TR-385: Methyl Bromide (CASRN 74-83-9)
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NATIONAL TOXICOLOGY PROGRAM Technical Report Series No. 385 TOXICOLOGY AND CARCINOGENESIS STUDIES OF METHYL BROMIDE (CAS NO. 74-83-9) IN B6C3F1 MICE (INHALATION STUDIES) U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service National Institutes of Health FOREWORD The National Toxicology Program (NTP) is made up of four charter agencies of the U.S. Department of Health and Human Services (DHHS): the National Cancer Institute (NCI), National Institutes of Health; the National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health; the National Center for Toxicological Research (NCTR), Food and Drug Administration; and the National Institute for Occupational Safety and Health (NIOSH), Centers for Disease Control. In July 1981, the Carcinogenesis Bioassay Testing Program, NCI, was transferred to the NIEHS. The NTP coordinates the relevant programs, staff, and resources from these Public Health Service agencies relating to basic and applied research and to biological assay development and validation. The NTP develops, evaluates, and disseminates scientific information about potentially toxic and hazardous chemicals. This knowledge is used for protecting the health of the American people and for the primary prevention of disease. The studies described in this Technical Report were performed under the direction of the NIEHS and were conducted in compliance with NTP laboratory health and safety requirements and must meet or exceed all applicable federal, state, and local health and safety regulations. Animal care and use were in accordance with the Public Health Service Policy on Humane Care and Use of Animals. The prechronic and chronic studies were conducted in compliance with Food and Drug Administration Good Laboratory Practice Regulations and all aspects of the chronic studies were subjected to retrospective quality assurance audits before being presented for public review. These studies are designed and conducted to characterize and evaluate the toxicologic potential, including carcinogenic activity, of selected chemicals in laboratory animals (usually two species, rats and mice). Chemicals selected for NTP toxicology and carcinogenesis studies are chosen primarily on the bases of human exposure, level of production, and chemical structure. Selection per se is not an indicator of a chemical's carcinogenic potential. These NTP Technical Reports are available for sale from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161 (703-487-4650). Single copies of this Technical Report are available without charge while supplies last from the NTP Central Data Management, NIEHS, P.O. Box 12233, MD A0-01, Research Triangle Park, NC 27709 (919-541-3991). NTP TECHNICAL REPORT ON THE TOXICOLOGY AND CARCINOGENESIS STUDIES OF METHYL BROMIDE (CAS NO. 74-83-9) IN B6C3F1 MICE (INHALATION STUDIES) NATIONAL TOXICOLOGY PROGRAM P.O. Box 12233 Research Triangle Park, NC 27709 March 1992 NTP TR 385 NIH Publication No. 92-2840 U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service National Institutes of Health 2 Methyl Bromide, NTP TR 385 CONTRIBUTORS National Toxicology Program NTP Pathology Working Group Evaluated and interpreted results and reported findings Evaluated slides, prepared pathology report for mice (6 January 1989) C.J. Alden, Ph.D. G.A. Boorman, D.V.M., Ph.D. J.C. Seely, D.V.M. Chair D.W. Bristol, Ph.D. PATHCO S.L. Eustis, D.V.M., Ph.D. J. Cullen, V.M.D., Ph.D. T.J. Goehl, Ph.D. North Carolina State University R.A. Griesemer, D.V.M., Ph.D. M.R. Elwell, D.V.M., Ph.D. National Toxicology Program J.K. Haseman, Ph.D. S.L. Eustis, D.V.M., Ph.D. M.M. McDonald, D.V.M., Ph.D. National Toxicology Program G.N. Rao, D.V.M., Ph.D. J.R. Leininger, D.V.M., Ph.D. K.L. Witt, M.S., Oak Ridge Associated Universities National Toxicology Program R.S.H. Yang, Ph.D. M.M. McDonald, D.V.M., Ph.D. National Toxicology Program Brookhaven National Laboratory G. Riley, M.V.Sc., Ph.D. Conducted studies, evaluated pathology findings Experimental Pathology Laboratories, Inc. R.T. Drew, Ph.D., Co-Principal Investigator Biotechnical Services, Inc. S.B. Haber, Ph.D., Co-Principal Investigator, Prepared Technical Report Study Director R.B. Aronson, Ph.D. L.G. Cockerham, Ph.D. Principal Investigator E.P. Cronkite, M.D. G.F. Corley, D.V.M. D.C. Graham, M.D., Ph.D. P.R. Dennis, M.C.M. Duke University (Subcontractor to BNL) B.B. Randolph, M.B.A. L.V. Hankes, Ph.D. D.D. Joel, D.V.M., Ph.D. G. Senum, Ph.D. Integrated Laboratory Systems Prepared quality assurance audits J.C. Bhandari, D.V.M., Ph.D., Principal Investigator Experimental Pathology Laboratories Provided pathology quality assurance J.F. Hardisty, D.V.M., Principal Investigator 3 CONTENTS ABSTRACT ............................................................................... 