Neonatal exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) causes neurobehavioural defects in adult mice

Spatial trends of perfluorochemicals in harbor seals (Phoca vitulina) from Danish waters

Spatial trends of concentrations of perfluorinated chemicals (PFCs) were investigated in harbour seal liver tissue from seven locations in Denmark, ranging from the Wadden Sea in the southern North Sea to the Western Baltic. All samples were collected during the phocine distemper epizootic in 2002 which provided access to a large number of comparable samples over a short time period. PFOS was dominating (mean: 92% of ∑PFC) among the PFCs in the samples, followed by considerably lower concentrations of PFHxS (1.8%), PFDA (1.7%), PFNA (1.6%) PFUnA (1.5%), PFOA (0.9%) and PFOSA (0.5%). The concentrations of all the investigated compounds showed significant differences among the seven locations. PFOS showed the highest concentrations in the Wadden Sea, where high burdens have also been recorded in German seals. Most compounds showed a trend towards higher concentrations at one or both extremes of the geographic range. Two different patterns of relative PFC concentrations were detected; one in the inner Danish waters where PFOSA and PFUnA were more prevalent and another in the Wadden Sea and Limfjord where PFOA, PFHxS and PFNA were found in greater proportions. These patterns probably represent Baltic and North Sea contamination sources.

Exposure to environmental and lifestyle factors and attention-deficit / hyperactivity disorder in children — A review of epidemiological studies

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders in children. Although the mechanisms that lead to the development of ADHD remain unclear, genetic and environmental factors have been implicated. These include heavy metals and chemical exposures, nutritional and lifestyle/psychosocial factors. The aim of this review was to investigate the association between ADHD or ADHD-related symptoms and widespread environmental factors such as phthalates, bisphenol A (BPA), tobacco smoke, polycyclic aromatic hydrocarbons (PAHs), polyfluoroalkyl chemicals (PFCs) and alcohol. Medline, PubMed and Ebsco search was performed to identify the studies which analyze the association of prenatal and postnatal child exposure to environmental toxicants and lifestyle factors and ADHD or ADHD-related symptoms. The review is restricted to human studies published since 2000 in English in peer reviewed journals. Despite much research has been done on the association between environmental risk factors and ADHD or ADHD symptoms, results are not consistent. Most studies in this field, focused on exposure to tobacco smoke, found an association between that exposure and ADHD and ADHD symptoms. On the other hand, the impact of phthalates, BPA, PFCs, PAHs and alcohol is less frequently investigated and does not allow a firm conclusion regarding the association with the outcomes of interest.

Endocrine disrupting properties of perfluorooctanoic acid

Perfluoroalkyl acids (PFAAs) have attracted attention in recent years for their environmental ubiquity, as well as their toxicity. Several PFAAs are found in human tissues globally, as humans are exposed on a daily basis through intake of contaminated food, water, and air, irrespective of proximity to industry. Perfluorooctanoic acid (PFOA) is a PFAA shown to be developmentally toxic in mice, with broad and varied health consequences that may include long-lasting effects in reproductive tissues and metabolic reprogramming. To date, the only demonstrated mode of action by which the health effects of PFOA are mediated is via the activation of the peroxisome proliferator-activated receptor alpha (PPARα). The endogenous roles for this receptor, as well as the adverse outcomes of activation by exogenous agents during development, are currently under investigation. Recent studies suggest that PFOA may alter steroid hormone production or act indirectly, via ovarian effects, as a novel means of endocrine disruption. Here we review the existing literature on the known health effects of PFOA in animal models, focusing on sensitive developmental periods. To complement this, we also present epidemiologic health data, with the caveat that these studies largely address only associations between adult exposures and outcomes, rarely focusing on endocrine-specific endpoints, susceptible subpopulations, or windows of sensitivity. Further research in these areas is needed.

Update on environmental risk factors for attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent neurobehavioral disorder affecting 5% to 10% of children. Although considered to be a highly familial disorder, ADHD heritability estimates of 60% to 80% highlight the considerable role that environmental factors may still play in disorder susceptibility. Proposed ADHD environmental risk factors include prenatal substance exposures, heavy metal and chemical exposures, nutritional factors, and lifestyle/psychosocial factors. This paper reviews the literature published in 2010 investigating the association between environmental risk factors and ADHD or related symptomatology. Sources of risk factor exposure and the proposed mechanism by which each exposure is linked to ADHD-related neurobehavioral changes are also reported. Methodologic limitations of the current literature are discussed, and guidelines for future study are proposed. An improved understanding of the role that environmental factors play in ADHD etiology is critical to future ADHD prevention efforts.

Perfluorochemical (PFC) exposure in children: associations with impaired response inhibition

BACKGROUND

Perfluorinated chemicals (PFCs) have been used widely in consumer products since the 1950s and are currently found at detectable levels in the blood of humans and animals across the globe. In stark contrast to this widespread exposure to PFCs, there is relatively little research on potential adverse health effects of exposure to these chemicals.

OBJECTIVES

We performed this cross-sectional study to determine if specific blood PFC levels are associated with impaired response inhibition in children.

METHODS

Blood levels of 11 PFCs were measured in children (N = 83) and 6 PFCs: perfluorooctane sulfonate (PFOS), perfluorohexane sulfate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctanesulfonamide (PFOSA), and perfluorodecanoic acid (PFDA) - were found at detectable levels in most children (87.5% or greater had detectable levels). These levels were analyzed in relation to the differential reinforcement of low rates of responding (DRL) task. This task rewards delays between responses (i.e., longer inter-response times; IRTs) and therefore constitutes a measure of response inhibition.

