Bioaccumulation of polyfluoroalkyl substances in the Lake Huron aquatic food web

A machine learning multimodal profiling of Per- and Polyfluoroalkyls (PFAS) distribution across animal species organs via clustering and dimensionality reduction techniques

Per- and polyfluoroalkyl substances (PFAS) contamination in aquatic and terrestrial organisms poses significant environmental and health risks. This study quantified 15 PFAS compounds across various tissues (liver, kidney, gill, muscle, skin, lung, blood, breast, feather) from fish (Clarias gariepinus, Oreochromis niloticus, Lates niloticus, Tilapia zilli), livestock (camel, cow, sheep, ram, goat), and birds (pigeon, chicken, turkey). Among the fishes, C. gariepinus exhibited the highest PFAS accumulation, with PFOA (46.5 ng/g) and PFTrDA (50.1 ng/g) dominant in liver and kidney, while O. niloticus showed elevated PFTrDA (56.87 ng/g) and PFUnDA (29.43 ng/g). In livestock, camel liver contained high PFNA (9.22 ng/g), and cow liver had the highest PFOS (8.1 ng/g). Among the birds, pigeon liver showed the highest PFNA (7.83 ng/g). To analyze PFAS distribution patterns, dimensionality reduction and clustering techniques were employed. Principal Component Analysis (PCA) captured 68.28 % of total variance, revealing two distinct clusters whereby fish species are strongly related with higher PFAS concentration, while poultry showed unique PFAS profiles when compared to other types of meat. Clustering of PFOS, PFOA, and other PFAS compounds near the center explained their influence across the general meat types particularly the fish species, while t-Distributed Stochastic Neighbor Embedding (t-SNE) confirmed clear separations in high-dimensional space. Clustering analyses, including K-means, hierarchical clustering, DBSCAN, and Gaussian Mixture Models (GMM), identified well-defined patterns, with DBSCAN and GMM detecting overlapping categories and outliers. Feature importance analysis using a Random Forest model highlighted total PFAS as the most significant predictor, with PFHxA and PFDODA also contributing strongly, while organ type and species played a lesser role. These findings demonstrate the effectiveness of unsupervised learning techniques in characterizing PFAS bioaccumulation patterns across species and tissues, providing valuable information for ecological and toxicological risk assessments.

Robust titanium suboxide anodes doped by sintering enhance PFOS degradation in water

Per- and Polyfluoroalkyl Substances (PFAS) are a class of persistent organic pollutants that are ubiquitous in the environment, while PFOS is one most representative PFAS of extraordinary persistence. Electrochemical oxidation (EO) is promising for destructive treatment of PFAS in water, and Magnéli phase titanium suboxide (TSO) is regarded as one of only few suitable anode materials for this application. We herein conducted an in-silico survey with Density Functional Theory (DFT) simulations to identify possible beneficial dopant elements, and then prepared TSO anodes doped with Niobium (Nb-TSO) or Cerium (Ce-TSO) by sintering. The doped TSO thus prepared exhibited great robustness, having service lifetimes longer than the pristine Ti4O7 anode, making them useful for EO applications in PFAS treatment. PFOS degradation by EO using Nb-TSO anode was faster than that on the pristine Ti4O7 anode, with energy consumption approximately 1.8 times lower. Further characterizations and DFT simulations reveal that the enhanced efficiency of Nb-TSO anode is attributed to its reduced charge transfer resistance and increased effective electroactive surface area (EESA). The EESA of the Ce-TSO anode was reduced in comparison to the pristine Ti4O7, but PFOS degradation rates normalized by EESA were increased significantly for EO with Ce-TSO anode, due to its increased oxygen evolution potential (OEP) and hydroxyl radical production. The doped TSO anodes prepared in this study by sintering will be useful in EO treatment of PFAS-contaminated waters, with improved service life and performance, and the study provides understandings to guide further improvements of the TSO anodes via doping.

Ecotoxicological effects of per- and polyfluoroalkyl substances in aquatic organisms: A review

Per- and polyfluoroalkyl substances (PFAS) are found throughout the environment due to their chemical stability. Their widespread use in industrial and consumer products has resulted in their frequent detection in aquatic environments, making them contaminants of significant concern. Recent studies focus on the adverse effects of PFAS on aquatic organisms in an effort to elucidate their toxic mechanisms and physiological changes. Here, we comprehensively review the major effects of PFAS on aquatic organisms, including general toxicity, metabolic disruption, and microbiome alterations, and explore how these changes affect biological function and ecosystem balance. In addition to toxic responses in aquatic organisms reported previously, PFAS disrupt metabolic pathways, causing abnormalities in carbohydrate metabolism, lipid homeostasis, and hormonal regulation. They also cause gut microbiome imbalances and reduce the prevalence of beneficial bacteria while promoting pathogen proliferation, which contributes to physiological dysfunction and damages liver and other organ tissues. Experimental evidence emphasizes the multifaceted threats PFAS pose to aquatic health and ecosystem stability and provide a crucial foundation for understanding their long-term impacts from both physiological and ecological perspectives.

