Perfluoroalkyl Substances (PFASs) in Marine Mammals from the South China Sea and Their Temporal Changes 2002-2014: Concern for Alternatives of PFOS?

Per- and polyfluoroalkyl substances (PFAS), trace elements and life history parameters of mass-stranded common dolphins (Delphinus delphis) in New Zealand

Profiles of 33 PFAS analytes and 12 essential and non-essential trace elements were measured in livers of stranded common dolphins (Delphinus delphis) from New Zealand. PFAS concentrations reported were largely comparable to those measured in other marine mammal species globally and composed mostly of long-chain compounds including perfluorooctanesulfonic acid (PFOS), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA) and perfluorooctanesulfonamide (FOSA). PFAS profiles did not vary significantly by location, body condition, or life history. Notably, significant positive correlations were observed within respective PFAS and trace elements. However, only negative correlations were evident between these two contaminant types, suggesting different exposure and metabolic pathways. Age-associated concentrations were found for PFTrDA and four trace elements, i.e. silver, mercury, cadmium, selenium, indicating differences in the bioaccumulation biomagnification mechanisms. Overall, our results contribute to global understanding of accumulation of PFAS by offering first insights of PFAS exposure in cetaceans living within South Pacific Australasian waters.

Occurrence, profiles, and ecotoxicity of poly- and perfluoroalkyl substances and their alternatives in global apex predators: A critical review

Certain poly- and perfluoroalkyl substances (PFASs) exhibit significant bioaccumulation/biomagnification behaviors in ecosystems. PFASs, such as perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS) and related precursors, have elicited attention from both public and national regulatory agencies, which has resulted in worldwide restrictions on their production and use. Apex predators occupy the top trophic positions in ecosystems and are most affected by the biomagnification behavior of PFASs. Meanwhile, the long lifespans of apex predators also lead to the high body burden of PFASs. The high body burden of PFASs might be linked to adverse health effects and even pose a potential threat to their reproduction. As seen in previous reviews of PFASs, knowledge is lacking between the current stage of the PFAS body burden and related effects in apex predators. This review summarized PFAS occurrence in global apex predators, including information on the geographic distribution, levels, profiles, and tissue distribution, and discussed the trophic transfer and ecotoxicity of PFASs. In the case where legacy PFASs were restricted under international convention, the occurrence of novel PFASs, such as 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) and perfluoroethylcyclohexane sulfonate (PFECHS), in apex predators arose as an emerging issue. Future studies should develop an effective analytical method and focus on the toxicity and trophic transfer behavior of novel PFASs.

Per and polyfluoroalkyl substances (PFAS) at high concentrations in neonatal Australian pinnipeds

Per and polyfluorinated substances (PFAS) exposure was investigated in Australian pinnipeds. Concentrations of 16 PFAS were measured in the livers of Australian sea lion (Neophoca cinerea), Australian fur seal (Arctocephalus pusillus doriferus) and a long-nosed Fur Seal (Arctocephalus forsteri) pup sampled between 2017 and 2020 from colonies in South Australia and Victoria. Findings reported in this study are the first documented PFAS concentrations in Australian pinnipeds. Median and observed range of values in ng/g wet weight were highest for perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) in the liver of N. cinerea (PFOS = 7.14, 1.00-16.9; PFOA = 2.73, 0.32-11.2; PFNA = 2.96, 0.61-8.22; n = 28), A. forsteri (PFOS = 15.98, PFOA = 2.02, PFNA = 7.86; n = 1) and A. p. doriferus (PFOS = 27.4, 10.5-2119; PFOA = 0.98, 0.32-52.2; PFNA = 2.50, 0.91-44.2; n = 20). PFAS concentrations in A. p. doriferus pups were significantly greater (p < 0.05) than in N. cinerea pups for all PFAS except PFOA and were of similar magnitude to those reported in northern hemisphere marine animals. These results demonstrate exposure differences in both magnitude and PFAS profiles for N. cinerea in South Australia and A. p. doriferus in Victoria. This study reports detectable PFAS concentrations in Australian pinniped pups indicating the importance of maternal transfer of these toxicants. As N. cinerea are endangered and recent declines in pup production has been reported for A. p. doriferus at the colony sampled, investigation of potential health impacts of these toxicants on Australian pinnipeds is recommended.

Antagonistic interaction between perfluorobutanesulfonate and probiotic on lipid and glucose metabolisms in the liver of zebrafish

Perfluorobutanesulfonate (PFBS) and probiotic bacteria can interact to induce hepatic hypertrophy. However, the molecular events occurring in the hypertrophic liver are still unknown. Therefore, we performed this follow-up study using adult zebrafish that were exposed for 40 days to 0 and 10 μg/L PFBS, with or without dietary supplementation of probiotic Lactobacillus rhamnosus. After PFBS or/and probiotic exposures, proteome perturbation, histological pathogenesis and glucose metabolism were investigated in the livers. Proteomic analysis showed potent intervention of PFBS or/and probiotic with hepatic functions. PFBS single exposure caused marked disturbances in lipid metabolisms, which may underlie the severe vacuolization in male liver. The addition of probiotic alleviated the lipid metabolic disorders of PFBS. Furthermore, probiotic supplementation enhanced ATP energy production using glucose in mitochondrial respiratory chain of male fish. However, PFBS alone caused remarkable increase in blood glucose level (by 2.5-fold relative to the control), underlining the onset of hyperglycemia symptom. In contrast, the liver of male fish from the coexposure group functioned appropriately, which immediately increased insulin levels by 2.2-fold to reduce the glucose accumulation in blood. In female liver, PFBS alone significantly decreased the blood glucagon concentration by 2.9-fold. The deficiency of glucagon hormone consequently contributed to the accumulation of glycogen (3.2-fold) therein. Vigorous antagonistic interaction between PFBS and probiotic was noted with respect to glucose metabolism, which restored ATP, glucose, glycogen and glucagon to the control levels. Overall, the present study finds that probiotic L. rhamnosus is efficient to mitigate the metabolic disorders of PFBS on lipid and glucose, highlighting the potential values of probiotic bacteria to protect the aquatic ecosystem.

Probiotic Lactobacillus rhamnosus modulates the impacts of perfluorobutanesulfonate on oocyte developmental rhythm of zebrafish

Potent interaction between probiotic bacteria and perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, was previously reported on reproduction of zebrafish. However, the underlying mechanism is largely unexplored. In this regard, the present study continued to focus on the interactive modes between probiotics and PFBS. Adult zebrafish were exposed for 28 days to 0 and 10 μg/L PFBS with or without dietary supplementation of probiotic Lactobacillus rhamnosus. With the relevance to fecundity outcome, a suite of reproductive indices at transcriptional, hormonal, proteomic and histological levels of biological organization were measured herein. The fecundity monitoring results showed that probiotic additive shifted the impacts of PFBS on egg spawn, gradually approaching the control level. Based on ovary histological observation, oocyte growth was significantly promoted by probiotics or/and PFBS exposures, while the presence of probiotic bacteria partially antagonized the effects of PFBS on oocyte growth. The combination of probiotics and PFBS increased the concentration of maturation inducing hormones in ovary. Despite the enhanced hormonal signals, gene transcriptions of ovarian local auto/paracrine factors were consistently decreased in all exposure groups, suggesting the blocked transition from oocyte growth phase toward oocyte maturation phase. Ovary proteomic analysis found that PFBS exposure with or without probiotic bacteria mainly affected the RNA metabolic processes, although the addition of probiotics exerted extra influences on amino acid metabolism. Overall, the present study provided more mechanistic evidence about the interactive behavior between probiotic bacteria and PFBS pollutant. Feed additive of probiotic bacteria modulated the impacts of PFBS on egg production rhythm through oocyte growth and maturation phases.

