Integrating bioavailability and aging in the criteria derivation of cadmium for the safe production of rice in paddy soils.

It is significant to derive an appropriate cadmium (Cd) threshold for the rice to ensure that the Cd concentration of rice grains meets the food safety standards. In the present study, soil thresholds for Cd were derived using the method of species sensitivity distribution based on aging time, cultivars, and soil properties. Dataset from thirty-nine rice cultivars planted in different soils published in literature of five bibliographic databases were screened using designated search strings to explore their differences in Cd accumulation capacity in paddy soil. The empirical soil-plant transfer model was used to normalize the bioaccumulation data. Later, the soil Cd concentration for protecting 95% (HC5) of the cultivars was calculated using species sensitivity distribution curves fitted by the Burr III function. The soil Cd criteria derived from the added approach for risk assessment were proposed as continuous criteria based on the combination of soil pH and organic carbon in soil. Soil Cd criteria ranged from 0.34 to 1.18 mg/kg. The prediction model for HC5 was applied to field experimental data to validate its validity and applicability. The predicted Cd thresholds were less than the field experiment Cd thresholds. In conclusion, this study provided valuable and scientific bases for setting soil Cd criteria for paddy soils.