Associations between drinking water disinfection byproducts and menstrual cycle characteristics: A cross-sectional study among women attending an infertility clinic

Exposure to disinfection by-products and risk of diminished ovarian reserve: Case-control evidence and cellular metabolomic insights

Disinfection of drinking water is a critical measure for ensuring water safety and controlling waterborne infectious diseases. However, during the disinfection process, a variety of disinfection by-products (DBPs), some of which exhibit reproductive toxicity, are generated. This study aimed to assess whether DBP exposure contributes to the risk of diminished ovarian reserve (DOR) and explored the underlying metabolic mechanisms. A total of 182 participants, including 91 healthy women and 91 women with DOR, were recruited for a case-control study conducted between October 2023 and February 2024. Serum concentrations of DBPs, including dibromoacetic acid (DBAA), monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chlorate, and perchlorate, were measured to evaluate DBP exposure. Key indicators for evaluating DOR included antral follicle count (AFC), anti-Mullerian hormone (AMH), and follicle-stimulating hormone (FSH). All six DBPs were higher in DOR patients (all p < 0.05). After controlling for covariates, all DBPs showed negative correlations with AMH and AFC, positive correlations with basal FSH, and a significant association with the risk of DOR (all p < 0.05). To further investigate the underlying mechanisms, we conducted an in vitro study using human ovarian granulosa cell line (KGN). KGN cells were exposed to DBAA and perchlorate for 48 hours, and metabolomic analysis was performed to identify altered metabolic pathways. Metabolomics data suggested that DBAA and perchlorate might have contributed to DOR by disrupting arginine biosynthesis and purine metabolism, respectively. In conclusion, DBPs exposure might have contributed to DOR risk by disrupting granulosa cell (GC) metabolism.

Urinary biomarkers of drinking water disinfection byproducts in relation to blood-based liver function parameters among reproductive-aged Chinese women

BACKGROUND

Toxicological studies have documented that disinfection byproducts (DBPs), the ubiquitous drinking water pollutants, induce hepatotoxicity. Yet epidemiological evidence is sparse.

OBJECTIVE

To assess urinary biomarkers of drinking water DBPs in relation to liver function parameters.

METHODS

We included 1204 reproductive-aged women from the Tongji Reproductive and Environmental (TREE) study in Wuhan, China between December 2018 and July 2021. Urinary trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) as biomarkers of drinking water DBPs were assessed. Serum liver function parameters such as albumin (ALB), total cholesterol (TC), and alkaline phosphatase (ALP) were determined. Urinary DCAA and TCAA concentrations in relation to liver function parameters were examined by multivariate linear regression or restricted cubic spline (RCS) models.

RESULTS

There was no evidence of urinary TCAA in relation to serum parameters of liver function. However, monotonic dose-response relationships were estimated between elevated tertiles of urinary DCAA concentrations and increased serum ALP (percent change = 4.25 %; 95 % CI: 0.34 %, 8.32 % for the upper vs. lower tertile) and TC levels (percent change = 3.84 %; 95 % CI: 0.63 %, 7.17 % for the upper vs. lower tertile). These associations remained for urinary DCAA modeled as the continuous exposure variable and were linear in the RCS models. Age, body mass index, and passive smoking status did not modify these associations.

CONCLUSION

DCAA but not TCAA exposure may contribute to damaged liver function in reproductive-aged women.

The last decade epidemiologic concern of drinking water contaminants of emerging concern (CECs) in Asian Countries: A scoping review

With the rapid industrialization and urbanization in Asian countries, the challenge of rising emerging contaminants in the environment, including the water cycle, has become more pronounced. Consequently, the presence of CECs in drinking water systems is inevitable due to their ubiquitous nature in aquatic environments. This scoping review aims to identify epidemiological concerns regarding drinking water CECs in Asian countries over the past decade by describing the types of assessed CECs, their associated health effects, and identifying gaps and future research prospects through a summary of relevant studies. Searches were conducted on PubMed and Scopus up to February 29, 2024. Included were epidemiological studies from the past 10 years (since January 2014) in Asian countries that assessed emerging contaminants in drinking water through direct measurement or analysis as factors. From an initial pool of 3198 results, 15 relevant studies were selected. These studies assessed various types of CECs, including disinfection byproducts (n = 10), endocrine disruptors (n = 2), pesticides (n = 2), and a protozoan pathogen (n = 1). The meticulous assessment of CECs and associated health outcomes in Asian epidemiological studies over the past decade has been deemed inadequate to address the wide range of ubiquitous CECs in drinking water and their potential health effects that have not yet been addressed. While not the sole objective, the primary aim of epidemiological studies is to inform policy decisions and increase awareness among the public and policymakers. Therefore, researchers in Asian countries, particularly in environmental and public health fields, should prioritize the development of research in this area by exploring more CECs type and associated health outcomes.