Unique per- and polyfluoroalkyl substances (PFAS) source suggested by a Lake Trout (Salvelinus namaycush) PFAS profile in a temperate lake

Per- and polyfluoroalkyl substances (PFAS) are detected in pelagic freshwater fish and have deleterious effects on their health. It is unclear if traditional proxies for uptake of contaminants in fish (e.g., length, weight, age) predict fish PFAS concentrations. Here, we observe that summed PFAS concentrations are significantly higher in Lake Trout (Salvelinus namaycush) than other sportfish in Seneca Lake, New York. Carbon source (as proxied by δ13C) predicted variability within species, and trophic level (as proxied by δ15N) trended among species. A moderate inverse correlation (r = -0.51) was found between mercury and summed PFAS in Lake Trout. Summed PFAS concentrations and length, weight, or age were not statistically related, suggesting these characteristics are not reliable proxies for PFAS bioaccumulation. Length, weight, and age were significant predictors for mercury, indicating these drivers may be resulting in differential bioaccumulation in PFAS and mercury. In Seneca Lake, a unique PFAS composition was found for Lake Trout, where PFOS represents a lower proportion of summed PFAS than in other species in Seneca Lake, as well as relative to Lake Trout from other neighboring Finger Lakes. In addition, compared to Lake Erie and Lake Ontario, Lake Trout from Seneca Lake have higher concentrations of PFOA, PFNA, and PFDA, but lower proportions of PFOS. Lake Trout from Seneca Lake have a PFAS composition that consists almost exclusively of perfluoroalkyl carboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), similar to the composition used in aqueous film forming foams (AFFF) before 2000 at a former military and current Superfund site in the lake's watershed.

Chemical mixtures of mercury, PCBs, PFAS, and pesticides in freshwater fish in the US and the risks they pose for fish consumption

BACKGROUND

Freshwater fish are important food sources that also pose risks to human and wildlife health because of the bioaccumulation of environmental chemicals in their tissues. Although most studies, fish consumption advisories, and regulations focus on individual contaminants, fish consumers are exposed to mixtures of chemicals, including legacy contaminants and contaminants of emerging concern, that can have combined effects. Chemicals of emerging concern represent one source of hazard, but legacy contaminants can still pose threats to fish consumers due to their persistence in the environment.

OBJECTIVES

We investigate the following questions: 1) Do different chemicals correlate with one another in fish tissue, and if so, how? 2) How do levels of different chemicals in fish tissue vary by time and location? and 3) How do observed chemical levels compare with risk-based screening levels?

METHODS

Using several national data sources established and maintained by the US Environmental Protection Agency (NRSA, NCCA-GL, GLENDA, and NLFTS), this study examines the co-occurrence of chemicals in freshwater fish in lakes, ponds, streams, and rivers in the US.

RESULTS

We determine that organic contaminants correlate with one another, but generally not with mercury; organic chemicals have declined over time, but mercury has not; and fish concentrations of legacy contaminants-even those banned for decades-continue to exceed risk-based screening levels.

DISCUSSION

Despite some successes in curtailing release of pollutants, some contaminants in fish tissue have not declined and legacy and emerging pollutants continue to pose risks to fish consumers in the US. Correlations between chemicals in fish tissue suggest that exposures to mixtures is prevalent in the US but that organic contaminants do not generally correlate with mercury-noteworthy particularly since fish consumption advisories in the US are frequently driven by the level of mercury, and do not account for exposure to multiple contaminants. While programs such as the National Aquatic Resource Surveys (NARS) Program seek to systematically monitor contaminants in fish tissue and other environmental indicators, continuous support from the US federal government is required to sustain this monitoring. Moreover, greater legislative and regulatory efforts are required at both the state and federal levels to reduce continuing sources and ongoing contamination.

Nanomolar PFOA Concentrations Affect Lipid Membrane Structure: Consequences for Bioconcentration Mechanisms

Independent methods show that sub-microMolar concentrations of perfluorooctanoic acid (PFOA), a member of the PFAS family of "forever chemicals", change the properties of DPPC vesicle bilayers. Specifically, calorimetry measurements show that PFOA at concentrations as low as 0.1 nM lowers DPPC's gel-liquid crystalline transition enthalpy by several J/g without changing the transition temperature (Tgel-LC), and dynamic light scattering (DLS) data illustrate that PFOA markedly broadens the size distribution of DPPC vesicles. Furthermore, DLS results from PFOA-containing, DPPC vesicle solutions also contain smaller objects having diameters of 30-50 nm. Close inspection of cryo-EM images reveals that DPPC vesicles formed in the presence of PFOA are multilamellar and the smaller objects have a clear bilayer structure similar to niosomes. A consequence of these PFOA-induced changes to DPPC bilayer structure is that the bilayers themselves are more susceptible to secondary solute accumulation. Time resolved emission measurements of Coumarin 152 (C152) report that C152 is 3-fold more likely to partition into the bilayer's acyl chain, hydrophobic interior when PFOA is present, and fluorescence lifetimes from C152 partitioned into the polar region of the lipid bilayer show evidence of PFOA-induced membrane hydration below Tgel-LC.

