Physico-chemical properties and gestational diabetes predict transplacental transfer and partitioning of perfluoroalkyl substances

Exposure to per- and polyfluoroalkyl substances and alterations in plasma microRNA profiles in children

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals that persist in the environment and can accumulate in humans, leading to adverse health effects. MicroRNAs (miRNAs) are emerging biomarkers that can advance the understanding of the mechanisms of PFAS effects on human health. However, little is known about the associations between PFAS exposures and miRNA alterations in humans.

OBJECTIVE

To investigate associations between PFAS concentrations and miRNA levels in children.

METHODS

Data from two distinct cohorts were utilized: 176 participants (average age 16.6 years; 75.6% female) from the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) cohort in the United States, and 64 participants (average age 6.5 years, 39.1% female) from the Rhea study, a mother-child cohort in Greece. PFAS concentrations and miRNA levels were assessed in plasma samples from both studies. Associations between individual PFAS and plasma miRNA levels were examined after adjusting for covariates. Additionally, the cumulative effects of PFAS mixtures were evaluated using an exposure burden score. Ingenuity Pathways Analysis was employed to identify potential disease functions of PFAS-associated miRNAs.

RESULTS

Plasma PFAS concentrations were associated with alterations in 476 miRNAs in the Teen-LABs study and 13 miRNAs in the Rhea study (FDR p < 0.1). Specifically, plasma PFAS concentrations were consistently associated with decreased levels of miR-148b-3p and miR-29a-3p in both cohorts. Pathway analysis indicated that PFAS-related miRNAs were linked to numerous chronic disease pathways, including cardiovascular diseases, inflammatory conditions, and carcinogenesis.

CONCLUSION

Through miRNA screenings in two independent cohorts, this study identified both known and novel miRNAs associated with PFAS exposure in children. Pathway analysis revealed the involvement of these miRNAs in several cancer and inflammation-related pathways. Further studies are warranted to enhance our understanding of the relationships between PFAS exposure and disease risks, with miRNA emerging as potential biomarkers and/or mediators in these complex pathways.

The effect of per and polyfluoroalkyl substance (PFAS) exposure on gestational diabetes mellitus and its subclinical risk factors: A systematic review and meta-analysis protocol

BACKGROUND

Multiple lines of evidence suggest that exposure to per- and polyfluoroalkyl substances (PFAS) may alter glucose homeostasis, particularly during pregnancy, and may affect risk for developing gestational diabetes mellitus (GDM). While previous systematic reviews have been conducted on this topic, they did not assess internal validity of the included studies and their search strategies were narrowly focused.

OBJECTIVE

The objective of this study is to assess the effect of higher PFAS exposure (defined by individual compounds or mixtures measured before or during pregnancy) on GDM and subclinical measures of impaired glucose homeostasis (measured during pregnancy) compared to lower PFAS exposure in pregnant.

METHODS

We developed our systematic review protocol in accordance with the Navigation Guide. Peer-reviewed journal and grey literature searches were piloted in to identify relevant studies and refine our search terms and strategy. We also piloted the study screening criteria and data extraction form in DistillerSR, and refined our protocol accordingly. The risk of bias assessment protocol was adapted from Navigation Guide guidance and will be piloted and performed in DistillerSR. Pending the identification of comparable studies, quantitative meta-analyses will be performed where possible. Study results that cannot be quantitatively synthesized will be included in a narrative synthesis. The quality and strength of the body of evidence will be evaluated using Navigation Guide methodology, which is informed by guidance from the Cochrane Collaboration and Grading of Recommendations Assessment, Development and Evaluation (GRADE). We also made refinements to the quality of evidence considerations based on guidance from the National Institute of Environmental Health Sciences (NIEHS) Office of Health Assessment and Translation (OHAT).

FUNDING

This work was supported by the Systematizing Data on Per- and Polyfluoroalkyl Substances and Health Northeastern University TIER 1 Award.

Effect modification by maternal vitamin D status in the association between prenatal exposure to per- and polyfluoroalkyl substances and neurodevelopment in 2-year-old children

BACKGROUND

Pregnant women in the Shanghai Birth Cohort (SBC) of China faced dual threats of per- and polyfluoroalkyl substances (PFAS) exposure and vitamin D (VD) insufficiency, potentially impacting offspring neurodevelopment. However, little is known about whether maternal VD status modifies PFAS-related neurodevelopment effect.

OBJECTIVES

To explore the modifying role of maternal VD status in the effect of prenatal PFAS exposure on childhood neurodevelopment.

METHODS

We included 746 mother-child pairs from the SBC. Ten PFAS congeners and VD levels were measured in maternal blood samples collected during the first and second trimester respectively. At 2 years of age, toddlers underwent neurodevelopment assessments using Bayley-III Scales. Multivariate linear, logistic regression, and weighted quantile sum approach were used to estimate associations of Bayley-III scores with individual and mixture PFAS. We stratified participants into VD sufficient and insufficient groups and further balanced PFAS differences between these groups by matching all PFAS levels. We fitted the same statistical models in each VD group before and after matching.

RESULTS

Nearly half (46.5 %) of pregnant women were VD insufficient (<30 ng/mL). In the overall population, PFAS exposure was associated with lower language scores and an increased risk for neurodevelopmental delay, but higher cognitive scores. However, adverse associations with PFAS were mainly observed in the VD sufficient group, while the VD insufficient group showed positive cognitive score associations. Higher PFAS concentrations were found in the VD sufficient group compared to the VD insufficient group. Post-matching, adverse associations in the VD sufficient group were nullified, whereas in the VD insufficient group, positive associations disappeared and adverse associations becoming more pronounced.

CONCLUSION

In this Chinese birth cohort, high prenatal PFAS exposure and low maternal VD levels collectively heighten the risk of adverse childhood neurodevelopment. However, disentangling PFAS and VD interrelationships is crucial to avoid paradoxical findings.

The sources and bioaccumulation of per- and polyfluoroalkyl substances in animal-derived foods and the potential risk of dietary intake

Per- and polyfluoroalkyl substances (PFAS) have attracted increasing attention due to their environmental persistence and potential toxicity. Diet is one of the main routes of human exposure to PFAS, particularly through the consumption of animal-derived foods (e.g., aquatic products, livestock and poultry, and products derived from them). This review summarizes the source, bioaccumulation, and distribution of PFAS in animal-derived foods and key influential factors. In most environmental media, perfluorooctanoic acid and perfluorooctane sulfonate are the dominant PFAS, with the levels of short-chain PFAS such as perfluorobutyric acid and perfluorohexane sulfonate surpassing them in some watersheds and coastal areas. The presence of PFAS in environmental media is mainly influenced by suspended particulate matter, microbial communities as well as temporal and spatial factors, such as season and location. Linear PFAS with long carbon chains (C ≥ 7) and sulfonic groups tend to accumulate in organisms and contribute significantly to the contamination of animal-derived foods. Furthermore, PFAS, due to their protein affinity, are prone to accumulate in the blood and protein-rich tissues such as the liver and kidney. Species differences in PFAS bioaccumulation are determined by diet, variances in protein content in the blood and tissues and species-specific activity of transport proteins. Carnivorous fish usually show higher PFAS accumulation than omnivorous fish. Poultry typically metabolize PFAS more rapidly than mammals. PFAS exposures in the processing of animal-derived foods are also attributable to the migration of PFAS from food contact materials, especially those in higher-fat content foods. The human health risk assessment of PFAS exposure from animal-derived foods suggests that frequent consumption of aquatic products potentially engender greater risks to women and minors than to adult males. The information and perspectives from this review would help to further identify the toxicity and migration mechanism of PFAS in animal-derived foods and provide information for food safety management.

A co-twin control study of in utero exposure to poly- and perfluoroalkyl substances and associations with neonatal thyroid-stimulating hormone

Research quantifying associations between early-life exposure to poly- and perfluoroalkyl substances (PFAS) and neonatal thyroid hormone levels is limited and reports inconsistent results. This study aimed to examine the associations of in utero PFAS exposure with neonatal thyroid-stimulating hormone (TSH), and to verify whether genetic and familial factors contribute to these associations. Within Wuhan Twin Birth Cohort study, we included 148 mother-twin pairs recruited between March 2016 and January 2018. Maternal plasma PFAS concentrations were measured at three different trimesters and averaged. Additionally, we measured cord plasma PFAS concentrations for twin newborns and retrieved their TSH levels from the medical system. Multivariable linear regression, generalized estimation equation, and linear mixed models were used to examine the covariate-adjusted associations. For maternal PFAS analyses, a 2-fold increment of average maternal perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) concentrations was linked with a 15% (95% CI: 2.5%, 28%) and 14% (95% CI: 2.4%, 28%) increase in neonatal TSH, respectively. For twin newborns discordant for PFAS exposure, a 2-fold increment of cord plasma PFOA, PFDA, perfluoroundecanoic acid (PFUdA), and perfluorohexanesulfonic acid (PFHxS) concentrations was related to a 7.1% (95% CI: 0.31%, 14%), 12% (95% CI: 4.8%, 20%), 7.5% (95% CI: 0.30%, 15%), and 8.5% (95% CI: 3.0%, 14%) increase in TSH among twins as individuals, respectively. Although these associations were mainly observed between twin pairs, certain PFAS exposure might have an independent association with increased TSH. Our present study suggests that higher maternal and cord plasma PFAS concentrations are associated with increased neonatal TSH, and genetic and familial factors contribute to these associations.

Prenatal Exposure to PFAS, Associations with Preterm Birth and Modification by Maternal Estrogen Levels: The Maoming Birth Study

BACKGROUND

Estrogens play a critical role in parturition, and poly- and perfluoroalkyl substances (PFAS), which have estrogenic effects, have been associated with preterm birth. However, the impact of estrogens on the association between PFAS and preterm birth is unknown.

OBJECTIVE

The objective of this study is to investigate if estrogens modified the association between PFAS and preterm birth, using a nested case-control study design.

METHODS

A total of 371 preterm births and 508 controls were selected from a birth cohort study in China between 2016 and 2018. Perfluorobutanoic acid (PFBA), perfluorohexanesulfonic acid (PFHxS) and its branched isomer, perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and its branched isomer, and perfluorononanoic acid (PFNA) were quantified in maternal serum (mean gestational age of 32 wk). Estradiol and estriol were quantified in cord serum. Preterm birth was defined as live delivery at < 37 gestational weeks. Causal mediation analysis was used to estimate the mediation and interaction effects of estrogen on the association between PFAS and preterm birth. Latent profile analysis was used to identify important estrogen profiles. Multiple linear regression was used to estimate associations between PFAS and preterm birth and interactions between PFAS and estrogens on preterm birth.