Acute Toxicity and Transgenerational Effects of Perfluorobutane Sulfonate on Caenorhabditis elegans

Perfluorobutane sulfonate (PFBS), due to its increasing use as an alternative to perfluooctane sulfonate (PFOS), is widely detected in humans and the environment, necessitating the evaluation of its potential ecotoxicological risk. We assessed the toxicity and bioaccumulation potential of PFBS in Caenorhabditis elegans, using lethality, locomotion, reproduction, life span, growth, and chemotactic behavior as the effect parameters. In addition, a total of 6 generations of exposed parent animals were monitored for locomotion, brood, and life span behaviors. Life span and brood size were significantly reduced in parent nematodes (P0) following exposure to ≥0.1 mM PFBS, but these negative effects did not transfer to the progeny. Although there was no remarkable effect on reproduction and life span in parent worms exposed to ≤0.01 mM PFBS, multigenerational exposure at 0.0005 mM significantly affected the F4 and F5 progeny. Furthermore, 0.01 to 2.0 mM of PFBS substantially retarded the locomotion behavior of P0 worms. At higher concentrations such as 1.0 mM, this negative effect on locomotion was transferred to the next generation (F1) but later recovered from F2 progeny onward. Our findings demonstrate for the first time that chronic exposure to PFBS at higher concentrations can cause behavioral toxicity and could be transferred to the progeny. These findings have significant implications for the environmental risk assessment of PFBS. Environ Toxicol Chem 2021;40:1973-1982. © 2021 SETAC.

Per- and polyfluoroalkyl substances and their alternatives in black-tailed gull (Larus crassirostris) eggs from South Korea islands during 2012-2018

The temporal and spatial trends of sixteen per- and polyfluoroalkyl substances (PFAS) and their three alternatives, chlorinated polyfluoroalkyl ether sulfonic acid (F-53B), hexafluoropropylene oxide dimer acid (GenX), and dodecafluoro-3H-4,8-dioxanonanoate (ADONA) in whole eggs of black-tailed gulls from two South Korean islands, Baengnyeongdo (BLD) and Hongdo (HD), were investigated during 2012-2018. A total of 16 analyzed compounds were detected at concentrations of 21.3-47.8 ng/g ww in BLD and 11.2-40.0 ng/g ww in HD. Meanwhile, the mean levels of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were detected at 6.92 ± 4.72 ng/g ww and 0.674 ± 0.993 ng/g ww, respectively. In particular, F-53B, a major alternative to PFOS was detected in each year of the study period with a level of up to 6.66 ng/g ww in all egg samples. Significant increasing temporal trends were observed for PFOS, perfluorononanoic acid (PFNA) and one alternative (F-53B) during the investigated period suggesting continuous use or accumulation of these in the Korean environment. Moreover, distinctive spatial distribution patterns such as a significantly higher F-53B level in HD and an increased PFAS (< C11) in BLD were also observed.

Shift in skin microbiota and immune functions of zebrafish after combined exposure to perfluorobutanesulfonate and probiotic Lactobacillus rhamnosus

Dysbiosis of fish skin microbiome and immunity by environmental pollutants are rarely studied in toxicological research in spite of their importance for fish health. In the present study, adult zebrafish were exposed to 0 and 10 μg/L of perfluorobutanesulfonate (PFBS) for 40 days, with or without the supplementation of probiotic Lactobacillus rhamnosus, with objectives to explore the interaction between PFBS pollutant and probiotic bacteria on skin mucosal microbiota and immune response. Amplicon sequencing analysis found that PFBS alone significantly disturbed the microbial community composition and abundance on the skin, favoring the growth of stress-tolerant bacteria (e.g., Deinococcus and Enhydrobacter genera). However, the administration of probiotic inhibited the dysbiosis of PFBS and shaped the skin microbiome in the combined exposure group. PFBS single exposure also promoted the production of mucus on the skin of male zebrafish, which may be related to the growth of Limnobacter bacteria. In contrast, probiotic supplements remarkably improved the immune functions in male skin mucus from the combined group, as evidenced by the consistent increases in lysozyme activity, immunoglobulin concentrations and peroxidase activity. Overall, the present study provides the first clue about the singular and combined effects of PFBS and probiotic on skin microbiota and immunity, highlighting the beneficial action of probiotic L. rhamnosus against PFBS stress.

Interaction between probiotic additive and perfluorobutanesulfonate pollutant on offspring growth and health after parental exposure using zebrafish

Perfluorobutanesulfonate (PFBS) pollutant and probiotic bacteria can interact to affect the reproductive outcomes of zebrafish. However, it is still unexplored how the growth and health of offspring are modulated by the combination of PFBS and probiotic. In the present study, adult zebrafish were exposed to 0 and 10 μg/L PFBS for 40 days, with or without dietary supplementation of probiotic Lactobacillus rhamnosus. After parental exposure, the development, growth and viability of offspring larvae were examined, with the integration of molecular clues across proteome fingerprint, growth hormone/insulin-like growth factor (GH/IGF) axis, calcium homeostasis, hypothalamic-pituitary-adrenal (HPA) axis and nutrient metabolism. Parental probiotic supplementation significantly increased the body weight and body length of offspring larvae. Despite the spiking of PFBS, larvae from the combined exposure group still had longer body length. RNA processing and ribosomal assembly pathways may underlie the enhancement of offspring growth by probiotic bacteria. However, the presence of PFBS remarkably increased the concentrations of cortisol hormone in offspring larvae as means to cope with the xenobiotic stress, which required more energy production. As evidenced by the proteomic analysis, the addition of probiotic bacteria likely alleviated the energy metabolism disorders of PFBS, thus allocating more energy for the larval offspring growth from the combined group. It was noteworthy that multiple molecular disturbances caused by PFBS were antagonized by probiotic additive. Overall, the present study elucidated the intergenerational interaction between PFBS and probiotic on offspring growth and health after parental exposure.

Perfluorooctanoic acid (PFOA) removal by flotation with cationic surfactants

Perfluorooctanoic acid (PFOA) was separated and recovered using a foam flotation process aided by cationic surfactants. The PFOA removal efficiency was in the following decreasing order: OTAB (C₈TAB) > DTAB (C₁₀TAB) > CTAB (C₁₆TAB) > TBAB, which indicates that cationic surfactants with an alkyl chain that had a similar length to that of PFOA had higher affinities to PFOA. PFOA removal slightly decreased with increasing ionic strength of the surfactant but did not change with the pH. PFOA could be completely removed in 20 min with 1.25 mM of OTAB in actual wastewater. The energy yield value of foam flotation with a cationic surfactant was much higher than those of other methods, which means that using foam flotation with a cationic surfactant as the collector is a simple, fast, and energy-efficient method to separate and recover PFOA from dilute water solutions.

Suspect and Nontarget Screening Revealed Class-Specific Temporal Trends (2000-2017) of Poly- and Perfluoroalkyl Substances in St. Lawrence Beluga Whales

The global use of >3000 per- and polyfluoroalkyl substances (PFASs) has given rise to chemical regulatory action. However, limited information exists regarding current and historical emissions for the majority of PFASs under currently implemented regulations. This study employed suspect and nontarget screening to examine the temporal trends of legacy and unregulated PFASs in liver of the endangered beluga whale (Delphinapterus leucas) population from the St. Lawrence Estuary in Canada collected from 2000 to 2017. A suite of 54 PFASs were tentatively identified, and were grouped into nine structurally distinct classes. Single-hydrogenated perfluoro carboxylic acids (H-PFCAs), single-hydrogenated sulfonamides (H-Sulfonamides), as well as other select sulfonamides were detected for the first time in wildlife. Greater concentrations of the majority of PFASs were determined in newborns and juveniles than in adults, suggesting effective placental and lactational transfer of PFASs. Legacy per- and polyfluoroalkyl acids and perfluorooctane sulfonamide in beluga whale liver were found to significantly decrease in concentration between 2000 and 2017, while unregulated short-chain PFAS alternatives, H-PFCAs, and odd-chain FTCAs were found to increase over time. The implementation of suspect and nontarget screening revealed class-specific temporal trends of PFASs in SLE beluga whales, and supported continuous emissions of unregulated PFASs into the environment.

Comparison of zebrafish in vitro and in vivo developmental toxicity assessments of perfluoroalkyl acids (PFAAs)

Perfluoroalkyl acids (PFAAs) are persistent environmental contaminants that are associated with various adverse health outcomes. Perfluorooctanoic acid (PFOA) is one of the most prominently detected PFAAs in the environment, which is now replaced with shorter chain carbon compounds including perfluorohexanoic acid (PFHxA) and perfluorobutyric acid (PFBA). The aim of this study was to compare the toxicity of four PFAAs as a function of chain length and head group (carboxylate versus sulfonate) with in vitro and in vivo zebrafish assessments, which were subsequently compared to other cell and aquatic models. Mortality rate increased with chain length (PFOA > PFHxA ≫ PFBA) in both whole embryo/larvae and embryonic cell models. The sulfonate group enhanced toxicity with perfluorobutane sulfonate (PFBS) showing higher toxicity than PFBA and PFHxA in both larvae and cells. Toxicity trends were similar among different aquatic models, but sensitivities varied. Discrepancies with other zebrafish studies were confirmed to be associated with a lack of neutralization of acidic pH of dosing solutions in these other investigations, demonstrating the need for rigor in reporting pH of exposure solutions in all experiments. The zebrafish embryonic cell line was also found to be similar to most other cell lines regardless of exposure length. Overall, results agree with findings in other cell lines and organisms where longer chain length and sulfonate group increase toxicity, except in investigations not neutralizing the exposure solutions for these acidic compounds.

