Abstract  Perfluorooctanesulfonic acid (PFOS) and its derivatives have been used in a range of industrial and commercial applications, including the manufacture of surfactants, adhesives, anticorrosion agents, and insecticides. PFOS is found at detectable concentrations in human and wildlife tissues and in the global environment. N-Substituted perfluorooctanesulfonamides are believed to be degraded to PFOS and, therefore, contribute to the accumulation of PFOS in the environment. N-Ethyl-N-(2-hydroxyethyl)perfluorooctanesulfonamide (N-EtFOSE) is converted to PFOS in experimental animals. The objective of this study was to elucidate the pathways for the biotransformation of N-EtFOSE, which is a major precursor and component of PFOS-based compounds. N-EtFOSE and several putative metabolites were incubated with liver microsomes and cytosol and with liver slices from male Sprague-Dawley rats. Microsomal fractions fortified with NADPH catalyzed the N-deethylation of N-EtFOSE to give N-(2-hydroxyethyl)perfluorooctanesulfonamide (FOSE alcohol) and of FOSE alcohol to give perfluorooctanesulfonamide (FOSA). These N-dealkylation reactions were catalyzed mainly by male rat P450 2C11 and P450 3A2 and by human P450 2C19 and 3A4/5. Rat liver microsomal fractions incubated with UDP-glucuronic acid catalyzed the O-glucuronidation of N-EtFOSE and FOSE alcohol and the N-glucuronidation of FOSA. Cytosolic fractions incubated with NAD(+) catalyzed the oxidation of FOSE alcohol to perfluooctanesulfonamidoacetate (FOSAA). The oxidation of N-EtFOSE to N-ethylperfluorooctanesulfonamidoacetate (N-EtFOSAA) was observed in liver slices but not in cytosolic fractions. FOSA was biotransformed in liver slices to PFOS, albeit at a low rate. These results show that the major pathway for the biotransformation of N-EtFOSE is N-dealkylation to give FOSA. The biotransformation of FOSA to PFOS explains the observation that PFOS is found in animals given N-EtFOSE.

Abstract  Perfluorochemicals (PFCs) are the subject of increasingly intense environmental research. Despite their detection both in biota and in aqueous systems, little attention has been paid to the possible presence of this class of compounds in solid environmental matrixes. The limited available data indicate that some PFCs such as perfluorooctane sulfonate (PFOS) may strongly sorb to solids, and sewage sludge is widely suspected as a major sink of PFCs entering municipal waste streams. A quantitative analytical method was developed that consists of liquid solvent extraction of the analytes from sediments and sludge, cleanup via solid-phase extraction, and injection of the extracts with internal standards into a high-performance liquid chromatography (HPLC) system coupled to a tandem mass spectrometer (LC/MS/MS). The limits of detections of the method were analyte and matrix dependent, but ranged from 0.7 to 2.2 ng/g and 0.041 to 0.246 ng/g (dry weight) for sludge and sediment, respectively. A demonstration of the method was performed by conducting a limited survey of domestic sludge and sediments. The concentration of PFCs in domestic sludge ranged from 5 to 152 ng/g for total perfluorocarboxylates and 55 to 3370 ng/g for total perfluoroalkyl sulfonyl-based chemicals. Data from a survey of San Francisco Bay Area sediments suggest widespread occurrence of PFCs in sediments at the low ng/g to sub-ng/g level. Furthermore, substances that may be transformed to PFOS, such as 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA) and 2-(N-methylperfluorooctanesulfonamido) acetic acid (N-MeFOSAA), are present in both sediments and sludge at levels often exceeding PFOS.

