Total Trihalomethanes Concentrations Research Articles

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.

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.

Trihalomethane prediction model for water supply system based on machine learning and Log-linear regression.

Laboratory determination of trihalomethanes (THMs) is a very time-consuming task. Therefore, establishing a THMs model using easily obtainable water quality parameters would be very helpful. This study explored the modeling methods of the random forest regression (RFR) model, support vector regression (SVR) model, and Log-linear regression model to predict the concentration of total-trihalomethanes (T-THMs), bromodichloromethane (BDCM), and dibromochloromethane (DBCM), using nine water quality parameters as input variables. The models were developed and tested using a dataset of 175 samples collected from a water treatment plant. The results showed that the RFR model, with the optimal parameter combination, outperformed the Log-linear regression model in predicting the concentration of T-THMs (N25 = 82-88%, rp = 0.70-0.80), while the SVR model performed slightly better than the RFR model in predicting the concentration of BDCM (N25 = 85-98%, rp = 0.70-0.97). The RFR model exhibited superior performance compared to the other two models in predicting the concentration of T-THMs and DBCM. The study concludes that the RFR model is superior overall to the SVR model and Log-linear regression models and could be used to monitor THMs concentration in water supply systems.

Leaching of organic matter from microplastics and its role in disinfection by-product formation

Natural organic matter (NOM) is the primary precursor of disinfection by-products (DBPs). However, as emerging environmental contaminants continue to increase in natural waters, there is a possibility of new precursors of DBPs. We investigated the potential of microplastics (MPs), a growing environmental concern, for leaching organic matter (OM) and subsequent DBP formation. Two experimental setups were used, including chlorinated water containing MPs (Cl2-MP), and non-chlorinated water containing MPs (Non-Cl2-MP), using polyethylene (PE), polyethylene tetrahydrate (PET), polypropylene (PP), and polyvinyl chloride (PVC) as MP materials. The UV absorbance spectra of Cl2-PET/PP/PVC showed peaks at 218 nm, which were significantly correlated with dissolved organic carbon (DOC), indicating lower aromaticity of the leached OM. The DOC concentrations in Cl2-MP samples were several times higher than those in Non-Cl2-MP samples. The leached OM from MPs formed trihalomethanes (THMs) and haloacetic acids (HAAs) in Cl2-MP samples. Among the MPs tested, PVC showed the highest total THM formation after 7 days, followed by PET, PE, and PP. Brominated THMs were predominant, while HAAs were highly chlorinated. THM formation increased with contact time for PE, PET, and PVC, and decreased for PP. Compared to THMs, the concentration of HAAs was low (highest total THM = 185.5 μg/L per g-MP and highest total HAA = 120.7 μg/L per g-MP). Further, the total THM concentration decreased and the total HAA concentration increased over the reaction period, indicating the leaching of different types of OM with increasing contact time. Additionally, the differences in the pattern of DOC leaching and DBP formation among different MPs suggested changes in the leached OM.

Trihalomethanes and physicochemical quality of drinking water in Addis Ababa, Ethiopia

BackgroundTrihalomethanes (THMs) are the most dominant fraction of all the byproducts formed during chlorination of water. Disinfection by product (DBP) formation in water is a function of numerous factors, including pH, temperature, residual chlorine, source water characteristics, and organic matter. No study has determined the THM level in the drinking water supply of Addis Ababa, Ethiopia. MethodsA cross-sectional design was conducted to collect water samples in the water supply distribution networks of Addis Ababa, Ethiopia. Twenty-one (21) sampling stations yielded a total of one hundred twenty (120) samples of drinking water. The sample handling and collection procedures were carried out in accordance with USEPA guidelines. A DB-5 capillary column was used to separate the THMs, which were detected using GC-ECD (gas chromatography-electron capture detector). Spectrophotometric and in situ methods were used for physicochemical parameters. Redundancy analysis (RDA) was used for data analysis of trihalomethanes and environmental variables using CANOCO 4.5. ResultsThe mean concentration of total trihalomethanes in drinking water in Addis Ababa was 76.3 μg/L. The concentration of chloroform in the drinking water supply in Addis Ababa, Ethiopia, ranged between 4.03 and 79.4 μg/L. The mean total THMs in the Legedadi and Gefersa water supply systems were 77.4 μg/L and 69.66 μg/L, respectively. The residual chlorine, phosphates, UV absorbance at 254 nm, and combined chlorine had positive correlations with THM formation. However, electron conductivity had a negative correlation with THM formation. ConclusionsChloroform contributed the most to TTHMs in nearly all samples. The residual chlorine, UV absorbance, phosphate and hardness as calcium, and electron conductivity were found to be the main predictors determining the abundance and distribution of trihalomethanes. The monitoring and regulation of the THMs is required on a regular basis to analyse trends and guide the water treatment and distribution system.

Beyond cyanotoxins: increased Legionella, antibiotic resistance genes in western Lake Erie water and disinfection-byproducts in their finished water.

Western Lake Erie is suffering from harmful cyanobacterial blooms, primarily toxic Microcystis spp., affecting the ecosystem, water safety, and the regional economy. Continued bloom occurrence has raised concerns about public health implications. However, there has been no investigation regarding the potential increase of Legionella and antibiotic resistance genes in source water, and disinfection byproducts in municipal treated drinking water caused by these bloom events. Over 2 years, source water (total n = 118) and finished water (total n = 118) samples were collected from drinking water plants situated in western Lake Erie (bloom site) and central Lake Erie (control site). Bloom-related parameters were determined, such as microcystin (MC), toxic Microcystis, total organic carbon, N, and P. Disinfection byproducts (DBPs) [total trihalomethanes (THMs) and haloacetic acids (HAAs)] were assessed in finished water. Genetic markers for Legionella, antibiotic resistance genes, and mobile genetic elements were quantified in source and finished waters. Significantly higher levels of MC-producing Microcystis were observed in the western Lake Erie site compared to the control site. Analysis of DBPs revealed significantly elevated THMs concentrations at the bloom site, while HAAs concentrations remained similar between the two sites. Legionella spp. levels were significantly higher in the bloom site, showing a significant relationship with total cyanobacteria. Abundance of ARGs (tetQ and sul1) and mobile genetic elements (MGEs) were also significantly higher at the bloom site. Although overall abundance decreased in finished water, relative abundance of ARGs and MGE among total bacteria increased after treatment, particularly at the bloom site. The findings underscore the need for ongoing efforts to mitigate bloom frequency and intensity in the lake. Moreover, optimizing water treatment processes during bloom episodes is crucial to maintain water quality. The associations observed between bloom conditions, ARGs, and Legionella, necessitate future investigations into the potential enhancement of antibiotic-resistant bacteria and Legionella spp. due to blooms, both in lake environments and drinking water distribution systems.

Application of black-box models based on artificial intelligence for the prediction of chlorine and TTHMs in the trunk network of Bogotá, Colombia

Abstract The chlorine and total trihalomethane (TTHM) concentrations are sparsely measured in the trunk network of Bogotá, Colombia, which leads to a high uncertainty level at an operational level. For this reason, this research assessed the prediction accuracy for chlorine and TTHM concentrations of two black-box models based on the following artificial intelligence techniques: artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS) as a modelling alternative. The simulation results of a hydraulic and water quality analysis of the network in EPANET and its multi-species extension EPANET-MSX were used for training the black-box models. Subsequently, the Threat Ensemble Vulnerability Assessment-Sensor Placement Optimization Tool (TEVA-SPOT) and Evolutionary Polynomial Regression-Multi-Objective Genetic Algorithm (EPR-MOGA-XL) were jointly applied to select the most representative input variables and locations for predicting water quality at other points of the network. ANNs and ANFIS were optimized with a multi-objective approach to reach a compromise between training performance and generalization capacity. The ANFIS models had a higher mean Training and Test Nash–Sutcliffe Index (NSI) in contrast with ANNs. In general, the models had a satisfactory mean prediction performance. However, some of them did not achieve suitable Test NSI values, and the prediction accuracy for different operational statuses was limited.

Trihalomethane Cancer Risk Assessment for Private and Shared Residences: Addressing the Differences in Inhalation Exposure.

