Perfluorooctanoic acid (PFOA) and its alternative perfluorobutanoic acid (PFBA) alter hepatic bile acid profiles via different pathways

Integrative transcriptomics analysis reveals convergent toxicological effects of perfluorooctanoic acid and perfluorooctane sulfonate on human liver: Evidence from multiple models

Perfluorooctanoic acid and perfluorooctane sulfonate are well-known eight-carbon per- and polyfluoroalkyl substances (8C-PFAS) potentially toxic for the human liver. However, direct experimental evidence demonstrating their toxicity on the human liver remains limited. Consequently, this study aimed to extrapolate the 8C-PFAS liver toxicity mechanisms by leveraging omics data to integrate mouse and human findings. Through integration analyses of nine datasets (one human, six murine, and two rat), we identified 199 genes with known biological functions that are commonly affected by 8C-PFAS across species. We delineated a comprehensive regulatory network of 8C-PFAS toxicity, demonstrating that 8C-PFAS may trigger fatty liver disease by up-regulating CD36 and PPARα pathway; dysregulate xenobiotic metabolism by disrupting CAR and CYP family genes; and induce cancer by dysregulating WNT, TGFβ, FGF21, and P53 pathways. We also identified ATF3, EGR1, ESR1, NFATC4, SNAI2, TP53, and EZH2 as transcriptionally regulated by 8C-PFAS, along with PPARα, RXRα, FGFR1, TCF3, and SMAD3 as potentially functionally impacted. Collectively, these factors account for over 90 % of 8C-PFAS-affected key genes. This study not only developed a novel method for extrapolating human toxicity risks by integrating scattered toxicity evidence based on transcriptomics data, but also proposes new mechanisms by which 8C-PFAS contributes to fatty liver disease and cancer.

Integrated PBPK Modelling for PFOA Exposure and Risk Assessment

Per- and polyfluoroalkyl substances (PFASs) pose significant public health concerns due to their environmental persistence, bioaccumulation, and ubiquitous presence in human biomonitoring (HBM) data, despite regulatory restrictions. This study establishes a deterministic pharmacokinetic model for perfluorooctanoic acid (PFOA), enabling the estimation of PFOA concentrations in major human organs, even at low doses. The model integrates accumulation and recirculation mechanisms of PFOA in hepatic and renal tissues, leveraging publicly available HBM datasets (e.g., HBM4EU, NHANES, literature) to reconstruct bodyweight-normalized intake levels. Importantly, due to the extremely low urinary excretion concentrations of PFOA, most datasets were derived from blood-based measurements, particularly serum while confirming urine as unreliable biomarker of exposure. The analysis underscores the effectiveness of regulatory efforts in reducing PFOA exposures, as evidenced by declining time-trends in estimated exposure levels in recent studies. Risk characterization ratios were calculated based on recommended limits set by the European Food Safety Authority (EFSA), the United States, and Australia. While EFSA's tolerable weekly intake (TWI) indicated a high risk, other regulatory limits suggested less concern about risk at these intake levels. These findings highlight the need for continuous re-evaluation of exposures and targeted studies to identify key determinants of PFOA exposure, informing future regulatory measures. The study emphasizes the critical role of physiologically based pharmacokinetic (PBPK) modeling, HBM data, and exposure reconstruction in advancing chemical risk assessment. These tools form a science-based framework integral to the Chemical Strategy for Sustainability (CSS), enabling accurate predictions of internal exposure levels, empirical validation of models, and robust assessments of real-world exposure scenarios. The integration of these approaches supports the CSS goals of minimizing chemical risks while promoting innovation, ultimately contributing to a sustainable and protective regulatory landscape for human health and the environment.

Mechanisms of PFBA toxicity in Chlorella vulgaris: Photosynthesis, oxidative stress, and antioxidant impairment

