Light pollution is a major issue worldwide, especially in urban areas. However, light pollution has largely been considered a nuisance to humans and something that really only interferes with other species. But a new study by scientists in the United States exhibited that light pollution may be increasing true air pollution.
The study regarding city lighting increasing air pollution was recently presented at the American Geophysical Union meeting which took place in San Francisco. The scientists found that lighting, especially from cities such as Los Angeles, interferes with the planet’s natural ability to combat air pollution.
The light from vehicles and a plethora of other things on the ground are preventing nitrate radicals to break down chemicals. These nitrate radicals are responsible for breaking down chemicals in the air, thereby reducing air pollution. Nitrate radicals actually assist in decreasing smog and ozone, which means interfering with the process simply makes smog and ozone worse in city zones where it is already high.
Nitrate radicals are only able to work at night due to them being destroyed by light from the sun. The scientists found that light going into the night sky from vehicles and other sources are having impacts similar to the sun, albeit on a lesser scale. Although the light from cities is on average 10,000 times less bright than the sun, the lights are decreasing the work of the nitrate radicals by nearly seven percent.
Harald Stark from the US National Oceanic and Atmospheric Administration stated: “Results indicate that city lights can slow down the night-time cleansing by up to seven percent and they can also increase the starting chemicals for ozone pollution the next day by up to five percent.”
The scientists believe that changing to a different type of lighting is not the solution. A method of reducing the impact city lights have on nitrate radicals would be to point lights away from the sky as much as possible. Such a solution would limit light pollution in general as well.
Stark stated: “[The impact of light] is more important up in the air than it is directly on the ground so if you manage to keep the light pointing downward and not reflected back up into the sky, into the higher parts of the air, then you would certainly have a much smaller effect of this.”
The scientists point to the fact that many cities in the United States are at or close to the limit for air pollution and minor changes to lighting may help them stay below these limits.