Brain region distribution and patterns of bioaccumulative perfluoroalkyl carboxylates and sulfonates in east greenland polar bears (Ursus maritimus)

The pollutant perfluorohexane sulfonate (PFHxS) reduces serum thyroxine but does not alter thyroid action in the postnatal rat brain

Known as "forever chemicals", per- and polyfluoroalkyl substances (PFAS) are synthetic compounds used in consumer goods but pose significant public health concerns, including disruption of the thyroid system. As thyroid hormones (THs) are required for normal brain development, PFAS may also be developmental neurotoxicants. However, this is not well understood. Here we examine the endocrine and neurodevelopmental consequences of perfluorohexane sulfonate (PFHxS) exposure in pregnant, lactating, and developing rats, and compare its effects to an anti-thyroid pharmaceutical (propylthiouracil, PTU) that induces thyroid-mediated developmental neurotoxicity. We show that PFHxS dramatically reduces maternal serum thyroxine (T4), nearly equivalently to PTU (-55 and -51%, respectively). However, only PTU increases thyroid stimulating hormone. The lactational transfer of PFHxS is significant and reduces pup serum T4 across the postnatal period. Surprisingly, brain THs are only minimally decreased by PFHxS, whereas PTU drastically diminishes them. Evaluation of brain TH action by phenotyping, RNA-Sequencing, and quantification of radial glia cell morphology supports that PTU interrupts TH signaling while PFHxS has limited to no effect. These data show that PFHxS induces abnormal serum TH profiles; however, there were no indications of hypothyroidism in the postnatal brain. We suggest the stark differences between the neurodevelopmental effects of PFHxS and a typical antithyroid agent may be due to its interaction with TH distributing proteins like transthyretin.

PFOS Elicits Cytotoxicity in Neuron Through Astrocyte-Derived CaMKII-DLG1 Signaling In Vitro Rat Hippocampal Model

Both epidemiological investigation and animal experiments demonstrated that pre-/postnatal exposure to perfluorooctane sulfonic acid (PFOS) could induce neurodevelopmental disorders. Previous studies showed that astrocyte was involved in PFOS-induced neurotoxicity, while little information is available. In the present study, the role of astrocyte-derived calmodulin-dependent protein kinase II (CaMKII)-phosphorylated discs large homolog 1 (DLG1) signaling in PFOS eliciting cytotoxicity in neuron was explored with primary cultured hippocampal astrocyte and neuron. The application of PFOS showed a decreased cell viability, synapse length and glutamate transporter 1 (GLT-1) expression, but an increased CaMKII, DLG1 and cyclic AMP response element binding protein (CREB) expression in primary cultured astrocyte. With 2-(2-hydroxyethylamino)-6-aminohexylcarbamic acid tert-butyl ester-9-isopropylpurine (CK59), the CaMKII inhibitor, the disturbed cell viability and molecules induced by PFOS could be alleviated (CREB expression was excluded) in astrocytes. The cytotoxic effect of neuron exposed to astrocyte conditional medium collected from PFOS (PFOS-ACM) pretreated with CK59 was also decreased. These results indicated that PFOS mediated GLT-1 expression through astrocyte-derived CaMKII-DLG signaling, which might be associated with injuries on neurons. The present study gave an insight in further exploration of mechanism in PFOS-induced neurotoxicity.

Tissue-specific distributions of organic ultraviolet absorbents in free-range chickens and domestic pigeons from Guangzhou, China

The ecological risks of organic ultraviolet absorbents (UVAs) have been of increasing concern. Studies have found that these chemicals could be accumulated in terrestrial animals and pose toxicities. However, tissue distribution of UVAs in terrestrial species was far from well understood. In this study, free-range chickens and domestic pigeons were selected to investigate the occurrence and tissue distribution of UVAs. Total concentrations of eleven UVAs in muscles ranged from 778 to 2874 (mean 1413 ± 666) ng/g lipid weight, which were higher than those in aquatic species worldwide. Since low UVA concentrations in local environment were previously reported, the results implied the strong accumulation of UVAs in studied species. Brain, stomach and kidney were main target organs for studied UVAs, differentiating from the strong liver sequestration in aquatic species. The mean tissue-to-muscle ratios of 1.02-4.23 further indicated the preferential accumulation of target UVAs in these tissues. The tissue-to-blood ratios of benzophenone (BP), 2-ethylhexyl salicylate (EHS) and homosalate (HMS) in brain were 370, 1207 and 52.0, respectively, implying their preferential accumulation in brain. More research is needed to characterize the toxicokinetics and tissue distribution of UVAs in terrestrial wild species, in order to further understand their potential risks.

Differential regulations of neural activity and survival in primary cortical neurons by PFOA or PFHpA

Perfluorinated compounds (PFCs), organofluoride compounds comprising carbon-fluorine and carbon-carbon bonds, are used as water and oil repellents in textiles and pharmaceutical tablets; however, they are associated with potential neurotoxic effects. Moreover, the impact of PFCs on neuronal survival, activity, and regulation within the brain remains unclear. Additionally, the mechanisms through which PFCs induce neuronal toxicity are not well-understood because of the paucity of data. This study elucidates that perfluorooctanoic acid (PFOA) and perfluoroheptanoic acid (PFHpA) exert differential effects on the survival and activity of primary cortical neurons. Although PFOA triggers apoptosis in cortical neurons, PFHpA does not exhibit this effect. Instead, PFHpA modifies dendritic spine morphogenesis and synapse formation in primary cortical neuronal cultures, additionally enhancing neural activity and synaptic transmission. This research uncovers a novel mechanism through which PFCs (PFHpA and PFOA) cause distinct alterations in dendritic spine morphogenesis and synaptic activity, shedding light on the molecular basis for the atypical behaviors noted following PFC exposure. Understanding the distinct effects of PFHpA and PFOA could guide regulatory policies on PFC usage and inform clinical approaches to mitigate their neurotoxic effects, especially in vulnerable population.

Concentrations of 45 Per- and Polyfluoroalkyl Substances in North American River Otters (Lontra canadensis) from West Virginia, USA

North American river otters (Lontra canadensis) are top predators in riverine ecosystems and are vulnerable to per- and polyfluoroalkyl substance (PFAS) exposure. Little is known about the magnitude of exposure and tissue distribution of PFAS in river otters. We measured 45 PFAS in various tissues of 42 river otters collected from several watersheds in the state of West Virginia, USA. The median concentrations of ∑All (sum concentration of 45 PFAS) varied among tissues in the following decreasing order: liver (931 ng/g wet weight) > bile > pancreas > lung > kidney > blood > brain > muscle. Perfluoroalkylsulfonates (PFSAs) were the predominant compounds accounting for 58-75% of the total concentrations, followed by perfluoroalkyl carboxylates (PFCAs; 21-35%). 8:2 fluorotelomer sulfonate (8:2 FTS), 10:2 FTS, and 6:2 chlorinated polyfluoroalkyl ether sulfonate were frequently found in the liver (50-90%) and bile (96-100%), whereas hexafluoropropylene oxide dimer acid (HFPO-DA) was rarely found. The hepatic concentrations of ∑All in river otters collected downstream of a fluoropolymer production facility located along the Ohio River were 2-fold higher than those in other watersheds. The median whole body burden of ∑All was calculated to be 1580 μg. PFOS and perfluorooctanoic acid (PFOA) concentrations in whole blood of some river otters exceeded the human toxicity reference values, which warrant further studies.

