Prenatal perfluorooctanoic acid exposure in CD-1 mice: low-dose developmental effects and internal dosimetry

Plasma per- and polyfluoroalkyl substance mixtures during pregnancy and duration of breastfeeding in the New Hampshire birth cohort study

BACKGROUND

Prior studies suggest that prenatal per- and polyfluoroalkyl substances (PFAS) exposures are associated with shorter breastfeeding duration. Studies assessing PFAS mixtures and populations in North America are sparse.

METHODS

We quantified PFAS concentrations in maternal plasma collected during pregnancy in the New Hampshire Birth Cohort Study (2010-2017). Participants completed standardized breastfeeding surveys at regular intervals until weaning (n = 813). We estimated associations between mixtures of 5 PFAS and risk of stopping exclusive breastfeeding before 6 months or any breastfeeding before 12 months using probit Bayesian kernel machine regression. For individual PFAS, we calculated the relative risk and hazard ratio (HR) of stopping breastfeeding using modified Poisson regression and accelerated failure time models respectively.

RESULTS

PFAS mixtures were associated with stopping exclusive breastfeeding before 6 months, primarily driven by perfluorooctanoate (PFOA). We observed statistically significant trends in the association of perfluorohexane sulfonate (PFHxS), PFOA, and perfluorononanoate (PFNA) (p-trends≤0.02) with stopping exclusive breastfeeding. Participants in the highest PFOA quartile had a 28% higher risk of stopping exclusive breastfeeding before 6 months compared to those in the lowest quartile (95% Confidence Interval: 1.04, 1.56). Similar trends were observed for PFHxS and PFNA with exclusive breastfeeding (p-trends≤0.05). PFAS were not associated with stopping any breastfeeding before 12 months.

CONCLUSIONS

In this cohort, we observed that participants with greater overall plasma PFAS concentrations had greater risk of stopping exclusive breastfeeding before 6 months and associations were driven largely by PFOA. These findings further support the growing literature indicating that PFAS may be associated with shorter duration of breastfeeding.

Adverse effects of gestational exposure to hexafluoropropylene oxide trimer acid (HFPO-TA) homologs on maternal, fetal, and placental health in mice

In an effort to identify and develop potential alternatives for perfluorooctanoic acid (PFOA), PFDMO2HpA and PFDMO2OA have been engineered by reducing the -CF2 content in the molecular structure of hexafluoropropylene oxide trimer acid (HFPO-TA). Yet, despite their subsequent presence in environmental samples, there is a paucity of information regarding their toxicity, particularly on pregnancy. Here, pregnant CD-1 mice were exposed to PFDMO2HpA (0, 0.04, 0.16, 0.63, 2.5, or 10 mg/kg/day) or PFDMO2OA (0, 0.01, 0.04, 0.16, 0.63, or 2.5 mg/kg/day) via oral gavage from gestational days 2 (GD2) to 12 or 18 to evaluate the detrimental effects on dams and embryo-placenta units. Both two chemicals can transfer across the placenta, with a higher transfer ratio in late-pregnancy (GD18) than in mid-pregnancy (GD12), and PFDMO2OA being transferred at a higher rate than PFDMO2HpA. PFDMO2HpA/PFDMO2OA exposure caused maternal hepatotoxicity and fetal hepatomegaly, showing the lowest no-observed-adverse-effect level among all observed endpoints, which were used for calculating their reference dose (13.33 ng/kg/day). In the 2.5 and 10 mg/kg/day PFDMO2HpA groups as well as 2.5 mg/kg/day PFDMO2OA group at GD18, besides the abnormally high abortion rates exceeding 5 %, survival fetal weight was notably reduced (2.33 %, 6.44 %, and 5.59 % decrease relative to corresponding controls, respectively). Concurrently, placentas exhibited significant enlargement following PFDMO2HpA or PFDMO2OA exposure at doses of 0.63 mg/kg/day or higher, resulting in diminished placental efficiency. The deleterious effects of two chemicals on dams, fetuses, and placentas were stronger than that of PFOA or HFPO-DA, suggesting that neither PFDMO2HpA nor PFDMO2OA is suitable PFOA alternative. Bioinformatics analyses revealed significant alterations in the expression of genes involved in inflammation and immunity in the placenta upon exposure to 10 mg/kg/day PFDMO2HpA and 2.5 mg/kg/day PFDMO2OA at GD18, potentially elucidating mechanism behind the observed decrease in placental efficiency and increase in abortion rates after exposure.

Association of adverse fetal outcomes with placental inflammation after oral gestational exposure to hexafluoropropylene oxide dimer acid (GenX) in Sprague-Dawley rats

Hexafluoropropylene oxide dimer acid (HFPO-DA), known as "GenX" for its trade name, is gradually taking the place of Perfluorooctanoic acid (PFOA). However, there is a poor understanding of the developmental effects of GenX. This study aims to explore whether GenX produces adverse effects on offspring development in Sprague-Dawley (SD) rats and the underlying mechanisms. Pregnant rats were orally administered with GenX (0, 1, 10 and 100 mg/kg/day) from gestational 0.5-19.5 days. Experimental data showed that the exposure to GenX resulted in increased rats' gestational weight gain, whereas both body weight and body length of their fetuses born naturally were significantly reduced. This could contribute to the developmental delays of fetal body weight, body length and tail length from postnatal 1-21 days. Histopathological evaluation of placenta indicated that GenX exposure led to neutrophil infiltration in decidual zone and congestion in labyrinth zone. Moreover, placental proteomics showed changes at the expression levels of the inflammation-related proteins in the Rap1 signaling pathway. In conclusion, gestational exposure to GenX induced fetal intrauterine and extrauterine development retardation in SD rats. Placental inflammation may play a key role in this process through the Rap1 signaling pathway.

Range of the perfluorooctanoate (PFOA) safe dose for human health: An international collaboration

Many government agencies and expert groups have estimated a dose-rate of perfluorooctanoate (PFOA) that would protect human health. Most of these evaluations are based on the same studies (whether of humans, laboratory animals, or both), and all note various uncertainties in our existing knowledge. Nonetheless, the values of these various, estimated, safe-doses vary widely, with some being more than 100,000 fold different. This sort of discrepancy invites scrutiny and explanation. Otherwise what is the lay public to make of this disparity? The Steering Committee of the Alliance for Risk Assessment (2022) called for scientists interested in attempting to understand and narrow these disparities. An advisory committee of nine scientists from four countries was selected from nominations received, and a subsequent invitation to scientists internationally led to the formation of three technical teams (for a total of 24 scientists from 8 countries). The teams reviewed relevant information and independently developed ranges for estimated PFOA safe doses. All three teams determined that the available epidemiologic information could not form a reliable basis for a PFOA safe dose-assessment in the absence of mechanistic data that are relevant for humans at serum concentrations seen in the general population. Based instead on dose-response data from five studies of PFOA-exposed laboratory animals, we estimated that PFOA dose-rates 10-70 ng/kg-day are protective of human health.

Per- and Polyfluoroalkyl Substances and Breastfeeding as a Vulnerable Function: A Systematic Review of Epidemiological Studies

Milk formation in the breast during breastfeeding is a complex hormonally regulated process, potentially sensitive to the effects of endocrine-disrupting chemical exposures. The environmental chemicals, per- and polyfluoroalkyl substances (PFAS) are known endocrine disruptors. PFAS exposure have been associated with insufficient mammary gland development in mice and reduced breastfeeding duration in humans. The aim of this review was to gather the epidemiological evidence on the association between PFAS exposure and breastfeeding duration. Using PubMed and Embase, we performed a systematic literature search (on 23 January 2023) to identify epidemiological studies examining the association between maternal PFAS exposure and breastfeeding duration. Animal studies, reviews, and non-English studies were excluded. The risk of bias was assessed using the risk of bias in non-randomized studies of exposures tool. Estimates describing the association between PFAS exposure and the duration of breastfeeding were identified, and the data were synthesized separately for each type of PFAS and for the duration of exclusive and total breastfeeding. Six studies with between 336 and 2374 participants each were identified. PFAS exposure was assessed in serum samples (five studies) or based on residential address (one study). Five out of six studies found shorter total duration of breastfeeding with higher PFAS exposure. The most consistent associations were seen for perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA). The finding of a potential causal association between PFAS exposure and breastfeeding duration is in agreement with findings from experimental studies.

