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AN IMPROVED UNDERSTANDING OF SOIL CD RISK TO HUMANS AND LOW COST METHODS TO PHYTOEXTRACT CD FROM CONTAMINATED SOILS TO PREVENT SOIL CD RISKS
Citation:
Chaney, R. L., P. G. Reeves, J. A. Ryan, R. W. Simmons, R.M. Welch, AND J. S. Angle. AN IMPROVED UNDERSTANDING OF SOIL CD RISK TO HUMANS AND LOW COST METHODS TO PHYTOEXTRACT CD FROM CONTAMINATED SOILS TO PREVENT SOIL CD RISKS. Winkelmann, G. (ed.), BioMetals. Kluwer Academic Publishers, Dordrecht, Netherlands, 17(5):549-553, (2004).
Description:
We have described a new paradigm for human risk from soil Cd that reflects many years of agronomic, nutritional and toxicological research. This new model for soil Cd risk reflects the ability of rice to accumulate soil Cd in grain while excluding Fe, Zn and Ca even though the soil contains 100-times more Zn than Cd. Further, polished rice grain for human consumption is deficient in Fe, Zn and Ca for humans, which promotes Cd adsorption into duodenal cells. New kinetic studies clarified that dietary Cd was accumulated in the duodenum enterocytes; 109 Cd from a single meal remained in the duodenum for up to 16 days; part of the turnover pool 109 Cd moved to the liver and kidneys by the end of the 64-day "chase" period. Thus malnutrition induced by subsistence rice diets caused a higher adsorption of dietary Cd and much higher risk from soil Cd than other crops.
Because the rice-induced Fe-Zn-Ca-malnutrition is so important in soil Cd risk, it seems evident that providing nutritional supplements to populations of exposed subsistence rice farmers could protect them against the Cd during a period of soil remediation. In the long term, high Cd rice soils need to be remediated. The process of removal and replacement of contaminated soil is very expensive (on the order of $3 million/ha); while phytoextraction using the high Cd accumulating ecotypes of the Zn-Cd hyperaccumulator, Thlaspi caerulescens, should provide low cost soil Cd remediation.