Exposure to unhealthy levels of ozone air pollution makes breathing difficult for more Americans all across the country than any other single pollutant. In the years 2019, 2020 and 2021, some 103 million people lived in the 124 counties that earned an F for ozone. More than 30% of the nation’s population, including 23.6 million children, 15.4 million people age 65 or older, and millions in other groups at high risk of health harm, are exposed to high levels of ozone on enough days to earn the air they breathe a failing grade.
More than 100 million Americans live in counties with F grades for ozone smog.
Although ozone air pollution remains a serious threat to public health, the trend in this year’s “State of the Air” report is continuing in a positive direction. The number of people living in counties with a failing grade for ozone declined by more than 19 million this year. Thirty-nine counties in 23 states dropped off the “F” list, including 8 states that left the list completely, some for the first time in the history of the report. At the same time, the number of counties that got an “A” increased by 26%.
Ambient ozone levels are influenced by a complex interaction of factors that can vary from year to year. Some fluctuation is to be expected and does not necessarily represent lasting change. However, at least some of the significant improvement in ozone levels in this year’s report can be attributed to the fact that the Clean Air Act has been working. Controls placed on emissions have increasingly resulted in the replacement of more polluting engines, fuels, and processes nationwide. The transition of the economy away from the coal, the dirtiest fossil fuel, has unquestionably had an impact, especially in parts of the eastern United States. It is also possible that pandemic-related changes in activity patterns in 2020 and 2021, such as increased telework, have made a difference, but that is still being studied and characterized.
The list of 25 cities with the worst ozone pollution in “State of the Air” 2023 and their order of ranking remained relatively stable compared with last year’s report. Only two cities improved enough to move off the list: Chico, California and Detroit, Michigan. They were replaced by Colorado Springs, Colorado and Hartford, Connecticut.
Cities in the West and the Southwest continue to dominate the list of most ozone-polluted. California retains its historic record of being the state with the most places on the list, with 10 of the 25 most-polluted cities. Cities in the Southwest fill most of the remaining slots, with twelve cities spread across six states in this year’s report. New York, Chicago and Hartford were the only three of the worst 25 cities for ozone east of the Mississippi River.
Of the cities on the worst 25 list, 13 saw an increase in the weighted average number of high ozone days and 12 had a decrease compared with last year’s report. Bakersfield, Fresno, San Diego and El Centro, California, along with Las Vegas and New York, all recorded their fewest days of high ozone in the report’s 24-year history. New York did so for the third year in a row.