Perfluoroalkyl Acids: A Review of Monitoring and Toxicological Findings

Waterborne exposure to PFOS causes disruption of the hypothalamus-pituitary-thyroid axis in zebrafish larvae

Thyroid hormones (THs) play an important role in the normal development and physiological functions in fish. Environmental chemicals may adversely affect thyroid function by disturbing gene transcription. Perfluorooctane sulfonate (PFOS), a persistent compound, is widely distributed in the aquatic environment and wildlife. In the present study, we investigated whether PFOS could disrupt the hypothalamic-pituitary-thyroid (HPT) axis. Zebrafish embryos were exposed to various concentrations of PFOS (0, 100, 200 and 400 microgL(-1)) and gene expression patterns were examined 15d post-fertilization. The expression of several genes in the HPT system, i.e., corticotropin-releasing factor (CRF), thyroid-stimulating hormone (TSH), sodium/iodide symporter (NIS), thyroglobulin (TG), thyroid peroxidase (TPO), transthyretin (TTR), iodothyronine deiodinases (Dio1 and Dio2) and thyroid receptor (TRalpha and TRbeta), was quantitatively measured using real-time PCR. The gene expression levels of CRF and TSH were significantly up-regulated and down-regulated, respectively, upon exposure to 200 and 400 microg L(-1) PFOS. A significant increase in NIS and Dio1 gene expression was observed at 200 microg L(-1) PFOS exposure, while TG gene expression was down-regulated at 200 and 400 microg L(-1) PFOS exposure. TTR gene expression was down-regulated in a concentration-dependent manner. Up-regulation and down-regulation of TRalpha and TRbeta gene expression, respectively, was observed upon exposure to PFOS. The whole body thyroxine (T(4)) content remained unchanged, whereas triiodothyronine (T(3)) levels were significantly increased, which could directly reflect disrupted thyroid hormone status after PFOS exposure. The overall results indicated that PFOS exposure could alter gene expression in the HPT axis and that mechanisms of disruption of thyroid status by PFOS could occur at several steps in the synthesis, regulation, and action of thyroid hormones.

Perfluorooctane sulfonate (PFOS) precursors can be metabolized enantioselectively: principle for a new PFOS source tracking tool

Perfluorooctane sulfonate (PFOS) is the most prominent perfluoroalkyl substance found in the serum of humans and wildlife, yet the major routes by which exposure occurs are not clear. An important issue facing both the scientific and chemical regulatory communities is the extent to which PFOS concentrations in biota are attributable to direct exposure versus metabolism of PFOS-precursors (higher molecular weight derivatives that can be biotransformed to PFOS). Given that certain branched PFOS-precursors are chiral, we hypothesized that nonracemic proportions of PFOS isomers in biological samples could be used as a marker of significant exposure to PFOS-precursors. In this proof-of-principle study we examined the enantiomer-specific biotransformation of a high-purity model PFOS-precursor isomer: C(6)F(13)C*F(CF(3))SO(2)N(H)CH(2)(C(6)H(4))OCH(3) (named 1m-PreFOS hereafter, and whereby * indicates the chiral carbon center). A method for the enantiospecific separation of a compound with a long perfluoroalkyl chain and a chiral center was developed and applied to evaluate the enantioselectivity of 1m-PreFOS biotransformation in human liver microsomes. Gradient elution in reversed-phase mode on a Chiralpak IC column permitted the near-baseline separation of the two enantiomers (E1 and E2, nomenclature based on retention order) in 65 min. Microsome incubations demonstrated that E1 and E2 were metabolized at significantly different rates; k(E1) = 6.5(+/-0.3) x 10(-2) min(-1) (half-life = 10.6 min) and k(E2) = 5.2(+/-0.3) x 10(-2) min(-1) (half-life = 13.3 min), respectively. These results suggest that tracking of PFOS exposure sources by enantiomeric fractionation is feasible, and that new analytical methods for the enantioselective analysis of PFOS isomers in human and environmental samples should be developed.

Prenatal and postnatal impact of perfluorooctane sulfonate (PFOS) on rat development: a cross-foster study on chemical burden and thyroid hormone system

Perfluorooctane sulfonate (PFOS), an environmentally persistent organic pollutant, has been reported to be transferred to the developing organisms via both placenta and breast milk. A cross-foster model was used to determine whether prenatal or postnatal exposure to PFOS alone can disturb the TH homeostasis in rat pups, and if so, which kind of exposure is a major cause of TH level alteration. Pregnant rats were fed standard laboratory rodent diet containing 0 (control) or 3.2 mg PFOS/kg throughout gestation and lactation period. On the day of birth, litters born to treated and control dams were cross-fostered, resulting in the following groups: unexposed control (CC), pups exposed only prenatally (TC), only postnatally (CT) or both prenatally and postnatally (TT). Serum and liver PFOS concentrations, serum total thyroxine (T4), total triiodothyronine (T3), reverse T3 (rT3) levels, and hepatic expression of genes involved in TH transport, metabolism, and receptors were evaluated in pups at the age of postnatal days (PNDs) 0, 7, 14, 21, or 35. PFOS body burden level in pups in group CT increased, while those in group TC dropped as they aged. Neither total T3 nor rT3 in pups was affected by PFOS exposure. Gestational exposure to PFOS alone (TC) significantly (p < 0.05) decreased T4 level in pups on PNDs 21 and 35, 20.3 and 19.4% lower than the control on the same PND, respectively. Postnatal exposure to PFOS alone (CT) also induced T4 depression on PNDs 21 and 35, 28.6 and 35.9% lower than controls, respectively. No significant difference in T4 level (p > 0.05) was observed between TC and CT on these two time points. None of the selected TH related transcripts was affected by PFOS in pups on PND 0. Only transcript level of transthyretin, TH binding protein, in group TT significantly increased to 150% of the control on PND 21. The results showed that prenatal PFOS exposure and postnatal PFOS exposure induced hypothyroxinemia in rat pups to a similar extent, which suggested that in utero PFOS exposure and postnatal PFOS accumulation, especially though maternal milk, are matters of great concern.

