Prenatal polybrominated diphenyl ethers exposure and anogenital distance in boys from a Shanghai birth cohort

The Effect of Various Environmental Pollutants on the Reproductive Health in Children: A Brief Review of the Literature

PURPOSE OF REVIEW

Environmental pollutants in air, water, soil, and food are a significant concern due to their potential adverse effects on fetuses, newborns, babies, and children. These chemicals, which pass to fetuses and babies through trans-placental transfer, breast milk, infant formula, dermal transfer, and non-nutritive ingestion, can cause health problems during childhood. This review aims to discuss how exposure to various environmental pollutants in early life stages can disrupt reproductive health in children.

RECENT FINDINGS

Environmental pollutants can affect Leydig cell proliferation and differentiation, decreasing testosterone production throughout life. This may result in cryptorchidism, hypospadias, impaired semen parameters, and reduced fertility. Although many studies on female reproductive health cannot be interpreted to support causal relationships, exposure to pollutants during critical windows may subsequently induce female reproductive diseases, including early or delayed puberty, polycystic ovary syndrome, endometriosis, and cancers. There is growing evidence that fetal and early-life exposure to environmental pollutants could affect reproductive health in childhood. Although diet is thought to be the primary route by which humans are exposed to various pollutants, there are no adopted nutritional interventions to reduce the harmful effects of pollutants on children's health. Therefore, understanding the impact of environmental contaminants on various health outcomes may inform the design of future human nutritional studies.

Adverse outcome pathways of PBDEs inducing male reproductive toxicity

Polybrominated diphenyl ethers (PBDEs) are widely used brominated flame retardants, they are easily released into environment and causing adverse effects to the ecosystem and human health. This review aims to summarize the research status of PBDEs-induced male reproductive toxicity and its mechanisms at various levels such as molecular/cellular, tissue/organ and individual/population. The Adverse Outcome Pathways (AOPs) diagram showed that PBDEs-induced reactive oxygen species (ROS) production, disruptions of estrogen receptor-α (ERα) and antagonism of androgen receptor (AR) were defined as critical molecular initiating events (MIEs). They caused key events (KEs) at the molecular and cellular levels, including oxidative stress, increased DNA damage, damaging mitochondria, increased glycolipid levels and apoptosis, depletion of ectoplasmic specialization and decreased Leydig cells numbers. These in turn lead to followed KEs at the tissue or organ levels, such as the impaired spermatogenesis, impaired blood-testis barrier and reduced testosterone synthesis and function. As a result, reproductive system-related adverse outcomes (AOs) were reported, such as the decreased sperm quantity or quality, shorten male anogenital distance and cryptorchidism in individual and reduced reproduction of the population. This review assembled information on the mechanisms of male reproductive toxicity induced by PBDEs, and constructed a causal mechanism relationship diagram from different levels using the an AOP framework to provide theoretical basis for ecological risk assessment and environmental management of PBDEs. The AOP framework makes it possible to develop risk management strategies based on toxicity mechanisms and support for development of Integrated Approach to Testing and Assessment (IATA) which are available for regulatory purposes.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Opportunities in Assessing and Regulating Organohalogen Flame Retardants (OFRs) as a Class in Consumer Products

BACKGROUND

In 2015, the U.S. Consumer Product Safety Commission (CPSC) received and then, in 2017, granted a petition under the Federal Hazardous Substances Act to declare certain groups of consumer products as banned hazardous substances if they contain nonpolymeric, additive organohalogen flame retardants (OFRs). The petitioners asked the CPSC to regulate OFRs as a single chemical class with similar health effects. The CPSC later sponsored a National Academy of Sciences, Engineering, and Medicine (NASEM) report in 2019, which ultimately identified 161 OFRs and grouped them into 14 subclasses based on chemical structural similarity. In 2021, a follow-up discussion was held among a group of scientists from both inside and outside of the CPSC for current research on OFRs and to promote collaboration that could increase public awareness of CPSC work and support the class-based approach for the CPSC's required risk assessment of OFRs.

OBJECTIVES

Given the extensive data collected to date, there is a need to synthesize what is known about OFR and how class-based regulations have previously managed this information. This commentary discusses both OFR exposure and OFR toxicity and fills some gaps for OFR exposure that were not within the scope of the NASEM report. The objective of this commentary is therefore to provide an overview of the OFR research presented at SOT 2021, explore opportunities and challenges associated with OFR risk assessment, and inform CPSC's work on an OFR class-based approach.

DISCUSSION

A class-based approach for regulating OFRs can be successful. Expanding the use of read-across and the use of New Approach Methodologies (NAMs) in assessing and regulating existing chemicals was considered as a necessary part of the class-based process. Recommendations for OFR class-based risk assessment include the need to balance fire and chemical safety and to protect vulnerable populations, including children and pregnant women. The authors also suggest the CPSC should consider global, federal, and state OFR regulations. The lack of data or lack of concordance in toxicity data could present significant hurdles for some OFR subclasses. The potential for cumulative risks within or between subclasses, OFR mixtures, and metabolites common to more than one OFR all add extra complexity for class-based risk assessment. This commentary discusses scientific and regulatory challenges for a class-based approach suggested by NASEM. This commentary is offered as a resource for anyone performing class-based assessments and to provide potential collaboration opportunities for OFR stakeholders. https://doi.org/10.1289/EHP12725.

Long-term effect of PBDE-99 prenatal exposure on spermatogenic injuries via the dysregulation of autophagy

Although it has been reported that perinatal, especially prenatal exposure to polybrominated diphenyl ethers (PBDEs) alters offspring's fertility, but little is known regarding their longitudinal effects over time. In the current study, we determined the associations between prenatal exposure to 2,2',4,4',5-pentabromodiphenyl ether (PBDE-99) of environmentally relevant levels in pregnant ICR mice and spermatogenic impairments in male offspring on postnatal day 70. Then, we monitored functional injuries in spermatogenic cells (GC-1 spg) exposed to PBDE-99 in vitro. Furthermore, transcriptome sequencing and bioinformatic analysis were used to investigate the underlying mechanism of PBDE-99 exposure to GC-1 spg. Additionally, the expression levels of key genes in the relevant pathways were quantified. Our findings indicated that exposure to PBDE-99 caused significantly spermatogenic injuries, which partly owing to the accumulation of reactive oxygen species, dysregulation of autophagy, and finally induced spermatogenic cell apoptosis. Rescue validation experiments showed that stimulating autophagy could alleviate spermatogenic cell injury induced by PBDE-99. In conclusion, our findings indicated that the dysfunction of autophagy played a significant role in long-term reproductive toxicity following prenatal exposure to environmental concentrations of PBDE-99.

Effects of UV radiation on natural and synthetic materials

The deleterious effects of solar ultraviolet (UV) radiation on construction materials, especially wood and plastics, and the consequent impacts on their useful lifetimes, are well documented in scientific literature. Any future increase in solar UV radiation and ambient temperature due to climate change will therefore shorten service lifetimes of materials, which will require higher levels of stabilisation or other interventions to maintain their lifetimes at the present levels. The implementation of the Montreal Protocol and its amendments on substances that deplete the ozone layer, controls the solar UV-B radiation received on Earth. This current quadrennial assessment provides a comprehensive update on the deleterious effects of solar UV radiation on the durability of natural and synthetic materials, as well as recent innovations in better stabilising of materials against solar UV radiation-induced damage. Pertinent emerging technologies for wood and plastics used in construction, composite materials used in construction, textile fibres, comfort fabric, and photovoltaic materials, are addressed in detail. Also addressed are the trends in technology designed to increase sustainability via replacing toxic, unsustainable, legacy additives with 'greener' benign substitutes that may indirectly affect the UV stability of the redesigned materials. An emerging class of efficient photostabilisers are the nanoscale particles that include oxide fillers and nanocarbons used in high-performance composites, which provide good UV stability to materials. They also allow the design of UV-shielding fabric materials with impressive UV protection factors. An emerging environmental issue related to the photodegradation of plastics is the generation of ubiquitous micro-scale particles from plastic litter exposed to solar UV radiation.

