Trihalomethanes and associated potential cancer risks in the water supply in Ankara, Turkey

Environmental Research 96 (2004) 345–352

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doi:10.1016/j.en

Trihalomethanes and associated potential cancer risks in the watersupply in Ankara, Turkey$

Burcu Tokmak, Goksen Capar, Filiz B. Dilek, and Ulku Yetis�

Department of Environmental Engineering, Middle East Technical University, 06531 Ankara, Turkey

Received 25 July 2003; received in revised form 13 November 2003; accepted 14 November 2003

Abstract

The occurrence of trihalomethanes (THMs) in the water supply in the Ankara, Turkey was investigated. Total THMs and total

organic carbon measurements were carried seasonally in the samples collected form 22 different districts along with the samples

taken from the Ivedik Water Treatment Plant serving 90% of the city. The average summer nonpurgeable organic carbon (NPOC)

concentration in the raw water was 4.2mg/L, and the NPOC removal achieved in the treatment plant was 31%. The concentration

of total THMs ranged from 25 to 74 mg/L, from 28 to 73mg/L, and from 25 to 110 mg/L in winter, spring, and summer, respectively.

In all of the samples chloroform existed at the highest concentrations, while bromoform was almost absent. The total THM

concentrations were highest in summer for all districts. However, none of the concentrations detected exceeded the USEPA’s Stage I

limit of 80 mg/L and the EU’s limit of 100 mg/L. However, the total THM level in 64% of the districts exceeded the USEPA’s Stage II

limit of 40mg/L. The risk estimations carried out indicated that each year 1 of the 5 million Ankara residents could get cancer from

the daily intake of water, mainly because of exposure to chloroform through oral ingestion.

Keywords: Chlorination; Cancer risk; Disinfection by-products; Trihalomethanes; Drinking water

1. Introduction

Disinfection is applied in water treatment plants toprevent the growth of microorganisms both in the plantand in the distribution system, thus protecting the publicfrom water borne diseases. However, chlorination,which is a widely used disinfection process, has beenreported to cause the formation of trihalomethanes(THMs) (Rook, 1974). THMs are formed due to thereactions between chlorine and the natural organicmatter in water supplies, especially surface waters.Chloroform, bromodichloromethane, dibromochloro-methane, and bromoform are the four main THMcompounds termed THMs.

The presence of chlorinated disinfection by-products(DBPs) in the drinking water is of concern from a publichealth aspect, as they are suspected to be carcinogenic

ch was funded by the State Planning Organization via

-03-11-DPT-97K 122140. This research included no

ork involving humans or test animals.

ing author. Fax: +90-312-2101260.

ess: uyetis@metu.edu.tr (U. Yetis).

vres.2003.11.005

(USEPA, 1975; Morrow and Minear, 1987; Lee et al.,2001; Xu et al., 2002; Gold et al., 2003). Several studieshave suggested that there exist increased risks ofbladder, stomach, large intestine, and rectal cancerin areas where chlorinated surface waters have beenused (Craun, 1991; Gallard and Gunten, 2002; Blacket al., 1996). Among all DBPs, THMs have receiveda lot of attention because chloroform has beenshown to be an animal carcinogen (Golfinopoulos,2000). Also, THM formation chemistry is relatively wellunderstood and THM speciation patterns are generallyapplicable to other by-product classes (Semmens andField, 1980; Cowman and Singer, 1996; Black et al.,1996). In 1986, as part of the Safe Drinking WaterAmendments, the US Environmental ProtectionAgency (USEPA) proposed the Disinfectants/DBPsRule. The rule was proposed by the USEPA intwo stages and the maximum contaminant level fortotal THMs was reregulated in 1998. Under Stage I, theMCL for total THMs was set at 80 mg/L; in Stage II, theMCL is expected to further decrease to 40 mg/L(Pontius, 1999; Golfinopoulos and Arhonditsis, 2002).European Union (EU) member countries are required to

ARTICLE IN PRESSB. Tokmak et al. / Environmental Research 96 (2004) 345–352346

apply a standard of 100 mg/L for total THMs (EECD,1997).

