On July 15, 2020, the US EPA released new guidance clarifying the number of treatment concentrations needed for acceptable fish bioconcentration factor (BCF) studies in pesticide registration process. The number of concentration levels can be reduced from three (two positive doses and one control) to two (one positive level and one control), which would save 240 test animals per year.
EPA routinely requires BCF studies to determine whether pesticide active ingredients can accumulate in fish, enter the food chain, and cause adverse effects in fish-eating predators.
According to the US pesticide data requirements, Fish Bioconcentration Factor (BCF) data (OCSPP Guideline 850.1730; USEPA 20163) are required to support applications for pesticide registrations under the following conditions:
The octanol-water partition coefficient (Kow) of the chemical is >1000 (log Kow> 3.0);
The use pattern results in potential exposure to fish and other non-target aquatic organisms; or, the hydrolytic half-life of the chemical is >5 days at pH 5, 7 and 9.
At least two test concentrations which are a factor of 10 apart, plus the appropriate control(s) are required to document that the potential to bioconcentrate is independent of the concentration of the test substance.
In April 2017, EPA was approached by the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3R) with scientific evidence that for a wide range of pesticides and industrial chemicals, the BCF factors obtained from high and low doses do not differ by a factor that would lead to a difference in conclusions regarding the potential for the tested chemical to exceed regulatory criteria for bioconcentrating substances.
EPA’s Office of Pesticide Programs (OPP) finally accepted a single treatment level concentration if the BCF value is less than or equal to 667. Based on historical data submission, OPP expects that most submitted Fish Bioconcentration Factor (BCF) studies will only need one treatment concentration. As always, companies must ensure that the study results meet the other guideline specifications and the raw data are determined to be scientifically sound. EPA also recommends that the selected concentration avoid toxic or metabolic effects in the fish that might affect the outcome of the study yet also be high enough to provide quantifiable concentrations of residues of concern in both fish tissue and water. It is also recommended that companies attach appropriate description in the study report, explaining the rationale and acceptability of the concentration used for the BCF study.
Last month, EPA announced a work plan that serves as a roadmap for meeting its animal testing reduction goals set forth last year by Administrator Wheeler. The agency also convened a conference in December 2019 to discuss New Approach Methods (NAMS) for achieving reduced animal testing in chemical safety research and issued guidance in February 2020 waiving the testing of pesticides on birds when the information yielded is unnecessary to support a pesticide registration decision.
