On January 13, 2013, the EPA published a final rule revising the national ambient air quality standards (NAAQS) for particulate matter (PM) (78 FR 3086). Specifically, the EPA revised the level of the annual PM2.5 standard to provide increased protection against the health effects of PM. The other primary and secondary PM standards were retained. On December 3, 2014, the EPA published a call for information for research studies on PM (79 FR 71764) in order to inform the development of the Integrated Science Assessment (ISA) for the next review of the PM NAAQS. This ISA will present a rigorous assessment of the most policy-relevant scientific evidence on PM. Building on the evidence assessed in the ISA, the EPA will conduct quantitative analyses of PM exposures and risks and, as appropriate, will prepare a risk and exposure assessment document (REA) presenting and assessing these analyses. The EPA will also prepare a Policy Assessment document (PA) synthesizing the scientific evidence from the ISA and the exposure/risk information from the REA (if an REA is prepared). The PA will present considerations and conclusions of the EPA staff regarding the range of policy options that could be supported by the available evidence and information. Draft versions of the ISA, REA (if prepared), and the PA will be reviewed at public meetings by the Clean Air Scientific Advisory Committee (CASAC). Final documents will reflect CASAC's advice and recommendations, as well as staff's consideration of the comments expressed by members of the public. After completion of the ISA, REA (if prepared), and PA, the Administrator's proposal to retain or revise the PM NAAQS will be published in the Federal Register with a request for public comment. Input received during the public comment period will be reflected in the Administrator's final decision.