Urinary biomarkers of drinking-water disinfection byproducts in relation to diminished ovarian reserve risk: A case-control study from the TREE cohort

BACKGROUND

Disinfection byproducts (DBPs) as ovarian toxicants have been documented in toxicological studies. However, no human studies have explored the effects of exposure to DBPs on diminished ovarian reserve (DOR).

OBJECTIVE

To assess whether urinary biomarkers of exposure to drinking-water DBPs were associated with DOR risk.

METHODS

A total of 311 women undergoing assisted reproductive technology were diagnosed with DOR in the Tongji Reproductive and Environmental (TREE) cohort from December 2018 to August 2021. The cases were matched to the controls with normal ovarian reserve function by age in a ratio of 1:1. Urinary trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were quantified as biomarkers of drinking-water DBP exposures. The conditional logistic regression and restricted cubic spline (RCS) were used to explore urinary biomarkers of drinking-water DBP exposures in associations with the risk of DOR.

RESULTS

Elevated urinary DCAA levels were associated with higher DOR risk [adjusted odds ratio (OR) = 1.87; 95 % confidence interval (CI): 1.16, 3.03 for the highest vs. lowest quartiles; P for trend = 0.016]. The association was confirmed in the RCS model, with a linear dose-response curve (P for overall association = 0.029 and P for non-linear association = 0.708). The subgroup analysis by age and body mass index (BMI) showed that urinary DCAA in association with DOR risk was observed among women ≥35 years old and leaner women (BMI < 24 kg/m2), but the group differences were not statistically significant. Moreover, a U-shaped dose-response curve between urinary TCAA and DOR risk was estimated in the RCS model (P for overall association = 0.011 and P for non-linear association = 0.004).

CONCLUSIONS

Exposure to drinking-water DBPs may contribute to the risk of DOR among women undergoing assisted reproductive technology.

Phthalate metabolites in urine and follicular fluid in relation to menstrual cycle characteristics in women seeking fertility assistance

BACKGROUND

Phthalates have been shown to disrupt the estrous cycle in animal studies. However, epidemiological research investigating their associations with menstrual cycle characteristics is limited.

OBJECTIVE

To explore the relationships between phthalate exposure and menstrual cycle characteristics among women seeking fertility assistance.

METHODS

We determined the levels of eight phthalate metabolites in both follicular fluid (FF) and urine specimens collected from 441 women in the Tongji Reproductive and Environmental (TREE) cohort, using high-performance liquid chromatography and tandem mass spectrometry. Information about menstrual cycle parameters was obtained through a questionnaire. The impacts of individual and joint exposure to phthalates on menstrual cycle characteristics were assessed using multivariable linear regression, Poisson regression, and quantile g-computation approaches.

RESULTS

After adjusting for relevant covariates, we found that per log10-unit increase in mono(2-ethylhexyl) phthalate (MEHP) level in urine specimens was associated with a decrease of 0.20 days (95 % CI: -0.37, -0.03) in bleeding duration. We also observed that mono(2-ethyl-5-carboxypentyl) phthalate (MECPP) and the sum of di(2-ethylhexyl) phthalate (DEHP) metabolites (∑DEHP) concentrations in FF samples were inversely related to cycle length [β = -1.92 (95 % CI: -3.10, -0.75) and -1.87 (95 % CI: -3.56, -0.19), respectively]. However, we generally observed null associations between phthalate metabolites and irregular cycle, dysmenorrhea, hypomenorrhea, or cycle length variation. Furthermore, we also found that phthalate metabolite mixtures in FF and urine were generally unrelated to menstrual cycle characteristics.

CONCLUSION

Our findings suggest that some DEHP metabolites in FF and urine are inversely associated with menstrual cycle length and menstrual bleeding duration in women attending a fertility center.

Association between Urinary Haloacetic Acid Concentrations and Liver Injury among Women: Results from the Tongji Reproductive and Environmental (TREE) Study

BACKGROUND

Experimental studies have shown that disinfection byproducts (DBPs) including haloacetic acids (HAAs) can cause liver toxicity, but evidence linking this association in humans is sparse.

