Individual Trihalomethanes Research Articles

Disinfection byproducts in US drinking water and cancer mortality

ABSTRACT Trihalomethanes, the main drinking water disinfection byproducts, may be carcinogenic and are regulated to amaximum total trihalomethanes (TTHM) of 80 µg/l in the US. We aimed to determine whether total and individual trihalomethanes in drinking water across the US are associated with higher cancer mortality in 6,260 adult participants to the National Health and Nutrition Examination Surveys from 1999 to 2008 followed for mortality until 2019 (median: 14.4 years). At baseline, the geometric mean (standard error) of TTHM in drinking water was 9.61 (0.85) µg/l. During follow-up, 873 deaths occurred, including 207 from cancer. In Cox proportional hazards regression adjusted for relevant covariates, drinking water TTHM (HR: 1.45, 95% CI: 1.16–1.82), chloroform (HR: 1.35, 95% CI: 1.12–1.64), and bromodichloromethane (HR: 1.30, 95% CI: 1.05–1.59) were associated with 30% to 45% higher cancer mortality. Therefore, drinking water trihalomethanes, especially chloroform and bromodichloromethane maybe risk factors for cancer mortality.

Bromoform exposure is associated with non-melanoma skin cancer: evidence from NHANES 2011-2020.

Non-melanoma skin cancer (NMSC) is a prevalent skin malignancy. It has been indicated in many studies that trihalomethanes (THMs) exposure has a strong association with tumors but has not been associated with NMSC. Our investigation aims to explore the association between THMs exposure and NMSC. Cross-sectional data from the 2011 to 2020 National Health and Nutrition Examination Survey (NHANES) was collected. Poisson regression and subgroup analyses were performed to evaluate the association between individual THMs components and NMSC. Fitted smoothing curves and generalized additive models were also used. This study involved 5,715 individuals, 98 (1.7%) of whom self-reported NMSC. After adjusting for covariates, Poisson regression showed that higher blood TBM levels were associated with an increased likelihood of NMSC (OR = 1.03; 95% CI: 1.01-1.05, p = 0.002). However, the correlation between the blood levels of TCM, DBCM, and BDCM and the likelihood of NMSC was not statistically significant (all p > 0.05). Subgroup analysis and interaction tests showed no significant differences between blood TBM concentration and the likelihood of NMSC, indicating that age, gender, and race were significantly independent of this positive association (all p < 0.05). Our results implied that among adults older than 65 years old in the U.S., elevated blood TBM concentrations were positively associated with NMSC. More prospective investigations are required to validate this relationship with the early prevention of NMSC.

Investigating bromide incorporation factor (BIF) and model development for predicting THMs in drinking water using machine learning

Many disinfection byproducts (DBPs) in drinking water can pose cancer risks to humans while several DBPs including trihalomethanes are typically regulated. Although trihalomethanes are regulated, brominated fractions (bromodichloromethane, dibromochloromethane and bromoform) are more toxic to humans than the chlorinated ones (chloroform). To date, >100 models have been reported to predict DBPs. However, models to predict individual trihalomethanes are very limited, indicating the needs of such models. Various factors including natural organic matter (NOM), bromide ions (Br−), disinfectants (e.g., chlorine dose), pH, temperature and reaction time affect the formation and distribution of trihalomethanes in drinking water. In this study, NOM was fractionated into four groups based on the molecular weight (MW) cutoff values and their respective contributions to dissolved organic carbon (DOC), trihalomethanes and bromide incorporation factors (BIF) were investigated. Models were developed for predicting chloroform, bromodichloromethane, dibromochloromethane, bromoform and trihalomethanes. Three machine learning techniques: Support Vector Regressor (SVR), Random Forest Regressor (RFR) and Artificial Neural Networks (ANN) were adopted for training and testing the models. The normalized BIFs were in the ranges of 0.08–0.16 and 0.07–0.15 per mg/L of DOC for pH 6.0 and 8.5 respectively. The BIFs were higher for lower pH and MW values while increase of bromide to chlorine ratios increased BIFs. The models showed excellent predictive performances in training (R2 = 0.889–0.998) and testing (R2 = 0.870–0.988) datasets. The SVR and RFR models showed the best performances with lower RMSE and MAE in most cases. These models can be used to better control different trihalomethanes in drinking water to maintain regulatory compliance, and to minimize the risks to humans.