Perfluorooctane Sulfonate (PFOS) Negatively Impacts Prey Capture Capabilities in Larval Zebrafish

Per- and polyfluoroalkyl substances (PFAS) are widely used in many industrial and domestic applications, which has resulted in unintentional human exposures and bioaccumulation in blood and other organs. Perfluorooctane sulfonate (PFOS) is among the most prevalent PFAS in the environment and has been postulated to affect brain functions in exposed organisms. However, the impacts of PFOS in early neural development have not been well described. We used zebrafish larvae to assess the effects of PFOS on two fundamental complex behaviors, prey capture and learning. Zebrafish exposed to PFOS concentrations ranging from 2 to 20 µM for differing 48-h periods were viable through early larval stages. In addition, PFOS uptake was unaffected by the presence of a chorion. We employed two different experimental paradigms; first we assessed the impacts of increasing organismal PFOS bioaccumulation on prey capture and learning, and second, we probed stage-specific sensitivity to PFOS by exposing zebrafish at different developmental stages (0-2 vs. 3-5 days post fertilization). Following both assays we measured the amount of PFOS present in each larva and found that PFOS levels varied in larvae from different groups within each experimental paradigm. Significant negative correlations were observed between larval PFOS accumulation and percentage of captured prey, whereas nonsignificant negative correlations were observed between PFOS accumulation and experienced-induced prey capture learning. These findings suggest that PFOS accumulation negatively affects larval zebrafish's ability to perform complicated multisensory behaviors and highlights the potential risks of PFOS exposure to animals in the wild, with implications for human health. Environ Toxicol Chem 2024;00:1-9. © 2023 SETAC.

Deleterious functional consequences of perfluoroalkyl substances accumulation into the myelin sheath

Exposure to persistent organic pollutants during the perinatal period is of particular concern because of the potential increased risk of neurological disorders in adulthood. Here we questioned whether exposure to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) could alter myelin formation and regeneration. First, we show that PFOS, and to a lesser extent PFOA, accumulated into the myelin sheath of postnatal day 21 (p21) mice, whose mothers were exposed to either PFOA or PFOS (20 mg/L) via drinking water during late gestation and lactation, suggesting that accumulation of PFOS into the myelin could interfere with myelin formation and function. In fact, PFOS, but not PFOA, disrupted the generation of oligodendrocytes, the myelin-forming cells of the central nervous system, derived from neural stem cells localised in the subventricular zone of p21 exposed animals. Then, cerebellar slices were transiently demyelinated using lysophosphatidylcholine and remyelination was quantified in the presence of either PFOA or PFOS. Only PFOS impaired remyelination, a deleterious effect rescued by adding thyroid hormone (TH). Similarly to our observation in the mouse, we also showed that PFOS altered remyelination in Xenopus laevis using the Tg(Mbp:GFP-ntr) model of conditional demyelination and measuring, then, the number of oligodendrocytes. The functional consequences of PFOS-impaired remyelination were shown by its effects using a battery of behavioural tests. In sum, our data demonstrate that perinatal PFOS exposure disrupts oligodendrogenesis and myelin function through modulation of TH action. PFOS exposure may exacerbate genetic and environmental susceptibilities underlying myelin disorders, the most frequent being multiple sclerosis.

Effects of subchronic exposure of perfluorooctane sulfonate on cognitive function of mice and its mechanism

Perfluorooctane sulfonate (PFOS) is an emerging persistent organic pollutant, and its potential impact on cognitive function remains unclear. We adopted the C57BL/6J mouse model to investigate the effect of PFOS on cognitive function, as well as the underlying mechanisms. Subchronic exposure was performed by administering PFOS via drinking water for 6 months (at doses of 0, 0.2, and 2.0 mg/kg/day), starting from 10.5 months old. The object recognition ability was tested at 2, 4, and 6 months of exposure, and spatial learning and memory were assessed at endpoint. The apoptosis of neurons and astrocytes in the cortex and hippocampus was analyzed, as well as the potential apoptotic signaling pathways. Our results showed that exposure to PFOS for 6 months caused a decrease in object recognition ability and a decline in learning and spatial memory. PFOS selectively increased apoptosis in neurons of the cerebral cortex and specifically activated the endoplasmic reticulum stress PERK/CHOP signaling pathway. In conclusion, our results confirmed that subchronic exposure to PFOS can lead to cognitive impairment in mice, which might be closely associated with the specific activation of an endoplasmic reticulum stress-induced pro-apoptosis pathway in the cerebral cortex neurons.

The development and function of the brain barriers - an overlooked consideration for chemical toxicity

It is well known that the adult brain is protected from some infections and toxic molecules by the blood-brain and the blood-cerebrospinal fluid barriers. Contrary to the immense data collected in other fields, it is deeply entrenched in environmental toxicology that xenobiotics easily permeate the developing brain because these barriers are either absent or non-functional in the fetus and newborn. Here we review the cellular and physiological makeup of the brain barrier systems in multiple species, and discuss decades of experiments that show they possess functionality during embryogenesis. We next present case studies of two chemical classes, perfluoroalkyl substances (PFAS) and bisphenols, and discuss their potential to bypass the brain barriers. While there is evidence to suggest these pollutants may enter the developing and/or adult brain parenchyma, many studies suffer from confounding technical variables which complicates data interpretation. In the future, a more formal consideration of brain barrier biology could not only improve understanding of chemical toxicokinetics but could assist in prioritizing environmental xenobiotics for their neurotoxicity risk.

Health-related toxicity of emerging per- and polyfluoroalkyl substances: Comparison to legacy PFOS and PFOA

Per- and polyfluoroalkyl substances (PFAS) are highly persistent, manufactured chemicals used in various manufacturing processes and found in numerous commercial products. With over 9000 compounds belonging to this chemical class, there is increasing concern regarding human exposure to these compounds due to their persistent, bioaccumulative, and toxic nature. Human exposure to PFAS may occur from a variety of exposure sources, including, air, food, indoor dust, soil, water, from the transfer of PFAS from non-stick wrappers to food, use of cosmetics, and other personal care products. This critical review presents recent research on the health-related impacts of PFAS exposure, highlighting compounds other than Perfluorooctanoic acid (PFOA) and Perfluoroctane sulfonate (PFOS) that cause adverse health effects, updates the current state of knowledge on PFAS toxicity, and, where possible, elucidates cause-and-effect relationships. Recent reviews identified that exposure to PFAS was associated with adverse health impacts on female and male fertility, metabolism in pregnancy, endocrine function including pancreatic dysfunction and risk of developing Type 2 diabetes, lipid metabolism and risk of childhood adiposity, hepatic and renal function, immune function, cardiovascular health (atherosclerosis), bone health including risk for dental cavities, osteoporosis, and vitamin D deficiency, neurological function, and risk of developing breast cancer. However, while cause-and-effect relationships for many of these outcomes were not able to be clearly elucidated, it was identified that 1) the evidence derived from both animal models and humans suggested that PFAS may exert harmful impacts on both animals and humans, however extrapolating data from animal to human studies was complicated due to differences in exposure/elimination kinetics, 2) PFAS precursor kinetics and toxicity mechanism data are still limited despite ongoing exposures, and 3) studies in humans, which provide contrasting results require further investigation of the long-term-exposed population to better evaluate the biological toxicity of chronic exposure to PFAS.

Legacy and emerging organic contaminants in the polar regions

The presence of numerous emerging organic contaminants (EOCs) and remobilization of legacy persistent organic pollutants (POPs) in polar regions have become significant concerns of the scientific communities, public groups and stakeholders. This work reviews the occurrences of EOCs and POPs and their long-range environmental transport (LRET) processes via atmosphere and ocean currents from continental sources to polar regions. Concentrations of classic POPs have been systematically monitored in air at several Arctic stations and showed seasonal variations and declining trends. These chemicals were also the major POPs reported in the Antarctica, while their concentrations were lower than those in the Arctic, illustrating the combination of remoteness and lack of potential local sources for the Antarctica. EOCs were investigated in air, water, snow, ice and organisms in the Arctic. Data in the Antarctica are rare. Reemission of legacy POPs and EOCs accumulated in glaciers, sea ice and snow may alter the concentrations and amplify their effects in polar regions. Thus, future research will need to understand the various biogeochemical and geophysical processes under climate change and anthropogenic pressures.

