Exposure to non-persistent chemicals in consumer products and fecundability: a systematic review

Infants exposure to chemicals in diapers: A review and perspective

Diapers are a staple care product for infants, yet concerns persist regarding the potential risks posed by dermal exposure to chemicals through their usage. This review provides a comprehensive summary of reported chemicals, highlighting the frequent detection of polychlorodibenzo-p-dioxins (PCDDs), phthalates (PAEs), volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), bisphenols (BPs), organotins, and heavy metals. Disposable diapers commonly exhibit higher concentrations of VOCs, PAEs, BPs, and heavy metals than other chemicals. Our estimation reveals formaldehyde as posing the highest dermal exposure dose, reaching up to 0.018 mg/kg bw/day. Conversely, perfluorooctanoic acid (PFOA) exhibits lower exposure, but its non-cancer hazard quotient (0.062) is the highest. In most scenarios, the risk of chemical exposure through diapers for infants is deemed acceptable, while the risk is higher under some extreme exposure scenarios. Using the cancer slope factor recently suggested by U.S. EPA, the cancer risk in diapers raised by PFOA is 5.5 × 10-5. It should be noted that our estimation is approximately 1000-10,000 folds lower than some previous estimations. The high uncertainties associated with exposure and risk estimations are primarily raised by unclear parameters related to chemical migration coefficients, absorption factors, concentrations, and toxicity data for skin exposure, which requires research attention in future. Besides that, future research endeavors should prioritize the identification of potential toxic chemicals and the development of hygiene guidelines and standards.

The mixture of non-persistent endocrine-disrupting chemicals in relation to endometriosis

Non-persistent endocrine-disrupting chemicals (EDCs) are of significant concern due to their reproductive toxicity. Previous research reported a relationship between a single type of EDCs and endometriosis. Yet, evidence regarding mixed exposure of multiple categories of EDCs is scarce. Between 2014 and 2018, our hospital-based case-control study recruited 238 endometriosis cases diagnosed by laparoscopy and 296 normal controls in China. Seventeen non-persistent EDCs (phthalates and bisphenols) were measured in urine. The association of single EDC with endometriosis was estimated using logistic regression, while the association between EDC mixture and endometriosis was modeled by Bayesian kernel machine regression (BKMR), quantile-based g-computation (q-gcomp), and principal component analysis (PCA). Consistent results were observed in both single and mixture models where phthalates and bisphenols were associated with increased risk of endometriosis (mixture effect: adjusted odds ratio (aOR)=1.44, 1.22-1.70) and the major contributors were bisphenol A (BPA) and the metabolites of di(2-ethylhexyl) phthalate (DEHP). Interaction analysis showed that bisphenols exhibited significant synergistic interactions with phthalates. Our results suggest that non-persistent EDCs are associated with endometriosis but the underlying mechanisms remain to be elucidated. Our finding may have important public health implications in preventing endometriosis.

Evaluating associations of bisphenol and phthalate exposure with time to pregnancy and subfecundity in a New York City pregnancy cohort

It is important to understand the impact of consumer chemical exposure and fecundity, a couple's measure of probability of successful conception, given approximately 15% of couples experience infertility. Prior research has generally found null associations between bisphenol and phthalate exposure and fecundability, measured via time to pregnancy (TTP). However, this research has not been updated with current chemical exposures and have often lacked diversity in their study populations. We evaluated the associations between common bisphenol and phthalate chemical exposure groups and TTP as well as subfecundity (TTP>12 months) in the New York University Children's Health Study, a diverse pregnancy cohort from 2016 onward. Using first-trimester spot-urine samples to measure chemical exposure and self-reported TTP from first-trimester questionnaires, we observed a significant adverse association between total bisphenol exposure and certain phthalate groups on TTP and odds of subfecundity. Furthermore, in a mixtures analysis to explore the joint effects of the chemical groups on the outcomes, we found evidence of a potential interaction between total bisphenol exposure and low-molecular weight phthalates on TTP. Future research should continue to update our knowledge regarding the complex and potentially interacting effects of these chemicals on reproductive health.

Mixed effects of ambient air pollutants on oocyte-related outcomes: A novel insight from women undergoing assisted reproductive technology

Air pollution is widely acknowledged as a significant risk factor for human health, especially reproductive health. Nevertheless, many studies have disregarded the potentially mixed effects of air pollutants on reproductive outcomes. We performed a retrospective cohort study involving 8048 women with 9445 cycles undergoing In Vitro Fertilization (IVF) and Intracytoplasmic Sperm Injection (ICSI) in China, from 2017 to 2021. A land-use random forest model was applied to estimate daily residential exposure to air pollutants, including sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), and fine particulate matter (PM2.5). Individual and joint associations between air pollutants and oocyte-related outcomes of ART were evaluated. In 90 days prior to oocyte pick-up to oocyte pick-up (period A), NO2, O3 and CO was negatively associated with total oocyte yield. In the 90 days prior to oocyte pick-up to start of gonadotropin medication (Gn start, period B), there was a negative dose-dependent association of exposure to five air pollutants with total oocyte yield and mature oocyte yield. In Qgcomp analysis, increasing the multiple air pollutants mixtures by one quartile was related to reducing the number of oocyte pick-ups by -2.00 % (95 %CI: -2.78 %, -1.22 %) in period A, -2.62 % (95 %CI: -3.40 %, -1.84 %) in period B, and -0.98 % (95 %CI: -1.75 %, -0.21 %) in period C. During period B, a 1-unit increase in the WQS index of multiple air pollutants exposure was associated with fewer number of total oocyte (-1.27 %, 95 %CI: -2.16 %, -0.36 %) and mature oocyte (-1.42 %, 95 %CI: -2.41 %, -0.43 %). O3 and NO2 were major contributors with adverse effects on the mixed associations. Additionally, period B appears to be the susceptible window. Our study implies that exposure to air pollution adversely affects oocyte-related outcomes, which raises concerns about the potential adverse impact of air pollution on women's reproductive health.

Phthalate exposure and subfecundity in preconception couples: A nested case-control study

BACKGROUND

Phthalates (PAEs) are endocrine-disrupting chemicals ubiquitously found in the environment. This study aimed to examine the association between exposure of PAEs and subfecundity in preconception couples.

METHODS

This is a nested case-control study based on preconception cohort. Preconception couples with intention to conceive were enrolled and followed up until a clinically confirmed pregnancy or 12 menstrual cycles of preparation for conception. A total of 107 couples with subfecundity- time to pregnancy (TTP) more than 12 menstrual cycles, and 144 couples ≤12 cycles were included in the analysis. The levels of PAE metabolites in one spot urine samples were detected and compared between the groups. The weighted quantile sum (WQS) regression model and Bayesian kernel machine regression (BKMR) model were used to examine the joint effects of couples' exposure to PAEs on subfecundity.

RESULTS

Using the multivariate binary logistic regression model, compared to the lowest quartile of urinary ∑PAEs concentration group, both preconception females (aOR=2.42, 95% CI: 1.10-5.30, p=0.027) and males (aOR=2.99, 95% CI: 1.36-6.58, p=0.006) in the highest quartile group had an increased risk of subfecundity, and a dose-response relationship was observed between PAEs and the risk of subfecundity. The WQS analyses found that co-exposure to PAE mixture was a risk factor for subfecundity in preconception female (aOR=1.76, 95% CI: 1.38-2.26, p<0.001), male (aOR=1.58, 95% CI: 1.20-2.08, p=0.001), and couple (aOR=2.39, 95% CI: 1.61-3.52, p<0.001). The BKMR model found a positive combined effect of mixed exposure to PAEs on the risk of subfecundity.

CONCLUSIONS

PAEs increase the risk of subfecundity in preconception couples. Our research reinforced the need of monitoring PAE exposure for the purpose of improving human reproductive health.

Distribution and potential risk factors of bisphenol a in serum and urine among Chinese from 2004 to 2019

Background

Bisphenol A (BPA) is an oil-derived, large-market volume chemical with endocrine disrupting properties and reproductive toxicity. Moreover, BPA is frequently used in food contact materials, has been extensively researched recently, and widespread exposure in the general population has been reported worldwide. However, national information on BPA levels in general Chinese people is lacking.

Methods

This study collected and analyzed 145 (104 in urine and 41 in serum) research articles published between 2004 and 2021 to reflect the BPA internal exposure levels in Chinese populations. The Monte Carlo simulation method is employed to analyze and estimate the data in order to rectify the deviation caused by a skewed distribution.

Results

Data on BPA concentrations in urine and serum were collected from 2006 to 2019 and 2004 to 2019, respectively. Urinary BPA concentrations did not vary significantly until 2017, with the highest concentration occurring from 2018 to 2019 (2.90 ng/mL). The serum BPA concentration decreased to the nadir of 1.07 ng/mL in 2011 and gradually increased to 2.54 ng/mL. Nationally, 18 provinces were studied, with Guangdong (3.50 ng/mL), Zhejiang (2.57 ng/mL), and Fujian (2.15 ng/mL) having the highest urine BPA levels. Serum BPA was investigated in 15 provinces; Jiangsu (9.14 ng/mL) and Shandong (5.80 ng/mL) were relatively high. The results also indicated that males' urine and serum BPA levels were higher than females, while the BPA levels in children were also higher than in adults (p < 0.001). Furthermore, the volume of garbage disposal (r = 0.39, p < 0.05), household sewage (r = 0.34, p < 0.05), and waste incineration content (r = 0.35, p < 0.05) exhibited a strong positive connection with urine BPA levels in Chinese individuals.

Conclusion

Despite using a data consolidation approach, our study found that the Chinese population was exposed to significant amounts of BPA, and males having a higher level than females. Besides, the levels of BPA exposure are influenced by the volume of garbage disposal, household sewage, and waste incineration content.

