Seasonal variation in drinking water concentrations of disinfection by-products in IZMIR and associated human health risks

Exposure to haloacetic acid disinfection by-products and male steroid hormones: An epidemiological and in vitro study

Haloacetic acids (HAAs) are ubiquitous in drinking water and have been associated with impaired male reproductive health. However, epidemiological evidence exploring the associations between HAA exposure and reproductive hormones among males is scarce. In the current study, the urinary concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the internal exposure markers of HAAs, as well as sex hormones (testosterone [T], progesterone [P], and estradiol [E2]) were measured among 449 Chinese men. Moreover, in vitro experiments, designed to simulate the real-world scenarios of human exposure, were conducted to assess testosterone synthesis in the Leydig cell line MLTC-1 and testosterone metabolism in the hepatic cell line HepG2 in response to low-dose HAA exposure. The DCAA and TCAA urinary concentrations were found to be positively associated with urinary T, P, and E2 levels (all p < 0.001), but negatively associated with the ratio of urinary T to E2 (p < 0.05). Combined with in vitro experiments, the results suggest that environmentally-relevant doses of HAA stimulate sex hormone synthesis and steroidogenesis pathway gene expression in MLTC-1 cells. In addition, the inhibition of the key gene CYP3A4 involved in the testosterone phase Ⅰ catabolism, and induction of the gene UGT2B15 involved in testosterone phase Ⅱ glucuronide conjugation metabolism along with the ATP-binding cassette (ABC) transport genes (ABCC4 and ABCG2) in HepG2 cells could play a role in elevation of urinary hormone excretion upon low-dose exposure to HAAs. Our novel findings highlight that exposure to HAAs at environmentally-relevant concentrations is associated with increased synthesis and excretion of sex hormones in males, which potentially provides an alternative approach involving urinary hormones for the noninvasive evaluation of male reproductive health following exposure to DBPs.

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

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

Haloacetonitriles adsorption using a low-cost adsorbent derived from canvas fabric

The characteristics of canvas fabric-derived adsorbents and their removal efficiency on five haloacetronitriles (HANs) were investigated. In addition, the effect of chemical activation with ferric chloride (FeCl3) and ferric nitrate (Fe(NO3)3) solutions on HANs removal efficiency was determined. The results indicated that the surface area increased from 262.51 m2/g to 577.25 and 370.83 m2/g, respectively, after being activated with FeCl3 and Fe(NO3)3 solutions. Increases in surface area and pore volume had a direct impact on the effectiveness of HANs removal. As compared to the non-activated adsorbent, the activated adsorbent effectively removed five species of HANs. TCAN was highly removed by the Fe(NO3)3-activated adsorbent (94%) due to the presence of mesoporous pore volume after activation with Fe(NO3)3. On the other hand, MBAN had the lowest removal efficiency of all adsorbents in this study. The activation with FeCl3 and Fe(NO3)3 showed equal removal efficiency for DCAN, BCAN, and DBAN, with percent removal higher than 50%. The hydrophilicity of HANs species affected the removal efficiency. The hydrophilicity order of five HANs species was MBAN, DCAN, BCAN, DBAN, and TCAN, respectively, which well corresponded to the obtained removal efficiency. The canvas fabric-derived adsorbents synthesized in this study were proven to be utilized as low-cost adsorbents to efficiently remove HANs from the environment. Future research will focus on the adsorption mechanism and recycling method to realize the potential for large-scale utilization.

Different levels of arsenic exposure through cooked rice and its associated benefit-risk assessment from rural and urban populations of West Bengal, India: a probabilistic approach with sensitivity analysis

