Dietary exposure and health risk assessment of perchlorate and chlorate in Shenzhen: a Monte Carlo simulation study.

Perchlorate and chlorate are environmental contaminants that competitively inhibit thyroidal iodide uptake, posing health risks particularly for vulnerable populations. This study developed an isotope dilution UPLC-MS/MS method to determine perchlorate and chlorate levels in 346 samples (vegetables, fruits, eggs, and drinking water) collected from Shenzhen. Probabilistic dietary exposure assessment was conducted across 11 age-gender groups using Monte Carlo simulation (10,000 iterations) with local consumption data (n = 853). Perchlorate was detected in 94% of samples (mean = 16.1 μg/kg), with leafy vegetables (78.5 μg/kg) and eggs (32.0 μg/kg) showing the highest mean levels; chlorate was detected in 45% of samples, whilst drinking water had a 100% detection rate and the highest concentrations (mean = 53.5 μg/L). Males aged 4-14 years had the highest 95th percentile perchlorate estimated daily intake (EDI) (1.19 μg/kg bw/day), with 4.0% exceeding the EFSA tolerable daily intake (TDI). For chlorate, the highest 95th percentile EDI was observed in the 0-3 years old group (14.8 μg/kg bw/day), with 55.2% exceeding the TDI under the lower bound scenario. Sensitivity analysis identified perchlorate concentration in leafy vegetables and drinking water intake as the key drivers of perchlorate and chlorate exposure, respectively. These findings indicate widespread contamination and notable health risks for children, supporting the need for regulatory measures to reduce chlorate in drinking water and monitor perchlorate in leafy vegetables and eggs.