Neurotransmission Targets of Per- and Polyfluoroalkyl Substance Neurotoxicity: Mechanisms and Potential Implications for Adverse Neurological Outcomes

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent environmental pollutants that are ubiquitously found in the environment and virtually in all living organisms, including humans. PFAS cross the blood-brain barrier and accumulate in the brain. Thus, PFAS are a likely risk for neurotoxicity. Studies that measured PFAS levels in the brains of humans, polar bears, and rats have demonstrated that some areas of the brain accumulate greater amounts of PFAS. Moreover, in humans, there is evidence that PFAS exposure is associated with attention-deficit/hyperactivity disorder (ADHD) in children and an increased cause of death from Parkinson's disease and Alzheimer's disease in elderly populations. Given possible links to neurological disease, critical analyses of possible mechanisms of neurotoxic action are necessary to advance the field. This paper critically reviews studies that investigated potential mechanistic causes for neurotoxicity including (1) a change in neurotransmitter levels, (2) dysfunction of synaptic calcium homeostasis, and (3) alteration of synaptic and neuronal protein expression and function. We found growing evidence that PFAS exposure causes neurotoxicity through the disruption of neurotransmission, particularly the dopamine and glutamate systems, which are implicated in age-related psychiatric illnesses and neurodegenerative diseases. Evaluated research has shown there are highly reproduced increased glutamate levels in the hippocampus and catecholamine levels in the hypothalamus and decreased dopamine in the whole brain after PFAS exposure. There are significant gaps in the literature relative to the assessment of the nigrostriatal system (striatum and ventral midbrain) among other regions associated with PFAS-associated neurologic dysfunction observed in humans. In conclusion, evidence suggests that PFAS may be neurotoxic and associated with chronic and age-related psychiatric illnesses and neurodegenerative diseases. Thus, it is imperative that future mechanistic studies assess the impact of PFAS and PFAS mixtures on the mechanism of neurotransmission and the consequential functional effects.

A Critical Review and Meta-Analysis of Impacts of Per- and Polyfluorinated Substances on the Brain and Behavior

Per- and polyfluoroalkyl substances (PFAS) are a class of structurally diverse synthetic organic chemicals that are chemically stable, resistant to degradation, and persistent in terrestrial and aquatic environments. Widespread use of PFAS in industrial processing and manufacturing over the last 70 years has led to global contamination of built and natural environments. The brain is a lipid rich and highly vascularized organ composed of long-lived neurons and glial cells that are especially vulnerable to the impacts of persistent and lipophilic toxicants. Generally, PFAS partition to protein-rich tissues of the body, primarily the liver and blood, but are also detected in the brains of humans, wildlife, and laboratory animals. Here we review factors impacting the absorption, distribution, and accumulation of PFAS in the brain, and currently available evidence for neurotoxic impacts defined by disruption of neurochemical, neurophysiological, and behavioral endpoints. Emphasis is placed on the neurotoxic potential of exposures during critical periods of development and in sensitive populations, and factors that may exacerbate neurotoxicity of PFAS. While limitations and inconsistencies across studies exist, the available body of evidence suggests that the neurobehavioral impacts of long-chain PFAS exposures during development are more pronounced than impacts resulting from exposure during adulthood. There is a paucity of experimental studies evaluating neurobehavioral and molecular mechanisms of short-chain PFAS, and even greater data gaps in the analysis of neurotoxicity for PFAS outside of the perfluoroalkyl acids. Whereas most experimental studies were focused on acute and subchronic impacts resulting from high dose exposures to a single PFAS congener, more realistic exposures for humans and wildlife are mixtures exposures that are relatively chronic and low dose in nature. Our evaluation of the available human epidemiological, experimental, and wildlife data also indicates heightened accumulation of perfluoroalkyl acids in the brain after environmental exposure, in comparison to the experimental studies. These findings highlight the need for additional experimental analysis of neurodevelopmental impacts of environmentally relevant concentrations and complex mixtures of PFAS.

Impairment of human dopaminergic neurons at different developmental stages by perfluoro-octanoic acid (PFOA) and differential human brain areas accumulation of perfluoroalkyl chemicals

Perfluoroalkyl substances (PFASs) are synthetic chemicals widely used in industrial and consumer products. The environmental spreading of PFASs raises concerns for their impact on human health. In particular, the bioaccumulation in humans due to environmental exposure has been reported also in total brain samples and PFAS exposure has been associated with neurodevelopmental disorders. In this study we aimed to investigate the specific PFAS bioaccumulation in different brain areas. Our data reported major accumulation in the brainstem region, which is richly populated by dopaminergic neurons (DNs), in brain autopsy samples from people resident in a PFAS-polluted area of Italy. Since DNs are the main source of dopamine (DA) in the mammalian central nervous system (CNS), we evaluated the possible functional consequences of perfluoro-octanoic acid (PFOA) exposure in a human model of DNs obtained by differentiation of human induced pluripotent stem cells (hiPSCs). Particularly, we analyzed the specific effect of the exposure to PFOA for 24 h, at the concentration of 10 ng/ml, at 3 different steps of dopaminergic differentiation: the neuronal commitment phase (DP1), the neuronal precursor phase (DP2) and the mature dopaminergic differentiation phase (DP3). Interestingly, compared to untreated cells, exposure to PFOA was associated with a reduced expression of Tyrosine Hydroxylase (TH) and Neurofilament Heavy (NFH), both markers of dopaminergic maturation at DP2 phase. In addition, cells at DP3 phase exposed to PFOA showed a severe reduction in the expression of the Dopamine Transporter (DAT), functionally involved in pre-synaptic dopamine reuptake. In this proof-of-concept study we show a significant impact of PFOA exposure, mainly on the most sensitive stage of neural dopaminergic differentiation, prompting the way for further investigations more directly relevant to risk assessment of these chemicals.

Absorption, distribution, and toxicity of per- and polyfluoroalkyl substances (PFAS) in the brain: a review

Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic chemicals colloquially known as "forever chemicals" because of their high persistence. PFAS have been detected in the blood, liver, kidney, heart, muscle and brain of various species. Although brain is not a dominant tissue for PFAS accumulation compared to blood and liver, adverse effects of PFAS on brain functions have been identified. Here, we review studies related to the absorption, accumulation, distribution and toxicity of PFAS in the brain. We summarize evidence on two potential mechanisms of PFAS entering the brain: initiating blood-brain barrier (BBB) disassembly through disrupting tight junctions and relying on transporters located at the BBB. PFAS with diverse structures and properties enter and accumulate in the brain with varying efficiencies. Compared to long-chain PFAS, short-chain PFAS may not cross cerebral barriers effectively. According to biomonitoring studies and PFAS exposure experiments, PFAS can accumulate in the brain of humans and wildlife species. With respect to the distribution of PFAS in specific brain regions, the brain stem, hippocampus, hypothalamus, pons/medulla and thalamus are dominant for PFAS accumulation. The accumulation and distribution of PFAS in the brain may lead to toxic effects in the central nervous system (CNS), including PFAS-induced behavioral and cognitive disorders. The specific mechanisms underlying such PFAS-induced neurotoxicity remain to be explored, but two major potential mechanisms based on current understanding are PFAS effects on calcium homeostasis and neurotransmitter alterations in neurons. Based on the information available about PFAS uptake, accumulation, distribution and impacts on the brain, PFAS have the potential to enter and accumulate in the brain at varying levels. The balance of existing studies shows there is some indication of risk in animals, while the human evidence is mixed and warrants further scrutiny.