RESULTS

Overall, higher odds ratios (ORs) of preterm birth were associated with each 1 ln-unit PFAS increase: PFBA [1.20, 95% confidence interval (CI): 1.14, 1.26], PFNA (1.30, 95% CI: 1.21, 1.39), PFOA (1.98, 95% CI: 1.54, 2.55), and PFOS (1.91, 95% CI: 1.76, 2.07) and its branched isomer (1.91, 95% CI: 1.90, 1.92). We detected statistically significant interactions between cord estradiol and PFAS on preterm birth, while no mediation effects of cord estrogen were observed. The ORs of PFOS (4.29, 95% CI: 1.31, 8.25), its branched isomer (6.71, 95% CI: 1.06, 11.91), and preterm birth were greater for participants with high cord estrogen levels than for participants with low cord estrogen levels.

DISCUSSION

Our findings suggest that estrogen modified the association between maternal PFAS exposure and preterm birth. Further studies on maternal PFAS exposure and preterm birth, taking interaction effects of cord estrogens into account, are warranted. https://doi.org/10.1289/EHP11377.

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

BACKGROUND

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Estimated exposure to perfluoroalkyl substances during infancy and serum-adipokine concentrations in later childhood

BACKGROUND

Perfluoroalkyl substances (PFASs) are transferred through human milk and may cause elevated exposure during infancy. Given the lack of early postnatal blood samples, PFAS concentrations can be estimated to serve as predictors of subsequent metabolic toxicity.

METHODS

A total of 298 children from a prospective birth cohort were followed up through to age 9 years. Serum-PFAS was measured at birth and 18 months of age, while exposures during infancy were estimated by structural equations. Adiponectin, resistin, leptin, and the leptin receptor were measured in serum at age 9. Adjusted regression coefficients for estimated serum-PFAS concentrations were calculated, with additional consideration of the duration of breastfeeding and potential effect modification by sex.

RESULTS

A doubling in estimated serum-PFAS concentrations, particularly at ages 6 and 12 months, was associated with a loss of about 10-15% in age 9 resistin concentrations, while other associations were much weaker. Sex dependence of the associations was not observed, and neither did the duration of breastfeeding affect outcomes at age 9.

CONCLUSION

Lowered serum-resistin concentrations at age 9 years were most strongly associated with early postnatal PFAS exposures. These findings suggest that infancy may represent a vulnerable time window for some aspects of metabolic programming that may be affected by PFAS exposure.

IMPACT

Serum-PFAS concentrations during infancy can be estimated in the absence of blood samples. Adipokine concentrations were measured at age 9 years as metabolic biomarkers. Resistin was significantly lower in children with elevated PFAS exposures in infancy. The findings suggest that early postnatal PFAS exposures may affect subsequent metabolic health. Assessment of infancy vulnerability to PFAS can be explored using estimated serum-PFAS concentrations.

Paired Liver:Plasma PFAS Concentration Ratios from Adolescents in the Teen-LABS Study and Derivation of Empirical and Mass Balance Models to Predict and Explain Liver PFAS Accumulation

Animal studies have pointed at the liver as a hotspot for per- and polyfluoroalkyl substances (PFAS) accumulation and toxicity; however, these findings have not been replicated in human populations. We measured concentrations of seven PFAS in matched liver and plasma samples collected at the time of bariatric surgery from 64 adolescents in the Teen-Longitudinal Assessment of Bariatric Surgery (Teen-LABS) study. Liver:plasma concentration ratios were perfectly explained (r2 > 0.99) in a multilinear regression (MLR) model based on toxicokinetic (TK) descriptors consisting of binding to tissue constituents and membrane permeabilities. Of the seven matched plasma and liver PFAS concentrations compared in this study, the liver:plasma concentration ratio of perfluoroheptanoic acid (PFHpA) was considerably higher than the liver:plasma concentration ratio of other PFAS congeners. Comparing the MLR model with an equilibrium mass balance model (MBM) suggested that complex kinetic transport processes are driving the unexpectedly high liver:plasma concentration ratio of PFHpA. Intratissue MBM modeling pointed to membrane lipids as the tissue constituents that drive the liver accumulation of long-chain, hydrophobic PFAS, whereas albumin binding of hydrophobic PFAS dominated PFAS distribution in plasma. The liver:plasma concentration data set, empirical MLR model, and mechanistic MBM modeling allow the prediction of liver from plasma concentrations measured in human cohort studies. Our study demonstrates that combining biomonitoring data with mechanistic modeling can identify underlying mechanisms of internal distribution and specific target organ toxicity of PFAS in humans.

Legacy and Emerging Per- and Polyfluoroalkyl Substances Surveillance in Bufo gargarizans from Inlet Watersheds of Chaohu Lake, China: Tissue Distribution and Bioaccumulation Potential

Amphibians are sensitive biomonitors of environmental pollutants but reports regarding per- and polyfluoroalkyl substances (PFAS), a class of synthetic organofluorine substances, are limited. In this study, samples of water and Chinese toads (Bufo gargarizans) were collected in Chaohu Lake, China. Tissue-specific bioaccumulation characteristics of 39 PFAS, including 19 perfluoroalkyl acids (PFAAs), 8 emerging PFAS, and 12 PFAA precursors, were investigated, and the levels of some biochemical indicators were determined. The highest PFAS concentrations were found in the liver [215.97 ng/g dry weight (dw)] of Chinese toads, followed by gonads (135.42 ng/g dw) and intestine (114.08 ng/g dw). A similar tissue distribution profile was found between legacy and emerging PFAS in the toads, and the occurrence of two emerging PFAS, 2,3,3,3-tetrafluoro-2-propanoate (HFPO-DA) and 6:2 hydrogen-substituted polyfluorooctane ether sulfonate (6:2 H-PFESA) in the amphibians were for the first time reported. Field-based bioaccumulation factors of HFPO-DA were higher than perfluorooctanoic acid, indicating the higher bioaccumulation potential of this emerging PFAS than the legacy C8 compound. Males had significantly higher gonad PFAS levels than females while estradiol levels in gonads increased with increasing concentrations of certain PFAS (e.g., 6:2 H-PFESA), implying that PFAS may trigger estrogenic effects in the toads, especially for male toads.

Extending Nontargeted Discovery of Environmental Chemical Exposures during Pregnancy and Their Association with Pregnancy Complications-A Cross-Sectional Study

BACKGROUND

Nontargeted analysis (NTA) methods identify novel exposures; however, few chemicals have been quantified and interrogated with pregnancy complications.

OBJECTIVES

We characterized levels of nine exogenous and endogenous chemicals in maternal and cord blood identified, selected, and confirmed in prior NTA steps, including linear and branched isomers perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), monoethylhexyl phthalate, 4-nitrophenol, tetraethylene glycol, tridecanedioic acid, octadecanedioic acid, and deoxycholic acid. We evaluated relationships between maternal and cord levels and between gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy in a diverse pregnancy cohort in San Francisco.

METHODS

We collected matched maternal and cord serum samples at delivery from 302 pregnant study participants from the Chemicals in Our Bodies cohort in San Francisco. Chemicals were identified via NTA and quantified using targeted approaches. We calculated distributions and Spearman correlation coefficients testing the relationship of chemicals within and between the maternal and cord blood matrices. We used adjusted logistic regression to calculate the odds of GDM and hypertensive disorders of pregnancy associated with an interquartile range increase in maternal chemical exposures.

RESULTS

We detected linear PFOS, PFHxS, octadecanedioic acid, and deoxycholic acid in at least 97% of maternal samples. Correlations ranged between - 0.1 and 0.9. We observed strong correlations between cord and maternal levels of PFHxS, linear PFOS, and branched PFOS (coefficient = 0.9 , 0.8, and 0.8, respectively). An interquartile range increase in linear and branched PFOS, tridecanedioic acid, octadecanedioic acid, and deoxycholic acid was associated with increased odds ratio (OR) of GDM [OR = 1.33 (95% CI: 0.89, 2.01), 1.24 (95% CI: 0.86, 1.80), 1.26 (95% CI: 0.93, 1.73), 1.24 (95% CI: 0.86, 1.80), and 1.23 (95% CI: 0.87, 1.75), respectively]. Tridecanedioic acid was positively associated with hypertensive disorders of pregnancy [OR = 1.28 (95% CI: 0.90, 1.86)].

DISCUSSION

We identified both exogenous and endogenous chemicals seldom quantified in pregnant study participants that were also related to pregnancy complications and demonstrated the utility of NTA to identify chemical exposures of concern. https://doi.org/10.1289/EHP11546.

Research Progress on Neurodevelopmental Toxicity in Offspring after Indirect Exposure to PFASs in Early Life

Per- and polyfluoroalkyl substances (PFASs) are widespread environmental pollutants. There is increasing evidence that PFASs have various adverse health effects, including renal toxicity, metabolic dysfunction, endocrine disruption, and developmental toxicity. PFASs have been found to accumulate in the placenta, and some PFASs can cross the placental barrier and subsequently accumulate in the fetus via the maternal-fetal circulation. An increasing number of studies have shown that early life exposure to PFASs can affect fetal neurodevelopment. This paper reviews the characteristics of indirect exposure to PFASs in early life, the effects on neurodevelopment in offspring, and the possible mechanisms of toxic effects.

Gene-environment interactions in the associations of PFAS exposure with insulin sensitivity and beta-cell function in a Faroese cohort followed from birth to adulthood

BACKGROUND

Exposure to perfluoroalkyl substances (PFAS) has been associated with changes in insulin sensitivity and pancreatic beta-cell function in humans. Genetic predisposition to diabetes may modify these associations; however, this hypothesis has not been yet studied.

OBJECTIVES

To evaluate genetic heterogeneity as a modifier in the PFAS association with insulin sensitivity and pancreatic beta-cell function, using a targeted gene-environment (GxE) approach.

