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Light Pollution, Its Effect, and Ways to Tackle It

Updated on November 29, 2017
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Varsha is an enthusiastic writer who loves to share informational content with the readers.

Satellite view of Paris at night
Satellite view of Paris at night | Source

What is Light Pollution?

Artificial illumination consists one of the most useful and integral parts of the human civilisation as it allows all human activities to expand during the night or to take place in areas where the lighting is inadequate. Its misuse though, causes a phenomenon known as photopollution/ light pollution/ luminous pollution. This phenomenon is caused because artificial light is being reflected from the various components of the atmosphere.

The International Dark-Sky Association define light pollution as:

"Any adverse effect of artificial lighting, including sky glow, glare, light trespass, light clutter, decreased visibility at night, and energy waste."
This definition identifies the negative aesthetic effects of artificial light but IDA also claims that energy waste is pollution. The definition indicates that light pollution is a waste of energy and therefore an indirect waste of nuclear energy and limited fossil resources.

Types of Light Pollution

The International Dark-Sky Association's definition of light pollution contains four lighting components that describe different kinds of light pollution:

  • Urban sky glow is the brightness of the sky over large inhabited areas.
  • Glare is a visual discomfort or decreased visibility due to excessive brightness.
  • Light trespass is unintended, unwanted or unnecessary light.
  • Light clutter is bright, confusing and excessive groupings of light that is common in urban areas.

A study published last year found that light pollution covers 80% of the globe which includes roughly 83% of Earth’s population, and more than 99% of Europeans and Americans.

Effect of Light Pollution on Humans

Affects the Circadian Rhythm-Many aspects of human physiology, behaviour and metabolism are dominated by the twenty-four-hour rhythms of light and dark(known as the circadian cycle) which has a major impact on health and well being. These rhythms not only effect sleep-wake cycles, performance and alertness pattern but also core body temperature and production of the hormones cortisol and melatonin. Inappropriate light exposure could cause circadian rhythm to become desynchronized with an impact on the human physiology and metabolism. It could result in reduced metabolism. It also has an indirect effect on diabetes and overweight.

Affects The Melatonin Production-Light also affects the melatonin production, which is a major biochemical signal depending on darkness. The production of melatonin is increased during the night and maintains the circadian cycle. Scientists have found that melatonin production decreases with the impact of light. A disruption in the circadian rhythm, like light exposure during the night, inhibits the signal system and therefore the production of melatonin. Melatonin suppression occurs instantly upon light exposure and stops when the lights are turned off. A prolonged, daily occurring, exposure to light during the melatonin-producing phase at night, could lead to chronic melatonin suppression - which could evoke depression and could also elevate heart rate, irregular core body temperature and affect cortisol production.

Causes Sleep Disorders-Circadian rhythm sleep disorder is caused by inappropriate exposure to light which may include sleep problems, fatigue, forgetfulness, performance problems and gastrointestinal problems. The long-term effects of these problems might be increased cardiovascular disease, type-2 diabetes and some types of cancer.

Causes Disability Glare- Glaring lights can distress the eyes. Lighting fixtures on the poorly designed roadways generally produce a condition called 'disability glare' which causes us to avert our eyes from the veil of light being scattered across our retinas. It reduces color perception and our ability to see contrasts.

Light pollution poses a threat to 30% of vertebrates and more than 60% of invertebrates.

Birds die due to collision with buildings.
Birds die due to collision with buildings. | Source

Effect of Light Pollution on Wildlife


Artificial lighting during night affects not only nocturnal mammals but also diurnal species, active during the day. Even crepuscular species that are active at dawn and dusk are affected by light at night. The artificial light triggers unnatural periods of repulsion and attraction that leads to disturbances in reproductive cycles. The light disorients and fixates animals and interferes with sustenance and feeding. The artificial light from the cities and towns cause a decline in the reproduction of mammals and difficulty in foraging for food. Impairment of night vision has increased mortality and vulnerability in some species. The mammals which are mostly affected by artificial light includes bats, raccoons, coyotes, deer and moose.


Amphibians are currently suffering population decline around the world and these species are especially disposed to reproduction disruption due to bright light. For example-Many pond-breeding salamanders show a strong fidelity to their home ponds and studies have shown that artificial light and illumination can disrupt salamanders’ ability to return to home ponds to breed. Therefore, artificial light can affect amphibians causing a decline in their reproduction and reduced foraging for food. They become confused and disoriented which makes them vulnerable prey.


Artificial light can paralyze the night-flying insects and make them more visible to predators. Moths, for example, have an incessant attraction toward artificial points of light. This disrupts the nocturnal pattern of predator species by creating an unnatural concentration of food. This disruption creates a dramatic change in quantity and location of food for predators like birds and bats. These imbalances in the predator-to-pray relationship have negative consequences for both species.

Firefly populations are also decreasing noticeably and artificial light at night interferes with several firefly behavioral mechanisms. Fireflies depend on light cues for flash pattern and flight altitude since these mechanisms are linked to feeding and reproduction. Artificial light causes some behaviour to be artificially triggered and others to stop, diminishing the time an adult spends attracting a mat but also decreases the effectiveness of flash patterns by making the mating behaviour less visible.


