Lawrence P. Burkhard

Workgroup report: review of fish bioaccumulation databases used to identify persistent, bioaccumulative, toxic substances.

Chemical management programs strive to protect human health and the environment by accurately identifying persistent, bioaccumulative, toxic substances and restricting their use in commerce. The advance of these programs is challenged by the reality that few empirical data are available for the tens of thousands of commercial substances that require evaluation. Therefore, most preliminary assessments rely on model predictions and data extrapolation. In November 2005, a workshop was held for experts from governments, industry, and academia to examine the availability and quality of in vivo fish bioconcentration and bioaccumulation data, and to propose steps to improve its prediction. The workshop focused on fish data because regulatory assessments predominantly focus on the bioconcentration of substances from water into fish, as measured using in vivo tests or predicted using computer models. In this article we review of the quantity, features, and public availability of bioconcentration, bioaccumulation, and biota–sediment accumulation data. The workshop revealed that there is significant overlap in the data contained within the various fish bioaccumulation data sources reviewed, and further, that no database contained all of the available fish bioaccumulation data. We believe that a majority of the available bioaccumulation data have been used in the development and testing of quantitative structure–activity relationships and computer models currently in use. Workshop recommendations included the publication of guidance on bioconcentration study quality, the combination of data from various sources to permit better access for modelers and assessors, and the review of chemical domains of existing models to identify areas for expansion.

In vitro‐in vivo extrapolation of quantitative hepatic biotransformation data for fish. II. Modeled effects on chemical bioaccumulation

Hypothetical in vitro biotransformation rate and affinity values for fish were extrapolated to a set of in vivo whole-body metabolism rate constants. A one-compartment model was then used to investigate potential effects of metabolism on chemical bioaccumulation as a function of octanol/water partitioning (Kow). In a second model-based effort, in vitro data were incorporated into a physiologically based toxicokinetic (PBTK) model for fish. The two models predict similar effects on bioaccumulation when calculated in vivo intrinsic clearance values (CL(IN VIVO,INT) are less than 50% of estimated liver blood flow (Q(LIVER). When CL(IN VIVO,INT) approaches Q(LIVER), the PBTK model predicts a greater effect on bioaccumulation than the one-compartment model. This result is attributed to the structure of the PBTK model, which provides for first-pass clearance of chemicals taken up from food. Uncertainties inherent to in vitro-in vivo extrapolations of hepatic metabolism data include the effects of protein binding, inaccurate estimation of in vivo metabolism by in vitro assays, and failure to account for metabolism in other tissues. Model-based predictions of bioaccumulation within a natural setting also must account for possible metabolism at multiple trophic levels. The models described in this study can be used to perform in vitro-in vivo metabolism comparisons with fish, estimate in vitro biotransformation parameters on the basis of measured chemical residues in field-collected animals, and calculate the level of in vitro metabolic activity required to limit bioaccumulation of all compounds to a specified value.

Estimation of vapor pressures for polychlorinated biphenyls: a comparison of eleven predictive methods.

Eleven methods were used to predict vapor pressures at 25.0/sup 0/C for 15 polychlorinated biphenyls with experimental values. These results permitted an assessment of the predictive ability of these methods for compounds with low vapor pressures (<1.0 Pa) and one or less experimental determinations. The error for theoretically based methods was high and increased with decreasing vapor pressure. The correlative methods, based on a set of compounds with known vapor pressures, had much better predictive power. The best correlative method was based on a relationship between ..delta..G/sub v/ and gas-liquid chromatographic retention indexes. The predictive error for this method was estimated to be a factor of 1.75. Vapor pressures obtained by using the three best correlative methods for all polychlorinated biphenyls are reported.

