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State Implementation Plans

The federal Clean Air Act (CAA) provides a framework for United States Environmental Protection Agency (U.S. EPA) and states to work together to reduce harmful pollutants in the air. One of U.S. EPA’s responsibilities is setting standards called National Ambient Air Quality Standards (NAAQS) for six common and widespread “criteria” air pollutants that can harm people and the environment.

States are responsible for implementing, maintaining and enforcing the NAAQS. Section 110 of the CAA requires states to maintain state implementation plans (SIPs) detailing how they will accomplish this. U.S. EPA is responsible for reviewing and approving SIPs. When U.S. EPA issues a new or revised NAAQS, states work with U.S. EPA to make appropriate SIP amendments. As such, SIPs are living documents that generally include numerous parts. IDEM maintains Indiana’s SIP and provides opportunities for citizens to participate in SIP amendments.