What is light pollution, its causes, types and prevention

It really astonishing that even light pollutes…Really? Does that happen? Is that the question on your mind? It is really sad to say a big bold YES. Let us look deeply into what light pollution is, its definition,  main sources or causes, different types of light pollution, and its effects. Something is lacking, right? Yes, we have also included the measures or steps to reduce light pollution.

Twinkle, Twinkle Little Star How I Wonder What You Are! The first nursery rhyme taught to most children. Children in cities have to be shown a book with the pictures of stars, while in rural areas they are more fortunate; they can see the stars if they step out at night.

Sun is our natural source of light, during the day. At night the moon and the stars provide sufficient light. The Creator meant for these to be enough for us. The inner clock of all the organisms and the Earth in general was tuned to sunrise and sunset. Everything began functioning at the first rays of the Sun; at the end of the day everything settled down to rest.

About light pollution

Definition of Light pollution:

Light pollution refers to the addition of excess light to the atmosphere in such a manner and intensity that causes disturbances to normal functioning of our bodies and even ecosystems.

Light pollution is also known as Photo pollution or luminous pollution. Thus, this is the explanation for those who search for photopollution or luminous pollution.

Light sources must be planned, designed and placed in spots where they are of maximum use. These should be made to focus on what requires to be lighted. A Street light should focus on the street. A display light should focus on the things that are on display. Any light that is not falling on the desired object is then directed away and upwards causing light pollution

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Sources (Causes) of light pollution

  • A light source that spills or scatters light in all directions is a major source of light pollution. This is because when an open bulb releases light, most of it is directed upward, instead of focusing on a specific spot. And that light that is scattered upwards is wasted and lost light. For e.g. a street light designed to direct light downwards towards the street is more suited for its purpose. It is also an effective use of energy in the form of electricity. Wasted light means waste of precious energy sources too.
  • Electronic advertising lights – most billboards have huge high intensity light that focus on them from below facing upwards. The light is also reflected off from the board.
  • Commercial centres- Malls restaurants discos shops pubs and other commercial centres attract their customers by using a lot of light sources that are not actually focussed on any particular spot. This ends up as scattered wasted light.
  • Night Sports Grounds- When a match is going on the brilliant halo is seen over the stadium or sports ground from miles away, because of the floodlights. This is scattered light.
  • Streetlight and car lights- Most of the light pollution in cities have their source in ill planned and unnecessary traffic lighting. Many street lights for hundreds of miles stay on all though the night causing light to be scattered in unwanted directions.
  • City parks, Airports and Public spaces- in some places one feels ‘is so much light really necessary?’ Is it necessary to illuminate every nook and cranny?
  • Residential Areas – Though landscape and garden lights are intended for aesthetic lighting they are also a source of nuisance to neighbours and walkers who find the excessive light disturbing.

Types of Light Pollution

Light pollution is differentiated into few types, but these are not separate from each other. A single source can fall into one or more category.

Light Trespass

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Remember that night when you were so tired and desperately trying to sleep. But the neighbours lights and street light combined brightened up your room and your sleep was disturbed. Or it could have been the other way round. You may have received a call in the night asking you to switch off your porch light because it was shining into the next door baby’s room.

This is light trespass. This happens when unwanted light enters someone’s property. It causes problems like sleep deprivation. There are strict rules concerning this in a number of cities in the US to protect the rights of their citizens against light trespass.

Over illumination

In order to enhance the architecture of beautiful buildings, their makers tend to place illumination all around these that face upward and are of a high intensity. This is called over illuminations as most of the light here does not illuminate the structure but escapes upwards. This is a type of light pollution but is also of concern as it is also a waste of precious energy. In the US itself, out of approximately 19 million barrels of oil that is used to generate power each day, energy created from at least 2 million barrels of oil is being wasted by over illumination.

Over illumination occur at all public spaces, commercial centres, industrial and residential sectors.


The blinding effect caused by reduced contrast because of light scattering in the eye by excessive brightness is Glare. The different kinds of glare are

  • Blinding glare- such as staring straight at the Sun.
  • Disability glare- blinded by oncoming car lights or scattering of light in fog; this leads to unsafe driving conditions. This kind of glare can also be intensified by a dirty wind shield.
  • Discomfort glare- staring at the screen of the computer or the mobile, causes fatigue if done for extended periods.

Light Clutter

Referring to excessive grouping of lights causing confusion and distracting from obstacles, clutter is noticed in badly planned street lighting, or in poorly placed advertising surrounding roadways. This is likely to cause accidents.

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Light clutter is a hazard for aviation industry, such as when runway lights are confused with an array of suburban lights.


Light that is reflected from illuminated surfaces, light escaping directly upwards from light fixtures is then scattered by the atmosphere back to the ground. This creates a diffuse glow over that area. It is mostly seen in populated areas.

White light sources contribute more to sky glow than yellow light.

Effects of Light Pollution

The consequences or effects of light pollution cannot be precised in few words. Thus please refer to our post effects of light pollution, in which the effects on human, wildlife and ecosystems etc. are explained in detail.Read about Effects of light pollution, detailing effects on Human, animals, wildlife, energy & night sky

Certain Measures That Can Be Taken To Reduce Light Pollution

  • Use the correct indoor and outdoor lighting hardware in our houses.
  • Demand a restriction on the advertising boards and their lighting in our cities and highways.
  • Design office and commercial spaces in such a way that minimal lighting can be used for maximum space
  • Use of technology such as motion sensors, dimmers and others that can reduce consumption of electricity when no one is using the space
  • Creating regulations for the use of correct lighting in public spaces especially of properly shielded light fixtures and properly focussed lights for the outdoors.
  • Many people think that having well lit spaces deters crime. This has not been proved true as can be seen in many instances and the well-known phrase “ in broad daylight.” Without negating their feelings, this can also be countered if intelligent lighting systems are used for lighting our spaces.

All parts of the environment are connected to one another be it physically or be it through time. The night time environment is a precious natural resource that must be protected.

The old Lakota was wise. He knew that man’s heart away from nature becomes hard. He knew that lack of respect for growing living things soon led to a lack of respect for humans too.

– Old Indian Proverb by Chief Luther Standing Bear