Temporal trends of perfluoroalkyl concentrations in American Red Cross adult blood donors, 2000-2010

Serum concentrations of legacy, alternative, and precursor per- and polyfluoroalkyl substances: a descriptive analysis of adult female participants in the MIREC-ENDO study

BACKGROUND

Several legacy and emerging per- and polyfluoroalkyl substances (PFAS) have been regulated around the world. There is growing concern over the proliferation of alternative PFAS, as well as PFAS precursors. Biomonitoring data for PFAS are critical for assessing exposure and human health risk.

METHODS

We collected serum samples from 289 adult female participants in a 2018-2021 follow-up study of the Maternal-Infant Research on Environmental Chemicals (MIREC) Canadian pregnancy cohort. Samples were analyzed for 40 PFAS using ultra-performance liquid chromatography-tandem mass spectrometry. For those compounds with > 50% detection, as well as the sum of these compounds, we describe serum concentrations and patterns of exposure according to sociodemographic and obstetrical history characteristics.

RESULTS

17 out of 40 PFAS were detected in > 50% of samples with 7 of these detected in > 97% of samples. Median [95th percentile] concentrations (µg/L) were highest for PFOS (1.62 [4.56]), PFOA (0.69 [1.52]), PFNA (0.38 [0.81]), and PFHxS (0.33 [0.92]). Geometric mean concentrations of PFOA and PFHxS were approximately 2-fold lower among those with more children (≥ 3 vs. 1), greater number of children breastfed (≥ 3 vs. ≤ 1), longer lifetime duration of breastfeeding (> 4 years vs. ≤ 9 months), and shorter time since last pregnancy (≤ 4 years vs. > 8 years). We observed similar patterns for PFOS, PFHpS, and the sum of 17 PFAS, though the differences between groups were smaller. Concentrations of PFOA were higher among "White" participants, while concentrations of N-MeFOSE, N-EtFOSE, 7:3 FTCA, and 4:2 FTS were slightly higher among participants reporting a race or ethnicity other than "White". Concentrations of legacy, alternative, and precursor PFAS were generally similar across levels of age, education, household income, body mass index, and menopausal status.

CONCLUSIONS

We report the first Canadian biomonitoring data for several alternative and precursor PFAS. Our findings suggest that exposure to PFAS, including several emerging alternatives, may be widespread. Our results are consistent with previous studies showing that pregnancy and breastfeeding are excretion pathways for PFAS.

A comprehensive review on PFAS including survey results from the EFLM Member Societies

OBJECTIVES

Per- and polyfluoroalkyl substances (PFASs) are a large class of synthetic chemicals widely used for their unique properties. Without PFAS, many medical device and in vitro diagnostic technologies would not be able to perform their intended purposes. Potential health risks associated with exposure to PFAS influence their use in IVD applications. This paper aims to assess the current situation concerning PFAS, including regulations and legislations for their use. It is important to know what happens to (PFAS) at the end of their lives in medical laboratories.

METHODS

A survey was conducted in March 2023 to collect information on the potential emission and end-of-life of PFAS-containing medical technologies in the medical laboratories of the EFLM member societies. A series of questions were presented to the EFLM national societies and the results were documented.

RESULTS

Eight respondents participated in the survey, representing EFLM member societies in seven different countries including hospital laboratories, university laboratories, and private laboratories.

CONCLUSIONS

PFAS uses in MD and IVD are influenced by several factors, including evolving regulations, advances in technology, safety and efficacy of these substances. Advancements in analytical techniques may lead to more sensitive and precise methods for detecting and quantifying PFAS in biological samples, which can be essential for IVD applications related to biomarker analysis and disease diagnosis. Collaboration among regulatory agencies, industry, research institutions, hospitals, and laboratories on a global scale can aid in establishing harmonized guidelines and standards for the use of PFAS, ensuring consistency and safety within their applications.

Distribution of per- and polyfluoroalkyl substances in blood, serum, and urine of patients with liver cancer and associations with liver function biomarkers

Studies have shown that per- and polyfluoroalkyl substances (PFASs) may be hepatotoxic in animals or humans. However, data on clinical epidemiology are very limited. In this study, 21 PFASs were determined in patients with liver diseases, with the highest median concentrations detected in the serum sample (26.7 ng/mL), followed by blood (10.7 ng/mL) and urine (5.02 ng/mL). Higher total PFAS concentrations were found in hepatocellular carcinoma (HCC) patients compared to non-HCC patients, with significant discrepancies in serum and blood samples. Besides, significant correlations were also found among PFAS concentrations and age, gender, body mass index (BMI), and liver function biomarkers levels. For example, PFAS concentrations are significantly higher in males than in females; Several serum PFASs concentrations increase with age and BMI, while the serum perfluorohexane sulfonic acid (PFHxS) concentrations are negatively correlated with age. In addition, multiple regression models adjusted for age, gender and BMI found that increased serum perfluorobutane sulfonic acid (PFBS), perfluoroheptane sulfonic acid (PFHpS) and perfluorohexylphosphonic acid (PFHxPA) conentrations are correlated with elevated alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alpha-fetoprotein (AFP) (p < 0.05). Our results provide epidemiological support for the future study on the potential clinical hepatotoxicity of PFAS.

Perfluoroalkyl/Polyfluoroalkyl Substances: Links to Cardiovascular Disease Risk

Conservative estimates by the World Health Organization suggest that at least a quarter of global cardiovascular diseases are attributable to environmental exposures. Associations between air pollution and cardiovascular risk have garnered the most headlines and are strong, but less attention has been paid to other omnipresent toxicants in our ecosystem. Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are man-made chemicals that are extensively used in industrial and consumer products worldwide and in aqueous film-forming foam utilized in firefighting. As such, our exposure to PFAS is essentially ubiquitous. Given the long half-lives of these degradation-resistant chemicals, virtually, all people are carrying a body burden of PFAS. Health concerns related to PFAS are growing such that the National Academies of Sciences, Engineering and Medicine has recommended standards for clinical follow-up of individuals with high PFAS blood levels, including prioritizing screening for dyslipidemia. The link between PFAS and dyslipidemia has been extensively investigated, and evidence for associations is compelling. However, dyslipidemia is not the only cardiovascular risk factor with which PFAS is associated. Here, we review the epidemiological evidence for links between PFAS of concern identified by the National Academies of Sciences, Engineering and Medicine and risk factors for cardiovascular disease, including overweight/obesity, glucose intolerance, hypertension, dyslipidemia, and hyperuricemia. Moreover, we review the potential connections of PFAS with vascular disease and atherosclerosis. While observational data support associations between the National Academies of Sciences, Engineering and Medicine PFAS and selected cardiac risk factors, additional research is needed to establish causation and better understand how exposure to PFAS leads to the development of these conditions.

In-Vitro Effects of Perfluorooctanoic Acid on Human Sperm Function: What Are the Clinical Consequences?

Background: Lifestyle and environmental pollution harm male fertility. Perfluoroalkyl substances (PFAS) are bio-accumulates in the environment as well as in several human tissues, and one of the most common PFAS is perfluorooctanoic acid (PFOA). Therefore, this study aimed to evaluate the in vitro effects of PFOA with hydrophobic and waterproofing properties on motility and bio-functional sperm parameters. Methods: To accomplish this, 50 healthy men with normozoospermia and not exposed to high doses of PFAS were enrolled. Their spermatozoa were incubated for 3 h with increasing concentrations of PFOA (0, 0.01, 0.1, and 1 mM) to evaluate its effects. In particular, we evaluated the effects of PFOA on total and progressive sperm motility and, by flow cytometry, on the following bio-functional sperm parameters: degree of chromatin compactness, viability, early and late apoptosis, mitochondrial membrane potential, the degree of lipoperoxidation, and concentrations of mitochondrial superoxide anion. Results: The results showed that PFOA decreased both total and progressive sperm motility, impaired chromatin compactness, and increased sperm lipid peroxidation and mitochondrial superoxide anion levels. Conclusions: This study showed that PFOA alters several sperm parameters and thus it may play a negative role in male fertility.

Mixtures of per- and polyfluoroalkyl substances (PFAS) alter sperm methylation and long-term reprogramming of offspring liver and fat transcriptome

Male fertility has been declining worldwide especially in countries with high levels of endocrine disrupting chemicals (EDCs). Per- and polyfluorinated alkyl Substances (PFAS) have been classified as EDCs and have been linked to adverse male reproductive health. The mechanisms of these associations and their implications on offspring health remain unknown. The aims of the current study were to assess the effect of PFAS mixtures on the sperm methylome and transcriptional changes in offspring metabolic tissues (i.e., liver and fat). C57BL/6 male mice were exposed to a mixture of PFAS (PFOS, PFOA, PFNA, PFHxS, Genx; 20 µg/L each) for 18-weeks or water as a control. Genome-wide methylation was assessed on F0 epidydimal sperm using reduced representation bisulfite sequencing (RRBS) and Illumina mouse methylation array, while gene expression was assessed by bulk RNA sequencing in 8-week-old offspring derived from unexposed females. PFAS mixtures resulted in 2,861 (RRBS) and 83 (Illumina) sperm DMRs (q < 0.05). Functional enrichment revealed that PFAS-induced sperm DMRs were associated with behavior and developmental pathways in RRBS, while Illumina DMRs were related to lipid metabolism and cell signaling. Additionally, PFAS mixtures resulted in 40 and 53 differentially expressed genes (DEGs) in the liver and fat of males, and 9 and 31 DEGs in females, respectively. Functional enrichment of DEGs revealed alterations in cholesterol metabolism and mitotic cell cycle regulation in the liver and myeloid leukocyte migration in fat of male offspring, while in female offspring, erythrocyte development and carbohydrate catabolism were affected in fat. Our results demonstrate that exposure to a mixture of legacy and newly emerging PFAS chemicals in adult male mice result in aberrant sperm methylation and altered gene expression of offspring liver and fat in a sex-specific manner. These data indicate that preconception PFAS exposure in males can be transmitted to affect phenotype in the next generation.

