Chlorination disinfection by-products and risk of congenital anomalies in England and Wales

Exposure to trichloromethane via drinking water promotes progression of colorectal cancer by activating IRE1α/XBP1 pathway of endoplasmic reticulum stress

Trichloromethane (TCM), a commonly recognized disinfection by-product formed during the chlorination of water, has been associated with the onset of colorectal cancer (CRC) in humans. Despite this, the impact of TCM on the progression of CRC remains uncertain. In this investigation, it was observed that exposure to TCM could augment the migratory capabilities of CRC cells and facilitate the advancement of colorectal tumors. To delve deeper into the mechanism responsible for TCM-induced CRC progression, we performed RNA-Seq analysis at cellular and animal levels after TCM exposure. Both the KEGG and GO enrichment analyses indicated the activation of endoplasmic reticulum stress (ERS) and the regulation of the cytoskeleton. Subsequently, we confirmed the activation of the IRE1α/XBP1 pathway of ERS through western blot and RT-qPCR. Additionally, we observed the aggregation of cytoskeletal proteins F-actin and β-tubulin at the cell membrane periphery and the development of cellular pseudopods using immunofluorescence following exposure to TCM in vitro. The downregulation of IRE1α and XBP1 through siRNA interference resulted in the disruption of cell cytoskeleton rearrangement and impaired cell migration capability. Conversely, treatment with TCM mitigated this inhibitory effect. Moreover, chronic exposure to low concentration of TCM also triggered CRC cell migration by causing cytoskeletal reorganization, a process controlled by the IRE1α/XBP1 axis. Our study concludes that TCM exposure induces cell migration through the activation of ERS, which in turn regulates cytoskeleton rearrangement. This study offers novel insights into the mechanism through which TCM facilitates the progression of CRC.

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.

Perspectives and understanding on the occurrence, toxicity and abatement technologies of disinfection by-products in drinking water

Disinfection by-products (DBPs) are one of the significant emerging contaminants that have caught the attention of researchers worldwide due to their pervasiveness. Their presence in drinking water, even in shallow concentrations (in levels of parts per billion), poses considerable health risks. Therefore, it is crucial to understand their kinetics to understand better their formation and persistence in the water supply systems. This manuscript demonstrates different aspects of research carried out on DBPs in the past. A systematic approach was adopted for the bibliographical research that started with choosing appropriate keywords and identifying the most relevant manuscripts through the screening process. This follows a quantitative assessment of the extracted literature sample, which included the most productive and influential journal sources, the most widely used keywords, the most influential authors active in the research domain, the most cited articles, and the countries most actively engaged in the research field. Critical observations on the literature sample led to the qualitative assessment, wherein the past and current research trends were observed and reported. Finally, we identified the essential gaps in the available literature, which further led to recommending the course ahead in the research domain. This study will prove fruitful for young and established researchers who are or wish to work in this emerging field of research.

The alternation of halobenzoquinone disinfection byproduct on toxicogenomics of DNA damage and repair in uroepithelial cells

Halobenzoquinones (HBQs) were recently discovered as an emerging class of drinking water disinfection byproducts with carcinogenic concern. However, the molecular mechanism underlying HBQs-induced DNA damage is not clear. In this study, we integrated in vitro genotoxicity, computational toxicology, and the quantitative toxicogenomic analysis of HBQs on DNA damage/repair pathways in human bladder epithelial cells SV-HUC-1. The results showed that HBQs could induce cytotoxicity with the descending order as 2,6-DIBQ > 2,6-DCBQ ≈ 2,6-DBBQ. Also, HBQs can increase DNA damage in SV-HUC-1 cells and thus generate genotoxicity. However, there is no significant difference in genotoxicity among the three HBQs. The results of molecular docking and molecular dynamics simulation further confirmed that HBQs had high binding fractions and stability to DNA. Toxicogenomic analysis indicated that HBQs interfered with DNA repair pathways, mainly affecting base excision repair, nucleotide excision repair and homologous recombination repair. These results have provided new insights into the underlying molecular mechanisms of HBQs-induced DNA damage, and contributed to the understanding of the relationship between exposure to DBPs and risks of developing bladder cancer.

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.

The chloroperoxidase immobilized on porous carbon nanobowls for the detection of trichloroacetic acid by electroenzymatic synergistic catalysis

Trichloroacetic acid (TCA), as a by-product of chlorination disinfection, is a highly carcinogenic chemical. Due to the widespread use of chlorination disinfection, it is critical to detect TCA in drinking water to decrease the incidence of disease. In this work, we developed an efficient TCA biosensor via electroenzymatic synergistic catalysis. The porous carbon nanobowls (PCNB) are prepared and wrapped by an amyloid like proteins formed by phase-transitioned lysozyme (PTL-PCNB), then, chloroperoxidase (CPO) is abounding to PTL-PCNB owing to its strong adhesion. The ionic liquid of 1-ethyl-3-methylimidazolium bromide (ILEMB) is co-immobilized on PTL-PCNB to from CPO-ILEMB@PTL-PCNB nanocomposite to assist the direct electron transfer (DET) of CPO. The PCNB plays two roles here. In addition, to increasing the conductivity, it serves as an ideal support for holding CPO; The CPO-ILEMB@PTL-PCNB nanocomposite modified electrode presents high efficiency for sensing TCA. Through electroenzymatic synergistic catalysis, a wide detection range of 33 μmol L-1 to 98 mmol L-1 can be achieved with a low detection limit of 5.9 μmol L-1, and high stability, selectivity as well as reproducibility, which ensures its potential practical applicability. This work provides a new platform for the electro-enzyme synergistic catalysis in one pot.

Maternal exposure to nitrosamines in drinking water during pregnancy and birth outcomes in a Chinese cohort

Maternal exposure to regulated disinfection by-products (DBPs) during pregnancy has been linked with adverse birth outcomes. However, no human studies have focused on drinking water nitrosamines, a group of emerging unregulated nitrogenous DBPs that exhibits genotoxicity and developmental toxicity in experimental studies. This cohort study included 2457 mother-infant pairs from a single drinking water supply system in central China, and maternal trimester-specific and entire pregnancy exposure of drinking water nitrosamines were evaluated. Multivariable linear and Poisson regression models were used to estimate the associations between maternal exposure to nitrosamines in drinking water and birth outcomes [birth weight (BW), low birth weight (LBW), small for gestational age (SGA) and preterm delivery (PTD)]. Elevated maternal N-nitrosodimethylamine (NDMA) exposure in the second trimester and N-nitrosopiperidine (NPIP) exposure during the entire pregnancy were associated with decreased BW (e.g., β = -88.6 g; 95% CI: -151.0, -26.1 for the highest vs. lowest tertile of NDMA; p for trend = 0.01) and increased risks of PTD [e.g., risk ratio (RR) = 2.16; 95% CI: 1.23, 3.79 for the highest vs. lowest tertile of NDMA; p for trend = 0.002]. Elevated maternal exposure of N-nitrosodiethylamine (NDEA) in the second trimester was associated with increased risk of SGA (RR = 1.80; 95% CI: 1.09, 2.98 for the highest vs. lowest tertile; p for trend = 0.01). Our study detected associations of maternal exposure to drinking water nitrosamines during pregnancy with decreased BW and increased risks of SGA and PTD. These findings are novel but require replication in other study populations.