RESULTS

Higher levels of blood PFOS, PFNA, PFDA, PFHxS, and PFOSA were associated with significantly shorter IRTs during the DRL task. The magnitude of these associations was such that IRTs during the task decreased by 29-34% for every 1 SD increase in the corresponding blood PFC.

CONCLUSIONS

This study suggests an association between PFC exposure and children's impulsivity. Although intriguing, there is a need for further investigation and replication with a larger sample of children.

Sensitive bioassay for detection of PPARα potentially hazardous ligands with gold nanoparticle probe

There are so many kinds of peroxisome proliferator-activated receptor α (PPARα) ligands with hazardous effect for human health in the environment, such as certain herbicides, plasticizers and drugs. Among these agonists, perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and mono-(2-ethylhexyl) phthalate (MEHP) are mostly investigated due to their persistence and accumulation in environment and their potential toxicity via PPARα. This investigation aims at developing a bioassay method to detect PPARα ligands based on the ligand-receptor interaction on microplate. PPARα, which formed heterodimers with retinoid X receptor-α (RXRα), were activated by PPARα ligands to form ligands-PPARα-RXRα complexes. Then the complexes were transferred into a microplate and captured via monoclonal anti-PPARα antibody. The PPARα responsive elements (PPRE) modified-gold nanoparticle probes were captured by the ligand-PPARα-RXRα complexes immobilized on the microplate, and then could be quantified through measuring the optical density after silver enhancement. The results showed that PFOS was quantified with a linear range from 100 pM to 1 μM and the detection limit was 10 pM. In addition to PFOS, PFOA and MEHP were also quantified within a proper range through the proposed bioassay. This bioassay was compared with that of liquid chromatography tandem-mass spectrometry (LC-MS) for water spiked samples with a significant correlation (r = 0.9893). This study provides a high-throughput detection method for PPARα ligands in microplate with high sensitivity and wide linear range. It may serve as an assistant of LC-MS for prescreening of PPARα ligands like PFOS.

Indoor environment and children's health: recent developments in chemical, biological, physical and social aspects

Much research is being carried out into indoor exposure to harmful agents. This review focused on the impact on children's health, taking a broad approach to the indoor environment and including chemical, microbial, physical and social aspects. Papers published from 2006 onwards were reviewed, with regards to scientific context. Most of publications dealt with chemical exposure. Apart from the ongoing issue of combustion by-products, most of these papers concerned semi volatile organic compounds (such as phthalates). These may be associated with neurotoxic, reprotoxic or respiratory effects and may, therefore, be of particular interest so far as children are concerned. In a lesser extent, volatile organic compounds (such as aldehydes) that have mainly respiratory effects are still studied. Assessing exposure to metals is still of concern, with increasing interest in bioaccessibility. Most of the papers on microbial exposure focused on respiratory tract infections, especially asthma linked to allergens and bio-aerosols. Physical exposure includes noise and electromagnetic fields, and articles dealt with the auditory and non auditory effects of noise. Articles on radiofrequency electromagnetic fields mainly concerned questions about non-thermal effects and papers on extremely low-frequency magnetic fields focused on the characterization of exposure. The impact of the indoor environment on children's health cannot be assessed merely by considering the effect of these different types of exposure: this review highlights new findings and also discusses the interactions between agents in indoor environments and also with social aspects.

Effects of perfluorinated compounds on development of zebrafish embryos

Perfluorinated compounds (PFCs) have been widely used in industrial and consumer products and frequently detected in many environmental media. Potential reproductive effects of perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) have been reported in mice, rats and water birds. PFOS and PFOA were also confirmed developing toxicants towards zebrafish embryos; however, the reported effect concentrations were contradictory. Polyfluorinated alkylated phosphate ester surfactants (including FC807) are precursor of PFOS and PFOA; however, there is no published information about the effects of FC807 and PFNA on zebrafish embryos. Therefore, this study was conducted to determine the effects of these four PFCs on zebrafish embryos. Normal fertilized zebrafish embryos were selected to be exposed to several concentrations of PFOA, PFNA, PFOS or FC807 in 24-well cell culture plates. A digital camera was used to image morphological anomalies of embryos with a stereomicroscope. Embryos were observed through matching up to 96-h post-fertilization (hpf) and rates of survival and abnormalities recorded. PFCs caused lethality in a concentration-dependent manner with potential toxicity in the order of PFOS > FC807 > PFNA > PFOA based on 72-h LC(50). Forty-eight-hour post-fertilization pericardial edema and 72- or 96-hpf spine crooked malformation were all observed. PFOA, PFNA, PFOS and FC807 all caused structural abnormalities using early stages of development of zebrafish. The PFCs all retarded the development of zebrafish embryos. The toxicity of the PFCs was related to the length of the PFC chain and functional groups.

