UNITED STATES ENVIRONMENTAL PROTECTION AGENCY NATIONAL CENTER FOR ENVIRONMENTAL ASSESSMENT WASHINGTON, DC 20460 OFFlCEOF RESEARCH AND DEVelOPMENT APR - 7 1011 Ann M. Mason Senior Director American Chemistry Co uncil 700 Second St NE Washington DC 20002 Subject: Draft IRJS Assessment of Hexavalent Chro mium Docket 10 EPA-HQ-ORD-2010-0540 Dear Dr. Mason: Thank you for your letter of March 18 seeking a delay ofthe peer review of the draft IRIS assessment of oral exposure to hexavalent chromium. The reason for this delay would be so that research conducted under the American Chemistry Co uncil' s hexavalent chromium mode-ofaction research program could be incorporated into the draft assessment. A related reason is EPA's timeline for completing this assessment based on program needs. EPA initiated the reassessment of the health hazards of hexavalent chromium in autumn 2008, fo llowing release of a new Nat ional Toxicology Program study that demonstrated clear evidence of carcinogenicity for ingested hexavalent chromium in male and female rats and mice. At that time, completion of the IRIS assessment had been projected for the July-September quarterof2012. In May 2009, in response to demands for sw.ifter completion of IRIS assessments, EPA implemented revisions to the IRIS process, which affected the pace of new and ongoing assessments, including hexavalent chromium. I commend the American Chemistry Council for investing $4 million in targeted research on hexavalent chromium However, considering that new studies on hexavalent chromium are published virtually every month, there will always be ongoing research that could be accommodated through further delay. Without prejudging the outcome of mechanistic studies being written up fo r publication, it is entirely poss ible that granting yo ur request could entail a delay of unknown duration with no public discussion or review of the strong new studies that are now available. Accordingly, we cannot interrupt the peer review planning that was well under way when your request anived, especially when there is another path forward. The results of soon-lo-be- submitted studies can be presented at the peer review meeting and we can obtain recommendations from external peer reviewers about the strength of the existing database and its robustness in the face of new results. You will soon see an announcement of the peer review meeting for ingested hexavalent chromium, which will occur during this quarter. Thank you again for the opportunity to meet last month with you and your colleagues at the American Chemistry Council. I look forward to your oomments with the results of the new research, and I share EPA's commitment to developing an asSessment that reflects current scientific knowledge and the comments made during the external peer review period. Sincerely. ?, ,'iJ C~ l-~ Vincent Cogliano, PhD Acting Director, Integrated Risk Information System (IRIS) 2