Utility of the avian sub-acute dietary toxicity test in ecological risk assessment and a path forward to reduce animal use.

The United States Environmental Protection Agency (USEPA) has long required both avian sub-acute dietary and acute oral studies to inform risk assessments for pesticides. Recently, the USEPA collaborated with People for the Ethical Treatment of Animals to determine whether the results of the acute oral avian toxicity test or the sub-acute dietary toxicity test consistently generated the greatest risk predictions in USEPA tier 1 assessments for pesticides first registered between 1998 and 2017. Their study concluded that in 99% of the cases, risk conclusions were driven by the acute oral study (OPPTS 850.2100, OCSPP 850.2100, or similar) because using these data results in higher risk quotients than sub-acute dietary data. Shortly after publishing these results, the USEPA released a formal memorandum providing guidance for waiving the sub-acute dietary study for most pesticides. The USEPA will, however, retain the option to require sub-acute dietary studies for pesticides with certain chemical properties. However, as the avian sub-acute dietary study has an exposure regimen that is often more representative of how birds are exposed to pesticides under actual use conditions than does the acute oral study (i.e., as part of a dietary item eaten over the course of a day and not a bolus dose), this study can provide useful context for risk assessment on a case-by-case basis. Decision criteria are needed to determine a path forward that both minimizes vertebrate animal testing and positions the avian sub-acute dietary data as an option for risk refinement. Decision criteria are proposed here with recommendations for refining the design of avian sub-acute dietary studies to ensure that the data generated are optimized to support a science-based acute avian risk assessment, supported by a case study demonstrating when and how sub-acute dietary studies may be used in a higher-tier risk assessment. Integr Environ Assess Manag 2022;18:1629-1638. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Evaluation of a multiplexed, multispecies nuclear receptor assay for chemical hazard assessment.

Sensitivity to potential endocrine disrupting chemicals in the environment varies across species and is influenced by sequence conservation of their nuclear receptor targets. Here, we evaluated a multiplexed, in vitro assay testing receptors relevant to endocrine and metabolic disruption from five species. The TRANS-FACTORIAL™ system of human nuclear receptors was modified to include additional species: mouse (Mus musculus), frog (Xenopus laevis), zebrafish (Danio rerio), chicken (Gallus gallus), and turtle (Chrysemys picta). Receptors regulating endocrine function and xenobiotic recognition were included, specifically: ERα, ERß, AR, TRα, TRß, PPARγ and PXR. The assay, ECOTOX-FACTORIAL™, was evaluated with 191 chemicals enriched with known receptor ligands. Hierarchical clustering of potency values demonstrated strong coherence of receptor families. Interspecies comparisons of responses within a receptor family showed moderate to high concordance for potencies under 50 µM. PPARγ showed high concordance between mammalian species, 89%, but only 63% between mammalian and zebrafish. For chemicals with potencies below 1 µM, concordances were 89-100% for all receptors except PXR. Concordance showed a strong positive relationship to ligand-binding domain sequence similarity and critical amino acid residues obtained by the Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) tool. In combination with SeqAPASS, ECOTOX-FACTORIAL may provide efficient screening of important receptors to identify species of high priority for effects monitoring.