Drinking Water Disinfection by-Products and Congenital Malformations: A Nationwide Register-Based Prospective Study

Exposure to drinking water pollutants and non-syndromic birth defects: a systematic review and meta-analysis synthesis

OBJECTIVES

To evaluate the association between drinking water pollutants and non-syndromic birth defects.

DESIGN

Systematic review and meta-analysis synthesis.

DATA SOURCES

A search of MEDLINE, EMBASE and Google Scholar was performed to review relevant citations reporting on birth defects in pregnancies exposed to water pollutants between January 1962 and April 2023.

ELIGIBILITY CRITERIA

Prospective or retrospective cohort, population studies and case-control studies that provided data on exposure to drinking water pollutants around conception or during pregnancy and non-syndromic birth defects. We included studies published in the English language after the Minamata Bay disaster to reflect on contemporary concerns about the effect of environmental pollution and obstetric outcomes.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently read the retrieved articles for content, data extraction and analysis. The methodological quality of studies was assessed using the Newcastle-Ottawa Scale. Included studies were assessed for comparability when considered for meta-analysis.

RESULTS

32 studies met inclusion criteria including 17 cohorts (6 389 097 participants) and 15 case-control studies (47 914 cases and 685 712 controls). The most common pollutants investigated were trihalomethanes (11 studies), arsenic (5 studies) and nitrates (4 studies). The studies varied in design with different estimates of exposure, different stages of gestation age and different durations of exposure to pollutants. 21 articles reported data on any birth defects in their population or study groups and the others on specific birth defects including congenital heart defects, neural tube defects, orofacial defects and hypospadias. An increased risk or higher incidence of overall birth defects was reported by 9 studies and for specific birth defects by 14 studies. Eight studies compared the risk or incidence of birth defects with exposure to different concentrations of the pollutants. The analysis showed an association between higher levels of trihalomethanes (TTMs) and arsenic increase in major birth defects (lower vs higher exposure (OR 0.76, 95% CI 0.65 to 0.89; p<0.001 and OR 0.56, 95% CI 0.39 to 0.82; p<0.005, respectively).

CONCLUSION

The evidence of an association between exposure to average levels of common drinking water chemical pollutants during pregnancy and an increased risk or incidence of birth defects is uncertain. Available evidence indicates that some common chemical pollutants currently found in drinking water may have a direct teratogenic effect at high maternal exposure, however, wide variation in methodology limits the interpretation of the results. Future prospective studies using standardised protocols comparing maternal levels during all three trimesters of pregnancy and cord blood levels at birth are needed to better understand the placental transfer of water pollutants and accurately evaluate individual fetal exposure to drinking water pollutants.

PROSPERO REGISTRATION NUMBER

CRD42018112524.

Maternal Exposure to Tap Water Disinfection By-Products and Risk of Selected Congenital Heart Defects

BACKGROUND

The use of chlorine to treat drinking water produces disinfection by-products (DBPs), which have been associated with congenital heart defects (CHDs) in some studies.

METHODS

Using National Birth Defects Prevention Study data, we linked geocoded residential addresses to public water supply measurement data for DBPs. Self-reported water consumption and filtration methods were used to estimate maternal ingestion of DBPs. We estimated adjusted odds ratios and 95% confidence intervals using logistic regression controlling for maternal age, education, body mass index (BMI), race/ethnicity, and study site to examine associations between CHDs and both household DBP level and estimated ingestion of DBPs.

RESULTS

Household DBP exposure was assessed for 2717 participants (1495 cases and 1222 controls). We observed a broad range of positive, null, and negative estimates across eight specific CHDs and two summary exposures (trihalomethanes and haloacetic acids) plus nine individual DBP species. Examining ingestion exposure among 2488 participants (1347 cases, 1141 controls) produced similarly inconsistent results.

CONCLUSIONS

Assessing both household DBP level and estimated ingestion of DBPs, we did not find strong evidence of an association between CHDs and DBPs. Despite a large study population, DBP measurements were available for less than half of participant addresses, limiting study power.

