|Title:||Plant and Soil Factors that Influence Bioavailability of Heavy Metals in Crops|
|Objective:||Higher levels of cadmium in foods cause food safety concern which affects marketing of several agricultural crops. But human absorption (bioavailability) of dietary Cd is strongly affected by crop species and bioavailable crop Fe-Zn-Ca. Food regulators consider all food Cd of equal risk; thus Cd limits may be set below levels needed to fully protect humans. To illustrate the importance of including crop species and crop Zn in crop Cd limits, lettuce will be grown to contain 25 or 450 mg kg-1 DW Zn and 4 mg Cd kg-1 DW to test whether intrinsic lettuce Zn inhibits absorption of lettuce Cd. Cooperation with durum wheat and soybean breeders will continue to aid development of lower Cd cultivars, and clarification of the effect of soil series on Cd accumulation. |
Growing interest in urban gardening has raised concerns about Pb levels; average urban gardens may be a Pb risk to gardeners� children. Most crops accumulate only low amounts of Pb when grown on Pb-rich soils; carrot but not potato accumulates Pb in the edible portion, which is now believed to be precipitated within the xylem inside the carrot storage root. Experiments will clarify localization, chemical forms and the bioavailability of carrot Pb. The principal risk from soil Pb is ingestion by children of Pb-contaminated house dust, but common gardening amendments (phosphate, compost) can strongly reduce soil Pb bioavailability. An inexpensive soil test is needed to measure the bioavailable rather than total Pb, to advise gardeners on the soil use. Lastly, improved science to assess risks from soil and crop trace elements will be sought.
|More Info:||Assuring that natural crop Cd accumulation does not limit marketing of U.S. crops is an important benefit. If Codex sets unnecessarily low Cd limits, several U.S. crops could not be exported. Better technical evidence about Cd bioavailability of different food crops, and the effect of crop Zn on crop Cd bioavailability, will illustrate flaws in present Codex limit setting procedures. And if cultivars with lower Cd are required for export, characterizing genetic variation must be achieved to support plant breeding of improved lower Cd cultivars. With Pb, improved understanding of the localization and forms of Pb in carrots will clarify if carrots with somewhat higher Pb should be prohibited from the market, and whether gardeners should be advised to cease growing of edible root vegetables. Similarly, providing inexpensive chemical tests for soil Pb bioaccessibility will help gardeners understand if they should use or abandon using Pb contaminated garden soils. Because most urban garden soils exceed U.S.-EPA recommended Pb limits based on total Pb level, better understanding of the bioavailability and bioaccessibility of Pb in garden soils could provide large savings, and continue to support urban gardening rather than suggest that urban gardening should be prohibited.|
|Funding Source:||United States Department of Agriculture (USDA), Agricultural Research Service (ARS)|
|Institutions:||USDA/ARS - Beltsville Area Research Center|
|Published USDA ARS Articles|
Effect of coal byproducts encapsulated ammonium nitrate fertilizer on wheat growth and uptake of nitrogen and metals - (Abstract Only)
Accepted Publication (20-May-11)
Environmental impact and remediation of residual lead and arsenic pesticides in soil - (Book / Chapter)
Codling, E.E. 2011. Environmental impact and remediation of residual lead and arsenic pesticides in soil. In: Stoytcheva, M., editor. Pesticide in the modern world-risks and benefits. www.intechopen.com: INTECH Open Access Publisher. p. 169-180.
|Food Safety Categories:||Contaminants and Contamination|
Government Policy and Regulations
Plant Science & Plant Products
|Farm-to-Table categories:||On-farm food production|
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