Perfluoroalkyl Acids (PFAAs) in Serum from 2-4-Month-Old Infants: Influence of Maternal Serum Concentration, Gestational Age, Breast-Feeding, and Contaminated Drinking Water

Prenatal exposure to hexafluoropropylene oxide trimer acid (HFPO-TA) disrupts the maternal gut microbiome and fecal metabolome homeostasis

Initially considered a "safe" substitute for perfluorooctanoic acid (PFOA), hexafluoropropylene oxide trimer acid (HFPO-TA) has been extensively used in the production of fluoropolymers for several years, leading to its environmental ubiquity and subsequent discovery of its significant bio-accumulative properties and toxicological effects. However, the specific impact of HFPO-TA on females, particularly those who are pregnant, remains unclear. In the present study, pregnant mice were exposed to 0.63 mg/kg/day HFPO-TA from gestational day (GD) 2 to GD 18. We then determined the potential effects of exposure on gut microbiota and fecal metabolites at GD 12 (mid-pregnancy) and GD 18 (late pregnancy). Our results revealed that, in addition to liver damage, HFPO-TA exposure during the specified window altered the structure and function of cecal gut microbiota. Notably, these changes showed the opposite trends at GD 12 and GD 18. Specifically, at GD 12, HFPO-TA exposure primarily resulted in the down-regulation of relative abundances within genera from the Bacteroidetes and Proteobacteria phyla, as well as associated Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. With extended exposure time, the down-regulated genera within Proteobacteria became significantly up-regulated, accompanied by corresponding up-regulation of human disease- and inflammation-associated pathways, suggesting that HFPO-TA exposure can induce intestinal inflammation and elevate the risk of infection during late pregnancy. Pearson correlation analysis revealed that disturbances in the gut microbiota were accompanied by abnormal fecal metabolite. Additionally, alterations in hormones related to the steroid hormone biosynthesis pathway at both sacrifice time indicated that HFPO-TA exposure might change the steroid hormone level of pregnant mice, but need further study. In conclusion, this study provides new insights into the mechanisms underlying HFPO-TA-induced adverse effects and increases awareness of potential persistent health risks to pregnant females.

Per- and Polyfluoroalkyl Substances (PFAS) in Serum of 2 to 5 year-Old Children: Temporal Trends, Determinants, and Correlations with Maternal PFAS Concentrations

Young children may experience higher per- and polyfluoroalkyl substances (PFAS) exposure than adults due to breastfeeding, higher dust ingestion rates, and frequent hand-to-mouth activities. We explored temporal trends and determinants of child serum PFAS concentrations and their correlations with paired maternal PFAS concentrations. From 2009 to 2017, we collected one blood sample from each of 541 children aged 2-5 years participating in the Childhood Autism Risks from Genetics and Environment (CHARGE) study and quantified 14 PFAS in serum. For nine frequently detected PFAS (>65% of samples), we performed multiple regression adjusting for potential determinants to estimate mean percent concentration changes. For a subset of 327 children, we also quantified nine PFAS in their mother's serum collected at the same visit and computed Spearman correlation coefficients (rsp) between maternal and child PFAS concentrations. During 2009-2017, child serum concentrations of all nine PFAS decreased by 6-25% annually. Several PFAS concentrations were higher among non-Hispanic white children and those with highly educated parents. Most maternal and child PFAS concentrations were moderately correlated (rsp = 0.13-0.39), with a strong correlation for N-methyl perfluorooctane sulfonamido acetic acid (rsp = 0.68). Breastfeeding duration appeared to contribute to higher child and lower maternal PFAS concentrations, resulting in relatively weak correlations between maternal and child PFAS concentrations for samples collected in early childhood. Considering that more than half of our study children had neurodevelopmental concerns, the generalizability of our findings might be limited.

Concentrations and association between exposure to mixed perfluoroalkyl and polyfluoroalkyl substances and glycometabolism among adolescents

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are widely used for industrial and commercial purposes and have received increasing attention due to their adverse effects on health.

OBJECTIVE

To examine the relationship of serum PFAS and glycometabolism among adolescents based on the US National Health and Nutrition Examination Survey.

METHODS

General linear regression models were applied to estimate the relationship between exposure to single PFAS and glycometabolism. Weighted quantile sum (WQS) regression models and Bayesian kernel machine regressions (BKMR) were used to assess the associations between multiple PFASs mixture exposure and glycometabolism.

RESULTS

A total of 757 adolescents were enrolled. Multivariable regression model showed that Me-PFOSA-AcOH exposure was negatively associated with fasting blood glucose. WQS index showed that there was marginal negative correlation between multiple PFASs joint exposure and the homeostasis model of assessment for insulin resistance index (HOMA-IR) (β = -0.26, p < .068), and PFHxS had the largest weight. BKMR models showed that PFASs mixture exposure were associated with decreased INS and HOMA-IR, and the exposure-response relationship had curvilinear shape.

CONCLUSIONS

The increase in serum PFASs were associated with a decrease in HOMA-IR among adolescents. Mixed exposure models could more accurately and effectively reveal true exposure.Key MessagesThe detection rates of different PFAS contents in adolescent serum remained diverse.Adolescent serum PFASs had negative curvilinear correlation with INS and HOMA-IR levels.PFHxS had the highest weight in the associations between multiple PFASs and adolescent glycometabolism.

Generation Mechanism of Perfluorohexanesulfonic Acid from Polyfluoroalkyl Sulfonamide Derivatives During Chloramination in Drinking Water

Per- and polyfluoroalkyl substances (PFASs), including perfluorohexanesulfonic acid (PFHxS), as emerging persistent organic pollutants widely detected in drinking water, have drawn increasing concern. The PFHxS contamination of drinking water always results from direct and indirect sources, especially the secondary generations through environmental transformations of precursors. However, the mechanism of the transformation of precursors to PFHXS during the drinking water treatment processes remains unclear. Herein, the potential precursors and formation mechanisms of PFHxS were explored during drinking water disinfection. Simultaneously, the factors affecting PFHxS generation were also examined. This study found PFHxS could be generated from polyfluoroalkyl sulfonamide derivatives during chlorination and chloramination. The fate and yield of PFHxS varied from different precursors and disinfection processes. In particular, monochloramine more favorably formed PFHxS. Several perfluoroalkyl oxidation products and decarboxylation intermediates were detected and identified in the chloraminated samples using Fourier-transform ion cyclotron resonance mass spectrometry. Combined with density functional theory calculations, the results indicated that the indirect oxidation via the attack of the nitrogen atom in sulfonamide groups might be the dominant pathway for generating PFHxS during chloramination, and the process could be highly affected by the monochloramine dose, pH, and temperature. This study provides important evidence of the secondary formation of PFHxS during drinking water disinfection and scientific support for chemical management of PFHxS and PFHxS-related compounds.

Bypassing the Identification: MS2Quant for Concentration Estimations of Chemicals Detected with Nontarget LC-HRMS from MS2 Data

Nontarget analysis by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) is now widely used to detect pollutants in the environment. Shifting away from targeted methods has led to detection of previously unseen chemicals, and assessing the risk posed by these newly detected chemicals is an important challenge. Assessing exposure and toxicity of chemicals detected with nontarget HRMS is highly dependent on the knowledge of the structure of the chemical. However, the majority of features detected in nontarget screening remain unidentified and therefore the risk assessment with conventional tools is hampered. Here, we developed MS2Quant, a machine learning model that enables prediction of concentration from fragmentation (MS2) spectra of detected, but unidentified chemicals. MS2Quant is an xgbTree algorithm-based regression model developed using ionization efficiency data for 1191 unique chemicals that spans 8 orders of magnitude. The ionization efficiency values are predicted from structural fingerprints that can be computed from the SMILES notation of the identified chemicals or from MS2 spectra of unidentified chemicals using SIRIUS+CSI:FingerID software. The root mean square errors of the training and test sets were 0.55 (3.5×) and 0.80 (6.3×) log-units, respectively. In comparison, ionization efficiency prediction approaches that depend on assigning an unequivocal structure typically yield errors from 2× to 6×. The MS2Quant quantification model was validated on a set of 39 environmental pollutants and resulted in a mean prediction error of 7.4×, a geometric mean of 4.5×, and a median of 4.0×. For comparison, a model based on PaDEL descriptors that depends on unequivocal structural assignment was developed using the same dataset. The latter approach yielded a comparable mean prediction error of 9.5×, a geometric mean of 5.6×, and a median of 5.2× on the validation set chemicals when the top structural assignment was used as input. This confirms that MS2Quant enables to extract exposure information for unidentified chemicals which, although detected, have thus far been disregarded due to lack of accurate tools for quantification. The MS2Quant model is available as an R-package in GitHub for improving discovery and monitoring of potentially hazardous environmental pollutants with nontarget screening.