Estimation of per- and polyfluoroalkyl substances (PFAS) half-lives in human studies: a systematic review and meta-analysis

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) constitute a heterogeneous group of synthetic compounds widely used in industrial applications. The estimation of PFAS half-life (t1/2) is essential to quantify their persistence, their toxicity and mechanism of action in humans.

OBJECTIVES

The purpose of this review is to summarize the evidence on PFAS half-lives in humans from the available literature, and to investigate the limitations and uncertainties characterizing half-life estimation.

METHODS

The search was conducted on PubMed, Scopus, and Embase databases up to July 03, 2023 and was aimed at identifying all papers that estimated PFAS half-life in human populations. We excluded studies on temporal trends or providing estimates of half-life based solely on renal clearance. As persistent and ongoing exposures can influence half-life estimation, we decided to include only studies that were conducted after the main source of exposure to PFAS had ceased. A random-effects meta-analysis was conducted on studies that reported perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) or perfluorohexanesulfonic acid (PFHxS) half-life estimation. Risk of bias was evaluated using the OHAT tool.

RESULTS

A total of 13 articles were included in the review, with 5 studies conducted in exposed general populations and 8 studies conducted in exposed workers; the estimated mean half-life ranged from 1.48 to 5.1 years for PFOA, from 3.4 to 5.7 years for total PFOS, and from 2.84 to 8.5 years for PFHxS. High heterogeneity among studies was observed; potential reasons include the variability among the investigated populations, discrepancies in considering ongoing exposures, variability in PFAS isomeric compositions, accounting for background exposure, time since exposure stopped and methods used for half-life estimation.

DISCUSSION

Despite the efforts made to better understand PFAS toxicokinetics, further studies are needed to identify important characteristics of these persistent chemicals. Biomonitoring studies should focus on persistent and unaccounted sources of exposure to PFAS and on individual characteristics potentially determining half-life, to ensure accurate estimates.

Evaluating the association between longitudinal exposure to a PFAS mixture and adolescent cardiometabolic risk in the HOME Study

Background

Exposure to per- and polyfluoroalkyl substances (PFAS) throughout gestation and childhood may impact cardiometabolic risk.

Methods

In 179 HOME Study participants (Cincinnati, OH; recruited 2003-2006), we used latent profile analysis to identify two distinct patterns of PFAS exposure from serum concentrations of four PFAS measured at birth and ages 3, 8, and 12 years. We assessed the homeostatic model of insulin resistance, triglycerides-to-high-density lipoprotein cholesterol ratio, leptin-to-adiponectin ratio, systolic blood pressure, visceral fat, and hemoglobin A1c levels at age 12 years. We used multivariable linear regression to assess the association of membership in the longitudinal PFAS mixture exposure group with a summary measure of overall cardiometabolic risk and individual components.

Results

One PFAS exposure profile (n = 66, 39%) had higher geometric means of all PFAS across all visits than the other. Although adjusted associations were null in the full sample, child sex modified the association of longitudinal PFAS mixture exposure group with overall cardiometabolic risk, leptin-to-adiponectin ratio, systolic blood pressure, and visceral fat (interaction term P values: 0.02-0.08). Females in the higher exposure group had higher cardiometabolic risk scores (ß = 0.43; 95% CI = -0.08, 0.94), systolic blood pressures (ß = 0.6; 95% CI = 0.1, 1.1), and visceral fat (ß = 0.44; 95% CI = -0.13, 1.01); males had lower cardiometabolic risk scores (ß = -0.52; 95% CI = -1.06, -0.06), leptin-to-adiponectin ratios (ß = -0.7; 95% CI = -1.29, -0.1), systolic blood pressures (ß = -0.14; 95% CI = -0.7, 0.41), and visceral fat (ß = -0.52; 95% CI = -0.84, -0.19).

Conclusions

Exposure to this PFAS mixture throughout childhood may have sex-specific effects on adolescent cardiometabolic risk.

Maternal co-exposure to mercury and perfluoroalkyl acid isomers and their associations with child neurodevelopment in a Canadian birth cohort

BACKGROUND

Perfluoroalkyl acids (PFAAs) within the broader class of per- and polyfluoroalkyl substances (PFAS) are present in human serum as isomer mixtures, but epidemiological studies have yet to address isomer-specific associations with child development and behavior.

OBJECTIVES

To examine associations between prenatal exposure to 25 PFAAs, including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) isomers, and child neurodevelopment among 490 mother-child pairs in a prospective Canadian birth cohort, the Alberta Pregnancy Outcomes and Nutrition (APrON) study. To consider the influence of a classic neurotoxicant, total mercury (THg), based on its likelihood of co-exposure with PFAAs from common dietary sources.

METHODS

Maternal blood samples were collected in the second trimester and child neurodevelopment was assessed at 2 years of age using the Bayley Scales of Infant and Toddler Development, 3rd Edition (Bayley-III). Linear or curvilinear multiple regression models were used to examine associations between exposures and neurodevelopment outcomes.

RESULTS

Select PFAAs were associated with lower Cognitive composite scores, including perfluoroheptanoate (PFHpA) (β = -0.88, 95% confidence interval (CI): -1.7, -0.06) and perfluorododecanoate (PFDoA) (β = -2.0, 95% CI: -3.9, -0.01). Non-linear relationships revealed associations of total PFOS (β = -4.4, 95% CI: -8.3, -0.43), and linear-PFOS (β = -4.0, 95% CI: -7.5, -0.57) and 1m-PFOS (β = -1.8, 95% CI: -3.3, -0.24) isomers with lower Language composite scores. Although there was no effect modification, including THg interaction terms in PFAA models revealed negative associations between perfluorononanoate (PFNA) and Motor (β = -3.3, 95% CI: -6.2, -0.33) and Social-Emotional (β = -3.0, 95% CI: -5.6, -0.40) composite scores.

DISCUSSION

These findings reinforce previous reports of adverse effects of maternal PFAA exposure during pregnancy on child neurodevelopment. The unique hazards posed from isomers of PFOS justify isomer-specific analysis in future studies. To control for possible confounding, mercury co-exposure may be considered in studies of PFAAs.

Early life exposure to low-dose perfluorooctane sulfonate disturbs gut barrier homeostasis and increases the risk of intestinal inflammation in offspring

Perfluorooctane sulfonate (PFOS), one of the legacy per- and poly-fluoroalkyl substances (PFAS), is associated with multiple adverse health effects on children. However, much remains to be known about its potential impacts on intestinal immune homeostasis during early life. Our study found that PFOS exposure during pregnancy in rats significantly increased the maternal serum levels of interleukin-6 (IL-6) and zonulin, a gut permeability biomarker, and decreased gene expressions of Tight junction protein 1 (Tjp1) and Claudin-4 (Cldn4), the tight junction proteins, in maternal colons on gestation day 20 (GD20). Being exposed to PFOS during pregnancy and lactation in rats significantly decreased the body weight of pups and increased the offspring's serum levels of IL-6 and tumor necrosis factor-α (TNF-α) on postnatal day 14 (PND14), and induced a disrupted gut tight junction, manifested by decreased expressions of Tjp1 in pup's colons on PND14 and increased pup's serum concentrations of zonulin on PND28. By integrating high-throughput 16S rRNA sequencing and metabolomics, we demonstrated that early-life PFOS exposure altered the diversity and composition of gut microbiota that were correlated with the changed metabolites in serum. The altered blood metabolome was associated with increased proinflammatory cytokines in offspring. These changes and correlations were divergent at each developmental stage, and pathways underlying immune homeostasis imbalance were significantly enriched in the PFOS-exposed gut. Our findings provide new evidence for the developmental toxicity of PFOS and its underlying mechanism and explain in part the epidemiological observation of its immunotoxicity.

Effects of exposure to per- and polyfluoroalkyl substances on vaccine antibodies: A systematic review and meta-analysis based on epidemiological studies

Vaccines are essential for children to defend against infection. Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants with the characteristics of persistence and bioaccumulation. PFAS exposure can affect the function of the nervous, endocrine, and immune system of animals and humans. We aimed to conduct a systematic review and meta-analysis of the epidemiological studies investigating potential relationships between PFAS exposure and vaccine antibody levels, and assessed whether PFAS would affect vaccine response in healthy children. A literature search was conducted in PubMed, Web of Science, and Scopus databases up to February 2022. We chose studies that measured serum vaccines antibodies and PFAS concentrations of the participants. Essential information, including mean difference of percentage change, regression coefficient, odds ratio, Spearman correlation coefficient, and 95% confidence intervals, were extracted from the selected studies to conduct descriptive analysis and meta-analysis where appropriate. The qualities of these studies were evaluated as well. Finally, nine epidemiological studies about children met our inclusion criteria. A high degree of heterogeneity is observed in terms of breastfeeding time, confounder control, and detection method. Exposure to perfluorooctanoic acid and perfluorohexane sulfonic acid is negatively associated with tetanus antibody level in children without heterogeneity by Cochran's Q test (p = 0.26; p = 0.55), and exposure to perfluorohexane sulfonate is negatively associated with tetanus antibody level but with heterogeneity (p = 0.04). This comprehensive review suggests that PFAS can have adverse health effects on children by hindering the production of vaccine antibodies. There are some consistent and negative associations between children exposure to certain PFAS and tetanus antibody level. The association of the other four vaccines (measles, rubella, mumps, and influenza) with PFAS remains uncertain, because very few studies are available. Further studies are needed to validate the possible associations.

