this field it sppears certain that ouonep free from nitro-gon oxidest ti not as toxic as once supposed, hell (62) quoted severalorganimations who accepted this figure. The 1958 meeting of the AmericanConference of Government Industrial Hygienist set the threshold limit forozone at 0,1 .ppm per volime or 0.2 milligram per oubic meter-of air (5)0

Millor and Ehrlich (211) recently studied the susceptibility of nice andhamsters to respiratory infection with leboiella gnMonia following ex-posure of the aninmls to one to four ppm ozone for various periods of time,Under the conditions of their tests pro-omone treatment, in every Instance,lowered the respiratory LD50 doese

Recently, a numbeo of animal studLoe have been made on the toxicity ofozone and on methods of therapWo While those will not be reviewd In de.tail met substantiate the reasonsableness of the present allowable oonoon.tration of 0.1 ppme

IEL PRODUCTION OF OZONE BY UV LAMPS

Som low pressure, mercury vapor, UV lamps produce a measurable amountof oxons, The type of glass used to make the tube determines the amount ofUV radiation below 2000A which will be emitted and consequently the amountof ozone produced. UV lamps are usually designated as high, or negligibleozone producers@ Sources of nfomtion giving precise amounts of ozonsproduced by UV lamps appear to be limited,

83

S•e • t of olone • oed • gY l•e deo•ue| atter tho f£ret ZOO

bemire of uee, after the |Z&ee hu been eeuonod. Yt hu boon ehowl• (310)thst if the oonoents'ltLon end deoompoeit£on ooefY£oLente (pep ?4) inknmmj the amount of ouo110 loner&ted by t lamp elm be ol•oulsted, Niq•|4vie the •'•rl| exiuIpl.o I!,,,,, Lf we &IIMliO the omono oonoont•tLon LjO.Oe pipe/V01 tn- s room 10 x 10 x 10 ft or 1000 eub£o foot p the amount ofomono would be qoooO•3 •ram per oubto meter& or s tots1 of' 0.00013 x 38038tor 0000888 |rm/looO f't , |4ultip1•vir4 thLe by the deoolpuj:Lt4on ooef'f£.©Lent we hsvet

0033 x 0000338--O.OOO3?? p/mLn

- 000636 Ipe./hr

'TO ,osloulste the ppg•volwleI Lf' we hsvo the •i 1141' howl

ppe/vol - o3 tn ,pUn, x 1,ooo . +.3 x0o33 x O0 xH8

The iversle osone output eP eevorsl t•'pll of' UY lellpl hll 541111 deter-a•Lned ue't11 the method of' Crsbtree trod Kemp (B1) with the •f'ollowtnl re-JUltll

Ift,-794 .,. L UV LIUlD,

o0ol p•.•. So.1 mw, v t/a.so • .OOO plpm/'vo3J'3SO fto

•.,703 -. - so uv+•Lame ,Icold o&,u..to..)+003 ip•o.,3 p,/,,/looo {t3 o.33:o.o,

m-tom- L - 3o, cv, ,.am+ (cold o,&md.,)+•' 0.033 im/hr 8

o01 •/•t/• • 3o.oe pt=/vol/3oo

w,<,?e3... 1o, uvl s•0033 p/• . 3o04? ppa/wt/looo f'• oaeo.1 ppe/vt/4?oo .a : •ppe•/•

' 0,060

g0

The above determinations were made in a 17•0-oubic foot room, with eachlamp hung in the geometric center of the room without any enclosing fixture,Placing the leaps in fixtures will reduce the oaone by a factor of one-halfto one-tenth. Proximity of a leap to surfaces such as coilin1g duot walls,otc., will'reduoe the ozone output further. For these reasons, the abovedata cannot substitute for actual practical determinations if the amount ofozone present at a particular installation is desired.

F. G14IICIDAL ACTIVITY OF OZONE

1. Surface and Air-Porne Microorganism

A review has been made of some of the articles and abstracts avail..able dealing with the gormicidl activity of oeon.. There appears to beconsiderable disagreement among investigators concerning concentrations andexposure times nocessary. This lack of agreement is probably the result ofthe uset in many cases 1, of impure ozone preparations, faulty axon* goner-torst or inadequate methods of measurement' These factors are discussed

elsewhere. In this review an attempt has been made to select material wherethe action of specific- mounts of osone are given.

The oaon* concentration germicidal for Achromobacter was found tobe about 300 ppm per vlume at 200C and 10 to 100 ppm per volume at OOC (111).iEwell (82), however, observed that at a given axon* concentration about thesai-,lethal effect occurred at 40C as at 20C0. Haines (112) indicated thatPosudamonas and Achroiobacter were more resistant to oson. then Staphylococci,Proteus, Bacillus sibtilis or Bacillus mosentericusl Bacteria suspended inwater (1 xlog lI per )were sterill•- in Two hours by 100 ppm pervolum omone. Haines (111) found that about equal amounts of ozone were re.quired to inhibit the growth of molds and bacteria growing on agar plates.Between 10 and 1000 ppm per volume were required depending upon tomperature,humidity, modium, and the age of the culture. The storage of eggs in threeppm per volume ouone in air markedly inhibited mold growth and caused no"off-flavors." In an atmosphere of high humidity, Dwell (82) reported thatan osone concontration' of 0.6 ppm per volume in the air within egg caseswould prevent the growth of molds on eggs, Hold growth on most was preve tedby, maintaining about 1.5 ppL ozone in a storage-room atmosphere@

According to studies by Giese and Christensen (101), a concentrationof 0004 ppm ozone is adequate to inactivate aerosols of ltreptoooouissalivarious and St ococcus albus, although concentratoion up -to 3 ppwererequired to X11 BROL1 1 ! W i-souSUM on a surfsoo or in blood serum.Hoiling and Soupin (13$• -stred --tt -fn l spores were more susceptiblethan bacteria to the lethal action of ozone. Spores of four mold speoies,however, were found by Lea (182) to be capable of ermination after exposureto 400 ppm of oIone- or 10 to 15 hours, but were killed in 20 hours.

91

Oenson, at concentrations as low as 0,025 ppm, has been shown to becapable of killing organisms at a relative humidity of 60 to 90 per cent(78)o Watson (298) mentioned a reduction of fungus spores and apple-rotdisease by adding Caone to the air of an apple storage rocm# The growthof organisms on meat was found by lallmann and Churchill (200) to be re-tarded by 0.1 ppm ozone* The control of mold upon cheddar cheese duringripening with 1.0 ppm osone has been mentioned.

Experiments on the application of osone for the sterilisation ofspun glass f•lter media have been conducted at Amour Research Foundation(15)a When sections of 50 MO spun glass were inoculated with up to 300spores of Bacillus subtilis var, nite per squareLcentimeter aid exposedstatically or dynamically to 0.02-II,5 per cent ozonet sterilization ofthe media did not occur at roam temperature after exposures for as long assix hours, It was concluded that ozone did not have the penetrating prop-erties for treatment ofthis type of filter media.

A review by Weaver, in 1951 (299), cited references which indicatedthat bacteria were difficult to destroy with ozone, even at high concentra-tions. Nagy (221) has criticised the inadequate techniques used by severalworkers cited in Weaver's references (165,264), Original experiments byNagy gave the following results!

(a) The presence of osone in a concentration of five ppm, in a• duct of an air conditioning system, showed no bactericidal action because

of the low humidity and short exposure time.

(b) Oxone concentrations from 0.05 to 04 ppm per weight inrefrigerators showed germicidal action against Boo arichia call and Peui.cilli~u ilatioum on agar plates when exposure timefomi--14 54 hours

(c) At 200C and with an exposure time of 20 to 33 hours, from90 to 100 per cent of the inoculum of - Soli on open Petri dishes wereinactivated by 0.1 ppm per weight oone.s

There is no doubt that abundant moisture is essential for the bac-tericidal reaction of osonCe Also, there can be no doubt that ozone caninactivate microorganisms if suffidient concentrations are used for thecorrect exposure times. Unless these special conditions are establishod,traces of ozone probably exert very little germicidal power. Omone pro-duced by low pressure germicidal UV lamps designated as low oxone producing,probably will show rno detectable germicidal effects because of the lowpenetration and short half-life of olone#

Wheeler (316) installed ceiling germicidal lamps in Naval barracks,and reported that very little ozone could be detected after the first 50' hours of use, Using a 30Owatt germicidal lamp in a 2500-cubic foot room

0 American Air Filter Co., Louisville Kentucky.

92

Luckiesh 485), in a sie,ýes of studies on osone productiont found that ,theequilibrium concentration of oaone is less than 0.1 ppm if there is theslightest dogree of ventilation. Koller (174) stated that the concontra-tions of omene produced by germicidal lamps do not kill dry, air-borneorganismso

In biological installations, care should be taken that only low-oaone producing UTV lamps are used.

2. Microorganisms Suspended in Liquid

Investigations of the germicidal action of osone gas go back as faras 1892 when Ohlmullor (228) demonstrated the inactivation by this gas ofthe etiological agents of typhoid fever, cholera, and anthrax# Ohlmullorrealiled that organic material in water had an ozone demand to be satisfiedbefore inactivvation of organism could proceed. In 18695 Van Emeng" (292)studied the rapid inactivation of several types of bacterial spores andSo coli is well as inactivation of a dilution of tetanus toxin by oone.N0 a-so noted improvements in the color, taste, and odor of ozoniled water.In 1899 Calmetto et al (41) studied the killing of microbes in water by theaction of osone of me S -city of Lille, France. A variety of other referencesare available describing procedures for treating municipal water suppliesin Francs and other European countries with asone.

In this country Smith and Bodkin (270) evaluated the influence ofpH on the germicidal action of chlorine and oxone, With residual ozonee ata concentration of 0.13 to .o2 ppm, a rise in pL necessitated a slightlyincreased exposure time to obtain sterility. Kessel at al (170) claimedthat oone was many times more affective than chlorinleM lenseinactivatingpoliomyelitis virus, Ohers hav" made similar studies ($49)o* In 1944Kessel et al (171) found that 0.3 ppm oone residual in Water was faster Inits ge•rUcl'l action than 0,5 to 1.0 ppm chlorine.

In liquids, osone has been found to be an effective Vermicdalagent if used under controlled conditions,, Water in the municipal systemsof London, Berlin and Paris has been treated with osone for many years,and, in this country? Hobart, Indianal Whiting, Indianal and Philadelphia,Pennsylvania use so0ng-treated water (287) , It has been stated that thereare a total of 186 municipal water plants in which ozone is employed, sertv-Ing approximately 8,000,000 peopleo Osone is usually added to water by anair Jet containing 2A8 to 5 grams of osone per cubic motor of water. Con-tact'time is usually 3 to 5 minutes, Pretreatment of the water is neces-sary. Although smine does not introduce an odor or taste problem in potablewater systems and is said to be more effective than chlorine against certainmiorooranisms, it lacks the residual effect typical in chlorinated waters,Although the effect of residual chlorine in case of pollution of a watersystem has been questioned from time to time, there has been no indicationof wholesale acceptance of alone as the preferred water sterilising agent.

.8

A recent study by Miller st al (212) showed that raw sewage highlycontaminated with infectious micrýornismes including spores, botulinumtoxin, and influenza virus could be effectively sterilized with ozoneoConcentrations between 100 and 200 ppm were used, A total of 90 minutesexpoaure was required to obtain sterility, but a 99.9 per cent reductionwas effected in five minutes. Most of the ozono could be recovered,

In 1954 Dickerman et a (64) showed that exposure of spore formingorganisms in water to 1#J 'pm of ozone caused comple'4 inactivation of thespores in fire minutes, The initial inoculum was 70p000 organisms per mil-liliter of waier. Raw stream water with low organic content was sterilizedin five minutes with two ppm of ozons

In Switzerland, in a modern soft drink factoryp bottles are steri-lizea by introducing air containing 30 milligrams per liter of ozone for apcwiod of 15 to 20 seconds (289).

It is clear that ozone is an excellent sterilizing agent for mnyliquids, including drinking water, swiming pool water, and sewage, Likeany other disinfectantp its use requires a thorough understanding of itslimitations and the proper methods of application. Although it has neverbeen done on a practical ,cale, it is probable that ozone could be used tosterilize infectious effluents from infectious disease labortoroies andhospitals.

3. Medical Uses

Many applications of ozone have been tried in medical and dentalresearchp including the injection of ozone or ozoe mixtures into the bloodstreaonfistulast and muscles, In addition, various devices have been ds-vised for exposing wounds and skin to osonos!gso Such references are in-cluded irn the bibliography by Thorp (267).

G. DEODORIZING EFFECTS OF OZONE

A substantial amount of, experimentation has been conducted to def4nothe doodorising effects of ozone gas# It is well established that ozoneoxidisoi many odor-producing compounds to produce loss odoriferous sub-stances. In some cases, however, ozone may produce a more obnoxious cos-pound. For example, the reaction of ozone with formaldehyde producesformic acid which is not only more odoriferous but also more toxic (267).In somq situations ozone may act only as a msking agent but, in general,it is believed to be an excellent deodorizing agent for many substances.Thorp (287) suggests that when ozone acts as a true deodorizer it shoulddemonstrate this property at nontoxic concentrations.

94

Franklin (•7) and Powell (242) gave results of tests on the oxidation ofvarious food, tobacco, and putrefactive odors. Host gases emanating fromthese products were oxidised, Olseon and Ulrioh (230) reported on the oxida-tion of ammonia and hydrogen sulfide, pointing out that oxidation of odorsis a chemical reaction and is quantitative in the sense that a definite a-mount of osone is necessary to oxidise a definite quantity of oxidisablematerial. This point was also discussed by MoCord and Witheridge (204),Kupper (177) reported on the oxidation of tobacco smoke and odors in hospi-tals and public buildingst using as low as 0,05 ppm osone. Hill (145) madetests wieh,8igarotto and cigar smoke as well as hydrogen sulfidoperare•uns,urine, butyric, and acrylic acid and found that all of these odor'si-can beoxidised by low ozone concentrations if suffioient tLme is allowed.

Cuaplowski (55) stated that som odors are oxidised while others areweakened' Foldner (88) showed that ozone eliminated odors in hospitalroom containing patients being treated for gastroanteritis. Bordas (83)found that odors formed as a result of fermentation of organic matter weredestroyed by omones Doyoer (35) reported that the underground railroad tun.nel in Paris was successfully deodorised by ozone# Other observations havebeen made on the removal of odors by ozone in air circulating systems oe..,the reports of Anderegg (8), Hallett (114) Franklin (87), Woodridge (824),and Yosmoer (295). Witheridge and Yaglou 1320) found that as low as 0.013ppm ozone was effective in reducing odorse

Ozone has been used in cold storage room to destroy odors from meats,fruit, vegetables, and putrefactiono The odors from fruit, probably ethyl-one, are destroyed as shown by the retardation of ripening. Dwell. (7,7J,60,81) conducted experiments on the use of ozone in cold storage room andsmaurized. the work of others on the subjeots Hartman (131) also has suc-oessfully used ozone for the oxidation of fruit and vegetable odomp in coldstorage ocmpartments.

There are some opinions that olone only acts as a masking agent, As an,example, Erlansden and Schwartz (76) are cited as having found olone to haveno effect on tobacco ruomke, indolo, skatole, anmonia, hydrogen sulfide, andother odoriferous compounds except as a masking agent, Sawyer st al (264)also state that osone masks odors.

Nagy (220) conducted a series of laboratory tests with ozone at a con-centration of approximately 0C1 ppm per weight. Aorolein, an ,aldohydehaving the odor of burning fat was converted, to a nonodot'iferous compoundin 10 to 16 hours., Allyl sufLde, methyl thiocyanate, indole, and skatolewere also rendered nonodoriferous by exposure to ozonse However, normalpropyl disulfide, a compound which does not contain double bonds and there-fore is not convertkd'to an osonide, was not deodorised by exposure toozone* It was concluded that compounds with' unsaturated bonds were themost readily oxidioze and that the amount of osone inst be in stoichiometricproportions.

95

VIII, FACTORS AFFECTING THE BIOLOGICAL ACTION OF UV RADIATION

In a report such as this on the practical use of germicidal radiationsin infectiqos disease laboratories, it is not necessary to present detaileddiscussions of the various related factors which have been the subject ofvast numbers of laboratory experiments. These studies, both past and pros-ent, have been adequately summarized (149) and are, in general, less perti-nent to the problem of practical uses for UV radiation than the basic studieson genetics, cytochemistry, ete Therefore, in -this chapter, only a limiteddiscussion of some, basic factors affecting the action of germic*idal UV radi-ation will be discussed. The reader is urged to consult other works formore complete discussionso

A, TEIPEATURE

Gates (94) determined the temperature coefficient of the bactericidalreaction of UV radiation at 2540A, Using temperatures of 860, 210, and 5°0and exposing inoculated agar plates, he plotted the progressive rate ofkilling and also calculated the average temperature coefficient of the bac-tericidil reaction for 100 per cent inactivation of Stagh !ooeus aureus,The temperature coefficient was 1.06. from this, he-iniluild-liit"tme-re-action is physical (or purely photochemical) rather than chemicals .

According to Luckiseh (1865) the tep erataur of the air does not appearto affect the resistivity of microorganisme for the range of temperaturecommonly encountered in interiors and in ventilation systems..

Be pH

A series of parallel experiments ,(94) indicated that slight changes inthe susceptibility of it aureus to UY radiation occurred when the pH of thesuspending medium was varl-W-UWom 4.5 to 7.5. At pH .00 and 10.0 there wasan increase ,in the susceptibility of the test organies. These results waeshown in Figure 23,

Other workers have shown that when acid media were used, the bactericidalaction was greatly accelerated. Bacteria in medium of pH 6 to 8 were aboutten times as resistant as when suspended in modim of pH 2.O.

C, AGE OF CULTURE

Gates (94), working with S, aureus, tested the differences in suscepti-bility of 4-, 28-, and 52-hour oTd--ures to UV radiation and found thatresistance imereases with the age of the cultureo

96

"2, 66p

10 .... if-4-,

200 250 3C0

ENERGY IN ERGS PER MM1

A pHi9.0S pH 10.0C pH! 4.5, 6.0, & 7.5 (averoged)

Figure 28, *Per Cent Bacteria lKillled at various Media Hydrogen IonConcentrations. Gates (94)

97

the susceptibility of organism in different growth phases has been re-ported by other workers (60,321,325). It is gener4ly ared that strainsof IsoheriohiC ,li are more resistant to UV radiation when in the station-

Studies by Giese et al (102) with Saoheromos cerviseas show thisorganism to be more r'=i-s=ant to UV radiltion when in •he ogariothoic phaseof growth than when just past the logarithmic phase. Nitrogen starvationincreased yeast susceptibility to 2537A radiation* Nitrogen starved cellsbecam more resistant to radiation inactivation when organic but not wheninorganic nitrogen was supplied* As in other testsl the presence or ab-sence of oxygen made little difference in ultravioleotsensitivity,

The most recent studies of Romig and Wyse (257) have helped to explatinthe differences which have been reported in the susceptibility to UV radia.tion between aerobic vegetative bacilli and their spores. By using the "endotrophio sporulation technique of Rarlwick and Foster (117)p these in-vestigalors showed that radiation resistance develops before the appearanceof the mature spores and, in fact, is mnifest before the development ofheat resistanceo In slowly sporulating cultures of Bacillus cereu theprespore stage (forespore) exhibited increased reis•ance-to PUeMPLontreat•ent and becam less susceptible to photoreactivation, whereas, resist-ance to heat treatment at 650C for 15 minutes was not muaimal until twohours later when mature spores predominatedb Thus, the exact state of thespores may determineL their relative resistance to UT irradiation. Thistheory is further supported by studies which have shown that when sporesare placed in an environment suitable for gemination, sensitivity to UVdestruction rapidly returns (208,277).

D, IRLATIVE HUMIDITY

1. Literature Review

Luckiesh (1865) and other workers (17t8,05,906) have published ef-faots of relative humidity on the germicidal effectiveness of UT radiation,Luckiesh concludes that the resistivity ofE , coli in air at a relativehumidity of 75 q.r cent is twice that for arreM-•ve humidity of 35 percents Wells (306) and Whisler (318) claim, that the bactericidal effective-ness of UV radiation oq air-borne Z. ooli decreases greatly as relativehumidities rise above 60 per cent," 11 results are similar to those ofGatet (94) shown in Figure 24.

The view that relative humidity affects the bactericidal reactionis not supported by other authors (245,46,#247). Nagy (220) states that theenergy necessary to inactivate a microorganism is the same reg•rdless of themoisture conditions and points out the followingi

98

L4 1500

1,000 I I

o0 20 30 40 50 60 70 60 90REL A T/ VE HUMID/TrK %

Figmure 24. Effect of Relative Humidity on the Bactericidal Actionof UY Radiation. Gatee (94)

(a) The sampling devices used by Whislor so Wells were sol•sative and did not give a true representation of the bacterial populations

The probe used by these authors sampled only the smallpartiale# at high air velocities while the contrifuge removed only thelargest particles collected by the probe, Relative humidity would affectthe ratio of the partiole suaes and thus the proportion of organismseapled. At high humidity and low air velocity a large number of organismswould be collected by this method, indicating poor UV ofeficiony. At highair velocity and low humidity the organisms would not be colloetodwhiohwas interpreted as high UT efficionoy. ) "

When these factors were oontrolled, the' amount of energyrequired to destroy an organism in air at low humdity was the Same as fora similar organism on a Petri plate.

(b) The greater apparent efficiency of UV radiaton In air ductscan be correlated with the Reynolds number which is a measure of air turbu-lence. Particles in turbulent air receive more energy than similar parti-

leso in liner air flow.

A recent study by Beebe and Pi•ech (24) on the offect ofsimualted sunlight radiation on air-borme Petur miti. and N W 1t.• an showed a radiation protection eW0.1t1ah1jW-Wmidif9O Tafuthos igeUted that the protective effect associated with the moistturecontent of the air night be explained b* the presence of dissolved solLdsoin the moisture surrounding the cell. This moisture lyer would not bemore than one mLcron in thickness. Howeverl many other factors such " airtemperaturet visible light, infrared radiation Nad particle temperature Mabe involved.

There appears adequate justification for considering therelative humidity in pnatical. UT applicationes Whislor (318) points outthat the effect may be physical rather than bo l"gIa;l in nature Atlower humidities it seems reasonable to suppose that there will be smaller

- partiolest and lose clumping and shielding, therefore, a greater poentageof the exposed organisms cam be "hits"

2. shEporimontal

In. view of the conflicting reports, on the effect of htmdity on thebactericidal effect of UT, an experiment was conduoted to dotermiLe the ef-foot of relative humidity on the survival of Bacillus isubtLo var. •itrspores exposed to UT radiation.

ao Methods

An aerosol of B, subtilis spores was passed through an aluminumtube five inches in diamete cont•a zg one 086 UT laVmp. The relativehumidity of the aerosol air mixture was regulated by controlling the soe-ondary (mixing) air supply. This was done by passing the air through watr.w

SJ

100

for adding moisture ,or through silica got for removing moisture, The con-trolled aerosol was passed through a mixing chamber, where large particles Wsettled outq and then past wet and dry bulb thermometers for I determina-tions. Air emerging from the exposure chauber was sampled with sLeve typeair samplera, using corn steep apr plates. A schematic diagrom of the ap.paratus is shown in Figure 15.

Air flow through the UV chamber was regulated to one cubic footper minutes The UV tube was partially covered with tape to reduce thegermioidal action and allow survival of a percentage of the sporeso

At each relative humidity tested, air samples woen taken withthe VV lamp off and with it on. From these data the per cent penetrationof the aerosol at that relative humidity was calculated*

b. Results

The results of $ tests - each including 6 trials at differenthumidities - are tabulated in Tables XX, XXI, and XXII. These results r•ealso shown in graphic form in Ligure 26. It can be seen that the per centrecovery of irradiated spores varied only slightly from trial to trial withno apparent relationship to the relative humidity. For bacterial spor•esunder the conditions of this eoxperoint, large changes in the moisture con-tent of the aerosol-air mixture had little or no effect on the germicidaloffectiveness of the radiation.

E, IRRADIATION OF lVVEDLA

Coblents and Fulton (46) exposed open sterile agar plates to UY radia.t ons of wave lengths 2100A to 2060A, They found no detrimental effects onthe subaeequent ability of the sodium to support growth except where veryhigh concentrations of radiation were used. In studies of this 'type by theauthors, four per cent blood agar, nutrient agar and eosin met•ylene blueagar plates were expsed to a radiation intensity of 85 microwatts per squarecontineter for varying lengths of time up to a maxioun time of four hours.Irradiated plates then were inoculated with 0o.1. milliliter of a diluted sus-pension of the test organismsu _S. majroesoes, D. subtilis vare. !Lgp and!. coli. Nonirradisted agar pie-too wer used fr the coUtrols, ' oir in-cublKn, the counts on the exposed and nonexposed plates were compared.Won after four hours of irradiation, there was no change in the ability ofthe agar plates to support gr•wth. Therefore, it was concluded that expo-sure of agar surfaces to UV radiation doses as high as 20,400 microwastminutes per square centimeter has no effect on subsequent inoculation andgrowth of S, marcescons, B3. jubtli•s or Ec coli. Open Petri dishes con-taining stoIe agar ,i Wften exposed in urchamber (e.g. a walk-inincubator) in order to dry the agar surfaces.

101

j

I

Ii14

ii

I

102

TABLE XX. SURVIVAL OF UV IRRADIATED B. SUBTIL_ SPORES ATVARIOUS RELATIVE HUHIIfIU 0

(Test 1)

REL.ATIVE TEST ORGANISMS RECOVEREDHUMIDITY , UV Off UV On PEtR CENITiper cent org per cu ft org per ou ft av|g per ou ft PENTRATION

29 1.4 x 102 2.6 -3.8 2.863.63.4

87 3,2 x 102 6.4 7.0 2.57.27.4

43 2.2 x 102 7.4 8.0 29.736.04.6

50 3.3 x 102 72 6.4 2.55,• 6.8

10,0

68 3,6 x 102 6.4 6.5 2.8e902"708

"72 4,2 x 103 9.6 9.5 2.l6S~10,6862

66 3.1 x 10 6.6 5.9 1.9005.85.2

a. The-radiation intensity was the same at all El's.

0

108

TABLE XXI. SURVIVAL O0 UV IRRADIATED 3. SU§ TILS SPORES ATVARIOUS RELATIVE HUNIDIYIE

(Test 2)

RELATIVE TEST OAANISHS RECVED PE CENT •HUMIDITY, UV Off UV on PENETRATIONper cent org per ou ft ors per ou ft avg per ou ft

88 1.24 x 102 3.00 8.52 2l654.0

40 1.930~) 86 38. 2.983024.6

48 1.45 x 102 5.8 5.18 8.584.0508

55 1.71 x 102 6.4 5098 8.475685.6

62 1.69 x 102 504 6.13 8662see

s6 1.61 x 102 7.0 7052 4.667.27.6

7.2

91 1.44 x 102 5.6 4.66 8.874.046e

a. The radiat~on £ntonelty vas the same it all N's.

104

TABLE XXII. SURVIVAL OF UV IRRADIATD B. SU&TILIS SPORES ATVARIOUS RELATIVE HUMIDITIE- -0

(Test 8)

RELATIVE TEST ORGANISMS RECOVERED P CHUMIDITY, UV Off UV On PEIETRATIONper cent org per ou ft org per ou ft svg per ou ft

29 1.24 x 102 3.6 3.08 3.0063.24.4

36 .89 x 102 1.8 2.3 2.51.2,

4.0

41 1.33 x 102 2.6 2.7 2.102,43.0 . .. ... .. . .

46 1.26 x 102 3.4 2.7 20142.2,3.0+

54 .76 x 102 2.4 2.1 2.761.6

2.2

63 1.35 x 1021 5.0 5 .66 4.165.66.4

70 1.23 x 102 4.0 4.43 3$64.4500

66 1.25 x 102 4.4 4.66 3.724.65.0

a. The ra4iatLon intensity was the smee at all WeH.e

0

105

____ ____ o oil

k__ __h N

NS M

__

____ i

U@I&DJ40usd 4W.D Aed

106

Eperiments conducted at the University of Michigan by laurence andOraikoski (160) indicatehowevert that certain liquid media my be adverselyaffected by UT irradiation to the extent that subsequent inoculation giveslowoeryields of total cells# A chemically defined modium (Dife, NiacinAssay Medium) was irradiated (wave length and intensity not g n) for var.ions lengths of time and then inoculated with Lotobillue arabinosus.Growth after incubation was measured turbidimetioll o- The results showeda linesr decrease in growth with the time of irradition The observed o.- QI

tfeat was not the result of a change in pH Attempts to reconstitute Irradi-ated aedis by adding certain ingredients after irradiation failed to give

h comparable to that of the unirradiated controls All of the componentsof the medium used in these tests were essential for growth of the test or-ganiesm It was postulated that the formation by'UV irradiation of toxicproducts, such as organic peroxides, my have been responsible for the dele.terious effect.s

F. HEAT SENSITIVITY

Cells which have been exposed to sublethal doses of UT radiation aemore sensitive to host than untreated cells, The experimental evidence has

ý\been smmarized in a review by Giese (100). This phenomenon has been noted"•on work with protein solutions, bacteria, yeasts, and tobacco mosaic virus*The thermal death of irradiated bacteria occurs at'a lower temperature orupon a shorter exposure *han unirradiated cells of the sam strain, This isnot a mere additive effect because, if host is aplied preceding the radial.tion exposure, no difference in the UV susceptibility of the cells is noted.1sntnohlor and Nag (246) show the'same phencmenon and state that It is"incompatible with single photon hit theory.w

0. FIOTOREACTIVATION

Under certain conditionst it has been found that cells made nonviableby exposure to UT radiation can be reactivated by exposure to vLsible light.This was first demonstrated by Kelner, who worked first with S p$ sR (167) and later with Esoherichias oli (168)s A si1lor" pheno nhaeibn shown to occr• with yeaslst bacteropfhag, sea urchin eggs, andprotoeoa (100) o In the technique usually employed wster suspensions oforganism areexposed to UV radiation doses sufficLent to prevent subsequent%multiplication of approximately 90 per cent of the cellos After exposure,duplicate cultur ,are held in the dark and exposed to a strong intensity,of visible light or long wave length ultraviolet, The capacity for photo.reactivation disappearl after storage in the dark for two to three hours.

Kilnerts discovery has led to several now theories regarding the moeh-anisn of UT actions Most of the theories involve the formation of toxicsubstances. It has been postulted, for Instance, that when bacteria areirradiated with UT radiation, a poisonous substance is produced in two

C4 107

forms one light labile and one light stable (100). Bacterial spores havebeen reported not to be subjeot to photoreaotivatLon following treatmentwith VV radiation (257)o • ...

One corplicatio n foor of the photoresactivation phenomenon is the faot

that some laboratory errs of Nomenwasme ensitive to the photo-revere"in wave length used (147t282t,57t,76)o

Although photoreactivation is easily demonstrated under controlledlaboratory conditionst it is questionable that it has any real applioationAin the praotioal use of UV radiation where generous dosages of giermoLdalenergy are applied in the presence of visible light.

Recent investigaltons on reactivation involve the use of various neta-bolLtes to restore cells Inactivated with UT, radiation,. The work of Neinaets,et al (186), for ewmplbf suggests that ýeollular death by UT radiation 'isUa single stop process and that aseri'so of Changes myoccur depending1upon the UT do$e. Incubation of irradiated cells for about 17 hours withimetabolites from the citric acid cysle causes an increase in the vialecell countf a phenomenon called "metabolic reactvaftion."

