Bromochloro-haloacetic acids: Effects on mouse embryos in vitro and QSAR considerations

Risks of obstructive genitourinary birth defects in relation to trihalomethane and haloacetic acid exposures: expanding disinfection byproduct mixtures analyses using relative potency factors

BACKGROUND

Some disinfection byproducts (DBPs) are teratogens based on toxicological evidence. Conventional use of predominant DBPs as proxies for complex mixtures may result in decreased ability to detect associations in epidemiological studies.

OBJECTIVE

We assessed risks of obstructive genitourinary birth defects (OGDs) in relation to 12 DBP mixtures and 13 individual component DBPs.

METHODS

We designed a nested registry-based case-control study (210 OGD cases; 2100 controls) in Massachusetts towns with complete quarterly 1999-2004 data on four trihalomethanes (THMs) and five haloacetic acids (HAAs). We estimated temporally-weighted average DBP exposures for the first trimester of pregnancy. We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for OGD in relation to individual DBPs, unweighted mixtures, and weighted mixtures based on THM/HAA relative potency factors (RPF) from animal toxicology data for full-litter resorption, eye defects, and neural tube defects.

RESULTS

We detected elevated aORs for OGDs for the highest of bromodichloromethane (aOR = 1.75; 95% CI: 1.15-2.65), dibromochloromethane (aOR = 1.71; 95% CI: 1.15-2.54), bromodichloroacetic acid (aOR = 1.56; 95%CI: 0.97-2.51), chlorodibromoacetic acid (aOR = 1.97, 95% CI: 1.23-3.15), and tribromoacetic acid (aOR = 1.90; 95%CI: 1.20-3.03). Across unweighted mixture sums, the highest aORs were for the sum of three brominated THMs (aOR = 1.74; 95% CI: 1.15-2.64), the sum of six brominated HAAs (aOR = 1.43; 95% CI: 0.89-2.31), and the sum of nine brominated DBPs (aOR = 1.80; 95% CI: 1.05-3.10). Comparing eight RPF-weighted to unweighted mixtures, the largest aOR differences were for two HAA metrics, which both were higher with RPF weighting; other metrics had reduced or minimally changed ORs in RPF-weighted models.

A novel method for predicting the emergence of toxicity interaction in ternary mixtures

The environment is teeming with a wide variety of pollutants, but the complexity and diversity of their combinations make it difficult to fully assess their toxicity interaction. A novel toxicity interaction prediction method (TIPM) based on the three-dimensional (3D) surface form of the concentration addition (CA) deviation model (dCA) was proposed to predict the emergence of toxicity interaction in ternary mixtures. Doxycycline hyclate (DH), bromoacetic acid (BAA) and iodoacetic acid (IAA) were used as target pollutants. The toxicity of binary and ternary mixtures designed by the direct equipartition ray design method (EquRay) and the uniform design ray method (UD-Ray) against Escherichia coli (E. coli) was determined by using a time-dependent microplate toxicity analysis (t-MTA) method. The toxicity interaction within mixtures was characterized qualitatively and quantitatively using dCA 3D surface modeling and the emergence of DH-MAA-IAA toxicity interaction was predicted by TIPM. The results showed that the dCA 3D surface model could well characterize the toxicity interactions of the mixtures, and toxicity interaction was closely related to the components' concentration ratio (pi). TIPM could predict the emergence of DH-MAA-IAA toxicity interactions well based on the relationship. Due the model is only related to the toxicity interactions and pi value of a mixture, so it can be suggested to predict toxicity interaction within the more complex multicomponent mixtures, which provides a novel approach for the environmental risk assessment and prediction of hazardous substances.

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.

Concentration Addition, Independent Action, and Quantitative Structure-Activity Relationships for Chemical Mixture Toxicities of the Disinfection By products of Haloacetic Acids on the Green Alga Raphidocelis subcapitata