Per-/polyfluoroalkyl substance concentrations in human serum and their associations with immune markers of rheumatoid arthritis

Per-/polyfluoroalkyl substances (PFASs) are ubiquitous in the environment and have been proved to be immunotoxic to humans. However, it remains unclear whether exposure to PFASs affects the risk of rheumatoid arthritis (RA). In this study, nine PFASs were determined in human serum collected from 280 health populations and 294 RA patients in a cohort enrolled between 2018 and 2020 in Hangzhou, China, and were examined their correlations with immune marker levels. Perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) were the predominant PFASs in human serum, with median (mean) concentrations of 5.4 (7.6), 2.8 (3.5), and 1.9 (2.5) ng/mL, respectively. Serum PFOA and 6:2 Cl-PFESA concentrations were positively correlated with anti-cyclic citrullinated peptide antibody (ACPA) (β_PFOA = 0.59, 95% confidence interval (CI): 0.37, 0.81; β_{6:2 Cl-PFESA} = 0.48, 95% CI: 0.29, 0.66), immunoglobulin G (β_PFOA = 0.25, 95% CI: 0.21, 0.29; β_{6:2 Cl-PFESA} = 0.16, 95% CI: 0.12, 0.19) as well as rheumatoid factors (RF) (β_PFOA = 0.57, 95% CI: 0.34, 0.80; β_{6:2 Cl-PFESA} = 0.54, 95% CI: 0.36, 0.72). The correlations between serum PFOS levels and RF (β = 0.52, 95% CI: 0.28, 0.77), ACPA (β = 0.48, 95% CI: 0.23, 0.73), as well as immunoglobulin M (β = -0.24, 95% CI: 0.64, 0.15) respectively were statistically stronger. We also found PFOA concentrations in serum were associated with the level of C-reactive protein (β = 0.52, 95% CI: 0.40, 0.65). To our knowledge, this is the first study reporting significant associations between several PFASs and change of specific immune marker levels, suggesting that PFAS exposure may increase the risk of RA in adults.

The relationship between multiple perfluoroalkyl substances and cardiorespiratory fitness in male adolescents

Exposure to perfluoroalkyl substances (PFASs) is associated with a number of adverse health outcomes. However, the relationship between mixed and individual PFAS exposure and cardiorespiratory fitness (CRF) in adolescents remains unclear. We used cross-sectional data from 491 teenagers (aged 13-19 years) from the 2003-2004 National Health and Nutrition Examination Survey (NHANES) and examined the association between mixed PFAS exposure and CRF via weighted quantile sum (WQS) regression. Maximal oxygen consumption (VO₂max) was used to evaluate CRF. Multivariate linear regression was performed to investigate the relationship between each PFAS and VO₂max as well as the relationship between PFAS exposure and the inflammation parameters and blood lipid content. Mediation analyses were performed to investigate possible explanations of the risk of low CRF due to PFAS exposure. The results showed that for males, mixed PFAS exposure was negatively related to VO₂max (beta =  - 0.80, 95% CI: - 1.53 to - 0.10, P = 0.028) and that of the PFASs, perfluorononanoic acid (PFNA) had the greatest influence on VO₂max. In the individual PFAS analysis, PFNA was negatively related to VO₂max in male adolescents (beta =  - 1.49, 95% CI: - 2.65 to - 0.32, P = 0.013). Additionally, significant relationships among serum PFNA levels and total cholesterol and the white blood cell (WBC) count were found. Mediation analyses revealed that WBC count accounted for 24.18% of the variation between PFNA level and CRF. The present results provide epidemiological evidence that exposure to PFASs, mainly PFNA, is negatively associated with CRF, possibly via alterations in WBC count.

Formation and fate of perfluoroalkyl acids (PFAAs) in a laboratory-scale urban wastewater system

The fate and formation of perfluoroalkyl acids (PFAAs) have been investigated during wastewater treatment processes but studies for the entire urban wastewater system comprising the sewage transport and wastewater and sludge treatment processes are scarce. This work performs an integrated assessment of the formation and fate of PFAAs in the urban wastewater system together with their behavior in separate components of the system. To achieve this, PFAAs were monitored over five weeks in a laboratory-scale urban wastewater system comprising sewer reactors, a wastewater treatment reactor, and an anaerobic sludge digester. The system was fed with real domestic wastewater. The total mass of 11 PFAAs flowing out of the laboratory wastewater system significantly (p < 0.05) increased by 112 ± 14 (mean ± standard error)% compared to that entering the system. Formation of PFAAs was observed in all three biological processes of the system. In anaerobic sewer process, perfluoropentanoic acid (PFPeA), perfluoroheptanoic acid (PFHpA), and perfluorooctane sulfonate (PFOS) exhibited significant formation (p < 0.05) with the mass flow increased by 79 ± 24%, 109 ± 31%, and 57 ± 17%, respectively. During the wastewater treatment process, perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), and perfluorododecanoic acid (PFDoDA) demonstrated significant increase (p < 0.05) in their mass flows by 176 ± 56%, 92 ± 21%, and 516 ± 184%, respectively. In contrast, only PFHxA was found to significantly (p < 0.05) increase by 130 ± 40% during anaerobic digestion process. The total mass of 11 PFAAs discharged through the effluent (201 ± 24 ng day^-1) was 5 times higher than that through the digested sludge (29 ± 6 ng day^-1).

Associations between exposure to perfluoroalkyl substances and birth outcomes: A meta-analysis

Although previous meta-analyses have shown that prenatal PFASs exposure is associated with reduction in birth weight, effects of prenatal PFASs exposure on birth outcomes have not been fully explored. We conducted a meta-analysis of 23 eligible studies searched from Embase, PubMed, and Web of Science before March 21, 2021 to analyze the association between prenatal PFASs exposure and birth outcomes, including premature birth (PTB), low birth weight (LBW), small for gestational age (SGA) and miscarriage. Odds ratio (OR) and corresponding confidence intervals were extracted for analysis. According to the heterogeneity of the included studies, fixed-effects (I² ≤ 50%) and random-effects (I² > 50%) models were applied respectively. The significant associations between PFOS and PTB (pooled OR = 1.54, 95% CI: 1.20-1.98), PFOA and miscarriage (pooled OR = 1.40, 95% CI: 1.15-1.70), and PFOS and LBW (pooled OR = 1.52, 95% CI: 1.19-1.94) were obtained. There were differences between included studies with different study regions, sampling time, and samples type used for PFASs assessment. These findings may provide insight in risk assessment and decision-making in producing products that contain PFASs.

Exposure to perfluoroalkyl substances in waste recycling workers: Distributions in paired human serum and urine

Occupational exposure to per- and polyfluoroalkyl substances (PFASs) is an emerging public health concern, because of their potential adverse health effects. In this study, concentrations of 21 legacy and alternative PFASs in paired serum and urine samples collected from 163 workers (from five waste recycling plants) were analyzed. The results showed that the average concentration of 21 PFASs in urine samples (66.6 ng mL^-1) were higher than in serum (31.3 ng mL^-1). Concentrations of perfluorocarboxylates (PFCAs) in urine were also considerably higher than perfluorosulfonates (PFSAs), especially for short-chain PFCAs. Demographic factors (such as sex, age, working age, and job assignment) on PFAS exposure were also assessed based on the obtained results. PFAS concentrations in serum samples from males were significantly higher than in females, and working age was positively (p < 0.05) associated with most PFAS serum levels. Higher levels of PFAS were found in sorters than in workers with other job assignments, such as managers, suggesting that sorters may be directly exposed to PFASs. Interestingly, perfluorophosphonates (PFPAs) were first to be detected in human urine with >80% detection frequency. The average level of three PFPAs in the serum (7.58 ng mL^-1) and urine (1.45 ng mL^-1) samples appeared to be higher in comparison with most PFCAs and PFSAs. Thus, the toxicity of PFPAs in human beings needs to be further studied.

Association between the total plasma isomers of per- and polyfluoroalkyl substances and erythrograms in young and middle-aged Taiwanese populations

PURPOSE

Per- and polyfluoroalkyl substances (PFAS) are human-made chemicals used in daily use products. Recent studies have shown that different perfluorooctanoic acid (PFOA) and/or perfluorooctane sulfonate (PFOS) isomers may have different biological effects. In vitro studies have also reported that PFAS exposure can alter the structure of hemoglobin (Hb). In epidemiology, however, few studies have investigated the relationship between PFAS exposure and erythrocytes. Additionally, the correlation between PFOA/PFOS isomers and full erythrograms has never been explored.

APPROACH AND RESULTS

In cohorts comprising young and middle-aged Taiwanese populations, we enrolled 1483 participants (aged between 12 and 63 years) to analyze the correlations between the plasma levels of PFOA/PFOS isomers and whole-blood erythrograms. The study comprised 868 men and 615 women with a mean age of 31.2 years. When all PFOA/PFOS isomers were entered into the multiple linear regression model, the linear PFOA (L-PFOA) levels were positively correlated with the Hb, hematocrit (HCT), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) levels while the branched PFOS (B-PFOS) levels were positively associated with the Hb, HCT, and mean corpuscular hemoglobin concentration (MCHC). The mean value of Hb was the highest (14.66 mg/dL (95% CI =14.52-14.80); P for trend <0.001) when both the L-PFOA and B-PFOS levels were above the 50th percentile.