Estimating Trihalomethane Concentrations in Bottled Spring Water

The chlorination of water has led to a substantial reduction in waterborne disease outbreaks. There are, however, concerns regarding the safety of trihalomethanes (major by-products of chlorination). One of the limitations of much of the existing evidence is the lack of individual trihalomethane exposure estimates, and these estimates should include the concentration of trihalomethanes in bottled water. In Australia, water advertised as ‘spring’ or ‘mineral’ water should, by definition, remain untreated, and should not, therefore, contain any trihalomethanes. We tested this assumption by assessing the concentration of trihalomethanes (bromodichloromethane, bromoform, chloroform, dibromochloromethane, and total trihalomethanes) in the six brands of bottled spring water most commonly consumed by pregnant women in Australia (here labelled A–F). For each water brand, two bottles were purchased from five locations, and this procedure was replicated approximately 2 weeks later. Standard water analysis techniques were used to determine the concentrations of bromodichloromethane, bromoform, chloroform, dibromochloromethane, and total trihalomethanes in each bottle. All 10 samples of brands A and B were positive for trihalomethanes, as was one bottle of brand C. No trihalomethanes were detected in any of the samples of the remaining three brands (D–F). The highest recorded total trihalomethane concentration was 30 µg/L. The trihalomethane concentration in Australian bottled spring water cannot be assumed to be zero. Studies estimating trihalomethane exposures should, therefore, collect data on the brand of the bottled water consumed, and test these brands contemporaneously for their trihalomethane exposures, to strengthen the evidence regarding trihalomethane exposure and human health outcomes.

Meta-analysis of Small for Gestational Age Births and Disinfection By-product Exposures

PDS 74: Pregnancy outcomes, Exhibition Hall (PDS), Ground floor, August 26, 2019, 1:30 PM - 3:00 PM Background: Epidemiological studies have shown associations between disinfection byproducts (DBPs) and adverse reproductive outcomes. Methods: We conducted a systematic review and meta-analysis of all available studies examining DBP exposure and small for gestational age (SGA) births. Eighteen studies were included following exclusions for non-English publications or other DBP measures that did not include trihalomethane (THM) or haloacetic acid (HAA) concentration data with at least three exposure categories. As part of the systematic review, a study quality evaluation was conducted with scores based on outcome and exposure data quality (e.g., temporal/spatial resolution) and potential for bias including confounding. We also conducted sub-group and meta-regression analyses that evaluated the impact of these scores along with other quantitative predictors and modifying factors. Results: We detected statistically significant risks for SGA associated with THM4 (OR=1.06; 95%CI: 1.03, 1.10), chloroform (OR=1.05; 95%CI: 1.01, 1.08), BDCM (OR=1.08; 95%CI: 1.05, 1.11) and brominated THMs (OR=1.05; 95%CI: 1.02, 1.09). Although no overall risk was detected among the seven HAA studies, statistically significant risks were associated with HAA5 (OR=1.10; 95%CI: 1.02, 1.19), dichloroacetic acid (DCA) (OR=1.25; 95%CI: 1.10, 1.41), and trichloroacetic acid (TCA) exposure (OR=1.21; 95%CI: 1.07, 1.37) following removal of statistical outliers after heterogeneity was detected. Sub-group analysis showed larger SGA risks for exposure to THM4 (OR=1.08; 95%CI: 1.04, 1.12), chloroform (OR=1.07; 95%CI: 1.02, 1.11), BDCM (OR=1.09; 95%CI: 1.06, 1.13), brominated THMs (OR=1.05; 95%CI: 1.02, 1.09) and dibromochloromethane (OR=1.16; 95%CI: 1.07, 1.25) among participants with chloraminated/other disinfectant supplies. In contrast, chlorinated sites showed larger risks for SGA and HAA5 (OR=1.22; 95%CI: 1.02, 1.46), DCA (OR=1.26; 95%CI: 1.11, 1.43), and TCA (OR=1.23; 95%CI: 1.08, 1.39) exposures. Conclusions: Our meta-analysis of 18 studies is consistent with a meta-analysis based on six THM4 studies but also presents data on individual THMs and HAAs not previously examined. Our results show an increased risk of SGA following exposure to many of the regulated DBPs and were robust after accounting for outliers, publication bias, type of SGA classification, different exposure windows, and other factors.

