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. 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; the availability of milking goats is being pursued. Objective 3B. Microsomal and S9 fractions have been isolated from dairy cows. Characterization methods are being validated for the in vitro metabolism assays. Objective 3C. The incurred feed (PFOA into alfalfa) needed to conduct the live (rat) phase study have been prepared and tested. Feed mixtures are prepared and animal protocols have been approved. Objective 3E. Milk partitioning experiments have been completed on a representative dioxin, polybrominated diphenyl ether, hexabromocyclododecane, polychlorinated biphenyl, and tetrabromo-bisphenol-A. Additional compounds to be tested will further span the water-solubility range, but need to be synthesized as radiochemicals.
1. Partitioning of persistent organic pollutants into milk products. It has long been acknowledged that human exposure to fat-loving persistent organic pollutants (POPs) occurs principally through our food. However, very little is known about how POPs may distribute in food products following commercial processing. It may be assumed that POPs would distribute into fatty compartments during processing, however, these types of data have not been generated for POPs that may be present in milk. ARS scientists at Fargo, North Dakota conducted a lab-scale milk processing study with a representative dioxin, polychlorinated biphenyl (PCB), polybrominated diphenyl ether (PBDE), and two high production volume brominated flame retardants (tetrabromobisphenol-A and hexabromocyclododecane) and determined their partitioning from whole milk into skim milk, milk fat, curd, whey, and concentrated whey proteins. Most of the fortified dioxin, PCB, PBDE, and hexabromocyclododecane (HBCD) distributed into the milk fat fraction, and what was left in the skim milk concentrated into the curd during further processing. Tetrabromobisphenol-A (TBBP-A), on the other hand, distributed evenly between milk fat and skim milk, and also between the curd and whey. Finally, liquid whey residues concentrated with the whey protein rather than the water fraction for all POPs tested. The researchers attempted to correlate the results with the chemical properties of each POP, but with no success. However, the result suggested that, depending on the POP, concentrations of these contaminants can increase in processed milk products.
Hakk, H., Shelver, W.L., Casey, F.X. 2016. Fate and transport of the ß-adrenergic agonist ractopamine hydrochloride in soil-water systems. Journal of Environmental Science. 45:40-48.