Abstract
Pesticides and antibiotics frequently co-occur in aquatic environments, yet their combined effects on aquatic life remain poorly understood. To address this gap, we evaluated whether antibiotic co-exposure alters pesticide toxicity in juvenile zebrafish (Danio rerio). We tested five pesticides, including chlorantraniliprole (CAP), chlorpyrifos (CPF), buprofezin (BPF), difenoconazole (DFZ), and boscalid (BO), both alone and in mixtures with three common antibiotics: rifampicin (RIF), ampicillin (AMP), and tetracycline (TET). Adding RIF significantly potentiated CAP toxicity, lowering its 96-hour LC50 from 61.85 to 40.72 mg/L, yielding an LC50 ratio (LCR) of 1.52. Notably, this potentiation was fully abolished by the co-addition of a second antibiotic (AMP or TET). For CPF, only the ternary mixture with RIF and AMP produced a slight but significant reduction in toxicity (LCR = 0.95). For BPF, only co-exposure with TET significantly potentiated toxicity (LCR = 1.18). In contrast, both DFZ and BO showed significantly reduced toxicity when combined with RIF or AMP, with LCRs ranging from 0.80 to 0.91. These varied responses reveal that antibiotic-pesticide interactions are highly chemical-specific rather than a generalized consequence of mixture exposure. Collectively, these findings underscore that single-compound toxicity data alone are insufficient for assessing pesticide hazards in multi-contaminant environments.