Target, Nontarget, and Suspect Screening and Temporal Trends of Per- and Polyfluoroalkyl Substances in Marine Mammals from the South China Sea

Per- and polyfluoroalkyl substances (PFASs) have been manufactured and widely used for over 60 years. Currently, there are thousands of marketed PFASs, but only dozens of them are routinely monitored. This work involved target, nontarget, and suspect screening of PFASs in the liver of Indo-Pacific humpback dolphin (Sousa chinensis) and finless porpoise (Neophocaena phocaenoides), two resident marine mammals in the South China Sea, stranded between 2012 and 2018. Among the 21 target PFASs, perfluorooctane sulfonate and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) predominated in the samples, accounting for 46 and 30% of the total PFASs, respectively. Significantly higher total target PFAS concentrations (p < 0.05) were found in dolphin liver samples [3.23 × 10³ ± 2.63 × 10³ ng/g dry weight (dw)] than in porpoise liver samples (2.63 × 10³ ± 1.10 × 10³ ng/g dw). Significant increasing temporal trends (p < 0.05) were found in the concentrations of two emerging PFASs, perfluoroethylcyclohexane sulfonate and 2,3,3,3-tetrafluoro-2-propanoate in porpoises, indicating increasing pollution by these emerging PFASs. Forty-four PFASs from 9 classes were additionally identified by nontarget and suspect screening, among which 15 compounds were reported for the first time in marine mammals. A primary risk assessment showed that the emerging PFAS 6:2 Cl-PFESA could have possible adverse effects in terms of reproductive injury potential on most of the investigated cetaceans.

Emerging and legacy per- and polyfluoroalkyl substances in house dust from South China: Contamination status and human exposure assessment

Our study investigated a large variety of per- and polyfluoroalkyl substances (PFASs) in house dust collected from Guangzhou, South China during 2015-2018. The perfluorobutane sulfonic acid (PFBS) exhibited the highest median concentration (17.6 ng/g), followed by linear perfluorooctanoic acid (L-PFOA; 4.8 ng/g), linear perfluorooctane sulfonic acid (L-PFOS; 4.2 ng/g), 6:2 fluorotelomer phosphate diester (6:2 diPAP; 3.4 ng/g), perfluorodecanoic acid (PFDA; 1.2 ng/g) and perfluoroundecanoic acid (PFUdA; 1.2 ng/g), and 6:2 chlorinated perfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA; 1.1 ng/g). Total concentrations of PFASs (median: 53 ng/g) were generally within the 25-50 percentile of the concentration range reported in global studies. However, our samples exhibited composition profiles different from those reported in many other regions. Analysis based on this and previous studies revealed that the compositions in house dust from East Asia, North America, and Europe exhibit a region-specific pattern. This may indicate region-specific market demands, application patterns, as well as associated human exposure risks. Exploration of dwelling characterizations suggested that renovation history appeared to be a significant factor influencing PFAS concentrations in house dust, although other factors may exist and play a role. Estimation of daily intakes via dust ingestion and dermal contact indicates low exposure risks from these two pathways. However, the PFAS chemical-specific biological effects, possible mixture effects, as well as additional exposure pathways, imply that the risk from indoor PFAS exposure should not be overlooked.

Calibration of organic-diffusive gradients in thin films (o-DGT) passive samplers for perfluorinated alkyl acids in water

The application of the organic-diffusive gradients in thin films (o-DGT) passive sampling technique for the monitoring of per- and polyfluoroalkyl substances (PFAS) in the environment is still limited. Six common PFAS with different chain lengths were evaluated in water by o-DGT. Measured diffusion coefficients (D) in agarose and polyacrylamide diffusive gels ranged from 4.55-8.63 × 10^-6 cm² s^-1 and 3.85-7.00 × 10^-6 cm² s^-1 at 23 °C, respectively. Experimental sampling rates (Rs) for both agarose- and polyacrylamide-WAX sampler configurations were within 22% relative error of D-based Rs for four of the PFAS. Larger differences for perfluorobutanesulfonic acid (PFBS) and perfluoroundecanoic acid (PFUnDA) ranged from 36% to 56%. In general, in-situ Rs can be predicted using measured D-values for perfluorinated alkyl acids. The mass accumulation of six PFAS in two o-DGT configurations was linear over 21 days (R² ≥ 0.97). Diffusion and uptake of o-DGT depended on the gel type and specific PFAS. Field demonstrations of o-DGT with WAX and HLB binding gels and polyacrylamide diffusive gels (not prone to biodegradation) found 0.3-19.5 ng L^-1 of PFAS in rivers near industrial areas around Guangzhou and Foshan, China, with no apparent differences between the two co-deployed samplers. This study demonstrates that the configurations of o-DGT tested provide a cost-effective monitoring tool for measuring perfluorinated alkyl acids in aquatic systems, in particular the four PFAS for which reasonable correlations were observed.

Fish and crustacean biodiversity in an outer maritime estuary of the Pearl River Delta revealed by environmental DNA

Understanding the faunal community structure in the estuary would be crucial in assessing the health of the ecosystem. The poor visibility in the estuarine area due to the outflow from the Pearl River hinders the conventional visual census in assessing the megafaunal biodiversity. In this study, the fish and crustacean biodiversity of Hong Kong's western waters, i.e. the outer maritime estuary of the PRD, were studied through the metabarcoding of environmental DNA (eDNA). eDNA from the seawater and sediment samples was extracted from five sites in the region. After testing the performance of two genetic markers, amplicons of the cytochrome oxidase I, amplified by polymerase chain reaction, were subjected to Illumina high-throughput sequencing (MiSeq) analysis. A total of 22 fish species from 17 families and 34 crustacean species from 27 families were identified by blasting the sequences against the NCBI GenBank database, demonstrating segregation between samples from different sites. This study provides insight on the detail distribution of fish assembly in PRD, when compared with a previous eDNA study in the inner brackish PRD.

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.

Electrocatalytic degradation of perfluoroocatane sulfonate (PFOS) on a 3D graphene-lead dioxide (3DG-PbO2) composite anode: Electrode characterization, degradation mechanism and toxicity

In this work, a three-dimension grapnene-PbO₂ (3DG-PbO₂) composite anode was prepared using coelectrodeposition technology for electrocatalytic oxidation of perfluorooctane sulfonate (PFOS). The effect of 3DG on the surface morphology, structure and electrocatalytic activity of PbO₂ electrode was investigated. The results indicated that the 3DG-PbO₂-0.08 anode (3DG concentration in electrodeposition solution was 0.08 g L^-1) possessed the best electrocatalytic activity due to its stronger ·OH radicals generation capacity, more active sites and smaller charge-transfer resistance. The degradation rate constant of PFOS on 3DG-PbO₂-0.08 anode was 2.33 times than that of pure PbO₂ anode. Additionally, the by-products formed in electrocatalytic degradation of PFOS were identified and a PFOS degradation pathway was proposed accordingly, which was dominated by the dissociation of -CF₂- groups via the attack of ·OH radicals. Finally, the toxicity evolution of degradation solution was examined to evaluate the ecological risk of electrocatalytic oxidation of PFOS by acute toxicity assays to zebrafish embryos.

Developing interim water quality criteria for emerging chemicals of concern for protecting marine life in the Greater Bay Area of South China

This study aimed to establish marine water quality criteria (MWQC) for emerging chemicals of concern (ECCs) for protecting aquatic life in the Greater Bay Area (GBA) of South China. Despite the frequent occurrence and elevated concentrations of these ECCs in the GBA, there is a lack of regional MWQC for these contaminants. We screened 21 common ECCs that were classified into the following six groups: (1) new persistent organic contaminants; (2) brominated flame retardants; (3) perfluoroalkyl and polyfluoroalkyl substances; (4) pharmaceutically active compounds (PhACs); (5) plasticizers; and (6) personal care products. Globally, MWQC for PhACs remain largely unavailable despite their increasing occurrence in marine environments. Using an integrative scientific approach, we derived interim MWQC for the GBA with specific protection goals. The approach described herein can be applied for the derivation of MWQC for ECCs and the establishment of guidelines for ecological risk assessment in the GBA and other regions.

