Browsing by Subject "PFOS"

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    The Effect of Perfluorooctane Sulfonate (PFOS) and Choline Supplementation on Hepatic Steatosis in Sprague Dawley Rats
    (2017-05) Bagley, Bradford
    Perfluorooctane sulfonate (PFOS) is bioaccumulative and prevalent in the human population. PFOS induces hepatic steatosis in male rats at dietary exposures of 100 ppm via an unknown mechanism. In vitro, PFOS creates a choline ion complex. Choline deficiency induces hepatic steatosis in rats by decreasing VLDL secretion. The primary hypothesis was that a hepatic PFOS:choline ion complex causes steatosis that could be prevented by dietary choline supplementation. PFOS activation of steatosis related nuclear receptors (i.e., LXR, PXR, CAR, and PPAR-gamma) was investigated as a secondary hypothesis. To identify a choline dietary concentration, Sprague Dawley rats (5-6/sex/group) were fed control diet or 5X, 10X, or 15X basal choline diets for four weeks. The 5X diet was selected based on decreased body weights and body weight gains in the 10X (females only) and 15X groups. Sprague Dawley rats (12/sex/group) were fed control, choline supplemented (CS), 100 ppm PFOS, or 100 ppm PFOS + CS diets for three weeks. The male PFOS (±CS) rats developed hepatic steatosis, decreased mean serum cholesterol, and increased liver choline concentrations; the supplemented diet did not prevent hepatic steatosis. Female rats did not have these findings, even though serum and liver PFOS concentrations were similar to the males. In vitro, 400 µM PFOS did not inhibit choline kinase activity, which does not support the primary hypothesis. Regarding the secondary hypothesis, there was no activation (LXR, PXR, and CAR) or very weak activation (PPAR-gamma) by PFOS in a luciferase-linked assay. Also, liver mRNA activated by these nuclear receptors were not upregulated in rats fed PFOS. There are no clear data from this project that support the primary or secondary hypothesis. However, increased hepatic choline concentrations in the male PFOS rats correlates with the primary hypothesis. This finding and the sex-related difference in PFOS-induced hepatic steatosis warrant further investigation.
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    Effects of perfluorooctanesulfonate (PFOS) on thyroid hormone status in rats
    (2009-07) Chang, Shu-Ching
    Perfluorooctanesulfonate (PFOS) is an environmentally stable and accumulative compound that has been found to be distributed worldwide in humans and wildlife. Although PFOS exposure has been associated with hypothyroxinemia without a compensatory elevation of thyrotropin (TSH) in the laboratory studies; human biomonitoring studies did not report any association between serum PFOS concentrations and serum thyroid hormones either. Because thyroid hormones have numerous important roles in growth and brain developments, the differences between human and laboratory rat thyroid hormone data in the presence of PFOS raise the questions of whether PFOS interferes with the thyroid homeostasis as well as whether laboratory rats serve as an appropriate model to study thyroid biology. This thesis investigated the effect of PFOS on thyroid hormone status in rats. Rats receiving PFOS appeared to maintain a euthyroid state despite significant reductions in serum total thyroid hormones and enhanced thyroid hormone turnover, likely due to competition for binding sites between PFOS and thyroid hormones in rat serum that can systematically introduces a negative bias when conventional analog methods were used to determine serum free thyroxine levels. The binding competition between PFOS and thyroid hormones did not appear to interfere with the central H-P-T axis because the ability of the pituitary to respond to hypothalamic thyrotropin-releasing hormone to release TSH in response to decreased thyroid hormone production after treatment with propylthiouracil was not altered in rats by co-treatment with PFOS. PFOS administration to maternal rats during gestation and lactation has no clear adverse effect with regards to thyroid morphology, thyroid hormone status, thyroid cell proliferation, and liver gene expression in rat offspring.In conclusion, PFOS treatment does not appear to suppress the physiological thyroid hormone status in rats.
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    Perfluoroalkyl substances in the Upper Mississippi River Basin: occurrence, source discrimination and treatment.
    (2012-07) Xiao, Feng
    Perfluoroalkyl substances (PFASs) are manufactured for use in non-stick cookware, fast-food containers, fire-fighting foams and many other products. These substances, including perfluorooctane sulfonate (PFOS) and perfluorooctane (PFOA), have recently been classified as emerging persistent organic pollutants that are of high concern in the Upper Mississippi River Basin. Several urban lakes in the State of Minnesota (USA) and a 53-km segment of the Upper Mississippi River (Pool 2) have been listed as impaired because of PFOS contamination in fish for human consumption. This dissertation thus examines: (1) the occurrence of PFASs in the Upper Mississippi River Basin; (2) basin-scale source discrimination of PFASs by exploratory data analysis; (3) PFAS (ad)sorption by clay and polar/non-polar resins; and (4) PFAS removal by coagulation. PFASs were observed in stormwater runoff from seven separate rain events (2009-2011) at various outfall locations corresponding to different watershed land uses. Elevated levels of PFOS were found on the particulate matter (PM) in runoff collected from both industrial and commercial areas. PFAS adsorption by kaolinite clay was then investigated and modeled, and the solid-water partition coefficient of PFOS was insufficient to explain PFOS associated with runoff PM. PFOS on the PM suggest that it may have originated from industrial/commercial products, entering the waste stream as PFOS containing particulates/substances. Then the current sources of PFASs were studied, confirming that ongoing industrial/commercial activities as a significant determinant of PFAS pollution in the Upper Mississippi River Basin. This was done after an exploratory data analysis of PFAS concentrations in the influent of 37 wastewater treatment plants (WWTPs) serving more than 40 cities by using a new methodology developed in this dissertation. Both runoff and WWTP discharge can be significant pathways for PFASs into the Mississippi River. Because the drinking water in many cities within this basin comes from the Mississippi River surface water, the mechanisms for removal of PFASs by sorption and coagulation were investigated. PFOS/PFOA removal was minimal under current water treatment operations. The moderately polar XAD-7HP resin, on the other hand, was found to have an excellent potential ability for removing PFASs, including shorter-chained PFASs, from water.