Association between PFAS congeners exposure and asthma among US children in a nationally representative sample

Over the past few decades, contamination with perfluorinated and polyfluoroalkyl substances (PFAS) has gradually become a worldwide problem. Now that common PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are being phased out and replaced, people may be exposed to other PFAS congeners, and their potential hazards should be fully studied. We assessed the association of serum PFAS levels (as biomarkers of exposure) with asthma, including 2-(N-methyl-perfluorooctane sulfonamido) acetic acid (Me-PFOSA-AcOH), pefluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA), using data from participants aged 3-11 from the 2013-2014 National Health and Nutrition Examination Surveys (n = 525), where PFAS was modeled as a binary variable.Me-PFOSA-AcOH (1.36; 95% CI 0.77, 2.38), PFDA (1.33; 95% CI 0.76, 2.33), and PFUnDA (1.89; 95% CI 0.83, 4.35) were nonsignificantly associated with increased odds of asthma. Age, sex, and race/ethnicity modified associations between serum PFUnDA, not other serum PFAS congeners exposure, and odds of asthma. Specifically, for male participants, the OR = 3.06 and 95% CI 1.23-7.62 for serum PFUnDA exposure; for participants aged 3-7 years old, the OR = 3.55 and 95% CI 1.04-12.10 for serum PFUnDA exposure; for non-Hispanic White participants, the OR = 3.44 and 95% CI 1.14-10.36 for serum PFUnDA exposure, all of which exhibited a significantly positive relationship. This cross-sectional study provides some evidence for associations between exposure to PFAS congeners and asthma in children. We believe this relationship deserves further exploration. More large-scale epidemiologic studies are needed to evaluate the association of serum PFAS congeners, especially for PFUnDA exposure, with asthma among children.

Predictors of serum- per- and polyfluoroalkyl substance (PFAS) concentrations among infants in Guinea-Bissau, West Africa

BACKGROUND

Knowledge about PFAS exposure in Africa is limited. We have previously detected six types of PFAS in the serum of infants from Guinea-Bissau, West Africa. The aim of this study was to identify predictors of the infant serum-PFAS concentrations.

METHODS

This cross-sectional study was based on a subset of data from a randomized controlled trial of early measles vaccination performed in 2012-2015 in three rural regions of Guinea-Bissau. Blood samples were obtained from 237 children aged 4-to-7 months, and six types of PFAS were quantified in serum. Location of residence was recorded, and information about predictors related to socioeconomic status as well as maternal and child characteristics were obtained through structured interviews with the mothers through routine surveillance. Associations between potential predictors and infant serum-PFAS concentrations were examined in linear regression models while adjusting for potential confounding and mediating factors as identified in a directed acyclic graph.

RESULTS

Infants from the Cacheu region had the lowest concentrations of perfluorooctanoic acid (PFOA), while infants from the Oio region had the lowest concentrations of all other PFAS. Compared to infants from Oio, infant serum-perfluorooctane sulfonic acid (PFOS) concentrations were 94.1% (95% CI: 52.4, 147.1%) and 81.9% (95% CI: 45.7, 127.1%) higher in Cacheu and Biombo, respectively. Higher maternal age and lower parity were associated with slightly higher child-serum perfluorohexane sulfonic acid (PFHxS) concentrations, while infants with higher socioeconomic status and infants breastfed without supplementary solid foods at inclusion had higher average concentrations of most PFAS, although the confidence intervals were wide and overlapped zero.

DISCUSSION

Location of residence was the most important determinant of serum-PFAS concentrations among Guinea-Bissau infants, indicating a potential role of diet as affected by the global spread of PFAS, but future studies should explore reasons for the regional differences in PFAS exposure.

Understanding the Chemical Exposome During Fetal Development and Early Childhood: A Review

Early human life is considered a critical window of susceptibility to external exposures. Infants are exposed to a multitude of environmental factors, collectively referred to as the exposome. The chemical exposome can be summarized as the sum of all xenobiotics that humans are exposed to throughout a lifetime. We review different exposure classes and routes that impact fetal and infant metabolism and the potential toxicological role of mixture effects. We also discuss the progress in human biomonitoring and present possiblemodels for studying maternal-fetal transfer. Data gaps on prenatal and infant exposure to xenobiotic mixtures are identified and include natural biotoxins, in addition to commonly reported synthetic toxicants, to obtain a more holistic assessment of the chemical exposome. We highlight the lack of large-scale studies covering a broad range of xenobiotics. Several recommendations to advance our understanding of the early-life chemical exposome and the subsequent impact on health outcomes are proposed.

Human serum poly- and perfluoroalkyl substance concentrations and their associations with gestational diabetes mellitus

Poly- and perfluoroalkyl substances (PFAS), which have been found in high concentrations in maternal serum, have the potential to impair glucose metabolism in pregnant women. However, the effects of PFAS exposure on the risk of gestational diabetes mellitus (GDM) remain inconsistent. In the current investigation, a case-control study involving 135 patients with GDM and 69 controls was conducted in Hangzhou, China. We determined the concentrations of 17 PFAS in maternal serum from each participant and elucidated the associations between those concentrations and the risk of GDM. Among the 17 PFAS, perfluorooctanesulfonate (median 7.53 and 7.44 ng/mL) was the predominant PFAS in both cases and controls, followed by perfluorooctanoic acid (PFOA; median 5.22 and 5.03 ng/mL) and 6:2 chlorinated perfluoroalkyl ether sulfonate (6:2 Cl-PFESA; median 2.58 and 2.42 ng/mL). Conditional logistic regression analysis showed that the maternal serum continuous levels of PFOA, perfluorononanoic acid (PFNA), perfluorohexanesulfonate (PFHxS), and 6:2 Cl-PFESA were significantly associated with the GDM risk, with adjusted odds ratios (ORs) of 1.84 (95% confidence interval (CI): 1.26, 3.51), 1.47 (1.17, 3.29), 1.33 (1.72, 3.48), and 1.34 (1.17, 2.53), respectively. In the adjusted model, the ORs of GDM for increasing tertiles of PFOA, PFNA, PFHxS, and 6:2 Cl-PFESA significantly increased. The adjusted ORs (95% CI) were 3.38 (2.16, 6.89), 2.61 (1.26, 5.40), 3.46 (1.64, 6.30), and 3.50 (1.62, 6.91) at the highest concentrations of PFOA, PFNA, PFHxS, and 6:2 Cl-PFESA, respectively. These results suggest that higher PFAS exposure, reflected in serum PFAS concentrations, was associated with GDM incidence in pregnant women.

Distribution of per- and poly-fluoroalkyl substances and their precursors in human blood

Many studies have examined per- and poly-fluoroalkyl substances (PFASs) in human blood. However, the distribution of PFASs in human blood remains not well known, especially for perfluorooctane sulfonate (PFOS) precursors. In this study, human blood samples (n = 162) were collected from general Chinese population, and then the isomer-specific partitioning of PFASs between human plasma and red blood cells (RBCs) were investigated. Perfluorooctanoate (PFOA) and PFOS were consistently the predominant PFASs in both human plasma and RBCs. In human blood, among C₄-C₇ perfluoroalkyl carboxylates (PFCAs), the calculated mean mass fraction in plasma (F_p) values increased from 0.76 to 0.82 with the increasing chain length. C₇-C₁₃ PFCAs exhibited a trend of gradually decreasing mean F_p with chain length. Among PFAS precursors, 6:2 fluorotelomer phosphate diester had the highest mean F_p value (0.87 ± 0.11). Calculated F_p values of N-methyl perfluorooctanesulfonamide (N-MeFOSA) and N-ethyl perfluorooctanesulfonamide (N-EtFOSA) were 0.66 ± 0.13 and 0.70 ± 0.12, respectively. Individual branched isomers consistently had greater F_p values than their corresponding linear isomers for PFOA, PFHxS, and perfluoroctane sulfonamide. To our knowledge, this study first reports the distribution of N-MeFOSA and N-EtFOSA in human blood, contributing to the better understanding of the occurrence and fate of PFASs in humans.