Transcriptional pathways linked to fetal and maternal hepatic dysfunction caused by gestational exposure to perfluorooctanoic acid (PFOA) or hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) in CD-1 mice

Per- and polyfluoroalkyl substances (PFAS) comprise a diverse class of chemicals used in industrial processes, consumer products, and fire-fighting foams which have become environmental pollutants of concern due to their persistence, ubiquity, and associations with adverse human health outcomes, including in pregnant persons and their offspring. Multiple PFAS are associated with adverse liver outcomes in adult humans and toxicological models, but effects on the developing liver are not fully described. Here we performed transcriptomic analyses in the mouse to investigate the molecular mechanisms of hepatic toxicity in the dam and its fetus after exposure to two different PFAS, perfluorooctanoic acid (PFOA) and its replacement, hexafluoropropylene oxide-dimer acid (HFPO-DA, known as GenX). Pregnant CD-1 mice were exposed via oral gavage from embryonic day (E) 1.5-17.5 to PFOA (0, 1, or 5 mg/kg-d) or GenX (0, 2, or 10 mg/kg-d). Maternal and fetal liver RNA was isolated (N = 5 per dose/group) and the transcriptome analyzed by Affymetrix Array. Differentially expressed genes (DEG) and differentially enriched pathways (DEP) were obtained. DEG patterns were similar in maternal liver for 5 mg/kg PFOA, 2 mg/kg GenX, and 10 mg/kg GenX (R2: 0.46-0.66). DEG patterns were similar across all 4 dose groups in fetal liver (R2: 0.59-0.81). There were more DEGs in fetal liver compared to maternal liver at the low doses for both PFOA (fetal = 69, maternal = 8) and GenX (fetal = 154, maternal = 93). Upregulated DEPs identified across all groups included Fatty Acid Metabolism, Peroxisome, Oxidative Phosphorylation, Adipogenesis, and Bile Acid Metabolism. Transcriptome-phenotype correlation analyses demonstrated > 1000 maternal liver DEGs were significantly correlated with maternal relative liver weight (R2 >0.92). These findings show shared biological pathways of liver toxicity for PFOA and GenX in maternal and fetal livers in CD-1 mice. The limited overlap in specific DEGs between the dam and fetus suggests the developing liver responds differently than the adult liver to these chemical stressors. This work helps define mechanisms of hepatic toxicity of two structurally unique PFAS and may help predict latent consequences of developmental exposure.

Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities

Population studies show worrisome trends towards earlier breast development, difficulty in breastfeeding, and increasing rates of breast cancer in young women. Multiple epidemiological studies have linked these outcomes with chemical exposures, and experimental studies have shown that many of these chemicals generate similar effects in rodents, often by disrupting hormonal regulation. These endocrine-disrupting chemicals (EDCs) can alter the progression of mammary gland (MG) development, impair the ability to nourish offspring via lactation, increase mammary tissue density, and increase the propensity to develop cancer. However, current toxicological approaches to measuring the effects of chemical exposures on the MG are often inadequate to detect these effects, impairing our ability to identify exposures harmful to the breast and limiting opportunities for prevention. This paper describes key adverse outcomes for the MG, including impaired lactation, altered pubertal development, altered morphology (such as increased mammographic density), and cancer. It also summarizes evidence from humans and rodent models for exposures associated with these effects. We also review current toxicological practices for evaluating MG effects, highlight limitations of current methods, summarize debates related to how effects are interpreted in risk assessment, and make recommendations to strengthen assessment approaches. Increasing the rigor of MG assessment would improve our ability to identify chemicals of concern, regulate those chemicals based on their effects, and prevent exposures and associated adverse health effects.

The development and function of the brain barriers - an overlooked consideration for chemical toxicity

It is well known that the adult brain is protected from some infections and toxic molecules by the blood-brain and the blood-cerebrospinal fluid barriers. Contrary to the immense data collected in other fields, it is deeply entrenched in environmental toxicology that xenobiotics easily permeate the developing brain because these barriers are either absent or non-functional in the fetus and newborn. Here we review the cellular and physiological makeup of the brain barrier systems in multiple species, and discuss decades of experiments that show they possess functionality during embryogenesis. We next present case studies of two chemical classes, perfluoroalkyl substances (PFAS) and bisphenols, and discuss their potential to bypass the brain barriers. While there is evidence to suggest these pollutants may enter the developing and/or adult brain parenchyma, many studies suffer from confounding technical variables which complicates data interpretation. In the future, a more formal consideration of brain barrier biology could not only improve understanding of chemical toxicokinetics but could assist in prioritizing environmental xenobiotics for their neurotoxicity risk.

Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland

Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.

Killing two birds with one stone: Pregnancy is a sensitive window for endocrine effects on both the mother and the fetus

Pregnancy is a complex process requiring tremendous physiological changes in the mother in order to fulfill the needs of the growing fetus, and to give birth, expel the placenta and nurse the newborn. These physiological modifications are accompanied with psychological changes, as well as with variations in habits and behaviors. As a result, this period of life is considered as a sensitive window as impaired functional and physiological changes in the mother can have short- and long-term impacts on her health. In addition, dysregulation of the placenta and of mechanisms governing placentation have been linked to chronic diseases later-on in life for the fetus, in a concept known as the Developmental Origin of Health and Diseases (DOHaD). This concept stipulates that any change in the environment during the pre-conception and perinatal (in utero life and neonatal) period to puberty, can be "imprinted" in the organism, thereby impacting the health and risk of chronic diseases later in life. Pregnancy is a succession of events that is regulated, in large part, by hormones and growth factors. Therefore, small changes in hormonal balance can have important effects on both the mother and the developing fetus. An increasing number of studies demonstrate that exposure to endocrine disrupting compounds (EDCs) affect both the mother and the fetus giving rise to growing concerns surrounding these exposures. This review will give an overview of changes that happen during pregnancy with respect to the mother, the placenta, and the fetus, and of the current literature regarding the effects of EDCs during this specific sensitive window of exposure.

Early Warnings by Liver Organoids on Short- and Long-Chain PFAS Toxicity

Short-chain per-fluoroalkyl substances (PFAS) have replaced long-chains in many applications, however the toxicity and its mode of action and interactions due to the large number of these compounds and their mixtures is still poorly understood. The paper aims to compare the effects on mouse liver organoids (target organ for bioaccumulation) of two long-chain PFAS (perfluorooctane sulfonate -PFOS-, perfluorooctanoic acid -PFOA) and two short-chain PFAS commonly utilized in the industry (heptafluorobutyric acid -HFBA-, Pentafluoropropionic anhydride-PFPA) to identify the mode of action of these classes of contaminants. Cytomorphological aberrations and ALT/GDH enzyme disruption were identified but no acute toxicity endpoint neither apoptosis was detected by the two tested short-chain PFAS. After cytomorphological analysis, it is evident that short-chain PFAS affected organoid morphology inducing a reduction of cytostructural complexity and aberrant cytological features. Conversely, EC50 values of 670 ± 30 µM and 895 ± 7 µM were measured for PFOS and PFOA, respectively, together with strong ALT/GDH enzyme disruption, caspase 3 and 7 apoptosis activation and deep loss of architectural complexity of organoids in the range of 500–1000 µM. Eventually, biochemical markers and histology analysis confirmed the sensitivity of organoid tests that could be used as a fast and reproducible platform to test many PFAS and mixtures saving time and at low cost in comparison with in vivo tests. Organoids testing could be introduced as an innovative platform to assess the toxicity to fast recognize potentially dangerous pollutants.