Long chain perfluorinated alkyl acids derivatisation and identification in biota and abiota matrices using gas chromatography

An analytical method involving derivatisation of perfluorocarboxylic acids for their analysis in abiotic and biotic matrices is presented. Derivatisation of the acid group to form a suitable alkyl ester provided a suitable compound for mass spectrometric detection in gas chromatography/mass spectroscopy (GC/MS) instrumental analysis. The acid is esterified by an alkyl halide i.e. benzyl bromide as the alkylating agent for perfluorocarboxylic acids quantification in fish and water by GC/MS. The gas chromatography method can be applied in the analysis perfluoro alkyl acids in water and biological matrices, especially where high levels of these compounds are expected. Typical values for precision obtained were 0.1%-10.0% with concentrations ranging from 0.2 to 1 microg/mL). Results demonstrate that GC/MS can supplement liquid chromatographic/mass spectroscopy method for quantification of fluorocarboxylic acid surfactants. The result indicates that there is need for more research on method analysis of perfluorinated acids in environmental matrices.

Determination of ten perfluorinated compounds in bluegill sunfish (Lepomis macrochirus) fillets

A rigorous solid phase extraction/liquid chromatography/tandem mass spectrometry method for the measurement of 10 perfluorinated compounds (PFCs) in fish fillets is described and applied to fillets of bluegill sunfish (Lepomis macrochirus) collected from selected areas of Minnesota and North Carolina. The 4 PFC analytes routinely detected in bluegill fillets were perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (C10), perfluoroundecanoic acid (C11), and perflurododecanoic acid (C12). Measures of method accuracy and precision for these compounds showed that calculated concentrations of PFCs in spiked samples differed by less than 20% from their theoretical values and that the %RSD for repeated measurements was less than 20%. Minnesota samples were collected from areas of the Mississippi River near historical PFC sources, from the St. Croix River as a background site, and from Lake Calhoun, which has no documented PFC sources. PFOS was the most prevalent PFC found in the Minnesota samples, with median concentrations of 47.0-102 ng/g at locations along the Mississippi River, 2.08 ng/g in the St. Croix River, and 275 ng/g in Lake Calhoun. North Carolina samples were collected from two rivers with no known historical PFC sources. PFOS was the predominant analyte in fish taken from the Haw and Deep Rivers, with median concentrations of 30.3 and 62.2 ng/g, respectively. Concentrations of C10, C11, and C12 in NC samples were among the highest reported in the literature, with respective median values of 9.08, 23.9, and 6.60 ng/g in fish from the Haw River and 2.90, 9.15, and 3.46 ng/g in fish from the Deep River. These results suggest that PFC contamination in freshwater fish may not be limited to areas with known historical PFC inputs.

Occurrence of antifouling biocides and fluorinated alkyl compounds in sediment core from deep sea: Suruga Bay, Tosa Bay, and Nankai tough, Japan

Contamination profiles of antifouling biocides were investigated in a deep-sea environment in Suruga Bay Japan. Significant differences in the tributyltin (TBT) and triphenyltin (TPT) concentrations in subsurface sediment between 850 and 800 m of water depth were not observed (p < 0.05). Organotin (OT) concentrations in sediment core of 0-30.5 cm from a water depth of 800 m were investigated. The butyltins (BTs) and phenyltins (PTs) concentrations were constant between 0 and 15 cm, and, subsequently, the concentration of these compounds increased. The peaks of the BTs and PTs concentrations were observed between 18 and 19 cm. The concentrations of Irgarol 1051 decreased until a core depth of 9 cm, and, the values then became near the detection limit under the 10 cm of core depth. Perfluorooctane sulfonate (PFOS) and perfluorooctanic acid (PFOA) were detected in the sediment core (0-30.5 cm) of Suruga Bay. The concentration of PFOS was high in the 0-5-cm core depth and then decreased. The concentrations of PFOA, however, were at the values near the detection limit throughout the sediment core. The BTs and PTs concentrations in surface sediment from Tosa Bay decreased with water depth. Although Irgarol 1051 was the only alternative compound detected, the value was near the detection limit. PFOS and PFOA were detected in sediment core from Tosa Bay. The concentrations of PFOS became low as the water depth became deeper. TBT, TPT, Sea Nine 211, Diuron and Irgarol 1051 were detected in sediment core (core depth: 10 cm) from the Nankai trough (water depth: 4010 m).

Perfluorononanoic acid-induced apoptosis in rat spleen involves oxidative stress and the activation of caspase-independent death pathway

Perfluoroalkyl acid (PFAA)-induced apoptosis has been reported in many cell types. However, minimal information on its mode of action is available. This study explored the possible involvement of apoptotic signaling pathways in a nine-carbon-chain length PFAA-perfluorononanoic acid (PFNA)-induced splenocyte apoptosis. After a 14-day exposure to PFNA, rat spleens showed dose-dependent levels of apoptosis. The production of pro-inflammatory and anti-inflammatory cytokines was significantly increased and decreased, respectively. However, protein levels of tumor necrosis factor receptor 1 (TNFR1), fas-associated protein with death domain (FADD), caspase 8 and caspase 3, which are involved in inflammation-related and caspase-dependent apoptosis, were discordant. Peroxisome proliferator-activated receptors alpha (PPARalpha) and PPARgamma genes expression was up-regulated in rats treated with 3 or 5 mg/kg/day of PFNA, and the level of hydrogen peroxide (H2O2) increased concurrently in rats treated with the highest dose. Moreover, superoxide dismutase (SOD) activity and Bcl-2 protein levels were dramatically decreased in spleens after treatment with 3 and 5 mg/kg/day of PFNA. However, protein levels of Bax were unchanged. Apoptosis-inducing factor (AIF), an initiator of caspase-independent apoptosis, was significantly increased in all PFNA-dosed rats. Thus, oxidative stress and the activation of a caspase-independent apoptotic signaling pathway contributed to PFNA-induced apoptosis in rat splenocytes.

