U.S. Environmental Protection Agency (U.S. EPA) designates an area as being in attainment if the area’s ambient (outdoor) air quality is meeting National Ambient Air Quality Standards (NAAQS). U.S. EPA sets NAAQS for six common air pollutants called “criteria pollutants” as required by the federal Clean Air Act (CAA) in order to protect human health and the environment. The Indiana Department of Environmental Management (IDEM) monitors Indiana’s air quality to be sure that NAAQS are being met.
U.S. EPA may designate an area as nonattainment if air monitoring over a period of time indicates that there are more pollutants in the air than the NAAQS allow or if the area contributes air pollutants to a neighboring area where NAAQS are being exceeded. U.S. EPA may redesignate an area from nonattainment to attainment if air monitoring data shows the area has attained the NAAQS and U.S. EPA has determined that the improvement in air quality is due to permanent and enforceable reductions in emissions, among other requirements.
Indiana has submitted attainment demonstrations for areas/counties within Indiana for the following criteria pollutants: