Aligning Behavioural Ecotoxicology with Real-World Water Concentrations: Current Minimum Tested Levels for Pharmaceuticals Far Exceed Environmental Reality

Jake Mitchell Martin , Jack A. Brand, Erin S. McCallum

Behavioural ecotoxicology has rapidly emerged as a key area of research, offering sensitive and ecologically meaningful endpoints for detecting sub-lethal effects of contaminants. Much of this work has focused on pharmaceutical pollutants, now widely recognised as contaminants of emerging concern in aquatic systems. Given the field’s rapid growth and the availability of large-scale open-access datasets, we have synthesized across four global databases to evaluate the environmental relevance of tested concentrations—using behavioural ecotoxicology and pharmaceutical pollutants as a case study. We compare exposure data from more than 760 behavioural studies with over 10 million aquatic pharmaceutical occurrence records from global monitoring databases. On average, minimum tested concentrations were 43 times higher than median surface water levels and 10 times higher than median concentrations in treated wastewater. Over half of all tested compounds were never evaluated at concentrations below the highest end of wastewater detections (upper 95% credible interval). Additionally, there was only weak alignment between the pharmaceuticals most frequently tested and those most commonly detected in aquatic environments. These findings reveal a disconnect between experimental design and environmental exposure, potentially limiting the ecological and regulatory relevance of behavioural endpoints in pharmaceutical risk assessment.