Influence of exposure to perfluoroalkyl substances (PFASs) on the Korean general population: 10-year trend and health effects

Maternal Levels of Perfluoroalkyl Substances (PFAS) during Early Pregnancy in Relation to Preeclampsia Subtypes and Biomarkers of Preeclampsia Risk

BACKGROUND

Prenatal exposure to perfluoroalkyl substances (PFAS) has been previously associated with preeclampsia, although findings are mixed with respect to the direction and magnitude of effect. To our knowledge, no studies have examined associations between PFAS and preeclampsia subtypes, which may have distinct etiologies.

OBJECTIVE

We examined associations between PFAS, any preeclampsia diagnosis, and early- and late-onset preeclampsia. In addition, we estimated associations between PFAS and the angiogenic biomarkers soluble fms-like tyrosine kinase-1 (sFLT-1) and placental growth factor (PlGF), which provide an estimate of pro- and anti-angiogenic activity within the placenta.

METHODS

This case-control study (n = 75 cases, n = 75 controls) was sampled from the LIFECODES birth cohort. Nine legacy PFAS were quantified in maternal plasma from early pregnancy (median = 10 wk) and angiogenic biomarkers were quantified in maternal plasma from four study visits (median = 10, 18, 26, and 35 wk). Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of the association between an interquartile range (IQR)-increase in PFAS and preeclampsia outcomes. Linear regression was used to estimate associations between an IQR-increase in PFAS and concentrations of angiogenic biomarkers.

RESULTS

Both perfluorodecanoic acid (OR = 1.64, 95% CI: 1.08, 2.47) and perfluorooctanesulfonic acid (OR = 1.60, 95% CI: 1.06, 2.43) were associated with higher odds of late-onset preeclampsia. Associations tended to be below the null for early-onset preeclampsia, although findings were imprecise. Few associations were noted between PFAS and angiogenic biomarkers.

DISCUSSION

Maternal PFAS concentrations were associated with higher odds of late-onset preeclampsia. Heterogeneity of preeclampsia should be considered in future studies because populations may have different distributions of disease subtypes. https://doi.org/10.1289/EHP9091.

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

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

Understanding the Impact of Perfluorinated Compounds on Cardiovascular Diseases and Their Risk Factors: A Meta-Analysis Study

Perfluorinated compounds (PFCs) are non-biodegradable synthetic chemical compounds that are widely used in manufacturing many household products. Many studies have reported the association between PFCs exposure with the risk of developing cardiovascular diseases (CVDs). However, those reports are still debatable, due to their findings. Thus, this review paper aimed to analyse the association of PFCs compound with CVDs and their risk factors in humans by systematic review and meta-analysis. Google Scholar, PubMed and ScienceDirect were searched for PFCs studies on CVDs and their risk from 2009 until present. The association of PFCs exposure with the prevalence of CVDs and their risk factors were assessed by calculating the quality criteria, odds ratios (ORs), and 95% confidence intervals (CIs). CVDs risk factors were divided into serum lipid profile (main risk factor) and other known risk factors. The meta-analysis was then used to derive a combined OR test for heterogeneity in findings between studies. Twenty-nine articles were included. Our meta-analysis indicated that PFCs exposure could be associated with CVDs (Test for overall effect: z = 2.2, p = 0.02; Test for heterogeneity: I² = 91.6%, CI = 0.92–1.58, p < 0.0001) and their risk factors (Test for overall effect: z = 4.03, p < 0.0001; Test for heterogeneity: I² = 85.8%, CI = 1.00–1.14, p < 0.0001). In serum lipids, total cholesterol levels are frequently reported associated with the exposure of PFCs. Among PFCs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) exposure increased the risk of CVDs than other types of PFCs. Although the risk of PFOA and PFOS were positively associated with CVDs and their risk factors, more observational studies shall be carried out to identify the long-term effects of these contaminants in premature CVDs development in patients.

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

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

Perfluorooctanoic acid induces liver and serum dyslipidemia in humanized PPARα mice fed an American diet

Per- and polyfluoroalkyl substances (PFAS) are pervasive in the environment resulting in nearly universal detection in people. Human serum PFAS concentrations are strongly associated with increased serum low-density lipoprotein cholesterol (LDL-C), and growing evidence suggests an association with serum triacylglycerides (TG). Here, we tested the hypothesis that perfluorooctanoic acid (PFOA) dysregulates liver and serum triacylglycerides in human peroxisome proliferator activated receptor α (hPPARα)-expressing mice fed an American diet. Mice were exposed to PFOA (3.5 mg/L) in drinking water for 6 weeks resulting in a serum concentration of 48 ± 9 μg/ml. In male and female hPPARα mice, PFOA increased total liver TG and TG substituted with saturated and monounsaturated fatty acids. Lack of expression of PPARα alone also increased total liver TG, and PFOA treatment had little effect on liver TG in PPARα null mice. In hPPARα mice, PFOA neither significantly increased nor decreased serum TG; however, there was a modest increase in TG associated with very low-density cholesterol particles in both sexes. Intriguingly, in female PPARα null mice, PFOA significantly increased serum TG, with a similar trend in males. PFOA also modified fatty acid and TG homeostasis-related gene expression in liver, in a hPPARα-dependent manner, but not in adipose. The results of our study and others reveal the importance of context (serum concentration and genotype) in determining the effect of PFOA on lipid homeostasis.