The multi-pathway cancer risk (CR) assessment of trihalomethanes (THM) involves considering exposure via ingestion, dermal contact, and inhalation. Inhalation occurs during showering due to the volatilization of THMs from chlorinated water to the air. When assessing inhalation risks, exposure models commonly assume that the initial THM concentration in the shower room is zero. However, this assumption is only valid in private shower rooms where single or infrequent showering events take place. It fails to account for continuous or successive showering events in shared showering facilities. To address this issue, we incorporated the accumulation of THM in the shower room air. We studied a community (population ≈ 20,000) comprising two types of residences with the same water supply: population A with private shower rooms, and population B with communal shower stalls. The total THM concentration in the water was 30.22 ± 14.45 µg L-1. For population A, the total CR was 58.5 × 10-6, including an inhalation risk of 1.11 × 10-6. However, for population B, the accumulation of THM in the shower stall air resulted in increased inhalation risk. By the tenth showering event, the inhalation risk was 2.2 × 10-6, and the equivalent total CR was 59.64 × 10-6. We found that the CR significantly increased with increasing shower duration. Nevertheless, introducing a ventilation rate of 5 L s-1 in the shower stall reduced the inhalation CR from 1.2 × 10-6 to 7.9 × 10-7.

Trihalomethanes in drinking water from three First Nation reserves in Manitoba, Canada.

Previous research indicates that the water distribution system used has a significant impact on the microbial quality of tap water sampled in First Nations reserves in Canada. This study tested tap water from homes in three First Nations reserves to compare the concentrations of four trihalomethanes and related water quality parameters between homes receiving piped water from a water treatment plant (WTP) versus homes equipped with cisterns that are filled by a water truck. Of all the samples collected across time from household taps, 75% of piped samples and 70% of cistern samples had TTHM concentrations exceeding Health Canada's maximum acceptable concentration (MAC) of 100µg L-1 total trihalomethanes (TTHMs) in treated water. In all communities and across sampling times, trichloromethane (CHCl3) was the dominant trihalomethane (42-96%) followed by bromodichloromethane (CHBrCl2) (3-37%) and dibromochloromethane (CHClBr2) (1-18%). Tribromomethane (CHBr3) always accounted for < 5% of TTHMs. Within each of the three First Nations reserves, the water distribution system had no significant effect on TTHM concentration at the household level. Sampling month had a significant effect on TTHM concentration due to temporal changes in dissolved organic carbon of the source water. Results suggest that families in the studied First Nations reserves receive drinking water with high TTHM concentrations and that improvements to the water treatment plant might be the most effective way to minimize trihalomethane formation.

Exposure and carcinogenic risk assessment of trihalomethanes (THMs) for water supply consumers in Addis Ababa, Ethiopia.

Trihalomethanes (THMs), a class of DBPs (disinfection byproducts) that includes chloroform, bromodichloromethane (BDCM), chlorodibromomethane (CDBM), and bromoform. To the best of authors' knowledge, no study has addressed the relationship between the concentration of THMs and lifetime cancer risks (LCR) in drinking water supply system in Addis Ababa, Ethiopia. Therefore, this study aimed to determine the lifetime cancer risks of exposure to THMs in Addis Ababa, Ethiopia. A total of 120 duplicate water samples were collected from 21 sampling points in Addis Ababa, Ethiopia. The THMs were separated by a DB-5 capillary column and detected by an electron capture detector (ECD). Cancer and non-cancer risk assessments were performed. The average total THMs (TTHMs)concentration in Addis Ababa, Ethiopia, was 76.3μg/L. Chloroform was the most dominant THM species identified. The total cancer risk for males was higher than that for females. The average LCR for TTHMs via ingestion in drinking water in this study was unacceptably high risk . An average LCR through dermal routes was also of unacceptably high risk . The LCR by chloroform contributes the highest (72%) of the total risk, followed by BDCM (14%), DBCM (10%) and bromoform (4%). The cancer risk of drinking water due to THMs in Addis Ababa was higher than the level recommended by the USEPA. The total LCR from the targeted THMs was higher via the three exposure routes. Males were at higher THM cancer risk than females. The hazard index (HI) indicated that the dermal route caused higher HI values than the ingestion route. It is essential to apply alternatives to chlorine, i.e., chlorine dioxide (ClO2), ozone and ultraviolet radiation, in Addis Ababa, Ethiopia. The monitoring and regulation of the THMs is required on a regular basis to analyse the trends and guide the water treatment and distribution system. The datasets generated for this analysis are available from the corresponding author upon reasonable request.

