Total 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.

Formation, speciation, and temporal variability of DBPs in drinking water distribution systems in the context of ASR operations and extended storage periods

As climate change induces changes in water quality and available water quantity of drinking water supply sources, the final product water quality changes in terms of trace organics including disinfection byproducts (DBPs) formed during water treatment. In this study, the seasonal variability and speciation of DBPs across nine sample sites within a drinking water distribution system serving ∼400k people over a one-year period was investigated considering the governing parameters of water quality and treatment/transport/storage of finished water. The system considered treats surface water from a river and practices aquifer storage and recovery to address seasons water availability changes. Eighty-eight (88) sample sets were collected and held for 6-months in the laboratory to simulate extended storage scenarios associated with ASR operations, and each was analyzed at 9 different timesteps for concentration and speciation of chlorinated DBPs. Samples from groundwater influenced sites exhibited significantly lower total organic carbon (TOC) compared to other sites from the river source, and also were observed to have the lowest DBP formation. Three sites exceeded the Maximum Contaminant Level (MCL) for four total trihalomethanes (THM4) within 30–60 days of storage. Chloroform was the predominant THM4 species, even in groundwater-influenced locations, whereas di- and tri-chloroacetic acid (DCA and TCA) were the most prevalent haloacetic acids (HAA5). Extended water age at one site, coupled with low initial chlorine concentrations exhibited higher initial THM4 concentrations and flat DBP formation curves. The study results provide new insights into DBP occurrence and fate in drinking water distribution systems which consider water storage such as in ASR.

Public drinking water contaminant estimates for birth cohorts in the Environmental Influences on Child Health Outcomes (ECHO) Cohort.

The United States Environmental Protection Agency (USEPA) regulates over 80 contaminants in community water systems (CWS), including those relevant to infant health outcomes. Multi-cohort analyses of the association between measured prenatal public water contaminant concentrations and infant health outcomes are sparse in the US. Our objectives were to (1) develop Zip Code Tabulation Area (ZCTA)-level CWS contaminant concentrations for participants in the Environmental Influences on Child Health Outcomes (ECHO) Cohort and (2) evaluate regional, seasonal, and sociodemographic inequities in contaminant concentrations at the ZCTA-level. The ECHO Cohort harmonizes data from over 69 extant pregnancy and pediatric cohorts across the US. We used CWS estimates derived from the USEPA's Six-Year Review 3 (2006-2011) to develop population-weighted, average concentrations for 10 contaminants across 7640 ZCTAs relevant to the ECHO Cohort. We evaluated contaminant distributions, exceedances of regulatory thresholds, and geometric mean ratios (with corresponding percent changes) associated with ZCTA sociodemographic characteristics via spatial lag linear regression models. We observed significant regional variability in contaminant concentrations across the US. ZCTAs were most likely to exceed the maximum contaminant level for arsenic (n = 100, 1.4%) and the health-protective threshold for total trihalomethanes (n = 3584, 64.0%). A 10% higher proportion of residents who were American Indian/Alaskan Native and Hispanic/Latino was associated with higher arsenic (11%, 95% CI: 7%, 15%; and 2%, 95% CI: 0%, 3%, respectively) and uranium (15%, 95% CI: 10%, 21%; and 9%, 95% CI: 6%, 12%, respectively) concentrations. Nationwide epidemiologic analyses evaluating the association between US community water system contaminant concentration estimates and associated adverse birth outcomes in cohort studies are sparse because public water contaminant concentration estimates that can be readily linked to participant addresses are not available. We developed Zip Code Tabulation Area (ZCTA)-level CWS contaminant concentrations that can be linked to participants in the Environmental Influences on Child Health Outcomes (ECHO) Cohort and evaluated regional, seasonal, and sociodemographic inequities in contaminant concentrations for these ZCTAs. Future epidemiologic studies can leverage these CWS exposure estimates in the ECHO Cohort to evaluate associations with relevant infant outcomes.

