Are Vertebrates Still Needed in Routine Whole Effluent Toxicity Testing for Oil and Gas Discharges?

Routine whole effluent toxicity (WET) testing is commonly used to monitor effluent discharges for regulatory compliance in North America. However, the use of fish in WET testing raises ethical concerns and therefore an important question to be explored is whether invertebrates can be used to reduce and/or replace the need for vertebrate testing. The present study evaluated WET data collected for regulatory compliance between 2003 and 2019 (n = 2581 endpoints) from 20 different stationary onshore and offshore oil and gas facilities located across Canada and the United States. Our objective was to assess the relative sensitivity between vertebrates (i.e., fish) and invertebrates in paired samples and to evaluate trends in WET compliance. Despite the variability in testing endpoints, invertebrates displayed equal to or greater sensitivity to tested effluents than fish. For example, based on no-observed-effect concentrations for survival and growth, Americamysis bahia was found to be protective of Menidia beryllina in 90% of endpoint comparisons (n = 336). The results also indicated that regulatory compliance was high (94–100%), with most WET tests passing the established criteria by large margins (79–251%). The results of this comprehensive analysis of historical WET data can be used to improve future permit testing requirements and help answer the question of whether fish tests are needed for routine WET testing. Environ Toxicol Chem 2021;40:1255–1265. © 2020 Shell Oil Company. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Abstract Historical whole effluent toxicity (WET) data collected for effluent discharge permits from oil and gas facilities were compiled into a database and analyzed. The objective was to explore the relative sensitivities of vertebrate (fish) and invertebrate test organisms in WET tests and to understand performance of oil and gas effluent discharges over time against WET criteria. These data can be used to support discussions on whether there could be opportunities to optimize WET testing such as reduce routine WET testing using vertebrate organisms. M. beryllina = Menidia beryllina; A. bahia = Americamysis bahia; O. mykiss = Oncorhynchus mykiss; D. magna = Daphnia magna; P. promelas = Pimephales promelas; C. dubia = Ceriodaphnia dubia; D. pulex = Daphnia pulex.