|Ryan, James - US-EPA, CINCINNATI, OH|
|Davis, Allen - UNIV MD, COLLEGE PK, MD|
Submitted to: Chemical Bioavailability in the Terrestrial Environment
Publication Type: Abstract Only
Publication Acceptance Date: October 24, 2001
Publication Date: November 19, 2001
Technical Abstract: In recent years, evidence that metals comprise unequal risk when supplied in different foods or matrices has become widely accepted, indicating that when risk assessment is to be conducted, that the specific bioavailability of the metal in the matrix supplied must be considered. This paper reviews the evidence that matrix strongly affects bioavailability of soil elements to animals, and of soil elements to plants, and that phytoavailability and bioavailability must be taken into consideration in site remediation plans. Specific examples will be discussed. In the case of soil Cd, our recent research has shown that in the case of subsistence rice farmers who suffered Cd health effects from soil contamination, that the dietary staple food, rice, induced malnutrition in the farmers which caused much higher absorption of rice Cd than has been observed from other food sources. Part of this difference is related to soil-plant interactions in paddy rice which causes Zn to be excluded from grain. Feeding tests with rats fed marginal or adequate levels of Zn, Fe, or Ca illustrated the higher absorption of Cd from malnourished animals, and from rice compared to sunflower kernels. Similarly, Pb in ingested soils has different bioavailability depending on soil properties, and soil amendments to precipitate Pb or to adsorb Pb can reduce bioavailability. A three year field test confirmed the lowered bioavailability. Use of these new understandings for risk assessment and remediation should provide much savings because in situ treatments can prevent risk of Pb, or no remediation was needed for Cd except for rice or tobacco soils.