Differences in neonatal neurotoxicity of brominated flame retardants, PBDE 99 and TBBPA, in mice

Flame retardants such as polybrominated diphenyl ethers (PBDE) and tetrabromobisphenol A are used as flame retardants and detected in the environmental, wildlife species and human tissues. Exposure to PBDEs during the neonatal development of the brain has been shown to affect behavior and learning and memory in adult mice, while neonatal exposure to TBBPA (another brominated flame retardant) did not affect behavioral variables in the adult. In this study, we hypothesized that the effects of these compounds could be reflected by changes in biochemical substrates and cholinergic receptors and have examined the levels of four proteins involved in maturation of the brain, neuronal growth and synaptogenesis and the densities of both muscarinic and nicotinic cholinergic receptors. We measured the levels of radioactivity in the brain after administration of (14)C-labelled TBBPA at different time points and saw that levels of TBBA peaked earlier and decreased faster than the earlier reported levels of PBDE 99. The protein analysis in the neonatal brain showed changes in the levels of calcium/calmodulin-dependent protein kinase II (CaMKII), growth associated protein-43 (GAP-43) and synaptophysin following neonatal exposure to PBDE 99 (21 μmol/kg body weight), but not following exposure TBBPA. Furthermore, neonatal exposure to PBDE 99 and TBBPA caused a decrease in binding sites of the nicotinic ligand cytisine in frontal cortex. These results confirm earlier reported data that PBDE 99 can act as a developmental neurotoxicant, possibly due to its different uptake and retention in the brain compared to TBBPA. In addition, the changes in protein levels are interesting leads in the search for mechanisms behind the developmental neonatal neurotoxicity of PBDEs in general and PBDE 99 in particular, since also other compounds inducing similar adult behavioral disturbances as PBDE 99, affect these proteins during the period of rapid brain development.

Temporal and life history related trends of perfluorochemicals in harbor porpoises from the Danish North Sea

Eighty-five stranded or bycaught harbor porpoises collected from the Danish North Sea between 1980 and 2005 were analyzed for perfluorochemicals in the liver. PFOS was the predominant compound, making up on average 88.9% of the ∑PFC, followed by PFOSA (7.8%). PFUnA (1.9%) and PFDA (1.2%) were detected in most samples. PFHxS, PFNA and PFOA were only found in a minority of the samples. We found substantial differences in PFC concentrations among life history stages, the highest concentrations were found in neonates, suckling juveniles and lactating females. Such differences should be considered when PFC levels in wildlife are evaluated. The high concentrations found in young porpoises are of concern as PFCs have known toxic effects on the development of the central nervous system and reproductive organs. Despite efforts to reduce PFC emissions, a decreasing temporal trend of concentrations was not detected for any compound. PFCA concentrations were found to be increasing.

Abnormal development of motor neurons in perfluorooctane sulphonate exposed zebrafish embryos

Perfluorooctane sulfonate (PFOS) is an environmental organic pollutant, the potential neurotoxicity of which is causing great concern in fish. In the present study, we examined the effects of PFOS on motor neurons, and investigated the potential toxicological mechanisms oxidative stress in zebrafish embryos. Six-hour post-fertilization (hpf) zebrafish embryos were exposed to 1.0 mg/L PFOS, then we examined the expression of alpha-tubulin, proliferating cell nuclear antigen (PCNA), cyclin-dependent kinase 5 (CDK5), and peroxiredoxin 2 (PRX2) after PFOS exposure until 120 hpf. The results showed that PFOS increased alpha-tubulin in the coccygeal spinal cord (CSC) at 96 hpf, whereas decreased alpha-tubulin in the brain and spinal cord at 120 hpf. PCNA expression was highly increased in CSC and abdomen compared with control at 96 and 120 hpf after PFOS exposure. In addition, PFOS exposure caused CDK5 expression to be highly increased in brain region following by down-regulation of PRX2 expression at 96 hpf. These results indicated that, at least in part, the effect on motor neurons induced by PFOS was mediated by dynamically interfering with the expression of alpha-tubulin and PCNA. Furthermore, PFOS-induced toxicity was associated with oxidative stress by deregulating CDK5 and PRX2.

Possible mechanism of perfluorooctane sulfonate and perfluorooctanoate on the release of calcium ion from calcium stores in primary cultures of rat hippocampal neurons

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are anthropogenic compounds manufactured since the 1950s and are distributed worldwide. Now, the pollutants are being challenged by entering into the brain and the toxic effect on the central nervous system due to calcium disorder, mainly through channels on cell membrane. However, little is known about the role of calcium store in PFOS- and PFOA-evoked abnormal calcium increase. In the present study, PFOA and PFOS were measured in primary cultures of rat hippocampal neurons by LC/MS/MS analysis. Flow cytometry was used to examine altered calcium patterns in neurons labeled with fluo-3/AM and to disclose the mechanism by which PFOS and PFOA induced calcium increase in cultured neurons. The results indicate that both PFOS and PFOA can accumulate in cultured neurons and elevate calcium concentrations via release of intracellular calcium stores. Furthermore, inositol 1,4,5-trisphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) were found to take part in PFOS or PFOA inducing calcium release from calcium stores. IP(3)Rs seem to serve a predominant role in PFOS-induced calcium release. Calcium release from intracellular stores may partially account for the perturbation of calcium homeostasis caused by PFOS or PFOA.

Prenatal exposure to perfluorooctanesulfonate in rat resulted in long-lasting changes of expression of synapsins and synaptophysin

Both animal and human studies have demonstrated that exposure to chemical pollutants during critical developmental period causes adverse consequences later in life. In uterus, perfluorooctanesulfonate (PFOS) exposure has been known to cause developmental neurotoxicity, such as increased motor activity, reduced habitation and impaired cognitive function. The possible mechanism of the impaired cognitive function induced by prenatal PFOS exposure was evaluated in this study. Pregnant Sprague Dawley (SD) rats were given 0.1, 0.6, and 2.0 mg kg(-1) birth weight (bw) d(-1) by gavage from gestation day (GD) 0 to GD20. Control received 0.5% Tween-20 vehicle (4 ml kg(-1) bw d(-1)). PFOS concentration in hippocampus of offspring was observed on postnatal day (PND) 0 and PND21. The ultrastructure of hippocampus and the gene expression of synaptic vesicle associated proteins in offspring hippocampus, which were important for the neurotransmitter release, were investigated. The transmission electron photomicrographs of the offspring hippocampus from PFOS-treated maternal groups showed the ultrastructure of synapses was negatively affected. The offspring from PFOS-treated maternal groups also differed significantly from controls with respect to the expression of synaptic vesicle associated proteins. The mRNA levels of synapsin1 (Syn1), synapsin2 (Syn2), and synaptophysin (Syp) were decreased in treated groups either on PND0 or on PND21. However, the mRNA level of synapsin3 (Syn3) decreased in 0.6- and 2.0-mg kg(-1) group on PND0, and showed no significant difference among control group and all treated groups on PND21. These results indicate that the impairment of cognitive function induced by PFOS may be attributed to the lower mRNA levels of synaptic vesicle associated proteins and the change of synaptic ultrastructure in hippocampus.

