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

Urinary haloacetic acid concentrations in relation to sex and thyroid hormones among reproductive-aged men

Sex and thyroid hormones are critical for male reproductive health. However, the associations between haloacetic acid (HAA) exposure - a known endocrine disruptor - and sex and thyroid hormones in humans remains unclear. We thus recruited 502 male participants seeking fertility evaluation from a reproductive center. We measured concentrations of sex and thyroid hormones in a single blood sample and dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in repeated urine samples. Multivariable linear regression models were constructed to evaluate the associations between HAA concentrations and hormone measurements. After adjusting for potential confounders and urinary creatinine concentrations, urinary concentrations of TCAA were inversely associated with serum levels of sex hormone-binding globulin (SHBG), testosterone (T), T/luteinizing hormone ratio (T/LH), and thyroid stimulating hormone (TSH) (all P for trend < 0.10). Compared with participants in the lowest quartile of TCAA concentrations, those in the highest quartile had reduced serum levels of SHGB by 14.2 % (95% CI: -26.7, -3.0 %), T by 11.1 % (95% CI: -21.7, -1.3 %), T/LH by 21.0 % (95% CI: -36.7, -7.1 %), and TSH by 19.1 % (95% CI: -39.7, -1.5 %). Additionally, we observed inverse associations between continuous measurements of urinary HAAs and serum levels of free T, bioactive T, and estradiol. Our findings suggest that male HAA exposure may be associated with disrupted sex and thyroid function.

Urinary haloacetic acid concentrations and thyroid function among women: Results from the TREE study

BACKGROUND

Disinfection byproducts (DBPs) have been shown to impair thyroid function in experimental models. However, epidemiological evidence is scarce.

METHODS

This study included 1190 women undergoing assisted reproductive technology (ART) treatment from the Tongji Reproductive and Environmental (TREE) cohort from December 2018 to August 2021. Serum thyrotropin (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) were measured as indicators of thyroid function. FT4/FT3 and TSH/FT4 ratios were calculated as markers of thyroid hormone homeostasis. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the two most abundant HAAs, in urine were detected to assess individual DBP exposures.

RESULTS

After adjusting for relevant covariates, positive associations were observed between urinary TCAA concentrations and serum TSH and TSH/FT4 levels (e.g., percent change = 5.82 %, 95 % CI: 0.70 %, 11.21 % for TSH), whereas inverse associations were found for serum FT3 and FT4 (e.g., percent change = -1.29 %, 95 % CI: -2.49 %, -0.07 % for FT3). There also was a negative association between urinary DCAA concentration and serum FT4/FT3 (percent change = -2.49 %, 95 % CI: -4.71 %, -0.23 %). These associations were further confirmed in the restricted cubic spline and generalized additive models with linear or U-shaped dose-response relationships.

CONCLUSION

Urinary HAAs were associated with altered thyroid hormone homeostasis among women undergoing ART treatment.

Urinary concentrations of bisphenol A and its alternatives: Potential predictors of and associations with antral follicle count among women from an infertility clinic in Northern China

BACKGROUND

Experimental studies have suggested exposure to bisphenol A (BPA) and its alternatives, such as bisphenol F (BPF) and bisphenol S (BPS), may exert adverse effects on ovarian reserve, but human evidence is limited. Moreover, the potential predictors of exposure to bisphenols among women seeking infertility treatment have not been reported.

OBJECTIVE

To explore whether individual or mixture of BPA, BPF, and BPS were related to antral follicle count (AFC), and further identify the predictors of exposure to bisphenols among women seeking assisted reproductive treatment.

METHODS

A total of 111 women from a reproductive center in Shenyang, China were enrolled in this study from September 2020 to February 2021. The concentrations of urinary BPA, BPF, and BPS were measured using ultra-high-performance liquid chromatography-triple quadruple mass spectrometry (UHPLC-MS/MS). AFC was measured by two infertility physicians through transvaginal ultrasonography on the 2-5 days of a natural cycle. Demographic characteristics, dietary habits, and lifestyles were obtained by questionnaires. The associations between individual and mixture of urinary bisphenols concentrations (BPA, BPF, and BPS) and AFC were assessed by the Poisson regression models and the quantile-based g-computation (QGC) model, respectively. The potential predictors of exposure to bisphenols were identified by the multivariate linear regression models.