Neurodevelopmental toxicity of a ubiquitous disinfection by-product, bromoacetic acid, in Zebrafish (Danio rerio)

Disinfection of public drinking water and swimming pools is crucial for preventing waterborne diseases, but it can produce harmful disinfection by-products (DBPs), increasing the risk of various diseases for those frequently exposed to such environments. Bromoacetic acid (BAA) is a ubiquitous DBP, with toxicity studies primarily focused on its in vitro cytotoxicity, and insufficient research on its neurodevelopmental toxicity. Utilizing zebrafish as a model organism, this study comprehensively explored BAA's toxic effects and uncovered the molecular mechanisms through neurobehavioral analysis, in vivo two-photon imaging, transcriptomic sequencing, pharmacological intervention and molecular biological detection. Results demonstrated BAA induced significant changes on various indicators in the early development of zebrafish. Furthermore, BAA disrupted behavioral patterns in zebrafish larvae across locomotion activity, light-dark stimulation, and vibration stimulation paradigms. Subsequent investigation focused on larvae revealed BAA inhibited neuronal development, activated neuroinflammatory responses, and altered vascular morphology. Transcriptomic analysis revealed BAA-stressed zebrafish exhibited downregulation of visual transduction-related genes and activation of ferroptosis and cellular apoptosis. Neurobehavioral disorders were recovered by inhibiting ferroptosis and apoptosis. This study elucidates the neurodevelopmental toxicity associated with BAA, which is crucial for understanding health risks of DBPs and for the development of more effective detection methods and regulatory strategies.

Maternal periconceptional exposure to drinking water disinfection by-products and neural tube defects in offspring

BACKGROUND

Associations between maternal periconceptional exposure to disinfection by-products (DBPs) in drinking water and neural tube defects (NTDs) in offspring are inconclusive, limited in part by exposure misclassification.

METHODS

Maternal interview reports of drinking water sources and consumption from the National Birth Defects Prevention Study were linked with DBP concentrations in public water system monitoring data for case children with an NTD and control children delivered during 2000-2005. DBPs analyzed were total trihalomethanes, the five most common haloacetic acids combined, and individual species. Associations were estimated for all NTDs combined and selected subtypes (spina bifida, anencephaly) with maternal periconceptional exposure to DBPs in public water systems and with average daily periconceptional ingestion of DBPs accounting for individual-level consumption and filtration information. Mixed effects logistic regression models with maternal race/ethnicity and educational attainment at delivery as fixed effects and study site as a random intercept were applied.

RESULTS

Overall, 111 case and 649 control children were eligible for analyses. Adjusted odds ratios for maternal exposure to DBPs in public water systems ranged from 0.8-1.5 for all NTDs combined, 0.6-2.0 for spina bifida, and 0.7-1.9 for anencephaly; respective ranges for average daily maternal ingestion of DBPs were 0.7-1.1, 0.5-1.5, and 0.6-1.8. Several positive estimates (≥1.2) were observed, but all confidence intervals included the null.

CONCLUSIONS

Using community- and individual-level data from a large, US, population-based, case-control study, we observed statistically nonsignificant associations between maternal periconceptional exposure to total and individual DBP species in drinking water and NTDs and subtypes.

US drinking water quality: exposure risk profiles for seven legacy and emerging contaminants

BACKGROUND

Advances in drinking water infrastructure and treatment throughout the 20th and early 21st century dramatically improved water reliability and quality in the United States (US) and other parts of the world. However, numerous chemical contaminants from a range of anthropogenic and natural sources continue to pose chronic health concerns, even in countries with established drinking water regulations, such as the US.

OBJECTIVE/METHODS

In this review, we summarize exposure risk profiles and health effects for seven legacy and emerging drinking water contaminants or contaminant groups: arsenic, disinfection by-products, fracking-related substances, lead, nitrate, per- and polyfluorinated alkyl substances (PFAS) and uranium. We begin with an overview of US public water systems, and US and global drinking water regulation. We end with a summary of cross-cutting challenges that burden US drinking water systems: aging and deteriorated water infrastructure, vulnerabilities for children in school and childcare facilities, climate change, disparities in access to safe and reliable drinking water, uneven enforcement of drinking water standards, inadequate health assessments, large numbers of chemicals within a class, a preponderance of small water systems, and issues facing US Indigenous communities.

RESULTS

Research and data on US drinking water contamination show that exposure profiles, health risks, and water quality reliability issues vary widely across populations, geographically and by contaminant. Factors include water source, local and regional features, aging water infrastructure, industrial or commercial activities, and social determinants. Understanding the risk profiles of different drinking water contaminants is necessary for anticipating local and general problems, ascertaining the state of drinking water resources, and developing mitigation strategies.

IMPACT STATEMENT

Drinking water contamination is widespread, even in the US. Exposure risk profiles vary by contaminant. Understanding the risk profiles of different drinking water contaminants is necessary for anticipating local and general public health problems, ascertaining the state of drinking water resources, and developing mitigation strategies.

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.

Comparison of Trihalomethane exposure assessment metrics in epidemiologic analyses of reproductive and developmental outcomes

BACKGROUND

Researchers have developed exposure assessment metrics for disinfection by-products (DBPs) utilizing drinking water monitoring data and accounting for spatial and temporal variability, water consumption, and showering and bathing time with an expectation of decreasing exposure misclassification compared to the use of measured concentrations at public water supply (PWS) monitoring locations alone.

