CONTACT DETAIL:

Prof. Nirav Goda - Contact no : 9869821021

Email ID: nir4uever@gmail.com

Animesh Choudhary – Contact no : 8108555817

Email ID: choudharyanimesh5@gmail.com

Vandana Jaiswal - Contact no : 9833096629

Email ID: jaiswalvandana15@gmail.com

LIGHT POLLUTION AND ENVIRONMENT

ABSTRACTThe main type of pollution people usually think of when theysee the word “pollution” might be air pollution caused by carsand factories. There’s another type of pollution thatnegatively effects the environment not quite as obvious ascars and factories belching smoke. If you live in an urban orsuburban area all you have to do to see this type of pollutionis go outside at night and look up at the sky. The glow yousee blocking the stars is called light pollution. Outdoorlighting has become a necessary integral part of society.Light pollution is a by-product of outdoor lighting. Lightpollution is the pollution caused by misplaced artificiallight. It is a growing problem that threatens wildlife,humans, natural habitats, our energy use and the heritage ofappreciation for our night sky. Leaving lights on in vacantbuildings, outdoor lights pointing up to the sky andunshielded outdoor lights all contribute to light pollution orsky glow. Air and water pollution have a more immediate impacton human health. However, by paying attention to lightpollution we would also be addressing the possibility of amore efficient use of energy for outdoor lighting that in turnwill address the issue of diminishing energy resources. Someof the damage can be reversed with timely action. Knowing thepollution level quantitatively might also help us fight itbetter. The extent of light pollution can be studied throughsatellite imagery. However, translating from there to thequestion of actual sky brightness as seen from the groundinvolves a lot of estimation of unknown factors like aerosolcontent over different regions. Light pollution can be reducedby lighting only what is actually needed, when it is needed,and to the appropriate level. This publication discusses thethree elements of light pollution, which are sky glow, lighttrespass, and glare, and gives examples and recommendationsfor minimizing or eliminating the undesirable effects of eachelement when designing and using outdoor lighting.

INTRODUCTION

We light our outdoor night time environment to meet certainsocietal goals, such as increasing safety and security,enhancing economic development, as well as highlightinghistoric areas or landmarks of cities or towns. Our societyhas become a 24-hour society, and night time lighting hasbecome a necessity to facilitate using our roadways anddowntown areas. Figure 1 is a composite image that depicts thelight emitted from the earth at night. The brighter areas inthe figure are regions of higher population density and, thus,more outdoor lighting.

Figure 1. The earth at night

Light pollution is a by-product of lighting at night,especially when we use inefficient luminaries and lamps andwhen we light to excessive levels. We can minimize our impacton light pollution by lighting more efficiently. When wechoose efficient luminaries and lamps, fewer lamps may berequired to meet the lighting objectives, resulting in lesswasted light emitted into areas where the light is not needed.

What is light pollution?

Light pollution is an unwanted consequence of outdoor lightingand includes such effects as sky glow, light trespass,and glare. An illustration of both useful light and thecomponents of light pollution are illustrated in Figure 2. Skyglow is a brightening of the sky caused by both natural and

human-made factors. The key factor of sky glow thatcontributes to light pollution is outdoor lighting.

Figure 2. Example of useful light and lightpollution from a typical pole-mounted outdoorluminaire

Light trespass is light being cast where it is not wanted orneeded, such as light from a streetlight or a floodlight thatilluminates a neighbour’s bedroom at night making it difficultto sleep.

Glare can be thought of as objectionable brightness. It can bedisabling or discomforting. There are several kinds of glare,the worst of which is disability glare, because it causes aloss of visibility from stray light being scattered within theeye. Discomfort glare is the sensation of annoyance or evenpain induced by overly bright sources. Think of driving alonga dark road when an oncoming car with bright headlightssuddenly appears. The sudden bright light can be uncomfortableand make it difficult to see. Discomfort and even disabilityglare can also be caused by streetlights, parking lot lights,floodlights, signs, sports field lighting, and decorative andlandscape lights.

TYPES OF LIGHT POLLUTION

Sky glow

Sky glow occurs from both natural and human-made sources. Thenatural component of sky glow has five sources: sunlightreflected off the moon and earth, faint air glow in the upperatmosphere (a permanent, low-grade aurora), sunlight reflectedoff interplanetary dust (zodiacal light), starlight scatteredin the atmosphere, and background light from faint, unresolvedstars and nebulae (celestial objects or diffuse masses ofinterstellar dust and gas that appear as hazy smudges oflight). Natural sky glow is well quantified. In thispublication, further discussion of sky glow considers onlyhuman-made sources.

Electric lighting also increases night sky brightness and isthe human-made source of sky glow. Light that is eitheremitted directly upward by luminaries or reflected from theground is scattered by dust and gas molecules in theatmosphere, producing a luminous background. It has the effectof reducing one’s ability to view the stars, as seen in Figure3. Sky glow is highly variable depending on immediate weatherconditions, quantity of dust and gas in the atmosphere, amountof light directed skyward, and the direction from which it isviewed. In poor weather conditions, more particles are presentin the atmosphere to scatter the upward-bound light, so skyglow becomes a very visible effect of wasted light and wastedenergy.

Figure 3. Example of sky glow over a city

Light trespass:

Light trespass occurs when spill light is cast where it is notwanted. Light trespass is somewhat subjective because it isdifficult to define when, where, and how much light isunwanted. An example of light trespass is when spilllight from a streetlight or floodlight enters a window andilluminates an indoor area. Figures 4 and 5 depict examples oflight trespass. The light trespass shown in Figure 4 would besignificantly reduced if a shield were placed on theluminaire. In Figure 5, the floodlight on the hotel castslight on the home across the street. Proper aiming of thefloodlight and shielding would significantly reduce the lighttrespass shown in this example.

Figure 4. Example of light trespass

Glare:

Glare is a visual sensation caused by excessive anduncontrolled brightness. It can be disabling or simplyuncomfortable. It is subjective, and sensitivity to glare canvary widely. Older people are usually more sensitive to glaredue to the aging characteristics of the eye. Disabilityglare is the reduction in visibility caused by intense lightsources in the field of view, while discomfort glare is thesensation of annoyance or even pain induced by overly brightsources (Rea 2000). Compare the glare from the streetlightshown in Figure 6 to the glare from the luminaries shown inFigure 7. Reducing glare is an effective way to improve thelighting.

Figure 5. Example of lighting that canresult in disability and discomfortglare

EFFECT OF LIGHT POLLUTION ON ENVIORNMENT

Light Pollution and Humans Light pollution has consequences for human health. Nightvision can be severely impacted. Glare on the eyes fromexcessive night lighting can cause disability glare.Disability glare is glare from roadway lighting that is sobright it causes us to avert our eyes. Older drivers areparticularly vulnerable to disability glare. Disability glarereduces:· Ability to distinguish contrast· Color perceptionThe aging eye is also susceptible to eyestrain and loss ofnight vision.The circadian rhythm is the 24-hour cycle that our bodies runon and what keeps us happy and healthy. Studies show thatdisruption of this cycle can lead to insomnia, depression,cancer, and cardiovascular disease. Over exposure toartificial light causes your circadian rhythm to be thrownoff, possibly leading up to these severe side effects overtime. 

Melatonin: a hormone called Melatonin is what maintains anatural sleeping rhythm. Artificial light affects this rhythm,decreasing the levels of melatonin in your body. Melatonin isonly produced in the darkness. Even a little exposure toartificial light will disturb the melatonin production. Ifthere is a light shining through your window, make sure toblock it with something.Light Pollution and Wildlife Light pollution also negatively affects animals in a biggerway than most would think. The sky glow from towns and citiescause nocturnal wildlife around the world to experience a lossof their night ecosystem.Mammals: Mammals lose a lot of their internal night systemsdue to over lit areas. Nocturnal animals such as raccoons,bats, and deer suffer greatly, causing a decrease inpopulation, difficulties with finding food, exposure topredators, and an increase in mortality.Amphibians: Light pollution causes amphibians to suffer bylowering population, decrease in body weight, and confusionbetween insects that protect nature rather than harming it. Ifan ecosystem is anywhere near an urban area with high amountsof light pollution, amphibians will suffer.Insects: You have probably seen insects fly around your porchlight. This is a striking example of how artificial lightaffects wildlife. Insects such as moths and flies suffer adecrease in population due to light pollution because it iseasier for predators to hunt the insects. The decreased insectpopulation impacts all the animals that feed on insects astheir main food source.Birds: If any animal species suffer from light pollution,birds definitely suffer the most. Over 100 million birds inthe United States die from collisions with lighted buildingsalone. The lighted buildings attract them. That’s not all;some migrating birds don’t reach their destination because theartificial lights interfere with their navigation and canthrow them off course.Reptiles: As you may know, sea turtles travel up on beachshores to bury their eggs in the sand. But what if the beachis near a bright urban area? Baby sea turtles rely on the moon

to lead them to the sea. Artificial light can lead them toroads where cars can run them over or to someplace far offuntil they die from exhaustion. This explains one reason whysea turtles are decreasing in population.HOW CAN WE REDUCE LIGHT POLLUTION?

Educating yourself regarding what does and does not constitutedark sky friendly lighting is a great first step towardimplementing simple, common sense strategies for outdoorlighting. Set a good example in your ownneighbourhood! Changing the way people use artificial light isone simple way to solve light pollution. You only need lightwhere you need it: ON THE GROUND. Your neighbours willappreciate your lighting choices if you consider lightpollution when selecting fixtures – no more lights shining intheir windows.  So here are some suggestions on how to improveexterior home lighting:To conclude, being dark sky friendly doesn’t mean no light. Itmeans using the light that you need for a particular task inthe most efficient manner.

Shield and lower the wattage of all outdoor lighting—both municipal and private.

