Browsing by Subject "Perfluorooctane sulfonate"
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Item The Effect of Perfluorooctane Sulfonate (PFOS) and Choline Supplementation on Hepatic Steatosis in Sprague Dawley Rats(2017-05) Bagley, BradfordPerfluorooctane 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.Item A Mechanistic Investigation of Perfluoroalkyl Acid Kinetics in Rainbow Trout (Oncorhynchus mykiss)(2017-05) Consoer, DanRainbow trout (Oncorhynchus mykiss) confined to respirometer-metabolism chambers were dosed with perfluorooctane sulfonate (PFOS) or perfluorooctanoate (PFOA) by intra-arterial injection and sampled to obtain concentration time-course data for plasma, urine and/or expired water. The data were then analyzed using 2-compartment clearance-volume models. Renal and branchial clearance rates determined for all PFOS experiments averaged 19% and 81% of total clearance, respectively. In contrast, PFOA renal and branchial clearance averaged 92% and 8% respectively. The terminal half-life was 86.8 d for PFOS and 12.6 d for PFOA. Tissue distributions for both compounds were consistent with previous studies. Additional animals were exposed to PFOS and PFOA in water, resulting in average calculated branchial uptake efficiencies of 0.36% and 0.1% respectively. The renal clearance rate determined for PFOS was approximately 75 times lower than that determined for PFOA. This study suggests that glomerular filtration may be sufficient to explain the observed renal clearance rate for PFOS, although a role for membrane transporters cannot be ruled out. However, the results for PFOA suggest that PFOA is a substrate for membrane transporters in the trout kidney. These findings demonstrate that models developed to predict the bioaccumulation of perfluoroalkyl acids by fish must account for differences in renal clearance of individual compounds.Item Perfluoroalkyl substances in the Upper Mississippi River Basin: occurrence, source discrimination and treatment.(2012-07) Xiao, FengPerfluoroalkyl 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.