RESULTS

After adjusting for confounders, elevated urinary concentrations of BPA, BPF and BPS were associated with reduced AFC (β = -0.016; 95%CI: -0.025, -0.006 in BPA; β = -0.017; 95%CI: -0.029, -0.004 in BPF; β = -0.128; 95%CI: -0.197, -0.060 in BPS). A quantile increase in the bisphenols mixture was negatively associated with AFC (β = -0.101; 95%CI: -0.173, -0.030). Intake of fried food had higher urinary concentrations of BPF, BPS, and total bisphenols (∑BPs) than women who did not eat, and age was related to increased urinary BPF concentrations.

CONCLUSION

Our findings indicated that exposure to individual BPA, BPF, BPS and bisphenol mixtures were associated with impaired ovarian reserve. Furthermore, the intake of fried food, as identified in this study, could serve as an important bisphenols exposure route for reproductive-aged women.

Exposure to haloacetic acid disinfection by-products and male steroid hormones: An epidemiological and in vitro study

Haloacetic acids (HAAs) are ubiquitous in drinking water and have been associated with impaired male reproductive health. However, epidemiological evidence exploring the associations between HAA exposure and reproductive hormones among males is scarce. In the current study, the urinary concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the internal exposure markers of HAAs, as well as sex hormones (testosterone [T], progesterone [P], and estradiol [E2]) were measured among 449 Chinese men. Moreover, in vitro experiments, designed to simulate the real-world scenarios of human exposure, were conducted to assess testosterone synthesis in the Leydig cell line MLTC-1 and testosterone metabolism in the hepatic cell line HepG2 in response to low-dose HAA exposure. The DCAA and TCAA urinary concentrations were found to be positively associated with urinary T, P, and E2 levels (all p < 0.001), but negatively associated with the ratio of urinary T to E2 (p < 0.05). Combined with in vitro experiments, the results suggest that environmentally-relevant doses of HAA stimulate sex hormone synthesis and steroidogenesis pathway gene expression in MLTC-1 cells. In addition, the inhibition of the key gene CYP3A4 involved in the testosterone phase Ⅰ catabolism, and induction of the gene UGT2B15 involved in testosterone phase Ⅱ glucuronide conjugation metabolism along with the ATP-binding cassette (ABC) transport genes (ABCC4 and ABCG2) in HepG2 cells could play a role in elevation of urinary hormone excretion upon low-dose exposure to HAAs. Our novel findings highlight that exposure to HAAs at environmentally-relevant concentrations is associated with increased synthesis and excretion of sex hormones in males, which potentially provides an alternative approach involving urinary hormones for the noninvasive evaluation of male reproductive health following exposure to DBPs.

Advances in understanding the reproductive toxicity of endocrine-disrupting chemicals in women

Recently, there has been a noticeable increase in disorders of the female reproductive system, accompanied by a rise in adverse pregnancy outcomes. This trend is increasingly being linked to environmental pollution, particularly through the lens of Endocrine Disrupting Chemicals (EDCs). These external agents disrupt natural processes of hormones, including synthesis, metabolism, secretion, transport, binding, as well as elimination. These disruptions can significantly impair human reproductive functions. A wealth of animal studies and epidemiological research indicates that exposure to toxic environmental factors can interfere with the endocrine system's normal functioning, resulting in negative reproductive outcomes. However, the mechanisms of these adverse effects are largely unknown. This work reviews the reproductive toxicity of five major environmental EDCs-Bisphenol A (BPA), Phthalates (PAEs), Triclocarban Triclosan and Disinfection Byproducts (DBPs)-to lay a foundational theoretical basis for further toxicological study of EDCs. Additionally, it aims to spark advancements in the prevention and treatment of female reproductive toxicity caused by these chemicals.