The chemical reactivation reported by neimeests at &l (185) has beenquestioned by several other workers (93lU)s, The oalel"ons were based ontests which showed that it was almost Impossible to remove all traces ofnitrogen from the solutions In which reactivation takes place0 Thus, nal-tiplLostion of small numbers of surviving orgasmi during incubation inthe metabolite might be confused with reactivation. uNhits t al- (158)-perfored experiments the results of which supporl this thesl7 TUs recentextensive review by Jagger (161) is recomsended for those Interested InphotoreactivatLonL

'1I

U ) !

10o

Mx. GIDICIMDL •EF•TS Of UY RADIATION

A. GINIAL

Of all UV phonomena, the lethal action of radiant energy against micro.organisme is probably the most frequently investigated, The voluminous Lin.formation available usually can be classified under one of the followingheadingst in terms of the wave length and UV source usedt

(a) Investigations using sunlight as the radiation source,

(b) ilyvestigations using the entire radiation from a source such asa orbon' Iar lap or a high-pressure mercury lesp,t

(a) investigations uising arci lamps and crude filters such as Petridish covers orwindow glass,

(d) investigations using selective filters or prisms which isolatefairly narrow regions of the spectrum, and

(e) investigations using low pressurst mercury vapor'lmp., which

.t aout 95 per cent of their radiations -in the 2587A wave-len5 th bud.

When summarizing the quantitative effects of monochromatic UV radiationon microorganioms only data undlr (c) and (d) can be considered. Iventhen# other limitations have been found that prevent accurate comprison ofdata obtained by various investigators.

Some of these limitations ae.i

(a) Differences in exposure tochniqueot

(b) differenceo in concentration of exposed mioroorganisms s and

(a) differences in determining and expressing the intonsity of theUV radiation.

This last limitation is encountered msot frequently, In nos reportsthe only indication of the intensity is the distance of the exposed material• _from the UT sources Other studies have simply ignored the UV intensity.'Ultraviolet reading& have been made in tome of energy (ergs)t power (wattsor mOirowatts) or in terms of radiant power per unit area per unit of time(miorowatt-minutes per square centimeter), Alsot other units have been eo.ployed which represented a certain percentage destruction of a standardtest strain under standard conditions. These terms ae disOussed in detailin the chaptre on measurement. The terms most oomeonly used today to om-press does of ultraviolet per unit area are miorowattLinuts per squarecentimeter and miorowatt-seconds per squre oentimoter.

ci

109

Although an enormous amount of experimental evidence has accumulatedwhich proves that microorganisms are susceptible to the lethal action ofUV radLation, the limitations listed above apply to much of this work#The following species or, genera have been. listed by various authors (76j151,17,4,183) as susceptible to UV radiation.

k African horse.,eickriis virusAlcaligenesAmebaBacillus anthracLiRacterium la~y~os

%acilus su5iFjIjiDatrg Ibttll•

Bacteriophag- dysenteryBrucellaCheose moldsChicken pox virusCholera bacteriophageColiformsCorynebacterium

lberthella&typhos

Eneephalomyslitis virushoot-and,,.aouth disease virusHemophilusHerpes virusInfluensa virusKlebsiella 4Lactobacillus"measles virusMicrococcusMumps virusMycobbcterium tuberculosiswelseerisParameciumPeliomyelitis virusProteusSaachaw e ellivoidseuhlone alSerratiaShigells,StaphylococciStaphylocooci baaterLophageStreptococcusTobacco mosadiTomato bushy stunt virusThermopht4lic sugar bacteriaVacciLniaVibric

110

B. EFFECTS ON BACTERIA

,// Literature Review

In studies on the effects of UV radiation on bacteria, three methodsof exposure are generally usedt the agar plate method, the liquid suspen.sion methodt and the air suspension methods The aga' plate method has beenwidely used and the results obtained can more easily be compared with otherdate of the same types The date in Table XXIII are taken from a sumuarytable in a review by Hollsender (149). The individual references are notshown, but may be found in the original reviews Table XXIV shows similarinformation supplied by Westinghouse Electric Corporation. Variations foundin the reported quantitative effects of UVradiation (2587A) on various

-strains of bacteria are vividly demonstrated in Table XXIV, For example,it is not likely that 3. ooli cells are more resistant to UV radiation thanare the spores of BDac ml'tZ" atweriu Uneoubtedlyt variables such as pig-mentation, cell concen-fationt-and pr~iiUseal state of the culture are re-sponsible for variances, The phenomenon of the shielding of one cell byanother must not be overlooked. Nany observations have indicated this tobe important in the exposure of bacterial cells on agar surfaces.

The amount of energy necessary to destroy a bacterium has beenstulied by Hollsender and Claus (152). The authors reported that 13.1 x10- ergo per bacterium are necessary to inactivate 3$,1 per oent of thecells in a 15-hour culture of E, coli Only 6.1 x 10"0o ergs per bacteriumwere necessary if the cells were MKst washed. In another paper on theeffect of ria4iation on nematode egp (154), approximately oneverg at 2640A

oduper egg preded a 50 per cent inactivation. Hold spores of "mentanofttes, were destroyed by Hollaender (149) by exposure -to7x1O-'-toe 15# x 301 .rge per spore,

Dasod on an assumed molecular weightt Spector (274) gives the fol-lowing values for T-1 and T42 phages which resulted in lose of activityagainst the host cell-, is coli B.

QUANTUN E M zIczuCPHAGE WAVE LMOTH (Number of molecules reacting

per number of quanta absorbedT

T-l 220A 5.0 x 10-4T-1 2587A 6.P x -T-1 3022A 7s3 x10:T-2 2220A 2.7 x 10-T-2 2587A 3.1 x 10.4T-2 3022A 1.8 x 10-4

TABLE XXIII * MICRO WATT-ýMINUTES PER SQUARE CENTINETER (ET VALUE)NECESSARY TO REDUCE COLONY VODEATION 00 PER CEI NT

AGAR PLATI (Hollasndop- 149)

oaoA~asxET VALUE FOR 90ORGANIS:PER CENT KILL

Bacillus anthraois 75.8

ýGpossl) - -45.503 asu (avg of 3 stati'ns) 58.8

11 suaiI- iied)lieI. ubtills 118.8) WO

300.0

C~!orye terLu dLphtherias 56.1_________a T os 50.0

Eschoncha o011 85.6mg v@Oo@@cuo comdus 100.8Hicroooaous a , oja 1388.0~rlooooous BOSO 1566,6Nalssers ala rrhalls~ 78.8

*No _________o105 7808_______s _______ 44.0resuadounas s5an::acs 91.6___________M resem 58.8

psalmoe la r 0~[L! 66.6saimoneira Ini (ag of 8 strains) 1868.EFlimirn t HI&3838.

ia inazanens 40.8866

Dyentery bacilli (avg of 5 strains) B'Shjqsla as Gn1riss Sel0

391ri m OWN78083j~jCq~c'us Mg 80.6

55.080.686.8

Sta~hyococcus album 438.

Stre O!! tooo hoyicus 86.0atregljjcu AM Iisi1 102.5

W 3885

112

TABLE XXIV. INCIDENT ENJERGIES AT 2537A KILLIMI4ICONS NECESSARYTO INHIBIT COLONY FONMATION IN 90 AND 100 PER CENT0

U ~ OF THE TEST ORGANISMS*

Note:. Divide each number by 60 to obtain miorowatt-min/eq cm(ET).

ENER3GYORGANT SK (NW-i e/Pq GO)

IX) per caent 100 per cent

IJACTIENTAI1actllusi anthracti 4250 6700

i;. eru op y~g 1:106 2500ii-t-f-r~ s .Norea) 2730 5200

11, ml -AjjA 06u 3200 61001!. mu5600 110001. -AUS M111 spore, 11.600 22000

foynej@ac.ertum diphtheria fl370 6500TwKmohfia~ % K 11140 4100Hicrocoacus -candidus 00510 12300Fre-rococcus ýjqro des 10000 15400Nfloserl-a catiaima1ili 4400 6500

tubonl e aclens 4400 60Fr_____ __UEARN 3000 6600ri'e-U36monal ierm inosa 5500 10500

-- 90omnati Iuo~rosce a 50____19700 26400

Terra a marceoeno 2420 6160UYmontery iA-cli 3200 4200

hfella paraysonerime 1660 3400

3i ycoodts al'bum 1640 5720um M uME m 2600 6600

I1~I! ccu y. ticus 2105500

11reN9000ccus -17Frano 206o) 300

YIFASTsacharoces elliosoideum (1000 1-3200

Micilrosyie 00revisyfaas 66000 13200Brower~'s Yowt 3300 6600naker's yeast 3900 6500Comon yeast cake 0000 13200

HOL.D SI'0NI ColorPenaicilium ropueforti. green 143000 26400YiGT1T% p~aisim olive 111000 22000

1'niallit m -Ti11ifim olive 44000 66000Asprgijlum ffau bluish green 44000 66000

~TT1I~ 1 Iii yellowish gr O000() 99000~jj~ii~i~ s iiF7black 132000 330000

RIlou iTfIricis black 111000 220000mucor racsmosup whi'to Aray 17000 35200_____r racemosum 11 white 5000 11000E0FsoorA Tactic W Ihit* 5000 11000

*Suppliod by West'inghouse Niectric Corporation,

(Il 113

In addition, Spector (274) has collected data on the LDo radiationdoes for vaious unicellular Organiouse For waso length 254 aflimi-4rone

(m), the LPJo values were as follows:

OUBANISX LDSO DOSi, e•re/sq (254 NP)

BACTIRAzsoherichis COlI 44-208MIGPoRooout 'aicano 341

-OE$ -•ons 291___________ suareus 86-275

oerralla maroescens 57

Sacohar cern orovLsesa (dark) 508.900jjjJo~creva (:Lght) 1400

Un ca , iscroconidia (dark)M 37Soasssl microconidis (light) 1020

MUTHP-olia or'ase I macroconidis dark) 1440________ crass&# macroconidio a light) 8000

"MKTZOAAmoeba M'otsuc; (dark) ,2110

For the practical application of UV radiation as a bactericidalagent, such information is not neoessary Data showing the intensities andexposure times required to inactivate test Organisms under a variety oftest conditions &ie applicable because variances due to shiolding, col eon-contrationt and physical state of; the culture are alredy included. If suchinformation is iocuraoto practical installations epicying radiant energycan be designed in aco0edance with the intensity requwrments ih, an asur-ManC that the desid' results will be obtained*

Luokiesh (165) presented a graph showing intensities and exposuretimes required to give various ratios for, bacteria molds This graphhas been duplioated in figure 27. Such data we diLfioult to apply inpractice, and are subject to several criticim No. mention is mde of thenumber or different species of mioroorpaism involved. There is an obviousdiscrepancy in'the line for "B. col." In water andN subtilis spores, asthe latter organism is definililFy My times more reS1 Ia to UY radiation.than the vegetative 3, COIL organis, MTe introcellular nature of viruseswould suggest that tdeLrnaotivation in practical instances night be dif-floult. Zn addition it is doubtful that all members of any biologlial popu-lation show equal susceptibility to UT radiation. Extrapolation of radiation

* data is not a good praotice.

114

100,0007

50,000

10,000 O

So

0l

0.001 0.005 0.01 0.05 0.1 0.5 1.0K Exposure Time in Minutes

figure 27. UV Intensity and Exposure Time Required to Give VariousValues of Survival Ratios for Blacteria and Holds.

"LIuokiesh (185)

115

2 Experimental

as In Water Suspensions

Thirty-wattp hot cathode lamps were used in these experiments.Test bacteria were grown on agar slants for 24 hours and washed twice insterile distilled water, Then, 20 milliliters of the suspension were placedin an open Petri dish. The depth of the bacterial suspension in the Petridish was approximately 0&5 centimeter. Control counts were made of the sus-pension and the Petri dishes were then placed below the UV Imp at variousdistances for varying periods of time, After exposure, counts were made todetermine the number of viable organisms remaining, and results were re-corded as per cent survival or per cent kill.

An UV intensity meter was used to make measurements at thespots where the plates were exposed, These measurements gave the intensi.ties of radiant energy in microwatte per square centimeters This value,multiplied by' the minutes of exposure gave an •T (intensity x time) valup.As seen in Table XXV, when the IT values varied from 7 to 50p, the per centinactivation of Serratia marcescens cells in water varied from 0 to999909,. Eagh v.uo es an aversge of at least three exposures@ iton thesevalues, the survival curve shown in 1igure 28 was made*

TABLE XXV. SURVIVAL OF WANHED S. KAROISCEDS CELLS IN DISTILLED WATEREXPOSED TO RADIATION FINT A 3-WATTWHOT CATHODE LAMN

ET MICROWATTS, PE PR CENT KLLS% CH X MINUTES

709 40

12*25 452.5 50I18 668.2

25 72.845 77s762 94.757296775 98569

100 99.62125 990905170 994989250 09.991255 99,991340 996996425 990999650 99.9999

N'

110

0.5CM. DEEP IN PETRI DISH COVERI0

400

0.I-

.0 1 L* JU ___100 200 300 400 500E.T.

Figure 26. Survival of S. maroesoens Calls in Distilled Water,.Exposed to riditon 'fT a 30-watt germicidal lIN.

117

Exposures were *ads of washed spores of Bacillus subtilis vTarSosuspended in water. The results are shown in TMble ,•w. An Avorjgo

•ofe counts on the control suspension in these experiments was 49 x100organisms per milliliter with the limits being 80 x 100 and 60 x 106.

TABLE XXVI, SUMMARY OF ST VALUES FOR 90,9 99 AND 100 PER CENTINACTIVATION OF TEST 02GANISMS IN WATER AND ON

SEVERAL DIFFERN T SURFACE

T E S ST VALUESTESA rOW EXPOSED NUIrI Per Cent InactivationORGANISM 0OF CELLS go, oEXPOSED 1o00],o

. oli Agar surface 200 900.4 119 138-S nreeons Agar surface 200 54.4 11.5 164

S. Marceseons Glass surface 200 16.6 41.6 45.7

S.S!mes. Water (0,5 cn deep) 49 x 106 45 65 425s* Ubti14 J

s. IMisli Agar surface 200 292 476.6 636.4

-, subtilis Glass6 surface 200 19905 305.9 532spores

-s3 subtilis Stainless steelspores surface 2050 B75 00 600

sporeis Water (0#5 cm deep) 50 x 106 1600 2400 8300spores

pore$ Agar surface 240 ass '550 750

b, On Surfaces

For determiningi,,nactivation of organism on agar surfacestsome workers expose ono half of an inoculated ag•r surface to radiationswhile the, ,Airradiated half servesas a contolOr Tests were made usingthis metho(d, but it was found to give inconsistent quantitative resultswhen oonWad to the method of exposing the entire aga plate and usingseveral inoculated, but unexposedt plates for controls. Thereforet the

* latter method was used in all expoeiments in which microorganisms were ir-radiated on agar surfaces.

118

Strains of Serratia marcescens, Staphylococcus albus, andBacillus cereus were grown in broth. An aliquo oeach culturF was placed Won glass, carboard, copper, painted or unpainted pine wood and the surfacesexposed overnight to UV radiation. In each toat, the panels were placed90, 180, 210, and 266 centimeters from the UV lamps. The 266-centimeterfigure was the distance from the ceiling lamp to the floor. Unexposedpanels were used for controls and recovery was made by.swabbing the surfaceswith a damp cotton swab and streaking the swab on blood agar plates. It wasfound that after an exposure time of 18 hours, no viable cells of S. mar-ocescens, So albus, or B, cereus could be recovered from the exposei ur'?aces,while surfaces not expose F=soed recovery of visAble organisms.

In order to secure more quantitative data, the following experi.ments were undertaken: Cells of S. coli, S. marcescens, and spores of B.subtilis were washed twice in sterile--dstille4 water and nebulised* onioglasI, stainless steel, and various agar surfaces. The surfaces woee inocu.lated by applying a constant number of squeeses to the rubber bulb of thenebuliser and using a standard distance between the nebuliser and surface.In this manner the surfaces were inoculated with approximately equal numbersof organisms. In each experiment two or three of the inoculated, noniriadi-.ated plates were used as controls; the average counts being used as thefinal control. After exposure to radiant energy, nutrient agar was poured.over the glass and stainless steel surfaces and the plates incubated withthe control plates. Coloty counts were made after 48 hours of incubation at37000

The survival curves of these organisms, plotted against the ETvalueso are shown in Figure 29. Each point on the graph is an average ofat least three tests which very closely duplicated themselves. The averagenumber of' colonies on the control plates was 200.

Table XXVI shows ET values for ()O 99y and 100 per cent inacti-vation of test organisms on surfaces and in water suspensions 0.5 centimeterdeep.

c. On Air-Borne Organisms

Experiments were conducted in four room. to determine the re-duction in number of air-borne bacteria when two bare 30-watt hot cathodelamps, located in the coiling, were turned on for one hour. The doors andwindows of these rooms were closed and activity kept Qt a minimam duringthe tests.

The general procedure was to take two, 20-minute sieve airsamples in the room before turning on the lamps, then three 20-minutesamples while the lamps. were on, followed by two more 20,ftinute samplesafter the lamps had been turned off. All samples were taken at the table

Vaponefrin Noebuliser, Vaponefrin Co., Upper Darby, Pa.

100

90 1

70~

*~60

'I - ~3~J~J~ON AGAR40 L 0LOIIIOII 0ON GLASS

I --S11O OOIION AGAR- .-- OLIOON AOAR

30 A21

ID10 0 0 -'0 - W 60 '0

I..iTNIYTIII IUI

Figue2.Srvlo roI nGasadAaSrae

I'sdtoV adxin

top level (180 cm from ceiling) and the samplers placed so as to be shieldedfsro direct or reflected UV radiation. The results of a typical experiment-conducted in an 1890 cubic-foot room are shown in Figure 30. In Table XXVIIis shown the averaged results from experiments in four test rooms. Theexperiments in each room were repeated two or three times.

Table XXVIII is taken from Luckiesh (185) and shows the survivalof irradiated "B. coli" in air. These data are rather typical of the aver.age resistance 3f 'ar-borne vegetative bacteria to UV radiation.

d, On Aacterial Spores

There is little doubt that bacterial spores are relatively re-sistant to UV radiation and that the order of magnitude of their resistivity,as compared with vegetative cells. is about the same as to heat and to somediainfectants. Koller (174) presented data showing the relative amounts ofUV energy necessary to inactivate a vegetative organism and a spore formingorganisms

HicrowattSeconds Per Sa Cm

B. call on agar 6,6001 u- ilis on agar 60,000

The spore former, in this case, was about nine times as resist-ant as Be ccli.

Table XXIX is taken from Table XXVI and Ahowb the relative re-sistance of two bacterial spores as compared with two vegetative bacteria.From 343 to 5.4 times as much radiation was required to kill B. subtilisspores as for the two vegetative strains. From 3.7 to 6,.1 tles as meucenergy was required for B. cereus spores. These values are somewhat lowerthan those shown by Kollrer"e. orences in UV source and type of measuringdevices may be responsible for some of the discrepancy. This type of ex-periment has been repeated many times and it has been consistently true thatbacterial spores are at least'three to five times as resistant to UV radia-tion as vegetative bacteria.

C. EFFECTS ON VIRUSES AND BACTERIOPHAGE

1, Viruses

The application of most of the data of earlier workers who exposedviruses to UV radiation is of little value except to demonstrate that viralparticles can be successfully inactivated. Honochromatio radiation was, forthe most part, not used, and few intensity measurements were furnished,Ellis et al (75) reviewed some of these studies with viruses, Susceptibletypes Are--noluded in the list on page 109.

LAMPS OFF I6 ORKIN 1

16 IN I

INIROOM I

14 I

!12'1 LAMPS OFF12 I

CLOSED, ROOM10 '

UV LAMPS TURNED ON

6

2

0-20 40 60 so 100 120 140

MINUTES AFTER S'ART OF TEST

0 VLpzm 80, ConoentratLons of Ar-JDorme Bacterla Ln a iW0O-Cubic foot Iom Beforezo Dunn, mad After IrradiatLonfor on Hour with Twoi io-vatt 'i Laws.

122

Ila V! • ct 4%0 ,1 ti I. ~ :

qt ifi @ if" • •. I I t I

4.21

128'

TABLE XXVIII. UV INACTIVATION Of 3. COLI IN AIl AlT ORDINARTEDPERATURES AND AT 93LITI IDITIES

LESS THAN 40 PER

EXPOSUIE Nicrowatt-Ninutes Per Sq Ca PFECD4TAGE ILLD

0.5 101.0 162.0 38

3.5 505.0 63o2

1000 86.5lies 90

15.0 951905 9628,0 9926.5 -99.5

3160 99.634M5 99.946.0 99.99

•a. Lukesh• (1I85). •

TABLE XXIX. RELATIVE AMN•• UV orSINY R•EQURETO INACTIVATE" BAOTUAL SPORES

- II 1 •• I -- I I il- l

RATIO USING VALUE Or 1 FOR MVTATIYE ONMANISMTJB• ~~~B COIL•eX]• 8, ,m1r, elleIe

TEST ONGANISM I.~3Peraentme KLl1 Peroent'"e Kill90 s 100 90 9 0

. ubth! ls spores 3.8 4.0 4.8 5.4 4, 8.9

B3 cerous spores 3,T 4,0 5.6 6.1 5.0 400

l•4

Tobacco mosaic Virus has been shown by Hollaender (150) to be ap.proximately 200 times more resistant to UV. radiation than bacteria. Kaximun Waction occurred at wave length 2600A. Aerosols of the influenza virus (Pr 8strain) were found by Wells and Brown (307) to lose their infectivity forferrets after exposure to radiations from a mercury arc.

Polson and Dent (239) used a high pressure quarts UV lamp to irradi.ate 11 strains of African horeesickness virus# Although inactivation rates,differed, all strains were susceptible to the lethal action of the radia-tions.

Carlson at al (42) found that treatment of water with artificial UVradiation was moz'; 'Ffective in inactivating poliomyelitis virus than wasexpoiur¶ to direct sunlight or treatment with common water purificationmethods such as coagulation and sedimentation, sand filtration, absorptionon inactivated charcoal, aeration, adjustment of pH and storage.

Data by Hollaender and Oliphant (153) showed that tobacco mosaicand chicken tumor 1 virus had maximum sensitivity at wave lengths shorterthan 2300A while vaccinia virus, influenza virus, and bacteriophagebshowedmaximum susceptibility at 2605A.

Studies with several strains of the rickettsiae of epidemic typhus,Rickettsia Prowaseki, (2) indicated that irradiation with 2538A prod•,ceslosm oe respTatowry activity and toxicity, in that order, Prolonged irra- '

diation produced loss of both properties.

2. Bacteriophage

a, Literature Review

Bacteriophage active against Streptocojous lacti. was found by.Whitelisad and Hunter (317) to be susceptile to UVY radiation ir sufficient

exposure was given. Applemans (12) and Zoeller (328) determined that shortexpqure to UV radiation killed Shigella bacteriophage, The time requiredfor the destruction by UV radiation of Shigella bacteriophage in solutionwas found to be influenced by the type of suspending lijuid, the depth ofthe liquid, and the concentration of bacteriophags.(214). According toSutton (279) bacteria-free filtrates containing bacteriophage active asainstStreptcoccus cremoris were destroyed by radiation in six minutes at a dis-tance of three inches from an UV lamp$

Gates (94) showed a culture of t ococcus aureus to be moresusceptible to the lethal action of UV radiaiont•han its ho•moo•lous bac-teriophage. B, coli bacteriophagel on the other hand, was noted by Latarjetand Wahl (1787 to-•e two to six times more sensitive to UV irradiation thaithe homologous strain of B. colo. Howeverg the bacteriophage was more re-sistant when a mixture of-ba•cte-iiophage and cells was irradiatedle'

125

Anderson (9) found that bacterial cells unable to form coloniesSafter UT irradiation were also unable to support the growth of the bacterial

viruso Apparently irradiation of host cells caused the liberation of avirus-inhibiting substance, reduced the burst #isi of the host and inacti-vated the virus and its host. Cells of Z. coli apparently lose theirability to liberate baoteriophage after Irrr-dation, because of the inacti-vation of the intracellular virus (193),

Greene and Babel (107) studied the suitability of UV radiationto control Srptococcus lactis bacteriophage in dairy plants and determinedthe exposurelinesi andistanes from the source that would-be necessary toobtain complete destruction@ Although intensity measurements were taken atthe surface of the UV lamps, these authors neglected to record the intensitypresent at the exposure surface. The lamps used were very weak sources ofUY radiation#

b, Experimental Studies on Agar Surfaces

Bacterial-free suspensions of bacteriophage T-8 for 3. ooli Bwere spread on the surface of tryptose phosphate agar plates, i t o•Z'plateswere exposed to the radiations from a 15-watt, hot cathode UT lamp, Theexposures were made a+ a distance of 12 Inches from the UV source and thelength of the exposures was accurately determined with the aid of a stopwatch* After the exposure, tharee millilitere of melted agar containing asuitable number of host bacteria, wore layered over each exposed surface,The plates were ircubated for 18 hours at room temperature and the numberof typical Tphtge plaques counted, The total number of phage particles ex-posed in each test was determined by plaque counts on the original phagesuspensions

Each test was repeated four time 1br Oach exposure, the aver-age number of plaques counted was deterumLed and expressed so a peroentageof the number .of phage particles originally exposed. The radiation dosereceived in each exposure was ,alculated in micrcvatt-domutes per squarecentimeter (ST value). #n -the four testst the average =mber of phage par-ticles exposed per plate was 2,5000

Table XXX shows the results obtained. These data were used Inthe preparation of the survival cum shown in Figure 31. By comparisonwith the survival curvos, forývegetative bacteria shown in Figure 290 coli-phage appear slightly more resistant than its host.

o, Experimental Studies on Air-Borne Clouds

Bacteriophage T-3 was used as a simulant for pathogenic viralstrains because 0 is a submicroscopi9 particle in the sam gone•al sixrange as maq human viruses, and it attacks a specific host# These were

*& made to determine the effectiveness of 2587A UV radiation against air-borne particles of ooliphago,, Air locks, door barriers, and other instal.lations equipped with germicidal lamps are intended to act mainly on aerial

128 I

90

80

TO

60

I

z I,

w 4

30-

I20-1

0 _100 200 300

ET. VALUE

Figure 81. Survival, of T-b Coliphage on Agar Surfacesr 3qosed toUV .adiation.

127

mioroorganisms in separating contaminated areas from clean areas. hoellentresults have been obtained with air-borne baoterias but less evidenoe hasbeen presented for the virus.

_ý TABLE XXX. INACTIVATION OF T-8 COLIPIlAOE ONAGAR SURFACES WITH UV RADIATION

EXPOSURE T IIU Seconds ET VAL P12 CENT KILL

Hie.-ONatt-Min Per Sq a

S65.32 616004 10,64 7868&6 15.90 $64.6a 21.26 91.76

10 26060 92.25-14 37.24 95.62

16 47.66 "a.920 53.2O 9M,07

30 60.00 ,6.7140 10o660 90,4650 133,20 99,O6

60 160,00 99090120 39:,00 99099

The tests were oonduoted In 'a closed mtal, chamber having avol*ne of 5i7, oubio feet and equipped with one l5.4att, coldo athode lamp.IMdoaust air from the chambor wan sterillsed by passage through a filters.The cabinet war equipped with two outlet sampling lines and one inlet airline.

Filtrates of coliphage contalning 1.6 x 10 phase particles permilliliter were prepared is.n a protolyrate broth solution, The stook sue-pension wasr sprayed, fron a aponefrmn atomiser to produce the phage cloudesAir samples were taken with critical orifice, impingers, Air samplers wereconnected to the sampling lines of the aerosol chamber and operated at therate of 14 liters per minute, The general test procedure was as followso

(a) Approximately 1.5 milliliteono the phage suspensionwere atonised into the test chaumber,

,/1

126

(b) The UT. Lamp was turned on for two minutes,

(a) Two 5Smainutel air samples /iere taken simultaneously whilethe DV lamps continued to bumn.

Control toot$ were exactly the same except that no UT. radiationwas used. The number of phage particles collected was determinr~d- by plaquecounts in tryptose phosphate agar using the susceptible E. ccli B hoststrain* In one test, samples of the cloud were taken wiTh 1rueve-type airsampler$

- UV intensity reading& were made in the chamber. Intensities ofapproximately 400 microwatte per square centimeter were obtained in the topof the chamber, and, at the bottom, near the sampling, outlets,0 the intensitywas 160 microwatti par square centimeter.

In Table XXXI are recorded the results of six tc~sts showing thenumber of phage particles collected during off and on periods and the percent reduction by the UT radiation. Complete inactivation occurred whencloude of T-nS coliphage, in a concentration of about 10.000 phago particlesper ~oubic toot, were exposed to the UV radiation for a two-minute exposureperiod followed by a five-minute sampling peri2d (total of seven minutes).Higher aerovol concentrations, up to 6.66 x 100 particles per cubic foot,were reduced over 99s9 per cent by similar exposures.

These tests demonstrate the susceptibility of T-8 coliphage inthe air-borne state to ,the germicidal action of UV radiation in the .2537A

TALE XXXI * INACTIVATION Or AIR-DORNE T-3 COLIPHAGE WITH UT RADIATION

NaUBE NUMBER OF EMS4 PARTICLES PER CENTTEST or PHS COLLECTED PER CU i' Or REDUCTION

NUMBER PARTICLES' AIR SAMPLED Dy UVATCHIZED Ultraviolet Off Ultraviolet On RDATIONS

1 &,0 x 108 2.64 x 106 2.44 x l03 9969082 s.o X 106 6.66 x 106 1.44 x iOj3 99*9643 AU.0 X 10 _ 4.961 X 106 1.02 x 103 99.9614 9-00 xl 10 189 X104 0 1005 a 0 x106 6.506x108 '0 1006 3:0 X105 1250 0* 0

*Sieve sampler used.

0

SD, EFFCTS ON FUNGI

Koller (174) states that molds and yeasts are 100 to 1000 times as re-sistant to the lethal action of UV radiation as are bacteria. Nagy (216)has shown that variation in resistance correlates approximately with thedoe.oo of pigmentation of the molds spores. Some of the colorless moldsand yeasts are only slightly more resistant to UV radiation than most bac-terLa Table XXIV. Colored mold spores are mny times more resistant. Itwas also shown that, at certain stages in their life cyole, molds, just asbacteria, are more susceptible to UV radiations i k Eposing the sold spore to:a low intensity of radiation for many hours required from one-fifth to one-tenth the energy to destroy the organisms as similar organisms exposed in aperiod of minutes to the same total amount of energy.

The treatment of tobacco leaves with UV to inactivate molds has beentried ooaosionally. Dorcas (66) pointed out that the color of the leavesis altered by UV treatment and that other changes occur in the quality ofthe tobacco.

Using a mercury tungsten arc, Fulton and Coblents (91) exposed sporesof 27 species of fungi to UT radiation for one minute. Spores of 16 of thespecies were completely inactivated and four species showed a survival ofless than one per cent, UV radiation in the Schumann region (lses than2000A) was found by Johnson (163) to be destructive to the upper layers ofthe mycelium of o dr jo•1at Scleroti/m batacicola, and ftsariumbatacia, RAssey AMl [14y %3431 roundtR&Irraiation y a quKT mercuryarc esTmlated, the formation of spores in cultures of Naorostorim tomatoand 1jasarium !1Rm The spores of Puccini& ljjlne tltiOl were somn-easily Ln---ia'an in a water suspension Mea•In, a r3 s'lvi when irradi-ated with UV radiation by Dillon-Weston (65)', Fatty or wVa secretionsundoubtedly offer protection to some species of fungi.

Luckiesh et al (192) reported the UY dosages required to destroy 90per cent of varous air-borne mold spores,.

Nicrovatts Per Sq Cm toInactivate, 95 Per .Cent

HOLD SPORESNucor mucedo 1250Venros ohrysor num 1150

1450

YEASTS Torula, s1baer oa 50

130

Studies also showed that when two bare 30-watt hot cathode UV lampswere burned in a room of approximately 3000 cubic feet, for two hours, the,number of air-borne Penicillium chryeogenum spores was reduced by 85 to 87per cent.

