Attainment demonstrations describe measures for achieving the National Ambient Air Quality Standards (NAAQS) in areas that are designated by United States Environmental Protection Agency (U.S. EPA) as “nonattainment” for one or more of six, common “criteria” pollutants. There is a NAAQS for each of these pollutants, which include carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM), and sulfur dioxide (SO2).
When U.S. EPA periodically reviews and may revise the NAAQS based on the latest health, environmental, and technological advances. When U.S. EPA issues a new or revised standard, it issues air quality designations determining which areas of the country are, or are not, meeting the NAAQS based on air quality data and any state recommendations. Areas that do not meet new standards or contribute significantly to nearby violations are designated by U.S. EPA as “nonattainment”.
When U.S. EPA designates an area as “nonattainment,” the state may be required to develop plans to demonstrate how the area will attain the NAAQS by the attainment date. As such, Indiana’s state implementation plan (SIP) includes such plans, called attainment demonstrations, describing measures to ensure designated nonattainment areas achieve the NAAQS in a timely manner.
Attainment demonstrations generally include technical data including: a comprehensive analysis of ambient air quality monitoring data for the given criteria air pollutant, emissions inventories of directly emitted pollutants and precursors (directly emitted pollutants that react chemically to form other pollutants) for source sectors in the nonattainment area, and air dispersion modeling (mathematical air quality simulations) demonstrating that planned control strategies and emissions reduction measures will bring the needed air quality improvements.
IDEM has submitted attainment demonstrations for specific areas/counties within Indiana for the following criteria pollutants:
IDEM’s Nonattainment Status for Indiana Counties page includes a map of Indiana’s nonattainment areas and historical information about designations under previous and current NAAQS.
The timeframe for submitting an attainment demonstration to U.S. EPA is generally 18 to 36 months following an area’s nonattainment designation, depending on the pollutant. When subsequent air quality monitoring data shows that a nonattainment area has achieved the NAAQS, IDEM develops and submits a request for redesignation and maintenance plan to U.S. EPA for review and approval.