OBJECTIVES

We aimed to explore the associations between HAA exposures and liver injury.

METHODS

We included 922 women between December 2018 and January 2020 from the Tongji Reproductive and Environmental (TREE) cohort study in Wuhan, China. Urinary HAA concentrations including trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) and serum indicators of liver function, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyltransferase (GGT) were measured. Liver injury was defined as if any of serum indicator levels were above the 90th percentile. Multivariate logistic and linear regression models were fitted to assess the associations of urinary HAA concentrations with the risk of liver injury and liver function indicators. Stratified analyses by age, body mass index (BMI), alcohol use, and passive smoking were also applied to evaluate the potential effect modifiers.

RESULTS

There is little evidence of associations of urinary TCAA concentrations with liver injury risk and liver function indicators. However, urinary DCAA concentrations were associated with a higher risk of liver injury [odds ratios (OR) for 1-interquartile range (IQR) increase in natural log (ln) transformed DCAA concentrations: 1.45; 95% confidence interval (CI): 1.07, 1.98]. This association was observed only among nondrinkers (p interaction = 0.058 ). We also found that a 1-IQR increase in ln-transformed DCAA concentrations was positively associated with ALT levels (percentage change = 6.06 % ; 95% CI: 0.48%, 11.95%) and negatively associated with AST/ALT (percentage change = - 4.48 % ; 95% CI: - 7.80 % , - 1.04 % ). In addition, urinary DCAA concentrations in relation to higher GGT levels was observed only among passive smokers (p interaction = 0.040 ).

CONCLUSION

Our findings suggest that exposure to DCAA but not TCAA is associated with liver injury among women undergoing assisted reproductive technology. https://doi.org/10.1289/EHP13386.

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.

Toxicological characteristics of drinking water in two large-scale municipal water supply systems of a metropolitan city in Central China

Drinking water safety is threatened by numerous toxic organic pollutants difficult to chemically monitor. This study aimed to determine the toxicological profiles of organic extracts (OEs) of water samples from source to tap in two drinking water supply systems in a metropolitan city, Central China, during different hydrological periods. Mortality, DNA damage, growth, and development of Caenorhabditis elegans were evaluated following exposure to OEs. The median lethal doses of OEs of drinking water samples (n = 48) ranged from 266 REF (relative enrichment factor) to > 1563 REF. When tested at a dose of 100 REF, 56.25% (27/48) of OEs induced genotoxicity, 4.17% (2/48) inhibited the growth, and 45.83% (22/48) decreased the offspring number in C. elegans. No clear temporal-spatial variation patterns of the OEs toxicity indicators were observed. The correlations among the toxicity indicators were generally poor. The observed toxicities were not closely related to the level of dissolved organic carbon in drinking water. These findings support using multiple endpoint bioassays, such as C. elegans-based approaches, as complementary tools to conventional chemical analysis for drinking water quality monitoring.

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.

2,4,6-triiodophenol exhibits embryotoxicity to pre-implantation mouse embryos in an in vitro exposure model

2,4,6-triiodophenol (TIP), a novel type of halophenolic disinfection byproducts, has been widely detected in water bodies, even in drinking water. Recently, TIP has drawn increasing concerns on account of considerable developmental toxicity towards lower organisms and cytotoxicity for mammalian cells. However, it remains unknown about its toxicity on mammalian pre-implantation embryos. Here, by exposing mouse zygotes derived in vitro fertilization to TIP, which ranged from 5 to 50 μM, we found that TIP impaired the quality of pre-implantation mouse embryos in a dose-dependent manner, inducing decline of both total and trophectoderm cell numbers, enhancing caspase 3/7 activity and reactive oxygen species generation, though it did not decrease blastocyst formation efficiency. For the sake that only high qualified embryos are able to implant in endometrium and generate health body finally, we applied a previously modified in vitro culture system to assess TIP-exposed blastocysts' further developmental potency beyond pre-implantation stage. Surprisingly, although the exposed dose was only 5 μM and TIP was removed as soon as the zygotes reached blastocyst stage, these blastocysts still nearly lost their implantation and egg cylinder formation ability, exhibiting abnormal embryonic lineage differentiation pattern as well. Therefore, our study not only entirely shows TIP embryonic toxicity on mouse pre-implantation embryos, but also proposes a model to evaluate embryotoxicity from the zygote to egg cylinder stage.