Investigating the effects of design and management factors on DBPs levels in indoor aquatic centres

Disinfection by-products (DBPs) in indoor swimming pool water and air have long been a critical human health risk concern. This study investigated the effects of several indoor swimming pool design and management factors (e.g. ventilation, water treatment, pool operations, pool type) on the concentrations of DBPs, such as trihalomethanes (THMs) and chloramines, in pool water and air. Two sampling campaigns, A and B, were carried out to measure the concentrations of DBPs under different conditions. In both campaigns, 46 pool water samples, seven tap water samples, and 28 ambient air samples were collected and analyzed. Regression models were also developed and validated for investigating the combined effects of design and management factors on total trihalomethanes (TTHM) and trichloramine. The model results show that pool water characteristics (e.g., total organic content, temperature, conductivity, pH and alkalinity) and management factors (e.g., the number of bathers and sprayers) have direct effects on DBP concentrations. Pool water characteristics such as UV absorbance, hardness, and oxidation-reduction potential and a management factor UV intensity have inverse effects on DBPs levels. Based on the correlation analysis, other factors such as fan speed, fresh air, pool age, and basin area were found to be correlated with the concentrations of individual THMs and trichloramine in both water and air. It was also observed that the concentration of THMs varies with pool type. It is note worthy that the effects of the number of sprayers was quantified for the first time. This study comprehensively assessed pool design and management factors and identified their effects on DBPs, providing indoor swimming pool facilities with useful information to control DBPs in the indoor swimming environment.

Interactions between CYP2E1, GSTZ1 and GSTT1 polymorphisms and exposure to drinking water trihalomethanes and their association with semen quality

Trihalomethanes (THMs) have been reported to be associated with altered semen quality, and this association may be modified by inherited differences in cytochrome P450 (CYP2E1) and glutathione S-transferase (GSTZ1 and GSTT1), which metabolize THMs. We conducted a cross-sectional study to examine the interactions between CYP2E1, GSTZ1 and GSTT1 polymorphisms and exposure to THMs on semen quality among 401 men from the Reproductive Center of Tongji Hospital in Wuhan China. The baseline blood concentrations of four individual THMs, chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (TBM), were measured as biomarkers of exposure to drinking water THMs. Genotypes were determined by real-time PCR, and semen-quality parameters were evaluated according to the World Health Organization guidelines. GSTT1 genotype significantly modified the association between exposure to Br-THMs (sum of BDCM, DBCM and TBM) and below-reference sperm motility (Pint=0.02). Men with above-median blood Br-THM levels had an increased odds ratio (OR) of below-reference sperm compared to men with below-median blood Br-THM levels (OR=2.15, 95% CI: 1.11, 4.19) in the GSTT1 null genotype only. In addition, we found that men with a TT of CYP2E1 rs 915,906 had higher blood TCM and TTHM (sum of TCM, BDCM, DBCM and TBM) concentrations than men with a CT/CC of CYP2E1 rs 915,906. Our results suggest that GSTT1 polymorphisms modify Br-THM exposure relation with semen quality, and CYP2E1 polymorphisms are associated with internal levels of exposure to THMs.

