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Cerium Oxide and Cerium Compounds DRAFT - DO NOT CITE OR QUOTE EPA/635/R-08/002 www.epa.gov/iris TOXICOLOGICAL REVIEW OF Cerium Oxide and Cerium Compounds (CAS No. 1306-38-3) In Support of Summary Information on the Integrated Risk Information System (IRIS) May 2009 NOTICE This document is a Final draft. This information is distributed solely for the purpose of pre- dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by EPA. It does not represent and should not be construed to represent any Agency determination or policy. It is being circulated for review of its technical accuracy and science policy implications. U.S. Environmental Protection Agency Washington, DC 1 DISCLAIMER 2 3 4 This document is a preliminary draft for review purposes only. This information is distributed 5 solely for the purpose of pre-dissemination peer review under applicable information quality 6 guidelines. It has not been formally disseminated by EPA. It does not represent and should not 7 be construed to represent any Agency determination or policy. Mention of trade names or 8 commercial products does not constitute endorsement or recommendation for use. 9 MAY, 2009 ii DRAFT - DO NOT CITE OR QUOTE 1 CONTENTS—TOXICOLOGICAL REVIEW OF CERIUM OXIDE 2 AND CERIUM COMPOUNDS (CAS NO. 1306-38-3) 3 4 5 LIST OF TABLES .......................................................................................................................... v 6 LIST OF FIGURES ....................................................................................................................... vi 7 LIST OF ABBREVIATIONS AND ACRONYMS ...................................................................... vii 8 FOREWORD ................................................................................................................................. ix 9 AUTHORS, CONTRIBUTORS, AND REVIEWERS ................................................................... x 10 11 1. INTRODUCTION ..................................................................................................................... 1 12 13 2. CHEMICAL AND PHYSICAL INFORMATION .................................................................... 3 14 15 3. TOXICOKINETICS .................................................................................................................. 8 16 3.1. ABSORPTION .................................................................................................................. 8 17 3.1.1. Oral Exposure .......................................................................................................... 8 18 3.1.2. Inhalation Exposure ............................................................................................... 11 19 3.2. DISTRIBUTION.............................................................................................................. 12 20 3.2.1. Oral Exposure ........................................................................................................ 12 21 3.2.2. Inhalation Exposure ............................................................................................... 13 22 3.3. METABOLISM ............................................................................................................... 14 23 3.4. ELIMINATION ............................................................................................................... 15 24 3.5. PHYSIOLOGICALLY BASED TOXICOKINETIC MODELS ..................................... 16 25 26 4. HAZARD IDENTIFICATION ................................................................................................ 17 27 4.1. STUDIES IN HUMANS—EPIDEMIOLOGY, CASE REPORTS, CLINICAL 28 CONTROLS ..................................................................................................................... 17 29 4.1.1. Oral Exposure ........................................................................................................ 17 30 4.1.2. Inhalation Exposure ............................................................................................... 18 31 4.2. SUBCHRONIC AND CHRONIC STUDIES AND CANCER BIOASSAYS IN 32 ANIMALS—ORAL AND INHALATION...................................................................... 20 33 4.2.1. Oral Exposure ........................................................................................................ 20 34 4.2.2. Inhalation Exposure ............................................................................................... 23 35 4.3. REPRODUCTIVE/DEVELOPMENTAL STUDIES—ORAL AND INHALATION ... 32 36 4.4. OTHER DURATION- OR ENDPOINT-SPECIFIC STUDIES ...................................... 33 37 4.4.1. Acute Toxicity Studies (Oral and Inhalation) ........................................................ 33 38 4.4.2. Acute Studies (Injection) ....................................................................................... 34 39 4.4.2.1. Neurobehavioral and Neurodevelopmental Effects ...................................... 34 40 4.4.2.2. Neurological Effects ..................................................................................... 34 41 4.4.2.3. Hepatic Effects .............................................................................................. 35 42 4.4.2.4. Cardiovascular Effects ................................................................................. 38 43 4.4.2.5. Hematological Effects ................................................................................... 38 44 4.4.2.6. Renal Effects ................................................................................................. 39 45 4.4.3. Genotoxicity ........................................................................................................... 40 46 4.5. MECHANISTIC DATA AND OTHER STUDIES ........................................................ 40 MAY, 2009 iii DRAFT - DO NOT CITE OR QUOTE 1 4.5.1. In Vitro Studies ..................................................................................................... 40 2 4.5.2. Ex Vivo Studies ..................................................................................................... 43 3 4.5.3. Nanoparticle Studies .............................................................................................. 43 4 4.6. SYNTHESIS OF MAJOR NONCANCER EFFECTS .................................................... 48 5 4.6.1. Oral ........................................................................................................................ 48 6 4.6.2. Inhalation ............................................................................................................... 49 7 4.6.3. Mode-of-Action Information ................................................................................. 49 8 4.6.3.1. Respiratory Tissues ....................................................................................... 49 9 4.6.3.2. Other Tissues ................................................................................................ 54 10 4.7. EVALUATION OF CARCINOGENICITY .................................................................... 55 11 4.7.1. Summary of Overall Weight of Evidence ............................................................. 55 12 4.7.2. Synthesis of Human, Animal, and Other Supporting Evidence ............................ 55 13 4.8. SUSCEPTIBLE POPULATIONS AND LIFE STAGES ................................................ 56 14 4.8.1. Possible Childhood Susceptibility ......................................................................... 56 15 4.8.2. Possible Gender Differences ................................................................................. 56 16 4.8.3. Possible Susceptible Populations .......................................................................... 56 17 18 5. DOSE-RESPONSE ASSESSMENTS ..................................................................................... 58 19 5.1. ORAL REFERENCE DOSE (RfD) ................................................................................. 58 20 5.1.1. Choice of Principal Study and Critical Effect—with Rationale and Justification 58 21 5.1.2. Previous RfD Assessment ..................................................................................... 59 22 5.2. INHALATION REFERENCE CONCENTRATION (RfC) ............................................ 59 23 5.2.1. Choice of Principal Study and Critical Effect—with Rationale and Justification 59 24 5.2.2. Methods of Analysis—Including Models (PBTK, BMD, etc.) ............................. 61 25 5.2.3. RfC Derivation—Including Application of Uncertainty Factors (UFs) ................ 63 26 5.2.4. RfC Comparison Information ................................................................................ 65 27 5.2.5. Previous RfC Assessment...................................................................................... 68 28 5.3. UNCERTAINTIES IN THE ORAL REFERENCE DOSE (RfD) AND INHALATION 29 REFERENCE CONCENTRATION (RfC) ...................................................................... 68 30 5.4. CANCER ASSESSMENT ............................................................................................... 71 31 32 6. MAJOR CONCLUSIONS IN THE CHARACTERIZATION OF HAZARD ........................ 72 33 AND DOSE RESPONSE ............................................................................................................. 72 34 6.1. HUMAN HAZARD POTENTIAL .................................................................................. 72 35 6.2. DOSE RESPONSE
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