Drinking water source and exposure to regulated water contaminants in the California Teachers Study cohort.

Pollutants including metals/metalloids, nitrate, disinfection byproducts, and volatile organic compounds contaminate federally regulated community water systems (CWS) and unregulated domestic wells across the United States. Exposures and associated health effects, particularly at levels below regulatory limits, are understudied. We described drinking water sources and exposures for the California Teachers Study (CTS), a prospective cohort of female California teachers and administrators. Participants' geocoded addresses at enrollment (1995-1996) were linked to CWS service area boundaries and monitoring data (N = 115,206, 92%); we computed average (1990-2015) concentrations of arsenic, uranium, nitrate, gross alpha (GA), five haloacetic acids (HAA5), total trihalomethanes (TTHM), trichloroethylene (TCE), and tetrachloroethylene (PCE). We used generalized linear regression to estimate geometric mean ratios of CWS exposures across demographic subgroups and neighborhood characteristics. Self-reported drinking water source and consumption at follow-up (2017-2019) were also described. Medians (interquartile ranges) of average concentrations of all contaminants were below regulatory limits: arsenic: 1.03 (0.54,1.71) µg/L, uranium: 3.48 (1.01,6.18) µg/L, GA: 2.21 (1.32,3.67) pCi/L, nitrate: 0.54 (0.20,1.97) mg/L, HAA5: 8.67 (2.98,14.70) µg/L, and TTHM: 12.86 (4.58,21.95) µg/L. Among those who lived within a CWS boundary and self-reported drinking water information (2017-2019), approximately 74% self-reported their water source as municipal, 15% bottled, 2% private well, 4% other, and 5% did not know/missing. Spatially linked water source was largely consistent with self-reported source at follow-up (2017-2019). Relative to non-Hispanic white participants, average arsenic, uranium, GA, and nitrate concentrations were higher for Black, Hispanic and Native American participants. Relative to participants living in census block groups in the lowest socioeconomic status (SES) quartile, participants in higher SES quartiles had lower arsenic/uranium/GA/nitrate, and higher HAA5/TTHM. Non-metropolitan participants had higher arsenic/uranium/nitrate, and metropolitan participants had higher HAA5/TTHM. Though average water contaminant levels were mostly below regulatory limits in this large cohort of California women, we observed heterogeneity in exposures across sociodemographic subgroups and neighborhood characteristics. These data will be used to support future assessments of drinking water exposures and disease risk.

Association of blood trihalomethane concentrations with diabetes mellitus in older adults in the US: a cross-sectional study of NHANES 2013-2018.

Previous studies have demonstrated that there is a correlation between trihalomethanes and disease progression, such as allergic diseases. As we know, only few studies focused on the relationship between trihalomethanes and metabolic diseases, such as diabetes mellitus. The aim of this study was to further explore the associations between blood trihalomethane concentrations and diabetes mellitus in older adults in the US. Data were collected from the National Health and Nutrition Examination Study (NHANES) database in the survey cycle during 2013 to 2018, including 2,511 older adults in the US whose blood trihalomethane concentrations were measured, involving chloroform (TCM) and brominated trihalomethanes (Br-THMs). Br-THMs include bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM). Meanwhile, the concentration of total trihalomethanes (TTHMs) was also measured later. A multivariate logistic regression and restricted cubic spline were used to examine the relationship between blood THMs and diabetes mellitus. Meanwhile, we performed a subgroup analysis, which aims to explore the stability of this relationship in different subgroups. In order to further consider the impact of various disinfection by-products on diabetes, we also used weighted quantile sum (WQS). To explore the correlation in trihalomethanes, we plot a correlation heatmap. Adjusting for potential confounders, we found that there was a significant negative association between chloroform and diabetes mellitus [Model 1 (adjusted for covariates including age, sex, and race, OR = 0.71; 95% CI: 0.50-1.02; p = 0.068; p for trend = 0.094); Model 2 (adjusted for all covariates, OR = 0.68; 95% CI: 0.48-0.96; p = 0.029; p for trend = 0.061)]. Inthe bromodichloromethane, we reached a conclusion that is similar to TCM [Model 1 (adjusted for covariates including age, sex, and race, OR = 0.54; 95% CI: 0.35-0.82; p = 0.005; p for trend = 0.002); Model 2 (adjusted for all covariates, OR = 0.54; 95% CI: 0.35-0.82; p = 0.003; p for trend = 0.002)]. Meanwhile, the restricted cubic spline curve also further confirms this result (p overall = 0.0027; p overall< 0.001). Based on the analysis in the subgroups, we found that the value p for interaction in the majority of subgroups is higher than 0.1. Trihalomethanes and diabetes were inversely associated, and in the WQS, chloroform and bromodichloromethane were found to be the major contributors to this relationship. In the correlation analysis, we found that most trihalomethanes have a weak correlation, except for TBM and TCM with a strong correlation. Our results in this study showed that blood chloroform, bromodichloromethane concentrations, and diabetes mellitus in older adults in the US are negatively correlated, suggesting that chloroform and bromodichloromethane can be protective factors for diabetes.