Tissue distribution, biomagnification, human health risk, and risk mitigation of perfluoroalkyl acids (PFAAs) in the aquatic food web of an urban fringe lake: Insights from urban-rural and seasonal scales

Perfluoroalkyl acids (PFAAs), renowned for their exceptional physical and chemical properties, are ubiquitous in urban and rural environments. Despite their widespread usage, more knowledge is needed concerning their accumulation and transfer mechanisms within the aquatic food webs of urban fringe lakes, especially across rural-urban and seasonal scales. This study investigated the tissue distribution, bioaccumulation, biomagnification, associated human health risks, and potential risk mitigation strategies of 15 PFAAs within the food web of Luoma Lake, a prototypical urban fringe lake. All targeted PFAAs were detected in samples, with ∑PFAA concentrations ranging from 116.97 to 564.26 ng/g dw in muscles and 26.96-1850.95 ng/g dw in viscera. Spatial variations revealed significantly higher ∑PFAA concentrations in the muscles from the urban subregion (∑PFAA: 359.66 ± 76.48 ng/g dw) compared to the rural subregion (∑PFAA: 328.86 ± 87.51 ng/g dw). Seasonal fluctuations impacted PFAA concentrations in fish and crustacean muscles but exhibited negligible effects on bivalve muscles. Spatial variations only influenced PFAA concentrations in specific viscera (gill, liver, kidney), while seasonal changes had minimal effects on viscera. The organisms demonstrated varying bioaccumulation capacities, with crustaceans displaying the highest bioaccumulation potential, followed by crustaceans and fish. Both spatial and seasonal variations modulated the bioaccumulation patterns of PFAA in muscles, whereas bioaccumulation in viscera was only influenced by seasonal factors. Notably, PFAA biomagnification along the food web was exclusively governed by spatial distribution, remaining unaffected by seasonal changes. The human health risk assessment underscored the potential adverse health impacts of PFOS and PFOA, particularly on young children (aged 2 to <6 years). This study further proposed comprehensive recommendations for mitigating PFAA-induced health risks, encompassing source control, selective consumption, pre-cooking treatments, and strategic cooking method selection. This research provides crucial insights into the ecological behaviors and health implications of PFAA in urban fringe lakes.

Fugacity model covering abiotic and biotic matrices to investigate the transfer and fate of perfluoroalkyl acids in a large shallow lake of eastern China

Solving the challenges faced during the measurement of the cross-interface transfer of perfluoroalkyl acids (PFAAs) in lakes is crucial for clarifying environmental behaviours of these chemicals and their efficient governance. This study developed a multimedia fugacity model based on the quantitative water-air-sediment interaction (QWASI) covering abiotic/biotic matrices to investigate the cross-interface transfer and fate of PFAAs in Luoma Lake, a typical PFAA-contaminated shallow lake in eastern China. The accuracy and reliability of the established model were confirmed using Percent bias and Monte Carlo simulation, respectively. Using the QWASI model, the multimedia transfer of the PFAAs and their accumulation and persistence in different sub-compartments were described and measured, and the differences among individual PFAAs were explored. The simulation results showed that the sedimentation and resuspension of PFAAs were the most intense cross-interfacial transfers, and the sediments served as a chemical sink in the long term. A significant negative correlation of NC-F (the number of CF bonds) with the relative outflow flux (TW·out-ct) but a positive correlation with the relative net transfer across the interface between water and aquatic plants (Tp-ct) was detected, indicating that the PFAA migration capacity decreased but the bioaccumulation potential increased with the CF bond number. The persistence in water (Pw) of individual PFAAs ranged from 19.65d (PFOA) to 32.22d (PFOS), with an average of 26.15d; their persistence in sediment (Ps) ranged from 432d (PFBA) to 3216d (PFOS), with an average of 1524d, increasing linearly with an increase in NC-F. The water advection flows into and out of the lake (QW·in and QW·out), the PFAA concentration of water inflow (CW·in), and bioconcentration factor of aquatic plants (BCFp) were the primary parameters sensitive to PFAAs in all sub-compartments, which are essential indexes for exploring promising remediation pathways for lacustrine PFAA contamination based on the fugacity model simulation.

Distribution, trophic magnification and risk of trace metals and perfluoroalkyl acids in marine organisms from Haizhou Bay

Haizhou Bay, a semi-enclosed key aquaculture area in East China, has had relatively limited research focused on trace metals and perfluoroalkyl acids (PFAAs) in its biota. This study characterized the distribution, biomagnification and health risks of selected trace metals and PFAAs in various marine organisms from Haizhou Bay. Among the species examined, zinc (Zn) was the most prevalent metal, followed by copper (Cu) and chromium (Cr), whereas cadmium (Cd), total mercury (THg), and methylmercury (MeHg) contents were relatively low. Perfluorooctane sulfonate (PFOS) was the most abundant PFAA, followed by perfluorooctanoic acid (PFOA). The calculated trophic magnification factors (TMFs) were above one for Cr, THg, MeHg, and all PFAAs except perfluorobutanoic acid (PFBA) and perfluorotetradecanoic acid (PFTeDA). Across animal groups, gastropods exhibited relatively low levels of THg, MeHg, and perfluorosulfonic acids (∑PFSAs). By comparison, fish generally had lower levels of Cd and Cu compared to other animal groups, and demersal fish had significantly higher MeHg compared to gastropods. Certain organisms, such as cephalopods and shrimps, were found to pose potential health risks due to elevated levels of Cd, while levels of other studied metals, PFOS and PFOA generally appeared to be within safe limits for human consumption. Further research is needed to assess the sources and impacts of these and other contaminants.