Effects of Pubertal Exposure to Butyl Benzyl Phthalate, Perfluorooctanoic Acid, and Zeranol on Mammary Gland Development and Tumorigenesis in Rats

Endocrine-disrupting chemicals (EDCs)—including butyl benzyl phthalate (BBP), perfluorooctanoic acid (PFOA), and zeranol (α-ZAL, referred to as ZAL hereafter)—can interfere with the endocrine system and produce adverse effects. It remains unclear whether pubertal exposure to low doses of BBP, PFOA, and ZAL has an impact on breast development and tumorigenesis. We exposed female Sprague Dawley rats to BBP, PFOA, or ZAL through gavage for 21 days, starting on day 21, and analyzed their endocrine organs, serum hormones, mammary glands, and transcriptomic profiles of the mammary glands at days 50 and 100. We also conducted a tumorigenesis study for rats treated with PFOA and ZAL using a 7,12-dimethylbenz[a]anthracene (DMBA) model. Our results demonstrated that pubertal exposure to BBP, PFOA, and ZAL affected endocrine organs and serum hormones, and induced phenotypic and transcriptomic changes. The exposure to PFOA + ZAL induced the most phenotypic and transcriptomic changes in the mammary gland. PFOA + ZAL downregulated the expression of genes related to development at day 50, whereas it upregulated genes associated with tumorigenesis at day 100. PFOA + ZAL exposure also decreased rat mammary tumor latency, reduced the overall survival of rats after DMBA challenge, and affected the histopathology of mammary tumors. Therefore, our study suggests that exposure to low doses of EDCs during the pubertal period could induce changes in the endocrine system and mammary gland development in rats. The inhibition of mammary gland development by PFOA + ZAL might increase the risk of developing mammary tumors through activation of signaling pathways associated with tumorigenesis.

Per- and poly-fluoroalkyl substances (PFAS) and female reproductive outcomes: PFAS elimination, endocrine-mediated effects, and disease

Per- and poly-fluoroalkyl substances (PFAS) are widespread environmental contaminants frequently detected in drinking water supplies worldwide that have been linked to a variety of adverse reproductive health outcomes in women. Compared to men, reproductive health effects in women are generally understudied while global trends in female reproduction rates are declining. Many factors may contribute to the observed decline in female reproduction, one of which is environmental contaminant exposure. PFAS have been used in home, food storage, personal care and industrial products for decades. Despite the phase-out of some legacy PFAS due to their environmental persistence and adverse health effects, alternative, short-chain and legacy PFAS mixtures will continue to pollute water and air and adversely influence women's health. Studies have shown that both long- and short-chain PFAS disrupt normal reproductive function in women through altering hormone secretion, menstrual cyclicity, and fertility. Here, we summarize the role of a variety of PFAS and PFAS mixtures in female reproductive tract dysfunction and disease. Since these chemicals may affect reproductive tissues directly or indirectly through endocrine disruption, the role of PFAS in breast, thyroid, and hypothalamic-pituitary-gonadal axis function are also discussed as the interplay between these tissues may be critical in understanding the long-term reproductive health effects of PFAS in women. A major research gap is the need for mechanism of action data - the targets for PFAS in the female reproductive and endocrine systems are not evident, but the effects are many. Given the global decline in female fecundity and the ability of PFAS to negatively impact female reproductive health, further studies are needed to examine effects on endocrine target tissues involved in the onset of reproductive disorders of women.

The impact of perfluoroalkyl substances on pregnancy, birth outcomes and offspring development: A review of data from mouse models1

Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are persistent in the environment and bioaccumulate in wildlife and humans, potentially causing adverse health effects at all stages of life. Studies from human pregnancy have shown that exposure to these contaminants are associated with placental dysfunction and fetal growth restriction; however, studies in humans are confounded by genetic and environmental factors. Here, we synthesize the available results from mouse models of pregnancy to show the causal effects of prenatal exposure to PFOA and PFOS on placental and fetal development and on neurocognitive function and metabolic disorders in offspring. We also propose gaps in the present knowledge and provide suggestions for future research studies.

Bayesian Refinement of the Permeability-Limited Physiologically Based Pharmacokinetic Model for Perfluorooctanoic Acid in Male Rats

Physiologically based pharmacokinetic (PBPK) modeling is a powerful technique to inform risk assessment of xenobiotic substances such as perfluorooctanoic acid (PFOA). In our previous study, a permeability-limited PBPK model was developed to simulate the toxicokinetics and tissue distribution of PFOA in male rats. However, due to limited information on some key model parameters (e.g., protein binding and active transport rates), the uncertainty of the permeability-limited PBPK model was quite high. To address this issue, a hierarchical Bayesian analysis with Markov chain Monte Carlo (MCMC) was applied to reduce the uncertainty of parameters and improve the performance of the PBPK model. With the optimized posterior parameters, the PBPK model was evaluated by comparing its prediction with experimental data from three different studies. The results show that the uncertainties of the posterior model parameters were reduced substantially. In addition, most of the PBPK model predictions were improved: with the posterior parameters, most of the predicted plasma toxicokinetics (e.g., half-life) and tissue distribution fell well within a factor of 2.0 of the experimental data. Finally, the Bayesian framework could provide insights into the molecular mechanisms driving PFOA toxicokinetics: PFOA-protein binding, membrane permeability, and active transport.

Pilot-scale expanded assessment of inorganic and organic tapwater exposures and predicted effects in Puerto Rico, USA

A pilot-scale expanded target assessment of mixtures of inorganic and organic contaminants in point-of-consumption drinking water (tapwater, TW) was conducted in Puerto Rico (PR) to continue to inform TW exposures and corresponding estimations of cumulative human-health risks across the US. In August 2018, a spatial synoptic pilot assessment of than 524 organic and 37 inorganic chemicals was conducted in 14 locations (7 home; 7 commercial) across PR. A follow-up 3-day temporal assessment of TW variability was conducted in December 2018 at two of the synoptic locations (1 home, 1 commercial) and included daily pre- and post-flush samples. Concentrations of regulated and unregulated TW contaminants were used to calculate cumulative in vitro bioactivity ratios and Hazard Indices (HI) based on existing human-health benchmarks. Synoptic results confirmed that human exposures to inorganic and organic contaminant mixtures, which are rarely monitored together in drinking water at the point of consumption, occurred across PR and consisted of elevated concentrations of inorganic contaminants (e.g., lead, copper), disinfection byproducts (DBP), and to a lesser extent per/polyfluoroalkyl substances (PFAS) and phthalates. Exceedances of human-health benchmarks in every synoptic TW sample support further investigation of the potential cumulative risk to vulnerable populations in PR and emphasize the importance of continued broad characterization of drinking-water exposures at the tap with analytical capabilities that better represent the complexity of both inorganic and organic contaminant mixtures known to occur in ambient source waters. Such health-based monitoring data are essential to support public engagement in source water sustainability and treatment and to inform consumer point-of-use treatment decision making in PR and throughout the US.

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

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

Perinatal exposure to a human relevant mixture of persistent organic pollutants: Effects on mammary gland development, ovarian folliculogenesis and liver in CD-1 mice

The ability of persistent organic pollutants (POPs) with endocrine disrupting properties to interfere with the developing reproductive system is of increasing concern. POPs are transferred from dams to offspring and the high sensitivity of neonates to endocrine disturbances may be caused by underdeveloped systems of metabolism and excretion. The present study aimed to characterize the effect of in utero and lactational exposure to a human relevant mixture of POPs on the female mammary gland, ovarian folliculogenesis and liver function in CD-1 offspring mice. Dams were exposed to the mixture through the diet at Control, Low or High doses (representing 0x, 5000x and 100 000x human estimated daily intake levels, respectively) from weaning and throughout mating, gestation, and lactation. Perinatally exposed female offspring exhibited altered mammary gland development and a suppressed ovarian follicle maturation. Increased hepatic cytochrome P450 enzymatic activities indirectly indicated activation of nuclear receptors and potential generation of reactive products. Hepatocellular hypertrophy was observed from weaning until 30 weeks of age and could potentially lead to hepatotoxicity. Further studies should investigate the effects of human relevant mixtures of POPs on several hormones combined with female reproductive ability and liver function.