Model and cell membrane partitioning of perfluorooctanesulfonate is independent of the lipid chain length

Perfluorooctanesulfonic acid (PFOS) is a persistent environmental pollutant that may cause adverse health effects in humans and animals by interacting with and disturbing of the normal properties of biological lipid assemblies. To gain further insights into these interactions, we investigated the effect of PFOS potassium salt on dimyristoyl- (DMPC), dipalmitoyl- (DPPC) and distearoylphosphatidylcholine (DSPC) model membranes using fluorescence anisotropy measurements and differential scanning calorimetry (DSC) and on the cell membrane of HL-60 human leukemia cells and freshly isolated rat alveolar macrophages using fluorescence anisotropy measurements. PFOS produced a concentration-dependent decrease of the main phase transition temperature (T(m)) and an increased peak width (DeltaT(w)) in both the fluorescence anisotropy and the DSC experiments, with a rank order DMPC>DPPC>DSPC. PFOS caused a fluidization of the gel phase of all phosphatidylcholines investigated, but had the opposite effect on the liquid-crystalline phase. The apparent partition coefficients of PFOS between the phosphatidylcholine bilayer and the bulk aqueous phase were largely independent of the phosphatidylcholine chain length and ranged from 4.4x10(4) to 8.8x10(4). PFOS also significantly increased the fluidity of membranes of cells. These findings suggest that PFOS readily partitions into lipid assemblies, independent of their composition, and may cause adverse biological effects by altering their fluidity in a manner that depends on the membrane cooperativity and state (e.g., gel versus liquid-crystalline phase) of the lipid assembly.

Serum levels of perfluorooctanoic acid and perfluorooctane sulfonate and pregnancy outcome

The authors examined the association of serum perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) with self-reported pregnancy outcome in Mid-Ohio Valley residents (2000-2006) highly exposed to PFOA. Data on 1,845 pregnancies within the 5 years preceding exposure measurement were analyzed for PFOA, and data on 5,262 pregnancies were analyzed for PFOS. Generalized estimating equations were used to calculate adjusted odds ratios and 95% confidence intervals. Neither PFOA nor PFOS showed any association with miscarriage or preterm birth. Preeclampsia was weakly associated with PFOA (adjusted odds ratio = 1.3, 95% confidence interval: 0.9, 1.9) and PFOS (adjusted odds ratio = 1.3, 95% confidence interval: 1.1, 1.7) exposures above the median. PFOA was not associated with an increase in low birth weight, but PFOS showed an increased risk above the median (adjusted odds ratio = 1.5, 95% confidence interval: 1.1, 1.9) and a dose-response gradient. Birth defects were weakly associated with PFOA exposures above the 90th percentile (adjusted odds ratio = 1.7, 95% confidence interval: 0.8, 3.6). This study identified modest associations of PFOA with preeclampsia and birth defects and of PFOS with preeclampsia and low birth weight, but associations were small, limited in precision, and based solely on self-reported health outcomes.

Perfluoroalkyl sulfonic and carboxylic acids: a critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods

Perfluorinated acids (PFAs) are an emerging class of environmental contaminants present in various environmental and biological matrices. Two major PFA subclasses are the perfluorinated sulfonic acids (PFSAs) and carboxylic acids (PFCAs). The physicochemical properties and partitioning behavior for the linear PFA members are poorly understood and widely debated. Even less is known about the numerous branched congeners with varying perfluoroalkyl chain lengths, leading to confounding issues around attempts to constrain the properties of PFAs. Current computational methods are not adequate for reliable multimedia modeling efforts and risk assessments. These compounds are widely present in surface, ground, marine, and drinking waters at concentrations that vary from pg L(-1) to microg L(-1). Concentration gradients of up to several orders of magnitude are observed in all types of aquatic systems and reflect proximity to known industrial sources concentrated near populated regions. Some wastewaters contain PFAs at mg L(-1) to low g L(-1) levels, or up to 10 orders of magnitude higher than present in more pristine receiving waters. With the exception of trifluoroacetic acid, which is thought to have both significant natural and anthropogenic sources, all PFSAs and PFCAs are believed to arise from human activities. Filtration and sorption technologies offer the most promising existing removal methods for PFAs in aqueous waste streams, although sonochemical approaches hold promise. Additional studies need to be conducted to better define opportunities from evaporative, extractive, thermal, advanced oxidative, direct and catalyzed photochemical, reductive, and biodegradation methods. Most PFA treatment methods exhibit slow kinetic profiles, hindering their direct application in conventional low hydraulic residence time systems.