MiR-24-3p/Dio3 axis is essential for BDE47 to induce local thyroid hormone disorder and neurotoxicity

BDE47 (2,2,4,4-tetrabromodiphenyl ether) is a member of the most important congeners of polybrominated diphenyl ethers (PBDEs) and has been identified as a developmental, reproductive and nervous system toxicant and endocrine system disruptor due to its frequent detection in human tissue and environmental samples. Our preliminary work suggested that high- and low-level of bromodiphenyl ethers have different effects on neuronal cells with differential targets of actions on neural tissues. In this study, we presented the underlying mechanism of BDE47 neurotoxicity from the perspective of thyroid hormone (TH) metabolism using in vitro model of human SK-N-AS neuronal cells. BDE47 could induce local TH metabolism disorder in neuronal cells by inhibiting the expression of the main enzyme, human type III iodothyronine deiodinase (Dio3). Further elucidation revealed that BDE47 effectively up-regulating miR-24-3p, which binds to the 3'-UTR of Dio3 and inhibits its expression. In addition, BDE47 could also inhibit the deiodinase activity of Dio3. Collectively, our study demonstrates the molecular mechanism of BDE47 regulating Dio3-induced TH metabolism disorder through inducing miR-24-3p, providing new clues for the role of miRNAs in neurodevelopmental toxicity mediated by environmental pollutants.

An Analysis of the Structural Relationship between Thyroid Hormone-Signaling Disruption and Polybrominated Diphenyl Ethers: Potential Implications for Male Infertility

Polybrominated diphenyl ethers (PBDEs) are a common class of anthropogenic organobromine chemicals with fire-retardant properties and are extensively used in consumer products, such as electrical and electronic equipment, furniture, textiles, and foams. Due to their extensive use, PBDEs have wide eco-chemical dissemination and tend to bioaccumulate in wildlife and humans with many potential adverse health effects in humans, such as neurodevelopmental deficits, cancer, thyroid hormone disruption, dysfunction of reproductive system, and infertility. Many PBDEs have been listed as chemicals of international concern under the Stockholm Convention on Persistent Organic Pollutants. In this study, the aim was to investigate the structural interactions of PBDEs against thyroid hormone receptor (TRα) with potential implications in reproductive function. Structural binding of four PBDEs, i.e., BDE-28, BDE-100, BDE-153 and BDE-154 was investigated against the ligand binding pocket of TRα using Schrodinger's induced fit docking, followed by molecular interaction analysis and the binding energy estimation. The results indicated the stable and tight binding of all four PDBE ligands and similarity in the binding interaction pattern to that of TRα native ligand, triiodothyronine (T3). The estimated binding energy value for BDE-153 was the highest among four PBDEs and was more than that of T3. This was followed by BDE-154, which is approximately the same as that of TRα native ligand, T3. Furthermore, the value estimated for BDE-28 was the lowest; however, the binding energy value for BDE-100 was more than BDE-28 and close to that of TRα native ligand, T3. In conclusion, the results of our study suggested the thyroid signaling disruption potential of indicated ligands according to their binding energy order, which can possibly lead to disruption of reproductive function and infertility.

Current status of indoor dust PBDE pollution and its physical burden and health effects on children

Polybrominated diphenyl ethers (PBDEs) are widely detected in indoor dust, which has been identified as a more important route of PBDE exposure for children than food intake. The physical burden and health hazards to children of PBDE exposure in house dust have not been adequately summarized; therefore, this article reviews the current status of PBDE pollution in indoor dust associated with children, highlighting the epidemiological evidence for physical burden and health risks in children. We find that PBDEs remain at high levels in indoor dust, including in homes, schools, and cars, especially in cars showing a significant upward trend. There is a trend towards an increase in the proportion of BDE-209 in household dust, which is indicative of recent PBDE contamination. Conversely, PBDE congeners in car and school indoor dust tended to shift from highly brominated to low brominated, suggesting a shift in current pollution patterns. Indoor dust exposure causes significantly higher PBDE burdens in children, especially infants in early life, than in adults. Exposure to dust also affects breast milk, putting infants at high risk of exposure. Although evidence is limited, available epidemiological studies suggest that exposure to indoor dust PBDEs promotes neurobehavioral problems and cancer development in children.

Exposure to Polybrominated Diphenyl Ethers and Phthalates in China: A Disease Burden and Cost Analysis

Increasing evidence indicates that endocrine-disrupting chemicals (EDCs) cause a variety of adverse health outcomes and contribute to substantial disease burden. This study summarized the exposure status of polybrominated diphenyl ethers (PBDEs) and phthalates (PAEs) in China and evaluated the disease burden attributable to PBDEs and PAEs in 2015. The results showed that PBDE and PAE concentrations were higher in coastal areas. The disease burden attributable to PBDEs was 0.77 million cases, and the economic costs were CNY 18.92 billion. Meanwhile, 3.02 million individuals suffered from diseases attributable to PAEs, and the economic costs were CNY 49.20 billion. The economic burden caused by PBDEs and PAEs accounted for 0.28% and 0.72% of China's Gross Domestic Product (GDP) in 2015, respectively. When comparing China's results from 2010, it was determined that the GDP ratio of economic costs caused by PAEs in 2015 (0.72%) was lower than in 2010 (1.42%). Finally, compared with the results of the European Union and North America, the GDP ratios of economic costs caused by PAEs in 2015 were 0.19% in Canada (lower than China), 0.29% in the United States (lower than China), and 1.44% in the European Union (higher than China). This study provides important reference values for China's health governance, and further research should be conducted in the future.

Decabromodiphenyl ethane induces male reproductive toxicity by glycolipid metabolism imbalance and meiotic failure

Decabromodiphenyl ethane (DBDPE) is a typical flame retardant found in various electrical and textile items. DBDPE is abundantly available in the surrounding environment and wild animals based on its persistence and bioaccumulation. DBDPE has been shown to cause apoptosis in rat spermatogenic cells, resulting in reproductive toxicity. However, the toxicity of DBDPE on the male reproductive system and the potential mechanisms are still unclear. This study evaluated the effect of DBDPE on the reproductive system in male SD rats and demonstrated the potential mechanisms of reproductive toxicity. DBDPE (0, 5, 50, and 500 mg/kg/day) was administered via gavage to male SD rats for 28 days. DBDPE caused histopathological changes in the testis, reduced sperm quantity and motility, and raised the malformation rate in rats, according to the findings. Furthermore, it caused DNA damage to rat testicular cells. It inhibited the expressions of spermatogenesis-and oogenesis-specific helix-loop-helix transcription factor 1 (Sohlh1), piwi-like RNA-mediated gene silencing 2 (MILI), cyclin-dependent kinase 2 (CDK2), and CyclinA, resulting in meiotic failure, as well as the expressions of synaptonemal complex proteins 1 and 3 (SYCP1 and SYCP3), leading to chromosomal association disorder in meiosis and spermatocyte cycle arrest. Moreover, DBDPE induced glycolipid metabolism disorder and activated mitochondria-mediated apoptosis pathways in the testes of SD rats. The quantity and quality of sperm might be declining due to these factors. Our findings offer further evidence of the harmful impact of DBDPE on the male reproductive system.