Total organic halogen in two drinking water supply systems: Occurrence, variations, and relationship with trihalomethanes

The spatiotemporal presence of overall disinfection by-products (DBPs) in two full-scale drinking water supply systems (DWSSs) were investigated using quantification of total organic halogen (TOX). The relationships of TOX with water quality parameters (especially the most regulated DBPs, trihalomethanes (THMs)) were also evaluated. The TOX levels ranged between 2.6 and 70.3 μg Cl/L and between 46.6 and 205.9 μg Cl/L in raw water and distribution water, respectively. The TOX concentration in water increased by an average of nine times after water treatment and varied slightly during distribution, suggesting that TOX in drinking water was mainly formed during chlorination disinfection rather than distribution. No clear seasonality in TOX level was observed. Positive correlations were found between raw water dissolved organic carbon (DOC) with an increase in TOX in treated water and between DOC level with TOX content in distributed water, emphasizing a key role of organics in TOX formation. Chloroform (TCM) was the dominant THM, followed by bromodichloromethane (BDCM) in the drinking water, and the levels of the other two measured THMs (dibromochloromethane and bromoform) were negligible. THM2 (sum of TCM and BDCM) made up average of 18% of the TOX, and was weakly correlated with TOX content (r_s = 0.321; P < 0.05), implying that THM is not a suitable surrogate measure for TOX in drinking water. This study provides basic data on the occurrence and variation of TOX within conventional DWSSs and highlights the importance of using TOX measurements to obtain more accurate information about DBP occurrence, for exposure assessment and regulatory determination.

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

BACKGROUND

Drinking water chlorination by-products have been associated with adverse reproductive outcomes, although the findings for congenital malformations are still inconclusive.

OBJECTIVE

We conducted a nationwide register-based prospective study to assess whether first trimester maternal exposure to the four most common trihalomethanes [total trihalomethanes (TTHM)] via municipal drinking water was associated with risk of congenital malformation among newborns.

METHODS

We included all births during 2005-2015 (live and stillbirths) of mothers residing in Swedish localities having >10,000 inhabitants, two or fewer operating water works, and sufficient municipal TTHM monitoring data. Individual maternal first trimester exposure was obtained by linking TTHM measurements to residential information, categorized into no chlorination and <5, 5-15, and >15μg TTHM/L. We also made chlorination treatment-specific analyses (exclusive use of chloramine or hypochlorite). Outcomes and covariates were obtained via linkage to health care and administrative registers. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression.

RESULTS

Based on 623,468 births and a prevalence of congenital malformation of ∼2 cases/100 births, we observed associations between TTHM exposure in areas using chloramine and malformations of the nervous system (OR=1.82; 95% CI: 1.07, 3.12), urinary system (OR=2.06; 95% CI: 1.53, 2.78), genitals (OR=1.77; 95% CI: 1.38, 2.26), and limbs (OR=1.34; 95% CI: 1.10, 1.64), comparing the highest exposed category with the unexposed. No associations were observed in areas using exclusively hypochlorite as the primary water treatment method. By contrast, for malformations of the heart, a significant inverse association was observed only in areas using hypochlorite.

DISCUSSION

TTHM exposure was associated with the increased risk of malformations of the nervous system, urinary system, genitals, and limbs in areas exclusively using chloramine. An association between chloramine-related chlorination by-products and congenital malformations has not previously been highlighted and needs further attention. https://doi.org/10.1289/EHP9122.

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water: Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics (FQs) in synthetic marine aquaculture water were subject to sodium hypochlorite (NaClO) disinfection scenario to investigate their reaction kinetics and transformation during chlorination. Reactivity of each FQ to NaClO was following the order of ofloxacin (OFL) > enrofloxacin (ENR) > lomefloxacin (LOM) > ciprofloxacin (CIP) ~ norfloxacin (NOR) >> pipemedic acid (PIP), while flumequine did not exhibit reactivity. The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO, while humic acid was inhibitable to their degradation. The bromide ions promoted degradation of CIP and LOM, but restrained oxidation of OFL and ENR. By analysis of liquid chromatography with tandem mass spectrometry (LC-MS/MS), eight kinds of emerging brominated disinfection byproducts (Br-DBPs) caused by FQ_S were primarily identified in the chlorinated synthetic marine culture water. Through density functional theory calculation, the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms. Their formation involved decarboxylation, ring-opening/closure, dealkylation and halogenation. Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position. The piperazine ring containing tertiary amine was comparatively stable, while this moiety with a secondary amine structure would break down during chlorination. Additionally, logK_ow and logBAF of transformation products were calculated by EPI-Suite^TM to analyze their bioaccumulation. The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.

Disinfection By-Product Exposures and the Risk of Musculoskeletal Birth Defects

Supplemental Digital Content is available in the text.

Epidemiologic studies suggest that exposure to water disinfection by-products (DBPs) may increase the risk of certain birth defects. However, evidence for musculoskeletal defects (MSDs) is limited. Previous MSD studies have not examined DBPs beyond trihalomethanes (THMs) and have not separately examined limb or diaphragm defects which may have distinct developmental etiologies.

Associations Between Disinfection By-Product Exposures and Craniofacial Birth Defects

OBJECTIVE

The aim of this study was to examine associations between craniofacial birth defects (CFDs) and disinfection by-product (DBP) exposures, including the sum of four trihalomethanes (THM4) and five haloacetic acids (HAA5) (ie, DBP9).

METHODS

We calculated first trimester adjusted odds ratios (aORs) for different DBPs in a matched case-control study of 366 CFD cases in Massachusetts towns with complete 1999 to 2004 THM and HAA data.

RESULTS

We detected elevated aORs for cleft palate with DBP9 (highest quintile aOR = 3.52; 95% CI: 1.07, 11.60), HAA5, trichloroacetic acid (TCAA), and dichloroacetic acid. We detected elevated aORs for eye defects with TCAA and chloroform.

