Fluorotelomer alcohol biodegradation yields poly- and perfluorinated acids

The widespread detection of environmentally persistent perfluorinated acids (PFCAs) such as perfluorooctanoic acid (PFOA) and its longer chained homologues (C9>C15) in biota has instigated a need to identify potential sources. It has recently been suggested that fluorinated telomer alcohols (FTOHs) are probable precursor compounds that may undergo transformation reactions in the environment leading to the formation of these potentially toxic and bioaccumulative PFCAs. This study examined the aerobic biodegradation of the 8:2 telomer alcohol (8:2 FTOH, CF3(CF2)7CH2CH2OH) using a mixed microbial system. The initial measured half-life of the 8:2 FTOH was approximately 0.2 days mg(-1) of initial biomass protein. The degradation of the telomer alcohol was monitored using a gas chromatograph equipped with an electron capture detector (GC/ECD). Volatile metabolites were identified using gas chromatography/ mass spectrometry (GC/MS), and nonvolatile metabolites were identified and quantified using liquid chromatography/ tandem mass spectrometry (LC/MS/MS). Telomer acids (CF3(CF2)7CH2COOH; CF3(CF2)6CFCHCOOH) and PFOA were identified as metabolites during the degradation, the unsaturated telomer acid being the predominant metabolite measured. The overall mechanism involves the oxidation of the 8:2 FTOH to the telomer acid via the transient telomer aldehyde. The telomer acid via a beta-oxidation mechanism was furthertransformed, leading to the unsaturated acid and ultimately producing the highly stable PFOA. Telomer alcohols were demonstrated to be potential sources of PFCAs as a consequence of biotic degradation. Biological transformation may be a major degradation pathway for fluorinated telomer alcohols in aquatic systems.     

Aerobic biotransformation of 14C-labeled 8-2 telomer B alcohol by activated sludge from a domestic sewage treatment plant

This study investigated the biodegradation potential of 3-(14)C,1H,1H,2H,2H-perfluorodecanol [CF3(CF2)6(14)CF2CH2CH2OH, 14C-labeled 8-2 telomer B alcohol or 14C-labeled 8-2 TBA] by diluted activated sludge from a domestic wastewater treatment plant under aerobic conditions. After sample extraction with acetonitrile, biotransformation products were separated and quantified by LC/ARC (on-line liquid chromatography/accurate radioisotope counting) with a limit of quantification about 0.5% of the 14C counts applied to the test systems. Identification of biotransformation products was performed by quadrupole time-of-flight mass spectrometry. Three transformation products have been identified: CF3(CF2)6(14)CF2CH2COOH (8-2 saturated acid); CF3(CF2)6(14)CF=CHCOOH (8-2 unsaturated acid); and CF3(CF2)6(14)COOH (perfluorooctanoic acid, PFOA), representing 27, 6.0, and 2.1% of the initial 14C mass (14C counts applied) after 28 days, respectively. A transformation product, not yet reported in the literature, has also been observed and tentatively identified as CF3(CF2)6(14)CH2CH2COOH (2H,2H,3H,3H-perfluorodecanoic acid); it accounted for 2.3% of the mass balance after 28 days. The 2H,2H,3H,3H-perfluorodecanoic acid is likely a substrate for beta-oxidation, which represents one of the possible pathways for 8-2 telomer B alcohol degradation. The 8-2 saturated acid and 8-2 unsaturated acid cannot be directly used as substrates for beta-oxidation due to the proton deficiency in their beta-carbon (C3 carbon) and their further catabolism may be catalyzed by some other still unknown mechanisms. The 2H,2H,3H,3H-perfluorodecanoic acid may originate either from the major transformation product CF3(CF2)6(14)CF2CH2COOH or from other unidentified transformation products via multiple steps. Approximately 57% of the starting material remained unchanged after 28 days, likely due to its strong adsorption to the PTFE (poly(tetrafluoroethylene)) septa of the test vessels. No CF3(CF2)6(14)CF2COOH (perfluorononanoic acid) was observed, indicating that alpha-oxidation of CF3(CF2)6(14)CF2CH2COOH did not occur under the study conditions. Several 14C-labeled transformation products that have not yet been identified (each less than 1% of the mass balance) were also observed and together accounted for 7% of the total 14C mass balance after 28 days. It is not clear whether these unidentified transformation products were resulting from further metabolism of 8-2 saturated acid or 8-2 unsaturated acid. The results suggest that perfluorinated acid metabolites such as perfluorooctanoic acid account for only a very small portion of the transformation products observed. Also, the observed volatility and bioavailability of 14C-labeled 8-2 TBA for microbial degradation was markedly decreased as a result of the presence of a strongly adsorbing matrix such as PTFE in the experimental systems. It is apparent that the biological fate of 8-2 telomer B alcohol is determined by multiple degradation pathways, with neither beta-oxidation nor any other enzyme-catalyzed reactions as a single dominant (principal) mechanism under the study conditions.     