Perfluorobutanoic acid (PFBA), an emerging alternative to perfluorooctanoic acid (PFOA), has become increasingly prevalent in aquatic ecosystems, yet its ecotoxicological impacts remain poorly understood. This study investigated the aquatic toxicity of PFBA using the freshwater algae Chlorella vulgaris (C. vulgaris) as a model organism, employing a 96h pre-exposure assay to determine the median effective concentration followed by acute toxicity experiments analyzing multiple endpoints including growth, photosynthetic parameters, oxidative stress markers, and antioxidant enzyme activities. Computer simulation techniques were utilized to illustrate the underlying molecular mechanisms of PFBA toxicity. The results showed that the 96h-EC50 value of PFBA was 154.88 mg/L, which is comparable to conventional per- and polyfluoroalkyl substances (PFAS). Acute toxicity experiments revealed a biphasic dose-response relationship to the algal growth with the hormetic effects at the lower concentrations (30.97-92.93 mg/L) but inhibition at the higher levels (123.91-185.86 mg/L) of PFBA. High dosages of PFBA significantly decreased the maximum photosynthetic yield (Fv/Fm) and relative electron transfer rate (rETR), while inducing oxidative stress and inhibiting superoxide dismutase (SOD) and catalase (CAT) activities. Future AlphaFold2 modeling and molecular docking simulations demonstrated the potential binding of PFBA to photosystem II D1 C-terminal processing protease (PSII D1 protein), SOD, and CAT. These findings reveal a complex toxicity mechanism of PFBA on C. vulgaris involving photosynthetic disruption, oxidative stress, and antioxidant system impairment, contributing to the understanding of short-chain PFAS alternative ecotoxicity in aquatic ecosystems.

Uncovering the effects of the North Pacific Subtropical Gyre on per- and polyfluoroalkyl substances distribution in the Tropical Western Pacific

The accumulation of per- and polyfluoroalkyl substances (PFAS) in subtropical gyres, commonly referred to as "garbage patches", remains insufficiently characterized. In this study, we collected surface seawater samples from 40 sites across the Tropical Western Pacific (TWP) and identified 19 different PFAS. Of them, perfluoro-n-butanoic acid (PFBA) exhibits the highest concentration (median 329.2 pg/L). The concentration of ΣPFAS in nearshore region (median 910.5 pg/L) is higher than those in two other oceanic regions (with medians of 773.8 pg/L in Philippine Sea and 863.1 pg/L in Equatorial Current, respectively). However, in North Pacific Subtropical Gyre (NPSG), the ΣPFAS concentration (median 1056.5 pg/L) is higher than that in the nearshore region and significantly higher than in North Equatorial Current (NEC) (p < 0.05) and the composition and concentrations of PFAS in this region significantly differ from those in other oceanic regions (p < 0.05). Additionally, PFBA, an alternative perfluoroalkyl carboxylic acid (PFCA), is significantly enriched in the NPSG (p < 0.05). These suggest that alternative PFAS have now become the main PFAS pollutants in the surface waters of TWP, with PFOA and its alternatives making up the majority. Enrichment of PFCA is observed in the surface seawater of NPSG, with enrichment factors influenced by chain length and human activities. This study provides the first comprehensive analysis of the distribution and migration characteristics of PFAS in TWP, emphasizing the influence of subtropical gyre on PFAS accumulation.

Per- and polyfluoroalkyl substances (PFAS) composition and distribution in surface water of the Miccosukee Indian Reservation, Everglades and tributaries in the coastal environment of Miami, Florida

PFAS have a well-documented history of adverse human health effects and have been detected in both urban environments and remote rural areas. In this study, PFAS concentrations were monitored in canals discharging into Biscayne Bay (Miami, FL) and compared to the surface water in canals and marshes within the Miccosukee Indian Reservation of Everglades National Park to assess PFAS contamination levels in urban and rural environments. Solid phase extraction was performed on 250 mL water samples using Strata-AW-XL cartridges, followed by liquid chromatography tandem mass spectrometry. The sum of PFAS concentrations ranged between 30.1 and 153 ng/L along the Miami canals. PFAS have been detected for the first time in the Miccosukee Indian Reservation, with levels ranging from 3.94 to 40.1 ng/L. The most abundant compounds were perfluorooctanesulfonate (PFOS) with a mean concentration of 15.2 ± 9.72 ng/L, perfluoro-n-pentanoic acid (PFPeA, mean = 10.2 ± 7.73 ng/L), perfluoro-n-butanoic acid (PFBA, mean = 10.7 ± 7.87 ng/L), and perfluoro-n-hexanoic acid (PFHxA, mean = 7.38 ± 5.16 ng/L). In the Everglades samples, 48 % of the total compounds identified were PFBA and 15 % was PFOS, while in the canals, 25 % was PFOS, 16 % PFPeA, and 14 % PFBA. The land uses of the area that could be contributing to PFAS concentrations are the production of textiles and stain resistant products, metal plating and finishing facilities, aqueous film forming foams, and various wastewater entering the watershed.