Associations of personal care products use with reproductive outcomes of IVF/ICSI treatment

Introduction

Personal care products (PCPs) contain a number of endocrine-disrupting chemicals (EDCs) that could potentially affect the reproductive function in women of childbearing age. However, studies focused on the effects of PCPs use on reproductive outcomes are very limited. The current study aimed to explore the relationships between PCPs use patterns and reproductive outcomes in women undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment.

Methods

A total of 1500 women from the Tongji Reproductive and Environmental (TREE) study between December 2018 and January 2020 were included in this study. Participants provided characteristics of PCPs use within the previous three months. Retrieved oocyte number, mature oocyte number, two distinct pronuclei (2PN) zygote number, fertilization rate, cleavage rate, blastocyst formation rate, implantation, clinical pregnancy, miscarriage, and live birth were followed up as reproductive endpoints. Generalized linear regression model was utilized to assess the associations between various categories of PCPs use and reproductive endpoints of IVF/ICSI.

Results

After adjusting for relevant covariates, women who used skin care products ≥14 times per week had a reduction of 22.4% in the maturation rate (95% CI: -39.2%, -1.6%) compared to participants who did not use skin care products. After transferring fresh embryos, women who used cosmetics 1-2 times per week (adjusted OR = 2.2, 95% CI: 1.0, 4.8) or 3-7 times per week (adjusted OR = 2.5, 95% CI: 1.2, 5.2) had a higher possibility of miscarriage than those who did not use cosmetics. There was negative association between the use of gel or soap and the cleavage rate among women aged < 30 years old (P for interaction = 0.01). Among women with BMI ≥ 24 kg/m2, the use of gel or soap was negatively associated with the blastocyst formation rate (P for interaction = 0.04), while cosmetics use was negatively associated with the maturation rate (P for interaction = 0.001).

Conclusion

Our findings suggest that the use of PCPs in women of reproductive age have a potential adverse impact on IVF/ICSI outcomes, particularly skin care and cosmetic products.

Interference of gut-brain-gonad axis originating from triclocarban exposure to parent zebrafish induces offspring embryonic development abnormality by up-regulation of maternal circSGOL1

Triclocarban (TCC) is a widely used antibacterial ingredient possessing acute toxicity effects; however, its chronic toxicity and underlying molecular mechanisms remain uncertain. Herein, we demonstrated that chronic TCC exposure affects the growth and development of adult zebrafish through inducing an intestinal flora disorder in the gut. The imbalance of intestinal flora caused functional barriers within the intestinal-brain-gonadal axis. This resulted in a series of anomalous nerve and motor behaviors, and reproductive toxicity as reflected in pathological damage to parental gonads and F1-larval developmental malformations. Abnormal development of F1 larvae was attributed to apoptosis induced by the up-regulation of circSGOL1. This up-regulation affected the activity and localization of the hnRNP A1 protein, which then promoted overexpression of pro-apoptotic related genes that ultimately lead to apoptosis during early embryonic development. Overall, these novel findings systematically elucidated the TCC toxicity mechanism in parent-offspring dyads, and provide important theoretical guidance for early risk warning and control of chronic TCC toxicity.

"Cocktail" of environmental chemicals and early reproductive outcomes of IVF: The insight from paternal and maternal exposure

BACKGROUND

Humans are exposed to various chemicals, including organophosphate esters (OPEs), phthalates (PAEs), and phenols. The effects on early reproductive outcomes of in vitro fertilization (IVF) remain unclear.

METHODS

We recruited 192 women and 157 men who underwent IVF treatment. A total of forty-nine urinary chemicals were detected, including six OPEs, fifteen PAEs, six parabens, two chlorophenols, nine bisphenols, five benzophenones, and six synthetic phenolic antioxidants. We examined the individual and joint effects of parental chemical exposure on early reproductive outcomes.

RESULTS

We found that certain chemicals were associated with early reproductive outcomes in Poisson regression models. For example, urinary diphenyl phosphate was negatively associated with high-quality embryos in both female (β: -0.12, 95%CI: -0.17, -0.07) and male partners (β: -0.09, 95%CI: -0.15, -0.03). A negative association was found between mixed chemicals and high-quality embryos in Bayesian kernel machine regression, weighted quantile sum regression (β: -0.34, 95%CI: -0.60, -0.07), and quantile-based g-computation model (β: -0.69, 95%CI: -1.34, -0.05) among female partners. Paternal mixture exposure was not associated with early reproductive outcomes.

CONCLUSIONS

Our results indicated that increased exposure to environmental chemicals was associated with adverse early reproductive outcomes of IVF, especially female partners.

Associations between Phthalate Metabolite Concentrations in Follicular Fluid and Reproductive Outcomes among Women Undergoing in Vitro Fertilization/Intracytoplasmic Sperm Injection Treatment

BACKGROUND

Phthalates have been reported to impair fertility in various studies. However, evidence exploring the associations between phthalate metabolites in follicular fluid (FF) and reproductive outcomes is lacking.

OBJECTIVES

To investigate the associations between phthalate metabolite concentrations in FF and in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcomes among women recruited from a fertility clinic.

METHODS

We included 641 women undergoing IVF/ICSI treatment from December 2018 to January 2020. The levels of eight phthalate metabolites, including monoethyl phthalate (MEP), mono-isobutyl phthalate (MiBP), mono-n -butyl phthalate (MBP), monobenzyl phthalate (MBzP), mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), were quantified in FF collected on the oocyte retrieval day. Associations between quartiles of individual phthalate metabolite concentrations and nine IVF/ICSI outcomes, including oocyte yield, mature oocyte number, two distinct pronuclei (2PN) zygote number, fertilization rate, blastocyst formation rate, implantation, clinical pregnancy, miscarriage, and live birth, were estimated with generalized linear models. The effects of phthalate mixtures on IVF/ICSI outcomes were assessed using Bayesian kernel machine regression (BKMR) models.

RESULTS

After adjusting for relevant confounders, elevated quartiles of MBzP, MEHHP, and MEHP in FF were inversely associated with the numbers of retrieved oocytes, mature oocytes, and 2PN zygotes (all p for trends < 0.10 ). In comparison with the lowest quartile, the highest quartile of molar sum of di(2-ethylhexyl) phthalate metabolites (Σ DEHP ) was associated with a reduction of 9.1% [95% confidence interval (CI): - 17.1 % , - 0.37 % ] and 10.3% (95% CI: - 18.8 % , - 0.94 % ) in yielded oocyte and mature oocyte numbers, respectively. Furthermore, the BKMR models revealed inverse associations between phthalate mixtures and the numbers of retrieved oocytes and mature oocytes. We generally found null results for implantation, clinical pregnancy, miscarriage, and live birth.

DISCUSSION

Certain phthalate metabolites in FF are inversely associated with the numbers of retrieved oocytes, mature oocytes, and 2PN zygotes among women undergoing IVF/ICSI treatment. https://doi.org/10.1289/EHP11998.

Preconception Phthalate Exposure and Women's Reproductive Health: Pregnancy, Pregnancy Loss, and Underlying Mechanisms

BACKGROUND

Phthalates are endocrine-disrupting chemicals linked to adverse pregnancy outcomes. Despite the sensitivity of female reproductive processes to oxidation-reduction reaction stress and endocrine disruption, evidence for the impact of women's phthalate exposure on the ability to establish and maintain pregnancy has been inconclusive.

OBJECTIVES

We aimed to determine the relationship of preconception phthalate metabolite exposure with a) fecundability and pregnancy loss and b) markers of potential biological mechanisms, including reproductive hormones, inflammation, and oxidative stress.

METHODS

Data were collected from the Effects of Aspirin in Gestation and Reproduction (EAGeR) trial, a preconception study following 1,228 women who were attempting pregnancy, for up to six menstrual cycles and throughout pregnancy if they became pregnant. Twenty phthalate metabolites were measured in a consecutive 3-d pooled urine sample at enrollment. Pregnancy was determined through urinary human chorionic gonadotropin (hCG) at the expected date of menses during each cycle and pregnancy loss as an observed loss following positive hCG. Highly sensitive C-reactive protein (hsCRP) and isoprostanes were measured at enrollment, and reproductive hormones were measured during the follicular phase, ovulation, and luteal phase. Discrete-time Cox proportional hazards models evaluated the relationship of phthalate metabolites with fecundability and weighted Poisson models with robust variance evaluated the risk of pregnancy loss.

RESULTS

An interquartile range (IQR) higher mono-(2-ethylhexyl) phthalate [fecundability odds ratio  ( FOR ) = 0.88 ; 95% confidence interval (CI): 0.78, 1.00], mono-butyl phthalate (FOR = 0.82 ; 95% CI: 0.70, 0.96), and mono-benzyl phthalate (FOR = 0.85 ; 95% CI: 0.74, 0.98) was associated with lower fecundability. No consistent associations were observed with pregnancy loss. Preconception phthalates were consistently associated with higher hsCRP and isoprostanes, as well as lower estradiol and higher follicle-stimulating hormone across the menstrual cycle.

DISCUSSION

Women's preconception exposure to phthalates was associated with lower fecundability, changes in reproductive hormones, and increased inflammation and oxidative stress. The pre- and periconception periods may represent sensitive windows for intervening to limit the reproductive toxicity of phthalate exposure. https://doi.org/10.1289/EHP12287.

Deteriorating Semen Quality: The Role of the Environment

Since the end of the last century, several reports have suggested that semen quality is declining, especially in Western countries. Furthermore, cross-sectional studies using similar protocols have suggested regional differences in semen quality of young and fertile men. Reasons for these regional differences and local adverse trends in semen quality are unknown, but environmental factors are suspected to have a role. Besides adulthood environmental exposures, those occurring during testicular development may also affect semen quality. Longitudinal follow-up studies and mixture risk analyses are needed to study the effect of fetal, childhood, and adult life environment on semen quality.

