Review: Evolution of evidence on PFOA and health following the assessments of the C8 Science Panel

United States Environmental Protection Agency's Perfluorooctanoic Acid, Perfluorooctane Sulfonic Acid, and Related Per- and Polyfluoroalkyl Substances 2024 Drinking Water Maximum Contaminant Level: Part 2 - Fifteen Misconceptions About the Health Hazards

This paper examines widely held beliefs about the six per- and polyfluoroalkyl substances (PFAS) addressed in the final U.S. Environmental Protection Agency's (EPA) rule on PFAS in drinking water (e.g., the Maximum Contaminant Levels - MCLs). Based on our understanding of the scientific literature and the comments submitted by stakeholders regarding the EPA's regulation that was promulgated in April 2024, we identified 15 misconceptions that had a weak scientific foundation. These are now memoralized in the MCLs for the six PFAS but remain debated due to ongoing ambiguous research findings. Many critics of the MCLs found the EPA's systematic review of the published relevant information, particularly the toxicology of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), to be inadequate. The following seven views are among the most important. First, the EPA asserted that the toxicology of these six chemicals was poorly understood and lacked sufficient data to determine a safe daily intake level for chronic health effects; nonetheless, they promulgated what may be the costliest environmental regulation to date. Notably, adverse effects remain difficult to demonstrate in occupationally exposed individuals even at blood concentrations 50-100 times higher than current background PFAS levels. Second, the Agency indicated that the epidemiology data showed that exposure to PFOA and PFOS caused kidney and potentially other cancers, yet the data were equivocal and do not support that assertion. Third, it was stated that specific non-cancer effects, such as heart disease, would be prevented under the promulgated rule; however, the studies that they relied upon do not show an increased incidence of heart disease even in highly exposed populations. Fourth, the Agency relied on animal data to support its views on the likely toxic effects in humans, despite ample toxicology data that animals, particularly rodents, are poor predictors of the human response to PFAS exposures. Fifth, the EPA predicted a reduction in healthcare expenditures that would offset much of the cost of complying with the MCL, but, they did not have adequate data to support this prediction. Sixth, the EPA suggested that these six PFAS act through a shared mechanism of action (i.e., PPARα pathway induction); however, data indicate that PPARα induction in humans may be 80% less than what is observed in rodents. Also, induction of the PPARα pathway is not a cause of systemic disease. Seventh, the Agency failed to disclose that achieving the new MCL would yield negligible reductions in blood PFAS levels even among highly exposed populations, given drinking water accounts for only 20% or less of total PFAS exposure. The survey that could answer that question, the EPA's fifth Unregulated Contaminant Monitoring Rule, was only 25% complete at the time the MCL was promulgated. Overall, our analysis concluded that while the EPA's intent to regulate these chemicals due to their environmental presence was necessary, the derivation of the MCLs and the alleged health effects was based on the application of the precautionary principle rather than robust scientific evidence.

Health impacts of exposure to synthetic chemicals in food

Humans are widely exposed to synthetic chemicals, especially via food. The types of chemical contaminants in food (including food contact chemicals) are diverse, and many of these are known to be hazardous, with mounting evidence that some contribute to noncommunicable diseases. The increasing consumption of ultra-processed foods, which contain synthetic chemicals, also contributes to adverse health. If the chemical contamination of foods were better characterized, then this issue would likely receive more attention as an important opportunity for disease prevention. In this Review, we discuss types and sources of synthetic food contaminants, focusing on food contact chemicals and their presence in ultra-processed foods. We outline future research needs and highlight possible responses at different food system levels. A sustainable transition of the food system must address the health impacts of synthetic chemicals in food; we discuss existing solutions that do justice to the complexity of the issue while avoiding regrettable substitutions and rebound effects.

Exposure to Per- and Polyfluoroalkyl Substances and the Risk of Prostate and Ovarian Cancer: An Epidemiologic Meta-Analysis

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants. Previous research has linked PFAS exposure to prostate and ovarian cancer risk, however, the conclusions have been inconsistent. This research purpose was to determine the relationship between PFAS exposure and prostate and ovarian cancer at the population level.

METHODS

We systematically reviewed three databases-PubMed, Web of Science, and Embase-for research from when these databases were established to April 15, 2024. The quality of the retrieved research was evaluated using the Newcastle-Ottawa Scale (NOS) quality measurement tool. Meta-analysis of the extracted data was conducted using Stata 18. We also conducted sensitivity and subgroup analyses, as well as Begg's and Egger's tests.

RESULTS

Twelve publications were involved in the analysis for prostate cancer, and six were included for ovary cancer. The outcomes indicated that PFOS exposure was positively related to prostate cancer (OR: 1.13, 95% CI: 1.00-1.28), while mixed PFAS exposure was positively related to ovarian cancer (OR: 1.63, 95% CI: 1.49-1.78). The source of heterogeneity identified in the subgroup analysis was primarily attributable to variations in study design. No significant study bias was detected in the analysis.

CONCLUSION

The study demonstrated an association between PFAS exposure and both prostate and ovarian cancers. Further investigation is required to clarify the underlying mechanisms and potential associations.

Longitudinal association of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) exposure with lipid traits, in a healthy unselected population

BACKGROUND

Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic Acid (PFOS) are synthetic substances with long half-lives. Their presence is widespread and pervasive, and they are noted for their environmental persistence. Research has shown these chemicals to be associated with dyslipidaemia, although few studies have considered the long-term associations in the general population.

OBJECTIVES

The aim of this study was to consider the longitudinal and cross-sectional associations with lipid phenotypes.

METHODS

We investigated the association of these chemicals with total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides (TG), and the total cholesterol: high-density lipoprotein ratio (TC:HDL), in a healthy unselected British population of twins (n = 2069), measured at three timepoints between 1996 and 2014.

RESULTS

Serum levels of PFOA and PFOS decreased over time during this period. We demonstrate longitudinal associations across serum levels of both PFOA and PFOS, finding positive associations with TC (PFOA:β = 0.51, p = 1.9e-07; PFOS:β = 0.24, p = 3.8e-05) and LDL (PFOA:β = 0.61, p = 1.7e-11; PFOS:β = 0.42, p = 1.6e-14), and consistent negative associations with HDL and PFOA (β = -0.12, p = 0.003) and PFOS (β = -0.25, p = <2e-16). We also observe cross-sectional associations of PFAS with lipids across all three timepoints.

IMPACT

PFAS remain persistent in the environment, despite regulations, due to their structural properties, leaving humans open to exposure. There is less understanding of how chronic low exposure to these chemicals, particularly within an unselected population, may impact health outcomes. This study reports the longitudinal associations of PFOA and PFOS over an 18-year window with 5 lipid phenotypes, highlighting that despite falling serum levels, PFAS exposure may lead to hyperlipidaemia. We further investigate the cross-sectional associations across three timepoints to understand time-dependent effects, demonstrating associations persist. This work aids our understanding on the long-term effect of chronic PFAS exposure.

The evolution of PFAS epidemiology: new scientific developments call into question alleged "probable links" between PFOA and kidney cancer and thyroid disease

The growing body of litigation alleging bodily injury from per- and polyfluoroalkyl substances (PFAS) exposure has put a spotlight on the available scientific literature regarding potential human health impacts, and the various data gaps within the literature. This review assesses the evolution of epidemiological findings for perfluorooctanoic acid (PFOA), a PFAS compound. In 2012, the C8 Science Panel published a series of reports determining "probable links" for certain health outcomes (including kidney cancer and thyroid disease); it was the first major research effort investigating potential adverse health effects following exposure to PFOA. At that time, there were only a handful of available studies investigating human effects (i.e., epidemiological studies). Now, over a decade later, the epidemiological body of literature for PFOA has grown substantially. As is the nature of evolving science, the additional research has spotlighted important improvements in exposure classification, confounding control, and statistical methods that strengthen more recent scientific investigations. As the body of epidemiological literature for PFAS health effects grows and evolves with improved methodology, the original C8 Science Panel's conclusions have not been supported by more recent investigations. Within the context of general causation, while gaps remain in the body of research, more recent epidemiological findings support that there is no causal relationship between PFOA exposure and kidney cancer or thyroid disease.

Distributions and partitioning of airborne Per- and Polyfluoroalkyl Substances (PFAS) in urban atmosphere of Northern New Jersey

This study collected gas-phase and particulate samples, wet deposition, and total deposition from the urban atmosphere in Northern New Jersey to determine the atmospheric characteristics of airborne ionic Per- and Polyfluoroalkyl Substances (PFAS). The results showed higher PFAS concentrations in the gas phase (197.7 ± 47.9 pg·m-3) compared to the particulate samples (48.3 ± 47.9 pg·m-3), indicating higher inhalation risks to human health. Short-chain alternative PFAS, such as perfluoroheptanoic acid (PFHpA), had higher concentrations in the gas-phase than the US EPA-regulated PFAS (e.g., PFHpA reached 142.6 ± 28.0 pg·m-3). Additionally, PFHpA had the lowest rain-air partition coefficient, suggesting its preferential distribution in the gas phase. In contrast, perfluorohexanoic acid (PFHxA) exhibited the highest levels of both the total deposition rate (12.4 ± 29.0 μg·m-2 yr-1) and wet deposition rate (40.2 ± 76.0 μg·m-2 yr-1) among the 24 PFAS analyzed in this study. Most PFAS had higher wet deposition fluxes than total deposition fluxes, indicating they may predominately accumulate at the water-air interfaces and could re-enter the atmosphere. Legacy perfluorooctanoic acid (PFOA) still had the highest concentrations (12.3 ± 8.5 pg·m-3) in particulate samples, ranking second in both gas-phase and total deposition samples and third in wet deposition samples. The results reveal that airborne PFAS in urban environments could pose negative impacts on human health and the natural environment.