Effects of perfluoroalkyl sulfonic acids on developmental, physiological, and immunological measures in northern leopard frog tadpoles

The chronic toxicity of short chain perfluoroalkyl sulfonic acids (PFSAs), such as perfluorobutanesulfonic acid (PFBS) and perfluorohexanesulfonic acid (PFHxS), are relatively understudied despite the increasing detection of these compounds in the environment. We investigated the chronic toxicity and bioconcentration of PFBS and PFHxS using northern leopard frog (Rana [Lithobates] pipiens) tadpoles. We exposed Gosner stage (GS) 25 tadpoles to either PFBS or PFHxS at nominal concentrations of 0.1, 1, 10, 100, and 1000 μg/L until metamorphosis (GS42). We then assessed tadpole growth, development, stress, and immune metrics, and measured fatty acid (FA) composition and PFSA concentrations in liver and whole-body tissues. Tadpole growth and development measures were relatively unaffected by PFSA exposure. However, tadpoles exposed to 1000 μg/L PFBS or PFHxS had significantly increased hepatosomatic indexes (HSI) relative to controls. Further, tadpoles from the 1000 μg/L PFHxS treatment had altered FA profiles relative to controls, with increased total FAs, saturated FAs, monounsaturated FAs, and omega-6 polyunsaturated FAs. In addition, tadpoles from the 1000 μg/L PFHxS treatment had a higher probability of waterborne corticosterone detection. These results suggest that PFBS and PFHxS influence the hepatic health of tadpoles, and that PFHxS may alter lipid metabolism in tadpoles. We also observed a higher probability of tadpoles being phenotypically female after exposure to an environmentally relevant concentration (0.1 μg/L) of PFHxS, suggesting that PFHxS may exert endocrine disrupting effects on tadpoles during early development. The measured bioconcentration factors (BCFs) for both compounds were ≤10 L kg-1 wet weight, suggesting low bioconcentration potential for PFBS and PFHxS in tadpoles. Many of the significant effects observed in this study occurred at concentrations several orders of magnitude above those measured in the environment; however, our work shows effects of PFSAs exposure on amphibians and provides essential information for ecological risk assessments of these compounds.

Identification and quantification of novel per- and polyfluoroalkyl substances (PFAS) contamination in a Great Lakes urban-dominated watershed

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic organic fluoro-compounds that are oil-, water-, and flame-resistant, making them useful in a wide range of commercial and consumer products, as well as resistant to environmental degradation. To assess the impact of urbanization and wastewater treatment processes, surface water and sediment samples were collected at 27 sites within the Great Lakes in the Lake Huron to Lake Erie corridor (HEC), an international waterway including the highly urbanized Detroit and Rouge Rivers. Samples were analyzed for 92 PFAS via UHPLC-MS/MS. Our previous data in the HEC found the highest amount of PFAS contamination at the Rouge River mouth. In addition to evaluating the input of the Rouge River into the HEC, we evaluated the transport of PFAS into the HEC from other major tributaries. PFAS were detected in both surface water and sediment at all sites in this study, with a total of 10 congeners quantified in all surface water samples and 16 congeners quantified in all sediment samples, indicating ubiquitous contamination. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were pervasive in the HEC as these two compounds were detected in all sites and matrices, often at concentrations above the US EPA's recommended lifetime interim updated health advisories. Surface water samples contained more perfluorohexanoic acid (PFHxA) than any other congener, with average aqueous PFHxA across all surface water samples exceeding the average concentration previously reported in the Great Lakes. Sediment samples were dominated by PFOS, but novel congeners, notably 3-Perfluoropentyl propanoic acid (FPePA), were also quantified in sediment. The Rouge River and other tributaries contribute significantly to the PFAS burden in the HEC including Lake Erie. Overall, our results indicate the need for expanding toxicological research and risk assessment focused on congeners such as PFHxA and PFAS mixtures, as well as regulation that is tighter at the onset of production and encompasses PFAS as a group at a national level.

Preferential Partitioning of Per- and Polyfluoroalkyl Substances (PFAS) and Dissolved Organic Matter in Freshwater Surface Microlayer and Natural Foam

Per- and polyfluoroalkyl substances (PFAS) are surfactants that can accumulate in the surface microlayer (SML) and in natural foams, with potential elevated exposure for organisms at the water surface. However, the impact of water chemistry on PFAS accumulation in these matrices in freshwater systems is unknown. We quantified 36 PFAS in water, the SML, and natural foams from 43 rivers and lakes in Wisconsin, USA, alongside measurements of pH, cations, and dissolved organic carbon (DOC). PFAS partition to foams with concentration ranging 2300-328,200 ng/L in waters with 6-139 ng/L PFAS (sum of 36 analytes), corresponding to sodium-normalized enrichment factors ranging <50 to >7000. Similar enrichment is observed for DOC (∼70). PFAS partitioning to foams increases with increasing chain length and is positively correlated with [DOC]. Modest SML enrichment is observed for PFOS (1.4) and FOSA (2.4), while negligible enrichment is observed for other PFAS and DOC due to low specific surface area and turbulent conditions that inhibit surfactant accumulation. However, DOC composition in the SML is distinct from bulk water, as assessed using high-resolution mass spectrometry. This study demonstrates that natural foams in unimpacted and impacted waters can have elevated PFAS concentrations, whereas SML accumulation in surface waters is limited.