With a view to understanding the consequences of thefuture application of this directive and also thedevelopment of a national regulation for THMs inTurkey, the occurrence of THMs in the drinking waterof the city of Ankara, Turkey was investigated. Inaddition, a cancer risk estimation was carried outconsidering exposure by ingestion, inhalation, anddermal contact. Ankara, being the capital, is the secondlargest city in the country, with a population of about 5million. The study was carried out between March 1999and January 2000, and the treatment plant servingnearly 80% of the city of Ankara and the waterdistribution system were investigated. Because noregulation, regarding THMs is present among Turkishregulations, the results were compared with the USEPAand EU Limits.

2. Materials and methods

2.1. Study area

In Ankara, there are three water treatment plants thatsupply water: Ivedik, Pursaklar, and Bayindir. TheIvedik Water Treatment Plant (IWTP), being the biggestone with a capacity of 1 128 000m3/day and serving to91.5% of the total population, was considered in thisstudy. This plant takes water from two surface waterreservoirs, namely Camlidere and Kurtbogazi, which areabout 80 km from the city center. Following aeration,

Fig. 1. Map of the study area, in

raw water from Kurtbogazi Reservoir is mixed withCamlidere Reservoir water at a one-to-one ratio andintroduced to the treatment plant. A conventionaltreatment scheme is applied in the plant and consistsof predisinfection, coagulation, flocculation–sedimenta-tion, filtration, and postdisinfection. Predisinfection isadapted at the coagulation stage with chlorine; alum isused as the coagulant at a typical dose of 30mg/Ltogether with a polyelectrolyte (0.1mg/L). The coagu-lated water is filtered in conventional rapid-sand filters,and chlorine is used as the final disinfectant before thetreated water is conveyed to the city. The typicalchlorine dose is reported to be 2.0mg/L. The retentiontime in the chlorine contact tank is reported to be lessthan 20min.

2.2. Sampling

To observe the occurrence of THMs in the distribu-tion system, samples were collected seasonally from thetaps of consumers of 22 districts (Fig. 1). Twenty ofthese districts receive water from the IWTP and arelocated at various distances from the plant. The othertwo districts, ODTU and Konutkent, receive water fromgroundwater resources unless these are insufficient.When the demand cannot be met by the local wells,the IWTP serves these districts. As shown in Fig. 1,Yenimahalle is the closest sampling point, with adistance of about 5 km to the treatment plant. TheOran and Konutkent sampling points represent theterminal points for the distribution system. The resi-dence times of water in the distribution system for the

cluding sampling locations.

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sampling points were not available due to variationsin the distribution system characteristics and waterdemand.

All the samples were collected in 300-mL glass bottles,and 1mL of 0.1N sodium thiosulfate was added for100mL sample to eliminate any remaining residualchlorine and to stop further DPP formation. Householdtaps were flushed for 15min prior to sampling. Samplebottles were carefully filled just to overflowing for theprevention of passage of air bubbles into the bottles.Duplicate samples were collected for all THM measure-ments. The samples were stored at 4�C.

2.3. Glassware

All of the glassware used in the experimental workwas washed with chromic acid and rinsed several timeswith tap water and then with distilled water. The itemswere dried at 105�C for 2–3 h and then cooled to roomtemperature in a location remained from the laboratory,where volatile compounds may have existed.

2.4. Analytical methods

THM quantification was carried out according toUSEPA Method 501 (USEPA, 1979) and liquid–liquidextraction gas chromatographic Method 6232 B (Stan-dard Methods, 1995). According to these methods,samples are prepared by extracting 10mL of samplewith 2mL of pentane by shaking for 1min in aseparation funnel of 25mL in volume. Phase separationoccurred within 2min and the upper phase was collectedinto 2mL vials having screw caps with PTFE septa. TheTHM calibration test mixture of 1000mg/mL inmethanol was purchased from Supelco and kept at+4�C. The calibration standards were prepared bydissolving varying amounts of the THM test mixture in100mL of organic free water, which was prepared bypassing double-distilled, deionized water through abench-scale activated-carbon column and used as ablank. The calibration standards, the blanks, and thesamples were extracted under identical conditions, suchas water and solvent temperatures and extraction time,in order to provide identical recoveries. Measurementswere made using Chrompack gas chromatography (GC)with a GC capillary technique, equipped with an ECDdetector. The column used in the GC is CP-Sil 13 CB forhalocarbons fused with silica WCOT. Each calibrationstandard and sample was analyzed three to five timesand the arithmetic averages were taken together withtheir standard deviations. For the THM species,analytical protocols ensured detection limits of 0.5 mg/L for chloroform and of 0.3 mg/L for bromodichlor-omethane, dibromochloromethane, and bromoform.

