The U.S. Environmental Protection Agency recently released data on U.S. air quality in 2015. When air pollution particles are smaller than 2.5 microns in diameter, they can penetrate the lungs and blood stream, triggering health problems like asthma and heart attacks. The map above illustrates where those particles (referred to as PM 2.5) were at their highest levels in the past year.
This pollution can come from forest fires, power plants, factories, and cars, and tends to be the most concentrated around cities. But PM 2.5 hotspots also occur out in the country, in places like California and Alaska. This is thanks to a record-bad year for wildfires, sparked by warmer temperatures and drought. Explore the data in an interactive map found here.
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