Blood transcriptome responses to PFOA and GenX treatment in the marsupial biomedical model Monodelphis domestica

Introduction: Perfluoroalkyl and poly-fluoroalkyl substances (PFASs) are widely used in industrial and consumer products. Due to their environmental persistence and bioaccumulation, PFASs can be found in the blood of humans and wild animals all over the world. Various fluorinated alternatives such as GenX have been developed to replace the long-chain PFASs, but there is limited information about their potential toxicity. Methods:The current study developed blood culture protocols to assess the response to toxic compounds in the marsupial, Monodelphis domestica. After whole-blood culture conditions were tested and optimized, changes in gene expression in response to PFOA and GenX treatment were assessed. Results: More than 10,000 genes were expressed in the blood transcriptomes with and without treatment. Both PFOA and GenX treatment led to significant changes in the whole blood culture transcriptomes. A total of 578 and 148 differentially expressed genes (DEGs) were detected in the PFOA and GenX treatment groups, 32 of which overlapped. Pathway enrichment analysis revealed that DEGs involved in developmental processes were upregulated after PFOA exposure, while those enriched for metabolic and immune system processes were downregulated. GenX exposure upregulated genes associated with fatty acid transport pathways and inflammatory processes, which is consistent with previous studies using rodent models. Discussion: To our knowledge, this study is the first to investigate the effect of PFASs in a marsupial model. The findings provide supportive evidence for significant transcriptomic alterations, suggesting that this mammalian model may provide a mechanism for exploring the potential toxicity of PFOA and GenX.

Perfluorooctanoic Acid and Perfluorooctane Sulfonate in Human Milk: First Survey from Lebanon

Human milk is the primary source of nutrition for infants in their first year of life. Its potential contamination with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), a group of toxic man-made chemicals, is a health concern that may threatens infants' health. Our study aims to assess the levels of PFOA and PFOS in the breast milk of Lebanese lactating mothers and the maternal factors associated with their presence. High-performance liquid chromatography (HPLC) coupled with a Micromass Quattro micro API triple quadrupole mass spectrometer was used to detect the level of contamination in 57 collected human milk samples. PFOA and PFOS were present in 82.5% and 85.7% of the samples, respectively, while PFOA levels ranged between 120 and 247 pg/mL with a median of 147 pg/mL, and those of PFOS ranged between 12 and 86 pg/mL with a median of 27.5 pg/mL. The median contamination for PFOA exceeded the threshold set by the European Food Safety Authority (EFSA) (60 pg/mL); however, that of PFOS was below the threshold (73 pg/mL). The consumption of bread, pasta, meat, and chicken more than twice per week and that of white tubers and roots at least once per week was significantly associated with higher levels of PFOA (p < 0.05). No significant association was found between maternal age, BMI, parity, level of education, place of residence, source of water used, and smoking with the levels of PFOA and PFOS in the human milk. Additionally, the consumption of cereals at least twice per week was significantly associated with higher levels of PFOS. These findings call for actions to improve the local environmental and agricultural practices, and the regulations and standards for inspecting imported food. It is important to highlight that the benefits of breastfeeding outweigh the reported contamination with PFOS and PFOA in our study.

Childhood exposure to per- and polyfluoroalkyl substances and neurodevelopment in the CHARGE case-control study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are shown to have neurotoxic effects on animals, but epidemiological evidence for associations between childhood PFAS exposure and neurodevelopment is inconclusive. We examined if childhood PFAS concentrations are associated with a diagnosis of autism spectrum disorder (ASD), developmental delay (DD), and other early concerns (OEC) in development.

METHODS

We included 551 children 2-5 years old from the CHildhood Autism Risks from Genetics and Environment (CHARGE) case-control study. Children were clinically diagnosed and classified as having ASD, DD, OEC, and typical development (TD). Fourteen PFAS were quantified in child serum samples collected when diagnostic assessments were performed. We used multinomial logistic regression models to investigate the cross-sectional associations of individual PFAS concentrations with neurodevelopmental outcomes and weighted quantile sum (WQS) regression models with repeated holdout validation to investigate the associations with PFAS mixtures.

RESULTS

Childhood perfluorooctanoic acid (PFOA) was associated with increased odds of ASD (odds ratio [OR] per ln ng/mL increase: 1.99, 95% confidence interval [CI]: 1.20, 3.29) and DD (OR: 2.16, 95% CI: 1.21, 3.84) versus TD. Perfluoroheptanoic acid (PFHpA) was associated with increased odds of ASD (OR: 1.61, 95% CI: 1.21, 2.13). However, perfluroundecanoic acid (PFUnDA) was associated with decreased odds of ASD (OR: 0.43, 95% CI: 0.26, 0.69). From mixture analyses, the WQS index was associated with increased odds of ASD (average OR: 1.57, 5th and 95th percentile: 1.16, 2.13). Child's sex and homeownership modified associations of perfluorodecanoic acid (PFDA) with DD and ASD, respectively.

CONCLUSIONS

In this case-control study, childhood PFOA, PFHpA, and a PFAS mixture was associated with increased odds of ASD, while PFUnDA was associated with decreased odds of ASD. Because we used concurrent measurements of PFAS, our results do not imply causal relationships and thus need to be interpreted with caution.

Occurrence of Perfluoroalkyl and Polyfluoroalkyl Substances in Ice Cream, Instant Noodles, and Bubble Tea

Food consumption is a significant exposure route to perfluoroalkyl and polyfluoroalkyl substances (PFAS). The concentrations of 27 PFAS in fast food were determined by ultrahigh-performance liquid chromatography-high resolution mass spectrometry. In ice cream, instant noodles, and bubble tea, some PFAS were detected, among which perfluorooctanoic acid, perfluoro-n-butanoic acid, and 6:2 polyfluoroalkyl phosphate monoester showed relatively high concentrations. PFAS migrating from bubble tea cups to the food simulant of 50% ethanol aqueous solution showed a difference compared with those migrating into bubble tea matrices. The migration of 27 PFAS to bubble tea samples indicated that long storage time increased PFAS levels (up to 4.8 times) and so did high storage temperature (up to 7.3 times). The hazard ratio, defined as the ratio of the estimated daily intake and the reference dose, was calculated, and it suggests that the total PFAS exposure risk due to consumption of bubble tea should be of concern.

Longitudinal Changes in Maternal Serum Concentrations of Per- and Polyfluoroalkyl Substances from Pregnancy to Two Years Postpartum

Exposure to per- and polyfluoroalkyl substances (PFAS) during pregnancy and lactation is of increasing public health concern, but little is known about longitudinal changes in maternal PFAS concentrations from pregnancy to a few years postpartum. We quantified 11 PFAS in 251 serum samples prospectively collected from 42 Northern California mothers during the first, second, and third trimesters of pregnancy and at 3, 6, and 24 months after delivery over 2009-2017. We fit separate linear mixed models during pregnancy, early postpartum, and late postpartum to estimate percent changes of PFAS for each subperiod. Among five PFAS detected in more than 99% of samples, linear and branched perfluorooctanesulfonate (n- and Sm-PFOS), linear perfluorooctanoate (n-PFOA), and perfluorononanoate (PFNA) concentrations changed -4% to -3% per month during pregnancy. During early postpartum, perfluorohexanesulfonate (PFHxS) and n-PFOA concentrations changed -6% and -5%, respectively, per month, and Sm-PFOS and PFNA concentrations changed -1% per month. During late postpartum, n-PFOS, Sm-PFOS, and PFNA concentrations changed -1% per month. Breastfeeding duration was the primary determinant of n-PFOA and PFNA concentrations during late postpartum, showing negative associations. Our findings might be useful for reconstructing reliable prenatal or early life PFAS exposures for offspring.

Association of emerging and legacy per- and polyfluoroalkyl substances with unexplained recurrent spontaneous abortion

Emerging per- and polyfluoroalkyl substances (PFAS) alternatives are increasingly used in daily life. Although legacy PFAS have been associated with miscarriage in previous studies, it remains unknown whether exposure to emerging and legacy PFAS has any impact on the risk of unexplained recurrent spontaneous abortion (URSA). We conducted a case-control study with 464 URSA cases who had at least 2 unexplained miscarriages and 440 normal controls who had at least one normal livebirth. Concentrations of 21 PFAS in plasma, including three emerging PFAS alternatives, eight linear and branched PFAS isomers, four short-chain PFAS, and six legacy PFAS, were measured by ultra-performance liquid chromatography coupled with a tandem mass spectrometry (UPLC-MS/MS). Multiple logistic regression was applied to evaluate the relationship between PFAS and URSA risk. Perfluorooctanoic acid (PFOA, median: 6.18 ng/mL), perfluorooctane sulfonate (PFOS, median: 4.10 ng/mL), and 6:2 chlorinated perfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA, median: 2.27 ng/mL) were the predominant PFAS in the controls. Exposure to 6:2 Cl-PFESA [adjusted odds ratio (aOR) = 1.18 (95% CI: 1.00, 1.39)] and hexafluoropropylene oxide dimer acid (HFPO-DA) [aOR = 1.35 (95% CI: 1.15, 1.59)] were significantly associated with increased risks of URSA. Women with older age (>30 years old) had a stronger association between PFAS and URSA. Our results suggest that emerging PFAS alternatives may be an important risk factor for URSA.