CONCLUSIONS

The results imply that PFOA/PFOS isomers may increase the weight and volume of Hb/RBC and that L-PFOA/B-PFOS may have an additive effect on the Hb levels. However, it is also possible PFAS detected at a higher concentration may due to its binding to higher levels of Hb. Further studies are needed to investigate the effects of PFOA/PFOS isomers on RBCs in humans.

External and internal human exposure to PFOA and HFPOs around a mega fluorochemical industrial park, China: Differences and implications

Hexafluoropropylene oxide dimer and trimer acids (HFPO-DA and HFPO-TA) are used as alternatives to legacy perfluorooctanoic acid (PFOA); however, little is known about their human exposure risks. In this study, the concentrations of PFOA and HFPO were measured in major human exposure matrices and human bio-samples of local residents near a mega fluorochemical industrial park in Shandong, China, to characterize their external and internal exposures. Although HFPO-DA was detected in drinking water and indoor dust, it exhibited a considerably low bioaccumulation potential in animal-origin food and human samples (urine, hair, and serum), implying that it might be a benign alternative to PFOA. Although the estimated daily intake (EDI) of HFPO-TA was comparable to that of PFOA, its concentration in urine was higher than that of PFOA, implying that it might be eliminated faster than PFOA. A simple one-compartment pharmacokinetic model was applied to estimate the serum concentrations of the target compounds and subsequently compare them with the measured concentrations. The predicted concentration of PFOA in serum based on its concentration in urine and half-life was close to the measured value, confirming the distinct internal exposure of PFOA in the local residents. However, the measured concentrations of HFPO in serum were considerably lower than those predicted from the external EDI and urine concentrations, implying that they were eliminated faster than expected in humans. Various perfluoroalkyl substances were detected in human hair, and their compositions were similar to those in human serum, suggesting that hair is a good non-invasive indicator for long-term exposure to legacy long-chain perfluoroalkyl carboxylic acids and HFPOs. This study provided valuable information about the human exposure to legacy PFOA and HFPOs in highly impacted areas near point sources and necessitates studies on the toxicokinetics of HFPOs.

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

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

Distribution characteristics of per- and polyfluoroalkyl substances (PFASs) in human urines of acrylic fiber plant and chemical plant

Per- and polyfluoroalkyl substances (PFASs) are persistent and bioaccumulative substances that have many adverse effects on human bodies. This study investigated the PFASs distribution characteristics in urine samples of workers from an acrylic fiber plant and a chemical plant. It was found that perfluorobutanoic acid (PFBA) was the predominant PFASs both in urine samples from the chemical plant (detection frequency: 86.52%; median value: 39.01 ng/mL) and the acrylic fiber plant (detection frequency: 88.16%; median value: 44.36 ng/mL). Meanwhile, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were detected with very low frequencies and low concentrations. Furthermore, the results showed that PFASs levels in urine samples of workers from different units of the plants were quite different. PFASs concentrations of urine samples in males were higher than those in females, especially for PFBA, PFHxA, and PFDoA. The age had limited effects on the PFASs distribution in urine samples in this study, as short-chain PFASs were the dominant compounds. The correlations between PFASs concentrations in urine and gender/ages of workers were finally analyzed by Pearson correlation. The overall results may indicate that short-chain PFASs (such as: PFBA and PFBS) were becoming dominant for human exposure, especially occupational workers.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Potency Ranking of Per- and Polyfluoroalkyl Substances Using High-Throughput Transcriptomic Analysis of Human Liver Spheroids

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications of human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this study was to compare the potencies (ie, benchmark concentrations: BMCs) of PFAS in primary human liver microtissues (3D spheroids) using high-throughput transcriptional profiling. Gene expression changes were measured using TempO-seq, a templated, multiplexed RNA-sequencing platform. Spheroids were exposed for 1 or 10 days to increasing concentrations of 23 PFAS in 3 subgroups: carboxylates (PFCAs), sulfonates (PFSAs), and fluorotelomers and sulfonamides. PFCAs and PFSAs exhibited trends toward increased transcriptional potency with carbon chain-length. Specifically, longer-chain compounds (7-10 carbons) were more likely to induce changes in gene expression and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses support the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the possible health effects of PFAS and will be used to inform read-across for human health risk assessment.

Potency Ranking of Per- and Polyfluoroalkyl Substances Using High-Throughput Transcriptomic Analysis of Human Liver Spheroids

Per- and polyfluoroalkyl substances (PFAS) are some of the most prominent organic contaminants in human blood. Although the toxicological implications of human exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are well established, data on lesser-understood PFAS are limited. New approach methodologies (NAMs) that apply bioinformatic tools to high-throughput data are being increasingly considered to inform risk assessment for data-poor chemicals. The aim of this study was to compare the potencies (ie, benchmark concentrations: BMCs) of PFAS in primary human liver microtissues (3D spheroids) using high-throughput transcriptional profiling. Gene expression changes were measured using TempO-seq, a templated, multiplexed RNA-sequencing platform. Spheroids were exposed for 1 or 10 days to increasing concentrations of 23 PFAS in 3 subgroups: carboxylates (PFCAs), sulfonates (PFSAs), and fluorotelomers and sulfonamides. PFCAs and PFSAs exhibited trends toward increased transcriptional potency with carbon chain-length. Specifically, longer-chain compounds (7-10 carbons) were more likely to induce changes in gene expression and have lower transcriptional BMCs. The combined high-throughput transcriptomic and bioinformatic analyses support the capability of NAMs to efficiently assess the effects of PFAS in liver microtissues. The data enable potency ranking of PFAS for human liver cell spheroid cytotoxicity and transcriptional changes, and assessment of in vitro transcriptomic points of departure. These data improve our understanding of the possible health effects of PFAS and will be used to inform read-across for human health risk assessment.

Analytical uncertainties in a longitudinal study - A case study assessing serum levels of per- and poly-fluoroalkyl substances (PFAS)

Per- and poly-fluoroalkyl substances (PFAS) are a range of persistent organofluorine contaminants, some of which have been found to accumulate in humans and have long half-lives. In longitudinal studies, when relying on measurements obtained at different points in time, it is critical to understand the associated analytical uncertainties when interpreting the data. In this manuscript we assess precision measurements of serum PFAS analysis in a follow-up study undertaken approximately 5 years after the initial study. These measurements included intra-(n = 58) and inter-batch duplicates (n = 57), inter-batch replicates (n = 58), inter-laboratory replicates (n = 10) and a re-analysis of 120 archived serum samples from the initial study. Average coefficients of variation (CV) for perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS) and perfluorooctane sulfonate (PFOS) associated with the reanalysis of archived samples ranged from 4 to 8%, which was greater than the inter- and intra -batch duplicates (<3%), but lower than the inter-laboratory comparison (CV ≥ 10%). Multi-centre analytical capacity in studies increases the variance within the dataset and implementation of variability-measures are useful to refine and maintain comparability. Due to long PFAS half-lives, this variance is an important consideration when deciding appropriate time intervals for sample collections in longitudinal studies, to ensure the difference is greater than the analytical uncertainty.

Male fertility as a marker for health

Male reproduction is a complex biological process, and male factor infertility is increasingly recognized as a biomarker for overall male health. Emerging data suggest associations between male reproduction and medical disease (genetic, infectious, chronic comorbid conditions), psychological disease, environmental exposures, dietary habits, medications and substances of abuse, and even socioeconomic factors. There is also evidence that a diagnosis of male fertility is associated with future disease risk including cancer, metabolic disease and mortality. As such, there is a growing view that the male fertility evaluation is an opportunity to improve a man's health beyond his immediate reproductive goals, and also highlights the necessity of a multidisciplinary approach.

Increased toxicity and retention of perflourooctane sulfonate (PFOS) in humanized CYP2B6-Transgenic mice compared to Cyp2b-null mice is relieved by a high-fat diet (HFD)

PFOS is a persistent, fluorosurfactant used in multiple products. Murine Cyp2b's are induced by PFOS and high-fat diets (HFD) and therefore we hypothesized that human CYP2B6 may alleviate PFOS-induced steatosis. Cyp2b-null and hCYP2B6-Tg mice were treated with 0, 1, or 10 mg/kg/day PFOS by oral gavage for 21-days while provided a chow diet (ND) or HFD. Similar to murine Cyp2b10, CYP2B6 is inducible by PFOS. Furthermore, three ND-fed hCYP2B6-Tg females treated with 10 mg/kg/day PFOS died during the exposure period; neither Cyp2b-null nor HFD-fed mice died. hCYP2B6-Tg mice retained more PFOS in serum and liver than Cyp2b-null mice presumably causing the observed toxicity. In contrast, serum PFOS retention was reduced in the HFD-fed hCYP2B6-Tg mice; the opposite trend observed in HFD-fed Cyp2b-null mice. Hepatotoxicity biomarkers, ALT and ALP, were higher in PFOS-treated mice and repressed by a HFD. However, PFOS combined with a HFD exacerbated steatosis in all mice, especially in the hCYP2B6-Tg mice with significant disruption of key lipid metabolism genes such as Srebp1, Pparg, and Hmgcr. In conclusion, CYP2B6 is induced by PFOS but does not alleviate PFOS toxicity presumably due to increased retention. CYP2B6 protects from PFOS-mediated steatosis in ND-fed mice, but increases steatosis when co-treated with a HFD.