Predictive capability of chlorination disinfection byproducts models

There are over 100 models that have been developed for predicting trihalomethanes (THMs), haloacetic acids (HAAs), bromate, and unregulated disinfection byproducts (DBPs). Until now no publication has evaluated the variability of previous THM and HAA models using a common data set. In this article, the standard error (SE), Marquardt's percent standard deviation (MPSD), and linear coefficient of determination (R2) were used to analyze the variability of 87 models from 23 different publications. The most robust models were capable of predicting THM4 with an SE of 48 μg L−1 and HAA6 with an SE of 15 μg L−1, both achieving R2 > 0.90. The majority of models were formulated for THM4. There is a lack of published models evaluating total HAAs, individual THM and HAA species, bromate, and unregulated DBPs.

A device for fully automated on-site process monitoring and control of trihalomethane concentrations in drinking water

An instrument designed for fully automated on-line monitoring of trihalomethane concentrations in chlorinated drinking water is presented. The patented capillary membrane sampling device automatically samples directly from a water tap followed by injection of the sample into a gas chromatograph equipped with a nickel-63 electron capture detector. Detailed studies using individual trihalomethane species exhibited method detection limits ranging from 0.01–0.04μgL−1. Mean percent recoveries ranged from 77.1 to 86.5% with percent relative standard deviation values ranging from 1.2 to 4.6%. Out of more than 5200 samples analyzed, 95% of the concentration ranges were detectable, 86.5% were quantifiable. The failure rate was less than 2%. Using the data from the instrument, two different treatment processes were optimized so that total trihalomethane concentrations were maintained at acceptable levels while reducing treatment costs significantly. This ongoing trihalomethane monitoring program has been operating for more than ten months and has produced the longest continuous and most finely time-resolved data on trihalomethane concentrations reported in the literature.

Pilot study of the removal of individual trihalomethanes (THMs) from chlorinated drinking water by GAC adsorption - Galatsi water treatment plant, Athens, Greece

&lt;p&gt;The objective of this pilot study was to evaluate the performance of Powdered Activated Carbon (PAC) for the removal of individual trihalomethanes (THMs) from chlorinated drinking water, Athens, Greece. The pilot treatment facility was located at the Water Treatment Plant of EYDAP (Athens Water Supply and Sewerage Company) in Galatsi, Athens, and consisted of two mixing tanks operating as open batch reactors, which were fed with chlorinated water from the overflow of the sedimentation tanks. Experimental cycles were performed, with different PAC doses ranging from 5 to 50 mg L-1 and with contact times 30 and 60 min for each cycle. Water samples taken at the start of each cycle and after contact with PAC, were analysed for individual THMs and Dissolved Organic Carbon (DOC). Bromide, free residual chlorine, pH and temperature were also measured. From the experimental results, it was shown that all THMs concentrations were decreased after PAC contact, the decrease being higher for higher PAC dose and higher contact time, with few exceptions. This fact probably indicates that adsorption rate plus volatilisation rate of THMs overcame formation rate, in most cases. It was also concluded that volatilisation and possible formation reactions of THMs had probably a more apparent effect to the total removal of most THMs at low PAC doses and low contact time. At higher PAC doses and higher contact time, PAC adsorption probably had an increased contribution to THMs removal, because of the larger carbon surface area and the longer contact time, resulting in higher adsorbed mass according to adsorption theory. By using isotherm results of individual THMs on activated carbon by other researchers, the theoretically adsorbed mass of THMs per g of PAC was roughly estimated and compared with the measured removed mass of THMs per g of PAC at PAC dose 50 mg L-1 and contact time 60 min for most THMs, on the assumption of equilibrium achievement. The removed mass of THMs by PAC appeared much higher than the theoretically adsorbed, especially for the most volatile members. The difference was attributed to volatilisation taking place in the open mixing tanks. In conclusion, the practical results from the application of PAC for the removal of THMs are much better than expected from single adsorption by PAC. Volatility of THMs, especially of chloroform (TCM), substitutes for weak adsorbability and gives increased removal. The influent DOC was almost constant in all experiments. The removal of DOC was generally higher for increased PAC dose and contact time. Although equilibration cannot have happened for DOC, the mass removal of DOC per g of PAC was higher by more than two orders of size than that of the smaller and in lower concentration THMs, as expected.&lt;/p&gt;

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

ObjectivesCongenital 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...