Form and Function of the Vertebrate and Invertebrate Blood-Brain Barriers

The need to protect neural tissue from toxins or other substances is as old as neural tissue itself. Early recognition of this need has led to more than a century of investigation of the blood-brain barrier (BBB). Many aspects of this important neuroprotective barrier have now been well established, including its cellular architecture and barrier and transport functions. Unsurprisingly, most research has had a human orientation, using mammalian and other animal models to develop translational research findings. However, cell layers forming a barrier between vascular spaces and neural tissues are found broadly throughout the invertebrates as well as in all vertebrates. Unfortunately, previous scenarios for the evolution of the BBB typically adopt a classic, now discredited 'scala naturae' approach, which inaccurately describes a putative evolutionary progression of the mammalian BBB from simple invertebrates to mammals. In fact, BBB-like structures have evolved independently numerous times, complicating simplistic views of the evolution of the BBB as a linear process. Here, we review BBBs in their various forms in both invertebrates and vertebrates, with an emphasis on the function, evolution, and conditional relevance of popular animal models such as the fruit fly and the zebrafish to mammalian BBB research.

Effects of an environmentally relevant PFAS mixture on dopamine and steroid hormone levels in exposed mice

In the present study, we investigated the dopaminergic and steroid hormone systems of A/J mice fed environmentally relevant concentrations of a perfluoroalkyl substance (PFAS) mixture over a period of 10 weeks. The PFAS mixture was chosen based on measured PFAS concentrations in earthworms at a Norwegian skiing area (Trondheim) and consisted of eight different PFAS. Dietary exposure to PFAS led to lower total brain dopamine (DA) concentrations in male mice, as compared to control. On the transcript level, brain tyrosine hydroxylase (th) of PFAS exposed males was reduced, compared to the control group. No significant differences were observed on the transcript levels of enzymes responsible for DA metabolism, namely - monoamine oxidase (maoa and maob) and catechol-O methyltransferase (comt). We detected increased transcript level for DA receptor 2 (dr2) in PFAS exposed females, while expression of DA receptor 1 (dr1), DA transporter (dat) and vesicular monoamine transporter (vmat) were not affected by PFAS exposure. Regarding the steroid hormones, plasma and muscle testosterone (T), 11-ketotestosterone (11-KT) and 17β-estradiol (E2) levels, as well as transcripts for estrogen receptors (esr1 and esr2), gonadotropin releasing hormone (gnrh) and aromatase (cyp19) were unaltered by the PFAS treatment. These results indicate that exposure to PFAS doses, comparable to previous observation in earthworms at a Norwegian skiing area, may alter the dopaminergic system of mice with overt consequences for health, general physiology, cognitive behavior, reproduction and metabolism.

Maternal exposure to a human based mixture of persistent organic pollutants (POPs) affect gene expression related to brain function in mice offspring hippocampus

Male and female mice pups were exposed to a low and high dose of a human relevant mixture of persistent organic pollutants (POPs) during pregnancy and lactation. Most compounds detected in the dams were found in offspring brains. The mice offspring exhibited changed expression of hippocampal genes involved in cognitive function (Adora2a, Auts2, Crlf1, Chrnb2, Gdnf, Gnal, Kcnh3), neuroinflammation (Cd47, Il1a), circadian rhythm (Per1, Clock), redox signalling (Hmox2) and aryl hydrocarbon receptor activation (Cyp1b1). A few genes were differentially expressed in males versus females. Mostly, similar patterns of gene expression changes were observed between the low and high dose groups. Effects on learning and memory function measured in the Barnes maze (not moving, escape latency) were found in the high dose group when combined with moderate stress exposure (air flow from a fan). Mediation analysis indicated adaptation to the effects of exposure since gene expression compensated for learning disabilities (escape latency, walking distance and time spent not moving in the maze). Additionally, random forest analysis indicated that Kcnh3, Gnal, and Crlf1 were the most important genes for escape latency, while Hip1, Gnal and the low exposure level were the most important explanatory factors for passive behaviour (not moving). Altogether, this study showed transfer of POPs to the offspring brains after maternal exposure, modulating the expression level of genes involved in brain function.

The role of transcription factor Nrf2 in the toxicity of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in C57BL/6 mouse astrocytes

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are members of perfluoroalkyl substances (PFAS). This study aimed to determine the protective role of Nrf2 against the toxicity of these agents. Nrf2-/- and wild-type astrocytes were exposed to PFOS (75-600 μM) and PFOA (400-1000 μM) for 24 h. Lactate dehydrogenase (LDH) release was significantly higher in nrf2-/- than in the wild-type astrocytes. Exposure to 600 μM PFOS and 800 μM PFOA showed significant increases in reactive oxygen species, lipid peroxidation, and apoptosis in nrf2-/- astrocytes as compared to wild-type astrocytes. The GSH/GSSG ratio was significantly decreased in nrf2-/- astrocytes when compared to wild-type astrocytes. Additionally, PFOS and PFOS caused dramatic ultrastructural alterations to the mitochondria. BHT pretreatment in wild-type cells decreased ROS production with exposure to both agents. Results of the present study conclude that PFOS and PFOA are cytotoxic to astrocytes and that nrf2 -/- cells are more sensitive to toxicity by these agents.

Prenatal Exposure to Endocrine-Disrupting Chemicals and Subsequent Brain Structure Changes Revealed by Voxel-Based Morphometry and Generalized Q-Sampling MRI

Previous studies have indicated that prenatal exposure to endocrine-disrupting chemicals (EDCs) can cause adverse neuropsychiatric disorders in children and adolescents. This study aimed to determine the association between the concentrations of prenatal EDCs and brain structure changes in teenagers by using MRI. We recruited 49 mother–child pairs during the third trimester of pregnancy, and collected and examined the concentration of EDCs—including phthalate esters, perfluorochemicals (PFCs), and heavy metals (lead, arsenic, cadmium, and mercury)—in maternal urine and/or serum. MRI voxel-based morphometry (VBM) and generalized q-sampling imaging (GQI) mapping—including generalized fractional anisotropy (GFA), normalized quantitative anisotropy (NQA), and the isotropic value of the orientation distribution function (ISO)—were obtained in teenagers 13–16 years of age in order to find the association between maternal EDC concentrations and possible brain structure alterations in the teenagers’ brains. We found that there are several specific vulnerable brain areas/structures associated with prenatal exposure to EDCs, including decreased focal brain volume, primarily in the frontal lobe; high frontoparietal lobe, temporooccipital lobe and cerebellum; and white matter structural alterations, which showed a negative association with GFA/NQA and a positive association with ISO, primarily in the corpus callosum, external and internal capsules, corona radiata, superior fronto-occipital fasciculus, and superior longitudinal fasciculus. Prenatal exposure to EDCs may be associated with specific brain structure alterations in teenagers.

Alteration of neuro-dopamine and steroid hormone homeostasis in wild Bank voles in relation to tissue concentrations of PFAS at a Nordic skiing area

Perfluoroalkyl substances (PFAS) are contaminants that are applied in a wide range of consumer products, including ski products. The present study investigated the neuro-dopamine (DA) and cellular steroid hormone homeostasis of wild Bank voles (Myodes glareolus) from a skiing area in Norway (Trondheim), in relation to tissue concentrations of PFAS. We found a positive association between brain DA concentrations and the concentration of several PFAS, while there was a negative association between PFAS and dopamine receptor 1 (dr1) mRNA. The ratio between DA and its metabolites (3,4-dihydroxyphenylacetic acid: DOPAC and homovanillic acid: HVA) showed a negative association between DOPAC/DA and several PFAS, suggesting that PFAS altered the metabolism of DA via monoamine oxidase (Mao). This assumption is supported by an observed negative association between mao mRNA and PFAS. Previous studies have shown that DA homeostasis can indirectly regulate cellular estrogen (E2) and testosterone (T) biosynthesis. We found no association between DA and steroid hormone levels, while there was a negative association between some PFAS and T concentrations, suggesting that PFAS might affect T through other mechanisms. The results from the current study indicate that PFAS may alter neuro-DA and steroid hormone homeostasis in Bank voles, with potential consequences on reproduction and general health.

