Thousands of adults and children in the Richmond metropolitan area are breathing easier because the air is cleaner, although still far from pristine, according to the American Lung Association.

The area improved to its best values on key measures of air pollution, the ALA reported in its annual national “State of the Air” report released Wednesday.

It is the 17th report the group has produced on the two most prevalent forms of pollution — ground-level ozone, also known as smog, and fine particulates, or man-made dust.

The area’s cleaner air is good news for the 3,500 children and 15,150 adults in the city diagnosed with asthma and the 10,400 residents with chronic obstructive pulmonary disease or COPD. The better air quality reduces the risk of lung damage to the most vulnerable populations, children and the elderly.

According to the ALA, cleaner cars and trucks and the reduction in coal-fired power plants are helping to improve air quality nationally and in the Richmond area.

The Richmond area now ranks 115th among 228 metro areas on the ALA’s clean air report card. In the 2015 report, Richmond ranked 160th among the 229 metro areas measured.

The report states that this area continues to stand out on the daily measure of fine particles in the air. For the fourth year in a row, the area received an “A” on that pollution measure — putting Metro Richmond on the list of the cleanest urban areas in the United States for that lung irritant.

The report also found that the Richmond area reduced fine air particulate pollution year-round, based on measurements from January 2012 through December 2014.

The ALA based its finding on results from state government monitoring sites in Chesterfield, Charles City and Henrico counties. The ALA did not report results specific to the city of Richmond, which does not have a measurement reporting site, despite the city population’s high levels of asthma.

The ALA also found smog, largely produced by vehicle exhausts in this area, to be less of a problem. The report noted the region got a lift from improvements in Henrico, whose ozone levels rose to a “D” grade from an “F” last year, despite having to meet more stringent standards.

Still, the area has a ways to go to gain clean air, according to Deborah Brown, president and CEO of the ALA’s Mid-Atlantic Division.

The 2016 report finds that there are still too many days when unhealthy levels of ozone occur throughout the Richmond metro area, Ms. Brown stated in a release on the report.

The report found that Henrico improved from 4.2 days of high ozone to 3.2 days. Charles City County remained at 3.8 days per year of high ozone, the same as in the 2015 report. The ALA graded that result an “F”.