Abstract  While (N-ethyl perfluorooctanesulfonamido)ethanol (FOSE) -based phosphate diester (diSPAP) has been proposed as a candidate precursor of perfluorooctanesulfonate (PFOS), its potential biotransformation to PFOS has not been verified. Metabolism of diSPAP was investigated in Japanese medaka ( Oryzias latipes ) after exposure in water for 10 days, followed by 10 days of depuration. Branched isomers of diSPAP (B-diSPAP) were preferentially enriched in medaka exposed to diSPAP, with the proportion of branched isomers (BF) ranging from 0.56 to 0.80, which was significantly greater than that in the water to which the medaka were exposed (0.36) (p < 0.001). This enrichment was due primarily to preferential uptake of B-diSPAP. PFOS together with perfluorooctanesulfonamide (PFOSA), N-ethyl perfluorooctanesulfonamide (NEtFOSA), 2-(perfluorooctanesulfonamido)acetic acid (FOSAA), NEtFOSAA, FOSE, and NEtFOSE were detected in medaka exposed to diSPAP, which indicated the potential for biotransformation of diSPAP to PFOS via multiple intermediates. Due to preferential metabolism of branched isomers, FOSAA and PFOSA exhibited greater BF values (>0.5) than those of NEtFOSA, NEtFOSAA, and NEtFOSE (<0.2). Such preferential metabolism of branched isomers along the primary pathway of metabolism and preferential accumulation of B-diSPAP led to enrichment of branched PFOS (B-PFOS) in medaka. Enrichment of B-PFOS was greater for 3-, 4-, and 5-perfluoromethyl PFOS (P3MPFOS, P4MPFOS, and P5MPFOS), for which values of BF were 0.58 ± 0.07, 0.62 ± 0.06, and 0.61 ± 0.05 (day 6), respectively; these values are 5.8-, 7.8-, and 6.4-fold greater than those of technical PFOS. This work provides evidence on the isomer-specific accumulation of PFOS from diSPAP and will be helpful to track indirect sources of PFOS in the future.

Abstract  Perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), and the substituted perfluorooctanesulfonamides perfluorooctanesulfonamidoacetate (FOSAA), and N-ethylperfluorooctanesulfonamidoacetate (N-Et-FOSAA) are widely used as surfactants on fabrics and papers, as anti-corrosion agents and fire retardants, as well as many other commercial applications. Their broad use, global distribution, and environmental persistence has generated considerable interest regarding the metabolic and potentially toxic effects of these compounds. We have previously shown that the perfluorooctanes disrupt mitochondrial bioenergetics and, more specifically, that perfluorinated carboxylic acids induce the mitochondrial permeability transition. The purpose of this study was to determine if, as structural fatty acid analogues, perfluorosulfonic acid and perfluorinated carboxylic acids deplete free coenzyme A. Freshly homogenized rat liver was incubated in the presence of the test compound at 37 C for 40 minutes. Caprylic acid was included as a positive control and the concentration of free coenzyme A determined by reversed-phase HPLC. The concentration of free CoA detected in the control incubations was 92.4 +/- 13.6 nmol/g liver. Incubation with caprylic acid caused a 5% decrease in free CoA, whereas there was a 15%-40% depletion of CoA when liver tissue was incubated with one or another of the perfluorinated acids. We conclude that PFOS and the perfluorinated carboxylic acids deplete free mitochondrial coenzyme A, and that this may contribute to the mechanism by which these compounds interfere with fatty acid metabolism in vivo

Abstract  Equivocal findings are reported for perfluoroalkyl and polyfluoroalkyl substances (PFASs) and self-reported pregnancy loss. We prospectively assessed PFASs and pregnancy loss in a cohort comprising 501 couples recruited preconception and followed daily through 7 post-conception weeks. Seven PFASs were quantified: 2-N-ethyl-perfluorooctane sulfonamide acetate (Et-PFOSA-AcOH); 2-N-methyl-perfluorooctane sulfonamido acetate (Me-PFOSA-AcOH); perfluorodecanoate (PFDeA); perfluorononanoate (PFNA); perfluorooctane sulfonamide (PFOSA); perfluorooctane sulfonate (PFOS); and perfluorooctanoate (PFOA). Women used home pregnancy test kits. Loss denoted conversion from a positive to a negative pregnancy test, onset of menses or clinical confirmation (n=98; 28%). Chemicals were log transformed and rescaled by their standard deviations to estimate adjusted hazard ratios (HRs) and 95% confidence intervals. No significantly elevated HRs were observed for any PFASs suggesting no association with loss: Et-PFOSA-AcOH (1.04; 0.87, 1.23), Me-PFOSA-AcOH (0.79; 0.61, 1.00; p<0.05), PFDeA (0.83; 0.66, 1.04), PFNA (0.86; 0.70, 1.06), PFOSA (0.74; 0.50, 1.09), PFOS (0.81; 0.65, 1.00), and PFOA (0.93; 0.75, 1.16).