Perfluoroalkyl substances in drinking water sources along the Yangtze River in Jiangsu Province, China: Human health and ecological risk assessment

Perfluoroalkyl substances (PFASs) in source water is of growing concern for its adverse effects on human health and wildlife as well. The Yangtze River is the vital drinking water source in Jiangsu Province of China, but little attention has been paid on PFASs. The occurrence, spatial distribution and temporal trend of PFASs in 21 water sources along the Jiangsu section of the Yangtze River was investigated with sampling from 2018 to 2020. Moreover, health risk of PFASs was assessed by estimated intake dose and derived tolerable intake dose, while ecological risk was assessed by selected effect concentration and environmental exposure. PFASs concentrations in source water ranged from 12.0 to 128 ng/L, with perfluorooctanoic acid (PFOA) as the dominated congener. Fluorine chemical industry lead to a great increase of perfluorohexanoic acid (PFHxA) in its nearest water source. The estimated daily intake of PFASs through drinking was 0.54 and 0.82 ng/kg bw/day for adults and children. The major health risk was from perfluorooctane sulfonate (PFOS) and PFOA for their toxicity on liver, reproduction, development and immunity, with the maximum hazard quotient of 0.029 and 0.043 for adults and children in the worst scenario. The ecological risks from PFASs on nine species groups ranged from 2.7 × 10-10 to 5.2. PFOA and Perfluorobutane sulfonate (PFBS) were causing significant risk on wildlife, particularly on worms, mussels, and fish, which may further influence the structure and processes in the foodweb. Overall, PFASs, especially PFOS, PFOA and PFBS, induced considerable risk on human health and aquatic species in some hotspot area. It would be necessary to include them into monitoring in China and develop standards for different protection purposes.

Endocrine disrupting chemicals and breast cancer: a systematic review of epidemiological studies

BACKGROUND

Endocrine-disrupting compounds (EDCs) are ubiquitous substances that are found in our everyday lives, including pesticides, plasticizers, pharmaceutical agents, personal care products, and also in food products and food packaging. Increasing epidemiological evidence suggest that EDCs may affect the development or progression of breast cancer and consequently lead to lifelong harmful health consequences, especially when exposure occurs during early life in humans. Yet so far no appraisal of the available evidence has been conducted on this topic.

OBJECTIVE

To systematically review all the available epidemiological studies about the association of the levels of environmental exposures of EDCs with breast cancer risk.

METHODS

The search was performed in accordance with the PRISMA guidelines. We retrieved articles from PubMed (MEDLINE) until 10 March 2021. The key words used in this research were: "Endocrine disruptor(s)" OR "Endocrine disrupting chemical(s)" OR any of the EDCs mentioned below AND "Breast cancer" to locate all relevant articles published. We included only cohort studies and case-control studies. All relevant articles were accessed in full text and were evaluated and summarized in tables.

RESULTS

We identified 131 studies that met the search criteria and were included in this systematic review. EDCs reviewed herein included pesticides (e.g. p,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-dichlorodiphenyldichloroethylene (DDE), atrazine, 2,3,7,8-tetrachloridibenzo-p-dioxin (TCDD or dioxin)), synthetic chemicals (e.g. bisphenol A (BPA), phthalates, per- and polyfluoroalkyl substances (PFAS), parabens, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), contraceptive pills), phytoestrogens (e.g. genistein, resveratrol), and certain mycotoxins (e.g. zearalenone). Most studies assessed environmental EDCs exposure via biomarker measurements.

CONCLUSION

We identified certain EDC exposures could potentially elevate the risk of breast cancer. As majority of EDCs are highly persistent in the environment and bio-accumulative, it is essential to assess the long-term impacts of EDC exposures, especially multi-generational and transgenerational. Also, since food is often a major route of exposure to EDCs, well-designed exposure assessments of potential EDCs in food and food packing are necessary and their potential link to breast cancer development need to be carefully evaluated for subsequent EDC policy making and regulations.

An evaluation of health-based federal and state PFOA drinking water guidelines in the United States

Perfluorooctanoic acid (PFOA) is a synthetic, perfluorinated organic acid previously used in fluoropolymer production in the United States. PFOA has been a recent focal point for regulation because of its ubiquitous presence in drinking water throughout the United States. In 2016, the United States Environmental Protection Agency (US EPA) issued a lifetime drinking water Health Advisory (HA) for PFOA of 0.07 μg/L; several states have also implemented their own drinking water guidelines for PFOA. The current study aimed to evaluate the basis and derivation of state and federal guidelines for PFOA in drinking water, with particular emphasis on the exposure parameters utilized. Twelve distinct PFOA drinking water standards were identified ranging from 0.0051 to 2 μg/L. The US EPA HA assumptions were evaluated using a Monte Carlo analysis that included distributions for drinking water intake (DWI) rate and the relative source contribution (RSC). We determined that US EPA's HA of 0.07 μg/L is protective of 99% of the population of lactating women. We also demonstrated that the health-based guidelines were highly variable across states and that the actual RSC of PFOA from drinking water is likely greater than 20%, based on studies of actual PFOA exposures from dust, water, and food. A sensitivity analysis was performed using the same equations as the US EPA, while substituting the RSC and DWI variables; resulting in HAs ranging from 0.074 to 0.346 μg/L. We also evaluated the contribution of PFOA in drinking water to the systemic PFOA body burden of the general population using an available biokinetic model. We conclude that more rigorous efforts are warranted to establish consistent health-based drinking water guidelines for PFOA, given that drinking water is a primary source of human exposure to PFOA in the United States.

N-acetyl cysteine co-treatment abates perfluorooctanoic acid-induced reproductive toxicity in male rats

Perfluorooctanoic acid is a synthetic perfluoroalkyl-persistent in the environment and toxic to humans. N-acetylcysteine is a pro-drug of both amino acid l-cysteine and glutathione-a non-enzymatic antioxidant. N-acetylcysteine serves as an antidote for paracetamol poisoning and alleviates cellular oxidative and inflammatory stressors. We investigated N-acetylcysteine role against reproductive toxicity in male Wistar rats (weight: 140-220 g; 10 weeks old) posed by perfluorooctanoic acid exposure. Randomised rat cohorts were dosed both with perfluorooctanoic acid (5 mg/kg; p.o) or co-dosed with N-acetylcysteine (25 and 50 mg/kg p.o) for 28 days. Sperm physiognomies, biomarkers of testicular function and reproductive hormones, oxidative stress and inflammation were evaluated. Co-treatment with N-acetylcysteine significantly (p < .05) reversed perfluorooctanoic acid-mediated decreases in reproductive enzyme activities, and adverse effect on testosterone, luteinising and follicle-stimulating hormone concentrations. N-acetylcysteine treatment alone, improved sperm motility, count and viability, and reduced total sperm abnormalities. Co-treatment with N-acetylcysteine mitigated perfluorooctanoic acid-induced alterations in sperm function parameters. N-acetylcysteine abated (p < .05) perfluorooctanoic acid-induced oxidative stress in experimental rats testes and epididymis, and generally improved antioxidant enzyme activities and cellular thiol levels. Furthermore, N-acetylcysteine suppressed inflammatory responses and remedied perfluorooctanoic acid-mediated histological injuries in rat. Cooperatively, N-acetylcysteine enhanced reproductive function in perfluorooctanoic acid dosed rats, by lessening oxidative and nitrative stressors and mitigated inflammatory responses in the examined organ.

Suggestions for Improving the Characterization of Risk from Exposures to Per and Polyfluorinated Alkyl Substances

Many state and federal environmental and health agencies have developed risk-based criteria for assessing the risk of adverse health effects of per- and polyfluorinated alkyl substances (PFAS) exposure to humans and the environment. However, the criteria that have been developed vary; drinking water criteria developed for perfluorooctanoic acid, for example, can vary by up to 750 fold. This is due to differences and variability in the data and information used, study/endpoint selection, assumptions and magnitude of uncertainty factors used in the absence and extrapolation of critical effect data, differences in underlying approaches to addressing exposure within criteria development, and/or policy decisions on levels of acceptable risk. We have critically evaluated the methods used to develop these criteria while focusing on derivation and application of drinking water criteria and discuss a range of improvements to risk-characterization practice recently presented at a Focused Topic Meeting on PFAS conducted by the Society of Environmental Toxicology and Chemistry in Durham, North Carolina, USA, 12 to 15 August 2019. We propose methods that consider maximizing the use of disparate data streams, seeking patterns, and proposing biologically based approaches to evidence integration toward informed criteria development. Environ Toxicol Chem 2021;40:883-898. © 2020 SETAC.

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.