Removal of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) Using Ion-Exchange and Nonionic Resins

Despite benefits to the firefighting industry, the release of per- and polyfluoroalkyl substances (PFASs) from aqueous film-forming foam (AFFF) into aquatic systems poses significant risks to human health and other organisms. While anion-exchange technologies have proven to be effective for removing perfluoroalkyl acids (PFAAs) from water, their effectiveness for removing the diverse PFAS structures discovered in AFFF remains unknown. Here, we report on the adsorption of 75 PFASs, including 63 polyfluorinated substances, in a diluted AFFF mixture using 14 commercially available ion-exchange (IX)/nonionic resins and granular activated carbon (GAC). Results showed that anion-exchange resins (AERs) exhibited significant adsorption of PFASs compared to cation-exchange resins (CERs), nonionic resins (NIRs), and GAC regardless of the PFAS's predicted charge. Isotherm data showed that macroporous AERs have a higher PFAS adsorption capacity compared to gel-type AERs. Cross-correlation comparison of PFAS/Cl^- selectivity coefficients (K_ex) for each PFAS-AER combination showed that the hydrophobicity of the AER functional group, and polymer matrix played a dominant role in determining resin affinity for PFASs. PFAS structural characteristics also significantly affected adsorption, with increasing chain length and a net negative charge increasing the extent of adsorption. Results from this study provide guidelines for the selection of resins to adsorb a wider range of PFASs and meaningful insights for the development of quantitative models for IX treatment of AFFF-impacted water.

Exposure to perfluoroalkyl substances (PFAS) and dyslipidemia, hypertension and obesity in adolescents. The Fit Futures study

BACKGROUND

Prevalence of obesity, hypertension and dyslipidemia has been increasing in children and adolescents worldwide. Exposure to environmental pollutants may contribute to this development. Our aim was to study associations between perfluoroalkyl substances (PFAS) and dyslipidemia, hypertension and obesity in a population-based sample of adolescents.

METHODS

Serum PFAS concentrations were measured in 940 adolescents, mean age 16.4 (SD 1.3) years, from the cross-sectional Fit Futures study by the UHPLC-MS/MS method. The following endpoints were used: hypertension (systolic blood pressure over 130 mmHg and/or diastolic blood pressure over 80 mmHg); obesity (body mass index over 2 z-score, WHO charts for adolescents); dyslipidemia (total cholesterol ≥ 5.17 mmol/L, and/or LDL-cholesterol ≥ 3.36 mmol/l, and/or apolipoprotein B ≥ 1.10 g/L).

RESULTS

Perfluorooctane sulfonate (PFOS), perfluorononanoate (PFNA), perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnDA) serum concentrations were positively associated with apolipoprotein B, total- and LDL cholesterol. The highest vs. lowest quartiles of total PFAS (∑PFAS), PFNA and PFDA concentrations were positively associated with the risk of dyslipidemia: OR 2.24 (95% CI 1.10-4.54), OR 2.30 (95% CI 1.16-4.57) and 2.36 (95% CI 1.08-5.16), respectively. The highest vs. lowest quartiles of ∑PFAS, perfluorohexane sulfonate (PFHxS), PFOS, perfluorooctanoate (PFOA) concentrations were positively associated with the risk of hypertension: OR 1.91 (95% CI 1.12-3.26), OR 2.06 (95% CI 1.16-3.65), 1.86 (95% CI 1.08-3.19) and 2.08 (95% CI 1.17-3.69) respectively. PFHxS and perfluoroheptane sulfonate (PFHpS) concentrations were positively associated with obesity.

CONCLUSIONS

This cross-sectional study showed a possible link between several PFAS and dyslipidemia, hypertension and obesity in Norwegian adolescents.

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

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

First report on the sources, vertical distribution and human health risks of legacy and novel per- and polyfluoroalkyl substances in groundwater from the Loess Plateau, China

In this study, legacy and novel per and polyfluoroalkyl substances (PFASs) were measured in groundwater samples collected from the Loess Plateau of China to understand their occurrence, sources and health risks. The total concentration of PFASs ranged from 2.78 to 115 ng/L, with perfluorooctanoic acid (PFOA) as the dominant compound. Many emerging PFASs, including 6:2 fluorotelomer sulfonates (FTS), 6:2 chlorinated polyfluorinated ether sulfonic acid (Cl-PFESAs), ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA), and hexafluoropropylene oxide (HFPO) homologues were frequently detected in 96.7-100% of the samples. Multiple source apportionment analyses indicated that the PFASs in the groundwater mainly originated from industrial activities, but in rural areas, agricultural activities also contributed. The total oxidizable precursor (TOP) assay indicated that there were substantial unknown precursors of perfluoroalkyl acids (PFAAs) in the groundwater samples. The total concentration of PFASs decreased with the well depth, while the PFAA-precursors displayed contrasting vertical profile trends, which might be due to the suppressed microbial transformation in the groundwater. The potential human health risk caused by PFAS exposure via drinking groundwater in the Loess Plateau was low, except for one site that was close to the industry bases.

Health and social concerns about living in three communities affected by per- and polyfluoroalkyl substances (PFAS): A qualitative study in Australia

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) is a public health issue globally. In Australia high concentrations of PFAS have been found in environments close to sites where Aqueous Film Forming Foams (AFFF) were historically used for firefighting activities. This has resulted in significant community concern about the potential long-term health effects of these chemicals.

OBJECTIVE

We describe residents' perceptions and experiences of PFAS in three regional Australian towns where exposure has occurred.

METHODS

We conducted focus groups to generate free-flowing open discussion on PFAS in three affected communities, including some with significant numbers of First Nations Peoples. We recruited participants using a range of media outlets and postal services. Focus group transcripts were analysed thematically to identify major shared concerns using Atlas Ti.