METHODS

We studied 85 single-nucleotide polymorphisms (SNPs) associated with type 2 diabetes, in 665 Faroese adults born in 1986-1987. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were measured in cord whole blood at birth and in participants' serum from age 28 years. We calculated the Matsuda-insulin sensitivity index (ISI) and the insulinogenic index (IGI) based on a 2 h-oral glucose tolerance test performed at age 28. Effect modification was evaluated in linear regression models adjusted for cross-product terms (PFAS*SNP) and important covariates.

RESULTS

Prenatal and adult PFOS exposures were significantly associated with decreased insulin sensitivity and increased beta-cell function. PFOA associations were in the same direction but attenuated compared to PFOS. A total of 58 SNPs were associated with at least one PFAS exposure variable and/or Matsuda-ISI or IGI in the Faroese population and were subsequently tested as modifiers in the PFAS-clinical outcome associations. Eighteen SNPs showed interaction p-values (PGxE) < 0.05 in at least one PFAS-clinical outcome association, five of which passed False Discovery Rate (FDR) correction (PGxE-FDR<0.20). SNPs for which we found stronger evidence for GxE interactions included ABCA1 rs3890182, FTO rs9939609, FTO rs3751812, PPARG rs170036314 and SLC12A3 rs2289116 and were more clearly shown to modify the PFAS associations with insulin sensitivity, rather than with beta-cell function.

DISCUSSION

Findings from this study suggest that PFAS-associated changes in insulin sensitivity could vary between individuals as a result of genetic predisposition and warrant replication in independent larger populations.

Exposure to per- and polyfluoroalkyl substances in early pregnancy, risk of gestational diabetes mellitus, potential pathways, and influencing factors in pregnant women: A nested case-control study

Although previous studies have reported an association between maternal serum perfluoroalkyl substance (PFAS) exposure and gestational diabetes mellitus (GDM) risk, results have been inconsistent. Few studies have focused on the combined effects of emerging and legacy PFASs on glucose homeostasis while humans are always exposed to multiple PFASs simultaneously. Moreover, the potential pathways by which PFAS exposure induces GDM are unclear. A total of 295 GDM cases and 295 controls were enrolled from a prospective cohort of 2700 pregnant women in Shanghai, China. In total, 16 PFASs were determined in maternal spot serum samples in early pregnancy. We used conditional logistic regression, multiple linear regression, and Bayesian kernel machine regression (BKMR) to examine individual and joint effects of PFAS exposure on GDM risk and oral glucose tolerance test outcomes. The mediating effects of maternal serum biochemical parameters, including thyroid and liver function were further assessed. Maternal perfluorooctanoic acid (PFOA) exposure was associated with an increased risk of GDM (odds ratio (OR) = 1.68; 95% confidence interval (95% CI): 1.10, 2.57), consistent with higher concentrations in GDM cases than controls. Based on mediation analysis, an increase in the free triiodothyronine to free thyroxine ratio partially explained the effect of this association. For continuous glycemic outcomes, positive associations were observed between several PFASs and 1-h and 2-h glucose levels. In BKMR, PFAS mixture exposure showed a positive trend with GDM incidence, although the CIs were wide. These associations were more pronounced among women with normal pre-pregnancy body mass index (BMI). Mixed PFAS congeners may affect glucose homeostasis by increasing 1-h glucose levels, with perfluorononanoic acid found to be a main contributor. Exposure to PFASs was associated with increased risk of GDM and disturbance in glucose homeostasis, especially in normal weight women. The PFAS-associated disruption of maternal thyroid function may alter glucose homeostasis.

Per- and Polyfluoroalkyl Substances (PFAS) Mixture during Pregnancy and Postpartum Weight Retention in the New Hampshire Birth Cohort Study (NHBCS)

Per- and polyfluoroalkyl substances (PFAS), widely used in industrial and consumer products, are suspected metabolic disruptors. We examined the association between a PFAS mixture during pregnancy and postpartum weight retention in 482 participants from the New Hampshire Birth Cohort Study. PFAS concentrations, including perfluorohexane sulfonate, perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), and perfluorodecanoate, were quantified in maternal plasma collected at ~28 gestational weeks. Postpartum weight change was calculated as the difference between self-reported weight from a postpartum survey administered in 2020 and pre-pregnancy weight abstracted from medical records. Associations between PFAS and postpartum weight change were examined using Bayesian kernel machine regression and multivariable linear regression, adjusting for demographic, reproductive, dietary, and physical activity factors; gestational week of blood sample collection; and enrollment year. PFOS, PFOA, and PFNA were positively associated with postpartum weight retention, and associations were stronger among participants with a higher pre-pregnancy body mass index. A doubling of PFOS, PFOA, and PFNA concentrations was associated with a 1.76 kg (95%CI: 0.31, 3.22), 1.39 kg (-0.27, 3.04), and 1.04 kg (-0.19, 2.28) greater postpartum weight retention, respectively, among participants who had obesity/overweight prior to pregnancy. Prenatal PFAS exposure may be associated with increased postpartum weight retention.

Determinants of maternal and neonatal PFAS concentrations: a review

Per- and polyfluoroalkyl substances (PFAS) are used for their properties such as stain and water resistance. The substances have been associated with adverse health outcomes in both pregnant mothers and infants, including pre-eclampsia and low birthweight. A growing body of research suggests that PFAS are transferred from mother to fetus through the placenta, leading to in utero exposure. A systematic review was performed using the PubMed database to search for studies evaluating determinants of PFAS concentrations in blood matrices of pregnant mothers and neonates shortly after birth. Studies were included in this review if an observational study design was utilized, exposure to at least one PFAS analyte was measured, PFAS were measured in maternal or neonatal matrices, at least one determinant of PFAS concentrations was assessed, and results such as beta estimates were provided. We identified 35 studies for inclusion in the review and evaluated the PFAS and determinant relationships among the factors collected in these studies. Parity, breastfeeding history, maternal race and country of origin, and household income had the strongest and most consistent evidence to support their roles as determinants of certain PFAS concentrations in pregnant mothers. Reported study findings on smoking status, alcohol consumption, and pre-pregnancy body mass index (BMI) suggest that these factors are not important determinants of PFAS concentrations in pregnant mothers or neonates. Further study into informative factors such as consumer product use, detailed dietary information, and consumed water sources as potential determinants of maternal or neonatal PFAS concentrations is needed. Research on determinants of maternal or neonatal PFAS concentrations is critical to estimate past PFAS exposure, build improved exposure models, and further our understanding on dose-response relationships, which can influence epidemiological studies and risk assessment evaluations. Given the potential for adverse outcomes in pregnant mothers and neonates exposed to PFAS, it is important to identify and understand determinants of maternal and neonatal PFAS concentrations to better implement public health interventions in these populations.

A Review on Per- and Polyfluoroalkyl Substances in Pregnant Women: Maternal Exposure, Placental Transfer, and Relevant Model Simulation

Per- and polyfluoroalkyl substances (PFASs) are important and ubiquitous environmental contaminants worldwide. These novel contaminants can enter human bodies via various pathways, subsequently posing risks to the ecosystem and human health. The exposure of pregnant women to PFASs might pose risks to the health of mothers and the growth and development of fetuses. However, little information is available about the placental transfer of PFASs from mothers to fetuses and the related mechanisms through model simulation. In the present study, based upon a review of previously published literature, we initially summarized the exposure pathways of PFASs in pregnant women, factors affecting the efficiency of placental transfer, and mechanisms associated with placental transfer; outlined simulation analysis approaches using molecular docking and machine learning to reveal the mechanisms of placental transfer; and finally highlighted future research emphases that need to be focused on. Consequently, it was notable that the binding of PFASs to proteins during placental transfer could be simulated by molecular docking and that the placental transfer efficiency of PFASs could also be predicted by machine learning. Therefore, future research on the maternal-fetal transfer mechanisms of PFASs with the benefit of simulation analysis approaches is warranted to provide a scientific basis for the health effects of PFASs on newborns.

Consequences of the exposome to gestational diabetes mellitus

The exposome is the cumulative measure of environmental influences and associated biological responses throughout the lifespan, including those from the environment, diet, behaviour, and endogenous processes. The exposome concept and the 2030 Agenda for the Sustainable Development Goals (SDGs) from the United Nations are the basis for understanding the aetiology and consequences of non-communicable diseases, including gestational diabetes mellitus (GDM). Pregnancy may be developed in an environment with adverse factors part of the immediate internal medium for fetus development and the external medium to which the pregnant woman is exposed. The placenta is the interface between maternal and fetal compartments and acts as a protective barrier or easing agent to transfer exposome from mother to fetus. Under and over-nutrition in utero, exposure to adverse environmental pollutants such as heavy metals, endocrine-disrupting chemicals, pesticides, drugs, pharmaceuticals, lifestyle, air pollutants, and tobacco smoke plays a determinant role in the development of GDM. This phenomenon is worsened by metabolic stress postnatally, such as obesity which increases the risk of GDM and other diseases. Clinical risk factors for GDM development include its aetiology. It is proposed that knowledge-based interventions to change the potential interdependent ecto-exposome and endo-exposome could avoid the occurrence and consequences of GDM.

High maternal glucose exacerbates the association between prenatal per- and polyfluoroalkyl substance exposure and reduced birth weight

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) exposure has been associated with reduced birth weight. However, the association may be complicated by glucose status due to PFAS impact on fetal growth and placental transport.

OBJECTIVES

To examine whether maternal glucose status modifies the association between prenatal PFAS exposure and birth weight z-score.

METHODS

We analyzed data of 1405 mother-child pairs from the prospective Shanghai Birth Cohort. Plasma concentrations of six PFAS were quantified in the first trimester. Fasting plasma glucose (FPG) was collected at 24-28 gestation weeks. A range of FPG cutoffs (4.9-5.4 mmol/L) covering current recommendations for gestational diabetes mellitus were used to define high and low FPG groups. Association between PFAS concentration and birth weight z-score was evaluated using multivariate linear regression in two FPG groups respectively, and the dose-response relationship was estimated with cutoffs ranging from low to high. We then used propensity score to counterbalance the effects of different PFAS concentrations between the high and low FPG groups, and run the regression again.

RESULTS

A doubling increase in concentrations of several PFAS was inversely associated with birth weight z-score. The association was more evident in high FPG groups and the magnitudes intensified when FPG cutoff increased. The strongest association was observed for PFOA, with the magnitude increased from -0.34 (95 % CI: -0.66, -0.03) for 5.0 mmol/L cutoff, to -0.41 (95 % CI: -0.77, -0.05) for 5.1 mmol/L cutoff, and further to -0.51 (95 % CI: -0.98, -0.03) for 5.3 mmol/L. Propensity score matching yielded similar results.