Chronic exposure to drinking water nitrate and trihalomethanes in the French CONSTANCES cohort

Trihalomethanes (THMs) and nitrate are widespread chemicals in drinking water. Chronic exposure has been associated with increased cancer risk despite inconclusive evidence, partly due to the challenges in long-term exposure assessment and potential exposure misclassification.We estimated concentrations of nitrate and THMs in drinking water using a public regulatory monitoring database (SISE-Eaux) for CONSTANCES, a French population-based prospective cohort.We obtained 26,322,366 measurements of drinking water parameters from 2000 to 2020. We excluded missing, implausible and duplicated measurements; we corrected or imputed missing geocodes of sampling locations; we calculated the annual median concentration of nitrate and THMs by surveillance area. To predict missing annual median concentrations, linear mixed models with random intercept using surveillance area as a clustering variable were developed for each region for nitrate and the four THM components (chloroform, chlorodibromomethane, bromodichloromethane and bromoform) separately. Concentrations in the nearest surveillance area from the household were merged per year among 75,462 participants with residential history geocoded for 2000–2020. Estimated concentrations resulting from this approach were compared with measured concentrations in 100 samples collected in Paris, Rennes and Saint-Brieuc in 2021.Median annual concentrations of total THMs and nitrate at study participants’ homes for 2000–2020 were, respectively, 15.7 μg/l (IQR: 15.2) and 15.2 mg/l (IQR: 20.8). Among these, 35% were based on measurements for nitrate (16% for THMs), 44% (46%) were predicted using on linear mixed models, and 21% (38%) were based on distribution unit median values. Conditional R2 predictive models ranged from 0.71 to 0.91 (median: 0.85) for nitrate, and from 0.48 to 0.80 for THMs (median: 0.68).These concentrations will allow future association analyses with risk of breast and colorectal cancer. Our cleaning process introduced here could be adapted to other large drinking water monitoring data.

Performance of Chitosan/Carbon Nanotube-Coated Ultrafiltration Membranes for Natural Organic Matter Removal from Drinking Water