Recent US State and Federal Drinking Water Guidelines for Per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS), a class of synthetic chemicals produced for over 70 years, are of increasing concern because of their widespread environmental presence, extreme persistence, bioaccumulative nature, and evidence for health effects from environmentally relevant exposures. In 2016, the United States Environmental Protection Agency (USEPA) established nonregulatory drinking water Health Advisories of 70 ng/L for individual and total concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), the 8-carbon perfluoroalkyl acids (PFAAs) that are the most thoroughly studied PFAS. As of May 2020, 9 US states had concluded that the USEPA Health Advisories are insufficiently protective and developed more stringent PFOA and PFOS guidelines. In addition, 10 states had developed guidelines for other PFAS, primarily PFAAs. This Critical Review discusses the scientific basis for state and USEPA drinking water guidelines for PFOA and PFOS; the same principles apply to guidelines for other PFAS. Similarities and differences among guidelines arise from both toxicity and exposure considerations. The approximately 4-fold range among state guidelines (8-35 ng/L for PFOA, 10-40 ng/L for PFOS) is not large or unexpected for guidelines developed by different scientists at different time points, especially when compared with older USEPA and state guidelines that were generally several orders of magnitude higher. Additional state guidelines for PFOA, PFOS, and other PFAS are expected to become available. Environ Toxicol Chem 2021;40:560-563. © 2020 SETAC.

Human biomonitoring (HBM)-II values for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) - Description, derivation and discussion

For evaluation of internal exposure to harmful substances, the Human Biomonitoring Commission of the German Environment Agency (HBM Commission) develops toxicologically justified assessment values (HBM-I and HBM-II). The HBM-I value corresponds to the concentration of a compound in human biological material below which no adverse health effects are expected to occur. Consequently, no action is required when the HBM-I value is not exceeded (HBM-Commission, 1996). In 2016, the HBM Commission developed HBM-I values of 2 ng PFOA/mL and 5 ng PFOS/mL in blood serum or plasma, respectively. A detailed delineation of supporting arguments was published in April 2018 (HBM-Commission, 2018). In contrast to the HBM-I, the HBM-II value corresponds to the concentration in human biological material which, when exceeded, may lead to health impairment which is considered as relevant to exposed individuals (HBM-Commission, 1996, HBM-Commission, 2014). HBM-II VALUES FOR PFOA AND PFOS: On September 17, 2019, the HBM Commission of the German Environment Agency established the following HBM-II values: Women at child-bearing age: 5 ng PFOA/mL blood plasma; 10 ng PFOS/mL blood plasma; All other population groups: 10 ng PFOA/mL blood plasma; 20 ng PFOS/mL blood plasma.

Endocrine-disrupting chemicals and breastfeeding duration: a review

PURPOSE OF REVIEW

The purpose of this review is to describe epidemiologic and toxicological literature investigating how endocrine-disrupting chemicals (EDCs) affect mammary gland development and function, thereby impacting lactation duration.

RECENT FINDINGS

Perfluoroalkyl and polyfluoroalkyl substances appear to reduce breastfeeding duration through impaired mammary gland development, lactogenesis, and suppressed endocrine signaling. Halogenated aromatic hydrocarbons have differing associations with lactation duration, likely because of the variety of signaling pathways that they affect, pointing to the importance of complex mixtures in epidemiologic studies. Although epidemiologic literature suggests that pesticides and fungicides decrease or have no effect on lactation duration, toxicology literature suggests enhanced mammary gland development through estrogenic and/or antiandrogenic pathways. Toxicological studies suggest that phthalates may affect mammary gland development via estrogenic pathways but no association with lactation duration has been observed. Bisphenol A was associated with decreased duration of breastfeeding, likely through direct and indirect action on estrogenic pathways.

SUMMARY

EDCs play a role in mammary gland development, function, and lactogenesis, which can affect breastfeeding duration. Further research should explore direct mechanisms of EDCs on lactation, the significance of toxicant mixtures, and transgenerational effects of EDCs on lactation.

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.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) induce epigenetic alterations and promote human breast cell carcinogenesis in vitro

Gene–environment interactions are involved in the development of breast cancer, the tumor type that accounts for the majority of the cancer-related deaths among women. Here, we demonstrate that exposure to PFOS (10 µM) and PFOA (100 µM)—two contaminants ubiquitously found in human blood—for 72 h induced breast epithelial cell (MCF-10A cell line) proliferation and alteration of regulatory cell-cycle proteins (cyclin D1, CDK6, p21, p53, p27, ERK 1/2 and p38) that persisted after a multitude of cell divisions. The contaminants also promoted cell migration and invasion by reducing the levels of E-cadherin, occludin and β-integrin in the unexposed daughter cells. The compounds further induced an increase in global DNA methylation and differentially altered histone modifications, epigenetic mechanisms implicated in tumorigenesis. This mechanistic evidence for PFOS- and PFOA-induced malignant transformation of human breast cells supports a role of these abundant contaminants in the development and progression of breast cancer. Increased knowledge of contaminant-induced effects and their contribution to breast tumorigenesis is important for a better understanding of gene–environment interactions in the etiology of breast cancer.

Does Low Maternal Exposure to Per- and Polyfluoroalkyl Substances Elevate the Risk of Spontaneous Preterm Birth? A Nested Case-Control Study in China

Previous animal and human studies suggest potential links between maternal exposure to per- and polyfluoroalkyl substances (PFASs) and adverse birth outcomes. As spontaneous preterm birth (SPB) represents a major cause of infant mortality and precursor to future morbidity, we conducted a prospective nested case-control study in Shanxi Province, China to investigate the association between prenatal PFAS exposure and SPB risk, as well as the associations with biomarkers of oxidative stress and systemic inflammation. Among 4229 women enrolled during 2009-2013, 144 SPB cases and 375 controls were included in this study. Seventeen PFASs, as well as monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and heme oxygenase-1 (HO-1), were measured in maternal plasma or serum collected during 4th-22nd gestational weeks. Perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and its alternative chlorinated polyfluoroether sulfonic acid (6:2 Cl-PFESA) were detected in more than 90% samples with a median concentration of 0.79, 1.79, and 0.34 ng/mL, respectively. The analyses revealed no significant associations between plasma PFASs and the SPB risk after adjusting for potential confounders. However, concentrations of PFOS and 6:2 Cl-PFESA were both significantly and positively associated with MCP-1 levels, while PFOA was inversely associated with IL-8. Our findings suggested that maternal exposure to the determined low levels of PFAS did not induce an elevated risk of SPB, but the exposure may disturb potential biochemical pathways of inflammation. The latter has important implications for possible birth outcome effects and developmental effects in fetuses and newborns, which warrants close attention.

Mixed organic and inorganic tapwater exposures and potential effects in greater Chicago area, USA

Safe drinking water at the point of use (tapwater, TW) is a public-health priority. TW exposures and potential human-health concerns of 540 organics and 35 inorganics were assessed in 45 Chicago-area United States (US) homes in 2017. No US Environmental Protection Agency (EPA) enforceable Maximum Contaminant Level(s) (MCL) were exceeded in any residential or water treatment plant (WTP) pre-distribution TW sample. Ninety percent (90%) of organic analytes were not detected in treated TW, emphasizing the high quality of the Lake Michigan drinking-water source and the efficacy of the drinking-water treatment and monitoring. Sixteen (16) organics were detected in >25% of TW samples, with about 50 detected at least once. Low-level TW exposures to unregulated disinfection byproducts (DBP) of emerging concern, per/polyfluoroalkyl substances (PFAS), and three pesticides were ubiquitous. Common exceedances of non-enforceable EPA MCL Goal(s) (MCLG) of zero for arsenic [As], lead [Pb], uranium [U], bromodichloromethane, and tribromomethane suggest potential human-health concerns and emphasize the continuing need for improved understanding of cumulative effects of low-concentration mixtures on vulnerable sub-populations. Because DBP dominated TW organics, residential-TW concentrations are potentially predictable with expanded pre-distribution DBP monitoring. However, several TW chemicals, notably Pb and several infrequently detected organic compounds, were not readily explained by pre-distribution samples, illustrating the need for continued broad inorganic/organic TW characterization to support consumer assessment of acceptable risk and point-of-use treatment options.

