IRIS Assessment Materials for Hexavalent Chromium

Please see the attached comments from the American Chemistry Council Hexavalent Chromium Panel.

Filed on regulations.gov — full text not in the inline record.

Filed on regulations.gov — full text not in the inline record.

Filed on regulations.gov — full text not in the inline record.

Please see the attached comments from the American Chemistry Council Hexavalent Chromium Panel.

Filed on regulations.gov — full text not in the inline record.

The attached comments are submitted on behalf of the American Chemistry Council. They address discussion question #8- defining mutagenicity and genotoxicity.

The American Chemistry Council (ACC) submits this letter to inform EPA about ongoing research that supports and adds to the science in the IRIS Assessment of Hexavalent Chromium. See attached letter for full text.

We request another science issue be added to the topics. In conferences, Dr. Flowers reported that there would be an issue related to problem formulation. However, there is no issue in the initial list. We have suggested some language to describe this issue as a starting point for EPA staff and indicated a couple of speakers. New Science Issue: Identification of critical effects and information for the weight of evidence analysis for hexavalent chromium. In the draft document, EPA identifies cancer and non-cancer effects [respiratory, gastrointestinal, hepatic, hematological, immunological, reproductive, and developmental] and provides animal data in the tables supporting the identification of these effects. EPA seeks an initial, high level discussion on the problem formation including critical effects, relevant hypotheses and key data associated with these effects along with the data used for 1) adverse outcome pathway and mode of action analysis; 2) dose-response analysis; and 3) assumptions and choices relative to an assessment. For example, two hypotheses exist to explain the observed dose-dependent increase in small intestinal tumors in mice exposed to hexavalent chromium in drinking water (McCarroll et al., 2010; Thompson et al., 2011). Small intestine tumors were not observed in similarly exposed rats. As part of problem formulation, EPA seeks public discussion on the hypothesized mode of action for the small intestinal tumor formation. Ideally, this discussion and the rich toxicological database on hexavalent chromium can help inform considerations of human relevance of this tumor endpoint and increase the scientific support for the assumption used and choices made in the IRIS dose-response assessment. Of note, EPA is preparing for a September meeting on the modes of action underlying the critical effects, human data, the use of toxicokinetic models, and other data that can be used for a weight-of-evidence analysis and to provide scientific support for the many assumptions and choices. EPA welcomes the public to identify an initial set of issues for the September discussion. Speakers: Ted Simon, Ted Simon LLC Ann M. Mason, American Chemistry Council Ann M. Mason | American Chemistry Council Senior Director, Chemical Products and Technology Division ann_mason@americanchemistry.com 700 2nd Street NE | Washington, DC | 20002 (o) 202.249.6704 www.americanchemistry.com