OBJECTIVE

We used exposure data collected for a previous study of DBPs to evaluate how different sources of information impact trihalomethane (THM) exposure estimates.

METHODS

We compared gestational exposure estimates to THMs based on water utility monitoring data alone, statistical imputation of daily concentrations to incorporate temporal variability, and personal water consumption and use (bathing and showering). We used Spearman correlation coefficients and ranked kappa statistics to compare exposure classifications.

RESULTS

Exposure estimates based on measured or imputed daily THM concentrations, self-reported consumption, or bathing and showering differed substantially from estimates based solely on concentrations from PWS quarterly monitoring reports. Ranked exposure classifications, high to low quartiles or deciles, were generally consistent across each exposure metric (i.e., a subject with "high" exposure based on measured or imputed THM concentrations generally remained in the "high" category across exposure metrics.) The measured concentrations and imputed daily (i.e., spline regression) concentrations were highly correlated (r = 0.98). The weighted kappa statistics comparing exposure estimates using different exposure metrics ranged from 0.27 to 0.89, with the highest values for the ingestion + bathing/showering metrics compared to metrics for bathing/showering only (0.76 and 0.89). Bathing and showering contributed the most to "total" THM exposure estimates.

IMPACT STATEMENT

We compare exposure metrics capturing temporal variability and multiple estimates of personal THM exposure with THM concentrations from PWS monitoring data. Our results show exposure estimates based on imputed daily concentrations accounting for temporal variability were very similar to the measured THM concentrations. We observed low agreement between imputed daily concentrations and ingestion-based estimates. Considering additional routes of exposure (e.g., inhalation and dermal) slightly increased agreement with the measured PWS exposure estimate in this population. Overall, the comparison of exposure assessment metrics allows researchers to understand the added value of additional data collection for future epidemiologic analyses of DBPs.

Lifetime exposure to brominated trihalomethanes in drinking water and swimming pool attendance are associated with chronic lymphocytic leukemia: a Multicase-Control Study in Spain (MCC-Spain)

BACKGROUND

Chronic lymphocytic leukemia (CLL) etiology is poorly understood, and carcinogenic chemicals in drinking and recreational water are candidates.

OBJECTIVE

To evaluate the association between drinking-water exposure to trihalomethanes (THMs) and nitrate as well as lifetime swimming pool attendance and CLL.

METHODS

During 2010-2013, hospital-based CLL cases and population-based controls were recruited in Spain, providing information on residential histories, type of water consumed and swimming pool attendance. Average THMs and nitrate levels in drinking water were linked to lifetime water consumption. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using mixed models.

RESULTS

Final samples for residential tap water analyses and swimming pool attendance analyses were 144 cases/1230 controls and 157 cases/1240 controls, respectively. Mean (SD) values for average lifetime residential brominated THMs and chloroform in tap water (μg/L), and ingested nitrate (mg/day) were 48.1 (35.6), 18.5 (6.7) and 13.7 (9.6) respectively in controls; and 72.9 (40.7), 17.9 (5.4), and 14.1 (8.8) in CLL cases. For each 10 μg/L increase of brominated THMs and chloroform lifetime-average levels, the ORs (95% CI) were 1.22 (1.14, 1.31) and 0.54 (0.34, 0.87), respectively. For each 5 mg/day increase of ingested nitrate, the OR of CLL was 0.91 (0.80, 1.04). The OR of lifetime pool users (vs. non-users) was 2.38 (1.61, 3.52). Upon performing annual frequency of attending pools analysis through categorization, the second and third categories showed an ORs of 2.36 (1.49, 3.72) and 2.40 (1.51, 3.83), respectively, and P-trend of 0.001.

IMPACT STATEMENT

This study identifies an association of long-term exposure to THMs in drinking water, at concentrations below the regulatory thresholds and WHO guidelines, and swimming pool attendance, with chronic lymphocytic leukemia (CLL). These unprecedented findings are highly relevant since CLL is an incurable cancer with still unknown etiology and because the widespread exposure to chlorination by-products that remain in drinking and recreational water worldwide. Despite the demonstrated carcinogenicity in animals of several chlorination by-products, little is known about their potential risks on human health. This study makes a significant contribution to the search for environmental factors involved in the etiology of CLL and to the evidence of the health impact of these high prevalent water contaminants.