Dichloroacetic acid and trichloroacetic acid as disinfection by-products in drinking water are endocrine-disrupting chemicals

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) are two typical non-volatile disinfection by-products (DBPs) found in drinking water. Increasing evidence has demonstrated that they show reproductive toxicity. However, whether they might have endocrine disrupting properties remains largely unknown. To discover this, we treated male mice or pregnant mice with 0, 1-, 102-, 103-, 104-, or 5 × 104-fold maximal concentration level (MCL) of DCAA or TCAA in drinking water. In male mice, the levels of testosterone in serum and androgen receptor (AR) in testis were declined with ≥ 103-fold MCL of DCAA (26.4 mg/kg/d) or TCAA (52.7 mg/kg/d). In pregnant mice, miscarriage rates were increased with ≥ 104-fold MCL of DCAA (264 mg/kg/d) or ≥ 103-fold MCL of TCAA. The levels of FSH in serum were increased and those of estradiol and progesterone were reduced with ≥ 103-fold MCL of DCAA or TCAA. The protein levels of estrogen receptors (ERα and ERβ) in ovary were reduced with ≥ 102-fold MCL of DCAA (2.64 mg/kg/d) or TCAA (5.27 mg/kg/d). Exposure to some certain fold MCL of DCAA or TCAA also altered the protein levels of ERα and ERβ in uterus and placenta. Exposure to 5 × 104-fold MCL of both DCAA and TCAA showed the combined effects. Therefore, both DCAA and TCAA could be considered as novel reproductive endocrine disrupting chemicals, which might be helpful for further assessment of the toxicological effects of DCAA and TCAA and the awareness of reproductive endocrine disrupting properties caused by DCAA and TCAA in drinking water.

Exposure to PM2.5, seminal plasma metabolome, and semen quality among Chinese adult men: Association and potential mediation analyses

Exposure to ambient fine particulate matter (PM2.5) has been linked to a decline in semen quality, but the underlying mechanisms for this association remain unclear. We aimed to examine whether specific metabolites act as mediators in the association between PM2.5 exposure and changes in semen quality. We conducted untargeted metabolomics analysis using LC-MS/MS platforms to identified seminal plasma metabolites associated with various semen quality parameters among 200 Chinese adult men. Additionally, we performed mediation analyses to examine the effects of the seminal plasma metabolites on the association between PM2.5 exposure and semen quality. We identified 140 differential metabolites between the normal and abnormal semen groups, involving two metabolic pathways: Alanine, aspartate and glutamate metabolism, and Aminoacyl-tRNA biosynthesis. We additionally identified 7 specific seminal plasma metabolites that were associated with discrepant metabolic networks related to semen quality. The mediation analysis revealed that D-Aspartate might play a mediating role in the adverse effects of ambient PM2.5 exposure on both total and progressive motility during spermatogenesis period (70-90 days before ejaculation), with a proportion of mediation up to 16% and 17%, respectively. Exposure to PM2.5 was associated with alterations in D-Aspartate levels, which might partially mediate the association between PM2.5 and reduced sperm motility.

Associations between urinary biomarkers of exposure to disinfection byproducts and semen parameters: A repeated measures analysis

Toxicological studies have demonstrated that disinfection byproducts (DBPs), particularly haloacetic acids, cause testicular toxicity. However, evidence from human studies is sparse and inconclusive. This study included 1230 reproductive-aged men from the Tongji Reproductive and Environmental (TREE) cohort to investigate the associations between repeated measures of DBP exposures and semen parameters. Urinary dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) as biomarkers of DBP exposures and semen parameters in up to three samples from each man were assessed. The linear mixed effect models were applied to explore the associations between urinary biomarkers of DBP exposures and semen parameters. We found inverse associations of urinary DCAA with sperm count, progressive motility, and total motility (e.g., -14.86%; 95% CI: -19.33%, -10.15% in sperm total motility for the highest vs. lowest quartiles; all P for trends < 0.05). Moreover, urinary TCAA modeled as a continuous variable was negatively associated with sperm progressive motility and total motility, while the inverse associations across increasing urinary TCAA quartiles were seen among leaner men (BMI < 25 kg/m2). Exposure to DBPs reflected by urinary DCAA and TCAA was inversely associated with sperm motility and such effects were more evident among leaner men.

Associations between Urinary Concentrations of Disinfection Byproducts and in Vitro Fertilization Outcomes: A Prospective Cohort Study in China

BACKGROUND

Experimental studies show that disinfection byproducts (DBPs) can inhibit oocyte maturation, decrease fertilization capacity, and impair embryo development, but human evidence is lacking.

OBJECTIVES

We aimed to evaluate the associations between exposure to drinking water DBPs and in vitro fertilization (IVF) outcomes.