Family-based exposure assessment of legacy and alternative poly- and perfluoroalkyl substances (PFASs) by multiple pathways

PFASs are persistent, amphiphilic chemicals that bioaccumulate and cause adverse health effects. Restrictions on major PFASs have increased exposure to precursors and alternatives, requiring examination of contamination from major sources and internal levels. We collected house dust (n = 45), dietary (n = 124), and serum (n = 123) from 48 families and analyzed 30 PFASs. Three PFCAs (PFOA, PFDA, and PFUnDA) and one precursor (6:2diPAP) showed detection rates >90 % in house dust. Among these compounds, 6:2diPAP showed the highest level, with median of 4.71 ng/g dry weight. In dietary, PFPeA (1.43 ng/g) and 6:2FTS (0.61 ng/g) had the highest medians and were detected in all samples. In serum, the highest median was PFOA (4.50 ng/mL), followed by linear (L)-PFOS (3.90 ng/mL), L-PFHxS (1.79 ng/mL), and PFNA (1.15 ng/mL) across all family groups. The study identified diet as a significant exposure pathway, underscoring the importance of dietary habits in PFASs intake. The estimated daily intake from PFOA for all family members exceeded the USEPA's threshold. Compared to the EFSA's threshold for a mixture of four PFASs, exceedances ranged from 18 % to 38 %. This study highlights the need for continuous monitoring and regulation of PFASs and their alternatives to mitigate health risks.

Target and Suspect Screening Reveal PFAS Exceeding European Union Guideline in Various Water Sources South of Lyon, France

Lyon, a major hub for chemical industries in France, has been identified as a contamination hotspot of per- and polyfluoroalkyl substances (PFAS). Major chemical companies in the Pierre-Bénite area have used PFAS in the production of fluoropolymers and fluorotelomers, with effluents discharged into the Rhône River. This together with other contamination sources, such as firefighting foam use at a vicinal harbor oil depot, likely resulted in a complex PFAS signature. This study investigated PFAS contamination in various water sources in southern Lyon, including ponds, rivers, factory channels, wells, springs, and tap water. Out of 47 samples, 22 had a Σ77PFAS above 100 ng/L (maximum: ∼700 ng/L), and 67% of the tap water samples exceeded the European guideline of 100 ng/L for Σ20PFAS. Target PFAS profiles were dominated by perfluoroalkyl carboxylates (particularly C4 to C8), in agreement with their historical or current industrial usage. Suspect screening also revealed the occurrence of electrochemical fluorination precursors such as N-sulfopropyldimethylammoniopropyl perfluorohexanesulfonamido acetic acid (N-SPAmP-FHxSAA) and bistriflimide (used in the composition of ionic liquids). Certain fluorotelomers, including ESI+ (e.g., 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTAB)) and ESI- (e.g., 6:2 FTS, 6:2 FTSAS-sulfone) compounds, were more prevalent in surface water than in tap or groundwater.

Arginine Metabolism Reprogramming in Perfluorooctanoic Acid (PFOA)-Induced Liver Injury

Perfluorooctanoic acid (PFOA) is a persistent pollutant that has gained worldwide attention, owing to its widespread presence in the environment. Previous studies have reported that PFOA upregulates lipid metabolism and is associated with liver injury in humans. However, when the fatty acid degradation pathway is activated, lipid accumulation still occurs, suggesting the presence of unknown pathways and mechanisms that remain to be elucidated. In this study, adult C57BL/6N mice were exposed to PFOA at 0.1, 1, and 10 mg/kg/day. Using integrated metabolomics and transcriptomics, it was uncovered that arginine metabolism was differentially downregulated in all three groups. In vitro studies confirmed the downregulation of arginine metabolism in MIHA cell lines treated with PFOA. Supplementation of arginine could effectively rescue liver injury and downregulate the chemokine levels caused by PFOA. This finding highlights the contribution of arginine metabolism in maintaining liver health following PFOA exposure and suggests potential mechanisms of metabolic and immune modulation.

Enhanced spatial analysis assessing the association between PFAS-contaminated water and cancer incidence: rationale, study design, and methods

BACKGROUND

Cancer is a complex set of diseases, and many have decades-long lag times between possible exposure and diagnosis. Environmental exposures, such as per- and poly-fluoroalkyl substances (PFAS) and area-level risk factors (e.g., socioeconomic variables), vary for people over time and space. Evidence suggests PFAS exposure is associated with several cancers; however, studies to date have various limitations. Few studies have used rigorous spatiotemporal approaches, and, to our knowledge, none have assessed cumulative exposures given residential histories or incorporated chemical mixture modeling. Thus, spatiotemporal analysis using advanced statistical approaches, accounting for spatially structured and unstructured heterogeneity in risk, can be a highly informative strategy for addressing the potential health effects of PFAS exposure.

METHODS

Using population-based incident cancer cases and cancer-free controls in a 12-county area of southeastern Pennsylvania, we will apply Bayesian spatiotemporal analysis methods using historically reconstructed PFAS-contaminated water exposure given residential histories, and other potential cancer determinants over time. Bayesian group index models enable assessment of various mixtures of highly correlated PFAS chemical exposures incorporating mobility/residential history, and contextual factors to determine the association of PFAS-related exposures and cancer incidence.

DISCUSSION

The purpose of this paper is to describe the Enhanced PFAS Spatial Analysis study rationale, study design, and methods.

DAMP-ing IBD: Extinguish the Fire and Prevent Smoldering

In inflammatory bowel diseases (IBD), the most promising therapies targeting cytokines or immune cell trafficking demonstrate around 40% efficacy. As IBD is a multifactorial inflammation of the intestinal tract, a single-target approach is unlikely to solve this problem, necessitating an alternative strategy that addresses its variability. One approach often overlooked by the pharmaceutically driven therapeutic options is to address the impact of environmental factors. This is somewhat surprising considering that IBD is increasingly viewed as a condition heavily influenced by such factors, including diet, stress, and environmental pollution-often referred to as the "Western lifestyle". In IBD, intestinal responses result from a complex interplay among the genetic background of the patient, molecules, cells, and the local inflammatory microenvironment where danger- and microbe-associated molecular patterns (D/MAMPs) provide an adjuvant-rich environment. Through activating DAMP receptors, this array of pro-inflammatory factors can stimulate, for example, the NLRP3 inflammasome-a major amplifier of the inflammatory response in IBD, and various immune cells via non-specific bystander activation of myeloid cells (e.g., macrophages) and lymphocytes (e.g., tissue-resident memory T cells). Current single-target biological treatment approaches can dampen the immune response, but without reducing exposure to environmental factors of IBD, e.g., by changing diet (reducing ultra-processed foods), the adjuvant-rich landscape is never resolved and continues to drive intestinal mucosal dysregulation. Thus, such treatment approaches are not enough to put out the inflammatory fire. The resultant smoldering, low-grade inflammation diminishes physiological resilience of the intestinal (micro)environment, perpetuating the state of chronic disease. Therefore, our hypothesis posits that successful interventions for IBD must address the complexity of the disease by simultaneously targeting all modifiable aspects: innate immunity cytokines and microbiota, adaptive immunity cells and cytokines, and factors that relate to the (micro)environment. Thus the disease can be comprehensively treated across the nano-, meso-, and microscales, rather than with a focus on single targets. A broader perspective on IBD treatment that also includes options to adapt the DAMPing (micro)environment is warranted.

PFAS, PCBs, PCDD/Fs, PAHs and extractable organic fluorine in bio-based fertilizers, amended soils and plants: Exposure assessment and temporal trends

Bio-based fertilizers (BBFs) produced from organic waste contribute to closed-loop nutrient cycles and circular agriculture. However, persistent organic contaminants, such as per- and poly-fluoroalkyl substances (PFAS), polychlorobiphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as well as polyaromatic hydrocarbons (PAHs) can be present in organic waste or be formed during valorization processes. Consequently, these hazardous substances may be introduced into agricultural soils and the food chain via BBFs. This study assessed the exposure of 84 target substances and extractable organic fluorine (EOF) in 19 BBFs produced from different types of waste, including agricultural and food industrial waste, sewage sludge, and biowaste, and through various types of valorization methods, including hygienization at low temperatures (<150 °C) as well as pyrolysis and incineration at elevated temperatures (150-900 °C). The concentrations in BBFs (ΣPFOS & PFOA: <30 μg kg-1, Σ6PCBs: <15 μg kg-1, Σ11PAHs: <3 mg kg-1, Σ17PCDD/Fs: <4 ng TEQ kg-1) were found to be below the strictest thresholds used in individual EU countries, with only one exception (pyrolyzed sewage sludge, Σ11PAHs: 5.9 mg kg-1). Five BBFs produced from sewage sludge or chicken manure contained high concentrations of EOF (>140 μg kg-1), so monitoring of more PFAS is recommended. The calculated expected concentrations in soils after one BBF application (e.g. PFOS: <0.05 μg kg-1) fell below background contamination levels (PFOS: 2.7 μg kg-1) elsewhere in the literature. This was confirmed by the analysis of BBF-amended soils from field experiments (Finland and Austria). Studies on target legacy contaminants in sewage sludge were reviewed, indicating a general decreasing trend in concentration with an apparent half-life ranging from 4 (PFOS) to 9 (PCDD/Fs) years. Modelled cumulative concentrations of the target contaminants in agricultural soils indicated low long-term risks. Concentrations estimated and analyzed in cereal grains were low, indicating that exposure by cereal consumption is well below tolerable daily intakes.

Mode of action Criteria for selection of the critical effect and safe dose range for PFOA by the Alliance for risk assessment

In response to the current disparity in risk assessment values for PFOA from different agencies and countries, an international effort facilitated by the Alliance for Risk Assessment (ARA) was recently undertaken to characterize the range of scientifically supportable safe dose estimates. In this assessment (Burgoon et al., 2023), an evaluation of the evidence regarding the potential modes of action (MOA) for PFOA toxicity was performed first, so that it could be used to inform subsequent decisions regarding potential critical effects and studies. This review describes the evidence considered in the MOA evaluations that were performed as part of the ARA effort. The overall conclusions of this evaluation are that the available mechanistic data do not support any conclusion that reported epidemiological associations of blood concentrations of PFOA as low as 10 ng/mL with various health effects should be considered causal. It is more likely that the reported associations may instead reflect reverse causality/pharmacokinetic confounding. These conclusions are consistent with the opinions of the World Health Organization (WHO, 2022).

Associations between per- and poly-fluoroalkyl substance (PFAS) exposure and immune responses among women in the California Teachers study: A cross-sectional evaluation

INTRODUCTION

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants that have been linked to a number of health outcomes, including those related to immune dysfunction. However, there are limited numbers of epidemiological-based studies that directly examine the association between PFAS exposure and immune responses.

METHODS

In this cross-sectional study nested in the California Teachers Study cohort, we measured nine PFAS analytes in serum. Of the 9 analytes, we further evaluated four (PFHxS [perfluorohexane sulfonate], PFNA [perfluorononanoic acid], PFOA [perfluorooctanoic acid], PFOS [perfluorooctanesulfonic acid]) that had detection levels of > 80 %, in relation to 16 systemic inflammatory/immune markers and corresponding immune pathways (Th1 [pro-inflammatory/macrophage activation], B-cell activation, and T-cell activation). Study participants (n = 722) were female, completed a questionnaire regarding various health measures and behaviors, and donated a blood sample between 2013-2016. The association between PFAS analytes and individual immune markers and pathways were evaluated by calculating odds ratios (OR) and 95 % confidence intervals (CI) in a logistic regression model. PFAS analytes were evaluated both as a dichotomous exposure (above or below the respective median) and as a continuous variable (per 1 unit increase [ng/mL]).

RESULTS

The prevalence of detecting any PFAS analyte rose with increasing age, with the highest PFAS prevalence observed among those aged 75 + years and the lowest PFAS prevalence observed among those aged 40-49 years (study participant age range: 40-95 years). Significant associations with BAFF (B-cell activating factor) levels above the median were observed among participants with elevated (defined as above the median) levels of PFHxS (OR=1.53), PFOA (OR=1.43), and PFOS (OR=1.40). Similarly, there were statistically significant associations between elevated levels of PFHxS and TNFRII (tumor necrosis factor receptor 2) levels (OR=1.78) and IL2Rα (interleukin 2 receptor subunit alpha) levels (OR=1.48). We also observed significant inverse associations between elevated PFNA and sCD14 (soluble cluster of differentiation 14) (OR=0.73). No significant associations were observed between elevated PFNA and any immune marker. Evaluation of PFAS exposures as continuous exposures in association with dichotomized cytokines were generally consistent with the dichotomized associations.

CONCLUSIONS

PFAS exposure was associated with altered levels of circulating inflammatory/immune markers; the associations were specific to PFAS analyte and immune marker. If validated, our results may suggest potential immune mechanisms underlying associations between the different PFAS analytes and adverse health outcomes.

Monitoring of per- and polyfluoroalkyl substances (PFAS) in human blood samples collected in three regions with known PFAS releases in the environment and three control regions in South Germany

Per- and polyfluoroalkyl substances (PFAS) are known as persistent and bioaccumulative chemicals. The present paper describes the analysis of 969 human blood samples collected in South Germany aiming to determine whether there are statistic significant differences in internal PFAS burden between three regions with known PFAS releases in the environment (study regions) and three regions without known PFAS releases in the environment (control regions). Nine environmental relevant PFAS were analyzed, including the perfluorooctanoic acid (PFOA) substitute 3H-perfluoro-3-[(3-methoxy-propoxy)propanoic acid] ammonium salt (ADONA). We found that concentrations of PFOA and perfluorooctane sulfonate (PFOS) were higher than for all other PFAS in all of the six regions, but all medians of PFOA (between 0.8 and 0.9 ng/ml for the study and control regions) and PFOS (between 1.3 and 1.5 ng/ml for the study regions and between 1.4 and 1.5 ng/ml for the control regions) were below the human biomonitoring values (HBM) I for PFOA (2 ng/ml) und for PFOS (5 ng/ml) derived by the German HBM Commission. Concentrations of ADONA were below the limit of quantification in all samples. Minor differences were observed in PFAS blood levels between study and control regions. Especially for PFOS and PFOA the medians for women are slightly lower compared to men. In summary, individuals living in regions with known environmental PFAS contaminations show no higher internal PFAS exposure to controls and in comparison to other studies in the literature.

Evaluation of the impact of L-Tryptophan on the toxicology of Perfluorooctanoic acid in Daphnia magna: Characterization and perspectives

Perfluorooctanoic acid (PFOA) is a pervasive environmental contaminant with well-documented toxic effects on both humans and animals, attracting significant scientific concern. Due to its affinity for proteins, research has predominantly focused on PFOA's interactions with biological macromolecules. However, the specific role of smaller molecules, such as amino acids, remains underexplored. This study uniquely evaluates the potential of l-tryptophan (L-Trp) to mitigate PFOA toxicity and investigates the interaction mechanisms involved. Results indicate that the presence of L-Trp in PFOA-contaminated water reduces acute toxicity in Daphnia magna, with an optimal molar ratio of approximately 1:2 (Trp:PFOA). The findings reveal that non-covalent interactions, particularly van der Waals forces and hydrogen bonds, are central to the Trp-PFOA complex formation. Additional contributions from hydrophobic interactions at the indole group and electrostatic forces between carbonyl and amine groups further stabilize the complex. These interactions likely reduce PFOA's toxicity by altering its bioavailability and distribution. While this study offers valuable insights into the binding mechanisms between L-Trp and PFOA, it raises important questions about the reversibility of this interaction and its applicability to other per- and polyfluoroalkyl substances (PFASs).

Possible mechanisms for adverse effects on zebrafish sperm and testes associated with low-level chronic PFOA exposure

Perfluorooctanoic acid (PFOA), which is widely used during the manufacturing of fluoropolymer coatings and polytetrafluoroethylene, is now a widespread pollutant in the environment and within the human body. This study used zebrafish, an aquatic model species, to investigate how low levels of chronic PFOA exposure affect the reproductive system. The results of the experiments in which zebrafish were exposed to 414 ng/L or 4140 ng/L for 60 days showed a variety of adverse effects on testicular tissue and sperm, including dose-dependent changes in plasma estradiol and testosterone levels, various sperm malformations, decreased sperm motility and concentration, and PFOA-induced oxidative stress and testicular damage with increased rates of apoptosis. In addition, offspring of the zebrafish that had been exposed to PFOA were characterized by increased malformation and mortality. Subsequent transcriptional analyses of the male gonads revealed the significant activation of oxidative stress bioprocesses and immuno-inflammatory signaling pathways, along with the dysregulation of reproductive bioprocesses. In conclusion, low-level chronic exposure to PFOA affects both the reproductive performance of adults and the development of offspring; the mechanisms for these adverse effects involve alterations in several molecular pathways that may be involved in PFOA-induced oxidative stress and reproductive abnormalities. The presented data can be used to assess the ecotoxicity of PFOA to the male reproductive system at environmentally-relevant concentrations.

Itaconic Acid Alleviates Perfluorooctanoic Acid-Induced Oxidative Stress and Intestinal Damage by Regulating the Keap1/Nrf2/Ho-1 Pathway and Reshaping the Gut Microbiota

Itaconic acid (IA) is recognized for its potential application in treating intestinal diseases owing to the anti-inflammatory and antioxidant properties. Perfluorooctanoic acid (PFOA) can accumulate in animals and result in oxidative and inflammatory damages to multi-tissue and organ, particularly in the intestinal tract. This study aimed to explore whether IA could mitigate intestinal damage induced by PFOA exposure in laying hens and elucidate its potential underlying mechanisms. The results showed that IA improved the antioxidant capacity of laying hens and alleviated the oxidative damage induced by PFOA, as evidenced by the elevated activities of T-SOD, GSH-Px, and CAT, and the decreased MDA content in both the jejunum and serum. Furthermore, IA improved the intestinal morphological and structural integrity, notably attenuating PFOA-induced villus shedding, length reduction, and microvillus thinning. IA also upregulated the mRNA expression of ZO-1, Occludin, Claudin-1, and Mucin-2 in the jejunum, thereby restoring intestinal barrier function. Compared with the PF group, IA supplementation downregulated the gene expression of Keap1 and upregulated the HO-1, NQO1, SOD1, and GPX1 expression in the jejunum. Meanwhile, the PF + IA group exhibited lower expressions of inflammation-related genes (NF-κB, IL-1β, IFN-γ, TNF-α, and IL-6) compared to the PF group. Moreover, IA reversed the PFOA-induced imbalance in gut microbiota by reducing the harmful bacteria such as Escherichia-Shigella, Clostridium innocuum, and Ruminococcus torques, while increasing the abundance of beneficial bacteria like Lactobacillus. Correlation analysis further revealed a significant association between gut microbes, inflammatory factors, and the Keap1/Nrf2/HO-1 pathway expression. In conclusion, dietary IA supplementation could alleviate the oxidative and inflammatory damage caused by PFOA exposure in the intestinal tract by reshaping the intestinal microbiota, modulating the Keap1/Nrf2/HO-1 pathway and reducing oxidative stress and inflammatory response, thereby promoting intestinal homeostasis.

Biochemical and haematological effects of serum PFOA, ADV and cC6O4 in workers of a chemical company producing fluoropolymers, Italy, 2013-2022

INTRODUCTION

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are widely used in the manufacture of fluoropolymers. We evaluated biochemical and haematological effects of three PFAS, serum perfluorooctanoic acid (PFOA), ADV, and cC6O4 in workers of a fluoropolymer company.

METHODS

Using data (2013-2022), we fitted random intercept regression models adjusted for several covariates and reciprocal adjustment between the three PFAS.

RESULTS

We analysed data of 814 workers (698 men, 116 women), 607 from the chemical plant, 207 from the research centre, for a total of 4912 blood samples (2065 with all three PFAS measured). Median levels of PFOA and ADV were 21.3 and 120 μg/L. Most (65.5%) cC6O4 measurements were below the limits of quantification (which varied over time from 5 to 0.1 μg/L). For PFOA, we observed positive associations with total cholesterol (+1.1% increase per ln(PFOA) increase) and apolipoprotein B (+1.4%) and negative associations with alkaline phosphatase (-1.5%); suggestive associations were also found with RBC (-0.4%), IgA (-1.5%), IgM (-1.4%). ADV was positively associated with total and LDL cholesterol (+1.0% and +1.6% per ln(ADV) increase), apolipoprotein B (+1.0%), GGT (+2.1%), IgM (+1.4%), and WBC (+1.5%) and negatively associated with direct bilirubin (-2.3%) and alpha-2-globulins (-0.7%); suggestive associations were found for indirect bilirubin (-2.0%), oestradiol (-2.1%), ad CRP (+6.0%). For samples with detectable cC6O4 levels we observed higher values of ALP (+2.3%), proteins (+0.5%), IgG (+0.7%) and platelets (+1.6%) and suggestively increased total bilirubin (+3.9%), RBC (+0.6%), and oestradiol (+5.8%). Some associations (total cholesterol, apolipoprotein B, WBC, total bilirubin, and alkaline phosphatase showed reverse time trends in parallel with the strong decrease of serum PFOA and ADV over the study period.

DISCUSSION

We found associations of serum PFOA and ADV with lipid metabolism, liver function, and immunoglobulins. The reverse time trends of some endpoints in parallel with decrease of serum PFOA and ADV reinforce causal interpretation of results. cC6O4 showed a different pattern of associations.

Emergency of per- and polyfluoroalkyl substances in drinking water: Status, regulation, and mitigation strategies in developing countries

The detection of per- and polyfluoroalkyl substances (PFAS) in water presents a significant challenge for developing countries, requiring urgent attention. This review focuses on understanding the emergence of PFAS in drinking water, health concerns, and removal strategies for PFAS in water systems in developing countries. This review indicates the need for more studies to be conducted in many developing nations due to limited information on the environmental status and fate of PFAS. The health consequences of PFAS in water are enormous and cannot be overemphasized. Efforts are ongoing to legislate a national standard for PFAS in drinking water. Currently, there are few known mitigation efforts from African countries, in contrast to several developing nations in Asia. Therefore, there is an urgent need to develop economically viable techniques that could be integrated into large-scale operations to remove PFAS from water systems in the region. However, despite the success achieved with removing long-chain PFAS from water, more studies are required on strategies for eliminating short-chain moieties in water.

Associations of perfluoroalkyl substances with metabolic-associated fatty liver disease and non-alcoholic fatty liver disease: NHANES 2017-2018

OBJECTIVES

This study investigated the potential effects of perfluoroalkyl substance (PFAS) in serum on MAFLD, NAFLD, and liver fibrosis.

METHODS

Our sample included 696 participants (≥ 18 years) from the 2017-2018 NHANES study with available serum PFASs, covariates, and outcomes. Using the first quartile of PFAS as the reference group, we used weighted binary logistic regression and multiple ordered logistic regression used to analyze the relationship between PFAS and MAFLD, NAFLD, and liver fibrosis and multiple ordinal logistic regression to investigate the relationship between PFAS and MAFLD, NAFLD, and liver fibrosis and calculated the odds ratio (OR) and 95% confidence interval for each chemical. Finally, stratified analysis and sensitivity analysis were performed according to gender, age, BMI, and serum cotinine concentration.

RESULTS

A total of 696 study subjects were included, including 212 NAFLD patients (weighted 27.03%) and 253 MAFLD patients (weighted 32.65%). The quartile 2 of serum PFOA was positively correlated with MAFLD and NAFLD (MAFLD, OR 2.29, 95% CI 1.05-4.98; NAFLD, OR 2.37, 95% CI 1.03-5.47). PFAS were not significantly associated with liver fibrosis after adjusting for potential confounders in MAFLD and NAFLD. Stratified analysis showed that PFOA was strongly associated with MAFLD, NAFLD, and liver fibrosis in males and obese subjects. In women over 60 years old, PFHxS was also correlated with MAFLD, NAFLD, and liver fibrosis.

CONCLUSION

The serum PFOA was positively associated with MAFLD and NAFLD in US adults. After stratified analysis, the serum PFHxS was correlated with MFALD, NAFLD, and liver fibrosis.

Risk assessment for perfluorooctanoic acid (PFOA) in air, blood serum and water: mortality from liver and kidney disease

BACKGROUND

Cancer and non-cancer associations have been observed with PFAS (perfluoroalkyl and polyfluoroalkyl) substances in the general population, in populations from locally contaminated environments and in exposed workers.

METHODS

A quantitative risk assessment on the PFAS substance perfluorooctanoic acid (PFOA) was conducted for six outcomes using two occupational mortality studies that reported sufficient data to estimate exposure-relationships in relation to serum PFOA levels. Excess lifetime mortality risks were calculated using a life table procedure that applies an exposure response to time-dependent PFOA serum levels for a surviving hypothetical population from ages 20 to 85. Both occupational and general population exposures were described as serum levels, and as air and drinking water concentrations.

RESULTS

The estimated occupational inhalation concentrations conferring the benchmark one-per-thousand lifetime risk were 0.21 µg/m3 for chronic kidney disease, 1.0 µg/m3 for kidney cancer and (from the two studies) 0.67 and 1.97 µg/m3 for chronic liver disease. Specific excess lifetime risks estimated in the general population at current PFOA serum levels (~ 1 ng/mL) range 1.5-32 per 100 000 which corresponds to drinking water concentrations of less than 10 ppt.

CONCLUSION

Over eight outcome risk estimates, the serum PFOA concentrations conferring 1/1000 occupational lifetime risk ranged 44 to 416 ng/mL corresponding to air concentrations ranging 0.21 to 1.99 µg/m3. The analyses provide a preliminary PFOA quantitative risk assessment for liver and kidney disease mortality which, together with reported assessments for several other end-points, would inform policy on PFAS.

Per- and polyfluoroalkyl substances (PFAS) exposure and thyroid cancer: Systematic review and meta-analysis

Per- and polyfluoroalkyl substances (PFAS) exposure is a potential risk factor for thyroid cancer and may be a contributor to the increasing thyroid cancer incidence rates. A systematic review and meta-analysis was performed to summarize all human studies to date investigating the association between PFAS exposure and thyroid cancer. A search of the National Library of Medicine and National Institutes of Health PubMed and Scopus databases was done to identify relevant articles published in English through January 2024. Studies reporting the association between PFAS exposure and thyroid cancer using odds ratios (OR) were included in the meta-analysis with summary estimate calculated using a random effects model (n=5). Perfluorooctanoic acid (PFOA) was the most investigated PFAS. Results of the included studies varied, ranging from significant positive to significant negative associations with thyroid cancer incidence for different PFAS. Meta-analyses of PFOA, Perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), perfluorohexanesulfonic acid (PFHxS) were not significant. This comprehensive review of the current literature highlights the limited knowledge and inconsistent results of this association. Large longitudinal cohort studies with varying time between sample collection and thyroid cancer diagnosis are needed to better understand the role of PFAS exposure on thyroid carcinogenesis.

Gene expression patterns associated with PFOA exposure in Czech young men and women

Perfluorooctanoic acid (PFOA), a member of per- and polyfluoroalkyl substances (PFASs), has been widely used in manufacturing for decades. Currently, PFOA is strictly regulated, but due to its high stability and persistence, it is detected in both environmental as well as in human matrices. To elucidate mechanisms of PFOA toxicity in humans, we determined the genome-wide transcriptomic changes of peripheral blood mononuclear cells (PBMC) responding to PFOA exposure in a sex-stratified analysis. This work employed samples from 145 female and 143 male participants of the CELSPAC: YA study to characterize PFOA-associated transcripts in a broader context using computational analysis. PFOA-associated gene expression differed significantly between men and women, as only 2 % of mapped genes were expressed in both sexes. Disease-specific enrichment analysis revealed cancer and immune-related disease terms as those most enriched in male and female populations. Patterns of enriched terms within the gene set enrichment analysis indicated three main targets of PFOA toxicity: i) lipid metabolism for women; ii) cell cycle regulation for men; and iii) immune system response for both sexes. In summary, our genome-wide transcriptomics analysis described sex-specific differences in PFOA-associated gene expression and provided evidence about biological pathways underlying PFOA toxicity in humans.

The perils of poly- and perfluorinated chemicals on the reproductive health of humans, livestock, and wildlife

Poly- and perfluoroalkyl substances (PFAS) are a prominent class of persistent synthetic compound. The widespread use of these substances in various industrial applications has resulted in their pervasive contamination on a global scale. It is therefore concerning that PFAS have a propensity to accumulate in bodily tissues whereupon they have been linked with a range of adverse health outcomes. Despite this, the true extent of the risk posed by PFAS to humans, domestic animals, and wildlife remains unclear. Addressing these questions requires a multidisciplinary approach, combining the fields of chemistry, biology, and policy to enable meaningful investigation and develop innovative remediation strategies. This article combines the perspectives of chemists, soil scientists, reproductive biologists, and health policy researchers, to contextualise the issue of PFAS contamination and its specific impact on reproductive health. The purpose of this article is to describe the challenges associated with remediating PFAS-contaminated soils and waters and explore the consequences of PFAS contamination on health and reproduction. Furthermore, current actions to promote planetary health and protect ecosystems are presented to instigate positive social change among the scientific community.

Involvement of per- and polyfluoroalkyl compounds in tumor development

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic persistent chemicals, which are used in many industrial and commercial applications. Hundreds of different PFAS have been identified in the environment and they are commonly found also in human blood. Due to the chemical stability and extensive use, PFAS pose a risk for human health and wildlife. Mounting evidence indicates that PFAS-exposure adversely affects many organs including liver, kidney, and reproductive tissues and induces tumors in laboratory rodents. Epidemiological studies show association between PFAS-exposure and some tumors also in humans. Effects of PFAS-exposure are complex and obviously do not depend only on the concentration and the structure of PFAS, but also on age and sex of the exposed individuals. It has been difficult to show a causal link between PFAS-exposure and tumors. Moreover, molecular mechanisms of the PFAS effects in different tissues are poorly understood. PFAS are not directly mutagenic and they do not induce formation of DNA binding metabolites, and thus are assumed to act more through non-genotoxic mechanisms. In this review, we discuss the involvement of PFAS-compounds in tumor development in tissues where PFAS exposure has been associated with cancer in epidemiological and animal studies (liver, kidney, testicle and breast). We will focus on molecular pathways and mechanisms related to tumor formation following PFAS-exposure.