Binary exposure to hypoxia and perfluorobutane sulfonate disturbs sensory perception and chromatin topography in marine medaka embryos

Perfluorobutane sulfonate (PFBS), an environmental pollutant of emerging concern, is previously shown to dynamically interact with hypoxia on aquatic developmental toxicities. However, the molecular mechanisms underlying the interaction remain unknown. In this follow-up study, marine medaka embryos were exposed to 0 and 3.3 mg/L of PFBS under normoxia (6.9 mg/L) or hypoxia (1.7 mg/L) condition till 15 days post-fertilization. High-throughput transcriptomic sequencing was employed to filter differentially expressed genes and provide mechanistic insight into interactive action between hypoxia and PFBS. The results showed that hypoxia alone and the coexposure paradigm were similarly potent to modify transcriptional profiles, with the majority of genes significantly down-regulated. In contrast, transcriptional toxicity of PFBS was relatively milder. Functional annotation analyses found that hypoxia and coexposure groups mainly impacted phototransduction signaling by decreasing the transcriptions of cyclic nucleotide-gated (CNG) cation channels and retinol transport genes. However, this study demonstrated the first toxicological evidence that toxic effects of PFBS targeted the perception of chemical stimulus through olfactory and gustatory receptors. The addition of PFBS moderately exacerbated the toxic actions of hypoxia, which largely shaped the transcriptional pattern of coexposure group. In addition, gene interactive networks were constructed for hypoxia and coexposure groups, underlining the increased chromatin deacetylation and methylation to epigenetically repress genome-wide transcriptional initiation. Overall, PFBS and hypoxia interact to interrupt the embryonic development of sensory systems, which may compromise the individual fitness and survival, especially during early life stages when precocious perception of food and escape from predators are essential.

Probiotic modulation of perfluorobutanesulfonate toxicity in zebrafish: Disturbances in retinoid metabolism and visual physiology

Perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb gut microbiota, retinoid metabolism and visual signaling in teleosts, while probiotic supplementation can shape gut microbial community to improve retinoid absorption. However, it remains unknown whether probiotic bacteria can modulate the toxicities of PFBS on retinoid metabolism and visual physiology. In the present study, adult zebrafish were exposed for 28 days to 0, 10 and 100 μg/L PFBS, with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic was examined regarding retinoid dynamics (intestine, liver and eye) and visual stimuli transmission. PFBS single exposures remarkably inhibited the absorption of retinyl ester in female intestines, which were, however, restored by probiotic to normal status. Although coexposure scenarios markedly increased the hepatic storage of retinyl ester in females, mobilization of retinol was reduced in livers by single or combined exposures regardless of sex. In the eyes, transport and catalytic conversion of retinol to retinal and retinoic acid were interrupted by PFBS alone, which were efficiently antagonized by probiotic presumably through an indirect action. In response to the availability of retinal chromophore, transcriptions of opsins and arrestin genes were altered adaptively to control visual perception and termination. Neurotransmission across retina circuitry was changed accordingly, centering on epinephrine and norepinephrine. In summary, the present study found the efficient modulation of probiotic on retinoid metabolic disorders of PFBS pollution, which subsequently impacted visual signaling. A future work is warranted to provide mechanistic clues in retinoid interaction.

Review on perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the Chinese atmospheric environment

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been manufactured and used for over 50 years, and now are worldwide distributed in the environment. The atmospheric environment is the main compartment for PFASs to be transported and transformed, and relevant research has highlighted the global occurrence and impacts of atmospheric PFASs in ecosystems and human health. With the phasing-out and restriction of eight‑carbon chain-length (C8) PFASs in developed countries, China has become the largest producer of C8 PFASs since 2004. Subsequently, a number of studies on PFASs in the Chinese atmospheric environment have been conducted in the recent decade. This review documented twenty-eight studies on PFASs in Chinese outdoor air published to date. Methods of sampling, extraction, cleanup, and instrumental analysis were summarized for both ionic and neutral PFASs. Levels, compositions, and spatial distribution of PFASs from different areas in China (i.e. source, urban, and remote regions, and north versus south China) were compared and discussed. Leaves and tree barks were proposed as effective bioindicators to reflect the contamination status of atmospheric PFASs. Special attention can be given to non-target screening for future research directions.

Dietary administration of probiotic Lactobacillus rhamnosus modulates the neurological toxicities of perfluorobutanesulfonate in zebrafish

Perfluorobutanesulfonate (PFBS), an aquatic pollutant of emerging concern, is found to disturb the neural signaling along gut-brain axis, whereas probiotic additives have been applied to improve neuroendocrine function of teleosts. Both PFBS and probiotics can commonly target nervous system. However, whether and how probiotic bacteria can modulate the neurotoxicities of PFBS remain not explored. It is thus necessary to elucidate the probiotic modulation of PFBS neurotoxicity, which can provide implications to the application of probiotic bacteria in aquaculture industry. In the present study, adult zebrafish were exposed to 0, 10 and 100 μg/L PFBS with or without dietary administration of probiotic Lactobacillus rhamnosus. Interaction between PFBS and probiotic along gut-brain axis was examined, covering three dominant pathways (i.e., neurotransmission, immune response and hypothalamic-pituitary-adrenal (HPA) axis). The results showed that, compared to the single effects, PFBS and probiotic coexposure significantly altered the acetylcholinesterase activity and neurotransmitter profiles in gut and brain of zebrafish, with mild effects on neuronal integrity. Neurotransmitters closely correlated reciprocally in intestines, which, however, was distinct from the correlation profile in brains. In addition, PFBS and probiotic were combined to impact brain health through absorption of bacterial lipopolysaccharides and production of inflammatory cytokines. Relative to neurotransmission and immune signaling, HPA axis was not involved in the neurotoxicological interaction between PFBS and probiotic. Furthermore, it needs to point out that interactive modes between PFBS and probiotic varied a lot, depending on exposure concentrations, sex and toxic indices. Overall, the present study provided the first evidence that probiotic supplement could dynamically modulate the neurotoxicities of PFBS in teleost.

Parental exposure to perfluorobutane sulfonate disturbs the transfer of maternal transcripts and offspring embryonic development in zebrafish

Parental exposure to perfluorobutane sulfonate (PFBS), an aquatic pollutant of emerging concern, is previously found to impair the embryonic development of offspring. However, the impairing mechanisms remain to clarify. In the present study, adult zebrafish were exposed to 0, 10 and 100 μg/L PFBS for 28 d, after which disturbances in maternal transcript transfer and offspring embryogenesis were investigated. Prior to zygotic genome activation, high-throughput transcriptomic sequencing revealed that parental PFBS exposure significantly altered the transcript profile of maternal origin in offspring eggs, while toxic actions varied as a function of PFBS concentrations. In offspring eggs derived from 10 μg/L exposure group, differential transcripts were mainly associated with the histone-DNA interaction of nucleosome, which would modify the compacted chromatin configuration and accessibility of transcriptional factors to DNA sequences. In this regard, the timing of zygotic genome activation was presumably disrupted. Parental exposure to 100 μg/L PFBS primarily interrupted the maternal transfer of adherens junction transcripts, which was supposed to dysregulate the cell-cell adhesion during early embryo formation. Development and growth of offspring embryos were significantly compromised by parental PFBS exposure, as exemplified by higher mortality, delayed hatching, slower heart rate, reduced body weight and neurobehavioral disorders. Overall, the present study presented the first toxicological evidence about the disturbances of PFBS in maternal transcript transfer, although the inherent linkage between maternal transcript modifications and offspring development defects still needs future works to construct.

Non-target and suspect screening of per- and polyfluoroalkyl substances in Chinese municipal wastewater treatment plants

Wastewater treatment plant (WWTP) is one of the major sources of per- and polyfluoroalkyl substances (PFASs) to the aquatic environment. In this study, wastewater samples were collected from 17 WWTPs in 17 cities of China to investigate emerging PFASs in WWTPs. To comprehensively identify PFASs in the wastewater samples, an integrated suspect screening, homologue-based and fragment-based non-target screening method is proposed. Sixty-three PFASs from 13 classes (25 subclasses) were identified, including 14 legacy and 49 emerging PFASs, and this study is the first to report on 12 of these PFASs. We found that emerging PFASs concentration had a significantly positive correlation with the gross domestic product, indicating more substitution of legacy PFASs in the developed area of China. We also analyzed the removal of the 13 PFAS classes, and found that all discovered PFAS classes were not completely removed after the treatment process, whereas the class of perfluoroalkyl ether alcohols significantly increased. All of these results imply that the release of emerging or unknown PFASs from WWTPs is a universal but not negligible problem in China.

