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The Absorption, Distribution, Metabolism, and Excretion of Perfluoro-[14C]Octanoic Sulfonate in Beef Animals


Perfluorooctanoic sulfonate (PFOS) is an industrial chemical used in the manufacture of numerous plastics, electronics, and textile industries. It has been widely used as a component of Scotchguard upholstery protectant and is also a main ingredient of firefighting foam materials. Because of its chemical and thermal stability, its high polarity, its high water solubility, and the hydrophobic properties of its fluoroalkyl tail, PFOS is an excellent surfactant. These properties also contribute to its environmental stability and its ability to bioaccumulate in living organisms. For example, various surveys have measured significant PFOS accumulations (ppb to ppm) in diverse wildlife populations and also in humans, indicating that significant environmental contamination has occurred.<P> The contributions of food animal products to dietary PFOS exposures in humans are unknown; however, it is believed that human exposure to PFOS could occur through dietary sources. Because PFOS tends to accumulate in animal tissues over time, and because of widespread and point contamination of PFOS in grazing areas, it is hypothesized that PFOS could accumulate in tissues of grazing animals such as cattle. Sources of point contamination include processed sludge that is applied to pastures and cropland as fertilizers. This hypothesis tends to be supported by European surveys which have measured PFOS concentrations as high as 1.3 ppm in beef kidney from animals consuming silage from contaminated fields.<P> Although PFOS has been measured in beef tissues, very little is known about the rate and extent of PFOS absorption, the metabolism of, nor the rate of PFOS excretion in cattle. Therefore, the objective of this proposal is to determine the absorption, tissue distribution, metabolism, and excretion of PFOS in beef animals.

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Approach: Perfluoro-[14C]octanoic sulfonate (PFOS) will be synthesized and purified to a radiochemical purity of greater than 98%. Mature beef animals, housed in metabolism crates, will be orally or intraruminally dosed with radiolabeled PFOS and blood will be withdrawn at specified periods after dosing to determine absorption and depletion kinetics. All urine and feces will be collected from dosed animals and assayed for radioactivity, parent PFOS, and metabolites. At a specified period, animals will be humanely euthanized and body tissues will be collected and weighed. The total amount of radiolabel will be determined in blood and tissues and the chemical composition of the radiolabel will be determined. The total amount of radiolabel in edible and non-edible tissues, urine, and feces will be determined and compared to the total amount of radiolabel dosed to determine recovery. This study will provide data to regulatory organizations, animal producer groups, and academic and industrial scientists who are charged with evaluating the relative contribution of diet to human PFOS exposure.

Smith, David
USDA - Agricultural Research Service
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