Scientists from academia, industry, and government reviewed current international regulations for the screening of commercial chemicals for bioaccumulation in the context of the current state of bioaccumulation science. On the basis of this review, several recommendations were proposed, including a scientific definition for "bioaccumulative substances," improved criteria for the characterization of bioaccumulative substances (including the trophic magnification factor and the biomagnification factor), novel methods for measuring and calculating bioaccumulation properties, and a framework for screening commercial chemicals for bioaccumulative substances. The proposed framework for bioaccumulation screening improves current practices by reducing miscategorization, making more effective use of available bioaccumulation data that currently cannot be considered, reducing the need for animal testing, providing simpler and cheaper test protocols for animal studies in case animal studies are necessary, making use of alternative testing strategies, including in vitro and in silico metabolic transformation assays, and providing a scientific foundation for bioaccumulation screening that can act to harmonize bioaccumulation screening among various jurisdictions.

A literature search was performed for dissolved organic carbon/water partition coefficients for nonionic organic chemicals (K DOC), and K DOC data were taken from more than 70 references. The K DOC data were evaluated as a function of the 1-octanol/water partition coefficients (K OW). A predictive relationship of K DOC = 0.08K OW with 95% confidence limits of a factor of 20 in either direction was developed using K DOC data based upon naturally occurring dissolved organic carbon. Inclusion of K DOC data for Aldrich humic acid, a reagent-grade organic carbon, resulted in a slightly different predictive relationship of K DOC = 0.11K OW with 95% confidence limits of a factor of 14 in either direction. The large uncertainties in these relationships are, in part, caused by the variability in structure and composition of dissolved organic carbon (DOC) in sediments, soils, and surface waters. This variability is not accounted for by the hydrophobicity parameter. For individual chemicals, ranges in K DOC values approaching 2 orders of magnitude were observed among investigations using Aldrich humic acid as the DOC. These large ranges of K DOC values suggest that measurement techniques are also, in part, responsible for the large uncertainties in these relationships.

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Bioaccumulation test procedures using the oligochaete Lumbriculus variegatus have been developed as a means of evaluating the accumulation of chemicals from freshwater sediments. To avoid including chemicals associated with gut contents as part of the measured tissue residue, a 24‐h period of purging in clean water after the uptake phase of the test has been recommended. While purging acts to reduce bias from gut contents, it also has the potential to introduce bias caused by depuration of chemicals from tissues. In this paper, a series of model calculations are used to assess the expected sensitivity of measured residues of nonionic organic chemicals to the presence of sediment in the gut and to varying lengths of purging. If organisms are not purged, the predicted influence of gut contents on measured residue is not large (generally <20%) when a biota‐sediment accumulation factor (BSAF) of one is assumed. However, if BSAFs substantially less than one apply, projected errors increase to 30‐fold or more. To derive a better estimate of the time required for L. variegatus to clear the gut of sediment, a sediment purging experiment was conducted; results indicate that >98% of sediment had cleared the gut in 6 h (half‐life = 0.98 h). Based on these results and model analyses, a much shorter purging period of 6 h, rather than 24 h, is suggested as a reasonable guideline for many test applications.

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.