You are here:
Deriving Predicted No-Effect Concentrations in Diverse Geographies for use in eco-TTC Estimations
Citation:
Belanger, S., A. Beasley, J. Brill, J. Krailler, K. Connors, M. Embry, M. Barron, AND A. Kienzler. Deriving Predicted No-Effect Concentrations in Diverse Geographies for use in eco-TTC Estimations. SETAC North America 38th Annual Mee, Minneapolis, MN, November 12 - 16, 2017.
Impact/Purpose:
This abstract summarizes the derivation of predicted no effect concentrations (PNEC) that are used to compute ecological thresholds of concern (TTC). The impact of the work is that this will further demonstrate the development and utility of TTCs to ecological risk assessment and chemical management.
Description:
cological Thresholds for Toxicologic Concern (eco-TTC) employs an assessment of distributions of Predicted No-Effect Concentrations (PNECs) for compounds following chemical grouping. Grouping can be by mode of action, structural fragments, or by chemical functional use. Thus, eco-TTCs summarize the wealth of ecotoxicological information as probability distributions of PNECs and the 5th percentile lower value is chosen to represent the eco-TTC per se. Ecotoxicological hazards for untested chemicals, grouped using the same attributes, could be conservatively estimated. PNEC determinations vary fundamentally by regulatory jurisdiction. Application factors assigned to different levels of ecotoxicological data (species breadth, acute or chronic toxicity) result in different extrapolations for a potential “safe concentration” of a chemical. We compared PNECs derived by US and European environmental regulatory PNEC approaches in detail for ~5000 compounds and Japan and Canadian environmental PNEC approaches for a subset of these. Algorithms were written in R for US and Europe PNEC processes, then implemented into an eco-TTC web application as envisioned in Belanger et al. (2015). Cumulative PNEC probability distributions for European, Canadian, and Japan approaches are somewhat more conservative than the US approach driven principally by smaller assessment factors applied to data sets at earlier stages of hazard assessment. For example, the AF for the US when a full toxicity data set is available for all 3 trophic levels and a chronic test is available on the most sensitive acute species is 10; however, in other jurisdictions this may be as high as 100. On average, European PNECs were 11 times more conservative than US PNECs. PNEC distributions across geographies are driven by the large number of compounds that lack full chronic toxicity data. All assessments derive similar PNECs when full chronic toxicity data sets are available but this is only ~5% of cases encountered. The PNEC derivation logic, embedded in the eco-TTC web application, will be a useful tool to allow assessors to quickly and consistently compare hazard extrapolations across geographies minimizing animal testing requirements and maximizing use of existing information.