When we consider all forms of pollution, light pollution is almost always overlooked. A starless sky is taken for granted in the city, as residents rely on bright street lights and house lights for safety and comfort. However, according to a recent study by researchers at the National Oceanographic and Atmospheric Administration (NOAA), the cost of this security is much higher than that of starless nights.
Many air toxins released in urban environments, such as ozone, accumulate during the day and are dispersed at night through a series of chemical reactions in the atmosphere. The main reagent studied, the nitrate radical, renders many toxins harmless, but is inactivated by sunlight. Although the lights used in homes, businesses and on the streets are not as powerful as the sun, the study shows that the nitrate radical is significantly affected by them.
Measurements of the atmosphere over Los Angeles found that city lights were responsible for decreasing the formation of nitrate radicals by 7% and increasing the amount of ozone precursors by 5% the next day. This may not sound like much, but a large number of US cities are already approaching or exceeding federal clean air guidelines. The problem becomes more significant when we consider that high pressure sodium and metal halide lights, the most common forms of street lighting, cause more pollution by operating at night.
Light pollution also has a number of other effects discovered in recent years. The mechanism behind a previously identified link between light pollution and an increase in breast cancer has been discovered by researchers studying the effects of melatonin. Melatonin production in the brain occurs primarily in the dark, and melatonin was found to inactivate the effects of sex hormones in reproductive tissues. Many disorders, from prostate cancer to insomnia and PMS, are exacerbated when lighting at night reduces melatonin production.
This is not surprising given that the reproductive cycles of animals are largely determined by the changing length of night throughout the year. Light pollution can cause serious problems for wildlife by disrupting breeding cycles and interfering with migratory patterns. According to the Purdue researchers, the light also damages many common deciduous trees and shrubs, as these plants also depend on the changing length of the night.
Policymakers, entrepreneurs, and individuals need to be aware of the costs of light pollution and make adjustments accordingly. There are immediate benefits to doing so, including lower energy bills and less pollution from fossil fuels. Fixing this problem is as easy as turning off the lights, but it doesn’t necessarily mean compromising safety or comfort. Traditional lights can be replaced with dark sky lighting, LED downlights or downlights, with extended canopy attachments, to significantly reduce sky glare.