PFOS and PFOA in environmental and tap water in China

There is a great concern about global contamination with persistent fluoroorganic compounds including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), however, few data are available on the environmental levels of these chemicals in China. In the present study, therefore, environmental or tap water samples collected from various regions of China were assayed for PFOS and PFOA by solid phase extraction and liquid chromatography-mass spectrometry technique. Median concentrations (maximum concentration) of PFOS and PFOA in environmental water were 0.4 (2.4) and 0.1 (1.3) ngL(-1) for the remote area (n=13), 4.0 (14.1) and 3.9 (30.8) ngL(-1) for the urban area (n=22), respectively. Systematic survey was also conducted in the Hun River (n=11) and the Yangtze River (n=34). In the Hun River, the median of PFOS concentration was 4.9ngL(-1), while PFOA was below the limit of quantitation (0.1ngL(-1)) at many of the sampling sites. The Yangtze River was moderately contaminated with both chemicals: median concentration was 4.2ngL(-1) for PFOS and 5.4ngL(-1) for PFOA. Remarkably high concentration of PFOA was found at 2 sampling sites of the Yangtze River (110.6 and 297.5ngL(-1)), but the concentration had declined to the average level at the next sampling site in both cases. Many cities provided tap water with low levels of PFOS and PFOA, however, tap water in Guangzhou and Shenzhen exceeded 10ngL(-1) for both chemicals. This study revealed obvious presence of perfluorinated compounds spread out the entire territory of China, and the levels in urban area of China were almost comparable to those in the US, Europe and Japan.

Polyfluorinated compounds in waste water treatment plant effluents and surface waters along the River Elbe, Germany

Polyfluorinated compounds (PFCs) were investigated in waste water treatment plant (WWTP) effluents and surface waters of the River Elbe from samples collected in 2007. Concentrations of various PFCs, including C(4)-C(8) perfluorinated sulfonates (PFSAs), C(6) and C(8) perfluorinated sulfinates, 6:2 fluorotelomer sulfonate, C(5)-C(13) perfluorinated carboxylic acids (PFCAs), C(4) and C(8) perfluoroalkyl sulfonamides and 6:2, 8:2 and 10:2 unsaturated fluorotelomercarboxylic acids were quantified. Sum PFC concentrations of the river water ranged from 7.6 to 26.4ngL(-1), whereas sum PFC concentrations of WWTP effluents were approximately 5-10 times higher (30.5-266.3ngL(-1)), indicating that WWTPs are potential sources of PFCs in the marine environment. PFC patterns of different WWTP effluents varied depending on the origin of the waste water, whereas the profile of PFC composition in the river water was relatively constant. In both kinds of water samples, perfluorooctanoic acid (PFOA) was the major PFC, whereas perfluorobutane sulfonate (PFBS) was the predominant PFSA.

Polyfluorinated compounds in the atmosphere of the Atlantic and Southern Oceans: evidence for a global distribution

High volume air samples taken onboard several research vessels in the Atlantic Ocean, the Southern Ocean, and the Baltic Sea as well as at one land-based site close to Hamburg, Germany, in 2007 and 2008 were analyzed for per- and polyfluorinated organic compounds (PFCs). A set of neutral, volatile PFCs such as fluorotelomer alcohols (FTOH) or perfluoroalkyl sulfonamides and ionic nonvolatile PFCs like perfluorinated carboxylates (PFCA) and sulfonates (PFSA) were collected on PUF/XAD-2/PUF cartridges and glass fiber filters and determined using GC-MS and HPLC-MS/MS. PFCs were detected in all air samples, even in Antarctic regions, and occurred predominantly in the gas phase. Total gas-phase concentrations of ship-based samples ranged from 4.5 pg m(-3) in the Southern Ocean to 335 pg m(-3) in European source regions. Concentrations of 8:2 FTOH, the analyte that was usually observed in highest concentrations, were between 1.8 and 130 pg m(-3). PFC concentrations decreased from continental regions toward marine regions and from Central Europe toward the Arctic and Antarctica. Southern hemispheric concentrations of individual PFCs were significantly lower than those of the northern hemisphere. On the basis of this data set, marine background PFC concentrations and atmospheric residence times were calculated. This study gives further evidence that volatile PFCs undergo atmospheric long-range transportto remote regions and may contribute to their contamination with persistent PFCA and PFSA.

Exposure to endocrine disrupting compounds via the food chain: Is packaging a relevant source?

Contamination of foodstuffs by environmental pollutants (e.g. dioxins, metals) receives much attention. Until recently, food packaging as a source of xenobiotics, especially those with endocrine disrupting properties, has received little awareness despite its ubiquitous use. This article reviews the regulations and use of endocrine disrupting compounds (EDCs) in food packaging and discusses their presence within the context of new toxicology paradigms. I focused on substances known to be legally used in food packaging that have been shown to exhibit endocrine disruptive effects in biological systems. I compiled a list of 50 known or potential EDCs used in food contact materials and examined data of EDCs leaching from packaging into food, with a focus on nonylphenol. I included recent advances in toxicology: mixture effects, the developmental origins of adult disease hypothesis, low-dose effects, and epigenetics. I especially considered the case of bisphenol A. The core hypothesis of this review is that chemicals leaching from packaging into food contribute to human EDCs exposure and might lead to chronic disease in light of the current knowledge. Food contact materials are a major source of food contaminants. Many migrating compounds, possibly with endocrine disruptive properties, remain unidentified. There is a need for information on identity/quantity of chemicals leaching into food, human exposure, and long-term impact on health. Especially EDCs in food packaging are of concern. Even at low concentrations, chronic exposure to EDCs is toxicologically relevant. Concerns increase when humans are exposed to mixtures of similar acting EDCs and/or during sensitive windows of development. In particular, non-intentionally added substances (NIAS) migrating from food contact materials need toxicological characterization; the overall migrate of the finished packaging could be evaluated for biological effects using bioassays. The widespread legal use of EDCs in food packaging requires dedicated assessment and should be updated according to contemporary scientific knowledge.