CONCLUSION

This is the first epidemiological study of DBPs to examine eye and ear defects, as well as HAAs and CFDs. The associations for cleft palate and eye defects highlight the importance of examining specific defects and DBPs beyond THM4.

Drinking water disinfection byproducts and risk of orofacial clefts in the National Birth Defects Prevention Study

BACKGROUND

Maternal exposure to drinking water disinfection byproducts (DBP)s may contribute to orofacial cleft (OFC) development, but studies are sparse and beset with limitations.

METHODS

Population-based, maternal interview reports of drinking water filtration and consumption for 680 OFC cases (535 isolated) and 1826 controls were linked with DBP concentration data using maternal residential addresses and public water system monitoring data. Maternal individual-level exposures to trihalomethanes (THM)s and haloacetic acids (HAA)s (µg/L of water consumed) were estimated from reported consumption at home, work, and school. Compared to no exposure, associations with multisource maternal exposure <1/2 or ≥1/2 the Maximum Contaminant Levels (MCL)s for total THMs (TTHM)s and HAAs (HAA5) or Maximum Contaminant Level Goals (MCLG)s for individual THMs and HAAs (if non-zero) were estimated for all OFCs and isolated OFCs, cleft palate (CP), and cleft lip ± cleft palate (CL/P) using logistic regression analyses.

RESULTS

Compared to controls, associations were near or below unity for maternal TTHM, HAA5, and individual THM exposures with all OFCs and isolated OFCs, CP, and CL/P. Associations also were near or below unity for individual HAAs with statistically significant, inverse associations observed with each OFC outcome group except CL/P.

CONCLUSIONS

This study examined associations for maternal reports of drinking water filtration and consumption and maternal DBP exposure from drinking water with OFCs in offspring. Associations observed were near or below unity and mostly nonsignificant. Continued, improved research using maternal individual-level exposure data will be useful in better characterizing these associations.

Impact of chloroform exposures on reproductive and developmental outcomes: A systematic review of the scientific literature

AIMS

We assessed the animal and epidemiological data to determine if chloroform exposure causes developmental and/or reproductive toxicity.

RESULTS AND DISCUSSION

Initial scoping identified developmental toxicity as the primary area of concern. At levels producing maternal toxicity in rats and mice, chloroform caused decrements in fetal weights and associated delays in ossification. In a single mouse inhalation study, exposure to a high concentration of chloroform was associated with small fetuses and increased cleft palate. However, oral exposure of mice to chloroform at a dose 4 times higher was negative for cleft palate; multiple inhalation studies in rats were also negative. Epidemiologic data on low birth weight and small for gestational age were generally equivocal, preventing conclusions from being drawn for humans. The animal data also show evidence of very early (peri-implantation) total litter losses at very high exposure levels. This effect is likely maternally mediated rather than a direct effect on the offspring. Finally, the epidemiologic data indicate a possible association of higher chloroform exposure with lower risk of preterm birth (<37 weeks gestation).

CONCLUSIONS

The available animal data suggest that exposures lower than those causing maternal toxicity should be without developmental effects in the offspring. Also, most studies in humans rely on group-level geographic exposure data, providing only weak epidemiologic evidence for an association with development outcomes and fail to establish a causal role for chloroform in the induction of adverse developmental outcomes at environmentally relevant concentrations.

Iodoacetic Acid Disrupting the Thyroid Endocrine System in Vitro and in Vivo

Exposure to drinking water disinfection byproducts (DBPs) is potentially associated with adverse developmental effects. Iodoacetic acid (IAA), an unregulated DBP, has been shown to be cytotoxic, mutagenic, genotoxic, and tumorigenic. However, its endocrine-disrupting effects remain unknown. This study evaluated the IAA-induced disruption of the thyroid endocrine system using in vitro and in vivo assays. Rat pituitary tumor GH3 cells were treated with IAA in the presence and absence of triiodothyronine (T3). IAA exposure significantly reduced T3-activated GH3 cell proliferation, indicating the antagonistic activity of IAA in vitro. Sprague-Dawley rats were also subjected to IAA treatment through oral gavage for 28 consecutive days. IAA exposure significantly down-regulated the mRNA expression levels of the thyrotropin receptor (TSHR), the sodium/iodide symporter (NIS), and type I deiodinase and simultaneously reduced the protein expression levels of TSHR and NIS. IAA exposure decreased T3 levels but increased the weights of hypothalamus and the levels of thyrotropin releasing hormone and thyrotropin. In addition, IAA induced the formation of smaller and more depleted follicles or even vacuolization in the thyroid. These results suggested that IAA potentially disrupts the thyroid endocrine system both in vitro and in vivo.

National scale assessment of total trihalomethanes in Irish drinking water

Ireland reported the highest non-compliance with respect to total trihalomethanes (TTHMs) in drinking water across the 27 European Union Member States for the year 2010. We carried out a GIS-based investigation of the links between geographical parameters and catchment land-uses with TTHMs concentrations in Irish drinking water. A high risk catchment map was created using peat presence, rainfall (>1400 mm) and slope (<5%) and overlain with a map comprising the national dataset of routinely monitored TTHM concentrations. It appeared evident from the map that the presence of peat, rainfall and slope could be used to identify catchments at high risk to TTHM exceedances. Furthermore, statistical analyses highlighted that the presence of peat soil with agricultural land was a significant driver of TTHM exceedances for all treatment types. PARAFAC analysis from three case studies identified a fluorophore indicative of reprocessed humic natural organic matter as the dominant component following treatment at the three sites. Case studies also indicated that (1) chloroform contributed to the majority of the TTHMs in the drinking water supplies and (2) the supply networks contributed to about 30 μg L^-1 of TTHMs.