Abstract  Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are thought to induce peroxisome proliferation and interfere with mitochondrial metabolic pathways. Direct measurements revealed that PFOA and the unsubstituted sulfonamide of perfluorooctane (FOSA) uncouple mitochondrial respiration by increasing proton conductance. The purpose of this investigation was to characterize structural determinants responsible for the mitochondrial uncoupling effect of several structurally related fluorochemicals. Included in the study were PFOA, PFOS, FOSA, the N-acetate of FOSA (perfluorooctanesulfonamidoacetate, FOSAA), N-ethylperfluorooctanesulfonamide (N-EtFOSA), and the N-ethyl alcohol [2-(N-ethylperfluorooctanesulfonamido)ethyl alcohol, N-EtFOSE] and N-acetic acid (N-ethylperfluorooctanesulfonamidoacetate, N-EtFOSAA) of N-EtFOSA. Each test compound was dissolved in ethanol and added directly to an incubation medium containing substrate-energized rat liver mitochondria. Mitochondrial respiration and membrane potential were measured concurrently using an oxygen electrode and a TPP+ -selective electrode, respectively. All of the compounds tested, at sufficiently high concentrations, had the capacity to interfere with mitochondrial respiration, albeit via different mechanisms and with varying potencies. At sufficiently high concentrations, the free acids PFOA and PFOS caused a slight increase in the intrinsic proton leak of the mitochondrial inner membrane, which resembled a surfactant-like change in membrane fluidity. Similar effects were observed with the sulfonamide N-EtFOSE. Another fully substituted sulfonamide, N-EtFOSAA, at high concentrations caused inhibition of respiration, the release of cytochrome c, and high-amplitude swelling of mitochondria. The swelling was prevented by cyclosporin A or by EGTA, indicating that this compound induced the mitochondrial permeability transition. The unsubstituted and mono-substituted amides FOSA, N-EtFOSA, and FOSAA all exerted a strong uncoupling effect on mitochondria resembling that of protonophoric uncouplers. Among these compounds, FOSA was a very potent uncoupler of oxidative phosphorylation, with an IC50 of approximately 1 microM. These data suggest that the protonated nitrogen atom with a favorable pKa is essential for the uncoupling action of perfluorooctane sulfonamides in mitochondria, which may be critical to the mechanism by which these compounds interfere with mitochondrial metabolism to induce peroxisome proliferation in vivo.