Stranded cetaceans warn of high perfluoroalkyl substance pollution in the western Mediterranean Sea

Perfluoroalkyl substances (PFASs) are a class of organohalogenated compounds of environmental concern due to similar characteristics as the well-studied legacy persistent organic pollutants (POPs) that typically show environmental persistence, biomagnification and toxicity. Nevertheless, PFAS are still poorly regulated internationally and in many aspects poorly understood. Here, we studied liver and muscle concentrations in five cetacean species stranded at the southeastern coast of Spain during 2009-2018. Twelve of the fifteen targeted compounds were detected in >50% of the liver samples. Hepatic concentrations were significantly higher than those in muscle reflecting the particular toxicokinetics of these compounds. Bottlenose dolphins Tursiops truncatus showed the highest hepatic ΣPFAS (n = 5; 796.8 ± 709.0 ng g^-1 ww) concentrations, followed by striped dolphin Stenella coeruleoalba (n = 29; 259.5 ± 136.2 ng g^-1 ww), sperm whale Physeter macrocephalus (n = 1; 252.8 ng g^-1 ww), short-beaked common dolphin Delphinus delphis (n = 2; 240.3 ± 218.6 ng g^-1 ww) and Risso's dolphin Grampus griseus (n = 1; 78.7 ng g^-1 ww). These interspecies differences could be partially explained by habitat preferences, although they could generally not be related to trophic position or food chain proxied by stable N (δ¹⁵N) and C (δ¹³C) isotope values, respectively. PFAS profiles in all species showed a similar pattern of concentration prevalence in the order PFOS>PFOSA>PFNA≈PFFUnA>PFDA. The higher number of samples available for striped dolphin allowed for evaluating their PFAS burden and profile in relation to the stranding year, stable isotope values, and biological variables including sex and length. However, we could only find links between δ¹⁵N and PFAS burdens in muscle tissue, and between stranding year and PFAS profile composition. Despite reductions in the manufacturing industry, these compounds still appear in high concentrations compared to more than two decades ago in the Mediterranean Sea and PFOS remains the dominating compound.

Internal distribution and fate of persistent organic contaminants (PCDD/Fs, DL-PCBs, HBCDs, TBBPA, and PFASs) in a Bos Taurus

While terrestrial organisms such as livestock are consumed regularly, studies of internal distribution and bioaccumulation of persistent organic pollutants (POPs) have been focused more on aquatic organisms. In this study, we have assessed the internal distribution and fate of legacy (PCDD/Fs and PCBs) and emerging POPs (HBCDs and PFASs), and TBBPA in 42 tissues of a Bos Taurus. PCDD/Fs, DL-PCBs, and HBCDs were found 3, 4, and 4-fold higher in the lipid-rich organs (subcutaneous fat, visceral fat, large intestine) compared to the remaining organs and muscles, owing to their hydrophobic properties. The TBBPA concentration in the excrement was 36-fold higher compared to the average tissues, suggesting a short internal half-life of TBBPA. Among PFASs, PFUnDA displayed 98% contribution from all ionic PFASs in the tissues due to its strong binding affinity, high exposure via feed and water, and increasing emergence of PFUnDA and its precursors in the Southeast Asian countries. While our study suggests that, at the moment, there is no significant health risks to the general Korean population, the future changes in environmental exposure as well as the internal dynamics and fate of various POPs species should be kept in mind when consuming various parts of livestock.

Scientific Basis for Managing PFAS as a Chemical Class

This commentary presents a scientific basis for managing as one chemical class the thousands of chemicals known as PFAS (per- and polyfluoroalkyl substances). The class includes perfluoroalkyl acids, perfluoroalkylether acids, and their precursors; fluoropolymers and perfluoropolyethers; and other PFAS. The basis for the class approach is presented in relation to their physicochemical, environmental, and toxicological properties. Specifically, the high persistence, accumulation potential, and/or hazards (known and potential) of PFAS studied to date warrant treating all PFAS as a single class. Examples are provided of how some PFAS are being regulated and how some businesses are avoiding all PFAS in their products and purchasing decisions. We conclude with options for how governments and industry can apply the class-based approach, emphasizing the importance of eliminating non-essential uses of PFAS, and further developing safer alternatives and methods to remove existing PFAS from the environment.

Occurrence and trophic transfer of per- and polyfluoroalkyl substances in an Antarctic ecosystem

Information on the occurrence and trophodynamics of per- and polyfluoroalkyl substances (PFASs) in the Antarctic region is limited. We investigated the occurrence of PFASs in an ecosystem in the Fildes Peninsula at King George Island and Ardley Island, Antarctica. The profiles, spatial distribution, and trophic transfer behavior of PFASs were further studied. ∑PFASs ranged from 0.50 ± 38.0 ng/g dw (dry weight) in algae to 4.97 ± 1.17 ng/g dw in Neogastropoda (Ngas), which was lower than those in the low- and mid-latitude regions and even Arctic regions. Perfluorobutyric acid (PFBA) was predominant with detection frequencies above 50% in all types of samples, and the relative contribution of PFBA ranged from 22% to 57% in the biota samples. The biomagnification factors of PFBA, perfluoroheptanoate (PFHpA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) between Archaeogastropoda (Agas) and Ngas were 0.67 ± 0.54, 0.77 ± 0.38, 1.04 ± 1.56, 3.30 ± 4.07, and 1.61 ± 0.89, respectively. The trophic magnification factors of PFHxS and PFOS were 2.09 and 2.92, respectively, which indicated that they could be biomagnified through the food chain. Considering the increasing production and uncertain toxicological risks of emerging PFASs and the sensitive ecosystems in Antarctic regions, more attention should be paid, especially for the short-chain ones in the Antarctic region.

Bioaccumulation and biomagnification of perfluoroalkyl acids and precursors in East Greenland polar bears and their ringed seal prey

The bioaccumulation and biomagnification of 22 major perfluoroalkyl substances (PFAS) were investigated in tissues of polar bears (Ursus maritimus) and their major prey species, the ringed seal (Pusa hispida), from the Scoresby Sound region of East Greenland. In polar bear liver the mean Σ₄PFSA (perfluoroalkyl sulfonic acid) concentration (C₄, C₆, C₈ and C₁₀) was 2611 ± 202 ng/g wet weight (ww; 99% perfluorooctane sulfonate (PFOS)) and two orders of magnitude higher than the 20 ± 3 ng/g ww (89% PFOS) concentration in fat. The mean Σ₄PFSAs in seal liver was 111 ± 5 ng/g ww (98% PFOS) and three orders of magnitude higher relative to the 0.05 ± 0.01 ng/g ww concentration in blubber (100% perfluorohexane sulfonate). Perfluoro-1-octane sulfonamide (FOSA) was quantifiable in bear (mean 10 ± 1.4 ng/g ww) and seal (mean 0.6 ± 0.1 ng/g ww) liver but not in fat or blubber. The mean Σ₁₃PFCAs (C₄-C₁₈; perfluoroalkyl carboxylic acids) in bear liver (924 ± 71 ng/g ww) was much greater than in seal liver (74 ± 6 ng/g ww). In bear fat and seal blubber, the mean Σ₁₃PFCAs were 15 ± 1.9 and 0.9 ± 0.1 ng/g ww, respectively. Longer chain C₁₁ to C₁₄ PFCAs dominated in bear fat and seal blubber (60-80% of Σ₁₃PFCA), whereas shorter-chain C₉ to C₁₁ PFCAs dominated in the liver (85-90% of Σ₁₃PFCA). Biomagnification factors (BMFs) were orders of magnitude greater for PFHxS and C₉ to C₁₃ PFCAs when based on bear liver to seal blubber rather than bear liver to seal liver, and PFCA (C₉ to C₁₃) BMFs decreased with increasing chain length. Seal blubber to bear liver BMFs better reflects the dietary exposure relationship of PFAS between bears and seals.