Urinary Paraben Concentrations and Associations with the Periconceptional Urinary Metabolome: Untargeted and Targeted Metabolomics Analyses of Participants from the Early Pregnancy Study

BACKGROUND

Parabens, found in everyday items from personal care products to foods, are chemicals with endocrine-disrupting activity, which has been shown to influence reproductive function.

OBJECTIVES

This study investigated whether urinary concentrations of methylparaben, propylparaben, or butylparaben were associated with the urinary metabolome during the periconceptional period, a critical window for female reproductive function. Changes to the periconceptional urinary metabolome could provide insights into the mechanisms by which parabens could impact fertility.

METHODS

Urinary paraben concentrations were measured in paired pre- and postconception urine samples from 42 participants in the Early Pregnancy Study, a prospective cohort of 221 women attempting to conceive. We performed untargeted and targeted metabolomics analyses using ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry. We used principal component analysis, orthogonal partial least-squares discriminant analysis, and permutation testing, coupled with univariate statistical analyses, to find metabolites associated with paraben concentration at the two time points. Potential confounders were identified with a directed acyclic graph and used to adjust results with multivariable linear regression. Metabolites were identified using fragmentation data.

RESULTS

Seven metabolites were associated with paraben concentration (variable importance to projection score > 1 , false discovery rate-corrected q -value < 0.1 ). We identified four diet-related metabolites to the Metabolomics Standards Initiative (MSI) certainty of identification level 2, including metabolites from smoke flavoring, grapes, and olive oil. One metabolite was identified to the class level only (MSI level 3). Two metabolites were unidentified (MSI level 4). After adjustment, three metabolites remained associated with methylparaben and propylparaben, two of which were diet-related. No metabolomic markers of endocrine disruption were associated with paraben concentrations.

DISCUSSION

This study identified novel relationships between urinary paraben concentrations and diet-related metabolites but not with metabolites on endocrine-disrupting pathways, as hypothesized. It demonstrates the feasibility of integrating untargeted metabolomics data with environmental exposure information and epidemiological adjustment for confounders. The findings underscore a potentially important connection between diet and paraben exposure, with applications to nutritional epidemiology and dietary exposure assessment. https://doi.org/10.1289/EHP12125.

CA, Catellier D, Cordero JF, Croen L, Dabelea D, Deoni S, D’Sa V, Duarte CS, Dunlop AL, Elliott AJ, Farzan SF, Ferrara A, Ganiban JM, Gern JE, Giardino AP, Towe-Goodman NR, Gold DR, Habre R, Hamra GB, Hartert T, Herbstman JB, Hertz-Picciotto I, Hipwell AE, Karagas MR, Karr CJ, Keenan K, Kerver JM, Koinis-Mitchell D, Lau B, Lester BM, Leve LD, Leventhal B, LeWinn KZ, Lewis J, Litonjua AA, Lyall K, Madan JC, McEvoy CT, McGrath M, Meeker JD, Miller RL, Morello-Frosch R, Neiderhiser JM, O’Connor TG, Oken E, O’Shea M, Paneth N, Porucznik CA, Sathyanarayana S, Schantz SL, Spindel ER, Stanford JB, Stroustrup A, Teitelbaum SL, Trasande L, Volk H, Wadhwa PD, Weiss ST, Woodruff TJ, Wright RJ, Zhao Q, Jacobson LP, Influences on Child Health Outcomes ,OBOPCFE. The Environmental Influences on Child Health Outcomes (ECHO)-Wide Cohort

The Environmental Influences on Child Health Outcomes (ECHO)-Wide Cohort Study (EWC), a collaborative research design comprising 69 cohorts in 31 consortia, was funded by the National Institutes of Health (NIH) in 2016 to improve children's health in the United States. The EWC harmonizes extant data and collects new data using a standardized protocol, the ECHO-Wide Cohort Data Collection Protocol (EWCP). EWCP visits occur at least once per life stage, but the frequency and timing of the visits vary across cohorts. As of March 4, 2022, the EWC cohorts contributed data from 60,553 children and consented 29,622 children for new EWCP data and biospecimen collection. The median (interquartile range) age of EWCP-enrolled children was 7.5 years (3.7-11.1). Surveys, interviews, standardized examinations, laboratory analyses, and medical record abstraction are used to obtain information in 5 main outcome areas: pre-, peri-, and postnatal outcomes; neurodevelopment; obesity; airways; and positive health. Exposures include factors at the level of place (e.g., air pollution, neighborhood socioeconomic status), family (e.g., parental mental health), and individuals (e.g., diet, genomics).

Adverse effects of triclosan exposure on health and potential molecular mechanisms

With the COVID-19 pandemic, the use of disinfectants has grown significantly around the world. Triclosan (TCS), namely 5-chloro-2-(2,4-dichlorophenoxy) phenol or 2,4,4'-trichloro-2'-hydroxydiphenyl ether, is a broad-spectrum, lipophilic, antibacterial agent that is extensively used in multifarious consumer products. Due to the widespread use and bioaccumulation, TCS is frequently detected in the environment and human biological samples. Accumulating evidence suggests that TCS is considered as a novel endocrine disruptor and may have potential unfavorable effects on human health, but studies on the toxic effect mediated by TCS exposure as well as its underlying mechanisms of action are relatively sparse. Therefore, in this review, we attempted to summarize the potential detrimental effects of TCS exposure on human reproductive health, liver function, intestinal homeostasis, kidney function, thyroid endocrine, and other tissue health, and further explore its mechanisms of action, thereby contributing to the better understanding of TCS characteristics and safety. Moreover, our work suggested the need to further investigate the biological effects of TCS exposure at the metabolic level in vivo.

Incorporation of Fast-Elimination Chemicals in Hair Is Governed by Pharmacokinetics-Implications for Exposure Assessment

Mechanisms governing chemicals' incorporation in hair are incompletely understood, and gaps remain to link the concentration of chemicals in hair to level of exposure and internal dose present in the body. This study assesses the relevance of hair analysis for the biomonitoring of exposure to fast-elimination compounds and investigates the role of pharmacokinetics (PK) in their incorporation in hair. Rats were administered with pesticides, bisphenols, phthalates, and DINCH over 2 months. Hairs were analyzed for 28 chemicals/metabolites to investigate correlations between their concentration in hair and the dose administered to the animals. Urine collected over 24 h after gavage was used to determine chemicals' PK and to investigate their influence on incorporation into hair by means of linear mixed models (LMMs). Eighteen chemicals presented a significant correlation between concentration in hair and level of exposure. In models combining all chemicals, agreement between concentration in hair predicted by LMM and experimental values was moderate (R² = 0.19) but significantly increased when PK were included in the models (R² = 0.37), and even more when chemical families were considered separately (e.g., R² = 0.98 for pesticides). This study shows that pharmacokinetics mediate incorporation of chemicals in hair and suggests the relevance of hair for assessing exposure to fast-elimination chemicals.

Paraben exposure and couple fecundity: a preconception cohort study

STUDY QUESTION

Is pre-conception exposure to parabens associated with fecundity in couples of childbearing age?

SUMMARY ANSWER

Paraben exposure in female partners was associated with reduced couple fecundity and anti-Müllerian hormone (AMH) might be one of the possible mediators.

WHAT IS KNOWN ALREADY

The reproductive toxicity of parabens, a class of widely used preservatives, has been suggested but evidence regarding their effects on couple fecundity is scarce.

STUDY DESIGN, SIZE, DURATION

In this couple-based prospective cohort study, a total of 884 pre-conception couples who participated in the Shanghai Birth Cohort between 2013 and 2015 were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Concentrations of six parabens were measured in urine samples collected from couples. Malondialdehyde, C-reactive protein, and AMH were assessed in female partners. The outcomes included couple fecundability (time-to-pregnancy, TTP) and infertility (TTP > 12 menstrual cycles). Partner-specific and couple-based models were applied to estimate the associations. The joint effect of paraben mixture on couple fecundity was estimated by quantile-based g-computation (q-gcomp). Mediation analysis was used to assess the mediating roles of oxidative stress, inflammation and ovarian reserve.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 525 couples (59.4%) conceived spontaneously. In the partner-specific model, propyl paraben (PrP), butyl paraben (BuP), and heptyl paraben (HeP) in female partners were associated with reduced fecundability (fecundability odds ratio (95% CI): 0.96 (0.94-0.98) for PrP; 0.90 (0.87-0.94) for BuP; 0.42 (0.28-0.65) for HeP) and increased risk of infertility (rate ratio (95% CI): 1.06 (1.03-1.10) for PrP; 1.14 (1.08-1.21) for BuP; 1.89 (1.26-2.83) for HeP). Similar associations were observed in the couple-based model. AMH played a significant mediation role in the association (average causal mediation effect (95% CI): 0.001 (0.0001-0.003)). Paraben exposure in male partners was not associated with couple fecundity. The joint effect of paraben mixture on couple fecundity was non-significant.

LIMITATIONS, REASONS FOR CAUTION

Self-reported pregnancy and single urine sample may lead to misclassification. The mediation analysis is limited in that levels of sex hormones were not measured. The inclusion of women with irregular menstrual cycles might affect the results. It is possible that the observed association was due to reverse causation.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to assess the effects of paraben exposure on couple fecundity in Asians. Given the widespread exposure to parabens in couples of childbearing age, the present findings may have important public health implications.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported in part by the National Natural Science Foundation of China (41991314), the Shanghai Science and Technology Development Foundation (22YF1426700), the Science and Technology Commission of Shanghai Municipality (21410713500), and the Shanghai Municipal Health Commission (2020CXJQ01). All authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Urinary phenol concentrations and fecundability and early pregnancy loss

STUDY QUESTION

Are urinary phenol concentrations of methylparaben, propylparaben, butylparaben, triclosan, benzophenone-3, 2,4-dichlorophenol or 2,5-dichlorophenol associated with fecundability and early pregnancy loss?

