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The present study examined photo-induced toxicity and toxicokinetics for acute exposure to selected polycyclic aromatic hydrocarbons (PAHs) in zebrafish. Photo-enhanced toxicity from co-exposure to ultraviolet (UV) radiation and PAHs enhanced the toxicity and exhibited toxic effects at PAH concentrations orders of magnitude below effects observed in the absence of UV. Because environmental exposure to PAHs is usually in the form of complex mixtures, the present study examined the photo-induced toxicity of both single compounds and mixtures of PAHs. In a sensitive larval life stage of zebrafish, acute photo-induced median lethal concentrations (LC50s) were derived for 4 PAHs (anthracene, pyrene, carbazole, and phenanthrene) to examine the hypothesis that phototoxic (anthracene and pyrene) and nonphototoxic (carbazole and phenanthrene) pathways of mixtures could be predicted from single exposures. Anthracene and pyrene were phototoxic as predicted; however, carbazole exhibited moderate photo-induced toxicity and phenanthrene exhibited weak photo-induced toxicity. The toxicity of each chemical alone was used to compare the toxicity of mixtures in binary, tertiary, and quaternary combinations of these PAHs, and a predictive model for environmental mixtures was generated. The results indicated that the acute toxicity of PAH mixtures was additive in phototoxic scenarios, regardless of the magnitude of photo-enhancement. Based on PAH concentrations found in water and circumstances of high UV dose to aquatic systems, there exists potential risk of photo-induced toxicity to aquatic organisms.

The biotransformation of tetrabromobisphenol A (TBBPA) was evaluated in anaerobic digester sludge, soils, and freshwater sediments. In anaerobic digester sludge, TBBPA biotransformed rapidly with a 50% disappearance time (DT50) of 19 days, though little mineralization (1.1%) was observed. In aerobic soils, mineralization of TBBPA ranged from 17.5% to 21.6% with 55.3-83.6% of the TBBPA incorporated into the soils as a non-extractable bound residue. The DT50 for TBBPA in aerobic soils ranged from 5.3 to 7.7 days. In anaerobic soils, 48.3-100% of the TBBPA was incorporated into the soils as non-extractable bound residue with <4% mineralized. The soil fate studies demonstrated extensive incorporation of TBBPA into the solid matrix and this association was related to the amount of organic carbon in the soils (i.e., greater association of TBBPA with soil at higher organic carbon content). In anaerobic sediments the DT50 for TBBPA ranged from 28 to 42 days, whereas in aerobic sediments the DT50 for TBBPA ranged from 48 to 84 days and depended on the initial dose concentration. Most of the TBBPA in the sediment studies was incorporated as a non-extractable bound residue with little mineralization observed. Sediment extracts revealed three unknown biotransformation products and bisphenol A (BPA). These results were consistent with previously published studies where TBBPA biotransformed in anaerobic environments (digester sludge and sediments) by debromination and slowly mineralized in the test environments (anaerobic digester sludge, soils, and freshwater sediments).

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State environmental agencies in the United States are charged with making risk management decisions that protect public health and the environment while managing limited technical, financial, and human resources. Meanwhile, the federal risk assessment community that provides risk assessment guidance to state agencies is challenged by the rapid growth of the global chemical inventory. When chemical toxicity profiles are unavailable on the U.S. Environmental Protection Agency's Integrated Risk Information System or other federal resources, each state agency must act independently to identify and select appropriate chemical risk values for application in human health risk assessment. This practice can lead to broad interstate variation in the toxicity values selected for any one chemical. Within this context, this article describes the decision-making process and resources used by the federal government and individual U.S. states. The risk management of trichloroethylene (TCE) in the United States is presented as a case study to demonstrate the need for a collaborative approach among U.S. states toward identification and selection of chemical risk values while awaiting federal risk values to be set. The regulatory experience with TCE is contrasted with collaborative risk science models, such as the European Union's efforts in risk assessment harmonization. Finally, we introduce State Environmental Agency Risk Collaboration for Harmonization, a free online interactive tool designed to help to create a collaborative network among state agencies to provide a vehicle for efficiently sharing information and resources, and for the advancement of harmonization in risk values used among U.S. states when federal guidance is unavailable.