Polychlorinated dioxins and dibenzofurans (PCDD/F), polybrominated dioxins and dibenzofurans (PBDD/F), polychlorinated biphenyls (PCB), polybrominated diphenyl ethers (PBDE), and per- and polyfluoroalkyl substances (PFAS) in German breast milk samples (LUPE 8)

Most organic pollutants (POP) are persistent in the environment, accumulate in fatty tissues, and so a transfer through the food chain is probably, thereby causing various health effects. We quantified PCDD/F, PBDD/F, PCB, PBDE, perfluorinated substances, and ADONA in breast milk samples collected in two German federal states and breast milk and blood samples from subjects additionally exposed to PFOA. The median (95th percentile) concentrations were 2.43 (6.58) pgWHO₂₀₀₅TEQ/g l.w. for PCDD/F, 2.45 (4.82) pgWHO₂₀₀₅TEQ/g l.w. for dioxin-like PCB (dl-PCB), and 0.62 (2.69) pgWHO₂₀₀₅TEQ/g l.w. for PBDD/F. The relative contributions of the median values of PCDD/F, dl-PCB, and PBDD/F to the total-TEQ were approximately 41%, 42%, and 11%, respectively. Nondioxin-like PCB (ndl-PCB) concentrations were clearly dominated by the higher chlorinated PCB congeners, with medians of 23.2 ng/g l.w. for PCB 153, 13.9 ng/g l.w. for PCB 138, and 13.0 ng/g l.w. for PCB 180. The sum of the 3 congeners (PCB 138, 153, and 180) were multiplied with 1.64 (total PCB) and showed a median of 82.16 ng/g l.w. and a 95th percentile of 173.3 ng/g l.w. Only PFOA and PFOS could be quantified in 29% and 17% of in total 180 samples with 95th percentiles of 53 ng/l and 33 ng/l, respectively. Milk samples (n = 13) from subjects living on PFOA contaminated sites showed higher levels between 33 and 854 ng/l PFOA (mean: 199 ng/l), whilst PFOS could be quantified only in three samples. The sum of 17 PBDE congeners showed medians (95th percentile) of 1737 pg/g l.w. (22,806 pg/g l.w.), with the highest medians of 422 pg/g l.w. for BDE 209 and 378 pg/g l.w. for BDE 153. Overall, our study confirms the declining contamination level in breast milk during the last decade, but points out the need to further reduce the environmental contamination with persistent substances and subsequently the exposure in childhood.

Demographic, life-style and physiological determinants of serum per- and polyfluoroalkyl substance (PFAS) concentrations in a national cross-sectional survey of Swedish adolescents

PER: and polyfluoroalkyl substances (PFAS) may affect adolescent health, yet factors related to PFAS concentrations in serum are poorly understood. We studied demographic, life-style and physiological determinants of serum PFAS concentrations in Swedish adolescents from a nation-wide survey, Riksmaten Adolescents 2016-17 (RMA, age 10-21 years, n = 1098). Serum samples were analyzed for 42 PFAS, using liquid chromatography-tandem mass spectrometry. The cumulative probability model was used to estimate associations between serum PFAS and determinants, using ordinal logistic regression. Legacy linear (lin-) perfluorooctanoic acid (PFOA), perfluorononaoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), lin-perfluorohexanesulfonic acid (PFHxS) and lin-/branched (br-) perfluorooctanesulfonic acid (PFOS) were quantifiable in ≥70% of the samples. The emerging PFAS 9-chlorohexanedecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS) was quantified in 5.4% of the samples, suggesting initiation of long-range transport far from production sites. Median concentrations of all legacy PFAS were <2 ng/g serum, with a few participants having very high (>100 ng/g serum) lin-PFHxS and lin-/br-PFOS concentrations due to previous high exposure from PFAS-contaminated drinking water. Legacy PFAS exposure was strongly associated with birth country of the participants and their mothers. 2-fold higher estimated adjusted mean (EAM) concentrations were seen among high income country participants with mothers from high income countries than among low/lower-middle income country participants with mothers from the same category. Menstruating females had lower br-PFOS EAM concentrations than those who were not. Iron status (plasma ferritin) among females may be a marker of intensity of menstrual bleeding, but it was not significantly associated with legacy PFAS concentrations among females. Further studies are needed to determine how physiological changes occurring around menstruation affect the toxicokinetics of PFAS in females. In conclusion, PFAS are pollutants of the industrialized world and some of the identified determinants may be overlooked confounders/effect modifiers that should be included in future PFAS/health studies among adolescents.

Quantitation of linear and branched perfluoroalkane sulfonic acids (PFSAs) in women and infants during pregnancy and lactation

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are associated with negative health effects, and exposure during fetal life and infancy are of concern. A subgroup of PFAS, linear and branched perfluoroalkane sulfonic acids (PFSA), have significant differences in biochemical reactions, bioaccumulation and potential toxic exposure effects, and data on transfer of PFSA isomers from mother to baby through placenta or in breastmilk are scarce.

OBJECTIVES

The objective was to investigate differences in branched and linear PFSA isomers in never-pregnant, pregnant and postpartum women and infants.

METHODS

Serum concentrations of branched and linear, perfluorohexane sulfonate (PFHxS), perfluoroheptane sulfonate (PFHpS) and perfluorooctane sulfonate (PFOS) were measured in never-pregnant women (n = 158), pregnant and postpartum women (n = 114) and their infants (n = 94) at age six months.

RESULTS

There was a linear relation between maternal PFSA concentrations in pregnancy week 18 and the infant at age six months. The PFSA concentrations in maternal and infant serum varied with a factor up to 20. The maternal branched/ linear PFHxS ratio increased in the latter part of pregnancy (+45%) and remained high postpartum, and was substantially lower in the infants. Branched/linear PFHpS ratio increased during pregnancy and was highest in the infants, while the branched/linear PFOS ratio decreased in the mothers and was high in the infants.

DISCUSSION

The linear relations between PFSA concentrations in infants aged six months and mothers in pregnancy week 18 confirm that pregnancy and lactation are major excretion routes for PFSA, but accumulate in the infant. The observed great variability in PFSA burden among mothers and infants, as well as the reduced maternal transfer of branched PFHxS isoforms and increased transfer of branched PFOS isoforms compared to the respective linear isoforms to the infant, might impact adverse health effects associated with PFSA exposure, but this should be confirmed in future studies.

The Nrf2a pathway impacts zebrafish offspring development with maternal preconception exposure to perfluorobutanesulfonic acid

Since the voluntary phaseout of perfluorooctanesulfonic acid (PFOS), smaller congeners, such as perfluorobutanesulfonic acid (PFBS) have served as industrial replacements and been detected in contaminated aquifers. This study sought to examine the effects of a maternal preconception PFBS exposure on the development of eggs and healthy offspring. Adult female zebrafish received a one-week waterborne exposure of 0.08, 0.14, and 0.25 mg/L PFBS. After which, females were bred with non-exposed males and embryos collected over 5 successful breeding events. PFBS concentrations were detected in levels ranging from 99 to 253 pg/embryo in the first collection but were below the limit of quantitation by fourth and fifth clutches. Therefore, data were subsequently binned into early collection embryos in which PFBS was detected and late collections, in which PFBS was below quantitation. In the early collection, embryo 24 h survival was significantly reduced. In the late collection, embryo development was impacted with unique patterns emerging between Nrf2a wildtype and mutant larvae. Additionally, the impact of nutrient loading into the embryos was assessed through measurement of fatty acid profiles, total cholesterol, and triglyceride content. There were no clear dose-dependent effects, but again unique patterns were observed between the genotypes. Preconception PFBS exposures were found to alter egg and embryo development, which is mediated by direct toxicant loading in the eggs, nutrient loading into eggs, and the function of Nrf2a. These findings provide insight into the reproductive and developmental effects of PFBS and identify maternal preconception as a novel critical window of exposure.

Exposure to legacy and novel perfluoroalkyl substance disturbs the metabolic homeostasis in pregnant women and fetuses: A metabolome-wide association study

BACKGROUND

Perfluoroalkyl substances (PFASs) exist extensively and several of these have been verified to be toxic. Prenatal exposure to PFASs has attracted much attention. Metabolome-wide association analyses can be used to explore the toxicity mechanisms of PFASs by identifying associated biomarkers.

OBJECTIVES

To evaluate associations between the metabolites in maternal and cord serum and internal exposure to several common PFASs.

