City Light Pollution

City Light Pollution

Dr Arvind Kumar

According to a recent study by scientists at the National Oceanic and Atmospheric Administration (NOAA) and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, it has been revealed that excess light at night can contribute to air pollution. The study further indicates that uplight from outdoor lighting that contributes to sky glow over cities also interferes with chemical reactions that naturally clean the air during nighttime hours. The chemicals from vehicle exhaust and other human created sources are broken down every night and prevented from becoming smog, ozone, or other irritants by a form of nitrogen oxide called the nitrate radical. Sunlight destroys the naturally occurring nitrate radical, so this process occurs only in hours of darkness.

Though the lights are 10,000 dimmer than the Sun, nevertheless, the study’s first results indicate that city lights can slow down the nighttime cleansing by up to 7% and they can increase the starting chemicals for ozone pollution the next day by up to 5%. As many cities are close to their limits of allowable ozone levels, this news is expected to generate immediate interest in light pollution reduction as a way to improve air quality among city, state, and federal bodies, including the Environmental Protection Agency.

Bob Parks, Executive Director of International Dark-Sky Association (IDA), has expressed hope that results of this study will encourage cities to adopt environmentally responsible dark sky lighting practices that include using fully shielded fixtures, minimum lighting levels, and lighting only when necessary.