Concentrations, distribution, and persistence of fluorotelomer alcohols in sludge-applied soils near Decatur, Alabama, USA

Soil samples were collected for fluorotelomer alcohol (FTOH) analyses from six fields to which sludge had been applied and one "background" field that had not received sludge. Ten analytes in soil extracts were quantified using GC/MS. Sludge-applied fields had surface soil FTOH concentrations exceeding levels found in the background field. For 8:2nFTOH, which can degrade to perfluorooctanoic acid, impacted surface-soils ranged from 5 to 73 ng/g dry weight, clearly exceeding the background field in which 8:2nFTOH was not detected. The highest [FTOH] generally was 10:2nFTOH, which had concentrations of <5.6 to 166 ng/g. For the first time, we document the persistence of straight-chained primary FTOHs (n-FTOHs) and branch-chained secondary FTOHs (sec-FTOHs), which are transformation products of n-FTOHs, in field soils for at least five years after sludge application. Ratios of sec-FTOHs to n-FTOHs were highest for 7:2sFTOH/8:2nFTOH (～50%) and decreased with increasing chain length to a minimum for the longest-chained analytes, 13:2sFTOH/14:2nFTOH (～10%). Disappearance half-lives for FTOHs, calculated with these data, ranged from 0.85 to 1.8 years. These analytical results show that the practice of sludge application to land is a pathway for the introduction of FTOHs and, accordingly, their transformation products, perfluorocarboxylic acids, into the environment.     

Partitioning of fluorotelomer alcohols to octanol and different sources of dissolved organic carbon

Interest in the environmental fate of fluorotelomer alcohols (FTOHs) has spurred efforts to understand their equilibrium partitioning behavior. Experimentally determined partition coefficients for FTOHs between soil/water and air/water have been reported, but direct measurements of partition coefficients for dissolved organic carbon (DOC)/water (K(doc)) and octanol/ water(K(ow)) have been lacking. Here we measured the partitioning of 8:2 and 6:2 FTOH between one or more types of DOC and water using enhanced solubility or dialysis bag techniques, and also quantified K(ow) values for 4:2 to 8:2 FTOH using a batch equilibration method. The range in measured log K(doc) values for 8:2 FTOH using the enhanced solubility technique with DOC derived from two soils, two biosolids, and three reference humic acids is 2.00-3.97 with the lowest values obtained for the biosolids and an average across all other DOC sources (biosolid DOC excluded) of 3.54 +/- 0.29. For 6:2 FTOH and Aldrich humic acid, a log K(doc) value of 1.96 +/- 0.45 was measured using the dialysis technique. These average values are approximately 1 to 2 log units lower than previously indirectly estimated K(doc) values. Overall, the affinity for DOC tends to be slightly lower than that for particulate soil organic carbon. Measured log K(ow) values for 4:2 (3.30 +/- 0.04), 6:2 (4.54 +/- 0.01), and 8:2 FTOH (5.58 +/- 0.06) were in good agreement with previously reported estimates. Using relationships between experimentally measured partition coefficients and C-atom chain length, we estimated K(doc) and K(ow) values for shorter and longer chain FTOHs, respectively, that we were unable to measure experimentally.     

Perfluorinated chemicals in the arctic atmosphere

Twenty high-volume air samples were collected during a crossing of the North Atlantic and Canadian Archipelago in July 2005 to investigate air concentrations of fluorotelomer alcohols (FTOHs) and perfluoalkyl sulfonamido ethanols (PFASs). These commercial chemicals are widely used as surface treatments and are believed to be precursors for perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS) that accumulate in humans and biota, including those from remote arctic regions. The highest concentrations (sum of gas- and particle-phase) of FTOHs were for 8:2 FTOH (perfluoroctyl ethanol) (5.8-26 pg/m(3)), followed by 10:2 FTOH (perfluorodecyl ethanol) (1.9-17 pg/ m(3)) and 6:2 FTOH (perfluorohexyl ethanol) [BDL (below detection limit) to 6.0 pg/m(3)]. For the PFASs, MeFOSE (N-methyl perfluorooctane sulfonamido ethanol) was dominant and ranged from 2.6 to 31 pg/m(3); EtFOSE (N-ethyl perfluorooctane sulfonamido ethanol) ranged from BDL to 8.9 pg/m(3) and MeFOSEA (N-methyl perfluorooctane sulfonamide ethylacrylate) was BDL in all samples. Air parcel back-trajectories showed that the sampled air was largely representative of the arctic air mass. Air concentrations of target compounds were of the same order of magnitude as reported air concentrations in source regions. For instance, the mean 8:2 FTOH concentration was only a factor of about 3 lower than for three urban samples that were collected in Toronto for comparison. These findings confirm model results that predictthe efficient, long-range atmospheric transport and widespread distribution of FTOHs and related compounds in the arctic region. Mean particulate percentages for FTOHs and PFASs in the cruise samples (mean temperature, 5+/-4 degrees C) were BDL for 6:2 FTOH, 23% for 8:2 FTOH, 15% for 10:2 FTOH, 32% for MeFOSE, and 22% for EtFOSE. Further, the partitioning to particles for MeFOSE and EtFOSE was significantly correlated with inverse absolute temperature, whereas the FTOHs did not show this trend. The Toronto samples (mean temperature, -1+/-1 degree C) showed similar particulate percentages for MeFOSE and EtFOSE; however, the FTOHs were substantially less particle-bound. Although the mechanism for this partitioning is not understood, the results do indicate the need to better account for particle phase transport when modeling the atmospheric fate of these chemicals.     