E, TOXIN-DESTROYING POWERS

Most available information concerning the action of UY radiation onbacterial toxins gives little information as to the intensity of the radia-tions or the wave length used, These studies have been conducted, for themostNpart, in special apparatus designed either for tho preparation of anti-gený' (110) or for irradiating the blood of individuals with bacterial in-fections (100), Little success was experienced in attompting to inactivatetoxins suspended in blood. The radiation source was a high-pressure, watercooled, mercury quartz lamp.

The following data, from Habel and Sockrider (,10) indicate the relativesensitivity of Shirella dysentery toxin to UV energy, as compared with abacterial suspension and a virus emulsions

Exposure Time toAntigen UV Necessary to Ratio

Inactivate Aintipen

Typhoid bacterial suspension 10 seconds 1Rabies virus emulsion 10-80 seconds 1-8Shiaella dysentery toxin 1200 seconds 120

(20 min)

The bacterial toxin was 120 times as resistant to thoi-destructive actionof UV radiation as was a bacterial suspension.

alundell et al (32) exposed four bacterial toxins in blood and in salineto UV radiatio3n T a Knott homo-irradiator. "Each 10 milliliters of thefluids received a 10-second exposure of UV irradiation which varied in wavelength from 2399 to 3654 angstrom units." Under the test conditions, UVradiation had no detoxifying action on the four toxins when they were sus-pended in blood, In saline solution, a slight detoxifying action was notedon tetanal and diphtherial toxins, but not on staphylococcal toxin or scarletfever streptococcal toxin,

In generalv it can be stated that bacterial toxins are difficult to in-activate with UV radiation; inactivation occurs only after long exposuresto high intensities,

131

X. PRACTICAL USES OF ULTRAVIOLET RADIATION

A. LITERATURE REVIEW

Since the advent of the low pressure mercury vapor lamp there has beenrenewed interest in the application of UT radiation for health protectionand product protection. Special device, have been made utilising the bac-tericidal, fungicidal, virucidal, toxin-inactivating, therapeutic (89), andosone producing properties of this radiation. Some of these devices are ofconsiderable value in preventing infections or preserving foods and otherproducts. Others are of questionable value because of insufficient radia-tion or lack of understanding of the properties of germicidal energy. Abrief survey of some of the applications of germicidal radiation will bepresented.

1, Toxins, Viruses, Vaccines, and Ilood Plasma

The early work on molds, toxins, and filtrates was summarised byWelch (808) in 1930. Unfortunately, the wave lengths and the quantity ofradiation were not always reported.

In 1982, Mayer and Dworski (208) reported the action of UT radia-tion on ���teri tuberculosis. A suspension of tuberele bacilli con-taming EFiIO'�janism� permi lliliter was killed within four minutesby absorption of 1.42 x lOW erg. per second per square centimeter frr theunfiltered radiation of a quarts mercury arc. Exposure to 5.98 x 10 erg.per second per square centimeter for 25 minutes did not alter the acid.faststaining qualities of the organisms. Trotskii et al (2d0) in 1985 foundthat bacteria exposed to UT radiation lost consUs�ble virulence for lab-oratory teat animals but retained their antigenic and ianising character-istics, The use of radiation as a means of inactivating bacterial andviral suspensions in the preparation of iunising antigens came into prcm-inence with the work of Modes et al (146) on rabies virus * Irradiation ofthe virus for 45 ilnutes produ�d suspensions which were avirulent for miceand which pe�sessed ten times the immunising properties pf chloroformtreated virus and 500 times the activity of phenolised vaccines.

These and other reports led to the develcpment by Oppenheimer andLevinson (281) in 1948 of an apparatus for exposing bacterial and viralsuspensions to UV radiation. Levinson et al (164) in 1945 described theproduction of rabies and St. Louis encejI�aT1'tis virus vaccines by thismethod. Kiluer St g (218) of the�'.ume laboratory simultaneously announcedthe production ola radiation inactivated polio�yelitis vaccine. Earlier,Taylor et al (282) in 1941 showed that the absorption curve for equineencepha1'a�litis virus resembles the absorption of radiation by bacteria.This virus was inactivated by the same order of magnitude of radiatiod asis required to inactivate Serratia marcescens. Sarber et g (268) used UTradiation to prepare experimental vaccines for tubercul�is.

132

Hollaender and Oliphant (153) in 1944 showed that the action spec-trum for influenza virus and B. coli were the same. About 20 per cent moreenergy was necessary to inactTva~e"nfluenza virus than to destroy E. coli.

In 1946 Oliphant and Hollaender (229) showed that hepatitis Virusin human blood plasma or serum can be destroyed by UV radiation. Wolf at al(322) in 1947 and Blanchard at al (28) in 1948 also described the inactrv!-'tion of this virus in human p-Taiaa.,-In 1950 Cutler at al (53) irradiatedhuman blood plasma to destroy the virus causing homologo us serum jaundice.

Variations of the preceding apparatus using ultraviolet lamps havebeen published. Habel and Sockrider (110) described an apparatus which in-corporated a 15-watt, hot cathode; germicidal lamp. The apparatus of Haboland Sockrider was modified by Boseman at al (36) for use in serum and vac-cine production. Bonesi (26) in 1956 rosiibed a high speed centrifugalfilmer for the irradiation of liquids. The liquid blood plasma or bacterialor virus suspensions are irradiated in this type of apparatus in a verythin film of approximately 0.25 millimeter. The absorption of UV by bloodis much greater than the absorption by water as shown by the coefficient ofabsorption of 2537A radiation for blood which is approximately 71 per centi-meter compared with water which is generally loss than 0.2 per centimeter.

Experience with the use of UV for the treatment of blood p-smaa toinactivate the causative agent of serum hepatitis demonstrates the impor-tance of correct dose in practical applications of UV. Hethods for irradi-ating thin films of plasma with 2537Ak', radiation established prior to 1950(28,322) appeared favorable because a dose not affecting the serum proteinsappeared effective in reducing the hasard of hepatitis. Experience between1950 and 1953 showed that administration of irradiated blood or blood prod-ucts frequently resulted in serum hepatitis (20,106,16I2216), although itwas later reported (217) that such cases exhibited linger incubation periodsand milder illnesses than oases developing after the injection of nonirradi-ated plasma. Hurray et il (217) found that the doak necessary to producesterilisation of the p'auma caused exteneive than&e* in the plasma protein.Subsequently other treatment methods have been employed in which UV irradia-tion is aombined with other means of disinfection and in which other viruseshave been used as a test agent in determining sterility.

Smolons and Stokes (271) added T4R coliphage to normal human sieruwhich was then irradiated in a Dill apparatus (J'. J. Dill Company, KalwasmooHiohigan) and also was treated with beta-propiolactone at several differentconcentrations. UV treatment alone reduced the phage count from 87 x 101 to1070 particles per milliliter of serum. Addition of L.5 milligrams of beta-propiolactone per liter of serum inactivated the remaining phage in 16 hours.Hartman et al (132) also used UV irradiation in conjunction with beta-propio-lactone ro M'eat plasma samples to which had been added 10 per cent suspen-sions of eastern equine encephalitis or incephilomnyocarditis virus. Hostof the viral particles were inactivated by the treatment. Amounts of beta-propiolactone sufficient to give consistant virus inactivation damaged theplasma proteins.

188

Buttolph (151) has suggested the use of Sarcina lutes as a testSorgisml for hepatitis virus because the charaoter=st~o packets of cellomay simulate clumps in plasma wherein viral particles may reside. Storageof irradiated plasna for prolonged periods at room temperature (8,4) isone method presently used to render plasma *afe for medical use.

In 1984, Knott and Hancock (172) published a method for irradiatingthe blood of individuals suffering from bacterial infections. The irradi-ating machine (commercially known as the Knott-Hemo-Irrsaiator) was designedso that blood from the patient was circulated in a closed# tubular systemthrough , quartz irradiation chamber. The radiation source was a watercooled mercury quartz laP. The wave length of radiation emitted from thelamp varied from 2399A to 3654A. Barger snd Knott (18) summarised a listof diseases which can be controlled by this method of irradiation. DBundellet a1 (82) in 1943' demonstrated that bacteria and toxins in the blood arenrot effectively destroyed by this method.

2. Water Sterilization

Ultraviolet energy from high pressure mercury arc lamps has beenused since 1909 for the sterilization of water (75). A number of cities inEurope as well as in this country have had installations capable of handlingas much as three million gallons of water per day. As late as 1985, UVlamp were installed in England and Germany for the iterilisation of waterin swilltng pools and city water supplies. Since the cost of this methodof treatment greatly exceeded that of chlorination or osone treatment, itsuse became limited to special applinations. Introduction of the low pres-sure mercury discharge lamps has revived this application.

Preliminary studies on the disinfection of water with low pressuredischarge Ilmps were published by Luckiesh and Holladay (186) and Luckieshet al (190). A-small practical unit was described by licks et al (248).

Factors of importance in treating waters with UT radiation are thecoefoficient of absorption of 2587A and the temperature of the water. Tem--pat'ature is importAnt because it may limit the UV output of mercury vaporlamps. Thuo at 50OF the UV output of a high intensity lamp will be only20 per cent of that obtained at the optimum of 1050F.

There have been various statements regarding the susceptibility oforganisms in water as compared to air-bornes or surfaoe-borne organims.Luckiesh (185) on the basis of his studies indicated that approximatelyfive times as much energy was required to inactivate I. ooli in water asfor the sae organism on agar surfaces. Others have "ta:-that 40 to 50times as much exposure is necessary to disinfect water as compared to or-ganisms suspended in dry air (98). Accurete comparison of the variousstudies ii difficult because of the factors of temperature and absorption

* coefficients. Consequently, these factors must always be determined andtheir influence noted. Another obvious consideration is that baffles and

*Cited in Hollaender.

134

other devices must be included to insure that all water will receive suffi'.oient radiant energy. Table XXXII shows results furnished by Nagy of ex-periments conducted in a six-inch diameter cylinder containing lamps emit-ting a total of 9.62 watts of 25387A. The water at 520F contained 1200Scoli organisms per milliliter before treatment.

Several models of an UV water "sterilizer" in which high-intensitylamps are used are commercially available.* Units capable of treating upto 166 gallons per minute are advertised. Tests conducted with E. colishowed that the units effectively reduce the bacterial count whes wa•with a low coefficient of absorption is used* When properly used withwater having an e. coli count of approximately 1200 organisms per milliliter,the units will gTves a"leait 99.99 per cent kill of the organisms.

TABLE XXXII. INACTIVATION OF E. COLI IN WATER IN ASIX-INCII DIAMETER VYL=R

GALLONS PER HOUR PER CENT INACTIVATION OF E. COLI

1460 1,002239 99.62768 99.53480 99.24500 98.55382 9410

Conditions: Water temperature - 52°FCoefficient of absorption of" water ... 0.19 per cmTest organisms - 1200 E. coli organisnms per ml of waterUV lamp output - 9.62 ;atT -of 2537A

Cortelyou at al (49) studied the effectivoness of a 1pall waterpurifier on severaTwj'Ter-borne bacteria. The purifier unit utilizes a4-,watt hot cathode lamp mounted in a metal head which is designed to, attachto a screw-on glass jar. Exposure, of water-borne particles at four flowrates between 0,5 and 2 quarts per minute is obtained by means of baffles.Dosage measurements with a depreciated lamp indicated that the expectedvalues for water-borne bacteria at the four flow rates was at least 300 to1240 milliwatt-sinutes per square foot. The highest dosage showed 100 percent destruction of as many as 20,000 Salmonella tyhoss organisms per milli-liter of treated water. c. coU in a concentration of 13 x 104 organisms

*Aquafine Corp., 1005 S. Santa Fe Ave., Los Angeles 21, California.** UR? UV water purifier, Model IC 1969 UN Products, Inc., River Forest,

Illinois.

136

per milliliter were 99.97 to 99.99 per cent removed at the four flow rates.From 99.69 to 99.9j per cent of S 1hocoocus aureus in an initial conoen-tration of 34 x 10 organisms perwre--"l"ewise inactivated.Lower efficiencies were obtained with Bacillus subtilis suspensions, mixed

c species of organisms, and naturally polluted water=s.The dose levels givenagree substantially with other data presented in this report.

A number of larger UV water treatment apparatus using one to fouror more G36TO UV lamps are also available (1t2,207). The newer units madeby these companies use quart. tubes to enclose the lamps so that the temper-ature of the water does not influence the output of the lamp. From 300 to3000 gallons per hour of potable water can be obtained. They have beenused in the dairy, brewing, and pharmaceutical industries where chlorinecould cause oxidation of the product. The efficienoy of any UV water ster-iliser is dependent upon the amount of radiation, the degree of mixing, theturbidity of the water and the transmission of UV through the water. Itis apparent, hovever, 4 hat UV purifier units for water cannot be dependedupon to completely inactivate all forms of microscopic life, especially ifsome turbidity is present.

Calculations have been made for the rates of disinfection of watersof various coefficients of absorption when seeded with vegetative bacteria.In general it was found that potable water usually can be produced by theapplication of one watt of 2537A radiation for each 100 gallons per hour ofwater flow, providing the water has had an absorption coefficient of 0.19per inch or loses

3. Hospitals

Since surgery was first performed, air-borne organisms have been aserious problem. Many post-operative infections and deaths result fromthese air-borne organisms. Lister sprayed carbolic Acid to eliminate in-fectious organisme from the air but this is not possible today.

Although bactericidal lamps are used in few hospitals, a consider-able amount of information ib available dee~aibing hospital applicationsof UV radiation. In addition, many of the applications found worthy of use"in infectious disease laboratories obviously can be used to advantage in thehospital. As with other applicatLonsp proper and successful application ofUV radiation in hospitals demands (a) use of the proper intensities andexposure times, (b) proper maintenance and replacement of U lampsa. and (c)personnel protection, where necessary.

As mentioned elsewhere, it is also necessary to have an understand-ing of the limitations of the use of UV radiation. UV radiation is not the"solver of all problems," and in no instance should its use be substitutedfor proper aseptic technique and good housekeeping.

136

In presenting a brief discussion of the hospital applications ofgermicidal radiationt it is pointless to do more than mention the numerousopportunities which may exist for the spread of infectious diseases in suchinstitutions. Infections have been spread by the air, through clothing,and by thermometers, instruments, and other fomaties. Hospital-incurredinfections can occur in the operating room, infant wards, patient wards,hospital laboratory, laundry or any other place in the hospital. Recently,epidemics of staphylococcal infections have been noted in many hospitals.

Based on a nine year study or operative wounds, Moloney (209) esti-mated that between 30,000 and 60,000 viable organisms fell upon the "sterile"field during the course of an hour's operation. These figures, however,are extremely high for present day hospitals. In a survey of 87 operatingrooms in 17 states, Hart (122) demonstrated the universal presence of patho-genic bacteria in operating rooms during occupancy. Host of the infectionsof clean wounds were believed to be caused by air-borne staphylococci fall-ing into the wound or on sterile supplies. The number of organisms set-tling on a Petri dish during an operation varied from 21 to 188 with anaverage of 67. An experiment carried out using Petri plates of blood agarplated with hemolytic Staphlococcus aureus were placed at an operativesite and exposed from one to thres'inute"to UV radiation. Air-borne bac-teria were reduced from 95 to 100 per cent. The intensity of radiation didnot cause an appreciable burn during an exposure of ninety minutes. Hart(120) first discussed the feasibility of an operating room with air currontsfrom other parts of the hospital eliminated and using direct sunlight.Artificial sources of UY radiation were used to prove or disprove that bac-teria in the air were the chief source of danger and "unexplained infections"and could be controlled by the elimination of air-borne organisms.

Hart and Jones (128) reported that pathogenic bacteria exhaled bythe operating room personnel were the predominant cause of infections in,",clean incisions.!ý" Hart (122) reduced the number of bacteria by rigid iso-lation in the operating rooms. Because of the low filtration efficiency ofsurgical gause masks (109), large heavy masks were UP=or over the nose andmouth by all occupants of the operating rooms at all timeS, regardless ofwhether an operation was in progress. By irradiating the air with UV radia-tiong it was possible to obtain less than one colony per open Petri plateper hour of exposure in the operative field. Unexplained infections in"clean incisions" are practically nonexistent.

In a series of publications starting in 1986 and extending over aperiod of years during which time thousands of operations were done, Dr. Hartand his associates (121-129,323) have clearly demonstrated the benefits ofusing UV radiation in the operating room. The reduction of pathogenic organ-isms in the operating room will have the following effectst

(a) Reduction of post-operative infections by 85 per cent.

(b) Eliminates occasional death from infection.

1(7

(a) Reduces the post-operative temperature.

(d) Reduces the duration of post-operative temperature.

(e) Improves wound healing.

(f) Lessons systemic reactions.

(g) Shortens convalescence.

These effects were most pronounoed in patients subject to ex-tended surgery.

Rentschler et al (247) and Sharp (266-268) have shown that lessthan 10,000 miorowaf-ir-oonds of 2587A radiation (166 miorowatt-minutes)will destroy most comon pathogenic organimsi. What effect would thisenergy have on living tissue? Hart st al (180) have shown that intonsi-ties of about 20 microwatte per square •ontimeter cause no demonstrablesharm to skin, peritoneum, meninges, or other tissues exposed during an'operation. Kraissi et al (176) and Fraser (69) demonstrated that micro-organisms are dostro~yo-fore injury to tissue occurs. Odom eot al (227)exposed the brains of twelve dogs to an intensity of 16 microw--ts persquare centimeter for as long as 30 minutes with no pronounced effect onthe tissue.

Extensive use of bactericidal radiation has been made in construc-tion of the new Duke University Hospital in Durhimp North Carolina. Allof the sir and personnel in the operating theaters are exposed to directradiation (Figure 32). A preparation room designed to supply all of theoperating rooms is also irradiated with direct bactericidal radiation(Figure 33), Protection of the face and nook is necessary when directradiation is employed (Figure 34). A one-half hour exposure of bare skinto an intensity of 20 microwatts per square centimeter will produce a mildorythema. Simple protective clothing and eye shields are used by the

2. operating team. This has not berin found to be a problem at this hospital.

Another method of irradiating air in an opersing room is to useindirect radiation. UY lamps in specially designed fixtures are hung onthe wall in a manner so that only the upper air of the rooa is irradiated.The recommended average intensity of 2587A radiation in the upper air loneis 50 microwatts per square centimeter. The fixtures are hung 6J to 7 feetfrom the floor. The normal circulation of air in the room exposes mostair-borne organisms to the high intensity radiation in the upper portion ofthe room. The average reduction of' air-borne organisms is about 60 to 70per cent. Published figures are not available on the reduction of the in-cidenoo of infection of glean wounds by this method. Based on previousdata it would be logical to assume that the reduction of infection would beproportional to the reduction of air-borne organisms.

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141

Special fixtures and cabinets with UV lamps have been used by Hart

and by Post (240,241) in eye surgery' to protect sterile instrumentsfrom air-borne organisms.

Generally, more attempts are made to supply sterile air to operat-ing room# than other sections of a hospital. Robertson and Doyle (254) haveshown that cubicles in an infant ward had an average of 61 organims percubic foot. A large ward had an average of 360 organisms per cubic foot,while tests in an outpatient department had an average of 407 organisms percubic foot but some days the counts were as high as 708 organisms per cubicfoot, A series of tests by Robertson et al (256) showed that barriers ofUV radiation were effective in prevent•'ngThe spread of artifically intro-duced bacteria from cubicle to cubicle. Robertson at &l (255)0 in a twoand one-half year study on the use of curtain_ of Uýrmi'iation and upperai'a irradiation in'a children's hospital, also showed that there was a re-duction in the number of respiratory infections in infants. Higgons andHyde (143,144) in a three-year studyt demonstrated that UV radiation in achildren's hospital reduced the incidence of respiratory infection by asmuch as 33 per cent. Friedorissick (90) showed that indirect UV radiationin a children's hospital reduced to a considerable degree the infections ofupper respiratory tract and their complications.

UV lamps have been employed in tuberculosis hospitals. MocVandiviereat al (198) demonstrated that indirect ultraviolet radiation in a hospitalroom destroyed over 70 per cent of air-borne organisms, some of which wereM. tuberculusis.

Recently RWaoy et al (21,p252) have conducted experiments in a tu-berculosis ward to evaluatethe value of UV radiation in preventing the air-borne spread of M1. tuberculosis. A curtain of radiation is used to preventthe spread of ail-borne tubarcie bacilli from the patient's rooms to otherportions of the hospital, and upper air irradiation is used in each patient'sroom. As a testing procedure all of the air exhausted from the rooms ispassed to a chamber in the attic where guinea pigs are housed, Preliminarytests with sprayed tubercle bacilli demonstrated the effe6tiveness of VVradiation. Control tests weres'conducted in the ward with the UV turned off.The authors hoped to relate a quantum of infection for a nurse to the rateof guinea pig infections. From the results of the first several months ofthe control test it was estimated that one guinea pig infectious dose wascontained in each 12,000 cubic feet of ward air, Further experiments arein progress to determine the effect of UV radiation on the infectiousnessof the ward air.

High intensity radiation has also been used in some hospital au-topsy rooms to destroy organisms on the tables, floor and in the air.

Rosenstern (261), in an adoption nursery (infants one to three0months) of 36 cribs compared three systems prevention of respira-

tory contagion in the cradle. They were (a) air conditioning, (b) airconditioning plus UV barriers in front of oubicles, and (c) barrier unitshaving each cubicle closed off and with a separate air-conditioning system.

142

Clinical observations over a period of two years showed that air-conditioningmethods did not prevent the spread of respiratory infection whereas the other Wtwo methods efficiently prevented cross-infection.

McKhann et al (206) reported that chicken pox failed, except in onecase; to spread Fom 12 cases treated over a period of five months, in anisolation ward to 120 other children on the same floor who were separatedfrom the infected room by an UV barrier.

Green et al (106) were engaged in a study of the effectiveness ofUV radiation inFas-ome for infants and children when an epidemic of chickenpox occurred. At that time they had under study two infants' wards, onewith and the other without UV lamps. Ninety-seven per cent (165 of 170) ofthe children who were housed in the unirradiated main building and 18 of 19in the unirradiated control ward contracted chicken pox. In the irradiatedward not a single case of chicken pox developed. It is interesting that anight nurse in the latter ward also cared for children in the adjoining wardwhere the incidence of infection was nearly 100 per cent.

4. Schools

Wells (305) reported that for three successive years, young childrenin UV irradiated rooms of a school were spared not only from chicken poxbut from mumps as well, when these diseases were prevalent in other partseof the school. He also has shown (304) that the use of UV radiation inschool rooms housing primary classes gaei a very marked reduction in thenumber of cases of moaslesýas compared with a similar group housed in unir-radiated rooms,

The school tests of Wells were duplicated in a modified form bymany investigators. Perkins et al (235) reported that UV radiation modifiedthe spread of measles. Dahlk"esTal (16) observed differences in the rateof spread of chickenpox but co•Id not find that the radiation had any ef-fect on the spread of mumps. Wells and Holla (309) reported that UV lam-pwere effective in disinfecting the air in the school room during the wintermonths but ineffective during the moist spring months. It should be notedthat the quantity of bactericidal radiation in these tests was loss thanthat used in other experiments (305). The amounts of radiation used byother authors was also different so that it is difficult to compare the re-sults of the various investigators. Gilcreas 11,al (103) reported that theyobserved, over a period of four years, an average of 42 per cent reductionof the total number of air-borne bacteria in school rooms with UV radiation.Downes (67), however, could not find evidence that UV radiation in schoolseffected the incidence of illness. However, in these studies only two 30-watt germicidal lamps in reflector fixtures were used per school room.Luckiesh et al (191 showed that four such lamps should be used to obtain areasonable gemicidal effect in a school room. Gelpherin et al (96)Nalsoobserved only a minor reduction of respiratory diseases of"hfldren inschools irradiated with UV radiation. Gilareas et •l (104) later reported

143

* a reduction of microorganisms in the school room without a reduction of theincidence of disease. They believed that the major transmission of diseaseoccurred on school buses and outside of school hours. Air in the busescontained from 620 to 3780 organisms per cubic foot with an average of 980.The average number of organisms in the school room was found to be 34 percubic foot of air.

The Medical Research Council, England, (207) reported the resultsof a three-year study of UV lamps in schools. The "examination of individ-ual causes of absenteeiem suggested that irradiation probably reduced thenumber of absences due tocortain diseases by amounts between 1.5 to 45 percent." The numbers of air-borne hemolytic streptococci counted over aperiod of six months were reduced by about 80 per cent while the over-allreduction in air-borne organisms was about 70 per cent. The radiation didnot appear to reduce the large group of ill-defined upper respiratory in-fections such as the common cold which accounted for most absences.

5. Miscellaneous Applications

UV is often employed to maintain sterile conditions during packag-ing of pharmaceutical and biological products-. One concern has reportedthe successful use of a special hood into which OV treated air is passed(156). A sketch of this hood is shown in Figure 35. A number of modifi-cations of this hood are in use in other pt*rmaoeutical houses at the preo-ent time.

Matelsky (202) has reported the use of UV radiation by a phaftaoeu-tical products company to prevent the spread of infectious agents from ex-perimental animals to workers,

Ultraviolet radiation has been %"e4 in the United States and Canadaby sugar refineries to eliminate thermophilic bacteria and yeasts presenton sugar crystals (27,113). Ultraviolet lamps also are used to preventmold growth on liquid sugar in the storajutenks.

Nelson and Hatelsky (222) reported good results with the use of UVradiation in a cherry packaging plant. The placement of lamps in vitalspots reduced the total bacterial air count, eliminated Mycoderm s@um onprocessed cherries and eliminated mold growth on the surface of caska.

Coblents (45) reported in 1942 on the testing of an artificiallUapplicator designed for use by the medical profession for irradiating thefundus of deep cavities. He concluded that the applicator was a dangerousinstrument unless the intensities received by the patient in the deepcavities were rigidly controlled.

The use of UV radiation has been suggested many times for thepasteurization of milk. As yet, no proved method has been developed forefficient, large scale treatment of such liquids. Most suggested methods

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*h have involved the exposure of a thin film of the liquid to high intensityUV radiation. Nicholson (224) in 1947, designed a small pasteurizing unitfor milk which he recomuended for use on small dairy farms. The apparatuswas reputed to produce milk with bacterial counts of less than 2500 organ-isms per milliliter. The milk was exposed to UV radiation as it flowedover rotating cylinders. By controlling the speed of the cylinders, thethickness of the film of milk could be adjusted, A fan was used to removethe ozone. Radiation was supplied by a battery of eight, 15-watt hotcathode lamps. In addition to the low bacterial count, it was claimed thatthe flavor of the milk was improved.

Nagy (220) reported on a method for the sterilization of opaqueliquid by passing the liquid through long sections of small diameter Vycortubes with the high intensity lamps on the outside of these tubes. Inthis manner the liquid would not be exposed to ozone or other gases. Rapidmovement of the liquid in the tubes would greatly increase the turbulenceso that all of the liquid would be exposed to the radiationa Milk exposedin this manner acquired an undesirable flavor. It was believed that the2537A radiation dttered some of the sulphur containing proteins. The "off"flavor was a result of this photochemical reaction rather than oxidationby ozone.

Laboratory devices using UV radiation have been used as a means ofsterilizing sugar solutions, culture media, and tissue. One such apparatuswas reported by Carlson ot al (43). A small aluminum lined box containingan 8-watt germicidal larpwas' used. Processed X-ray film was used over thetop of the box to prevent the rpdiations from reaching the 'eyes. Liquidswere sterilized in small quartz flasks. Advantages claimed for this methodof sterilization were (a) no loss of water, (b) no heat-induced chemicalreactions, (o) solutions may be prepared with unsterile pipettes and (d)time saving; exposure times as short as five minutes were sufficient. Theprimary disadvantage listed was that prolonged exposure to UV radiation mayproduce chemical changes in some substances.

A device called the "Baryaire" has been manufactured by HanoviaChemical and Manufacturing Company. It was recommended that these unitsbe placed in hospital corridors to prevent cross-infection by isolatingcertain areas. A blower was utilized to draw the air over the UV lamp.Magondeaux (199) claimed that air-borne microorganisms coulddnot be car-ried past the UV barrier. A sketch of this unit is shown in Figure 380.

Dr. H. B. Lurie of the University of Pennsylvania has reported overa period of years on air-borne transmission of tuberculosis and its controlby UV radiation. These studies contain many valuable data applicable tothe problem of safe storage and handling of infected animals. Lurie (194)demonstrated that air is a natural vehit'le of the contagion of tuberculosisin animals and that normal rabbits and guinea pigs acquired pulmonary tuber-

* culosis when placed in individual open cages in a room housing animals in-fected with tubercle bacilli.

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Otere publidcatio nsdesrbedo the uaerss.Te of V aiapor n tow parriedntther spreaid of i-orne linfectron of~s tuberculosishein6animalste (10197,08)Toidn tica animalito rooms weriued. oc uorsuoome hred to cahe racksnforhuigrabbits pevlaed severaleuw mincheeos prt. nectled animl noedwere plaed_teein onsog ac ndii~y uNinfeted rabthesoro-lb in the other. One rosws qipewinth Vratdiatlieon ith !thlle lamp plaeoriconta!-llyinthe spoac btuwoeeni

tetwocae rap~cks at eOhsef leveiidl Iradiatindownward.ls oiii Unt lampwleorle plrcdu abotecto and belownthe crgeeracks. The e~mnt ws caried oninthe u irradiatn roose odired ofo tubruosis. he of posthepremaioningthurabit deeloped an "regessiveldo mbicrscopic tulborcloe" anidnoet deeop, wiltubrculbFin sensitite None of thnidle-ntrol orabisi threoo irraditeroomto

Thowie aplicatedione of ghermpicidaloeo UV radition falllgcad setino two

dustries in which germicidal 1lamps are commonly uti4ized:

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Applications for Germicidal UV Radiation@

(1) Preparation and packaging pharmaceutioal products(2) Sanitation of drinking glasses# plates and cutlery(3) Sanitation of walls and fixtures in bathrooms

ý4) Killing thermophilic bacteria in sugarVaccine production(6) In air-conditioning units(7) Hospital nursery rooms(8) Operating rooms(9) Dairies(10) Bottling plants(11) Preparation of blood plasma(12) Poultry and animal protection(13.) Protection of baked goods from mold14) Protection of meat from mold and bacteria(15) Tenderization of meat(16) Cold storage of fruits and vegetables(17) Sterilization of waterS18)Schools19 Aging of cheese

(20) Breweries(21) Sterilization of supply or exhaust air(22) Preparation of wine

UV radiations can be used in infectious disease laboratories forpersonnel protection as well as for product protection. In the literaturereviewed, no comprehensive study of practical types of installations forpersoMel protection could be found except those studies dealing with theusei, of UV in air-conditioning systems, Various types of barriers and lockshave been reported but design details and adequate evaluation tests werelacking.

A comprehensive experimental program directed towardthe designand evaluation of specific UV installaIions, suitable for use in infectiousdisease laboratories has been conducted by the authors over a period of ap-proximately eight years. A detailed account of some of these studies ispresented on the following pages.

B. AIR LOCKS,

An air lock is defined as a small empty room with a door at each end,constructed to create a dead air space for a safer passageway between twoareas. Germicidal lamps are installed on the coiling of such rooms. Ex-periments were conduc'ted to determine the effectiveness of UV radiation inpreventing the passage of air-borne microorganisms from area to area*

148

Cultures of S. marcescens wore used in most of these studies. In sometests, normal bacte"tjT MRa of the air or surface contaminants were usedas indicators of germicidal effectiveness. Aerosols of S. indica. or S.marcescens were produced 'from 24-hour broth cultures by 1 D*VMI's Co. 40

To evaluate the effectiveness of UV air locks, air wasa'ampled for bac-terial content by sieve-type air samplers (Figure 37) with the UV lamps offand on. In some instances liquid impinger samplers were used for the UVoff air samples, The comparative number of organisms recovered and the percent reduction allowed an estimation of the effectiveness of the germicidalradiation. Some tests were done to evaluate the action of the radiation onsurfaces in an air lock.