RESULTS

One hundred and eighty residents attended fifteen focus groups that were conducted in the three communities. They included 69 First Nations People living in three communities near the town of Katherine in the Northern Territory. Study participants were concerned about potential physical health effects of exposure to PFAS, such as cancer clusters, unexplained deaths, potential exacerbation of existing health conditions, and the future health of their children. They expressed feelings of stress and anxiety about living with uncertainty related to the possible health and the socio-economic impacts of PFAS contamination in their communities.

CONCLUSION

While research has concentrated on the physical health effects of PFAS, more attention needs to be given to the immediate psychosocial impacts of living in an affected community.

Challenges and Current Status of the Biological Treatment of PFAS-Contaminated Soils

Per- and polyfluoroalkyl substances (PFAS) are Synthetic Organic Compounds (SOCs) which are of current concern as they are linked to a myriad of adverse health effects in mammals. They can be found in drinking water, rivers, groundwater, wastewater, household dust, and soils. In this review, the current challenge and status of bioremediation of PFAs in soils was examined. While several technologies to remove PFAS from soil have been developed, including adsorption, filtration, thermal treatment, chemical oxidation/reduction and soil washing, these methods are expensive, impractical for in situ treatment, use high pressures and temperatures, with most resulting in toxic waste. Biodegradation has the potential to form the basis of a cost-effective, large scale in situ remediation strategy for PFAS removal from soils. Both fungal and bacterial strains have been isolated that are capable of degrading PFAS; however, to date, information regarding the mechanisms of degradation of PFAS is limited. Through the application of new technologies in microbial ecology, such as stable isotope probing, metagenomics, transcriptomics, and metabolomics there is the potential to examine and identify the biodegradation of PFAS, a process which will underpin the development of any robust PFAS bioremediation technology.

PFAS concentration during pregnancy in relation to cardiometabolic health and birth outcomes

INTRODUCTION

Poly- and perfluoroalkyl substances (PFAS) are persistent organic pollutants with pervasive exposure and suspected associations with metabolic abnormalities and adverse pregnancy outcomes. The goal of the present study was to examine the relationship between serum-PFAS concentrations measured in late pregnancy with relevant outcomes.

METHODS

The study sample included 433 pregnant women enrolled in the Vanguard Pilot Study of the National Children's Study. Six PFAS were measured in primarily third trimester serum, as well as fasting insulin, total cholesterol, and triglycerides. The PFAS were examined in quartiles in relation to serum biomarkers, gestational age at birth and birth weight standardized for gestational age using multivariable-adjusted regression models.

RESULTS

Over 98% of the study population had detectable concentrations of four of the PFAS, and concentrations varied by race/ethnicity. Total cholesterol was positively associated with PFDA, PFNA, and PFOS, and triglycerides with PFDA, PFNA, PFOS, and PFOA, but PFAS were not associated with fasting insulin in adjusted models. Only PFNA was associated with an increased odds of birth at <37 weeks gestation. PFAS were generally not associated with birth weight, though PFHxS was associated with the first quartile of birth weight among males only.

CONCLUSIONS

This study of pregnant U.S. women supports the ubiquitous exposure to PFAS and positive associations between PFAS exposure with serum-lipid concentrations. PFAS were largely unassociated with gestational age at birth and birth weight, though PFNA was associated with preterm birth. The results support the vulnerability to PFAS exposure of pregnancy.

Serum albumin mediates the effect of multiple per- and polyfluoroalkyl substances on serum lipid levels

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are synthetically manufactured chemicals recognized to be toxic, bioaccumulative, and persistent. Previous studies on PFAS exposure and serum lipid levels have mainly focused on individual PFASs; however, the influence of multiple-PFAS exposure on the serum lipid profile remains unclear. This study was performed to evaluate the combined effects of multiple PFASs on serum lipid levels. Based on the National Health and Nutrition Examination Survey (NHANES) data (2011-2014), we first established a linear regression model to estimate the association between single-PFAS exposure and the serum lipid profile. Then, a weighted quantile sum (WQS) regression model and a Bayesian kernel machine regression (BKMR) model were used to evaluate the effects of multiple-PFAS exposure on the serum lipid profile. A mediating effect model was used to assess how albumin mediates these effects. We found that PFASs were significantly associated with the levels of serum lipids, including high-density lipoprotein (HDL), low-density lipoprotein (LDL) and total cholesterol (TC). The WQS index was significantly correlated with the levels of HDL (β: 2.03, 95% CI: 0.74-3.32, P-value = 0.002), LDL (β: 4.16, 95% CI: 1.07-7.24, P-value = 0.008) and TC (β: 6.54, 95% CI: 3.00-10.1, P-value < 0.001). In the BKMR analysis, our results demonstrated that the effect of PFASs on serum lipids increased significantly when the concentrations of the PFASs were at their 60th percentiles or above compared to those at their 50th percentile. Mediation analysis showed that albumin mediated the effects of selected PFASs on the levels of serum lipids except for triglycerides (TG). PFAS exposure was correlated with the levels of serum lipids, and this correlation was mediated by albumin. Our results suggest that a comprehensive evaluation of multi-PFAS exposure could better characterize real-life exposure compared with single-PFAS exposure.