SUMMARY ANSWER

2,5-dichlorophenol concentrations were associated with an increased odds of early pregnancy loss, and higher concentrations of butylparaben and triclosan were associated with an increase in fecundability.

WHAT IS KNOWN ALREADY

Phenols are chemicals with endocrine-disrupting potential found in everyday products. Despite plausible mechanisms of phenol reproductive toxicity, there are inconsistent results across few epidemiologic studies examining phenol exposure and reproductive function in non-fertility treatment populations.

STUDY DESIGN, SIZE, DURATION

Specimens and data were from the North Carolina Early Pregnancy Study prospective cohort of 221 women attempting to conceive naturally from 1982 to 1986. This analysis includes data from 221 participants across 706 menstrual cycles, with 135 live births, 15 clinical miscarriages and 48 early pregnancy losses (before 42 days after the last menstrual period).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants collected daily first-morning urine specimens. For each menstrual cycle, aliquots from three daily specimens across the cycle were pooled within individuals and analyzed for phenol concentrations. To assess sample repeatability, we calculated intraclass correlation coefficients (ICCs) for each phenol. We evaluated associations between phenol concentrations from pooled samples and time to pregnancy using discrete-time logistic regression and generalized estimating equations (GEE), and early pregnancy loss using multivariable logistic regression and GEE.

MAIN RESULTS AND THE ROLE OF CHANCE

ICCs for within-person variability across menstrual cycles in pooled phenol concentrations ranged from 0.42 to 0.75. There was an increased odds of early pregnancy loss with 2,5-dichlorophenol concentrations although the CIs were wide (5th vs 1st quintile odds ratio (OR): 4.79; 95% CI: 1.06, 21.59). There was an increased per-cycle odds of conception at higher concentrations of butylparaben (OR: 1.62; 95% CI: 1.08, 2.44) and triclosan (OR: 1.49; 95% CI: 0.99, 2.26) compared to non-detectable concentrations. No associations were observed between these endpoints and concentrations of other phenols examined.

LIMITATIONS, REASONS FOR CAUTION

Limitations include the absence of phenol measurements for male partners and a limited sample size, especially for the outcome of early pregnancy loss, which reduced our power to detect associations.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the first to use repeated pooled measures to summarize phenol exposure and the first to investigate associations with fecundability and early pregnancy loss. Within-person phenol concentration variability underscores the importance of collecting repeated samples for future studies. Exposure misclassification could contribute to differences between the findings of this study and those of other studies, all of which used one urine sample to assess phenol exposure. This study also contributes to the limited literature probing potential associations between environmental exposures and early pregnancy loss, which is a challenging outcome to study as it typically occurs before a pregnancy is clinically recognized.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the National Institute of Environmental Health Sciences of the National Institutes of Health (award number F31ES030594), the Intramural Research Program of the National Institutes of Health, the National Institute of Environmental Health Sciences (project numbers ES103333 and ES103086) and a doctoral fellowship at the Yale School of Public Health. The authors declare they have no competing interests to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Endocrine Disrupting Chemicals in Polycystic Ovary Syndrome: The Relevant Role of the Theca and Granulosa Cells in the Pathogenesis of the Ovarian Dysfunction

Polycystic ovary syndrome (PCOS) is the most common heterogeneous endocrine disorder among women of reproductive age. The pathogenesis of PCOS remains elusive; however, there is evidence suggesting the potential contribution of genetic interactions or predispositions combined with environmental factors. Among these, endocrine disrupting chemicals (EDCs) have been proposed to potentially contribute to the etiology of PCOS. Granulosa and theca cells are known to cooperate to maintain ovarian function, and any disturbance can lead to endocrine disorders, such as PCOS. This article provides a review of the recent knowledge on PCOS pathophysiology, the role of granulosa and theca cells in PCOS pathogenesis, and the evidence linking exposure to EDCs with reproductive disorders such as PCOS.

Environmental and occupational factors and higher risk of couple infertility: a systematic review study

Background

Infertility is a global health problem that represents an increasing trend due to new lifestyles following technological advances since individuals are facing more risk factors than before. The present systematic review study aimed to investigate the impact of environmental and occupational factors on reproductive parameters and increased risk of couple infertility.

Main body

Scopus, PubMed, SID, and Web of Science databases were searched for the available observational (i.e., cohort, case-control, and cross-sectional) systematic review, meta-analysis, and clinical trial studies between 2007 and 2019. To this end, keywords such as ‘Environmental exposure’, ‘Occupational exposure’, ‘Environmental pollutants’, ‘Environmental pollution’, ‘Couple infertility’, ‘Sterility’, and ‘Sub-fertility’ were used. The retrieved investigations examined the impact of environmental and occupational risk factors on reproductive indices and increased infertility risk. Totally, 66 out of 9519 papers were evaluated after considering the inclusion and exclusion criteria. The reported risk factors in the reviewed studies were heavy metals, cigarette smoking, and exposure to chemicals through consumer goods, urban life, and proximity to main roads. In addition, occupational factors included heavy physical activity, prolonged sitting, exposure to a hot environment, contact with formaldehyde, pesticides, insecticides, mechanical vibration, and contact with ionizing radiation, all of which affected the reproductive parameters. However, some researchers found no significant associations in this regard.

Short conclusion

In general, individuals with known impairments in reproductive parameters were more exposed to risk factors. Nonetheless, more studies are needed to determine the risk of infertility in the population.

Redox Status, Estrogen and Progesterone Production by Swine Granulosa Cells Are Impaired by Triclosan

Triclosan is a chlorinated biphenolic with a broad spectrum of antiseptic activities used in cosmetics and hygiene products. Continuous exposure can lead to absorption and bioaccumulation of this substance with harmful health effects. In fact, previous studies have shown that Triclosan acts as an endocrine-disrupting chemical on reproductive organs, with consequent negative effects on reproductive physiology. Therefore, to assess potential adverse impacts on fertility, we tested Triclosan on swine granulosa cells, a model of endocrine reproductive cells. We examined its effects on the main features of granulosa cell functions such as cell growth (BrdU incorporation and ATP production) and steroidogenesis (17-β estradiol and progesterone secretion). Moreover, since oxidant−antioxidant balance plays a pivotal role in follicular function, redox status markers (superoxide, hydrogen peroxide and nitric oxide production, enzymatic and non-enzymatic scavenging activity) were studied. Our results show that Triclosan significantly inhibits cell growth (p < 0.001), steroidogenesis (p < 0.001), superoxide and nitric oxide production (p < 0.001), while it increases (p < 0.05) enzymatic defense systems. Collectively, these data suggest a disruption of the main granulosa cell functions, i.e., proliferation and hormone production, as well as an imbalance in redox status. On these bases, we can speculate that Triclosan would impair granulosa cell functions, thus exerting negative effects on reproductive function. Further studies are needed to explore lower Triclosan concentrations and to unravel its mechanisms of action at gene level.

Lifestyle interventions to reduce endocrine-disrupting phthalate and phenol exposures among reproductive age men and women: A review and future steps

Non-persistent endocrine-disrupting chemicals (EDCs), including phthalates and phenols, are ubiquitous in both the environment and human body. A growing body of epidemiologic studies have identified concerning links between EDCs and adverse reproductive and developmental health effects. Despite consistent evidence, risk assessments and policy interventions often arrive late. This presents an urgent need to identify evidence-based interventions for implementation at both clinical and community levels to reduce EDC exposure, especially in susceptible populations. The reproductive life cycle (menarche to menopause for females and after pubertal onset for males) includes some of the most vulnerable periods to environmental exposures, such as the preconception and perinatal stages, representing a key window of opportunity to intervene and prevent unfavorable health outcomes. This review aims to synthesize and assess behavioral, dietary, and residential EDC-driven interventions to develop recommendations for subsequent, larger-scale studies that address knowledge-gaps in current interventions during the reproductive life cycle. We selected 21 primary interventions for evaluation, in addition to four supplemental interventions. Among these, accessible (web-based) educational resources, targeted replacement of (known) toxic products, and personalization of the intervention through meetings and support groups, were the most promising strategies for reducing EDC concentrations. However, we document a paucity of interventions to prevent phthalate and phenol exposures during the reproductive years, especially among men. Accordingly, we recommend additional, larger clinical and community-based intervention studies to reduce EDC exposure. Specifically, future intervention studies should focus on short-term, mid-, and long-term exposure reduction to phthalates and phenols. The latter, especially, is required for the development of clinical and public health guidelines to promote reproductive and developmental health globally.

Urinary concentrations of polycyclic aromatic hydrocarbon and phthalate metabolite mixtures in relation to semen quality among men attending an infertility clinic

Previous studies have reported that exposure to phthalates and polycyclic aromatic hydrocarbons (PAHs) is individually associated with altered semen quality, but no human studies have evaluated their joint effects of exposure mixtures, a more real-world scenario. We aimed to explore urinary metabolite mixtures of phthalates and PAHs in associations with semen quality. Repeated spot-urine samples gathered from 695 men attending a fertility clinic were analyzed for urinary metabolites of eight phthalates and ten monohydroxylated-PAHs (OH-PAHs). Principal component analysis (PCA)-multivariable linear regression (MLR) model, quantile g-computation (qg-comp), and Bayesian kernel machine regression (BKMR) were applied to estimate the associations of urinary mixtures of phthalate and OH-PAH metabolites with semen quality. The overall effects of urinary mixtures of phthalate and PAH metabolites on semen quality were not statistically significant. However, hydroxynaphthalene (OHNa) factor identified from PCA was monotonically associated with decreased total sperm count and sperm concentration, whereas di(2-ethylhexyl) phthalate (DEHP) factor was non-monotonically related to increased progressive sperm motility and total sperm motility. Qg-comp and BKMR models confirmed these findings and identified 2-OHNa and 2-OHFlu as the primary negative contributors, whereas MEOHP and MEHP as the primary positive contributors. Our findings suggest that exposure to mixtures of naphthalene and DEHP is associated with altered semen quality. The finding is warranted to confirm in further well-designed epidemiological studies.

