A new report shows some improvements in ozone levels in metro Atlanta and in Macon, though both areas still have significant air-quality problems.

The American Lung Association’s “State of the Air 2015” report, released April 29, gave a failing grade on ozone to six Georgia counties: Cobb, DeKalb, Fulton, Gwinnett, Henry and Rockdale. All are in metro Atlanta.

The report, which includes data from 2011, 2012 and 2013, gave Bibb County (where Macon is located) a D on ozone. The Macon/Warner Robins area was ranked 20th among U.S. cities with the highest year-round particle pollution.

Georgia counties getting A’s for ozone levels were Chatham and Glynn along the coast; Chattooga in northwest Georgia; Muscogee (the Columbus area); Coweta, south of Atlanta; Dawson, north of Atlanta; and Sumter in south Georgia.

Among the cleanest U.S. cities for ozone were Brunswick, Savannah/Hinesville/ Statesboro, Rome/Summerville, and Bainbridge.