Perfluorooctane sulfonic acid, a persistent organic pollutant, inhibits iodide accumulation by thyroid follicular cells in vitro

Poly- and perfluoroalkyl substances (PFAS) are a class of endocrine disrupting chemicals (EDCs) reported to alter thyroid function. Iodide uptake by thyroid follicular cells, an early step in the synthesis of thyroid hormones, is a potential target for thyroid disruption by EDCs. The aim of the present study was to evaluate the acute effects of perfluorooctane sulfonic acid (PFOS) and perfluorooctane carboxylic acid (PFOA), two of the most abundant PFAS in the environment, on iodide transport by thyroid follicular cells in vitro. Dynamic changes in intracellular iodide concentration were monitored by live cell imaging using YFP-H148Q/I152, a genetically encoded fluorescent iodide biosensor. PFOS, but not PFOA, acutely and reversibly inhibited iodide accumulation by FRTL-5 thyrocytes, as well as by HEK-293 cells transiently expressing the Sodium Iodide Symporter (NIS). PFOS prevented NIS-mediated iodide uptake and reduced intracellular iodide concentration in iodide-containing cells, mimicking the effect of the NIS inhibitor perchlorate. PFOS did not affect iodide efflux from thyroid cells. The results of this study suggest that disruption of iodide homeostasis in thyroid cells may be a potential mechanism for anti-thyroid health effects of PFOS. The study also confirms the utility of the YFP-H148Q/I152 cell-based assay to screen environmental PFAS, and other EDCs, for anti-thyroid activity.

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

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

Perfluoroalkyl substances (PFASs) in special management sea areas of Korea: Distribution and bioconcentration in edible fish species

Thirteen PFASs in water (n = 58), sediment (n = 58) and edible fish samples (n = 81) collected from three special management sea areas of Korea including Gwangyang bay, Masan bay and Busan harbor in July 2018 were investigated. The mean PFASs concentration in water (ng/L) were in order Masan (5.09) > Busan (2.82) > Gwangyang (1.74). PFASs levels were found as the low concentration in sediment. The greatest total PFASs concentration in each fish tissue was found as 3.04 (ng/g ww) in a Japanese amberjack fish for muscle in Busan, 66.23 (ng/mL) in Japanese amberjack fish for blood in Masan and 125.03 (ng/g ww) flathead grey mullet in Busan bay. The BCF (L/kg) of PFDoDA was found as the highest in muscle of all species with values from 30,922 (grey mullet in Gwangyang) to 69,131 (grey mullet in Busan). PFDS was the highest BCF's PFASs (110,599 L/kg) in muscle which was found in Japanese amberjack in Busan bay.

The phase out of and restrictions on per-and polyfluoroalkyl substances: Time for a rethink

Industrial manufacture boom in the past decades had resulted in the release of new chemicals to the environment. A group of manmade chemicals called per-and polyfluoroalkyl substances (PFASs) are among these chemicals that have gained traction in recent years which are used in myriad consumer and industrial products worldwide. Since some PFASs are persistent, bioaccumulative, and toxic in nature, series of programs and regulatory initiatives have been introduced to end their production; and gradually replacing them with short chain alternatives. However, concerns have been expressed in the scientific literature about the characteristics and effects of some of these short chain alternatives on environmental and living systems. Here, we suggest that professional scientific bodies should be part of the review process of alternatives short chain PFASs, owing to their immeasurable contribution to knowledge and understanding of these chemicals. Per and poly fluoroalkyl substances are understudied and poorly regulated in developing countries. Therefore, in order for these countries to contribute meaningfully to the global regulatory initiatives on PFASs, transfer of technology and capacity building must be explicitly considered, given the developed competencies, technical expertise and skills that are required for evidence-based policy development and implementation. Furthermore, the issue of transparency of the production and use of PFASs which some companies consider as confidential business information (CBI) must be closely paid attention to by regulators. Confidential business information if not properly addressed may undermine regulatory and risk reduction measures as it may limit most of the relevant information pertaining to PFASs.

Removal of COD, NH4-N, and perfluorinated compounds from wastewater treatment plant effluent using ZnO-coated activated carbon

This study investigated the removal of chemical oxygen demand (COD), NH₄-N, and perfluorinated compounds (PFCs) in the effluent from a wastewater treatment plant (WWTP) using ZnO coated activated carbon (ZnO/AC). Results suggested that the optimal dosage of the ZnO/AC was 0.8 g/L within 240 min of contact time, at which the maximum removal efficiency of COD was approximately 86.8%, while the removal efficiencies of PFOA and PFOS reached 86.5% and 82.1%. In comparison, the removal efficiencies of NH₄-N, PFBA, and PFBS were lower, at approximately 47.9%, 44.0%, and 55.4%, respectively. In addition, COD was preferentially adsorbed before PFCs and NH₄-N, when the contact time ranged from 0 to 180 min, and the order of PFCs removal showed a positive correlation with C-F chain length. The kinetic study revealed that the removal of COD, NH₄-N, and PFCs could be better depicted and predicted by the Lagergren quasi-second order dynamic model with high correlation coefficients, which involved liquid membrane diffusion, intraparticle diffusion, and photocatalytic reactions. The saturated ZnO/AC was finally regenerated using ultrasound for 3 h and retained excellent performance, which proved it could be considered as an effective and alternative technology.

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.

Efficient removal of GenX (HFPO-DA) and other perfluorinated ether acids from drinking and recycled waters using anion exchange resins

Carcinogenic GenX chemicals, heptafluoropropylene-oxide-dimer-acid (HFPO-DA), have been recently detected in surface, ground and recycled water sources worldwide. However, GenX removals under the influence of variable characteristics of the organic and inorganic compounds present in the natural water sources, have often been overlooked in scientific literature. This is critically important given that the ionic composition and characteristics of organic matter in natural waters are spatially and seasonally variable. A strongly basic anion exchange (IX) resin was used to remove GenX and two other perfluorinated ether acids (PFEAS) from natural surface and recycled water sources. Factors influencing the uptake behavior included the PFEAS concentrations, resin dosage, and background anion characteristics. The equivalent background compound was employed to evaluate the competitive uptake between natural organic matter (NOM), inorganic ions and PFEAS in natural water matrices. Experimental data were compared with different mathematical and physical models and it was depicted that approximately 4-6% of the initial NOM competed with PFEAS for active exchange sites. Further, IX was able to achieve complete PFEAS removal (C_final<10 ng/L) with simultaneous removal of>60% NOM and >80% inorganic ions. Results of this study indicate that IX exhibits great potential for PFEAS removal from natural drinking water sources.

