Bioaccumulation of decabromodiphenylethane (DBDPE) in aquatic and terrestrial biota in the global environment and its toxicological significance assessed by chemical activity

Many industrial substances cannot be assessed for their bioaccumulation potential using the octanol-water partition coefficient (K_OW), bioconcentration factor (BCF), or bioaccumulation factor (BAF) criteria typically used in the United Nations Stockholm Convention for Persistent Organic Pollutants (POPs) and in regulations and laws of many countries including Canada, the European Union (EU), the United States (US), and Japan. This presents an impediment to an efficient, effective, and expedient environmental assessment of many substances. However, the Stockholm Convention includes a second criterion for bioaccumulation assessments that is focussed on "Evidence that a chemical presents other reasons for concern, such as high bio-accumulation in other species, high toxicity, or ecotoxicity." But this criterion has received little attention; is not recognized or used in national regulations; and lacks a framework for evaluation. This study investigates the application of this second criterion to (i) assess the bioaccumulation potential of difficult-to-test and difficult-to-evaluate substances that cannot be adequately evaluated with K_OW, BCF, or BAF due to very low aqueous solubility, ionization poor solubility in lipids, large molecular size, or other reasons; and (ii) present and test a framework for bioaccumulation assessments that aims to determine whether substances bioaccumulate to levels of concern. The framework is tested using evidence of bioaccumulation for decabromodiphenyl ethane (DBDPE; CAS: 84852-53-9), which is a super-hydrophobic substance that is difficult to test in aqueous and dietary bioaccumulation tests. To evaluate DBDPE with this framework, we compiled bioaccumulation and toxicological data from the published literature, evaluated the exposure concentration data for quality, and applied a chemical activity-based evaluation. Our results indicate that based on available information to date, DBDPE does not appear to bioaccumulate to levels of concern that would affect environmental health at a global or local scale. The results also suggest that our evaluative framework may be a useful alternative for other super-hydrophobic and/or ionizing substances like perfluoroalkyl and polyfluoroalkyl substances and/or aromatic brominated flame retardants that cannot be assessed for bioaccumulation potential based on K_OW, BCF, or BAF.