Pressure-driven membrane filtration technology for terminal control of organic DBPs: A review

Disinfection by-products (DBPs), a series of undesired secondary contaminants formed during the disinfection processes, deteriorate water quality, threaten human health and endanger ecological safety. Membrane-filtration technologies are commonly used in the advanced water treatment and have shown a promising performance for removing trace contaminants. In order to gain a clearer understanding of the behavior of DBPs in membrane-filtration processes, this work dedicated to: (1) comprehensively reviewed the retention efficiency of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) for DBPs. (2) summarized the mechanisms involved size exclusion, electrostatic repulsion and adsorption in the membrane retention of DBPs. (3) In conjunction with principal component analysis, discussed the influence of various factors (such as the characteristics of membrane and DBPs, feed solution composition and operating conditions) on the removal efficiency. In general, the characteristics of the membranes (salt rejection, molecular weight cut-off, zeta potential, etc.) and DBPs (molecular size, electrical property, hydrophobicity, polarity, etc.) fundamentally determine the membrane-filtration performance on retaining DBPs, and the actual operating environmental factors (such as solute concentration, coexisting ions/NOMs, pH and transmembrane pressure) exert a positive/negative impact on performance to some extent. Current researches indicate that NF and RO can be effective in removing DBPs, and looking forward, we recommend that multiple factors should be taken into account that optimize the existed membrane-filtration technologies, rationalize the selection of membrane products, and develop novel membrane materials targeting the removal of DBPs.

Bromoacetic acid induces neurogenic injury in the chicken brain by activating oxidative stress and NF-κB inflammatory pathway

The bromoacetic acid (BAA) is one of the most teratogenic and neurotoxic disinfection byproducts. Birds take environmental water as their habitat and are inevitably affected by BAA in the environment. However, the neurotoxicity caused by BAA in birds has not been reported and the mechanism remains unclear. In this study, we chose chickens as the avian model to explore the effects of different concentrations of BAA on the brain tissues. Here, we selected the 3 μg/L dose of BAA detected in Tai Lake basin as a reference, and designed 1-, 100-, and 1000-fold of the environmental exposure dose as the experimental doses to explore the neurotoxicity of BAA in birds. Results showed that BAA increased the number of pyknotic nuclear neurons, deformed vascular sheaths, and glial cells in the brain. BAA inhibited the activity of antioxidant enzymes and the expression of antioxidant genes. With the increase of BAA concentration, the oxidative stress-responsive transcription factor NF-κB was activated. Furthermore, BAA remarkably changed the expression of lipid metabolism related genes (i.e., acc, gpat, hmgr, pparα, cpt1, and ampkα). Importantly, BAA decreased the mRNA and protein expression levels of autophagy-related genes (i.e., atg5, ulk1, beclin1, and lc3). Meantime, BAA increased the mRNA and protein levels of apoptotic and pro-apoptotic genes, such as p53, bax, cytochrome c, caspase-9, and caspase-3. Overall, our study provided new insights into the potential neurotoxic effects of BAA in birds, which was important for the clinical monitoring and prevention of BAA.

Estimating National Exposures and Potential Bladder Cancer Cases Associated with Chlorination DBPs in U.S. Drinking Water

BACKGROUND

Disinfection byproducts (DBPs) in public water systems (PWS) are an unintended consequence resulting from reactions between mostly chlorine-based disinfectants and organic and inorganic compounds in source waters. Epidemiology studies have shown that exposure to DBP (specifically trihalomethanes) was associated with an increased risk of bladder cancer.

OBJECTIVE

Our goal was to characterize the relative differences in exposures and estimated potential bladder cancer risks for people served by different strata of PWS in the United States and to evaluate uncertainties associated with these estimates.

METHODS

We stratified PWS by source water type (surface vs. groundwater) and population served (large, medium, and small) and calculated population-weighted mean trihalomethane-4 (THM4) concentrations for each stratum. For each stratum, we calculated a population attributable risk (PAR) for bladder cancer using odds ratios derived from published pooled epidemiology estimates as a function of the mean THM4 concentration and the fraction of the total U.S. population served by each stratum of systems. We then applied the stratum-specific PARs to the total annual number of new bladder cancer cases in the U.S. population to estimate bladder cancer incidence in each stratum.

RESULTS

Our results show that approximately 8,000 of the 79,000 annual bladder cancer cases in the United States were potentially attributable to DBPs in drinking water systems. The estimated attributable cases vary based on source water type and system size. Approximately 74% of the estimated attributable cases were from surface water systems serving populations of > 10,000 people. We also identified several uncertainties that may affect the results from this study, primarily related to the use of THM4 as a surrogate measure for DBPs relevant to bladder cancer.

DISCUSSION

Despite significant reductions in exposure over the past several decades, our study suggests that ∼ 10 % of the bladder cancer cases in the United States may still be attributed to exposure to DBPs found in drinking water systems. https://doi.org/10.1289/EHP9985.