Thyroid Disrupting Effects of Old and New Generation PFAS

Per- and polyfluoroalkyl substances (PFAS) represent a group of synthetic compounds widely used in industry plants due to their low grade of degradation, surfactant properties, thermic and flame resistance. These characteristics are useful for the industrial production, however they are also potentially dangerous for human health and for the environment. PFAS are persistent pollutants accumulating in waters and soil and recoverable in foods due to their release by food packaging. Humans are daily exposed to PFAS because these compounds are ubiquitous and, when assimilated, they are difficult to be eliminated, persisting for years both in humans and animals. Due to their persistence and potential danger to health, some old generation PFAS have been replaced by newly synthesized PFAS with the aim to use alternative compounds presumably safer for humans and the environment. Yet, the environmental pollution with PFAS remains a matter of concern worldwide and led to large-scale epidemiological studies both on plants' workers and on exposed people in the general population. In this context, strong concern emerged concerning the potential adverse effects of PFAS on the thyroid gland. Thyroid hormones play a critical role in the regulation of metabolism, and thyroid function is related to cardiovascular disease, fertility, and fetal neurodevelopment. In vitro, ex vivo data, and epidemiological studies suggested that PFASs may disrupt the thyroid hormone system in humans, with possible negative repercussions on the outcome of pregnancy and fetal-child development. However, data on the thyroid disrupting effect of PFAS remain controversial, as well as their impact on human health in different ages of life. Aim of the present paper is to review recent data on the effects of old and new generation PFAS on thyroid homeostasis. To this purpose we collected information from in vitro studies, animal models, and in vivo data on exposed workers, general population, and pregnant women.

Distribution of novel and legacy per-/polyfluoroalkyl substances in serum and its associations with two glycemic biomarkers among Chinese adult men and women with normal blood glucose levels

In recent years, the occurrence of novel per-/polyfluoroalkyl substances (PFASs) such as polyfluoroalkyl ether sulfonates (PFAESs) in human samples have aroused attention due to the change in PFASs production profile, however, the data are still lacking. Furthermore, epidemiological studies have examined the associations of PFAS exposure with glucose homeostasis, but with inconsistent results. Therefore, in this study, fasting serum samples from 252 participants with an age range from 19 to 87 years old were collected in Tianjin, China. A total of 21 target PFASs were determined to analyze the levels and distribution of novel and legacy PFASs in serum and to further evaluate the cross-sectional associations of serum PFAS concentrations with two glycemic biomarkers (i.e., fasting glucose and glycated hemoglobin (HbA1c)). 6:2 chlorinated PFAES (6:2 Cl-PFAES) and trifluoroacetic acid (TFA) were widely detected novel PFASs (greater than90%) with relatively high median concentrations (8.64 ng/mL and 8.46 ng/mL, respectively), which were second only to the two dominant legacy PFASs, i.e., perfluorooctanoic acid (PFOA, 14.83 ng/mL) and perfluorooctane sulfonic acid (14.24 ng/mL). The percentage contributions to the total known PFASs were separately 17.6% and 17.2% for 6:2 Cl-PFAES and TFA. The levels of 6:2 Cl-PFAES were significantly correlated with age and BMI, and the concentrations of TFA were also significantly correlated with age. Furthermore, 1% increase in serum PFOA and perfluorononanoic acid (PFNA) was separately significantly associated with 0.018% [95% confidence interval (CI): 0.004%, 0.033%] and 0.022% (95% CI: 0.007%, 0.037%) increment in fasting glucose levels. Similarly, 1% increase in serum perfluorohexanoic acid, PFNA, and perfluorohexane sulfonic acid was significantly associated with 0.030% (95% CI: 0.010%, 0.051%), 0.018% (95% CI: 0.003%, 0.033%), 0.007% (95% CI: 0.003%, 0.011%) increment in HbA1c levels, respectively. These findings suggested that 6:2 Cl-PFAES and TFA showed greater contributions to PFASs in serum and supported an association of exposure to PFASs with fasting glucose and HbA1c.

Isomers of per- and polyfluoroalkyl substances and uric acid in adults: Isomers of C8 Health Project in China

BACKGROUND

Greater levels of serum per- and polyfluoroalkyl substances (PFAS) are known to be associated with higher uric acid which itself leads to a number of chronic diseases. However, whether this association varies across PFAS isomers which recently have been found to be associated with human health remains unknown.

OBJECTIVES

To address this research gap, we explored isomer-specific associations between serum PFAS and uric acid in Chinese adults.

METHODS

We conducted a cross-sectional study of associations between serum PFAS isomer and serum uric acid in 1612 participants from the Isomer of C8 Health Project. We used multivariable linear and logistic regression models to analyze serum isomers of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and other PFASs as continuous and categorical predictors of uric acid, adjusted for confounders. The association was also stratified by kidney function stage based on estimated glomerular filtration rate (GF-1, GF-2, GF-3a, and GF-3b/4).

