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.
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.
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.
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.