Nonpurgeable dissolved organic carbon (NPOC)measurements were conducted according to Standard

Method 3510B using a Shimadzu 5000A Model TOCanalyzer. Filtered samples were acidified to pHo2 withHCl and purged with high-purity air at a flow rate of150mL/min for 15min to remove inorganic carboncontent. Two calibration curves with total carbonstandards at two different ranges were obtained byprocessing the peak areas. The NPOC content ofsamples was determined from these curves. Each samplewas injected automatically to the instrument at leastthree times to obtain repetitive results.

To account for the other halogenated compounds, theabsorbable organic halide (AOX) content of the sampleswas also determined by using a Euroglass AOX analyzeraccording to Standard Method 5320B. Before theanalysis, the pH of the sample of 100mL in volumewas adjusted to 2.0 by nitric acid and then 5mL ofsodium nitrate at a concentration of 0.017mg/L wasadded to eliminate the interaction of carbon withinorganic chloride. After the addition of 5 g of activatedcarbon to the samples, they were shaken for 1 h, filteredthrough a polycarbonate filter, and finally analyzed forAOX content.

To characterize the raw water coming to the inletof IWTP; in addition to NPOC and THMs, conven-tional water quality parameters of alkalinity, pH,turbidity, color, hardness, and suspended solids werealso analyzed following standard methods (APHA/AWWA/WEF, 1995). UV absorbance was measuredwith a UV/Vis spectrophotometer (Varian Cary, Model100) at 254 nm in 10mm of quartz cells. Inorganiccarbon was determined with a carbon analyzer (TOC-500, Shimadzu); pH was measured with a pHmeter (Jenway Ltd., Essex, UK). Bromine was measuredby DPD method using a DR/2400 portable spectro-photometer.

2.5. Cancer risk estimation

In estimating the lifetime cancer risk of THMs; themethod developed by the USEPA (1999, 2002) andrecently adopted by Lee et al. (2004a,b) for theestimation of cancer risk of THMs for Hong Kongwas used. The cancer risks for exposure throughingestion, dermal absorption, and inhalation exposurewere considered. In these estimations, body weight wastaken as 72 and 65 kg for male and female, respectively.The average life span for males in Turkey is 71, whilethat for females is 72 years. The average water ingestionrate considered for oral cancer risk calculations was2.0 L/day, as assumed for adults by the USEPA. Ininhalation risk calculations, the daily dose was calcu-lated by assuming 20m3 aspirated air per day (Lee et al.,2004a,b). The chloroform concentration in air used forthe estimation of risk through inhalation was calculatedusing a volatilization factor of 0.5 as suggested byUSEPA (1991).

3. Results and discussion

3.1. General water quality parameters

The characteristics of raw water from the Camlidereand Kurtbogazi reservoirs are presented in Table 1. Therewas a relatively high concentration of organic matter thatmay have caused color in both reservoir waters. However,there were no THMs in the raw water to be treated at theIWTP. Gur (1999) studied the THM formation potentialof these surface water reservoirs and determined yearlyaverage values of 242.0 and 250.0mg/L for the Camlidereand Kurtbogazi reservoirs, respectively.

3.2. Concentrations of organic matter and THMs

in the treatment plant

To examine the organic matter removal achieved atthe IWTP, a series of measurements were carried out inSummer 1999 and the results presented in Table 2 wereobtained. The treatment plant inlet and outlet NPOCvalues indicated a NPOC removal of 31%, which isabout 5% less than the USEPA Step 1 enhancedcoagulation requirement (White et al., 1997). Asexpected, the total THM content of raw water enteringthe treatment plant was zero; of water leaving theIWTP, the content was 35.0 mg/L THMs. This relativelyhigh THM concentration was obviously due to the preand postchlorination adopted and in accordance withthe formation potential reported by Gur (1999). When

Table 1

Raw water characteristics

Parameter Unit Camlidere Kurtbogazi

NPOC mg/L 4.1 4.4

UV(A)254 — 0.17 0.15

AOX mg/L 0.023 0.016

TTHMs mg/L 0 0

Alkalinity mg/L as CaCO3 93 105

pH — 7.6 7.7

Turbidity NTU 7 8

Color Pt–Co 35 85

Hardness mg/L as CaCO3 77 86

Suspended solids mg/L 8 12

Bromine mg/L 30 56

All of the figures in the table are the yearly averages.