METHODS

Paired maternal and cord serum samples were collected from 84 pregnant women who gave birth between 2015 and 2016. Seven legacy and two novel PFASs were measured. A nontarget metabolomic method and an iterative metabolite annotation based on metabolic pathways were applied to characterize the metabolic profiles. Linear regression adjusted with the false discovery rate and covariates was used to indicate the associations.

RESULTS

A total of 279 features in maternal serum and 338 features in cord serum were identified as metabolites associated with PFAS exposure. Perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS) were two PFASs associated with more metabolites, while the two novel chlorinated polyfluorinated ether sulfonic acids (Cl-PFESAs) showed less relevance to the metabolome. With pathway enrichment analysis, we found that three fatty acid metabolisms and retinol metabolism were correlated with PFAS exposure in maternal blood, and that sterol metabolism showed the correlation in both maternal serum and cord serum.

CONCLUSIONS

We identified metabolites and pathways in pregnant women and fetuses associated with the exposure to several PFAS, indicating a promising application for metabolome-wide association studies. Additional research is needed to confirm causation.

The role of maternal high fat diet on mouse pup metabolic endpoints following perinatal PFAS and PFAS mixture exposure

Per- and polyfluoroalkyl substances (PFAS) are a family of chemicals that are ubiquitous in the environment. Some of these chemicals, such as perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonate (PFHxS) and perfluorooctanoic acid (PFOA), are found in human sera and have been shown to cause liver steatosis and reduce postnatal survival and growth in rodents. The purpose of this work is to evaluate the impact of diet and PFAS exposure to mouse dam (mus musculus) on the risk to pup liver and metabolism endpoints later in life, as well as evaluate PFAS partitioning to pups. Timed-pregnant dams were fed a standard chow diet or 60 % kcal high fat diet (HFD). Dams were administered either vehicle, 1 mg/kg PFOA, 1 mg/kg PFOS, 1 mg/kg PFHxS, or a PFAS mixture (1 mg/kg of each PFOA, PFOS, and PFHxS) daily via oral gavage from gestation day 1 until postnatal day (PND) 20. At PND 21, livers of dams and 2 pups of each sex were evaluated for lipid changes while remaining pups were weaned to the same diet as the dam for an additional 10 weeks. Dam and pup serum at PND 21 and PND 90 were also evaluated for PFAS concentration, alanine aminotransferase (ALT), leptin and adiponectin, and glycosylated hemoglobin A1c. Perinatal exposure to a HFD, as expected, increased pup body weight, maternal liver weight, pup liver triglycerides, pup serum ALT, and pup serum leptin. PFOA and the PFAS mixture increased liver weights, and. treatment with all three compounds increased liver triglycerides. The maternal HFD increased dam and pup serum PFAS levels, however, was protective against PFOA-induced increase in serum ALT and observed increases in liver triglycerides. The PFAS mixture had very distinct effects when compared to single compound treatment, suggesting some cumulative effects, particularly when evaluating PFAS transfer from dam to pup. This data highlights the importance of diet and mixtures when evaluating liver effect of PFAS and PFAS partitioning.

Development of a Gestational and Lactational Physiologically Based Pharmacokinetic (PBPK) Model for Perfluorooctane Sulfonate (PFOS) in Rats and Humans and Its Implications in the Derivation of Health-Based Toxicity Values

BACKGROUND

There is a great concern on potential adverse effects of exposure to perfluorooctane sulfonate (PFOS) in sensitive subpopulations, such as pregnant women, fetuses, and neonates, due to its reported transplacental and lactational transfer and reproductive and developmental toxicities in animals and humans.

OBJECTIVES

This study aimed to develop a gestational and lactational physiologically based pharmacokinetic (PBPK) model in rats and humans for PFOS to aid risk assessment in sensitive human subpopulations.

METHODS

Based upon existing PBPK models for PFOS, the present model addressed a data gap of including a physiologically based description of basolateral and apical membrane transporter-mediated renal reabsorption and excretion in kidneys during gestation and lactation. The model was calibrated with published rat toxicokinetic and human biomonitoring data and was independently evaluated with separate data. Monte Carlo simulation was used to address the interindividual variability.

RESULTS

Model simulations were generally within 2-fold of observed PFOS concentrations in maternal/fetal/neonatal plasma and liver in rats and humans. Estimated fifth percentile human equivalent doses (HEDs) based on selected critical toxicity studies in rats following U.S. Environmental Protection Agency (EPA) guidelines ranged from 0.08 to 0.91 μ g / kg  per day . These values are lower than the HEDs estimated in U.S. EPA guidance (0.51 - 1.6 μ g / kg  per day ) using an empirical toxicokinetic model in adults.

CONCLUSIONS

The results support the importance of renal reabsorption/excretion during pregnancy and lactation in PFOS dosimetry and suggest that the derivation of health-based toxicity values based on developmental toxicity studies should consider gestational/lactational dosimetry estimated from a life stage-appropriate PBPK model. This study provides a quantitative tool to aid risk reevaluation of PFOS, especially in sensitive human subpopulations, and it provides a basis for extrapolating to other per- and polyfluoroalkyl substances (PFAS). All model codes and detailed tutorials are provided in the Supplemental Materials to allow readers to reproduce our results and to use this model. https://doi.org/10.1289/EHP7671.

Per- and Polyfluoroalkyl Substance Toxicity and Human Health Review: Current State of Knowledge and Strategies for Informing Future Research

Reports of environmental and human health impacts of per- and polyfluoroalkyl substances (PFAS) have greatly increased in the peer-reviewed literature. The goals of the present review are to assess the state of the science regarding toxicological effects of PFAS and to develop strategies for advancing knowledge on the health effects of this large family of chemicals. Currently, much of the toxicity data available for PFAS are for a handful of chemicals, primarily legacy PFAS such as perfluorooctanoic acid and perfluorooctane sulfonate. Epidemiological studies have revealed associations between exposure to specific PFAS and a variety of health effects, including altered immune and thyroid function, liver disease, lipid and insulin dysregulation, kidney disease, adverse reproductive and developmental outcomes, and cancer. Concordance with experimental animal data exists for many of these effects. However, information on modes of action and adverse outcome pathways must be expanded, and profound differences in PFAS toxicokinetic properties must be considered in understanding differences in responses between the sexes and among species and life stages. With many health effects noted for a relatively few example compounds and hundreds of other PFAS in commerce lacking toxicity data, more contemporary and high-throughput approaches such as read-across, molecular dynamics, and protein modeling are proposed to accelerate the development of toxicity information on emerging and legacy PFAS, individually and as mixtures. In addition, an appropriate degree of precaution, given what is already known from the PFAS examples noted, may be needed to protect human health. Environ Toxicol Chem 2021;40:606-630. © 2020 SETAC.

Endocrine Disruptor Potential of Short- and Long-Chain Perfluoroalkyl Substances (PFASs)-A Synthesis of Current Knowledge with Proposal of Molecular Mechanism

Endocrine disruptors are a group of chemical compounds that, even in low concentrations, cause a hormonal imbalance in the body, contributing to the development of various harmful health disorders. Many industry compounds, due to their important commercial value and numerous applications, are produced on a global scale, while the mechanism of their endocrine action has not been fully understood. In recent years, per- and polyfluoroalkyl substances (PFASs) have gained the interest of major international health organizations, and thus more and more studies have been aimed to explain the toxicity of these compounds. PFASs were firstly synthesized in the 1950s and broadly used in the industry in the production of firefighting agents, cosmetics and herbicides. The numerous industrial applications of PFASs, combined with the exceptionally long half-life of these substances in the human body and extreme environmental persistence, result in a common and chronic exposure of the general population to their action. Available data have suggested that human exposure to PFASs can occur during different stages of development and may cause short- or/and long-term health effects. This paper synthetizes the current literature reports on the presence, bioaccumulation and, particularly, endocrine toxicity of selected long- and short-chain PFASs, with a special emphasis on the mechanisms underlying their endocrine actions.

Exposure characteristics for congeners, isomers, and enantiomers of perfluoroalkyl substances in mothers and infants

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment, making it inevitable for humans to be exposed to these pollutants. The exposure begins while in utero and continues in infancy, during the potentially most sensitive early stages of life. This review summarizes the current knowledge on pre- and neo-natal exposures based on more than 200 articles published from 2000 to date. All relevant biological matrices used in the cited studies were included, such as maternal blood, umbilical cord blood, breast milk, placenta, amniotic fluid, fetal organs, newborns' dried blood spots, and infant serum. We show that such exposures are geographically global with significant discrepancies among countries and continents, and that while the levels of major legacy PFASs (PFOS and PFOA) have declined since 2000, those of others may have not. We also show that levels of PFOS and PFOA exceed those of some major environmental toxins, such as p,p'-DDE, BDE-47, PCB-153, PBB-153, and OH-PBDEs in maternal blood. Given that the behavior and potential effects have an origin in molecular structure, biomonitoring and research at the levels of isomers and enantiomers are critically important. Through critical analysis of these works, we summarize the major achievements, consensus, and the deficiencies of existing research. To our knowledge, this is the first review on the overall internal exposure status of mothers and infants to PFASs during pregnancy and lactation.

