People across America regularly breathe unhealthy air that increases their risk of premature death, asthma attacks and other adverse health impacts.
In 2016, 73 million Americans experienced more than 100 days of degraded air quality with the potential to harm human health. That is equal to more than three months of the year in which smog and/or particulate pollution was above the level that the EPA has determined presents “little to no risk.” Millions more people in urban and rural areas experienced less frequent but still damaging levels of air pollution.
To safeguard public health, the nation needs to preserve and strengthen existing air quality protections at the federal and state level and move to reduce the future air pollution threats posed by global warming.
Burning fossil fuels such as coal, diesel, gasoline and natural gas creates air pollution in the form of smog, particulates and air toxics. Wildfires, wood stoves, agricultural dust and other sources create additional air pollution. There is no documented safe level of exposure to some of these pollutants.
Millions of Americans live in urban and rural areas that experience frequent smog and/or particulate pollution.
Table ES-1. Ten Most Populated Metropolitan Areas with More than 100 Days of Elevated Air Pollution in 2016
Note: This count includes air pollution at or above the level the EPA labels “moderate” and indicates in yellow or worse in its Air Quality Index.
Figure ES-1. Both Urban and Rural Areas Experienced Frequent Smog and/or Particulate Pollution in 2016
Smog pollution is a frequent health threat in some regions.
Particulate pollution affected people living in a broad range of places in 2016.
Global warming threatens to exacerbate the nation’s smog and particulate pollution problems. Higher temperatures will facilitate formation of smog and altered wind patterns may increase the number of days with stagnant air that prevents dilution of contaminants. Wildfires, which generate particulate pollution and smog precursors that can travel hundreds of miles, are predicted to become more frequent and intense.
To reduce the pollution that threatens the health of people across the country, and to avoid global warming-related increases in air pollution in the future, the nation should:
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 The map shows Census-designated metropolitan and micropolitan areas, plus rural counties that have an air pollution monitor. Note that Macon, Georgia, is mapped to Macon County. The towns of Bishop, CA; Rockland, ME; and Walterboro, SC, are not shown because they are not included in the Census Bureau shapefiles for mapping.
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 George Luber et al., “Chapter 9: Human Health,” Climate Change Impacts in the United States: The Third National Climate Assessment, U.S. Global Change Research Program, doi:10.7930/J0PN93H5, 2014.
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