The Dynamic Soil-rice-human Transfer Model Of Cadmium And The Health Risk Assessment

Cadmium is a toxic pollutant that poses severe health risk to humans.Rice consumption is identified as a major contributor of cadmium exposure in China.Soil,as the main medium that transfers cadmium to rice,can be used as a helpful indicator to predict cadmium exposure in humans.There is,however,very little work that links a soil-rice transfer model with a biokinetic model to assess health risks due to cadmium exposure in humans.In this work,we introduce a soil-rice-human transfer model to address this issue.The present model consists of three basic steps:(?)development and validation of a soil-rice transfer model based on 189 pairs of measured data,(?)calculation of weekly exposure based on nationwide monitoring and survey results,(?)linking the exposure model with a modified biokinetic model proposed by Kjellstrom and Nordberg(1978)to predict urinary cadmium,which is a biomarker to assess the health risks.Results indicate that the developed soil-rice-human transfer model can well predict urinary cadmium concentration in humans under age and exposure uncertainties.Sensitive analysis was also conducted to detect the sensitive parameters that have the biggest influences on the output of the model.(1)The modelling results showed that the urinary cadmium excretion increases with cadmium concentration in the rice and the age.We observed a maximum of 0.71?g g-1 creatinine in males and 1.53 ?g g-1 creatinine in females at 70 years old under median cadmium exposure.The urinary cadmium excretion in the female is twice that in the male,indicating a higher health risk in the female.(2)Rice and vegetables represented the major dietary sources of cadmium in our study area,contributing 71.9%and 21.9%,respectively.The contribution of flour,meat,bean,fish and fruit were much lower,which in total accounted for less than 6.3%of the cadmium intake.(3)Kriging maps of urinary cadmium concentration indicated that the risk was high in the southwest of our study area.(4)The sensitivity analysis highlights the influence of the fraction of cadmium transferred to the kidney-urinary pathway,the weekly cadmium intake and gastrointestinal absorption on the model output of urinary cadmium excretion.The new risk assessment strategy proposed in this work is beneficial to predict cadmium concentrations under a variation of age and exposure and to quickly identify risk areas from basic soil properties.