Nearly Half of US Breathes Unhealthy Levels of Pollution—Cars and Trucks Largely to Blame
Union of Concerned Scientists
MAY 21, 2025
Between 1990 and 2020, national concentrations of ozone were reduced by 25 percent, but this progress is eroding. From 2000 to 2020, national PM 2.5 These are the criteria air pollutants, namely PM 2.5 , ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide and lead. and ozone in central and eastern states.
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