The objective of this study is to improve the filtration efficiency of commercially available polyethersulfone (PES) ultrafiltration (UF) membranes, with a specific focus on removing natural organic matter (NOM) and preventing membrane fouling. The modification of UF membranes was accomplished by utilizing chitosan/multi-walled carbon nanotubes (CS/MWCNT-OH) and employing both dip and spin coating techniques. The membrane surface morphologies were evaluated using the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Energy-Dispersive X-ray Spectroscopy (EDX) techniques. Tests were carried out to assess the effectiveness of the membranes in a laboratory-scale system using two primary water sources from Istanbul, specifically the Melen River and Terkos Lake. Total organic carbon (TOC), UV254 absorbance, turbidity, and trihalomethane formation potential (THMFP) were all measured as part of a thorough analysis. The surface morphology investigations verified the effective deposition of MWCNT-OH nanoparticles onto the membrane surface. This was corroborated by the reduction in the water contact angle, showing an improvement in the hydrophilicity of the membrane. The modified membranes demonstrated much higher TOC removal rates compared to the original membranes. Specifically, the removal efficiencies for Melen River and Terkos Lake were 37.14% and 56.86%, respectively. Nevertheless, the alteration of the surface led to a decline in membrane flux as a result of the concurrent drop in pore size. To summarize, the results of this work highlights the considerable capability of surface modification using CS/MWCNT-OH to improve the performance and antifouling characteristics of commercial PES UF membranes.

Formation and health risk assessment of trihalomethanes in coastal wells impacted by seawater intrusion

The formation of trihalomethanes (THMs) in coastal wells impacted by seawater intrusion (SWI) is relatively understudied. Coastal wells, unlike typical groundwater sources, frequently exhibit elevated levels of chloride and bromide ions, potentially influencing the formation and speciation of THMs. The current study investigated the THM formation in coastal well water from a location affected by SWI. Samples were chlorinated with 2.5 mg L−1 and 5 mg L−1 chlorine doses to replicate field conditions. The THM concentration in the samples exceeded the maximum permissible limit for drinking water. The well with the highest chloride-to-bromide (Cl/Br) ratio (Cl/Br = 645) exhibited the highest total THM concentration (503.2 μg L−1). Samples with high bromide concentration had more brominated THMs over the 5-day reaction period. The bromine substitution factors for wells after 24 h with a chlorine dose of 2.5 mg L−1 were 1.89, 2.21, and 2.78, corresponding to bromide concentrations of 0.098, 0.109, and 1.275 mM, respectively. The average cancer risk associated with the well water was estimated to be 20.9 × 10−06 through dermal contact and 6.84 × 10−04 through inhalation. The study area had an estimated average cancer risk of 705 cases per million population. The study area's common diseases and cancer incidence data for the past four decades indicated a decreasing trend for waterborne diseases and a steep increase in cancers. While several factors may contribute to increasing cancer cases, our study highlights chlorinated coastal well water as an additional potential cancer risk agent.

Comparison of chlorine and chlorine dioxide disinfection in drinking water: Evaluation of disinfection byproduct formation under equal disinfection efficiency

Disinfection efficiency and disinfection byproduct (DBP) formation are two important aspects deserving careful consideration when evaluating different disinfection protocols. However, most of the previous studies on the selection of disinfection methods by comparing DBP formation were carried out under the same initial/residual dose and contact time of different disinfectants, and such a practice may cause overdose or underdose of a certain disinfectant, leading to the inaccurate evaluation of disinfection. In this study, a comprehensive and quantitative comparison of chlorine (Cl2) and chlorine dioxide (ClO2) disinfection was conducted with regard to their DBP formation under equal disinfection efficiency. The microbial inactivation models as well as the Cl2 and ClO2 demand models were developed. On such basis, the integral CT (ICT) values were determined and used as a bridge to connect disinfection efficiency and DBP formation. For 3-log10 and 4-log10 reductions of Pseudomonas aeruginosa, ClO2 had 1.5 and 5.8 times higher inactivation ability than Cl2, respectively. In the premise of equal disinfection efficiency (i.e., the ICT ratios of Cl2 to ClO2 = 1.5 and 5.8), the levels of total organic chlorine, total organic bromine, and total organic halogen formed in the Cl2 disinfection were significantly higher than those formed in the ClO2 disinfection. Among the 35 target aliphatic DBPs, trihalomethanes (THMs) and haloacetic acids (HAAs) were the dominant species formed in both Cl2 and ClO2 disinfection. The total THM levels formed in Cl2 disinfection were 14.6 and 30.3 times higher than those in ClO2 disinfection, respectively. The total HAA levels formed in Cl2 disinfection were 3.5 and 5.4 times higher than those in ClO2 disinfection, respectively. Formation of the target 48 aromatic DBPs was much favored in Cl2 disinfection than that in ClO2 disinfection, and the formation levels was dominated by contact time. This study demonstrated that ClO2 had significant advantages over Cl2, especially at higher microorganism inactivation and lower DBP formation requirements.