Abstract  In 2000, 3M Company, the primary global manufacturer, announced a phase-out of perfluorooctanesulfonyl fluoride (POSF, C8F17SO2F)-based materials after perfluorooctanesulfonate (PFOS, C8F17SO3−) was reported in human populations and wildlife. The purpose of this study was to determine whether PFOS and other polyfluoroalkyl concentrations in plasma samples, collected in 2006 from six American Red Cross adult blood donor centers, have declined compared to nonpaired serum samples from the same locations in 2000−2001. For each location, 100 samples were obtained evenly distributed by age (20−69 years) and sex. Analytes measured, using tandem mass spectrometry, were PFOS, perfluorooctanoate (PFOA), perfluorohexanesulfonate (PFHxS), perfluorobutanesulfonate (PFBS), N-methyl perfluorooctanesulfonamidoacetate (Me-PFOSA-AcOH), and N-ethyl perfluorooctanesulfonamidoacetate (Et-PFOSA-AcOH). The geometric mean plasma concentrations were for PFOS 14.5 ng/mL (95% CI 13.9−15.2), PFOA 3.4 ng/mL (95% CI 3.3−3.6), and PFHxS 1.5 ng/mL (95% CI 1.4−1.6). The majority of PFBS, Me-PFOSA-AcOH, and Et-PFOSA-AcOH concentrations were less than the lower limit of quantitation. Age- and sex-adjusted geometric means were lower in 2006 (approximately 60% for PFOS, 25% for PFOA, and 30% for PFHxS) than those in 2000−2001. The declines for PFOS and PFHxS are consistent with their serum elimination half-lives and the time since the phase-out of POSF-based materials. The shorter serum elimination half-life for PFOA and its smaller percentage decline than PFOS suggests PFOA concentrations measured in the general population are unlikely to be solely attributed to POSF-based materials. Direct and indirect exposure sources of PFOA could include historic and ongoing electrochemical cell fluorination (ECF) of PFOA, telomer production of PFOA, fluorotelomer-based precursors, and other fluoropolymer production.

Abstract  N-alkyl perfluorooctane sulfonamides have been widely used as surfactants on fabrics and papers, fire retardants, and anti-corrosion agents, among many other commercial applications. The global distribution and environmental persistence of these compounds has generated considerable interest regarding potential toxic effects. We have previously reported that perfluorooctanesulfonamidoacetate (FOSAA) and N-ethylperfluorooctanesulfonamidoacetate (N-EtFOSAA) induce the mitochondrial permeability transition (MPT) in vitro. In this study we tested the hypothesis that FOSAA and N-EtFOSAA interact with the adenine nucleotide translocator (ANT) resulting in a functional inhibition of the translocator and induction of the MPT. Respiration and membrane potential of freshly isolated liver mitochondria from Sprague-Dawley rats were measured using an oxygen electrode and a tetraphenylphosphonium-selective (TPP(+)) electrode, respectively. Mitochondrial swelling was measured spectrophotometrically. The ANT ligands bongkregkic acid (BKA) and carboxyatractyloside (cATR) inhibited uncoupling of mitochondrial respiration caused by 10 microM N-EtFOSAA, 40 microM FOSAA, and the positive control 8 microM oleic acid. ADP-stimulated respiration and depolarization of mitochondrial membrane potential were inhibited by cATR, FOSAA, N-EtFOSAA, and oleic acid, but not by FCCP. BKA inhibited calcium-dependent mitochondrial swelling induced by FOSAA, N-EtFOSAA, and oleic acid. Seventy-five micromolar ADP also inhibited swelling induced by the test compounds, but cATR induced swelling was not inhibited by ADP. Results of this investigation indicate that N-acetyl perfluorooctane sulfonamides interact directly with the ANT to inhibit ADP translocation and induce the MPT, one or both of which may account for the metabolic dysfunction observed in vivo.

Abstract  A fluorosurfactant, the anionic N-ethyl-N-[(heptadecafluorooctyl)sulfonyl]glycine potassium salt, trade name FC-129 [CAS 2991-51-7] was investigated for possible application in micellar electrokinetic capillary chromatography (MEKC). The surfactant was characterized with conductometric titration and test sample mixtures were investigated in MEKC systems, and compared with sodium dodecylsulphate. An increased efficiency and interesting selectivity differences were observed.