Perfluoroalkyl substance pollutants activate the innate immune system through the AIM2 inflammasome

Perfluoroalkyl substances (PFAS) are widely used in various manufacturing processes. Accumulation of these chemicals has adverse effects on human health, including inflammation in multiple organs, yet how PFAS are sensed by host cells, and how tissue inflammation eventually incurs, is still unclear. Here, we show that the double-stranded DNA receptor AIM2 is able to recognize perfluorooctane sulfonate (PFOS), a common form of PFAS, to trigger IL-1β secretion and pyroptosis. Mechanistically, PFOS activates the AIM2 inflammasome in a process involving mitochondrial DNA release through the Ca2+-PKC-NF-κB/JNK-BAX/BAK axis. Accordingly, Aim2-/- mice have reduced PFOS-induced inflammation, as well as tissue damage in the lungs, livers, and kidneys in both their basic condition and in an asthmatic exacerbation model. Our results thus suggest a function of AIM2 in PFOS-mediated tissue inflammation, and identify AIM2 as a major pattern recognition receptor in response to the environmental organic pollutants.

PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding

We synthesize current understanding of the magnitudes and methods for assessing human and wildlife exposures to poly- and perfluoroalkyl substances (PFAS). Most human exposure assessments have focused on 2 to 5 legacy PFAS, and wildlife assessments are typically limited to targeted PFAS (up to ~30 substances). However, shifts in chemical production are occurring rapidly, and targeted methods for detecting PFAS have not kept pace with these changes. Total fluorine measurements complemented by suspect screening using high-resolution mass spectrometry are thus emerging as essential tools for PFAS exposure assessment. Such methods enable researchers to better understand contributions from precursor compounds that degrade into terminal perfluoroalkyl acids. Available data suggest that diet is the major human exposure pathway for some PFAS, but there is large variability across populations and PFAS compounds. Additional data on total fluorine in exposure media and the fraction of unidentified organofluorine are needed. Drinking water has been established as the major exposure source in contaminated communities. As water supplies are remediated, for the general population, exposures from dust, personal care products, indoor environments, and other sources may be more important. A major challenge for exposure assessments is the lack of statistically representative population surveys. For wildlife, bioaccumulation processes differ substantially between PFAS and neutral lipophilic organic compounds, prompting a reevaluation of traditional bioaccumulation metrics. There is evidence that both phospholipids and proteins are important for the tissue partitioning and accumulation of PFAS. New mechanistic models for PFAS bioaccumulation are being developed that will assist in wildlife risk evaluations. Environ Toxicol Chem 2021;40:631-657. © 2020 SETAC.

Environmental and dietary exposure of perfluorooctanoic acid and perfluorooctanesulfonic acid in the Nakdong River, Korea

This study performed the first environmental and dietary exposure assessment to explore plant uptake of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) from agricultural soil and irrigation water in the Nakdong River delta, South Korea. Annual average concentrations of total PFOA and PFOS ranged from 0.026 to 0.112 µg L^-1 (irrigation water), and from 0.818 to 1.364 µg kg^-1 (soil), respectively. PFOA and PFOS hotspots were identified downstream of the Nakdong River and were influenced by seasonal climatic variations. The observed average biennial concentration of the sum of PFOA and PFOS decreased in irrigation water, from 0.112 µg L^-1 in 2013 to 0.026 µg L^-1 in 2015, suggests that the 2013 Persistent Organic Pollutants Control Act may have helped to reduce levels of PFAS at this location. This study calculated some of the highest plant uptake factors reported to date, with values ranging from 0.962 in green onions to < 0.004 in plums. Leafy vegetables and rice are important components of the Korean diet; these groups had the largest contribution to the estimated dietary intake of PFOA and PFOS, which was calculated at 0.449 and 0.140 ng kg _bw ^-1 day^-1, respectively. This corresponded to 66.4% for PFOA and 7.9% for PFOS of the EFSA reference dose (RfD). The dietary intake of PFOA and PFOS from crops alone did not exceed the RfD. However, when the estimated daily intake (EDI) from other sources such as tap water, meat, fish, dairy, and beverages was included in the exposure risk assessment, both of the EDIs to PFOA and PFOS exceeded the RfDs, indicating that there may be a risk to human health. This study concludes that consumption of crops might, therefore, be a significant and underappreciated pathway for human exposure to PFAS.

Pre- and post-diagnostic blood profiles of perfluoroalkyl acids in type 2 diabetes mellitus cases and controls

BACKGROUND

Studies exploring the associations between perfluoroalkyl acids (PFAAs) and type 2 diabetes mellitus (T2DM) are rather limited and have reported conflicting results. All studies to date, including prospective ones, have relied on a single blood sample to study this association. Similarly, studies investigating how T2DM status may influence the longitudinal changes in PFAA concentrations have not been previously performed. As PFAA concentrations in humans have changed considerably over the last two decades, and as individuals diagnosed with T2DM usually undergo lifestyle changes that could influence these concentrations, a single blood sample may not necessarily reflect the life-time exposure to PFAA concentrations. Hence, repeated measurements from the same individuals will extend our understanding of how PFAAs are associated with T2DM. The present study, therefore, aimed to explore associations between pre- and post-diagnostic PFAA blood profiles and T2DM and assess factors associated with longitudinal changes in PFAAs in T2DM cases and controls.

METHODS

Questionnaire data and blood samples from women participating in the Norwegian Women and Cancer study were used to conduct a nested case-control study among 46 T2DM cases matched to 85 non-diabetic controls. PFAAs were measured in blood samples collected prior to (2001/02) and after (2005/6) T2DM diagnosis. We investigated the association between PFAAs and incident and prevalent T2DM using conditional logistic regression. We assessed the longitudinal changes in PFAA concentrations within and between matched cases and controls using t-tests and linear regression models.

RESULTS

We observed no significant associations between pre-diagnostic PFAA concentrations and T2DM incidence. Similar results were observed for the post-diagnostic PFAA concentrations and T2DM prevalence. Decrease over time in PFAA concentrations were observed for PFOA and ∑PFOS concentrations, whereas increase over time were observed for PFNA, PFDA and PFUnDA concentrations. Longitudinal trends in PFAA concentrations among T2DM cases were similar to the changes observed in controls.

CONCLUSIONS

The study did not find evidence of association between PFAAs and incident or prevalent T2DM. The longitudinal changes in PFAAs concentrations were not influenced by T2DM status.

Ecological and health risk assessment of perfluorooctane sulfonate in surface and drinking water resources in China

Perfluorooctane sulfonate (PFOS) is a synthetic substance with a great number of applications. However, it persists in the environment and is potentially toxic to organisms. Although China has been the main manufacturer and consumer for PFOS, the national pollution level and potential risk of this chemical are yet to be determined. This study aimed to provide an overview of PFOS contamination in surface and drinking water across China and to assess the potential ecological and health risks. Available monitoring data for PFOS in surface and drinking water were evaluated. PFOS was found to be ubiquitous in China, but the overall level of contamination was low compared with that in other countries. The southeast coastal area of China, with major PFOS-related companies, was characterized by relatively high PFOS exposure concentrations. The most sensitive effects was screened and applied to assess the ecological risk using the joint probability curve method. The probability of exceeding the growth and development toxicity for 5% of aquatic species was 0.65% in Chinese surface waters, while the highest probability of 0.90% was in Tai Lake in east China. Considering the average daily dose (ADD) for the Chinese population, the health risk posed by PFOS through drinking water ranged from 1.31 × 10^-4 to 13.91. Besides the relatively high health risk existed in east China, most health risks in China were acceptable.

Per- and polyfluoroalkyl substances (PFASs) in blood of captive Siberian tigers in China: Occurrence and associations with biochemical parameters

Per- and polyfluoroalkyl substances (PFASs) have been ubiquitously detected in the environment and marine animals. However, little is known about these substances and their associations with health parameters in wild terrestrial mammals. In this study, we determined PFAS levels and distribution in the blood of captive Siberian tigers in Harbin, China, and evaluated potential exposure pathways by daily intake. In addition, for the first time, we explored the associations between serum PFAS concentrations and clinical parameters. Results showed that perfluorooctanoate (PFOA) was the dominant PFAS compound in blood (accounting for 64%), followed by perfluorooctanesulfonate (PFOS). In addition, 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) concentrations were also detected in blood and dietary food. Furthermore, significant positive age relationships were observed for levels of perfluoroheptanoate (PFHpA), PFOA, PFOS, and 6:2 Cl-PFESA in the blood of female tigers. Results showed that PFOA and PFOS in dietary food accounted for over 70% of total daily intake of PFASs, indicating that meat consumption is a predominant exposure pathway in tigers. We also found positive associations between higher exposure to PFASs (including PFOA, PFOS, and 6:2 Cl-PFESA) and elevated serum levels of alanine transaminase (ALT), a marker of liver damage. Thus, comprehensive health assessments of PFAS burdens in wildlife are needed.

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

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

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) and their effects on the ovary

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are found widespread in drinking water, foods, food packaging materials and other consumer products. Several PFAS have been identified as endocrine-disrupting chemicals based on their ability to interfere with normal reproductive function and hormonal signalling. Experimental models and epidemiologic studies suggest that PFAS exposures target the ovary and represent major risks for women's health.

OBJECTIVE AND RATIONALE

This review summarises human population and toxicological studies on the association between PFAS exposure and ovarian function.

SEARCH METHODS

A comprehensive review was performed by searching PubMed. Search terms included an extensive list of PFAS and health terms ranging from general keywords (e.g. ovarian, reproductive, follicle, oocyte) to specific keywords (including menarche, menstrual cycle, menopause, primary ovarian insufficiency/premature ovarian failure, steroid hormones), based on the authors' knowledge of the topic and key terms.