Serum concentrations of persistent organic pollutants mixture during pregnancy and anogenital distance in 8-year-old children from the INMA-Asturias cohort

BACKGROUND

During pregnancy, women are commonly exposed to several endocrine-disrupting chemicals, including persistent organic pollutants (POPs). These compounds can transfer to the fetus through the placenta. Prenatal POP exposure is related to altered fetal genital and reproductive tract development. However, the relationship between exposure to POP mixtures and anogenital distance (AGD) is poorly investigated. This study investigated the association between prenatal exposure to POP mixtures and AGD in 8-year-old children.

METHODS

Data were collected from the INMA-Asturias cohort. Maternal serum POP concentrations were measured during the first trimester of pregnancy. Anoscrotal distance (AGD_AS) and anopenile distance (AGD_AP) in males and anofourchetal distance (AGD_AF) and anoclitoral distance (AGD_AC) in females were recorded in 362 8-years-olds. Conventional linear regression, and the novel weighted quantile sum regression (WQSR) and Bayesian kernel machine regression (BKMR) models were applied to assess the relationships between AGD and POPs exposure stratified by sex.

RESULTS

Among males, in the linear regression, b-hexachlorocyclohexane, PCB138, PCB153, and PCB180 were inversely associated with the anogenital index (AGI)_AS (-0.06 mm/kg (95% confidence interval [CI]: -0.11, -0.02), -0.07 mm/kg (95% CI: -0.14, -0.01), -0.07 mm/kg (95% CI: -0.13, -0.01), and -0.08 mm/kg (95% CI: -0.14, -0.02), respectively). Among females, polybrominated diphenyl ether (PBDE)47 and PBDE154 were positively associated with increased AGI_AF (0.02 mm/kg (95% CI: 0.00, 0.03) and 0.09 mm/kg (95% CI: 0.01, 0.17), respectively). BKMR confirmed these associations. WQSR found a negative combined effect of the POP mixture on AGD, and PCB138, PCB153, and PCB180 (weighted 0.18, 0.13, and 0.09, respectively) were identified as the most impacting chemicals. In females, WQSR found a positive combined effect and determined PBDE47 (weighted 0.35) as the most impacting.

CONCLUSIONS

Maternal exposure to a POP mixture was negatively associated with AGD in male children and positively associated with AGD in female children, thus providing evidence of the adverse effects of POPs on genital development.

Association of prenatal exposure to polybrominated diphenyl ethers at low levels with adiposity measures in children up to 6 years

The effects of prenatal PBDEs exposure, especially at low levels, on childhood obesity are scarce. No previous studies have investigated the effect modification by breastfeeding on the associations of PBDEs exposure with childhood obesity. We aimed to investigate the associations of prenatal PBDEs exposure with adiposity measures in children up to 6 years, and the effect modification by breastfeeding. Participants were mother-child pairs from the Shanghai-Minhang Birth Cohort study. Nine PBDE congeners were assessed in cord blood plasma. We obtained information about child weight (0-6 years), height (0.5-6 years), arm circumference (0-6 years), and waist circumference (0-6 years) at each follow-up visit. Breastfeeding duration was collected when children were aged 1 year and was categorized as short (≤6 months) and adequate (>6 months). Multiple linear regression models were used to examine the associations of PBDE concentrations with adiposity measures of the children at each age. Generalized estimating equation (GEE) models were used to estimate the overall associations of PBDEs exposure with adiposity measures. We examined the effect modification by breastfeeding using stratified analyses and by including interaction terms into GEE models. For boys, there was a general profile of positive associations of several PBDE congeners exposure with adiposity measures. Especially, boys with higher BDE-153 concentration had higher adiposity measures at each time point. For girls, we also found positive associations of BDE-100 and -153 exposure with adiposity measures. The GEE models showed consistent patterns for BDE-153 in boys and for BDE-100 and -153 in girls. In breastfeeding-stratified analyses, stronger associations of PBDEs exposure with adiposity measures were generally found in children who were shortly breastfed. Our findings suggest that prenatal exposure to PBDEs at low levels may influence childhood adiposity measures, and the potential effects of PBDEs were attenuated by adequate breastfeeding.

Association of pre-pregnancy body mass index and gestational weight gain with neonatal anogenital distance in a Chinese birth cohort

Background

This study aimed to investigate the associations of pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) with anogenital distance (AGD) among newborns.

Methods

The study included 556 mother-newborn pairs from the Jiashan birth cohort. AGD was measured as AGD_AP (from the center of the anus to the anterior base of the penis, where the penile tissue meets the pubic bone) and AGD_AS (from the center of the anus to the posterior base of the scrotum, where the skin changes from rugate to smooth) in males and AGD_AC (from the center of the anus to the clitoris) and AGD_AF (from the center of the anus to the posterior convergence of the fourchette) in females. Multiple linear regression models were used to estimate the associations of pre-pregnancy BMI and GWG, with AGD.

Results

After adjusting for pre-pregnancy BMI and other potential confounders, male newborns whose mothers had excessive GWG had shorter AGD_AP than those whose mothers had normal GWG. Male newborns whose mothers had normal pre-pregnancy BMI and inadequate/excessive GWG had shorter AGD_AP than the reference group where mothers had normal pre-pregnancy BMI and GWG in stratified analyses.

Conclusion

Gestational weight gain during pregnancy was associated with AGD in newborns in this birth cohort.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12978-022-01458-y.

In China, the prevalence of underweight and overweight/obesity remained high among women. Appropriate pre-pregnancy body mass index (BMI) and gestation weight gain (GWG) were critical to reduce the risk of adverse birth outcomes. The anogenital distance (AGD) was measured as an indicator of neonatal reproductive function and was associated with adverse reproductive outcomes in adults. Thus, we investigated the associations of both sub-optimal pre-pregnancy BMI, as well as GWG, with AGD among newborns to draw a picture about their effect on offspring reproductive health.

A total of 556 mother-newborns were included in the study from the Jiashan birth cohort in China. We extracted information about maternal lifestyles, social demographic characteristics, diet, and medical history from questionnaires conducted during 8–16 gestational weeks and medical records. AGD among newborns was measured within 3 days of delivery.

We found that maternal excessive GWG was associated with shorter AGD in male newborns after adjusting for maternal pre-pregnancy BMI in multiple linear regression models. The study also suggested that maternal inadequate GWG was associated with a shorter AGD in male newborns, which needed to be corroborated in further studies with a larger sample size.

In conclusion, health professionals shall implement sufficient intervention to prevent suboptimal GWG during prenatal checkups.

Effects of endocrine disrupting chemicals on gonad development: Mechanistic insights from fish and mammals

Over the past century, evidence has emerged that endocrine disrupting chemicals (EDCs) have an impact on reproductive health. An increased frequency of reproductive disorders has been observed worldwide in both wildlife and humans that is correlated with accidental exposures to EDCs and their increased production. Epidemiological and experimental studies have highlighted the consequences of early exposures and the existence of key windows of sensitivity during development. Such early in life exposures can have an immediate impact on gonadal and reproductive tract development, as well as on long-term reproductive health in both males and females. Traditionally, EDCs were thought to exert their effects by modifying the endocrine pathways controlling reproduction. Advances in knowledge of the mechanisms regulating sex determination, differentiation and gonadal development in fish and rodents have led to a better understanding of the molecular mechanisms underlying the effects of early exposure to EDCs on reproduction. In this manuscript, we review the key developmental stages sensitive to EDCs and the state of knowledge on the mechanisms by which model EDCs affect these processes, based on the roadmap of gonad development specific to fish and mammals.