Electrochemical Reduction of Perfluorooctanoic Acid (PFOA): An Experimental and Theoretical Approach

Perfluorooctanoic acid (PFOA) is an artificial chemical of global concern due to its high environmental persistence and potential human health risk. Electrochemical methods are promising technologies for water treatment because they are efficient, cheap, and scalable. The electrochemical reduction of PFOA is one of the current methodologies. This process leads to defluorination of the carbon chain to hydrogenated products. Here, we describe a mechanistic study of the electrochemical reduction of PFOA in gold electrodes. By using linear sweep voltammetry (LSV), an E0' of -1.80 V vs Ag/AgCl was estimated. Using a scan rate diagnosis, we determined an electron-transfer coefficient (αexp) of 0.37, corresponding to a concerted mechanism. The strong adsorption of PFOA into the gold surface is confirmed by the Langmuir-like isotherm in the absence (KA = 1.89 × 1012 cm3 mol-1) and presence of a negative potential (KA = 3.94 × 107 cm3 mol-1, at -1.40 V vs Ag/AgCl). Based on Marcus-Hush's theory, calculations show a solvent reorganization energy (λ0) of 0.9 eV, suggesting a large electrostatic repulsion between the perfluorinated chain and water. The estimated free energy of the transition state of the electron transfer (ΔG‡ = 2.42 eV) suggests that it is thermodynamically the reaction-limiting step. 19F - 1H NMR, UV-vis, and mass spectrometry studies confirm the displacement of fluorine atoms by hydrogen. Density functional theory (DFT) calculations also support the concerted mechanism for the reductive defluorination of PFOA, in agreement with the experimental values.

All-cause, cardiovascular disease and cancer mortality in the population of a large Italian area contaminated by perfluoroalkyl and polyfluoroalkyl substances (1980-2018)

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are associated with many adverse health conditions. Among the main effects is carcinogenicity in humans, which deserves to be further clarified. An evident association has been reported for kidney cancer and testicular cancer. In 2013, a large episode of surface, ground and drinking water contamination with PFAS was uncovered in three provinces of the Veneto Region (northern Italy) involving 30 municipalities and a population of about 150,000. We report on the temporal evolution of all-cause mortality and selected cause-specific mortality by calendar period and birth cohort in the local population between 1980 and 2018.

METHODS

The Italian National Institute of Health pre-processed and made available anonymous data from the Italian National Institute of Statistics death certificate archives for residents of the provinces of Vicenza, Padua and Verona (males, n = 29,629; females, n = 29,518) who died between 1980 and 2018. Calendar period analysis was done by calculating standardised mortality ratios using the total population of the three provinces in the same calendar period as reference. The birth cohort analysis was performed using 20-84 years cumulative standardised mortality ratios. Exposure was defined as being resident in one of the 30 municipalities of the Red area, where the aqueduct supplying drinking water was fed by the contaminated groundwater.

RESULTS

During the 34 years between 1985 (assumed as beginning date of water contamination) and 2018 (last year of availability of cause-specific mortality data), in the resident population of the Red area we observed 51,621 deaths vs. 47,731 expected (age- and sex-SMR: 108; 90% CI: 107-109). We found evidence of raised mortality from cardiovascular disease (in particular, heart diseases and ischemic heart disease) and malignant neoplastic diseases, including kidney cancer and testicular cancer.

CONCLUSIONS

For the first time, an association of PFAS exposure with mortality from cardiovascular disease was formally demonstrated. The evidence regarding kidney cancer and testicular cancer is consistent with previously reported data.

Threats of per- and poly-fluoroalkyl pollutants to susceptible populations

Environmental exposure to per- and poly-fluoroalkyl substances (PFAS) has raised significant global health concerns due to potential hazards in healthy adults. However, the impact of PFAS on susceptible populations, including pregnant individuals, newborns, the older people, and those with underlying health conditions, has been overlooked. These susceptible groups often have physiological changes that make them less resilient to the same exposures. Consequently, there is an urgent need for a comprehensive understanding of the health risks posed by PFAS exposure to these populations. In this review, we delve into the potential health risks of PFAS exposure in these susceptible populations. Equally important, we also examine and discuss the molecular mechanisms that underlie this susceptibility. These mechanisms include the induction of oxidative stress, disruption of the immune system, impairment of cellular metabolism, and alterations in gut microbiota, all of which contribute to the enhanced toxicity of PFAS in susceptible populations. Finally, we address the primary research challenges and unresolved issues that require further investigation. This discussion aims to foster research for a better understanding of how PFAS affect susceptible populations and to pave the way for strategies to minimize their adverse effects.

Inconsistencies in the EU regulatory risk assessment of PFAS call for readjustment

Recognition of per- and polyfluoroalkyl substances (PFAS) as widespread environmental pollutants and a consequent risk to human health, has recently made the European Union (EU) adopt several regulatory measures for their management. The coherence of these measures is challenged by the diversity and the ubiquitous occurrence of PFAS, which also complicates the EU's endeavor to advance justified, harmonized, and transparent approaches in the regulatory assessment of chemical risks. Our study critically reviews the European approach for the risk assessment of PFAS, by applying a comparative analysis of the current and pending regulatory thresholds issued for these chemicals in water bodies, drinking water, and certain foodstuffs. Our study shows that the level of health protection embedded in the studied thresholds may differ by three orders of magnitude, even in similar exposure settings. This is likely to confuse the common understanding of the toxicity and health risks of PFAS and undermine reasonable decision-making and the equal treatment of different stakeholders. We also indicate that currently, no consensus exists on the appropriate level of required health protection regarding PFAS and that the recently adopted tolerable intake value in the EU is too cautious. Based on our analysis, we propose some simple solutions on how the studied regulations and their implicit PFAS thresholds or their application could be improved. We further conclude that instead of setting EU-wide PFAS thresholds for all the environmental compartments, providing the member states with the flexibility to consider case-specific factors, such as regional background concentrations or food consumption rates, in their national regulatory procedures would likely result in more sustainable management of environmental PFAS without compromising the scientific foundation of risk assessment, the legitimacy of the EU policy framework and public health.

A structural basis for the activation of peroxisome proliferator-activated receptor gamma (PPARγ) by perfluorooctanoic acid (PFOA)

Perfluorooctanoic acid (PFOA) is a widespread environmental pollutant of the perfluoroalkyl substance (PFAS) class that is extremely resistant to environmental and metabolic degradation, leading to bioaccumulation. PFOA exposure has been linked to many health effects including endocrine disruption and metabolic dysregulation, but our understanding of the molecular mechanisms resulting in these outcomes remains incomplete. One target affected by PFOA is the ligand regulated nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) which plays a critical role in controlling metabolic homeostasis through regulating processes such as adipogenesis, glucose homeostasis, inflammation and osteogenesis. It has been previously established that PFOA activates PPARγ through binding to the PPARγ ligand binding domain (PPARγ LBD) leading to increased expression of PPARγ controlled target genes. However, the mechanism by which PFOA achieves this has remained elusive. Here, we employed a combination of X-ray crystallography and fluorescence polarization assays to provide a structural basis for PFOA mediated activation of PPARγ via binding to the PPARγ LBD. Using X-ray crystallography, the cocrystal structure of the PPARγ LBD:PFOA complex was solved. This revealed that PFOA occupies three distinct sites, two within the PPARγ LBD and one within the activation function 2 (AF2) on the protein surface. Structural comparison of PFOA binding with previously reported PPARγ:ligand complexes supports that PFOA activates PPARγ by a partial agonist mechanism at micromolar concentrations. Fluorescence polarization assays also revealed that PFOA binding to the AF2 is unlikely to occur in a cellular context and confirmed that PFOA behaves as a partial agonist in vitro, weakly recruiting a coactivator peptide to the AF2 of the PPARγ LBD. This discovery provides an advancement in understanding PFOA mediated regulation of PPARγ, giving new insight regarding regulation of PPARγ by PFAS and PFAS substitutes in general and can be applied to the design and assessment of safer PFAS.

Perfluorooctanesulfonic Acid Alters Pro-Cancer Phenotypes and Metabolic and Transcriptional Signatures in Testicular Germ Cell Tumors

The potential effects of poly- and perfluoroalkyl substances (PFAS) are a recently emergent human and environmental health concern. There is a consistent link between PFAS exposure and cancer, but the mechanisms are poorly understood. Although epidemiological evidence supporting PFAS exposure and cancer in general is conflicting, there is relatively strong evidence linking PFAS and testicular germ cell tumors (TGCTs). However, no mechanistic studies have been performed to date concerning PFAS and TGCTs. In this report, the effects of the legacy PFAS perfluorooctanesulfonic acid (PFOS) and the newer "clean energy" PFAS lithium bis(trifluoromethylsulfonyl)imide (LiTFSi, called HQ-115), on the tumorigenicity of TGCTs in mice, TGCT cell survival, and metabolite production, as well as gene regulation were investigated. In vitro, the proliferation and survival of both chemo-sensitive and -resistant TGCT cells were minimally affected by a wide range of PFOS and HQ-115 concentrations. However, both chemicals promoted the growth of TGCT cells in mouse xenografts at doses consistent with human exposure but induced minimal acute toxicity, as assessed by total body, kidney, and testis weight. PFOS, but not HQ-115, increased liver weight. Transcriptomic alterations of PFOS-exposed normal mouse testes were dominated by cancer-related pathways and gene expression alterations associated with the H3K27me3 polycomb pathway and DNA methylation, epigenetic pathways that were previously showed to be critical for the survival of TGCT cells after cisplatin-based chemotherapy. Similar patterns of PFOS-mediated gene expression occurred in PFOS-exposed cells in vitro. Metabolomic studies revealed that PFOS also altered metabolites associated with steroid biosynthesis and fatty acid metabolism in TGCT cells, consistent with the proposed ability of PFAS to mimic fatty acid-based ligands controlling lipid metabolism and the proposed role of PFAS as endocrine disrupters. Our data, is the first cell and animal based study on PFAS in TGCTs, support a pro-tumorigenic effect of PFAS on TGCT biology and suggests epigenetic, metabolic, and endocrine disruption as potential mechanisms of action that are consistent with the non-mutagenic nature of the PFAS class.