RESULTS

We found positive associations between serum PFAS isomer concentrations and uric acid. Uric acid levels were greater for each log-unit increase in branched PFOA (β = 0.30, 95% CI: 0.21, 0.40), linear PFOA (β = 0.18, 95% CI: 0.09, 0.26), branched PFOS (β = 0.09, 95% CI: 0.02, 0.17) and linear PFOS (β = 0.06, 95% CI: -0.01, 0.14) concentration. The associations between PFAS and uric acid showed an inverted 'U' shaped pattern across kidney function stages. For example, uric acid level was greater with each log-unit increase in total-PFOA among GF-1 (β = 0.21, 95% CI: 0.06, 0.37), this relationship was greater in GF-3a (β = 0.49, 95% CI: 0.09, 0.89) and decreased in GF-3b/4 (β = -0.22, 95% CI: -0.83, 0.39). We also found the odds of hyperuricemia increased linearly with increasing branched PFOA in quartiles (odds ratio = 2.67, 95% CI: 1.86, 3.85 at the highest quartile).

CONCLUSION

We report novel results in which PFAS associations with uric acid varied according to isomer and adult kidney function. Besides, our findings are consistent with previous epidemiologic studies in finding a positive association between serum PFAS concentrations and serum uric acid, especially for PFOA. Our results indicate that more research is needed to more clearly assess the impact of PFAS isomers on human health, which will help to refine regulation policies for PFAS.

Effects of environmental stressors on stem cells

Environmental toxicants are ubiquitous, and many are known to cause harmful health effects. However, much of what we know or think we know concerning the targets and long-term effects of exposure to environmental stressors is sadly lacking. Toxicant exposure may have health effects that are currently mischaracterized or at least mechanistically incompletely understood. While much of the recent excitement about stem cells (SCs) focuses on their potential as therapeutic agents, they also offer a valuable resource to give us insight into the mechanisms and risks of toxicant effects. Not only as a response to the increasing ethical pressure to reduce animal testing, SC studies allow us valuable insight into the true effects of human exposure to environmental stressors under controlled conditions. We present a review of the history of publications on the effects of environmental stressors on SCs, followed by a consolidation of the literature over the past five years on a subset of key environmental stressors of importance to human health and their effects on both embryonic and tissue SCs. The review will make constructive suggestions as to areas of toxicant research where further studies are needed, as well as making indications of the potential utility for advancing knowledge and directing research on environmental toxicology.

Evidences for replacing legacy per- and polyfluoroalkyl substances with emerging ones in Fen and Wei River basins in central and western China

Legacy per- and polyfluoroalkyl substances (PFASs), mainly long-chain ones, are being substituted by short-chain homologues and novel fluorinated alternatives, whereas their occurrence, spatial distribution, sources and substitution characteristics are not well understood. For the first time, the occurrence and replacing trend of the legacy and novel fluorinated alternatives were examined in the surface water from Fen and Wei rivers, which are the two major rivers located in the underdeveloped and ecology vulnerable areas of central and western China. Results showed that the contamination of legacy and emerging PFASs in both river basins was widespread, and mainly caused by industrial activities. In both rivers, perfluorohexane sulfonic acid (PFHxS), as a substitute for perfluorooctane sulfonic acid (PFOS), was predominant in the urban areas. In the Fen River, more substitutes of PFOS, such as 6:2 fluorotelomer sulfonate (6:2 FTS) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), were distinct, while significant replacing for PFOA with short-chain perfluoroalkyl carboxylic acids (C4-C7) and Ammonium salt of 4,8-dioxa-3H-per-fluorononanoate (ADONA) was observed in Wei River. Besides, advanced oxidation experiment indicated that there were unknown PFASs which could be the precursors of perfluorocarboxylic acids in Wei River. Isomeric analyses indicated that there was contribution of telomerization related sources for PFOA in both rivers, whereas PFOS was mainly from ECF. The estimated total mass discharge of PFASs derived from Wei and Fen River to the Yellow river were 239 and 62.6 kg/year, respectively.

Multiple crop bioaccumulation and human exposure of perfluoroalkyl substances around a mega fluorochemical industrial park, China: Implication for planting optimization and food safety

Perfluoroalkyl substances (PFASs) have become a recognized concern due to their mobility, persistence, ubiquity and health hazards in the environment. In this study, ten types of vegetables and three types of grain crops were collected in two open-air fields with different distances (0.3 km, 10 km) from a mega fluorochemical industrial park (FIP), China. Bioaccumulation characteristics of PFASs in light of crop types and organs were explored, followed by analyzing human exposure and risks to local residents with different age groups and dietary habits. Elevated levels of ∑PFASs were found nearby the FIP ranging from 79.9 ng/g to 200 ng/g in soils and from 58.8 ng/g to 8085 ng/g in crops. Perfluorooctanoic acid (PFOA) was the predominant PFAS component in soil; while shorter-chain perfluoroalkyl carboxylic acids (PFCAs), especially perfluorobutanoic acid (PFBA), were the major PFAS contaminants in multiple crops, resulting from their bioaccumulation preference. Depending on the crop types, the bioaccumulation factors (BAFs) of ∑PFASs for edible parts varied from 0.36 to 48.0, and the highest values were found in shoot vegetables compared with those in fruit vegetables, flower vegetables, root vegetables and grain crops. For typical grains, the BAFs of ∑PFASs decreased in the order of soybean (Glycine max (Linn.) Merr.), wheat (Triticum aestivum L.) and corn (Zea mays L.), possibly related to their protein and lipid content. Among specific organs in the whole plants, leaves exhibited the highest BAFs of ∑PFASs compared with corresponding roots, stems, husks or grains. With increasing carbon chain lengths of individual PFCAs (C4-C8), the logarithm of their BAFs for edible parts of various crops showed a linear decrease (0.1-1.16 log decrease per CF₂ unit), and the largest decrease was observed in grains. Human exposure to PFOA via the consumption of contaminated crops represents a health risk for local residents, especially for low-age consumers or urban consumers with higher vegetable diet. Implications for planting optimization and food safety were provided aiming to reduce health hazards of PFASs.