Emerging per- and polyfluoroalkyl substances (PFAS) in human milk from Sweden and China

Twenty per- and polyfluoroalkyl substances (PFAS) were determined in human milk from residents of three Chinese cities (Shanghai, Jiaxing, and Shaoxing; [n = 10 individuals per city]), sampled between 2010 and 2016. These data were compared to a combination of new and previously reported PFAS concentrations in human milk from Stockholm, Sweden, collected in 2016 (n = 10 individuals). Across the three Chinese cities, perfluorooctanoate (PFOA; sum isomers), 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS; also known as 6:2 Cl-PFESA or by its trade name "F53-B"), and perfluorooctane sulfonate (PFOS; sum isomers) occurred at the highest concentrations among all PFAS (up to 411, 976, and 321 pg mL^-1, respectively), while in Stockholm, PFOA and PFOS were dominant (up to 89 and 72 pg mL^-1, respectively). 3H-Perfluoro-3-[(3-methoxy-propoxy)propanoic acid] (ADONA) was intermittently detected but at concentrations below the method quantification limit (i.e. <10 pg mL^-1) in Chinese samples, and was non-detectable in Swedish milk. The extremely high concentrations of F53-B in Chinese milk suggest that human exposure assessments focused only on legacy substances may severely underestimate overall PFAS exposure in breastfeeding infants.

Perfluorobutane sulfonate exposure disrupted human placental cytotrophoblast cell proliferation and invasion involving in dysregulating preeclampsia related genes

We reported that maternal PFBS, an emerging pollutant, exposure is positively associated with preeclampsia which can result from aberrant trophoblasts invasion and subsequent placental ischemia. In this study, we investigated the effects of PFBS on trophoblasts proliferation/invasion and signaling pathways. We exposed a human trophoblast line, HTR8/SVneo, to PFBS. Cell viability, proliferation, and cell cycle were evaluated by the MTS assay, Ki-67 staining, and flow cytometry, respectively. We assessed cell migration and invasion with live-cell imaging-based migration assay and matrigel invasion assay, respectively. Signaling pathways were examined by Western blot, RNA-seq, and qPCR. PFBS exposure interrupted cell proliferation and invasion in a dose-dependent manner. PFBS (100 μM) did not cause cell death but instead significant cell proliferation without cell cycle disruption. PFBS (10 and 100 μM) decreased cell migration and invasion, while PFBS (0.1 μM) significantly increased cell invasion but not migration. Further, RNA-seq analysis identified dysregulated HIF-1α target genes that are relevant to cell proliferation/invasion and preeclampsia, while Western Blot data showed the activation of HIF-1α, but not Notch, ERK1/2, (PI3K)AKT, and P38 pathways. PBFS exposure altered trophoblast cell proliferation/invasion which might be mediated by preeclampsia-related genes, suggesting a possible association between prenatal PFBS exposure and adverse placentation.

Distribution and effects of branched versus linear isomers of PFOA, PFOS, and PFHxS: A review of recent literature

Perfluorinated alkyl substances (PFAS) have come to attention recently due to their widespread presence in the environment, recalcitrance, and potential negative health associations. Because of the long-term production of PFAS using ECF, which created branched isomers as byproducts in addition to the intended linear product, branched isomers of PFAS account for a significant portion of PFAS load in the environment. The distribution of isomers is not consistent in the environment, however. Geographic location appears to be a major factor in determining the isomer makeup of PFAS in surface and groundwater as well as in humans and animals. This is largely to differences in production methods; a region that produced PFAS via ECF for many years would have a higher ratio of branched isomers than one that produces PFAS using telomerization. In addition, the different structures of branched PFAS isomers as compared to linear PFAS appear to affect transport in the environment. Research suggests that linear PFAS sorb preferentially to soil and sediments, whereas branched isomers are more likely to remain in water. The higher polarity of the branched structure explains this difference. Studies in humans and animals show that most animals preferentially accumulate the linear PFOS isomer, but humans appear to preferentially accumulate the branched isomers as they are often found in human serum at percentages higher than that of ECF product. In addition, some studies have indicated that linear and branched PFAS isomers have some unique negative health associations. Very few studies, however, account for linear and branched PFAS separately.

Mechanochemical degradation of perfluorohexane sulfonate: Synergistic effect of ferrate(VI) and zero-valent iron

Perfluorohexane sulfonate (PFHxS) has been newly recommended to be added into the Stockholm Convention on persistent organic pollutants (POPs). As one of the major perfluoroalkyl pollutants, its long half-time in human serum and neurotoxicity are cause for significant concern. Although mechanochemical degradation has been evaluated as a promising ecofriendly technology to treat pollutants, the extraordinary stability of poly- and perfluoroalkyl substances (PFASs) raises harsh requirements for co-milling reagents. In the present study, zero-valent iron (ZVI) and ferrate(VI) were for the first time used as the co-milling reagents to degrade PFHxS. When ZVI and ferrate(VI) were used alone, both the degradation and defluorination efficiencies were low. However, after milling at the optimum ratio (ferrate(VI):ZVI = 1:2) for 4 h, the synergistic effect of ZVI and ferrate(VI) resulted in almost complete degradation (100%) and defluorination (95%). Two points can account for this excellent performance: (1) the mechanochemical energy input in the system initiates and prominently promotes related reactions; and (2) the active species generated from the reactions among ZVI, ferrate(VI) and other high-valent iron species will accelerate the process of electron transfer. The sulfonate group comprises the favorable attack sites, as corroborated by both the identified intermediates and quantum chemical calculations. The homolysis of the C-S bond is not only the triggering step, but also the rate-limiting step. In summary, the present work confirms the feasibility and underlying mechanism of the ZVI-ferrate(VI) co-milling system to defluorinate PFHxS, which might be a promising technology to treat PFASs in solid wastes.

Cytotoxicity of perfluorodecanoic acid on mouse primary nephrocytes through oxidative stress: Combined analysis at cellular and molecular levels

Long-chain perfluoroalkyl acids (PFAAs) such as perfluorodecanoic acid (PFDA) are toxic, persistent organic pollutants. This study investigated the harmful effect of PFDA on mouse primary nephrocytes and its mechanism at cellular and molecular levels. Cellular results showed that PFDA exhibited nephrotoxicity with decreased cell viability and increased apoptosis. The increase of intracellular reactive oxygen species (ROS) content and the decrease of intracellular superoxide dismutase (SOD) activity were significant (p < 0.01) when PFDA concentration exceeded 10 μM. Additionally, the molecular results indicated that PFDA bind with Val-A98 in the surface of Cu/Zn-SOD by a 3.11 Å hydrogen bond driven by Van der Waals' force and hydrogen bonding force, which triggered the structural changes and decreased activity of Cu/Zn-SOD. Altogether, the intracellular oxidative stress is the main driver of nephrocyte apoptosis; and the interaction of PFDA and Cu/Zn-SOD exacerbated the oxidative stress in nephrocytes, which is also a nonnegligible reason of cytotoxicity induced by PDFA. This study represented a meaningful method to explore the toxic effect and mechanism of xenobiotics at cellular and molecular levels. The findings have implications for revealing the clearance of long-chain PFAAs in vivo.