The potential toxicity of haloacetic acids (HAAs), common disinfection by products (DBPs), has been widely studied; but their combined effects on freshwater green algae remain poorly understood. The present study was conducted to investigate the toxicological interactions of HAA mixtures in the green alga Raphidocelis subcapitata and predict the DBP mixture toxicities based on concentration addition, independent action, and quantitative structure-activity relationship (QSAR) models. The acute toxicities of 6 HAAs (iodoacetic acid [IAA], bromoacetic acid [BAA], chloroacetic acid [CAA], dichloroacetic acid [DCAA], trichloroacetic acid [TCAA], and tribromoacetic acid [TBAA]) and their 68 binary mixtures to the green algae were analyzed in 96-well microplates. Results reveal that the rank order of the toxicity of individual HAAs is CAA > IAA ≈ BAA > TCAA > DCAA > TBAA. With concentration addition as the reference additive model, the mixture effects are synergetic in 47.1% and antagonistic in 25%, whereas the additive effects are only observed in 27.9% of the experiments. The main components that induce synergism are DCAA, IAA, and BAA; and CAA is the main component that causes antagonism. Prediction by concentration addition and independent action indicates that the 2 models fail to accurately predict 72% mixture toxicity at an effective concentration level of 50%. Modeling the mixtures by QSAR was established by statistically analyzing descriptors for the determination of the relationship between their chemical structures and the negative logarithm of the 50% effective concentration. The additive mixture toxicities are accurately predicted by the QSAR model based on 2 parameters, the octanol-water partition coefficient and the acid dissociation constant (pK_a ). The toxicities of synergetic mixtures can be interpreted with the total energy (E_T ) and pK_a of the mixtures. Dipole moment and E_T are the quantum descriptors that influence the antagonistic mixture toxicity. Therefore, in silico modeling may be a useful tool in predicting disinfection by-product mixture toxicities. Environ Toxicol Chem 2021;40:1431-1442. © 2021 SETAC.

Impacts of pre-oxidation on the formation of disinfection byproducts from algal organic matter in subsequent chlor(am)ination: A review

Algae cells and algal organic matter (AOM) present in algae impacted source water pose a serious threat to the safety of drinking water. Conventional water treatment processes poorly remove AOM that can transform to harmful disinfection byproducts (DBPs) during ensuing disinfection. This article offers a comprehensive review on the impacts of pre-oxidation on the formation of DBPs from AOM in subsequent chlor(am)ination. Various characterization techniques for algal cells and AOM are first overviewed with an effort to better understanding of correlation between the AOM properties and downstream DBP formation. Then, the present work reviews recent studies on application of different pre-oxidation technologies, such as chlor(am) ination, UV irradiation, ozonation, ferrate (VI), permanganate oxidation and UV-based advanced oxidation processes (AOPs), to remove algal cells and degrade AOM. Pre-oxidation can reduce the stability of algal cells and inactivate algal cells for promoting cell aggregation and thus favoring coagulation. Meanwhile, pre-oxidation can mitigate and degrade AOM into small molecular weight organic compounds to reduce DBP formation potential during subsequent chlor(am)ination. Finally, this review provides an overall evaluation on the applicability of different pre-oxidation processes, and identifies future research demands.

Trimester-Specific Blood Trihalomethane and Urinary Haloacetic Acid Concentrations and Adverse Birth Outcomes: Identifying Windows of Vulnerability during Pregnancy

BACKGROUND

Some disinfection by-products (DBPs) are reproductive and developmental toxicants in laboratory animals. However, studies of trimester-specific DBP exposure on adverse birth outcomes in humans are inconsistent.

OBJECTIVE

We examined whether trimester-specific blood and urinary biomarkers of DBP were associated with small for gestational age (SGA), low birth weight (LBW), and preterm birth.

METHODS

A total of 4,086 blood and 3,951 urine samples were collected across pregnancy trimesters among 1,660 mothers from Xiaogan City, China. Blood samples were quantified for biomarkers of trihalomethanes (THMs): chloroform (TCM), bromodichloromethane, dibromochloromethane, and bromoform. Urine samples were quantified for biomarkers of haloacetic acids (HAA): dichloroacetic acid and trichloroacetic acid. Birth outcomes were abstracted at delivery from medical records. We used Poisson regression models with log link functions to estimate risk ratios (RRs) and 95% confidence intervals (CIs) for SGA, LBW, and preterm birth across tertiles (or categories) of DBP biomarker concentrations measured across pregnancy trimesters. We also examined the relative exposure differences across gestation comparing adverse outcomes with normal births using mixed-effects models.

RESULTS

Blood TCM concentrations in the second trimester were associated with an elevated risk of SGA comparing middle vs. lowest (RR, 2.34; 95% CI: 1.02, 5.35) and highest vs. lowest (RR, 2.47; 95% CI: 1.09, 5.58) exposure groups. Third-trimester blood TCM concentrations were also associated with an increased risk of SGA comparing the second tertile with the first (RR, 2.61; 95% CI: 1.15, 5.92). We found that maternal blood TCM concentrations were significantly higher for SGA compared with non-SGA births across the period from 23 to 34 wk gestation. Other blood and urinary DBP biomarkers examined were unrelated to SGA, LBW, or preterm birth.

CONCLUSION

Blood TCM concentrations in mid to late pregnancy were associated with an increased risk of SGA, whereas other biomarkers of DBPs examined across pregnancy were not associated with birth outcomes. https://doi.org/10.1289/EHP7195.