Prenatal exposure to environmentally relevant levels of PBDE-99 leads to testicular dysgenesis with steroidogenesis disorders

Polybrominated diphenyl ethers (PBDEs) are a widely used class of brominated flame retardants. Exposure to PBDEs could induce testicular damage in mammals, but the effects and potential mechanism of action of prenatal exposure to environmentally relevant PBDEs on testicular development remain unclear. For the in vivo study, pregnant ICR mice were exposed to environmentally relevant levels of 2,2',4,4',5-pentabromodiphenyl ether (PBDE-99), a major component of commercial PBDE mixtures. We found that the anogenital index and testicular organ coefficient were significantly decreased, the incidence of cryptorchidism was increased, and testicular histology was disturbed in male offspring. Transcriptomic profiling showed that steroidogenesis disorders were significant in all PBDE-99 exposure groups. The testosterone levels, expressions of testosterone regulators, and the number of CYP11A1-positive and 11β-HSD1-positive Leydig cells were significantly decreased after PBDE-99 exposure. For the in vitro study, TM3 Leydig cells were exposed to PBDE-99 at gradient concentrations. Transcriptomic profiling and validation experiments showed that PBDE-99 upregulated reactive oxygen species, activated the ERK1/2 pathway, inhibited the ubiquitination degradation pathway, and finally induced Leydig cell apoptosis. Cumulatively, these findings revealed that prenatal exposure to environmentally relevant levels of PBDE-99 leads to steroidogenesis disorders by inducing the apoptosis of Leydig cells, causing testicular dysgenesis.

Preconceptional paternal alcohol consumption and the risk of child behavioral problems: a prospective cohort study

Animal studies demonstrated that paternal alcohol exposure before conception increases the risk of adverse neurodevelopment in offspring, but limited evidence is known in humans. Based on Shanghai-Minhang Birth Cohort Study, we aimed to examine associations between preconceptional paternal alcohol consumption and child behavioral problems. Paternal alcohol consumption during the last 3 months before conception was obtained by maternal report. Children born to fathers who drank alcohol at least once a week were classified as exposed. Child behavioral problems were assessed using the Child Behavior Checklist (CBCL) at age of 2, 4, and 6. Negative binomial regression was used to estimate the rate ratio (RR) of CBCL raw scores in 796 offspring. The risks of rating scores on anxious/depressed were increased by 33% (RR 1.33, 95% CI 1.09, 1.61) and 37% (RR 1.37, 95% CI 1.02, 1.84) among boys in the exposed group at age of 4 and 6, respectively. We also found that risks of somatic complaints were increased by 18% (RR 1.18, 95%CI 1.00, 1.40) and 65% (RR 1.65, 95%CI 1.14, 2.38) among girls in the exposed group at age of 4 and 6. The increased risks of sleep problems (RR 1.25, 95% CI 1.00, 1.55) in girls at age 4, thought problems (RR 1.32, 95% CI 1.01, 1.73) in girls at age 6, rule-breaking behaviors (RR 1.35, 95% CI 1.09, 1.67) in boys at age 6 were also found. The risks of CBCL scores on anxious/depressed and sleep problems in girls at age 4, as well as the risks of somatic complaints and rule-breaking behaviors in boys at age 6 increased with the level of exposure to paternal alcohol consumption. Our findings provided preliminary evidence that preconceptional paternal alcohol consumption may increase risks of child behavioral problems.

Developmental exposure to the DE-71 mixture of polybrominated diphenyl ether (PBDE) flame retardants induce a complex pattern of endocrine disrupting effects in rats

Polybrominated diphenyl ethers (PBDEs) are legacy compounds with continued widespread human exposure. Despite this, developmental toxicity studies of DE-71, a mixture of PBDEs, are scarce and its potential for endocrine disrupting effects in vivo is not well covered. To address this knowledge gap, we carried out a developmental exposure study with DE-71. Pregnant Wistar rat dams were exposed to 0, 40 or 60 mg/kg bodyweight/day from gestation day 7 to postnatal day 16, and both sexes were examined. Developmental exposure affected a range of reproductive toxicity endpoints. Effects were seen for both male and female anogenital distances (AGD), with exposed offspring of either sex displaying around 10% shorter AGD compared to controls. Both absolute and relative prostate weights were markedly reduced in exposed male offspring, with about 40% relative to controls. DE-71 reduced mammary gland outgrowth, especially in male offspring. These developmental in vivo effects suggest a complex effect pattern involving anti-androgenic, anti-estrogenic and maybe estrogenic mechanisms depending on tissues and developmental stages. Irrespective of the specific underlying mechanisms, these in vivo results corroborate that DE-71 causes endocrine disrupting effects and raises concern for the effects of PBDE-exposure on human reproductive health, including any potential long-term consequences of disrupted mammary gland development.

Polybrominated diphenyl ethers in the environmental systems: a review

PBDEs are human-influenced chemicals utilized massively as flame retardants. They are environmentally persistent, not easily degraded, bioaccumulate in the biological tissue of organisms, and bio-magnify across the food web. They can travel over a long distance, with air and water being their possible transport media. They can be transferred to non-target organisms by inhalation, oral ingestion, breastfeeding, or dermal contact. These pollutants adsorb easily to solid matrices due to their lipophilicity and hydrophobicity; thus, sediments from rivers, lakes, estuaries, and ocean are becoming their major reservoirs aquatic environments. They have low acute toxicity, but the effects of interfering with the thyroid hormone metabolism in the endocrine system are long term. Many congeners of PBDEs are considered to pose a danger to humans and the aquatic environment. They have shown the possibility of causing many undesirable effects, together with neurologic, immunological, and reproductive disruptions and possible carcinogenicity in humans. PBDEs have been detected in small amounts in biological samples, including hair, human semen, blood, urine, and breastmilk, and environmental samples such as sediment, soil, sewage sludge, air, biota, fish, mussels, surface water, and wastewater. The congeners prevailing in environmental samples, with soil being the essential matrix, are BDE 47, 99, and 100. BDE 28, 47, 99, 100, 153, 154, and 183 are more frequently detected in human tissues, whereas in sediment and soil, BDE 100 and 183 predominate. Generally, BDE 153 and 154 appear very often across different matrices. However, BDE 209 seems not frequently determined, owing to its tendency to quickly breakdown into smaller congeners. This paper carried out an overview of PBDEs in the environmental, human, and biota niches with their characteristics, physicochemical properties, and fate in the environment, human exposure, and health effects.

Transgenerational effects of BDE-209 on male reproduction in F3 offspring rats

Decabromodiphenyl ether (BDE-209), a congener of polybrominated diphenyl ethers, is a commonly used brominated flame retardant and a known endocrine disrupting chemical (EDC). Knowledge about the effects of prenatal BDE-209 exposure on male reproduction and whether transgenerational effects occur in subsequent generations are scant. Therefore, in this study, we tested the hypothesis that prenatal exposure to BDE-209 disrupted sperm function in the F1, F2, and F3 generations of male rats. Pregnant Sprague-Dawley rats were treated by gavage from gestation day 0 to birth with 5 mg BDE-209/kg/day. This treatment was based on the lowest-observed-adverse-effect level for DNA damage to sperm in male offspring. On postnatal day 84 for all generations, epididymal sperm counts, motility, morphology, reactive oxygen species generation, sperm chromatin DNA structure integrity, testicular DNA content in spermatogenesis, and serum testosterone levels were assessed. DNA methyltransferase (Dnmts) mRNA expression and methyl-CpG binding domain sequencing were also examined to analyze DNA methylation status in the F3 generation. In the F1 generation, prenatal exposure to BDE-209 disrupted body weight, decreased anogenital distance (AGD), sperm count, and motility; and increased bent tail rates of sperm. In the F2 generation, exposure to BDE-209 decreased AGD, sperm count, normal morphology rates, Dnmt1 expression, and increased Dnmt3a expression. In the F3 generation, BDE-209 exposure decreased AGD and normal sperm morphology, disrupted testicular elongated spermatid and round spermatid rates, reduced serum testosterone levels, and inhibited the mRNA expression of Dnmt1 and Dnmt3b. Compared with the control group, there existed 215 differentially hyper-methylated and 83 hypo-methylated genes in the BDE-209 group. BDE-209 is an EDC to disrupt the male reproduction from F1 to F3. BDE-209-induced changes in sperm function and hyper- or hypo-DNA methylation in the F3 generation might therefore explain the possible mechanism underlying BDE-209-mediated epigenetic transgenerational effects on the male reproductive system.

