Impacts of disinfection byproduct exposures on male reproductive health: Current evidence, possible mechanisms and future needs

Non-suppressed ion chromatography-tandem electrospray mass spectrometry using a short column for simultaneous analysis of dichloroacetic acid, trichloroacetic acid, and bromate: aqueous ammonia as the eluent additive

Dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and bromate (BrO3-) are disinfection byproducts (DBPs) formed during drinking water treatment and pose health risks. Rapid and reliable detection of these DBPs is essential for ensuring water safety. Non-suppressed ion chromatography (IC)-electrospray ionization mass spectrometry (IC-ESI-MS/MS) offers a promising approach for simultaneous analysis of organic haloacetic acids (HAAs) and inorganic oxyhalides, but previous methods using toxic methylamine can pose health risks. Herein, a new rapid non-suppressed IC-ESI-MS/MS method using a short AG18 guard column (13 μm, 2 mm × 50 mm) with aqueous ammonia as the alkaline modifier was developed for the simultaneous quantification of DCAA, TCAA, and BrO3-. This method allows direct sample injection without pretreatment and achieves sub-μg L-1 detection limits within 5 minutes. Aqueous ammonia (0.4 M) and acetonitrile were used as mobile phases in a gradient elution mode, providing good linearity (R2 >0.995), low limits of quantification (0.48-1.13 μg L-1), and high recoveries (76.3-107.3%). Intra-day (n = 9) and inter-day (3 days, n = 9) precision were validated with relative standard deviations of 5.8-8.9% and 6.4-7.7%, respectively. The method also demonstrated limited matrix interference from common water parameters such as Cl-, SO42-, HCO3-/CO32-, and natural organic matter (NOM), making it suitable for real water analysis. The applicability of this method was confirmed by monitoring DBP formation during the chlorination of NOM, showing that two-step chlorine dosing strategies reduce DBP formation compared to single-stage dosing. This newly established method provides a robust and efficient tool for DBP monitoring in drinking water treatment processes.

Meta-analysis and Mendelian randomization study on the association between exposure to chlorinated disinfection byproducts and preterm birth risk

OBJECTIVE

This study aims to investigate the correlation between exposure to disinfection byproducts of chlorination and preterm birth (PTB) through evidence-based medicine Meta-analysis and Mendelian randomization (MR) analysis.

STUDY DESIGN

Meta-analysis was conducted on 17 studies involving 1,251,426 neonates, revealing a higher risk of PTB with exposure to total trihalomethanes (TTHMs) and chloroform. Mendelian randomization (MR) analysis confirmed a causal relationship between chlorides and PTB.

RESULTS

TTHMs and chloroform were associated with increased PTB risk, while haloacetic acids showed no significant association. TTHMs were linked to small gestational age. Ethnicity and study design influenced heterogeneity.

CONCLUSIONS

Exposure to chlorination byproducts, particularly TTHMs and chloroform, poses a significant risk for PTB. MR analysis supports a causal relationship between chlorides and PTB, highlighting the importance of water disinfection byproduct control in preventing PTB.

Decline in reproductive health and its transgenerational lag effect

In the last two decades, there has been a fast-growing prevalence of infertility reported in China. Moreover, Chinese reproductive health has shown a clear decline. Thus, it is imperative to determine the precipitating causes and the root causes of this decline. Environmental and climate risks (ECRs) may cause the decline in reproductive health. Experimental findings have shown that the impact of ECRs on reproductive health can be passed down from both males and females to their offspring, demonstrating an intergenerational and transgenerational lag effect. We perceive that the declined reproductive health may lead to negative demographic consequences in China; therefore, we suggest the following five regulations be implemented: (i) prevent Chinese of childbearing age from exposure to ECRs; (ii) further develop and promote assisted reproductive technology and set up sperm and ovum banks on a national scale; (iii) quantitatively establish the causality between fathers and mothers who suffer from ECRs and the impaired reproductive health in their progeny; (iv) teach ECRs-health knowledge in psychotherapeutic training and continuing education; and (v) propagate and further promote common prosperity.

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.

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.

Exposures to drinking water disinfection byproducts and kidney function in Chinese women

BACKGROUND

Disinfection byproducts (DBPs), the ubiquitous contaminants in drinking water, have been shown to impair renal function in experimental studies. However, epidemiological evidence is sparse.

OBJECTIVE

To investigate exposures to DBPs in associations with renal function among women.

METHODS

A total of 920 women from December 2018 to January 2020 were abstracted from the Tongji Reproductive and Environmental (TREE) Study, an ongoing cohort study in Wuhan, China. Urine samples were gathered at baseline recruitment and analyzed for dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) as biomarkers of DBP exposures. Serum uric acid (UA), creatinine, and estimated glomerular filtration rate (eGFR) were measured as indicators of renal function. Multivariate linear regression and restricted cubic spline (RCS) models were conducted to assess urinary DCAA and TCAA concentrations in associations with renal function indicators. Stratified analyses by age and body mass index (BMI) were also performed.

RESULTS

We found null evidence of urinary TCAA in associations with renal function indicators. However, elevated urinary DCAA tertiles were related to decreased eGFR (β = -1.78%, 95% CI: 3.21%, -0.36%, comparing the upper vs. lower tertile; P for trend = 0.01). This inverse association still existed when urinary DCAA concentration was treated as a continuous variable, and the dose-response relationship was linear based on the RCS model (P for overall association = 0.002 and P for non-linear associations = 0.44). In the stratified analyses, we found an association of urinary DCAA concentration with decreased UA level among women <30 years but an association with increased UA level among women ≥30 years (P for interaction = 0.04).

CONCLUSION

Urinary DCAA but not TCAA was associated with impaired renal function among women undergoing assisted reproductive technology.

Trihalomethane prediction model for water supply system based on machine learning and Log-linear regression

Laboratory determination of trihalomethanes (THMs) is a very time-consuming task. Therefore, establishing a THMs model using easily obtainable water quality parameters would be very helpful. This study explored the modeling methods of the random forest regression (RFR) model, support vector regression (SVR) model, and Log-linear regression model to predict the concentration of total-trihalomethanes (T-THMs), bromodichloromethane (BDCM), and dibromochloromethane (DBCM), using nine water quality parameters as input variables. The models were developed and tested using a dataset of 175 samples collected from a water treatment plant. The results showed that the RFR model, with the optimal parameter combination, outperformed the Log-linear regression model in predicting the concentration of T-THMs (N25 = 82-88%, rp = 0.70-0.80), while the SVR model performed slightly better than the RFR model in predicting the concentration of BDCM (N25 = 85-98%, rp = 0.70-0.97). The RFR model exhibited superior performance compared to the other two models in predicting the concentration of T-THMs and DBCM. The study concludes that the RFR model is superior overall to the SVR model and Log-linear regression models and could be used to monitor THMs concentration in water supply systems.