Pollution is defined as contamination of the environment by waste created by humans. Typically, people only think of pollution of the air, land, or water by chemicals, trash, or sewage. Most often, light is not something that many people would consider to be a form of pollution; however, it is a very real problem, particularly in areas with large amounts of artificial lighting. Because it is a less - recognized form of pollution, there is not a high level of public awareness. Although some measures have been taken by governments and cities to address light pollution, education can increase efforts by not only government s but also by homeowners, businesses, and citizens in general.
What is Light Pollution?
Cities across the world produce artificial light from sources that range from street lights to the lighting at a stadium at night. The illumination from these sources is often excessive and misdirected. The resulting "wasted" or inefficiently used light often spreads beyond the area for which it was intended. This occurrence is called light pollution. It is caused predominately by outdoor lighting and is an unwanted consequence of its use.
There are four different types of light pollution, each representing a different way that artificial lighting spreads and affects the environment. These categories are urban sky glow, clutter, glare, and light trespass. The glowing, often yellow, pink, or orange haze that hovers over urban areas at night is referred to as urban glow. This glow is the result of the unhindered upward projection or spill of light that comes from a multitude of artificial light sources. Another type of light pollution comes from large groupings of lights that are poorly placed, and it is known as "clutter." The type of light pollution that occurs when light is uncomfortably and excessively bright to your eye is called glare. The final primary type of light pollution is called light trespass. With light trespass, the illumination of a light shines on areas where it does not belong and where it is not wanted. For example, when a person's outdoor lighting shines into a neighbor's yard or window, it is called light trespass.
Light pollution has numerous disruptive and potentially dangerous side effects for the environment, animal life, and human health. One of the most visible and frequently discussed side effects is the way that it blocks out stars in the night sky. This is a hindrance to the casual stargazer and to astronomers, but it is also problematic for certain animals that use the stars to help orient and guide them, such as migrating birds. The brightness of artificial lighting at night is also a problem for animals that instinctively seek out light sources. Baby turtles, for example, may become confused by the light and mistake it for the moon's glow over water. As a result, they head away from the water and toward these light sources and potential danger from predators and humans. Birds flying towards light sources may fly into buildings or other birds or may become disoriented around bright night lights. Even insects that are drawn to light are at an increased risk, as they become easy prey for nocturnal, insect-devouring animals. In terms of the environment, plant life often requires both daylight and darkness to grow properly. Certain plants flower only at night, and their pollination occurs from nocturnal animals. Continuous light from artificial lighting may prevent these plants from flowering entirely and, as a result, inhibit reproduction. Some types of artificial light can also affect trees that are sensitive to day length and prevent them from going dormant in the winter.
Lastly, human health and functionality is also affected by light pollution. The human body has a day and night cycle that is called the circadian rhythm or clock. This reflects the body's natural rhythm, and it can be disrupted by insufficient amounts of darkness. When the circadian clock is disrupted, certain bodily processes such as one's ability to sleep, the production of melatonin, and the regulation of cells are also disrupted and can result in health problems. For example, according to the National Institutes of Health (NIH), the human body functions at its best when activity is performed during the day and sleeping is done at night. Artificial lighting, however, can alter a person's ability to sleep at night. When a person does not receive an appropriate amount of sleep at night, he or she may have an increased risk of depression, diabetes, and weight gain. A person's motor and cognitive skills are also affected by failure to sleep at night. Light pollution also decreases the production of some hormones, such as melatonin. Melatonin is secreted from the pineal gland in the brain at night. It regulates the body's natural biological clock and is the trigger for certain biological activities. Artificial light reduces the amount of melatonin that is secreted and as a result can cause a number of health problems, such as increasing the risk of depression as well as breast and other cancers.
Reducing Light Pollution
The reduction of light pollution is the responsibility of everyone. Citizens, businesses, and governments must take action in order to achieve a reduction of harmful light output. The average person can help by using motion-detecting lights to illuminate the outsides of their homes. Any outdoor lights should be pointed so that the bulb faces downward, toward the ground. Another option is to purchase shielded lights for outdoor residential use. The use of blackout curtains can help prevent indoor light from escaping outside, where it can disrupt wildlife and spread unnecessarily. Spreading the word about light pollution to one's family and neighbors will help raise awareness of the problem and can prompt more people to make changes in their light usage. City residents should bring obvious sources of light pollution to the attention of city and government officials. Cities may reduce light pollution by switching to shielded lighting, which will help to reduce both glare and light trespass by controlling the direction of the light.