Dynamics of associations between perfluoroalkyl substances and uric acid across the various stages of glomerular function

National Health and Nutrition Examination Survey 2007-2014 data (N = 6844) for adults aged ≥ 20 years were analyzed to estimate associations of perfluoroalkyl substances (PFAS), namely, PFOA, PFOS, PFDA, PFHxS, and PFNA with uric acid across stages of declining glomerular function. The population was stratified by the estimated glomerular filtration rates (eGFR) stages accompanying kidney disease: GF-1 with eGFR > 90 mL/min/1.73 m²; GF-2 with eGFR 60-89 mL/min/1.73 m²; GF-3A with eGFR 45-59 mL/min/1.73 m²; and GF-3B/4 with eGFR 15-44 mL/min/1.73 m². Adjusted and unadjusted geometric means of uric acid increased from GF-1 to GF-3B/4 for males and females. Adjusted geometric means for uric acid were higher for males by 1.38, 1.03, and 0.62 mg/dL for GF-1, GF2, and GF-3 respectively but for GF-3B/4, females had higher adjusted geometric means than males by 0.16 mg/dL, revealing narrowing of sex differences in uric acid as glomerular function declines. The direction of association between PFAS and uric acid was positive for GF-1 and GF-2 for males and for every PFAS except PFDA for females. For males for GF-3B/4, association between every PFAS except PFHxS and uric acid was found to be negative (p < 0.01). For females, only PFHxS actually reverses its relationship with increasing stages of renal disease. Uric acid associations with PFAS reverse in males with advanced renal failure. An implication is that previously reported association of PFAS exposure with uric acid is not due to renal failure. Understanding of other biomarkers associated with both PFAS exposure and renal failure may benefit from similar evaluation.

Synergistic impact of co-exposures to toxic metals cadmium, lead, and mercury along with perfluoroalkyl substances on the healthy kidney function

Impact of co-exposures to toxic metals cadmium, lead, and mercury along with perfluoroalkyl substances on the healthy kidney function was evaluated among US adults aged > = 20 years by analyzing data (N = 7857) from National Health and Nutrition Examination Survey for 2003-2014. Perfluoroalkyl substances selected for analysis were: perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA). High levels of exposures to Cd, Pb, total Hg, and PFAS were said to occur if their observed levels in blood/serum were greater than 75th percentiles. A healthy kidney function was defined if estimated glomerular filtration rate was found to be > = 60 mL/min/1.73 m² and urine albumin creatinine ratio was ≤ 30 mg/g creatinine. Adjusted odds of a healthy kidney function due to co-exposures to high levels of Cd along with high levels of PFOA, PFOS, and PFNA were found to be 0.713, 0.576, and 0.640 respectively. Adjusted odds of a healthy kidney function due to co-exposures to high levels of Pb along with high levels of PFOA, and PFNA were found to be 0.657, and 0.671 respectively. Co-exposures to high levels of Hg as measured by the total mercury in blood was not found to affect the odds of a healthy kidney function.

Perfluoroalkyl acids in serum of Korean children: Occurrences, related sources, and associated health outcomes

Perfluoroalkyl acids (PFAAs) have been widely used in human environment, and their exposure among general population has been frequently reported. However, extent of PFAAs exposure and their potential effects among children are not well characterized. In this study, children of between 3 and 18 years of age (n = 150) were recruited in Seoul and Gyeonggi, Korea, and the serum levels of 16 PFAAs along with lipids and thyroid hormones were measured. Questionnaire survey was conducted for dietary and behavioral characteristics of the children. Among the measured PFAAs, PFOA, PFNA, PFHxS, and PFOS were detected in all the samples, and PFUnDA and PFDA were detected in over 75% of the samples. PFOS was detected at the highest concentration with a median of 5.68 ng/mL. PFUnDA was detected at higher levels (median of 0.652 ng/mL) compared to those reported for children in USA. Serum PFAA levels were not different by sex among the children of <10 years of age, but in older children, those of boys are significantly higher than girls. Physiological characteristics like menstruation may explain lower PFAAs levels of the girls. In addition, breastmilk consumption, fish/shellfish consumption, non-stick frying pan use, and waterproof cloth use were identified as potential sources of PFAAs exposure. Serum PFUnDA level was positively associated with total cholesterol and low-density lipoprotein level of the children. PFNA was positively associated with free T4 level. High levels of PFUnDA among children and its association with serum lipids warrant replication and confirmation in other populations and/or supports by experimental studies.

Time trends over 2003-2014 in the concentrations of selected perfluoroalkyl substances among US adults aged ≥20 years: Interpretational issues

Data (N = 9650) for US adults aged ≥20 years downloaded from National Health and Nutrition Examination Survey for 2003-2014 were analyzed to study trends in adjusted and unadjusted concentrations of selected perfluoroalkyl substances (PFAS), namely, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFDA), perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA). Over 2003-2014, unadjusted concentrations of PFOA decreased by 50%, by 75% for PFOS, by 32% for PFDA, by 27% for PFHxS, and by 30% for PFNA. Females not only had substantially lower concentrations of every PFAS than males but rate of decrease was also higher for females than males, for example, 36.7% for females and 30.6% for males every two years for PFOS. For each survey period of two years, percent decrease in adjusted concentrations was 17% for PFOA, 33.5% for PFOS, 11.5% for PFDA, 6.3% for PFHxS, and 7.6% for PFNA. However, these trend data must be examined within the context of design changes in NHANES over 2003-2014 resulting in oversampling of Hispanics other than Mexican Americans starting 2007-2008 survey cycle and oversampling of non-Hispanic Asians starting 2011-2012 survey cycle. In order to examine how design changes may have affected computations of adjusted and unadjusted concentrations, the data were analyzed using the racial/ethnic categories prior to and after oversampling of Hispanics other than Mexican Americans and non-Hispanic Asians was put into place.

