You are here:
Prioritizing chemicals of ecological concern in Great Lakes tributaries using high-throughput screening data and adverse outcome pathwaysPrioritizing Chemicals of Ecological Concern in Great Lakes Tributaries using High-Throughput Screening Data and Adverse Outcome Pathways
Citation:
Corsi, S., L. DeCicco, D. Villeneuve, B. Blackwell, K. Fay, G. Ankley, AND A. Baldwin. Prioritizing chemicals of ecological concern in Great Lakes tributaries using high-throughput screening data and adverse outcome pathwaysPrioritizing Chemicals of Ecological Concern in Great Lakes Tributaries using High-Throughput Screening Data and Adverse Outcome Pathways. ENVIRONMENTAL POLLUTION. Elsevier Science Ltd, New York, NY, 686:995-1009, (2019). https://doi.org/10.1016/j.scitotenv.2019.05.457
Impact/Purpose:
As part of the Great Lakes Restoration Initiative (GLRI) Action Plan I over 700 water samples were collected from 57 Great Lakes tributary streams and analyzed for 69 organic contaminants. Water quality guidelines were available for only 27 of these compounds, leaving the potential biological significance of over 50% of the chemicals unknown. The present study employed data from EPA’s ToxCast program to help screen and prioritize an additional 21 chemicals, allowing 80% of the chemicals detect to be evaluated with regard to potential biological effects. This screening method, while not definitive for predicting risk, accounts for both differences in chemical potency and relative concentrations detected in the environment, making it an effective prioritization tool when conventional in vivo benchmarks are lacking. Additionally, the manuscript demonstrates how biological activities linked with chemicals or chemical mixtures based on their response in cell-based ToxCast assays and be linked to potential in vivo hazards using the adverse outcome pathway framework. These results support the application of new sources of pathway-based high throughput screening data in environmental monitoring and surveillance. Results of this work directly address goal 5 of Focus Area 1 (Toxic Substances and Areas of Concern) of the GLRI and are thus of direct interest to Region 5.
Description:
There are growing numbers of chemicals being detected in the environment for which no established water quality guidelines or toxicity benchmarks are available to support risk assessment. The present study analyzed over 700 water samples from different Great Lakes tributaries for organic contaminants. In addition to comparing the concentrations detected to traditional toxicity benchmarks, concentrations were also compared with data from the ToxCast screening program to rank and prioritize chemicals with regard to their potential for biological effects. This allowed over 80%, rather than just 50%, of the chemicals to be evaluated with regard to their potential for biological effects. The approach also allowed greater consideration of potential mixture effects. The adverse outcome pathway framework was employed to help link the biological activities measured in ToxCast assays to traditional toxicity outcomes considered relevant to ecological risk assessment (e.g., effects on survival, growth, or reproduction). The results demonstrate how these pathway-based approached can be used to aid environmental surveillance and monitoring. Chemical monitoring data were collected in surface waters from 57 Great Lakes tributaries from 2010-13 to identify chemicals of potential biological relevance and sites at which these chemicals occur. Among 65 trace organic contaminants evaluated, traditional water quality benchmarks based on in vivo toxicity data were available for less than 50% (27 chemicals). To expand evaluation of the detected compounds in terms of potential biological effects, the measured surface water concentrations were compared to chemical-specific biological activities determined in high-throughput (ToxCast) in vitro assays. The resulting exposure-activity ratios (EARs) were used to prioritize the chemicals of potential greatest concern: 4-nonylphenol, bisphenol A, metolachlor, atrazine, DEET, caffeine, Tris(2-butoxyethyl) phosphate, tributyl phosphate, triphenyl phosphate, benzo(a)pyrene, fluoranthene, and benzophenone. Formal water quality benchmarks were unavailable for five of these chemicals, but for the remaining seven the EAR-based prioritization was consistent with that based on toxicity quotients (TQ) calculated from in vivo effects benchmarks. Water quality benchmarks identified three additional PAHs in the dataset that were not prioritized using the EAR approach. Comparing EAR estimates with TQ results, an EAR of 10-3 was identified as a reasonable threshold level for assessment of chemicals detected in the tributaries. To better understand apical hazards potentially associated with the biological activities captured in the ToxCast assays, the in vitro bioactivity data were matched with available adverse outcome pathway (AOP) information. The 46 ToxCast assays prioritized via EAR analysis aligned with 38 potentially-relevant AOPs present in the AOP-Wiki. Possible mixture effects were evaluated by summation of EAR values for multiple chemicals by individual assay or individual AOP, and sites where these mixtures occurred were identified.