[Impact of lifestyle and environmental factors on male reproductive health]

The identification of potential environmental hazards is of clinical relevance for the diagnosis of male infertility. Knowledge about these factors will improve prevention of fertility disorders. Apart from drugs or factors related to lifestyle such as alcohol and tobacco smoke, various environmental and occupational agents, both chemical and physical, may impair male reproduction. Reproductive toxicity may evolve at the hypothalamic-pituitary, testicular, or posttesticular level; endpoints comprise deterioration of spermatogenesis and sperm function as well as endocrine disorders and sexual dysfunction. However, due to the complex regulation of the male reproductive system, information regarding single exogenous factors and their mechanisms of action in humans is limited. This is also due to the fact that extrapolation of results obtained from experimental animal or in vitro studies remains difficult. Nevertheless, the assessment of relevant exposures to reproductive toxicants should be carefully evaluated during diagnostic procedures of andrological patients.

Connexin-43 is a promising target for lycopene preventing phthalate-induced spermatogenic disorders

INTRODUCTION

Male infertility is a multifactorial pathological condition and may be a harbinger of future health. Phthalates are ubiquitous environmental contaminants that have been implicated in the global decline in male fertility. Among them, di-(2-ethylhexyl) phthalate (DEHP) is the most prevalently used. Lycopene (LYC) is a possible preventive and therapeutic agent for male infertility owing to its antioxidant properties. The blood-testis barrier (BTB) is formed between Sertoli cells where it creates a unique microenvironment for spermatogenesis.

OBJECTIVES

We hypothesize that phthalate caused male infertility and LYC plays an important role in phthalate-induced male fertility disorders.

METHODS

Hematoxylin-eosin (H&E) staining, ultrastructure observation, and fluorescence microscopy were used to examine the morphological changes. RNA-Seq, and western blotting were conducted to detect gene and protein levels. Routine testing for sperm morphology and sperm-egg binding assay were conducted to examine the morphological structure and function of sperm. Cell scratch assay and transepithelial electrical resistance (TER) were used to detect cell migration capacity and barrier integrity.

RESULTS

In vivo experiments, we showed that LYC prevented DEHP-induced impairment of BTB integrity, which provided a guarantee for the smooth progress of spermatogenesis. LYC improved DEHP-induced change in sperm parameters and fertilization ability. Subsequent in vitro experiments, LYC alleviated MEHP-induced disruption of intercellular junctions in mouse Spermatogonia cells (GC-1 cells) and mouse Sertoli cells (TM4 cells). In MEHP-induced BTB impairment models of Sertoli cells, treatment with LYC or overexpressing connexin-43 (Cx43) promoted cell migration capacity and normalized BTB integrity. Cx43 knockdown inhibited cell migration capacity and perturbed BTB reassembly in LYC preventing DEHP-induced BTB impairment.

CONCLUSION

Our study provides evidence for the role of LYC in phthalates-induced spermatogenic disorders and points to Cx43 as a potential target for male fertility.

Per- and polyfluoroalkyl substances (PFAS) and male reproductive function in young adulthood; a cross-sectional study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are a large family of persistent industrial chemicals with endocrine disrupting properties.

OBJECTIVES

To examine biomarkers of reproductive function in young adult males according to current environmental exposure to single and combined PFAS.

METHODS

The study population consisted of young men (n = 1041, age 18-21) from the Fetal Programming of Semen Quality (FEPOS) cohort. These men were recruited from pregnancies included in the Danish National Birth Cohort (DNBC) between 1996 and 2002. From 2017 to 2019, participants answered an online questionnaire, completed a clinical examination and provided a blood and a semen sample. Exposure to 15 PFAS was measured in plasma. Six compounds were quantified above the limit of detection in at least 80% of the participants. We applied negative binomial regression and weighted quantile sum (WQS) regression models to assess associations between single and combined exposure to PFAS and measures of semen quality, testicular volume and reproductive hormones among the young men.

RESULTS

We found no consistent associations between plasma concentrations of PFAS, semen quality and testicular volume. Higher levels of single and combined PFAS were associated with slightly higher levels of follicle-stimulating hormone (FSH) (WQS 4% difference, 95% confidence interval: 0, 9). Perfluorooctanoic acid (PFOA) was the main contributor to this finding with positive signals also from perfluorodecanoic acid (PFDA) and perfluorohexane sulfonic acid (PFHxS).

DISCUSSION

We examined exposure to a range of common PFAS in relation to biomarkers of male reproductive function and found an association with higher levels of FSH among young men from the general population in Denmark. Further studies on especially combined exposure to PFAS are needed to expand our understanding of potential endocrine disruption from both legacy and emerging compounds in relation to male reproductive function.

Biomaterials and advanced technologies for the evaluation and treatment of ovarian aging

Ovarian aging is characterized by a progressive decline in ovarian function. With the increase in life expectancy worldwide, ovarian aging has gradually become a key health problem among women. Over the years, various strategies have been developed to preserve fertility in women, while there are currently no clinical treatments to delay ovarian aging. Recently, advances in biomaterials and technologies, such as three-dimensional (3D) printing and microfluidics for the encapsulation of follicles and nanoparticles as delivery systems for drugs, have shown potential to be translational strategies for ovarian aging. This review introduces the research progress on the mechanisms underlying ovarian aging, and summarizes the current state of biomaterials in the evaluation and treatment of ovarian aging, including safety, potential applications, future directions and difficulties in translation.

Indoor and outdoor air pollution and couple fecundability: a systematic review

BACKGROUND

Air pollution is both a sensory blight and a threat to human health. Inhaled environmental pollutants can be naturally occurring or human-made, and include traffic-related air pollution (TRAP), ozone, particulate matter (PM) and volatile organic compounds, among other substances, including those from secondhand smoking. Studies of air pollution on reproductive and endocrine systems have reported associations of TRAP, secondhand smoke (SHS), organic solvents and biomass fueled-cooking with adverse birth outcomes. While some evidence suggests that air pollution contributes to infertility, the extant literature is mixed, and varying effects of pollutants have been reported.

OBJECTIVE AND RATIONALE

Although some reviews have studied the association between common outdoor air pollutants and time to pregnancy (TTP), there are no comprehensive reviews that also include exposure to indoor inhaled pollutants, such as airborne occupational toxicants and SHS. The current systematic review summarizes the strength of evidence for associations of outdoor air pollution, SHS and indoor inhaled air pollution with couple fecundability and identifies gaps and limitations in the literature to inform policy decisions and future research.

SEARCH METHODS

We performed an electronic search of six databases for original research articles in English published since 1990 on TTP or fecundability and a number of chemicals in the context of air pollution, inhalation and aerosolization. Standardized forms for screening, data extraction and study quality were developed using DistillerSR software and completed in duplicate. We used the Newcastle-Ottawa Scale to assess risk of bias and devised additional quality metrics based on specific methodological features of both air pollution and fecundability studies.

OUTCOMES

The search returned 5200 articles, 4994 of which were excluded at the level of title and abstract screening. After full-text screening, 35 papers remained for data extraction and synthesis. An additional 3 papers were identified independently that fit criteria, and 5 papers involving multiple routes of exposure were removed, yielding 33 articles from 28 studies for analysis. There were 8 papers that examined outdoor air quality, while 6 papers examined SHS exposure and 19 papers examined indoor air quality. The results indicated an association between outdoor air pollution and reduced fecundability, including TRAP and specifically nitrogen oxides and PM with a diameter of ≤2.5 µm, as well as exposure to SHS and formaldehyde. However, exposure windows differed greatly between studies as did the method of exposure assessment. There was little evidence that exposure to volatile solvents is associated with reduced fecundability.

WIDER IMPLICATIONS

The evidence suggests that exposure to outdoor air pollutants, SHS and some occupational inhaled pollutants may reduce fecundability. Future studies of SHS should use indoor air monitors and biomarkers to improve exposure assessment. Air monitors that capture real-time exposure can provide valuable insight about the role of indoor air pollution and are helpful in assessing the short-term acute effects of pollutants on TTP.

Endocrine disrupting chemicals impact on ovarian aging: Evidence from epidemiological and experimental evidence

Endocrine-disrupting chemicals (EDCs) are ubiquitous in daily life, but their harmful effects on the human body have not been fully explored. Recent studies have shown that EDCs exposure could lead to infertility, menstrual disorder and menopause, resulting in subsequent effects on female health. Therefore, it is of great significance to clarify and summarize the impacts of EDCs on ovarian aging for explaining the etiology of ovarian aging and maintaining female reproductive health. Here in this review, we focused on the impacts of ten typical environmental contaminants on the progression of ovarian aging during adult exposure, including epidemiological data in humans and experimental models in rodents, with their clinical phenotypes and underlying mechanisms. We found that both persistent (polychlorinated biphenyls, perfluoroalkyl and polyfluoroalkyl substances) and non-persistent (phthalates) EDCs exposure could increase an overall risk of ovarian aging, leading to the diminish of ovarian reserve, decline of fertility or fecundity, irregularity of the menstrual cycle and an earlier age at menopause, and/or premature ovarian insufficiency/failure in epidemiological studies. Among these, the loss of follicles can also be validated in experimental studies of some EDCs, such as BPA, phthalates, parabens and PCBs. The underlying mechanisms may involve the impaired ovarian follicular development by altering receptor-mediated pro-apoptotic pathways, inducing signal transduction and cell cycle arrest and epigenetic modification. However, there were inconsistent results in the impacts on fertility/fecundity, menstrual/estrous cycle and hormone changes response to different EDCs, and differences between human and animal studies. Our review summarizes the current state of knowledge on ovarian disrupters, highlights their risks to ovarian aging and identifies knowledge gaps in humans and animals. We therefore propose that females adopt healthy lifestyle changes to minimize their exposure to both persistent and non-persistent chemicals, that have the potential damage to their reproductive function.