Within-day variation and health risk assessment of trihalomethanes (THMs) in a chlorinated indoor swimming pool in China.

Trihalomethanes (THMs) are the most common species of disinfection by-products (DBPs) in swimming pools and have received widespread attention due to their risk to public health. However, studies examining within-day variation and the carcinogenic health risks from exposure to THMs in indoor swimming pools are limited. Our study aimed to detect the within-day variation of four THMs categories and carcinogenic health risk in indoor swimming pool water in Taiyuan, China, and to examine the correlations between THMs and environmental parameters. Our results showed chloroform (TCM) was the most abundant component in THMs with median concentrations from 0.038-0.118μg/m3. TCM and THMs were significantly positively correlated with FCl and significantly negatively correlated with the cumulative number of swimmers (CNS) in the swimming pool. The concentration of total THMs and TCM, lifetime average daily doses (LADD) of TCM, and the total lifetime cancer risks (ELCR) values of THMs declined with time with the highest level occurring at 8:00 am. ELCR values of THMs were in the range of 1.368 × 10-5-1.968 × 10-5, which exceeded the negligible risk level (10-6) defined by US EPA. Our results suggest that THM occurrence and the carcinogenic health risks in pool water varied temporally. Exposure to pool water THMs may pose a carcinogenic risk to human health, especially at the pool's opening time.

Pilot Study of Pollution Characteristics and Ecological Risk of Disinfection Byproducts in Natural Waters in Hong Kong.

Increased disinfection efforts in various parts of China, including Hong Kong, to prevent the spread of the novel coronavirus may lead to elevated concentrations of disinfectants in domestic sewage and surface runoff in Hong Kong, generating large quantities of toxic disinfection byproducts. Our study investigated the presence and distribution of four trihalomethanes (THMs), six haloacetic acids (HAAs), and eight nitrosamines (NAMs) in rivers and seawater in Hong Kong. The concentrations of THMs (mean concentration: 1.6 µg/L [seawater], 3.0 µg/L [river water]), HAAs (mean concentration: 1.4 µg/L [seawater], 1.9 µg/L [river water]), and NAMs (mean concentration: 4.4 ng/L [seawater], 5.6 ng/L [river water]) did not significantly differ between river water and seawater. The total disinfection byproduct content in river water in Hong Kong was similar to that in Wuhan and Beijing (People's Republic of China), and the total THM concentration in seawater was significantly higher than that before the COVID‐19 pandemic. Among the regulated disinfection byproducts, none of the surface water samples exceeded the maximum index values for THM4 (80 μg/L), HAA5 (60 μg/L), and nitrosodimethylamine (100 ng/L) in drinking water. Among the disinfection byproducts detected, bromoform in rivers and seawater poses the highest risk to aquatic organisms, which warrants attention and mitigation efforts. Environ Toxicol Chem 2022;41:2613–2621. © 2022 SETAC

Drinking water sources and water quality in a prospective agricultural cohort.

We describe drinking water sources and water quality for a large agricultural cohort. We used questionnaire data from the Agricultural Health Study (N = 89,655), a cohort of licensed pesticide applicators and their spouses in Iowa (IA) and North Carolina (NC), to ascertain drinking water source at enrollment (1993-1997). For users of public water supplies (PWS), we linked participants' geocoded addresses to contaminant monitoring data [five haloacetic acids (HAA5), total trihalomethanes (TTHM), and nitrate-nitrogen (NO3-N)]. We estimated private well nitrate levels using random forest models accounting for well depth, soil characteristics, nitrogen inputs, and other predictors. We assigned drinking water source for 84% (N = 74,919) of participants. Among these, 69% of IA and 75% of NC participants used private wells; 27% in IA and 21% in NC used PWS. Median PWS nitrate concentrations (NO3-N) were higher in IA [0.9 mg/L, interquartile range (IQR): 0.4-3.1 mg/L] than NC (0.1 mg/L, IQR: 0.1-0.2 mg/L), while median HAA5 and TTHM concentrations were higher in NC (HAA5: 11.9 µg/L, IQR: 5.5-33.4 µg/L; TTHM: 37.7 µg/L, IQR: 10.7-54.7 µg/L) than IA (HAA5: 5.0 µg/L, IQR: 3.7-10.7 µg/L; TTHM: 13.0 µg/L, IQR: 4.2-32.4 µg/L). Private well nitrate concentrations in IA (1.5 mg/L, IQR: 0.8-4.9 mg/L) and NC (1.9 mg/L, IQR: 1.4-2.5 mg/L) were higher than PWS. More private wells in IA (12%) exceeded 10 mg/L NO3-N (regulatory limit for PWS) than NC (<1%). Due to the proximity of their drinking water sources to farms, agricultural communities may be exposed to elevated nitrate levels.

