Placental inflammatory injury induced by chlorinated polyfluorinated ether sulfonate (F-53B) through NLRP3 inflammasome activation

Chlorinated polyfluorinated ether sulfonate, commercially known as F-53B, has been associated with adverse birth outcomes. However, the reproductive toxicology of F-53B on the placenta remains poorly understood. To address this gap, we examined the impact of F-53B on placental injury and its underlying molecular mechanisms in vivo. Pregnant C57BL/6 J female mice were randomly allocated to three groups: the control group, F-53B 0.8 µg/kg/day group, and F-53B 8 µg/kg/day group. After F-53B exposure through free drinking water from gestational day (GD) 0.5-14.5, the F-53B 8 µg/kg/day group exhibited significant increases in placental weights and distinctive histopathological alterations, including inflammatory cell infiltration, heightened syncytiotrophoblast knots, and a loosened trophoblastic basement membrane. Within the F-53B 8 µg/kg/day group, placental tissue exhibited increased apoptosis, as indicated by increased caspase3 activation. Furthermore, F-53B potentially induced the NF-κB signaling pathway activation through IκB-α phosphorylation. Subsequently, this activation upregulated the expression of inflammatory cytokines and components of the NLRP3 inflammasome, including activated caspase1, IL-1β, IL-18, and cleaved gasdermin D (GSDMD), ultimately leading to pyroptosis in the mouse placenta. Our findings reveal a pronounced inflammatory injury in the placenta due to F-53B exposure, suggesting potential reproductive toxicity at concentrations relevant to the human population. Further toxicological and epidemiological investigations are warranted to conclusively assess the reproductive health risks posed by F-53B.

Exposure characteristics of legacy and novel per- and polyfluoroalkyl substances in blood and association with hypertension among low-exposure population

The exposure characteristics of per- and polyfluoroalkyl substances (PFAS) in blood and their associations with hypertension have been well investigated in high-exposure populations, yet limited information is available concerning low-exposure populations. We conducted a cross-sectional study in a low-exposure population in China. A total of 394 females, including 162 with hypertension, were recruited and 30 PFAS were measured in whole blood samples. General linear model, generalized additive model, and logistic model were used to identify the associations with hypertension. Additionally, a Bayesian kernel machine regression model was conducted to test the mixture effects. Fourteen PFAS, including two novel species, 6:2 and 8:2 chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), were detected, among which PFOS predominated with the highest median level of 1.47 ng/mL. The median levels of individual PFAS were, however, below the 25th, and even the 5th percentile of previous reports, except for PFHxA, which was above the 50th percentile (median of 0.10 ng/mL). After adjusting for covariates, PFHxA showed a positive association with hypertension (OR=1.54, 95% CI: 1.25, 1.89), while 6:2 Cl-PFESA showed a negative association (OR=0.73, 95% CI: 0.56, 0.95). PFAS didn't show significant mixture effects. We proposed that PFHxA may contribute to hypertension and 6:2 Cl-PFESA may have a hormesis effect.

Associations between per and polyfluoroalkyl ether sulfonic acids and vitamin D biomarker levels in Chinese newborns

Skeleton develops extremely fast during fetal and neonatal stages; thus, fetuses and newborns exhibit unique vulnerabilities to vitamin D metabolism dysregulation, giving vitamin D's principal role in calcium homeostasis. Previous studies linked legacy per and polyfluoroalkyl ether sulfonic acids (PFAS) with vitamin D biomarker status in adults and children; however, how PFAS, especially emerging CI-PFESAs, influence vitamin D among newborns is unknown. This study focused on the epidemiological linkages between PFAS and vitamin D biomarkers. Eleven PFAS, including legacy PFAS and emerging CI-PFESAs, as well as two vitamin D metabolites [25-hydroxyvitamin D2 (25(OH)D2) and 25-hydroxyvitamin D3 (25(OH)D3)], were determined in cord sera of 992 newborns from a birth cohort in Wuhan, China. The cord serum levels of 25(OH)D2 and 25(OH)D3 were summed as total 25(OH)D, which is a reliable biomarker of vitamin D status. The associations of separated PFAS with vitamin D biomarker levels were analyzed via multiple linear models, whereas the mixture effect was estimated by utilizing the weighted quantile sum (WQS) regression. We observed that per doubling changes in perfluorotridecanoate (PFTrDA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) were associated with a 6.04 to 9.05 % change in total 25(OH)D levels. PFHxS contributed over half of the PFAS mixture effect on total 25(OH)D. Stratified analysis indicated that the associations of certain PFAS with vitamin D biomarkers were more pronounced among boys. The emerging CI-PFESAs were not robustly related to vitamin D biomarker levels. The results suggested that exposure to legacy PFAS might disturb vitamin D status in newborns. Future epidemiological studies are required to confirm the association and to determine healthy implications at a later age.