Does Older Age Modify Associations between Endocrine Disrupting Chemicals and Fecundability?

Urinary concentrations of several endocrine disrupting chemicals, including phthalate metabolites, bisphenol A (BPA), and benzophenone (BP)-type ultraviolet (UV) filters, have been associated with a longer time-to-pregnancy (TTP). Potential modification of these associations by couple’s age has not been studied. TTP was defined as the number of prospectively observed menstrual cycles a couple attempted pregnancy until the occurrence of a human chorionic gonadotropic-detected pregnancy. Urinary concentrations of two BP-type UV filters and three phthalate metabolites were measured at baseline. Fecundability odds ratios (FORs) and 95% confidence intervals (CIs) were estimated for each chemical adjusting for age, body mass index, serum cotinine, creatinine, and accounting for right censoring and left truncation. Models evaluated effect modification between EDC concentrations and TTP by partner’s age, dichotomized at 35 years. Separate models were run for male and female partners. No significant effect modification was observed for any EDC for either partner, but data were suggestive of a longer TTP among females aged ≥35 years, particularly for BP-2 (FOR = 0.61, 95% CI 0.36, 1.05) and 4-hydroxybenzophenone (FOR = 0.71, 95% CI: 0.46, 1.09) reflecting 39% and 29% reductions in fecundability, respectively. We saw no evidence of effect modification by couples’ age on associations between TTP and urinary phthalate or BPA metabolite concentrations. Across the EDCs we examined, we found little evidence that age modifies TTP-exposure associations.

Exposure to disinfection by-products and reproductive hormones among women: Results from the Tongji Reproductive and Environmental (TREE) study

BACKGROUND

Disinfection by-products (DBPs) have been shown to impair female reproductive function. However, epidemiological evidence on reproductive hormones is scarce.

OBJECTIVE

To investigate the associations between DBP exposures and reproductive hormones among women undergoing assisted reproductive technology.

METHODS

We included 725 women from the Tongji Reproductive and Environmental (TREE) Study, an ongoing cohort conducted in Wuhan, China during December 2018 and January 2020. Urine samples collected at recruitment were quantified for dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) as biomarkers of DBP exposures. At day 2-5 of menstruation, serum reproductive hormones including luteinizing hormone (LH), estradiol (E₂), total testosterone (T), progesterone (PRGE), and prolactin (PRL) were determined. Multivariate linear regression models were performed to assess the associations of urinary DCAA and TCAA concentrations with reproductive hormone levels. Dose-response relationships were investigated using natural cubic spline (NCS) and restricted cubic spline (RCS) models.

RESULTS

After adjusting for relevant confounders, we observed that higher urinary DCAA levels were associated with increased serum PRGE (9.2%; 95% CI: -0.55%, 19.8% for the highest vs. lowest tertile; P for trend = 0.06). Based on NCS models, we observed U-shaped associations of urinary DCAA with serum PRGE and PRL; each ln-unit increment in urinary DCAA concentrations above 3.61 μg/L and 6.30 μg/L was associated with 18.9% (95% CI: 4.8%, 34.7%) and 23.3% (95% CI: -0.92%, 53.5%) increase in serum PRGE and PRL, respectively. The U-shaped associations were further confirmed in RCS models (P for overall association ≤0.01 and P for non-linear associations ≤0.04). We did not observe evidence of associations between urinary TCAA and reproductive hormones.

CONCLUSION

Urinary DCAA but not TCAA was associated with altered serum PRGE and PRL levels among women undergoing assisted reproductive technology.

Associations of Urinary Trichloroacetic Acid Concentrations with Spermatozoa Apoptosis and DNA Damage in a Chinese Population

Exposure to trichloroacetic acid (TCAA) has been associated with impaired semen quality; however, its association with spermatozoa apoptosis and DNA damage remains unclear. We, therefore, collected single semen and repeated urine samples from male partners of couples attending a reproductive center, which were measured for spermatozoa apoptosis and DNA damage parameters and TCAA concentrations, respectively. Multivariable linear regression models were used to explore the associations between urinary TCAA concentrations and spermatozoa apoptosis (n = 462) and DNA damage parameters (n = 512). After adjusting for potential confounders, positive dose-response relationships were found between urinary TCAA concentrations and percentage of tail DNA (tail%) and tail-distributed moment (TDM) (both p for trend <0.10). Compared with men in the lowest tertile of urinary TCAA concentrations, men in the highest tertile had a greater tail% and TDM of 6.2% (95% CI: 0.7, 12.2%) and 8.9% (95% CI: -1.9, 20.5%), respectively. Urinary TCAA concentrations were unrelated to spermatozoa apoptosis parameters in a dose-response manner. However, urinary TCAA concentrations were positively associated with the percentage of Annexin V⁺/PI^- spermatozoa (apoptotic cells), when urinary TCAA concentrations were modeled as continuous variables. Our results suggest that exposure to TCAA at concentrations in real-world scenarios may be associated with spermatozoa apoptosis and DNA damage.

Endocrine disruptors: Challenges and future directions in epidemiologic research

Public concern about the impact of endocrine disrupting chemicals (EDCs) on both humans and the environment is growing steadily. Epidemiologic research provides key information towards our understanding of the relationship between environmental exposures like EDCs and human health outcomes. Intended for researchers in disciplines complementary to epidemiology, this paper highlights the importance and challenges of epidemiologic research in order to present the key elements pertaining to the design and interpretation of an epidemiologic study on EDCs. The conduct of observational studies on EDCs derives from a thoughtful research question, which will help determine the subsequent methodological choices surrounding the careful selection of the study population (including the comparison group), the adequate ascertainment of exposure(s) and outcome(s) of interest, and the application of methodological and statistical concepts more specific to epidemiology. The interpretation of epidemiologic results may be arduous due to the latency occurring between EDC exposure and certain outcome(s), the complexity in capturing EDC exposure(s), and traditional methodological and statistical issues that also deserve consideration (e.g., confounding, effect modification, non-monotonic responses). Moving forward, we strongly advocate for an integrative approach of expertise in the fields of epidemiology, exposure science, risk assessment and toxicology to adequately study the health risks associated with EDCs while tackling their challenges.

Predictive models of pregnancy based on data from a preconception cohort study

STUDY QUESTION

Can we derive adequate models to predict the probability of conception among couples actively trying to conceive?

SUMMARY ANSWER

Leveraging data collected from female participants in a North American preconception cohort study, we developed models to predict pregnancy with performance of ∼70% in the area under the receiver operating characteristic curve (AUC).

WHAT IS KNOWN ALREADY

Earlier work has focused primarily on identifying individual risk factors for infertility. Several predictive models have been developed in subfertile populations, with relatively low discrimination (AUC: 59-64%).

STUDY DESIGN, SIZE, DURATION

Study participants were female, aged 21-45 years, residents of the USA or Canada, not using fertility treatment, and actively trying to conceive at enrollment (2013-2019). Participants completed a baseline questionnaire at enrollment and follow-up questionnaires every 2 months for up to 12 months or until conception. We used data from 4133 participants with no more than one menstrual cycle of pregnancy attempt at study entry.

PARTICIPANTS/MATERIALS, SETTING, METHODS

On the baseline questionnaire, participants reported data on sociodemographic factors, lifestyle and behavioral factors, diet quality, medical history and selected male partner characteristics. A total of 163 predictors were considered in this study. We implemented regularized logistic regression, support vector machines, neural networks and gradient boosted decision trees to derive models predicting the probability of pregnancy: (i) within fewer than 12 menstrual cycles of pregnancy attempt time (Model I), and (ii) within 6 menstrual cycles of pregnancy attempt time (Model II). Cox models were used to predict the probability of pregnancy within each menstrual cycle for up to 12 cycles of follow-up (Model III). We assessed model performance using the AUC and the weighted-F1 score for Models I and II, and the concordance index for Model III.

MAIN RESULTS AND THE ROLE OF CHANCE

Model I and II AUCs were 70% and 66%, respectively, in parsimonious models, and the concordance index for Model III was 63%. The predictors that were positively associated with pregnancy in all models were: having previously breastfed an infant and using multivitamins or folic acid supplements. The predictors that were inversely associated with pregnancy in all models were: female age, female BMI and history of infertility. Among nulligravid women with no history of infertility, the most important predictors were: female age, female BMI, male BMI, use of a fertility app, attempt time at study entry and perceived stress.

LIMITATIONS, REASONS FOR CAUTION

Reliance on self-reported predictor data could have introduced misclassification, which would likely be non-differential with respect to the pregnancy outcome given the prospective design. In addition, we cannot be certain that all relevant predictor variables were considered. Finally, though we validated the models using split-sample replication techniques, we did not conduct an external validation study.

WIDER IMPLICATIONS OF THE FINDINGS

Given a wide range of predictor data, machine learning algorithms can be leveraged to analyze epidemiologic data and predict the probability of conception with discrimination that exceeds earlier work.

