Urinary Biomonitoring and Risk Prioritization of Traditional and Emerging Neonicotinoids in School-Aged Children, South China

The widespread use of neonicotinoids (NEOs) poses a significant risk to school-aged children. However, critical knowledge gaps remain regarding their comprehensive exposure profiles and associated health risks. This study assessed the co-exposure levels and non-carcinogenic risks of 16 NEOs (including both traditional and emerging compounds) in 184 school-aged children recruited from a typical rural and urban area of South China. The sum concentrations of 16 NEOs (∑16NEOs) ranged from 0.648 to 227 μg/L (median: 8.99 μg/L). The predominant compounds were clothianidin (CLO, 1.93 μg/L), N-desmethyl-acetamiprid (N-dm-ACE, 1.64 μg/L), thiamethoxam (THM, 0.792 μg/L), and dinotefuran (DIN, 0.222 μg/L). To our knowledge, this is the first report of emerging NEOs—paichongding (IPP), sulfoxaflor (SUL), and flonicamid (FLO)—in children urine, with detection frequencies of 11.4%, 68.2%, and 53.4%, respectively. Significant rural–urban disparities in urinary concentrations were observed. The metabolite-to-parent ratios (e.g., N-dm-ACE/ACE, 5-OH-IMI/IMI, and THCP-AM/THCP) may serve as a useful biomarker for assessing human exposure to NEOs, as it provides valuable insight into the metabolic fate of the target compounds and aids in distinguishing exposure pathways. The median estimated daily intake (EDI) values for CLO, N-dm-ACE, THM, and ∑12NEOs were 0.127, 0.117, 0.046, and 0.696 μg/kg-bw/day, respectively. Although the hazard quotient for individual compounds was below 1 for vast majority of school-aged children, cumulative exposure assessment indicated that 1.09% of participants had a hazard quotient exceeding 1 for both IMIeq and ∑12NEOs, suggesting potential health concerns under co-exposure scenarios. Using a multi-criteria Toxicological Priority Index (ToxPi) model, CLO, THM, thiacloprid-amid (THCP-AM), and N-dm-ACE were identified as the high-priority compounds requiring regulatory attention in children’s environmental health. This study provides the first comprehensive biomonitoring and ToxPi-based prioritization of both traditional and emerging NEOs in school-aged children in South China. The findings highlight the urgent need for continued monitoring, refined mixture risk assessment, and regulatory consideration of emerging substitutes and their metabolites, which are not adequately covered by current safety guidelines.