The effects of Cl-PFESAs exposure on blood lipids - A community-based large population study in Guangzhou

Numerous epidemiological studies have investigated the lipid interference effects of legacy PFASs, however, no studies on PFAS alternatives and blood lipids have been published. In this study, we explored the association between Cl-PFESAs, a typical PFASs alternative in China, and blood lipid profiles in 1336 Guangzhou community residents using linear and non-linear regression models. The results showed a deleterious effect of Cl-PFESAs and blood lipids: adjusted estimates (β) for TC, TG, LDL-C and HDL-C per natural log unit increase of 6:2 Cl-PFESA were 0.029 (95% CI: 0.020, 0.038), 0.075 (95% CI: 0.049, 0.101), 0.035 (95% CI: 0.021, 0.049) and -0.071 (95% CI: -0.084, -0.058), respectively. The association between Cl-PFESAs and dyslipidemia was also positively significant (P < 0.05). Furthermore, a non-linear relationship was observed in Cl-PFESAs and serum lipid levels using a restricted cubic splines (RCS) model. In summary, our research suggested a negative impact of Cl-PFESAs on blood lipid patterns and a possible non-linear association.

Chlorinated polyfluoroalkyl ether sulfonic acids in fish, dust, drinking water and human serum: From external exposure to internal doses

Exposure to per- and polyfluoroalkyl substances (PFASs) has raised significant public health concerns due to their persistence and toxicity in the human body. Here, we aimed to investigate the characteristics of exposure to chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) and legacy PFASs and the relative contribution from different external pathways to human exposure. Three Cl-PFESAs and fourteen legacy PFASs were detected in human serum, fish, indoor dust and drinking water collected from Shijiazhuang, China. Results showed that 6:2 Cl-PFESA was the third most predominant compound, with an average concentration of 2.70 ng/mL in serum, which was lower than those of perfluorooctane sulfonate (PFOS) and perfluorooctane acid (PFOA) (14.79 and 4.91 ng/mL). The estimated daily intake of 6:2 Cl-PFESA via dust ingestion (mean: 0.008 ng/kg bw/day) was found to be highest among all detected PFASs, while the highest value via fish and drinking water was found for PFOS and PFOA (0.438-9.799 and 0.034-0.155 ng/kg bw/day), respectively. The similar composition of PFASs between serum and fish suggests that fish consumption is a major contributor to human exposure to PFASs. However, the increasing ratios of EDI_{indoor dust}/EDI_fish for PFOS, PFOA and 6:2 Cl-PFESA indicated that the contribution of dust ingestion for PFASs, especially 6:2 Cl-PFESA, could not be ignored. The modeled serum concentrations of 6:2 Cl-PFESA higher than its observed levels hint at its gradually increasing exposure levels in the general population. Combined with the lower modeled levels of PFOS than the observed levels, the substituent with 6:2 Cl-PFESA for PFOS is obvious in China. Therefore, further studies on contributions from more detailed external sources and risk assessments of Cl-PFESAs are recommended, especially for some vulnerable subpopulations, considering their widespread exposure and similar environmental behaviors compared with those of their predecessors.