Influence of manganese oxide‐coated granular media on disinfection byproduct formation

AbstractThe objective of this study was to determine the influence of manganese oxide (MnOx) coated granular media on disinfection byproduct (DBP) formation for dissolved manganese (Mn(II)) and natural organic matter (NOM) concentrations typical in drinking water treatment (DWT). Instantaneous and 24‐h haloacetic acid and total trihalomethane concentrations of influent and effluent samples from two DWT plants, one using MnOx‐coated dual media (DM) filters and the other using second‐stage contactors for Mn(II) sorption by coarse MnOx‐coated ceramic media after DM filtration, were examined. Results showed that interaction with MnOx‐coated surfaces did not increase measured DBP concentrations. Observed increases in 24‐h DBP concentrations for the surface water plant were attributed to filter‐associated NOM, and not the MnOx coating. The findings of this study indicate that a second‐stage contactor – with MnOx‐coated media utilized for Mn(II) removal after a particle removal filter – does not increase DBP formation under typical treatment conditions.

Modeling the formation of trihalomethanes in rural and semi-urban drinking water distribution networks of Costa Rica

Chlorination is one of the most important stages in the treatment of drinking water due to its effectiveness in the inactivation of pathogenic organisms. However, the reaction between chlorine and natural organic matter (NOM) generates harmful disinfection by-products (DBPs), such as trihalomethanes (THMs). In this research, drinking water quality data was collected from the distribution networks of 19 rural and semi-urban systems that use water sources as springs, surfaces, and a mixture of both, in three provinces of Costa Rica from April 2018 to September 2019. Twelve models were developed from four data sets: all water sources, spring, surface, and a mixture of spring and surface waters. Linear, logarithmic, and exponential multivariate regression models were developed for each data set to predict the concentration of total trihalomethanes (TTHMs) in the distribution networks. Concentrations of TTHMs were found between < 0.20 and 91.31µg/L, with chloroform being the dominant species accounting for 62% of TTHMs on average. Turbidity, free residual chlorine, total organic carbon (TOC), dissolved organic carbon (DOC), and ultraviolet absorbance at 254nm (UV254) showed a significant correlation with TTHMs. In all the data sets the linear models presented the best goodness-of-fit and were moderately robust. Four models, the best of each data set, were validated with data from the same systems, and, according to the criteria of R2, standard error (SE), mean square error (MSE), and mean absolute error (MAE), spring water and mixed spring/surface water models showed a satisfactory level of explanation of the variability of the data. Moreover, the models seem to better predict TTHM concentrations below 30µg/L. These models were satisfactory and could be useful for decision-making in drinking water supply systems.

Multi-exposure human health risks assessment of trihalomethanes in drinking water of Egypt

The present study aims to assess the probable lifetime cancer and non-cancer risks of exposure to the trihalomethanes in Egypt's drinking water through ingestion, dermal contact, and inhalation. A total of 1667 drinking water samples were collected from twenty-three Egyptian governorates over a three-years period. The concentrations of total trihalomethanes ranged between 29.07 and 86.01 μg/L and were always below the maximum contamination level recommended by the Egyptian standards (100 μg/L). Chloroform was the most prominent trihalomethanes species, while bromoform was rarely detected.The cancer risk study revealed that, among the investigated paths, inhalation poses the greatest risk. And bromodichloromethane had the highest impact to cancer (69%), followed by chlorodibromomethane (28%). Geographically, the highest cancer risk value was found in Matruh governorate (42.2 × 10−6) and the lowest was in Minya governorate (1.0 × 10−6). The cancer risk for the studied governorates, except Minya governorate, was higher than the level recommended by the USEPA (1.0 × 10−6).Hazard index (HI) study revealed that the ingestion pathway caused higher HI values than the dermal pathway and that chloroform had the highest contribution to HI value. However, the values of HI were below unity in all studied governorates demonstrating that there would be negligible non-cancer risk.