Mixed organic and inorganic tapwater exposures and potential effects in greater Chicago area, USA

Safe drinking water at the point of use (tapwater, TW) is a public-health priority. TW exposures and potential human-health concerns of 540 organics and 35 inorganics were assessed in 45 Chicago-area United States (US) homes in 2017. No US Environmental Protection Agency (EPA) enforceable Maximum Contaminant Level(s) (MCL) were exceeded in any residential or water treatment plant (WTP) pre-distribution TW sample. Ninety percent (90%) of organic analytes were not detected in treated TW, emphasizing the high quality of the Lake Michigan drinking-water source and the efficacy of the drinking-water treatment and monitoring. Sixteen (16) organics were detected in >25% of TW samples, with about 50 detected at least once. Low-level TW exposures to unregulated disinfection byproducts (DBP) of emerging concern, per/polyfluoroalkyl substances (PFAS), and three pesticides were ubiquitous. Common exceedances of non-enforceable EPA MCL Goal(s) (MCLG) of zero for arsenic [As], lead [Pb], uranium [U], bromodichloromethane, and tribromomethane suggest potential human-health concerns and emphasize the continuing need for improved understanding of cumulative effects of low-concentration mixtures on vulnerable sub-populations. Because DBP dominated TW organics, residential-TW concentrations are potentially predictable with expanded pre-distribution DBP monitoring. However, several TW chemicals, notably Pb and several infrequently detected organic compounds, were not readily explained by pre-distribution samples, illustrating the need for continued broad inorganic/organic TW characterization to support consumer assessment of acceptable risk and point-of-use treatment options.

Evaluation of Maternal, Embryo, and Placental Effects in CD-1 Mice following Gestational Exposure to Perfluorooctanoic Acid (PFOA) or Hexafluoropropylene Oxide Dimer Acid (HFPO-DA or GenX)

BACKGROUND

Perfluorooctanoic acid (PFOA) is a poly- and perfluoroalkyl substance (PFAS) associated with adverse pregnancy outcomes in mice and humans, but little is known regarding one of its replacements, hexafluoropropylene oxide dimer acid (HFPO-DA, referred to here as GenX), both of which have been reported as contaminants in drinking water.

OBJECTIVES

We compared the toxicity of PFOA and GenX in pregnant mice and their developing embryo-placenta units, with a specific focus on the placenta as a hypothesized target.

METHODS

Pregnant CD-1 mice were exposed daily to PFOA (0, 1, or 5mg/kg) or GenX (0, 2, or 10mg/kg) via oral gavage from embryonic day (E) 1.5 to 11.5 or 17.5 to evaluate exposure effects on the dam and embryo-placenta unit. Gestational weight gain (GWG), maternal clinical chemistry, maternal liver histopathology, placental histopathology, embryo weight, placental weight, internal chemical dosimetry, and placental thyroid hormone levels were determined.

RESULTS

Exposure to GenX or PFOA resulted in increased GWG, with increase in weight most prominent and of shortest latency with 10mg/kg/d GenX exposure. Embryo weight was significantly lower after exposure to 5mg/kg/d PFOA (9.4% decrease relative to controls). Effect sizes were similar for higher doses (5mg/kg/d PFOA and 10mg/kg/d GenX) and lower doses (1mg/kg/d PFOA and 2mg/kg/d GenX), including higher maternal liver weights, changes in liver histopathology, higher placental weights and embryo-placenta weight ratios, and greater incidence of placental abnormalities relative to controls. Histopathological features in placentas suggested that PFOA and GenX may exhibit divergent mechanisms of toxicity in the embryo-placenta unit, whereas PFOA- and GenX-exposed livers shared a similar constellation of adverse pathological features.

CONCLUSIONS

Gestational exposure to GenX recapitulated many documented effects of PFOA in CD-1 mice, regardless of its much shorter reported half-life; however, adverse effects toward the placenta appear to have compound-specific signatures. https://doi.org/10.1289/EHP6233.

PFAS health effects database: Protocol for a systematic evidence map

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) confer waterproof, greaseproof, and non-stick properties when added to consumer products. They are also used for industrial purposes including in aqueous film forming foams for firefighting. PFAS are ubiquitous in the environment, are widely detected in human biomonitoring studies, and are of growing regulatory concern across federal, state, and local governments. Regulators, scientists, and citizens need to stay informed on the growing health and toxicology literature related to PFAS.

OBJECTIVES

The goal of this systematic evidence map is to identify and organize the available health and toxicology related literature on a set of 29 PFAS of emerging and growing concern.

SEARCH AND STUDY ELIGIBILITY

We will search the electronic database PubMed for health or toxicological studies on 29 PFAS of emerging concern. Eligible studies must contain primary research investigating the link between one or more of the PFAS of interest and a health effect, toxicological, or biological mechanistic endpoint.

STUDY APPRAISAL AND SYNTHESIS METHODS

Title and abstract screening and full text review will require a single reviewer for inclusion to the next level and two independent reviewers for exclusion. Study quality will not be conducted for this evidence mapping. Study characteristics will be extracted and coded from the included studies and checked for accuracy by a second reviewer. The extracted and coded information will be visualized in a publicly available, interactive database hosted on Tableau Public. Results of the evidence mapping will be published in a narrative summary.

Data derived Extrapolation Factors for developmental toxicity: A preliminary research case study with perfluorooctanoate (PFOA)

Guidelines of the United States Environmental Protection Agency (EPA, 1991) and the International Programme on Chemical Safety (IPCS, 2005) suggest two different default positions for dosimetric extrapolation from experimental animals to humans when the dosimetry of the critical effect is not known. The default position of EPA (1991) for developmental toxicity is to use peak concentration (or Cmax) for this dosimetric extrapolation. In contrast, IPCS (2005, page 39) states its default position for dosimetric choice in the absence of data is to use the area under the curve (or AUC). The choice of the appropriate dose metric is important in the development of either a Chemical Specific Adjustment Factor (CSAF) of IPCS (2005) or a Data Derived Extrapolation Factor (DDEF) of EPA (2014). This research shows the derivation of a DDEF for developmental toxicity for perfluorooctanoate (PFOA), a chemical of current interest. Here, identification of the appropriate dosimetric adjustment from a review of developmental effects identified by EPA (2016) is attempted. Although some of these effects appear to be related to Cmax, most appear to be related to the average concentration or its AUC, but only during the critical period of development for a particular effect. A comparison was made of kinetic data from PFOA exposure in mice with newly available and carefully monitored kinetic data in humans after up to 36 weeks of PFOA exposure in a phase 1 clinical trial by Elcombe et al. (2013). Using the average concentration during the various exposure windows of concern, the DDEF for PFOA was determined to be 1.3 or 14. These values are significantly different than comparable extrapolations by several other authorities based on differences in PFOA half-life among species. Although current population exposures to PFOA are generally much lower than both the experimental animal data and the clinical human study, the development of these DDEFs is consistent with current guidelines of both EPA (2014) and IPCS (2005).

Maternal exposure to perfluorooctanoic acid (PFOA) causes liver toxicity through PPAR-α pathway and lowered histone acetylation in female offspring mice

The study was conducted to investigate the liver toxicity in female offspring mice induced by maternal exposure to perfluorooctanoic acid (PFOA). Fifty pregnant Kunming mice were randomly divided into 5 groups with 10 of each, which were treated with 0.2 mL PFOA solution dissolved with deionized water at 0, 1, 2.5, 5, and 10 mg/kg BW, respectively, from the pregnancy day (PND) 0 to day 17. Female offspring mice were sacrificed to collect serum and liver at postpartum day 21. The results showed that PFOA significantly reduced the body weight at weaning and the survival rate of the female offspring mice (P < 0.01) increased the liver index of the pups (P < 0.01). Meanwhile, PFOA also caused hepatic bleeding, local necrosis, and enlargement of hepatocytes and vacuolization. The levels of serum AST, ALT, SOD, and CAT in PFOA treatment group were upregulated significantly (P < 0.01). The expressions of Acot1, Acox1, and Acsl1 genes were increased significantly (P < 0.01). The expression of PPAR-α gene was decreased significantly (P < 0.01). There was no significant difference in the expression of Cpt1a gene among the 5 groups. HAT activity was reduced significantly and HDAC activity was increased significantly. The expression of anti-acetyl-histone H3 and acetyl-histone H4 was reduced significantly. Thus, our findings indicate that exposure to PFOA during pregnancy affects the growth and development of the pups and causes liver damage, disrupting the secretion of enzymes involved in fatty acid oxidation induced by PPAR-α, leading to liver oxidative stress and a decrease in the degree of histone acetylation. Elevated HDAC may aggravate downstream fatty acid metabolism disorders through PPAR-α.

