On Tuesday, January 31, EPA Administrator Michael Regan finalized EPA’s disapproval of State Implementation Plan (SIP) submissions for 19 states regarding the interstate transport of ozone under the 2015 eight-hour ozone national ambient air quality standards (NAAQS) of 70 parts per billion. Under the Clean Air Act, states were required to submit SIPs for the 2015 eight-hour ozone standard by October 1, 2018. The Clean Air Act required the SIPs to include “good neighbor” provisions, which prohibit emissions that either significantly contribute to nonattainment in a neighboring state or interfere with maintenance of the NAAQS in a neighboring state.

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