Use only the light you need to get the job done. Use timers, dimmers, and sensors. Shut off the lights

when you can. Work with your neighbours and local government to keep

the light on the ground and the skies natural. Use light emitting diodes (LED) technology with long

wave length light in a red or yellow tint to minimizeimpact and save energy

Glare and light trespass are of special concern wheninstalling floodlights. The Commission Internationale del’Eclairage (CIE) provides design guidelines on the siting andaiming of floodlights (CIE in press). One objective when thelighting is installed is to ensure that, to the extentpracticable, direct view of the bright parts of thefloodlights is prevented from positions of importance at eye-height on neighbouring properties. Where possible, shieldingshould be considered. To determine the mounting height ofluminaries, the CIE suggests the following considerations:

  Higher mounting heights can often be more effective incontrolling spill light, because floodlights with a morecontrolled light distribution (i.e., narrower beam) may beused, and the floodlights may be aimed in a more downwarddirection, making it easier to confine the light to the designarea.

Lower mounting heights increase the spill light beyondthe property boundaries. To illuminate the spacesatisfactorily, it is often necessary to use floodlightswith a broader beam and to aim the floodlights indirections closer to the horizontal than would occur whenusing higher mounting heights.

Lower mounting heights make bright parts of thefloodlights more visible from positions outside theproperty boundary, which can increase glare.

Figures 9 and 10 show how a higher mounting height compares toa lower mounting height for providing a given amount of light.

Figure 6. Floodlight at ahigher mounting height withnarrow beam angle, resultingin less spill light

Figure 7. Floodlight at a lower mounting heightwith wider beam angle, resulting in more spilllight

How can sky glow be reduced?

While it is difficult to accurately model sky glow, at thispoint it is presumed that the most important factors are lightoutput and lamp spectral characteristics, light distributionfrom the luminaries, reflected light from the ground, andaerosol particle distribution in the atmosphere. If thequantity of light going into the sky is reduced, then sky glowis reduced. Thus, current practice is to reduce sky glow by 1)using full cutoff luminaries to minimize the amount of lightemitted upward directly from the luminaries; 2) reducing lightlevels; 3) turning off unneeded lights; 4) limiting lightedhours of outdoor sales areas, parking areas, and signs aroundimportant observing sights; 5) limiting lightinginstallations; and 6) mandating low-pressure sodium lightsources, which allows astronomers to filter the line spectrafrom telescopic images. For reducing sky glow, the Institutionof Lighting Engineers (ILE) has suggested limits on the amountof luminaries-emitted light that goes directly into the sky.The ILE’s limits are specified by environmental zone.

CASE STUDY:

"When thefirst

How can sky glow be reduced?

While it is difficult to accuratelymodel sky glow, at this point it is presumedthat the most important factors are lightoutput and lamp spectral characteristics,light distribution from the luminaire,reflected light from the ground, and aerosolparticle distribution in the atmosphere. Ifthe quantity of light going into the sky isreduced, then sky glow is reduced. Thus,current practice is to reduce sky glow by 1)using full cutoff luminaries to minimize theamount of light emitted upward directly fromthe luminaire; 2) reducing light levels; 3)turning off unneeded lights; 4) limitinglighted hours of outdoor sales areas,parking areas, and signs around importantobserving sights; 5) limiting lightinginstallations; and 6) mandating low-pressuresodium light sources, which allowsastronomers to filter the line spectra fromtelescopic images. For reducing sky glow,the Institution of Lighting Engineers (ILE)has suggested limits on the amount ofluminaire-emitted light that goes directlyinto the sky. The ILE’s limits are specifiedby environmental zone, as shown in Table 1.

Table 1. Limits on sky glow for differentenvironmental zones

Environmental zone Sky glow ULR* (max %)

E1 0.0

E2 2.5

E3 5.0

E4 15.0

* ULR is the Upward Light Ratio of the

observational facilities of the 20th century were coming up inIndia they were being shifted far away from cities. Theobservatory in Hyderabad shifted to Rangapur, and the IndianInstitute of astrophysics set up an observatory at Hanle, inthe Himalayas," N Ratnashree, director, Nehru Planetariumsaid. 

"The Uttar Pradesh State Observatory - shifted its locationfrom Varanasi and set up an observatory at Nainital but thelocation became so polluted with light that the new telescopeof this observatory, which is the largest in India, is nowbeing built far away at Devsthal," she says

CONCLUSION:Light Pollution is that disease about which most of us are notaware , which makes it more dangerous, first we need to make people aware about it and then work upon suggested solutions given above.

REFERENCES:

Articles from “THE HINDU” Articles of Lighting Research Centre. Ecological Consequences of Artificial Night Lighting. www.darksky.org

APPENDIX:

i. Luminaries: Any object which illuminates light.ii. Spill Lights: Light emitted by a lighting installation

which falls outside the boundaries of the property onwhich the installation is sited.

iii. Disability Glare: It impairs the vision of objectswithout necessarily causing discomfort.

iv. Discomfort Glare: It is an instinctive desire to lookaway from a bright light source or difficulty in seeing atask.