CONCLUSIONS

High maternal glucose level may increase the risk of reduced birth weight z-score related to prenatal PFAS exposure. Moreover, exploring the effects with different FPG cutoffs may contribute to providing intervention strategies for pregnant women with high PFAS exposure.

Plasma concentrations of perfluoroalkyl acids and their determinants in youth and adults from Nunavik, Canada

Perfluoroalkyl acids (PFAAs), a subset of per- and poly-fluoroalkyl substances (PFAS), are environmentally stable, mobile and bioaccumulative compounds. This leads to high concentrations in wildlife species essential to the cultural identity and subsistence of Arctic populations. Our objective was to characterize the distribution and exposure determinants of PFAAs among Nunavik Inuit adults. The study included up to 1322 Nunavik residents aged 16-80 years who participated in the Qanuilirpitaa? 2017 Nunavik Inuit Health Survey (Q2017). Plasma concentrations were compared to those the general Canadian population using data from the Canadian Health Measures Survey Cycle 5 (2016-2017). Associations between plasma concentrations of nine PFAAs, determined by liquid chromatography-tandem mass spectrometry, and sociodemographic factors and traditional activity participation were examined using multiple linear regression models. Overall exposure to PFAAs was twice as high compared to the general Canadian population and less regulated perfluorononanoic acid (PFNA) and perfluoroundecanoic acid (PFUnDA) concentrations were 7-fold higher, and perfluorodecanoic acid (PFDA) concentrations were 4-fold higher. Males had higher concentrations of perfluorooctanoic acid (PFOA) and perfluorohexane sulfonate (PFHxS), whereas females had higher concentrations of PFDA and PFUnDA. PFAAs concentrations increased with age and were highest among those aged 60+ years. PFNA and PFOA concentrations followed a J-shaped pattern: those aged 16-29 years had higher concentrations than those aged 20-29 and 30-39 years. Ungava Bay generally had lower concentrations of all PFAAs congeners compared to Hudson Bay and Hudson Strait, with the exception of PFNA, which tended to have the lowest concentration in Hudson Strait. PFAAs concentrations were highly associated with hunting activity, omega-3 polyunsaturated fatty acids, and drinking water from environmental sources. The results highlight the importance of characterizing PFAAs exposure sources in Arctic communities and provide further evidence for the long-range transport of long-chain PFAAs and their precursors that necessitate international action.

Fetal exposure to organic contaminants revealed by infant hair: A preliminary study in south China

Fetal exposure to multiple organic contaminants (OCs) is a public concern because of the adverse effects of OCs on early life development. Infant hair has the potential to be used as an alternative matrix to identify susceptible fetuses, owing to its reliability, sensitivity, and advantages associated with sampling, handling, and ethics. However, the applicability of infant hair for assessing in utero exposure to OCs is still limited. In this study, 57 infant hair samples were collected in Guangzhou, South China, to evaluate the levels and compositions of typical OCs in the fetus. Most of the target OCs were detected in infant hair, with medians of 144 μg/g, 17.7 μg/g, 192 ng/g, 46.9 ng/g, and 1.36 ng/g for phthalate esters (PAEs), alternative plasticizers (APs), organophosphorus flame retardants (OPFRs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs), respectively. Meanwhile, paired maternal hair (0-9 cm from the scalp) was collected to examine the associations between maternal and infant hair for individual compounds. Low-brominated PBDEs tended to deposit in infant hair, with median concentrations approximately two times higher than those in maternal samples. Levels of PBDEs and 4,4'-dichlorodiphenyldichloroethylene (p,p'-DDE) in paired maternal and infant hair showed strong positive correlations (p < 0.05), while most plasticizers (PAEs and APs) were poorly correlated between paired hair samples. Exposure sources were responsible for the variation in correlation between OC levels in the paired infant and maternal samples. Crude relationships between fetal exposure to OCs and birth size were examined using the Bayesian kernel machine regression (BKMR) model. BDE-28 was found to be adversely associated with the birth size. This study provides referential information for evaluating in utero exposure to OCs and their health risks based on infant hair.

First Evidence of Prenatal Exposure to Emerging Poly- and Perfluoroalkyl Substances Associated with E-Waste Dismantling: Chemical Structure-Based Placental Transfer and Health Risks

Limited information is available about prenatal exposure to per- and polyfluoroalkyl substances (PFAS) in electronic waste (e-waste) recycling sites. In this study, we determined 21 emerging PFAS and 13 legacy PFAS in 94 paired maternal and cord serum samples collected from an e-waste dismantling site in Southern China. We found 6:2 fluorotelomer sulfonate (6:2 FTSA), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), and perfluorooctanephosphonate (PFOPA) as the major emerging PFAS, regardless of matrices, at median concentrations of 2.40, 1.78, and 0.69 ng/mL, respectively, in maternal serum samples, and 2.30, 0.73, and 0.72 ng/mL, respectively, in cord serum samples. Our results provide evidence that e-waste dismantling activities contribute to human exposure to 6:2 FTSA, 6:2 Cl-PFESA, and PFOPA. The trans-placental transfer efficiencies of emerging PFAS (0.42-0.94) were higher than that of perfluorooctanesulfonic acid (0.37) and were structure-dependent. The substitution of fluorine with chlorine or hydrogen and/or hydrophilic functional groups may alter trans-placental transfer efficiencies. Multiple linear regression analysis indicated significant associations between maternal serum concentrations of emerging PFAS and maternal clinical parameters, especially liver function and erythrocyte-related biomarkers. This study provides new insights into prenatal exposure to multiple PFAS in e-waste dismantling areas and the prevalence of emerging PFAS in people living near the sites.

Effects of Lifetime Exposures to Environmental Contaminants on the Adult Gut Microbiome

Emerging experimental evidence indicates that toxicant-induced alterations in gut microbiota composition and activity may affect host homeostasis. However, data from human studies are scarce; to our knowledge, no previous studies have quantified the association of lifetime exposure to environmental chemicals, across multiple time points, with the composition of the adult gut microbiome. Here we studied 124 individuals born in the Faroe Islands in 1986-1987 who were followed approximately every seven years from birth through age 28 years. Organochlorine compounds, including polychlorinated biphenyls (PCBs) and pesticides, perfluoroalkyl substances (PFAS), and mercury (Hg), were measured in cord blood and longitudinally in participants' blood. At age 28, the gut microbiome was assessed using shotgun metagenomic sequencing. Historical contaminant exposures had little direct effect on the adult gut microbiome, while a small number of fastidious anaerobes were weakly linked to recent PFAS/PFOS exposures at age 28. In this cohort, our findings suggest no lasting effects of early life exposures on adult gut microbial composition, but proximal exposures may contribute to gut microbiome alterations. The methods developed and used for this investigation may help in future identification of small but lasting impacts of environmental toxicant exposure on the gut microbiome.

Modeling the transplacental transfer of small molecules using machine learning: a case study on per- and polyfluorinated substances (PFAS)

BACKGROUND

Despite their large numbers and widespread use, very little is known about the extent to which per- and polyfluoroalkyl substances (PFAS) can cross the placenta and expose the developing fetus.

OBJECTIVE

The aim of our study is to develop a computational approach that can be used to evaluate the of extend to which small molecules, and in particular PFAS, can cross to cross the placenta and partition to cord blood.

METHODS

We collected experimental values of the concentration ratio between cord and maternal blood (R_CM) for 260 chemical compounds and calculated their physicochemical descriptors using the cheminformatics package Mordred. We used the compiled database to, train and test an artificial neural network (ANN). And then applied the best performing model to predict R_CM for a large dataset of PFAS chemicals (n = 7982). We, finally, examined the calculated physicochemical descriptors of the chemicals to identify which properties correlated significantly with R_CM.

RESULTS

We determined that 7855 compounds were within the applicability domain and 127 compounds are outside the applicability domain of our model. Our predictions of R_CM for PFAS suggested that 3623 compounds had a log R_CM > 0 indicating preferable partitioning to cord blood. Some examples of these compounds were bisphenol AF, 2,2-bis(4-aminophenyl)hexafluoropropane, and nonafluoro-tert-butyl 3-methylbutyrate.

SIGNIFICANCE

These observations have important public health implications as many PFAS have been shown to interfere with fetal development. In addition, as these compounds are highly persistent and many of them can readily cross the placenta, they are expected to remain in the population for a long time as they are being passed from parent to offspring.

IMPACT

Understanding the behavior of chemicals in the human body during pregnancy is critical in preventing harmful exposures during critical periods of development. Many chemicals can cross the placenta and expose the fetus, however, the mechanism by which this transport occurs is not well understood. In our study, we developed a machine learning model that describes the transplacental transfer of chemicals as a function of their physicochemical properties. The model was then used to make predictions for a set of 7982 per- and polyfluorinated alkyl substances that are listed on EPA's CompTox Chemicals Dashboard. The model can be applied to make predictions for other chemical categories of interest, such as plasticizers and pesticides. Accurate predictions of R_CM can help scientists and regulators to prioritize chemicals that have the potential to cause harm by exposing the fetus.

Exposure to per- and polyfluoroalkyl substances as a risk factor for gestational diabetes mellitus through interference with glucose homeostasis

Per- and polyfluoroalkyl substances (PFASs) are hypothesized to trigger gestational diabetes mellitus (GDM) through modulation of glucose metabolism. However, studies investigating links between joint PFASs to GDM are limited and led to discrepant conclusions. This study included 171 women with GDM development in pregnancy and 169 healthy controls from Hangzhou, China between October 2020 and September 2021. By using the solid-phase extraction (SPE)-ultra performance liquid chromatography-tandem-mass-spectrometry (UPLC/MS-MS), 15 PFASs were detected to be widely distributed in maternal serum, with highest median concentrations of 7.43, 4.23, and 3.64 ng/mL for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and 6:2 chlorinated polyfluorinated ether sulfonates (6:2 Cl-PFESA). Multivariable logistic regressions suggested that the adjusted odds ratios (ORs) with 95% confidence intervals (CI) of GDM for second and highest tertiles of PFOA were 2.57 (1.24, 4.86), p = 0.001 and 1.98 (1.06, 3.65), p = 0.023. Compared with the reference tertile, the ORs of GDM were also significantly increased at the highest tertile of perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoA), PFOS and 6:2Cl-PFESA. Multiple linear regressions further indicated that exposure to these PFASs congeners were positively associated with continuous glycemic outcomes of fasting blood glucose (FBG), 1-h, and 2-h glucose after 75 g oral glucose tolerance (OGTT) test as well as glycohemoglobin (HbA1c). Nevertheless, perfluorohexane sulfonic acid (PFHxS), 4:2 fluorotelomer sulfonates (FTSs), and 3H-perfluoro-3-[(3-methoxy-propoxy) propanoic acid] (ADONA) exhibited protective effects on some of these glycemic outcomes. When assessing the PFASs as mixtures by conducting the Bayesian kernel machine regression (BKMR), the risks of GDM and values of glycemic outcomes increased significantly as the concentrations of the PFASs mixture increased, with PFOA being the largest contributor. We therefore propose that although the effects on glucose homeostasis varied between different PFAS congeners, the elevated combined exposures to PFASs may be associated with substantially increased GDM risks by altering glucose metabolism.