Perfluorononanoic acid induces apoptosis involving the Fas death receptor signaling pathway in rat testis

Perfluorononanoic acid (PFNA, C9), a synthetic perfluorinated chemical containing nine carbons, accumulates and is biomagnified through food webs. This compound has been detected in the serum of humans and wildlife and has the potential for reproductive interference. Few studies, however, have reported the effects of PFNA exposure on male reproduction. To determine this, male rats were orally dosed for 1, 3 and 5mg/kgday PFNA or with vehicle for 14 days. In the present study, serum testosterone levels were decreased, while estradiol levels were increased dramatically in rats receiving 5mg PFNA/kgday. Spermatogenic cells from rats that received 5mg PFNA/kgday exhibited apoptotic features including crescent chromatin condensation and chromatin margination. Flow cytometric analysis and TUNEL assays revealed a dose-dependent increase of apoptotic cell numbers. In addition, expression of Fas and Bax mRNA levels were upregulated significantly, and Bcl-2 mRNA levels were downregulated markedly in the 3 and 5mg/kgday groups. A dose-dependent increase in levels of active caspase-8 and no significant changes of active caspase-9 were observed. Our results indicate that PFNA exposure can lead to cell apoptosis in rat testis, and this apoptosis was probably associated with the Fas death receptor-dependent apoptotic pathway.

Organic anion transporting polypeptide (Oatp) 1a1-mediated perfluorooctanoate transport and evidence for a renal reabsorption mechanism of Oatp1a1 in renal elimination of perfluorocarboxylates in rats

Organic anion transporting polypeptide (Oatp) 1a1 has been hypothesized to play a key role in rat renal reabsorption of perfluorooctanoate (PFO). We have investigated PFO uptake kinetics in Chinese Hamster Ovary (CHO) cells that have been stably transfected with the cDNA encoding Oatp1a1. The Oatp1a1-expressing CHO cells have been validated by their Oatp1a1 gene expression, estrone-3-sulfate (E3S) uptake kinetics, and the correlation between Oatp1a1 gene expression and E3S uptake activity that were both induced by the treatment of sodium butyrate. Oatp1a1-mediated PFO uptake underwent a saturable process with a K(m) value of 162.2+/-20.2microM, which was effectively inhibited by known Oatp1a1 substrates sulfobromophthalein and taurocholate, and a major flavonoid in grapefruit juice, naringin. The inhibition of Oatp1a1-mediated E3S uptake has been compared for linear perfluorocarboxylates with carbon chain lengths ranged from 4 to 12. There was no apparent inhibition by perfluorobutanoate and perfluoropentanoate at 1mM. Inhibition was observed for perfluorohexanoate at 1mM and the level of inhibition increased as the increase of the chain length up to perfluorodecanoate. The values of apparent inhibition constant (K(i,app)) were determined for perfluorocarboxylates with chain lengths between 6 and 10. The log values of K(i,app) exhibited a negative linear relationship to the chain lengths and a positive linear relationship to the log values of the total clearance of perfluorocarboxylates in male rats. This in vitro-to-in vivo correlation strongly supports a tubular reabsorptive role of Oatp1a1 in rat renal elimination of perfluorocarboxylates. Due to the sex-dependent expression of Oatp1a1 in rat kidney, Oatp1a1-mediated tubular reabsorption is suggested to be the mechanism for the sex-dependent renal elimination of PFO in rats.

The C8 health project: design, methods, and participants

Background

The C8 Health Project was created, authorized, and funded as part of the settlement agreement reached in the case of Jack W. Leach, et al. v. E.I. du Pont de Nemours & Company (no. 01-C-608 W.Va., Wood County Circuit Court, filed 10 April 2002). The settlement stemmed from the perfluorooctanoic acid (PFOA, or C8) contamination of drinking water in six water districts in two states near the DuPont Washington Works facility near Parkersburg, West Virginia.

Objectives

This study reports on the methods and results from the C8 Health Project, a population study created to gather data that would allow class members to know their own PFOA levels and permit subsequent epidemiologic investigations.

Methods

Final study participation was 69,030, enrolled over a 13-month period in 2005–2006. Extensive data were collected, including demographic data, medical diagnoses (both self-report and medical records review), clinical laboratory testing, and determination of serum concentrations of 10 perfluorocarbons (PFCs). Here we describe the processes used to collect, validate, and store these health data. We also describe survey participants and their serum PFC levels.

Results

The population geometric mean for serum PFOA was 32.91 ng/mL, 500% higher than previously reported for a representative American population. Serum concentrations for perfluorohexane sulfonate and perfluorononanoic acid were elevated 39% and 73% respectively, whereas perfluorooctanesulfonate was present at levels similar to those in the U.S. population.

Conclusions

This largest known population study of community PFC exposure permits new evaluations of associations between PFOA, in particular, and a range of health parameters. These will contribute to understanding of the biology of PFC exposure. The C8 Health Project also represents an unprecedented effort to gather basic data on an exposed population; its achievements and limitations can inform future legal settlements for populations exposed to environmental contaminants.

Expression of a novel cytochrome P450 4T gene in rare minnow (Gobiocypris rarus) following perfluorooctanoic acid exposure

Cytochrome P450s play an important role in the biotransformation of endogenous substrates and xenobiotics; however, little is known about the function of the CYP4T subfamily in the transformation of environmental pollutants in fish. We isolated a full-length cDNA sequence (designated as CYP4T11) from rare minnow (Gobiocypris rarus) liver by rapid amplification of cDNA ends. The open reading frame encoded a 467-residue protein that exhibited 87% and 71% identity with zebrafish CYP4T8 and European sea bass CYP4T2, respectively. CYP4T11 was predominantly expressed in liver and intestine with lower expression in the gill and brain. To further examine the function of CYP4T11 in pollutant metabolism, the effects of perfluorooctanoic acid (PFOA) exposure on the transcriptional expression of CYP4T11 and two possible upstream regulators, peroxisome proliferator-activated receptor alpha (PPARalpha) and peroxisome proliferator-activated receptor gamma (PPARgamma), were determined in rare minnow gills and livers. PFOA induced a consistent significant upregulation of both PPARalpha and PPARgamma and a nonsignificant increase of CYP4T11 in the gill. In the liver, induced expression of PPARgamma was observed, although no obvious changes in PPARalpha expression were observed. Induction of CYP4T11 was only observed in males at the highest concentration of PFOA. These results suggest that the PPAR-CYP4T11 signaling pathway may be involved in PFOA-induced gill toxicity. Since the induced expression of CYP4T11 in liver was not consistent with the PPAR regulators, complex tissue-specific transcriptional regulation of CYP4T11 following PFOA exposure likely occurs.