Rice arsenic (As) contamination and its consumption poses a significant health threat to humans. The present study focuses on the contribution of arsenic, micronutrients, and associated benefit-risk assessment through cooked rice from rural (exposed and control) and urban (apparently control) populations. The mean decreased percentages of As from uncooked to cooked rice for exposed (Gaighata), apparently control (Kolkata), and control (Pingla) areas are 73.8, 78.5, and 61.3%, respectively. The margin of exposure through cooked rice (MoE_{cooked rice}) < 1 signifies the existence of health risk for all the studied exposed and control age groups. The respective contributions of iAs (inorganic arsenic) in uncooked and cooked rice are nearly 96.6, 94.7, and 100% and 92.2, 90.2, and 94.2% from exposed, apparently control, and control areas. LCR analysis for the exposed, apparently control, and control populations (adult male: 2.1 × 10^-3, 2.8 × 10^-4, 4.7 × 10^-4; adult female: 1.9 × 10^-3, 2.1 × 10^-4, 4.4 × 10^-4; and children: 5.8 × 10^-4, 4.9 × 10^-5, 1.1 × 10^-4) through cooked rice is higher than the recommended value, i.e., 1 × 10^-6, respectively, whereas HQ > 1 has been observed for all age groups from the exposed area and adult male group from the control area. Adults and children from rural area showed that ingestion rate (IR) and concentration are the respective influencing factors towards cooked rice As, whereas IR is solely responsible for all age groups from urban area. A vital suggestion is to reduce the IR of cooked rice for control population to avoid the As-induced health risks. The average intake (μg/day) of micronutrients is in the order of Zn > Se for all the studied populations and Se intake is lower for the exposed population (53.9) compared to the apparently control (140) and control (208) populations. Benefit-risk assessment supported that the Se-rich values in cooked rice are effective in avoiding the toxic effect and potential risk from the associated metal (As).

Development of an embedded molecular structure-based model for prediction of micropollutant treatability in a drinking water treatment plant by machine learning from three years monitoring data

In this study, an autoencoder-based molecular structure embedding model was developed to predict treatability of micropollutant in a drinking water treatment plant (DWTP) by machine learning using 69 micropollutants monitoring data at 18 DWTPs for three years. The molecular structure, which contains physicochemical characteristics, was embedded as a fixed-length vector that is advantageous for data-driven analysis and machine learning. First, the molecular structure of the micropollutants was converted to a sequence of tokens using the simplified molecular-input line-entry system (SMILES) pair encoding tokenizer, a frequency-based tokenization method. It was then compressed into fixed-length vectors using an autoencoder trained on various molecular structures within the Chemical Entities of Biological Interest. To validate the proposed models, a binary classification of micropollutant treatability was performed using the embedded molecular structure of micropollutants with various external features, such as concentration, season, and the presence of specific drinking water treatment processes by machine learning. The accuracy of the developed model for the 69 micropollutants in this study was 0.86, and the molecular structure was determined to be the most important feature. Furthermore, an accuracy of 0.71 was obtained in external validation for pharmaceuticals and personal care products that were not used for training. This shows that the proposed embedding vector can be generalized to unseen molecules during the training process, which means that it reflects the characteristics of the molecular structures.

The occurrence, formation and transformation of disinfection byproducts in the water distribution system: A review

Disinfection is an effective process to inactivate pathogens in drinking water treatment. However, disinfection byproducts (DBPs) will inevitably form and may cause severe health concerns. Previous research has mainly focused on DBPs formation during the disinfection in water treatment plants. But few studies paid attention to the formation and transformation of DBPs in the water distribution system (WDS). The complex environment in WDS will affect the reaction between residual chlorine and organic matter to form new DBPs. This paper provides an overall review of DBPs formation and transformation in the WDS. Firstly, the occurrence of DBPs in the WDS around the world was cataloged. Secondly, the primary factors affecting the formation of DBPs in WDS have also been summarized, including secondary chlorination, pipe materials, biofilm, deposits and coexisting anions. Secondary chlorination and biofilm increased the concentration of regular DBPs (e.g., trihalomethanes (THMs) and haloacetic acids (HAAs)) in the WDS, while Br^- and I^- increased the formation of brominated DBPs (Br-DBPs) and iodinated DBPs (I-DBPs), respectively. The mechanism of DBPs formation and transformation in the WDS was systematically described. Aromatic DBPs could be directly or indirectly converted to aliphatic DBPs, including ring opening, side chain breaking, chlorination, etc. Finally, the toxicity of drinking water in the WDS caused by DBPs transformation was examined. This review is conducive to improving the knowledge gap about DBPs formation and transformation in WDS to better solve water supply security problems in the future.

