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Transportation Air Quality Facts and Figures January 2006

Air Quality Trends

Air Pollutant Concentrations (percent decrease in concentration of Criteria Pollutants)

Carbon Monoxide (CO)
Nitrogen Dioxide (NO2)
Ozone (O3) (1-Hour)
Particulate Matter (PM10)*

*1993 – 2002

As air pollutant emissions have declined over time, air quality has improved. Reductions in air pollutant concentrations are impressive, with concentrations of carbon monoxide decreasing by more than 50 percent. All of the years in the 1990s had better air quality than any of the years in the 1980s, showing a steady trend of improvement.

Source: U.S. Environmental Protection Agency, Office of Air and Radiation. National Air Quality and Emissions Trends Report 2003 Special Studies Edition. Publication No. EPA 454/R-03-005,
September 2003. 28 June 2005.

Average Number of Exceedances Per Monitor 1994-2002

Average Numer of Exceedances Per Monitor 1994-2002. Click image for source data.

The number of exceedances of the air quality standards remained below an average of one per monitor over the past five years.

Source: U.S. Environmental Protection Agency. Air Data - Monitor Trends Report.
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Updated: 12/16/2015
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