A sensitive and specific solid-phase extraction-gas chromatography-tandem mass spectrometry method for the determination of 11 haloacetic acids in aqueous samples

A method for the analysis of 11 haloacetic acids in water samples has been developed. It involves enrichment of the target analytes from water samples by solid-phase extraction, derivatization to methyl esters, and gas chromatography coupled with tandem mass spectrometry determination. Gas chromatography conditions were optimized for a good separation of all haloacetic acids in a short runtime. Data were acquired in the multiple reaction monitoring mode. Six solid-phase extraction sorbents among the most widely used in environmental analysis were tested. Bakerbond SDB was retained because it has been shown to provide the best results for a large class of targeted haloacetic acids. The performances of the developed method have been assessed according to the French Standard NF T 90-210. The calibration curves for all the studied haloacetic acids had consistent slopes with r² values > 0.99. Quantification limits between 0.01 and 0.50 µg l^-1 were achieved. Satisfactory repeatability (relative standard deviation ≤ 14.3%) and intermediate precision (relative standard deviation ≤ 15.7%) were obtained. Applied to the analysis of 15 untreated water samples collected from three rivers, the method allowed the detection of five haloacetic acids including monochloroacetic acid (in 100% of the samples, <0.5-1.85 µg l^-1), dichloroacetic acid (87%, <0.05-0.22 µg l^-1), trichloroacetic acid (93%, <0.05-0.52 µg l^-1), dibromoacetic acid (53%, <0.01-0.40 µg l^-1), tribromoacetic acid (20%, <0.05-0.14 µg l^-1), and bromodichloroacetic acid (6%, < 0.05 µg l^-1).

Predictive QSAR Models for the Toxicity of Disinfection Byproducts

Several hundred disinfection byproducts (DBPs) in drinking water have been identified, and are known to have potentially adverse health effects. There are toxicological data gaps for most DBPs, and the predictive method may provide an effective way to address this. The development of an in-silico model of toxicology endpoints of DBPs is rarely studied. The main aim of the present study is to develop predictive quantitative structure–activity relationship (QSAR) models for the reactive toxicities of 50 DBPs in the five bioassays of X-Microtox, GSH+, GSH−, DNA+ and DNA−. All-subset regression was used to select the optimal descriptors, and multiple linear-regression models were built. The developed QSAR models for five endpoints satisfied the internal and external validation criteria: coefficient of determination (R²) > 0.7, explained variance in leave-one-out prediction (Q²_LOO) and in leave-many-out prediction (Q²_LMO) > 0.6, variance explained in external prediction (Q²_F1, Q²_F2, and Q²_F3) > 0.7, and concordance correlation coefficient (CCC) > 0.85. The application domains and the meaning of the selective descriptors for the QSAR models were discussed. The obtained QSAR models can be used in predicting the toxicities of the 50 DBPs.

Development of quantitative structure activity relationship (QSAR) model for disinfection byproduct (DBP) research: A review of methods and resources

Quantitative structure-activity relationship (QSAR) models are tools for linking chemical activities with molecular structures and compositions. Due to the concern about the proliferating number of disinfection byproducts (DBPs) in water and the associated financial and technical burden, researchers have recently begun to develop QSAR models to investigate the toxicity, formation, property, and removal of DBPs. However, there are no standard procedures or best practices regarding how to develop QSAR models, which potentially limit their wide acceptance. In order to facilitate more frequent use of QSAR models in future DBP research, this article reviews the processes required for QSAR model development, summarizes recent trends in QSAR-DBP studies, and shares some important resources for QSAR development (e.g., free databases and QSAR programs). The paper follows the four steps of QSAR model development, i.e., data collection, descriptor filtration, algorithm selection, and model validation; and finishes by highlighting several research needs. Because QSAR models may have an important role in progressing our understanding of DBP issues, it is hoped that this paper will encourage their future use for this application.

Risk of congenital anomalies in relation to the uptake of trihalomethane from drinking water during pregnancy

OBJECTIVES

Congenital anomalies have been inconsistently associated with maternal crude estimated exposure to drinking water trihalomethane (THM). We investigated the relationship between individual THM uptake during the first trimester of pregnancy and congenital anomalies.

METHODS

We estimated maternal THM uptake for 3074 live births using residential tap water concentrations, drinking water ingestion, showering and bathing, and uptake factors of THM in the blood. Multiple logistic regression was used to investigate the association of THM exposure with congenital anomalies.

