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:
Objective 1: A survey of dioxins, furans, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in domestic US meat and poultry was initiated with FSIS. Beef, pork, chicken, and turkey samples are being collected monthly by FSIS and sent to ARS for analysis. Samples are being analyzed for persistent dioxins/furans, dioxin-like PCBs, and PBDEs by high resolution gas chromatography-mass spectrometry. Objective 2: An immunoassay-based analytical method capable of detecting some of the most common chemical contaminants that are of major food safety concern was developed. The results for the brominated flame retardant tetrabromobisphenol-A were compared with the conventional, but more complicated and expensive, mass spectral system. Objective 4: The major bacteria from dioxin-contaminated soils were isolated and identified. Bacterial isolates capable of growing on a dioxin media as a sole carbon source were inoculated into contaminated soils to determine if they were capable of degrading toxic dioxins and furans. Successful bacterial isolates will be considered for remediation purposes. The pharmacokinetics of the brominated flame retardant hexabromocyclododecane (HBCD) was investigated in male rats. Adsorption, disposition, and excretion were monitored for 4 days. Metabolites in tissues and excreta were quantitated and identified. The persistent brominated flame retardant BDE-153 was synthesized in a radiolabeled version to facilitate mammalian metabolism studies. The compound has been purified so that is can be used in a lactating goat (ruminant) metabolism study.
1. Mammalian pharmacokinetics of a persistent brominated flame retardant. Hexabromocyclododecane (HBCD) is manufactured with a particular pattern of alpha-, beta-, and gamma-stereoisomers, but biota consist of a vastly different pattern. ARS researchers at Fargo dosed male rats individually with radiolabeled HBCD stereoisomers and measured their adsorption, disposition, metabolism and excretion. Each isomer was readily eliminated in feces and urine, but the total elimination depended on the isomer. A metabolic pathway for each isomer was elucidated, and isomer conversion of gamma- into alpha- was observed. Lipophilic tissues contained the greatest concentration of HBCD residues. The results demonstrated that the changing isomer patterns observed among the HBCD isomers during environmental monitoring efforts were due to isomer-specific metabolism, elimination and stereoisomerization.
2. Immunoassay-based method for the multi-contaminant detection of pollutants in fish. Rapid screening assays for chemical contamination of food products are in high demand by government agencies. In collaboration with scientists from RIKILT- Institute of Food Safety, an ARS researcher in Fargo developed an immunological assay method capable of simultaneously determining three of the most common types of environmental contaminants that are of major food safety concern; i.e. polychlorinated biphenyls, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons. The method was successfully tested on fish fillets consisting of different fat contents with sensitivities capable of meeting regulatory limits. The new platform, which is more compact and affordable than the current instrumental method, works well for multiplex measurements of priority pollutants in food samples.
Meimaridou, A., Haasnoot, W., Shelver, W.L., Franek, M., Nielen, M.W.F. 2013. Multiplex immunoassay for persistent organic pollutants in tilapia: Comparison of imaging- and flow cytometry-based platforms using spectrally encoded paramagnetic microspheres. Food Additives & Contaminants: Part A. 30(5):843-852.
Fan, Z.Y., Keum, Y.S., Li, Q.X., Shelver, W.L., Guo, L.H. 2012. Development of indirect competitive fluorescence immunoassay for 2,2',4,4'-tetrabromodiphenyl ether using DNA/dye conjugate as antibody multiple labels. Journal of Environmental Science. 24(7):1334-1340.
Wang, D., Atkinson, S., Hoover-Miller, A., Shelver, W.L., Li, Q.X. 2012. Organic halogenated contaminants in mother-fetus pairs of harbor seals (Phoca vitulina richardii) from Alaska, 2000-2002. Journal of Hazardous Materials. 223-224:72-78.
Xu, T., Wang, J., Liu, S.-Z., Lu, C., Shelver, W.L., Li, Q.X., Li, J. 2012. A highly sensitive and selective immunoassay for the detection of tetrabromobisphenol A in soil and sediment. Analytica Chimica Acta. 751:119-127.
Hakk, H., Szabo, D.T., Huwe, J.K., Diliberto, J.J., Birnbaum, L.S. 2012. Novel and distinct metabolites identified following a single oral dose of alpha- or gamma-hexabromocyclododecane in mice. Environmental Science and Technology. 46:13494-13503.