Silver patches and strands represent nitrogen dioxide emissions, a gas produced by combustion that contributes to acid rain, haze, and lung problems. While there are natural sources of nitrogen dioxide, people are major emitters, according to the Environmental Protection Agency.
Fuel-burning cars, trucks, power plants, factories, and even lawn mowers and construction equipment can pump nitrogen dioxide into the atmosphere. Forest fires and agricultural burning can, too. “You’re looking at a map showing where things are being burned,” says Laura Mazzaro, an atmospheric scientist and environmental engineer at Descartes.