During these studies some attention was given to the phenomenon of photo-reactivation, first described by Kelner (169). Recovery plates were some-times prepared in duplicate and incubated under white light and in the dark.However, our exp~eriments called for lethal concentrations of radiation andwere performed during the day when generous amounts of white light werepresent before and during the tests, and no photoreactivation was demon-strated.

1. Air Lock for Field Change Room

The effectiveness of an UV installation used during A series of sum-mer field tests was determined. The installation consisted of an UV airlock room through which contaminated personnel returning from field testspassed before entering a contaminated change robin. The bacteriologicalstudies conducted in this ISV barrier are grouped under three, headings:

(a) Killing of air-borne clouds passing through the air lock,

(b) decontamination of surfaces, and

(c) decontamination of protective field clothing.

The floor plan of the lock is shown in Figure 38. Nine 86-inch,30-ýwatt hot cathode USV lamps were installed in the lock. Eight of the lampswere located vertically on the side walls while the remaining lamp was inthe ceiling at a distance of about eight test from the floor. None of thelamps were equippe4-with reflectors. Before tests were conducted the lampswere carefully cleaý.Ad with 95 per cent ethyl alcohol and their outputmeasured.

The test organism used in these studies was S. indica. Re-covery of the test organism was accomplishad with ocotto~nswabs and sieve-type air samplers. The plating medium in bOth owse was Difco's TryptoseAgar. All agar plates were incubated for 48 hours at room temperature.

149

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a. Inactivation of AirBorne Clouds Passing Through the UVAir Look

The UV air look led to the contaminated change room. Thechange room was equipped with an exhaust air blower and filter unit. Withthe exhaust air blower in operation, a constant flow of air was maintainedthrough the UV barrier in the direction of the"change room.

"P-- Nebulizer3 wore set up at the outside opening of the UV lock,two feet from the floor. Air samples were taken at the same height in thedoorway leading to the contaminated change room. Control air samples weretaken before each test. During the testst the bacterial cloud was gener-ated continuously. Five-minute air samples were taken first with the UVlamps burning and then with them off. This procedure was continued forseveral successive off and on periods. The results of the two tests(Table XXXIII) showýa marko reduction of viable air-borne organisms ob-tained by the treatment with the UV radiation. The initial cloud concgn-tration passing through the lock wag-estimated at approximately 1 x Ov0air-borne S. indica cells per minute. It will be noticed that the number"of coloniei rseFed when the lamps were on increased as each test pro-ceeded. This is due to incomplete removal, by the exhaust system, of thecloud which passed into the dressing room during the time when the lampswere off.

TABLE XXXIII. INACTIVATION OF AIR-BORNES. INDICA IN A FIELD AIR LOCK

COLONIES ON 5-HINUTE AIR SAMPLESOPIERATILN Test I Test 2

UV on 4 2UV off TNTC TNTC

UV on 26 250U'11 off TNTC TNTC

UV on 300 300UV off TNTC TNTC

Because the concentration of air-borne bacteria in these tootsfar exceeds the maximum number that would be expected during actual use ofthe lock, it is apparent that a considerable amount of protection is affordedby this UV installation.

152

b. Decontamination or Surfaces

bran The four surfaces used in these tests were plywood, glass, rub-ber, and canvas. Duplicate sections of each surface were obtained. Onesection served as control and the other was exposed to the radiations inthe UV look. The surfaces were contaminated by holding them for severalminutes i short distance in front of three DeVilbiss No. 40 nebulizers. Allsurfaces were contaminated in a like manner. The control surfaces wereplaced outside in t'i. shade and the test surfaces were placed on the floorin the center of the UV air look. Thea lamps in the lock were turned on andsamples taken with cotton swabs at five-, ten-, and fifteen-minute intervals.The swabs were streaked onto Difco's Tryptose Agar plates and incubated for48 hours at room temperature. Except for one colony recovered from the glasssurf'ace after the frv-minu~r exposure period, no S. indica was recoveredon any of the surfaces exposed to the UV radiation. =e"results of thetests are shown in Table XXXIV. Viable organisms were obtained from allcontrol samples throughout the test. These data show that any organismsthat may be shaken off onto the floor or walls of the look will be inacti-vated unless protected from the UV radiations.

TABLE XXXIV. INACTIVATION OF $, INDICA ON SURFACESIN A FIELD AlltRLOIm

NUWMMJM MY j. WAýDICA COLONIES

SURFACE Expo-ure Time5 Minutes 10 Minutes 15 1inutoe

Control UV Control UV Control UV

Plywood 12 0 7 0 3 0Glass TNTC 1 TNTC 0 TNTC 0Rubber TNTC 0 TNTC 0 33 0Canvas TNTC 0 TNTC 0 TNTC 0

c. Decontamination of Personnel Wearing Protective FieldClothing

In each of these tests two persons wearing protective fieldclothing and assault-type gas masks were exposed to a heavy cloud of S.indics organisms for a period of time in a closed room. The aerosol wasgeeated by three DeVilbiss No. 40 nebulisers which were placed in theroom. For the first test, the persons remained in the room for a periodof 15 minutes, and for the second test the exposure time was 30 minutes.

2153

After the artificial contamination, the test proceeded as fol-lowis Control surface samples were taken at seven locations on the suitand mask of each individual. One individual entered and walked about inthe UV look with the lamps on, while the other individual ('the control) re-mained outside in the shade. After selected intervals of exposure, thetest individual left the lock, and samples weri taken from seven locationson the suit and mask of each individual. The test individual then re-enter-ed the UV lock and the process was repeated. The sampling locations were:Top of hood, right arm, left arm, right leg, left leg, chest, and back.The surface samples.were streaked onto Difcots Tryptose Agar plates, theplates incubated for 48 hours at room temperature and colonies of !. indioscounted.

Tables XXXV and XXXVI show the efficiency of the UV radiationin inactivating the bacteria present on the protective clothing and masksof the test individual. All of the areas sampled were those exposed tothe UV radiation. No swabs were taken of protettive areas such as underthe arms, as no germicidal action would be expGted in these areas.

An interesting observation was made during these tests. Numer-ous organisms (mostly spore forming bacteria and yeasts) were present onthe surfaces of the protective clothing assault maskes tnd in theoair inthe lock, These were recovered in significant number on the control sur-face and air samples. It was observedthat as each test proceeded thenumbes ).' these contaminants on the recovery plates became less. Thesamples taken during the last sampling period were sterile and no growthof the contaminants was noted.

These tests conducted on an UV barrier at the entrance to afield dressing room show the germicidal barrier to be efficient in inacti-vating test organisms on exposed surfaces, on protective clothing and inthe air.

2. Laboratory Air Look Number 1

lc Three 30-watt UV lamps were installed on the ceiling in an airlook 6feet long, 3* feet wide and 10 feet high (Figure 39). Movement ofair between the rooms separated by this air lock was controlled duringtesting by means of exhaust fansp although in practice the room of greaterinfectious hazard is kept at a negative pressure.

A meter employing a WL-775 Tantalum photocell and calibrated forresponse at wave length 2537A was used to determine the radiant intensitiesof energy throughout the air lock. All measurements were taken on a hori-zontal plane, and tho radiation measured represented energy received fromabove. With the exception of one reading, all areas received at least 30microwatts per square centimeter (Table XXXVII).

154

TABLE XXXV. DECONTAMINATION OF PERSONNEL IN A FIELD AIR LOCK,ONE TO FIVE MINUTESI EXPOSURI/

NUMBER OF S. INDICA COLONIES

SWAB POSITION Test Individual Control IndividualExposure Time to UV Exposure Time in Shade

1 min 2 min 5min 1, min 2 min 5 min

Top of hood 1 0 0 TNTC TNTC TNTCRight arm 3 0 0 TNTC TNTC TNTCLeft arm 2 0 0 TNTC TNTC TNTCRight leg 2 0 0 TNTC TNTC TNTCLeft leg 4 0 0 TNTC TNTC TNTCChest 10 2 0 TNTC TNTC TNTCBack 4 1 1 TNTC TNTC TNTC

a. Individuals were exposed to the aerosol for 15 minutes.

TABLE XXXVI. DECONTA2INATION OF PERSONNEL IN AFIELD AIR LOCK,FIVE TO ThNTY MINUTES' EXPOSUREPI

N-M•BER OF S. INDICA COLONIES

Test Individual Control IndividualSWAB POSITION Exposure Time to UV E j ure Time in Shade

5 10 15 20 5 -10 15 20min min min min min min min mi

Top of hood: 0 0 0 0 TNTC TNTC TNTC TNTCRight anm 1 0 0 0 TNTC TNTC TNTC TNTCLeft anm 0 0 0 0 TNTC TNTC TNTC TNTCRight leg 2 0 0 0 TNTC TNTC TNTC TNTCLeft leg 0 0 0 0 TNTC TNTC TNTC TNTCChest 16 0 0 0 TNTC TNTC TNTC TNTCBack 9 0 0 0 TNTC TNTC TNTC TNTC

a. Individuals were exposed to the aerosol for 30 minutes, S

155

0.

qI

bm3

100

156

TABLE XXXVII. UV INTENSITIES IN AN 8' x x 10' AIR LOCKEQUIPPED WITHITHREE 30-WATT LAMPS

MICROWATTS PER SQUARE CENTIHETER

DISTANCE FROM FLOOR LEVEL, Distance in Feet from Northinches to South End

1 2 3 4 3 2 1

8 10 38 43 44 41 40 3324 33 43 44 49 50 48 4640 52 56 ý57 59 59 59 5460 81 81 80 75 75 74 8590 (30 inches below ceiling) 157 118 115 147 112 110 144

Bacteriological tests were conducted with the doors open and closed,A4erosols of S. indica were pýoduced outside the air lock on the upwindside, and saples•were taken outside the air lock on the dmwnwind side.The bacterial aerosol concentration was controlled by nebulizing a culturethat had been diluted to the desired concentration. Generation of the aero-sol continued throughout each test. The results show at least a 99-per centreduction of the bacterial aerosol in every case (Table XXXVIII).

In one case complete removal of the aerosol was accomplished. Theefficiency of the UV air lock under the stated test conditions was of ahigh order. __

In test four, the direction of the flow of air was reversed and thedoors of the lock were closed. Reverse movement of air was effected byoperating the two wall exhaust units located on the clean side of the look.The aerosol in this case was generated in an adjacent roome. The door lead-ing from this room to the rest of the building wasr tt this time, open.Even though there wasaa slight negative pressure in the main hallway at thetime of the test, large numbers of the test organisms were pulled throughthe lock into the clean area. However, operating the UV lamps under theseconditions resulted in a 99 per cent removal of the test organism.

3. Laboratory Air Lock Number 2

Three tests were conducted to determini the bactericidal effective-ness of an UV air lock seven feet long installed in the hallway separatingtwo buildings. A small glass window was removed from one of the doors onone side of the lock to allow the movement of air from the first buildingthrough the lock and into the other building at the rate of approximatelytwo linear feet per second.

157

Ln Moris

*r44M

bOi

N N~

I1Ij

158

Radiation in the lock was supplied by two Slimline lamps. Theseunits were mounted horizontally on the side walls of the look 12 inches 0below the ceiling, and each lamp was equipped with a reflector.

Using a meter with a WL-775 phototube, intensity measurements weretaken in the lock. Readings were made at measured distances from the endsof the lock and from the floor level (Table XXXIX). Low concentrations ofUV radiation were at the floor lovel and in tho corners of the lock at upperlevels. Because of the reflector system high intensity UV radiation wasdirected across the upper part of the chamber with lesser amounts of energyreaching the floor and corners of the room. S. indics culture was dilutedin physiological saline and nebulized on the positive pressure side of theair lock with a DeVilbiss number 40 glass nebulizer. The diluted culturewas dispersed at the rate of approximately 0.7 milliliter per minute. Forthe three tests conducted, three different dilutions of the S. indica wereused.,

TABLE XXXIX. UV INTENSITIES IN AIR LOCK NUMBER 2 -

DISTANCE FROM FLOOR, INTENSITIES IN MICROWATTS PER SQUARE CENTIMETERfeet East End Middle West End

Throuhj Center of Air Lock

1 13.6 26.6 7.43 8.0 .18.0 6,45 2.0 3.6 2.07 2.0 2.0 2.0

.Side of Air Lock

1 2.0 4.0 3.3 2.0 3.0 2.05 2.0 49.2 6.07 14.8 1418 4.0

Noteg Measuremants were made on a horizontal plane of radiation receivedfrom above. Intensities at the 3- to 5-feet level of side radiationwere on the order of 100 to 150 microwatts per square centimeter.

0

159

Nebulization of the test organism was continued at a constant rate* during each experiment. Liquid impinger air samples were taken on the posi-

tive pressure side of the lock to establish the aerosol concentration. Airsamples were taken with two sieve-type samplers on the low pressure side ofthe air lock. One sampler was placed at a distance of two feet in front ofeach door, and two feet above the floor level. The samplers containedplates of corn steep molasses agar. The rate of sampling was one cubic footof air per minute, and the duration of each sample was five minutes. Eachtest was divided into three parts as follows:

(a) Samples taken on the negative pressure side of the air lockbefore nebulization started (control samples).

(b) Samples taken on the negative pfressure side of the air lookduring the first five minutes of nebulization. UV lamps on.

(c) Samples taken on the negative pressure side of the air lookduring the second five minutes of nebulisation. UV lamps off.

The results obtained from the three tests are sunmarized in TableXL. A high reduction of organisms was obtained under the stated test con-ditions. The over-all average reduction of viable S. indica cells was 97per cent. Aerosol concentr,~atLons ranging from 33 t; 3Af rganiums percubic foot were used.

TABLE XL. RESULTS OF BACTERIOLOGICAL TESTS IN AN UV AIR LOCK

TOTAL NUMBER OF S. INDICA COLONIES RECOVEREDTEST CONDITION FROM TWO SIEVE" SMP= IN FINE MINUTES

Test I Test 2 Test 3

Control 0 0 0UV on 0 12 123UV off 108 554 v 19405/Cloud cone at

nebulizing position, 33 280 3883org per cu ft

Percentage reduction 100 98 94of cloud with UV on

a. This figure was obtained by calculating the percentage of the generatedcloud whic6h passed through the lock during the first two tests when theUV was off, The actual number of colonies on the sampler plates weretoo numerous to gount.

The over-all average per cent reduction for the three tests was 97.

16U

4. Laboratory Air Lock Number 3

Tests were conducted to determine the bactericidal effectiveness ofan UV lock 24 feet long, seven feet wide, and ten feet high. There werethree doors leading into the air lock, and three bare 30-watt hot cathodegermicidal lamps were installed in the ceiling.

Studies wore made, using smoke, to determine the rate and directionof movement of air through the lock. 'The direction of air movement was to.ward the more contaminated building. The rate of movement waz: slow, esti-mated to be one-half foot per second. There was a considerable degree ofturbulence within the lock, and smoke entering one end of the look was wellmixed by the time it reached the outlet end.

New, clean lamps were installed -n the three ceiling fixtures andintensity measurements wore made as shown in Table XLI (A). Readings werealso made of the radiant energy flux directly below the center lamp whileall lamps were burning. These results are also shown in Table XLI (B).

TABLE XLI. UV INTENSITIESA/ IN AIR LOCK NUMBER 3

A.DISTANCE FROM EAST DISTANCE ABOVE FLOOR LEVEL

END OF AIR LOCK 8 inches 3 feet •5 feet

0 8.4 5.18 5083 feet 19.9 19.2 45.16 feet 13.2 19.2 29.29 feet 18.9 9.2 8.0

12 feet 20.5 41.6 81.8"15 feet 14.4 11.5 15.418 feet 23.0 23.1 19.221 feet 11.8 28.5 72.0

Averages 16.3 19.8 34.5

13. DISTANCE ABOVEFLOOR LEVEL M-CRONATT$-PER SQ CHL

8 inches 23.42 feet 31.24 feet 49.25 feet 71.16 feet 112.0

Average 57,4

a. Microwatts per square centimeter.

161

The bacteriological tests were conducted in the usual mannereS. indica culture was nebulized in the doorway on the upwind side and thesieovo r samplers were operated in the roam on the downwind side. Controlair samples taken before nebulization started were negative. The resultsare shown in Table XLII.

TABLE XLII. RESULTS OF BACTERIOLOGICAL TESTS IN AN UV AIR LOCK

NUMBU OF S. INDICA COLONIES RECOVERED FROM

TEST CONDITION TWO S2V(1MERS IN FIVE MINUTES

Test 1 Test 2

Control 0 0UV on 0 2UV off 303 600 approx.UV on 9 3UV off 146 600 approx.Cloud concen-

tration, orga 160 100per cu ft

Over-all per centefficiehcy Os 00

In spite of the low UV intensities presentp,excellent lethal effectson the air-borne S. indica were-obtained. The UV air look was 98 to 99 percent effective in-inlactvating the test organisms. These results indicatethe importance of air velocity and air lock site. Both larger exposureareas and slower rates of air movement increase the exposure time of air-borne orgmarnim paasin-g through the lock,,-

Our experience with a varieto of similarly radiated air looks hasshown that fewp if any, air-borne vegetative bacteria or bacteriophageparticles will penetrate such a barrier if air velocities of about twofeet per second or below are involved and if the number of UY l1Wap at-tached to the ceiling provide a floor intensity of 20 to 30 microwatts persquare centimeter.

C. DOOR BARRIERS

In the absence of an air lock, an effective barrier can be made bySproviding a radiation screen across a doorway. A design we recommend for

162

this purpose uses five 17-watt cold cathode UV lamps with aluminum reflec-tors placed in a wood or metal channel built around the doorway (Figure 40). WThe channel is placed so that the door opens away from the barrier. Inthis manner a screen of high-intensity ultraviolet radiation is projectedacross the doorway.

Tests on an UV door barrier are presented on the following pages. Theexperimental methods wore essentially the same as those used in testing UVair locks. The door leading from the main hallway of a laboratory buildinginto a clean waiting room was equipped with an UV barrier consisting of five30-watt, 36-inch, hot cathode germicidal lamps. Thu air system in the hall-way was such that a negative pressure was present. Before beginning thetests, all lamps were carefully cleaned with ethyl alcohol.

Intensity measurements were taken within the UV barrier using a meterwith a W"L-7W' phototube. All readings were expressed in tome of microwattaper square centimeter. Table XLIII shows the results obtained from thesereadings. It is apparent that the intensities obtained in the barrier arequite high. Because lamps of this typo drop in UV output the first fewhours of operation, a more accurate estimate of the intensities to be en-countered may be obtained by reducing each value in Table XLIII by 10 percent. S. indica cultAwref sdiluted in physiological #aline and nebulized witha DeVil~is-e -nmer 40 glass nebulizer. Three dilutions of the S. indicaculture were used with a dispersal rate of approximately 0.5 millierper minute. Nebulization was continued at a constant rate during each ex-periment. Liquid impingor air samples wore taken to establish the initialaerosol concentration. Four tests were made with ,this door barrier.

TABLE XLIII. UV INTENSITIES IN MICROWATTS PER SQ CM ATTHE VERTICAL CENTER OF A DOOR BARRIER

FEAR ABOVE RADIATION RADIATIONr RADIATION TOTAL ENERGYTHil FLOOR FROM ABOVE FROM LEFT FROM RIGHT FLUX RECEIVED

8 166 142 144 4525 96 126 126 3484 66 113 .10 289S52 126 144 3222 36 96 120 252

28 40 30 98

S

168

Channel UV Fixture

UV Lamp

Warning

switch &"It flux at ,Indloetor Light

this point otI •IGeeOt 250 mw/

40m l

Figure 40. INy Lep Xnstallation at Door'way.

164

Test It An aerosol containing 40 organisms per cubic, foot was generatedin tle-Enfrance waiting room which was on the positive pressure side of the WUV door barrier. All doors remained closed during the test, and air sampleswere taken with two sieve samplers on the negative pressure side (main hall-way). Control air samples taken before the aerosol was generated were nega.,tive. The results are shown belowi

Number of S. indica Colonies RecoveredTest Conditions from Two 3iove~o•plers in 5 Minutes

control 0UV on 0UV off 27

The efficiency of the UV barrier was 100 per cent under these conditions.

Test 2v S. indica aerosol was generated on the negative pressure-:;ideof the door blrrTi'o a7nd the sieve samplers were located on the positivepressure side (small waiting room). The aerosol concentration was 10,800cells per cubic foot. All doors were closed during this test. The cloudwas generatedcontinuously for 20 minutes and two sets of air samples weretaken with the UV lamps on and two sets with the UV lamps off.

No S. indict organisms were collected on the positive pressure side ofthe UV Sarnrr This test shows that air-borne organisms in the main hall-way of the building will not escape into the waiting room when the conditionsare static (no movement of personnel or opening of doors).

Test 3g By using smoke it was found that the pumping action of a dooron the positive side of the door barrier momentarily upset the air balancein the building and drew smoke through the door barrier to the positive pros-sure side from the negative pressure area. This test was designed to deter-mine the efficiency of the UV radiation in preventing "back flow" of air-borne organisms when the outside door is opened.

An aerosol containing 214,000 particles per cubic foot was generated inthe main hallway. Air samples were taken in the waiting room, Throughoutthe test, at intervals of one-half minute, the outside door was opened.Control air samples taken before the aerosol was generated were negative.The results are shown belowr

Number of S. indica ColoniesTest Conditions Recovered frem T'wo Seve Samplers

in 5 Hinutes

Control • 0UV on (outside door' 1

opened 10 times)UV off' (outside door 291

opened 10 times)

165

The efficiency of the UV door barrier under these conditions was greaterthan 99 per cent.

Test 4t This test was designed to determine the efficiency of the UVdoor =arr er in preventing the escape of air-borne organisms from withinthe building when entrances and exits were made through the barrier door.At intervals of two and one-half minutes, a person made an entrance into andan exit from the main hallway through the barrier door. The generated cloudin the main hallway contained 214,000 organisms per cubic foot. Sampleswere taken in the waiting room. Control air samples taken before the aero-sol was generated were negative. The results obtained are shown belowt

Number of S. indica ColoniesTest Conditions Recovered friom YWSeove Samplers

in 5 Minutes

Control 0UV on (two entrances

and two exits) 67UV off (two entrances

and two exits) Sao

The efficiency of the UV door barrier under these test conditions was92.5 per cent.

Sumnary Table XLII presenta,lthe test conditionstand the respecti•v of-Ificiencies of the UV door barrier. The efficienciei of the UV door barrierunder the stated test conditions were very high. In most cases the cloud'concentrations were many timeb that which would be expected under normalconditions. Efficiencies varying from 92.5 per cent to 100 per cent wereobtalned under the, stated test conditions.

Curtains made of strips of plastic sheeting provide a convenient method"-of limiting stray radiation from a door barrier. Figure 41 shows a curtain

made of clear vinyl plastic installed in front of a door barrier.

D. ULTRAVIOLET ANIMAL CAGE RACKS

Surveys of laboratory acquired infections (278), studies on cross-in-fections among animals (194,237 238) and institutional outbreaks with in-fectious agents (48,141,205t253), have demonstrated the need for adequateseparation of infectious animals from laboratory workers and from otheranimals. Although the best isolation is obtained by the use of closedcages equipped with filters and artificially ventilated (59,155,300), in. many laboratories the expense of this equipment is prohibitive.

1461

lin

S SC§ 4d~

-4J

Figure 41. Vinyl Plastic Curtain. (FD Neg C-3700)

168

The use of germicidal radiation to prevent cross-infection of animalshas been reported by Lurie (195) who irradiated an area between wire cageshousing rabbits with tuberculosis and cages housing normal rabbits, thuspreventing the 71 per cent cross-infection rate which occurred without theuse of UV. UV radiations have also been used by Henle et al (188) to pro-tect laboratory animals from air-borne infection. We hVe--oevised and eval-uated a method of attaching UV limps and fixtures to animal cage racks whichprovides a radiation barrier across the open top of solid-aided animal cagesand thereby prevents the escape of a portion of the air-borne organisms fromwithin the cage.*

1. Materials and Methods

UV cage racks The UV cage rack, shown in Figure 42, is 5 feet high,4 feet wide, and 22 inches deep with solid metal shelves. Two 15-watt,16-inch hot cathode UV lamps with fixtures are needed for each $helf. Eachfixture is equipped with a reflector' of Altak (Aluminum Company of America)aluminum to direct the radiation in a band across the top of the cages.The fixtures are attached to the upright angle-iron corners at 'the side ofthe cage rack and are adjustable to any height above the shelf.

Only cages of equal height can be used on any one shelf. Cagesmust have solid sides to protect the animals from radiation. The positionof the UV fixtures is adjusted so that the bottom edge of the lamps is levelwith the top edge of the cages. If large, open-top cages are used (esg.,a cage large enough to occupy one entire shelf) it may be necessary to placethe bottom edge of the lamps slightly below the level of the top of the cageto prevent excess radiation from entering the cage. This is not necessarywhen screen wire or hardware cloth cage tops are used because thes6`matori-als reduce the entrance of radiant enery. The underside of each shelfshould be painted with a lowoflectingt nonglose paint to reduce reflect-ance of radiation into the cagels.

Test bacteria used were Serratia indica and spores of Bacillussubtilis var. nixer. For the foIr'er1-F3ur4= roth cultures grown at 270Cwere used. Spore preparations were obtained by heat shocking, for 10 min-utes at 800Ct the growth harvested from heavily inoculated tryptose agarplates or broth incubated for 5 days at 370C.

Recovery of test organisms from the air was accomplished by meansof sieve air samplers operated at the rate of one cubic foot per minute,and liquid impingers operated at 0.5 cubic foot per minute. The platingmedium used in all tests was corn steep agar, adjusted to pH 7.0 to 7.5before sterilisation. Aerosols of the test organisms were produced with aDeVilbiss No. 40 nebuliser or a Chicago-type atomiser (260). Stainlesssteel animal cagesp 9 inches x 10 inches x 18 inches, without tops or withone-fourth-inch wire-mesh tops were used on the cage racks.

109

S2

170

Operating efficiencies of all UV lamps used in the tests werecheocked by means of a SH-600 ultraviolet meters Intensity readings atvarious positions on the rack weri taken with a Luckiesh-Taylor germicidalmotor or with SW-200 ultraviolet motor and expressed in terms of microwattsper square centimeter. To standardise the UV intensity each lamp was"seasoned" by burning for 100 hours before uses Before each experimentcareful measurements were made of the radiation present above the cages.Typical intensities in microwatti per square centimeter are shown in Figure43. The energy flux, or intensity recorded by the meter from three direc-tions, was at least 250 microwatts per square centimeter. This figure hasbeen used as a "yardstick" to assure that UV cage racks are operating cor-rectly.

Preliminary experiments with artificially produced aerosols ofSo indica were conducted in the absence of cage liter, aninal hair, andlebFr.Empty animal cages, without tops, were placed onYUV cage racksand aerosols were produced in such a manner that when air samples were takenwith the UV lamps on and then off a comparison could be made of the ratio ofbacteria inactivated.

Further experiments utilized secondary aerosols produced by organ-isms naturally liberated from the hair of guinea pigs exposed to primaryaerosols of test bacteria. Four guinea pigs were exposed bodily to aerosolsof S. indica or B. subtilis spores for five minutes in a sealed cabinet.Thebac er a percuboc foot of air, as determined by liq~id impinger samplers,averaged 3 x 107 per cubic foot for So indisa and 5 x 10 per cubic foot forB. subtilis spores. Immediately after exposure, each animal was transferredTn a sterile closed cage to the UV cage rack. Two cages, each with a singleguinea pig, were placed on the top shelf and two on the second shelf. Hesh-wire tops were then substituted for the closed tops and sieve air samplerswere operated at the 9 positions shown in Figure 44. When the effect of DVradiation was to be tested, the lamps were turned on 30 minites before thecages were placed on the racks. Five cubic feet of air were sampled at eachsampling station at the following intervasls (a) just before placing cageson the rack, in tha absence of UV (this was a control for the presence oftest organisms in the room); (b) immediately after placing cages on the rack$(c) 80 minutes after exposure of the guinea pigs to the aerosoll (d) 60 min-utes after exposure; and (e) 240 minutes after exposure. Each test and con-trol was repeated at least seven times for each test organism.

2. Results

a. Experiment I - Artificially Produced Aerosols

An empty open-top cage was placed in the center of a shelf on aUV cage rack. S. indicg culture was nebulized in the bottom of the cageand four sieve air "amp ore were operated one foot from the cage duringalternate on and off periods of the UV lampso. The results obtained in fivereplicate experiments are given in Table XLV. The UV radiations preventedthe escape of 97 to 100 per cent of the organitms which, in the absence ofUV, were recovered by the four air samplers,

171

READINGS ON FRONT EDGE OF CAGES

TOTAL FLUi lox $35it 555

READINGS AT CENTER OF CAGES

TOTAL FLUX 1111553 e

Figure 48. Typical VV Intensities Obtained on an Aniasi lackSIhelf Equipped with Two Cages and Two UV fixtures.Arrows indicate the direction of the radiation.Readings are given in microwatte per sq on,

1720

I

06'

173

TABLE XLV. PASSAGE OF ARTIFICIALLY PRODUCED AEROSOL4 OFS. INDICA FROM A CAGE ON AN UV RACK TO THE ROOK-A

TOTAL COLONIES COLLECTED IN 5 HINUTESk/ PER CENT REDUCTIONUVOff UV On BY UV

Test 1 U200 0 100Test 2 1267 34 97

a. Control air samples taken immediately prior to nebulization were nega-tive for S, indics.

b. Average o? f ve"xperiments.

The second test war concerned with crose-oontamination betweencages. 'S indica was nebulized in the bottom of the center cap of threeopen cages on the center shelf of a UV cage rack while air sample. werebeing taken by means of sieve saplere in the bottom of the other capeoNebulisation war continuous throughout the test, The results are shown inTable XLY. Cross-contamination between cages did not occur when the lampswere on; no colonies grow oeA the sample plate@ in three duplicate tests.Air saople. taken when the lamps were off always showed S. indie coloniesto. numerous to counto.

TABLE XLVI. PASSAGE OF ARTIFICIALLY PRODUCED AERQOLS OFS. INDICA FROM CAGE TO CAGE ON:AN UV RACKS'

COLONIES COLLECTED IN CAGES PER CENT REDUCTIONUV Off UV On BY UV

Test 1 TNTCh/ 0 100Test 2 TNTC 0 100Test 3 TNTC 0 100

a. Control.&Lr samples taken immediately prior to nobulisation were nega-tive for So indict.

b. Too numerrous o count.

174

b. Experiment II - Secondary Aerosols

Tables XLVII and XLVIII and Figure 45 summarize results obtainedwith secondary aerosols. Guinea pigs whose hair was contaminated with S.indica or with Be subtilis spores released a considerable number of organ-T=nsnto the room =n T absence of UV an average of 479 colonies ofS. indiea and lp824 colonies of B, mubtilis per 5 cubic feet of air wan ob-faime"; the 9 samplers immediaiEely after placing the exposed animals onthe cage racks Air-borne organisms were not confined to the immediate areaof the cage rack because recoveries were obtained by the samplers locatedfive and six feet from the racks Control air samples taken immediatelyprior to the beginning of each test were negative for S. indies and Besubtilis.

TABLE XLVII. EFFECT OF UV RADIATION ON AIR-BORI' S. INDICARELEASED FROM THE HAIR OF GUINEA PIGS

SAMPLING TIME AFTER NUMBER OF COLONIES COLLECTEDS/ PER CENIT RE3VCTIONSTART OF TEST UV Off UV On BY UVtb

0-5 minutes 479 13.0 97.830-35 minutes 150 1.4 991.60-65 minutes 104 0.8 99.2240-245 minutes 84 0.3 90.6

a. Average of 8 experiments.b. Obtained by comparing the recoveries with the UV on and off at each

sampling time.

