A new study shows that millions of Americans live in areas that experienced more than 100 days of poor air quality in 2018. These are days when ozone or particulate pollution was above levels the Environmental Protection Agency considers moderate. Conditions of degraded air quality are often linked to a variety of health problems like asthma, heart attack, and stroke.

In North Carolina, residents of Greensboro experienced 80 high pollution days, and in Winston-Salem, 107 — the most in the state.

The primary source of pollutants statewide is transportation, with electricity generation coming in at a distant second place.

Jamie Lockwood is a climate and clean energy associate with Environment North Carolina Research & Policy Center. She says that global warming will only exacerbate the problem.

“Just rising temperatures alone increase that ozone smog layer we’re seeing in this report," says Lockwood. "So, as one problem gets worse, the other one is going to go hand in hand. But that does mean our solutions are the same.”

Lockwood says that reducing vehicle emissions is key, and cities should encourage walking, biking, using public transportation, and have the infrastructure in place for electric vehicles.