Assessing the skin irritation and sensitizing potential of concentrates of water chlorinated in the presence of iodinated X-ray contrast media

Chemical disinfection of water provides significant public health benefits. However, disinfectants like chlorine can react with naturally occurring materials in the water to form disinfection byproducts (DBPs). Natural levels of iodine have been reported to be too low in some source waters to account for the levels of iodinated DBPs detected. Iodinated X-ray contrast media (ICM) have been identified as a potential source of iodine. The toxicological impact of ICM present in source water at the time of disinfection has not been fully investigated. Iopamidol, iohexol, iopromide, and diatrizoate are among the ICM most frequently detected in water. In this study, source water containing one of these four ICM was chlorinated; non-chlorinated ICM-containing water samples served as controls. Reactions were conducted at an ICM concentration of 5 µM and a chlorine dose of 100 µM over 72 hr. Water concentrates (20,000-fold) were prepared by XAD-resin/ethyl acetate extraction and DMSO solvent exchange. We used the MatTek® reconstituted human epithelial skin irritation model to evaluate the water concentrates and also assessed the dermal irritation and sensitization potential of these concentrates using the LLNA:BrdU ELISA in BALB/c mice. None of the water concentrates tested (2500X) resulted in a skin irritant response in the MatTek® skin irritation model. Likewise, none of the concentrates (2500X, 1250X, 625X, 312.5X, 156.25X) produced a skin irritation response in mice: erythema was minimal; the maximum increase in ear thickness was less than 25%. Importantly, none of the concentrates produced a positive threshold response for allergic skin sensitization at any concentration tested in the LLNA:BrdU ELISA. We conclude that concentrates of water disinfected in the presence of four different ICM did not cause significant skin irritation or effects consistent with skin sensitization at the concentrations tested.

Degradation pathways and kinetics of chloroacetonitriles by UV/persulfate in the presence of bromide

Chloroacetonitriles (CANs) are highly toxic nitrogenous disinfection by-products (N-DBPs), which frequently appear in water supply systems and have attracted widespread attention. UV/persulfate (PS) is an effective method to degrade CANs. Bromide (Br^-) is widespread in aquatic environments and reacts with oxidative radicals to produce secondary reactive bromine species (RBS), which affects the degradation of CANs by UV/PS. It was found that the degradation of CANs was highly inhibited by Br^-. The apparent first-order reaction rate constants of monochloroacetonitrile (MCAN), dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCAN) decreased from 2.63 × 10^-3, 2.00 × 10^-3 and 8.66 × 10^-4 s^-1 to 2.58 × 10^-4, 1.61 × 10^-4 and 1.59 × 10^-4 s^-1, respectively after adding 20 μM of Br^-. HO• was the main radicals contributing to the degradation of CANs when the concentration of Br^- was less than 10 μM, compared with SO₄^•- and direct photolysis. When the concentration of Br^- was up to 20 μM, the contributions of RBS accounted for 85.7%, 90.7% and 89.9% of the apparent degradation rate constants of CANs, respectively. During the reaction, about 65% of nitrogen atoms were transformed into NO₃^- by the CC bond cleavage and oxidation. The yields of Cl^- by dechlorination reaction accounted for 83.5%, 71.0% and 41.2% of the chlorine contents in MCAN, DCAN and TCAN, respectively. It was verified that CANs react with free bromine (HOBr) to produce bromochloroacetonitrile (BCAN). DCAN and TCAN are hydrolyzed to produce corresponding haloacetamides (HAMs), which are further reacted with HOBr to produce bromodichloroacetic acid (BDCAA). Furthermore, the generation of bromate was also worth noting via the oxidation of Br^- in the UV/PS system.

Spatial/temporal distribution and multi-pathway cancer risk assessment of trihalomethanes in low TOC and high bromide groundwater