Most migratory birds are diurnal, active during the day, but hundreds of species
do migrate at night. Birds flying at low altitudes are particularly vulnerable to dangers posed by light at night. Especially during fog, birds often fly directly into the lit windows of skyscrapers. Many birds are killed outright but others are shocked and dazed for hours before recovering. Birds that survive a nighttime collision are still in danger during the day as they try to escape the city. Many birds collide with buildings during the day or become trapped in a maze of bright, reflective buildings and therefore fall victims to gulls, raccoons, crows or cats.

Shiny building exteriors reflect the surrounding trees, sky and clouds and give the migratory birds an illusion of a safe passage.Lighthouses, emission stacks, tall monuments and other high structures can be devastating to a huge flock of birds in the vicinity at a foggy, cloudy or rainy night.


Reptiles are greatly affected by artificial light. Sea turtles provide a dramatic example of how artificial light can disrupt behaviour. Many species of sea turtles lay their eggs on beaches. The hatchlings, then point themselves seaward by orientating toward the center of a broad and bright horizon. Hatchlings crawl in the precise direction toward the bright seaward if the beaches are lit only by the twinkle of stars or glowing moon. However, beaches lit by the glare of electric light deceive hatchlings who often attempt to reach the overlit artificial brightness which contributes to exhaustion, dehydration or death by crossing roads.

Beaches that are brightly lit at night may also discourage female turtles from nesting in them. The bright light disorientates the turtles that often wander onto nearby roads where they encounter several dangers.

Light Pollution disrupts the behaviour of sea turtle by disorienting them.
Light Pollution disrupts the behaviour of sea turtle by disorienting them. | Source

Effect of Light Pollution on Plants

Artificial light at night interferes with the light-detection system of plants further disrupting the reproduction cycles. Trees fail to lose their leaves or bud prematurely when given false cues from outdoor artificial night lighting. Migration paths of birds and bats are timed to coincide with the blossom of edible trees and flowers along the migration routes. These symbioses feed animals and pollinate plants, but if a tree is budding prematurely it is no longer a viable food source and is less liable to become pollinated. Artificial lighting can, directly displace animal and plant activity and therefore indirectly affect other organisms that interact with them.

There has been a 2.2% increase in the Earth's outdoor artificial lighting each year between 2012 and 2016.

Effect of Light Pollution on Astronomy

Light pollution has affected astronomy to a great extent. It interferes with our ability to study the sky. Increase in artificial lightning caused by cities and towns makes it difficult to see dim objects in the sky. It has also limited the numbers and types of objects observable in the sky. Most of the visible stars and other astronomical objects can no longer be seen due to the pollution and bright light.

An office building is illuminated by high pressure sodium (HPS) lamps shining upward, of which much light goes into the sky and neighboring apartment blocks and causes light pollution.
An office building is illuminated by high pressure sodium (HPS) lamps shining upward, of which much light goes into the sky and neighboring apartment blocks and causes light pollution. | Source

How to Tackle Light Pollution

Light pollution can be easily dealt with if we cut down on inefficient and unnecessary lighting. Some easy and cost-effective ways to solve light pollution are:

  • Shield your outdoor lighting to avoid glare. Use light and fittings that are shielded and aim these thoughtfully.
  • Only use the light when you need it.
  • Use timers and dimmers. They are useful energy savers and also help to reduce light pollution.
  • Shut off the lights when you can.
  • Use only enough light to get the job done.
  • Use long wavelength light with a red or yellow tint to minimize impact.
  • Keep your bedroom as dark as possible by using blackout curtains when sleeping.
  • Avoid unnecessary reflections which can create unwanted glare and light

A shielded light uses less wattage and saves you money. Work with your neighbours and local government to keep the skies natural. You save money while simultaneously reducing the impact of artificial light at night.


  • Anisimov, V. N. (2006). Light pollution, reproductive function and cancer risk. Neuro Endocrinol Lett, 27(1-2), 35-52.
  • Chepesiuk, R. (2009). Missing the dark: health effects of light pollution. Environ Health Perspect, 117(1), A20-27.
  • Falchi, F., Cinzano, P., Elvidge, C. D., Keith, D. M., & Haim, A. (2011). Limiting the impact of light pollution on human health, environment and stellar visibility. J Environ Manage, 92(10), 2714-2722. doi: 10.1016/j.jenvman.2011.06.029
  • Kerenyi, N. A., Pandula, E., & Feuer, G. (1990). Why the incidence of cancer is increasing: the role of 'light pollution'. Med Hypotheses, 33(2), 75-78.
  • Pun, C. S., & So, C. W. (2012). Night-sky brightness monitoring in Hong Kong: a city-wide light pollution assessment. Environ Monit Assess, 184(4), 2537-2557. doi: 10.1007/s10661-011-2136-1
  • Raven, J. A., & Cockell, C. S. (2006). Influence on photosynthesis of starlight, moonlight, planetlight, and light pollution (reflections on photosynthetically active radiation in the universe). Astrobiology, 6(4), 668-675. doi: 10.1089/ast.2006.6.668
  • Reiter, R. J., Gultekin, F., Manchester, L. C., & Tan, D. X. (2006). Light pollution, melatonin suppression and cancer growth. J Pineal Res, 40(4), 357-358. doi: 10.1111/j.1600- 079X.2006.00325.x


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