Effect of perfluoroalkyl exposure in pregnancy and infancy on intrauterine and childhood growth and anthropometry. Sub study from COPSAC2010 birth cohort

BACKGROUND

Perfluoroalkyl substances PFOS and PFOA are persistent and bioaccumulative exogenous chemicals in the human body with a range of suspected negative health effects. It is hypothesised that exposure during prenatal and early postnatal life might have particularly detrimental effects on intrauterine and childhood growth. In a Danish longitudinal mother-child cohort we investigate effect of PFOS and PFOA in pregnancy and infancy on intrauterine and childhood growth and anthropometry.

METHODS

COPSAC₂₀₁₀ is an ongoing population based mother-child cohort of 738 pregnant women and their children followed from 24 week gestation with longitudinal deep clinical phenotyping until age 10 years. In this observational cohort sub study plasma PFOS and PFOA concentrations were semi-quantified by untargeted metabolomics in the mothers at week 24 and 1 week postpartum and in the children at ages 6 and 18 months and calibrated using a targeted pipeline. We examined associations to intrauterine and childhood growth and anthropometry, including interactions with child sex. Untargeted and targeted blood metabolomics profiles were integrated to investigate underlying mechanisms.

FINDINGS

Pregnancy plasma PFOA concentrations were associated with lower birth size -0.19 [-0.33; -0.05] BMI z-score per 1-ng/mL and increased childhood height (z-scored) at age 6: 0.18 [0.05; 0.31], but there was no association between childs' own infancy plasma PFOA concentration and height. Pregnancy plasma PFOS concentrations were also associated with lower birth BMI (-0.04 [-0.08; -0.01]), but in childhood pregnancy plasma PFOS concentration interacted with child sex on BMI and fat percentage at 6 years with negative associations in girls and positive in boys. The effect of maternal plasma PFOS concentration on lower girl BMI was borderline mediated through increasing child plasma lactosyl-ceramide levels (p-mediation=0.08). Similarly the effect of maternal plasma PFOS concentration on higher boy fat percentage was borderline mediated through increasing child plasma lactosyl-ceramide levels (p-mediation=0.07). Infancy concentrations of plasma PFOS associated with lower height in childhood, -0.06 z-score at age 6 [-0.19; -0.03].

INTERPRETATION

Higher PFOS and PFOA plasma concentrations during pregnancy had detrimental effects on fetal growth. The effects on childhood growth were not similar as PFOA increased child height, opposite of PFOS in multipollutant models suggesting a differing fetal programming effect. Sex specific growth effects were borderline mediated through an altered lactosyl-ceramide metabolism, proposing a possible mechanism of PFOS that has long-lasting health consequences in this observational study.

FUNDING

All funding received by COPSAC are listed on www.copsac.com. The Lundbeck Foundation (Grant no R16-A1694); The Novo Nordic Foundation (Grant nos NNF20OC0061029, NNF170C0025014, NNF180C0031764) The Ministry of Health (Grant no 903516); Danish Council for Strategic Research (Grant no 0603-00280B) and The Capital Region Research Foundation have provided core support to the COPSAC research center. Effort from JALS is supported by R01HL123915, R01HL141826, and R01HL155742 from NIH/NHLBI. CEW was supported by the Swedish Heart Lung Foundation (HLF 20180290, HLF 20200693). BC has received funding for this project from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 946228). The funding agencies did not have any role in design and conduct of the study; collection, management, and interpretation of the data; or preparation, review, or approval of the manuscript.

Exposure to GenX and Its Novel Analogs Disrupts Hepatic Bile Acid Metabolism in Male Mice

Due to its wide usage and recent detection in environmental matrices, hexafluoropropylene oxide dimer acid (HFPO-DA, commercial name GenX) has attracted considerable attention. Here, we explored and compared the toxicity of GenX and its novel analogs with that of perfluorooctanoic acid (PFOA) to provide guidance on the structural design and optimization of novel alternatives to poly- and perfluoroalkyl substances (PFASs). Adult male BALB/c mice were continuously exposed to PFOA, GenX, perfluoro-2-methyl-3,6-dioxo-heptanoic acid (PFMO2HpA), and perfluoro-2-methyl-3,6,8-trioxo-nonanoic acid (PFMO3NA; 0, 0.4, 2, or 10 mg/kg/d) via oral gavage for 28 days. The PFOA, GenX, and PFMO3NA treatment groups showed an increase in relative liver weight, and bile acid metabolism was the most significantly affected pathway in all treatment groups, as shown via weighted gene coexpression network analysis. The highest total bile acid levels were observed in the 2 and 10 mg/kg/d PFMO3NA groups. The ratios of primary bile acids to all bile acids increased in the high-dose groups, while the ratios of secondary bile acids showed a downward trend. Thus, bile acid metabolism disorder may be a prominent adverse effect induced by exposure to GenX, its analogs, and PFOA. Results also showed that the hepatotoxicity of PFMO2HpA was lower than that of GenX, whereas the hepatotoxicity of PFMO3NA was stronger, suggesting that PFMO2HpA may be a potential alternative to GenX.

Exposure to per- and Polyfluoroalkyl Substances and Markers of Liver Injury: A Systematic Review and Meta-Analysis

BACKGROUND

Experimental evidence indicates that exposure to certain pollutants is associated with liver damage. Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals widely used in industry and consumer products and bioaccumulate in food webs and human tissues, such as the liver.

OBJECTIVE

The objective of this study was to conduct a systematic review of the literature and meta-analysis evaluating PFAS exposure and evidence of liver injury from rodent and epidemiological studies.

METHODS

PubMed and Embase were searched for all studies from earliest available indexing year through 1 December 2021 using keywords corresponding to PFAS exposure and liver injury. For data synthesis, results were limited to studies in humans and rodents assessing the following indicators of liver injury: serum alanine aminotransferase (ALT), nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, or steatosis. For human studies, at least three observational studies per PFAS were used to conduct a weighted z-score meta-analysis to determine the direction and significance of associations. For rodent studies, data were synthesized to qualitatively summarize the direction and significance of effect.

RESULTS

Our search yielded 85 rodent studies and 24 epidemiological studies, primarily of people from the United States. Studies focused primarily on legacy PFAS: perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid. Meta-analyses of human studies revealed that higher ALT levels were associated with exposure to PFOA (z-score= 6.20, p<0.001), PFOS (z-score= 3.55, p<0.001), and PFNA (z-score= 2.27, p=0.023). PFOA exposure was also associated with higher aspartate aminotransferase and gamma-glutamyl transferase levels in humans. In rodents, PFAS exposures consistently resulted in higher ALT levels and steatosis.

CONCLUSION

There is consistent evidence for PFAS hepatotoxicity from rodent studies, supported by associations of PFAS and markers of liver function in observational human studies. This review identifies a need for additional research evaluating next-generation PFAS, mixtures, and early life exposures. https://doi.org/10.1289/EHP10092.

How to investigate human health effects related to exposure to mixtures of per- and polyfluoroalkyl substances: A systematic review of statistical methods

BACKGROUND

Humans are exposed to several per- and polyfluoroalkyl substances (PFAS) daily; however, most previous studies have focused on individual PFAS. Although attention to effects of exposure to mixtures of PFAS has grown in recent years, there is no consensus on the appropriate statistical methods that can be used to assess their combined effect on human health.

OBJECTIVES

We aim to perform a comprehensive review of the statistical methods used in the existing studies which evaluate the association between exposure to mixtures of PFAS and any adverse human health effect.

METHODS

The online databases PubMed, Embase and Scopus were searched for eligible studies, published during the last ten years (last search performed on April 08, 2021). Covidence software was used by two different reviewers to perform a title/abstract screening, followed by a full text revision of the selected papers.

RESULTS

A total of 3640 papers were identified, and after the screening process, 53 papers were included in the current review. Most of the studies were published between 2019 and 2021 and were conducted mainly in North America and Europe; more than half of the studies (28 out of 53) were conducted on mother and child pairs. WQS (Weighted Quantile Sum) Regression and BKMR (Bayesian Kernel Machine Regression) were used in 36 out of 53 papers to model mixtures' effects. Health outcomes included in the studies are immunotoxicity (n = 8), fetal development (n = 7), neurodevelopment (n = 9), reproductive hormones (n = 6), thyroid hormones (n = 7), outcomes related to metabolic pathways (n = 16).

CONCLUSION

Studies on human exposure to PFAS as complex mixtures and health consequences have substantially increased in the last few years. Based on our findings, we propose that addressing risk from PFAS mixtures will likely require combinations of approaches and implementation of constantly evolving statistical methods. Specific guidelines and tools for quality assessment and publication of mixture observational studies are warranted.