Prenatal perfluorooctanoic acid exposure in CD-1 mice: low-dose developmental effects and internal dosimetry

Perfluorooctanoic acid (PFOA) is an environmental contaminant that causes adverse developmental effects in laboratory animals. To investigate the low-dose effects of PFOA on offspring, timed-pregnant CD-1 mice were gavage dosed with PFOA for all or half of gestation. In the full-gestation study, mice were administered 0, 0.3, 1.0, and 3.0 mg PFOA/kg body weight (BW)/day from gestation days (GD) 1-17. In the late-gestation study, mice were administered 0, 0.01, 0.1, and 1.0 mg PFOA/kg BW/day from GD 10-17. Exposure to PFOA significantly (p < 0.05) increased offspring relative liver weights in all treatment groups in the full-gestation study and in the 1.0 mg PFOA/kg group in the late-gestation study. In both studies, the offspring of all PFOA-treated dams exhibited significantly stunted mammary epithelial growth as assessed by developmental scoring. At postnatal day 21, mammary glands from the 1.0 mg/kg GD 10-17 group had significantly less longitudinal epithelial growth and fewer terminal end buds compared with controls (p < 0.05). Evaluation of internal dosimetry in offspring revealed that PFOA concentrations remained elevated in liver and serum for up to 6 weeks and that brain concentrations were low and undetectable after 4 weeks. These data indicate that PFOA-induced effects on mammary tissue (1) occur at lower doses than effects on liver weight in CD-1 mice, an observation that may be strain specific, and (2) persist until 12 weeks of age following full-gestational exposure. Due to the low-dose sensitivity of mammary glands to PFOA in CD-1 mice, a no observable adverse effect level for mammary developmental delays was not identified in these studies.

Prenatal exposure to perfluorinated chemicals and behavioral or coordination problems at age 7 years

OBJECTIVE

Potential neurotoxic effects of perfluorinated compounds (PFCs) have been reported in highly exposed animals, but whether these chemicals are neurotoxic in humans is not known. We therefore investigated whether prenatal exposure to perfluorooctanoic acid (PFOA) or perfluorooctane sulfate (PFOS), two of the most prevalent PFCs, are associated with behavioral or coordination problems in early childhood.

METHODS

We used data from the Danish National Birth Cohort, which enrolled mothers in early pregnancy, and we measured maternal blood levels of PFOA and PFOS using specimens drawn around 8 weeks of gestation. When the children reached 7 years of age, mothers completed the Strengths and Difficulties Questionnaire (SDQ, n=787) and the Developmental Coordination Disorder Questionnaire (DCDQ, n=526) to assess behavioral health and motor coordination of their children. SDQ scores above the 90th percentile were a priori defined to identify behavioral problems and DCDQ scores below the 10th percentile were defined as a potential DCD.

RESULTS

The median concentrations of PFOS and PFOA in maternal blood were 34.4 ng/mL [interquartile range (IQR), 26.6-44.5] and 5.4 ng/mL (IQR, 4.0-7.1), respectively, similar to distributions reported for populations without occupational exposure. We found no association between higher SDQ scores and maternal levels of PFOS or PFOA, nor did we see any statistically significant association with motor coordination disorders.

CONCLUSION

The findings suggest that background levels of PFOA and PFOS are not associated with behavioral and motor coordination problems in childhood. However, effects on other developmental end points, including cognitive, attentional, and clinical mental disorders not measured in this study, cannot be ruled out.

Interaction of PFOS and BDE-47 co-exposure on thyroid hormone levels and TH-related gene and protein expression in developing rat brains

Perfluorooctane sulfonate (PFOS) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) are two persistent environmental contaminants that are toxic to developing nervous systems, particularly via their disruption of thyroid hormone (TH) function. To investigate whether an interaction existed between PFOS and BDE-47 on TH-mediated pathways, adult female Wistar rats were exposed to 3.2 and 32 mg/kg of PFOS or BDE-47 in their diet and co-exposed to a combination of each chemical (3.2 mg/kg) from gestational day 1 to postnatal day (PND) 14. Serum and brain tissues from both male and female neonates were collected on PNDs 1, 7, and 14 to examine TH-regulated gene and protein expression. The results revealed that (1) a significant accumulation difference occurred between the two chemicals; (2) On a equimolar basis, BDE-47 and PFOS affected serum total triiodothyronine and total thyroxine differently in adults and offspring; (3) there were region-specific and exposure- and time-dependent alterations in TH concentrations and tested gene and protein expression levels; and (4) interaction for the combined chemicals was only observed for brain-derived neurotrophic factor (BDNF), which exhibited a synergistic effect on PND 1 in the cortex and an antagonistic effect on PND 14 in the hippocampus. Our results suggest a complex TH-mediated gene and protein response to BDE-47 and/or PFOS exposure that seems little related to TH homeostasis and that little combined interaction of co-exposures was observed except on BDNF. The underlying mechanisms remain uncertain but seem to involve more actions than just TH-regulated pathway.