US and international per- and polyfluoroalkyl substances surface water quality criteria: A review of the status, challenges, and implications for use in chemical management and risk assessment

Regulation of per- and polyfluorinated substances (PFAS) in surface water is a work-in-progress with relatively few criteria promulgated in the United States and internationally. Surface water quality criteria (SWQC) or screening values derived for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) by Australia, Canada, the European Union (EU), and four US states (Florida, Michigan, Minnesota, and Wisconsin), and the San Francisco Bay Regional Water Quality Control Board (SFB RWQCB; California) were compared. Across these eight jurisdictions, promulgated numeric criteria for the same compound and receptor span over five orders of magnitude as a result of different approaches and data interpretations. Human health criteria for PFOS range from 0.0047 to 600 ng/L depending on route of exposure (e.g., fish consumption or drinking water) and are lower than most ecological criteria for protection of aquatic and wildlife receptors. Data gaps and uncertainty in chronic toxicity and bioaccumulation of PFOS and PFOA, as well as the use of conservative assumptions regarding intake and exposure, have resulted in some criteria falling at or below ambient background concentrations and current analytical detection limits (around 1 ng/L for commercial laboratories). Some jurisdictions (e.g., Australia, Canada) have deemed uncertainty in quantifying water-fish bioaccumulation too great and set fish tissue action levels in lieu of water criteria. Current dynamics associated with the emerging and evolving science of PFAS toxicity, exposure, and environmental fate (i.e., data gaps and uncertainty), as well as the continuous release of scientific updates, pose a challenge to setting regulatory limits. Integr Environ Assess Manag 2024;20:36-58. © 2023 AECOM Technical Services, Inc and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Hexafluoropropylene oxide trimer acid exposure triggers necroptosis and inflammation through the Wnt/β-catenin/NF-κB axis in the liver

Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging alternative to perfluorooctanoic acid (PFOA), has recently been identified as a significant environmental pollutant. Nevertheless, there is a scarcity of studies regarding the hepatotoxic effects of HFPO-TA. Here, we investigated the types and potential mechanisms of liver damage caused by HFPO-TA. Initially, we validated that the introduction of HFPO-TA resulted in the Wnt/β-catenin signaling (W/β signaling) activation, as well as the induction of necroptosis and inflammation, both in the liver of mice and in HepG2 cells. Subsequently, we established that the W/β signaling mediated the necroptosis and inflammation observed in the liver and HepG2 cells exposed to HFPO-TA. Finally, we demonstrated that the phosphorylated form of NF-κB p65 (p-NF-κB p65) played a role in mediating the necroptosis and inflammation, and its activity could be regulated by the W/β signaling pathway in the liver of mice and HepG2 cells exposed to HFPO-TA. In conclusion, our investigation elucidates the role of HFPO-TA in inducing necroptosis and inflammation in the liver, which is facilitated through the activation of the W/β/NF-κB axis.

Physicochemical properties and interactions of perfluoroalkyl substances (PFAS) - Challenges and opportunities in sensing and remediation

Per- and polyfluoroalkyl substances (PFAS) is a class of persistent organic pollutants that presents health and environmental risks. PFAS are ubiquitously present in the environment, but current remediation technologies are ineffective in degrading them into innocuous chemicals, especially high energy degradation processes often generate toxic short chain intermediates. Therefore, the best remediation strategy is to first detect the source of pollution, followed by capturing and mineralising or recycling of the compounds. The main objective of this article is to summarise the unique physicochemical properties and to critically review the intermolecular and intramolecular physicochemical interactions of PFAS, and how these interactions can become obstacles; and at the same time, how they can be applied to the PFAS sensing, capturing, and recycling process. The physicochemical interactions of PFAS chemicals are being reviewed in this paper includes, (1) fluorophilic interactions, (2) hydrophobic interactions, (3) electrostatic interactions and cation bridging, (4) ionic exchange and (5) hydrogen bond. Moreover, all the different influential factors to these interactions have also been reported. Finally, properties of these interactions are compared against one another, and the recommendations for future designs of affinity materials for PFAS have been given.

Association between per- and polyfluoroalkyl substances (PFAS) and depression in U.S. adults: A cross-sectional study of NHANES from 2005 to 2018

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are widespread persistent organic pollutants (POPs) associated with diseases including osteoporosis, altered immune function and cancer. However, few studies have investigated the association between PFAS mixture exposure and Depression in general populations.

METHODS

Nationally representative data from the National Health and Nutrition Examination Survey (NHANES) (2005-2018) were used to analyze the association between PFAS and Depression in U.S. adults. Total 12,239 adults aged 20 years or older who had serum PFAS measured and answered Patient Health Questionnaire-9 (PHQ-9) were enrolled in this study. PFAS monomers detected in all 7 investigation cycles were included in the study. Generalized additive model (GAM) was used to fit smooth curves and threshold effect analysis was carried out to find the turning point of smooth curves. Generalized linear model (GLM) was used to describe the non-linear relationship between PFAS and depression and unconditioned logistic regression was used to risk analysis.

RESULTS

The median of total serum PFAS concentration was 14.54 ng/mL. The curve fitting results indicated a U-shaped relationship between total serum PFAS and depression: PFAS< 39.66 ng/mL, A negative correlation between PHQ-9 score and serum PFAS concentration was observed (β 0.047,95%CI -0.059, -0.036). The depression PHQ-9 score decreased with the increase of serum PFAS concentration. PFAS ≥ 39.66 ng/mL, A positive correlation was observed between PFAS and PHQ-9 score (β 0.010,95% CI 0.003, 0.017). The depression PHQ-9 score increased with the increase of serum PFAS concentration.

CONCLUSIONS

Our study provides new clues to the association of PFAS with depression, and large population-based cohort studies that can validate the causal association as well as toxicological mechanism studies are needed for validation.

Per- and polyfluoroalkyl substances (PFAS) exposure and thyroid cancer risk

BACKGROUND

Although per- and polyfluoroalkyl substances (PFAS) exposure is a potential contributor to the increasing thyroid cancer trend, limited studies have investigated the association between PFAS exposure and thyroid cancer in human populations. We therefore investigated associations between plasma PFAS levels and thyroid cancer diagnosis using a nested case-control study of patients with thyroid cancer with plasma samples collected at/before cancer diagnosis.

METHODS

88 patients with thyroid cancer using diagnosis codes and 88 healthy (non-cancer) controls pair-matched on sex, age (±5 years), race/ethnicity, body mass index, smoking status, and year of sample collection were identified in the BioMe population (a medical record-linked biobank at the Icahn School of Medicine at Mount Sinai in New York); 74 patients had papillary thyroid cancer. Eight plasma PFAS were measured using untargeted analysis with liquid chromatography-high resolution mass spectrometry and suspect screening. Associations between individual PFAS levels and thyroid cancer were evaluated using unconditional logistic regression models to estimate adjusted odds ratios (ORadj) and 95% confidence intervals (CI).

FINDINGS

There was a 56% increased rate of thyroid cancer diagnosis per doubling of linear perfluorooctanesulfonic acid (n-PFOS) intensity (ORadj, 1.56, 95% CI: 1.17-2.15, P = 0.004); results were similar when including patients with papillary thyroid cancer only (ORadj, 1.56, 95% CI: 1.13-2.21, P = 0.009). This positive association remained in subset analysis investigating exposure timing including 31 thyroid cancer cases diagnosed ≥1 year after plasma sample collection (ORadj, 2.67, 95% CI: 1.59-4.88, P < 0.001).

INTERPRETATION

This study reports associations between exposure to PFAS and increased rate of (papillary) thyroid cancer. Thyroid cancer risk from PFAS exposure is a global concern given the prevalence of PFAS exposure. Individual PFAS studied here are a small proportion of the total number of PFAS supporting additional large-scale prospective studies investigating thyroid cancer risk associated with exposure to PFAS chemicals.

FUNDING

National Institutes of Health grants and The Andrea and Charles Bronfman Philanthropies.

Prenatal Exposure to Perfluoroalkyl Substances and Child Behavior at Age 12: A PELAGIE Mother-Child Cohort Study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are chemical substances spread throughout the environment worldwide. Exposure during pregnancy represents a specific window of vulnerability for child health.

OBJECTIVE

Our objective was to assess the impact of prenatal exposure to multiple PFAS on emotional and behavioral functions in 12-y-old children.

METHOD

In the PELAGIE mother-child cohort (France), prenatal exposure to nine PFAS was measured from concentrations in cord serum samples. Behavior was assessed at age 12 y using the parent-reported Strengths and Difficulties Questionnaire (SDQ) and the self-reported Dominic Interactive for Adolescents (DIA) for 444 children. Associations were estimated using negative binomial models for each PFAS. Bayesian kernel machine regression (BKMR) models were performed to assess the exposure mixture effect on children's behavior.

RESULTS

In our study population, 73% of mothers had spent more than 12 y in education. Higher scores on SDQ externalizing subscale were observed with increasing cord-serum concentration of perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) [adjusted mean ratio ( aMR ) = 1.18 , 95% confidence interval (CI): 1.03, 1.34, and aMR = 1.14 (95% CI: 1.00, 1.29) for every doubling of concentration, respectively]. Results for the hyperactivity score were similar [aMR = 1.20 (95% CI: 1.04, 1.40) and aMR = 1.18 (95% CI: 1.02, 1.36), respectively]. With regard to major depressive disorder and internalizing subscales, perfluorodecanoic acid (PFDA) was associated with higher self-reported DIA scores [aMR = 1.14 (95% CI: 1.01, 1.27) and aMR = 1.11 (95% CI: 1.02, 1.21), respectively]. In terms of the anxiety subscale, PFDA and PFNA were associated with higher scores [aMR = 1.11 (95% CI: 1.02, 1.21) and aMR = 1.10 (95% CI: 1.01, 1.19), respectively]. Concurrent increases in the PFAS concentrations included in the BKMR models showed no change in the SDQ externalizing and DIA internalizing subscales scores.

CONCLUSION

Prenatal exposure to PFNA and PFOA were associated with increasing scores for measures of externalizing behaviors, specifically hyperactivity. We also identified associations between PFNA and PFDA prenatal exposure levels and increasing scores related to internalizing behaviors (general anxiety and major depressive disorder), which adds to the as yet sparse literature examining the links between prenatal exposure to PFAS and internalizing disorders. https://doi.org/10.1289/EHP12540.

