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United States Department of Agriculture

Agricultural Research Service

Research Project: PLANT VARIATION IN CD, PB, ZN AND AS ACCUMULATION AND BIOAVAILABILITY AND METHODS TO LIMIT RISK
2008 Annual Report


1a.Objectives (from AD-416)
Characterize the influence of zinc and iron concentrations in edible crop tissues on bioavailability of crop cadmium to animals; characterize potential transfer of soil lead, arsenic, and copper by vegetable crps grown on long-term orchard soils and other contaminated agricultural soils and methods to prevent this transfer; characterize genetic resources and inheritance of grain Cd to reduce cadmium in durum wheat, flax, and nonoilseed sunflower and release improved lower Cd germplasm; develop methods to identify levels of heavy metals, such as lead, arsenic and cadmium that might be food safety/security risks to give us the tools to prevent contamination of food of both plant and animal origin.


1b.Approach (from AD-416)
1) conduct animal feeding studies on the effect of dietary iron, zinc and calcium supply, and crop Zn level, on absorption of Cd in lettuce, polished rice and other crops for which Cd is important in understanding of human Cd risks from foods (durum wheat; bread wheat; etc.).
2)Grow commercial and garden carrot varieties with a wide range of properties on contaminated orchard soils rich in Pb and As; include tests of soil amendments expected to reduce uptake of Pb or As. Measure in vitro bioaccessibility and if needed bioavailability of crop Pb or As to animals. Examine metal residues in peel layer vs. internal storage root tissue..
3)Complete testing of inheritance of grain Cd concentration in sunflower hybrids, flax genotypes shown to differ in grain Cd accumulation, and durum wheat breeding lines; assist plant breeders develop germplasm releases with lower Cd than present commercial types. Examine physiology of genetic differences in Cd accumulation in relation to soil properties where crops are grown..
4)Test methods for rapid direct analysis, or preparation or extraction of Cd, As, and/or Pb in foods of plant or animal origin for spectrometric analysis at lower cost than present usual methods of analysis and verify the application of the methods developed for commercial food samples.


3.Progress Report
Objective 1: Detailed plan for feeding experiment had been developed to test the effect of intrinsic Zn in lettuce on bioavailability of intrinsic Cd. The complete amount of lettuce needed for the feeding experiment to test whether Zn in lettuce affected bioavailability of Cd in lettuce was grown and prepared for feeding trial. Unfortunately, the animal scientist who cooperated in conducting previous feeding trials died during the FY. Presently seeking alternative animal scientist to conduct feeding tests to answer these questions.

Objective 2: Orchard soil was amended with phosphate; the phosphate amended soil was mixed with several metal and organic rich byproducts (aluminum, calcium, iron, organic matter and carbon). The amended soil was leached with deionized water to determine the effectiveness of these byproducts in reducing solubility and leachability of lead and arsenic from an orchard soil.

Carrots are being grown on two orchard soils amended with a high calcium coal bed ash, high carbon coal ash, compost and a high Fe byproduct. The effectiveness on these materials to reduce lead and arsenic uptake by carrots will be determined using ICP-OES and ICP-MS.

Objective 3: Cooperated with durum wheat breeders in MT, and AZ in analyzing genetic lines from replicated field plots to aid in selection of genetic materials for field testing in 2007. Data provided to cooperators in time to prepare seed for planting. Also cooperated in testing other crops potentially grown on dryland as new crops, e.g., camelina, to allow characterization of relative Cd accumulation compared to known crops.

The progress made addressed the needs of NP 108 in the Program Component on Food Safety and within the Problem Area "Pathogens, Toxins and Chemical Contaminants Postharvest". (Objective 3.1: Provide Science-Based Knowledge on the Safe Production, Storage, Processing, and Handling of Plant and Animal Products and on the Detection and Control of Toxin-producing and/or Pathogenic Bacteria and Fungi Parasites, Mycotoxins, Chemical Residues, and Plant Toxins so as to Assist Regulatory Agencies and the Food Industry in Reducing the Incidence of Foodborne Illnesses.)


4.Accomplishments
1. Reviewed the interactions between Cd and dietary status of Fe, Zn and Ca in the absorption of rice Cd by rats as a model for human risk from food Cd. The overwhelming evidence of epidemiologic studies is that rice easily carries soil Cd to subsistence farmers causing renal tubular dysfunction, while other crop-diet systems seldom transfer excessive Cd from contaminated soils. The unusual properties of rice grown in flooded soil allows rapid uptake of Cd to grain when the field is drained at flowering. In addition, kinetics of Cd absorption were shown to be markedly altered when diet Fe, Zn and Ca are marginal. Further, by using metallothionein null mice and diets with marginal vs. adequate Fe, Zn and Ca, it was shown that metallothionein played no role in absorption of Cd at dietary levels relevant to human exposures. Impact: Paper challenges international community to accept the measured variation in crop Cd bioavailability due to crop properties and crop Zn accumulation. ARS Strategic Goal 3: Enhance protection and safety of the nation’s agriculture and food supply.