Exposure sources of perfluoroalkyl acids and influence of age and gender on concentrations of chlorinated polyfluorinated ether sulfonates in human serum from China

The presence of perfluoroalkyl acids (PFAAs) and chlorinated polyfluoroalkyl ether sulfonates (Cl-PFAESs) in humans has attracted great attention in recent decades. However, information on their exposure sources and the influence of age and gender on Cl-PFAES concentrations in human serum is still limited. In this study, eighty-five serum samples were collected from the general population in Anji, China, and analyzed for perfluoroalkyl carboxylates (PFCAs), perfluoroalkyl sulfonates (PFSAs), and Cl-PFAESs. Perfluorooctane sulfonate (PFOS; mean, 5.9 ng/mL) and perfluorooctanoate (PFOA; 3.3 ng/mL) were the predominant PFAAs in human serum. The serum concentrations of C₈-C₁₂ PFCAs, perfluorohexane sulfonate, and PFOS were significantly (r_s = 0.40-0.98, p < 0.01) correlated with one another. In human serum, the mean percentages of branched isomers for PFOA, perfluorohexane sulfonate, and PFOS were 97.3%, 92.6%, and 66%, respectively. These results suggest that the major source of PFCAs and PFSAs in human serum was direct exposure. The mean 6:2Cl-PFAES (6.0 ng/mL) serum concentration was higher than PFOA (p < 0.01). The mean 6:2Cl-PFAES concentrations in male and female serum were 6.5 ng/mL and 5.6 ng/mL, respectively. A significant increase in 6:2Cl-PFAES concentrations with age was found in males (r_s = 0.50, p = 0.001). The 6:2Cl-PFAES concentration was positively correlated with C₈-C₁₂ PFCAs and PFOS in human serum (r_s = 0.44-0.91, p < 0.01), indicating that they may have common exposure sources. Overall, this study first investigated the roles of age and gender on human serum concentrations of Cl-PFAESs and provided baseline information on the occurrence of Cl-PFAESs in the general Chinese population.

Temporal trends of suspect- and target-per/polyfluoroalkyl substances (PFAS), extractable organic fluorine (EOF) and total fluorine (TF) in pooled serum from first-time mothers in Uppsala, Sweden, 1996-2017

A combined method for quantitative analysis, along with suspect and non-target screening of per- and polyfluoroalkyl substances (PFAS) was developed using ultra-high pressure liquid chromatography-ultra-high resolution (Orbitrap) mass spectrometry. The method was applied together with measurements of total- and extractable organofluorine (TF and EOF, respectively), to pooled serum samples from 1996-2017 from first-time mothers living in the county of Uppsala, Sweden, some of which (i.e. 148 of 472 women sampled 1996-2012) were exposed to drinking water contaminated with perfluorohexane sulfonate (PFHxS) and other PFAS until mid-2012. Declining trends were observed for all target PFAS as well as TF, with homologue-dependent differences in year of onset of decline. Only 33% of samples displayed detectable EOF, and amongst these samples the percentage of EOF explained by target PFAS declined significantly (-3.5% per year) over the entire study period. This finding corroborates prior observations in Germany after the year 2000, and may reflect increasing exposure to novel PFAS which have not yet been identified. Suspect screening revealed the presence of perfluoro-4-ethylcyclohexanesulfonate (PFECHS), which displayed declining trends since the year 2000. Non-target time trend screening revealed 3 unidentified features with time trends matching PFHxS. These features require further investigation, but may represent contaminants which co-occurred with PFHxS in the contaminated drinking water.

Determinants of serum concentrations of perfluoroalkyl acids (PFAAs) in school children and the contribution of low-level PFAA-contaminated drinking water

Little is known about the demographic/life-style/physiological determinants explaining the variation of serum perfluoroalkyl acid (PFAA) concentrations in children. We identified significant determinants in children and investigated the influence of low-level PFAA-contaminated drinking water (DW) (<10 ng L-1 of single PFAAs) on serum concentrations. Four perfluorosulfonic acids (PFSAs) and 11 perfluorocarboxylic acids (PFCAs) were analyzed in serum from 5th grade children from 11 Swedish schools (N = 200; average age: 12 years) using liquid chromatography-tandem-mass-spectrometry. Data on demography and life-style/physiological factors were obtained by questionnaires. PFAA concentrations in raw and drinking water (DW) were obtained from the water works supplying DW to the schools. In multiple regression analyses school was the determinant contributing most to the variation in PFAA concentrations, with the lowest contribution for PFHpA (10%) and the highest for PFHxS (81%). Girls had lower adjusted mean concentrations of PFHxS, PFOS, PFNA and PFDA than boys, but a higher concentration of PFHxA. Girls reporting onset of menstruation had lower PFHxS and PFOA concentrations than other girls, suggesting menstrual bleeding elimination. Children born by mothers from less industrialized countries had lower mean concentrations of both PFSAs and PFCAs than children with mothers from highly industrialized countries, suggesting differences in early-life exposure. Life-style factors associated with paternal education levels appeared to influence PFAA concentrations differently than maternal education level. Already at an average DW PFHxS concentration of 2 ng L-1, children had a significantly higher adjusted mean serum PFHxS concentration than at an average DW concentration of <1.6 ng PFHxS L-1. Similar results were observed for PFOS and PFOA. The DW variable explained 16% (PFOA) to 78% (PFHxS) of the variation in serum PFAA concentrations, suggesting that low-level-contaminated DW is a significant source of exposure for children in Sweden. Although some of the associations, especially those with menstruation and maternal birth country, should be interpreted with extra caution due to the small size of the study, the results contribute to future work on identifying populations of children at risk of elevated PFAA exposures.

Transplacental Transfer of Per- and Polyfluoroalkyl Substances Identified in Paired Maternal and Cord Sera Using Suspect and Nontarget Screening

Novel per- and polyfluoroalkyl substances (PFASs) in various environmental media have attracted increasing attention; however, the information regarding PFASs exposure in pregnant women and fetuses is insufficient. In this study, we built and applied suspect and nontarget screening strategies based on the mass difference of the CF₂, CF₂O, and CH₂CF₂ units to select potential novel PFASs from 117 paired maternal and cord sera. In total, 10 legacy PFASs and 19 novel PFASs from 10 classes were identified to be above confidence levels 3, among which 14 were not previously reported in human serum. Novel PFASs accounted for a considerable percentage of total PFASs in pregnant women and can be transferred to fetuses at non-negligible concentrations (i.e., 27.9% and 30.3% of total PFAS intensities in maternal and cord sera, respectively). The transplacental transfer efficiency (TTE) of PFASs showed a U-shape trend in the series of perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonic acids, and unsaturated perfluorinated alcohols. The TTE of novel PFASs is suggested to be structure-dependent, based on a flexible docking experiment. This study provides comprehensive TTE information on legacy and novel PFASs for the first time, and additional toxicity studies are needed to evaluate the risk of novel PFASs further.

Developmental exposure to a mixture of perfluoroalkyl acids (PFAAs) affects the thyroid hormone system and the bursa of Fabricius in the chicken

Perfluoroalkyl acids (PFAAs) are ubiquitous environmental contaminants and eggs and nestlings of raptors and fish-eating birds often contain high levels of PFAAs. We studied developmental effects of a mixture of ten PFAAs by exposing chicken embryos to 0.5 or 3 μg/g egg of each compound in the mixture. Histological changes of the thyroid gland were noted at both doses and increased expression of mRNA coding for type III deiodinase was found at 0.5 μg/g egg. Serum concentrations of the free fraction of thyroid hormones (T3 and T4) were reduced by the PFAA mixture at 3 µg/g egg, which is in line with a decreased synthesis and increased turnover of thyroid hormones as indicated by our histological findings and the decreased mRNA expression of type III deiodinase. The relative weight of the bursa of Fabricius increased at a dose of 3 μg/g egg in females. The bursa is the site of B-cell development in birds and is crucial for the avian adaptive immune system. Analysis of plasma and liver concentrations of the mixture components showed differences depending on chain length and functional group. Our results highlight the vulnerability of the thyroid hormone and immune systems to PFAAs.

Perfluoroalkyl Acids (PFAAs) in Children's Serum and Contribution from PFAA-Contaminated Drinking Water

We investigated associations between serum perfluoroalkyl acid (PFAA) concentrations in children aged 4, 8, and 12 years (sampled in 2008-2015; n = 57, 55, and 119, respectively) and exposure via placental transfer, breastfeeding, and ingestion of PFAA-contaminated drinking water. Sampling took place in Uppsala County, Sweden, where the drinking water has been historically contaminated with perfluorobutanesulfonate (PFBS), perfluorohexanesulfonate (PFHxS), perfluorooctanesulfonate (PFOS), perfluoroheptanoate (PFHpA), and perfluorooctanoate (PFOA). PFOS showed the highest median concentrations in serum (3.8-5.3 ng g^-1 serum), followed by PFHxS (1.6-5.0 ng g^-1 serum), PFOA (2.0-2.5 ng g^-1 serum), and perfluorononanoate (PFNA) (0.59-0.69 ng g^-1 serum) in children. Including all children, serum PFOA, PFHxS, and PFOS concentrations in children increased 10, 10, and 1.3% (adjusted mean), respectively, per unit (ng g^-1 serum) of increase in the maternal serum level (at delivery), the associations being strongest for 4 year-old children. PFHxS and PFOS significantly increased 3.9 and 3.8%, respectively, per month of nursing, with the highest increase for 4 year-olds. PFOA, PFBS, PFHxS, and PFOS increased 1.2, 207, 7.4, and 0.93%, respectively, per month of cumulative drinking water exposure. Early life exposure to PFOA, PFHxS, and PFOS is an important determinant of serum concentrations in children, with the strongest influence on younger ages. Drinking water with low to moderate PFBS, PFHxS, PFOS, and PFOA contamination is an important source of exposure for children with background exposure from other sources.