PFAS levels in paired drinking water and serum samples collected from an exposed community in Central North Carolina

The community of Pittsboro, North Carolina has been documented to have extensive per- and polyfluoroalkyl substances (PFAS) contamination in its drinking water source, the Haw River, over the last 20 years. However, a detailed exposure assessment has never been conducted. In this study, we sought to characterize the PFAS in paired drinking water and blood samples collected from a small cohort of Pittsboro residents (n = 49). Drinking water and serum from blood were collected from adults in late 2019 and early 2020 and were analyzed to quantify 13 PFAS analytes. In order to explore potential health effects of PFAS exposure, serum was further analyzed for clinical chemistry endpoints that could be potentially associated with PFAS (e.g., cholesterol, liver function biomarkers). PFAS were detected in all serum samples, and some serum PFAS concentrations were 2 to 4 times higher than the median U.S. serum concentrations reported in the general U.S. population. Of the 13 PFAS in drinking water, perfluorohexanoic acid (PFHxA) was measured at the highest concentrations. PFAS levels in the current drinking water were not associated with current serum PFAS, suggesting that the serum PFAS in this cohort likely reflects historical exposure to PFAS with long half-lives (e.g., PFOS and PFOA). However, one PFAS with a shorter half-life (PFHxA) was observed to increase in serum, reflecting the temporal variability of PFHxA in river and drinking water. Statistical analyses indicated that serum PFOA and PFHxS were positively associated with total cholesterol and non-HDL cholesterol. No serum PFAS was associated with HDL cholesterol. In the clinical chemistry analyses, serum PFHxA was found to be negatively associated with electrolytes and liver enzymes (e.g., AST and ALT), and serum PFOS was found to be positively associated with the ratio of blood urea nitrogen to creatinine (BUN:Cre). While small in size, this study revealed extensive exposure to PFAS in Pittsboro and associations with clinical blood markers, suggesting potential health impacts in community residents.

Relative Risks of Adverse Perinatal Outcomes in Three Australian Communities Exposed to Per- and Polyfluoroalkyl Substances: Data Linkage Study

INTRODUCTION

Firefighting foams containing per- and polyfluoroalkyl substances (PFAS) have caused environmental contamination in several Australian residential areas, including Katherine in the Northern Territory (NT), Oakey in Queensland (Qld), and Williamtown in New South Wales (NSW). We examined whether the risks of adverse perinatal outcomes were higher in mothers living in these exposure areas than in selected comparison areas without known contamination.

METHODS

We linked residential addresses in exposure areas to addresses collected in the jurisdictional Perinatal Data Collections of the NT (1986-2017), Qld (2007-2018), and NSW (1994-2018) to select all pregnancies from mothers who gave birth while living in these areas. We also identified one comparison group for each exposure area by selecting pregnancies where the maternal address was in selected comparison areas. We examined 12 binary perinatal outcomes and three growth measurements. For each exposure area, we estimated relative risks (RRs) of adverse outcomes and differences in means of growth measures, adjusting for sociodemographic characteristics and other potential confounders.

RESULTS

We included 16,970 pregnancies from the NT, 4654 from Qld, and 7475 from NSW. We observed elevated risks of stillbirth in Oakey (RR = 2.59, 95% confidence interval (CI) 1.25 to 5.39) and of postpartum haemorrhage (RR = 1.94, 95% CI 1.13 to 3.33) and pregnancy-induced hypertension (RR = 1.88, 95% CI 1.30 to 2.73) in Williamtown. The risks of other perinatal outcomes were not materially different from those in the relevant comparison areas or were uncertain due to small numbers of events.

CONCLUSIONS

There was limited evidence for increased risks of adverse perinatal outcomes in mothers living in areas with PFAS contamination from firefighting foams. We found higher risks of some outcomes in individual areas, but these were not consistent across all areas under study and could have been due to chance, bias, or confounding.

Serum concentrations of per- and polyfluoroalkyl substances and risk of renal cell carcinoma in the Multiethnic Cohort Study

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent organic pollutants detectable in the serum of most U.S. adults. We previously reported a positive association between serum perfluorooctanoate (PFOA) concentrations and risk of renal cell carcinoma (RCC) within the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, comprising predominantly White individuals enrolled in 1993-2001. To extend our investigations to a larger and more racially and ethnically diverse population, we conducted a nested case-control study of serum PFAS concentrations and RCC within the Multiethnic Cohort Study. We measured pre-diagnostic serum concentrations of nine PFAS among 428 RCC cases and 428 individually matched controls. We estimated odds ratios (ORs) and 95 % confidence intervals (CIs) for risk of RCC in relation to each PFAS using conditional logistic regression, adjusting for RCC risk factors and other PFAS. PFOA was not associated with RCC risk overall [doubling in serum concentration, ORcontinuous = 0.89 (95 %CI = 0.67, 1.18)]. However, we observed suggestive positive associations among White participants [2.12 (0.87, 5.18)] and among participants who had blood drawn before 2002 [1.49 (0.77, 2.87)]. Furthermore, higher perfluorononanoate (PFNA) concentration was associated with increased risk of RCC overall [fourth vs. first quartile, OR = 1.84 (0.97, 3.50), Ptrend = 0.04; ORcontinuous = 1.29 (0.97, 1.71)], with the strongest association observed among African American participants [ORcontinuous = 3.69 (1.33, 10.25)], followed by Native Hawaiian [2.24 (0.70, 7.19)] and White [1.98 (0.92, 4.25)] participants. Most other PFAS were not associated with RCC. While PFOA was not associated with RCC risk overall in this racially and ethnically diverse population, the positive associations observed among White participants and those with sera collected before 2002 are consistent with previous PLCO findings. Our study also provided new evidence of a positive association between PFNA and RCC risk that was strongest in African American participants. These findings highlight the need for additional epidemiologic research investigating PFAS exposures and RCC in large racially and ethnically diverse populations.

Immune response to COVID-19 vaccination in a population with a history of elevated exposure to per- and polyfluoroalkyl substances (PFAS) through drinking water

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) has been linked to lower vaccine-induced antibody concentrations in children, while data from adults remains limited and equivocal. Characteristics of PFAS exposure and age at vaccination may modify such effects.

OBJECTIVE

We used the mass administration of novel COVID-19 vaccines to test the hypothesis that prior exposure to environmentally-relevant concentrations of PFAS affect antibody response to vaccines in adolescents and adults.

METHODS

Between April and June 2021, 226 participants aged 12-90 years with a history of exposure to PFAS in drinking water and who received an mRNA COVID-19 vaccine participated in our prospective cohort study. SARS-CoV-2 anti-spike and anti-nucleocapsid antibodies (IgG) were quantified before the first and second vaccine doses and again at two follow-ups in the following months (up to 103 days post dose 1). Serum PFAS concentrations (n = 39 individual PFAS) were measured once for each participant during baseline, before their first vaccination. The association between PFAS exposure and immune response to vaccination was investigated using linear regression and generalized estimating equation (GEE) models with adjustment for covariates that affect antibody response. PFAS mixture effects were assessed using weighted quantile sum and Bayesian kernel machine regression methods.

RESULTS

The geometric mean (standard deviation) of perfluorooctane sulfonate and perfluorooctanoic acid serum concentrations in this population was 10.49 (3.22) and 3.90 (4.90) µg/L, respectively. PFAS concentrations were not associated with peak anti-spike antibody response, the initial increase in anti-spike antibody response following vaccination, or the waning over time of the anti-spike antibody response. Neither individual PFAS concentrations nor their evaluation as a mixture was associated with antibody response to mRNA vaccination against COVID-19.

IMPACT STATEMENT

Given the importance of understanding vaccine response among populations exposed to environmental contaminants and the current gaps in understanding this relationship outside of early life/childhood vaccinations, our manuscript contributes meaningful data from an adolescent and adult population receiving a novel vaccination.

Temporal decline in serum PFAS concentrations among metropolitan firefighters: Longitudinal study on post-exposure changes following PFAS foam cessation

Firefighters are at a high risk of exposure to per- and polyfluoroalkyl substances (PFAS) due to their frequent use of PFAS-containing foams in training and emergency situations. This longitudinal study aimed to investigate the changes in serum PFAS levels among firefighters following cessation of their exposure to PFAS-containing foams. The study involved 130 firefighters from the South Australian Metropolitan Fire Services (SAMFS), and serum samples were collected at two time points: baseline in 2018-19 and follow-up in 2021-22. Along with the collection of samples, a survey questionnaire was administered to gather information on firefighters' employment and demographic characteristics. Regression models were employed to assess the association between these factors and the outcome variable (annual percentage change in serum PFAS concentration). The results indicated a decline in serum PFAS concentrations over time, with the main contaminants being perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctanoic acid (PFOA). The median and Interquartile Range (IQR) of total PFAS (∑PFAS) concentration reduced from 21.5 ng/ml (IQR: 11 to 53 ng/ml) at baseline to 15 ng/ml (IQR: 8 to 33 ng/ml) at follow-up. On average, there was an annual reduction of 13%, 7%, and 4.4% in serum concentrations of PFOS, PFHxS, and PFOA, respectively. Firefighters under the age of 55, those who used PFAS in the past ten years, or those who had little to no frequency of PFAS exposure in their previous employment, encountered a significantly higher annual percentage reduction (P < 0.05) in both ∑PFAS and PFOS concentrations. None of the independent variables analysed could significantly predict the annual percentage change in PFOA and PFHxS. This study provides evidence for a declining temporal trend in serum PFAS concentrations among metropolitan firefighters following workplace interventions that involved the removal of PFAS-containing foams.

Behavioral outcomes and exposure to perfluoroalkyl substances among children aged 6-13 years: The TEDDY child study

BACKGROUND

Although some studies report that exposure to per- and polyfluoroalkyl substances (PFAS) during pregnancy and early life stages of a child could adversely impact neurodevelopment, literature shows mixed evidence.