The Effect of Different Boiling and Filtering Devices on the Concentration of Disinfection By-Products in Tap Water

Disinfection by-products (DBPs) are ubiquitous contaminants in tap drinking water with the potential to produce adverse health effects. Filtering and boiling tap water can lead to changes in the DBP concentrations and modify the exposure through ingestion. Changes in the concentration of 4 individual trihalomethanes (THM4) (chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)), MX, and bromate were tested when boiling and filtering high bromine-containing tap water from Barcelona. For filtering, we used a pitcher-type filter and a household reverse osmosis filter; for boiling, an electric kettle, a saucepan, and a microwave were used. Samples were taken before and after each treatment to determine the change in the DBP concentration. pH, conductivity, and free/total chlorine were also measured. A large decrease of THM4 (from 48% to 97%) and MX concentrations was observed for all experiments. Bromine-containing trihalomethanes were mostly eliminated when filtering while chloroform when boiling. There was a large decrease in the concentration of bromate with reverse osmosis, but there was a little effect in the other experiments. These findings suggest that the exposure to THM4 and MX through ingestion is reduced when using these household appliances, while the decrease of bromate is device dependent. This needs to be considered in the exposure assessment of the epidemiological studies.

Exposure to Drinking Water Trihalomethanes and Their Association with Low Birth Weight and Small for Gestational Age in Genetically Susceptible Women

Little is known about genetic susceptibility to individual trihalomethanes (THM) in relation to adverse pregnancy outcomes. We conducted a nested case-control study of 682 pregnant women in Kaunas (Lithuania) and, using individual information on drinking water, ingestion, showering and bathing, and uptake factors of THMs in blood, estimated an internal THM dose. We used logistic regression to evaluate the relationship between internal THM dose, birth outcomes and individual and joint (modifying) effects of metabolic gene polymorphisms. THM exposure during entire pregnancy and specific trimesters slightly increased low birth weight (LBW) risk. When considering both THM exposure and maternal genotypes, the largest associations were found for third trimester among total THM (TTHM) and chloroform-exposed women with the GSTM1–0 genotype (OR: 4.37; 95% CI: 1.36–14.08 and OR: 5.06; 95% CI: 1.50–17.05, respectively). A test of interaction between internal THM dose and GSTM1–0 genotype suggested a modifying effect of exposure to chloroform and bromodichloromethane on LBW risk. However, the effect on small for gestational age (SGA) was not statistically significant. These data suggest that THM internal dose may affect foetal growth and that maternal GSTM1 genotype modifies the THM exposure effects on LBW.

CHLORINATION DISINFECTION BY-PRODUCTS AND RISK OF STILLBIRTHS AND CAUSE-SPECIFIC STILLBIRTHS IN ENGLAND AND WALES

Background and Objective: We investigated the association between still births and Trihalomethanes (THM) concentrations in tap water across a large population residing in 12 regions of England and Wales. The study data cover the period 1993 – 2001 and include 2.79 million births with 14,265 stillbirths. Two cause-specific subgroups of stillbirths, as defined by Wigglesworth codes, were also investigated. Trihalomethanes are one of the main groups of disinfection byproducts and are widely used in epidemiological studies as a marker for DBPs as they are routinely collected by the water companies. Methods: Routinely collected THM data from each water company were modelled using a hierarchical mixture model. The modelled individual and total THM concentrations for the final trimester of the pregnancy were categorized into one of three predefined exposure categories and linked to the outcome data via the postcode of the maternal birth address. Logistic regression was carried out with maternal age, split into 5 categories, and deprivation, as measured by quintiles of the Carstairs Index, included in the model as confounders. Results: Analyses were conducted to investigate the relationship between total THMs and risk of stillbirths. Further analyses using individual THMs and also the cause specific subgroups of stillbirths were also undertaken. Full results will be presented. Conclusion: This is the largest study to date worldwide. Previous studies have shown inconsistent evidence for the association between stillbirths and trihalomethanes. Concern remains of the possible adverse impact of disinfection by products on births outcomes due to the large population at risk. More detailed exposure assessment including information on water consumption, showering and swimming diaries and, in particular, the use of urinary biomarkers is recommended to move this important field of research forward.