ARS National Program #108 (Objective 3.1: Provide Science-Based Knowledge on the Safe Production, Storage, Processing, and Handling of Plant and Animal Products and on the Detection and Control of Toxin-producing and/or Pathogenic Bacteria and Fungi Parasites, Mycotoxins, Chemical Residues, and Plant Toxins So as To Assist Regulatory Agencies and the Food Industry in Reducing the Incidence of Foodborne Illnesses.)

2. Conducted test of combining Zn fertilization with limestone application to minimize Cd accumulation by leafy vegetables grown on Lockwood soil from Salinas Valley, CA. Previous tests in CA in the 1970s indicated that liming alone did not decrease crop Cd in contrast with many other studies, but failed to consider high Cd:Zn ratio in these soils. By adding Zn fertilizer in addition to making the soil calcareous, lettuce Cd was lowered from levels which strongly violate international limits for Cd in leafy vegetables (12-20 mg/kg dry weight) to levels below the limit (4.0 mg/kg dry weight) as low as 2.5 mg/kg dry weight. Alternative use of ground rubber as Zn fertilizer was much less effective because of the slow release of Zn from this material. Method could permit growers to return these soils to production of leafy vegetables which meet Cd limits. Seeking cooperators for field test of this method in CA. Impact: The demonstration that Zn fertilizer can markedly reduce Cd concentration in lettuce and spinach grown on Cd-mineralized Lockwood and related soils of Salinas Valley, CA, will offer growers a method to return to using these soils for vegetable crop production. ARS Strategic Goal 3: Enhance protection and safety of the nation’s agriculture and food supply.

ARS National Program #108 (Objective 3.1: Provide Science-Based Knowledge on the Safe Production, Storage, Processing, and Handling of Plant and Animal Products and on the Detection and Control of Toxin-producing and/or Pathogenic Bacteria and Fungi Parasites, Mycotoxins, Chemical Residues, and Plant Toxins So as To Assist Regulatory Agencies and the Food Industry in Reducing the Incidence of Foodborne Illnesses.)

3. Tested treatments reduced the solubility of lead and arsenic in orchard soils. This addresses concerns about lead and arsenic solubility and uptake by crops grown on these soils. The effectiveness of calcium, iron, phosphorus and carbon materials on the solubility of lead and arsenic were determined. Phosphorus application decrease leachable lead but increased arsenic. The high calcium and iron byproducts were the most effective in reducing the leachability of arsenic. The compost and high carbon coal ash were the least effective in reducing the leachability of arsenic, probably because phosphate competed for adsorption on the amended soil with arsenate. Impact: These findings will provide valuable information to: A) US Environmental Protection Agency on the potential leaching of arsenic to ground water; B) byproduct producers on the environmentally safe use of these byproducts as an amendment to immobilize lead and arsenic; and.
3)researcher’s, vegetable crop producers and the Food and Drug Administration (FDA) on the risk of using such lead arsenate contaminated orchard soils for crop production. ARS Strategic Goal 3: Enhance protection and safety of the nation’s agriculture and food supply.

ARS National Program #108 (Objective 3.1: Provide Science-Based Knowledge on the Safe Production, Storage, Processing, and Handling of Plant and Animal Products and on the Detection and Control of Toxin-producing and/or Pathogenic Bacteria and Fungi Parasites, Mycotoxins, Chemical Residues, and Plant Toxins So as To Assist Regulatory Agencies and the Food Industry in Reducing the Incidence of Foodborne Illnesses.)

4. In cooperation with breeders in MT and AZ, analyzed germplasm samples from genetic trials in these states to support durum wheat breeders information needs to select lower Cd cultivars. Also tested Cd levels in alternative dryland crop species being consiered for wider production to assure that crop Cd will not limit sales to international markets in the way that durum wheat, flax and sunflower kernel sales are limited by Cd conentration. Impact: By analysis of grain of durum wheat and alternative new crops for dryland soils in western US, the breeders and growers have been provided information needed to breed improved lower Cd cultivars or choose alternative crops with lower Cd accumulation. ARS Strategic Goal 3: Enhance protection and safety of the nation’s agriculture and food supply.

ARS National Program #108 (Objective 3.1: Provide Science-Based Knowledge on the Safe Production, Storage, Processing, and Handling of Plant and Animal Products and on the Detection and Control of Toxin-producing and/or Pathogenic Bacteria and Fungi Parasites, Mycotoxins, Chemical Residues, and Plant Toxins So as To Assist Regulatory Agencies and the Food Industry in Reducing the Incidence of Foodborne Illnesses.)


5.Significant Activities that Support Special Target Populations
None.


6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings3

Review Publications
Codling, E.E. 2007. Long-Term Effects of Lime, Phosphorus and Iron Amended Orchard Soils on In Vitro, Water and Nitric Acid Extractable Lead. Soil Science. 172:811-819.

Grant, C.A., Clarke, J.M., Duguid, S., Chaney, R.L. 2007. Selection of Plant Cultivars to Minimize Cadmium Uptake. Science of the Total Environment. 390:301-310.

Last Modified: 12/17/2014
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