Effects of perfluoroalkyl compounds on mRNA expression levels of thyroid hormone-responsive genes in primary cultures of avian neuronal cells

There is growing interest in assessing the neurotoxic and endocrine disrupting potential of perfluoroalkyl compounds (PFCs). Several studies have reported in vitro and in vivo effects related to neuronal development, neural cell differentiation, prenatal and postnatal development and behavior. PFC exposure altered hormone levels and the expression of hormone-responsive genes in mammalian and aquatic species. This study is the first to assess the effects of PFCs on messenger RNA (mRNA) expression in primary cultures of neuronal cells in two avian species: the domestic chicken (Gallus domesticus) and herring gull (Larus argentatus). The following thyroid hormone (TH)–responsive genes were examined using real-time reverse transcription-PCR: type II iodothyronine 5′-deiodinase (D2), D3, transthyretin (TTR), neurogranin (RC3), octamer motif–binding factor (Oct-1), and myelin basic protein. Several PFCs altered the mRNA expression levels of genes associated with the TH pathway in avian neuronal cells. Short-chained PFCs (less than eight carbons) altered the expression of TH-responsive genes (D2, D3, TTR, and RC3) in chicken embryonic neuronal cells to a greater extent than long-chained PFCs (more than or equal to eight carbons). Variable transcriptional changes were observed in herring gull embryonic neuronal cells exposed to short-chained PFCs; mRNA levels of Oct-1 and RC3 were upregulated. This is the first study to report that PFC exposure alters mRNA expression in primary cultures of avian neuronal cells and may provide insight into the possible mechanisms of action of PFCs in the avian brain.

Distribution of perfluorochemicals between sera and milk from the same mothers and implications for prenatal and postnatal exposures

The levels of six perfluorocarboxylates (PFCAs), four perfloroalkylsulfonates (PFASs), and one sulfonamide were measured in paired samples of maternal serum, umbilical cord serum, and breast milk. The maternal and cord sera were strongly correlated with each other for all measured compounds (r>0.5 and p<0.01). Nevertheless, there was a significant difference in compound composition profile between the two sera matrices, with a more depletion of the longer chain compounds in cord serum. The transfer efficiency values from maternal to cord serum (TFCS/MS) decreased by 70% with each increasing unit of -CF2 chain within a PFCA group, and for perfluorooctanesulfonate (PFOS), by a half compared to perfluorooctanoate (PFOA). In contrast to the strong correlation in concentrations between the two sera matrices, the pattern of compounds in breast milk differed considerably with those in sera. Accordingly, compound- and matrix-specific transfer must be considered when assessing prenatal and postnatal exposure.

Exposure to polyfluoroalkyl chemicals and attention deficit/hyperactivity disorder in U.S. children 12-15 years of age

BACKGROUND

Polyfluoroalkyl chemicals (PFCs) have been widely used in consumer products. Exposures in the United States and in world populations are widespread. PFC exposures have been linked to various health impacts, and data in animals suggest that PFCs may be potential developmental neurotoxicants.

OBJECTIVES

We evaluated the associations between exposures to four PFCs and parental report of diagnosis of attention deficit/hyperactivity disorder (ADHD).

METHODS

Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 1999-2000 and 2003-2004 for children 12-15 years of age. Parental report of a previous diagnosis by a doctor or health care professional of ADHD in the child was the primary outcome measure. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS) levels were measured in serum samples from each child.

RESULTS

Parents reported that 48 of 571 children included in the analysis had been diagnosed with ADHD. The adjusted odds ratio (OR) for parentally reported ADHD in association with a 1-μg/L increase in serum PFOS (modeled as a continuous predictor) was 1.03 [95% confidence interval (CI), 1.01-1.05]. Adjusted ORs for 1-μg/L increases in PFOA and PFHxS were also statistically significant (PFOA: OR = 1.12; 95% CI, 1.01-1.23; PFHxS: OR = 1.06; 95% CI, 1.02-1.11), and we observed a nonsignificant positive association with PFNA (OR = 1.32; 95% CI, 0.86-2.02).

CONCLUSIONS

Our results, using cross-sectional data, are consistent with increased odds of ADHD in children with higher serum PFC levels. Given the extremely prevalent exposure to PFCs, follow-up of these data with cohort studies is needed.

Health ranking of ingested semi-volatile organic compounds in house dust: an application to France

People spend most of their time indoors. Dust settled in the home may be contaminated by semi-volatile organic compounds (SVOCs). Exposure to these compounds is of great concern, in particular for infants. Their number is large so arose the question of which ones should be selected for dust ingestion exposure assessment. This work proposes a health ranking of SVOCs ingested through settled dust. This ranking is based on the toxicity and contamination of SVOCs in dust. Data on compounds and contamination was retrieved from a bibliographic review. Where possible, toxicity data was retrieved from databases, otherwise it was calculated from raw data. One hundred and fifty-six SVOCs were selected, 66 of which were prioritized. Forty-two could not be prioritized because contamination data was below the limit of detection, and 48 could not be prioritized because there was no contamination or toxicity data. The top-ranked compounds were phthalates, pesticides, short-chain chlorinated paraffins, PBDEs, PFCs, organotins, PCBs, and PAHs. As most of these have reprotoxic and neurotoxic properties, an integrated multi-pollutants approach to exposure is required and simultaneous measurement methods should be developed.