Polyfluoroalkyl chemicals in house dust

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.

Subacute exposure to N-ethyl perfluorooctanesulfonamidoethanol results in the formation of perfluorooctanesulfonate and alters superoxide dismutase activity in female rats

Perfluorooctanesulfonamides, such as N-ethyl perfluorooctanesulfonamidoethanol (N-EtFOSE), are large scale industrial chemicals but their disposition and toxicity are poorly understood despite significant human exposure. The hypothesis that subacute exposure to N-EtFOSE, a weak peroxisome proliferator, causes a redox imbalance in vivo was tested using the known peroxisome proliferator, ciprofibrate, as a positive control. Female Sprague-Dawley rats were treated orally with N-EtFOSE, ciprofibrate or corn oil (vehicle) for 21 days, and levels of N-EtFOSE and its metabolites as well as markers of peroxisome proliferation and oxidative stress were assessed in serum, liver and/or uterus. The N-EtFOSE metabolite profile in liver and serum was in good agreement with reported in vitro biotransformation pathways in rats and the metabolite levels decreasing in the order perfluorooctanesulfonate >> perfluorooctanesulfonamide ~ N-ethyl perfluorooctanesulfonamidoacetate >> perfluorooctanesulfonamidoethanol approximately N-EtFOSE. Although N-EtFOSE treatment significantly decreased the growth rate, increased relative liver weight and activity of superoxide dismutases (SOD) in liver and uterus (total SOD, CuZnSOD and MnSOD), a metabolic study revealed no differences in the metabolome in serum from N-EtFOSE-treated and control animals. Ciprofibrate treatment increased liver weight and peroxisomal acyl Co-A oxidase activity in the liver and altered antioxidant enzyme activities in the uterus and liver. According to NMR metabolomic studies, ciprofibrate treated animals had altered serum lipid profiles compared to N-EtFOSE-treated and control animals, whereas putative markers of peroxisome proliferation in serum were not affected. Overall, this study demonstrates the biotransformation of N-EtFOSE to PFOS in rats that is accompanied by N-EtFOSE-induced alterations in antioxidant enzyme activity.

High-dose, short-term exposure of mice to perfluorooctanesulfonate (PFOS) or perfluorooctanoate (PFOA) affects the number of circulating neutrophils differently, but enhances the inflammatory responses of macrophages to lipopolysaccharide (LPS) in a similar fashion

Having found previously that high-dose, short-term dietary exposure of mice to perfluorooctanesulfonate (PFOS) or perfluorooctanoate (PFOA) suppresses adaptive immunity, in the present study we characterize the effects of these fluorochemicals on the innate immune system. Male C57BL/6 mice receiving 0.02% (w/w) PFOS or PFOA in their diet for 10 days exhibited a significant reduction in the numbers of total white blood cells (WBC), involving lymphopenia in both cases, but neutropenia only in response to treatment with PFOA. Moreover, both compounds also markedly reduced the number of macrophages (CD11b(+) cells) in the bone marrow, but not in the spleen or peritoneal cavity. The ex vivo production of tumor necrosis factor-alpha (TNF-alpha) and interleukin 6 (IL-6) by peritoneal macrophages isolated from animals treated with PFOA or PFOS was increased modestly. Moreover, both fluorochemicals markedly enhanced the ex vivo production of these same cytokines by peritoneal and bone marrow macrophages stimulated either in vitro or in vivo with lipopolysaccharide (LPS); whereas there was no such effect on splenic macrophages. The serum levels of these inflammatory cytokines observed in response to in vivo stimulation with LPS were elevated substantially by prior exposure to PFOA, but not by PFOS. None of these parameters of innate immunity were altered in animals receiving a dietary dose of these compounds that was 20-fold lower (0.001%, w/w). These findings reveal that in addition to suppressing adaptive immunity, high-dose, short-term exposure of mice to either PFOS or PFOA augments inflammatory responses to LPS, a potent activator of innate immunity.

Occurrence and potential significance of perfluorooctanoic acid (PFOA) detected in New Jersey public drinking water systems

After detection of perfluorooctanoic acid (PFOA) in two New Jersey (NJ) public water systems (PWS) at concentrations up to 0.19 microg/L, a study of PFOA in 23 other NJ PWS was conducted in 2006. PFOA was detected in 15 (65%) of the systems at concentrations ranging from 0.005 to 0.039 microg/L. To assess the significance of these data, the contribution of drinking water to human exposure to PFOA was evaluated, and a health-based drinking water concentration protective for lifetime exposure of 0.04 microg/L was developed through a risk assessment approach. Both the exposure assessment and the health-based drinking water concentrations are based on the previously reported 100:1 ratio between the concentration of PFOA in serum and drinking water in a community with highly contaminated drinking water. The applicability of this ratio to lower drinking water concentrations was confirmed using data on serum levels and water concentrations from other communities. The health-based concentration is based on toxicological end points identified by U.S. Environmental Protection Agency (USEPA) in its 2005 draft risk assessment Recent information on PFOA's toxicity not considered in the USEPA risk assessment urther supports the health-based concentration of 0.04 microg/L. In additional sampling of 18 PWS in 2007-2008, PFOA in most systems was below the health-based concentration. However, PFOA was detected above the health-based concentration in five systems, including one not previously sampled.