METHODS

The study included 1,048 women undergoing assisted reproductive technology (ART) treatment between December 2018 and January 2020 from a prospective cohort study, the Tongji Reproductive and Environmental study in Wuhan, China. Exposure to DBPs was assessed by dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in up to four urine samples, which were collected on the day of both enrollment and oocyte retrieval. Multivariable generalized linear mixed models, accounting for multiple IVF cycles per woman, were applied to evaluate the associations between urinary biomarkers of DBP exposures and IVF outcomes. Stratified analyses were used to explore the potential effect modifiers.

RESULTS

The included 1,048 women underwent 1,136 IVF cycles, with 960 (91.6%), 84 (8.0%), and 4 (0.4%) women contributing one cycle, two cycles, and three cycles, respectively. We found that elevated quartiles of urinary DCAA and TCAA concentrations were associated with reduced numbers of total oocytes and metaphase II oocytes and that urinary DCAA concentrations with a lower proportion of best-quality embryos (all p for trends < 0.05 ). Moreover, elevated quartiles of urinary DCAA concentrations were associated with decreased proportions of successful implantation, clinical pregnancy, and live birth (14%, 15%, and 15% decreases in adjusted means comparing the extreme quartiles, respectively; all p for trends < 0.05 ). Stratification analyses showed that the inverse associations of urinary TCAA concentrations with multiple IVF outcomes were stronger among women ≥ 30 y of age (p for interactions < 0.05 ).

DISCUSSION

Exposure to drinking water DBPs was inversely associated with some IVF outcomes among women undergoing ART treatment. Further study is necessary to confirm our findings. https://doi.org/10.1289/EHP12447.

Individual and joint associations of urinary phthalate metabolites with polycystic ovary and polycystic ovary syndrome: Results from the TREE cohort

Phthalates are widespread endocrine disrupting chemicals that adversely affect female reproductive health. We aimed to investigate the individual and joint associations of phthalate exposures measured by repeated urinary metabolites with polycystic ovary (PCO) and polycystic ovary syndrome (PCOS) (96 PCO cases, 96 PCOS cases and 370 controls). In single-pollutant analyses, mono-isobutyl phthalate (MiBP), monobenzyl phthalate (MBzP) and the sum of di(2-ethylhexyl) phthalate (∑DEHP) were associated with increased prevalence of PCO. Mono(2-ethylhexyl) phthalate (MEHP), MBzP and ∑DEHP were associated with elevated prevalence of PCOS. In multiple-pollutant analyses, one-quartile increase of weighted quantile sum index in phthalate metabolite mixtures was associated with increased prevalence of PCO and PCOS, and MBzP was the most major contributor. Our findings suggest a potential role for phthalate exposures, both individually and in mixtures, in the development of PCO and PCOS.

Trihalomethanes and physicochemical quality of drinking water in Addis Ababa, Ethiopia

Background

Trihalomethanes (THMs) are the most dominant fraction of all the byproducts formed during chlorination of water. Disinfection by product (DBP) formation in water is a function of numerous factors, including pH, temperature, residual chlorine, source water characteristics, and organic matter. No study has determined the THM level in the drinking water supply of Addis Ababa, Ethiopia.

Methods

A cross-sectional design was conducted to collect water samples in the water supply distribution networks of Addis Ababa, Ethiopia. Twenty-one (21) sampling stations yielded a total of one hundred twenty (120) samples of drinking water. The sample handling and collection procedures were carried out in accordance with USEPA guidelines. A DB-5 capillary column was used to separate the THMs, which were detected using GC-ECD (gas chromatography-electron capture detector). Spectrophotometric and in situ methods were used for physicochemical parameters. Redundancy analysis (RDA) was used for data analysis of trihalomethanes and environmental variables using CANOCO 4.5.

Results

The mean concentration of total trihalomethanes in drinking water in Addis Ababa was 76.3 μg/L. The concentration of chloroform in the drinking water supply in Addis Ababa, Ethiopia, ranged between 4.03 and 79.4 μg/L. The mean total THMs in the Legedadi and Gefersa water supply systems were 77.4 μg/L and 69.66 μg/L, respectively. The residual chlorine, phosphates, UV absorbance at 254 nm, and combined chlorine had positive correlations with THM formation. However, electron conductivity had a negative correlation with THM formation.

Conclusions

Chloroform contributed the most to TTHMs in nearly all samples. The residual chlorine, UV absorbance, phosphate and hardness as calcium, and electron conductivity were found to be the main predictors determining the abundance and distribution of trihalomethanes. The monitoring and regulation of the THMs is required on a regular basis to analyse trends and guide the water treatment and distribution system.