STUDY FUNDING/COMPETING INTEREST(S)

The research was partially supported by the U.S. National Science Foundation (under grants DMS-1664644, CNS-1645681 and IIS-1914792) and the National Institutes for Health (under grants R01 GM135930 and UL54 TR004130). In the last 3 years, L.A.W. has received in-kind donations for primary data collection in PRESTO from FertilityFriend.com, Kindara.com, Sandstone Diagnostics and Swiss Precision Diagnostics. L.A.W. also serves as a fibroid consultant to AbbVie, Inc. The other authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Human health impacts of exposure to phthalate plasticizers: An overview of reviews

In this review of reviews, we overview the current global body of available evidence from structured reviews of epidemiological studies that explore human health outcomes associated with exposure to phthalates (chemical plasticisers commonly found in plastics). We found robust evidence for an association with lower semen quality, neurodevelopment and risk of childhood asthma, and moderate to robust evidence for impact on anogenital distance in boys. We identified moderate evidence for an association between phthalates/metabolites and low birthweight, endometriosis, decreased testosterone, ADHD, Type 2 diabetes and breast/uterine cancer. There was some evidence for other outcomes including anofourchette distance, fetal sex hormones, pre-term birth, lower antral follicle count, reduced oestrodiol, autism, obesity, thyroid function and hearing disorders. We found no reviews of epidemiological human studies on the impact of phthalates from recycled plastics on human health. We recommend that future research should use urine samples as exposure measures, consider confounders in analyses and measure impacts on female reproductive systems. Our findings align with emerging research indicating that health risks can occur at exposure levels below the "safe dose" levels set out by regulators, and are of particular concern given potential additive or synergistic "cocktail effects" of chemicals. This raises important policy and regulatory issues for identifying and controlling plastics and health related impacts and highlights a need for more research into substances of concern entering plastics waste streams via recycling.

Ethylene oxide derived glycol ethers: A review of the alkyl glycol ethers potential to cause endocrine disruption

The 'ethylene glycol ethers' (EGE) are a broad family of solvents and hydraulic fluids produced through the reaction of ethylene oxide and a monoalcohol. Certain EGE derived from methanol and ethanol are well known to cause toxicity to the testes and fetotoxicity and that this is caused by the common metabolites methoxy and ethoxyacetic acid, respectively. There have been numerous published claims that EGE fall into the category of 'endocrine disruptors' often without substantiated evidence. This review systematically evaluates all of the available and relevant in vitro and in vivo data across this family of substances using an approach based around the EFSA/ECHA 2018 guidance for the identification of endocrine disruptors. The conclusion reached is that there is no significant evidence to show that EGE target any endocrine organs or perturb endocrine pathways and that any toxicity that is seen occurs by non-endocrine modes of action.

Optimizing natural fertility: a committee opinion

This committee opinion provides practitioners with suggestions for optimizing the likelihood of achieving pregnancy in couples or individuals attempting conception who have no evidence of infertility. This document replaces the document of the same name previously published in 2013 (Fertil Steril 2013;100:631-7).

Update about the disrupting-effects of phthalates on the human reproductive system

Phthalate esters are synthetic chemicals used in the plastic industry as plasticizers and consumable products. According to United Nations, about 400 million tons of plastic are produced every year. In parallel with increased production, the concerns about its effects on human health have increased because phthalates are endocrine-disrupting compounds. Humans are continuously exposed to phthalates through different routes of exposure. Experimental data have associated the phthalates exposure to adverse effects on development and reproduction in women (e.g., earlier puberty, primary ovarian insufficiency, endometriosis, preterm birth, or in vitro fertilization) and men (e.g., anogenital distance, cryptorchidism, hypospadias, and changes in adult reproductive function) although there is no consensus. Therefore, one question arises: could the increase in infertility be related to phthalates exposure? To answer this question, we aimed to assess the disrupting-effects of phthalates on the human reproductive system. For this, we reviewed the current literature based on epidemiological and experimental data and experimental studies in humans. The phthalate effects were discussed in a separate mode for female and male reproductive systems. In summary, phthalates induce toxicity in the reproductive system and human development. The increased plastic production may be related to the increase in human infertility.

Effects of Endocrine-Disrupting Chemicals on Endometrial Receptivity and Embryo Implantation: A Systematic Review of 34 Mouse Model Studies

Several available studies have already analyzed the systemic effects of endocrine-disrupting chemicals (EDCs) on fertile woman and neonatal outcomes, but little is still known in humans about the precise mechanisms of interference of these compounds with the endometrial receptivity. There is consistent evidence that continuous and prolonged exposure to EDCs is a risk factor for reduced fertility and fecundity in women. Preliminary studies on mammalian models provide robust evidence about this issue and could help gynecologists worldwide to prevent long term injury caused by EDCs on human fertility. In this systematic review, we aimed to systematically summarize all available data about EDC effects on blastocyst endometrial implantation. We performed a systematic review using PubMed^®/MEDLINE^® to summarize all in vivo studies, carried out on mice models, analyzing the molecular consequences of the prolonged exposure of EDC on the implantation process. 34 studies carried out on mouse models were included. Primary effects of EDC were a reduction of the number of implantation sites and pregnancy rates, particularly after BPA and phthalate exposure. Furthermore, the endometrial expression of estrogen (ER) and progesterone receptors (PR), as well as their activation pathways, is compromised after EDC exposure. Finally, the expression of the primary endometrial markers of receptivity (such as MUC1, HOXA10, Inn and E-cadherin) after EDC contact was analyzed. In conclusion EDC deeply affect blastocyst implantation in mouse model. Several players of the implantation mechanism are strongly influenced by the exposure to different categories of EDC.

Endocrine disrupting chemicals: Impacts on human fertility and fecundity during the peri-conception period

It is becoming increasingly difficult to avoid exposure to man-made endocrine disrupting chemicals (EDCs) and environmental toxicants. This escalating yet constant exposure is postulated to partially explain the concurrent decline in human fertility that has occurred over the last 50 years. Controversy however remains as to whether associations exist, with conflicting findings commonly reported for all major EDC classes. The primary aim of this extensive work was to identify and review strong peer-reviewed evidence regarding the effects of environmentally-relevant EDC concentrations on adult male and female fertility during the critical periconception period on reproductive hormone concentrations, gamete and embryo characteristics, as well as the time to pregnancy in the general population. Secondly, to ascertain whether individuals or couples diagnosed as sub-fertile exhibit higher EDC or toxicant concentrations. Lastly, to highlight where little or no data exists that prevents strong associations being identified. From the greater than 1480 known EDCs, substantial evidence supports a negative association between exposure to phthalates, PCBs, PBDEs, pyrethroids, organochloride pesticides and male fertility and fecundity. Only moderate evidence exists for a negative association between BPA, PCBs, organochloride pesticides and female fertility and fecundity. Overall fewer studies were reported in women than men, with knowledge gaps generally evident for both sexes for all the major EDC classes, as well as a paucity of female fertility studies following exposure to parabens, triclosans, dioxins, PFAS, organophosphates and pyrethroids. Generally, sub-fertile individuals or couples exhibit higher EDC concentrations, endorsing a positive association between EDC exposure and sub-fertility. This review also discusses confounding and limiting factors that hamper our understanding of EDC exposures on fertility and fecundity. Finally, it highlights future research areas, as well as government, industry and social awareness strategies required to mitigate the negative effects of EDC and environmental toxicant exposure on human fertility and fecundity.

Evaluation of Triclosan Effects on Cultured Swine Luteal Cells

Simple Summary

A great concern has been raised against many chemicals, both natural and man-made, that can mimic or interfere with the hormones. Among these, using swine ovarian cells, we were aimed to explore the potential effect of triclosan, an antimicrobial agent widely used in cosmetics and home products. Our results demonstrate that triclosan disrupts cellular function, in particular interfering with hormone production and proliferation, thus suggesting a critical evaluation of its effects.

Abstract

Triclosan is a chlorinated phenolic, used in many personal and home care products for its powerful antimicrobial effect. Several studies have shown triclosan toxicity and the American Food and Drug Administration (FDA) in 2016 has limited its use. It has been recently included in endocrine-disrupting chemicals (EDCs), a list of chemicals known for their ability to interfere with hormonal signaling with particular critical effects on reproduction both in animals and humans. In order to deepen the knowledge in this specific field, the present study was undertaken to explore the effect of different concentrations of triclosan (1, 10, and 50 µM) on cultured luteal cells, isolated from swine ovaries, evaluating effects on growth Bromodeoxyuridine (BrDU) incorporation and Adenosine TriPhosphate (ATP) production, steroidogenesis (progesterone secretion) and redox status (superoxide and nitric oxide production, enzymatic and non-enzymatic scavenging activity). A biphasic effect was exerted by triclosan on P4 production. In fact, the highest concentration inhibited, while the others stimulated P4 production (p < 0.05). Triclosan significantly inhibited cell proliferation, metabolic activity, and enzymatic scavenger activity (p < 0.05). On the contrary, nitric oxide production was significantly increased by triclosan (p < 0.01), while superoxide anion generation and non-enzymatic scavenging activity were unaffected.

Persistent organic pollutants and couple fecundability: a systematic review

BACKGROUND

Despite increasing regulation, exposure to persistent organic pollutants (POPs) remains a serious public health concern due to their accumulation in the environment and ability to biomagnify up the food chain. POPs are associated with endocrine-disrupting effects including adverse reproductive outcomes that could affect fecundability, i.e. the capacity to conceive a pregnancy, quantified as time to pregnancy (TTP).

OBJECTIVE AND RATIONALE

Results of epidemiologic studies that examine the impact of various chemical classes of POPs on TTP have not been synthesised. We undertook a systematic review to summarise the strength of evidence for associations of four common groups of POPs with couple fecundability and to identify gaps and limitations in the literature in order to inform policy decisions and future research.

SEARCH METHODS

We performed an electronic search of literature published between 1 January 2007 and 6 August 2019 in MEDLINE, EMBASE.com, Global Health, DART/TOXLINE and POPLINE. We included empirical research papers that examined human exposure to organochlorine (OC) pesticides, brominated flame retardants, polychlorinated organic compounds and/or per- and polyfluoroalkyl substances (PFAS) and considered TTP or fecundability as an outcome. Standardised forms for screening, data extraction and study quality were developed using DistillerSR software, and all reviews were completed in duplicate. We used the Newcastle-Ottawa Scale to assess risk of bias and devised additional quality metrics based on specific methodological features of fecundability studies.

