Page 1 of 2Department of Defense Comments on theDraftToxicological Review of Hexavalent Chromium ChargeQuestionsComments submitted by: ChemicalMaterial Risk Management DirectorateOrganization: Department of DefenseDate Submitted: May 6, 2010*Comment categories: Science or methods (S); Editorial, grammar/spelling, clarifications needed (E);or Other (O). Also please indicate if Major i.e. affects theoutcome, conclusions or implementation of the assessment.CommentNo.SectionPage &Paragraph(enter“Global” ifreportsectionwide)CommentSuggested Action, Revisionand References (if necessary)Category*1. (A); (B).Pages 1 and2.The reviewers should be asked if they agree withthe species selected to derive the toxicity valuesfrom the NTP 2008 studies, that is, the mouse datarather than the rat data, which some may believemay be more relevant to humans. For thecarcinogenicity endpoint, the oral mucosa avoidsthe uncertainty of amount of reduction in the GItract.Please add the question: “Do you agree withthe selection of the mouse as the key speciesfor derivation of a human oral cancer potencyestimate?”S, M2. (B).NewQuestion.We understand that both EPA’s National Centerfor Environmental Assessment and Office ofPrevention, Pesticides, and Toxic Substances(OPPTS) both have prepared hexavalent chromiumtoxicology/risk assessment-related draftdocuments. We believe that a comparison betweenthe two would be beneficial for the reviewers andall documents should be made available.Please add the question: “Are the conclusionsof the assessments of hexavalent chromiumtoxicity performed by NCEA and OPPTScomparable?”S,M3. (B). Page 2. #2.Because of considerable uncertainty regarding thespecific mode of action by which chromiumcaused either the mouse intestinal tumors and therat oral mucosa tumors we believe that there isinsufficient evidence to support the conclusion ofamutagenic mode of action.We appreciate EPA’s including the questionconcerning mutagenic mode of carcinogenicaction in the charge questions. We would liketo add a sentence to that question, to ask, “Doyou believe there is sufficient information todetermine a mode of action as defined bycurrent Agency guidance and policies?”S,MPage 2 of 2Department of Defense Comments on theDraftToxicological Review of Hexavalent Chromium ChargeQuestionsComments submitted by: ChemicalMaterial Risk Management DirectorateOrganization: Department of DefenseDate Submitted: May 6, 2010*Comment categories: Science or methods (S); Editorial, grammar/spelling, clarifications needed (E);or Other (O). Also please indicate if Major i.e. affects theoutcome, conclusions or implementation of the assessment.CommentNo.SectionPage &Paragraph(enter“Global” ifreportsectionwide)CommentSuggested Action, Revisionand References (if necessary)Category*4. (B) Page 2. #3. We acknowledge that EPA includeda chargequestion concerning whether the 2008 rodent studyshould be selected for derivation of the oral cancerslope factor. We suggest EPA consider adding theadditional question specifically about human datato this charge question.Please add the additional question: “Areexisting human data related to hexavalentchromium carcinogenicity sufficient todetermine whether the two-year drinking waterstudy in rodents (NTP, 2008) was the best datato use as a point of departure to derive thehuman oral cancer slope factor for Cr+6?”S,M