This study aims (1) to determine the seasonal and spatial distribution of THMs formed in chlorinated groundwater containing low levels of organic matter (0.4-0.8 mg L^-1) and low to high levels of bromine (40-380 μg L^-1), and (2) to evaluate the multi-route cancer risks associated with them. The study was conducted in Kayseri (Turkey), where drinking water is supplied from groundwater after chlorination only. THM formation in 50 water samples from 18 storage tanks and 32 distribution points was investigated to evaluate the spatial and temporal changes in THM concentrations for 12 months. The lifetime cancer risk associated with exposure to THMs through multiple pathways (i.e., oral ingestion, dermal absorption, and inhalation) was estimated for males and females. For a 12 month sampling period, the minimum and maximum THM concentrations varied from 2 μg L^-1 to 17 μg L^-1 and from 2 μg L^-1 to 29 μg L^-1 in storage tanks and distribution points, respectively. The ranges of median concentrations of THM were 5 μg L^-1 to 9 μg L^-1 in storage tanks and 5 μg L^-1 to 12 μg L^-1 in distribution points. In all samples dibromochloromethane was the dominant species, followed by bromoform, chloroform, and bromodichloromethane. The average values of total cancer risk associated with exposure to THMs via oral ingestion, dermal absorption, and inhalation for females and males were 1.31 × 10^-5 and 1.25 × 10^-5 in storage tanks, and 1.46 × 10^-5 and 1.39 × 10^-5 in distribution points, respectively. Although THM concentrations were very low, cancer risk values are 1.0 × 10^-6 < CR < 1.0 × 10^-4, which are higher than the negligible risk level (1.0 × 10^-6).

Assessment of C-DBP and N-DBP formation potential and its reduction by MIEX® DOC and MIEX® GOLD resins using fluorescence spectroscopy and parallel factor analysis

This study investigated the applicability of parallel factor analysis (PARAFAC) of fluorescence excitation-emission matrices (EEM) spectra to assess the formation potentials (FP) of carbonaceous and nitrogenous disinfection byproducts (C-DBP and N-DBP) and the FP reduction by the magnetic ion exchange resins, MIEX® DOC and MIEX® GOLD. Two source waters of different nature - a surface water and a secondary treated wastewater effluent - were studied. The samples were analyzed for formation potentials of trihalomethanes (THM4), haloacetonitriles (HAN4), haloketones (HK2), and chloropicrin (CPN). A 4-component PARAFAC model was developed from 150 EEM samples generated from the raw source waters and their treatment with MIEX® resins. Components C1, C2, and C3 corresponded to humic-like dissolved organic matter (DOM) while C4 corresponded to protein-like DOM. Both MIEX® resins preferentially removed components C1, C2, and C3 over C4, indicating affinity with humic materials. MIEX® resins were shown to be more effective to treat surface water than secondary effluent, including effective removal of DBP precursors with extended bed volume treatment. Among all parameters investigated, THM4-FP strongly correlated with humic-like component C3, while HAN4-FP strongly correlated with protein-like component C4 (ρ > 0.89 and p < 0.01); CPN-FP and HK2-FP both correlated with anthropogenic DOM C2 (ρ > 0.89 and p < 0.01). Our results indicate that EEM-PARAFAC was valuable for assessing DBP formation potentials and removal of their precursors by MIEX® resins in different water sources.

Age-sex specific and cause-specific health risk and burden of disease induced by exposure to trihalomethanes (THMs) and haloacetic acids (HAAs) from drinking water: An assessment in four urban communities of Bushehr Province, Iran, 2017

Health risk and burden of disease induced by exposure to trihalomethanes (THMs, four compounds) and haloacetic acids (HAAs, 5 compounds) from drinking water through ingestion, dermal absorption, and inhalation routes were assessed based on one-year water quality monitoring in four urban communities (Bandar Deylam, Borazjan, Bushehr, and Choghadak) of Bushehr Province, Iran. The total average concentrations of THMs and HAAs at all the communities level were determined to be 92.9 ± 43.7 and 70.6 ± 26.5 μg/L, respectively. The dominant components of the THMs and HAAs were determined to be tribromomethane (TBM, 41.6%) and monobromoacetic acid (MBAA, 60.8%), respectively. The average contributions of ingestion, dermal absorption, and inhalation routes in exposure to the chlorination by-products (CBPs) were respectively 65.0, 15.4, and 19.6%. The total average non-carcinogenic risk as the hazard index (HI) and incremental lifetime cancer risk (ILCR) of the CBPs at all the communities level were found to be 4.03 × 10^-1 and 3.16 × 10^-4, respectively. The total attributable deaths, death rate (per 100,000 people), age-weighted disability-adjusted life years (DALYs), and age-weighted DALY rate for all ages both sexes combined at all the communities level were estimated to be 1.0 (uncertainty interval: UI 95% 0.3 to 2.8), 0.27 (0.08-0.75), 30.8 (11.3-100.1), and 8.1 (3.0-26.4), respectively. The average contribution of mortality (years of life lost due to premature mortality: YLLs) in the attributable burden of disease was 94.7% (94.4-95.6). Although in most of cases the average levels of the CBPs were in the permissible range of Iranian standards for drinking water quality, the average values of ILCRs as well as attributable burden of disease were not acceptable (the ILCRs were higher than the boundary limit of 10^-5); therefore, implementation of interventions for reducing exposure to CBPs through drinking water especially in Kowsar Dam Water Treatment Plant is strictly recommended.

