What is Light Pollution?

Tricia Christensen
Tricia Christensen

Light pollution incorporates many different types of overuse of lights. It can refer to the way lights in a city obscure viewing the stars, the effects of too much light in a work or home setting, the pollution caused by energy consumption due to lighting, or the negative effects of too much human light on ecology. With so many possible definitions it can be challenging to determine what one means by light pollution, without specific reference to examples.

A fluorescent light bulb.
A fluorescent light bulb.

Light pollution when it refers to obscuring the night sky is most common in highly populated areas, like cities. The degree of light pollution is influenced not only by the many lit apartments but also by the headlights of cars, billboards, and lighting on buildings. City dwellers are often amazed when they camp or vacation in areas where not much exterior lighting exists. They see more stars than they could possibly see in a city environment because the area is lower in light pollution. Such a view can be a revelation to many who are used to a much higher degree of lighting during nighttime hours.

Areas with low light pollution allow people to see more stars.
Areas with low light pollution allow people to see more stars.

Workers have also been studied to see how they handle the effects of working in environments that are lit too brightly. Studies have linked light pollution in the workplace to higher blood pressure, tendency toward anxiety, headaches, and lowered libido. A few studies have suggested that light pollution may be a causal factor in producing breast cancer, especially among people who work at night. Melatonin, which is a breast-cancer fighting chemical the body produces is manufactured at night. Light pollution during nighttime hours may suppress melatonin production.

Observatories are often situated out of cities so their view of the skies is not polluted by light.
Observatories are often situated out of cities so their view of the skies is not polluted by light.

When light pollution refers to energy consumption, it generally means that the amount of power used to keep the lights on is in excess of what is needed, and is often using up valuable resources too quickly. Efforts have been made to reduce light pollution of this fashion by manufacturing fluorescent light bulbs. Power companies also encourage people to use the minimum amount of light needed for work, and to turn off lights in rooms that are not being used. Still more work is needed in this area to reduce light pollution that creates energy consumption.

The negative effects of light pollution on both plants and animals have been and continue to be studied. Certain lights can change the way animals behave, particularly nocturnal creatures. More outside light pollution translates to fewer “dark” hours for an animal to gather food, mate, or perform needed activities.

Outdoor lights can also affect the behavior of plants. Some deciduous trees, for example, fail to lose their leaves at the appropriate times if exposed to low level outside lighting. This can contribute to tree disease or simply become a nuisance for people who must clean up the leaves from a tree that sheds leaves constantly, instead of all in one batch.

Light pollution is also often considered annoying. For example, the lights in someone else’s home can be seen in your home. This could affect ability to sleep and is called light trespass. People who live close to flashing signs or streetlights that flood their rooms at night are also being subjected to light trespass. This can range from mildly irritating to extremely disturbing.

Scientists recognize that having light is a good and valuable thing, but that especially in urban areas, we have much more light than we actually need. Research has shown that light pollution has a detrimental effect on not only plants and animals, but also on humans. Many look for ways to illuminate new paths that will reduce light pollution.

Fluorescent lights use less energy and last up to six times longer than incandescent lights.
Fluorescent lights use less energy and last up to six times longer than incandescent lights.
Tricia Christensen
Tricia Christensen

Tricia has a Literature degree from Sonoma State University and has been a frequent wiseGEEK contributor for many years. She is especially passionate about reading and writing, although her other interests include medicine, art, film, history, politics, ethics, and religion. Tricia lives in Northern California and is currently working on her first novel.

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Discussion Comments


Outdoor application of light at night -- and that includes blue spectrum -- should be avoided in nearly all cases. The World Health Organization declared shift work is a probable carcinogen due to the circadian disruption and interference of essential melatonin production from exposure to light at night. The American Medical Association delegation unanimously voted light pollution is harmful and hazardous to human health. It is up to each of us to learn more about light pollution and how we can reduce it.

The lighting industry profited billions of dollars at the health expense of us and the planet's ecosystem. We're damn fools for letting them do it. Take a look at NASA video Earth-at-night shot from space called Black Marble. It shows how the lighting industry turned night into day.


A solution to light pollution might be a curfew of some sort. If people had regular sleeping patterns, we could regulate how much light is needed and when. Imagine if New York city turned off all of its lights and you could see the night sky from such a charming setting? Life might be more normal if this were the case.


Dark skies are conducive to a beautiful view that will just take your breath away. Have you ever been on a hike in the dark and suddenly come to a bright meadow, lit by starlight? This experience is jaw-dropping, and opens your eyes to how truly small we are in the universe. A full array of distant stars is viewable against the trees, and as you step out into that meadow, you feel like you are before a vast audience of stars in the distant sky above.


Pollution of the air can also cause light pollution, since the light will reflect off of chemicals in the air which aren't supposed to be there, or obstruct the night sky in a negative way.


I love to visit the mountains, where I can get a clear view of the stars and of the milky way, far away from the light pollution of the Boswash region. In areas like New York City, some people never get to truly experience the wonder of the vast and wonderful night sky. This is due to excessive light pollution which adversely affects people on a daily basis and can even ruin sleeping patterns, affecting psychology.

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