Impact of London's road traffic air and noise pollution on birth weight: retrospective population based cohort study

Objective To investigate the relation between exposure to both air and noise pollution from road traffic and birth weight outcomes.Design Retrospective population based cohort study.Setting Greater London and surrounding counties up to the M25 motorway (2317 km²), UK, from 2006 to 2010.Participants 540 365 singleton term live births.Main outcome measures Term low birth weight (LBW), small for gestational age (SGA) at term, and term birth weight.Results Average air pollutant exposures across pregnancy were 41 μg/m³ nitrogen dioxide (NO₂), 73 μg/m³ nitrogen oxides (NO_x), 14 μg/m³ particulate matter with aerodynamic diameter <2.5 μm (PM_2.5), 23 μg/m³ particulate matter with aerodynamic diameter <10 μm (PM₁₀), and 32 μg/m³ ozone (O₃). Average daytime (L_Aeq,16hr) and night-time (L_night) road traffic A-weighted noise levels were 58 dB and 53 dB respectively. Interquartile range increases in NO₂, NO_x, PM_2.5, PM₁₀, and source specific PM_2.5 from traffic exhaust (PM_{2.5 traffic exhaust}) and traffic non-exhaust (brake or tyre wear and resuspension) (PM_{2.5 traffic non-exhaust}) were associated with 2% to 6% increased odds of term LBW, and 1% to 3% increased odds of term SGA. Air pollutant associations were robust to adjustment for road traffic noise. Trends of decreasing birth weight across increasing road traffic noise categories were observed, but were strongly attenuated when adjusted for primary traffic related air pollutants. Only PM_{2.5 traffic exhaust} and PM_2.5 were consistently associated with increased risk of term LBW after adjustment for each of the other air pollutants. It was estimated that 3% of term LBW cases in London are directly attributable to residential exposure to PM_2.5>13.8 μg/m³during pregnancy.Conclusions The findings suggest that air pollution from road traffic in London is adversely affecting fetal growth. The results suggest little evidence for an independent exposure-response effect of traffic related noise on birth weight outcomes.

A two-stage predictive model to simultaneous control of trihalomethanes in water treatment plants and distribution systems: adaptability to treatment processes

The trihalomethanes (TTHMs) and others disinfection by-products (DBPs) are formed in drinking water by the reaction of chlorine with organic precursors contained in the source water, in two consecutive and linked stages, that starts at the treatment plant and continues in second stage along the distribution system (DS) by reaction of residual chlorine with organic precursors not removed. Following this approach, this study aimed at developing a two-stage empirical model for predicting the formation of TTHMs in the water treatment plant and subsequently their evolution along the water distribution system (WDS). The aim of the two-stage model was to improve the predictive capability for a wide range of scenarios of water treatments and distribution systems. The two-stage model was developed using multiple regression analysis from a database (January 2007 to July 2012) using three different treatment processes (conventional and advanced) in the water supply system of Aljaraque area (southwest of Spain). Then, the new model was validated using a recent database from the same water supply system (January 2011 to May 2015). The validation results indicated no significant difference in the predictive and observed values of TTHM (R ² 0.874, analytical variance <17%). The new model was applied to three different supply systems with different treatment processes and different characteristics. Acceptable predictions were obtained in the three distribution systems studied, proving the adaptability of the new model to the boundary conditions. Finally the predictive capability of the new model was compared with 17 other models selected from the literature, showing satisfactory results prediction and excellent adaptability to treatment processes.

Disinfection By-Product Exposures and the Risk of Specific Cardiac Birth Defects

BACKGROUND

Epidemiological studies suggest that women exposed to disinfection by-products (DBPs) have an increased risk of delivering babies with cardiovascular defects (CVDs).

OBJECTIVE

We examined nine CVDs in relation to categorical DBP exposures including bromoform, chloroform, dibromochloromethane (DBCM), bromodichloromethane (BDCM), monobromoacetic acid (MBAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), and summary DBP measures (HAA5, THMBr, THM4, and DBP9).

METHODS

We calculated adjusted odds ratios (aORs) in a case-control study of birth defects in Massachusetts with complete quarterly 1999-2004 trihalomethane (THM) and haloacetic acid (HAA) data. We randomly matched 10 controls each to 904 CVD cases based on week of conception. Weight-averaged aggregate first-trimester DBP exposures were assigned to individuals based on residence at birth.

RESULTS

We detected associations for tetralogy of Fallot and the upper exposure categories for TCAA, DCAA, and HAA5 (aOR range, 3.34-6.51) including positive exposure-response relationships for DCAA and HAA5. aORs consistent in magnitude were detected between atrial septal defects and bromoform (aOR = 1.56; 95% CI: 1.01, 2.43), as well as DBCM, chloroform, and THM4 (aOR range, 1.26-1.67). Ventricular septal defects (VSDs) were associated with the highest bromoform (aOR = 1.85; 95% CI: 1.20, 2.83), MBAA (aOR = 1.81; 95% CI: 0.85, 3.84), and DBCM (aOR = 1.54; 95% CI: 1.00, 2.37) exposure categories.

CONCLUSIONS

To our knowledge, this is the first birth defect study to develop multi-DBP adjusted regression models as well as the first CVD study to evaluate HAA exposures and the second to evaluate bromoform exposures. Our findings, therefore, inform exposure specificity for the consistent associations previously reported between THM4 and CVDs including VSDs. Citation: Wright JM, Evans A, Kaufman JA, Rivera-Núñez Z, Narotsky MG. 2017. Disinfection by-product exposures and the risk of specific cardiac birth defects. Environ Health Perspect 125:269-277; http://dx.doi.org/10.1289/EHP103.

Routinely collected English birth data sets: comparisons and recommendations for reproductive epidemiology

BACKGROUND

In England there are four national routinely collected data sets on births: Office for National Statistics (ONS) births based on birth registrations; Hospital Episode Statistics (HES) deliveries (mothers' information); HES births (babies' information); and NHS Numbers for Babies (NN4B) based on ONS births plus gestational age and ethnicity information. This study describes and compares these data, with the aim of recommending the most appropriate data set(s) for use in epidemiological research and surveillance.

METHODS

We assessed the completeness and quality of the data sets in relation to use in epidemiological research and surveillance and produced detailed descriptive statistics on common reproductive outcomes for each data set including temporal and spatial trends.

RESULTS

ONS births is a high quality complete data set but lacks interpretive and clinical information. HES deliveries showed good agreement with ONS births but HES births showed larger amounts of missing or unavailable data. Both HES data sets had improved quality from 2003 onwards, but showed some local spatial variability. NN4B showed excellent agreement with ONS and HES deliveries for the years available (2006-2010). Annual number of births increased by 17.6% comparing 2002 with 2010 (ONS births). Approximately 6% of births were of low birth weight (2.6% term low birth weight) and 0.5% were stillbirths.

CONCLUSIONS

Routinely collected data on births provide a valuable resource for researchers. ONS and NN4B offer the most complete and accurate record of births. Where more detailed clinical information is required, HES deliveries offers a high quality data set that captures the majority of English births.

