Comprehensive risk assessment of heavy metals in national soil-rice systems and prediction of metal concentration in human blood

The risk assessment of soil-rice system at the cross-provincial and national scales is of great significance for the prevention of heavy metal pollution and corresponding hazards. In this study, based on 183 studies, the concentrations of heavy metals in soil-rice systems, and the associated ecological and health risks in three main rice cultivated regions in China were determined. The species sensitivity distribution (SSD) curves were used to evaluate the predicted no effect concentrations (PNEC), hazardous concentration for 5 % of species (HC₅) and the percentages of local species affected. The average Cd content in paddy soils in YRB (0.50 mg/kg) and SCR (0.64 mg/kg) exceeded the standards (0.4 mg/kg for YRB, 0.3 mg/kg for SCR). The ecological risks caused by Cadmium (Cd) and Mercury (Hg) were unneglectable. Chromium (Cr) and Arsenic (As) had the greatest effects on all local species, and the affected ratios in YRB, NP, and SCR were 46.4 % and 21.3 %, 45.7 % and 18.0 %, 42.1 % and 21.9 %, respectively. Arsenic (As) was the main contributor of non-carcinogenic health risks and influenced 41.9 %, 38.1 % and 86.6 % of men, women, and child, respectively. The estimated blood lead (Pb) concentration of child was approximately 8 times higher than adult groups, which was mainly caused by higher Pb gastrointestinal absorption rate due to long-term high demand for iron. This study provides a reference for the large-scale and long-term management of heavy metal pollution in soil-rice systems in China. In the future, in-field experiments should be conducted to further validate the outcomes based on literatures.