OUTCOMES

The search returned 4573 articles, and 28 papers from 19 different studies met inclusion criteria. Among them, four studies measured TTP prospectively, three had data on participants' prenatal exposure, three examined associations in both male and female partners and one focused exclusively on males. Analyses varied widely in terms of exposure characterisation, precluding a meta-analytic approach. Evidence was strongest for adverse associations of female exposure to polychlorinated biphenyls with TTP, with some additional support for associations of female exposure to polybrominated diphenyl ethers and PFAS with longer TTP. Our review provided little or no support for associations between female exposure to OC pesticides or male exposure to any of the POP groups and TTP.

WIDER IMPLICATIONS

Evidence suggests that female exposure to at least some POPs may reduce fecundability. Although many of these chemicals are no longer in production, they are still detectable in human biosamples because of their persistence in the environment. Replacement chemicals that are being introduced as older ones are restricted may have similar reproductive consequences. Future studies should examine these newer POPs, assess interactions between POPs and other chemical and non-chemical exposures, investigate how POPs are distributed in and metabolised by the human body and focus on populations that may be disproportionately exposed.

Endocrine Disruptors Acting on Estrogen and Androgen Pathways Cause Reproductive Disorders through Multiple Mechanisms: A Review

Increasing contamination of the environment by toxic compounds such as endocrine disrupting chemicals (EDCs) is one of the major causes of reproductive defects in both sexes. Estrogen/androgen pathways are of utmost importance in gonadal development, determination of secondary sex characteristics and gametogenesis. Most of the EDCs mediate their action through respective receptors and/or downstream signaling. The purpose of this review is to highlight the mechanism by which EDCs can trigger antagonistic or agonistic response, acting through estrogen/androgen receptors causing reproductive defects that lead to infertility. In vitro, in vivo and in silico studies focusing on the impact of EDCs on estrogen/androgen pathways and related proteins published in the last decade were considered for the review. PUBMED and PUBCHEM were used for literature search. EDCs can bind to estrogen receptors (ERα and ERβ) and androgen receptors or activate alternative receptors such as G protein-coupled receptors (GPCR), GPR30, estrogen-related receptor (ERRγ) to activate estrogen signaling via downstream kinases. Bisphenol A, dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene, polychlorinated biphenyls and phthalates are major toxicants that interfere with the normal estrogen/androgen pathways leading to infertility in both sexes through many ways, including DNA damage in spermatozoids, altered methylation pattern, histone modifications and miRNA expression.

Endocrine Disruptor Compounds-A Cause of Impaired Immune Tolerance Driving Inflammatory Disorders of Pregnancy?

Endocrine disrupting compounds (EDCs) are prevalent and ubiquitous in our environment and have substantial potential to compromise human and animal health. Amongst the chronic health conditions associated with EDC exposure, dysregulation of reproductive function in both females and males is prominent. Human epidemiological studies demonstrate links between EDC exposure and infertility, as well as gestational disorders including miscarriage, fetal growth restriction, preeclampsia, and preterm birth. Animal experiments show EDCs administered during gestation, or to either parent prior to conception, can interfere with gamete quality, embryo implantation, and placental and fetal development, with consequences for offspring viability and health. It has been presumed that EDCs operate principally through disrupting hormone-regulated events in reproduction and fetal development, but EDC effects on maternal immune receptivity to pregnancy are also implicated. EDCs can modulate both the innate and adaptive arms of the immune system, to alter inflammatory responses, and interfere with generation of regulatory T (Treg) cells that are critical for pregnancy tolerance. Effects of EDCs on immune cells are complex and likely exerted by both steroid hormone-dependent and hormone-independent pathways. Thus, to better understand how EDCs impact reproduction and pregnancy, it is imperative to consider how immune-mediated mechanisms are affected by EDCs. This review will describe evidence that several EDCs modify elements of the immune response relevant to pregnancy, and will discuss the potential for EDCs to disrupt immune tolerance required for robust placentation and optimal fetal development.

Female Fertility and Environmental Pollution

A realistic picture of our world shows that it is heavily polluted everywhere. Coastal regions and oceans are polluted by farm fertilizer, manure runoff, sewage and industrial discharges, and large isles of waste plastic are floating around, impacting sea life. Terrestrial ecosystems are contaminated by heavy metals and organic chemicals that can be taken up by and accumulate in crop plants, and water tables are heavily contaminated by untreated industrial discharges. As deadly particulates can drift far, poor air quality has become a significant global problem and one that is not exclusive to major industrialized cities. The consequences are a dramatic impairment of our ecosystem and biodiversity and increases in degenerative or man-made diseases. In this respect, it has been demonstrated that environmental pollution impairs fertility in all mammalian species. The worst consequences are observed for females since the number of germ cells present in the ovary is fixed during fetal life, and the cells are not renewable. This means that any pollutant affecting hormonal homeostasis and/or the reproductive apparatus inevitably harms reproductive performance. This decline will have important social and economic consequences that can no longer be overlooked.

Metabolism-Disrupting Chemicals and the Constitutive Androstane Receptor CAR

During the last two decades, the constitutive androstane receptor (CAR; NR1I3) has emerged as a master activator of drug- and xenobiotic-metabolizing enzymes and transporters that govern the clearance of both exogenous and endogenous small molecules. Recent studies indicate that CAR participates, together with other nuclear receptors (NRs) and transcription factors, in regulation of hepatic glucose and lipid metabolism, hepatocyte communication, proliferation and toxicity, and liver tumor development in rodents. Endocrine-disrupting chemicals (EDCs) constitute a wide range of persistent organic compounds that have been associated with aberrations of hormone-dependent physiological processes. Their adverse health effects include metabolic alterations such as diabetes, obesity, and fatty liver disease in animal models and humans exposed to EDCs. As numerous xenobiotics can activate CAR, its role in EDC-elicited adverse metabolic effects has gained much interest. Here, we review the key features and mechanisms of CAR as a xenobiotic-sensing receptor, species differences and selectivity of CAR ligands, contribution of CAR to regulation hepatic metabolism, and evidence for CAR-dependent EDC action therein.

Ambient air pollution exposed during preantral-antral follicle transition stage was sensitive to associate with clinical pregnancy for women receiving IVF

Maternal exposure to air pollution is associated with poor reproductive outcomes in in vitro fertilization (IVF). However, the susceptible time windows are still not been known clearly. In the present study, we linked the air pollution data with the information of 9001 women receiving 10,467 transfer cycles from August 2014 to August 2019 in The Second Hospital of Hebei Medical University, Shijiazhuang City, China. Maternal exposure was presented as individual average daily concentrations of PM_2.5, PM₁₀, NO₂, SO₂, CO, and O_3, which were predicted by spatiotemporal kriging model based on residential addresses. Exposure windows were divided to five periods according to the process of follicular and embryonic development in IVF. Generalized estimating equation model was used to evaluate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for association between clinical pregnancy and interquartile range increased average daily concentrations of pollutants during each exposure period. The increased PM_2.5 (adjusted OR = 0.95, 95% CI: 0.90, 0.99), PM₁₀ (adjusted OR = 0.93, 95% CI: 0.89, 0.98), NO₂ (adjusted OR = 0.89, 95% CI: 0.85, 0.94), SO₂ (OR = 0.94, 95% CI: 0.90, 0.98), CO (adjusted OR = 0.93, 95% CI: 0.89, 0.97) whereas decreased O₃ (OR = 1.08, 95% CI: 1.02, 1.14) during the duration from preantral follicles to antral follicles were the strongest association with decreased probability of clinical pregnancy among the five periods. Especially, women aged 20-29 years old were more susceptible in preantral-antral follicle transition stage. Women aged 36-47 years old were more vulnerable during post-oocyte retrieve period. Our results suggested air pollution exposure during preantral-antral follicle transition stage was a note-worthy challenge to conceive among females receiving IVF.

Use of Personal Care Products and Semen Quality: A Cross-Sectional Study in Young Danish Men

Personal care products (PCPs) may contain multiple chemicals capable of harming male reproductive function. The aim of this study was, therefore, to assess aggregated PCP exposure and potential associations with measures of semen quality in young men. Participants (n = 1058, age 18–21) were sampled among young men from the Danish National Birth Cohort (DNBC). Upon recruitment in 2017–2019, each man answered an online questionnaire and provided a semen sample. Exposure to 12 common types of PCPs was derived from the questionnaire, and the extent of use and co-use was analyzed. We applied a negative binomial regression model to estimate percentage differences in semen parameters between low, medium and high PCP exposure groups. All participants were exposed to at least one PCP more than once a week, resulting in a mean number (SD) of 5.3 (2.0) PCPs currently used. Most participants (92%) were also exposed to fragranced products on a weekly basis. Little association was observed between aggregated exposure to PCPs and sperm concentration, total sperm count, semen volume, sperm motility and morphology. Despite prevalent use of multiple PCPs, we found little indication of adverse effects of aggregated overall or fragranced PCP exposure on semen quality.

Per- and polyfluoroalkyl substances and male reproductive health: a systematic review of the epidemiological evidence

Exposure to environmental pollutants may produce impairment of male reproductive health. The epidemiological literature evaluating potential consequences of human exposure to per- and polyfluoroalkyl substances (PFAS) has grown in recent years with concerns for both pre- and postnatal influences. The aim of this systematic review was to assess available evidence on associations between PFAS exposures in different stages of life and semen quality, reproductive hormones, cryptorchidism, hypospadias, and testicular cancer. A systematic search of literature published prior to March 9th, 2020, was performed in the databases PubMed and Embase®. Predefined criteria for eligibility were applied by two authors screening study records independently. Among the 242 study records retrieved in the literature search, 26 studies were eligible for qualitative assessment. While several investigations suggested weak associations for single compounds and specific outcomes, a lack of consistency across studies limited conclusions of overall evidence. The current gap in knowledge is particularly obvious regarding exposures prior to adulthood, exposure to combinations of both PFAS and other types of environmental chemicals, and outcomes such as cryptorchidism, hypospadias, and testicular cancer. Continued efforts to clarify associations between PFAS exposure and male reproductive health through high-quality epidemiological studies are needed.