RESULTS

We observed no statistically significant relationships between congenital anomalies and the total THM internal dose. We found little indication of a dose-response relationship for brominated THM and congenital heart anomalies. The relationship was statistically significant for bromodichloromethane (BDCM) (OR=2.16, 95% CI 1.05 to 4.46, highest vs lowest tertile) during the first month of pregnancy. During the first trimester of pregnancy, the probability of developing heart anomalies increased for every 0.1 μg/d increase in the BDCM and for every 0.01 μg/d increase in the internal dibromochloromethane (DBCM) dose (OR 1.70, 95% CI 1.09 to 2.66, and OR 1.25, 95% CI 1.01 to 1.54, respectively). A dose-response relationship was evident for musculoskeletal anomalies and DBCM exposure during the first and second months of pregnancy, while BDCM exposure tended to increase the risk of urogenital anomalies.

CONCLUSIONS

This study shows some evidence for an association between the internal dose of THM and the risk of congenital anomalies. In particular, increased prenatal exposure to brominated THM might increase the risk of congenital heart and musculoskeletal anomalies.

Mouse embryonic stem cell adherent cell differentiation and cytotoxicity (ACDC) assay

An adherent cell differentiation and cytotoxicity (ACDC) assay was developed using pluripotent J1 mouse embryonic stem cells (mESCs). Adherent mESCs were used to evaluate chemical-induced effects on both stem cell viability and differentiation using an in-cell western technique after a 9-day culture. DRAQ5/Sapphire700 stains were used to quantify cell number. Myosin heavy chain protein was used as a marker of cardiomyocyte differentiation and was corrected for cell number, thereby separating cytotoxicity and effects on differentiation. Acetic acid, 5-fluorouracil and bromochloroacetic acid were evaluated using the embryonic stem cell test and ACDC assay. Both systems distinguish the relative potencies of these compounds. TaqMan low-density arrays were used to characterize the time course of differentiation and effects of chemical exposure on multiple differentiation gene markers. The ACDC assay is a technique that can be used to evaluate the effects of xenobiotics on mESC differentiation and cell number using a single assay.

Trace determination of nine haloacetic acids in drinking water by liquid chromatography-electrospray tandem mass spectrometry

A simple, fast and sensitive liquid chromatography-electrospray tandem mass spectrometry method was established for trace levels of nine haloacetic acids (HAAs) in drinking water. Water samples were removed of residual chlorine by adding L-ascorbic acid, and directly injected after filtered by 0.22 microm membrane. Nine HAAs were separated by liquid chromatography in 7.5 min, and the limits of detection were generally between 0.16 and 0.99 microg/L except for chlorodibromoacetic acid (1.44 microg/L) and tribromoacetic acid (8.87 microg/L). The mean recoveries of nine target compounds in spiked drinking water samples were 80.1-108%, and no apparent signal suppression was observed. Finally, this method was applied to determine HAAs in the tap water samples collected from five waterworks in Shandong, China. Nine HAAs except for monochloroacetic acid, monobromoacetic acid, dibromochloroacetic acid and tribromoacetic acid were detected, and the total concentrations were 7.79-36.5 microg/L. The determination results well met the first stage of the Disinfectants/Disinfection By-Products (D/DBP) Rules established by U.S.EPA and Guidelines for Drinking-water Quality of WHO.

The epidemiology and possible mechanisms of disinfection by-products in drinking water

This paper summarizes the epidemiological evidence for adverse health effects associated with disinfection by-products (DBPs) in drinking water and describes the potential mechanism of action. There appears to be good epidemiological evidence for a relationship between exposure to DBPs, as measured by trihalomethanes (THMs), in drinking water and bladder cancer, but the evidence for other cancers including colorectal cancer is inconclusive and inconsistent. There appears to be some evidence for an association between exposure to DBPs, specifically THMs, and little for gestational age/intrauterine growth retardation and, to a lesser extent, pre-term delivery, but evidence for relationships with other outcomes such as low birth weight, stillbirth, congenital anomalies and semen quality is inconclusive and inconsistent. Major limitations in exposure assessment, small sample sizes and potential biases may account for the inconclusive and inconsistent results in epidemiological studies. Moreover, most studies have focused on total THMs as the exposure metric, whereas other DBPs appear to be more toxic than the THMs, albeit generally occurring at lower levels in the water. The mechanisms through which DBPs may cause adverse health effects including cancer and adverse reproductive effects have not been well investigated. Several mechanisms have been suggested, including genotoxicity, oxidative stress, disruption of folate metabolism, disruption of the synthesis and/or secretion of placental syncytiotrophoblast-derived chorionic gonadotropin and lowering of testosterone levels, but further work is required in this area.