Prenatal Exposure to Cigarette Smoke and Anogenital Distance at 4 Years in the INMA-Asturias Cohort

Smoking by women is associated with adverse pregnancy outcomes such as spontaneous abortion, preterm delivery, low birth weight, infertility, and prolonged time to pregnancy. Anogenital distance (AGD) is a sensitive biomarker of prenatal androgen and antiandrogen exposure. We investigated the effect of smoking and passive smoke exposure during pregnancy on anogenital distance in offspring at 4 years in the INMA-Asturias cohort (Spain). Women were interviewed during pregnancy to collect information on tobacco consumption, and anogenital distance was measured in 381 children: Anoscrotal distance in boys and anofourchetal distance in girls. We also measured maternal urinary cotinine levels at 32 weeks of pregnancy. We constructed linear regression models to analyze the association between prenatal smoke exposure and anogenital distance and adjusted the models by relevant covariates. Reported prenatal smoke exposure was associated with statistically significant increased anogenital index (AGI), both at week 12 of pregnancy (β = 0.31, 95% confidence interval: 0.00, 0.63) and at week 32 of pregnancy (β = 0.31, 95% confidence interval: 0.00, 0.63) in male children, suggesting altered androgenic signaling.

Global distribution and trends of polybrominated diphenyl ethers in human blood and breast milk: A quantitative meta-analysis of studies published in the period 2000-2019

Polybrominated diphenyl ethers (PBDEs) are a class of flame-retardants that are found throughout the human body. However, global trends and diversity of the concentrations in human body and the potential risks remain largely unresolved. Based on published data during 2000-2019, we conducted a systematic meta-analysis to understand the burden and risks of PBDEs in humans and their spatiotemporal variations. The report provides a global picture of PBDE concentrations in human blood and breast milk. We found the levels of body PBDE burden in the North American population were higher than those from Asia and Europe. However, high concentrations of blood PBDEs in occupational population from Asia were observed, largely because of poorly controlled e-waste recycling operations. Penta- and deca-BDE were the main contributors in North America and Asia, respectively, reflecting the difference in the production and use of these chemicals. On a global scale, no substantial decreases in the concentrations of PBDEs in the blood and breast milk were observed, although most of the chemicals have been phased out. The results suggested that humans will be exposed to PBDEs with relatively high concentrations in a certain period because of the legacy in products and the environmental media. And the potential health risks necessitate careful study in the future. Our results also remind that the uses of degradation-resistant chemicals should be attached great importance to their safety.

Association between prenatal exposure to polybrominated diphenyl ethers and anogenital distance in girls at ages 0-4 years

Anogenital distance (AGD) is a sensitive marker for the effect of in utero hormonal disturbance. However, studies on the associations between prenatal exposure to polybrominated diphenyl ethers (PBDEs), a group of endocrine disruptors, and AGD are limited. We examined the associations between prenatal PBDE exposure and AGD in girls at ages 0-4 years in the Shanghai-Minhang Birth Cohort Study. We measured PBDE in cord plasma collected from 148 girls at birth. Of them, two AGD metrics (AGD_AC: from the anterior surface of the clitoral hood to the center of the anus; AGD_AF: from the posterior end of the fourchette to the center of the anus) were measured in 142, 114, 104 and 120 of girls at birth, 6, 12, and 48 months of age, respectively. Linear regression models and linear mixed models were used to evaluate the associations between PBDE exposure and AGD at ages 0-4 years. We found positive associations of PBDE exposure with AGD_AF and AGD_AC in linear regression models, although some associations only reached significance at 6 and 48 months of age. For AGD_AF, the associations were statistically significant for BDE-47, -99, and -100 at 6 months of age (β = 2.34, 95% CI (0.21, 4.48) for BDE-47; β = 2.21, 95% CI (0.05, 4.36) for BDE-99; β = 2.12, 95% CI (0.01, 4.23) for BDE-100), and for BDE-99 and -100 at 48 months of age (β = 4.49, 95% CI (1.27, 7.71) for BDE-99; β = 5.04, 95% CI (1.87, 8.22) for BDE-100), while statistically significant associations with AGD_AC were only observed for BDE-99, -100, -153, and ∑₅PBDEs at 48 months of age (β = 7.62, 95% CI (2.59, 12.64) for BDE-99; β = 7.04, 95% CI (2.01, 12.07) for BDE-100; β = 5.41, 95% CI (0.45, 10.38) for BDE-153; β = 5.05 mm, 95% CI (0.09, 10.01 for ∑₅PBDEs). A consistent pattern of positive associations between prenatal exposure to PBDEs and AGD was also observed in linear mixed models. The finding provided further insights into the adverse effects of PBDEs on reproductive development at low dose exposure.

Impaired sperm quantity and motility in adult rats following gestational and lactational exposure to environmentally relevant levels of PBDE-47: A potential role of thyroid hormones disruption

Polybrominated diphenyl ethers (PBDEs) are flame retardants and the congener 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47) is capable of inducing thyroid endocrine disruption and developmental toxicity. However, little is known about whether developmental PBDE-47 exposure-elicited alterations in semen quality is associated with thyroid hormones (THs) perturbation. In this research, we sought to explore the impacts of gestational and lactational PBDE-47 exposure on adult sperm quantity and motility, and its link with THs levels. For this purpose, female Sprague-Dawley rats were administered environmentally relevant PBDE-47 levels (0.1, 1.0, 10 mg/kg/day) by oral gavage from prepregnancy through lactation cessation to achieve early-life exposure of offspring and to mimic the actual exposure. Sperm quantity and motility together with serum THs levels from male offspring were determined on postnatal day 88. In utero and lactational exposure to PBDE-47 boosted the weight gain while reduced the relative testis weight in adult male offspring. These were accompanied with the reductions in sperm counts (total and living sperm counts), the percentage of progressive sperm motility, sperm velocities (curvilinear velocity, straight-line velocity and average path velocity), motion path (beat cross frequency, linearity and wobble) and linear motile sperm parameters (count, motility and concentration). Further studies identified that the levels of serum triiodothyronine (T₃) were increased by PBDE-47 exposure and negatively associated with those differential semen parameters on quantity and motility. Collectively, our results indicate that exposure to low-level PBDE-47 during early-life development impairs semen quality in adult rats, which could be mediated partially by abnormal T₃ levels.

Endocrine Disrupting Chemicals and Reproductive Health in Boys and Men

Male reproductive health has declined as indicated by increasing rates of cryptorchidism, i.e., undescended testis, poor semen quality, low serum testosterone level, and testicular cancer. Exposure to endocrine disrupting chemicals (EDCs) has been proposed to have a role in this finding. In utero exposure to antiandrogenic EDCs, particularly at a sensitive period of fetal testicular development, the so-called 'masculinization programming window (MPW)', can disturb testicular development and function. Low androgen effect during the MPW can cause both short- and long-term reproductive disorders. A concurrent exposure to EDCs may also affect testicular function or damage testicular cells. Evidence from animal studies supports the role of endocrine disrupting chemicals in development of male reproductive disorders. However, evidence from epidemiological studies is relatively mixed. In this article, we review the current literature that evaluated relationship between prenatal EDC exposures and anogenital distance, cryptorchidism, and congenital penile abnormality called hypospadias. We review also studies on the association between early life and postnatal EDC exposure and semen quality, hypothalamic-pituitary-gonadal axis hormone levels and testicular cancer.