TABLE XLVIII. EFFECT OF UV RADIATION ON AIR-BORNE B. SUBTILISSPORES RELEASED FROM THE HAIR OF GUINEA PIOS

SAMPLING TIME AFTER NUMBER OF COLONIES COLLECTEDM/ PER CENT R OCTIONSTART OF TEST UV Off UV On BY UVRIf

0-5 minutes 1824 1668 68.80-35 minutes 1442 864 40o160-65 minutes 1168 626 4604240-245 minutes 674 350 48.1

(UV turned off)250-255 minutes --- n 614 "'

a. Average of 7 experiments.b. Obtained by comparing the recoveries with the UV on and off at each

sampling time.

175

100

#A

4750z0

a L N IATIR SSRES UX OFF

~50

0

S25 U m f

050 100 150 200 250

MINUTES AFTER EXPOSURE

Figure 45. Recovery of AirwDorne S, indica, Celle and Be subtilesSpores Released from HIrir-Wrour Asrosoli-I-oseG Guea,Pigs Housed in Solid-Sided, Screened-Top Capes Placed onan UV Cale lack.

17e

In the absence of the UV barriert air-borne spores were stillpresent in large numbers and the vegetative organimss to a lesser degree, 0240 minutes after exposure of the animals to the aerosol. The strikingeffect of the UV barrier on the vegetative organisms (Table XLVII) isshown by almost complete elimination of recoverable bacteria. By compari-sent although there was a considerable reduction of air-borne sporest alarge amount still survived the radiation treatment (Table XLVII)o Thebarrier effect, howevert is clearly shown by the sharp rime in recoverablespores obtained five minutes after the UV was turned off (Figure 45),

The reductions in recovery of air-borne S. indiea and B, subtilisspores from aerosol-exposed guinea pigs brought abouE by s use o? t|s"Y'"lamps on the cap rack are wmnarised in Table XLIX, With S, indica, reduc-tions ranged from 97 to 99 per cent. With B. lUbt4lis spors--he-i reductionsranged from 9 to 48 per cent.

TABLE XLIX. EFFECTIVENESS OF THE UV CAGE RACK IN REDUCING THE NUMBEROF S. INDICA CELLS AND B. SUBTILIS SPORES RELEASED FROM WITHIN

THE CAGE-FR•W!XTFOF GUINEA PIGS

INTERVAL BETWEEN AEROSOL EXPOSURE OF PER CENT REDUCTIONANIMAL AND AIR SAMPLING, minutes S. indioo B. subtilis Spores

0 97 930 99 4000 g9 46

240 99 48

Average Reduction 98.5 86.6

3. Discussion

These studies demonstrate the usefulness of germicidal radiation asa barrier over animal cages to reduce the entrance and exit of air-borneorganisms. Although there was only a slight difference in the amounts ofvegetative organisms sad spores in the aerosols to which the gpinea pigswere exposed, the secondary aerosols produced with spores were considerablygreater, This probably can be accounted for by the greater survival abilityof the spore. The fact that the UV barrier had a reduced effect on thespores is not surprising because Duggar and Hollaender (71) observed B.subtilis spores to be several times as resistant to UV as the vegetatIvecello of the same strain. This was confirmed by Herdik (140) with

177

13. mxeoaterium and by Rentechler et al (247) with B. subtilisp and by experi-monte by the authors described on page 168. The Inoldont enoeru at 2587Anecessary to inhibit colony formation in 90 per cent of the organisms forB. subtilis spores is sixfold over the energy necessary to inhibit

oar. scOns (15).

The value of the UY cage rack has been demonstrated in our labora-tories over a period of approximately eight years. In animal rooms con-taining 10 to 20 UV cage racks, the radiation level in the room is suffi-cient to eliminate almost all air-borne and many surface organisms, Notrouble with animal epidemics has been observed and cross-infection be-tween cages has not been noted. Some stray radiation enters the cages andalthough these radiations have been found to inactivate S, indics on thesurface of agar plates, no deleterious effects of UY rad~atlon-aveo beennoted on the eyes or exposed skin of animals.

Animal workers must wear skin and eye protection when working inrooms with UV cage racks, In our laboratories ventilated personnel hoods(Snyder Hanufacturing Company Now Philadelphia, Ohio) are worn for skinand eye protection (Figure 465.

E. ULTRAVIOLET IN £NCUBATORS AND REFRIGERATORS

1. Effect of UV Radiation on Stored Cultures

In considering the applicability of germicidal UV radiation foruse in incubators, refrigerators, cabinetes and other enclosed spaces sev-oral phenomena must be investigated and any resulting limitations appliedin practical installations. The pertinent points for consideration are:

(a) Will cultures being usedt stored, or incubated under DVradiation be adversely affected because of penetration of the gormic.dalradiation, through the walls of the containing vesslle

(b) What detrimental effects may be caused by the ozoneproduced by UV lImps?

a. Preliminary Experiments

A series of preliminary- experiments were conducted in refrig-erators and incubators, One shelf in a walk-in type refrigerator room wasequipped with two overhead 30-watt, hot cathode lamps located 20 inchesabove the shelf. The purpose of the tests was to detect any detrimental -effects to glass enclosed cultures when stored under the radiations at 50Cor when inqubated under the radiations at 370 or 300C.

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178 (

F~igure 46. Vontiiatted Personnel Hood. (FD Neg C-3701)

179

A 5.5-cubic foot incubator was equipped with a 15-watt hotcathode UY lamp in its coiling. A similar incubator without the UV lampwas used for the control tests. Agar and broth cultures of S. indica andBrucolla abortus strain 19 were used as test organisms. Incrubat onwascarried osuton two shelves. The bottom shelf was located 17 inches fromthe radiation source and received an average UV intensity of 150 microwattsper square centimeter. The top shelf was eight inches below the UV lampand received an average of 250 microwatts per square centimeter.

Test organisms were inoculated onto the surface of agar platesor into flasks of brothl duplicate samples were incubated in the two in-cubators and the total numbers of organisms or colonies obtained were com-pared. Agar plates were first incubated agar side down. It was found thatcultures incubated undor those intensities of UV radiation showed lowernumbers of colonies or of total cells than the control cultures. The de-crease ranged from 10 to 90 per cent, the higher figure being obtained withcultures on the top shelf. Because ordinary laboratory glassware is opaqueto 2537A radiation, it was assumed that the reduction in cell yield was dueto penetration of the glass by the small percentage of longer waves in theorythemal range. The germicidal effectiveness of these radiations is lses(Table XII) than that of UY radiation in the 2537A range, but the long ex-posure time provides a sufficient dose to effect a noticeable killing. Acovered set of controls, which was included in the incubator with the UVlamp with each experiment, showed that very little or none of the lethalaction was due to the presence of ozone. When the UV intensities in theincubator imt reduced to 100 microwatts per square centimeter or lens verylittle inhibition of the two test strains was noted.

The average intensity of UV radiation falling upon the testshelf in the walk-in refrigerator room was 280 microwatts per square centi-meter, When broth cultures of S. indics and B. abortus strain 19 werestored-, at V°C under the lamps for por ods as londg"as days, no signifi-cant reduction in the number of viable cells was found. The control cul-tures were stored at the same temperature but not exposed to the radiation.

The above results are conflicting because an intensity of 250microwatts per square centimeter for 42 days in the refrigerator showed nodeleterious effects on stored test organisms, whereas in the incubatortests, 150 mLcrowatts per square centimeter for two or three days yieldedcounts 10 to 90 per cent below that of the control cultures, It has beenshown, however, that UV has a more deleterious effect on young growing cul.-tures than on old resting cells.

b. Quantitative Experiments

Further tests were made to determine quantitatively the inhibi-* tcOry effects of various amounts of germicidal energy on Petri dish cultures.

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160

The tests were conducted in an air-conditioned room containing a reiorou-lating air blower and sufficient natural ventilation to remove all, traos Sof ozone. S. indioa was used as the test organism. Inoculated agar plates(closed) wee T d and incubated on open shelves in the room where thetemperature (25 0 C) permitted good growth of the test organism in 24 hours.The intensity of the radiation falling on the dishes was varied by changingthe distances from the UV lamp to the shelf below. The Petri dishes wereincubated agar side up and agar side down.

An inoculum sufficient to give 30 to 300 colonies per Petriplate was spread evenly over the surface of a group of agar plates., Eachplate received the same inoculum. One-half of the inoculated plates werecontrols (shielded from the UV radiation). The remaining plates were in.cubated adjacent to the controls and exposed to UV radiation from above.The plates were placed so that each received the same amount of radiation.The Petri dishes were allowed to incubate under theme conditions for 18 to24 hours. The colonies were then counted and compared with the total numberof colonies appearing on the exposed and the nonexposed agar plates. Thetest was repeated a number of times to insure consistent and reproducibleresults. Four radiation intensity levels were used.

a. Plates Exposed Agar Side Up

It is a general practice to incubate agar plates with the agarside up (inoculated surtaoe•oward the bottom) to prevent excessive moistureoondensation on the agar surfaces. If plates incubating in this manner areirradiated from above U~ht Wives must penetrate both the Pyrex glass andthe agar before reaching the growing bacterial cell.

Fifteen to twenty milliliters of melted corn steep agar wereused in each Petri dish. The solidified agar was dark brown in color andtranslucent to white light. A total of 26,662 S. indics agar colonies werecounted. Of these, 13p325 colonies were countoH o =con -rol plates not ex-posed to UV radiation but exposed in the same room, and consequently to ayosono present. The remaining 13,337 colonies were counted on an equalnumber of plates exposed agar side up during incubation to four differentUV inoensities. The results of these tests and the intensities used areshown in Table L.

Intensities of UV as high as 400 microwatts per square centi-meter did not result in detectable inhibition. There was no noticeabledifference in the site or pipent in the S. indica colonies counted. Ap-parently, 2537A radiation at this 4ntensi:y =evl has no effect when di-rected toward the agar side of an incubating Petri dish.

S

TABLE L. GROWTH OF S. INDICA COLONIES ON AGAR SURFACES WHEN THEPETIT DISHES WERE IVUD AGAR SIDE UP TO UV RADIATION

UV INTENSITY NUMBER S. INDICA COLONIES COUNTED

microwatte per eq om Control Plates Exposed Plates Total

100 3104 3040 6144300 3504 3652 7156350 328 3858 se68400 3431 3292 6723

Over-all totals 13325, 13337 26662

d. Plates Elxposed Agar Side Down

When incubated agar plates are placed agar side down and ir-radiated from above, the agar colonies are inhibited according to the in-tensity of the radiation falling upon the glass surface. These tests wereperformed in exactly the same manner as the previous tests except that allplates were placed agar side down.

A total of 48,584 colonies were counted during the tests. Ofthese, 28,000 were counted on control plates not exposed to UV radiation.The remaining 20,684 colonies appeared on an equal number of plates thathad been incubated agar side down but exposed to four UV intensitiess Asshown in Table LI, a reduction of almost 70 per cent was obtained on theplates exposed to 400 microwatte per square centimeter 2587A radiationwhile at 100 microwatte per square centimeter the reduction was six per cent.In addition, colonies appearing on the agar surfaces tended to be smallerthan the control colonies and showed a pink instead of a red pipgent. Thiseffect was more marked as higher intensities were used. Thust if inoculatedagar plates are incubated agar side down and irradiated with 2587A radia-tion at intensities of 100 microwatts per square centimeter or more, inhibi-tion oi' bacterial growth will occur.

At first glance the results of these bacteriological testsseem to conflict with the data which show the inability of Pyrex and othertypes of glass to transmit 2537A UV, The bacteriological tests were con-ducted in such a way that inhibition by ozone was impossible. If PyrexPetri dishes do not transmit wave lengths of 2537AI how maynthe inhibitionof the exposed test cultures be expý.ained? The most logical explanation

* is that the reduction in count on the exposed Petri plates was a result ofpenetration of wave lengths other than 2537A. The germicidal UV lamp pro-duces 95 per cent of its radiation in the 2537A band, The remaining fiveper cent consists of longer and shorter radiation. Table X shows that the

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" leaps a it 0.22 per cent of the total energy in the 3022A band, 1.90 percent in the 8130A band, and 2.0 per cent in the 3650A band. A sheet ofPyrex glass three millimeters in thicimess (Table XII) will transmit 21, 47,and 89 per cent respectively of ihe light of these wave lengths. Also, theestimated relative germicidal effectiveness of 3650A is 0625 per cent, Withthe long exposures possible during incubationt it is likely that the detri-mental effects demonstrated in theme tests can be attributed to the actionof radiation longer than 2537Ad

TABLE LI. GROWTH OF S.' INDXCA COLONIES ON AGAR SURFACES WIHEN THE"" PETRI' DISHES hRWEIU')GAR SIE DOWN TO UVY RADIATION

NUMBER S. INDICA COLONIES COUNTED PER CENTUV INTENSITY, RDICTION

microwatts per sq on Control Exposed BY UVPlates Plates Total RADIATIONS

100 14193 13291 27464 6.35300 7170 4930 12000 31.24350, 3366 1320 4717 60077400 3249 1034 4283 66.17

Over-all totals 26000 20664 46564 26,13

That such a supposition is possible may be emphasised by con-ideridsg a theoretical example. If a certain culture is inactivated by

direct exposure to 2537A UY at an intensity of 100 microwatts per squarecentimeter for one mintan_.,hen 1.90 per cent of this radiation will be ofwave length 3l30A. •iupposo lha -wa liiigth 3130A is one per cent as effec-tive as 2537A. If th. culture is covered with a sheet of Pyrex glassp noneof the 2537A radiations will penetrate, and 47 per cent of the 3180A wavelengths will be transmitted. Therefore, the equivalent germicidal UT radia-tion reaching the culture would be 0.00893 miorowatts per square centimeterand, in 11 198 minutes or 166.6 hours, the covered culture would receive adosage of 1380A radiation equal in germicidal activity to the original direatexposure of 100 miorowatte of 2537A per square centimeter for one minute.Thus, althoigh Pyrex glass will not transmit light of wave length 25387A,penetration of the longer UV radiation for long periods of time mWy showdefinite germicidal action.

A'I

lea

se. Conclusions

The regular 15- or 17-watt UV lamps should not be used in non-walk-in type incubators and refrigerators. If a smaller size of lamp isused the intensity should be below 100 microwatts per square centimeter.

It is desirable to use UV lamps in walk-in type inoubators,refrigerators and hoodst but care must be taken that the lvmpe are in-stalled in such a manner that the maximum intensities reaching glass on-closed cultures is less than 100 microwatte per square centimeter. Bac-terial cultures should be kept at distances from VV lamps greater than thefollowings

(a) 15-inch, hot cathode lamps cultures to be kept at adistance of 18 inches or morel f

(b) 36-inoh, hot cathode lamps cultures to be kept at adistance of 36 inches or morel (Hot cathode limps are not designed to beused in refrigerators.)

(c) 34-inch, cold cathode lampt cultures to be kept at adistance of 24 inches.

2. Effects of VV Radiation in a Walk-In Incubator

Conditionsit'n walk-in incubators are generally favorable for thesurvival or growth of contaminating microorganisms. Since incubatorsusually are not ventilated, the microbial population may be quite high.When infectious cultures are incubated, escape of pathogens from brokenflasks or from flasks with missing stoppers may constitute a hasard topersons entering the incubator. Breakage or spillage on a shaking machineor from a culture aeration apparatus may be especially dangerous.

Evaluation studies were made of the effectiveness of UV radiationin reducing surface and air-borne microbial flora in a 9 x 8-foot walk-4nincubator room with an-6-foot ceiling., Triplicate samples of air and sur-faces in ,the room (303C)t were taken for six days under three separate con-ditions and examined for common bacteria and fungi. The conditions werest

(a) Control - no UV.

(b) Indirect UV - one 17-watt cold cathode UV lamp mountedeight inches below the ceiling in the center of the room and shielded toirradiate upwards.

(o) Indirect and direct UV - condition (b) plus one 17-watt*1lamp mounted 12 inches below the coiling and irradiating downward.

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indirect UY radiation of low intensity (due mostly to reflectance)was present on the upper shelves in the room, but no radiation reached thefloor. When both lamps were burning, 17 to 82 microwatts per square centi-meter of radiant energy vmr present on the shelvest and the exposed floorarea received approximately 13 microwatts per square centimeter (Figure 47).

During the six-day test for each condition, normal use of the in-cubator was continued. The bacteria and fungi recoverable from the air bysieve samplers and from the walls by moistened sterile swabs during thetest periods were reduced by 83 to 100 per cent as compared to the controls(Table LII). Indirect UV radiation reduced the number of microorganisms onthe floor only slightly. Direct radiation caused an 86.5 per cent reductionin floor bacteria on exposed surfaces, but the reduction in numbers of fungiwas not determined because of overgrowth by bacteria in the control samples.

TABLE LII. REDUCTION OF ORGANISMS BY CONTINUOUS UV RADIATIONIN AN INCUBATOR ROOM (800C)

PER CENT REDUCTION BY ULTRAVIOLU•T/

CONDITION TEOTED Indirect Ultraviolet Direct andIndirect ______ Indiectaltraiole

Bacteria Fungi Bacteria Fungi

Air-borne organisms 8361 4 7 91.8 84.7Organisms on the floor a-uar Womp 86.5 ..-. /Organisms on the walls 99.4 92.0 100 100

as Averaged from samples in triplicate taken on each of 6 days.b. Very little reduction.o. Reduction not determined.

Obviously, when UV is used the microbial population is reduced andthen remains rather oorntant. Equilibrium conditions were maintained alathough normal use of the incubator continued. When indirect UV was usedtall air samples were taken close to the floor where no radiation was present.Air circulation was therefore responsible for lower air counts in all partsof the incubator. Of course, no decontamination occurred on surfaces notexposed to radiation.

The reduction of fungi was about the same as foO' bacteriat in spiteof the fact that molds are considered to be 100 to 1,O00 times as resistantas bacteria (174). This parallelism suggests that the exposure times were W

sufficient to kill even the hardiest microorganisms, and, in reality, the-,limiting 'factor for destruction was the ability or inability of the radia-tion to reach the cells.

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43.3 1300•0-----> --V *• - •f 2 COLD CATHODE

34.6 - LAMPS

69.3 J- /

S!, .oo. , .__ __000 00216r.O0

4 7.6; /4 .0/ /87.0 * 34.6

26.6/ 4 3/3~ 34.61 \/ . ,26.026.0o .,o0I'73 17~3

__ ,.,.,13.o0 1,o __1 0.-

I FOOT

figure 47. UV Intensities in icrowatts Per Sq Cm in an Incubatorbomo. Two Cold Cathode Lam0• v. .OA rows indicate the direction of the radiations.Sketch represents a vertical section through thecenter of the roam.

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186

Besides constantly functioning to eliminate ordinary bacteria andmolds in walk-in incubatorst UV lamps should be capable of reducing oreliminating aerosols of infectious agents that might be suddenly producedin a room by an accident. Tests were carried out to evaluate the effective-ness of the UV lamps in the test room when large numbers of test organismswere suddenly released. Broth cultures of S. indica were nebulized in theincubator room under the same conditions of-OV exposure as in the previoustests. Sieve samplers were used to recover the test organisms. Four mil-liliters of a j. indic culture (2 x .O1 cells per ml) were nebulized andair samples taken at various time intervals, beginning at the start of neb.ulisation.

The results are shown in Table LIIIM During the control run (UVlasps off)t test organisms were present in the air one hour after nebulim-ing, but not after two, The use of the indirect UV lamp eliminated allrecoverable air*borne S. indica in les than ten minutes. Using both thedirect' and indirect UVtraiL Ton, a rapid kill of the organisms was ob-tained, as evidenced by the fact that no viable cells could be recoveredduring the first sampling period (zero minutes). The nebulizer was locatedin the center of the roomf about three feet from the floor.

UV radiation is not recommended for incubators if it is criticallyimportant to preserve the genetic or nutritional characteristics of themicroorganiasm in use. In other situations, however, the use of germicidalradiation can provide good protection in walk-in type refrigeratorc andincubators to control hamards created by the escape of infectious micro-organisms.

TABLE LIII. RECOVERY OF S. INDICA IN A WALK-IN INCUBRAATORi --DURING AND AFTER NEBUTIZITTrAND THlE EFFECT OF

UV RADIATION ON RECOVERY

NUMBER OF AIR-BORNE S. INDICA CELLS RECOVERED PER CU FT

TINE, minutes Condition

UV Off Indirect UV On Direct and Indirect UV On

0 60 60 010 0 020 0 0

,60 44.6 0 0120 0. 0 0' 0 9

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O FF. THE UV DECONTAMINATION CHAMBER

The UV decontamination chamber is a two door, rectangular shaped,stainless steel box, designed to be installed in the wall or door separat-ing contaminated areas from clean areas (Figures 48 and 49). The purposeof the chamber is to provide a mechanism by which small articles can betransferred from clean to potentially contaminated areas and by whichsheets of paper and similar small articles may be decontaminated and passedfrom contaminated to clean areas. The doorst which comprise the two endsof the box, have small eight glasses. The over-all dimensions are: height,38 incheos width,22 inches; and depth, 16 inches, Two 36-inch, 30-watt hotcathode UV lamps are mounted vertically on the inside of each door. Anactivating switch with blue indicator lightp is located on the outside ofeach door enabling operators to turn the lamps off or on fr&,seither side.The stall window can be used to see if all lamps are lit. '

The presence of the four UV lamps in the cabinet causes a considerablerise in temperature within the chamber. When the temperature of the out-side air is approximately 25°C, a temperature of 440C is reached withinthe chamber.,

High intensities of UV radiation are present throughout the chamberlfrom 500 to 1500 microwatts per square centimeter. The vertically mountedlamps extend almost the entire length of the chamber and consequently thereis very little shadowing when papers are placed on the horizontal shelvesoExcept for the small area where the sheets of paper rest upon the shelf,9the entire shoot is irradiated.

1. Effect of UV Radiation on Plastic Recording Discs

Plastic reoording discs are sometimes used in contaminated areasand after use, they are taken to the clean area. Voice transcriptionswere made on plastic discs which were then placed in the UV chamber for aperiod of 48 hours. The exposure caused the discs to change from a lightgrey to a dark green, No brittleness or stickiness was observed and theywere otherwise in perfect condition. On the playback machine, the clear-ness and volume of the voice was the same as on an unexposed transcription.

2. Decontamination of Plastic Recording Discs

Plastic recording discs were artifically contaminated with severalmillion cells of S, indics, exposed in the chamber for a short period oftime and subjectel to--s 'a to recover viable cells. No S. indics was re-covered after ten minutes exposure time in the UV chambei.

0

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I I

oll

,Figur-s 48. BJV Paper !)ocontamination Chamber, Closed. (FD) Neg 1•-6217)

ISO

Figure 49. UV Paper Decontamination Chamber, Opened'. (FD:Neg B-6216)

100

3, Effect of UV Radiation on Paper

Bond typing paper, notebook paper, and other types of paper avail-able in the laboratory were exposed to radiation in the UV chambers forperiods up to 24 hours, There was no effect other than a slight curlingof the edges of the paper. Prolonged exposures (one week to one month)produced yellowing of paper and brittleness but were not considered impor-tant because the time necessary to decontaminate usually does not exceedten minutes.

4. Decontamination of Paper

a, Experimental Tests

Tests were conducted using a smooth surface paper (bond typingpaper) and a relatively rough paper (scratch pad paper). Test strips were,sterilised and artificially contaminated with test organims. After expo-sure in the UV chamber, the strips were placed in a small quantity of brothand an attempt made to recover viable cells,

In the first test S, indica was used as the test organim. Thetest strips were contaminated By j!MTV wetting the surface with a brothculture of S. indica containing I x l0v cells per milliliter. Periods of80 to 90 milutesi""7 oexposure were required to eliminate all viable cells.

Next, a broth suspension of 3.B subtilis var. ,ntr spores wasused to inoculate test strips. When hoa@vil contaminatedibihis manner,irradiation in the chamber failed to inactivate all spores in reasonableperiods of time. Strips of smooth paper were sterile in 72 hours.

Further tests involved paper strips that had been contaminatedwith atomised S, indica cells. A total of 60 smooth paper strips and 60rough paper strips were exposed from 5 to 30 minutes in the UV chamber, Foreach type of paper, 10 strips each were exposed for 5, 10, 15, 20, 25, and30 minutes. Unexposed controls were covered and placed in the chamber toinsure that the observed effects were not due solely to the temperature,

All of the exposed smooth paper strips samples were sterile andall controls showed growth. All but one of the rough paper samples weresterile, and all controls were positive. The on* positive rough paperstrip was from a ten-minute exposure test and, since the five-minute expo-sures were sterilet this positive sample probably resulted from contamina-tion occurring after the exposure. The five-minute exposure period was suf-ficient to sterilize both types of paper contaminated with S. indica.

In the UV chamber, the contact area of the paper to the shelfis kept to a minimum by using smallp circular rods. During these testspattempts were made to recover viable S. indica cells from the place of con-tact on contaminated tost strips of pAper,"•"• viable cells could be recov-ered, It is logical however, to assume that this would be a function ofthe degree of contamination of the paper,

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b. Conclusions

(1) The UV chamber should not be used to treat papers contami-noted with epore-forming microorganisms.

(2) It' should not be used to treat papers known to be grosslyoontaminatedt e.go, contaminated with liquid cultures.

(8) The chamber may be used to treat papers potentially oor-taminated with vegetative microorganisme.

(4) Papers to be treated should be separated individually sothat all sides are exposed to the radiations.

(5) An exposure time of at least 10 minutes for each sheit ofpaper is reoomended.

(6) UV lamps should always be turned off before opening thecabinet.

(7) The loaps should be cleaned frequently and replaced whenthey deteriorate.

G. UV PASS-THRDUGH CHAMBER FOR SINGLE SHEETS OF PAPER

In infectious disasoe laboratories "contanii~ted" areas are sometimesphysically separated from adjoining clean areas such as offices librariesand conference rooms. In such instances it is desirable to, disinfect orsterilise papers used for recording data in the laboratory before they arpassed to the clean area. Although sterilisation can be effected by auto-claving or by treatment with ethylene oxide Sas (166), time or facilitiesmay make these methods impractical. A pass-thrbuh chambor utilising highintensity, radiations has been developed for disinfecting single sheets ofpaper. This chamber eliminates objections to the chamber previously tested.The apparatus has been tested using strips of paper contaminated with tourdifferent species of organisms.

1. Materials and Methods

Exterior and interior views of the chamber are shown in Figure 50and 51. The housing is fabAicated from sheet alumim and measures x5 x 5 inches. When a single sheet of paper 15 inches or less in width isinserted in the slot, it is caught by two synchronously revolving rollerswhich push the paper at. a controlled rate past four 15-watt UV laps.Each side of the sheet receives radiation from two Ilmps. Jhe rollers aredriven by a mall ten revolutions per minute electric motor which moves

* Holtser-Cabot Gear Head Motor, RVE 2505, Holtoor-Cabot Divisions,National Pneumatic Co., Inc., Boston, Massachusetts.

Shot)2

ps v 'p 5 e (I Neg 114364,F-igure 50 ýxero i

199

*the paper at the rate of one inch every 3.25 seconds. The paper as itpasses through the apparatus is subjeoted on each side to UV intensitiesvarying from 8tOO0 to approximately 268000 microwatts per square centimeter.The total UV radiation is about 7,500 microwatte-minutes per square centi-meter or 4,500,000 ergo per square centimeter.

The chamber is designed for installation in a wall or doorwayseparating an infectious unit from a clean section. To faoilitate mainte-nance, the front panel of the unit is hinged to permit removal of the in-side structure (Figure 51). ;A switch located on the front of the chamberoperates the motor and two of the UV lamps. The other two lamps burn con-tinuously to prevent the passage of air-borne mioroorganims. Laboratoriesin infectious disease units are often maintained under a reduced air pres-sure as compared to clean office, areas to prevent cross-contamination.When the chamber is installed between areas of unequal air pressure, it isnecessary to provide an air-tight catch box to receive the disinfectedsheets of paper. A suitable catch box of clear Plexiglas is shown in Figure52. The box has a bottom-opening door which utilises a magnetic fastener.The design described herein represents the most effective of several devel-oped and evaluated.

The effectiveness of the apparatus was tested by passing artificial-ly contaminated strips of white bond paper, 8 inches x li inches, throughthe machine and comparing the number of viable organisms remaining persquare inch of paper with the number before UV treatment. Test organisms

reL Baoillus subtilis var. nizer spores, Serratia maroescens, aecherichiacoli D/r and T-3 cooxphaget-7e|trips were contaminated winh speri sbyFexposing them in a rectangular plastic cabinet (2386) in which an aerosol ofbacterial spores was generated. Liquid cultures of the other organismewere spread evenly over the paper strips. Unirradiated inoculated stripsserved as controls. Organisms were washed from the strips by shaking in100 milliliters of sterile saline. Dilutions wore made and aliquots wereplated from the controli'; but the entire 100 milliliters of wash fluid fromthe irradiated strips wm cultured.

2. Results

The results are shown in Table LIV. The UV chamber was 100 per centeffective against S. marceseans and coliphage, and 99.07 per cent effectiveagainst bacterial spores,

To determine the possible effect of photoreactivation (158) oncells "killed" in the chambert experiments were included in which VY re-sistant So coli B/r cells on paper were treated with 25387A radiation addexposedTo 'reativating illumination in the visible or near-ultravioletrange. Without reactivating l.',ght, UV treatment in the apparatus reducedthe cell concentration from 19,000 to 0.55 cells per square inch of paper(Table LZV). When UV treated cells were washed from the paper and exposed

194

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I/I' PLASTIC

Figure 52. Receiving lox for W'V Paper Sterilimer.

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* for 50 minutes to illumination from daylight fluorescent leaps or fluores-cent "black light" lamps (maximum spectral peak at 360oA), no significantincrease in cell recovery was noted. The average kill as determined afterexposure to UV plus reactivating light was 99.996 per cent and after UValone 99.997 per cent. Using B/r calls exposed in Petri plates to radia-tion intensities lower than those obtained in the paper chamberp reactiva-tion of a portion of the irradiated cells was demonstrated.

Although it is evident that the UV chamber will not provide steri-lization of paper heavily contaminated with bacterial sparest it is be-lieved suitable for normal operations in infectious disease laboratories,It is possible the UY chamber would prove useful in other types of instal-lations, for exampleo for introducing sheots of paper into sterile fillingrooms and for the treatment of sheets of paper from contagious wards ofhospitals.

TABLE LIV. BACTERICIDAL EFFECTIVENESS OF AN UV PASS-THROUGH CHAMBER

CONTROL PAPER UV EXPOSED PAPERNumber Average Number Average INACTI-

of Number of of Number of VATIONTEST ORGANISM Paper Organims Paper Organisms OF TEST

Strips Recovered Strips Recovered ORGANISM,Tested Per Sq Exposed Per Sq PER CENT

Inch of Inch ofPaper Paper

Bacillus subtilisvar. n___r spores 20 8,300 40 0.72 99.97

Serrats, I5 i0marescons 5 41,00 15 0.0 100

T-3 coliphage 5 1,160tO00 15 0.0 100

Escherichia 19000 9 0.55

E /cherichi, 190000 26 0.605/ 99.996

a. Wash liquid or recovery plates exposed to reactivating light.

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H. UV CLOTHING DISCARD RACKS

All change rooms in infectious disease laboratories should be equippedwith a receptacle to hold discarded laboratory clothing. The containerusually is a large canvas laundry bag hold in a frame or rack. Sometimesa metal bin or a rectangular, push!.type laundry hamper is provided, When aquantity of discarded clothing has collected, it should be sterilized byautoclaving before laundering.

