The Clean Air Act requires the United States Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six “Criteria Pollutants” – Particulate Matter, Ozone, Nitrogen Dioxide, Carbon Monoxide, Sulfur Dioxide, and Lead in order to protect human health and the environment from unsafe levels of these pollutants. These pollutants are regulated through the EPA setting maximum limits on exposure levels that are reviewed periodically based on current science and health studies. Regions which are found to be out of compliance with those limits based on actual measurements of pollution at monitoring sites may be designated by EPA as a “Nonattainment Area”.
Most of the Knoxville Region has recently been, or is currently in non-attainment for two criteria pollutants (ground-level ozone and fine particulate matter) under federal NAAQS. While air quality monitoring data has shown significant improvement in the lowering of levels of ozone and fine particulate matter in the Knoxville Region, the NAAQS have also been made more stringent essentially setting the bar higher for this area to be able to achieve attainment status for all pollutants.
One consequence of being designated as a nonattainment area is the requirement to demonstrate “Transportation Conformity” for the TPO’s Plans and Programs. Transportation conformity is the link between air quality planning and transportation planning and its purpose is to ensure that federal funds will not be spent on projects that cause or contribute to any new violations of the NAAQS or delay timely attainment of the standards. Since portions of the nonattainment area extend beyond the TPO Planning Area, the TPO has entered an agreement with the Tennessee Department of Transportation to conduct the transportation conformity process for the entire nonattainment area.
The most current Air Quality Conformity Determination covers the updated 2014-2017 Transportation Improvement Program and Amendments to the 2040 Knoxville Regional Mobility Plan. The Air Quality Conformity Determination was adopted by the TPO Executive Board on March 10, 2015 and approved by the U.S. Department of Transportation on March 26, 2015.
Air Quality Conformity Determination
Map of Knoxville Region Air Quality Status