Comparing laboratory and field measured bioaccumulation endpoints

An approach for comparing laboratory and field measures of bioaccumulation is presented to facilitate the interpretation of different sources of bioaccumulation data. Differences in numerical scales and units are eliminated by converting the data to dimensionless fugacity (or concentration-normalized) ratios. The approach expresses bioaccumulation metrics in terms of the equilibrium status of the chemical, with respect to a reference phase. When the fugacity ratios of the bioaccumulation metrics are plotted, the degree of variability within and across metrics is easily visualized for a given chemical because their numerical scales are the same for all endpoints. Fugacity ratios greater than 1 indicate an increase in chemical thermodynamic activity in organisms with respect to a reference phase (e.g., biomagnification). Fugacity ratios less than 1 indicate a decrease in chemical thermodynamic activity in organisms with respect to a reference phase (e.g., biodilution). This method provides a holistic, weight-of-evidence approach for assessing the biomagnification potential of individual chemicals because bioconcentration factors, bioaccumulation factors, biota-sediment accumulation factors, biomagnification factors, biota-suspended solids accumulation factors, and trophic magnification factors can be included in the evaluation. The approach is illustrated using a total 2393 measured data points from 171 reports, for 15 nonionic organic chemicals that were selected based on data availability, a range of physicochemical partitioning properties, and biotransformation rates. Laboratory and field fugacity ratios derived from the various bioaccumulation metrics were generally consistent in categorizing substances with respect to either an increased or decreased thermodynamic status in biota, i.e., biomagnification or biodilution, respectively. The proposed comparative bioaccumulation endpoint assessment method could therefore be considered for decision making in a chemicals management context.

Identification of ammonia, chlorine, and diazinon as toxicants in a municipal effluent

A toxicity identification evaluation (TIE) was performed on a municipal effluent, and three toxicants were identified, ammonia, chlorine, and diazinon. Ammonia and chlorine were the only toxicants present at toxic concentrations in all sample sets, and diazinon was present in toxic concentrations in one of the effluent sample sets. Six effluent sets taken over an 8-month period were evaluated in this TIE. The nonpolar toxicity, primarily due to diazinon, was intermittent since it was present at toxic concentrations only once in the 8-month time period.This report illustrates the types of data and logic used in performing a TIE which contains common municipal toxicants. Emphasis in this report was place on the data needed for generating the “weight of evidence” in toxicant confirmation, Phase III, to support the suspect toxicants identified in the TIE process. Multiple Phase III manipulations, when applied to numerous effluent samples, provided consistent results for generating the “weight of evidence” for the confirmation of ammonia and chlorine as the primary causes of toxicity in this effluent.

Guidance for Evaluating In Vivo Fish Bioaccumulation Data

ABSTRACT Currently, the laboratory-derived fish bioconcentration factor (BCF) serves as one of the primary data sources used to assess the potential for a chemical to bioaccumulate. Consequently, fish BCF values serve a central role in decision making and provide the basis for development of quantitative structure–property relationships (QSPRs) used to predict the bioaccumulation potential of untested compounds. However, practical guidance for critically reviewing experimental BCF studies is limited. This lack of transparent guidance hinders improvement in predictive models and can lead to uninformed chemical management decisions. To address this concern, a multiple-stakeholder workshop of experts from government, industry, and academia was convened by the International Life Sciences Institute Health and Environmental Sciences Institute to examine the data availability and quality issues associated with in vivo fish bioconcentration and bioaccumulation data. This paper provides guidance for evaluating key aspects of study design and conduct that must be considered when judging the reliability and adequacy of reported laboratory bioaccumulation data. Key criteria identified for judging study reliability include 1) clear specification of test substance and fish species investigated, 2) analysis of test substance in both fish tissue and exposure medium, 3) no significant adverse effects on exposed test fish, and 4) a reported test BCF that reflects steady-state conditions with unambiguous units. This guidance is then applied to 2 data-rich chemicals (anthracene and 2,3,7,8-tetrachlorodibenzo-p-dioxin) to illustrate the critical need for applying a systematic data quality assessment process. Use of these guidelines will foster development of more accurate QSPR models, improve the performance and reporting of future laboratory studies, and strengthen the technical basis for bioaccumulation assessment in chemicals management.

