Potential exposure to endocrine disrupting chemicals and selected adverse pregnancy outcomes: a follow-up study of pregnant women referred for occupational counselling

Exposure to endocrine disrupting chemicals (bisphenols, parabens, and triclosan) and their associations with preterm birth in humans

Preterm birth in humans (PTB), defined as birth prior to 37 weeks of gestation, is one of the most important causes of neonatal morbidity and mortality and is associated with adverse health outcomes later in life. Attributed to many different etiological factors, estimated 15.1 million or 11.1% of births each year are preterm, which is more than 1 per 10 livebirths globally. Environmental pollution is a well-established risk factor that could influence the pathogenesis of PTB. Increasing evidence has shown an association between maternal exposure to endocrine disrupting chemicals (EDCs) and PTB. This scoping review aims to summarize current research on the association between EDC exposure and PTB in humans. Database PubMed was used to identify articles discussing the effect of selected EDCs, namely bisphenol A, bisphenol S, bisphenol F, parabens, and triclosan, found in plastics, cosmetics and other personal care products, on PTB occurrence. Regardless of some inconsistences in the findings across studies, the reviewed studies suggest a potential association between involuntary exposure to reviewed EDCs and the risk of PTB. However, further studies are needed to delineate exact correlations and mechanisms through which EDC exposure causes PTB so that efficient preventative measures could be implemented. Until then, health care providers should inform women about possible EDC exposure thus empowering them to make healthy choices and at the same time decrease the EDC negative effects.

What to Expect When Expecting in Lab: A Review of Unique Risks and Resources for Pregnant Researchers in the Chemical Laboratory

Pregnancy presents a unique risk to chemical researchers due to their occupational exposures to chemical, equipment, and physical hazards in chemical research laboratories across science, engineering, and technology disciplines. Understanding “risk” as a function of hazard, exposure, and vulnerability, this review aims to critically examine the state of the science for the risks and associated recommendations (or lack thereof) for pregnant researchers in chemical laboratories (labs). Commonly encountered hazards for pregnant lab workers include chemical hazards (organic solvents, heavy metals, engineered nanomaterials, and endocrine disruptors), radiation hazards (ionizing radiation producing equipment and materials and nonionizing radiation producing equipment), and other hazards related to the lab environment (excessive noise, excessive heat, psychosocial stress, strenuous physical work, and/or abnormal working hours). Lab relevant doses and routes of exposure in the chemical lab environment along with literature and governmental recommendations or resources for exposure mitigation are critically assessed. The specific windows of vulnerability based on stage of pregnancy are described for each hazard, if available. Finally, policy gaps for further scientific research are detailed to enhance future guidance to protect pregnant lab workers.

Prenatal urinary concentrations of phenols and risk of preterm birth: exploring windows of vulnerability

OBJECTIVE

To explore windows of vulnerability to prenatal urinary phenol concentrations and preterm birth.

DESIGN

Prospective cohort.

SETTING

A large fertility center in Boston, Massachusetts.

PATIENT(S)

A total of 386 mothers who sought fertility treatment and gave birth to a singleton between 2005 and 2018.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Singleton live birth with gestational age <37 completed weeks.

RESULT(S)

Compared with women with non-preterm births, urinary bisphenol A (BPA) concentrations were higher across gestation among women with preterm births, particularly during mid-to-late pregnancy and among those with female infants. Second trimester BPA concentrations were associated with preterm birth (Risk Ratio [RR] 1.24; 95%CI: 0.92, 1.69), which was primarily driven by female (RR 1.40; 95%CI: 1.04, 1.89) and not male (RR 0.85; 95%CI 0.50, 1.46) infants. First trimester paraben concentrations were also associated with preterm birth (RR 1.17; 95%CI: 0.94, 1.46) and similarly the association was only observed for female (RR 1.46; 95% CI: 1.10, 1.94) and not male infants (RR 0.94; 95%CIC: 0.72, 1.23). First trimester urinary bisphenol S concentrations showed a suggested risk of preterm birth (RR 1.25; 95%CI: 0.82, 1.89), although the small case numbers precluded sex-specific examination.

CONCLUSION(S)

We found preliminary evidence of associations between mid-to-late pregnancy BPA and early pregnancy paraben concentrations with preterm birth among those with female infants only. Preterm birth risk may be compound, sex, and window specific. Given the limited sample size of this cohort, results should be confirmed in larger studies, including fertile populations.

Parental preconception exposure to phenol and phthalate mixtures and the risk of preterm birth

BACKGROUND

Parental preconception exposure to select phenols and phthalates was previously associated with increased risk of preterm birth in single chemical analyses. However, the joint effect of phenol and phthalate mixtures on preterm birth is unknown.