Adsorption kinetics, isotherms, and selectivity of trihalomethanes and haloacetonitriles by granular activated carbon

The performance capability of granular activated carbon (GAC) adsorption in terms of disinfection by-product (DBPs) removal was investigated with synthetic water containing 1) trihalomethanes (THMs), 2) haloacetronitriles (HANs), and 3) Mix-THMs & HANs. The initial 20 min of adsorption resulted in the maximum adsorption rate, with the total THMs, total HANs, and total Mix–THMs & HANs being 4.972, 2.071, and 6.460 µg/gGAC-min, respectively. GAC dosage affects the adsorption selectivity of THMs and HANs. Under a low GAC dosage, the selectivity of GAC adsorbs more bromo-THMs than chloro-THMs. The adsorption selectivity of THMs on GAC following bromoform > dibromochloromethane > bromodichloromethane > chloroform was investigated. As the GAC concentration increased, the selectivity of THM adsorption by GAC became comparable. Chloro-HAN, in contrast to THMs, has a higher adsorption selectivity than bromo-HAN. Trichloroacetonitrile was removed by GAC more rapidly than the other HAN species when the GAC dose was increased. The toxin of bromoform was primarily eliminated through GAC adsorption, caused by a greater removal rate than that of the other THMs. As an implemented measure, GAC is introduced to reduce THMs and HANs and the toxic contents associated with THMs and HANs.

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

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. 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. 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. 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.

Urinary and household chemical exposures in pet dogs with urothelial cell carcinoma.

Urothelial cell carcinoma (UCC) has been linked to environmental chemical exposures in people, but these risk factors are not well understood in dogs with UCC. We hypothesised that household chemical exposures contribute to the risk of UCC in pet dogs. This prospective cross-sectional case-control study included 37 dogs with UCC and 37 unaffected breed-, sex-, and age-matched controls. Dog owners completed an environmental questionnaire and household samples were collected and analysed for arsenic (in tap water and room dust) and acrolein (in room air). Urine samples from UCC dogs, control dogs, and consenting owners were analysed for inorganic arsenic species, the acrolein metabolite 3-HPMA, and the phenoxy herbicide 2,4-D. Public data on chlorination byproducts (total trihalomethanes) in municipal drinking water were also compared between case and control households. Dogs with UCC were more likely to swim in a pool (15.2%) compared with control dogs (0%) (OR 1.69, 95% CI = 1.69-∞; p = .02). Dogs with UCC also had more than 4-fold higher reported municipal water concentrations of chlorination byproducts (median 28.0 ppb) compared with controls (median 6.9 ppb; p < .0001). Dust arsenic concentrations were unexpectedly lower in case households (median 0.277 ng/cm2) compared with control households (median 0.401 ng/cm2; p = .0002). Other outcomes were not significantly different between groups. These data suggest that dog owners, especially those of breeds known to be at higher risk for UCC, consider limiting access to swimming pools and installing water filtration units that remove total trihalomethanes.

Impact of source water quality on total organic carbon and trihalomethane removal efficiency in a water treatment plant: A case study of Upper Awash, Ethiopia.