Human exposure to environmental contaminants and congenital anomalies: a critical review

Congenital anomalies are an important cause of infant mortality and disability. Developmental exposure to environmental contaminants is thought to increase the risk for congenital anomalies. Herein, we describe a critical review of the literature conducted between February and March 2014 yielding 3057 references from which 97 unique relevant articles published from 2003 through 2014 were evaluated. Common congenital anomalies including hypospadias, cryptorchidism, anogenital distance (AGD), congenital heart defects and oral clefts were well represented in the literature whereas other outcomes such as neural tube defects, limb deficiency defects and gastroschisis were rarely described. While definitions used for congenital anomalies and methods of ascertainment were usually consistent across studies, inconsistencies were frequently found in grouping of different congenital heart defects. Despite strong links between some congenital anomalies and parental occupation, these studies are unable to provide clear insight into the specific chemicals responsible owing to lack of direct measures of exposure. In comparison, data are mixed for contaminant exposures at concentrations representative of results from contemporary biomonitoring studies. Of the environmental contaminants studied, the association between phthalate exposures and developmental abnormalities of the male reproductive tract received the greatest attention. Important limitations of the literature studied relate to adequacy of sample size, absence of or weaknesses in exposure assessment methodologies, failure to account for biological plausibility and grouping of congenital anomalies with divergent mechanisms. We conclude that the literature is inadequate at this time to support a conclusion that exposure to environmental contaminants are or are not associated with increased risks for congenital anomalies in the general population.

Birth Weight, Ethnicity, and Exposure to Trihalomethanes and Haloacetic Acids in Drinking Water during Pregnancy in the Born in Bradford Cohort

BACKGROUND

Evidence for a relationship between trihalomethane (THM) or haloacetic acid (HAA) exposure and adverse fetal growth is inconsistent. Disinfection by-products exist as complex mixtures in water supplies, but THMs and HAAs have typically been examined separately.

OBJECTIVES

We investigated joint exposure at the individual level to THMs and HAAs in relation to birth weight in the multi-ethnic Born in Bradford birth cohort.

METHODS

Pregnant women reported their water consumption and activities via questionnaire. These data were combined with area-level THM and HAA concentrations to estimate integrated uptake of THMs into blood and HAA ingestion, accounting for boiling/filtering. We examined the relationship between THM and HAA exposures and birth weight of up to 7,438 singleton term babies using multiple linear regression, stratified by ethnicity.

RESULTS

Among Pakistani-origin infants, mean birth weight was significantly lower in association with the highest versus lowest tertiles of integrated THM uptake (e.g., -53.7 g; 95% CI: -89.9, -17.5 for ≥ 1.82 vs. < 1.05 μg/day of total THM) and there were significant trends (p < 0.01) across increasing tertiles, but there were no associations among white British infants. Neither ingestion of HAAs alone or jointly with THMs was associated with birth weight. Estimated THM uptake via showering, bathing, and swimming was significantly associated with lower birth weight in Pakistani-origin infants, when adjusting for THM and HAA ingestion via water consumption.

CONCLUSIONS

To our knowledge, this is the largest DBP and fetal growth study to date with individual water use data, and the first to examine individual-level estimates of joint THM-HAA exposure. Our findings demonstrate associations between THM, but not HAA, exposure during pregnancy and reduced birth weight, but suggest this differs by ethnicity. This study suggests that THMs are not acting as a proxy for HAAs, or vice-versa.

CITATION

Smith RB, Edwards SC, Best N, Wright J, Nieuwenhuijsen MJ, Toledano MB. 2016. Birth weight, ethnicity, and exposure to trihalomethanes and haloacetic acids in drinking water during pregnancy in the Born in Bradford cohort. Environ Health Perspect 124:681-689; http://dx.doi.org/10.1289/ehp.1409480.

Determinación de trihalometanos en aguas de consumo humano por microextracción en fase sólida- cromatografía de gases en Pereira, Colombia

<p>La desinfección del agua con cloro, genera subproductos como los trihalometanos (THM´s), a los cuales se les atribuyen propiedades cancerígenas y con un potencial efecto adverso en el sistema reproductivo. El nivel máximo permitido de THM´s en Estados Unidos es 80 µg/L, mientras que en Colombia es 200 µg/L. En este estudio un método simple, rápido y libre de solventes fue estandarizado para la determinación de THM´s  en aguas para consumo humano utilizando microextracción en fase sólida con espacio de cabeza combinada con cromatografía de gases con detector de microcaptura de electrones  (HS-SPME-GC-mECD) y utilizado para la cuantificación de THM´s en aguas de consumo humano. Fueron estudiados parámetros experimentales así como el tiempo de adsorción, la temperatura de adsorción y desorción, la agitación de la muestra y la adición de NaCl. Se determinaron los límites de detección y cuantificación del método y se realizó el análisis de los trihalometanos de 75 muestras de agua de la planta de tratamiento de Aguas y Aguas de la ciudad de Pereira. Las condiciones optimizadas fueron 20 min de extracción a 37 °C en presencia de 25% de NaCl y con una agitación de 200 rpm; con  tiempo de desorción de 4 min a 250 °C. El rango lineal de 5-100 mg/L fue establecido con una desviación estándar relativa (%RSD) en el rango 6,1-10,1 %. Los límites de detección estuvieron en el rango 3,8-7,8 mg/L. El promedio de la concentración de THM´s fue de 55,5 mg/L el cual cumple con los límites máximos permitidos en la regulación internacional y nacional.</p>

Trihalomethanes in public drinking water and stillbirth and low birth weight rates: an intervention study

During 2003-2004, United Utilities water company in North West England introduced enhanced coagulation (EC) to four treatment works to mitigate disinfection by-product (DBP) formation. This enabled examination of the relation between DBPs and birth outcomes whilst reducing socioeconomic confounding. We compared stillbirth, and low and very low birth weight rates three years before (2000-2002) with three years after (2005-2007) the intervention, and in relation to categories of THM change. We created exposure metrics for EC and trihalomethane (THM) concentration change (n=258 water zones). We linked 429,599 live births and 2279 stillbirths from national birth registers to the water zone at birth. We used Poisson regression to model the differences in birth outcome rates with an interaction between before/after the intervention and EC or THM change. EC treatment reduced chloroform concentrations more than non-treatment (mean -29.7 µg/l vs. -14.5 µg/l), but not brominated THM concentrations. Only 6% of EC water zones received 100% EC water, creating exposure misclassification concerns. EC intervention was not associated with a statistically significant reduction in birth outcome rates. Areas with the highest chloroform decrease (30 - 65 μg/l) had the greatest percentage decrease in low -9 % (-12, -5) and very low birth weight -16% (-24, -8) rates. The interaction between before/after intervention and chloroform change was statistically significant only for very low birth weight, p=0.02. There were no significant decreases in stillbirth rates. In a novel approach for studying DBPs and adverse reproductive outcomes, the EC intervention to reduce DBPs did not affect birth outcome rates. However, a measured large decrease in chloroform concentrations was associated with statistically significant reductions in very low birth weight rates.