Prenatal and postnatal exposure to emerging and legacy per-/polyfluoroalkyl substances: Levels and transfer in maternal serum, cord serum, and breast milk

Gestation and lactation are critical and vulnerable stages for fetuses and newborns. During these periods, per-/polyfluoroalkyl substances (PFASs) accumulated in mothers can be transferred to newborns through placenta and/or breastfeeding, causing potential health risks. To investigate the pre- and postnatal PFAS exposure of newborns, we analyzed 21 emerging and legacy PFASs in 60 sets of matched maternal serum, cord serum, and breast milk samples. In serum, perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and 6:2 chlorinated polyfluorinated ether sulfonates (6:2 Cl-PFESA) were the most predominant PFASs, while PFOA, PFOS and 6:2 fluorotelomer phosphate diester (6:2 diPAP) contributed most to breast milk. For most PFASs, the levels followed the order of maternal serum > cord serum > breast milk. The 6:2 Cl-PFESA was positively associated with birth weight and ponderal index (p < 0.05). The breastfeeding transfer efficiencies (R_BM, median: 0.02-0.10) of most PFASs were 1-2 orders of magnitude lower than transplacental transfer efficiencies (R_CM, median: 0.40-1.45), except for perfluorobutanesulfonic acid (PFBS) showing high transfer efficiency both through placenta (median at 0.89) and breastfeeding (median at 0.86). The one-month postnatal exposure to PFASs via breastfeeding was much higher than prenatal exposure in utero. This study enhances the understanding of transplacental and breastfeeding transfer of PFASs and provides assessments of prenatal and postnatal exposure of newborns to emerging and legacy PFASs.

Prenatal Exposure to Per- and Polyfluoroalkyl Substances and Child Growth Trajectories in the First Two Years

BACKGROUND

Pregnant women are ubiquitously exposed to per- and polyfluoroalkyl substances (PFAS). Prenatal exposure to PFAS has been associated with lower birth weight but also with excess adiposity and higher weight in childhood. These mixed findings warrant investigation of the relationship between PFAS and dynamic offspring growth.

OBJECTIVES

To investigate the association between prenatal PFAS exposure and early-life growth trajectories during the first 2 y.

METHODS

Pregnant women (n=3,426) were recruited from 2013 to 2016 from the Shanghai Birth Cohort (SBC) Study, and their children were followed up from birth to 2 y of age. Seven PFAS congeners were quantified in pregnant women's serum during the first trimester. Our study population was restricted to 1,350 children who had five repeated measurements for at least one anthropometric measure. Four anthropometric measures, including weight, length/height, weight-for-length, and head circumference, were evaluated at birth, 42 d, 6 months, 12 months, and 24 months, and standardized into z-scores using the World Health Organization reference. Trajectories of each measure were classified into five groups using group-based trajectory modeling. Multinomial logistic regression was used to estimate odds ratio (OR) and 95% confidence interval (CI) for trajectory groups according to log2-transformed PFAS concentrations, and the moderate-stable group was selected as the reference group for all measures.

RESULTS

Higher prenatal exposure to PFAS was associated with elevated odds for the low-rising weight-for-age z-score (WAZ) trajectory, and the high-rising length-for-age z-score (LAZ) trajectory. Meanwhile, PFAS levels were associated with decreased odds for the low-rising and high-rising weight-for-length z-score (WLZ) trajectories. In addition, the associations of PFAS with growth trajectory groups differed by sex, where males had greater odds for the low-rising and low-stable WAZ trajectories and for the high-stable and low-rising WLZ trajectories. In contrast, inverse associations were consistently observed with trajectories of the high-stable, low-stable, and low-rising head-circumference-for-age z-score (HCZ) in relation to most individual PFAS congeners. PFAS mixtures analysis further confirmed the above findings.

DISCUSSION

Trajectory analysis approach provided insight into the complex associations between PFAS exposure and offspring growth. Future studies are warranted to confirm the present findings with trajectory modeling strategies and understand the clinical significance of these trajectory groups. https://doi.org/10.1289/EHP9875.

Human exposure to F-53B in China and the evaluation of its potential toxicity: An overview

Chlorinated polyfluoroalkyl ether sulfonic acid (Cl-PFESAs, trade name F-53B), an alternative to perfluorooctane sulfonate (PFOS), has been widely used as a mist suppressant in the Chinese electroplating industry since the 1970 s. Due to greater restrictions on PFOS globally in recent years, the production and use of F-53B correspondingly increased, consequently causing more emissions into the environment. In China, an increasing number of studies report frequent detection and broad exposure to F-53B in the natural environment, various wildlife and the human body. In human blood, the detection rate of F-53B is almost 80%, accounting for 8.69 to 28% of ∑per- and polyfluoroalkyl substances (PFASs). F-53B is the most biopersistent PFAS in humans to date, with a half-life of 15.3 years. In addition, F-53B displays protein binding affinity and high human placental permeability. Recently, some epidemiological studies have reported the health risks associated with F-53B in humans, including abnormal serum lipid metabolism, vascular dysfunction, endocrine disorders and even adverse birth outcomes. Various in vivo and in vitro studies have demonstrated the toxicity of F-53B, such as hepatotoxicity, interference effects on the endocrine system, as well as reproductive and developmental toxicity. Our aims are to review studies on human F-53B exposure levels, trends and associated health effects; evaluate the potential toxicity; and predict directions for future research.

Current Breast Milk PFAS Levels in the United States and Canada: After All This Time, Why Don't We Know More?

BACKGROUND

Despite 20 y of biomonitoring studies of per- and polyfluoroalkyl substances (PFAS) in both serum and urine, we have an extremely limited understanding of PFAS concentrations in breast milk of women from the United States and Canada. The lack of robust information on PFAS concentrations in breast milk and implications for breastfed infants and their families were brought to the forefront by communities impacted by PFAS contamination.

OBJECTIVES

The objectives of this work are to: a) document published PFAS breast milk concentrations in the United States and Canada; b) estimate breast milk PFAS levels from maternal serum concentrations in national surveys and communities impacted by PFAS; and c) compare measured/estimated milk PFAS concentrations to screening values.

METHODS

We used three studies reporting breast milk concentrations in the United States and Canada We also estimated breast milk PFAS concentrations by multiplying publicly available serum concentrations by milk:serum partitioning ratios for perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA). Measured and estimated breast milk concentrations were compared to children's drinking water screening values.

DISCUSSION

Geometric means of estimated breast milk concentrations ranged over approximately two orders of magnitude for the different surveys/communities. All geometric mean and mean estimated and measured breast milk PFOA and PFOS concentrations exceeded drinking water screening values for children, sometimes by more than two orders of magnitude. For PFHxS and PFNA, all measured breast milk levels were below the drinking water screening values for children; the geometric mean estimated breast milk concentrations were close to-or exceeded-the children's drinking water screening values for certain communities. Exceeding a children's drinking water screening value does not indicate that adverse health effects will occur and should not be interpreted as a reason to not breastfeed; it indicates that the situation should be further evaluated. It is past time to have a better understanding of environmental chemical transfer to-and concentrations in-an exceptional source of infant nutrition. https://doi.org/10.1289/EHP10359.

Thermal decomposition of heptafluoropropylene-oxide-dimer acid (GenX)

Incineration appears as a viable strategy in the disposal of the notorious perfluoroalkyl substances (PFASs) in a process that typically leads to fluorine mineralization. Central in the design of such operation is to comprehend the underlying chemical mechanisms that dictate thermal fragmentation of PFASs into smaller perfluorinated cuts and HF. Among notable short-chain PFASs entities is the heptafluoropropylene-oxide-dimer acid (HFPO-DA, C₅F₁₁C(O)OH), commercially known as GenX synthesized as a possible replacement of other PFASs compounds. However, reaction pathways that underpin the degradation of GenX at temperatures relevant to its decomposition in incinerators (i.e., cement kilns), remain unknown. Herein, we map out all plausible initial reactions that govern the thermal decomposition of GenX. Simultaneous elimination of HF and CO₂ appears as the kinetically most favored channel with an accessible activation enthalpy of ∼62.0 kcal/mol. Fission of the ether linkage in the 1,1,1,2,2,3,3-heptafluoro-3-[(1-fluoroethenyl)oxy] propane molecule (that forms after HF/CO₂ elimination) affords a wide array of C_nF_m cuts, most notably CF₂ at elevated temperatures. Constructed kinetic model plots temperature-dependent profiles of important species. It is predicted that GenX to commence decomposition around 700 K at a residence time of 2.0 s, a value that is generally applied in incinerators. Findings from the study call to further investigate interactions between the predicted major fluorine carriers (HF and CF₂) and other constituents encountered in relevant incineration mediums, most notably, calcium hydroxides and polymeric materials.

Understanding the dynamics of physiological changes, protein expression, and PFAS in wildlife

Per- and polyfluoroalkyl substances (PFAS) accumulation and elimination in both wildlife and humans is largely attributed to PFAS interactions with proteins, including but not limited to organic anion transporters (OATs), fatty acid binding proteins (FABPs), and serum proteins such as albumin. In wildlife, changes in the biotic and abiotic environment (e.g. salinity, temperature, reproductive stage, and health status) often lead to dynamic and responsive physiological changes that alter the prevalence and location of many proteins, including PFAS-related proteins. Therefore, we hypothesize that if key PFAS-related proteins are impacted as a result of environmentally induced as well as biologically programmed physiological changes (e.g. reproduction), then PFAS that associate with those proteins will also be impacted. Changes in tissue distribution across tissues of PFAS due to these dynamics may have implications for wildlife studies where these chemicals are measured in biological matrices (e.g., serum, feathers, eggs). For example, failure to account for factors contributing to PFAS variability in a tissue may result in exposure misclassification as measured concentrations may not reflect average exposure levels. The goal of this review is to share general information with the PFAS research community on what biotic and abiotic changes might be important to consider when designing and interpreting a biomonitoring or an ecotoxicity based wildlife study. This review will also draw on parallels from the epidemiological discipline to improve study design in wildlife research. Overall, understanding these connections between biotic and abiotic environments, dynamic protein levels, PFAS levels measured in wildlife, and epidemiology serves to strengthen study design and study interpretation and thus strengthen conclusions derived from wildlife studies for years to come.

The transplacental transfer efficiency of per- and polyfluoroalkyl substances (PFAS): a first meta-analysis

Per- and polyfluorinated substances (PFAS), ubiquitously present in the environment and biota, are transferred to the fetus via the placenta. PFAS can be distinguished, among other things, by their different carbon chain lengths and functional groups. The aim of this study was to provide comprehensive evidence on PFAS transfer rates across the human placental barrier by means of a meta-analysis based upon a systematic review. The available literature up to April 2021 was reviewed and transplacental transfer efficiencies (TTEs) of PFAS assessed. A total of 39 studies reporting data on 20 PFAS were included in the systematic review. Of these, 20 studies with data on 19 compounds were included in the meta-analysis. Comprehensive Meta-Analysis (CMA v3.0) was used for quantitative, statistical analyses with random effects models. A curvilinear relationship was found with short and long chains of perfluorocarboxylic acids (PFCAs) exhibiting higher TTE than compounds with intermediate chain length. Among the less well studied PFAS, perfluorohexanoic acid (PFHxA), 6:2 fluorotelomersulfonic acid (6:2 FTS) and perfluorobutanoic acid (PFBA) stood out the most with a high TEEs. The dependence of TTEs on chain length and functional group is clearly shown in this first meta-analysis on PFAS transfer across the human placenta. More data on effects of less well studied PFAS in pregnant women and neonates are needed to assess the potential risk for fetal exposure.

