Probabilistic risk assessment of heavy metal exposure via diet in Southwest China: Temporal changes and driving factors in Chongqing (2012–2022)

Chongqing, a traditional industrial base and agricultural hub in inland Southwest China, exhibits dietary patterns representative of this rapidly developing region. Following early 21st-century environmental policies targeting soil heavy metal remediation, this study employed probabilistic risk assessment (2012–2022) to evaluate policy impacts on population health. Results revealed significant contaminant reductions in commercially available foods during 2018–2022 versus 2012–2014, with lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) concentrations declining to 0.016–0.061, 0.002–0.092, 0.006–0.075, and 0.002–0.006 mg/kg respectively. These declines align with Chongqing's regulatory evolution and industrial transformation, driving progressive health risk reductions: hazard quotients (HQ) for Pb and Hg remained below 1.0 (indicating negligible risks), while Cd and As posed sustained yet decreasing concerns with 6.9% and 49.5% of residents exceeding HQ = 1. Additionally, cumulative exposure to the four heavy metals yielded hazard index values of 1.57–7.60, highlighting potential health implications from combined heavy metal exposure. Notably, significant reductions observed at the 95th exposure percentile demonstrate a persistent downward trend in health risks for highly exposed subpopulations. Rice products and leafy vegetables emerged as primary exposure vectors requiring prioritized surveillance, establishing this probabilistic assessment as an evidence base for food safety policy optimization in Southwest China through comprehensive exposure characterization across core food categories.