This study addresses the limited understanding of factors affecting the efficiency of water treatment plants in reducing trihalomethane (THM) formation through total organic carbon (TOC) removal, highlighting significant challenges in improving treatment effectiveness. The aim of this study was to examine the influence of water quality on the efficiency of water treatment plants to remove TOC and reduce THM formation. Linear regression and correlation analyses were conducted to examine the relationship between water quality parameters and THM concentrations. The results showed that there was a negative relationship between turbidity, metals, and TOC concentration with TOC removal efficiency. Positive correlations were found between parameters and the formation of THMs in water. Of these parameters, water temperature was observed to have relatively less influence on THM formation. It was observed that seasonal variations in water quality affect the efficiency of TOC removal and THM content in treated water. THM levels in chlorinated water were found to be within the permissible range of the World Health Organization's drinking water quality guidelines. However, it is still important to maintain continuous monitoring and take measures to reduce THMs. The model demonstrated a strong correlation (R2 = 0.906) between predicted and measured THM values.

Modeling chloramine stability and disinfection byproduct formation in groundwater high in bromide

AbstractBromide can promote monochloramine decomposition and disinfection byproduct (DBP) formation. Monochloramine and total chlorine stability as well as total trihalomethane and haloacetic acid formation were examined in groundwater with high bromide levels (300–1700 μg/L) following chlorine or KMnO₄ preoxidation. An N,N‐Diethyl‐p‐phenylenediamine (DPD)‐based total chlorine method detected chloramines and brominated amines (e.g., NH2Br, NHBrCl). An indophenol‐based monochloramine method showed minimal interference from brominated amines. Differences between these methods' measurements likely indicated brominated amine concentrations. Substantial total chlorine demands (up to ~3.5 mg/L in 4 days) following chlorine preoxidation were observed due to the presence of brominated amines. Total chlorine measurements were more stable and DBP formation was limited following KMnO₄ preoxidation because ammonia was dosed before chlorine, which inhibited brominated amine formation. A kinetic model developed elsewhere for dissolved organic matter (DOM)‐free water generally tracked with experimental results but some deviations occurred possibly because DOM consumed bromochloramine or its reaction intermediates.

Water Quality Trade-offs for Risk Management Interventions in a Green Building.

Premise plumbing water quality degradation has led to negative health impacts from pathogen outbreaks (e.g., Legionella pneumophila and non-tuberculous mycobacteria), as well as chronic effects from exposure to heavy metals or disinfection by-products (DBP). Common water quality management interventions include flushing, heat shock (thermal disinfection), supplemental disinfection (shock or super chlorination), and water heater temperature setpoint change. In this study, a Legionella pneumophila- colonized Leadership in Energy and Environmental Design (LEED) certified building was monitored to study health-relevant water quality changes before and after three controlled management interventions: (1) flushing at several points throughout the building; (2) changing the water heater set point; and (3) a combination of interventions (1) and (2) by flushing during a period of elevated water heater set point (incompletely performed due to operational issues). Microbial (culturable L. pneumophila, the L. pneumophila mip gene, and cATP) and physico-chemical (pH, temperature, conductivity, disinfectant residual, disinfection by-products (DBPs; total trihalomethanes, TTHM), and heavy metals) water quality were monitored alongside building occupancy as approximated using Wi-Fi logins. Flushing alone resulted in a significant decrease in cATP and L. pneumophila concentrations (p = 0.018 and 0.019, respectively) and a significant increase in chlorine concentrations (p = 0.002) as well as iron and DBP levels (p = 0.002). Copper concentrations increased during the water heater temperature setpoint increase alone to 140°F during December 2022 (p = 0.01). During the flushing and elevated temperature in parts of the building in February 2023, there was a significant increase in chlorine concentrations (p = 0.002) and iron (p = 0.002) but no significant decrease in L. pneumophila concentrations in the drinking water samples (p = 0.27). This study demonstrated the potential impacts of short term or incompletely implemented interventions which in this case were not sufficient to holistically improve water quality. As implementing interventions is logistically- and time-intensive, more effective and holistic approaches are needed for informing preventative and corrective actions that are beneficial for multiple water quality and sustainability goals.