In vitro survival and development of goat preantral follicles in two different oxygen tensions

The aim of the present study was to evaluate the effect of two different oxygen (O(2)) concentrations on survival and development of preantral follicles of goats cultured in vitro. Preantral ovarian follicles (> or =150 microm) were isolated from ovarian cortex fragments of goats and individually cultured for 30 days under two different O(2) concentrations (5% and 20% O(2)). Follicle development was evaluated on the basis of antral cavity formation, increase in follicular diameter, presence of healthy cumulus oocyte complexes and fully grown oocytes. Results showed with progression of culture period from 6 to 12 days, a decrease in follicular survival was observed in both O(2) concentrations (P<0.05). When the O(2) tensions were compared to each other in the different days of culture, 20% O(2) was more efficient in promoting an increase in follicular diameter from day 24 of culture onward than 5% O(2) (P<0.05). However, follicles cultured with 5% O(2) had an increased percentage of antrum formation from 12 days to the end of culture, compared with 20% O(2) (P<0.05). Moreover, there was no difference in percentage of fully developed oocytes with the different O(2) tensions. However, only oocytes (16.7%) from follicles cultured in 20% O(2) resumed meiosis. In conclusion, concentration of 20% O(2) was more efficient in promoting follicular growth and oocyte meiosis resumption from preantral follicles of goats when grown in vitro.

Oxidative stress status and development of late organogenesis stage rat whole embryos cultured from gestational days 13.5 to 14.5

A new method for culturing rodent whole embryos at the late organogenesis stage was developed using a roller-bottle system with intermittent gassing. Rat embryos were cultured for 24 h from gestational day (GD) 13.5 to 14.5. Growth and metabolic comparisons were made between in vivo embryos and embryos of the same GD cultured under various media and conditions. Crown-rump length, head length and protein content were used as growth indicators. Biologic markers such as embryonic tissue concentration of glutathione (GSH), glutathione disulfide (GSSG) and lipid peroxidation were used as assessments of metabolic activity in terms of oxidative stress. Embryos cultured with media consisting of either 15% or 20% male rat serum and balanced with Dulbecco's Modified Eagle Medium (DMEM) were found to most closely match in vivo embryos. 6 h gassing intervals and 5 mL medium volume/embryo provided optimal conditions for cultured embryos. By shortening the 24 h embryo culture period to 12 h, embryonic haemorrhaging was avoided. Moreover, the 12-h cultured embryos showed similar redox GSH/GSSG ratios and similar GSH content to the in vivo embryos, which was not observed in the embryos cultured under 24 h culture conditions. The present work demonstrates the utility of late organogenesis stage embryo culture as a model for the assessment of in vivo embryonic growth and oxidative stress indices.

Short-term exposures to dihaloacetic acids produce dysmorphogenesis in mouse conceptuses in vitro

The haloacetic acids (HAAs) are a family of xenobiotics found in tap water as a result of drinking water disinfection. Administration of HAAs to rats produces a variety of adverse effects, including developmental toxicity. The dysmorphogenic potencies of all nine bromo/chloro-acetic acids have been determined in rodent whole embryo culture using standard 26-h exposure. Since the half-lives of the HAAs in vivo are typically <8 h, the developmental effects of short-term exposures to dihaloacetates were evaluated. Gestation day 8 (3-6 somite pairs) CD-1 mouse conceptuses were exposed to 11,000 microM dichloroacetic acid (DCA), 300 microM dibromoacetic acid (DBA) or 300 microM bromochloroacetic acid (BCA) for culture periods of 1, 3, 6 or 26 h. Following 1, 3 or 6 h of exposure to HAAs, conceptuses were transferred to control medium to complete a 26-h culture period. The amounts of HAAs present in embryos after 1, 3 and 6h of exposure were determined. Increased incidences of dysmorphic embryos were produced by 6 or 26-h exposures to DCA; a 26-h exposure to DBA; or 3, 6 or 26-h exposures to BCA. The dysmorphology produced was dependent upon the length of exposure and chemical. The embryonic concentration of each HAA (104.5, 2.5 and 2.6 pmol/microg protein for DCA, DBA and BCA, respectively) was reached by 1h of exposure and did not change at the subsequent time points examined. The current studies demonstrate that BCA is more potent than DBA or DCA at disrupting embryogenesis since shorter exposures alter morphogenesis. Since the embryonic HAA concentrations were the same at the three time points measured, the time-dependence in dysmorphogenesis does not appear to be a simple function of increasing embryonic concentration of these chemicals. These studies demonstrate that for these dihaloacetic acids relatively high concentrations and long exposures are needed to alter rodent development in vitro.