OBJECTIVES

Using an ecological framework for human development, we assessed the association of risk factors for environmental PFAS exposure and childhood PFAS concentrations with behavioral difficulties among school-age children exposed to PFAS from birth, while also controlling for the important influence of the parenting and familial environment.

METHODS

The study participants included 331 school-age children (6-13 years) born in a PFAS-contaminated area in the Veneto Region (Italy). We study the associations between environmental risk factors of maternal PFAS exposure (residential time, consumption of tap water, residence in Red zone A or B), and breastfeeding duration with parent assessments of children's behavioral problems (using the Strengths and Difficulties Questionnaire [SDQ]), adjusting for socio-demographic, parenting and familial variables. The direct relationships between serum blood PFAS concentrations and SDQ scores was evaluated in a subset of children (n = 79), both with single PFAS and weighted quantile sum (WQS) regressions.

RESULTS

Poisson regression models reported positive associations between high consumption of tap water and externalizing SDQ scores (Incidence Rate Ratio [IRR]: 1.18; 95% confidence interval [CI]: 1.04-1.32) and total difficulty scores (IRR: 1.14; 95% CI: 1.02-1.26). Childhood perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS) were associated with higher internalizing SDQ scores (4th vs. 1st quartile, PFOS IRR: 1.54, 95% CI: 1.06-2.25), externalizing scores (4th vs. 1st quartile, PFHxS IRR: 1.59, 95% CI: 1.09-2.32), and total difficulty scores (4th vs. 1st quartile, PFOS IRR: 1.37, 95% CI: 1.05-1.71; PFHxS IRR: 1.54, 95% CI: 1.09-1.90). The WQS regressions confirmed the associations reported by single-PFAS analyses.

CONCLUSIONS

We observed cross-sectional associations of tap water consumption and childhood PFOS, and PFHxS concentrations with greater behavioral difficulties.

Per- and Polyfluoroalkyl Substances (PFAS) and Lipid Trajectories in Women 45-56 Years of Age: The Study of Women's Health Across the Nation

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are associated with less favorable blood lipid profiles in epidemiological studies. However, little is known about the potential role of PFAS in longitudinal changes in lipids among midlife women even though women become more susceptible to metabolic alterations during the menopausal transition.

OBJECTIVES

To examine associations of serum PFAS concentrations with longitudinal trajectories of blood total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides in midlife women undergoing menopausal transition.

METHODS

The sample included 1,130 women from the Study of Women's Health Across the Nation 45-56 y of age at baseline (1999-2000). We measured serum PFAS concentrations including linear perfluorooctanoic acid (n-PFOA), perfluorononanoic acid (PFNA), linear and branched perfluorooctanesulfonic acid (n-PFOS and Sm-PFOS, respectively), and perfluorohexanesulfonic acid (PFHxS) at baseline. We used k-means clustering to identify subgroups with different patterns of PFAS mixture. Blood lipids were measured annually or biannually through 2016 with an average follow-up of 14.8 y. We identified longitudinal trajectories of each lipid using latent class growth models. We used multinomial log-linear models adjusted for covariates to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of lipid trajectory classes by PFAS and their mixtures.

RESULTS

Three distinct trajectories (low, middle, high) of total, LDL, and HDL cholesterol and two distinct trajectories (low and high) of triglycerides were identified. n-PFOS, Sm-PFOS, and PFHxS were positively associated with total and LDL cholesterol trajectories. n-PFOS was inversely associated with triglycerides trajectories. PFAS mixtures (high vs. low) showed positive associations with total and LDL cholesterol trajectories (high vs. low), showing ORs (95% CIs) of 1.69 (95% CI: 1.36, 2.12) and 1.79 (95% CI: 1.44, 2.22), respectively.

DISCUSSION

Concentrations of serum PFAS were positively associated with trajectories of total and LDL cholesterol, providing a line of evidence supporting adverse effects of PFAS on lipid homeostasis. https://doi.org/10.1289/EHP12351.

Firefighters' exposure to per-and polyfluoroalkyl substances (PFAS) as an occupational hazard: A review

The term "firefighter" and "cancer" have become so intertwined in the past decade that they are now nearly inseparable. Occupational exposure of firefighters to carcinogenic chemicals may increase their risk of developing different types of cancer. PFAS are one of the major classes of carcinogenic chemicals that firefighters are exposed to as occupational hazard. Elevated levels of PFAS have been observed in firefighters' blood serum in recent studies. Possible sources of occupational exposure to PFAS include turnout gear, aqueous film-forming foam, and air and dust at both the fire scene and fire station. Preliminary discussion on PFAS includes definition, classification, and chemical structure. The review is then followed by identifying the sources of PFAS that firefighters may encounter as an occupational hazard. The structural properties of the PFAS used in identified sources, their degradation, and exposure pathways are reviewed. The elevated level of PFAS in the blood serum and how this might associate with an increased risk of cancer is discussed. Our review shows a significant amount of PFAS on turnout gear and their migration to untreated layers, and how turnout gear itself might be a potential source of PFAS exposure. PFAS from aqueous film-forming foams (AFFF), air, and dust of fire stations have been already established as potential exposure sources. Studies on firefighters' cancer suggest that firefighters have a higher cancer risk compared to the general population. This review suggests that increased exposure to PFAS as an occupational hazard could be a potential cancer risk for firefighters.

Perfluorooctanoic acid induces tight junction injury of Sertoli cells by blocking autophagic flux

Perfluorooctanoic acid (PFOA), a man-made chemical widely used in consumers, could cause male reproductive toxicity by disrupting blood-testis barrier (BTB) integrity. Autophagy in Sertoli cells is essential for regulation of spermatogenesis and BTB. However, it remains a mystery that whether PFOA-induced BTB injury is associated with autophagy in Sertoli cells. In this study, we found that PFOA dose-dependently disrupted tight junction (TJ) function in Sertoli cells in vivo and in vitro. Furthermore, the results from transmission electron microscopy, Western blot and immunofluorescence analysis revealed that PFOA induced the accumulation of autophagosome in testicular Sertoli cells as well as TM4 cells. Further study confirmed that autophagosome accumulation resulted from the blockage of autophagic degradation because of disruption of autophagosome and lysosome fusion via downregulation of the expression of α-SNAP. In parallel, the overexpressed MMP9 was also observed in vivo and in vitro. Conversely, overexpression of α-SNAP inhibited the expression of MMP9 in TM4 cells. In conclusion, PFOA blocks autophagic flux through downregulating the expression levels of α-SNAP in Sertoli cells, and then induces the accumulation of MMP9 leading to disruption of TJ function. This finding will provide clues for effective prevention and treatment of PFOA-induced male reproductive toxicity.

Consideration of pathways for immunotoxicity of per- and polyfluoroalkyl substances (PFAS)

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are of public health concern, because of their ubiquitous and extremely persistent occurrence, and depending on their structure, their bio-accumulative, mobile and toxic properties. Human health effects associated with exposure to PFAS include adverse effects on the immune system. In 2020, EFSA (the European Food Safety Authority) defined adverse effects on the immune system as the most critical effect for human health risk assessment, based on reduced antibody responses to childhood vaccines and similar effects observed in experimental animal studies. Likewise, the U.S. EPA (Environmental Protection Agency) considers PFAS-induced immunotoxicity, especially in children, as the critical effect for risk assessment. However, the mechanisms by which antibody concentrations are impacted are not completely understood. Furthermore, other targets of the immune system functions have been reported in the literature.

OBJECTIVE

The aim of this review is to explore PFAS-associated immune-related effects. This includes, relevant mechanisms that may underlie the observed effects on the immune system, immunosuppression as well as immunoenhancement, such as i) modulation of cell signalling and nuclear receptors, such as NF-κB and PPARs; ii) alteration of calcium signalling and homoeostasis in immune cells; iii) modulation of immune cell populations; iv) oxidative stress and v) impact on fatty acid metabolism & secondary effects on the immune system.

METHODS

A literature research was conducted using three databases (Web of Science, PubMed, and Scopus), which were searched in July 2021 for relevant studies published in the time frame from 2018 to 2021. In total, 487 publications were identified as potentially eligible and following expert-based judgement, articles relevant for mechanisms of PFAS induced immunotoxicity are discussed.

CONCLUSIONS

Taken together, we show that there is substantial evidence from both in vitro and in vivo experimental as well as epidemiological studies, supporting that various PFAS, not only PFOA and PFOS, affect multiple aspects of the immune system. Timing of exposure is critical, because the developing immune system is especially vulnerable to toxic insults, resulting in a higher risk of particularly adverse immune effects but also other organs later in life.

Hexafluoropropylene oxide trimer acid (HFPO-TA) disturbs embryonic liver and biliary system development in zebrafish

Hexafluoropropylene oxide trimer acid (HFPO-TA), a novel alternative to perfluorooctanoic acid (PFOA), has emerged as a potential environmental pollutant. Here, to investigate the toxic effects of HFPO-TA on liver and biliary system development, zebrafish embryos were exposed to 0, 50, 100, or 200 mg/L HFPO-TA from 6 to 120 h post-fertilization (hpf). Results showed that the 50 % lethal concentration (LC₅₀) of HFPO-TA was 231 mg/L at 120 hpf, lower than that of PFOA. HFPO-TA exposure decreased embryonic hatching, survival, and body length. Furthermore, HFPO-TA exerted higher toxicity at the specification stage than during the differentiation and maturation stages, leading to small-sized livers in Tg(fabp10a: DsRed) transgenic larvae and histopathological changes. Significant decreases in the mRNA expression of genes related to liver formation were observed. Alanine transaminase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and direct bilirubin (DBIL) levels were significantly increased. HFPO-TA decreased total cholesterol (TCHO) and triglyceride (TG) activities, disturbed lipid metabolism through the peroxisome proliferator-activated receptor (PPAR) pathway, and induced an inflammatory response. Furthermore, HFPO-TA inhibited intrahepatic biliary development in Tg(Tp1:eGFP) transgenic larvae and interfered with transcription of genes associated with biliary duct development. HFPO-TA reduced bile acid synthesis but increased bile acid transport, resulting in disruption of bile acid metabolism. Therefore, HFPO-TA influenced embryonic liver and biliary system morphogenesis, caused liver injury, and may be an unsafe alternative for PFOA.