Widespread neonicotinoid exposure in companion dogs reveals an emerging risk in urban chemical landscapes.

As climate-driven expansion of tick populations intensifies the use of neonicotinoid-based veterinary products worldwide, the extent of internal exposure and associated health risks in companion animals remains poorly understood. This study measured the concentrations of nine neonicotinoids and eight of their metabolites in urine samples collected from 47 companion dogs. The results showed that neonicotinoids and their metabolites were detected in 97% of the samples. The most frequently detected compounds were clothianidin-desmethyl (51%), imidacloprid-olefin (43%), and imidacloprid (34%). Imidacloprid-olefin showed the highest concentration (383 ng/mL), followed by 5-hydroxy-imidacloprid (44 ng/mL). Urinary neonicotinoid concentrations showed no consistent associations with sex, body weight, or age, suggesting that chemical use patterns may be a more influential factor in exposure than individual traits. The highest chronic daily intake (CDI) was estimated for imidacloprid-olefin (28.6 μg/kg BW/day), followed by 5-hydroxy-imidacloprid (2.67 μg/kg BW/day) and N-desmethyl-thiamethoxam (1.84 μg/kg BW/day). While median hazard quotient (HQ) values remained below 1, the maximum HQ for imidacloprid-olefin reached 0.47, a level that warrants caution given uncertainties in human-derived reference doses. The widespread co-detection of multiple compounds indicates chronic co-exposure and raises concern over uncharacterized mixture effects. Their extensive use and environmental release highlight the need to better understand potential secondary exposure among cohabitants and non-target organisms within urban ecosystems.