The Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to set health-based limits, called National Ambient Air Quality Standards (NAAQS), for six dangerous outdoor air pollutants: particulate matter, ozone, nitrogen oxides, sulfur dioxide, carbon monoxide and lead. “State of the Air” looks at two of the most widespread and dangerous pollutants from this group, fine particulate matter and ozone.
The NAAQS identify what is considered a safe level of each pollutant to breathe, based on the most recent health and medical science, including an adequate margin of safety for those most at risk. These standards require states and local governments to take steps to reduce emissions to attain the standards. The standards also serve to alert families with children, seniors, individuals with lung or heart conditions, and others about dangerous air pollution levels through color-coded air quality alerts. This enables them to take necessary precautions to minimize their exposure. Under the Clean Air Act, the standards must be based solely on what is needed to protect health and must be periodically updated as the science evolves.1
Setting national health-based standards and requiring states that violate the standards to enact plans to clean up their air pollution problems have been a great benefit to the public health of the nation. Since the Clean Air Act was passed in 1970, the combined emissions of six key air pollutants have fallen by 78%, according to EPA. But as “State of the Air” 2024 shows, millions of people in this country are still breathing unhealthy air.
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In February 2024, after a lengthy wait, EPA announced a new, more protective annual standard for fine particle pollution. That standard is being used in the 2024 “State of the Air” report. The ozone standard is also overdue for a revision based on the science, but that process has faced multiple delays.
Page last updated: May 2, 2024