Risk associated with increasing bromide in drinking water sources in Yancheng City, China

The bromide concentration in water source (WS) of Yancheng City in China increased unexpectedly due to industrial discharge and saltwater intrusion, which leads to the formation of trihalomethane (THMs) in finished water of water treatment plants (WTP), especially brominated THMs. In Yancheng City, drinking water is supplied by WTP1 and WTP2, primarily sourced by WS1 and WS2, respectively. In this paper, the seasonal variations of bromide in WS1 and WS2 and THMs species in WTP1 and WTP2 were analyzed and compared. The effects of bromide in WS on THMs formation in finished water of WTP in terms of bromine substitution factor (BSF) were simulated by statistical linear model. Although the THMs concentrations in WTP1 were approximate to that in WTP2, the brominated THMs concentrations in WTP1 were higher than that in WTP2 due to higher bromide concentration in WS1 than WS2. The cancer risk analysis indicated that THMs' species of DBCM is the dominant THMs for WTP1 as well as WTP2, which can provide more information for WTPs with higher bromide concentration in water source.

A one-year long survey of temporal disinfection byproducts variations in a consumer's tap and their removals by a point-of-use facility

In order to better understand the occurrence of disinfection byproducts (DBPs) in tap water and their real impacts on consumers, this study made a one-year long survey of the temporal variations of a series of DBPs before and after a point-of-use (POU) treatment facility installed in a building serving for ∼300 people. Water samples were collected every week at a fixed location and time for 1 year, and frequent samplings were carried out every 6 h a day for 1 month at selected seasons, which ultimately amounted to 322 samples. The results show that the concentrations of DBPs were higher in the summer than other seasons, with the lowest DBP levels being observed in spring. Within one week, higher levels of haloacetic acids (HAAs) were identified on weekdays than those on weekends. Diurnally, trihalomethanes, HAAs, and haloacetaldehydes were found to be higher at noon but lower in the evening. Consistent with other studies, the variations of most DBPs were somewhat positively related to the changes of temperature and organic matter, but negatively related to the quantity of free chlorine. With the use of a POU facility, which equips with two activated carbon cartridges and a boiler in sequence, most of DBPs were dramatically reduced, leading to 62-100% lower cytotoxicity for the measured DBPs. The study hence provides a real-water evidence about the DBP occurrences in a typical distribution system endpoint and the efficiency of a typical POU on mitigating DBP risks.

Adsorption of single and mixed haloacetonitriles on silica-based porous materials: Mechanisms and effects of porous structures

Adsorption mechanisms and the role of different porous and crystalline structures on the removal of five haloacetonitriles (HANs) over hexagonal mesoporous silica (HMS), titanium substituted mesoporous silica (Ti-HMS), rod-shaped SBA-15 and microporous zeolite NaY were investigated. In addition, the effect of pH on adsorption mechanism and selective adsorption of five HANs individually and in an equimolar mixed solution were evaluated. The results indicated that the intraparticle diffusion rate constants of the mesoporous adsorbents were higher than that of the microporous NaY. In single solute, the order of adsorption preference (highest to lowest) was mono-HANs > di-HANs > tri-HAN. However, in mixed solute, the large molecular weight of the tri-HAN and di-HANs are more easily adsorbed than the smaller molecular weight mono-HANs. Except for SBA-15, the order of adsorption capacities in mixed HANs solute was not different compared to that observed for the single HAN solute, which might be caused by the higher accessibility to the active sites due to larger pore size. The ion-dipole electrostatic interaction was likely to be the main adsorption mechanism, and was favored at high pH values due to the high negative surface charge density of the adsorbent. The molecular structure of the HANs and hydrophilic/hydrophobic nature affected the adsorption capacities and their selective adsorption from mixed solutes.

