EPA creates air quality trends using measurements from monitors located across the country. The table below show that air quality based on concentrations of the common pollutants has improved nationally since 1980.
|1980 vs 2017||1990 vs 2017||2000 vs 2017||2010 vs 2017|
|Nitrogen Dioxide (annual)||-63||-56||-49||-21|
|Nitrogen Dioxide (1-hour)||-60||-50||-35||-14|
|Sulfur Dioxide (1-hour)||-90||-88||-79||-66|
Despite great progress in air quality improvement, approximately 111 million people nationwide lived in counties with pollution levels above the primary NAAQS in 2017.