Exposure to GenX and its novel analogs disrupts fatty acid metabolism in male mice

Perfluoroalkyl ether carboxylic acids (PFECAs), including hexafluoropropylene oxide dimer acid (HFPO-DA, GenX), have been widely used as alternatives to perfluorooctanoic acid (PFOA) and subsequently detected in various environmental matrices. Despite this, public information regarding their hepatotoxicity remains limited. Here, to compare the hepatotoxicity of PFECAs and identify better alternatives for GenX, adult male mice were exposed to different concentrations (0.4, 2, and 10 mg/kg/d) of PFOA, GenX, and its analogs (PFMO2HpA and PFMO3NA) for 28 d. Results demonstrated increased hepatomegaly and disturbed fatty acid metabolism with increasing treatment doses. After dimensionality reduction analysis, significant differences were observed in the relative liver weights and liver and serum biochemical parameters among the four clusters. Furthermore, when chemical concentrations in the liver were similar, no differences in the indicators of liver injury associated with fatty acid metabolism were observed among groups in the same clusters. Our results suggest that dimensionality reduction analysis is a useful strategy for analyzing samples exposed to multiple compounds at different doses. Furthermore, PFECAs exhibit similar hepatotoxicities at the same cumulative hepatic concentration in mice with constant body weight, while PFMO2HpA exhibits lower hepatotoxicity compared to GenX at the same dose.

Associations between Exposures to Perfluoroalkyl Substances and Diabetes, Hyperglycemia, or Insulin Resistance: A Scoping Review

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental pollutants that are commonly found in the human body due to exposures via drinking water, surfactants used in consumer materials, and aqueous film-forming foams (AFFFs). PFAS exposure has been linked to adverse health effects such as low infant birth weights, cancer, and endocrine disruption, though increasingly studies have demonstrated that they may perturb metabolic processes and contribute to dysfunction. This scoping review summarizes the chemistry of PFAS exposure and the epidemiologic evidence for associations between exposure to per- and polyfluoroalkyl substances and the development of diabetes, hyperglycemia, and/or insulin resistance. We identified 11 studies on gestational diabetes mellitus, 3 studies on type 1 diabetes, 7 studies on type 2 diabetes, 6 studies on prediabetes or unspecified diabetes, and 15 studies on insulin resistance or glucose tolerance using the SCOPUS and PubMed databases. Approximately 24 reported positive associations, 9 negative associations, 2 non-linear associations, and 2 inverse associations, and 8 reported no associations found between PFAS and all diabetes search terms. Cumulatively, these data indicate the need for further studies to better assess these associations between PFAS exposure and diabetes.

Exposome and foetoplacental vascular dysfunction in gestational diabetes mellitus

A balanced communication between the mother, placenta and foetus is crucial to reach a successful pregnancy. Several windows of exposure to environmental toxins are present during pregnancy. When the women metabolic status is affected by a disease or environmental toxin, the foetus is impacted and may result in altered development and growth. Gestational diabetes mellitus (GDM) is a disease of pregnancy characterised by abnormal glucose metabolism affecting the mother and foetus. This disease of pregnancy associates with postnatal consequences for the child and the mother. The whole endogenous and exogenous environmental factors is defined as the exposome. Endogenous insults conform to the endo-exposome, and disruptors contained in the immediate environment are the ecto-exposome. Some components of the endo-exposome, such as Selenium, vitamins D and B₁₂, adenosine, and a high-fat diet, and ecto-exposome, such as the heavy metals Arsenic, Mercury, Lead and Copper, and per- and polyfluoroakyl substances, result in adverse pregnancies, including an elevated risk of GDM or gestational diabesity. The impact of the exposome on the human placenta's vascular physiology and function in GDM and gestational diabesity is reviewed.

Early-life associations between per- and polyfluoroalkyl substances and serum lipids in a longitudinal birth cohort

BACKGROUND

Exposures to per- and polyfluoroalkyl substances (PFASs) may affect metabolic outcomes, including lipid concentrations in the blood. However, few studies have evaluated potential associations between PFASs and lipids longitudinally.

OBJECTIVES

We estimated associations between PFAS and lipid concentrations at birth and at several points in childhood.

METHODS

We measured concentrations of five major PFASs in cord serum and in serum collected at 18 months, five years and nine years in 490 children from a prospective cohort in the Faroe Islands. Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) concentrations were measured at birth, 18 months and nine years. We estimated associations between PFAS and lipid concentrations and evaluated possible effect modification by sex. We also tested whether PFAS associations with age-nine lipids varied by exposure period.

RESULTS

Serum PFAS concentrations at ages five and nine were positively associated with lipid concentrations at age nine. Cross-sectional associations between PFASs and lipids at age nine were the strongest, with increases in serum concentrations of perfluorodecanoic acid (PFDA), perfluorononanoic acid (PFNA) and perfluorooctanesulfonic acid (PFOS) associated with increases in TC, HDL-C and LDL-C. We found statistically significant differences in estimated PFAS effects by sex, where girls had stronger positive associations between PFASs and TC and LDL-C and boys had stronger positive associations with HDL-C. In repeated measure models, exposure period was a significant modifier of PFAS effects.

CONCLUSIONS

Our findings suggest that childhood PFAS exposures may be associated with elevated serum lipid concentrations. This is a public health concern, as a detrimental lipid profile in childhood is a risk factor for later development of hyperlipidemia and cardiovascular disease.

A Comprehensive Non-targeted Analysis Study of the Prenatal Exposome

Recent technological advances in mass spectrometry have enabled us to screen biological samples for a very broad spectrum of chemical compounds allowing us to more comprehensively characterize the human exposome in critical periods of development. The goal of this study was three-fold: (1) to analyze 590 matched maternal and cord blood samples (total 295 pairs) using non-targeted analysis (NTA); (2) to examine the differences in chemical abundance between maternal and cord blood samples; and (3) to examine the associations between exogenous chemicals and endogenous metabolites. We analyzed all samples with high-resolution mass spectrometry using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) in both positive and negative electrospray ionization modes (ESI+ and ESI-) and in soft ionization (MS) and fragmentation (MS/MS) modes for prioritized features. We confirmed 19 unique compounds with analytical standards, we tentatively identified 73 compounds with MS/MS spectra matching, and we annotated 98 compounds using an annotation algorithm. We observed 103 significant associations in maternal and 128 in cord samples between compounds annotated as endogenous and compounds annotated as exogenous. An example of these relationships was an association between three poly and perfluoroalkyl substances (PFASs) and endogenous fatty acids in both the maternal and cord samples indicating potential interactions between PFASs and fatty acid regulating proteins.

Yale School of Public Health Symposium: An overview of the challenges and opportunities associated with per- and polyfluoroalkyl substances (PFAS)

On December 13, 2019, the Yale School of Public Health hosted a symposium titled "Per- and Polyfluoroalkyl Substances (PFAS): Challenges and Opportunities" in New Haven, Connecticut. The meeting focused on the current state of the science on these chemicals, highlighted the challenges unique to PFAS, and explored promising opportunities for addressing them. It brought together participants from Yale University, the National Institute of Environmental Health Sciences, the University of Massachusetts Amherst, the University of Connecticut, the Connecticut Agricultural Experiment Station, the Connecticut Departments of Public Health and Energy and Environmental Protection, and the public and private sectors. Presentations during the symposium centered around several primary themes. The first reviewed the current state of the science on the health effects associated with PFAS exposure and noted key areas that warranted future research. As research in this field relies on specialized laboratory analyses, the second theme considered commercially available methods for PFAS analysis as well as several emerging analytical approaches that support health studies and facilitate the investigation of a broader range of PFAS. Since mitigation of PFAS exposure requires prevention and cleanup of contamination, the third theme highlighted new nanotechnology-enabled PFAS remediation technologies and explored the potential of green chemistry to develop safer alternatives to PFAS. The fourth theme covered collaborative efforts to assess the vulnerability of in-state private wells and small public water supplies to PFAS contamination by adjacent landfills, and the fifth focused on strategies that promote successful community engagement. This symposium supported a unique interdisciplinary coalition established during the development of Connecticut's PFAS Action Plan, and discussions occurring throughout the symposium revealed opportunities for collaborations among Connecticut scientists, state and local officials, and community advocates. In doing so, it bolstered the State of Connecticut's efforts to implement the ambitious initiatives that its PFAS Action Plan recommends.

Placental Transfer and Composition of Perfluoroalkyl Substances (PFASs): A Korean Birth Panel of Parent-Infant Triads

Exposure to perfluoroalkyl substances (PFASs) is of public concern due to their persistent exposure and adverse health effects. Placental transfer of PFASs is an important excretion pathway of these chemicals in pregnant women and exposure route in fetuses. We measured PFAS concentrations in maternal, paternal, and umbilical cord serum collected from 62 pregnant Korean women and matched biological fathers of the fetuses. Placental transfer rates (cord to maternal serum ratio) of PFASs were also calculated. Demographics and pregnancy-related factors determining the placental transfer rates were identified using linear regression models. Maternal, paternal, and cord serum showed different PFASs compositions. Among the PFASs, perfluorooctane sulfonate (PFOS) showed the highest concentrations in maternal and paternal serum, while perfluorooctanoic acid (PFOA) showed the highest concentration in cord serum. There was a higher proportion of perfluoroalkyl carboxylic acids (PFCAs) with 9–12 carbon chains than those with 13–14 carbon chains in maternal and paternal serum, but this proportion was in the opposite direction in cord serum. PFOA and perfluorohexane sulfonate (PFHxS) had higher placental transfer rates (means of 0.32 and 0.36, respectively) than PFOS (mean of 0.12), which is in line with the results of previous studies. Gestational age and birth weight were positively associated with placental transfer rate of PFOA, PFHxS, and PFOS, while pre-pregnant BMI and weight were inversely associated with PFOS. This study showed that placental transfer of PFASs differs by compounds and is associated with pregnancy-related factors. Further studies on novel PFASs are warranted for Korean pregnant women.