Epidemiologic tools to study the influence of environmental factors on fecundity and pregnancy-related outcomes

Adverse pregnancy outcomes entail a large health burden for the mother and offspring; a part of it might be avoided by better understanding the role of environmental factors in their etiology. Our aims were to review the assessment tools to characterize fecundity troubles and pregnancy-related outcomes in human populations and their sensitivity to environmental factors. For each outcome, we reviewed the possible study designs, main sources of bias, and their suggested cures. In terms of study design, for most pregnancy outcomes, cohorts with recruitment early during or even before pregnancy allow efficient characterization of pregnancy-related events, time-varying confounders, and in utero exposures that may impact birth outcomes and child health. Studies on congenital anomalies require specific designs, assessment of anomalies in medical pregnancy terminations, and, for congenital anomalies diagnosed postnatally, follow-up during several months after birth. Statistical analyses should take into account environmental exposures during the relevant time windows; survival models are an appropriate approach for fecundity, fetal loss, and gestational duration/preterm delivery. Analysis of gestational duration could distinguish pregnancies according to delivery induction (and possibly pregnancy-related conditions). In conclusion, careful design and analysis are required to better characterize environmental effects on human reproduction.

A case-control study of maternal bathing habits and risk for birth defects in offspring

BACKGROUND

Nearly all women shower or take baths during early pregnancy; however, bathing habits (i.e., shower and bath length and frequency) may be related to the risk of maternal hyperthermia and exposure to water disinfection byproducts, both of which are suspected to increase risk for multiple types of birth defects. Thus, we assessed the relationships between bathing habits during pregnancy and the risk for several nonsyndromic birth defects in offspring.

METHODS

Data for cases with one of 13 types of birth defects and controls from the National Birth Defects Prevention Study delivered during 2000-2007 were evaluated. Logistic regression analyses were conducted separately for each type of birth defect.

RESULTS

There were few associations between shower frequency or bath frequency or length and risk for birth defects in offspring. The risk for gastroschisis in offspring was increased among women who reported showers lasting ≥15 compared to <15 minutes (adjusted odds ratio: 1.43, 95% confidence interval: 1.18-1.72). In addition, we observed modest increases in the risk for spina bifida, cleft lip with or without cleft palate, and limb reduction defects in offspring of women who showered ≥15 compared to <15 minutes. The results of comparisons among more specific categories of shower length (i.e., <15 minutes versus 15-19, 20-29, and ≥ 30 minutes) were similar.

CONCLUSIONS

Our findings suggest that shower length may be associated with gastroschisis, but the modest associations with other birth defects were not supported by analyses of bath length or bath or shower frequency. Given that showering for ≥15 minutes during pregnancy is very common, further evaluation of the relationship between maternal showering habits and birth defects in offspring is worthwhile.

Occurrence of regulated and emerging iodinated DBPs in the Shanghai drinking water

Drinking water chlorination plays a pivotal role in preventing pathogen contamination against water-borne disease. However, chemical disinfection leads to the formation of halogenated disinfection by products (DBPs). Many DBPs are highly toxic and are of health concern. In this study, we conducted a comprehensive measurements of DBPs, including iodoacetic acid (IAA), iodoform (IF), nine haloacetic acids and four trihalomethanes in drinking waters from 13 water plants in Shanghai, China. The results suggested that IAA and IF were found in all the water treatment plants, with maximum levels of 1.66 µg/L and 1.25 µg/L for IAA and IF, respectively. Owing to deterioration of water quality, the Huangpu River has higher IAA and IF than the Yangtze River. Our results also demonstrated that low pH, high natural organic matter, ammonia nitrogen, and iodide in source waters increased IAA and IF formation. Compared to chlorine, chloramines resulted in higher concentration of iodinated DBP, but reduced the levels of trihalomethanes. This is the first study to reveal the widespread occurrence of IAA and IF in drinking water in China. The data provide a better understanding on the formation of iodinated disinfection byproducts and the findings should be useful for treatment process improvement and disinfection byproducts controls.

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.

Appraisal of chlorine contact tank modelling practices

With new water directives imposing strict regulations to reduce the footprint of treatment operations and contaminant levels, a performance review of water treatment facilities, including Chlorine Contact Tanks (CCTs) is required. This paper includes a critical appraisal of the international literature on CCT modelling practices to date, aiming to assist the identification of areas requiring further development, in particular, relating to the computational modelling capability and availability of tools to assist hydraulic design and optimisation studies of CCTs. It notes that the hydraulic optimisation practice of poorly designed tanks commenced with experimental studies undertaken in the 1960s and 1970s, which involved mainly two types of studies, namely in situ tracer tests and laboratory physical modelling. The former has traditionally been conducted to diagnose the hydraulic performance of existing CCTs, typically based on results such as Residence Time Distribution (RTD) curves and values of the Hydraulic Efficiency Indicators (HEIs). The latter has been useful in trial and error testing of the impact of certain design modifications on those results, with suggestions for later improvements of the field scale unit. In the 1980s mathematical and numerical modelling studies started to be used to assist CCT investigations, offering a greater level of detail in a more cost-effective manner than equivalent experimentally based investigations. With the growth of computing power and the popularisation of computational models, the 1990s saw the development and application of Computational Fluid Dynamics (CFD) tools to simulate the hydraulic performance of CCTs, sometimes independently of experimentation, other than by using available data to calibrate and validate modelling predictions. This has led to the current scenario of CFD models being invaluable assistive tools in optimisation studies of CCTs, with the experimentation practice continuing to allow for specific diagnostics and to supply data for the calibration and validation of CFD modelling results. The vast majority of CCT modelling studies published to date have focused on simulating CCT hydrodynamic and conservative solute transport processes. The chlorination kinetics and Disinfection By-Product (DBP) formation have rarely been contemplated in computer modelling studies of CCTs. Commercially available CFD models have not traditionally been applied with this purpose, while research studies undertaken using open source codes to produce tailor-made applications are rare. Aspects that could benefit from further understanding and/or development include the impact of scale when conducting experimentation with prototypes, adequate turbulence closure for a given situation, adequate numerical schemes vis-à-vis CFD model complexity vis-à-vis cost-benefit ratio of simulations and the inclusion of state of the art chlorination kinetics and DBP formation modelling in the CFD tools that can assist modern design and retrofit studies of CCTs.