Role of niche and micro-habitat preferences in per- and polyfluoroalkyl substances occurrence in the gills of tropical lake fish species

The present study has investigated per- and poly-fluoroalkyl substances (PFAS) in the gill tissues of various fish species inhabiting different trophic levels within Eleyele Lake, a tropical freshwater lake in Nigeria. The mean concentrations of PFAS congeners were determined, and their trends and patterns were analyzed across different trophic species. The results revealed variations in congener abundance and species-specific patterns that was influenced by habitat and niche preferences. Multivariate associations using canonical-correlation analysis (CCA) revealed distinct trends in the relationships between gill concentrations of specific PFAS congeners and different trophic groups. The strongest congener relationships were observed in the pelagic omnivore (Oreochromic niloticus: ON) with positive associations for 4:2 FTS, 9CL-PF3ONS, PFTDA, MeFOSA and PFHxS. The differences in congener profiles for the two herbivorous fish (Sarotherodon melanotheron (SM) and Coptodon galilaeus (CG)) reflect possible divergence in microhabitat and niche preferences. Furthermore, the congener overlaps between the herbivore (CG), and benthic omnivore (Clarias gariepinus: ClG) indicate a possible niche and microhabitat overlap. Our study provides valuable insights into the congener dynamics of PFAS at Eleyele Lake. However, the dissimilarity and overlapping PFAS congener profile in fish gills reflects the interplay of species niche preference and microhabitat associations. The present study highlights the need for further research to assess ecological risks and develop effective PFAS management strategies.

Extraordinary levels of per- and polyfluoroalkyl substances (PFAS) in vertebrate animals at a New Mexico desert oasis: Multiple pathways for wildlife and human exposure

Per- and polyfluoroalkyl substances (PFAS) in the environment pose persistent and complex threats to human and wildlife health. Around the world, PFAS point sources such as military bases expose thousands of populations of wildlife and game species, with potentially far-reaching implications for population and ecosystem health. But few studies shed light on the extent to which PFAS permeate food webs, particularly ecologically and taxonomically diverse communities of primary and secondary consumers. Here we conducted >2000 assays to measure tissue-concentrations of 17 PFAS in 23 species of mammals and migratory birds at Holloman Air Force Base (AFB), New Mexico, USA, where wastewater catchment lakes form biodiverse oases. PFAS concentrations were among the highest reported in animal tissues, and high levels have persisted for at least three decades. Twenty of 23 species sampled at Holloman AFB were heavily contaminated, representing middle trophic levels and wetland to desert microhabitats, implicating pathways for PFAS uptake: ingestion of surface water, sediments, and soil; foraging on aquatic invertebrates and plants; and preying upon birds or mammals. The hazardous long carbon-chain form, perfluorooctanosulfonic acid (PFOS), was most abundant, with liver concentrations averaging >10,000 ng/g wet weight (ww) in birds and mammals, respectively, and reaching as high 97,000 ng/g ww in a 1994 specimen. Perfluorohexanesulfonic acid (PFHxS) averaged thousands of ng/g ww in the livers of aquatic birds and littoral-zone house mice, but one order of magnitude lower in the livers of upland desert rodent species. Piscivores and upland desert songbirds were relatively uncontaminated. At control sites, PFAS levels were strikingly lower on average and different in composition. In sum, legacy PFAS at this desert oasis have permeated local aquatic and terrestrial food webs across decades, severely contaminating populations of resident and migrant animals, and exposing people via game meat consumption and outdoor recreation.

Trophic transfer and interfacial impacts of micro(nano)plastics and per-and polyfluoroalkyl substances in the environment

Both micro(nano)plastics (MNPs) and per-and polyfluoroalkyl substances (PFAS) possessed excellent properties and diverse applications, albeit gained worldwide attention due to their anthropogenic, ubiquitous, degradation resistant nature and a wide variety of ecological and human health impacts. MNPs and PFAS discharged from discrete sources and extensively bioaccumulated in the food chain through trophic transfer and their long-distance transport potential assist in their dispersal to pristine but vulnerable ecosystems such as Antarctica. They inevitably interacted with each other in the environment through polarized N-H bond, hydrogen bond, hydrophobic interaction, and weak bond energies such as Van der Waals, electrostatic, and intramolecular forces. During co-exposure, they significantly impact the uptake and bioaccumulation of each other in exposed organisms, which may increase or decrease their bioavailable concentration. Hence, this review compiles the studies on the co-occurrence and adsorption of PFAS and MNPs in the environment, their trophic transfer, combined in vivo and in vitro impacts, and factors influencing the MNP-PFAS interface. A significant proportion of studies were conducted in China, Europe, and the US, while studies are rare from other parts of the world. Freshwater and marine food chains were more prominently investigated for trophic transfers compared to terrestrial food chains. The most notable in vivo effects were growth and reproductive impairment, oxidative stress, neurotoxicity and apoptosis, DNA damage, genotoxicity and immunological responses, behavioral and gut microbiota modifications, and histopathological alterations. Cellular uptake of PFAS and MNPs can impact cell survival and proliferation, photosynthesis and membrane integrity, ROS generation and antioxidant responses, and extracellular polymeric substances (EPS) release in vitro. MNP characteristics, PFAS properties, tissue and species-dependent distribution, and environmental medium properties were the main factors influencing the PFAS and MNP nexus and associated impacts. Last but not least, gaps and future research directions were highlighted to better understand the interplay between these critical persistent chemicals.