Abstract  Faced with freshwater shortages, water authorities are increasingly utilizing wastewater reclamation to augment supplies. However, concerns over emerging trace contaminants that persist through wastewater treatment need to be addressed to evaluate potential risks. In the present study, perfluorinated surfactant residues were characterized in recycled water from four California wastewater treatment plants that employ tertiary treatment and one that treats primary sewage in a wetland constructed for both treatment and wildlife habitat. Effluent concentrations were compared with surface and groundwater from a creek where recycled water was evaluated as a potential means to augment flow (Upper Silver and Coyote Creeks, San Jose, CA). In the recycled water, 90-470 ng/l perfluorochemicals were detected, predominantly perfluorooctanoate (PFOA; 10-190 ng/l) and perfluorooctanesulfonate (PFOS; 20-190 ng/l). No significant removal of perfluorochemicals was observed in the wetland (total concentration ranged 100-170ng/l across various treatment stages); in this case, 2-(N-ethylperfluorooctanesulfonamido) acetic acid (N-EtFOSAA), perfluorodecanesulfonate (PFDS), and PFOS were dominant. Though there is currently no wastewater discharge into the creeks, perfluorochemicals were found in the surface water and underlying groundwater at a total of 20-150 ng/l with PFOS and PFOA again making the largest contribution. With respect to ecotoxicological effects, perfluorochemical release via recycled water into sensitive ecosystems requires evaluation.

Abstract  We developed a high throughput analytical method using on-line solid phase extraction coupled with isotope dilution high-performance liquid chromatography-tandem mass spectrometry (on-line SPE-HPLC-MS/MS) to simultaneously determine the concentrations of 17 polyfluoroalkyl chemicals (PFCs) in house dust. The sample preparation includes dispersion of the dust samples in 0.1 M formic acid:MeOH (1:1), followed by agitation and filtration, addition of the isotope-labeled internal standard solution to the filtrate, and analysis by on-line SPE-HPLC-MS/MS. The limits of quantitation were <4.0 ng/g. The method accuracies ranged between 73.2% and 100.2% for the different analytes at two spike levels. We confirmed the validity of the method by analyzing 39 household dust samples collected in 2004. Of the 17 PFCs measured, 6 of them--perfluorobutane sulfonate (PFBuS), N-ethyl-perfluorooctane sulfonamide, 2-(N-ethyl-perfluorooctane sulfonamido) acetic acid (Et-PFOSA-AcOH), 2-(N-methyl-perfluorooctane sulfonamido) ethanol (Me-PFOSA-EtOH), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS)--had detection frequencies >70%. We detected PFOS, PFBuS, and PFHxS at the highest median concentration, followed by Et-PFOSA-AcOH and Me-PFOSA-EtOH.

Abstract  N-Alkyl perfluorooctane sulfonamides have been widely used as surfactants on fabrics and papers, fire retardants, and anticorrosion agents, among many other commercial applications. The broad use, global distribution, and environmental persistence of these compounds has generated considerable interest regarding potentially toxic effects. We have previously reported that perfluorooctanesulfonamidoacetate (FOSAA) and N-ethylperfluorooctanesulfonamidoacetate (N-EtFOSAA) induce the mitochondrial permeability transition (MPT) in vitro, resulting in cytochrome c release, inhibition of respiration, and generation of reactive oxygen species. By synthesizing the corresponding methyl esters of FOSAA and N-EtFOSAA (methyl perlfuorinated sulfonamide acetates), we tested the hypothesis that the N-acetate moiety of FOSAA and N-EtFOSAA is the functional group responsible for induction of the MPT. Swelling of freshly isolated liver mitochondria from Sprague-Dawley rats was monitored spectrophotometrically and membrane potential (DeltaPsi) was measured using a tetraphenylphosphonium-selective (TPP(+)) electrode. In the presence of calcium, 40 microM FOSAA and 7 microM N-EtFOSAA each induced mitochondrial swelling and a biphasic depolarization of membrane potential. Mitochondrial swelling and the second-phase depolarization were inhibited by cyclosporin-A or the catalyst of K(+)/H(+) exchange nigericin, whereas the first-phase depolarization was not affected by either. In contrast, the methyl esters of FOSAA and N-EtFOSAA exhibited no depolarizing or MPT inducing activity. Results of this investigation demonstrate that the carboxylic acid moiety of the N-acetates is the active functional group, which triggers the MPT by perfluorinated sulfonamides.