Probabilistic approach for health hazard assessment of trihalomethanes through successive showering events.

Trihalomethanes (THMs) are common disinfection by-products in chlorinated tap waters. They can cause various cancers and non-cancer health hazards. Ingestion, dermal contact, and inhalation are the three exposure routes considered in the THM hazard or risk assessments. Among these, inhalation hazard is generally calculated by assuming the initial concentration as zero. This assumption fails to address the case of continuous or successive showers that can happen in shared showering facilities such as student hostels or gymnasiums. In the present study, the leftover THM concentration from the previous bath was considered to assess the chronic daily intakes (CDI) and hazard index (HI) for successive showers. For this, tap water of a university campus was analyzed to understand the extent of THM exposure at consumer points and the result obtained was used for the hazard assessment. Total THM concentrations varied from 0.51 to 68.9µg L-1. To address the variability of the model input parameters, 50,000 iterations of Monte Carlo simulation were carried out. Maximum HI values of 7.94E - 02 ± 3.63E - 02, and 6.69E - 02 ± 3.08E-02 were observed for the 1st shower for females and males, respectively. This value increased exponentially up to the 5th shower and thereafter, the value was constant. The methodology followed in the present study successfully determines the risk and hazard of THMs through successive showers.

Relationship between Blood Trihalomethane Concentrations and Serum Thyroid Function Measures in U.S. Adults.

Toxicological studies show that exposure to disinfection byproducts, including trihalomethanes (THMs), negatively affects thyroid function; however, few epidemiological studies have explored this link. This study included 2233 adults (ages ≥20 years) from the 2007-2008 National Health and Nutrition Examination Survey (NHANES) who were measured for blood THM concentrations [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), or bromoform (TBM)] and serum thyroid function biomarkers [thyroid-stimulating hormone, free thyroxine (FT4), total thyroxine (TT4), free triiodothyronine (FT3), total triiodothyronine (TT3), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb)]. Multivariable linear regression models showed positive associations between blood TCM, BDCM, and total THMs (the sum of all four THMs) concentrations and serum FT4, whereas inverse associations were found between blood DBCM and total brominated THM (Br-THM; the sum of BDCM, DBCM, and TBM) concentrations and serum TT3 (all p < 0.05). Besides, positive associations were observed between blood TCM concentrations and FT4/FT3 ratio, between BDCM, DBCM, and Br-THM concentrations and TT4/TT3 ratio, and between DBCM and Br-THM concentrations and FT3/TT3 ratio (all p < 0.05). Blood THM concentrations were unrelated to the serum levels of thyroid autoantibodies TgAb or TPOAb. In summary, exposure to THMs was associated with altered serum biomarkers of thyroid function but not with thyroid autoimmunity among U.S. adults.

Trihalomethanes in exhaled air, indoor air and water: A parallel design trial in chlorine and ozone-chlorine disinfected swimming pools

We measured the concentrations of Trihalomethanes (THMs), Chloroform (TCM), Bromodichloromethane (BDCM), Dibromochloromethane (DBCM) and Bromoform (TBM), in water, indoor air and exhaled air before and after using chlorine and ozone-chlorine disinfected swimming pools from September 2020 to January 2021. Two parallel panels of adult subjects swam for 60 min in a chlorine and an ozone-chlorine indoor swimming pool. The concentration of total THMs (tTHMs) in water samples of chlorine and ozone-chlorine swimming pools were in the ranges of 170.8–192.5 μg/L and 161.3–180.4 μg/L, respectively which exceeded the WHO guideline value. High levels of THMs were found in indoor air at the height of 10 cm compared to 150 cm above water surface. We found a statistically significant correlation between the concentration of THMs in water and indoor air samples. The results showed that the levels of all detected THMs in participant’ exhaled air after 60 min swimming were 11–13 times higher than those of before exposure. A statistically significant linear correlation was observed between THMs levels in the exhaled air and indoor air at the height of 10 cm above the water surface, but not with the levels at the height of 150 cm. We also found that the levels of THMs in exhaled air were associated with the energy expenditure, swimming distance and time, but not correlated with BMI and skin area.