The Environmental Protection Agency (EPA) is approving, under the Clean Air Act (CAA), revisions to Ohio's state implementation plan (SIP) as requested by the Ohio Environmental Protection Agency (OEPA) on March 10, 2017, and supplemented on July 18, 2017. The revisions to Ohio's SIP implement certain EPA regulations for particulate matter smaller than 2.5 micrometers (PM<INF>2.5</INF>) for nonattainment areas by establishing definitions related to PM<INF>2.5</INF> and defining PM<INF>2.5</INF> precursors. The revisions also incorporate the findings of a comprehensive precursor demonstration performed by OEPA, which determined that volatile organic compounds (VOC) and ammonia (NH<INF>3</INF>) are an insignificant source of PM<INF>2.5</INF> for the purpose of new source review in nonattainment areas in Ohio.