Analysis of PFOA in dosed CD-1 mice. Part 2. Disposition of PFOA in tissues and fluids from pregnant and lactating mice and their pups

Previous studies in mice with multiple gestational exposures to perfluorooctanoic acid (PFOA) demonstrate numerous dose dependent growth and developmental effects which appeared to worsen if offspring exposed in utero nursed from PFOA-exposed dams. To evaluate the disposition of PFOA in the pregnant and lactating dam and her offspring, time-pregnant CD-1 mice received a single 0, 0.1, 1, or 5mg PFOA/kg BW dose (n=25/dose group) by gavage on gestation day 17. Maternal and pup fluids and tissues were collected over time. Pups exhibited significantly higher serum PFOA concentrations than their respective dams, and their body burden increased after birth until at least postnatal day 8, regardless of dose. The distribution of milk:serum PFOA varied by dose and time, but was typically in excess of 0.20. These data suggest that milk is a substantial PFOA exposure route in mice and should be considered in risk assessment modeling designs for this compound.

Perfluoroalkyl contaminants in an Arctic marine food web: trophic magnification and wildlife exposure

To better understand the bioaccumulation behavior of perfluoroalkyl contaminants (PFCs), we conducted a comparative analysis of PFCs and lipophilic organohalogens in a Canadian Arctic marine food web. Concentrations of perfluorooctane sulfonic acid (PFOS), perfluorooctansulfoamide (PFOSA), and C7-C14 perfluorocarboxylic acids (PFCAs) ranged between 0.01 and 0.1 ng x g(-1) dry wt in sediments and 0.1 and 40 ng x g(-1) wet wt in biota, which was equivalent to or higher than levels of PCBs, PBDEs, and organochlorine pesticides. In beluga whales, PFOS and PFCA concentrations were higher (P < 0.05) in protein-rich compartments (liver and blood), compared to other tissues/fluids (milk, blubber, muscle, and fetus). In the marine mammalian food web, concentrations of PFOSA and lipophilic organochlorines (ng x g(-1) lipid equivalent) and proteinophilic substances (i.e., PFOS and C8-C14 PFCAs, ng x g(-1) protein) increased significantly (P < 0.05) with trophic level. Trophic magnification factors (TMFs) of organochlorines ranged between 5 and 14 and exhibited significant curvilinear relationships (P < 0.05) with octanol-water and octanol-air partition coefficients (KOW, KOA). TMFs of perfluorinated acids (PFAs) ranged between 2 and 11 and exhibited similar correlation (P < 0.05) with protein-water and protein-air partition coefficients (KPW, KPA). PFAs did not biomagnify in the aquatic piscivorous food web (TMF range: 0.3-2). This food web specific biomagnification behavior was attributed to the high aqueous solubility and low volatility of PFAs. Specifically, the anticipated phase-partitioning of these proteinophilic substances, represented by their protein-water (KPW) and protein-air (KPA) partition coefficients, likely results in efficient respiratory elimination in water-respiring organisms but very slow elimination and biomagnification in air-breathing animals. Lastly, the results indicate that PFOS exposure in nursing Hudson Bay beluga whale calves (CI95 range = 2.7 x 10(-5) to 1.8 x 10(-4) mg x kg bw(-1) x d(-1)), exceedsthe oral reference dose for PFOS (7.5 x 10(-5) mg x kg bw(-1) x d(-1)), which raises concern for potential biological effects in these and other sensitive Arctic marine wildlife species.

Polyfluoroalkyl chemicals in pooled blood serum from infants, children, and adults in Australia

Polyfluoroalkyl chemicals (PFCs) have been used worldwide for more than 50 years in a wide variety of industrial and consumer products. Limited data exist on human exposure to PFCs in the Southern Hemisphere. Human blood serum collected in southeast Queensland, Australia, in 2006-2007 from 2420 donors was pooled according to age (cord blood, 0-0.5, 0.6-1, 1.1-1.5, 1.6-2, 2.1-2.5, 2.6-3, 3.1-3.5, 3.6-4, 4.1-6, 6.1-9, 9.1-12, 12.1-15, 16-30, 31-45, 46-60, and > 60 years) and gender and was analyzed for eight PFCs. Across all pools, perfluorooctane sulfonate (PFOS) was detected at the highest mean concentration (15.2 ng/mL) followed by perfluorooctanoate (PFOA, 6.4 ng/mL), perfluorohexane sulfonate (PFHxS, 3.1 ng/mL), perfluorononanoate (PFNA, 0.8 ng/mL), 2-(N-methylperfluorooctance sulfonamide) acetate (Me-PFOSA-AcOH, 0.66 ng/mL), and perfluorodecanoate (PFDeA, 0.29 ng/mL). Perfluorooctane sulfonamide was detected in only 24% of the pools, and 2-(N-ethylperfluorooctane sulfonamide) acetate was detected in only one. PFOS concentrations were significantly higher in pools from adult males than from adult females (p = 0.002); no gender differences were apparent in the pools from children (< 12 years old). The highest mean concentrations of PFOA, PFHxS, PFNA, PFDeA, and Me-PFOSA-AcOH were found in children < 15 years, while PFOS was highest in adults > 60 years. Investigation into the sources and exposure pathways in Australia, in particular for children, is necessary as well as continued biomonitoring to determine the potential effects on human concentrations as a result of changes in the PFC manufacturing practices, including the cessation of production of several PFCs.

Perfluorooctane sulfonate (PFOS) toxicity in domestic chicken (Gallus gallus domesticus) embryos in the absence of effects on peroxisome proliferator activated receptor alpha (PPARalpha)-regulated genes

Perfluorooctane sulfonate (PFOS) is a widely distributed industrial compound that has been detected in the eggs of various wild avian species. Laboratory studies have indicated that PFOS is embryotoxic to domestic chickens (Gallus gallus domesticus), but the mechanisms of toxicity in the developing avian embryo remain unknown. We recently demonstrated that PFOS acts as a peroxisome proliferator by causing increased expression of peroxisome proliferator activated receptor alpha (PPARalpha)-regulated genes in cultured primary chicken embryo hepatocytes. The present study examined whether PPARalpha-regulated genes were dose-dependently affected in chicken embryos exposed in ovo to PFOS. White leghorn chicken eggs were injected with 0.1, 5.0 or 100.0 microg PFOS/g egg into the air cell prior to incubation. Embryos were incubated until pipping, after which the expression of PPARalpha-regulated genes was measured in the liver tissue of surviving embryos using real-time reverse transcription polymerase chain reaction. A dose-dependent decrease in embryo pippability was observed with an LD50 of 93 microg/g (3.54 microg/g-672,910 microg/g, 95% confidence interval). Hepatic PFOS concentrations increased concomitantly with dose. The PPARalpha-regulated genes measured were peroxisomal acyl CoA oxidase, bifunctional enzyme, liver fatty acid binding protein and peroxisomal 3-ketoacyl thiolase. PFOS exposure via egg injection prior to incubation did not affect the transcriptional activity of any of the assayed PPARalpha-regulated genes at any of the doses examined in day 21 chicken embryos.

Effects of perfluorooctane sulfonate on ion channels and glutamate-activated current in cultured rat hippocampal neurons

Concern on an emerging persistent contaminant, perfluorooctane sulfonate (PFOS), is increasingly growing. Although the fate, transport, distribution and bioaccumulation of PFOS have been documented, its toxicological effects especially neurotoxicity remain largely unknown. In this study, the effects of PFOS on ion channels including potassium and sodium channels and exogenous glutamate-activated current in cultured rat hippocampal neurons were examined, based on whole-cell patch-clamp recording. PFOS markedly increased two subtypes of potassium currents, including transient outward current and delayed rectifier current, at doses over 10μM. PFOS did not affect the amplitude of sodium current at all administrated doses (1, 10 or 100μM) but clearly shifted the activation current-voltage curve toward negatively potential. Further, PFOS significantly altered the glutamate-activated current at all doses. Taken together these findings indicated that PFOS disturbs the neuronal physiological processes, which revealed the damage of this pollutant to nerve system and will be helpful for further exploration to its underlying mechanism.

Relationship between dietary exposure and serum perfluorochemical (PFC) levels--a case study

Daily dietary intake of perfluorinated chemicals (PFCs) in relation to serum levels was assessed by determination of nine PFCs including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in matched daily diet duplicates and serum samples. Diet and serum were collected in year 2004 from 20 women in Osaka and Miyagi, Japan. Only PFOS and PFOA were detected in the diet samples and no significant difference between cities was seen. After adjusted by water content, diet concentration of PFOA was significantly higher in Osaka. The median daily intake calculated using the measured diet concentrations was 1.47 ng PFOS/kg b.w. and 1.28 ng PFOA/kg b.w. for Osaka, and 1.08 ng PFOS/kg b.w. and 0.72 ng PFOA/kg b.w. for Miyagi. A significant difference between cities was seen for the serum concentrations with median of 31 ng/mL PFOS and PFOA in Osaka, compared to 14 ng/mL PFOS and 4.6 ng/mL PFOA in Miyagi. Carboxylates such as perfluorononanoic acid (PFNA) and perfluoroundecanoic acid (PFUnDA) were also detected in serum at median levels 6.9 ng/mL and 3.2 ng/mL (Osaka), and 2.8 ng/mL and 5.1 ng/mL (Miyagi). Based on one-compartment model under steady state, dietary intake of PFOS and PFOA accounted for only 22.4% and 23.7% of serum levels in Osaka females, and in contrast 92.5% and 110.6% in Miyagi females, respectively.

Differential hepatic effects of perfluorobutyrate mediated by mouse and human PPAR-alpha

Perfluorobutyrate (PFBA) is a short chain perfluoroalkyl carboxylate that is structurally similar to perfluorooctanoate. Administration of PFBA can cause peroxisome proliferation, induction of peroxisomal fatty acid oxidation and hepatomegaly, suggesting that PFBA activates the nuclear receptor, peroxisome proliferator-activated receptor-alpha (PPAR-alpha). In this study, the role of PPAR-alpha in mediating the effects of PFBA was examined using PPAR-alpha null mice and a mouse line expressing the human PPAR-alpha in the absence of mouse PPAR-alpha (PPAR-alpha humanized mice). PFBA caused upregulation of known PPAR-alpha target genes that modulate lipid metabolism in wild-type and PPAR-alpha humanized mice, and this effect was not found in PPAR-alpha null mice. Increased liver weight and hepatocyte hypertrophy were also found in wild-type and humanized PPAR-alpha mice treated with PFBA, but not in PPAR-alpha null mice. Interestingly, hepatocyte focal necrosis with inflammatory cell infiltrate was only found in wild-type mice administered PFBA; this effect was markedly diminished in both PPAR-alpha null and PPAR-alpha humanized mice. Results from these studies demonstrate that PFBA can modulate gene expression and cause mild hepatomegaly and hepatocyte hypertrophy through a mechanism that requires PPAR-alpha and that these effects do not exhibit a species difference. In contrast, the PPAR-alpha-dependent increase in PFBA-induced hepatocyte focal necrosis with inflammatory cell infiltrate was mediated by the mouse PPAR-alpha but not the human PPAR-alpha. Collectively, these findings demonstrate that PFBA can activate both the mouse and human PPAR-alpha, but there is a species difference in the hepatotoxic response to this chemical.