The use of these collection devices may present a safety hazardi Al-thouh each discarded garment may contain only a low order of contamination,the method of collection has a cumulative effect. Also the container it-self becomes contaminated. One contaminated article in a bag may contami-nate the rest of the clothing. Clothing known to be contaminated should beinmediately and separately treated... .-Infectious microorganisms in the dis-card container will be in a relatively dry form. When clothing is throwninto or removed from the container, aerosols of the agent may be produced.Certain microorganisms such as those causing Q feoer are notorious fortransmission via clothing. If the hamper has a large opening, the tendencyis to throw the discarded clothIng at the hamper. Some of this potentiallycontaminated clothing finds its mark, but much of it goes on the floor andis subsequently handled once again. The use of metal bins to receive dis'card clothing is not recomuended because this necessitates the removal ofthe potentially contaminated clothing to another container before auto-Gloving.

1. The Discard Rack

A clothing discard rack (Figure 53) was designed which utilises aprotective barrier of UV radiation to isolate discarded articles in a canvaslaundry bag. The unit consists essentially of two partst (a) a metallaundry bag holder, and (b) a shielded box containing two 15-watt, hotcathode UV lamps. Both parts are mounted on a wall. The bag holder ismounted at such a height that the bottom of the canvas bag is held severalinches off the fluor. Tho UV lamps are in an invertod aluminum tray mountedabove the bag holder. A curtain hangs from the lower edge of the UV box andextends down past the top edge of the laundry bag. In this manner, the UVradiation is confined, and most of the intensity is directed into the openbag.

a. Intensity Measurements

The UV box originally contained only one 15-watt UV tube. Anadditional tube was added because it was found that complete coverage of thebag opening was not obtained with one lamp. Intensity readings were takenof the UV radiation at the bag opening and at face level outside the unit.The average UV intensity at the opening (which is about eight inches belowthe lamps) taken on a horisontal plane was 653 miorowatte per square centi-motor. Measurements made at face level in the area surrounding the rackshowed no intensities greater than 0.5 microwatts per square centimeter.

197

O I

e . .. ! .AiI

ii

Figure 53. UV L~aundry Btag IHoldiLng Duloyd.€ (FI) Nog li-62I•LU)

198

I Al

Fl puvo 54 . 11V Clothing 1)1S.Card R~ack.(i'I0) INo1 H.-Or~' 31

1). Rusu~l ts of' Iot,,1

' 1o tost tli' i l H Ni\ 'I it( of' thilo barvhI1' iii j)2'IVUnti g the os-Cape of' alr-horno iw'gln I r IulIturcoi of' ý. honiIcit wore nobulized in-side tho laundry h)agr,1 ami 41N-t-txpo it i:~srnpoiw :voTlo on the out-s i'd or the bag. '1th, sampj'l-i i wi CIllolu'otud durlr IN FIvit-minute periods whenthe UA' l~amps wIL1,1u Oil Ahi, t h nr wh~i-t th, 1 ivipti wurti if'[F. Pour sieve samplersplaced around thu out j ii id Hill ha Ig wi-Pf opora'tm ti dImuilta~naou sly. Nebuli za-t ion or the test orfJm(I I milfl (IIO In i Iw'i Iuri mg thu i~il and off periods. The tioutwas ropoate I thrut f- Imi iril I hr I FF chionvy (if' this hmlpr'i or cal culated fromth j total, nUmbhe of' 0Foilon I , (ooilctof1, Nitnh 1'tio flumI Irou s to count'll platewits counted as 350 col onhi '. On this b asis (192,1 (lI IonbIls were collectedwhen the try l1amps woro nVP tindi- i colIonfii U5wor4, obt~nind when the lamps wereon.* Thus, an of'l'c incy o)f gi'uit tur thatn 99l.109 por ctint' wag obtained. Theactual concontration of" ~ Ii lil10 I Ott [(I l POj4) 1'iIAU(-d in thoso toost was approx-i'mately 200,000 coul IT i C1i11r71riot (ii' atir. T1hl, Is, (if' oourme far ina xce its of whAit m~t :in I gh1 1 x)i A i id u oin III o rd hIit ry c on (IIt Io(n .

a. Conclusionsi

Ihotio Oto~tn Il ir thint tho usk' of, it prutoct lye barrier of'11V radiation ovot, thit vinvii" IfA10" Ioundry n wI" 1 oh U~rI ntU tho oscape of almostall air-borno organ ismn4 Ppopi (otidrttliInittod clothing, Anothor version of theclothing discard rack IN s hown in0 Fi gure 194.

199

. 1. PORTABLE UV FLOODLIGHT

A portable UV floodlight has been constructed anid used in various waysin the infectious disease laboratories (Figure 55). The floodlight containssix, 15-watt, hot cathode UV lamps mounted in a reflector that can be ad-justed to direct the radiations to any desired position. The unit is mountedon wheels and can be used to help decontaminate areas in case of accidental,spills of infectious fluids. Intensity measurements of the radiation pro-duced by this apparatus are as follows: 1.5 feet - 650 miorowatts per sq cm,3 feet - 251 miorowatts per sq om, 6 feet - 61 hicrowatts per sq om of 2537Aradiation. Other intensities are shown in Fillure 6.,

J. SAFE-T-AIRE INIDSTRIAL STERILIZER

1. Design

The Safe-T-Aire Industrial Sterilizer (Hanovia Chemical ManufacturingCompany, Newark, New Jersey) is a mobilet high-pressure UV irradiator withself-contained generating plant and operating controls. The generating plantconsists of a transformer, a capacitor, and a cooling fan with a safety re-lay to break the circuit in the event of fan failure. The plant supplies1200 watts for a fused quartz mercury vapor Imp which is Vyoor jacketed toeliminate ozone. The opertting controls oonsils of a key operated powerswitch a 1 to 15-minute adjustable starting control and an automatictimer (15 minutes to 10 hours). These controls permit the operator to setthe unit for desired operating periods and still have adequate time to leavethe area before irradiation begins. Roller-bearing casters and a push-typehandle permit wheeling the sterilizer from place to place. The unit is sup-plied for operation at 115t, 220, or 440 volts.

2. Testing Methods

Bactericidal evaluation of the sterilizer was accomplished througha series of tests in which 15-milliliter quantities of Bacillus subtilisvar. nnig spore cultures (3 x I V ml) and 15-milliliter quantites ofSerra=& ndio cultures (5 x 10r ml) were nebulized in a closed room.Sieve &tr'sample* and surface samples were taken in the area at differenttime intervals during the period of irradiation. Control tests were run inwhich similar samples were taken without the sterilizer in operation. In-tensity readings were taken at various distances from the lmp and at vari-ous angles off the horizontal plane from the center of the lmp.(Figure 57).

3. Results

Table LV shows the results of a test in which aerosolized B. sub-tilis spores were exposed to the sterilizer. There was a significint"re-S -u-tion in the number of spores at all sampling stations, with the possibleexception of No. 7. The control test, during which the sterilizer was notin operation, showed TNTC colonies at all sampling stations, at all timeperiods.

Ii

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201

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202

TABLE LV. B. SUBTILIS SPORES RECOVERED AFTER DIFFERENTIXPMU"RIODS TO UV RADIATION

DISTANCE TIME PERIODS. hoursSAMPLING STATION FROM CENTER

OF BULB, feet 0 1 2 4

1. Floor I. TNTC 95 22 2102. Floor 3 TNTC 134 79 563. Door 9 TNTC 88 63 424. Left Wall 7 TNTC 33 63 985. Right Wall 5-3/4 TNTC 5 72 06, Exhaust Duct - Air Sample TNTC TNTC 21 2507. Shower Stall - Air Sample TNTC TNTC 220 TNTC8. Floor - Air Sample TNTC 66 276 999. Coiling - Air Sample TNTC 33 150 91

When So indica was used, ten minutes of irradiationwero sufficientto eliminate The 'Teorganism from all but one sampling station. TableLVI showv the results obtained ten minutes after nebulization, with thelamp on and with it off*.

TABLE LVI. S. INDICA CELLS RECOVERED AFTER TEN-MINUTE EXPOSURETO UV RADIATION

SAMPLING STATION DISTANCE FROM CENTER UV OFF UV ONOF LAMP,feet

1. Floor 1 32 . 02. Floor 3 s9 03. Door 9 62 04. Left Wall 7 181 05. Right Wall 5-3/4 18 08. Exhaust Duct - Air Sample TNTC 07, Shower Stall - Air Sample TNTC 08. Floor - Air Sample TNTC .9. Coiling - Air Sample TNTC 0

0O

203

4. Conclusions

The Safe-T-Aire Sterilizer can effectively decontaminate the airand exposed surfaces in a small room (1740 cubic feet) contaminated with avegetative organism and will greatly reduce contamination by spores.

K. ULTRAVIOLET RADIATION IN VENTILATED CABINETS

Ventilated cabinets used for laboratory manipulations with infectiousdisease organisms are often equipped with interior UV lamps (Figure 58).The radiation is usually supplied at the rate of approximately four wattsof UV loop output per cubic foot of cabine•t space, Thus, generous amountsof UV energy are present to provide quick and rapid inactivation of air-borne microorganims. Because most interior cabinet surfaces are smooth,continuous, and nonporousp good decontamination of exposed surfaces is as-sured. The utse of 2W53•Ai'aiation, therefore, $@ helpful in decontaminatingthe -interior of the cabinet. It muot be emphasized that UV treatment shouldnot substi•utut for other mean:s of cabinet decontamination (e.g., formaldehydeor betaapropLolactone) whi*oh assure complete sterility.

L. ULTRAVIOLET SHOE RACK

Shoes worn in the infectious disease laboratory are apt to harbor andspread pathogenic microorganisms. In many laboratories, shoos are left inthe change room and are not worn outside the laboratory. It is usuallyrecommended that the shoos be periodically daoon'aminated. UV lamps havebeen used in shoe racks as a sanitizing feature but not as a substitute fordecontamination with a gas such as ethylene oxide. A shoe rack is shown inFigure 59.

M. ULTRAVIOLET RADIATION FOR DIRECT IRRADIATION OF LABORATORY ROOMSAND IN THE TREATMENT OF MOVING AIR

The practical use, of UV radiation in the ceilings of laboratory roomsand in air ducts are discussed in this section and in section XI. Figure

60 shows lamps installed in the ceilings of laboratory rooms.

204

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206

XI. THE TREATMENT OF MOVING AIR WITH UV RADIATION

A. GENERAL OBSERVATIONS

Ultraviolet radiation can be employed for the treatment of air in air-conditioning or air-moving systems. However, certain limitations and prob-lems are involved which must be thoroughly understood. These limitationsmust be weighed against the advantages offered by UV radiation air treat-ment systems.

The most important consideration is the fact that it is difficult toemploy UV radiation to inactivate 100 per cent of the air-borne microorgan-isms in moving-air systems. For this reason the action should be termedsanitatmon:rather than sterilization. Treatment usually inv6lves the place-ment of UV lamps directly in air ducts or plenum chambers. Depending uponthe volume of air handled, the duct siste temperature, and other variables,a specific number of lamps are employed in a system to give a calculatedgermicidal action. Installations may be designed to give 80, 90, or even99 per cent kill of air-borne microorganisms per air passage. It is im-practical to design a large system that is 100 per cent effective againstall types of organisms.

Because UV air-treatment systems are not apt to produce sterile air,their usefulness in buildings where infectious materials are handled isrestricted. In particular, UV radiation should not be used in recirculat-ing systems where air exhausted from contaminated areas is drawn into acommon chamber and then redistributed. If levels of contamination differwithin areas, it is obvious that any system which is lose than 100 per centeffective would act as a mechanism for oross-oontamination. For reciroulat-ing air systems, UV treatment of the air should be used only when one roomor one general arma is involved. In this case continuous protection is pro-vided because air-borne organisms are constantly being removed.

For air handling systems of the one-passage type, air sanitation by UVradiation may be used to treat the incoming air or, in certain cases, fortreatment of exhaust air. If the exhaust air is to be treated, it must beascertained that the release of a certain number of organisms to the outsideatmosphere does not create a hazardous condition. The sanitation of theincoming air in infectious disease laboratories by UV radiation is oftendesirable. A properly designed installation should give an efficiency equalto or greater than that provided by most electrostatic or air scrubbing sys-tems,

UV air-tetatment systems have several characteristics which are notfound in air-filter systems. The installation of germicidal lamps in ductsor plenum chambers does not create a noticeable increased air resistance inthe system. Filters always create a resistance which must be compensatedfor by the use of fans or blowers with larger load capacities. UV lamps can

207

Susually be installed in an existing air-treatment system if adequate ductspace is available. The cost of an UV air-treatment system should be lessthan that of other systems.

The same problems and limitations inherent in all uses of germicidal UVradiation also apply to its use for sanitizing moving air. The intensity ofthe radiation and the exposure time must be adequate. Variations in theambient temperature effect the operation of the lamps and consequently thegermicidal action. Variations in relative humidity are, according to some,responsible for variations in the germicidal reaction. Provisions must bemade for periodic testing and cleaning of the UV lamps.

B. DESIGN CRITERIA

The Slimline high-intensity lamp is recomended for moving-air-treat-ment systems. Lamps should be operated at a current of 420 milliamperes.Air velocities affect the lamp wall temperatures which in turn determine,in partp the total UV output. Slimline lamps are designed to operate at aslightly elevated temperature in still air so that the cooling effect ofmoving air improves the efficiency of the lamps.

Consideration must be given to the exact location of the lamps. Ingeneral, lamps should be placed in the ducts or plenum where the air veloc-ity is lowest. If dust collectors or dust filters are used in the system,the lamps should always be placed after the filters. Lamps should be in-stalled so as to provide maximum irradiation of the air. This is usuallyaccomplished by placing the lamps at right angles to the flow of air. Anopening into the duct must be provided to facilitate cleaning and testingof lamps.

A review has been made of the design criteria furnished by several UVlamp manufacturers, Various methods of calculating the number of lampsrequired are given, and a variety of correction factors are furnished.For a comparison of these methodes the essential information furnished bythree manufacturers is outlined below.

1, Westinghouse Electric Corporation (315)

This company recomends that the average installation be designedfor a 90 per cent kill of'bacteria in the air. For special applications,such as in hospitals and pharmaceutical laboratories, the greatest degreeof bacterial reduction possible is desired (at least 98 per cent). A curve(Figure 61) is presented to calculate th. correction factor to be appliedto obtain any degree of inactivation up to 98 per cent after the number oflImps for 90 per cent kill ham been determined.

208

80 0

so \6050403 0 . . . . ..

, 20 -... . -,-

' -

1" 5

3 -

2---------------------

.5 I 1.5 2 2.5FACTOR

figure 61. Curve to Calculate Lap Requirements. To determine thenumber of laps for various percentage survival firstcalculate for 10-per cent survival (90 per cent kill)and multiply by factor.

6

209

Where possible, lamps should be placed so that the lamp is at rightangles to the flow of air and in an area where the air velocity is lowest.Lamps should be placed after filters thus decreasing the dust and increas-ing lamp effectiveness. Maximum utilization of the radiation can be ac-complished by painting inside duct walls with aluminum paint to increasereflectance. Lamps should be placed in a row, not loss than -our inchesapart. If more than one row is requirsd, the additional rows should be onfour-inoh centers with the lamps staggered.

The Slimline lamp is recommended. This lamp, including sockets,is approximately 36 inches long. Calculations are made on the basis thatone dimension of the duct is 36 inches, or a multiple of 36 inches. Eachinstallation should be equipped with a service door and inspection windowin the duct. The door should be equipped with an electrical circuit breakerto turn off the lamps automatically when the door is opened.

To calculate the lamp requirements for my given installation, thefollowing information is requiredt (a) width (W) and length (L) of the ir-radiation chamber (Height is the dimension parallel to the lamps and is

1 alwa:ye 36 inches or a multiple thereOof.), (b) volume of air handled (CFK),I:;(c) air velocity (LFH), and (d) temperature of air (OF).

The first step Ji to calculate the volume of air disinfected byone watt of UV (VDW). The duct width (W) and length (L) is usod in Figure62 to obtain this value. If the duct height is greater than 36 inches, andtwo or more banks of lamps in the same vertical plane are used, a correc-tion iaotor must be applied to the VDW value. The correction factor isfound in Figure 63 and has the net effset of lowering the number of lampsrequired.

The next step is to calculate the corrected lamp output (G36T6Slimline Sterilamp at 420 ma). Using the values of the minimum ambienttemperature in the duct and the air velocity, the UV output in watts, isfound in Figure 64o

Finally the numbor of lamps required is found by the followingformulat

Number of Slimline lamps required * Co dp¶1W x corrected lamp output

This method gives the number of lamps required for a 90 per centdestruction of bacteria. Higher rates of disinfection are obtained bymultiplying by the correction factors found in Figure 61.

210

3600. 520

ISO.00IG

900

0000- 000' s

0 .0 000 40060so0 o0DUTo IDop- NCE

Soir 62201sShvn .. W aus

2U

CURVE FOR TWO BANKS OF LAMPS

.80

.70

.60

.50 CURVE FOR THREE BANKS OF LAMPS -

0 20 40 60 60 100 120 140 16o 18o 200 220o240DUCT LENGTH (INCHES)

figure 63. Corneotion Curve for Two or Three Banks of Laps.

0l

212

18

Is -F--

I14

200 400 600 Bo0 1000AIR VELOCITY (FEET PER MINUTE)

Figure 64. UV Output as Affected by Tomperature and Air Flow.G36T6 Slisline Sterilemp at 420 ma.

S

213

2. General Electric Company (97, 98)

General Electric Company recoomends that lamps be placed lengthwiseon the duct walls on four- to five-inch centers and grouped in the centerhalf of the duct walls. The duct walls should be made of polished chromiumplate or aluminum. Arrangements must be made for cleaning the lamps. Hingedpanels on the sides or bottom of the duct should be providedl the lamps maybe mounted on these panels if necessary.

A theoretical 99 per cent disinfection of air is recomended andinstallation data are calculated on this basis. The total UV watts lUVm)required in nonreflective ducts for a theoretical 99 per cent disinfectionis calculated from the following formula:

UVW a ClPH

3 xd

where d - the lesser duct dimension in inches, provided it is not exceededby more than 50 per cent by the larger dimension. If the duct has onedimension which is two or more times as great as the other, the formula canbe used by subdividing the duct and air capacity so that the dimensions areas required.

The total UV watts required (UVW) is divided by the average outputof the type of lamps to be used to obtain the number of lamps required. Theconditi.ors specified are 807F, relative humidity of 60 per cent or below andnonreflective ducts. The following correction factors, if applicable, shouldbe applieds

Condition Increase the Number of Laps Used b?

Temperature of 500F 10%Temperature of 1000F 10%Temperature of 40QF 20%Temperature of 110OF 20%Temperature of 350F 30ORelative humidity of 70% 50%Relative humidity of 80% 605Relative humidity of 90% 75$

If the duct walls have a reflectance of 75 per cent a theoretical,99 per cent disinfection of air can be obtained with one-half the calcu-lated number of lamps. For nonreflective duct walls, a reduction of 90per cent can be obtained with one-half the number of lamps required for 99per cent disinfection.

0 Figure 65 is supplied by General Electric Company to assist incalculating duct lamp requirements.

214

604000

60,000

51000040,000

zeIL F ~ T 5.0000

R ~ ~ ~ ~ ~ ~ i 343 61 0 3 O07~'

.on. f .o. ....t.

21.5

3. Hanovia Chemical and Manufacturing Company (116)

Information supplied by the Hanovia Company states that "bacterio-logical tests in rooms have shown that each person in a room which containsa nvabor of persons must receive 500 cubic feet of complete air change ofpure air per minute if the air he breathem is to be maintained in a sani-tary condition.", The "lathe" is equivalent to one complete air change bypure air or a reduction of 63.2 per cent in the bacterial content of the 7'air in an unoccupied room. One lethe of disinfection results from uni•formradiation of wave length 2537A angstroms at an intensity of S$ x 10-6 watt-hour per square foot in a room in which the relative humidity is below 50per cent. It was therefore postulated that each person in a room needs500 ,cubic-foot lathes per minute or 30,000 cubic-foot lethes per hour andthat UV radiation may be used to provide equivalent sanitary ventilation.This basis is used to devise formulas for calculating lamp requirements.

For each installation the following data should be obtained.

V - volume of air duct, cubic feetC a volume of room, cubic feetN - maximum number of persons in roomR - radiation length factor, average distance between the

lamp centers and the nearest duct wallDuct dimensions, feetAir flow, cubic feet per hourRelative humidity, normally taken as 50 per cent

Stop 1:- Calculate the requirements of the room in terms oflethes per hour. Lathes per hour m

N x 30,000 cu ft lothes/hr/oersonC

Stop 2 - Calculate the maximum available lathes per hourthrough the duct. Maximum lathes per hour through the duct

air flow, ou ft per hour or

air flow, cu ft per hour x lathes per hourN x 30,000 ou ft per hour per person

Stop 3 - Calculate Id, the theoretical average intensity in

the duct in terms of watts per square foot.

Id a lethes per hour through duct x 35 x 10-6 watts per sq ft

Hanovia Company recommends that the energy value (35 x l0-6)be changed according to Figure 66 if higher humidities are present.

2.6

220

200

ISO-

140

1 20

S100- - - -

2

6r 0

40

20

0 F10 20 30 40 50O 60 TO0 so

,RELATIVE HUMIDITY0 %

Yipn 66. Variation of Radiation 2587A in Lathe For Hour withChealpo in Relative HunsLdity.

• m -p-

In1

217

Step 4 - Calculate Ed, the theoretical total flux in watts of2537A radiation.

Ed -Id V2/3

Step 5 - Calculate the number of lamps required

Number of lamps . Ed x*4LR

4 is the "efficiency factor for lamps in ducts"L is the lamp rating of lamp to be usedR is the radiation length factor obtained from

Figure 67

C. APPLICATIONS

The methods of application of radiation in air ducts have been takennearly verbatim from the literature of the various manufacturers, A com-parison of the calculations given in their literature shows that sometimesthere are differences in the amount of radiation required to accomplish agiven disinfection. Although it is questionable, Rentschler and Jamedi(142),reported that air-borne pathogenic bacteria could be inactivated with one-tenth the radiation necessary to inactivate the same bacteria on agar plates.These differences are probably due to the fact that each of the investigatorsused different types of bacterial air samplers, different ratas of air flow,humidities, microorganisns, and probably different methods of reasoning fortheir calculations. Some of those variations have been discussed by Nagy

c (218). It would appear that more tests would be necessary to standardizethis method of disinfecting air.

Unfortunately there are few adequate evaluations in ,the literature onthe sanitising efficiency of moving-air systems provided withUV lamps.However literature available from lamp manufacturers illustrate some of thesystems which have been used.

It has been pointed out (314) that UV lamps can be installed in smallair.-conditioning units to provide a reduction in air.borne contaminationequal to the reduction obtained in larger systems. Lamps were installed ina unit which supplied air to six operating rooms in a dental office. Eight17-watt tubes were mounted in the incoming air duct. Tests made before in-stallation showed that oross-infection of air-borne particles between dif-ferent rooms occurred. Later tests showed that the installation of UV radia-tion greatly reduced the incidence of cross-infection between rooms.

Tests of an air-conditioning system of an auditorium have been reportedby Rentschler and Nagy (245). The system was designed to circulate 5800cubic feet per minute of air. Different numbers of lamps were placed in a

* Cited in Hibben et ale

216

1.0

0.9 - -- - - - -

0.6 I.........0.--

0.4

0.3

0.2 ---

0.1

•0 I mhI L. I. .I i.L Im .In mi

2 4 6 a 10 12 14 16DISTANCE IN FEET FROM LAMP TO CEILING OR NEAREST SIDE OF DUCT

Figure 67. •ay Length Factors for Various Distances Between Lampsand Ceiling, or Between Lms and Nearest Duct Wall.

219

75 by 30 inch irradiation chamber and tests of efficiency were made usingW sprayed cultures of E. coli. Air samples were taken at various points

while the lamps were',f?''a'd again with the lamps on. The use of 40 coldcathode lamps gave an average reduction of air-borne E. coli of 99.5 percent, while 32 lamps gave a reduction of 98.2 per cenT. "Toschler drewthe conclusions that (a) there is no difference in the bactericidal effectof UV radiation over a range of relative humidity between 35 and 95 percent and no difference over the normal range of temperatures usually foundin air.conditioning systems, (b) curves can be prepared to estimate thenumber of lamps required for any particular systemp and (c) UV radiationhas the particular advantage that nothing is added or removed from the air.

Successful use of UV lamps in the air systems of several pharmaceuticalplants has been reported (202,314).

D. SAFETY REQUIPRXENTS FOR UV INSTALLATIONS

Host of the essential industrial safety considerations involved in UVinstallations for sanitizing moving air have been outlined by Dennington(62). The information listed below has been taken from his report.

1. Fire and Smoke HazardsQ,

Fire underwriters require that air ducts bo constructed, equipped,and maintained in such a manner that there is no chance of damage by fireand smoke originating within the duct. When ordinary electric lights aremounted in air ducts, they must be equipped with vapor proof covers becausetheotemperature of the heated filaments, in case of lamp breakage, cancause ignition of dust or other materials. The temperatures at the warmestpoints on UV lamps used in air-conditioning ducts (cold cathode or Slimlinelamps) are not high enough to be considered a fire hazard. With an ambientair temperature of 700F, the average temperature directly over the activedischarge portion of the cold cathode lamp is 122*F. At the warmest pointover the cold cathode lamp, directly over the electrode, the temperaturedoes not exceed 2140F.

In order to allow for the installation of UV lamps, paragraph 181of the Standards of the National Uoard of Fire Underwriters for the Instal-lation of Air Conditioning, Warm Air Heating, Air Cooling and VentilatingSystems, has been modified to read as followst;

"Electrical wiring and equipment shall, be installed in accord..ance with the National Electrical Code. Lamps within the enclosureof the conditioning system shall be enclosed in fixtures of themarine (vapor-tight) type, except that germicidal lamps of a typenot using filament and which operate at relatively low exposed sur-face temperatures, need not be so enclosed."

220

2. Wiring

In an UV installation, the only material which can be classified ascombustible is the insulation on the wires connecting the various limpro0qtacles. Current regulating transformers should be placed outside theduct. Insulated wires should be GTO-5 gas tube sign cable or the equivalent.Wires should be placed in enclosed raceways wherever possible as a protectionagainst abrasion.

3. Windows

Glass windows are usually provided for inspection purposes. Wiredglass is required for mechanical strength and resistance to shattering.Underwriters' regulations specify that no individual window shall exceed720 square inches in area. The glass must be "...supported by metal troughsor clips of not less than 24 U.S.G., one-half inch in width, overlapping theglass one-half inch and spaced not more than six inches along each edge ofthe glass nor closer than 1* inches from a corner. Windows must be fittedsubstantially airtight to prevent leakage of air from the duct. However,if gaskets are used, they must be of felt or synthetic material not affectedby osone.,,,"

4. Doors

Service doors must be provided to permit the testing and replacingof UV lups. It is usually necessary to provide interlocking switches onservice doors which will open the primary circuit supplying the transformers.This system is recommended to provide safety protection from high intensityUV radiation and from possible contact with high voltage wires. If inter-looking service door switches are used, an alternate method must also beprovided to allow for the testing of lamps, For this, the circuits may bearranged so that one or two transformers may be put into operation individ-ually.

5. Circuits and Lap Mountings.

Underwriterst regulations specify that, "Primary circuits shall beso arranged that no group of transformers on any one circuit shall requirein excess of 15 amperes. It is desirable to keep the number of transformersper circuit eight or less to permit greater flexibility in operating andtesting."

There may be instances where the dimension of the air duct is a fewinches shorter than the lamp to be installed. In this case, the lamps maypass through holes in the wall of the duct, and the electrode receptaclesmay be supported on brackets outside the duct, For this, a tight covermust be provided over the receptacles to prevent leakage. Transformersshould be enclosed singly or in groups in metal enclosures of material notless than No. 24 U,S,G. in thickness and mounted on the outside top or sideof the air duct.

221.

eE. EXPERIMENTS WITH UV RADIATION IN AIR-HANDLING SYST34S

1. Large-Volume Air System

An UV installation designed to treat the air in a recirculatingair-conditioning system in an infectious disease building has been tested.The system handles air from one large room and reciroulates and conditionsit in large ducts and plenum chambers which are housed in an adjoiningutility room. UV radiation was chosen as the best means of treating thisair because the design of' the system was such that the resistance affordedby bacterial filters would seriously reduce the capacity of the system.

a. Ultraviolet Installation

UV lamps were installed at the opening of the air return ductlocated on the ground level of the building. The duct opening at this pointmeasures approximately 128 by 102 inchoop or 90.66 square feet. After theinstallation of UV lamps and suitable dust filters, the average air flowthrough the duct return opening was 42,400 cubic feet per minute. SixtyUV, high-intensity Slimlino lamps were mounted in the duct opening. Thirtylamps were placed vertically in each of two banks (Figure 68). Each lampwas operatud at a current of 420 milliamperes. To prevent the radiationfrom creating a hazard 3n the adjacent working area, it was necessary toinstall metal dust filters around the lamps. Tests showed that the levelof radiation in the working area was thus reduced below the maximum allow-able concentration. The distance from each lamp to the dust filters wasabout 41 inches. In the other direction (into the duct), the radiationscould be effective over a distance of from 5 to 15 feet. Westinghouse datawere used as a guide for the design, which was made on the basis of anestimated 99 per cent reduction of air-borne microorganisms per unit of airpassing the lamps.

UV lamps, when new, produce abnormally high amounts of radiantenerg. Accordingly, the lamps were allowed to burn for approximately sixweeks before testing was begun. Intensity measurements were made of alllamps with an SM 600 UV meter. The average intensity per lamp at one meter

- was 98.6 microwatts per square centimeter, with a range of 85 to 117 micro-watts per square centimeter. All lamps were cleaned before each test.

b. Test Methods

The tests were conducted in the following manners Aýculture ofS. indica was sprayed continuously into the air in the large room (125,000oub =T7t)t approximately 15 feet from the duct intake opening, for aperiod of 40 minutos. The culture was sprayed at the rate of 20 to 25 mil-liliters per minute. Approximately one liter of culture was used for eachtest. Aerosol recovery samples wers taken with sieve air samplers fromsampler adapter lines installed in the air,,handling ducts onthe downstreamside of the UV lamps. Usually one sieve sampler was located in the largetest room several feet from the spray device. During the first 20 minutes

222

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223

* of each test the UV lamps were on and for the last half, samples were takenwith the lamps off. Control samples also were taken before each teat.Aerosol concentrations wore recorded as organisms per cubic foot of air.

c. Results

In Test 1 a 24-hour broth oulture of'S. indica was sprayed.The results are shown in Table LVII. All control-siT'iploes taken beforethe test wore negative for S. indica. Aerosol concentration# during theoff period averaged 49 orgaisua per cubic foot of air, No test organiasmwere recovered during the on period indicating a 100 per cent efficiencyat this aerosol concentration. During the teat, the dust filters were inplace.

TABLE LVII * RECOVERY OF S NIA AN AIR-CONDITIONING DUCT

NUHBER OF S. INDICA CELLS RECOVERED PER CUBIC FOOTTIME, minutes UV Lights On UV Lights OfT

Location A Location B Location A Looation

0-5 0 0 63.6 49005-10 0 0 50.0 40.6

10-15 0 0 49.0 400.15-20 0 0

a. Control air samples taken immediately prior to the test were noeatiefor S. indica.

b. Not Too =a.

In Toot 2 th•, procedures used were the smne as in Toot 1except that the dust filters woro removed during the test. Removal of thefilters allowed h'igher aerosol concentration to enter the air duct. A86-hour broth culture having a count of' 36 x 107 S, indios cells per milli-liter was sprayed.. The results are given in Tabl LVfI.7 The UV radiationagain was 100 per cent effective in inactivating the S, indios aorosolt al-though in this caasO the samples taken with the UV of? s Fcolonies toonumerous to count. The aerosol concentration was estimated to be approxi-mately 200 particles per cubic foot.