State of knowledge on current exposure, fate and potential health effects of contaminants in polar bears from the circumpolar Arctic

The polar bear (Ursus maritimus) is among the Arctic species exposed to the highest concentrations of long-range transported bioaccumulative contaminants, such as halogenated organic compounds and mercury. Contaminant exposure is considered to be one of the largest threats to polar bears after the loss of their Arctic sea ice habitat due to climate change. The aim of this review is to provide a comprehensive summary of current exposure, fate, and potential health effects of contaminants in polar bears from the circumpolar Arctic required by the Circumpolar Action Plan for polar bear conservation. Overall results suggest that legacy persistent organic pollutants (POPs) including polychlorinated biphenyls, chlordanes and perfluorooctane sulfonic acid (PFOS), followed by other perfluoroalkyl compounds (e.g. carboxylic acids, PFCAs) and brominated flame retardants, are still the main compounds in polar bears. Concentrations of several legacy POPs that have been banned for decades in most parts of the world have generally declined in polar bears. Current spatial trends of contaminants vary widely between compounds and recent studies suggest increased concentrations of both POPs and PFCAs in certain subpopulations. Correlative field studies, supported by in vitro studies, suggest that contaminant exposure disrupts circulating levels of thyroid hormones and lipid metabolism, and alters neurochemistry in polar bears. Additionally, field and in vitro studies and risk assessments indicate the potential for adverse impacts to polar bear immune functions from exposure to certain contaminants.

Refining uptake and depuration constants for fluoroalkyl chemicals in Chironomus riparius larvae on the basis of experimental results and modelling

The aims of this study were to determine depuration rates for a range of per- and polyfluoroalkyl substances (PFASs) using Chironomus riparius, and to test a concentration-dependency hypothesis for the long-chain perfluorotridecanoic acid (PFTrDA) for this species. Midge larvae were exposed to field sediments collected downstream of a fluorotelomer plant, and to the same sediment spiked with PFTrDA. Elimination kinetics results indicated complete elimination of all PFASs by chironomids after 42h. These data were used to develop two PFTrDA bioaccumulation models accounting for chironomid growth and for compound concentration dependency or not. There was much better agreement between observed and simulated data under the concentration-dependency hypothesis than under the alternative one (passive diffusion). The PFTrDA uptake rate derived from the concentration-dependency model equaled 0.013 ± 0.008g_ocg_wwh^-1, and the depuration rate 0.032 ± 0.009h^-1.

Evaluating parameter availability for physiologically based pharmacokinetic (PBPK) modeling of perfluorooctanoic acid (PFOA) in zebrafish

Physiologically based pharmacokinetic (PBPK) models are considered useful tools to describe the absorption, distribution, metabolism and excretion of xenobiotics. For accurate predictions, PBPK models require species-specific and compound-specific parameters. Zebrafish are considered an appropriate vertebrate model for investigating the toxicity of a wide variety of compounds. However, no specific mechanistic model exists for the pharmacokinetics of perfluoroalkyl acids (PFAAs) in zebrafish, despite growing concern about this class of ubiquitous environmental contaminants. The purpose of this study was to evaluate the current state of knowledge for the parameters that would be needed to construct such a model for zebrafish. We chose perfluorooctanoic acid (PFOA) as a model PFAA with greater data availability. We have updated a previous PBPK model for rainbow trout to simulate PFOA fate in zebrafish following waterborne exposure. For the first time, the model considers hepatobiliary circulation. In order to evaluate the availability of parameters to implement this model, we performed an extensive literature review to find zebrafish-specific parameters. As in previous approaches, we broadened our search to include mammalian and other fish studies when zebrafish-specific data were lacking. Based on the method used to measure or estimate parameters, or based on their species-specific origin, we scored and ranked the quality of available parameters. These scores were then used in Monte Carlo and partial rank correlation analyses to identify the most critical data gaps. The liver, where fatty acid binding proteins (FABPs) and plasma proteins are considered, represented the best model-data agreement. Lack of agreement in other tissues suggest better parameters are needed. The results of our study highlight the lack of zebrafish-specific parameters. Based on sensitivity and uncertainty analysis, parameters associated with PFAA-protein interactions and passive diffusion need further refinement to enable development of predictive models for these emerging chemicals in zebrafish.

Biotransformation of 8:2 polyfluoroalkyl phosphate diester in gilthead bream (Sparus aurata)

Polyfluoroalkyl phosphate esters (PAPs) are high production volume surfactants used in the food contact paper and packaging industry. PAPs may transform to persistent perfluoroalkyl carboxylic acids (PFCAs) under biotic conditions, but little is known about their fate and behavior in aquatic organisms. Here we report for the first time on the uptake, tissue distribution, and biotransformation of 8:2 polyfluoroalkyl phosphate diester (8:2 diPAP) in fish. Gilt-head bream (Sparus aurata) were dosed via the diet (8:2 diPAP at 29μg/g) for 7days, during which time 8:2 diPAP and its transformation products were monitored in plasma, liver, muscle, gills, bile and brain. 8:2 diPAP tended to accumulate in liver, plasma and gills, and to a lesser extent in muscle, bile and brain. Several transformation products (observed previously in other organisms) were also observed in most tissues and biofluids, including both saturated and unsaturated fluorotelomer acids (8:2 FTCA, 8:2 FTUCA, 7:3 FTCA), and perfluorooctanoic acid (PFOA). 8:2 FTCA was the major metabolite in all tissues/biofluids, except for bile, where PFOA occurred at the highest concentrations. Unexpectedly high PFOA levels (up to 3.7ng/g) were also detected in brain. Phase 2 metabolites, which have been reported in fish following exposure to fluorotelomer alcohols, were not observed in these experiments, probably due to their low abundance. Nevertheless, the detection of PFOA indicates that exposure to PAPs may be an indirect route of exposure to PFCAs in fish.

A veterinary perspective on One Health in the Arctic

Exposure to long-range transported industrial chemicals, climate change and diseases is posing a risk to the overall health and populations of Arctic wildlife. Since local communities are relying on the same marine food web as marine mammals in the Arctic, it requires a One Health approach to understand the holistic ecosystem health including that of humans. Here we collect and identify gaps in the current knowledge of health in the Arctic and present the veterinary perspective of One Health and ecosystem dynamics. The review shows that exposure to persistent organic pollutants (POPs) is having multiple organ-system effects across taxa, including impacts on neuroendocrine disruption, immune suppression and decreased bone density among others. Furthermore, the warming Arctic climate is suspected to influence abiotic and biotic long-range transport and exposure pathways of contaminants to the Arctic resulting in increases in POP exposure of both wildlife and human populations. Exposure to vector-borne diseases and zoonoses may increase as well through range expansion and introduction of invasive species. It will be important in the future to investigate the effects of these multiple stressors on wildlife and local people to better predict the individual-level health risks. It is within this framework that One Health approaches offer promising opportunities to survey and pinpoint environmental changes that have effects on wildlife and human health.

Per- and polyfluoroalkyl substances (PFASs) - New endocrine disruptors in polar bears (Ursus maritimus)?

