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Quantifying Conservatism in ecoTTC and CTD: Case Study of Chemicals with Regulatory Water Quality Values
Citation:
Kienzler, A., M. Barron, K. Connors, K. Fay, A. Bejarano, AND M. Embry. Quantifying Conservatism in ecoTTC and CTD: Case Study of Chemicals with Regulatory Water Quality Values. SETAC Europe virtual meeting, Virtual Meeting - Dublin, Virtual Meeting, IRELAND, May 03 - 07, 2020.
Impact/Purpose:
The purpose of this Poster is to communicate a computational approach to developing No Observed Effect Concentrations (NOECs) for a diversity of chemicals. The impact is that predictive methods that address aquatic hazards of chemicals remain essential as thousands of compounds have yet to be tested. The approach presented is intended to be useful for assessing chemicals at early tiers of the risk assessment process, providing hazard perspective on chemicals that toxicity data, guiding product development discussions, and assisting read across or category justifications. If the approach is successful and can be adopted internationally it will facilitate chemical screening using existing data, and thus reducing the need for animal testing and expediting chemical assessments.
Description:
The EnviroTox* database brings together ecotoxicological data for more than 3900 chemicals across 1563 aquatic species, associated with physical chemistry data and curated taxonomic information. Several mode of action (MOA) schemes are also included to facilitate chemical grouping. The database is integrated with an online tool which automatically calculate Predicted No-Observed Effect Concentrations (PNEC) for each chemicals of the underlying dataset by applying the relevant assessment factors (according to US or European regulation). This tool also allows for the building of statistical distribution of either toxicity hazard values or PNECs. The fifth percentile of these distributions is used to derive two types of environmental threshold concentrations: chemical toxicity distribution (CTD) values and the more conservative Ecological Thresholds for Toxicological Concern (eco-TTC) values, respectively. These two approaches enable toxicity prediction for untested chemicals based on chemical grouping according to mode of action (MOA) or structural features. This case study quantitatively assesses the level of conservatism in extrapolation approaches used in ecoTTC and CTD generation with the EnviroTox tool in comparison to available regulatory water quality criteria (WQC) for aquatic life as benchmark values.