0

224

TABLE LVIII. RECOVERY OF S. INDICA IN AN AIR-CONDITIONING DUCT

NUMBER OF S. IDICA CELLS RECOVERED PER CUBIC FOOT

TIME, minutes UV Lights On UV Lights Off

Location A Location B Location A Location B

0-5 0 0 TNTC TNTC5-10 0 0 TNTC TNTC

10-15 0 0 TNTC TNTC15-20 0 0 TNTC TNTC

a. Control air samples taken immediately prior to the test were negativefor S. India&.

During this test, sample, also were taken at the point where thespray was generated, which was approximately 15 foet from the duot intakeopening. With the dust filters removed from the opening, the UV radiationemanating from the duct apparently was effective even in the area around thespray position. Air, samples taken at the spray position while the duct UVlights were off contained S. indica cells too numerous to count, Air samplestaken at the spray position wI•The duct UV lights were on contained onlyI to 10 S. Indias cells per cubic foot.

Sieve samplers also were used to ample the air In the adjoiningutility room during this test. During the 20 minutes when the lamps were onno test crganists were recoveredt but during the off period three out ofeight samples showed recovery of S. Lndica. This result indicated that theplastic coating on the ducts in tle UMY room was not aerosol-tight andthat the use of UV radiation prevented escape of test organisms into theutility room.

In Test 3 samples were taken at four locations in the air duct.Samplers were operated for only one minute each in order to obtain a count-able number of colonies on the agar plates. The dust filters were removedfor the test. One 1ter of S. indica broth culture (9 x 10 cells per ml)was sprayed during the 40-minute period. The results are shown in TableLIX. Excopt for one colony appearing on the ample taken at Station Dduring the third sample period# complete inactivation was obtained of aero-sols containing as many as 196 S. indioa cells per cubic foot.

0

225

TABLE LIX. RECOVERY OF S. INDICA I5 THE AIR-CONDITIONING DUCT

NUMBER OF S. INDICA CELLS RECOVERED PER CUBIC FOOT

SAMPLE NUMBER UV Lights On UV Li4hts OffStation Station

A B C D A B C D

1 0 0 0 0 25 187 41 282 0 0 0 0 12 90 22 125 0 0 0 1 11 113 32 19

0 0 0 0 15 64 42 185 0 0 0 0 12 187 99 546 0 0 0 0 17 168 8s SO7 0 0 0 0 25 I96 95 55

0 0 0 0 s0 ISO 81 88

a. Control air samples taken immediately prior to the test were negativefor S. indica.

d, Conclusions

From these tests it was concluded that the installation was100 per cent effective in inactivating air-borne S. indica in concentrationsas high as 196 cells per cubic toot when the air'syt•e•mwas handling ap-proximately 42,400 cubic feet per minute of air.

2. Room-Typ Air-Conditioning Units

In infectious disease laboratories room-type air-conditioningunits are seometimes used to provide local temperature control. Sincethese units often recycle the air, sanitation of such air may be requiredfor the safety of workers,

In the following experiments the utilization of UV lemps installedin a room air-conditioner was evaluated to determine whether there would bea resultant reduction in bacterial contamination of room air without exoes-sive radiation exposure of animals or laboratory workers (118).

a. Methods

The window-type room air-oonditioner (Model 7975D4) used was a3/4 HP unit of a standard oommeroial design manufactured by the UnitedStates Air Conditiuning Corporation, Minneapolis, Minnesota (Figure 69).

Dust Stop '

Air FilterFresh Air Inlet

Condensat Drain

Firm 69. Wind4w-IP.e l Air COmitlmsw.

227

It had air-circulating capacity of 310 cubic feet per minute, an exhau'stair capacity of 150 cubic feet per minute and a fresh air capacity of 60cubic feet per minute. For the tests the exhaust dampor was closed andthe 310 cubic feet per minute of air consisted of 30 cubic feet per minuteofoutside air and 280 cubic feet per minute of room air. In this type ofconditioner, condensate resulting from dehumidification of room air issprayed against hot condenser coils by a slinger ring on the condenser fanand disposed of in vapor form. However, the system was altered for testpurposes and the oondensate was collected and sampled for bacteria. Theunit was equipped with a "dust stop" to filter out large dust particlesfrom the return air. The conditioner was installed in a laboratory room10 by 12 by 9 ftet. The test room, air conditioner, and additional appa-ratus for testing the air conditioner are shown in Figure 70. Cultures ofS. indica were atomized into the room by a Chicago-type atomiser. A propel-er1 an mixed the aerosol with the room air.

Figure" 1 shows the air conditioner adapted for this study. Theduct was equipped to hold one or two UV lamps and painted aluminum to in-,crease reflectance. Supply air and UV-absorbing ducts were added for sam-pling purposes. The duct was coated with a zinc oxide oil-base paint formaxium absorption of 2537A radiation so that return air samplers placed inthis duct would not be affected by radiation from the UV lomps. Air samplersplaced in tho supply duct assured a sample of supply air only. Wet and drybulb thermometers located in the UV-absorbent duct recorded the relativehumidity and temperature of the room air returning to the air conditioner.

UV irradiation was supplied by G36TO-L Slimline lamps. The in-tensity of the lamps was measured in microwatts per square centimeter at onemeter by a Westinghouse S-e000 meter. The temperature and velocity of theair were measured because these factors affect UV lamp intensity. Velocityacross the lmps during intensity measurements was approximately ten feetper minute, but during all testo, the velocity in the duct was 200 feet perminute. The temperature varied from 70.50 to 75.5 0F. Defore my measure-ments were taken, the lamps were cleaned with an alcohol dampened cloth andallowed to operate for approximately 15 minutes to warm.

Air samples were collected with liquid impinger samplers in theabsorbent duct to determine the concentration of the test aerosol returningto the air conditioner. Samples of supply air were collected in the supplyduct with sieve-air samplers operated at the rate of one cubic foot perminute.

Penetration of air-borne organisms through the air conditionerwithout utilisation of UV lamps not sti Led in the first two tests. Thepenetrations were 35 per cent and 45 per cent, respectively, Partial re-moval of the test organism from the air strem was attributed to impinge-ment on the dust-stop filter and on internal surfaces of the air conditionerand duct work.

225

Figure 70. Air Conditioner Tht Roam.

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figure 70. U Air Conditioner To o.

" Not

Thwmmw Retn A

229

The procedure was identical for all experiments., Before eachtest series, the air conditioner was placed in operation and sufficienttime allowed to cool the room air. The intensity of 2537A radiation wasmeasured for each UV lamtp as previously described, The UV lamps wereturned on, and a control test was made before atomization. A 24-hour brothculture of S. indica diluted in water was then atomized continuously intothe test room S"ymaThicago-typo atomizer. Air sampling was initiated afterthe atomizer had been in operation for a minimum of 30 minutes. The propel-ler type room fan shown in Figure 70 assisted in mixing the air in the room.

Each test included (a) air samples collected by two sieveoamplers located in the supply duct, (b) air samples collected by two liquidimpingers placed in the UV-absorbent duct, (c) culture samples of the con-densate liquid, and (d) relative humidity and temperature measurements of theair returning to the air conditioner. Each test series consisted of a mini-mum of five tests.

b. Results

Table LX shows the results of two series of control tests'(whenultraviolet lamp. were not in use, and ten series of testewhen the airconditioner was equipped with (a) a single Slimline lamp and (b) two Slim-line lmps.

Test series I and 2 (Table LX) show the results of controltests when UV radiation was absent. The amounts of the bacterial aerosolwhich passed through the air conditioner in the absence of UV Imps were34.9 per cent and 45.0 per cent, respectively. Test or'ganims were recov-ered in the condensate in test series 1.

When one Slimline lmp was used, penetrations in the five seriesof tests (3 through 7) varied from 0,0426 per cent (series 5) to 0.0721 percent (series 6). The five series of tests were conducted on five differentdays but under essentially the some conditions. The intensity of theSlimline lmp ranged from 156 to 160 miorowatts per square centimeter atone motor. The average penetration of all test series was 0.0585 per cent.No test organisms were recovered in the condensate.

Table LX also shows the results of five series of tests (8through 12) when two lamps were installed in the system. The penetrationvaried from 0.0116 per cent in test series 11 to 0.0814 per cent in testseries 12, The average penetration was 0.0208 per cent. The combined in-tensity of the two Slimline lamps ranged from 314 to 326 microwatte persquare centimeter at one meter. Test organisms were collected in the con-densate in test series 9, 10v and 12.

280

TABLE LX. USE OF UV IRRADIATION IN A ROOM AIR CONDITIONESAFOR IRMOVAL OF BACTERIA

PER CENT PENETRATION OF TEST AVERAGE RECOVERY OFTEST SEIZES ORGANISMS (S. INDICA) THROUGH PER CENT S. INDICA IN

THE AIX CM 0MNER PENETRATION "COIhTI

No UV Lame/

185 402 45

Singls Slielino Uv L,-,1.

3 0.0534 -4 0.0559 0.05355 0.0428 -61 0.07217 0.0437

Two Slimline UV Lm, Q/

8 0.01309 0.0237 ÷

10 0.0241 0.0208 +11 0.0116 -12 0.0814

a. Control tests (penetration through air conditioner using no UV 1opes).b, Intensity range from 155 to 160 microwatto per sq c at one meter.a. Intensity range from 314 to 326 miorowatts per sq on at one meter.

Test ConditionsoVelooity of air across UV lamps - 200 ft per mnmietuin air - 280 oftFresh air - 30 oftSupply air - 810 oftRelative humidity variation - 42 to 51 per centConditioner return air temperatdre variation - 72.90 to 82,4F7

0

2,31

0. Conclusions,

These results show that a 8/4 HP recirculating air conditionerequipped with UV lamps operated at 420 milliamperes substantially reducedthe number of air-borne microorganisms in roou air by a faotor of 90,98per cent. This reduction was due almost entirely to the germicidal actionof UV radiation.

When equipped with UV lamps, the room air conditioner recirou-lates relatively clean air at constant temperatures and relative humiditiesand provides the room with purified air comparable to a system which utilises100 per cent fresh air. This system also is much more economical than onewhich requires complete make-up air.

8ý. Steriliastion of Air Flows of One to Ten Cubic Feet Per WinuteIEhaust air from forcibly-aerated bacterial cultures often contain

viable orlainss (Table LXI). Air from small air-tight chmbers used tostudy the characteristics of bacterial aerosols or used for respiratorychallenge of small animals likewise contains residual organisms, In bothinstances when the organisms are infectious for man, the exhaust air shouldbe sterilisod,

TABLE LXI, RECOVERY OF ORGANISMS FROM EXHAUST AIL;R FORCIBLYAERATED BROTH CULTURES OF S. INDICAI

RAT OfCOLONIE•/RATE OF I2RATION OF RCOVEREDIN CU FT SAmPLINGt PER LIQUID

PER MINUTE minutes IMPINGER

50 m* in 250 cc 0.46 5 4.0 x'1O4Erlenmeyer flask 0.46 5 4.2 x 104

100 ml in 00 occ 0.46 5.4 x 104

Erlenmeyer flask 0.46 5 4.6 x 104

200 ml in 1000 cc 0.46 5 4.0 x 104Erlenmeyer flask 0,46 5 36 x 104

a. 20 cc tryptose broth per impinger.b. The conaentration of the original S. indica cultures was approximately

8.3 x 10 organisms per milliliter -

282

Possible methods for treatment of such air are electrostatic pro-cipitatorst filtration, incinerationt and UV irradiation. Although eachmethod has certain advantages and disadvantageso sterilisation by UV seasemost practical. UV treatment of moving air is not usually considered capableof yielding sterile air becausep when large volumes of air are involved,the theoretical number of lmps required become so great that physicallocation is often impractical. For mall volu s of air under relativelylow flow rateop however, it would appear that a high degree of disinfectionmay be obtained if the proper mount of energy is employed for the propertime period. UTV irradiation offers advantages as follows:

a No resistance to air flow,b no significant generation of heattc relatively ineoxpqnsivep,d low operational costte suitable for small volumes of air,f light weightt andg1 easily moved from place to place.

Several UV sterilisers for mall volumes of air were constructedand tested prior to the development of the apparatus described here. Theseconsisted of one or two high intensity-UV lamps, sometimes in combinationwith high ozone producing lmps, inclosed in glass or aluminum tubes. Testsshowed that these models did not completely sterilise air oontaining bacteri-al spores, although all vegetative bacteria were killed. The apparatus de-scribed below storilisos air &I a flow of one cubic foot per minute when theair contains as much as I x 10" bacterial spores per cubic foot of air,

a. Description of the UV Air Sterilimer

The steriliser consists of four aluminum tubes. joined alternate-ly top to bottom to provide a continuous flow path for air (Figure 72).Each tube is 86 inches long and 1-8/8 inches in diameter and contains oneG86T6 UV lmp. The lsop are hold in the tubes by means of rubber stopperssealed in each end and are operated from an outside ballast supplying 420milliamperes current to each lmp.

The apparatus has a total volume of approximately 0.092 cubic'foot and weighs 20 pounds. It is designed for a flow rate of one cubicfoot per minute and a linear flow of approximately two feet per second, Atthis flow the exposure time of air-borne particles is 5452 seconds (1,86seconds per tube). Each UV lmp used produced an intensity of approximately116 microwatts per square centimeter on a flat surface one motor from thebar lmp and a total UI output of approximately 18 watts. In operation thetopoerature of the air in the steriliser is 116,00tF

0,

288

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284

b. Test Methods

Spores of Bacillus subtilis var. n were used as the majortoes organism. Bacteriale.rOoOlO were gener--atewith a Chicago-type glassnoebuli4er (260) and paosed through the steriliser. The exhaust air fromthe apparatus was sampled with the lops on and off. The off samples werecollected by passing the air through a small tube filled with sterile cot-ton. Collected spores were subsequently washed from the cotton and platedin the usual manner. The on samples were collected by sieve samplers orslit Samaplers (58). The concentration of spores entering the tube wasdetermined with cotton samplers.

Suspensions of approximately 1 x 108 spores per milliliter werenebulised at the rate of two to three milliliters per minute for two tofour hours continuously. Tests were fonducted using one, two, three# andfour lamps.

c, Results

Three separate experiments, representing over eight hours ofnlebulizing, in whifh the aerosol concentration entering the sterilimervaried from 9 x 10 to 5 x 100 spores per cubic foot showed that the use offour lamps inactivated all test organisms in the exhaust air (Table LXUI).Experiments in which fewer than four lamps were lighted in the apparatusshowed that complete sterility could also be obtained with three lapspwhile two lamps and one lmp gave penetrations of 0.000004 and 0.0002 percent, respectively, Additional tests at increased air flows of four andten cubic feet per minute showed that aerosois of Serratia indica could beinactivated by four lamps (Table LXII). -

The results of these studies show that the apparatus is an ef-ficient means of steriliting wmill volumes of highly contaminated air andthat the use of four Ilmps provides a generous safety factor. In practicalapplications several important maintenance coniderations must be kept inmind. Since visual inspection of a lighted UT lap is not an accuratemethod of estimati&XgUV output, no inspection windows were provided in the <-

apparatus. The outside temperature of each of the aluminum tubes will in-dicate whether the enclosed lamp is burning* Records should be kept of the-periods of use of the apparatus so that replacement lamps may be installedafter approximately 750 hours of use. In addition, the lamps should becleaned with alcohol after each 1000 hours of use. Small intensity moterspsuch as the Westinghouse- S-600 motor, may be used periodically to checkthe UV output. A lamp should be replaced when it tests, lses than 60 percent of its initial output (100-hour rating). Poealdehyde vapors may beused to sterilize the entire apparatus before removLng the lamps.

6)

285

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236

XII. *4AINTENANCE OF UV INSTALLATIONS

A, TESTING

Ultraviolet lamps sometimes continue to burn and emit a blue light evenafter the 263UA output has decreased beyond usefulness, This means thatvisual inspection of the lamps cannot be employed to judge UV output.Special UV intensity motors must be used* The most uoeful life of an UVlmp is usually during the time when the Imp is generating between 100 and00 per cent of its rated UV output. Therefore, Imps are generally discard-id when motor readings show that the UV output has fallen below 60 per centof the 100-hour value.

Routine testing of all UV lamps is an essential part o6 tnstallationmaintenance. Lmps should be tested at intervals which are determined bythe type of lampt the number of hours per month the lamp is in operation,and the frequency of starts. Normallyp lamps should be tested every threemonths except in special locations such as animal rooms and other installa-tions where hot cathode lamps are operated continuously. In general, it isadvisable to test all hot cathode lamps more frequently than the cold oath-ode because of their shorter life expectancy,

The Westinghouse M-600 meter is preferred for routine Imp testing.Before testing each Imp must be cleaned and allowed to warm up for fiveminutes. It is common practice to express the lmp intensity readings interms of microwatts per square centineter at a distance of one meter fromthe lamp, The intensity which represents 100 per cent output for each typeof lamp is known. An intensity reading of 40 per cent below this figureindioates that the lamp should be replaced. The use of a mimeographed form,Figure 7S8 is recommended for keeping records of the periodic intensitychecks*

B. CLEANING

Wave length 25U7A is not particularly penetrating. Dried films fromtap water or from disinfectant solutions, grease, oil, or dust on an UVImp will seriously reduce its output. All lamps should be cleaned routine-ly at two-week intervals, or more often if the lamps are located in an areawhich is abnormally dusty. Lamps and reflectors should be wiped with asoft cloth pad which has been moistened with alcohol without being removedfrom the fixtures. Lamps must be turned off while cleaning.

K)

387

INITALo NOe 0 Go Hil Mao

TYPEC" NFCT on10 - cat. USC/OAY

EULI OATR i OATE MW OATI 11W OAT- W

Figure~lll 78 VIsalto eod

C., DISPOSAL

VV lamps contain mercury vapor and small quantities of metallic morcurythereforso methods for disposal of' used and worn-out latpe shoul.d most thef'ollowing requiremontast

(a) Lampe should be broken in the open so that the-mercury vaporwill be quickly dissipasted.

(b) Liquid mercury from the Umop# should not be allowed to enter,th- building -ower system-

(c) The smem care and procedures should be used in the disposal ofUV lamps a are used ig the d.posal o stalndardo eluords.ent lmpsoC.DSOA

UV~~~~~~ ~6 lap oti"ecr ao n al uniiso ealcmruy

288

XIII. EFFECTS OF UV RADIATION ON EXPOSED PERSONNEL

A. EFECTS ON THE EYES AND SKIN

Numerous reports are available on the beneficial and detrimental effectsof UV radiation on the body (74,175,161). The effect the radiation willproduce is determined by such factors as the dosage of radiation, wavelength# the portion of the body exposed, and sensitivity of the individualat the time of irradiation. In the application of ultraviolet lamps thereis always a danger of an accidental over-exposure of the eyes and skin.

1. Effeate on the Eyes (Bl0pharoconjunctivitis)

An over-exposure of the eyes to UV radiation will result in a pain-ful irritation of the conjungtiva and eyelids. The latent period is fromthree to twelve hours depending upon the mount of radiation received; thegreater the exposure, the sooOner and more severe are the symptome. Thereis a very unpleasant foreign body sensation accompanied by lacrimation. Thesymptoms usually disappear ir/A a day or two.

a. Medical Effects 0

Ultraviolet radiation on the eye is absorbed successively by theoornea, the aqueous humor, the lensp and the vitreous humor, before reachingthe retinae The relative absorption in these various parts differs. It isgreatest in the l.onst next in the cornea, then in the vitreous humor, andleast in the aqueous humor, With an increase in age there is also an in-crease of absorption by the lons. The rode and cones are quite sensitive toUV radiation, as has been observed by those vho have had a lens removed.About the only effect of UV radiation on the\\retina that the normal eye candetect is an indirect one; UV radiation of wsie length 8O00A causes the eyemedia to fluoresce. The fluorescence producedWby the stimulating UY radial'tion is in the visible spectrsm; thus stimulation of the reti-na results (174).,

Wave lengths of lose than 2800A are more effective in producingoonjunctivitis of the eye than erythema of the skin. This is probably dueto the absence of the strongly absorbing horny layer on the conjunctiva.Experiments indicate that the wave lengths causing conjunctivitis are simi-lar to the absorption curve for nucleic said (174). The characteristiceffects on the human eye produced by prolonged exposure to artificial UVsources ares inflamation of the conjunctiva# cornea, and irisl photophobia;copious lacrimation. The cornea is hyperemio swollen, and covered with aslimy secretion (181).

0

289

b. Effect# on Nice

Several experiments hve" been reported pertaining to the effectsof UV radiation on the eyes of mice. Duschke et al. (40) carried out aseries of experiments observing histological saowul as microscopic effects.Using the corneal epithelium as the basis for the investigation, they foundthat mitotic activity of the cells was inhibited. Severe exposures led tonuclear fragmentation in the superficial Layers which eventually resultedin the death of the cells. Severe fragmentation is correlated with theclinically visible roughing and stippling of the corneal surface in photo-phthalmia. These changes are first observed two to three hours after ex-posure. A loss of cohesion between the epithelium and the stroma, occurredwith a sloughing off of the loosened cells and, in some cases, layers ofcells, in 6 to 46 hours after treatments

c. Effects on Guinea Pigs

An experiment was carried out in the authors' laboratories todetermine the gross effects of UV radiation on forty-two guinea pigs. Thepigs were placed one meter from an UV lamp smiting 45 microwatte per squarecentimeter of 2537A radiation at the distance of one meter. The time ofexposure was varied so as to determine the maximum amount 'of UV radiationthat could be tolerated by a guinea pig.

The first exposure was 10 minutes; then 15, 30p and 60 minutes.Thirty-,six animals received only a single UVexposure. Four-animals wereexposed in a series, four times 24 hours apart, and the other two animalswere exposed 40 times over a two month period, the minim~mi interval being24 hours. Following exposure the eyes and ears of each animal were care-fully examined at appropriate intervals for asustained period of time.An opthalmoscope was employed as necessary.

No ýsignificant effects were observed. Guinea pigs appear tosuffer no ismmediate effects from radiation doses& of 2537A which are morethan enough to cause blopharoconjunctivitis in the human eye. Furthermore,observations for asolong as ten maonths showed no obvious loss of eight or,other visual abnormalities.

d. Effects on Humans

The degree of cphthalmis is dependent upon the wae" length ofradiation as well as the doese. Short wave length radiation, such as 2587Apemitted by bactericidal lamps is mainly absorbed by the conjunctiva andcornea. Some radiation above 3000A is absorbed by the iris and lens aswell as the co njunctiva and comnea. The fact that nearly all of the bac-tericidal (2587A) radiation is absorbed by the immediate surface of the

* eye would explain why this radiation is more harmful, at a given dosage,than longer radiation that can penetrate through a greater volume of tissue,

240

Thus Masoher ot &1 (84) reported, that about four milliwatt-seconds per squarecentimeter orT'ft radiation will produce a keratitis while as much as 60milliwatt-seconds per square centimeter was neoessary for radiation at

O00A, Rooks (259) found, on self-investigation, that an exposure of three7' mi2lliwatt-asoonds per square centimeter of 2537A was suffioient to cause a

slight ophthalmia occurring 12 hours after exposure. It is, thureforet notsurprising that several authors (45,181,259))have emphasised the detrimental'offsets which can be caused by over-exposure to 2537A radiation, one re-ported case, resulted in a temporary partial blindness of the patient foreleven days. In a soon of recent literature no case of permanent blindnessdue to 2587A UV burns could be found, but there have been many cases of con-unotivitis of the eyes which were quite painful for several days. Kovacs175) reports the use of ultraviolet radiation in the treatment of eye dis-

eases.

S. Conclusions

An accidental over-exposure of the eye to 2587A UV radiation isa painful experience. Records of permanent damage to the eye by this radia-tion have not been found. To relieve pain Kovacs (175) suggests the use ofinfrared radiation applied to the closed eyelids. An ordinary incandescentbulb can be hold near the eyelids for 20 to 80 minutes. Another method torelieve pain is to bathe the eyes in warm, sterile boric said solution usingsterile cotton pads. This is followed by a drop of sweet oil into each eye.The irritation produced by germicidal laps disappears within a day or twolmuch more quickly than a corresponding degree of irritation produced bylonger wave length ultraviolet. There is apparently no permanent injury andno hypersensitivity to sunlight as sometimes results fron eye burns producedby high intensity quarts mercury arcsp carbon rarsp or welditi. arcs.

2. Effects on the Skin (Erythema)

a. General Radiation Effects,

Exposure of the skin to radiation between 2400A and 8200A willproduce an erythema which develops in one to eight hours depending upon theintensity of radiation, the type of radiation, and the sensitivity of thesubject. The orythemal offectiveness of different wave lengths is repro-duced in Figure 74 from the work of Coblents, et Ll (47),

The effects of UV radiation on the skin have been studied moreextensively than effects on the eye. Most experimental work has been doneon the formation of orythema. The primary effect is a reddening of theskin, which is due to a temporary increase of blood in the small vessels ofthe skin.

O,

34

46Iw

30- - - - - - - - - -

20-- -

0

WAVELENOTH (ANGhTROMO

Figure 74. IrythemaResponse cume,

242

A common biological unit of ultraviolet dosage is the miniwmperceptible erythema (KPZ) which is equal to approxLmately 20,000 microwatt-seconds per square centimeter of 2967A radiation equivalent. A MPE dis-appears in 24 hours. Greater exposure results in various degrees of infla-mation or even blistering and hemorrhage. Below is a chart of the degreesof erythem p•roduced by exposure to mid-summer noon-day suns

Relative Exposure Degree of Erythema

1 HuE2.5 Vivid, with moderate tan5 Painful "burn"10 Blistering

Erythema is followed by pigmentation (or tanning) of the skin,which is noticeable two to three days after irradiation. Tanning usuallydoes not occur when the erythema is due to 2587A radiation.

Radiation between 2800A and 3200A can cause many reactions inthe skin. Some of the radiation can penetrate down through the pricklecells down to the basal cells. About 26G000 miorowatt - seconds per squarecentimeter of radiation at 2967A, the peak of the erythemal curve, willproduce a minimum perceptible erythema. There will be a stimulation ofthe prickle cells to produce pigment and a thickening of the whole spider-mis. Large doses of radiatiun can cause blistering and metabolic disturb-ances in the entire body as a result of release of photodeoomposition prod-ucts into the blood stream, Ellinger (74) gives examples of increasedsensitivity to radiation as a result of application or ingestion of photo-sensitizing compounds. Both the bactericidal and the longer radiation canconvert some of the sterols to vitamin D. Kovacs (175) gives other thern.peutic uses of radiation.

The erythmal curve (Figure 74) shows the relative effectivenessof equal mounts of energy in different parts of the spectrum in producingerythema. Thus an exposure of several times the threshold value of solarradiation will produce more severe burns than a similar over-exposure to agermicidal lImp.

Table LXIII summarises information concerning the transmissionof UV through the different layers of the human skin.

Tanning or pigmentation is due to the migration of the pigmentalready present in the basal cells to the more superficial layers and tothe formation of new pigment. The tanning response curve follows theerythema curve in a general way. Migration of the pigment from the un-damaged basal cells into the injured cells of the outer epithelitl layer isdue to the tropic action of the chemical substance set free by the injuredcells (181). 0

WAVELENTHOA LYERLS OF SUZN

i , 243

WAVEo LENGme A Corneu Nalpighi Corium Suboutaneous

2000 0 0 0 02500 19 11 0 02800 15 9 0 03000 34 16 0 04000 80 57 1 05500 87 77 5 07500 78 65 21 1

10,000 71 865 17 014,000 44 26 9 0

Notes:

2000A - All UY absorbed by the corneum, No radiation reachesthe germinatium. Surface organims are killed, Sur-face layer of cells also may be destroyed.

2500A to 3000A - Oreatest absorption is in the stratum cornem. Someradiation reaches the corium, but none reaches thesubcutaneous layers. Erythema and pigient are pro-duced.

3000A to 4000A - Relatively large absorption in the stratum malpighi.There is pigment and tanning produced, but very littleerythemas.

4000A to 7500A - there is a minimum mount of absorption in the stratumcorneum, most of the radiation is absorbed in the corium.Pronounced radiation reaches the subcutaneous layers.Hyperemia is caused.

7500A to 14,OOOA - There is increased absorption in upper layers, de-creasing in lower areas.

* Adapted from Bachem and Reed in Koller (174).

244

One process which occurs in the skin (the conversion of certainsterols into the vitamins of the D groups) is imown to account for the Wbeneficial results of irradiation in the prevention and treatment of rickets.

UV irradiation forms or liberates active substances which areresponsible for the erythemal response and tanning. The autive substanceis probably a protein, or a simple derivative of the cells of the stratummalpighi (germinativum), an H-substance, a substance with some of the func-tions of histamine, if not histamine itself. It is in the form of a H col-loid, It is believed that the injury is caused by the denaturation andcoagulation of the proteins of the cells. Protein denaturation by UV radia-tion has been considered to be a fundamental effect which may lie at thebottom of more complex radiation changes (181).

Repeated irritation by UV rays between 2800A and 3200A (9) cancause chronic lesions which smy be precancerous. Malignancy of human skinmay result from excessive exposure, perhaps by increasing an already presentpredispositiont causing a tumor to appear earlier and to become malignant.Erythema and pipentation are both due to injury to the prickle cell layerof the epidermis, and the production of cancer may be the result of similarphotochemical changes,

If the cells of the basal layer of the skin receive an exces-sive quantity of radiant enersw, the two protective processes, cornificationand pipientation, become abnormally great, and a third degenerative processstarts. The developing neoplasm occurs in the place of greatest prolifera-tion, beginning in a wart-like hyperkerotosis (cornification, ga precancerouschange). A cancer develops from a precancerous lesion not only as a resultof a continuation of the initial insult but also as a result of any con-tinued trauma, Thus, UV radiation is thought only to play a role in theinitiation of the process (181).

b. Effects on Mice

Ricsh et &l (262) found that UV radiation appears to cause ham-ful effects in mice"qu-Ite independent of the processes that lead to tumorformation. With very high intensities of radiation the animalsAost weight,their physical condition was visibly poorer, they were less animated, andreproduction ceased.

These workers produced cancerous tumors in test mice, but thetime required was two and one-half months. No matter how great the dailydosage, this timelcould not be reduced. Neither the intensity of the energynor the length of the daily exposure altered the rate of tumor production.

In the precancerous period there were two phases: (a) the periodof exposure, and (b) the latent period. In general the length of the latentperiod was inversely proportional to the length of the period of exposure, s

245

* The existence of a latent period in the development of human cancer is wellknownt particularly in cancers due to radiums, roontgen, and UV radiation*The carcinogenic wave lengths were found to lie between 2900A and 3341A.Wave lengths below 2537A and above 3841A were found to be nonoaroinogenic.The carcinogenic wave lengths thus coinoided in part with those most potentin the production of erythema. Wave lengths of 2537A produced erythemawithout producing tumors.

Given over a three-month period, 69 to 64 x 107 ergs per squarecentimeter of effective radiation were adequate to form tumors. Onceinitiatedt the carcinogenic process proceeded without further exposure, aswas shown by suspending exposure on one group of animals each day over speriod of several weeks. In some cases several months lapsed between, the•end of the exposure period and the time the tumors appeared.

Blum (29) and Blum et al (31) studied the relationship betweendose and rate of tumor inductirn'briUV radiation. The time in which 50per cent tumor incidence (T50) occurs will not be reduced if the weeklydosage is increased to five days a week. Howeverp increasing the exposureto seven days. a week will decrease the induction time. It the weekly doseis given in one exposure, TSO is longer than for five or seven days-a-weekexposure. Intensity may be varied over a wide range with no significantchange in T50. At h,4. dosages a considerable number of cells are destroyed,thus affecting the induction time because it decreases the amount of tissuein which the tumor may develop.

