Acute fish toxicity testing in pesticide risk assessment: still a necessary requirement for the future?

Background

The reliance on traditional acute fish toxicity testing in the environmental risk assessment (ERA) of plant protection products (PPPs) raises ethical and scientific concerns, particularly considering the EU’s commitment to the 3Rs principle (replacement, reduction, refinement) and animal welfare legislation. This study assesses the contribution of acute fish toxicity tests to ERAs for 224 pesticidal active substances (a.s.) approved for use in PPPs in the EU. We analyzed regulatory acceptable concentrations (RACs) across various aquatic organisms, including fish, invertebrates, sediment-dwelling organisms, algae, and macrophytes using data from publicly available European Food Safety Authority (EFSA) conclusions.

Results

Our tiered assessment revealed that only 22 a.s. (approximately 9.8% of the total) were driven by acute fish toxicity in a first-tier assessment. The risk for 20 out of these 22 a.s. was covered considering higher tiers such as geomean RAC calculations, EFSA adaptations of the assessment factor and similar RACs within a factor of 3. For only 2 out of 224 a.s. (0.89%), acute fish toxicity remained the driver in ERA. However, for one substance no chronic fish toxicity test was available. Furthermore, both substances degrade rapidly in water under environmental conditions. As the acute fish toxicity tests were performed under constant exposure, the real acute hazard to fish is substantially lower than indicated by the available data.

Conclusions

The findings advocate for a paradigm shift in regulatory ecotoxicology towards the integration of new approach methodologies, thereby reducing the reliance on vertebrate testing while maintaining environmental protection with regard to acute fish toxicity. This research underscores the potential for regulatory frameworks to minimize animal testing without compromising safety and calls for further investigation into alternative testing methods for specific modes of action.