OUTCOMES

Clinical evidence demonstrates the presence of PFAS in follicular fluid and their ability to pass through the blood-follicle barrier. Although some studies found no evidence associating PFAS exposure with disruption in ovarian function, numerous epidemiologic studies, mostly with cross-sectional study designs, have identified associations of higher PFAS exposure with later menarche, irregular menstrual cycles, longer cycle length, earlier age of menopause and reduced levels of oestrogens and androgens. Adverse effects of PFAS on ovarian folliculogenesis and steroidogenesis have been confirmed in experimental models. Based on laboratory research findings, PFAS could diminish ovarian reserve and reduce endogenous hormone synthesis through activating peroxisome proliferator-activated receptors, disrupting gap junction intercellular communication between oocyte and granulosa cells, inducing thyroid hormone deficiency, antagonising ovarian enzyme activities involved in ovarian steroidogenesis or inhibiting kisspeptin signalling in the hypothalamus.

WIDER IMPLICATIONS

The published literature supports associations between PFAS exposure and adverse reproductive outcomes; however, the evidence remains insufficient to infer a causal relationship between PFAS exposure and ovarian disorders. Thus, more research is warranted. PFAS are of significant concern because these chemicals are ubiquitous and persistent in the environment and in humans. Moreover, susceptible groups, such as foetuses and pregnant women, may be exposed to harmful combinations of chemicals that include PFAS. However, the role environmental exposures play in reproductive disorders has received little attention by the medical community. To better understand the potential risk of PFAS on human ovarian function, additional experimental studies using PFAS doses equivalent to the exposure levels found in the general human population and mixtures of compounds are required. Prospective investigations in human populations are also warranted to ensure the temporality of PFAS exposure and health endpoints and to minimise the possibility of reverse causality.

Characterizing and Comparing Per- and Polyfluoroalkyl Substances in Commercially Available Biosolid and Organic Non-Biosolid-Based Products

There is increasing concern over the presence of per- and polyfluoroalkyl substances (PFAS) in biosolids, while sales in commercially available biosolid-based products used as soil amendments are also increasing. Here, the occurrence of 17 perfluoroalkyl acids (PFAAs) present in 13 commercially available biosolid-based products, six organic composts (manure, mushroom, peat, and untreated wood), and one food and yard waste compost were studied. The PFAA concentration ranges observed are as follows: biosolid-based products (9.0-199 μg/kg) > food and yard waste (18.5 μg/kg) > other organic products (0.1-1.1 μg/kg). Analysis of 2014, 2016, and 2018 bags produced from one product line showed a temporal decrease in the total PFAAs (181, 101, and 74 μg/kg, respectively). The total oxidizable precursor (TOP) assay revealed the presence of PFAA precursors in the biosolid-based products at much higher levels, when the soluble carbon was removed by the ENVI-Carb clean-up prior to the TOP assay. Time-of-flight mass spectrometry confirmed the presence of three sulfonamides, two fluorotelomer sulfonates, and several polyfluoroalkyl phosphate diesters. Pore-water concentrations of water-saturated products were primarily of short-chain PFAAs and increased with increasing PFAA concentrations in the products. A strong positive log-linear correlation between organic carbon (OC)-normalized PFAA partition coefficients and the number of CF_n units indicates that OC is a good predictor of PFAA release concentrations.

Temporal trends and determinants of serum concentrations of per- and polyfluoroalkyl substances among Northern California mothers with a young child, 2009-2016

BACKGROUND/OBJECTIVE

Human exposure to per- and polyfluoroalkyl substances (PFAS) has changed since the early 2000s, in part, because of the phase-out and replacement of some long-chain PFAS. Studies of PFAS exposure and its temporal changes have been limited to date mostly to adults and pregnant women. We examined temporal trends and determinants of PFAS serum concentrations among mothers with a young child who participated in the CHARGE (CHildhood Autism Risk from Genetics and Environment) case-control study.

METHODS

We quantified nine PFAS in serum samples collected from 2009 to 2016 in 450 Northern California mothers when their child was 2-5 years old. With five compounds that were detected in more than 50% of the samples, we performed multiple regression to estimate least square geometric means (LSGMs) of PFAS concentrations with adjustment for sampling year and other characteristics that may affect maternal concentrations (e.g., breastfeeding duration). We also used time-related regression coefficients to calculate percent changes over the study period.

RESULTS

LSGM concentrations of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexane sulfonate (PFHxS) decreased over the study period [percent change (95% confidence interval): -10.7% (-12.7%, -8.7%); -10.8% (-12.9%, -8.5%); -8.0% (-10.5%, -5.5%), respectively]. On the other hand, perfluorononanoate (PFNA) and perfluorodecanoate (PFDA) showed mixed time trends. Among the selected covariates, longer breastfeeding duration was associated with decreased maternal serum concentrations of PFOA, PFOS, PFHxS, PFNA and PFDA.

CONCLUSIONS

Our study demonstrated that body burden of some common long-chain PFAS among California mothers with a young child decreased over the study period and that breastfeeding appears to contribute to the elimination of PFAS in lactating mothers.

Per- and Polyfluoroalkyl Substances and Obesity, Type 2 Diabetes and Non-alcoholic Fatty Liver Disease: A Review of Epidemiologic Findings

Per- and polyfluoroalkyl substances, a group of fluoro-surfactants widely detected in the environment, wildlife and humans, have been linked to adverse health effects. A growing body of literature has addressed their effects on obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis. This review summarizes the brief historical use and chemistry of per- and polyfluoroalkyl substances, routes of human exposure, as well as the epidemiologic evidence for associations between exposure to per- and polyfluoroalkyl substances and the development of obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis. We identified 22 studies on obesity and 32 studies on diabetes, while only 1 study was found for non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis by searching PubMed for human studies. Approximately 2/3 of studies reported positive associations between per- and polyfluoroalkyl substances exposure and the prevalence of obesity and/or type 2 diabetes. Causal links between per- and polyfluoroalkyl substances and obesity, diabetes and non-alcoholic fatty liver disease/ non-alcoholic steatohepatitis, however, require further large-scale prospective cohort studies combined with mechanistic laboratory studies to better assess these associations.

Poly- and perfluoroalkyl substance concentrations in human breast milk and their associations with postnatal infant growth

Perfluoroalkyl carboxylates (PFCAs) and perfluoroalkyl sulfonates are widespread in human breast milk. However, the occurrence of chlorinated polyfluorinated ether sulfonates (Cl-PFESAs) and fluorotelomer alcohols (FTOHs) in breast milk and their effects on postnatal growth of infants through breast milk consumption are still not well known. This study characterized the occurrence of 16 poly- and perfluoroalkyl substances (PFASs) in breast milk from 174 women in Hangzhou, China and investigated the association between lactation exposure to these PFASs through breast milk consumption and the postnatal growth of infants. Our results showed that perfluorooctanoate (mean 87 pg/mL) was the predominant PFAS in breast milk, followed by perfluorohexanoate (41 pg/mL), 6:2 Cl-PFESA (28 pg/mL), and perfluorooctane sulfonate (25 pg/mL). The occurrence and levels of Cl-PFESAs in Chinese breast milk were firstly reported in the current study. The 8:2 and 10:2 FTOH were detected in half of breast milk samples, with the mean concentration of 9.0 pg/mL and 10 pg/mL, respectively. Breast milk concentrations of C₈-C₁₀ PFCAs and 6:2 Cl-PFESA were negatively correlated with infant's length gain rate. Exposed to higher levels of 8:2 FTOH were correlated with decreased infant's weight gain rate. Daily intakes of PFASs via the consumption of breast milk were calculated for infants. Overall, this study firstly demonstrated that lactation exposure to C₈-C₁₀ PFCAs, 8:2 FTOH, and 6:2 Cl-PFESA through breast milk consumption may affect the postnatal growth of infants.

The association between total serum isomers of per- and polyfluoroalkyl substances, lipid profiles, and the DNA oxidative/nitrative stress biomarkers in middle-aged Taiwanese adults

Per- and polyfluoroalkyl substances (PFAS) have been widely used in consumer products. In vitro and animal studies have demonstrated that exposure to perfluorooctanoic acid (PFOA) and/or perfluorooctane sulfonate (PFOS) increases oxidative/nitrative stress. Recent studies have also found that isomers of PFOA/PFOS may have unique biological effects on clinical parameters. However, the correlation between PFOA/PFOS isomers and markers of oxidative/nitrative stress has never been investigated in the general population. In the current study, 597 adult subjects (ages between 22 and 63 years old) were enrolled from a control group of a case-control study entitled "Work-related risk factors and coronary heart disease". We investigated the correlation between the serum isomers of PFOA/PFOS, lipid profiles, and the urine compounds 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-nitroguanine (8-NO2Gua) in these participants. There were 519 men and 78 women with a mean age of 45.8 years. Linear PFOA levels were positively correlated with serum low density lipoprotein cholesterol (LDL-C), small dense LDL, and triglyceride, and linear PFOS levels were positively correlated with LDL-C and HDL-C in multiple linear regression analyses. After controlling for potential confounders, the mean levels of 8-OHdG and 8-NO2Gua significantly increased across the quartiles of linear PFOS in multiple linear regression analyses. When both the 8-OHdG and 8-NO2Gua levels were above the 50th percentile, the odds ratio (OR) of higher levels of LDL-C (>75th percentile) with one unit increase in ln linear PFOS level was the highest (OR 3.15 (95% CI = 1.45-6.64), P = 0.003) in logistic regression models. In conclusion, serum linear PFOA/PFOS were correlated with lipid profiles, and linear PFOS was associated with urine oxidative/nitrative stress biomarkers. The positive correlation between linear PFOS and LDL-C was more marked when concentrations of urine oxidative/nitrative stress biomarkers were elevated. Further studies are needed to elucidate the causal relationships among PFAS isomers, lipid profiles, and oxidative/nitrative stress.