Suların Klorla Dezenfeksiyonunda Trihalometan Oluşumuna Hümik Asit ve Bromürün Etkisi

Chlorination is one of the most important methods used in water disinfection. Chlorine reacts with natural organic substances in water and causes the formation of disinfection byproducts that might cause health problems. The predominant by-product of chlorination is trihalomethanes. Humic substances, which make up the majority of natural organic substances, are the primary precursors of trihalomethanes. In this study, the effect of different doses of chlorine on the formation of chloroform, bromodichloromethane, dibromochloromethane and bromoform in the presence of natural organic matter and bromide in drinking water was evaluated. Artificial raw water samples prepared with the addition of 2, 3 and 5 mg/L humic acid representing natural organic matter were subjected to chlorination at doses of 1, 2 and 3 mg/L and analysed on the 0th, 3rd and 7th day. The only trihalomethane formed was chloroform with a concentration of 20.52-131.13 μg/L. Increased humic acid and chlorine levels resulted in increased chloroform content. Free chlorine in the water caused chloroform formation to continue even on the 7th day. Accordingly, the amount of chloroform formed increased with the contact time. While the chlorine dose was constant, increased humic acid resulted in decreased free chlorine. To evaluate the effect of bromide on trihalomethane formation, 200 μg/L bromide was added to 2 mg/L humic acid containing water, and 1 mg/L and 2 mg/L chlorination was applied. At the end of the chlorination process in bromide-free waters, only 23.46-41.90 μg/L of chloroform was formed. In the presence of bromide, chloroform, bromodichloromethane, dibromochloromethane and bromoform were formed and the total trihalomethane level increased to 50.03-85.59 μg/L. While the ratio of brominated trihalomethane increased, the amount of chlorinated species decreased.

UV-LED cocatalytic Fe3+/peroxymonosulfate process for the degradation of sulfamethoxypyridazine: Performance, mechanism and DBP formation during postchlorination

Herein, a UV-LED-catalytic Fe3+/peroxymonosulfate homogeneous advanced oxidation process (UV-LED/Fe3+/PMS) was adopted for the removal of sulfamethoxypyridazine (SMP), a commonly used sulfonamide antibiotic (SA), in water. Quenching experiments showed that SO4●–, •OH and Fe(IV) were generated in this system and contributed to the rapid removal of SMP. Generally, acidic media favored SMP degradation, and the contribution rate of active species to SMP removal was highly pH dependent. Higher light intensity and an equal Fe3+/PMS ratio (1:1) were appropriate for SMP removal. The introduction of HCO3−, NO3− and humic acid suppressed the degradation of SMP to different extents, but obvious acceleration was observed in the presence of halide ions. The transformation products were investigated, and their toxicity was also assessed. UV-LED/Fe3+/PMS was capable of controlling trichloromethane (TCM) during postchlorination while increasing the formation of dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) owing to the generation of precursors having certain functional groups. Prolonging pretreatment time had a positive effect on reducing DBP formation. The presence of humic acid increased the formation of both TCM and DCAN. Furthermore, total trihalomethanes and dihaloacetonitriles increased with increasing bromide concentration, which needs to be considered when adopting the UV-LED/Fe3+/PMS as pretreatment for the abatement of SMP.

Exposure to Trihalomethanes and Bone Mineral Density in US Adolescents: A Cross-Sectional Study (NHANES).