Review of research on residential mobility during pregnancy: consequences for assessment of prenatal environmental exposures

Studies on environmental exposures during pregnancy often have limited residential history (e.g., at delivery), potentially introducing exposure misclassification. We reviewed studies reporting residential mobility during pregnancy to summarize current evidence and discuss research implications. A meaningful quantitative combination of results (e.g., meta-analysis), was infeasible owing to variation in study designs. Fourteen studies were identified, of which half were from the US. Most were case-control studies examining birth defects. Residential history was typically assessed after delivery. Overall mobility rates were 9-32% and highest in the second trimester. Mobility generally declined with age, parity, and socioeconomic status, although not consistently. Married mothers moved less frequently. Findings were dissimilar by race, smoking, or alcohol use. On the basis of the few studies reporting distance moved, most distances were short (median often <10 km). Results indicate potential misclassification for environmental exposures estimated with incomplete residential information. This misclassification could be associated with potential confounders, such as socioeconomics, thereby affecting risk estimates. As most moves were short distances, exposures that are homogenous within a community may be well estimated with limited residential data. Future research should consider the implications of residential mobility during pregnancy in relation to the exposure's spatial heterogeneity and factors associated with the likelihood of moving and distance moved.

Urinary trichloroacetic acid levels and semen quality: a hospital-based cross-sectional study in Wuhan, China

Toxicological studies indicate an association between exposure to disinfection by-products (DBPs) and impaired male reproductive health in animals. However, epidemiological evidence in humans is still limited. We conducted a hospital-based cross-sectional study to investigate the effect of exposure to DBPs on semen quality in humans. Between May 2008 and July 2008, we recruited 418 male partners in sub-fertile couples seeking infertility medical instruction or assisted reproduction services from the Tongji Hospital in Wuhan, China. Major semen parameters analyzed included sperm concentration, motility, and morphology. Exposure to DBPs was estimated by their urinary creatinine-adjusted trichloroacetic (TCAA) concentrations that were measured with the gas chromatography/electron capture detection method. We used linear regression to assess the relationship between exposure to DBPs and semen quality. According to the World Health Organization criteria (<20 million/mL for sperm concentration and <50% motile for sperm motility) and threshold value recommended by Guzick (<9% for sperm morphology), there were 265 men with all parameters at or above the reference values, 33 men below the reference sperm concentration, 151 men below the reference sperm motility, and 6 men below the reference sperm morphology. The mean (median) urinary creatinine-adjusted TCAA concentration was 9.2 (5.1) μg/g creatinine. Linear regression analyses indicated no significant association of sperm concentration, sperm count, and sperm morphology with urinary TCAA levels. Compared with those in the lowest quartile of creatinine-adjusted urinary TCAA concentrations, subjects in the second and third quartiles had a decrease of 5.1% (95% CI: 0.6%, 9.7%) and 4.7% (95% CI: 0.2%, 9.2%) in percent motility, respectively. However, these associations were not significant after adjustment for age, abstinence time, and smoking status. The present study provides suggestive but inconclusive evidence of the relationship between decreased sperm motility and increased urinary TCAA levels. The effect of exposure to DBPs on human male reproductive health in Chinese populations still warrants further investigations.

Chlorination disinfection by-products in drinking water and congenital anomalies: review and meta-analyses

This study aims to review epidemiologic evidence of the association between exposure to chlorination disinfection by-products (DBPs) and congenital anomalies. All epidemiologic studies that evaluated a relationship between an index of DBP exposure and risk of congenital anomalies were analyzed. For all congenital anomalies combined, the meta-analysis gave a statistically significant excess risk for high versus low exposure to water chlorination or TTHM (17%; 95% CI, 3-34) based on a small number of studies. The meta-analysis also suggested a statistically significant excess risk for ventricular septal defects (58%; 95% CI, 21-107), but based on only three studies, and there was little evidence of an exposure-response relationship. It was observed no statistically significant relationships in the other meta-analyses and little evidence for publication bias, except for urinary tract defects and cleft lip and palate. Although some individual studies have suggested an association between chlorination disinfection by-products and congenital anomalies, meta-analyses of all currently available studies demonstrate little evidence of such association.

Spatial and temporal evaluations of disinfection by-products in drinking water distribution systems in Beijing, China

Disinfection by-products were determined in 15 water treatment plants in Beijing City. The effects of different water sources (surface water source, mixture water source and ground water source), seasonal variation and spatial variation were examined. Trihalomethanes and haloacetic acids were the major disinfection by-products found in all treated water samples, which accounted for 42.6% and 38.1% of all disinfection by-products respectively. Other disinfection by-products including haloacetonitriles, chloral hydrate, haloketones and chloropicrin were usually detected in treated water samples but at lower concentrations. The levels of disinfection by-products in drinking water varied with different water sources and followed the order: surface water source > mixture water source > ground water source. High spatial and seasonal variation of disinfection by-products in the drinking water of Beijing was shown as a result.

Patterns of water use and exposure to trihalomethanes among children in Spain

Few studies characterizing trihalomethane (THM) exposure or examining potential health effects were conducted in children. The present study describes patterns of water use in children as a source of THM exposure, and estimates the daily THM uptake and the relative contribution of each pathway of exposure. A cross-sectional population-based study was conducted in children 9-12 years of age in Sabadell, Catalonia, Spain (N=2037). We collected individual information on ingestion, frequency and duration of showering, bathing and swimming, source of drinking water, age, sex and parental education. Chloroform, dibromochloroform, bromodichloroform and bromoform in tap, bottled and swimming pool water were measured. The daily chloroform and brominated THM uptakes were estimated combining environmental levels with individual water activities using algorithms reported in the literature. Among the studied group, 80% of children drank bottled water and 20% regularly attended swimming pools. Mean THM concentration in bottled, tap and chlorinated pool water were, respectively, 0.3, 117 and 92 microg/L. Brominated THM predominated in the tap water (84% of total THM) and chloroform predominated in the swimming pool (84% of total THM). Children attending swimming pools had four times higher THM uptake compared to non-swimmers (p-value<0.05). Showering was the main pathway of exposure for non-swimmers. Girls and children with low parental education had a higher THM uptake (p-value<0.05) as they reported taking longer showers and more frequent baths. In conclusion, total and specific THM uptake varied considerably with the personal water uses among children. As drinking water was mainly bottled and bathing was infrequent, showering and swimming in pools were the main pathways of THM exposure. Specific water uses among children slightly differed by sociodemographic characteristics.

