Scientific American VW scandal causes small but irreversible environmental damage Still, experts agree that nitrogen oxide (pdf) is a nasty pollutant. Once released into the air it quickly converts into nitrogen dioxide—a reddish-brown gas with a pungent odor—and then absorbs sunlight to transform into the yellow-brown haze that blankets cities. It is this smog that can exacerbate dozens of health problems, including asthma, bronchitis and […]