Recent press reports note that air quality has improved worldwide and in the United States during the ongoing pandemic1. Shortly prior to the pandemic, though, stories lamented declining American air quality2. What’s really going on?  Is the news good or bad?

Certainly, the pandemic and the resulting orders to Americans to stay at home and to pause nonessential business activities have decreased activities such as driving and manufacturing that generate air pollution. Even before those events, however, significant progress had been made in reducing air pollution in the United States. The American Lung Association recognizes in its 2020 report on the State of the Air that there have been “dramatic improvements” in air quality over the past fifty years.

Data from the Environmental Protection Agency confirms this progress. EPA’s most recent report on Our Nation’s Air explains that since 1990, levels of each of the common air pollutants in the air regulated by EPA’s National Ambient Air Quality Standards (so-called  criteria pollutants) have decreased substantially. Those decreases range from an 89 percent decrease in the concentration of sulfur dioxide (SO2) to a 21 percent decrease in ozone (O3).  Concentrations of air toxics have also declined. Indeed, EPA provides data showing air quality has continued to improve during the Trump administration – SO2 down 10 percent, O3, down 4 percent, lead (Pb) down 28 percent.

These improvements in air quality have led to a decline in the number of areas that are designated nonattainment for one or more criteria air pollutants. The number of nonattainment areas dropped from 166 in late 2017 to 139 by the end of March 2020. Furthermore, air quality in 53 of the remaining nonattainment areas meets the applicable air quality standards. These areas remain nonattainment only because they have not yet completed the steps necessary to be redesignated to attainment3.

The improvements in air quality result from reductions in emissions of both criteria air pollutants, of other substances that form criteria air pollutants after being emitted into the air, and of air toxics.  Specifically, EPA reports that emissions of criteria air pollutants and their precursors declined 77 percent between 1970 and 2019. For example, emissions of ammonia and volatile organic compounds, both of which contribute to the formation of criteria air pollutants, declined by 8 and 47 percent, respectively, between 1990 and 2019. Emissions of SO2 declined by 91 percent, while those of carbon monoxide (CO) declined 69 percent. In addition, emissions of air toxics declined 74 percent between 1990 and 2017. Finally, EPA’s 2020 inventory of greenhouse gas emissions, also shows a long-term decline in the emissions of these substances since 2005.

In short, the news is good.  Air quality in the U.S. is not declining.  In fact, it has improved dramatically since the enactment of the Clean Air Act. Although room for further improvement remains, the Yale Center for Environmental Law and Policy ranks air quality in the United States above that of many developed countries, including Germany, Belgium, Russia, and China. This air quality improvement has taken place at a time when – as noted in the EPA report — the Gross Domestic Product grew 285%. Moreover, air quality in U.S. air quality should continue to improve as EPA, states, industries, and consumers continue to fulfill the requirements of the Clean Air Act.


Environmental Protection Agency. (2019). Declining National Air Pollutant Emissions (2017-2019) [Table]. Retrieved from













          1 IQAir, COVID-19 Air Quality Report, Apr. 22, 2020,; Andrew Freedman & Lauren Tierney, The silver lining to coronavirus lockdowns: Air quality is improving, Washington Post, Apr. 9, 2020,

          2 Drew Kann, Air quality in the US is getting worse and could be killing thousands, study finds, CNN, Oct. 23, 2019,

          3 Scott Mathias, EPA, NAAQS/SIP, Permitting & Other Air Quality Planning Updates 4 (Apr. 29, 2020),