Prenatal exposure to perfluoroalkyl substances and cord plasma lipid concentrations

The effect of prenatal exposure to perfluoroalkyl substances (PFAS) on lipid concentrations in newborns is unknown. Using data from the Shanghai-Minhang Birth Cohort Study, we prospectively assessed the health effects of prenatal exposure to individual and multiple PFAS on cord lipid concentrations. Maternal plasma samples collected at 12-16 weeks of gestation were analyzed for eleven PFAS, and cord blood samples were analyzed for lipids: total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). We used multiple linear regression models to evaluate the associations of each individual PFAS with each lipid parameter, and used Bayesian Kernel Machine Regression (BKMR) models to assess the overall and single-exposure effects of eight PFAS with the detection rate above 80% on cord lipid concentrations. In multiple linear regression models, for each unit increase in ln-transformed maternal concentrations of perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUdA), and perfluorotridecanoic acid (PFTrDA), ln-transformed TC concentration decreased by 0.15 mg/dL (95% confidence interval (CI): -0.25, -0.05), 0.12 mg/dL (95% CI: -0.19, -0.05), 0.12 mg/dL (95% CI: -0.19, -0.05), and 0.05 mg/dL (95% CI: -0.09, -0.01), respectively, and ln-transformed HDL-C concentration decreased by 0.17 mg/dL (95% CI: -0.29, -0.05), 0.12 mg/dL (95% CI: -0.20, -0.03), 0.12 mg/dL (95% CI: -0.20, -0.03), and 0.06 mg/dL (95% CI: -0.11, -0.00), respectively. Statistically significant inverse associations were also observed between ln-transformed concentrations of PFDA, PFUdA, or PFTrDA and ln-transformed cord concentrations of TG and LDL-C. In BKMR models, the mixture of eight PFAS showed suggestively inverse association with all ln-transformed lipid concentrations, such that ln-transformed TC concentration of exposure to the 75th percentile of the mixture was 0.11 units (95% credible interval, -0.21, -0.01) lower than the 25th percentile exposure. Our findings indicated that prenatal exposure to PFAS may disrupt lipid metabolism in newborns.

Association Between Neonatal Thyroid Function and Anogenital Distance from Birth to 48 Months of Age

BACKGROUND

Evidence from animal studies has indicated that neonatal thyroid function is vital for the reproductive development. Anogenital distance (AGD), a sensitive biomarker of the fetal hormonal milieu, can be used to predict adult reproductive disorders. However, few human studies have examined the association between neonatal thyroid function and AGD. We aimed to explore their associations in a birth cohort study.

METHODS

Concentrations of thyroid stimulating hormone (TSH) and thyroid hormones (THs), including total triiodothyronine (TT₃), total thyroxine (TT₄), free triiodothyronine (FT₃), and free thyroxine (FT₄) were measured in cord plasma in the Shanghai-Minhang Birth Cohort. The offspring AGD (AGD_AP [anus-penis] and AGD_AS [anus-scrotum] for boys and AGD_AC [anus-clitoris] and AGD_AF [anus-fourchette] for girls), body weight and anogenital index (AGI = AGD/weight [mm/kg]) were obtained at each follow-up visit. In total, 344 children (194 boys and 150 girls) with cord plasma concentrations of THs and TSH and at least one AGD measurement at birth and at 6, 12, and 48 months of age were included. Multiple linear regression and generalized estimating equation (GEE) models were used to examine the associations of cord plasma concentrations of THs and TSH with AGI.

RESULTS

Multiple linear regression models showed inverse associations of TT₄, FT₃, and FT₄ with female AGI, although statistical significance was only reached at birth, 6 and 48 months of age. These associations were also found in GEE models: higher TT₄ and FT₄ concentrations were associated with lower AGI_AC (TT₄: β = -0.27, 95% CI: -0.50, -0.03 for middle vs. lowest tertile; FT₄: β = -0.38, 95% CI: -0.61, -0.16 for middle and β = -0.30, 95% CI: -0.55, -0.04 for highest vs. lowest tertile). Besides, girls with the highest tertile of FT₃ concentrations had lower AGI_AF than those with the lowest tertile (the highest vs. lowest tertile: β = -0.22, 95% CI: -0.36, -0.08). Positive associations between TSH and AGI at birth and at 12 months of age were observed in boys.

CONCLUSIONS

This study provides further evidence on the effects of neonatal thyroid function on reproductive development at an early life stage.

Effects of prenatal exposure to polybrominated diphenyl ethers (PBDEs) on the second to fourth digit ratio in children aged 4 years

BACKGROUND

The second to fourth digit ratio (2D:4D) is assumed to be a biomarker of prenatal sex steroid exposure, correlating negatively with prenatal testosterone and positively with prenatal estrogen. The ratio has been suggested to be influenced by endocrine disrupting chemicals (EDCs). However, evidence regarding effects of prenatal exposure to polybrominated diphenyl ethers (PBDEs) on 2D:4D of children was sparse.

OBJECTIVES

We investigated the associations between prenatal exposure to PBDEs and 2D:4D of children aged 4 years.

METHODS

Participants were mother-child pairs from the Shanghai-Minhang Birth Cohort Study (S-MBCS) which enrolled pregnant women at 12-16 weeks of gestation from April to December 2012. Nine PBDE congeners in venous umbilical cord plasma of 340 children were measured. Digit lengths were measured using a vernier caliper in children aged 4 years and 2D:4D for left and right hands and average 2D:4D value of both hands were calculated. A total of 281 children (160 boys and 121 girls) who had data on both 2D:4D and PBDE concentrations were included in the final analysis. Associations between prenatal PBDE exposures and 2D:4D were investigated using multiple linear regression models.

RESULTS

Among the nine congeners, BDE-47 had the highest detection rate of 86.12% with the highest median concentration of 0.20 ng/ml lipid. Five PBDE congeners with detection rates greater than or close to 50% (BDE-28, -47, -99, -100 and -153) and Σ₅PBDEs (the sum of them) were included in final analysis. For girls, a consistent pattern for the positive associations between prenatal PBDE exposures and 2D:4D of children was observed mainly for the left hand, where those in the highest exposure groups had higher 2D:4D compared to the lowest exposure groups (a feminizing effect), with statistically significant associations observed for BDE-47 (β = 0.0247, 95% confidence interval (CI): 0.0017, 0.0477), -100 (β = 0.0264, 95% CI: 0.0087, 0.0441) and Σ₅PBDEs (β = 0.0201, 95% CI: 0.0027, 0.0374). For boys, compared with the lowest exposure groups, statistically significantly higher (feminized) 2D:4D for both hands was observed in those with the highest exposure levels of BDE-100 (β = 0.0147, 95% CI: 0.0005, 0.0289 for the left hand; β = 0.0182, 95% CI: 0.0046, 0.0318 for the right hand) and those with the middle and the highest exposure levels of BDE-153 (middle vs. undetected, β = 0.0215, 95% CI: 0.0072, 0.0358 for the left hand; β = 0.0155, 95% CI: 0.0015, 0.0295 for the right hand; highest vs. undetected, β = 0.0162, 95% CI: 0.0017, 0.0307 for the left hand; β = 0.0152, 95% CI: 0.0011, 0.0294 for the right hand).

CONCLUSIONS

Our study provides preliminary evidence that prenatal exposure to PBDEs might be associated with higher 2D:4D in boys and girls.