The effects of two short-chain perfluoroalkyl carboxylic acids (PFCAs) on northern leopard frog (Rana pipiens) tadpole development

Short-chain perfluoroalkyl carboxylic acids (PFCAs) have been detected in the environment globally. The presence and persistence of these compounds in the environment may lead to chronic wildlife exposure. We used northern leopard frog (Rana pipiens) tadpoles to investigate the chronic toxicity and the bioconcentration of two short-chain PFCAs, perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA). We exposed Gosner stage 25 tadpoles to PFBA and PFHxA (as individual chemicals) at nominal concentrations of 0.1, 1, 10, 100, and 1000 µg/L for 43-46 days. Tadpoles exposed to 0.1 to 100 µg/L of PFBA and PFHxA had significantly higher mean snout-to-vent lengths, mean masses, and scaled mass indexes than control tadpoles. These results indicate that exposure to short-chain PFCAs influences tadpole growth. Further investigation into the mechanism(s) causing the observed changes in tadpole growth is warranted. We observed a significantly higher proportion of males in the PFBA 1 µg/L treatment group, however further histological analyses are required to confirm visual sex identification before making concrete conclusions on the effects of PFCAs on amphibian sex ratios. PFBA concentrations in tissues were higher than PFHxA concentrations; a pattern that contrasts with previously published studies using fish, suggesting potential differences between taxa in PFBA and PFHxA bioconcentration. Bioconcentration factors were <10 L/kg wet weight, indicating low bioconcentration potential in tadpoles. Our results suggest that PFBA and PFHxA may have effects at environmentally-relevant concentrations (0.1-10 µg/L) and further investigation is required before these compounds can be deemed a "safe" alternative to their long-chain counterparts.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water and edible fish species of Karun River, Ahvaz, Iran: spatial distribution, human health, and ecological risk assessment

Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are environmental contaminants with unfavorable impacts on human health and nature. This study aimed to determine the PFOA and PFOS concentration in water and fish samples from Karun, the largest river in Iran. According to the results, the PFOA and PFOS in water samples were 5.81-69.26 ng/L and not detected (n.d.)-35.12 ng/L, respectively. The dry season displayed higher concentrations in water samples than in the wet season. The maximum PFOS concentration measured was related to Barbus barbules sp. (27.89 ng/g). The human health risk assessment indicated minor risks (hazard ratio, HR < 1) from PFOA and PFOS through consuming contaminated drinking water and fish. Only HR value of PFOS in downstream area exceeded slightly 1.0, indicating potential health risk due to consumption of the river fish. Considering the average PFASs concentration, the risk quotients (RQs) showed low ecological risk.

Dietary exposure to per- and polyfluoroalkyl substances: Potential health impacts on human liver

Per- and polyfluoroalkyl substances (PFAS), dubbed "forever chemicals", are widely present in the environment. Environmental contamination and food contact substances are the main sources of PFAS in food, increasing the risk of human dietary exposure. Numerous epidemiological studies have established the link between dietary exposure to PFAS and liver disease. Correspondingly, PFAS induced-hepatotoxicity (e.g., hepatomegaly, cell viability, inflammation, oxidative stress, bile acid metabolism dysregulation and glycolipid metabolism disorder) observed from in vitro models and in vivo rodent studies have been extensively reported. In this review, the pertinent literature of the last 5 years from the Web of Science database was researched. This study summarized the source and fate of PFAS, and reviewed the occurrence of PFAS in food system (natural and processed food). Subsequently, the characteristics of human dietary exposure PFAS (population characteristics, distribution trend, absorption and distribution) were mentioned. Additionally, epidemiologic evidence linking PFAS exposure and liver disease was alluded, and the PFAS-induced hepatotoxicity observed from in vitro models and in vivo rodent studies was comprehensively reviewed. Lastly, we highlighted several critical knowledge gaps and proposed future research directions. This review aims to raise public awareness about food PFAS contamination and its potential risks to human liver health.

Occurrence and biomagnification of perfluoroalkyl substances (PFAS) in Lake Michigan fishes

We measured perfluoroalkyl substances (PFAS) in prey and predator fish from Lake Michigan (USA) to investigate the occurrence and biomagnification of these compounds in this important ecosystem. Twenty-one PFAS were analyzed in 117 prey fish obtained from sites across Lake Michigan and in 87 salmonids collected in four lake quadrants. The mean concentration of sum (∑) PFAS above the method detection limit was 12.7 ± 6.96 ng g-1 wet weight in predator fish (all of which were salmonids) and 10.7 ± 10.4 ng g-1 in prey fish, with outlier levels found in slimy sculpin, Cottus cognatus (187 ± 12.2 ng g-1 ww). Perfluorooctanoic sulfonic acid (PFOS) was the most frequently detected and most abundant compound of the 21 PFAS, occurring in 98 % of individuals with a mean concentration of 9.86 ± 6.36 ng g-1 ww without outliers. Perfluoroalkyl carboxylates (PFCA) concentrations were higher in prey fish than in predators, with some compounds such as perfluorooctanoic acid (PFOA) being detected in higher frequency in prey fish. Besides PFOS, detection of several long-chain (C8-C12) PFCAs were observed in >80 % of the prey fish. Overall, the observed concentrations in Lake Michigan fish were lower than those reported in other Laurentian Great Lakes except for Lake Superior. Biomagnification factors (BMFs) for PFOS exceeded 1.0 (range, 1.80 to 5.12) in all predator-prey relationships analyzed, indicating biomagnification of these compounds, whereas BMFs of other long-chain PFCAs varied according to the fish species. PFAS were found in all fish species measured from Lake Michigan and commonly biomagnified from prey to predator fish, strongly suggesting a dietary connection.