Per- and polyfluoroalkyl substances (PFASs) are emerging in the Arctic and accumulate in brain tissues of East Greenland (EG) polar bears. In vitro studies have shown that PFASs might possess endocrine disrupting abilities and therefore the present study was conducted to investigate potential PFAS induced alterations in brain steroid concentrations. The concentrations of eleven steroid hormones were determined in eight brain regions from ten EG polar bears. Pregnenolone (PRE), the dominant progestagen, was found in mean concentrations of 5-47ng/g (ww) depending on brain region. PRE showed significantly (p<0.01) higher concentrations in female compared to male bears. Dehydroepiandrosterone (DHEA) found in mean concentrations 0.67-4.58ng/g (ww) was the androgen found in highest concentrations. Among the estrogens estrone (E1) showed mean concentrations of 0.90-2.21ng/g (ww) and was the most abundant. Remaining steroid hormones were generally present in concentrations below 2ng/g (ww). Steroid levels in brain tissue could not be explained by steroid levels in plasma. There was however a trend towards increasing estrogen levels in plasma resulting in increasing levels of androgens in brain tissue. Correlative analyses showed positive associations between PFASs and 17α-hydroxypregnenolone (OH-PRE) (e.g. perflouroalkyl sulfonates (∑PFSA): p<0.01, r=0.39; perfluoroalkyl carboxylates (∑PFCA): p<0.01, r=0.61) and PFCA and testosterone (TS) (∑PFCA: p=0.03, r=0.30) across brain regions. Further when investigating correlative associations in specific brain regions significant positive correlations were found between ∑PFCA and several steroid hormones in the occipital lobe. Correlative positive associations between PFCAs and steroids were especially observed for PRE, progesterone (PRO), OH-PRE, DHEA, androstenedione (AN) and testosterone (TS) (all p≤0.01, r≥0.7). The results from the present study generally indicate that an increase in PFASs concentration seems to concur with an increase in steroid hormones of EG polar bears. It is, however, not possible to determine whether alterations in brain steroid concentrations arise from interference with de novo steroid synthesis or via disruption of peripheral steroidogenic tissues mainly in gonads and feedback mechanisms. Steroids are important for brain plasticity and gender specific behavior as well as postnatal development and sexually dimorph brain function. The present work indicates an urgent need for a better mechanistic understanding of how PFASs may affect the endocrine system of polar bears and potentially other mammal species.

Alteration to Dopaminergic Synapses Following Exposure to Perfluorooctane Sulfonate (PFOS), in Vitro and in Vivo

Our understanding of the contribution exposure to environmental toxicants has on neurological disease continues to evolve. Of these, Parkinson’s disease (PD) has been shown to have a strong environmental component to its etiopathogenesis. However, work is still needed to identify and characterize environmental chemicals that could alter the expression and function of the nigrostriatal dopamine system. Of particular interest is the neurotoxicological effect of perfluorinated compounds, such as perfluorooctane sulfonate (PFOS), which has been demonstrated to alter aspects of dopamine signaling. Using in vitro approaches, we have elaborated these initial findings to demonstrate the neurotoxicity of PFOS to the SH-SY5Y neuroblastoma cell line and dopaminergic primary cultured neurons. Using an in vivo model, we did not observe a deficit to dopaminergic terminals in the striatum of mice exposed to 10 mg/kg PFOS for 14 days. However, subsequent exposure to the selective dopaminergic neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) significantly reduced the expression of dopamine transporter (DAT) and tyrosine hydroxylase (TH), and resulted in an even greater reduction in DAT expression in animals previously exposed to PFOS. These findings suggest that PFOS is neurotoxic to the nigrostriatal dopamine circuit and this neurotoxicity could prime the dopamine terminal to more extensive damage following additional toxicological insults.

Determination of perfluorinated sulfonate and perfluorinated acids in tissues of free-living European beaver (castor fiber L.) by d-SPE/ micro-UHPLC-MS/MS

Perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the main representatives of an rising class of persistent organic pollutants (POPs), perfluorochemicals (PFCs). In this study, determination of selected PFCs concentration in liver, brain, tail, adipose and peritoneum tissues of free-living European beaver (Castor fiber L.) was addressed. Tissue samples, collected from beavers living in Masurian Lakeland (NE Poland), were analyzed by dispersive Solid Phase Extraction (d-SPE) with micro-UHPLC-MS/MS system. In a group of ten selected pefrluorinated compounds only two perfluorinated acids (PFOA and PFNA) and one perfluorinated sulfonate (PFOS) were quantified. PFOA was detected in all analysed tissue samples in both female and male beavers in a range from 0.55 to 0.98ngg(-1) ww whereas PFOS was identified in all analyzed female beaver tissues and only in liver, subcutaneous adipose and peritoneum tissues of male beavers at the concentration level from 0.86 to 5.08ngg(-1) ww. PFNA was only identified in female beaver tissues (liver, subcutaneous adipose and peritoneum) in a range from 1.50 to 6.61ngg(-1) ww. This study demonstrated the bioaccumulation of PFCs in tissue samples collected from beavers living in area known as green lungs of Poland. The results provided in this study indicate for the increasing risk of PFCs occurrence in the environment and the level of PFCs in tissue of free-living European beavers may serve as bioindicator of environmental pollution by these compounds.

QuEChERs Combined with Online Interference Trapping LC-MS/MS Method for the Simultaneous Determination of 20 Polyfluoroalkane Substances in Dietary Milk

In this study, a highly sensitive and reliable method for the determination of 20 polyfluoroalkane substances (PFASs) in milk was established using the QuEChERS approach and an online interference trapping LC-MS/MS analysis. By a calibration with stable-isotope-labeled internal standards, we showed that the method displayed excellent linear dynamic ranges for 20 PFASs (correlation coefficients ≥0.997). The LOQs for the two types of PFASs, perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), were 0.010 and 0.050 μg/L, respectively. At the three spiking levels, the average recoveries for PFCAs ranged from 78.5 to 111% with the RSD (n = 6) within 1.20-13.1%, and those for PFSAs ranged from 72.8 to 105% with the RSD (n = 6) within 3.53-14.9%. By the developed method, 16 PFASs were found to be positive in 46 milk samples, and the levels for the PFASs with longer chains were significantly higher than those reported from other known regions.

Brain region-specific perfluoroalkylated sulfonate (PFSA) and carboxylic acid (PFCA) accumulation and neurochemical biomarker responses in east Greenland polar bears (Ursus maritimus)

Perfluoroalkyl substances (PFASs) is a growing class of contaminants in the Arctic environment, and include the established perfluorinated sulfonates (PFSAs; especially perfluorooctane sulfonate (PFOS)) and carboxylic acids (PFCAs). PFSAs and PFCAs of varying chain length have been reported to bioaccumulate in lipid rich tissues of the brain among other tissues such as liver, and can reach high concentrations in top predators including the polar bear. PFCA and PFSA bioaccummulation in the brain has the potential to pose neurotoxic effects and therefore we conducted a study to investigate if variations in neurochemical transmitter systems i.e. the cholinergic, glutaminergic, dopaminergic and GABAergic, could be related to brain-specific bioaccumulation of PFASs in East Greenland polar bears. Nine brain regions from nine polar bears were analyzed for enzyme activity (monoamine oxidase (MAO), acetylcholinesterase (AChE) and glutamine synthetase (GS)) and receptor density (dopamine-2 (D2), muscarinic cholinergic (mAChR) and gamma-butyric acid type A (GABA-A)) along with PFSA and PFCA concentrations. Average brain ∑PFSA concentration was 25ng/g ww where PFOS accounted for 91%. Average ∑PFCA concentration was 88ng/g ww where PFUnDA, PFDoDA and PFTrDA combined accounted for 79%. The highest concentrations of PFASs were measured in brain stem, cerebellum and hippocampus. Correlative analyses were performed both across and within brain regions. Significant positive correlations were found between PFASs and MAO activity in occipital lobe (e.g. ∑PFCA; rp=0.83, p=0.041, n=6) and across brain regions (e.g. ∑PFCA; rp=0.47, p=0.001, ∑PFSA; rp=0.44, p>0.001; n=50). GABA-A receptor density was positively correlated with two PFASs across brain regions (PFOS; rp=0.33, p=0.02 and PFDoDA; rp=0.34, p=0.014; n=52). Significant negative correlations were found between mAChR density and PFASs in cerebellum (e.g. ∑PFCA; rp=-0.95, p=0.013, n=5) and across brain regions (e.g. ∑PFCA; rp=-0.40, p=0.003, ∑PFSA; rp=-0.37, p=0.007; n=52). AChE activity and D2 density were negatively correlated with single PFCAs in several brain regions, whereas GS activity was positively correlated with PFASs primarily in occipital lobe. Results from the present study support the hypothesis that PFAS concentrations in polar bears from East Greenland have exceeded the threshold limits for neurochemical alterations. It is not known whether the observed alterations in neurochemical signaling are currently having negative effects on neurochemistry in East Greenland polar bears. However given the importance of these systems in cognitive processes and motor function, the present results indicate an urgent need for a better understanding of neurochemical effects of PFAS exposure to wildlife.