Blum et al (30) in another study induced 100 per cent incidenceof tumors of the lairi"of mice by exposure to mercury arc radiation undercarefully controlled conditions. The production of tumors depends upon thequantity of radiant energy applied rather than upon the intensity of theradiation. There was a wide spread in the time of appearance of the first-tumors and of the time of appearance of the last tumors in each series,eJ.g 102 dens for the first tumor and 221 days for the last tumor. fiftyper cent incidfince was reached in 135 days with an exposure dose of approxi-mately 100 MPE's per,.days.

Photorecovery from the effects of UY radiation was demonstratedby Rieck and Carlson (250) in 1955. Their work was probably the firstexample of photoreactivation in mammels. Mice were exposed for 35 to 40minutes a dayt 5 days a week for 45 days. The wave longlhs of UV radiation"were 2000A to 3130A. The highest dose used was 1.6 x 100 ergs per squarecentimeter of radiant energy. Criteria for the detection of effects worst(a) the difference in the death rate of animals kept in darkness as com-,pared to animals exposed to visible illumination between each exposure, and(b) the damage done to the ears of the animals. The results showed thatthere was about a 35 per cent difference in the death rate, Thirty per cent

*of the mice kept in the dark survived and about 65 per cent of the mice keptin the light survived. The ears of the animals kept in the dark receivedmuch more damage than the ones kept in the light.

246

c. Effects of 2537A

Radiation from a bactericidal lmp, mainly 2587Ap is absorbedby the horny layer and outemost cells of the malpighian layer and neverreaohes the basal cell layer. The horny layer is the protecting screen forthe living epidermal cells. Approximately 30,000 microwatt-seoonds per.q..a-.. oa•ameter of 2837A radiation will produce a minimal perceptibleerythen,m Greater dosages of 2537A radiation will increase the erythems,followed by the loss of most of the outer layer of the skin. Blisteringand hemorrhage of the skin does not occur. Very little or no pipentationis observed* Laurens (181) states, based on the work of Rusch et &I (262)tthat "radiant energy of 2537A produces erythema but no tumors nis"ter howlarge the deos.,"

The Council of Physical Medicine of the American Medical Associa-tion (6) has established a maximum allowable level for 2537A radiation. 'Forpersons exposed seven hours dailyp the UW intensity falling on the face andhands is limited to 0.5 microwatts per square centimeter of 2587A radiationor a total daily dose of 12,600 microwatt-seconds per square centimeter.This is well under the exposure necessary to produce an NPB on an averageuntanned exposed skin. The established maximum allowable radiation levelfor constant exposure has been set at 0,1 microwatt per square centimeteror a total daily dose of •640 microwatt-seconds por square centimeter, TableLXIV, taken from Buttolph*(151), gives extrapolated values of permissible ex-posures for different intensities and times.

TABLE LXIV. PEISSIBLE DAILY EXPOSURE TO UV RADIATIONA/

EXPOSURE TIME INTENSITY OF FACE TOTAL CALCULATED DOSE,PER 24-HOUR PERIOD LEVEL, microwatts microwatt-minutes

per sq cm per eq em

24 hours 0.1 14412 hours 018 2167 hours 0.5 2106 hours 0.O 2164 hours 0.9 2168 hours 1.2 2102 hours 1'6 2161 hour 3.6 21030 minutes 7,2 21010 minutes 21.6 216

1 minute 216,0 2165 seconds 2600,0 216

a, Based on American Medical Association standards,

* Cited in Hollaender.

247

Tests were made by the authors on the white, untanned skin ofthe upper am of an individual. An erythemal exposure slide was constructedof cardboard. This slidep when taped to the anm, allowed the intermediateexposure of six circular areas of skin approximately two centimeters indiameter. One 15-watt, hot cathode UV lamp was used as the energy source.The am of the test individual was held three inches from the center of thelm&p. At this point the intensity falling upon the skin was 1000 microwattsper square centimeter. Six circular areas of skin were exposed to the UVfrom 0.5 to 8 minutes. The ET values received varied from 500 in the 0.5minute exposure to 8000 in the 8 minute exposure. After exposure, theskin was observed for a period of 24 hours. For this test individual thefollowing results were observeds

(a) Skin areas 'roceiving an IT of 500 showed a (HPE) mini-mum perceptible erythema (very light pink).

(b) Skin areas receiving an ST of 1000 to 3000 showed defi-nite erythema with increasingly darker pink discoloration of the skin. Theareas were not painful to the touch.

(c) Skin areas receiving an ST of 8000 had moderate tosevere erythema. The areas were medium to dark red in color and werePlightly sensitive to the touch. No blister formatlon resulted.

Tho ,T value required to produce a MPH on this individual wasabout tho same as the value given by Luckiesh.

An experiment was conducted with six adult males to determineif any injurious effects could be caused by short exposures to UV radiationin an air lock. The air lock used was eight feet long, three feet sixinches wide, and ten feet high. The radiation was supplied by three bare30-watt, hot cathode lamps mounted in the ceiling. The average UV intensityin the air lock was 79 microwatts per square centimeter at a five-foot levelabove the floor and 129 microwatts per square centimeter at the seven-footlevel.

The six individuals were exposed to the radiations in the airlock for periods of time varying from 10 to 60 seconds. Three of the in-dividuals wore their personal eye glasses, three did not. All were bare-headed. Five of the men had bare arms and shoulders during the test whichwas conducted during the winter months when the exposed skin areas werewhite and untann~d. None of the exposed individuals experienced any de-gree of eye burn (conjunctivitis) and no perceptible erythema was noted onthe skin. It was estimated that the maximum time that would be requiredfor an individual to pass through this eight-foot air look under normalcircumstances was five seconds. The 60-second exposure did not affect the

*oeyes or skin of the men. Therefore, normal passage through the air lookwhen the UV lamps were operating was considered to be safe.

248

d. Conclusions

When evaluating the hazards of UV radiationy the effect on theeyes should be given first attention* If the intensities involved are with-in the allowable limits set by the American Medical Associationno protectionfor the eyes or skin is required. Slightly higher intensities may requireprotection for thie eyes, and when very high intensities are present, it maybe necessary to protect the skin as well as the eyes. Justification for theprotection of the eyes before the skin stems from the fact that the eyes aremore sensitive and that no real ham results from a minimu erythema of theskin; the skin usually adepts itself rathere rapidly.

B. PERSONNEL PROTECTION

The general problem of protection of personnel from injury by UV radia-tion may be divided into two oategories. Under the first category suchvisual aids as warning signs and indicator lights may be considered, whilethe second includes protective equipment to be worn by exposed personnel,

Some specific rules for the use of visual aids are listed below%

(a) When UV lamps are controlled by manual switches, the switchesshould be located outside the room, preferably near the entrance door.

(b) When manual switches are usedp a small oolbalt blue indicatorlight should be mounted near the switch. The indicator light will serve asa constant reminder that the UV leamps are burning.

(a) arnaing signs must be used at every UV installation. The exactlocation of the signs and the message they convey will vary with differenttypes of installations. In general it is desirable to post a sign outsidea room housing an UV installation. The wording on the sign will coincidewith the safety regulations reoomended for the particular type of instal-lation. The sentences listed below illustrate the type of message to beused on the signs:

(1) Caution - Ultraviolet lamps in use, protect your eyes.

(2) Caution - Ultraviolet lamps in use, do not enter.

(3) Caution - Turn off ultraviolet lmps before entering,

(4) Caution - Strong ultraviolet in use, protect your skin andeyes.

(d) In some installations (such as UV door barriers) a danger pat-tern may be painted on the floor or walls to designate areas of high UVintensity.

'<249

UV radiation in the 2537A rango has little penetrating offset. Ordinaryglass completely absorbs the energy, as do most plastics, rubber, and simi-lar materials. The penetration of UV through clothing will depend upon thecloseness of weave of the fabr•ic. Practical experience has shown that theskin is usually adequately protected by ordinary cotton laboratory clothing.

1. Eye Protection

While nrdiniry spectacles will in many instances offer adequate eyeprotection, it is recommended that safety glasses or goggles with solidside pieces be used. The 'side pieces prevent the entranec of the radiationwhen the source is to the left or right of the exposed individual. Casesof eye conjunctivitis have been known to occur when the individual woreordinary spectacles.

2. Skin Protection

Installations requiring skin protection also require eye pritection.The main portion of the body and the arms, and legs are protected by ordi-nary clothing. Rubber or cotton gloves csan be used to protect the hands.'A plastic personnel hood (Figure 75) may be conveniently used to protectthe eye, head, and neck.. In some oases face shields adequately protect theface and eyes. If the face shield is used, it is recomended that sometype of cap be worn to protect the area of the upper part of the head.Personnel working in areas where respirators are required can be providedwith a modified face shield as illustrated in Figure 75. The type ofequipment used when UV radiation is installed in hospital operating roomsis illustrated in Figure 32.

In installations where personnel are exposed to high intensitiesfor long periods of time, it has been necessary to wear safety goggles in•addition to plastic personnel hoods (eolg. animal rooms with UV cage raoks).This is because of penetration of the plastic by the longer UV wave longthsemitted in small quantities by the low pressure mercury vapor lamps.

Whenever plastic items, such as face shields, are used for UV radia-tion protection, tests should be made to assure that the formulation haeszero transmission of 2537A, Lucite face shields, for example, have on oc-casion been found to transmit germicidal radiation.

250(

II

*11

ýOp

Fiue7.Plastic PoI'8onnoll Hoiod t'or Protection Against UV Radiation.4Figue 75 (FD Neg C-3389)

251

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-,••Moore, FJ., 92 263\-korgan-, Ht., 25 252

261

Hoses, S.G., 239 253Moulder# P.V., 133 251Nouvouseff, Go, 24, 1-87, 177 266Murphy, WP., Jr., 132 2660Murray, : 1.,182 266

Niatr Rot 33, 68, 72, 74, 75, 79, 87, 69t 91, 94, 266, 266106, 129, 137, 145, 177, 217

Neal, J.J.p 131 264Neill, Mot. 136 274Nelson, J., 143 267Nevoambert K.S., 2520;Nicholson, E., 145 20TNielsen, l.A., 75 267Noethlingq we, 25 256Nordberg'i N.E., 26 267Novak, F.3.0 198 266Nungester, W.J., 131 270Nyka, we, 141 269

Odom# G.L,j 137 267Ohlmullert we, 92 267Oliphant, Jew., 22t 124, 132, 262, 266, 267Oliver, A.Je? 17 -278Olseno JeC't 94 267Oppenheimser, Fop 181 264, 266, 267Oppenoortht W.FeFe p 107 267

P'aneth, F.A., 75, 79 256, 267Perkins, Jo.L, 142 267Peterson, RoJ., 98 266Phillips, GoE., 17, 165, 198 see6Pike, RA.N. 17 165 271Pirsoht G.W., ;9 252Pollard, E.. 22 256Polson, A., 124 266Post, N.H., Jr., 141 266Powell, S.T., 94 266

Quiros, N., 92 263

Ramsey, GoE., 129 266Ratner, F., 132 266;Read, H.R.,f 142 256Reed, C.!., 243Reeves, G.R., 138 .266

*Reitman, N., 17, 165 266Rentschler, Mop. 24, 106, 187, 177# 217 266Ricks, MoCt 133 266Riddiford, N.S,., 61, 184 254

282

Ridenour, G.M., 92, 124 253, 269hieck, A.F., 245 269

RieR.L., 141 269Robbins, F.C., 165 269Roberts, H.V.,t 142 258Robertson, S.C., 141 269Romig, W.R., 97, 107 269Ron~e, H.E., 28, 57, 62 263, 269Rooks, R'pj 4940 269Rosano, C.OL. 1071, 193 262Rosebury, T., 168, 234 269Rosenstern lip, 141 269Rusch, H.P., 244, 246 269-Rustigan, R.9 165 269

Sand.,rs, R.T., 97 256Sarbir, R.N., 131 270Sawyer, W.A, 866 91 262Schiebel, H4MI.q 137 260Schneckenberg, E., 66 270Schwartz, L., 94 256Schwartz, S.C., 132 274Scupin, Lot 90 260Seitz, 5.0., 34 266Searad, J.E., 81, 133, 134 254, 268Setlow? R.B., 22 257Sharp, D*G., 131, 137 260, 270, 271Shaughnessyp H*J.p 131 264Silvezinang H.P., 1,42 252, 267SiL-ftrman? L., 86 270SkuN1fieldt EA.?. 91, 94 270Slaitn, J.Q~t 132 -258

Smith, C.E., 141 265Smith, W*W., 92 270SmolensI t. 132 270

j Snavely, J.G.,-132 252Snell, C.T.9 75 270Snell, F.D., 75 270Snyder, J.C., 124, 135 251Sockriderp, Ro.t, 130, 132 258Sollmamn MeH, 87 270Somesr, H.E., 168 260§p~otort VES., 110, 113 270Spiszimen, J.p 132 252Stair, Rat 240 \\254

Stanford Research Institute, 83, 85 270Steeger, A., 142 265Staimportg P.D.t 131 270Stokes, J. 132, 168 252, 260Stokes, J.,I Jr., 132 270

288

Stuy, J.H., 97, 107 270, 27nSulkin, E.S., 17 165 271Sunkes, F.S., 141 265Supert L.P., 181 271Sutton, V.S., 124 271Sviridova, T.A., 181 271Sykesp C., 133 251

Taylor, ASHI., 36, 37, 89, 40, 50v 62, 65, 129, 142 / 264t 271Taylor, A.R., 131 271Taylor, P.F., 17 273Taylor, W.., 24, 107 260Temple, J.W., 70 88 252 -Terrill, R.J., 12 2568Thorp,. C.E.9 72, 73, 74, 75, 61, 83, 85p 86, 87, 92, 93 271Tiedall, F.F., 141 269Tomli.nson, A.J.H., 17 271Torricelli, A., 93 271Tripp, J.T., 132 258, 266Trotskli, V.L., 131 271

Ulrich, W.H., 94 267Underwood, F.J., 133 266Upchuroh, S.E., 186 260

Van Atta, F.A., 72, 8, as 272Van d "'Endes , 87, 91 256Van Emenge, L., 92 272Vermsulen, D., 240 256Von Jeney, A., 25 253Vol Kupffer, L.A., 67 272Voogd, Jo., 21 272Voomaer, A., 94 272

Wade, G.L, 132 252Wahl, R.9 124 263Ward, FeS., 141 269Ward, H,.K, 19 272Watson, R.D., 91 272Weaver, E.R., 91 272Webster, L.T., 131 261Webster, T.A., 21 266Wedum, AoG., 17, 165, 225 259, 268, 272Weinstein, 1., 25, 26 272Welch, H ,181 272Wells, A.A., 22, 28, 50, 109, 120, 188 256Wells, HOW., 142 278Wells, W.F., 25, 60, 97, 124, 141, 142, 146 269, 272, 273Westinghouse Eleotric Corporation, 28, 80, 63, 65, 278

207, 217

264

Wheeler, SoH., 91 273Whistler, BoA., 97 99 278Whitohead, H.R., IM4 278Whitwello, F. 17 27-tWilaon, M.e., 234 255Witheridge, W.N., 86, 94 265, 274Witkin, M.e., 9v 274 --

Woodhall•-B.e 136 '274Woodridge, F.V., 94 274Woodside, E.E.p 97 274Worknan, W.G., 132 266Wright, A.W... 132 262Wyckoff, R.W.G., 25 274Wyss, 0., 97f 107 265? 269

Yaglou, C.P.M 86, 94 274

Zelle, H.R., 22t 25 274Zoeller, G., 124 274

I'

285

SUDJECT INDEX

Abiotic region, 21Absorption coefficient, 53, 56Absorption of UV radiation by

albur.int 21-22eyes, 238-240

of guinea pigs, 239of humans, 239-240of mice, 239

microorganims, 22-24nuclei@ acid, 21-22, 25, 238plastic, 53 -

skin, 240-248of humans, 242-244of mice, 244-245

Achromobactert 90Action spectrum of ultraviolet, 21-22African horse sickness virus, 109, 124Air-borne diseases, 17-1.8, 135-136, 165Air-borne microorganims

in hospitals, 135-142, 147inactivation of, 90, 95, 97, 99-100, 118-120, 125-1286 185-148, 151,

154, 156-180, 162, 164-177Air locks, UVdescription, 147-146, 150, 155evaluation with microorganims, 149-161protective clothing testst 152-153type of reflector, 39, 42-43S use-of Llidn -aint, 40, 44-45

Air-moving systems, UVair conditioning

"auditorium, 215room type unit, 225-281

air flows 1-10 cubic feet per minute, 231-234design criteria, 207-213general obsorvations 206-207laboratory roomst 199-203large air volume system, 221-225safety requirements, 219-220ventilated cabizet, 203-204walk-in incubators, 184-186

Air samplersliquid impinger, 127, 148, 157t 159, 162, 166t 168, 170, 227, 231sieve type, 100-101t 118, 148-149, 157, 159, 161, 164-166, 168, 170t,

172, 174-175#, 108-199, 221-224, 227, 229, 234S slit type, 234

Alcaligenes, 109

286

Aluminum, 39-41, 43, 144Alzak, 39, 41-44, 46t 166spectral finishes, 45spectral reflecotance, 39,t 41, 40

Aluminum paints,O 39-40, 44-45Amoebat, 109Amoeba crtsa 113

=queous humorý 238Artificial ultraviolet, types, 19

As~rilium amstelodami, 129evergilus flayimt 112

11jverijfllj Aga , 112

Bacillus anthracis, 109, 111-112,Ba~cius ýcereus, 97, 118, 120Ba-cilus Ngaasrium. 110-112, 177Ba-cilu i mesentiricus, 90Me =,lus ar ~oa 109, 111-112TA=cilus al Mdgious,' 90

193, 195, 199, 202Bacillus typhosa, 109Socter a

ef fect of ozone on, 89-93Bacillus mubtilis, 90-91NoAcheriChia LOcVo24 9192

efzect of ultraiolet 69i, 24-25p 106,; 109t 111, 143, 145,284air-;borne organismmm, 135-136p 137-143, 145-146t 148, 150, 1704176,

-206-207t 213-217Bacillus cereus, 97, 117-118Ba-cilus me atrium, 110, 112, 177Ba~clus mu st 37-30t 99-100, 102-104, 111, 117, 135, 168-177,

- 190, 193, 195, 199, 202, 234-235bacterial spores, 120Drucella abortus, 179Escherichia coi 25, 97, 100,ý 106, 110-111, 113, 117-119, 123-125t

133-134, 193-195t 219Lactobacillus arabinosus 108My2cbactrium tuperculos a, 109, 131, 141

aSturella iiiiiioi$V 99Pseudomonas IpY!Y~Lav 11:3Salmonella ioss,134Sarcina lu gti13Se-r-RTI&MMQst 148, 151-154p 156-162, 164-168p 170,1 173-176 179-

- 182, 186, 190, 198, 202, 221-225, 227-231t 214-235

287

________ mare______ 22, 25-26, '111-113, 115-119, 123, 131, 1489 \S ta' 193, 195, 199, 202

thococus albus, 111, 118a"ycreus, 25, 95, 111, :s1, 124, 186

311ejtoiolf I , 124-125surfaces, 117t 152water suspensionst 115

Bacteria oli,,25, 113-114, 120, 123Bacterii oMi bacteriophap, 109Bacterial-"Meperature ooefficiont due to ultraviolet, 95Bacteriophage

effect of ultraviolet on, 22, 25, 109, 124-125, 128, 193-195agar surfaces, 125air-borne, 126-128, 193, 195

Baoteriophage dysentery, 109Bacteriophage T-3, 125-128, 198,,195Baker's yeast, 112Basal metabolim rate (MR), 87Benuophenones, 53Beta-propiolactone, 132, 203Biological action of UV, factors

age of culture, 95, 97heat sensitivity, 106irradiation of media, 100t 106pH, 95-96photoreactivation, 106-108relative humidity, 97-105temperature, 95

Illpharoconjunotivitis, 238-283Brower',* yeast, 112Brucella, 109Brucella ,bertut, 179Bunsen-RoUose reioprocity law, 24

Cage rack, animalevaluation by cross-infeotion studies, 165-177use of aluminum paint, 44-45

Cancer, produced by UV radiationin humans, 244-245in mice, 245

Cell death, causes of, 24, 26, 131Cell division retardation, photoreactivation, 24, 106-108Chicken pox, 109, 141-142Chicken tumor 1 virus, 124Cholera bacteriophapg 109Cladoporium harbarum, 129

conjunctivit, 435t 240, 247, 249Cornea, 238-239, 243Corneban oteriumodi A ballu, 109, 111-112

288

(Decontamination chamber, UV, 187-191DI ococcus pneumoniaep 109Disinfection by ozone, 90-93,Disinfection by UV radiation

air, 17-18, 118-128, 135-148, 151-186, 206-234liquids, 124, 147

milkt 143, 145plasma, 131,.133, 147toxins, 130-433vaccinesi, 131-133water, 115-117, 124, 129, 183-135

media, 100p '06, lllp 117, 125, 127-128, 145-147, 181, 163surfaces, 117-118, 145, 147, 152-153, 165-168, 164-198

Door barriers, 161.164Dosage, unit of, 594,61Duke University Hospital, 137-141Dysentery bacilli, 111-112Dysentery bacteriophage, 109

Eastern equine encephalitis, 132Eberthella typhosaV 109, 111-112Encephalitis virus, 109Encephalomyelitis virus 109Encephalomyocorditisp, 152Erythems, 21t 238.444

dogreest 27-28, 137-,238p 240-248versus tan, 27f, 240

Erythemal actlon, UV, 240248curve, 2404241

Erythemal energy in sunlight, 89, 240, 242Escherichia col, 25901-92? 97? 100, 106, 109-113, 117-119, 128, 182-134,S. .. . . 196, 195, 219

Escherichia colirbac'triophage, 25, 124-125, 127-128ET value, 397-M-62, 115, 125, 247E ,,,v i t o n 059

Eyes, effect of UV radiation onguinea pigs, 239human 239,.,240mice, 239 ^

Floodlight, UV portable, 199-200Fluorescent lmps&, 27, 36-38, 195Fluorescent sunle•Vp, 27Foot and mouth disease virus, 109Fungi

effect of ozone on, 90effect of ultraviolet on, 22, 112-114, 129-180, 184

As ergillus amstelodami, 129Asporgillus flavist illA__erillus glaucus, 112

269

Clahv-hb-m am, 129

uor raoemosus At 112Mucor racemosus B, 112NOW MU&Jp~ crassa, 110H '63eraaot, 1 2Fen OMi iiimi 5 nu.mp 129-130

PeiiTM risc 112

!'A1onas Tueilon, 111-112G ue in t a•Iral s tr tIci, 129batear ass oerev0-a"# 112• Sae 113 9 110 ust l09, 112

Olbraviiaulis, 1,29

Tonrich on 08-109tef11

rusaIUMbRULAt INrusakevae, 129

Glanders, 17Glass that transmits VV radiation, 28-29, 82, 50-58Germicidal effects of UV radiation

bacteria, 110-120bacteriophagg,~ 120, 124-128mfungi, 113 , 129-130goneral, 10o-109Itickettsias,q 124toxins, 130viruses, 120-124

Germicidal energymeasurement of, 39, 57, 59-76, 207, 209, 213, 215, 217sources of, 19

Germicidal installations, 207-217Germicidal leaps

characteristics, 27-28, 37cold cathode, 32-33, 48-49explosion proof, 34 -high int\nlity 31, 83, 43, 207hot cath6\de. 26-81. 38: 43: 40, 57, 180incandesoen, 4, t 64 5

mercury pressure, 26, 33-34f 50, 68sunlamps, 27-28xenon, 27xenon mercury rc, 27

Germicidal tes and units, 19, 60-61, 69, 106, 209, 218, 215, 217

290

Guinea pigseffeot of UV on S

eyest 239skiLn 242

H-oolloid, 244Herpos virus, 109Hemophilus, 109High ozone lomps, 29History of ultraviolet, 19

use in bacteriological laboratories, 17ype'orerotosisp 244

Q Incubators, UV inp 177-179, 183-186Industrial steriliser 199-201Influenza virus, 25, 93, 109, 132Intensity of UV, 48

calculation of, 68-69increased by reflectors, 43-45

Klebsiella, 109Klebsiella nesumonise, 88

Lactobacillust 109Lactobacillus arabinosus, 106Lamp requirements for installation formula, 209-218Lamp s

cleaningt 236disposal, 237explosion proof, 34fluorescent 27, 36-36germicidal (See germicidal lamps)testing, 236

Lethal exposure, unit oft60Lethe, 60, 213, 215Literature Cited, 251-274

H.aoroeorium tomato, 129Nalnieoance or'W"installations

cleaning, 236disposal, 237testing, 286

Measles, 109, 142measurement of germicidal energy

definitibn, 59-61meters, 62-63, 65-68methods, 61-62 co

Mechanism of biological lotion 21Media, irradiation off, 100, log" 145Mercury vapor lamps, 27,- 33-34, 88

201

,+-

* Metabolic reactivation, 108Hotals, spectral reflectance of, 39, 41, 48Hice, effect of UV on

eyes, 239ekin, 244-245

Micrococcus candicans, 109, 111-113l-icrococcu pjjnej, 111Microoocous Whiaoides, 111-112Hibt ii persceii le s s hems (HPM)p 242, 247Moistureproof UV fixturet 37Monochromatic wave length, 21Mucor mucodo, 129RUoor ýr |osus A, 112,tucor ýracemosus D, 112Rps virus, 109, 142LHcobacterium tuberculosis, 109t 181,t 141

Neisseria, 109Neisseria, catarrhal-is - 111-1-12Nematoe', action pOa4ruL A22Neuropsora trassa# 115.NUC1eLO sci-,-absorption of UV, 21-23, 238

Occupational illnesses in laboratory, 17"One-hit" processes, 24Owepar&a laj•ri, 112 -

characteristics, 72-74, 83doo•.mposition goaffioient, 74definition, 72deodorising effects, 98-94germicidal activity (See Bacteria, effect of oxone on)

(See, Viruses., effeot of aeons on)history, 72, Slt88injurious effects to

animalsm, 87-88man, 87-88

,measurement of, 74-81, 89-90production, 31, 88-90threshold limitt 88toxic limits, 85-88

Paints, 39-45Paper decontsminat.on chamber, UV, 191-195Paper, effect of UV radiation on, 190-195Paramecium, 23, 25, 109Pasteurells, Dejjs, 99Pasteurell aularensis, 90enicillium z nu 129-130Feiiiu GIdll t ~m•11Z

Personnel iffe le oFrUV radiation, 288-2429 244, 246-246Personnel protection frosm UV radiation, 240, 278,t 246-250Photodynamic reaotion, 24Photo-etythema, 19Photoreactivat ion, 106-106Photo-sensitive call, 62Phototube, cadmium magnesium alloy, 62-65

Ph~omonas tumefaciens, 111-112

Plastic, transmittance of ultraviolet, 50, 53-54tbe8Plastic recording disc-

decontamination of, 167effect of ultraviolet on 187

Poliomyelitis virus, 912, 10iPractical uses of UV radiation with and/or in

blood plasma, 131-133t 147cross-infections, 146"culture media, 145food packaging, 143, 147.hospitals# 135-142. 1.43t 147pasteurizsat ion of milk, 1,45pharmaceutical houses, 143, 147.sohoolai, 142-143, 147sterilization of water, 133-135sugar refineryt, 143, 147toxins, 131-133vaccines, 131-133viruxses, 3-3

Prespore, 97Proteus, 90, 109Proteg us ais 111-112Fieudmoii4se 0 goPseudomona' s r!gigos, 111-112

resud'mnas RO2Zg.Las 113

Fuccinia araminis triti&, 129

Q fever, 17Quantum phenomenon, 19

Reactivation, by light (See Photoreactivation)Rsf2?actors? UV

design,ý 45-47f 49metal0

aluminum, 39-w41, 43-44p 46stainlesai steel, 40

293

paintsaluminum, 39-40, 44-45oi'!"; 40, 42, 44-45'Ater soluble , 40

Refrigerators, UV in, 177-1688Respirat~ory disease., 17

Rous' sar ooma-Ur-um 25

Saccharomo-es oereviesae 97, 112-113Saca ass 'IM =0Gdu , 109, 112Saiey equirements for UiV installations, 219-220Sabnonella, 109Salmonella enteritides#, I11Salmonella Tyiilg 111-112

TaO =rotu I aaioa 129COW rlovols brevlculis, 129

Serratia inis 148, 151-154 156-162t 164-168p 170, 178-176t 179-182t186,t 190, 19i, 202,t'2-21-225, 227:231, 234-235

Serratia, marceoons. 22, 25-26t 100, 111-113j 115-119, 123, 131, 148,177, 198, 195, 199, 202

Serum hepa~titis 132-138Shigellat 109Shigella bacteriop, age, 124h4g9lla sol~ 180

Shlla ardsent. na., 111- 112Shos rac 19 03 0Shumann region, 1Sieve air sompler, 100-101, 116, 148-149,t 1571t 1b9, 161, 164-166, 168t,

170, 172, 174-175, 196-199, 221-224, 227, 229, 234Single photon hit theory, 24, 106Slit air sampler, 234Sj~irillum 'rubtwi, 111-112Stia1iyloo~cc1 109t 135Staphlococcus alus 90, 111-112, 116a !yoc ocaus aureus, 25t 95, 112-113,? 124, 135-136

IaSyiIoocous Saffieriophaget 109Streptococci, 109, 143trpoocs cremoris, 124

rfojIccus =$allario-us , 90

r,, os 'inus =F106

spectral_ T.iry emitted by, 27-28types? ,17e

294

Sunlightgermicidal effect oft 19, 21ultraviolet energy in, 106

Survival ratio, 60-61, 114, 208

Tanproduction of, 27-28versus eiythems. 27,0 242

Temperature coefficient of bacterial action of ultraviolet, 95Threshold limit of osone, 88Tobacco mosaic virus, 25, 106, 109, 124Tomato bushy stunt virus, 109Torula sphor 129Toxns130Transmission of UV by

clothing 57-56glass, U6-53, 55, 61, 68paper, 57-56plastic, 50, 53-54, 57-568water, 56-47

Triohooh~vton mentgo~hytesp 110•-• Tubercle bao4111, 1310 141 L

Tuberculosis, 17, 141, 146Tularemia, 17Tumors, development of, 244-240

Unit lethal exposure, 60Ultraviolet absorption (See Abeorption of UV radiation by)Ultraviolet air looks (See Air locks, UV)Ultravio.et air-moving systems (See Air-movinzg systems, UV)Ultraviolet biological action factors (See iological action of U, factors)Ultraviolet decontamination chamber (See Decontiaiation chimber, VV)Ultraviolet, portable floodlight (See Floodlilht,. UV portable)Ultraviolet germicidal effects (See Germicidal effects of UV radiation)Ultraviolet history (See History of ultraviolet)Ultraviolet lamps (See Lamps)Ultraviolet decontamination climber for paper (See Paper decontamination'chamber, UT)

Ultraviolet refloetor (See Reflecoot UT)

Ultraviolet shoe rack (See Sho drack, UV)Ultraviolet warning signe (See Warning eisne UT)

Vacoinia virus, 25, 109Ventilated obinet, UT, 208-204Vibrrio, 109Viruses,

action spectrum, 22effect of ozone on, 92.93effect of ultraviolet on, 25, 131-1821ý

295

aning sigpns, UVt 248-249Water, UV

disinfeating, 138-185transmission, 58 56-57

Wave lengtht ultraqolet oharacteristiose 21,p 24t 26

Xenon 1tpos, 27X-ray, 19

Yeasts, 106, 112

¾ ¾

1/ t

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UNCLASSI FI

UNCLASSIFIED 1'>