The U.S. Environmental Protection Agency (EPA) announced in June that Atlanta had officially attained the 2008 eight-hour ozone standard.

“This is a significant accomplishment and means cleaner air for approximately 3.5 million people,” Dawn Harris-Young, Region 4 EPA press officer, wrote in a recent email.

According to the Atlanta-based Region 4 EPA, this action is based on air quality monitoring data for 2013, 2014, and 2015 that meets the standard of 2008’s 75 parts per billion (ppb) of ground level ozone. For more than 20 years, Georgia’s Atlanta-Sandy Springs-Roswell area has worked collaboratively with the EPA and other stakeholders to make improvements.

Ozone in the stratosphere protects humans from the sun’s harmful rays. But down where people live, the EPA explains, ozone forms from nitrogen oxides and volatile organic compounds emitted from solvents, cars and power plants then cook in the sun causing damage to trees and plants. The ozone also irritates the lungs of healthy individuals, as well as aggravating conditions such as asthma and bronchitis.

In 2015 the EPA revised the 2008 8-hour standard that Atlanta just achieved, and set a new standard for 70 ppb for ground level ozone.

“This is a final action for the 2008 ozone standard,” Harris-Young wrote. “Georgia will continue to implement their maintenance plan to assure Atlantans continue to experience cleaner air.”

For more information, visit Epa.gov.