PRACTICAL IMPLICATIONS

The large number of compounds identified in settled dust in recent years should be considered for the assessment of exposure to dust ingestion. This work provides a health ranking of SVOCs ingested through settled dust. Most of the top-ranked compounds have reprotoxic and neurotoxic properties, and particular attention should, therefore, be paid to them in future studies.

Perfluorooctane Sulfonate Induces Apoptosis in N9 Microglial Cell Line

Perfluorooctane sulfonate (PFOS) is an environmental persistent acid found at low levels in human, wildlife, and environmental media samples. To study the apoptosis effects of PFOS on microglia, murine N9 cell line was used as a model in current research. The results showed that PFOS could reduce the cell viability significantly, and the cellular apoptosis induced by PFOS was closely accompanied with dissipation of mitochondria membrane potential, upregulation messenger RNAs (mRNAs) of p53, Bax, caspase 9, and caspase 3, and decreased expression of Bcl-2 mRNA. These results suggested that PFOS could disturb homeostasis of N9 cells, impact mitochondria, and affect gene expression of apoptotic regulators, all of which resulted in a start-up of apoptosis.

MicroRNA expression changes during zebrafish development induced by perfluorooctane sulfonate

Perfluorooctane sulfonate (PFOS), a kind of widely distributed environmentally organic compound, has been found to cause developmental toxicity. Although microRNAs (miRNAs) play an important role in many metabolic tasks, whether and how they are involved in the process of PFOS-induced toxicity is largely unknown. To address this problem, PFOS-induced changes in miRNAs and target gene expression in zebrafish embryos, and the potential mechanism of PFOS-induced toxic action were studied in this research. Zebrafish embryos were exposed to 1 µg ml(-1) PFOS or DMSO control from 6 h post-fertilization (hpf) to 24 or 120 hpf. Subsequently, RNA was isolated from the embryo pool and the expression profiles of 219 known zebrafish miRNAs were analyzed using microarray. Finally, quantitative real-time polymerase chain reaction was used to validate several miRNAs expression of microarray data. The analysis revealed that PFOS exposure induced significant changes in miRNA expression profiles. A total of 39 and 81 miRNAs showed significantly altered expression patterns after PFOS exposure 24 and 120 hpf. Of the changed miRNAs, 20 were significantly up-regulated and 19 were significantly down-regulated (p < 0.01) at 24 hpf, whereas 41 were significantly up-regulated and 40 were significantly down-regulated (p < 0.01) at 120 hpf. These miRNAs were involved in development, apoptosis and cell signal pathway, cell cycle progression and proliferation, oncogenesis, adipose metabolism and hormone secretion, whereas there is still little functional information available for 32 miRNAs. Our results demonstrate that PFOS exposure alters the expression of a suite of miRNAs and may induce developmental toxicity.

Transcriptional effects of prenatal and neonatal exposure to PFOS in developing rat brain

Perfluorooctane sulfonate (PFOS), a persistent and bioaccumulative compound, is widely distributed in the environment. To explore the molecular mechanism of neonatal neurotoxic effects, we evaluated the transcriptional effects of prenatal and neonatal exposure to PFOS in developing rat brain by performing gene expression profiling in the cerebral cortex. Dams received 3.2 mg/kg PFOS in their feed from gestational day 1 (GD1) to weaning (PND 21). Pups then had free access to treated feed until PND 35. Six Illumina RatRef-12 Expression BeadChips were used to identify gene expression changes on postnatal days (PNDs) 1, 7, and 35. Significantly affected genes (P < 0.05) were involved in neuroactive ligand-receptor interaction, calcium signaling pathways, cell communication, long-term potentiation/depression, the cell cycle, and peroxisome proliferator-activated receptor (PPAR) signaling. To compare prenatal and lactational exposure contributions to transcriptional effects, a subset of altered genes obtained from the gene-profile study that represented neurobiological functions was analyzed using RT-PCR in a follow-up cross-foster study lasting from PND1 to 21. Prenatal and postnatal exposure to PFOS caused potential neurotoxicity as demonstrated by developmentally different global transcriptional changes. Prenatal exposure was more effective in altering expression of several genes. Also, transcriptional effects of PFOS exposure on neurodevelopment occurred primarily by disrupting the neuroendocrine system.

Oxidative stress from diverse developmental neurotoxicants: antioxidants protect against lipid peroxidation without preventing cell loss

Oxidative stress has been hypothesized to provide a mechanism by which apparently unrelated chemicals can nevertheless produce similar developmental neurotoxic outcomes. We used differentiating PC12 cells to compare the effects of agents from four different classes and then to evaluate antioxidant amelioration: fipronil, perfluorooctanesulfonamide (PFOSA), dieldrin and chlorpyrifos. The rank order for lipid peroxidation corresponded to the ability to evoke cell loss: fipronil>PFOSA>dieldrin>chlorpyrifos. The same sequence was found for an index of cell enlargement (protein/DNA ratio) but the effects on neurite outgrowth (membrane/total protein) diverged, with fipronil producing a decrease and PFOSA an increase. Cotreatment with antioxidants reduced (ascorbate) or eliminated (Vitamin E) lipid peroxidation caused by each of the agents but failed to protect against cell loss, with the sole exception of chlorpyrifos, for which we earlier showed partial protection by Vitamin E; addition of higher NGF concentrations protected neither against oxidative stress nor cell loss. Despite the failure to prevent cell loss, ascorbate protected the cells from the effects of PFOSA on neuritic outgrowth; NGF, and to a lesser extent, ascorbate, offset the effects of fipronil on both cell enlargement and neuritogenesis. At the same time, the ameliorant treatments also worsened some of the other toxicant effects. Our results point out the problems in concluding that, just because a neurotoxicant produces oxidative stress, antioxidant therapy will be effective in preventing damage. Instead, additional mechanisms for each agent may provide alternative routes to neurotoxicity, or may be additive or synergistic with oxidative stress.