Temporal variability in trihalomethane and haloacetic acid concentrations in Massachusetts public drinking water systems

Previous epidemiological studies in Massachusetts have reported a risk of adverse health outcomes in relation to disinfection by-product (DBP) exposures. Measurement error due to the use of indirect exposure surrogates can lead to misclassification bias in epidemiological studies; therefore, it is important to characterize exposure variability in these populations to assess the potential for exposure misclassification. We used 19,944 trihalomethane (THM) samples and 9291 haloacetic acid (HAA) samples collected in 201 public water systems (PWSs) in Massachusetts to examine temporal variability under different drinking water sources and disinfection types. Annual and seasonal variability was also examined in 46 PWSs with complete quarterly THM4 (i.e., the sum of 4 individual THMs) data from 1995 to 2004 and 19 PWSs with complete HAA5 (i.e., the sum of 5 individual HAAs) data from 2001 to 2004. The quarterly ratio of THM4 and HAA5 and correlations between THM4, HAA5 and individual DBP species were examined to determine the adequacy of using different exposure surrogates in epidemiological studies. Individual PWSs were used to examine monthly variability in relation to quarterly averages. Based on all available matched samples ( n=9003) from 1995 to 2004 data, we found a correlation of 0.52 for THM4 and HAA5. The correlation was stronger among the 62 ground water systems ( r s =0.62) compared to the 81 surface water ( r s =0.45) and 40 mixed water ( r s =0.39) systems. Mean THM4 levels were fairly stable over the 10-year study period for 46 PWSs including 39 PWSs that did not change disinfection. Large reductions (∼40 μg/L) in mean THM4 data were found among seven systems that switched from chlorination to alternative disinfectants. As expected, the highest mean THM4 values were detected for Quarter 3, while the lowest values were found in Quarter 1. The highest HAA5 values were detected in Quarters 2 and 3 and the lowest was found in Quarter 4. Data from four systems showed mean differences up to 66 μg/L (67% change) in successive months and by 46 μg/L compared to quarterly mean concentrations. Although longer-term disinfection by-product temporality may be minimal in this study population, the use of monthly average concentrations for exposure assessment may be needed for some PWSs to minimize misclassification of narrow critical periods of exposure in epidemiological studies.

Chlorination Disinfection By-products and Risk of Stillbirths in England and Wales

PP-30-179 Background/Aims: We investigated the association between trihalomethane (THM) concentrations in drinking water and stillbirths across a large population residing in 12 regions of England and Wales. THM concentrations in drinking water are routinely measured by the water companies; therefore, they are often used in epidemiological studies as a marker for disinfection by-products. The study comprises 2.79 million births during the period 1993–2001, of which 14,265 were all-cause stillbirths. Additionally, we investigated 2 cause-specific subgroups of stillbirths, as defined by Wigglesworth codes. Methods: A hierarchical mixture model was used to model routinely collected THM data from each water company. For the third trimester of pregnancy, the modeled concentrations for total THMs and individual THM species were categorized into predefined low, medium, and high exposure categories and linked, through postcode of the maternal address at birth, to the birth outcome data. Logistic regression was performed adjusting for potential confounding by maternal age (split into 5 categories), and socioeconomic status (as measured by quintiles of the Carstairs Index). Fifteen company/period specific analyses were carried out for each disease endpoint and THM exposure combination, and then company/period specific results were combined through meta-analysis. Results: Mean total THM concentrations ranged from 16.5 μg/L in the low exposure category to 71.9 μg/L in the high exposure category. Prevalence rates of all-cause and cause-specific stillbirths differed according to maternal age category and according to socioeconomic status (trend of increasing prevalence rates from least to most deprived group). Meta-analysis results were suggestive of a small excess risk of stillbirth associated with chloroform, but not with total THMs or the other individual THM species examined. Conclusion: There was no evidence to support an association of stillbirth or cause-specific stillbirth with total THMs; however, there was evidence suggestive of a small excess risk of stillbirth with levels of chloroform.

