1a. Objectives (from AD-416)
Objective 1: Update data on levels of dioxins and related compounds in the domestic food supply to provide Food Safety agencies with an adequate profile of the situation and confirm the safety and competitiveness of U.S. foods. Objective 2: Develop inexpensive, rapid, sensitive assays or improved diagnostic tools to screen samples for pesticides and other environmental contaminants such as dioxins. Objective 3: Investigate sources which contribute to levels of these contaminants in food animals, that are, feed components, dust or soils, treated wood, and identify intervention strategies that may reduce the levels. Objective 4: Investigate the uptake, metabolism, distribution, excretion, and fate after excretion of environmental contaminants in animal systems with the goal of developing pharmacokinetic rate and volume constants pertinent to residue depletion modeling and real time calculation of withdrawal intervals to protect both food products and the environment. Subobjectives include in vivo and in vitro metabolism studies and fate and transport in the environment studies.
1b. Approach (from AD-416)
Persistent organic pollutants, e.g. dioxins, dioxin-like compounds, brominated flame retardants, and perfluorinated compounds are ubiquitous environmental contaminants that can enter the food chain as animals are exposed through their surroundings and feeds. Because these compounds can cause numerous health effects in animals including cancers, developmental and neurological problems, and immune and reproductive systems disruptions, U.S. and international health organizations recommend continuing to decrease human exposure by lowering levels in foods and the environment. Our research efforts focus on reducing exposure to these contaminants using four approaches. First, surveys of the general food supply (especially meat, poultry, and farm-raised catfish) will be conducted and will provide background levels of these compounds in U.S. foods, serve as a periodic monitor of domestic foods, and track temporal trends. These data are critical to regulatory agencies for developing risk assessments. Second, rapid, inexpensive assays will be developed for detecting contaminants in food products. If successful, these assays may result in widespread monitoring of the food supply and environment, which currently is not feasible due to the high costs or lack of analytical methods. Third, sources that contribute to livestock exposure throughout the production process will be investigated and cataloged. Once identified, these sources may be eliminated, controlled, or avoided in farming practices. Fourth, basic research to determine pharmacokinetic parameters for these pollutants in laboratory and farm animals, potential remediation methods such as bacterial degradation or composting practices, and transport in soils and into plants will be investigated through controlled laboratory studies. These data will be used to estimate animal withdrawal intervals, evaluate source attribution, and elucidate strategies to decrease contaminant levels in food animals or the environment.
3. Progress Report
As part of our investigation into feeds and feed components as sources of dioxins to beef cattle, we have developed a modified dioxin cleanup method to analyze various feed ingredients for dioxins, furans, and dioxin-like PCBs. We are validating and beginning the analysis of over 50 feed samples that have been collected. A survey of dioxins and other environmental contaminants in 203 domestically-marketed catfish samples was completed in collaboration with the USDA Food Safety Inspection Service. (see progress report for subordinate project 5442-32000-011-04R). Pharmacokinetic studies with radiolabeled stereoisomers of the flame retardant hexabromocyclododecane (HBCD) have continued in collaboration with the US EPA, Research Triangle Park, NC. We have synthesized and purified the three most common forms of HBCD and conducted dosing studies in mice and rats to determine whether differences in tissue uptake and persistence exist for the three forms and whether this may indicate a greater relative risk of one form over another.
1. Pharmacokinetics of the industrial contaminant perfluorooctanoic acid in beef cattle. Perfluorooctanoic acid (PFOA) is a “nonstick” compound used in many industrial, commercial, and consumer products. Due to its extensive use, PFOA is widely found in humans, wildlife, and the environment. Cattle are exposed to PFOA while grazing in contaminated areas, but the extent to which PFOA accumulates in their meat is not known. ARS researchers at Fargo, ND, together with scientists at the USDA Food Safety and Inspection Service, have conducted a study to determine to what degree PFOA concentrates in the edible tissues of beef cattle and whether this may be a concern for human exposure. Four beef cattle were fed a single dose of radiolabeled PFOA which could easily be tracked in the animals. The PFOA was quickly excreted in the cattles’ urine and no detectable amounts were left in the animals after 8 days. This study showed that PFOA was not likely to accumulate in beef and that consumption of beef should not be a significant source of exposure to PFOA.