Accumulation and potential health effects of organohalogenated compounds in the arctic fox (Vulpes lagopus)--a review

This review addresses biological effects of anthropogenic organohalogenated compounds in the arctic fox (Vulpes lagopus). When considering the current levels, spatial and tissue distributions of selected organic pollutants in arctic fox subpopulations, especially the Svalbard based populations accumulate high levels. The dominating contaminant groups are the polychlorinated biphenyls (PCBs) and chlordanes (CHLs), which reach high levels in adipose tissues, adrenals and liver. Recent controlled exposure studies on domesticated arctic fox and Greenland sledge dogs, show adverse health effects associated with OC concentrations lower than those measured in free-ranging populations. This indicates that especially populations at Svalbard may be at risk of experiencing OC related effects. The arctic fox as such may be an overlooked species in the Arctic Monitoring and Assessment Programs and it would add further information about pollution in the Arctic to include this species in the monitoring program.

Comparative hepatic in vitro depletion and metabolite formation of major perfluorooctane sulfonate precursors in Arctic polar bear, beluga whale, and ringed seal

Perfluorooctane sulfonate (PFOS) has been reported to be among the most concentrated persistent organic pollutants in Arctic marine wildlife. The present study examined the in vitro depletion of major PFOS precursors, N-ethyl-perfluorooctane sulfonamide (N-EtFOSA) and perfluorooctane sulfonamide (FOSA), as well as metabolite formation using an assay based on enzymatically viable liver microsomes for three top Arctic marine mammalian predators, polar bear (Ursus maritimus), beluga whale (Delphinapterus leucas), and ringed seal (Pusa hispida), and in laboratory rat (Rattus rattus) serving as a general mammalian model and positive control. Rat assays showed that N-EtFOSA (38 nM or 150 ng mL(-1)) to FOSA metabolism was >90% complete after 10 min, and at a rate of 23 pmol min(-1) mg(-1) protein. Examining all species in a full 90 min incubation assay, there was >95% N-EtFOSA depletion for the rat active control and polar bear microsomes, ∼65% for ringed seals, and negligible depletion of N-EtFOSA for beluga whale. Concomitantly, the corresponding in vitro formation of FOSA from N-EtFOSA was also quantitatively rat≈polar bear>ringed seal>>>beluga whale. A lack of enzymatic ability and/or a rate too slow to be detected likely explains the lack of N-EtFOSA to FOSA transformation for beluga whale. In the same assays, the depletion of the FOSA metabolite was insignificant (p>0.01) and with no concomitant formation of PFOS metabolite. This suggests that, in part, a source of FOSA is the biotransformation of accumulated N-EtFOSA in free-ranging Arctic ringed seal and polar bear.

In vitro metabolic formation of perfluoroalkyl sulfonamides from copolymer surfactants of pre- and post-2002 scotchgard fabric protector products

Currently there is a scientific debate on whether fluorinated polymers (or copolymers) are a source, as a result of their degradation and subsequent formation, of perfluorinated carboxylic acids (PFCAs) and perfluorinated alkanesulfonates (PFSAs). The present study investigated whether commercially available fluorinated surfactants, such as Scotchgard fabric protector (3M Company), can be metabolically degraded, using a model microsomal in vitro assay (Wistar-Han rats liver microsomes), and with concomitant formation of PFCAs, PFASs, and/or their precursors. The results showed that the main in vitro metabolite from the pre-2002 product was perfluorooctane sulfonamide (FOSA), and coincident with the detection of the major fabric protector components, which contains the N-ethyl-perfluorooctanesulfonyl chemical moiety (C8F17SO2N(C2H5)-); the main in vitro metabolite of the post-2002 product was perfluorobutane sulfonamide (FBSA), which was coincident with the detection of the major fabric protector components, and contains the N-methyl-perfluorobutanesulfonyl chemical moiety (C4F9SO2N(CH3)-). FOSA or FBSA metabolite concentrations increased over the 0-60 min microsomal incubation period. However, concentrations of their small molecule precursors such as alkylated FOSAs or FBSAs were not detectable (<LODs) in these fabric protector original standard solutions. Thus, the FOSA or FBSA metabolites were derived from the copolymer product itself rather than nonreacted reagents in the Scotchgard products. This result is consistent with reports of high concentrations of PFASs detected in the plasma of persons in households where Scotchgard products are heavily used.

Fetal exposure to perfluorinated compounds and attention deficit hyperactivity disorder in childhood

Background

The association between exposure to perfluorinated compounds (PFCs) and attention deficit hyperactivity disorder (ADHD) diagnosis has been sparsely investigated in humans and the findings are inconsistent.

Objectives

A matched case-control study was conducted to investigate the association between fetal exposure to PFCs and ADHD diagnosis in childhood.

Methods

The study base comprised children born in Malmö, Sweden, between 1978 and 2000 that were followed up until 2005. Children with ADHD (n = 206) were identified at the Department of Child and Adolescent Psychiatry. Controls (n = 206) were selected from the study base and were matched for year of birth and maternal country of birth. PFC concentrations were measured in umbilical cord serum samples. The differences of the PFC concentrations between cases and controls were investigated using Wilcoxon's paired test. Possible threshold effects (above the upper quartile for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and above limit of detection [LOD] for perfluorononanoic acid (PFNA)) were evaluated by conditional logistic regression.

Results

The median umbilical cord serum concentrations of PFOS were 6.92 ng/ml in the cases and 6.77 ng/ml in the controls. The corresponding concentrations of PFOA were 1.80 and 1.83 ng/ml. No associations between PFCs and ADHD were observed. Odds ratios adjusted for smoking status, parity, and gestational age were 0.81 (95% confidence interval [CI] 0.50 to 1.32) for PFOS, 1.07 (95% CI 0.67 to 1.7) for PFOA, and 1.1 (95% CI 0.75 to 1.7) for PFNA.

Conclusions

The current study revealed no support for an association between fetal exposure to PFOS, PFOA, or PFNA and ADHD.

Linear and branched perfluorooctane sulfonate (PFOS) isomer patterns differ among several tissues and blood of polar bears

Perfluorooctane sulfonate (PFOS) is a globally distributed persistent organic pollutant that has been found to bioaccumulate and biomagnify in aquatic food webs. Although principally in its linear isomeric configuration, 21-35% of the PFOS manufactured via electrochemical fluorination is produced as a branched structural isomer. PFOS isomer patterns were investigated in multiple tissues of polar bears (Ursus maritimus) from East Greenland. The liver (n = 9), blood (n = 19), brain (n = 16), muscle (n = 5), and adipose (n = 5) were analyzed for linear PFOS (n-PFOS), as well as multiple mono- and di-trifluoromethyl-substituted branched isomers. n-PFOS accounted for 93.0 ± 0.5% of Σ-PFOS isomer concentrations in the liver, whereas the proportion was significantly lower (p<0.05) in the blood (85.4 ± 0.5%). Branched isomers were quantifiable in the liver and blood, but not in the brain, muscle, or adipose. In both the liver and blood, 6-perfluoromethylheptane sulfonate (P6MHpS) was the dominant branched isomer (2.61 ± 0.10%, and 3.26 ± 0.13% of Σ-PFOS concentrations, respectively). No di-trifluoromethyl-substituted isomers were detectable in any of the tissues analyzed. These tissue-specific isomer patterns suggest isomer-specific pharmacokinetics, perhaps due to differences in protein affinities, and thus differences in protein interactions, as well transport, absorption, and/or metabolism in the body.