Tire-rubber related pollutant 6-PPD quinone: A review of its transformation, environmental distribution, bioavailability, and toxicity

The antioxidant 6-PPD has been widely used to prevent cracking and thermal oxidative degradation and to extend the service life of tire rubber. 6-PPD quinone (6-PPDQ) is formed via the reaction of 6-PPD with O3. Due to its acute lethality in coho salmon, 6-PPDQ has become an emerging pollutant of increasing concern. In this review, we provide a critical overview of the generation, environmental distribution, bioavailability, and potential toxicity of 6-PPDQ. The transformation pathways from 6-PPD to 6-PPDQ include the N-1,3-dimethylbutyl-N-phenyl quinone diamine (QDI), intermediate phenol, and semiquinone radical pathways. 6-PPDQ has been frequently detected in water, dust, air particles, soil, and sediments, indicating its large-scale and potentially global pollution trend. 6-PPDQ is bioavailable to both aquatic animals and mammals and acute exposure to 6-PPDQ can be lethal to some organisms. Exposure to 6-PPDQ at environmentally relevant concentrations could induce several types of toxicity, including neurotoxicity, intestinal toxicity, and reproductive toxicity. This review also identifies and discusses knowledge gaps and research needs for the study of 6-PPDQ. This review facilitates a better understanding of the environmental occurrence and exposure risk of 6-PPDQ.

Developing Methods for Assessing Trophic Magnification of Perfluoroalkyl Substances within an Urban Terrestrial Avian Food Web

We investigated the trophic magnification potential of perfluoroalkyl substances (PFAS) in a terrestrial food web by using a chemical activity-based approach, which involved normalizing concentrations of PFAS in biota to their relative biochemical composition in order to provide a thermodynamically accurate basis for comparing concentrations of PFAS in biota. Samples of hawk eggs, songbird tissues, and invertebrates were collected and analyzed for concentrations of 18 perfluoroalkyl acids (PFAAs) and for polar lipid, neutral lipid, total protein, albumin, and water content. Estimated mass fractions of PFCA C8-C11 and PFSA C4-C8 predominantly occurred in albumin within biota samples from the food web with smaller estimated fractions in polar lipids > structural proteins > neutral lipids and insignificant amounts in water. Estimated mass fractions of longer-chained PFAS (i.e., C12-C16) mainly occurred in polar lipids with smaller estimated fractions in albumin > structural proteins > neutral lipids > and water. Chemical activity-based TMFs indicated that PFNA, PFDA, PFUdA, PFDoA, PFTrDA, PFTeDA, PFOS, and PFDS biomagnified in the food web; PFOA, PFHxDA, and PFHxS did not appear to biomagnify; and PFBS biodiluted. Chemical activity-based TMFs for PFCA C8-C11 and PFSA C4-C8 were in good agreement with corresponding TMFs derived with concentrations normalized to only total protein in biota, suggesting that concentrations normalized to total protein may be appropriate proxies of chemical activity-based TMFs for PFAS, which predominantly partition to albumin. Similarly, TMFs derived with concentrations normalized to albumin may be suitable proxies of chemical activity-based TMFs for longer-chained PFAS, which predominantly partition to polar lipids.

Occurrence and Bioaccumulation Patterns of Per- and Polyfluoroalkyl Substances (PFAS) in the Marine Environment

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic compounds used in commercial applications, household products, and industrial processes. The concern around the environmental persistence, bioaccumulation and toxicity of this vast contaminant class continues to rise. We conducted a review of the scientific literature to compare patterns of PFAS bioaccumulation in marine organisms and identify compounds of potential concern. PFAS occurrence data in seawater, sediments, and several marine taxa was analyzed from studies published between the years 2000 and 2020. Taxonomic and tissue-specific differences indicated elevated levels in protein-rich tissues and in air-breathing organisms compared to those that respire in water. Long-chain perfluoroalkyl carboxylic acids, particularly perfluoroundecanoic acid, were detected at high concentrations across several taxa and across temporal studies indicating their persistence and bioaccumulative potential. Perfluorooctanesulfonic acid was elevated in various tissue types across taxa. Precursors and replacement PFAS were detected in several marine organisms. Identification of these trends across habitats and taxa can be applied towards biomonitoring efforts, determination of high-risk taxa, and criteria development. This review also highlights challenges related to PFAS biomonitoring including (i) effects of environmental and biological variables, (ii) evaluation of protein binding sites and affinities, and (iii) biotransformation of precursors.

Bioaccumulation of per- and polyfluoroalkyl substances by freshwater benthic macroinvertebrates: Impact of species and sediment organic carbon content