Neurobehavioral teratogenicity of perfluorinated alkyls in an avian model

Perfluorinated alkyls are widely-used agents that accumulate in ecosystems and organisms because of their slow rate of degradation. There is increasing concern that these agents may be developmental neurotoxicants and the present study was designed to develop an avian model for the neurobehavioral teratogenicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Fertilized chicken eggs were injected with 5 or 10mg/kg of either compound on incubation day 0. On the day of hatching, imprinting behavior was impaired by both compounds. We then explored underlying mechanisms involving the targeting of protein kinase C (PKC) isoforms (alpha, beta, gamma) in the intermedial part of the hyperstriatum ventrale, the region most closely associated with imprinting. With PFOA exposure, cytosolic PKC concentrations were significantly elevated for all three isoforms; despite the overall increase in PKC expression, membrane-associated PKC was unaffected, indicating a defect in PKC translocation. In contrast, PFOS exposure evoked a significant decrease in cytosolic PKC, primarily for the beta and gamma isoforms, but again without a corresponding change in membrane-associated enzyme; this likely partial, compensatory increases in translocation to offset the net PKC deficiency. Our studies indicate that perfluorinated alkyls are indeed developmental neurotoxicants that affect posthatch cognitive performance but that the underlying synaptic mechanisms may differ substantially among the various members of this class of compounds, setting the stage for disparate outcomes later in life.

Congenital anomalies, labor/delivery complications, maternal risk factors and their relationship with perfluorooctanoic acid (PFOA)-contaminated public drinking water

BACKGROUND

We have previously examined the associations between perfluorooctanoic acid (PFOA) exposure, birth weight and gestational age in individuals exposed to PFOA-contaminated residential drinking water from the Little Hocking Water Association (LHWA). In this investigation, we expand the scope of our analysis to examine the associations between PFOA, congenital anomalies, labor and delivery complications and maternal risk factors.

OBJECTIVES

To compare the likelihood of congenital anomalies, labor and delivery complications and maternal risk factors in neonates and their mothers residing in zip codes with public water service provided completely, partially or not at all by the LHWA.

METHODS

Logistic regression analyses were performed on singleton neonatal birth outcome data supplied by the Ohio Department of Health to examine the associations between LHWA water service category and the outcomes of interest. When possible, models were adjusted for maternal age, preterm birth, neonatal sex, race, maternal education, alcohol use, tobacco use and diabetic status.

RESULTS

Increased PFOA exposure, as assessed by water service category, was not associated with an overall increase in the likelihood of congenital anomalies or any specific diagnosis (adjusted OR: 1.4, 95% CI: 0.34-3.3). The overall likelihood of labor and delivery complications was significantly lower among mothers with water service provided by the LHWA, as compared to mothers not serviced by the LHWA (adjusted OR: 0.65, 95% CI: 0.46-0.92). A significant increase in the likelihood of anemia (crude OR: 11, 95% CI: 1.8-64) and dysfunctional labor (crude OR: 5.3, 95% CI: 1.2-24) was noted for mothers residing within zip codes serviced by the LHWA, but the number of reported cases was very small.

CONCLUSION

At the levels measured in the LHWA, we conclude that PFOA is not associated with increased risk of congenital anomalies, most labor and delivery complications and maternal risk factors. Additional research is required to assess the observed associations between PFOA, anemia and dysfunctional labor.

Financial disclosure and toxic products: encouraging wall street to anticipate product risk and exercise precaution

Amidst discussion by policymakers about how regulators' failure to ensure disclosure of risks contributed to the current financial crisis, we assess how emerging product toxicity risks are addressed in companies' financial reports. Will corporations blindside investors with "the next asbestos?" Existing disclosures are found lacking in the specificity needed to forewarn of liabilities and reputational damage from the use of potentially harmful materials-from nanotechnologies, to asthmagens, to perfluorinated compounds. Improved standards could protect investors while also enhancing corporate incentives to use safer materials. Reforms by the Securities and Exchange Commission and the Financial Accounting Standards Board are recommended.

Binding of PFOS to serum albumin and DNA: insight into the molecular toxicity of perfluorochemicals

Background

Health risk from exposure of perfluorochemicals (PFCs) to wildlife and human has been a subject of great interest for understanding their molecular mechanism of toxicity. Although much work has been done, the toxigenicity of PFCs remains largely unknown. In this work, the non-covalent interactions between perfluorooctane sulfonate (PFOS) and serum albumin (SA) and DNA were investigated under normal physiological conditions, aiming to elucidate the toxigenicity of PFCs.

Results

In equilibrium dialysis assay, the bindings of PFOS to SA correspond to the Langmuir isothermal model with two-step sequence model. The saturation binding number of PFOS was 45 per molecule of SA and 1 per three base-pairs of DNA, respectively. ITC results showed that all the interactions were spontaneous driven by entropy change. Static quenching of the fluorescence of SA was observed when interacting with PFOS, indicating PFOS bound Trp residue of SA. CD spectra of SA and DNA changed obviously in the presence of PFOS. At normal physiological conditions, 1.2 mmol/l PFOS reduces the binding ratio of Vitamin B₂ to SA by more than 30%.