Perfluoroalkyl substances (PFASs) in special management sea areas of Korea: Distribution and bioconcentration in edible fish species

Thirteen PFASs in water (n = 58), sediment (n = 58) and edible fish samples (n = 81) collected from three special management sea areas of Korea including Gwangyang bay, Masan bay and Busan harbor in July 2018 were investigated. The mean PFASs concentration in water (ng/L) were in order Masan (5.09) > Busan (2.82) > Gwangyang (1.74). PFASs levels were found as the low concentration in sediment. The greatest total PFASs concentration in each fish tissue was found as 3.04 (ng/g ww) in a Japanese amberjack fish for muscle in Busan, 66.23 (ng/mL) in Japanese amberjack fish for blood in Masan and 125.03 (ng/g ww) flathead grey mullet in Busan bay. The BCF (L/kg) of PFDoDA was found as the highest in muscle of all species with values from 30,922 (grey mullet in Gwangyang) to 69,131 (grey mullet in Busan). PFDS was the highest BCF's PFASs (110,599 L/kg) in muscle which was found in Japanese amberjack in Busan bay.

Probiotic Modulation of Lipid Metabolism Disorders Caused by Perfluorobutanesulfonate Pollution in Zebrafish

To determine whether and how probiotic supplement can alter gut microbiota dysbiosis and lipid metabolism disorders caused by perfluorobutanesulfonate (PFBS), the present study exposed adult zebrafish to 0, 10, and 100 μg/L PFBS for 28 days, with or without dietary administration of probiotic Lactobacillus rhamnosus. Regarding intestinal health and gut microbiota, probiotic supplement altered the innate toxicities of PFBS, depending on exposure concentration and the sex of the fish. Lactobacillus genus correlated positively (P < 0.001; r > 0.5) with other beneficial bacteria in the gut microbiota, thereby indirectly regulating host metabolic activities. In female fish, the PFBS and probiotic combination enhanced fatty acid synthesis and β-oxidation, but mitigated the accumulation of cholesterol in the blood compared with PFBS single exposure, highlighting the benefits of the probiotic to host health. In male zebrafish, probiotic administration antagonized the PFBS-induced disturbances of bile acid metabolism, presumably via farnesoid X receptor signaling. However, coexposure to PFBS and probiotic caused significant accumulation of triglyceride in male livers (2.6-fold relative to the control), implying the induction of hepatic steatosis. Overall, the present study underlined the potential of probiotics to modulate gut microbial dysbiosis and lipid metabolism disorders caused by PFBS exposure, which could provide implications to the application of probiotics in aquaculture.

Per- and Polyfluoroalkyl Substances and Obesity, Type 2 Diabetes and Non-alcoholic Fatty Liver Disease: A Review of Epidemiologic Findings

Per- and polyfluoroalkyl substances, a group of fluoro-surfactants widely detected in the environment, wildlife and humans, have been linked to adverse health effects. A growing body of literature has addressed their effects on obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis. This review summarizes the brief historical use and chemistry of per- and polyfluoroalkyl substances, routes of human exposure, as well as the epidemiologic evidence for associations between exposure to per- and polyfluoroalkyl substances and the development of obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis. We identified 22 studies on obesity and 32 studies on diabetes, while only 1 study was found for non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis by searching PubMed for human studies. Approximately 2/3 of studies reported positive associations between per- and polyfluoroalkyl substances exposure and the prevalence of obesity and/or type 2 diabetes. Causal links between per- and polyfluoroalkyl substances and obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis, however, require further large-scale prospective cohort studies combined with mechanistic laboratory studies to better assess these associations.

Interaction between hypoxia and perfluorobutane sulfonate on developmental toxicity and endocrine disruption in marine medaka embryos

The co-occurrence of hypoxia and xenobiotics is extremely common in natural environments, highlighting the necessity to elicit their interaction on aquatic toxicities. In the present study, marine medaka embryos were exposed to various concentrations (nominal 0, 1, 3.3 and 10 mg/L) of perfluorobutane sulfonate (PFBS), an environmental pollutant of emerging concern, under either normoxia (6.9 mg/L) or hypoxia (1.7 mg/L) condition. After acute exposure till 15 days post-fertilization, single or combined toxicities of PFBS and hypoxia on embryonic development (e.g., mortality, hatching and heartbeat) and endocrine systems were investigated. Sex and thyroid hormones were measured by enzyme-linked immunosorbent assay. Transcriptional changes of endocrine genes were determined by quantitative real-time PCR assays. Co-exposure to 10 mg/L PFBS and hypoxia caused a further reduction in survival rate and heart beat compared to single exposure. PFBS induced a precocious hatching, while no larvae hatched under hypoxia condition. By disturbing the balance of sex hormones, either PFBS or hypoxia single exposure produced an anti-estrogenic activity in medaka larvae. However, PFBS and hypoxia combinations reversed to estrogenic activity in co-exposed larvae. Variation in disrupting pattern may be attributed to the interactive effects on steroidogenic pathway involving diverse cytochrome P450 enzymes. Regarding thyroid system, PFBS exposure caused detriments of multiple processes along thyroidal axis (e.g., feedback regulation, synthesis and transport of thyroid hormones, receptor-mediated signaling and thyroid gland development), while hypoxia potently impaired the development and function of thyroid gland. Combinations of PFBS and hypoxia interacted to dysregulate the function of thyroid endocrine system. In summary, the present study revealed the dynamic interaction of PFBS pollutant and hypoxia on aquatic developmental toxicities and endocrine disruption. Considering the frequent co-occurrence of xenobiotics and hypoxia, current results would be beneficial to improve our understanding about their interactive mechanisms and provide baseline evidences for accurate ecological risk evaluation.

Occurrence and trophic magnification profile of triphenyltin compounds in marine mammals and their corresponding food webs

The occurrence of triphenyltin (TPT) compounds, a highly toxic antifouling biocide, has been documented in marine environments and organisms all over the world. While some studies showed that marine mammals can be used as sentinel organisms to evaluate the pollution status of emerging contaminants in the environment because of their long lifespans and high trophic levels, information regarding the contamination status of TPT in marine mammal species has been limited over the past decade. More importantly, the primary bioaccumulation pathway of TPT in these long-lived apex predators and the corresponding marine food web is still uncertain. Therefore, this study aimed to evaluate the contamination statuses of TPT in two marine mammal species, namely the finless porpoise and the Indo-Pacific humpback dolphin, and assess the trophic magnification potential of TPT along the food webs of these two species, using stable isotope analysis, and chemical analysis with gas chromatography-mass spectrometry. The results showed that TPT is the predominant residue in majority of the analyzed individuals of two marine mammals, with concentrations ranging from 426.2 to 3476.6 ng/g wet weight in their muscle tissues. Our results also demonstrated an exponential increase in the concentration of TPT along the marine food web, indicating that trophic magnification occurs in the respective food webs of the two marine mammals. The range of trophic magnification factors of TPT in the food webs of finless porpoise and Indo-Pacific humpback dolphin was 2.51-3.47 and 2.45-3.39, respectively. These results suggest that high trophic organisms may be more vulnerable to the exposure of TPT-contaminated environments due to the high trophic magnification potential, and thus ecological risk of these compounds ought to be assessed with the consideration of their bioaccumulation potentials in these marine mammals.