DNA damage and oxidative stress in human liver cell L-02 caused by surface water extracts during drinking water treatment in a waterworks in China

Because of the daily and life-long exposure to disinfection by-products formed during drinking water treatment, potential adverse human health risk of drinking water disinfection is of great concern. Toxicological studies have shown that drinking water treatment increases the genotoxicity of surface water. Drinking water treatment is comprised of different potabilization steps, which greatly influence the levels of genotoxic products in the surface water and thus may alter the toxicity and genotoxicity of surface water. The aim of the present study was to understand the influence of specific steps on toxicity and genotoxicity during the treatment of surface water in a water treatment plant using liquid chlorine as the disinfectant in China. An integrated approach of the comet and oxidative stress assays was used in the study, and the results showed that both the prechlorination and postchlorination steps increased DNA damage and oxidative stress caused by water extracts in human derived L-02 cells while the tube settling and filtration steps had the opposite effect. This research also highlighted the usefulness of an integrated approach of the comet and oxidative stress assays in evaluating the genotoxicity of surface water during drinking water treatment.

Estimation of chlorination by-products presence in drinking water in epidemiological studies on adverse reproductive outcomes: a review

Chlorination of drinking water is essential to prevent waterborne disease. However, chlorine reacts with organic matter present in surface waters to form various by-products. In the last decade, several epidemiological studies have been conducted to determine the connection between exposure to these chlorination by-products (CBPs) and human health defects, such as adverse reproductive outcomes. However, the methodology used to assess exposure of pregnant women in these studies had serious limitations, particularly in relation to determining CBP presence in the subject's tap water. The purpose of this paper is to critically review of methods used to evaluate the CBP presence in a subject's tap water for exposure assessment purposes in epidemiological studies focused on adverse reproductive outcomes and CBPs in drinking water. Interest is directed more precisely at space-time features related to CBPs for an optimal estimation of their presence in a subject's tap water.

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.

Chlorination disinfection by-products in drinking water and congenital anomalies: review and meta-analyses

OBJECTIVES

The aim of this study was to review epidemiologic evidence, provide summary risk estimates of the association between exposure to chlorination disinfection by-products (DBPs) and congenital anomalies, and provide recommendations for future studies.

DATA SOURCES AND EXTRACTION

We included all published epidemiologic studies that evaluated a relationship between an index of DBP exposure (treatment, water source, DBP measurements, and both DBP measurements and personal characteristics) and risk of congenital anomalies. When three or more studies examined the same exposure index and congenital anomaly, we conducted a meta-analysis to obtain a summary risk estimate comparing the highest exposure group with the lowest exposure group. When five or more studies examined total trihalomethane (TTHM) exposure and a specific congenital anomaly, we conducted a meta-analysis to obtain exposure-response risk estimates per 10 microg/L TTHM.

DATA SYNTHESIS

For all congenital anomalies combined, the meta-analysis gave a statistically significant excess risk for high versus low exposure to water chlorination or TTHM [17%; 95% confidence interval (CI), 3-34] based on a small number of studies. The meta-analysis also suggested a statistically significant excess risk for ventricular septal defects (58%; 95% CI, 21-107), but this was based on only three studies, and there was little evidence of an exposure-response relationship. We observed no statistically significant relationships in the other meta-analyses. We found little evidence for publication bias, except for urinary tract defects and cleft lip and palate.

CONCLUSION

Although some individual studies have suggested an association between chlorination disinfection by-products and congenital anomalies, meta-analyses of all currently available studies demonstrate little evidence of such an association.

Risk of birth defects in Australian communities with high levels of brominated disinfection by-products

BACKGROUND

By international standards, water supplies in Perth, Western Australia, contain high trihalomethane (THM) levels, particularly the brominated forms. Geographic variability in these levels provided an opportunity to examine cross-city spatial relationships between THM exposure and rates of birth defects (BDs).

OBJECTIVES

Our goal was to examine BD rates by exposure to THMs with a highly brominated fraction in metropolitan locations in Perth, Western Australia.

METHODS

We collected water samples from 47 separate locations and analyzed them for total and individual THM concentrations (micrograms per liter), including separation into brominated forms. We classified collection areas by total THM (TTHM) concentration: low (< 60 microg/L), medium (> 60 to < 130 microg/L), and high (> or = 130 microg/L). We also obtained deidentified registry-based data on total births and BDs (2000-2004 inclusive) from post codes corresponding to water sample collection sites and used binomial logistic regression to compare the frequency of BDs aggregately and separately for the TTHM exposure groups, adjusting for maternal age and socioeconomic status.

RESULTS

Total THMs ranged from 36 to 190 microg/L. A high proportion of the THMs were brominated (on average, 92%). Women living in high-TTHM areas showed an increased risk of any BD [odds ratio (OR) = 1.22; 95% confidence interval (CI), 1.01-1.48] and for the major category of any cardiovascular BD (OR = 1.62; 95% CI, 1.04-2.51), compared with women living in low-TTHM areas.

CONCLUSIONS

Brominated forms constituted the significant fraction of THMs in all areas. Small but statistically significant increases in risks of BDs were associated with residence in areas with high THMs.

Water disinfection by-products and the risk of specific birth defects: a population-based cross-sectional study in Taiwan

BACKGROUND

Recent findings suggest that exposure to disinfection by-products may increase the risk of birth defects. Previous studies have focused mainly on birth defects in general or groups of defects. The objective of the present study was to assess the effect of water disinfection by-products on the risk of most common specific birth defects.

METHODS

We conducted a population-based cross-sectional study of 396,049 Taiwanese births in 2001-2003 using information from the Birth Registry and Waterworks Registry. We compared the risk of eleven most common specific defects in four disinfection by-product exposure categories based on the levels of total trihalomethanes (TTHMs) representing high (TTHMs 20+ microg/L), medium (TTHMs 10-19 microg/L), low exposure (TTHMs 5-9 microg/L), and 0-4 microg/L as the reference category. In addition, we conducted a meta-analysis of the results from the present and previous studies focusing on the same birth defects.

RESULTS

In multivariate logistic regression analysis the risk of ventricular septal defects (adjusted odds ratio 1.81, 95% confidence interval: 0.98 3.35), cleft palate (1.56. 95% CI: 1.00, 2.41), and anencephalus (1.96, 95% CI: 0.94, 4.07) were elevated in the high exposure compared to the reference category. In the meta-analysis, the summary odds ratio for ventricular septal defects (1.59, 95% CI: 1.21, 2.07) was consistently elevated.

CONCLUSION

The present study suggests that prenatal exposure to disinfection by-products increases the risk of ventricular septal defects, cleft palate, and anencephalus. The evidence on ventricular septal defects is consistent in the three available studies.