A Critical Review and Weight of Evidence Approach for Assessing the Bioaccumulation of Phenanthrene in Aquatic Environments
Bioaccumulation (B) assessment is challenging because there are various B-metrics from laboratory and field studies, various criteria and thresholds for classifying bioaccumulative (“B”) and non-bioaccumulative (“nB”) chemicals, and inherent variability and uncertainty in the data. These challenges can be met using a weight of evidence (WoE) approach. The Bioaccumulation Assessment Tool (BAT) provides a transparent WoE assessment framework that follows Organisation for Economic Coordination and Development (OECD) principles for performing a WoE analysis. The BAT guides an evaluator through the process of data collection, generation, evaluation, and integration of various lines of evidence (LoE) to inform B assessment decision-making. Phenanthrene (PHE) is a naturally occurring chemical for which extensive B and toxicokinetic data are available. To illustrate the BAT, a B assessment for PHE that includes a critical evaluation of 74 measured in vivo LoE for various fish and invertebrate species from laboratory and field studies is described. The number of LoE are reasonably well balanced across taxa (i.e., fish and invertebrates) and the different B-metrics. Additionally, in silico and in vitro biotransformation rate estimates and corresponding model predicted B-metrics are included as corroborating evidence. An analysis of the data using fugacity ratios is also provided showing phenanthrene does not biomagnify in aquatic food webs. Fundamental errors in previous B assessments of PHE are identified and explained. Application of the BAT provides a consistent, coherent, and scientifically-defensible WoE evaluation to conclude that PHE is not bioaccumulative (“nB”) using bioconcentration, bioaccumulation and biomagnification metrics and criteria for both fish and invertebrates. The critical review identifies recommendations to increase the consistency of B assessments, such as improved standardization of B testing guidelines, data reporting requirements for invertebrate studies and consideration of temperature and salinity effects on certain B-metrics.
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