What is interstate pollution under the Clean Air Act?

The CAA statutes are poorly designed to address interstate externalities, as no programs require consideration of the effects in other states of the placement or number of new pollution sources. The EPA addresses this concern by conditioning SIP approval on a states plan not contributing significantly to non-attainment in, or interfere with maintenance by, any other state of a primary or secondary NAAQS. Also, the SIP cannot interfere with measures required in another states SIP.

Note: This allows a downwind state to sue the EPA Administrator for approving a SIP (or revision) that interferes with downwind attainment. The 1977 Amendments authorized states or political subdivisions to petition the EPA (at any time) for a finding that a major source or group of sources in another state are causing theim to violate NAAQS. It also requires a state to provide notice to nearby states when it proposes to build a new or modified PSD source or one that might contribute significantly to compliance with downwind NAAQS.