Prenatal exposure to residential PM2.5 and anogenital distance in infants at birth: A birth cohort study from Shanghai, China

Fine particulate matter (PM_2.5) is believed to be one of the most hazardous air pollution with a ubiquitous presence. Animal studies have reported the association between prenatal exposure to traffic pollutant (not exclusively including PM_2.5) and reproductive development in male offspring. However, the effects of prenatal exposure to PM_2.5 on reproductive health in children are still unknown. The present study was based on the Shanghai-Minhang Birth Cohort Study (S-MBCS). A total of 876 pregnant women and their infants were included. Infants' anogenital distance (AGD, the distance from the anus to the genitals; AGDap [anus-penis] and AGDas [anus-scrotum] for boys, and AGDac [anus-clitoris] and AGDaf [anus-fourchette] for girls) were measured at birth. PM_2.5 concentrations during pregnancy were estimated using satellite based modeling approach. Multiple linear regression analysis and multiple informant model were conducted to examine the associations between prenatal exposure to PM_2.5 (pre μg/m³) and offspring's AGDs (mm). In order to minimize the misclassification of exposure, a sensitivity analysis restricted to mothers being off work during pregnancy was performed. In multiple linear regression models, we found that prenatal exposure to PM_2.5 during the 1^st and 3^rd trimesters was associated with shorter AGDs. In multiple informant model, similar patterns were found, and statistically significant reductions were observed in AGDap (β=-0.278, 95%CI: -0.343∼-0.212), AGDac (β=-0.188, 95%CI: -0.247∼-0.130) and AGDaf (β= -0.163, 95%CI: -0.238∼-0.088) with PM_2.5 exposure during the 1^st trimester, and AGDap (β=-0.201, 95%CI: -0.247∼-0.155), AGDas (β=-0.158, 95%CI: -0.198∼-0.117), AGDac (β=-0.128, 95%CI: -0.167∼-0.089) and AGDaf (β = -0.144, 95%CI: -0.194∼-0.094) with PM_2.5 exposure during the 3^rd trimester. The sensitivity analysis restricted to women being off work during pregnancy showed similar results. PM_2.5 exposure during the 1^st and 3^rd trimesters was associated with shortened AGDs in offspring at birth. Our findings provide preliminary evidence that prenatal exposure to PM_2.5 might be associated with the reproductive development of offspring.

Maternal plasma concentrations of perfluoroalkyl and polyfluoroalkyl substances during pregnancy and anogenital distance in male infants

STUDY QUESTION

Are maternal plasma concentrations of perfluoroalkyl and polyfluoroalkyl substances (PFASs) during pregnancy associated with anogenital distance (AGD) in male infants at birth, 6, and 12 months of age?

SUMMARY ANSWER

Higher maternal plasma concentrations of some PFASs were associated with shorter AGD in male infants at birth and 6 months of age.

WHAT IS KNOWN ALREADY

Two animal studies have found that exposure to PFASs was associated with shorter AGD in male rat fetuses and wild male minks. There is only one human study on the topic that did not identify consistent patterns between maternal serum concentrations of PFASs during pregnancy and AGD in male infants.

STUDY DESIGN, SIZE, DURATION

In the prospective cohort study, a total of 1292 eligible pregnant women were recruited at 12-16 weeks of gestation between April and December 2012 at the Maternal and Child Health Hospital of Minhang district in Shanghai, China. At delivery, 667 male singletons were born. They were then followed up at birth (n = 439) and at 6 (n = 411) and 12 months (n = 376) of age when anopenile distance (AGDAP) and anoscrotal distance (AGDAS) were measured.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 500 male infants who had both maternal plasma concentrations of PFASs and at least one AGD measurement of at three time points were included in the present study. Multiple linear regression models were used to evaluate the potential linear associations between maternal concentrations of PFASs and AGD.

MAIN RESULTS AND THE ROLE OF CHANCE

Maternal plasma concentrations (ln-transformed) of perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUdA) were inversely associated with AGDAS or AGDAP at birth (AGDAS: per ln unit increase in PFAS concentrations: β (95% CI): -0.65 (-1.27 to -0.02) mm for PFOS; -0.58 (-1.11 to -0.06) mm for PFDA; and -0.57 (-1.09 to -0.06) mm for PFUdA; AGDAP: per ln unit increase in PFAS concentrations: β (95% CI): -0.63 (-1.24 to -0.01) mm for PFDA and - 0.76 (-1.36 to -0.16) mm for PFUdA). At 6 months of age, per unit increase in maternal ln concentrations of PFOS and perfluorotridecanoic acid (PFTrDA), AGDAS decreased on average by -2.21 (95% CI: -4.28 to -0.14) and -1.11 (95% CI: -2.17 to -0.06) mm, respectively. Additionally, ln-transformed perfluorooctanoic acid (PFOA) showed nonsignificant but inverse associations with both AGDAS and AGDAP at 6 months of age. We found no significant associations between ln-transformed maternal concentrations of PFASs and either AGDAS or AGDAP at 12 months of age. However, significantly inverse association of ln-transformed PFOA with AGDAP was observed in male infants who never or shortly breastfed (<3 months) at 12 months of age.

LIMITATIONS, REASONS FOR CAUTION

AGD measurements were performed by different examiners at each follow-up visit, and the intra-examiner variation was not assessed, which might cause intra-rater and inter-rater measurement errors. Additionally, our study may have selection bias since a considerable number of participants withdrew from the cohort although the differences in demographic characteristics were not statistically significant between included mother-infant pairs and those excluded. No statistical correction was made for multiple comparisons.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings may have important implications for the early development of genital health in male infants since PFASs can be detected in almost all pregnant women and infants worldwide.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the National Key Research and Development program of China (2018YFC1002801 and 2016YFC1000505), the Science and Technology Commission of Shanghai Municipality (16ZR1430100), the National Natural Science Foundation of China (81428011), and the Innovation-Oriented Science and Technology Grant from National Health Commission Key Laboratory of Reproduction Regulation (CX2017-06). The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Prenatal bisphenol A exposure, fetal thyroid hormones and neurobehavioral development in children at 2 and 4 years: A prospective cohort study

Findings about the association between prenatal Bisphenol A (BPA) exposure and neurobehavioral development in children are still inconsistent. In addition, whether fetal thyroid hormones (THs) mediate the reported association remains unclear. The present study aimed to examine the association between prenatal BPA exposure and risks of child behavioral problems at 2 and 4 years of age and whether the association could be explained by alteration of fetal THs as measured in cord plasma. Using the Shanghai-Minhang Birth Cohort Study (S-MBCS), BPA concentration was measured in maternal urine samples collected at 12-16 weeks of gestation. Children's neurobehavioral development was assessed using the Child Behavior Checklist/1.5-5 (CBCL), at 2 and 4 years of age. Using generalized estimating equation (GEE) models, 745 mother-pairs were included to examine associations of BPA with CBCL scores, Using multiple linear regression models, 348 mother-pairs were included to evaluate the association between maternal BPA and THs in cord plasma. A mediation analysis was conducted to explore the potential mediating role of THs. After adjusting for potential confounders, prenatal BPA level was associated with increased risks of Emotionally Reactive problem, Anxious/Depressed problem, having Somatic Complaints, exhibiting Aggressive Behavior, and Internalizing and Externalizing Problems: compared to the lowest tertile, the risks in the highest tertile and middle tertile, ranged between 1.55-fold (95% CI: 1.09, 2.21) and 2.59-fold (95% CI: 1.52, 4.42). The association was more pronounced among boys. None of the associations reached statistical significance among girls. An inverse association between prenatal BPA and fetal TH level was also observed. However, the observed neurotoxic effects of prenatal BPA exposure did not appear to be mediated by THs levels. The current findings suggest that prenatal exposure to BPA may disrupt fetal THs levels and may induce long-lasting behavioral alterations, especially in boys.