Prenatal exposure to 11 perfluoroalkyl substances and fetal growth: A large-scale, prospective birth cohort study

BACKGROUND

Prenatal maternal exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) has been reportedly associated with decreased birth weight. Although a majority of epidemiological studies concerning perfluoroalkyl substances (PFAS) have focused on PFOS and PFOA, epidemiological studies of PFAS with longer carbon chains are scarce. In this study, we investigated whether prenatal maternal exposure to 11 PFAS, in particular those with longer carbon chains, is associated with fetal growth.

METHODS

The study included 1985 mother-infant pairs (inclusive of preterm and post-term infants), who enrolled in a large-scale, prospective birth cohort study in any of the 37 hospitals in Hokkaido, Japan between 2003 and 2009. The concentration of 11 PFAS was measured in maternal plasma collected during the third trimester of pregnancy, using ultra-performance liquid chromatography in combination with triple quadrupole mass spectrometry. Associations between the measured PFAS values and weight, length, and head circumference of all newborns at birth were examined using multiple regression analyses with adjustment for potential confounders based on data collected from medical records, questionnaires, and those for maternal plasma samples.

RESULTS

Of the 11 PFAS analyzed, prenatal perfluorononanoic acid (PFNA) [per log10-unit: regression coefficient (β) = -96.2 g, 95% confidence intervals (95% CI), -165.3 to -27.1] and perfluorodecanoic acid (PFDA) (β = -72.2 g, 95% CI, -138.1 to -6.3) concentrations were inversely associated with birth weight. Furthermore, PFNA concentrations were inversely associated with birth length (per Log₁₀ unit: β = -0.48 cm, 95% CI; - 0.86 to -0.11). Maternal perfluorotridecanoic acid (PFTrDA) exposure showed a significant inverse association with birth weight only for female infants (per Log₁₀ unit: β = -99.8 g, 95% CI, - 193.7 to -6.0) (P for interaction = 0.04).

CONCLUSIONS

Our findings suggest that prenatal, maternal exposure to PFAS with longer carbon chains tends to be inversely associated with birth size of newborn infants, which may indicate that these commercially used compounds have an adverse effect on fetal growth.

Perfluoroalkyl substances and bone health in young men: a pilot study

PURPOSE

Perfluoroalkyl substances (PFAS) are a class of endocrine-disrupting chemicals. Toxicological studies indicate that PFAS accumulate in bone tissue and could cause alterations in bone metabolism. The primary objective of this study was to examine the association between PFAS exposure and bone status in a cohort of young men resident in a well-defined area with high PFAS environmental pollution.

METHODS

Bone status was assessed in 117 subjects aged 18-21 by quantitative ultrasound (QUS) at the heel. Subjects underwent an accurate medical visit. Socio-demographic characteristics, lifestyle, and medical histories were collected. We also verified the interaction between PFAS and hydroxyapatite by computational modelling. The organic anion-transporting peptide (OATP), the putative transporter of PFAS, was evaluated by qPCR in bone biopsies from femoral heads discarded during arthroplasty in three male subjects.

RESULTS

Exposed subjects showed significantly lower stiffness index, which resulted in lower t-score and higher prevalence of subjects at medium-high risk of fracture (23.6%) compared with controls (9.7%). Data from computational modelling suggested that PFOA exhibits a high affinity for hydroxyapatite, since the estimated change in free energy is in the order of that exhibited by bisphosphonates. Finally, we observed consistent expression of OATP1A2 gene in primary human osteoblasts.

CONCLUSIONS

This is the first study reporting increased osteoporosis risk in young men exposed to PFAS and provide preliminary information on molecular mechanisms that could explain this observation, in agreement with previous studies on animal models and humans. However, these results must be interpreted with caution given the cross-sectional study design and the small number of cases.

Longitudinal trends in perfluoroalkyl and polyfluoroalkyl substances among multiethnic midlife women from 1999 to 2011: The Study of Women's Health Across the Nation

BACKGROUND

Limited information exists regarding longitudinal trends in midlife women's exposure to perfluoroalkyl and polyfluoroalkyl substances (PFAS). Further, little is known about how patterns of exposure differ by race/ethnicity and reproductive characteristics including parity and menopause.

OBJECTIVE

We aimed to examine temporal variations in serum PFAS concentrations among midlife women from the Study of Women's Health Across the Nation.

METHODS

Serum concentrations of 11 PFAS homologues were measured in 75 White, Black and Chinese women with blood samples collected in 1999-2000, 2002-2003, 2005-2006, and 2009-2011. Rates of changes in PFAS concentrations were calculated assuming a first-order elimination model. Associations between PFAS concentrations and race/ethnicity, menstruation and parity were evaluated with linear mixed models, adjusting for age, body mass index and study site.

RESULTS

Serum concentrations of linear-chain perfluorooctanoic acid (n-PFOA), linear- and branched-chain perfluorooctane sulfonic acid (n-PFOS and sm-PFOS) decreased significantly (-6.0%, 95% CI: -8.3%, -3.6% per year for n-PFOA; -14.8%, 95% CI: -17.3%, -12.3% per year for n-PFOS; -16.9%, 95% CI: -19.1%, -14.6% per year for sm-PFOS); whereas perfluorononanoic acid (PFNA) increased (16.0%, 95% CI: 10.6%, 21.6% per year). Detection rates of perfluorodecanoic acid (PFDeA) and perfluoroundecanoic acid (PFUA) doubled. Temporal trends varied significantly by race/ethnicity. Chinese women tended to have consistently higher PFNA concentrations at each follow-up visit, compared with White and Black women. Serum PFHxS concentrations significantly decreased in White and Black women, but not in Chinese. Menstruating women consistently had lower concentrations. Parity was associated with lower concentrations at baseline but the differences between nulliparous and parous women became smaller over time.

CONCLUSIONS

Our results suggest longitudinal declines in serum concentrations of legacy PFAS and increases in serum concentrations of emerging compounds from 1999 to 2011 in midlife women. Temporal trends in PFAS concentrations are not uniform across race/ethnicity and parity groups.

Temporal Trends (1981-2013) of Per- and Polyfluoroalkyl Substances and Total Fluorine in Baltic cod (Gadus morhua)

Temporal trends from 1981 to 2013 of 28 per- and polyfluoroalkyl substances (PFASs) were investigated in liver tissue of cod (Gadus morhua) sampled near southeast Gotland, in the Baltic Sea. A total of 10 PFASs were detected, with ∑₂₈ PFAS geometric mean concentrations ranging from 6.03 to 23.9 ng/g ww. Perfluorooctane sulfonate (PFOS) was the predominant PFAS, which increased at a rate of 3.4% per year. Most long-chain perfluoroalkyl carboxylic acids increased at rates of 3.9 to 7.3% per year except for perfluorooctanoate (PFOA), which did not change significantly over time. The perfluoroalkyl acid precursors perfluorooctane sulfonamide (FOSA) and 6:2 fluorotelomer sulfonic acid were detected, of which the former (FOSA) declined at a rate of -4.4% per year, possibly reflecting its phase-out starting in 2000. An alternate time trend analysis from 2000 to 2013 produced slightly different results, with most compounds increasing at slower rates compared to the entire study period. An exception was perfluorohexane sulfonate (PFHxS), increasing at a faster rate of 3.7% measured from 2000 on, compared to the 3.0% per year measured starting from 1981. Analysis of the total fluorine content of the samples revealed large amounts of unidentified fluorine; however, its composition (organic or inorganic) remains unclear. Significant negative correlations were found between concentrations of individual PFASs (with the exception of PFOS) and liver somatic index. In addition, body length was negatively correlated with PFOA and perfluorononanoate, but positively correlated with perfluorododecanoate (PFDoDA) and FOSA. Additional studies on endocrine, immunological, and metabolic effects of PFAS in marine fish are essential to assess the environmental risk of these substances. Environ Toxicol Chem 2020;39:300-309. © 2019 SETAC.

Using Machine Learning to Classify Bioactivity for 3486 Per- and Polyfluoroalkyl Substances (PFASs) from the OECD List

A recent OECD report estimated that more than 4000 per- and polyfluorinated alkyl substances (PFASs) have been produced and used in a broad range of industrial and consumer applications. However, little is known about the potential hazards (e.g., bioactivity, bioaccumulation, and toxicity) of most PFASs. Here, we built machine-learning-based quantitative structure-activity relationship (QSAR) models to predict the bioactivity of those PFASs. By examining a number of available molecular data sets, we constructed the first PFAS-specific database that contains the bioactivity information on 1012 PFASs for 26 bioassays. On the basis of the collected PFAS data set, we trained 5 different machine learning models that cover a variety of conventional models (e.g., random forest and multitask neural network (MNN)) and advanced graph-based models (e.g., graph convolutional network). Those models were evaluated based on the validation data set. Both MNN and graph-based models demonstrated the best performance. The average of the best area-under-the-curve score for each bioassay is 0.916. For predictions on the OECD list, most of the biologically active PFASs have perfluoroalkyl chain lengths less than 12 and are categorized into fluorotelomer-related compounds and perfluoroalkyl acids and their precursors.