METHODS

We included 384 female and 211 male (203 couples) participants seeking infertility treatment in the Environment and Reproductive Health (EARTH) Study who gave birth to 384 singleton infants between 2005 and 2018. Mean preconception urinary concentrations of bisphenol A (BPA), parabens, and eleven phthalate biomarkers, including di(2-ethylhexyl) phthalate (DEHP) metabolites, were examined. We used principal component analysis (PCA) with log-Poisson regression and Probit Bayesian Kernel Machine Regression (BKMR) with hierarchical variable selection to examine maternal and paternal phenol and phthalate mixtures in relation to preterm birth. Couple-based BKMR model was fit to assess couples' joint mixtures in relation to preterm birth.

RESULTS

PCA identified the same four factors for maternal and paternal preconception mixtures. Each unit increase in PCA scores of maternal (adjusted Risk Ratio (aRR): 1.36, 95%CI: 1.00, 1.84) and paternal (aRR: 1.47, 95%CI: 0.90, 2.42) preconception DEHP-BPA factor was positively associated with preterm birth. Maternal and paternal BKMR models consistently presented the DEHP-BPA factor with the highest group Posterior Inclusion Probability (PIP). BKMR models further showed that maternal preconception BPA and mono(2-ethyl-5-hydroxyhexyl) phthalate, and paternal preconception mono(2-ethylhexyl) phthalate were positively associated with preterm birth when the remaining mixture components were held at their median concentrations. Couple-based BKMR models showed a similar relative contribution of paternal (PIP: 61%) and maternal (PIP: 77%) preconception mixtures on preterm birth. We found a positive joint effect on preterm birth across increasing quantiles of couples' total mixture concentrations.

CONCLUSION

In this prospective cohort of subfertile couples, maternal BPA and DEHP, and paternal DEHP exposure before conception were positively associated with preterm birth. Both parental windows jointly contributed to the outcome. These results suggest that preterm birth may be a couple-based pregnancy outcome.

Multicenter biomonitoring of polybrominated diphenyl ethers (PBDEs) in colostrum from China: Body burden profile and risk assessment

Polybrominated diphenyl ethers (PBDEs) were listed in the Stockholm Convention due to their persistent and toxic nature. In utero exposure to PBDEs might affect fetal development as it is sensitive when exposed to even low dose of xenobiotic substances during the pregnancy. In this study, a multi-centre human biomonitoring study of tri-to hexa-BDEs was conducted in three Chinese cities using 60 colostrum samples from local residents. The patterns and influencing factors, correlation with the birth outcome, and potential health risks during the breastfeeding of tri-to hexa-BDEs in the colostrum samples were assessed. The median concentration of tri-to hexa-BDEs was 9.1 (Interquartile range: 3.1-19.5) ng g^-1 lipid weight, and BDE-153 contributed 68% of the detected PBDEs. The PBDE levels were mostly associated with maternal age and drinking water sources, while correlations with other factors including weight gain, BMI, parity and the number of aborted pregnancies was not significant. The level of BDE-28 was positively correlated with the birth weight, while the BDE-99 was positively correlated with the head circumference, using multilinear regression. For the total hazard quotients, 60% of the infants have an estimated value higher than 1, showed potential chronic hazard for future development and possible adverse health effects to the babies from the exposure to PBDE congeners. Alternative food source seems to have a lower risk for neonates than the colostrum, but the advantages of breastfeeding undoubtedly outweigh the risks and potential adverse health effects caused by environmental PBDEs and other xenobiotic chemical exposure.

Effects of Bisphenol A and 4-tert-Octylphenol on Embryo Implantation Failure in Mouse

Miscarriage due to blastocyst implantation failure occurs in up to two-thirds of all human miscarriage cases. Calcium ion has been shown to be involved in many cellular signal transduction pathways as well as in the regulation of cell adhesion, which is necessary for the embryo implantation process. Exposure to endocrine-disrupting chemicals (EDs) during early gestation results in disruption of intrauterine implantation and uterine reception, leading to implantation failure. In this study, ovarian estrogen (E2), bisphenol A (BPA), or 4-tert-octylphenol (OP), with or without ICI 182,780 (ICI) were injected subcutaneously from gestation day 1 to gestation day 3 post-coitus. The expression levels of the calcium transport genes were assessed in maternal uteri and implantation sites. The number of implantation sites was significantly low in the OP group, and implantation sites were absent in the E2, ICI and EDs + ICI groups. There were different calcium transient transport channel expression levels in uterus and implantation site samples. The levels of TRPV5 and TRPV6 gene expression were significantly increased by EDs with/without ICI treatment in utero. Meanwhile, TRPV5 and TRPV6 gene expression were significantly lower in implantation sites samples. NCX1 and PMCA1 mRNA levels were significantly decreased by OP and BPA in the implantation site samples. Compared to vehicle treatment in the uterus, both the MUC1 mRNA and protein levels were markedly high in all but the BPA group. Taken together, these results suggest that both BPA and OP can impair embryo implantation through alteration of calcium transport gene expressions and by affecting uterine receptivity.