Oxidatively generated DNA damage mediates the associations of exposure to phthalates with uterine fibroids and endometriosis: Findings from TREE cohort

BACKGROUND

Epidemiological studies on phthalate exposures in associations with uterine fibroids (UF) and endometriosis (EMT) are inconsistent. The underlying mechanisms are poorly understood.

OBJECTIVES

To investigate the relationships of urinary phthalate metabolites with UF and EMT risks, and further to examine the mediating role of oxidative stress.

METHODS

This study included 83 and 47 women separately diagnosed with UF and EMT, as well as 226 controls from the Tongji Reproductive and Environmental (TREE) cohort. Two spot urine samples from each woman were analyzed for two oxidative stress indicators and eight urinary phthalate metabolites. Unconditional logistic regression models or multivariate regression models were fitted to evaluate the associations among phthalate exposures, oxidative stress indicators, and the risks of UF and EMT. The potential mediating role of oxidative stress was estimated by the mediation analyses.

RESULTS

We observed that each ln-unit increase in urinary mono-benzyl phthalate (MBzP) concentrations was associated with increased UF risk [adjusted OR (aOR): 1.56, 95% CI: 1.20, 2.02], and that each ln-unit increase in urinary MBzP (aOR: 1.48, 95% CI: 1.09, 1.99), mono-isobutyl phthalate (MiBP) (aOR: 1.83, 95% CI: 1.19, 2.82), and mono-2-ethylhexyl phthalate (MEHP) (aOR: 1.66, 95% CI: 1.19, 2.31) concentrations were associated with increased EMT risk (all FDR-adjusted P < 0.05). Moreover, we observed that all tested urinary phthalate metabolites were positively associated with two oxidative stress indicators [4-hydroxy-2-nonenal-mercapturic acid (4-HNE-MA) and 8-hydroxy-2-deoxyguanosine (8-OHdG)], in which 8-OHdG was associated with increased risks of UF and EMT (all FDR-adjusted P < 0.05). The mediation analyses showed that 8-OHdG mediated the positive relationships of MBzP with UF risk, and of MiBP, MBzP, and MEHP with EMT risk, with the estimated intermediary proportion ranging from 32.7% to 48.1%.

CONCLUSIONS

Oxidatively generated DNA damage may mediate the positive associations of certain phthalate exposures with the risks of UF and EMT. However, further investigation is warranted to confirm these findings.

Urinary phthalate metabolites and the risk of endometrial polyp: A pilot study from the TREE cohort

Phthalates, as endocrine disrupting chemicals that can alter the endogenous hormones, may be involved in the incidence of endometrial polyp, a benign hormone-dependent condition. We conducted a pilot case-control study from the Tongji Reproductive and Environmental (TREE) cohort to investigate the associations between phthalate exposures and the risk of endometrial polyp. A total of 40 endometrial polyp patients were matched to 80 controls by age and body mass index in the ratio of 1:2. Two spot urine samples from each subject were quantified for eight phthalate metabolites to enhance exposure assessment. The conditional logistic regression and quantile-based g-computation models were separately used to explore the associations between individual and mixture of urinary phthalate metabolites and the risk of endometrial polyp. After adjusting for covariates, individual chemical analyses showed that urinary monobenzyl phthalate (MBzP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono(2-ethylhexyl) phthalate (MEHHP) and the sum of di(2-ethylhexyl) phthalate (ΣDEHP) were associated with increased risks of endometrial polyp, with adjusted odds ratios ranging from 2.62 (95% CI: 0.88, 7.84) for MECPP to 6.96 (95% CI: 1.87, 25.87) for ΣDEHP comparing the extreme exposure categories (all P for trends <0.05 or = 0.057). These associations still persisted when these exposures were modeled as continuous variables. Chemical mixture analyses showed that a simultaneous one-quartile increase in concentrations of eight phthalate metabolites was associated with an elevated odds ratio of 3.14 (95% CI: 1.49, 6.60) in endometrial polyp. Our data suggests that exposure to individual benzylbutyl phthalate (BBzP) and DEHP, as well as mixture of phthalates is associated with increased risk of endometrial polyp. This may inform public health recommendations and policies to avoid phthalate exposures for improving female reproductive health.