Table 2

THM formation and NPOC removal at the IWTP

Raw water Finished water

NPOC (mg/L) 4.2670.09 2.9770.06

THMs (mg/L) — 35.073.0

Chloroform — 30.6771.88

Chlorodibromometan — 4.2971.20

individual THM compounds are considered, the maincomponent was chloroform, followed by bromodichlor-omethane. The other two THMs were not detected inthe treated water. In all of the samples analyzed, it wasobserved that chloroform made up to 90% of the totalTHM compounds.

3.3. Concentrations of THMs in the distribution system

In an attempt to assess the THM levels throughoutthe water distribution system of Ankara, samples from22 districts were collected seasonally and analyzed fortheir THM and NPOC contents. Only in Winter 1998samples were also analyzed for AOX to assess theoccurence of other halogenated compounds.

The first sampling season was Winter 1998. The THMand AOX measurement results obtained are presented inFig. 2. THM concentrations increased with increasingdistance from the treatment plant (the numbers inparentheses in Fig. 2 are the distance in kilometers fromthe plant). On the other hand, AOX measurementsindicated that some other DBPs or halogenatedorganics, apart from THMs, also existed in the water,as the AOX content was comparably higher than theTHM content of the samples. Samples taken from theODTU and Cayyolu stations, which receive ground-water, had very low AOX and THM contents.

The next sampling, carried out in Spring of 1999,provided the results presented in Fig. 3. THMs andNPOC measurements were carried out on the samples

Fig. 2. Total THM and AOX levels in tap water of Ankara in Winter

1998. Numbers in parantheses are the distance in kilometers from the

plant.

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Fig. 3. Total THM (a) and NPOC (b) levels in the tap water of Ankara

in Spring 1999.

in Summer 1999.

B. Tokmak et al. / Environmental Research 96 (2004) 345–352 349

collected. The total THM concentrations detected in allsamples were comparably lower than those measured inWinter 1998. However, the highest THMs observedwere again at the terminal points of the distributionsystem, and the lowest were in close proximity to thetreatment plant. As presented in Fig. 3b, the NPOClevels determined were quite low during this samplingperiod. There appeared almost a constant NPOC valueof about 2.5mg/L for all of the sampling stations. Thislow NPOC level was in accord with the relatively lowTHM levels measured in the samples.

Fig. 4 shows the total THM and NPOC levels in thedistribution system in the city for Summer 1999. In thisseason, there was an increase in both the THM and theNPOC levels compared to Spring 1999. The increase inthe THM level was about three folds; the 35-mg/L THMconcentration at the outlet of the IWTP increased to110 mg/L at Konutkent, which is one of the distantdistricts from the IWTP. Several of the previouslyconducted works on the seasonal variation of THMshave reported highest THM concentrations for warm

seasons due to the high organic matter content of rawwater and also the higher doses of chlorine used(Golfinopoulos, 2000; Lee et al., 2001).

The next season for which the sampling wasconducted was Winter 1999. Fig. 5 shows the occurrenceof THMs in the distribution system. In this season, acertain decrease of the THM level was detected;probably due to the decreased temperature, whichaffects the THM formation reaction rate and also theoccurrence of relatively low NPOC levels. The lowNPOC levels in the water supplies are due to tempera-ture effects and the lesser intrusion of organic matter,mainly humics, into the reservoirs.

When the annual average of total THM (TTHM)measurements presented in Fig. 6 was compared withthe USEPA Stage I and Stage II limits, the THM levelsin none of the districts exceeded the Stage I limit.However, the Stage II limit was exceeded in 64% of thedistricts surveyed. The districts, which are far from theIWTP, such as Konutkent, Elvankent, Dikmen, Umit-koy, and Oran, exhibited the highest levels of THMs in

ARTICLE IN PRESS

in Winter 1999.