Profiling of emerging and legacy per-/polyfluoroalkyl substances in serum among pregnant women in China

Emerging per-/polyfluoroalkyl substances (PFASs), such as chlorinated polyfluorinated ether sulfonates (Cl-PFESAs), have been detected in human samples, yet investigation on their occurrence in pregnant women remains limited. Herein, ten legacy PFASs, branched perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA), two Cl-PFESAs, perfluoro-2-propoxypropanoic acid (HFPO-DA), and ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA) were detected in serum samples from 480 pregnant women in Tianjin, China. The influencing effects of age, body mass index, gravidity, and parity were also evaluated. PFOS [geographic mean (GM): 7.05 ng/mL], 6:2Cl-PFESA (GM: 5.31 ng/mL), and PFOA (GM: 2.82 ng/mL) were the dominant PFASs in the serum of pregnant women, while neither HFPO-DA nor ADONA was detectable in any serum. The serum concentration of Cl-PFESAs and 6:2Cl-PFESA/PFOS ratio in the present study were 2-5 times higher than that in previous studies of pregnant women in China. Serum concentrations of Cl-PFESAs were significantly correlated with all detected PFAAs (Spearman's Rho: 0.15-0.69, p < 0.01) excepting perfluoropentanesulfonate (PFPeS), indicating common exposure sources for Cl-PFESAs and PFAAs and some particular exposure source for PFPeS. Younger age and multi-parity were associated with lower serum concentrations of PFOS and several perfluoroalkyl sulfonates but not associated with Cl-PFESAs or PFOA, suggesting an increasing exposure to Cl-PFESAs and PFOA which neutralized the impact of age and parity. Overall, this study indicated a relatively high exposure level and composition of 6:2Cl-PFESA in pregnant women in the north coast of China, which highlights the need to investigate the exposure sources in this area.

The occurrence of PFAS in human placenta and their binding abilities to human serum albumin and organic anion transporter 4

Both legacy and emerging per- and polyfluoroalkyl substances (PFAS) have been found to be threats to human health. In particular, fetuses are sensitive to xenobiotics and the placenta functions as a significant barrier for environmental pollutants. The placental transfer of PFAS is closely related to their interactions with proteins. In this study, 54 human placental samples were collected to investigate the occurrence of legacy and emerging PFAS in human placenta, including perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs), and fluorotelomer sulfonates (FTSAs). Among the legacy PFAS, perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) were detected in all samples, with PFOS and PFOA being the two predominant (mean: 0.457 and 0.242 ng/g wet weight, respectively). Among the emerging PFAS, 6:2 Cl-PFESA was detected in all samples with the mean value of 0.104 ng/g wet weight, while the detect frequency (DF) of 8:2 Cl-PFESAs was only 24%. The concentration and DF of the four FTSA congeners were low in the placentas. Molecular docking calculation results showed that the binding affinities of PFAS to the human serum albumin (HSA) were increased with chain length in each category except for the PFCAs, of which the perfluoroundecanoic acid (PFUnDA) was the turning point of binding affinity to HSA. For PFSAs, their binding affinities to organic anion transporter 4 (OAT4) were increased with the chain length except for the sodium perfluoro-1-heptanesulfonate (PFHpS) and sodium perfluoro-1-nonanesulfonate (PFNS). The calculation results demonstrated that the placental transfer of PFAS is closely related to chain length. The findings in the study can help better understand the occurrence of the PFAS in the human placenta and the placental transfer mechanisms of PFAS in human beings.

Occurrence and risk of chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) in seafood from markets in Beijing, China