Per- and polyfluoroalkyl substances display structure-dependent inhibition towards UDP-glucuronosyltransferases

Per- and polyfluoroalkyl substances (PFASs) are a large group of chemicals and can be detected in environmental and human samples all over the world. Toxicity of existing and emerging PFASs will be a long-term source of concern. This study aimed to investigate structure-dependent inhibitory effects of 14 PFASs towards the activity of 11 UDP-glucuronosyltransferase (UGT) isoforms. In vitro UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was employed to determine the inhibition of PFASs towards different UGT isoforms. All the PFASs showed <75% of inhibition or stimulation effects on UGT1A3, UGT1A7, UGT1A9, UGT2B4, UGT2B7 and UGT2B17. However, PFASs showed broad inhibition on the activity of UGT1A1 and UGT1A8. The activity of UGT1A1 was inhibited by 98.8%, 98%, 79.9%, 77.1%, and 76.9% at 100 μmoL/L of perfluorodecanoic acid (PFDA), perfluorooctanesulfonic acid potassium salt (PFOS), perfluorotetradecanoic acid (PFTA), perfluorooctanoic acid (PFOA) and perfluorododecanoic acid (PFDoA), respectively. UGT1A8 was inhibited by 97.6%, 94.8%, 86.3%, 83.4% and 77.1% by PFDA, PFTA, perfluorooctadecanoic acid (PFOcDA), PFDoA and PFOS, respectively. Additionally, PFDA significantly inhibited UGT1A6 and UGT1A10 by 96.8% and 91.6%, respectively. PFDoA inhibited the activity of UGT2B15 by 88.2%. PFDA and PFOS exhibited competitive inhibition towards UGT1A1, and PFDA and PFTA showed competitive inhibition towards UGT1A8. The inhibition kinetic parameter (K_i) were 3.15, 1.73, 13.15 and 20.21 μmoL/L for PFDA-1A1, PFOS-1A1, PFDA-1A8 and PFTA-1A8, respectively. The values were calculated to be 0.3 μmoL/L and 1.3 μmoL/L for the in vivo inhibition of PFDA towards UGT1A1-and UGT1A8-catalyzed metabolism of substances, and 0.2 μmoL/L and 2.0 μmoL/L for the inhibition of PFOS towards UGT1A1 and the inhibition of PFTA towards UGT1A8, respectively. Molecular docking indicated that hydrogen bonds and hydrophobic interactions contributed to the interaction between PFASs and UGT isoforms. In conclusion, exposure to PFASs might inhibit the activity of UGTs to disturb metabolism of endogenous compounds and xenobiotics. The structure-related effects of PFASs on UGTs would be very important for risk assessment of PFASs.

Human blood-based exposure levels of persistent organic pollutant (POP) mixtures antagonise androgen receptor transactivation and translocation

INTRODUCTION

Human exposure to persistent organic pollutants (POPs) has been linked to genitourinary health-related conditions such as decreased sperm quality, hypospadias, and prostate cancer (PCa). Conventional risk assessment of POPs focuses on individual compounds. However, in real life, individuals are exposed to many compounds simultaneously. This might lead to combinatorial effects whereby the global effect of the mixture is different from the effect of the single elements or subgroups. POP mixtures may act as endocrine disruptors via the androgen receptor (AR) and potentially contribute to PCa development.

AIM

To determine the endocrine disrupting activity of a POP mixture and sub-mixtures based upon exposure levels detected in a human Scandinavian population, on AR transactivation and translocation in vitro.

MATERIALS AND METHODS

The Total POP mixture combined 29 chemicals modelled on the exposure profile of a Scandinavian population and 6 sub-mixtures: brominated (Br), chlorinated (Cl), Cl + Br, perfluorinated (PFAA), PFAA + Br, PFAA + Cl, ranging from 1/10× to 500× relative to what is found in human blood. Transactivation was measured by reporter gene assay (RGA) and translocation activity was measured by high content analysis (HCA), each using stably transfected AR model cell lines.

RESULTS

No agonist activity in terms of transactivation and translocation was detected for any POP mixtures. In the presence of testosterone the Cl + Br mixture at 100× and 500× blood level antagonised AR transactivation, whereas the PFAA mixture at blood level increased AR transactivation (P < 0.05). In the presence of testosterone the Cl and PFAA + Br mixtures at 1/10×, 1×, and 50× blood level antagonised AR translocation (P < 0.05).

CONCLUSION

Taken together, some combinations of POP mixtures can interfere with AR translocation. However, in the transactivation assay, these combinations did not affect gene transactivation. Other POP combinations were identified here as modulators of AR-induced gene transactivation without affecting AR translocation. Thus, to fully evaluate the effect of environmental toxins on AR signalling, both types of assays need to be applied.

Investigation of binding and activity of perfluoroalkyl substances to the human peroxisome proliferator-activated receptor β/δ

Previously, perfluoroalkyl substances (PFASs) have been found to be associated with many adverse effects mediated by the peroxisome proliferator-activated receptor α (PPARα) and PPARγ. Here, we found another subtype of the peroxisome proliferator-activated receptors (PPARs); the PPARβ/δ mediated pathway might also be a potential adverse outcome pathway for PFASs. We investigated the direct binding and transcriptional activity of PFASs toward human PPARβ/δ, and further revealed the structure-binding and structure-activity relationship between PFASs and PPARβ/δ. The receptor binding experiment showed that their binding potency was dependent on the carbon chain length and the terminal functional group. For twelve perfluoroalkyl carboxylic acids (PFCAs), an inverted U-shaped relationship existed between the PPARβ/δ binding potency and the carbon chain length, with perfluorododecanoc acid (C12) showing the highest binding potency. The three perfluoroalkane sulfonic acids (PFSAs) exhibited a stronger binding potency than their PFCA counterparts. The two fluorotelomer alcohols (FTOHs) showed no binding potency. In receptor transcriptional activity assays, they enhanced the PPARβ/δ transcriptional activity. Their transcriptional activity was also related to the carbon chain length and the terminal functional group. Molecular docking analysis showed the PFASs fitted into the ligand binding pocket of PPARβ/δ with a binding geometry similar to a fatty acid.

Adsorption behaviour and mechanism of the PFOS substitute OBS (sodium p-perfluorous nonenoxybenzene sulfonate) on activated carbon

Perfluorooctane sulfonate (PFOS) was listed as a persistent organic pollutant by the Stockholm Convention. As a typical alternative to PFOS, sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has recently been detected in the aquatic environment which has caused great concern. For the first time, the adsorption behaviour and mechanism of OBS on activated carbon (AC) with different physical and chemical properties were investigated. Decreasing the particle size of AC can accelerate its adsorption for OBS, while AC with too small particle size was not conducive to its adsorption capacity due to the destruction of its pore structure during the mechanical crushing process. Intra-particle diffusion had a lesser effect on the adsorption rate of AC with smaller particle size, higher hydrophilicity and larger pore size. Reactivation of AC by KOH can greatly enlarge their pore size and surface area, greatly increasing their adsorption capacities. The adsorption capacity of two kinds of R-GAC exceeded 0.35 mmol g^-1, significantly higher than that of other ACs. However, increasing the hydrophilicity of AC would decrease their adsorption capacities. Further investigation indicated that a larger pore size and smaller particle size can greatly enhance the adsorptive removal of OBS on AC in systems with other coexisting PFASs and organic matter due to the reduction of the pore-blocking effect. The spent AC can be successfully regenerated by methanol, and it can be partly regenerated by hot water and NaOH solution. The percentage of regeneration for the spent AC was 70.4% with 90°C water temperature and up to 95% when 5% NaOH was added into the regeneration solution. These findings are very important for developing efficient adsorbents for the removal of these newly emerging PFASs from wastewater and understanding their interfacial behaviour.

Neurodevelopmental and Metabolomic Responses from Prenatal Coexposure to Perfluorooctanesulfonate (PFOS) and Methylmercury (MeHg) in Sprague-Dawley Rats

Methylmercury (MeHg) and perfluorooctanesulfonate (PFOS) are major contaminants of human blood that are both common in dietary fish, thereby raising questions about their combined impact on human development. Here, pregnant Sprague-Dawley rats ingested a daily dose, from gestational day 1 through to weaning, of either 1 mg/kg bw PFOS (PFOS-only), 1 mg/kg MeHg (MeHg-only), a mixture of 0.1 mg/kg PFOS and 1 mg/kg MeHg (Low-Mix), or of 1 mg/kg of PFOS and 1 mg/kg MeHg (High-Mix). Newborns were monitored for physical milestones and reflexive developmental responses, and in juveniles the spontaneous activity, anxiety, memory, and cognition were assessed. Targeted metabolomics of 199 analytes was applied to sectioned brain regions of juvenile offspring. Newborns in the High-Mix group had decreased weight gain as well as delayed reflexes and innate behavioral responses compared to controls and individual chemical groups indicating a toxicological interaction on early development. In juveniles, cumulative mixture effects increased in a dose-dependent manner in tests of anxiety-like behavior. However, other developmental test results suggested antagonism, as PFOS-only and MeHg-only juveniles had increased hyperactivity and thigmotaxic behavior, respectively, but fewer effects in Low-Mix and High-Mix groups. Consistent with these behavioral observations, a pattern of antagonism was also observed in neurochemicals measured in rat cortex, as PFOS-only and MeHg-only juveniles had altered concentrations of metabolites (e.g., lipids, amino acids, and biogenic amines), while no changes were evident in the combined exposures. The cortical metabolites altered in PFOS-only and MeHg-only exposed groups are involved in inhibitory and excitatory neurotransmission. These proof-of-principle findings at relatively high doses indicate the potential for toxicological interaction between PFOS and MeHg, with developmental-stage specific effects. Future mixture studies at lower doses are warranted, and prospective human birth cohorts should consider possible confounding effects from PFOS and mercury exposure on neurodevelopment.