Emerging perfluoroalkyl substance impacts soil microbial community and ammonia oxidation

Legacy perfluoroalkyl and poly-fluoroalkyl substances (PFASs) are gradually phased out because of their persistence, bioaccumulation, toxicity, long-distance transport and ubiquity in the environment. Alternatively, emerging PFASs are manufactured and released into the environment. It is accepted that PFASs can impact microbiota, although it is still unclear whether emerging PFASs are toxic towards soil microbiota. However, it could be assumed that OBS could impact soil microorganisms because it had similar chemical properties (toxicity and persistence) as legacy PFASs. The present study aimed to explore the influences of an emerging PFAS, namely sodium p-perfluorous nonenoxybenzene sulfonate (OBS), on archaeal, bacterial, and ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities and ammonia oxidation. Grassland soil was amended with OBS at different dosages (0, 1, 10 and 100 mg/kg). After OBS amendment, tolerant microorganisms (e.g., archaea and AOA) were promoted, while susceptive microorganisms (e.g., bacteria and AOB) were inhibited. OBS amendment greatly changed microbial structure. Potential nitrifying activity was inhibited by OBS in a dose-dependent manner during the whole incubation. Furthermore, AOB might play a more important role in ammonia oxidation than AOA. Overall, OBS influenced ammonia oxidation by regulating the activity, abundance and structure of ammonia-oxidizing microorganisms, and could also exert influences on total bacterial and archaeal populations.

Temporal Trends in Per- and Polyfluoroalkyl Substances in Bottlenose Dolphins (Tursiops truncatus) of Indian River Lagoon, Florida and Charleston, South Carolina

Temporal trends in plasma concentrations of per- and polyfluoroalkyl substances (PFAS) in free-ranging bottlenose dolphins (Tursiops truncatus) inhabiting two geographic areas: Indian River Lagoon, Florida over the years 2003-2015 and the waters surrounding Charleston, South Carolina over 2003-2013, were examined. Nine PFAS met the inclusion criteria for analysis based on percent of values below level of detection and sampling years. Proportionate percentiles parametric quantile regression assuming lognormal distributions was used to estimate the average ratio of PFAS concentrations per year for each chemical. Plasma concentrations decreased over time for perfluorodecanoate (PFDA), perfluorohexane sulfonate (PFHxS), perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and perfluoroundecanoate (PFUnDA) in both locations. Perfluorononanoate (PFNA) decreased with time in Indian River Lagoon dolphins. Perfluorododecanoate (PFDoDA) concentrations significantly increased over time among female Indian River Lagoon dolphins. Regulation and phaseout of specific PFAS groups may have led to the decreasing levels of those PFAS and increasing levels of other replacement PFAS.

Parental Exposure to Perfluorobutanesulfonate Impairs Offspring Development through Inheritance of Paternal Methylome

Perfluorobutanesulfonate (PFBS), an environmental pollutant of emerging concern, significantly impairs offspring development and overall health after parental exposure. However, the true inducer of offspring developmental defects among the complexity of parental influences remains unknown. In the present study, marine medaka (Oryzias melastigma) were exposed to environmentally realistic concentrations of PFBS (0, 1, 3, and 10 μg/L) for an entire life cycle. By mixing and mating control and exposed medaka (male or female), a crossbreeding strategy was employed to produce offspring eggs from various crossbreeds, with the aim of differentiating the maternal and paternal influences. Measurements of swimming performance in larval offspring showed that larvae of exposed male parents swam hyperactively in comparison to the control larvae. Contrasting trends in PFBS transfer and maternal factor transfer (e.g., proteins and lipids) to that of swimming behavior eliminated these two factors as major inducers of offspring developmental impairment. Inheritance of the exposed paternal methylome marks in offspring may be partially responsible for abnormal swimming behavior, although different toxic mechanisms may be involved depending on the exposure concentration. Overall, these findings suggest that inheritance of epigenetic modifications implicates a long-lasting threat of PFBS to the fitness and sustainability of fish populations.

Organic ultraviolet (UV) filters in the South China sea coastal region: Environmental occurrence, toxicological effects and risk assessment

Organic ultraviolet (UV) filters are common ingredients of personal care products and occur ubiquitously in the aquatic environment; however, little is known about their distribution in and potential effects to the marine environment. This study reports the occurrence, toxicological effects and risk assessment of eleven commonly consumed UV filters in marine surface water collected from the South China Sea (SCS) coastal region. The concentrations of UV filters ranged from <MDL to 145 ng/L in the SCS, in which benzophenone-3, octocrylene and butyl methoxydibenzoylmethane were the most dominant compounds with their detection frequencies over 97%. Relatively higher levels of total UV filters were found near the highly industrialized and urbanized Pearl River Estuary (PRE) and the concentrations gradually decreased towards the SCS. In general, the environmental levels of UV filters were higher at the western marine waters in Hong Kong than the eastern marine waters. Significant negative correlations were observed between benzophenone-4 and water temperature, as well as ethylhexyl methoxycinnamate and salinity (P < 0.001; r < -0.5). Immobilization test of barnacle nauplius larvae (Balanus amphitrite) was conducted to assess the acute toxicity of organic UV filters to marine organisms. Benzophenone-8 and 4-methylbenzylidene camphor showed relatively higher toxicity with the 50% effect concentrations (EC₅₀) of 2.2 and 3.9 mg/L, respectively. A preliminary risk assessment was conducted by the results obtained from our field and laboratory studies. Results showed that the risk to cause immobilization in barnacle nauplius larvae in associated with exposure to current levels of organic UV filters in the SCS was minimal.

Trace elements accumulation in the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) - A threat to the endangered freshwater cetacean

As a freshwater cetacean with a population of only approximately 1000 individuals, the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is threatened by water pollution. However, studies of contaminants accumulated in the Yangtze finless porpoise remain limited. In this study, concentrations of 11 trace elements in different tissues sampled from 38 Yangtze finless porpoise individuals were determined. The elements V, Ni, Zn, and Pb were mostly accumulated in the epidermis, Cr, Mn, Cu, Se, and Hg were mostly accumulated in the liver, while As and Cd were mostly accumulated in the blubber and kidney, respectively. The results show that trace elements concentrations in the epidermis do not reliably indicate concentrations in internal tissues of the Yangtze finless porpoises. Positive correlations between different trace elements concentrations in tissues with the highest concentrations suggested the similar mechanism of metabolism or uptake pathway of those elements. Concentrations of As, Se, Cd, Hg, and Pb in the tissues with the highest concentrations were significantly positively correlated with the body length. Furthermore, significantly higher trace elements concentrations were measured in the reproductive organs of females (ovaries) than males (testis). However, no significant difference of trace elements concentrations between habitats was found. In consideration of higher Hg and Cd level in Yangtze finless porpoises compared to other small cetaceans, the potential risk of Hg (in particular) and Cd toxicity to Yangtze finless porpoises needs further attention.

Occurrence and distribution of per- and polyfluoroalkyl substances (PFASs) in the seawater and sediment of the South China sea coastal region

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are anthropogenic chemicals widely used in industrial and consumer products. PFASs can be readily transported by water due to their relatively high solubility and polarity, and oceans are believed to be their final global sink. The heavily industrialized and urbanized Pearl River Delta in South China represents a major source of PFASs. In the present study, samples of surface waters, bottom waters, and sediments of the South China Sea (SCS) were collected during summer 2017 and 2018 to determine the level, distribution, and potential regional risk of PFASs. The PFAS concentrations in surface seawater, bottom seawater, and sediment were 125-1015 pg/L, 38-779 pg/L, and 7.5-84.2 pg/g dry weight, respectively. Perfluorobutanoic acid (PFBA) and perfluorooctanoic acid (PFOA) were the dominant PFASs in seawater, while perfluorooctanesulfonic acid (PFOS) was dominant in sediment. The PFAS alternatives 6:2 and -8:2 Cl-polyfluorinated ether sulfonate (6:2 and 8:2 Cl-PFESA) as well as hexafluoropropylene oxide dimer (HFPO-DA) were detected in the SCS for the first time. The spatial distribution of PFASs in seawater and sediment were impacted by river outflows and sea currents, and concentrations decreased from the estuaries to the offshore regions due to the dilution effect. PFAS concentrations were relatively low compared to other coastal regions worldwide, and a preliminary environmental hazard assessment showed that PFASs posed minimal risk to marine organisms in the coastal region of the SCS, with the exception of PFOS.