Association between pre/perinatal exposure to POPs and children's anogenital distance at age 4 years: A study from the INMA-Asturias cohort

BACKGROUND

Prenatal exposure to endocrine-disrupting chemicals may impair genital development and alter reproductive tract anatomy. Anogenital distance (AGD) is a useful biomarker of exposure to chemicals that act as endocrine disruptors. We evaluated associations between prenatal and perinatal exposure to several persistent organic pollutants (POPs) and AGD in 4-year-old children.

METHODS

Data were drawn from the INMA-Asturias cohort. Pediatricians measured the anofourchetal distance in female children and anoscrotal distance in male children. The anogenital index (AGI) was defined as the AGD divided by the child's weight at age of examination. We measured the levels of two hexachlorocyclohexane isomers, hexachlorobenzene, dichlorodiphenyltrichloroethane (DDT) and its metabolites, six polychlorinated biphenyl (PCB) congeners, and six polybrominated diphenyl ether (PBDE) congeners in maternal serum at 12 gestational weeks (n = 155) and in cord blood serum (n = 229). Anthropometric and parental sociodemographic variables were collected via face-to-face interviews. Linear regression models were used to evaluate the relationship between exposure to POPs and AGI, adjusted for confounders and stratified by sex.

RESULTS

In male children, we found inverse associations between AGI and maternal concentrations of PCB-138 (ß = -0.041, 95% confidence interval [CI]: -0.074, -0.008, second tertile), PCB-153 (ß = -0.052, 95% CI: -0.085, -0.020, second tertile), PCB-180 ß = -0.065, 95% CI: -0.096, -0.035, second tertile; ß = -0.042, 95% CI: -0.073, -0.011, third tertile), PBDE-209 (ß = -0.031, 95% CI: -0.058, -0.006), cord serum concentrations of PCB-153 (ß = -0.029, 95% CI: -0.059, -0.000, second tertile; ß = -0.047, 95% CI: -0.085, -0.008, third tertile), and PCB-180 (ß = -0.041, 95% CI: -0.078, -0.005, third tertile). In female children, AGI was positively associated with maternal serum concentrations of PCB-101 (ß = 0.039, 95% CI: 0.002, 0.076, second tertile), and higher cord serum levels of 4,4'-DDT (ß = 0.032, 95% CI: 0.003, 0.061, third tertile) and 4,4'-DDE (ß = 0.040, 95% CI: 0.011, 0.069, third tertile).

CONCLUSIONS

Our findings provide evidence of associations between specific POPs and AGI in boys and girls aged 4 years, and suggest that pre/perinatal exposure to POPs has a feminizing effect in males and a masculinizing effect in females.

Toxicity of polybrominated diphenyl ethers (PBDEs) on rodent male reproductive system: A systematic review and meta-analysis of randomized control studies

Polybrominated diphenyl ethers (PBDEs) are a group of environmental endocrine-disrupting chemicals (EDCs). According to recent studies, the associations between PBDEs and rodent male reproductive system are controversial. Therefore, we performed this systematic review and meta-analysis to clarify the effects of PBDEs on rodent male reproductive system. Data were extracted from articles collected from PubMed, Web of Science, and other databases. The pooled standard mean deviation (SMD) with 95% confidence interval (95% CI) was used to evaluate the association between the male rodent reproductive system impairment and PBDE exposure. Ten articles were included in the present meta-analysis and systematic review. The summary SMD of reproductive toxicity associated with PBDEs was -0.46 (95% CI: -0.69, -0.22), and the overall association between DE-71 along with BDE-209 and male reproductive system damage was statistically significant (SMD = -0.7 95% CI: -1.18, -0.21, p = .041; SMD = -0.41, 95% CI: -0.77, -0.05, p = .000). The adverse impact of PBDEs on rodent male reproductive system, especially seminal vesicle (SMD = -1.09, 95% CI: -1.49, -0.49, p = .523) and ventral prostate (SMD = -1.27, 95% CI: -1.88, -0.65, p = .821), were clearly demonstrated. Moderate (SMD = -0.81, 95% CI: -1.182, -0.437, p = .197) and high (SMD = -0.41, 95% CI: -0.76, -0.05, p = .000) dosage may have exerted effect than relatively low (SMD = -0.29, 95% CI: -0.17, 0.12, p = .136) dosage. In conclusion, our meta-analysis and systematic review suggested PBDE toxicity on the male reproductive system.

In utero exposure to persistent and nonpersistent endocrine-disrupting chemicals and anogenital distance. A systematic review of epidemiological studies†

Anti-androgenic endocrine-disrupting chemicals (EDCs) can cross the placenta to modify early offspring sexual dimorphic markers. These changes are linked to anogenital distance (AGD), which is an androgen-sensitive anthropometric parameter used as a biomarker of perineal growth and caudal migration of the genital tubercle. This review aimed to summarize strength of evidence for associations of in utero exposure to EDCs with AGD and to identify gaps and limitations in the literature so as to inform future research. We performed an electronic search of English literature in September 2019 in medical literature analysis and retrieval system online (MEDLINE), Web of Science and Toxline. We included epidemiological studies that examined in utero exposure to persistent and nonpersistent EDCs and considered AGD in offspring as an outcome. Our review contained 16 investigations examining exposure to persistent EDCs (nine studies) and nonpersistent EDCs (seven studies). Some individual studies reported an inverse association between exposure to bisphenol A (BPA), dioxins, perfluoroalkyl substances, and organochlorides and AGD in both male and female offspring. Meta-analysis of three studies found a small reduction of AGD in female offspring exposed to BPA. The number of studies per chemical is small, and number of subjects examined is limited; so, replication of these results is needed. To achieve more specificity and better replication of results, future studies should establish the association of nonpersistent EDCs using multiple urine samples, evaluate the cumulative impact of exposure to a mixture of anti-androgenic chemicals, and offer adequate consideration of more maternal- and children-related confounding factors.

Associations of prenatal exposures to low levels of Polybrominated Diphenyl Ether (PBDE) with thyroid hormones in cord plasma and neurobehavioral development in children at 2 and 4 years

BACKGROUND

Neurotoxic effects of Polybrominated Diphenyl Ethers (PBDEs) at low levels have not been well studied in human population, and whether the associations can be explained by thyroid hormones (THs) remains unclear.

OBJECTIVES

We examined the associations of prenatal PBDE exposures with THs in cord plasma and neurobehavior of children at 2 and 4 years among general population in China.

METHODS

Participants were mother-child pairs in the Shanghai-Minhang Birth Cohort Study. Nine PBDE congeners and THs (thyroid stimulating hormone, total thyroxine, free thyroxine, total triiodothyronine, and free triiodothyronine) were determined in cord plasma. Child Behavior Checklist (CBCL/1.5-5) were completed by caregivers to assess children's neurobehavioral development at 2 and 4 years. In the final analyses, 199 and 307 mother-child pairs at 2 and 4 years were included to examine associations of PBDEs with CBCL scores using Pearson-scale-adjusted Poisson regressions, and 339 subjects were included in linear regression models to investigate the associations between PBDEs and THs.

RESULTS

BDE-47 had the highest detection rate of 83.82% with the median concentration of 0.19 ng/g lipid, followed by BDE-28, -99, -100 and -153 with detection rates nearly 50%. We found positive associations between prenatal PBDE concentrations and children's neurobehavior, including Somatic Complaints, Withdrawn, Sleep Problems and Internalizing Problems in girls, and Somatic Complaints and Attention Problems in boys. We also observed inverse associations of the sum of BDE-47, -28, -99, -100 and -153 with THs. However, by adding THs to the models examining associations between PBDEs and CBCL, the main results didn't measurably change.

CONCLUSIONS

This study adds new knowledge that prenatal PBDEs at low levels may be related to long-lasting behavioral abnormalities in children and reduced THs in cord plasma. However, the hypothesis that the neurotoxic impact of PBDEs may be explained by alterations in cord THs was not supported.