Since March 1, the state has recorded just four unhealthy ozone days with concentrations higher than the 70 parts per billion ozone standard set by the Environmental Protection Agency in 2015, the best outcome since the previous record low of five unhealthy ozone days in 2013. None of this year’s unhealthy ozone days occurred in Western North Carolina.

“This is a positive indicator that our partnerships focused on curbing air pollution are working,” said Mike Abraczinskas, director of the Division of Air Quality (DAQ) in the N.C. Department of Environmental Quality. “This year’s ozone data provides clear evidence that a robust economy and healthy environment can thrive at the same time.”

Ozone forms when nitrogen oxides react with hydrocarbons on warm, sunny days with little wind. It can be unhealthy to breath, and exposure to high levels can cause even healthy people to develop asthma over time. It also causes millions of dollars in tree and crop damage each year in the U.S.

In the early 2000s, about one-third of N.C. counties were classified as non-attainment zones for ozone, but air quality has improved due to declining emissions from vehicles, power plants and other industrial sources, spurred by the 2002 Clean Smokestacks Act that required the state’s coal-fired power plants to reduce emissions by 75 percent and EPA requirements leading to lower emissions from other sources.