100CHCl3CHCl2B rCHClB r2CHBr3

Fig. 6. Average THM (a) and NPOC (b) levels in the tap water of 22

districts of Ankara.

B. Tokmak et al. / Environmental Research 96 (2004) 345–352350

the distribution system due to a longer period of contactfor water with the residual chlorine in the system during theperiod of travel to the far districts. Also, the intermediatechlorine pumping stations in the city, which supplyadditional residual chlorine to the system, are thought toplay an important role in the ongoing formation of THMs.These findings were in accord with other works reportingvariable DBP concentrations with time and distance withindistribution systems (Brett and Calverley, 1979; Schereiber,1981; Clark and Sivagenesan, 1998).

In all of the samples, the major halogenatedcompound was chloroform, being 90–95% of the total,followed to a much lesser degree by bromodichloro-methane. The reason that the brominated DBP wereabsent in the samples was the low levels of bromine inthe raw water samples (Table 1).

3.4. Evaluation of the cancer risk for THMs

The results of multi-pathway cancer risk evaluation intap water are shown in Figs. 7 and 8 for male and female

residents of Ankara, respectively. These two figuresdepict that the major cancer risk for both male andfemale residents is through oral ingestion and that thetotal risk is over the USEPA’s lower end of the acceptablerisk level of 10�6 for all districts. The cancer risk for thedistrict of Umitkoy exceeded the acceptable level by afactor of over 20 for both sexes. The lowest contributionto the total cancer risk was due to dermal uptake.

When the average lifetime multiway cancer risks foreach THM in Ankara were estimated, it appeared thatthe average risk due to chloroform was the highestamong the four THMs (Fig. 9). The average lifetimecancer risk of about 1.2� 10�5 caused by chloroformwas almost 12 times higher than the lower end of theacceptable risk level of 10�6 defined by the USEPA. Onthe other hand, while there was no bromoform andtherefore no associated risk in the tap water of Ankara,there was a considerable lifetime cancer risk associatedwith CHBrCl2 for male residents. For CHBr2Cl, thelifetime cancer risk was below the above-mentionedEPA level by a factor of 5–6 in all districts. Hence, the

ARTICLE IN PRESS

Inhalation Dermal Oral

2.00E-05

2.50E-05

1.50E-05

1.00E-05

5.00E-06

0.00E+00

çelie

itköy

Districts

Fig. 8. Multipathway cancer risk for females from THMs in the tap water of 22 districts of Ankara.

2.00E-05

2.50E-05

çelie

itköy

Inhalation Dermal Oral

1.50E-05

1.00E-05

5.00E-06

0.00E+00

Districts

Fig. 7. Multipathway cancer risk for males from THMs in the tap water of 22 districts of Ankara.

0.00E+00

2.00E-06

4.00E-06

6.00E-06

8.00E-06

1.00E-05

1.20E-05

1.40E-05

CHCl3 CHBr3 CHBr2Cl CHBrCl2

Female

Fig. 9. Average multipathway cancer risk for the male and female

residents of Ankara.

B. Tokmak et al. / Environmental Research 96 (2004) 345–352 351

average lifetime cancer risk for THMs was, in descend-ing order, chloroform, dichlorobromomethane, anddibromochloromethane for both males and females.

4. Conclusion

The study showed that the THM levels in the tapwater of Ankara are at levels below the USEPA’s Stage Ilimit of 80 mg/L as well as the EU limit of 100 mg/L.Nevertheless, the THM formation potentials of surfacewaters that supply the raw water and the organic matterremoval achieved in the water treatment facility servingAnkara indicate that the affiliated organizations musttake care of these compounds even though there are no

limits set for them at present. The THM levels werehighly variable and were found to change from season toseason as well as from district to district. The THMconcentrations were observed to be higher during thewarm months of the year and also at districts far awayfrom the IWTP. The variations associated with locationwere obviously due to the differences in travel time forthe water within the distribution system and theintermediate chlorination carried out at the pumpingstations along the distribution system.

On the other hand, the risk estimations carried outindicate that, although the THM levels are not above thelimits set by the USEPA and the EU, each year 1 of the 5million Ankara residents could get cancer from the dailyintake of water. Among the four THMs, chloroformappears to pose the highest risk through oral ingestion.

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Trihalomethanes and associated potential cancer risks in the water supply in Ankara, Turkey

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