Animal and human studies have suggested that trihalomethane (THM) has toxicity to bone. In this study, we included adolescents from the National Health and Nutrition Examination Survey who had quantified blood and tap water THM concentrations [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)] and lumbar spine or total body less head (TBLH) bone mineral density (BMD). A 2.7-fold increase in concentrations of blood TCM, DBCM, chlorinated THMs (the sum of TCM, BDCM, and DBCM), and total THMs (the sum of 4 THMs) was associated with lower lumbar spine BMD z-scores by -0.06 [95% confidence interval (CI): -0.12, -0.01], -0.06 (95% CI: -0.11, -0.003), -0.08 (95% CI: -0.14, -0.02), and -0.07 (95% CI: -0.13, -0.003), respectively, in adjusted models. Similarly, a 2.7-fold increase in blood BDCM, DBCM, and chlorinated THM concentrations was associated with lower TBLH BMD z-scores by -0.10 (95% CI: -0.17, -0.02), -0.10 (95% CI: -0.17, -0.03), and -0.11 (95% CI: -0.20, -0.01), respectively. Low-to-moderate predictive power was attained when tap water THM concentrations were used to predict blood THM measurements. Notably, the inverse associations for blood THMs persisted exclusively between water concentrations of DBCM and Br-THMs and the TBLH BMD z-scores. Our findings suggest that exposure to THMs may adversely affect the adolescent BMD.

Evaluation of water quality via determination of trihalomethanes in water distribution networks of Riyadh city in Kingdom of Saudi Arabia

Trihalomethane (THM) has been classified as a possible human carcinogen by the International Agency for Research on Cancer (IARC). This study was conducted to assess the levels of trihalomethane compounds in the Riyadh city water network in two different years (2015 and 2020) and to understand the factors affecting the formation of these compounds. The study covered 15 sites in Riyadh city, distributed between the north, south, east, west and middle of the city. The results of the study indicated that the sum of the ratio of the concentration of each THM compound to its respective World Health Organization(WHO) guideline value not exceed 1 (unitless) where the combined toxicity of all total trihalomethanes THMs concentrations did not exceed the permissible limits, with values ranging between 0.01 and 0.24 at all study sites. These results were less than the recommended guide values form WHO for individual maximum concentrations of each of the THM in water for human consumption. In addition, the average concentration of free chlorine was 0.04 ppm and 0.09 ppm in 2015 and 2020, respectively, indicating that the disinfection had evolved in 2020 compared to 2015. Moreover, there was a weak relationship between trihalomethane formation and the presence of bromide ions and organic carbon, whereas a positive correlation was observed with free chlorine and pH values. The concentration of heavy metals such as cadmium, arsenic, cobalt and chromium were analysed by inductively coupled plasma-optical emission spectroscopy. The results indicated that all heavy metals were within the standard limits: the maximum values were 123 ppb in 2015 and 70.39 ppb in 2020, with lead having the lowest concentration and aluminium having the highest concentration in both years. Furthermore, the ion chromatography results of the cations (sodium Na±, potassium K±, calcium Ca2+and magnesium Mg2+) and the anions (fluoride F-, bromide Br-, chloride Cl-, sulphate SO42- and nitrate NO3–) indicated that the water in this study was suitable for human consumption based on the WHO regulation and the Ministry of Environment, Water and Agriculture (MEWA) standards for drinking water.

Modeling source water disinfection byproducts formation potential using environmental variables

AbstractPredictive models of disinfection byproducts (DBPs) formation in treated drinking water have been widely used to guide operational decisions. However, very few studies have addressed the issue of managing DBPs through watershed protection programs and proactive management of water supply systems through predictive modeling of DBP formation potential in source waters. Here, we propose a two‐component, simple statistical approach to predict the formation potentials of the sum of five haloacetic acids (HAA5fp) and total trihalomethanes (TTHMfp) in source water streams using environmental variables and ultraviolet absorbance at 254 nm wavelength (UV254) as a surrogate for DBP precursors. In the first component of the model, using three feature selection regression models and cross‐validation of subsets of the selected predictors, we identified three commonly monitored variables—streamflow, soil temperature, and total phosphorus for predicting UV254. In the second component, HAA5fp and TTHMfp are predicted from UV254. The approach is successfully demonstrated for two source water streams of the New York City water supply system (R2 was 0.8, and 0.7–0.8 for the two model components). Long‐term predictions of HAA5fp and TTHMfp showed distinct seasonal patterns that are linked to differences in land uses of the two watersheds. Moreover, sensitivity analysis showed that transport processes were important in one watershed whereas production processes were more important in the other.