The American Lung Association's annual air quality report is out. It gives good grades overall for air quality in the Carolinas, though some cities saw slight increases in bad air days between 2014 and 2016 - the latest data available.
The lung association's "State of the Air" report looks at two measures: ozone and particle pollution, or soot. Both can be harmful to health, especially for young people, seniors and anyone with lung or heart disease.
Ozone is formed when emissions from cars and industrial plants react to sunlight. In North Carolina, 10 cities saw an increase in the number of high-ozone days in 2016, including Asheville, Charlotte, Greensboro, Winston-Salem and Raleigh.
"2016 was, I think, the second hottest summer on record," June Deen, a North Carolina executive with the American Lung Association, said. "So we're beginning to see some of the impact of climate change and the warming of the climate, which contributes to that as well."
The statistics on particle pollution were better. Most major cities in the state had no high-particle pollution days between 2014 and 2016.
Deen said environmental laws have helped in recent decades.
"We've seen graded improvements in the quality of the air we breathe due to the provisions of the Clean Air Act," she said. "Our concern is that the Clean Air Act is under attack."
Deen is worried that current federal policies and budget cuts will reverse the positive trend.
The report said 4 in 10 Americans still live in counties that have unhealthy levels of either ozone or particle pollution.
Megan Green, of Mecklenburg County's air quality office, said there will always be year-to-year changes in the data.
"One of the factors that impacts how many poor air quality days we see is weather," Green said. "So rather than focusing on individual years, we as a local air quality agency are really looking at that overall trend."
The overall trend is that emissions of pollutants that form ozone are decreasing, and overall air quality is getting better, Green said.
Automobile exhaust is the major source of pollution in the region. Reducing vehicle travel and emissions is the main way residents can help, Green said.
"We're always looking for ways to improve air quality," she said. "So we focus on providing programs that involve local citizens and businesses as part of the solution."
Those include a program that offers grants to businesses to help replace aging diesel engines and an annual "Clean Commute Challenge," which tries to get people to leave their cars at home.