US EPA

EPA has completed the process of updating and revising, where appropriate, its Air Quality Criteria for Particulate Matter (PM) as issued in 1996 (usually referred to as the Criteria Document). Sections 108 and 109 of the Clean Air Act require that EPA carry out a periodic review and revision, where appropriate, of the air quality criteria (embodied in the Criteria Document) and national ambient air quality standards (NAAQS) for criteria air pollutants such as PM. Details of EPA's plans for the review of the NAAQS for PM were initially announced in the Federal Register (62 FR 55201, October 23, 1997). EPA made a First External Review Draft of the updated Air Quality Criteria for Particulate Matter available for review by the Clean Air Scientific Advisory Committee (CASAC) and members of the public in October 1999 (64 FR 57884, October 27, 1999). Following that public review period and a meeting of the CASAC in December 1999 (64 FR 61875, November 15, 1999), EPA revised the document as appropriate to incorporate CASAC and public comments, as well as to reflect many new studies on the effects of PM that were not available in time for discussion in the First External Review Draft.

EPA then made a Second External Review Draft of the Air Quality Criteria for Particulate Matter available for CASAC and public review in April 2001 (66 FR 18929, April 12, 2001). Following that public review period and a second CASAC meeting in July 2001 (66 FR 34924, July 2, 2001), EPA again revised the document as appropriate to incorporate changes in response to CASAC and public comments and also made further revisions reflecting new studies on PM effects that had become available between issuance of the First and Second External Review Drafts.

EPA then made a Third External Review Draft of the Air Quality Criteria for Particulate Matter available for CASAC and public review in May 2002 (67 FR 31303, May 9, 2002). Following that public review period and a third CASAC meeting in July 2002 (67 FR 41723, June 19, 2002), EPA again revised the document as appropriate to incorporate revisions in response to CASAC and public comments and also made further revisions reflecting new studies on PM effects that had become available between issuance of the Second and Third External Review Drafts, as well as reanalyses of certain existing studies occasioned after discovery of problems with applications of statistical software.

EPA made a Fourth External Review Draft available for CASAC and public review in June 2003 (68 FR 36985). A public meeting with CASAC was held August 25-26, 2003, during which CASAC reached closure on Chapters 1,2,3,4,5, and 6, with only relatively minor final revisions to be made. No further public review is requested on these chapters. However, CASAC did not reach closure on Chapters 7 (toxicology), 8 (human health), and 9 (integrative synthesis), each of which had to be more extensively revised or, in the case of chapter 9, significantly restructured. CASAC then provided additional review comments on revised drafts of Chapters 7 and 8 (dated December 2003) and on further revised drafts of Chapters 7, 8, and 9 made available for CASAC and public review in June 2004. These revised draft chapters were reviewed by CASAC at a public meeting held July 20-21, 2004. Closure was reached on Chapters 7 and 8. A revised Chapter 9 (August 2004) was made available for public comment and was reviewed by CASAC via a publically accessible teleconference on September 20, 2004, at which time closure was reached on Chapter 9 and CASAC completed its overall review of the Criteria Document. The final version of the entire PM Criteria Document was issued in October 2004.

U.S. EPA. Air Quality Criteria for Particulate Matter (Final Report, 2004). U.S. Environmental Protection Agency, Washington, DC, EPA 600/P-99/002aF-bF, 2004.