Exploring a health effect sensitivity distribution method for deriving microplastic toxicity thresholds: Application to microplastic risk assessment of school-aged children in Pudong, Shanghai

Microplastics (MPs) are increasingly recognized as food contaminants, yet human health guidance values (HGVs) are still lacking. For the first time, gender-specific human toxicity thresholds for MPs were derived by integrating the Health Effect Sensitivity Distribution (HESD) method with human equivalent dose extrapolation of rodent toxicity data. The overall hazardous concentration for 5% of effects (HC) was determined to be 0.596 μg/(kg-bw·d), with gender-specific HC values of 1.273 and 0.126 μg/(kg-bw·d) for males and females, respectively. They correspond to intake ranges of 1.36 × 10 to 184.49 MPs/(kg-bw·d) for males and 5.04 × 10 to 18.26 MPs/(kg-bw·d) for females. Building on a comprehensive food contamination dataset of MPs (2015-2025) and seasonal food consumption surveys (winter 2023, spring 2024, summer 2024), we conducted a thorough risk assessment of dietary MPs exposure among children (6-15 years) in the Pudong area of Shanghai, China. Median intake levels ranged from 2.58 to 5.32 MPs/(kg-bw·d) across age groups, with higher median intakes observed in urban compared to suburban and rural areas. Risk analysis showed that 14.10% of children exceeded the HC-based criterion (hazard quotient, HQ > 1), with a higher prevalence among females. This study establishes alternative HGVs for MPs to facilitate health risk assessment of human exposure to MPs.