In recent years, chlorinated polyfluoroalkyl ether sulfonic acid (Cl-PFESA, trade name: F-53B), one of the alternatives to perfluorooctane sulfonate (PFOS), has been widely detected in environmental matrices and organisms in China. However, sufficient information regarding its presence in seafood is not available. Therefore, we investigated the levels of Cl-PFESAs and legacy per- and polyfluoroalkyl substances (PFASs) in 276 seafood samples collected from markets in Beijing and assessed the human exposure risks of Cl-PFESAs through seafood intake. C8 Cl-PFESA was the dominant congener with significantly higher concentrations (<LOD-1.27 ng/g) than those of C10 Cl-PFESA (<LOD-0.109 ng/g) and C12 Cl-PFESA (<LOD-0.141 ng/g). The mean concentrations of ∑Cl-PFESAs (0.013-0.412 ng/g) contributed to 0.6-11.4% for ∑PFASs in different seafood species. Generally, the concentrations of C8 Cl-PFESA were lower than those of PFOS. However, their concentration trends in four categories of seafood were consistent, with the highest mean concentrations being in shrimps (0.279 and 0.749 ng/g), followed by crabs (0.275 and 0.714 ng/g), fish (0.141 and 0.317 ng/g), and mollusks (0.032 and 0.135 ng/g). A significantly positive correlation was observed between the concentrations of C8 Cl-PFESA and PFOS in all seafood samples (p < 0.001), indicating that they have similar sources and undergo similar environmental processes. The average daily intake of C8 Cl-PFESA (0.067 ng/kg-bw/day) for residents in Beijing via the consumption of seafood was lower than that of PFOS (0.167 ng/kg-bw/day) and far below the most stringent health-based reference dose of PFOS (1.86 ng/kg-bw/day), which implies a low risk for Beijing residents exposed to C8 Cl-PFESA by ingestion of seafood. However, considering the omnipresence of Cl-PFESAs and their stronger bioaccumulation than PFOS, further study on the potential environmental and human exposure risks of Cl-PFESAs is required.

Spatial distribution, seasonal variation and risks of legacy and emerging per- and polyfluoroalkyl substances in urban surface water in Beijing, China

In the current study, we investigated the occurrence, spatial distribution and seasonal variation of per- and polyfluoroalkyl substances (PFASs), including one group of emerging PFASs, the chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs), in urban surface water (river and lake) samples from October 2013 to September 2014 (except during the frozen period) in Beijing, China. Perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA) were the dominant compounds, with average concentrations of 12.79 and 9.90 ng/L, respectively. For Cl-PFESAs, only C8 Cl-PFESA could be detected, and its concentration ranged from <MLQ to 6.93 ng/L. Higher concentrations of ∑PFASs were observed in the northern and eastern regions of Beijing. The highest and lowest levels of ∑PFASs were found in summer and winter, respectively. For C8 Cl-PFESA, there were no significant differences in the concentrations among different sampling sites. Additionally, risk assessments indicated that the studied PFASs at present levels might pose a low risk to aquatic organisms (green algae, Daphnia sp. and fish). However, further studies should be conducted on the combined risk from PFASs or the risk to other sensitive species in aquatic environments.

Using hair, nail and urine samples for human exposure assessment of legacy and emerging per- and polyfluoroalkyl substances

Non-invasive samples present ethical and practical benefits for investigating human exposure to hazardous contaminants, but analytical challenges and difficulties to interpret the results limit their application in biomonitoring. Here we investigated the potential for using hair, nail and urine samples as a measure of internal exposure to an array of legacy and emerging per- and polyfluoroalkyl substances (PFASs) in two populations with different exposure conditions. Paired urine-serum measurements of PFASs from a group of highly exposed fishery employees displayed strong correlations for PFASs with three to eight perfluorinated carbons (ρ > 0.653; p < 0.01). Consistent statistical correlations and transfer ratios in nails and hair from both populations demonstrated that these non-invasive samples can be used as a measure of internal exposure to perfluorooctane sulfonic acid and C8 chlorinated polyfluoralkyl ether sulfonic acid (C8 Cl-PFESA). Contrastingly, the infrequent detections and/or lack of consistent transfer ratios for perfluorooctanoic acid, perfluorononanoic acid and short-chain PFASs in hair and nail samples indicate passive uptake from the external environment rather than uptake and internal distribution. Collectively, the study supports the use of urine samples as a valid measure of internal exposure for a range of short- and medium-chain PFASs, while the validity of nail and hair samples as a measure of internal exposure may vary for different PFASs and populations. The ubiquitous detection of C8 Cl-PFESA in all sample matrices from both populations indicates widespread exposure to this contaminant of emerging concern in China.