Guideline levels for PFOA and PFOS in drinking water: the role of scientific uncertainty, risk assessment decisions, and social factors

Communities across the U.S. are discovering drinking water contaminated by perfluoroalkyl and polyfluoroalkyl substances (PFAS) and determining appropriate actions. There are currently no federal PFAS drinking water standards despite widespread drinking water contamination, ubiquitous population-level exposure, and toxicological and epidemiological evidence of adverse health effects. Absent federal PFAS standards, multiple U.S. states have developed their own health-based water guideline levels to guide decisions about contaminated site cleanup and drinking water surveillance and treatment. We examined perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) water guideline levels developed by the U.S. Environmental Protection Agency (EPA) and state agencies to protect people drinking the water, and summarized how and why these levels differ. We referenced documents and tables released in June 2018 by the Interstate Technology and Regulatory Council (ITRC) to identify states that have drinking water and groundwater guideline levels for PFOA and/or PFOS that differ from EPA's health advisories (HAs). We also gathered assessment documents from state websites and contacted state environmental and health agencies to identify and confirm current guidelines. Seven states have developed their own water guideline levels for PFOA and/or PFOS ranging from 13 to 1000 ng/L, compared to EPA's HA of 70 ng/L for both compounds individually or combined. We find that the development of PFAS guideline levels via exposure and hazard assessment decisions is influenced by multiple scientific, technical, and social factors, including managing scientific uncertainty, technical decisions and capacity, and social, political, and economic influences from involved stakeholders. Assessments by multiple states and academic scientists suggest that EPA's HA is not sufficiently protective. The ability of states to develop their own guideline levels and standards provides diverse risk assessment approaches as models for other state and federal regulators, while a sufficiently protective, scientifically sound, and enforceable federal standard would provide more consistent protection.

Chemical-PDMS binding kinetics and implications for bioavailability in microfluidic devices

Microfluidic organ-on-chip devices constructed from polydimethylsiloxane (PDMS) have proven useful in studying both beneficial and adverse effects of drugs, supplements, and potential toxicants. Despite multiple advantages, one clear drawback of PDMS-based devices is binding of hydrophobic chemicals to their exposed surfaces. Chemical binding to PDMS can change the timing and extent of chemical delivery to cells in such devices, potentially altering dose-response curves. Recent efforts have quantified PDMS binding for selected chemicals. Here, we test a wider set of nineteen chemicals using UV-vis or infrared spectroscopy to characterize loss of chemical from solution in two setups with different PDMS-surface-to-solution-volume ratios. We find discernible PDMS binding for eight chemicals and show that PDMS binding is strongest for chemicals with a high octanol-water partition coefficient (log P > 1.85) and low H-bond donor number. Further, by measuring depletion and return of chemical from solution over tens to hundreds of hours and fitting these results to a first order model of binding kinetics, we characterize partitioning into PDMS in terms of binding capacities per unit surface area and both forward and reverse rate constants. These fitted parameters were used to model the impact of PDMS binding on chemical transport and bioavailability under realistic flow conditions and device geometry. The models predict that PDMS binding could alter in-device cellular exposures for both continuous and bolus dosing schemes by up to an order of magnitude compared to nominal input doses.

Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in food. Regarding PFOS and PFOA occurrence, the final data set available for dietary exposure assessment contained a total of 20,019 analytical results (PFOS n = 10,191 and PFOA n = 9,828). There were large differences between upper and lower bound exposure due to analytical methods with insufficient sensitivity. The CONTAM Panel considered the lower bound estimates to be closer to true exposure levels. Important contributors to the lower bound mean chronic exposure were 'Fish and other seafood', 'Meat and meat products' and 'Eggs and egg products', for PFOS, and 'Milk and dairy products', 'Drinking water' and 'Fish and other seafood' for PFOA. PFOS and PFOA are readily absorbed in the gastrointestinal tract, excreted in urine and faeces, and do not undergo metabolism. Estimated human half-lives for PFOS and PFOA are about 5 years and 2-4 years, respectively. The derivation of a health-based guidance value was based on human epidemiological studies. For PFOS, the increase in serum total cholesterol in adults, and the decrease in antibody response at vaccination in children were identified as the critical effects. For PFOA, the increase in serum total cholesterol was the critical effect. Also reduced birth weight (for both compounds) and increased prevalence of high serum levels of the liver enzyme alanine aminotransferase (ALT) (for PFOA) were considered. After benchmark modelling of serum levels of PFOS and PFOA, and estimating the corresponding daily intakes, the CONTAM Panel established a tolerable weekly intake (TWI) of 13 ng/kg body weight (bw) per week for PFOS and 6 ng/kg bw per week for PFOA. For both compounds, exposure of a considerable proportion of the population exceeds the proposed TWIs.

Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in food. Regarding PFOS and PFOA occurrence, the final data set available for dietary exposure assessment contained a total of 20,019 analytical results (PFOS n = 10,191 and PFOA n = 9,828). There were large differences between upper and lower bound exposure due to analytical methods with insufficient sensitivity. The CONTAM Panel considered the lower bound estimates to be closer to true exposure levels. Important contributors to the lower bound mean chronic exposure were 'Fish and other seafood', 'Meat and meat products' and 'Eggs and egg products', for PFOS, and 'Milk and dairy products', 'Drinking water' and 'Fish and other seafood' for PFOA. PFOS and PFOA are readily absorbed in the gastrointestinal tract, excreted in urine and faeces, and do not undergo metabolism. Estimated human half-lives for PFOS and PFOA are about 5 years and 2-4 years, respectively. The derivation of a health-based guidance value was based on human epidemiological studies. For PFOS, the increase in serum total cholesterol in adults, and the decrease in antibody response at vaccination in children were identified as the critical effects. For PFOA, the increase in serum total cholesterol was the critical effect. Also reduced birth weight (for both compounds) and increased prevalence of high serum levels of the liver enzyme alanine aminotransferase (ALT) (for PFOA) were considered. After benchmark modelling of serum levels of PFOS and PFOA, and estimating the corresponding daily intakes, the CONTAM Panel established a tolerable weekly intake (TWI) of 13 ng/kg body weight (bw) per week for PFOS and 6 ng/kg bw per week for PFOA. For both compounds, exposure of a considerable proportion of the population exceeds the proposed TWIs.

Evaluation of Prenatal Exposure to Bisphenol Analogues on Development and Long-Term Health of the Mammary Gland in Female Mice

BACKGROUND

Continued efforts to phase out bisphenol A (BPA) from consumer products have been met with the challenges of finding safer alternatives.

OBJECTIVES

This study aimed to determine whether early-life exposure to BPA and its related analogues, bisphenol AF (BPAF) and bisphenol S (BPS), could affect female pubertal mammary gland development and long-term mammary health in mice.

METHODS

Timed pregnant CD-1 mice were exposed to vehicle, BPA (0.5, 5, 50 mg/kg), BPAF (0.05, 0.5, 5 mg/kg), or BPS (0.05, 0.5, 5 mg/kg) via oral gavage between gestation days 10–17. Mammary glands were collected from resulting female offspring at postnatal day (PND) 20, 28, 35, and 56, and at 3, 8, and 14 months for whole mount, histopathological evaluation, and quantitative real-time polymerase chain reaction (qPCR); serum steroid concentrations were also measured at these time points.

RESULTS

In the bisphenol-exposed mice, accelerated mammary gland development was evident during early puberty and persisted into adulthood. By late adulthood, mammary glands from bisphenol-exposed female offspring exhibited adverse morphology in comparison with controls; most prominent were undifferentiated duct ends, significantly more lobuloalveolar hyperplasia and perivascular inflammation, and various tumors, including adenocarcinomas. Effects were especially prominent in the BPAF 5 mg/kg and BPS 0.5 mg/kg groups. Serum steroid concentrations and mammary mRNA levels of Esr1, Pgr, Ar, and Gper1 were similar to controls.

