1a. Objectives (from AD-416):
Objective 1: Develop and/or validate rapid screening assays for the detection of environmental chemicals relevant to U.S. food production. Sub-objective 1.A: Development of immunochemically based rapid screening methods for new and emerging persistent organic pollutants. Sub-objective 1.B: Development of immunochemical purification methods for new and emerging persistent organic pollutants. Objective 2: Determine levels and sources of dioxins and related compounds in the domestic food supply. Provide food safety agencies with data to confirm or refute the wholesomeness and competitiveness of beef, pork, chickens, turkeys and/or catfish. Sub-objective 2.A: Conduct a nationally-based survey of PCDD/PCDF/PCB/PBDE levels in the domestic meat supply (beef, pork, chicken, turkey, and/or catfish) by collection of adipose tissues from U.S. slaughter facilities. Sub-objective 2.B: Identify potential production-based or environmental sources of PCDDs/PCDFs/PCBs/PBDEs in food-producing animals. Objective 3: Determine the uptake, metabolism (in vitro or in vivo), distribution, excretion, and fate of environmental contaminants with the goal of developing pharmacokinetic rate and volume constants pertinent to residue depletion, selection of marker compounds, and calculation of withdrawal intervals. Sub-objective 3.A: Characterize the absorption, disposition, metabolism, and excretion (ADME) of POPs in food animals. Sub-objective 3.B: Identify cellular fractions and enzyme classes responsible for the metabolism and putative dehalogenation of POPs. Sub-objective 3.C: Characterize the bioavailability of POPs in animal systems from major exposure routes. Sub-objective 3.D: Determine the fate and transport of POPs through soil during ambient weather conditions. Sub-objective 3.E: Determine the effect of milk processing on POP concentrations in finished products.
1b. Approach (from AD-416):
Ubiquitous environmental contaminants enter the human meat supply when animals are exposed through surroundings and feeds. These compounds, known as persistent organic pollutants (POPs) satisfy the standards for chemicals of concern in that they are persistent, bioaccumulative, globally transported, and toxic. 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 animal and human exposures to these contaminants using three approaches. First, we will develop rapid, inexpensive assays and cleanup tools for isolating and detecting POPs in food products. These assays could result in broad monitoring of the food supply, which currently is not feasible due to the high analysis costs. Second, we will continue to survey the U.S. meat supply (beef, pork, chicken, turkey and/or catfish) for POPs, and will track current levels with trends measured over the last two decades. These data are critical to regulatory agencies for risk assessment, and have revealed POP sources that have contributed to livestock exposures and contamination. Once identified sources of contamination may be eliminated or avoided. Third, we will perform basic research to determine pharmacokinetic parameters for POPs in laboratory and farm animals and will develop potential remediation methods using animal feeding studies. We will use these data to calculate withdrawal intervals, and elucidate strategies to decrease contaminant levels in food animals.
3. Progress Report:
Objective 1A. The TBB hapten has been conjugated to bovine serum albumin and keyhole limpet hemocyanin (KLH). The TBB-KLH conjugate has been shipped to a commercial firm to generate rabbit antisera. The sensitivity of the TBB-antisera towards TBB was determined. Objective 2B. Turkey producer associations across Minnesota, North Dakota and South Dakota have been contacted about participation in sample collection (animal tissue, feed, environmental, and housing). Two associations have pledged support for a study to analyze for polybrominated diphenyl ethers. Objective 3A1. Radiolabeled [14C]BDE-153 has been synthesized to allow milking goat metabolism study to be conducted. Objective 3A2. [14C]BDE-153 has been synthesized; animal use protocols are being developed. Due to difficulty in obtaining milking goats a different species for study is being considered. Objective 3B. Microsomal and S9 fractions have been isolated from dairy cows. Characterization methods and experimental procedures are being validated for the in vitro metabolism assays. Objective 3C. The bioavailability study with incurred feed has been completed, and animal tissues are being processed and analyzed. Objective 3E. Milk partitioning experiments have been completed on a representative dioxin, polybrominated diphenyl ether, hexabromocyclododecane, polychlorinated biphenyl, and tetrabromo-bisphenol-A; metabolites of dioxin and PCB have also been formed through in vitro metabolism and tested in the milk system.
1. Plant uptake and mammalian bioavailability of PFOA. Perfluoroctanoic acid (PFOA) is used in industrial and consumer products including coatings for paper and fabrics, fire-fighting foams, and stain-resistant household items. The presence of PFOA in bio-solids from wastewater treatment plants, which are commonly used as fertilizers on agricultural lands, has raised concerns because of potential PFOA uptake by plants and consumption by animals or humans. ARS scientists at Fargo, North Dakota conducted sequential studies to quantify the uptake of soil-borne PFOA into alfalfa and then to determine the extent of PFOA absorption from alfalfa by rats (a model for humans). PFOA residues were transferred from soil to alfalfa and most of the PFOA incorporated into alfalfa was absorbed by rats after feeding. However, the PFOA absorbed by rats was rapidly eliminated. The research clearly demonstrated that PFOA is absorbed by plants and subsequently by mammals consuming contaminated forage. This data will help risk assessors determine the long-term hazards of using PFOA contaminated soils for food production.
2. Rapid screening method for environmental contaminants. Polybrominated diphenyl ethers (PBDEs) are fire retardants that have been widely used extensively in building materials, electronics, and plastics. Because of their toxicity, environmental persistence, bioaccumulation in animals, and global transport, a variety of PBDEs have been banned in the European Union since 2008. Nevertheless, PBDEs are still consistently detected in environmental and food samples. In collaboration with researchers at University of Florence, Italy, an ARS scientist at Fargo, North Dakota developed an electrochemical immunoassay screening assay for PBDEs. An array of electrodes allows the rapid, reliable and economical measurements of several samples simultaneously and when used for the analysis of food samples the results correlated well with those obtained using slower, more tedious instrumental analysis. The developed assay could reduce the expense and time required to determine PBDEs in food and environmental samples.
Hakk, H. 2016. Comparative metabolism studies of hexabromocyclododecane (HBCD) diastereomers in male rats following a single oral dose. Environmental Science and Technology. 50(1):89-96.
Lupton, S.J., O'Keefe, M., Muniz Ortiz, J.G., Clinch, N., Basu, P. 2017. Survey of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and non-orthopolychlorinated biphenyls in U.S. meat and poultry from 2012-2013: Toxic equivalency levels, patterns, temporal trends, and implication. Food Additives & Contaminants. 34(11):1970-1981. https://doi.org/10.1080/19440049.2017.1340674.
Lupton, S.J., Hakk, H. 2017. Polybrominated diphenyl ethers (PBDEs) in U.S. meat and poultry: 2012-13 levels, trends, and estimated consumer exposures. Food Additives & Contaminants. Part A. 34(9):1584-1595. https://doi.org/10.1080/19440049.2017.1340675.