5 EXPLANATION OF LEVELS OF EVIDENCE OF CARCINOGENIC ACTIVITY .................... 8 PEER REVIEW PANEL .................................................................... 9 SUMMARY OF PEER REVIEW COMMENTS ................................................ 10 INTRODUCTION ......................................................................... 11 MATERIALS AND METHODS ............................................................. 19 RESULTS ................................................................................ 29 DISCUSSION AND CONCLUSIONS. ......................................................... 45 REFERENCES. ........................................................................... 49 APPENDIX A Summary of Lesions in Male Mice in the 2-Year Inhalation Study of Methyl Bromide............................................................ 55 APPENDIX B Summary of Lesions in Female Mice in the 2-Year Inhalation Study of Methyl Bromide............................................................ 93 APPENDIX C Organ Weights and Organ-Weight-to-Body-Weight Ratios ......................... 133 APPENDIX D Neurobehavioral Analyses .................................................... 145 APPENDIX E Hematology and Pseudocholinesterase Results .................................... 159 APPENDIX F Genetic Toxicology .......................................................... 167 APPENDIX G Chemical Characterization, Analysis, and Generation of Chamber Concentrations ..... 175 APPENDIX H Ingredients, Nutrient Composition, and Contaminant Levels in NIH-07 Rat and Mouse Ration............................................... 185 APPENDIX I Sentinel Animal Program ..................................................... 191 APPENDIX J Special 6-Week Target Organ Toxicity Studies ................................... 195 4 Methyl Bromide, NTP TR 385 5 ABSTRACT METHYL BROMIDE CAS No. 74-83-9 Chemical Formula: CH3Br Molecular Weight: 94.95 1 mg/m3 = 0.257 ppm 1 ppm = 3.891 mg/m3 Synonym: Bromomethane Methyl bromide is widely used as a fumigant and pronounced in the three highest dose groups. Red pesticide. Toxicology and carcinogenesis studies were urine was noted in the mice exposed to 200 ppm. conducted by exposing groups of male and female B6C3F1 mice to methyl bromide (99.8% pure) by 13-Week Studies: Groups of 10 mice of each sex inhalation 6 hours per day, 5 days per week, for 14 were exposed to 0, 10, 20, 40, 80, or 120 ppm methyl days, 6 weeks, 13 weeks, or 2 years. Six-week and bromide by inhalation 6 hours per day, 5 days per 13-week inhalation toxicity studies in F344/N rats were week for 13 weeks. Additional groups of eight to 17 conducted concurrently with the mouse studies. mice were concurrently exposed for neurobehavioral Hematology parameters were measured during the and genetic toxicology studies. The final mean body 6-week, 13-week, and 2-year studies. Quantitative weight of males exposed to 120 ppm was significantly neurobehavioraltesting was performed during the 14 (12%) lower than that of the controls. Four of 24 day, 13-week and 2-year studies. Genetic toxicology males exposed to 120 ppm died during the study. studies were conducted for gene mutation induction in Salmonella typhimurium and for induction of sister Groups of 10 rats of each sex were exposed to 0, 30, chromatid exchanges in mousebone marrow cells and 60, or 120 ppm methyl bromide by inhalation 6 hours of micronuclei from peripheral blood erythrocytes. per day, 5 days per week for 13 weeks. Additional groups of eight rats were concurrently exposed for 14-Day Studies: Groups of five B6C3F1 mice of neurobehavioral studies. Final mean body weights of each sex were exposed to 0, 12, 25, 50, 100, or rats exposed to 120 ppm were 12% lower than those 200 ppm methyl bromide by inhalation 6 hours per of the controls for males and 13% lower for females. day, 5 days per week for 2 weeks. Only four female No rats died as a result of methyl bromide exposure mice and one male mouse survived 10 exposures at during the studies. 200 ppm. No deaths occurred at the lower doses. Neurobehavioral effects including trembling and Special 6-Week Target Organ Toxicity Studies: paralysis were noted in all groups, but were most Neither the 14-day nor the 13-week studies provided 6 Methyl Bromide, NTP TR 385 strong evidence for specific organ toxicity. Six-week Exposure to methyl bromide was not carcinogenic studies were therefore conducted to identify target under the conditions of these studies. However, there organs for the 2-year studies. Groups of 20 rats and was an increase in the incidence of several mice of each sex were exposed to methyl bromide by nonneoplastic lesions in the brain,