Conclusion

The ion bond, van der Waals force and hydrophobic interaction contributed to PFOS binding to peptide chain of SA and to the groove bases of DNA duplex. The non-covalent interactions of PFOS with SA and DNA alter their secondary conformations, with the physiological function of SA to transport Vitamin B₂ being inhibited consequently. This work provides a useful experimental method for further studying the toxigenicity of PFCs.

Neonatal exposure to PFOS and PFOA in mice results in changes in proteins which are important for neuronal growth and synaptogenesis in the developing brain

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) belong to the family of perfluorinated compounds. They are used in industrial and consumer applications, e.g., clothing fabrics, carpets, and food packaging. PFOS and PFOA are present in the environment and are found in dust and human milk, which implies that newborns and toddlers can be directly exposed to these agents during brain development. Recently, we reported that PFOS and PFOA can cause neurobehavioral defects and changes in the cholinergic system, in the adult animal, when given directly to neonatal mice, and thereby showing similarities with other investigated persistent organic pollutants, such as dichloro-diphenyl-trichloroethan, polychlorinated biphenyls, and polybrominated diphenyl ethers (PBDEs). In recent studies, we have also seen that highly brominated PBDEs can affect the levels of proteins that are important for neuronal growth and synaptogenesis in the neonatal mouse brain. The present study shows that a single oral dose of either 21 micromol PFOS or PFOA/kg body weight (11.3 or 8.70 mg), given directly to the neonatal mice on postnatal day 10, significantly increased the levels of CaMKII, GAP-43, and synaptophysin in the hippocampus of the neonatal mouse. Both compounds significantly increased the levels of synaptophysin and tau in cerebral cortex, and PFOA also increased the levels of tau in hippocampus. These proteins are important for normal brain development, and altered levels of these proteins during a critical period of the brain growth spurts could be one of the mechanisms behind earlier reported behavioral defects.

Gestational and lactational exposure to potassium perfluorooctanesulfonate (K+PFOS) in rats: developmental neurotoxicity

Perfluorooctanesulfonate (PFOS), a persistent and bioaccumulative compound, is widely distributed in humans and wildlife. Exposure of the human fetus and neonate to PFOS can occur in utero and via the mother's milk, respectively. Developmental studies have been conducted with PFOS in the past, including some developmental neurotoxicity endpoints. The objective of this study was to evaluate the functional and morphological changes to the nervous system in rats having gestational and lactational exposures to PFOS per current test guidelines (EPA OPPTS 870.6300 and OECD 426). Female SD rats (25/dosage group) were given daily oral doses of either 0.0, 0.1, 0.3, or 1.0mg/kg-d potassium PFOS (K(+)PFOS) from gestation day (GD) 0 through postnatal day (PND) 20. Offspring were observed through PND 72 for growth, maturation, motor activity, learning and memory, acoustic startle reflex, various behavioral manifestations, and brain weight. Specimens were taken from dams, fetuses, and pups for serum and tissue PFOS concentration, thyroid status endpoints, and liver mRNA transcript analysis, and those results are reported in a companion article. No significant effect was noted on maternal health or reproductive outcomes from dosing of maternal rats with K(+)PFOS throughout gestation. Maternal body weights were statistically significantly lower in the 1.0mg/kg-d dosage group from PND 4 through the end of lactation. Offspring from K(+)PFOS-treated maternal groups did not differ significantly from controls with respect to birth weight, growth, age and weight at attainment of sexual maturation, learning and memory, acoustic startle, various behavioral endpoints, and brain weight. Male offspring from the 1.0mg/kg-d maternal treatment group displayed increased motor activity and reduced habituation on PND 17 but not on PND 13, 21, and 61. The maternal no-observed-adverse-effect-level (NOAEL) was 0.3mg/kg-d based on decreased body weights observed in lactation. The maternal dose associated with the NOAEL for male offspring was 0.3mg/kg-d based on increased motor activity and reduced habituation in the 1.0mg/kg-d maternal dose-group male offspring on PND 17. The maternal dose associated with the NOAEL for female offspring was >1.0mg/kg-d. Mean serum concentrations of PFOS reported in a companion article for the 0.3mg/kg-d group maternal rats are several hundred times higher than those reported for females in the United States general population.

The relationship between birth weight, gestational age and perfluorooctanoic acid (PFOA)-contaminated public drinking water

BACKGROUND

Recent studies have examined the associations between perfluorooctanoic acid (PFOA) levels in cord blood and maternal plasma with lowered birth weight and gestational age in humans; however, no study has examined these effects in a population of known high PFOA exposure. Residents drinking PFOA-contaminated water from the Little Hocking Water Association (LHWA) in Washington County, Ohio have serum PFOA levels approximately 80 times those in the general U.S. population.

OBJECTIVES

To compare birth weights and gestational ages of neonates born to mothers residing in zip codes with water service provided completely, partially or not at all by the LHWA.

METHODS

Multiple logistic and linear regression analyses were performed on singleton neonatal birth weight data supplied by the Ohio Department of Health to examine the associations between LHWA water service category (used as a surrogate for PFOA exposure) with mean birth weight, mean gestational age, the likelihood of low birth weight (<2500 g), and the likelihood of preterm birth (<37 completed weeks of gestation). All models were adjusted for maternal age, gestational age, sex, race and population-level socioeconomic status.

RESULTS

The incidence of low birth weight, preterm birth, mean birth weight and mean gestational age of neonates did not significantly differ among water service categories.

CONCLUSION

Markedly elevated PFOA exposure, as categorized by water service category, is not associated with increased risk of lowered birth weight or gestational age. This study does not confirm earlier findings of an association between PFOA and lowered birth weight observed at normal population levels.