Serum polyfluoroalkyl chemicals are associated with risk of cardiovascular diseases in national US population

BACKGROUND

Perfluoroalkyl chemicals (PFCs) as possible cardiovascular disrupters are universally detected in humans. However, evidence from epidemiological studies appears insufficient and ambiguous.

OBJECTIVES

We aim to examine the serum PFCs levels and their associations with the prevalence of cardiovascular diseases (CVD) and related outcomes in general US population.

METHODS

We investigated the serum levels of 12 major PFCs, including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), 2-(N-ethyl-perfluorooctane sulfonamido) acetate (EPAH), 2-(N-methyl-perfluorooctane sulfonamido) acetate (MPAH), perfluorodecanoic acid (PFDE), perfluorobutane sulfonate (PFBS), perfluoroheptanoic acid (PFHP), perfluorononanoic acid (PFNA), perfluorooctane sulfonamide (PFSA), perfluoroundecanoic acid (PFUA), and perfluorododecanoic acid (PFDO), in 10,859 participants from the National Health and Nutritional Examination Survey (NHANES) 1999-2014. Logistic regression models were used to estimate the associations between serum PFCs and 5 self-reported CVD outcomes, including congestive heart failure, coronary heart disease, angina pectoris, heart attack, and stroke. Linear regression analyses were used to estimate the PFCs and their associations with 8 traditional CVD risk factors like serum triglyceride and total cholesterol.

RESULTS

In multivariable-adjusted models, total PFCs were positively associated with total CVD (p for trend = 0.0166), independent of traditional CVD risk factors, such as smoking status, diabetes, hypertension and serum cholesterol level. Compared with reference quartile of total PFCs levels, the multivariable adjusted odds ratios in increasing quartiles were 1.23 [95% confidence interval (CI): 0.91-1.66], 1.47 (95% CI: 1.14-1.89) and 1.45 (95% CI: 1.06-1.98) for total CVD. Similar positive associations were found if considering individual PFCs including PFOS, PFUA, MPAH, EPAH, PFDO, PFSA and PFBS. In addition, serum levels of MPAH and PFDO were positively associated with congestive heart failure; PFNA, PFDE, and PFUA were positively associated with coronary heart disease; PFUA and PFDO were positively associated with angina pectoris; and PFNA was positively associated with heart attack.

CONCLUSIONS

Our findings suggested that exposure to PFCs was positively associated with risk of CVD. Further longitudinal studies are needed to increase our understanding about the role of PFCs exposure in the prevalence of CVD.

Monthly Variations in Perfluorinated Compound Concentrations in Groundwater

Large-scale manufacturing of poly- and perfluorinated compounds in the second half of the 20th century has led to their ubiquity in the environment, and their unique structure has made them persistent contaminants. A recent drinking water advisory level issued by the United States Environmental Protection Agency lowered the advisory level concentration of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) from 200 nanograms per liter and 400 nanograms per liter, respectively, to 70 nanograms per liter separately or combined. Small temporal variations in PFOS and PFOA concentrations could be the difference between meeting or exceeding the recommended limit. In this study, newly sampled data from a contaminated military site in Alaska and historical data from former Pease Air Force Base were collected. Data were evaluated to determine if monthly variations within PFOS and PFOA existed. No statistically significant temporal trend was observed in the Alaska data, while the results from Pease, although statistically significant, showed the spread of observed contaminant concentrations around the fitted line is broad (as indicated by the low R² values), indicating that collection date has little value in predicting contaminant concentrations. Though not currently the subject of a US EPA health advisory, data on perfluorobutanesulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), perfluoroheptanoic acid (PFHpA), and perfluorononanoic acid (PFNA) were collected for each site and their average concentrations evaluated.

Association between perfluoroalkyl substances exposure and thyroid function in adults: A meta-analysis

Objective

Many people are exposed to perfluoroalkyl substances (PFASs) because these substances are widely used as industrial products. Although epidemiological studies suggest that PFASs can disrupt thyroid hormones, the association between PFAS exposure and thyroid function remains inconclusive. Therefore, we performed a comprehensive meta-analysis to investigate the association between PFASs exposure and thyroid hormones.

Methods

We searched medical literature databases for articles on the association between PFASs–perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS)–and thyroid hormone levels in adults. Twelve articles were included in the meta-analysis, and the pooled z values were calculated with correlation or regression coefficients.

Results

The blood PFOS concentration was positively correlated with free T4. The pooled z value was 0.05 (95% confidence interval (CI): 0.03, 0.08). PFOS was negatively correlated with total T4 and total T3 when excluding outlier studies. In a subgroup analysis stratified by mean PFOS concentration, PFOS was observed to be positively associated with free T4 and TSH and negatively associated with total T3 in the intermediate concentration group (8–16 ng/mL). PFOA concentration was negatively correlated with total T4 (z value, -0.06; 95% CI: -0.09, -0.03) after omitting one outlier study. PFHxS also showed a negative correlation with total T4 (z value, -0.04; 95% CI: -0.07, -0.01). A subgroup analysis of pregnant women showed that there was no association between PFASs and thyroid hormones.

Conclusions

Our meta-analysis suggests that PFASs are negatively associated with total T4, and their effect can be different depending on the PFAS concentration.