An interesting news regarding how pollution actually works and how nature tries to combat it comes from a National Oceanic and Atmospheric Administration researcher, Harald Stark. He says that during nighttime there’s a chemical called the nitrate radical, that breaks down the harmful chemicals emitted during the day by cars and factories.
One more important thing about the nitrate radical is that it doesn’t exist during the day – the light suppresses it. Only at night it is the time for this chemical to do its intended job, but even so it’s stopped by the artificial lighting in the cities, which diminishes its potential.
Tests that have been made over Los Angeles show that the light coming from the streets suppresses the nitrate radical, even if it’s much dimmer than the Sun. “Our first results indicate that city lights can slow down the night-time cleansing by up to 7% and they can also increase the starting chemicals for ozone pollution the next day by up to 5%,” Stark told the BBC.
“More work needs to be done to really quantify the next step which would be how much ozone could we actually have the next day. This work would be important to undertake because many cities are close to their regulatory limits in terms of ozone levels, so even a small effect such as this could be important,” he added.
He says one solution to this issue would be switching to another light color, such as red, but it’s hard to imagine Los Angeles lit in red during nighttime. The only viable solution would be focusing the lights downwards, so only a minimal quantity of it reaches the higher layers of the atmosphere and has an effect on the nitrate radical.