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What Does the Clean Air Act Say about the Interstate Transport of Air Pollution?

The Clean Air Act  requires states to address interstate transport of air pollution that affects downwind states' ability to attain and maintain National Ambient Air Quality Standards (NAAQS) through section 110(a)(2)(D)(i)(I) (also called the “good neighbor” provision). This section requires each state in its State Implementation Plan (SIP) to prohibit emissions that will contribute significantly to nonattainment of a NAAQS, or interfere with maintenance of a NAAQS, in a downwind state.  The Act requires EPA to backstop state actions by promulgating Federal Implementation Plans (FIPs) in the event that states fail to submit or EPA disapproves good neighbor SIPs.

Additional Provisions Addressing Interstate Air Pollution Transport

Under section 126, states can petition EPA for a finding that upwind sources emit in violation of the good neighbor provision, discussed above.  Specifically, section 126(b) allows any state or political subdivision to petition EPA to find that a major source or group of stationary sources emits or would emit any air pollutant at amounts that violate the good neighbor provisions of the Act. Section 126(c) provides that a source for which such a finding is made must, within specified timeframes, either cease operation or comply with emissions limitations established by EPA to bring about compliance with the good neighbor provision.  EPA has received several 126 petitions regarding the 2008 or 2015 ozone NAAQS.

Section 176A provides that, when the EPA Administrator has reason to believe that the interstate transport of air pollutants from one or more states contributes significantly to a violation of the NAAQS in one or more other states, he or she may establish a transport region comprised of those states to address such pollution.  Under this provision, the Administrator may also add any state (or portion thereof) to a transport region to address interstate air pollution transport.  When the Administrator establishes an ozone transport region, he or she shall also establish an associated transport commission to assess the degree of interstate pollution transport and control strategies to mitigate interstate air pollution transport. 

Section 184 of the Clean Air Act itself established a single transport region for ozone—the Ozone Transport Region (OTR)—covering portions of the northeast and mid-Atlantic.  This section also specifies control requirements to address interstate ozone pollution transport within the OTR.

EPA has received the following 176A petitions: