National Toxicology Program Toxicity Report Series Number 38 NTP Technical Report on Toxicity Studies of Sodium Selenate and Sodium Selenite (CAS Nos. 13410-01-0 and 10102-18-8) Administered in Drinking Water to F344/N Rats and B6C3F1 Mice Kamal M. Abdo, Ph.D., Study Scientist National Toxicology Program Post Office Box 12233 Research Triangle Park, NC 27709 NIH Publication 94-3387 July 1994 These studies were supported in part by funds from the Comprehensive Environmental Response, Compensation, and Liability Act trust fund (Superfund) by an interagency agreement with the Agency for Toxic Substances and Disease Registry, U.S. Public Health Service. United States Department of Health and Human Services Public Health Service National Institutes of Health Note to the Reader The National Toxicology Program (NTP) is made up of four charter agencies of the United States Department of Health and Human Services (DHHS): ! the National Cancer Institute (NCI) of the National Institutes of Health; ! the National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health; ! the National Center for Toxicological Research (NCTR) of the Food and Drug Administration; and ! the National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control. In July 1981, the Carcinogenesis Bioassay Testing Program was transferred from NCI to NIEHS. NTP coordinates the relevant Public Health Service programs, staff, and resources that are concerned with basic and applied research and with biological assay development and validation. 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. NTP designs and conducts studies to characterize and evaluate the toxicologic potential of selected chemicals in laboratory animals (usually two species, rats and mice). Chemicals selected for NTP toxicology 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 toxic potential. The studies described in this toxicity study report were performed under the direction of NIEHS and were conducted in compliance with NTP laboratory health and safety requirements. These studies met or exceeded all applicable federal, state, and local health and safety regulations. Animal care and use were in accord and compliance with the Public Health Service Policy on Humane Care and Use of Animals. Single copies of this report are available without charge, while supplies last, from the NTP Central Data Management (telephone number 919/541-1371). NTP Central Data Management NIEHS Post Office Box 12233 Research Triangle Park, NC 27709 National Toxicology Program Toxicity Report Series Number 38 NTP Technical Report on Toxicity Studies of Sodium Selenate and Sodium Selenite (CAS Nos. 13410-01-0 and 10102-18-8) Administered in Drinking Water to F344/N Rats and B6C3F1 Mice Kamal M. Abdo, Ph.D., Study Scientist National Toxicology Program Post Office Box 12233 Research Triangle Park, NC 27709 NIH Publication 94-3387 July 1994 These studies were supported in part by funds from the Comprehensive Environmental Response, Compensation, and Liability Act trust fund (Superfund) by an interagency agreement with the Agency for Toxic Substances and Disease Registry, U.S. Public Health Service. United States Department of Health and Human Services Public Health Service National Institutes of Health 2 SODIUM SELENATE & SELENITE, NTP TOXICITY REPORT NUMBER 38 CONTRIBUTORS This NTP report on the toxicity studies of sodium selenate and sodium selenite is based primarily on 13-week studies that took place from August 1988 through January 1989. National Toxicology Program NTP Pathology Review Evaluated experiment, interpreted results, and Sodium selenite: Evaluated slides and prepared reported findings pathology report Kamal M. Abdo, Ph.D., Study Scientist Joel R. Leininger, D.V.M., Ph.D., Chair John R. Bucher, Ph.D. Pathology Associates, Inc. Leo T. Burka, Ph.D. Michael R. Elwell, D.V.M., Ph.D. Robert E. Chapin, Ph.D. National Toxicology Program Rajendra S. Chhabra, Ph.D. Michael R. Elwell, D.V.M., Ph.D. Joel Mahler, D.V.M. Experimental Pathology Laboratories, Bernard A. Schwetz, D.V.M., Ph.D. Inc. Gregory S. Travlos, D.V.M. Provided pathology quality assessment Kristine L. Witt, M.S. John Peckham, D.V.M., M.S., Ph.D. Oak Ridge Associated Universities Gary Riley, M.V.Sc., Ph.D. EG&G Mason Research Institute Environmental Health Research and Principal contributors Testing, Inc. Andrew G. Braun, Sc.D., Principal Investigator Provided sperm morphology and vaginal cytology Herman S. Lilja, Ph.D., Principal Investigator evaluation Robert L. Taber, Ph.D., Principal Investigator Teresa Cocanougher, B.A. Louis E. Sendelbach, Ph.D., Assistant Dushant K. Gulati, Ph.D. Principal Investigator Susan Russell, B.A. Mary E. P. Goad, D.V.M., Ph.D. Frank A. Voelker, D.V.M. Analytical Sciences, Inc. Provided statistical analyses NTP Pathology Working Group Steven Seilkop, M.S. Sodium selenate: Evaluated slides and prepared pathology report Janet L. Teague, M.S. Michael A. Stedham, D.V.M., M.S., Chair Pathology Associates, Inc. Biotechnical Services, Inc. Michael R. Elwell, D.V.M., Ph.D. Provided toxicity report preparation National Toxicology Program William F. MacKenzie, D.V.M., M.S. Daphne D. Lambright, Ph.D., Principal Investigator Experimental Pathology Laboratories, Inc. Joel Mahler, D.V.M. Janet L. Elledge, B.A. National Toxicology Program Waynette D. Sharp, B.A., B.S. SODIUM SELENATE & SELENITE, NTP TOXICITY REPORT NUMBER 38 3 PEER REVIEW The draft report on the toxicity studies of sodium selenate and sodium selenite was evaluated in July 1993 by the reviewers listed below. These reviewers serve as independent scientists, not as representatives of any institution, company, or governmental agency. In this capacity, reviewers determine if the design and conditions of these NTP studies are appropriate and ensure that the toxicity study report presents the experimental results and conclusions fully and clearly. Robert E. Taylor, M.D., Ph.D. Jerry W. Spears, Ph.D. Department of Pharmacology College of Agriculture and Life Sciences Howard University College of Medicine North Carolina State University Washington, DC Raleigh, NC 4 SODIUM SELENATE & SELENITE, NTP TOXICITY REPORT NUMBER 38 TABLE OF CONTENTS ABSTRACT ......................................................... 5 INTRODUCTION ..................................................... 7 Physical and Chemical Properties, Occurrence, and Exposure .............. 7 Absorption, Distribution, and Excretion ............................... 8 Metabolism .................................................... 11 Toxicity ....................................................... 11 Study Rationale and Design ........................................ 17 MATERIALS AND METHODS ............................................. 19 Procurement and Characterization of Sodium Selenate and Sodium Selenite . 19 Dose Formulations............................................... 20 Toxicity Study Designs............................................ 21 Statistical Methods .............................................. 28 Quality Assurance ............................................... 28 RESULTS .......................................................... 29 13-Week Drinking Water Studies in F344/N Rats ....................... 29 13-Week Drinking Water Studies in B6C3F1 Mice ....................... 41 DISCUSSION ........................................................ 47 REFERENCES ....................................................... 55 APPENDIXES Appendix A Summary of Nonneoplastic Lesions in Rats ................. A-1 Appendix B Summary of Nonneoplastic Lesions in Mice .................B-1 Appendix C Organ Weights and Organ-Weight-to-Body-Weight Ratios ......C-1 Appendix D Hematology, Clinical Chemistry, and Urinalysis Results .......D-1 Appendix E Reproductive Tissue Evaluations and Estrous Cycle Characterization.......................E-1 SODIUM SELENATE & SELENITE, NTP TOXICITY REPORT NUMBER 38 5 ABSTRACT Sodium Selenate Sodium Selenite Na2SeO4 Na2SeO3 CAS Number 13410-01-0 10102-18-8 Molecular Weight 188.94 172.95 Sodium selenate and sodium selenite are used as supplements to poultry and livestock feed to promote growth and prevent selenium deficiency diseases. Both compounds have been found in chemical waste sites. Thirteen-week toxicity studies were conducted by administering the chemicals to groups of male and female F344/N rats and B6C3F1 mice in drinking water. Animals were evaluated for hematology, clinical chemistry, urinalysis (rats only), histopathology, and reproductive system effects. In the studies of sodium selenate, groups of 10 male and 10 female rats and mice received 0, 3.75, 7.5, 15, 30, or 60 ppm sodium selenate for 13 weeks. These concentrations were estimated to deliver 0, 0.1, 0.2, 0.4, 0.6, 1.1 (males), or 0.8 (females) mg selenium/kg body weight for rats and 0, 0.3, 0.5, 0.8, 1.5, or 2.6 mg/kg selenium for mice. All male and female rats exposed to 60 ppm died. The final mean body weights of rats exposed to 30 ppm sodium selenate and of mice exposed to 30 or 60 ppm were 13% to 29% lower than those of the controls. Water consumption by rats and mice exposed to 15 ppm or greater was decreased. Decreases in urine volume and increases in erythrocyte counts,