Quantitation of gas-phase perfluoroalkyl surfactants and fluorotelomer alcohols released from nonstick cookware and microwave popcorn bags

Fluoropolymer dispersions are used for coating certain cookware products and food-contact packaging to impart oil and water repellency. Since salts of perfluorooctanoic acid (PFOA) are used as a processing aid in the manufacture of many fluoropolymers, it is necessary to determine if these compounds are still present as residuals after the process used to coat nonstick cookware or packaging, and could be released during typical cooking conditions. In this study, we identified and measured perfluoroalkyl carboxylates (PFCAs), particularly PFOA, and fluorotelomer alcohols (FTOHs; 6:2 FTOH and 8:2 FTOH), released from nonstick cookware into the gas phase under normal cooking temperatures (179 to 233 degrees C surface temperature). PFOA was released into the gas phase at 7-337 ng (11-503 pg/cm2) per pan from four brands of nonstick frying pans. 6:2 FTOH and 8:2 FTOH were found in the gas phase of four brands of frying pans, and the sources of FTOHs released from nonstick cookware are under investigation. We observed a significant decrease in gas-phase PFOA following repeated use of one brand of pan, whereas the other brand did not show a significant reduction in PFOA release following multiple uses. PFOA was found at >5 ng during the fourth use of both brands of pans. FTOHs were not found after the second use of either brand of pans. PFOA was found at 5-34 ng in the vapors produced from a prepacked microwave popcorn bag. PFOA was not found in the vapors produced from plain white corn kernels popped in a polypropylene container. 6:2 FTOH and 8:2 FTOH were measured in the vapors produced from one brand of prepacked microwave popcorn at 223 + 37 ng and 258 +/- 36 ng per bag, respectively, but not measured at >20 ng (LOQ) in the other two brands. On the packaging surface of one brand of microwave popcorn several PFCAs, including C5-C12, 6:2 FTOH, and 8:2 FTOH, were found at concentrations in the order of 0.5-6.0 ng/cm2. This study suggests that residual PFOA is not completely removed during the fabrication process of the nonstick coating for cookware. They remain as residuals on the surface and may be off-gassed when heated at normal cooking temperatures.     

Semivolatile fluorinated organic compounds in Asian and western U.S. air masses

Semivolatile fluorinated organic compounds (FOCs) were measured in archived air sample extracts collected from Hedo Station Observatory (HSO) on Okinawa, Japan and Mount Bachelor Observatory (MBO), Oregon U.S. during the springs of 2004 (MBO and HSO) and 2006 (MBO). Fluorotelomer alcohols (FTOHs) were measured in both Asian and western U.S. air masses, though western U.S. air masses had significantly higher concentrations. Concentrations of fluorotelomer olefins in Asian air masses and 8:2 fluorotelomer acrylate in U.S. air masses were reported for the first time. N-ethyl perfluorooctane sulfonamide, N-methyl perfluorooctane sulfonamido ethanol, and N-ethyl perfluorooctane sulfonamido ethanol were also measured in Asian and western U.S. air masses but less frequently than FTOHs. The atmospheric sources and fate of FTOHs were investigated by estimating their atmospheric residence times, calculating FTOH concentration ratios, investigating FTOH correlations with nonfluorinated semivolatile organic compound concentrations, and determining air mass back trajectories. Estimated atmospheric residence times for 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH were 50, 80, and 70 d, respectively, and the average concentration ratio of 6:2 FTOH to 8:2 FTOH to 10:2 FTOH at MBO in 2006 was 1.0 to 5.0 to 2.5. The relative order of these atmospheric residence times may explain the observed enhancement of 8:2 FTOH and 10:2 FTOH (relative to 6:2 FTOH) at MBO compared to North American indoor air (FTOH average ratio of 1.0 to 2.0 to 1.0). FTOH concentrations in western U.S. air masses were positively correlated (p < 0.05) with gas-phase polycyclic aromatic hydrocarbon and polychlorinated biphenyl concentrations and negatively correlated (p < 0.05) with agricultural pesticide concentrations. In comparison to western U.S. air masses, trans-Pacific air masses did not contain elevated concentrations of these compounds, whereas lower boundary layer air masses that passed over urban areas of the western U.S. did. This suggests that semivolatile FOCs are emitted from urban areas in the western U.S.     