Trihalomethane Levels in Relation to Rates of Stillbirth and Low Birth Weight: An Intervention Study

S-29C6-5 Background/Aims: In North West England, drinking water is supplied to 7 million people by the water company United Utilities. The company introduced enhanced coagulation for some of their treatment works during 2003 and 2004. Compared to conventional coagulation, enhanced coagulation improves removal of disinfection byproduct (DBP) precursors and should therefore reduce DBP formation potential. This intervention provided a unique opportunity to study potential effects of DBPs, in particular trihalomethanes (THMs), on birth outcomes, particularly since potential confounders (eg, socioeconomic factors) did not change over the short period. Areas where no treatment changes occurred acted as a control. Our aim was to compare rates of stillbirth and low birth weight 3 years prior (2000–2002) to treatment changes occurring with rates 3 years after (2005–2007) the changes took place. Methods: We linked information on THMs and enhanced coagulation status of water supply zones to births and stillbirths from the national birth register, using the point-in-polygon method in geographical information systems, with the third trimester as the critical exposure period. Differences in small-area rates of stillbirth and low birth weight before and after treatment changes were modelled against change in mean annual total THM (TTHM) concentrations using Poisson regression. Additionally, areas were categorized into low, medium, and high change in TTHM concentrations and the changes in rates of stillbirth and low birth weight were estimated in each category using Poisson regression. Models were adjusted for potential confounders such as maternal age and social deprivation (Carstairs' deprivation score). Results: Enhanced coagulation reduced TTHM levels. Preliminary results suggest an association between reduction of stillbirth rates and change to enhanced coagulation, possibly mediated by reduction in TTHM. However, we found little association between reduction of low birth weight rates and change to enhanced coagulation. Conclusion: Our preliminary findings are inconclusive. Further, analyses will investigate the individual THMs, bromodichloromethane, bromodichloromethane, bromoform, and chloroform.

Comparison of Byproduct Formation in Waters Treated with Chlorine and Iodine: Relevance to Point-of-Use Treatment

Due to their efficacy in deactivating a range of microbial pathogens, particularly amoebic cysts, iodine-based disinfectants have been a popular option for point-of-use (POU) drinking water disinfection by campers, the military, and rural consumers in developing countries. Recently, concerns regarding the formation of cytotoxic and genotoxic iodinated disinfection byproducts (I-DBPs) have arisen during chloramine disinfection of iodide-containing waters in the developed world; similar concerns should pertain to iodine-based POU disinfection. Because there are alternative POU disinfection techniques, including chlorine-based disinfectants, this paper compared disinfection byproduct formation from a range of iodine-based disinfectants at their recommended dosages to chlorination and chloramination under overdosing conditions. Just as chloroform was the predominant trihalomethane (THM) forme during chlorination or chloramination, iodoform was the predominant THM formed during iodination. Conditions fostering THM formation were similar between these treatments, except that THM formation during chlorination increased with pH, while it was slightly elevated at circumneutral pH during iodination. Iodoform formation during treatment with iodine tincture was higher than during treatment with iodine tablets. On a molar basis, iodoform formation during treatment with iodine tincture was 20-60% of the formation of chloroform during chlorination, and total organic iodine (TOI) formation was twice that of total organic chlorine (TOCl), despite the 6-fold higher oxidant dose during chlorination. Based upon previous measurements of chronic mammalian cell cytotoxicity for the individual THMs, consumers of two waters treated with iodine tincture would receive the same THM-associated cytotoxic exposure in 4-19 days as a consumer of the same waters treated with a 6-fold higher dose of chlorine over 1 year. Iodoacetic acid, diiodoacetic acid, and other iodo-acids were also formed with iodine tincture treatment, but at levels <11% of iodoform. However, testing of a Lifestraw Personal POU device, which combines an iodinated anion exchange resin with activated carbon post-treatment, indicated minimal formation of I-DBPs and no iodine residual. Although N-nitrosamines have been associated with oxidant contact with anion exchange resins, N-nitrosamine formation rapidly declined to low levels (4 ng/L) using the Lifestraw device after the first few flushes of water.