A pathway level analysis of PFAS exposure and risk of gestational diabetes mellitus

Per- and polyfluoroalkyl substances (PFAS) have been found to be associated with gestational diabetes mellitus (GDM) development, a maternal health disorder in pregnancy with negative effects that can extend beyond pregnancy. Studies that report on this association are difficult to summarize due to weak associations and wide confidence intervals. One way to advance this field is to sharpen the biologic theory on a causal pathway behind this association, and to measure it directly by way of molecular biomarkers. The aim of this review is to summarize the literature that supports a novel pathway between PFAS exposure and GDM development. Epidemiological studies demonstrate a clear association of biomarkers of thyroid hormones and glucose metabolism with GDM development. We report biologic plausibility and epidemiologic evidence that PFAS dysregulation of maternal thyroid hormones and thyrotropin (TSH) may disrupt glucose homeostasis, increasing the risk of GDM. Overall, epidemiological studies demonstrate that PFAS were positively associated with TSH and negatively with triiodothyronine (T3) and thyroxine (T4). PFAS were generally positively associated with glucose and insulin levels in pregnancy. We propose dysregulation of thyroid function and glucose metabolism may be a critical and missing component in the accurate estimation of PFAS on the risk of GDM.

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.

Prenatal exposure and transplacental transfer of perfluoroalkyl substance isomers in participants from the upper and lower reaches of the Yangtze River

Data on gestational exposure characteristics and transplacental transfer are quite limited for perfluoroalkyl substance (PFAS) isomers, especially those from large-scale comparative studies. To fill this gap, we examined isomers of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) in matched maternal and cord serum from Mianyang and Hangzhou, which are located in the upper and lower reaches of the Yangtze River, China, respectively. These data were compared with those from our previous study on Wuhan in the middle reach. The average ΣPFAS concentration increased from upstream to downstream (Mianyang (4.44 ng/mL) < Wuhan (9.88 ng/mL) < Hangzhou (19.72 ng/mL)) and may be related to the per capita consumption expenditure of each city. The ln-transformed PFAS concentrations showed significant differences between Mianyang and Hangzhou after adjusting confounding factors (p < 0.05). The percentages of linear PFOS and PFOA in maternal and cord serum from these cities all exceeded those in electrochemical fluorination products. The isomer profiles of PFASs in maternal and cord serum might be greatly influenced by local production processes of PFASs and residents' dietary habits. The transplacental transfer efficiencies decreased significantly with increasing concentrations in maternal serum for ΣPFAS, ΣPFOS, ΣPFOA, ΣPFHxS, n-PFOS, iso-PFOS, 4m-PFOS, 1m-PFOS, n-PFOA, n-PFHxS, and br-PFHxS (Spearman rank correlation coefficients (r) = 0.373-0.687, p < 0.01). These findings support an understanding of the regional characteristics in maternal exposure to PFASs along the Yangtze River, isomeric profiles of PFASs in these regions, and the transplacental transfer processes of PFAS isomers.

Regulating PFAS as a Chemical Class under the California Safer Consumer Products Program

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of manmade chemicals containing at least one fully fluorinated carbon atom. The widespread use, large number, and diverse chemical structures of PFAS pose challenges to any sufficiently protective regulation, emissions reduction, and remediation at contaminated sites. Regulating only a subset of PFAS has led to their replacement with other members of the class with similar hazards, that is, regrettable substitutions. Regulations that focus solely on perfluoroalkyl acids (PFAAs) are ineffective, given that nearly all other PFAS can generate PFAAs in the environment.

OBJECTIVES

In this commentary, we present the rationale adopted by the State of California's Department of Toxic Substances Control (DTSC) for regulating PFAS as a class in certain consumer products.

DISCUSSION

We at the California DTSC propose regulating certain consumer products if they contain any member of the class of PFAS because: a) all PFAS, or their degradation, reaction, or metabolism products, display at least one common hazard trait according to the California Code of Regulations, namely environmental persistence; and b) certain key PFAS that are the degradation, reaction or metabolism products, or impurities of nearly all other PFAS display additional hazard traits, including toxicity; are widespread in the environment, humans, and biota; and will continue to cause adverse impacts for as long as any PFAS continue to be used. Regulating PFAS as a class is thus logical, necessary, and forward-thinking. This technical position may be helpful to other regulatory agencies in comprehensively addressing this large class of chemicals with common hazard traits. https://doi.org/10.1289/EHP7431.

Effect of prenatal exposure to per- and polyfluoroalkyl substances on childhood allergies and common infectious diseases in children up to age 7 years: The Hokkaido study on environment and children's health

Per- and polyfluoroalkyl substances (PFAS) are widely used bio-accumulative chemicals in many industrial and household products. Experimental studies reported that exposure to PFAS results in immunotoxicity. We have previously reported that prenatal exposure to PFAS decreased the risk of allergies, while it increased the risk of infectious diseases at ages 2 and 4 years. However, it remains unclear whether the adverse effects of PFAS on allergies and infectious diseases continue until a reliable age of diagnosing allergies. This study aimed at investigating the effects of prenatal exposure to PFAS on the prevalence of allergies and infectious diseases in children up to age 7, from the Hokkaido Study. Among mother-child pairs enrolled in the Hokkaido study and followed up until the age of 7 years, 2689 participants with maternal PFAS, 1st trimester of pregnancy and 7-year-old questionnaire survey data were included in this study. Eleven PFAS in the 3rd-trimester plasma were measured using ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry. Wheeze, rhino-conjunctivitis, and eczema were defined using the International Study of Asthma and Allergies on Childhood (ISAAC) questionnaire. History childhood infectious diseases diagnosed by a doctor was assessed by a mother-reported questionnaire at child's age 7. The relative risk of childhood allergies was calculated by generalized estimating equation models. The odds ratio of an episode of infectious diseases was calculated by logistic regression analysis, adjusted for potential confounders. The prevalence of various allergies and infectious diseases was: wheeze, 11.9%; rhino-conjunctivitis, 11.3%; eczema, 21.0%; chickenpox, 61.5%; otitis media, 55.7%; pneumonia, 30.6%; and respiratory syncytial virus infection, 16.8%. Prenatal exposure to perfluorooctanoic acid, perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA) was inversely associated with rhino-conjunctivitis, while that for perfluorooctanoate (PFOA), perfluorooctane sulfonate, PFUnDA, perfluorododecanoic acid (PFDoDA), and perfluorotridecanoic acid was inversely associated with eczema. For infectious diseases, PFDA and PFDoDA were associated with increased risk of pneumonia and PFOA was associated with increased risk of RSV infection among children not having any siblings (only-one-child). Our results corroborate the hypothesis on immunosuppressive and immunomodulating effects of PFAS on allergies and infectious diseases in children. These effects observed previously at 2 and 4 years continued until the age of 7 years. However, additional studies assessing inflammatory biomarkers along with ISAAC questionnaires, doctor-diagnosed allergies, and longer follow-ups are necessary to better assess the effects of exposure to chemicals on human immune outcomes.

Perfluorooctane sulfonic acid (PFOS) exposure during pregnancy increases blood pressure and impairs vascular relaxation mechanisms in the adult offspring

Perfluorooctanesulfonate (PFOS) is a persistent environmental agent. We examined whether PFOS exposure during pregnancy alters blood pressure in male and female offspring, and if this is related to sex-specific changes in vascular mechanisms. PFOS was administered through drinking water (50 μg/mL) to pregnant Sprague-Dawley rats from gestational day 4 until delivery. PFOS-exposure decreased maternal weight gain but did not significantly alter feed and water intake in dams. The male and female pups born to PFOS mothers were smaller in weight by 29 % and 27 %, respectively. The male PFOS offspring remained smaller through adulthood, but the female PFOS offspring exhibited catch-up growth. The blood pressure at 12 and 16 weeks of age was elevated at similar magnitude in PFOS males and females than controls. Mesenteric arterial relaxation to acetylcholine was reduced in both PFOS males and females, but the extent of decrease was greater in females. Relaxation to sodium-nitroprusside was reduced in PFOS females but unaffected in PFOS males. Vascular eNOS expression was not changed, but phospho(Ser¹¹⁷⁷)-eNOS was decreased in PFOS males. In PFOS females, both total eNOS and phospho(Ser¹¹⁷⁷)-eNOS expression were reduced. In conclusion, PFOS exposure during prenatal life (1) caused low birth weight followed by catch-up growth only in females (2) lead to hypertension of similar magnitude in both males and females; (2) decreased endothelium-dependent vascular relaxation in males but suppressed both endothelium-dependent and -independent relaxation in females. The endothelial dysfunction is associated with reduced activity of eNOS in males and decreased expression and activity of eNOS in females.

Risk to human health related to the presence of perfluoroalkyl substances in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluoroalkyl substances (PFASs) in food. Based on several similar effects in animals, toxicokinetics and observed concentrations in human blood, the CONTAM Panel decided to perform the assessment for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS. These made up half of the lower bound (LB) exposure to those PFASs with available occurrence data, the remaining contribution being primarily from PFASs with short half-lives. Equal potencies were assumed for the four PFASs included in the assessment. The mean LB exposure in adolescents and adult age groups ranged from 3 to 22, the 95th percentile from 9 to 70 ng/kg body weight (bw) per week. Toddlers and 'other children' showed a twofold higher exposure. Upper bound exposure was 4- to 49-fold higher than LB levels, but the latter were considered more reliable. 'Fish meat', 'Fruit and fruit products' and 'Eggs and egg products' contributed most to the exposure. Based on available studies in animals and humans, effects on the immune system were considered the most critical for the risk assessment. From a human study, a lowest BMDL 10 of 17.5 ng/mL for the sum of the four PFASs in serum was identified for 1-year-old children. Using PBPK modelling, this serum level of 17.5 ng/mL in children was estimated to correspond to long-term maternal exposure of 0.63 ng/kg bw per day. Since accumulation over time is important, a tolerable weekly intake (TWI) of 4.4 ng/kg bw per week was established. This TWI also protects against other potential adverse effects observed in humans. Based on the estimated LB exposure, but also reported serum levels, the CONTAM Panel concluded that parts of the European population exceed this TWI, which is of concern.