The Indoor Distribution Patterns and Exposure Risks of Meperfluthrin in Different Mosquito-Repellent Incenses

Mosquito-repellent incenses are extensively employed in households; nevertheless, the potential hazards associated with exposure to their active ingredients have not garnered widespread attention. This study systematically evaluates airborne distribution dynamics, surface deposition patterns, and human exposure risks associated with meperfluthrin-based mosquito-repellent incenses (disc, electric liquid, and electric mat) under the conditions of open and closed windows. The highest concentration of meperfluthrin derived from disc incense in the respiratory zone (0.0223 mg/m3) was 2-3-fold higher than other electric incenses (0.0075-0.0078 mg/m3). More than 73.8% of the active ingredient of mosquito-repellent incense can be transferred into the water system through cleaning activities. Quantitative risk assessment indicated an acceptable level of risk (risk quotients <1) for all products under recommended conditions of use. However, biomonitoring revealed a ubiquitous urinary presence of the meperfluthrin metabolite trans-DCCA in 100% of residential samples (0.1373-3.3027 μg/g creatinine, n = 19), suggesting bioaccumulation potential. Acute exposure experiments in mice revealed that the disc incense induced a 23-fold elevation in serum trans-DCCA levels compared to electric incenses, in addition to a significant increase in the levels of hepatotoxicity biomarkers (alanine transaminase and aspartate transaminase). These findings provide critical evidence for risk evaluation and rational use of mosquito-repellent products.