Trihalomethanes and Semen Quality in England and Wales

ISEE-0663 Background and Objective: Disinfection by-products (DBPs) have been associated with adverse semen outcomes in laboratory animals. Of the DBPs, there is stronger evidence for the bromo- and chloro-acetic acids, while that for trihalomethanes (THMs) is heterogenous. However, two small epidemiological studies have found no association between DBPs and adverse semen outcomes in humans. In a large case-control study, we investigated the association between individual and total trihalomethanes (TTHM) and low motile sperm concentration (MSC) in six water regions in England and Wales between 1999 and 2002. Methods: Men were recruited from 13 fertility clinics in 9 centres across England and Wales between 1999 and 2002. THM concentrations in water zones were linked to data on semen quality for 647 cases and 936 controls, based on the men’s residence at the time the semen sample was obtained. Low MSC was calculated relative to time since last ejaculation. TTHM levels were categorized as low (< 35.71 μg/l), medium (35.71–49.86 μg/l), or high (49.87–95 μg/l). Results: Preliminary analyses using a crude measure of THM exposure (annual average THM) found no increased risk associated with TTHM. There were some excess risks found with the individual THMs. Conclusion: Our preliminary findings are inconclusive. Further analyses will use quarterly THM exposure data weighted to the time of sampling for more precise exposure, and adjust for potential confounders.

Determination of odour threshold concentration ranges for some disinfectants and disinfection by-products for an Australian panel

Taste-and-odour complaints are a leading cause of consumer dissatisfaction with drinking water. The aim of this study was to determine odour threshold concentration ranges and descriptors, using a Western Australian odour panel, for chlorine, bromine, chlorine added to bromide ions, the four major regulated trihalomethanes (THMs), and combined THMs. An odour panel was established and trained to determine odour threshold concentration ranges for odorous compounds typically found in drinking water at 25 degrees C, using modified flavour profile analysis (FPA) techniques. Bromine and chlorine had the same odour threshold concentration ranges and were both described as having a chlorinous odour by a majority of panellists, but the odour threshold concentration range of bromine expressed in free chlorine equivalents was lower that that of chlorine. It is likely that the free chlorine equivalent residuals measured in many parts of distribution systems in Western Australia are comprised of some portion of bromine and that bromine has the potential to cause chlorinous odours at a lower free chlorine equivalent concentration than chlorine itself. In fact, bromine is the likely cause of any chlorinous odours in Western Australian distributed waters when the free chlorine equivalent concentration is between 0.04 and 0.1 mg L(-1). Odour threshold concentrations for the four individual THMs ranged from 0.06-0.16 mg L(-1), and the odour threshold concentration range was 0.10 + or - 0.09 mg L(-1) when the four THMs were combined (in equal mass concentrations). These concentrations are below the maximum guideline value for total THM concentration in Australia so odours from these compounds may possibly be observed in distributed waters. However, while the presence of THMs may contribute to any sweet/fragrant/floral and chemical/hydrocarbon odours in local drinking waters, the THMs are unlikely to contribute to chlorinous odours.