CONCLUSIONS

These data demonstrate that prenatal exposure of mice to BPAF or BPS induced precocious development of the mammary gland, and that siblings were significantly more susceptible to spontaneous preneoplastic epithelial lesions and inflammation, with an incidence greater than that observed in vehicle- and BPA-exposed animals. https://doi.org/10.1289/EHP3189.

Predicting Relative Protein Affinity of Novel Per- and Polyfluoroalkyl Substances (PFASs) by An Efficient Molecular Dynamics Approach

With the phasing out of long-chain per- and polyfluoroalkyl substances (PFASs), production of a wide variety of alternative PFASs has increased to meet market demand. However, little is known about the bioaccumulation potential of these replacement compounds. Here, we developed a modeling workflow that combines molecular docking and molecular dynamics simulation techniques to estimate the relative binding affinity of a total of 15 legacy and replacement PFASs for human and rat liver-type fatty acid binding protein (hLFABP and rLFABP). The predicted results were compared with experimental data extracted from three different studies. There was good correlation between predicted free energies of binding and measured binding affinities, with correlation coefficients of 0.97, 0.79, and 0.96, respectively. With respect to replacement PFASs, our results suggest that EEA and ADONA are at least as strongly bound to rLFABP as perfluoroheptanoic acid (PFHpA), and as strongly bound to hLFABP as perfluorooctanoic acid (PFOA). For F-53 and F-53B, both have similar or stronger binding affinities than perfluorooctanesulfonate (PFOS). Given that interactions of PFASs with proteins (e.g., LFABPs) are important determinants of bioaccumulation potential in organisms, these alternatives could be as bioaccumulative as legacy PFASs, and are therefore not necessarily safer alternatives to long-chain PFASs.

Significance thresholds for the assessment of contaminated groundwater: perfluorinated and polyfluorinated chemicals

BACKGROUND

Per- and polyfluorinated chemicals (PFC) do not occur naturally in the environment and are, therefore, of anthropogenic origin. As a consequence of their wide range of everyday applications and their extreme persistence in the environment, PFC have become ubiquitous in nature and can, therefore, be detected in groundwater as well as in many other environmental matrices. The German States' Water and Soil Consortia have compiled 'significance thresholds' (GFS) to assess groundwater contaminated with PFC. The GFS serve as criteria for the decision whether actions to remediate polluted groundwater are necessary. Thirteen of these PFC had been detected in groundwater at levels above their limit of quantitation and were assigned first priority.

RESULTS

The data regarding human health effects were sufficient to derive guide values according to the criteria of the German Drinking Water Ordinance for 7 of the 13 first-priority PFC. With regard to available ecotoxicological data, predicted no-effect concentration values from official risk assessments existed for 2 of the 13 first-priority PFC. A predicted no-effect concentration for protection of the aquatic biocenosis could be derived for eight more substances.

CONCLUSIONS

After evaluation of data from available literature regarding both human health and ecotoxicological effects, significance thresholds ranging from 0.06 to 10.0 µg/L could be derived for 7 of the 13 priority PFC in groundwater. As a practical guide valid solely for human health-based values, a summation rule was proposed for exposures to mixtures of these seven PFC.

Animal models of endocrine disruption

Endocrine disrupting chemicals (EDCs) are compounds that alter the structure and function of the endocrine system and may be contributing to disorders of the reproductive, metabolic, neuroendocrine and other complex systems. Typically, these outcomes cannot be modeled in cell-based or other simple systems necessitating the use of animal testing. Appropriate animal model selection is required to effectively recapitulate the human experience, including relevant dosing and windows of exposure, and ensure translational utility and reproducibility. While classical toxicology heavily relies on inbred rats and mice, and focuses on apical endpoints such as tumor formation or birth defects, EDC researchers have used a greater diversity of species to effectively model more subtle but significant outcomes such as changes in pubertal timing, mammary gland development, and social behaviors. Advances in genomics, neuroimaging and other tools are making a wider range of animal models more widely available to EDC researchers.

Incorporation of fetal and child PFOA dosimetry in the derivation of health-based toxicity values

BACKGROUND

Multiple agencies have developed health-based toxicity values for exposure to perfluorooctanoic acid (PFOA). Although PFOA exposure occurs in utero and through breastfeeding, current health-based toxicity values have not been derived using fetal or child dosimetry. Therefore, current values may underestimate the potential risks to fetuses and nursing infants.

OBJECTIVE

Using fetal and child dosimetry, we aimed to calculate PFOA maternal human equivalent doses (HEDs), corresponding to a developmental mouse study lowest observed adverse effect level (LOAEL, 1mg/kg/day). Further, we investigated the impact of breastfeeding duration and PFOA half-life on the estimated HEDs.

METHODS

First, a pharmacokinetic model of pregnancy and lactation in mice was used to estimate plasma PFOA levels in pups following a maternal exposure to 1mg PFOA/kg/day for gestational days 1-17. Four plasma PFOA concentration metrics were estimated in pups: i) average prenatal; ii) average postnatal; iii) average overall (prenatal and postnatal); and iv) maximum. Then, Monte Carlo simulations were performed using a pharmacokinetic model of pregnancy and lactation in humans to generate distributions of maternal HEDs that would result in fetal/child plasma levels equivalent to those estimated in pups using the mouse model. Median (HED₅₀) and 1st percentile (HED₀₁) of calculated HEDs were calculated.

RESULTS

Estimated PFOA maternal HED₅₀s ranged from 3.0×10^-4 to 1.1×10^-3mg/kg/day and HED₀₁s ranged from 4.7×10^-5 to 2.1×10^-4mg/kg/day. All calculated HEDs were lower than the HED based on adult dosimetry derived by the Environmental Protection Agency (EPA) (5.3×10^-3mg/kg/day).

CONCLUSION

Our results suggest that fetal/child dosimetry should be considered when deriving health-based toxicity values for potential developmental toxicants.

Issues raised by the reference doses for perfluorooctane sulfonate and perfluorooctanoic acid

On 25th May 2016, the U.S. EPA released reference doses (RfDs) for Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) of 20ng/kg/day, which were much more conservative than previous values. These RfDs rely on the choices of animal point of departure (PoD) and the toxicokinetics (TK) model. At this stage, considering that the human evidence is not strong enough for RfD determination, using animal data may be appropriate but with more uncertainties. In this article, the uncertainties concerning RfDs from the choices of PoD and TK models are addressed. Firstly, the candidate PoDs should include more critical endpoints (such as immunotoxicity), which may lead to lower RfDs. Secondly, the reliability of the adopted three-compartment TK model is compromised: the parameters are not non-biologically plausible; and this TK model was applied to simulate gestation and lactation exposures, while the two exposure scenarios were not actually included in the model structure.

Risk, Uncertainty and Precaution in Science: The Threshold of the Toxicological Concern Approach in Food Toxicology

Environmental risk assessment is often affected by severe uncertainty. The frequently invoked precautionary principle helps to guide risk assessment and decision-making in the face of scientific uncertainty. In many contexts, however, uncertainties play a role not only in the application of scientific models but also in their development. Building on recent literature in the philosophy of science, this paper argues that precaution should be exercised at the stage when tools for risk assessment are developed as well as when they are used to inform decision-making. The relevance and consequences of this claim are discussed in the context of the threshold of the toxicological concern approach in food toxicology. I conclude that the approach does not meet the standards of an epistemic version of the precautionary principle.

Recent experimental results of effects of perfluoroalkyl substances in laboratory animals - Relation to current regulations and guidance values

The detection of perfluoroalkyl substances (PFAS) in surface and drinking water from various countries raised the attention to the presence of these chemicals in environmental probes and led to several regulatory actions to limit exposure in human beings. There was particular concern about perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), due to their former wide-spread use. Recently, several institutions published revisions of former regulatory or recommended maximum concentrations in drinking water and food, which are markedly lower than the former values. The present short overview describes the current regulations for PFAS and compares them with the outcome of several experimental studies in laboratory animals at low-level exposure to PFOA and PFOS. In addition, regulations for short-chain PFAS are presented which, due to lack of toxicological information, are evaluated according to the concepts of Threshold of Toxicological Concern (TTC) or the Health-related Indication Values (HRIV).