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Could ecological thresholds of toxicological concern (eco-TTCs) be used to support development of ambient water quality criteria?
Citation:
Belanger, S., M. Barron, T. Norberg-King, AND M. Embry. Could ecological thresholds of toxicological concern (eco-TTCs) be used to support development of ambient water quality criteria? SETAC North America 37th Annual Meeting, Orlando, FL, November 06 - 10, 2016.
Impact/Purpose:
This abstract presents the thresholds of toxicological concern for aquatic organisms (ecoTTC). This work is important because it is an invited presentation in the Office of Water session at SETAC on new approaches for water quality criteria development.
Description:
The Threshold of Toxicologic Concern (TTC) is an approach used for a decades in human hazard assessment. A TTC establishes an exposure level for a chemical below which no appreciable risk to human health is expected based upon a de minimis value for toxicity identified for many toxicologically similar chemicals. The TTC concept applied in an environmental context (eco-TTC) has been proposed to be a Predicted No-Effect Concentration (PNEC) for ecological communities and establishes a concentration expected to have a de minimis probability that effects would be observed for a given group of compounds. Chemical grouping could be defined by mode of action, functional use, or some other relevant criterion. TTCs and eco-TTCs use a form of statistical distribution analysis highly similar to that of a Species Sensitivity Distribution, except that an eco-TTC is based on distributions of PNECs for groups of compounds rather than distributions of test organism endpoints for a specific chemical. Similarly, chemical tolerance distributions (CTDs) are defined as distributions of response values (LC50’s or NOECs) for a specific taxonomic units (e.g., algae, invertebrates, fish, or even specific species) within a chemical group. In this presentation we develop eco-TTCs and CTDs and compare the results to water quality criteria values for existing chemicals using approaches from the US and Canada. Based on these results we provide recommendations for what role eco-TTCs or CTDs could play in developing new ambient water quality criteria for chemicals lacking sufficient data to develop chemical-specific values.