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.
124 counties — fewer than ever in the history of the State of the Air — got and F for ozone smog.
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.
The geographical distribution of cities with the worst ozone problems confirms a pattern seen over the past seven reports: nearly all are western cities and only a few lie in the East. Although cleanup of ozone precursor pollutants has been working to reduce ozone concentrations, the impact of climate change in the West has meant higher temperatures, dry, sunny skies and more frequent stagnation events that are contributing to the number of unhealthy ozone days being higher than it would otherwise be. Simply, climate change is undercutting the progress we would have made.
Monitoring the State of the Air in Indian Country
EPA’s National Ambient Air Quality Monitoring System is a network of more than 4,300 sites in over 900 counties across the country measuring air pollutants such as ozone and fine particle pollution. The information these monitors gather is essential for the functioning of the Clean Air Act and protecting public health and welfare. Many of these monitors are maintained and operated by state and local governments with funding and direction from EPA. Tribes across the U.S. also act as partners, conducting programs to monitor and improve air quality on Tribal lands.
As sovereign nations, Tribes have express authority under the Clean Air Act and the Tribal Authority Rule to manage air quality in Indian country. Unlike requirements applying to state agencies, there are no mandates for Tribes to conduct air quality monitoring. However, many Tribes recognize the value in doing so and for decades have been active participants in the nationwide monitoring program, following EPA’s specific requirements to assure the quality of the data gathered.
In the years 2019-2021, 38 Tribes collected and submitted air quality data to EPA from monitors in 37 counties across 14 states. In most of those counties, state and local governments also contributed data from their monitoring networks. However, in some cases the Tribal monitors were the sole source of air quality information available to the residents of that county.
Indian Country covers a wide diversity of environments, from frontier (which is less population-dense than rural) to semi-urban. In many places, the air quality on Tribal lands suffers from the same threats as elsewhere in the U.S. Of the 37 counties with data from Tribal monitors in this year’s “State of the Air” report, 15 of them, covering a population of more than 12 million people, received at least one failing grade. They included some of the most polluted counties in the country, including Riverside (ranked 2nd worst for ozone), Fresno (2nd worst for short-term particle pollution), and Kings (5th worst for annual particle pollution), all in California.
At least 46 tribes that had been active in monitoring ozone and fine particle pollution at some time in the past were not identified as having collected data during the 2019-2021 period. Resources are often spread very thin in Indian country, and that can have a negative impact on the sustainability of air quality and other environmental programs. Considering how important these programs are to protecting the health and well-being of people living on Tribal lands and in the surrounding communities, expanding and sustaining adequate investment needs to be a priority for the nation. In particular, Congress should increase funding for Tribes’ air quality work.
For more information about Tribal air quality programs, see the Status of Tribal Air report published annually by the National Tribal Air Association.