Perfluorobutanesulfonate Exposure Skews Sex Ratio in Fish and Transgenerationally Impairs Reproduction

Perfluorobutanesulfonate (PFBS) is increasingly polluting aquatic environments due to worldwide manufacturing and application. However, toxicological knowledge regarding PFBS exposure remains scarce. Here, we showed that PFBS life-cycle exposure at environmentally realistic concentrations (0, 1.0, 2.9, and 9.5 μg/L) skewed the sex ratio in fish toward male dominance, while reproductive functions of female fish were greatly impaired, as characterized by extremely small ovaries, blocked oocyte development, and decreased egg production. Endocrine disruption through the hypothalamus-pituitary-gonad axis was induced by PFBS exposure, showing antiestrogenic activity in females but estrogenic activity in males. PFBS was found to gradually accumulate in F0 adults during continuous exposure but can be rapidly eliminated when depurated in clean water. Parental exposure also transferred PFBS pollutant to F1 offspring eggs. Although no trace of PFBS was detected in F1 adults and F2 eggs, adverse effects from parental exposure persisted in F1 and F2 offspring. These transgenerational effects implicate PFBS as an ongoing threat to the fitness and sustainability of fish populations. The dramatic impairment of fish reproduction highlights the urgency of re-evaluations of the ecological and evolutionary consequences of PFBS exposure.

Bioconcentration and tissue distribution of shorter and longer chain perfluoroalkyl acids (PFAAs) in zebrafish (Danio rerio): Effects of perfluorinated carbon chain length and zebrafish protein content

Perfluoroalkyl acids (PFAAs) are a class of emerging pollutants. However, the bioconcentration and tissue distribution of shorter chain PFAAs in aquatic animals are not well understood. Here, we investigated the effects of perfluorinated carbon chain length of PFAAs and protein content of tissues on the bioconcentration and tissue distribution of both shorter chain PFAAs (linear C-F = 3-6) and longer chain PFAAs (linear C-F = 7-11) in zebrafish. The results showed that the uptake rate constants (k_u) and the bioconcentration factors (BCF_ss) of the shorter chain PFAAs (0.042-32 L·kg_ww^-1·d^-1 and 0.12-24 L·kg_ww^-1, respectively) in tissues were significantly lower than those of the longer chain PFAAs (2.8-1.4 × 10³ L·kg_ww^-1·d^-1 and 9.7-1.9 × 10⁴ L·kg_ww^-1, respectively). Moreover, the concentrations of both longer and shorter chain PFAAs were lowest in the muscle where the protein content was lowest, and they were highest in blood and liver where the protein content was highest among tissues except brain. The protein content of the brain was higher than that of the liver but the concentrations of PFAAs in the brain were significantly lower than those in the liver because of the blood-brain barrier. In addition, the ovary/blood and brain/blood ratios of concentrations for the shorter chain PFAAs were lower than those for the longer chain PFAAs. Generally, both log k_u and log BCF_ss showed a significantly positive correlation with either perfluorinated carbon number of PFAAs or protein content of tissues (P < 0.05). Further nonlinear surface fitting revealed that the effect of perfluorinated carbon number was more significant than protein content on the PFAA bioconcentration in zebrafish tissues. These results suggest that there are differences in the bioconcentration and tissue distribution between longer and shorter chain PFAAs and the shorter chain PFAAs seem to be safe compared with the longer chain PFAAs.

Occurrence and Degradation Potential of Fluoroalkylsilane Substances as Precursors of Perfluoroalkyl Carboxylic Acids

Polyfluoroalkylsilanes (PFASis) are a class of artificial chemicals with wide applications in surface coating, which arouse attention due to their hydrophobic/oleophobic properties and potential biological effects. In this study, a robust high-resolution mass spectrometry method through direct injection into a Fourier transform ion cyclotron resonance instrument was established, with the aid of CF₂-scaled Kendrick mass defect analysis and isotope fine structure elucidation. The occurrence of 8:2 polyfluoroalkyl trimethoxysilane (8:2 PTrMeOSi) and 8:2 polyfluoroalkyl triethoxysilane (8:2 PTrEtOSi), as well as their cationic adducts, solvent substitutions, and other compound analogues, were identified in commercial antifingerprint liquid products. In the hydroxyl radical-based total oxidizable precursor assay, differential molar yields of products were observed with regard to varied PFASi carbon-chain lengths and terminal groups. The yields of perfluoroalkyl carboxylic acids (PFCAs) from 8:2 PTrMeOSi conversion were the highest (92 ± 9%, n = 3), with the C ( n - 1) perfluoroheptanoic acid (PFHpA, 49 ± 11%, n = 3) as the dominating product. Distinct conversion of 8:2 PTrMeOSi in the simulated solar exposure experiments found that C ( n) perfluorooctanoic acid (PFOA, 0.6 ± 0.04 ‰, n = 3) was predominant, and 8:2 fluorotelomer carboxylic acid (8:2 FTCA, 0.59 ± 0.08‰, n = 3), 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA, 0.09 ± 0.00‰, n = 3) intermediates were also observed. To our knowledge, this is the first report regarding the occurrence and degradation potential of several fluoroalkylsilane substances as PFCA precursors.

Variation in microbial community structure in surface seawater from Pearl River Delta: Discerning the influencing factors

Contamination of perfluoroalkyl acids (PFAAs) is ubiquitously detected in various environments. However, their potential effects on microbial communities remain largely unknown. In this study, surface seawater of the Pearl River Delta (PRD) is sampled to measure PFAA concentrations and profile the structure of free-living microbial community. Total PFAAs concentrations range from 131 to 1563 pg L^-1 in surface seawater. PFOS (16-470 pg L^-1), PFOA (27-272 pg L^-1), PFHpA (18-201 pg L^-1) and PFBA (25-152 pg L^-1) are the major homologues, indicating continued industrial application or release of PFOS and a gradual shift towards using shorter-chain PFAAs. Concentrations of PFAAs from this recent cruise are much lower than previous reports, which may be due to the effective management of PFAA usage around PRD region. In addition, the microbial community in PRD surface seawater is predominantly colonized by the Proteobacteria phylum (27.2 to 61.5%) and the Synechococcus genus (5.6 to 38.6%). The structure of the microbial communities varies among stations, mainly resulting from different abundances of Synechococcus, Prochlorococcus and Nitrosopumilus. Geochemical parameters (e.g., nutrients and salinity) and phytoplankton are significantly associated with the microbial community dynamics in surface seawater. In the interactive network of microbiota, a subset of bacteria (i.e., Fluviicola, Nitrosopumilus, Limnohabitans, Sediminibacterium, C39 and Polynucleobacter) shows significantly positive correlations with PFAAs (R > 0.6; P < 0.001). Overall, this study gives a timely monitoring of PFAA pollution around PRD area. Shift in environmental microbiota by geochemical factors and phytoplankton is also observed, which may affect biogeochemical cycling.

Bioaccumulation behavior and spatiotemporal trends of per- and polyfluoroalkyl substances in Indo-Pacific humpback dolphins from the Pearl River Estuary, China

Sixteen per- and polyfluoroalkyl substances (PFASs) were measured in liver (n = 52) and kidney (n = 18) tissues of Indo-Pacific humpback dolphins (Sousa chinensis) stranded in the Pearl River Estuary (PRE) of China between 2004 and 2016. The average concentrations of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and most of other PFASs in the liver samples were respectively greater than any records previously reported in cetaceans globally. PFOS levels in 46% of dolphin liver samples exceeded the hepatic toxicity threshold in cetaceans. For the first time, we found a U-shaped trend for the distribution pattern of perfluorinated carboxylic acids (PFCAs) between liver and kidney with increasing carbon chain lengths (C5-C16), whereas a descending trend (C4-C10) was found for perfluoroalkane sulfonic acids (PFASs), which may be explained by binding efficiencies of PFAS analogues to proteins. Dolphins with the highest levels of ∑PFASs (age-corrected) were clustered near the river outlets in Lingdingyang area, which agrees with the spatial distribution of PFASs in the environment. Significant temporal trends were observed for many PFASs. Concentrations of PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA) and perfluoroheptanoic acid (PFHpA) all peaked in year 2011, followed by a decreasing trend, while a consistently descending trend was shown for perfluoroundecanoic acid (PFUdA) and perfluorodecane sulfonate (PFDS). Our findings contribute to the knowledge of tissue distribution and spatiotemporal trends of PFASs in the PRE dolphins, which are valuable for us to understand the PFASs exposure risk and their industrial emission in Southern China.