The behavior and identification of toxic metals in complex mixtures: Examples from effluent and sediment pore water toxicity identification evaluations

Toxicity caused by heavy metals in environmental samples can be assessed by performing a suite of toxicity identification evaluation (TIE) methods. The behavior of metals during TIEs can vary greatly according to sample matrix. Some approaches and precautions in using TIE to identify metal toxicants in a sample are discussed, using case studies from three effluent and one sediment TIEs. These approaches include responses of metals that erroneously suggest the presence of other toxicants, the bioavailability of metals retained by glass-fiber filtration, and cautionary steps in Phase III to avoid dilution water effects on sample toxicity.

Improving the quality and scientific understanding of trophic magnification factors (TMFs).

Magnification Factors (TMFs) Lawrence P. Burkhard,†,* Katrine Borga,̊‡ David E. Powell, Pim Leonards, Derek C. G. Muir, Thomas F. Parkerton, and Kent B. Woodburn †Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 6201 Congdon Blvd, Duluth, Minnesota 55804, United States ‡Norwegian Institute for Water Research (NIVA), Oslo, Norway Dow Corning Corporation, Health and Environmental Sciences, Midland, Michigan 48640, United States Institute for Environmental Studies, VU University, The Netherlands Aquatic Contaminants Research Division, Water, Science, and Technology Directorate, Environment Canada, Burlington, Ontario, Canada ExxonMobil Biomedical Sciences, Houston, Texas 77002, United States

Comparing laboratory‐ and field‐measured biota–sediment accumulation factors

Standardized laboratory protocols for measuring the accumulation of chemicals from sediments are used in assessing new and existing chemicals, evaluating navigational dredging materials, and establishing site-specific biota-sediment accumulation factors (BSAFs) for contaminated sediment sites. The BSAFs resulting from the testing protocols provide insight into the behavior and risks associated with individual chemicals. In addition to laboratory measurement, BSAFs can also be calculated from field data, including samples from studies using in situ exposure chambers and caging studies. The objective of this report is to compare and evaluate paired laboratory and field measurement of BSAFs and to evaluate the extent of their agreement. The peer-reviewed literature was searched for studies that conducted laboratory and field measurements of chemical bioaccumulation using the same or taxonomically related organisms. In addition, numerous Superfund and contaminated sediment site study reports were examined for relevant data. A limited number of studies were identified with paired laboratory and field measurements of BSAFs. BSAF comparisons were made between field-collected oligochaetes and the laboratory test organism Lumbriculus variegatus and field-collected bivalves and the laboratory test organisms Macoma nasuta and Corbicula fluminea. Our analysis suggests that laboratory BSAFs for the oligochaete L. variegatus are typically within a factor of 2 of the BSAFs for field-collected oligochaetes. Bivalve study results also suggest that laboratory BSAFs can provide reasonable estimates of field BSAF values if certain precautions are taken, such as ensuring that steady-state values are compared and that extrapolation among bivalve species is conducted with caution.

The relationship of bioaccumulative chemicals in water and sediment to residues in fish: A visualization approach

A visualization approach is developed and presented for depicting and interpreting bioaccumulation relationships and data (i.e., bioaccumulation factors [BAFs], biota-sediment accumulation factors [BSAFs], and chemical residues in fish) using water-sediment chemical concentration XY plots. The approach is based on five basic parameters that affect bioaccumulation of nonionic organic chemicals: The distribution of chemical between sediment and water, the hydrophobicity of the compound (expressed as the n-octanol/water partition coefficient, K(OW)), the relationship of food chains to water and sediment, the length of the food chains, and the degree to which the chemical is metabolized. The visualization approach using water-sediment XY plots captures and visually presents the existing bioaccumulation knowledge in a form that is readily understandable from chemical, biological, and ecological aspects and, therefore, useful in the assessment, communication, and management of risk for persistent bioaccumulative toxicants.