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Issue Paper on the Bioavailability and Bioaccumulation of Metals

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Issue Paper on the Bioavailability and Bioaccumulation of Metals ISSUE PAPER ON THE BIOAVAILABILITY AND BIOACCUMULATION OF METALS Jim McGeer,1 Gerry Henningsen,2 Roman Lanno,3 Nicholas Fisher,4 Keith Sappington5, and John Drexler6 Contributor: Michael Beringer7 Submitted to: U.S. Environmental Protection Agency Risk Assessment Forum 1200 Pennsylvania Avenue, NW Washington, DC 20460 Contract #68-C-02-060 Submitted by: Eastern Research Group, Inc. 110 Hartwell Avenue Lexington, MA 02421 August 19, 2004 1Natural Resources Canada, Ottawa, ON 2H&H Scientific Services, Centennial, CO 3Ohio State University, Columbus, OH 4State University of New York, Stony Brook, NY 5NCEA, ORD, U.S. EPA, Washington, DC 6University of Colorado, Boulder, CO 7U.S. EPA Region 7, Kansas City, KS TABLE OF CONTENTS 1. PROBLEM STATEMENT, CONCEPTUAL FRAMEWORK, AND DEFINITIONS ............ 1 1.1 Conceptual Framework ................................................................................................ 2 1.2 Definitions ................................................................................................................... 2 1.2.1 Bioaccessibility or Environmental Availability ............................................ 3 1.2.2 Bioavailability ............................................................................................... 5 1.2.3 Bioaccumulation ........................................................................................... 7 1.2.4 Other Definitions .......................................................................................... 7 2. PRINCIPLES ON BIOAVAILABILITY AND BIOACCUMULATION ................................ 8 2.1 Principles and Issues Common to Both Aquatic and Terrestrial Systems ................... 8 2.2 Membrane Interactions with Metals: Physicochemical Factors in Transfer of Metals Across Membranes ............................................................................................... 10 2.2.1 Factors That Modify Absorption ................................................................ 10 2.3 Toxicokinetics (ADME) and Bioaccumulation of Metals ......................................... 11 3. CURRENT AGENCY PRACTICE ......................................................................................... 11 3.1 Site-Specific Assessments ......................................................................................... 11 3.1.1 Superfund Program ..................................................................................... 12 3.1.2 Ambient Water Quality Criteria ................................................................. 13 3.2 National-Scale Assessments ...................................................................................... 14 3.2.1 Assessing Health Risks of Lead Exposure ................................................. 14 3.2.2 Derivation of Reference Doses (RfDs) ...................................................... 15 3.2.3 National Risk Assessments ......................................................................... 15 3.2.4 National Criteria and Screening Levels ...................................................... 15 3.3 National Hazard Ranking and Classification ............................................................. 17 3.3.1 Toxics Release Inventory (TRI) ................................................................. 17 3.3.2 Waste Minimization Prioritization Tool ..................................................... 19 4. CURRENT STATE OF THE SCIENCE ON BIOACCUMULATION AND BIOAVAILABILITY ISSUES ........................................................................................ 19 4.1 Aquatic ....................................................................................................................... 19 4.1.1 Aquatic Exposure ........................................................................................ 19 4.1.2 Dietary Exposure ........................................................................................ 20 4.2 Bioaccumulation of Metals in Aquatic Biota ............................................................ 21 4.2.1 Uptake Mechanisms .................................................................................... 21 4.2.2 Accumulation Strategy ............................................................................... 23 4.2.3 Trophic Transfer ......................................................................................... 24 4.2.4 Adaptation and Acclimation ....................................................................... 26 4.2.5 Intra/Intercellular Speciation ...................................................................... 28 4.2.6 Empirical Models/Methods ......................................................................... 29 4.2.7 Metabolism/Detoxification ......................................................................... 40 4.2.8 Biomonitoring as a Tool for Bioaccumulation ........................................... 42 4.3 Terrestrial ................................................................................................................... 43 ii 4.3.1 Human ......................................................................................................... 45 4.3.2 Wildlife ....................................................................................................... 52 4.3.3 Plants ........................................................................................................... 57 4.3.4 Soil Community: Invertebrates and Microorganisms ................................. 62 4.4 Speciation: Its Role in Assessing Bioavailability in the Terrestrial Environment .... 71 4.4.1 Speciation .................................................................................................... 71 4.4.2 Tools ........................................................................................................... 73 4.5 Predictive Assays for Terrestrial Mammals ............................................................... 76 5. FUTURE DIRECTIONS TO IMPROVE CURRENT AGENCY PRACTICE ...................... 81 5.1 Aquatic-Based Assessments ...................................................................................... 81 5.2 Research Needs .......................................................................................................... 93 5.2.1 Aquatic ....................................................................................................... 93 5.2.2 Terrestrial .................................................................................................... 94 6. LITERATURE CITED ............................................................................................................ 95 iii LIST OF FIGURES Figure 1. Conceptual diagram of processes controlling the bioavailability and the bioaccumulation, both toxic and benign, of metals from the environment ....................... 3 Figure 2. Conceptual diagram for evaluating bioavailability processes and bioaccessibility for metals in soil, sediment, or aquatic systems ...................................................................... 4 Figure 3. Bioaccumulation factors (BAF, L/Kg based on dissolved metal concentration) for 42 different elements in Daphnia magna sampled from a natural source (i.e., field studies) devoid of anthropogenic impact ...................................................................................... 32 Figure 4. Swine feeding studies using 17 field soils contaminated with lead and two laboratory- prepared soils (paint in soil and galena in soil) ............................................................... 50 Figure 5. Hypothetical conceptual model for direct and indirect exposure of ecological receptors to soil contaminants ......................................................................................................... 55 Figure 6. Linkages between dietary toxicity threshold, bioaccumulation in prey organisms and waterborne exposure ........................................................................................................ 90 LIST OF TABLES Table 1. Mean concentration factors (L/kg on a wet weight or, for phytoplankton, cell volume basis) of metals in marine organisms ............................................................................... 35 Table 2. Examples of relative bioavailability adjustments (RBA) in human health risk assessment ........................................................................................................................ 53 Table 3. Where bioavailability information is used in ecological risk assessment ..................... 54 Table 4. Examples of including bioavailability processes in ecological risk assessments .......... 58 Table 5. Characteristics for direct speciation techniques ............................................................ 75 Table 6. Overall comparison of in vitro methods for metal bioaccessibility in terrestrial mammals .......................................................................................................................... 80 Table 7. Mean BCF/BAF as well as ACF values (with standard deviation) for metals .............. 87 Table 8. Regression coefficients (slope and intercept given with SEM) for the linear relationship of waterborne metal exposure concentration and BCF value .......................................... 88 iv 1. PROBLEM STATEMENT, CONCEPTUAL FRAMEWORK, AND DEFINITIONS The bioaccessibility, bioavailability, and bioaccumulation properties of inorganic metals in soil, sediments, and aquatic systems are complex. Similar to organic compounds,
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