Elucidation of contamination sources for poly- and perfluoroalkyl substances (PFASs) on Svalbard (Norwegian Arctic)

A combination of local (i.e. firefighting training facilities) and remote sources (i.e. long-range transport) is assumed to be responsible for the occurrence of per- and polyfluoroalkyl substances (PFASs) in Svalbard (Norwegian Arctic). However, no systematic elucidation of local PFASs sources has been conducted yet. Therefore, a survey was performed aiming at identifying local PFAS pollution sources on the island of Spitsbergen (Svalbard, Norway). Soil, freshwater (lake, draining rivers), seawater, meltwater run-off, surface snow and coastal sediment samples were collected from Longyearbyen (Norwegian mining town), Ny-Ålesund (research facility) and the Lake Linnévatnet area (background site) during several campaigns (2014-2016) and analysed for 14 individual target PFASs. For background site (Linnévatnet area, sampling during April to June 2015), ΣPFAS levels ranged from 0.4 to 4 ng/L in surface lake water (n = 20). PFAS in meltwater from the contributing glaciers showed similar concentrations (~ 4 ng/L, n = 2). The short-chain perfluorobutanoate (PFBA) was predominant in lake water (60-80% of the ΣPFASs), meltwater (20-30%) and run-off water (40%). Long-range transport is assumed to be the major PFAS source. In Longyearbyen, five water samples (i.e. 2 seawater, 3 run-off) were collected near the local firefighting training site (FFTS) in November 2014 and June 2015, respectively. The highest PFAS levels were found in FFTS meltwater run-off (118 ng/L). Perfluorooctane sulfonic acid (PFOS) was the most abundant compound in the FFTS meltwater run-off (53-58% PFASs). At the research station Ny-Ålesund, seawater (n = 6), soil (n = 9) and freshwater (n = 10) were collected in June 2016. Low ΣPFAS concentrations were determined for seawater (5-6 ng/L), whereas high ΣPFAS concentrations were found in run-off water (113-119 ng/L) and soil (211-800 ng/g dry weight (dw)) collected close to the local FFTS. In addition, high ΣPFAS levels (127 ng/L) were also found in freshwater from lake Solvatnet close to former sewage treatment facility. Overall, at both FFTS-affected sites (soil, water), PFOS was the most abundant compound (60-69% of ΣPFASs). FFTS and landfill locations were identified as major PFAS sources for Svalbard settlements.

Renal function and isomers of perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS): Isomers of C8 Health Project in China

Perfluoroalkyl substances (PFASs) are widely-utilized synthetic chemicals commonly found in industrial and consumer products. Previous studies have examined associations between PFASs and renal function, yet the results are mixed. Moreover, evidence on the associations of isomers of PFASs with renal function in population from high polluted areas is scant. To help to address this data gap, we used high performance liquid chromatography-mass spectrometry to measure serum isomers of perfluorooctanoate (PFOA), perfluorooctanesulfonate (PFOS), and other PFASs from 1612 adults residing in Shenyang, China, and characterized their associations with estimated glomerular filtration rate (eGFR) and chronic kidney disease (CKD). Results showed that after adjusted for multiple confounding factors, most of the higher fluorinated PFASs, except for PFOA and PFDA, were negatively associated with eGFR and positively associated with CKD. Compared with linear PFOS (n-PFOS), branched PFOS isomers (Br-PFOS) were more strongly associated with eGFR (Br-PFOS; β = -1.22, 95%CI: 2.02, -0.42; p = 0.003 vs. n-PFOS; β = -0.16, 95%CI: 0.98, 0.65; p = 0.691) and CKD (Br-PFOS; OR = 1.27; 95% CI: 1.02, 1.58; p = 0.037 vs. n-PFOS; OR = 0.98; 95% CI: 0.80, 1.20; p = 0.834). In conclusion, branched PFOS isomers were negatively associated with renal function whereas their linear counterparts were not. Given widespread exposure to PFASs, potential nephrotoxic effects are of great public health concern, Furthermore, longitudinal research on the potential nephrotoxic effects of PFASs isomers will be necessary to more definitively assess the risk.

Contamination by perfluoroalkyl substances and microbial community structure in Pearl River Delta sediments

Environmental microbiota play essential roles in the maintenance of many biogeochemical processes, including nutrient cycling and pollutant degradation. They are also highly susceptible to changes in environmental stressors, with environmental pollutants being key disruptors of microbial dynamics. In the present study, a scientific cruise was launched on July 2017 around Pearl River Delta, a suitable studying site for perfluoroalkyl substances (PFASs) in the wake of the severe PFAS pollution. Surface sediment samples were collected from 18 representative stations to assess PFAS accumulation and profile microbial community. PFAS concentrations ranged from 24.2 to 181.4 pg/g dry weight in sediment, and perfluorooctanesulfonic acid (PFOS) was the dominant homologue. The concentrations of PFAS homologues in the current study were much lower than those reported in previous studies, implying effective management and control of pollution from PFAS-related industries. 16S rRNA gene amplicon sequencing revealed that Proteobacteria was the dominant phylum, while nitrogen-metabolizing Nitrosopumilus and sulfate-reducing Desulfococcus genera were the most abundant. Variations in microbial communities among sampling stations were mainly due to the differences in abundances of Escherichia, Nitrosopumilus, and Desulfococcus. The outbreak of Escherichia bacteria at specific coastal stations potentially indicated the discharge of fecal matter into the marine environment. Dissolved oxygen (DO) in bottom seawater significantly influenced the structure of microbial communities in the sediment, while current study failed to observe significant effects from PFAS pollutants. Positive correlations were found between DO and sulfate-reducing bacteria in Desulfococcus and GOUTA19 genera. Overall, this study explored relationships between environmental variables (e.g., PFAS pollutants) and sediment bacteria. Biogeochemical parameters significantly influenced the structure and composition of microbial communities in sediment.

Probing mechanisms for bioaccumulation of perfluoroalkyl acids in carp (Cyprinus carpio): Impacts of protein binding affinities and elimination pathways

With regulations on the manufacture and usage of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and related compounds, short-chain perfluoroalkyl acids (PFAAs) are increasingly being used as alternatives. However, there are limited studies on their bioaccumulation mechanisms, especially for short-chain PFAAs. In this study, we examined the binding affinity of PFAAs with fish serum proteins and tissue distributions of perfluoroalkyl carboxylates (C7-C11 PFCAs) and perfluoroalkyl sulfonates (C4, C6, and C8 PFSAs) in carp (Cyprinus carpio), including the isomers of PFOS and perfluorohexane sulfonate (PFHxS). For both PFCAs and PFSAs, the fish serum protein binding constant (K_A) and bioconcentration factor (BCF) increased with an increase in the carbon chain length. PFHxS (C6 PFSA) had a much higher K_A but displayed a much lower BCF than those of C7-C11 PFCAs. It indicated that not only fish blood proteins, but also other proteins in the liver and kidney, mediated the accumulation of PFAAs in fish. The lowest concentration ratios of PFHxS in liver to blood and in kidney to blood suggested that it could not be effectively transported to liver and kidney by fatty acid binding proteins and organic anion transporters. PFOS and PFHxS displayed different elimination pathways, although their linear (n-) isomers were accumulated more in fish than the corresponding branched (br-) isomers. The n-PFOS was eliminated more via the feces but br-PFOS was eliminated more via the urine; while the opposite trend was observed for PFHxS isomers.

Occurrence and distribution of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in natural forest soils: A nationwide study in China

Forests serve as the primary reservoir for organic carbon above ground. Previous studies have revealed that forest soils play key roles in the retention of persistent organic pollutants (POPs). In this study, the occurrence and distribution of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) were investigated in 54 surface soil samples from 28 natural forested mountain sites across China between 2012 and 2013. The detection frequency of PFOA (70%) was significantly higher than that of PFOS (4%). PFOA levels ranged from <0.9 to 9.0 pg·g^-1 dry weight (dw). Levels of PFOA and PFOS in forest soils were significantly lower than those in agricultural, urban and rural areas in China. Relatively high levels of PFOA were detected in Hubei Province (Jiugong Mountain, average: 3.4 pg·g^-1 dw) and Jiangxi Province (Wugong Mountain, average: 4.4 pg·g^-1 dw), where many domestic fluoropolymer manufacturers are located. PFOS was only detected in these two provinces (2.2 pg·g^-1 dw and 2.7 pg·g^-1 dw, respectively). From most of the surveyed mountains, the concentrations of PFOA increased with elevation. The lower temperature and greater precipitation probably made PFOA and its precursors available to transport and degrade more readily at higher altitude sites. A relatively higher level (1.9 ± 1.3 pg·g^-1 dw) of PFOA was found in the broadleaf evergreen forest area, mainly due to the high industrial emissions, plant retention, and precipitation rate in this area. Source were the dominant factor controlling the spatial distribution of PFOA in natural forest soils in China.