Per- and polyfluoroalkyl substances (PFAS) in aquatic environments have caused global concern due to their persistence, toxicity, and potential bioaccumulation of some compounds. As an important compartment of the aquatic ecosystem, sediment properties impact PFAS partitioning between aqueous and solid phases, but little is known about the influence of sediment organic carbon content on PFAS bioaccumulation in benthic organisms. In this study, three freshwater benthic macroinvertebrates - worms (Lumbriculus variegatus), mussels (Elliptio complanata) and snails (Physella acuta) - were exposed for 28 days to PFAS spiked synthetic sediment equilibrated with a synthetic surface water. Using microcosms, sediment organic carbon content - 2%, 5% and 8% - was manipulated to assess its impact on PFAS bioaccumulation. Worms were found to have substantially greater PFAS bioaccumulation compared to mussels and snails. The bioaccumulation factors (BAFs) and biota sediment accumulation factors (BSAFs) in worms were both one to two magnitudes higher than in mussels and snails, likely due to different habitat-specific uptake pathways and elimination capacities among species. In these experiments, increasing sediment organic carbon content decreased the bioaccumulation of PFAS to benthic macroinvertebrates. In worms, sediment organic carbon content was hypothesized to impact PFAS bioaccumulation by affecting PFAS partitioning and sediment ingestion rate. Notably, the BSAF values of 8:2 fluorotelomer sulfonic acid (FTS) were the largest among 14 PFAS for all species, suggesting that the benthic macroinvertebrates probably have different metabolic mechanisms for fluorotelomer sulfonic acids compared to fish evaluated in published literature. Understanding the impact of species and sediment organic carbon on PFAS bioaccumulation is key to developing environmental quality guidelines and evaluating potential ecological risks to higher trophic level species.

Suspect Screening and Nontargeted Analysis of Per- and Polyfluoroalkyl Substances in a Lake Ontario Food Web

Per- and polyfluoroalkyl substances (PFAS) are globally distributed in the natural environment, and their persistent and bioaccumulative potential illicit public concern. The production of certain PFAS has been halted or controlled by regulation due to their adverse effect on the health of humans and wildlife. However, new PFAS are continuously developed as alternatives to legacy PFAS. Additionally, many precursors are unknown, and their metabolites have not been assessed. To better understand the PFAS profiles in the Lake Ontario (LO) aquatic food web, a quadrupole time-of-flight mass spectrometer (QToF) coupled to ultrahigh-performance liquid chromatography (UPLC) was used to generate high-resolution mass spectra (HRMS) from sample extracts. The HRMS data files were analyzed using an isotopic profile deconvoluted chromatogram (IPDC) algorithm to isolate PFAS profiles in aquatic organisms. Fourteen legacy PFAAs (C5-C14) and 15 known precursors were detected in the LO food web. In addition, over 400 unknown PFAS features that appear to biomagnify in the LO food web were found. Profundal benthic organisms, deepwater sculpin(Myoxocephalus thompsonii), and Mysis were found to have more known precursors than other species in the food web, suggesting that there is a large reservoir of fluorinated substances in the benthic zone.

Efficient Removal of Perfluorinated Chemicals from Contaminated Water Sources Using Magnetic Fluorinated Polymer Sorbents

Efficient removal of per- and polyfluoroalkyl substances (PFAS) from contaminated waters is urgently needed to safeguard public and environmental health. In this work, novel magnetic fluorinated polymer sorbents were designed to allow efficient capture of PFAS and fast magnetic recovery of the sorbed material. The new sorbent has superior PFAS removal efficiency compared with the commercially available activated carbon and ion-exchange resins. The removal of the ammonium salt of hexafluoropropylene oxide dimer acid (GenX) reaches >99 % within 30 s, and the estimated sorption capacity was 219 mg g-1 based on the Langmuir model. Robust and efficient regeneration of the magnetic polymer sorbent was confirmed by the repeated sorption and desorption of GenX over four cycles. The sorption of multiple PFAS in two real contaminated water matrices at an environmentally relevant concentration (1 ppb) shows >95 % removal for the majority of PFAS tested in this study.

Comparison of sub-lethal metabolic perturbations of select legacy and novel perfluorinated alkyl substances (PFAS) in Daphnia magna

Per- and polyfluoroalkyl substances (PFAS) are a class of pollutants of concern due to their ubiquitous presence, persistence, and toxicity in aquatic environments. Legacy PFAS pollutants such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have been more widely studied in aquatic environments. However, replacement PFAS, such as ammonium perfluoro (2-methyl-3-oxahexanoate; GenX) are increasingly being detected with little known information surrounding their toxicity. Here, Daphnia magna, a model organism for freshwater ecotoxicology was used to compare the acute sub-lethal toxicity of PFOS, PFOA, GenX, and PFAS mixtures. Using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the targeted polar metabolic profile extracted from single Daphnia was quantified to investigate perturbations in the exposure groups versus the unexposed organisms. Multivariate statistical analyses demonstrated significant non-monotonic separation in PFOA, GenX, and PFAS mixture exposures. Sub-lethal exposure to concentrations of PFOS did not lead to significant separation in multivariate analyses. Univariate statistics and pathway analyses were used to elucidate the mode of action of PFAS exposure. Exposure to all individual PFAS led to significant perturbations in many amino acids including cysteine, histidine, tryptophan, glycine, and serine. These perturbations are consistent with biochemical pathway disruptions in the pantothenate and Coenzyme A (CoA) biosynthesis, thiamine metabolism, histidine metabolism, and aminoacyl-tRNA biosynthesis pathways. Overall, the collected metabolomic data is consistent with disruptions in energy metabolism and protein synthesis as the primary mode of action of sub-lethal PFAS exposure. Secondary modes of action among individual pollutant exposures demonstrated that the structural properties (carboxylic acid vs. sulfonic acid group) may play a role in the metabolic perturbations observed. Sub-lethal exposure to PFAS mixtures highlighted a mixed response when compared to the individual pollutants (PFOS, PFOA, and GenX). Overall, this study emphasizes the niche capability of environmental metabolomics to differentiate secondary modes of action from metabolic perturbations in both single pollutant and pollutant mixtures within the same chemical class.