Derivation of a chronic reference dose for perfluorohexane sulfonate (PFHxS) for reproductive toxicity in mice

Perfluorohexane sulfonate (PFHxS) is a six-carbon perfluoroalkyl sulfonic acid that was used as an industrial surfactant, but is now found as an environmental contaminant worldwide. In addition to its use as an industrial surfactant, it is a legacy contaminant from the use of aqueous film-forming foams. Despite its widespread occurrence in the environment and evidence of biological activity associated with PFHxS and similar perfluoroalkyl sulfonic acids in rodents, there is no oral toxicity value currently available from the IRIS Database. To derive an oral reference dose (RfD) for PFHxS, available toxicity studies were reviewed using a weight-of-evidence approach. A 42-day mouse reproductive study was chosen as the critical study for the derivation of the oral RfD. Benchmark dose modeling was utilized to derive a point of departure (POD) for a reduction in litter size. A 95% lower confidence limit on the benchmark dose (BMDL) of 13,900 ng/mL (serum PFHxS) was modeled for a reduction in litter size. An oral RfD for PFHxS of 4.0 ng/kg/d was calculated by conversion of the BMDL to a human equivalent oral dose using a human half-life adjusted dosimetric conversion factor and the application of a total uncertainty factor of 300. Additional research is needed to better characterize the toxicity associated with oral exposure to PFHxS and refine the development of toxicity values.

Efficient removal of perfluorinated compounds from water using a regenerable magnetic activated carbon

Adsorption by powder activated carbon (PAC) is recognized as an efficient method for the removal of perfluorinated compounds (PFCs) in water, while the poor separation of spent PAC makes it difficult for further regeneration, increasing the treatment cost significantly. In this study, an ultrafine magnetic activated carbon (MAC) consisting of Fe₃O₄ and PAC was prepared by ball milling to remove PFCs from water efficiently. Increasing the percentage of Fe₃O₄ and balling milling time decreased its adsorption capacity for perfluoroctane sulfonate (PFOS), whereas increased the magnetic separation property to some degree. The optimized MAC was prepared with a Fe₃O₄ to PAC mass ratio of 1:3 after ball milling for 2 h, and the adsorption equilibriums of all the four PFCs on the optimal MAC were reached within less than 2 h, with the adsorption capacities of 1.63, 0.90, 0.33 and 0.21 mmol/g for PFOS, perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS), respectively. Increasing the solution pH hindered the adsorption of PFOS significantly when the pH was less than the zero potential point (around 6) of the MAC, due to the decreased electrostatic attraction. The spent MAC could be easily separated with a magnet and regenerated by a small volume of methanol, and the regenerated MAC could be reused for more than 5 time and remain stable adsorption capacity for PFOS after 3 cycles. This study provides useful insights into the removal of PFCs by separable magnetic PAC in wastewater.

Per- and polyfluoroalkyl substances (PFAS) in Australia: Current levels and estimated population reference values for selected compounds

BACKGROUND

Increased public awareness of PFAS contamination in Australia has resulted in serum biomonitoring efforts in individuals in potentially affected communities. However, population-based reference values for assessing whether individual results exceed the typical range in the Australian general population are not currently available.

OBJECTIVE

Estimate population upper bound reference values based on updated serum PFAS concentrations in pooled samples from southeast Queensland, Australia and population variation observed in the US National Health and Nutrition Examination Survey (NHANES) datasets.

METHODS

We calculated ratios of 95th percentile to arithmetic mean (P95:AM ratios) using data from the NHANES 2013-14 and 2015-16 cycle samples for frequently detected PFASs: PFOA, linear and branched PFOS, perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluorohexanesulfonate (PFHxS). We estimated Australian age-specific means for PFAS using pooled serum samples collected in 2014-15 and 2016-17. We used the P95:AM ratios to estimate 95th percentile concentrations in the Australian population based on the results of the 2016-17 pooled samples.

RESULTS AND CONCLUSIONS

P95:AM ratios for each PFAS were similar across NHANES cycle and age group, so overall compound-specific ratios were estimated for PFOA (2.1), PFNA (2.4), PFDA (2.7), PFHxS (2.7), and linear (2.4) and summed PFOS (2.3). Australian mean PFAS concentrations continued previously reported declining trends. The estimated P95 values can be used as preliminary substitutes for more rigorous population reference values to identify samples with clearly elevated serum PFAS concentrations in Australian biomonitoring efforts. Given uncertainties and variability inherent in this evaluation, the estimated P95 values should be interpreted with caution. Mean and estimated P95 serum PFAS concentrations in Australia should continue to be monitored to document declining trends in population serum concentrations.

Characterization of age-based trends to identify chemical biomarkers of higher levels in children

BACKGROUND

Chemical biomarker concentrations are driven by complex interactions between chemical use patterns, exposure pathways, and toxicokinetic parameters such as biological half-lives. Criteria to differentiate legacy from current exposures are helpful for interpreting variation in age-based and time trends of chemical exposure and identifying chemicals to which children are highly exposed. A systematic approach is needed to study temporal trends for a wide range of chemicals in the US population.

OBJECTIVES

Using National Health and Nutrition Examination Survey (NHANES) data on measured biomarker concentrations for 141 chemicals from 1999 to 2014, we aim to 1) understand the influence of temporal determinants, in particular time trends, biological half-lives, and restriction dates on age-based trends, 2) systematically define an age-based pattern to identify chemicals with ongoing and high exposure in children, and 3) characterize how age-based trends for six Per- and Polyfluoroalkyl Substances (PFASs) are changing over time.

METHODS

We performed an integrated analysis of biological half-lives and restriction dates, compared distributions of chemical biomarker concentrations by age group, and then applied a series of regression models to evaluate the linear (β_age) and nonlinear (β_age²) relationships between age and chemical biomarker levels.

RESULTS

For restricted chemicals, a minimum persistence of 1 year in the human body is needed to observe substantial differences between the less exposed young population and historically exposed adults. We define a metric ( [Formula: see text] ) that identifies several phthalates, brominated flame retardants, pesticides, and metals such as lead and tungsten as elevated and ongoing exposures in children. While a substantial reduction in children's exposures was reflected in PFOS and PFOA, levels of PFNA and PFHxS in children were higher in 2013-2014 compared to those in 1999-2000.

CONCLUSIONS

Integrating a series of regression models with systemized stratified analyses by age group enabled us to define an age-based pattern to identify chemicals that are of higher levels in children.

Inter-individual, inter-city, and temporal trends of per- and polyfluoroalkyl substances in human milk from Swedish mothers between 1972 and 2016

Inter-individual, inter-city, and temporal trends of 19 per- and polyfluoroalkyl substances (PFASs) were investigated in human milk collected in Stockholm (1972-2016) and Gothenburg (2007-2015), Sweden. The concentrations of perfluorohexane sulfonate (PFHxS), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA), and perfluorotridecanoate (PFTrDA) in human milk from Stockholm increased significantly over the entire monitoring periods, whereas branched (Br) and linear (L) isomers of perfluorooctane sulfonamide (FOSA) decreased. In human milk from Gothenburg, significant downward trends were detected for perfluorododecanoate (PFDoDA), PFHxS and Br-perfluorooctane sulfonate (Br-PFOS) over the last decade. This declining trend was also observed for perfluorohexanoate (PFHxA), PFHxS, perfluorooctanoate (PFOA) and Br-PFOS in Stockholm over the same time period. No significant differences were observed in concentrations or relative PFAS profiles between Stockholm and Gothenburg. However, a comparison of the PFAS profile in Stockholm milk revealed distinct profiles for the time periods 1972-1996, 2000-2012, and 2013-2016, reflecting a shift in exposure over time. The lower bound estimated daily intake (EDI) for ∑PFAS concentrations in infants ranged from 7.1-40 ng per kg body weight per day (ng/kg bw/d) in Stockholm and from 5.2-25 ng/kg bw/d in Gothenburg over the studied time period, consistent with other European countries. Overall these data indicate that exposure to some legacy PFASs via breastmilk is declining, presumably as a result of regulation and phase-out initiatives. However, increasing concentrations for other PFASs and a shift in the overall PFAS profile in recent years may pose an ongoing health risk to infants.