High-resolution atmospheric modeling of fluorotelomer alcohols and perfluorocarboxylic acids in the North American troposphere

A high spatial and temporal resolution atmospheric model is used to evaluate the potential contribution of fluorotelomer alcohol (FTOH) and perfluorocarboxylate (PFCA) emissions associated with the manufacture, use, and disposal of DuPont fluorotelomer-based products in North America to air concentrations of FTOH, perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) in North America and the Canadian Arctic. A bottom-up emission inventory for PFCAs and FTOHs was developed from sales and product composition data. A detailed FTOH atmospheric degradation mechanism was developed to simulate FTOH degradation to PFCAs and model atmospheric transport of PFCAs and FTOHs. Modeled PFCA yields from FTOH degradation agree with experimental smog-chamber results supporting the degradation mechanism used. Estimated PFCA and FTOH air concentrations and PFCA deposition fluxes are compared to monitoring data and previous global modeling. Predicted FTOH air concentrations are generally in agreement with available monitoring data. Overall emissions from the global fluorotelomer industry are estimated to contribute approximately 1-2% of the PFCAs in North American rainfall, consistent with previous global emissions estimates. Emission calculations and modeling results indicate that atmospheric inputs of PFCAs in North America from fluorotelomer-based products will decline by an order of magnitude in the near future as a result of current industry commitments to reduce manufacturing emissions and lower the residual fluorotelomer alcohol raw material and trace PFCA product content.     

Fluorotelomer carboxylic acids and PFOS in rainwater from an urban center in Canada

A method based on LC/MS/MS analysis of fluorotelomer carboxylic acids (FTCAs: CnF2n+1CH2COOH, n = 6, 8, and 10) and fluorotelomer unsaturated carboxylic acids (FTUCAs: CnF2nCHCOOH, n = 6, 8, and 10) in rainwater using negative ionization electrospray multiple reaction monitoring conditions is described. These compounds are thought to be oxidative products of atmospherically transported fluorotelomer alcohols (FTOHs: CnF2n+1CH2CH2CH2OH). Preconcentration from rainwater samples collected in Winnipeg, Manitoba, Canada, was achieved using solid-phase extraction on C18 sorbent. Low parts per trillion levels of the C10- and C12-FTCAs and FTUCAs were detected, suggesting that one possible pathway of removing FTOHs from the atmosphere is through oxidation and wet deposition. Perfluorocarboxylic acids (PFCAs) and perfluorooctane sulfonate (PFOS) were simultaneously analyzed in the rainwater samples using established LC/MS/MS methods. PFOS was deposited in rainwater with a concentration of 0.59 ng/L while PFCAs were not detected above their respective method detection limits.     

Effect of fluorotelomer alcohol chain length on aqueous solubility and sorption by soils

Fluorotelomer alcohols (FTOHs) are a group of polyfluorinated alkyl chemicals that have been widely studied as precursorsto perfluorocarboxylates such as perfluorooctanoic acid and for which knowledge on their fate in soils is sparse. The solubility and sorption by soil of the homologous 4:2 to 10:2 FTOHs were measured in water or cosolvent/ water solutions. For the smaller 4:2 and 6:2 FTOHs, solubility and sorption could be measured adequately in aqueous systems although transformation was apparent even in gamma-irradiated and autoclaved systems. Sorption coefficients estimated by measuring both sorbed and solution-phase concentrations were not significantly affected by the biotransformation process. The use of cosolvents was employed for probing the behavior of the longer-chain FTOHs with limited aqueous solubility. A single log-linear correlation between aqueous solubility and modified McGowan molar volumes resulted for the n-alkanols and FTOHs. Soil organic carbon (OC) consistently appeared to be the key soil property influencing sorption of the FTOHs while the perfluorocarbon chain length was the dominant structural feature influencing solubility and sorption. Each CF2 moiety decreased the aqueous solubility by -0.78 log units (compared to 0.60 log units for each CH2 addition in hydrogenated primary alcohols), and increased OC-normalized sorption coefficients (Koc) by -0.87 log units. Good log-log linear correlations between Koc and both octanol-water partition coefficients and solubility were observed for the FTOHs.