Health risk assessment of trihalomethanes in water treatment plants in Jiangsu Province, China

Probabilistic lifetime cancer risks and non-cancer risks of trihalomethanes (THMs) through ingestion, dermal contact, and inhalation exposure in 88 drinking water treatment plants (WTPs) with raw waters from five water systems (WSs) in Jiangsu Province were analyzed and compared. Concentrations of THMs in finished water of study WTPs varied, ranging from 18.81 to 38.96 μg/L, which are lower than the maximum of 80 μg/L recommended by USEPA. The results of health risk assessment indicated that cancer risk as well as non-cancer risks of THMs in WTPs sourced from five water systems decreased in the order of WS3 > WS5 > WS2 > WS1 > WS4. The comparison among multiple exposure routes indicated that when non-boiled drinking water is consumed, ingestion has the highest exposure route, with exposure values greater than dermal contact and inhalation for WTPs with raw water from all five water systems. However, when drinking boiled water, dermal contact is the major risk source for WTPs with raw water from WS1 and WS2, instead of dermal contact, inhalation becomes the major risk source for WTPs with raw water from WS3, WS4, and WS5. In WTPs with raw water from water systems WS1, WS3, WS4, and WS5, dibromochloromethane (DBCM) in THMs has the highest contribution to cancer risk, while chloroform in THMs has the highest contribution to non-cancer risk. However, in WTPs with raw water from water system WS2, bromodichloromethane (BDCM) has the highest contribution to both cancer risk and non-cancer risk. The results also indicated that females are prone to cancer risk induced by THMs since Chinese people are accustomed to drinking boiled water. The results supply valuable information for health departments to put forward more specific and efficient policies to control water borne diseases.

Unregulated disinfection By-products in drinking water in Quebec: A meta analysis

Disinfection by-products (DBPs) are formed primarily by the reaction of natural organic matter and disinfectants. DBPs that are not regulated are referred to as unregulated DBPs (U-DBPs) and they are in majority in total DBPs. U-DBPs can be more toxic than regulated DBPs. U-DBPs such as haloacetonitriles (HANs), haloacetonitriles (HKs) and halonitromethanes (HNMs) are widely present in drinking water supplies in different regions of the world. This study investigated the occurrence of U-DBPs and their variability in drinking water in the Province of Quebec (Canada), using the water quality database of 40 municipal water systems generated by our research group. The concentrations of HANs, HKs, and their compounds, including chloropicrin (CPK), were highly variable in different water systems in Quebec. The concentration range of these U-DBPs is in line with drinking water concentration ranges in different regions of the world. Factors such as system size, water source, season, pH, total organic carbon content, free residual chlorine and disinfectant types cause significant variations in the concentrations of HANs, HKs and their constituent compounds, including CPK, in drinking water in Quebec. This information is valuable for decision making concerning source water selection, water distribution planning, water treatment plant design including disinfection, and overall drinking water quality management related to U-DBPs. Moreover, U-DBPs and regulated DBPs are strongly correlated, although the degree of correlation can vary with water source, system size and season, indicating that regulated DBPs can be used as surrogates of U-DBPs.

Variation and relationship of THMs between tap water and finished water in Yancheng City, China

In this paper, spatial and temporal variations of trihalomethane (THM) concentrations were analyzed including chloroform trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) in Yancheng City in Jiangsu Province, China. The water samples were collected monthly from January 2014 to January 2017 from four tap water sampling sites (S1, S2, S3, and S4) and two finished water sampling sites (WTP1 and WTP2) for THM analysis. The results showed that the mean concentrations during the study period for TCM, BDCM, DBCM, and TBM were 7, 15.9, 21, and 10.4 μg/L in tap water samples and 3.2, 17.2, 22.7, and 10 μg/L in finished water samples, which indicated that brominated THM concentrations were higher than chlorinated THM concentrations. The results of spatial analysis showed that THM concentrations in WTP1 were related to those in S1 and S4 and THM concentrations in WTP2 were related to those in S2 and S3. The concentrations of TCM, BDCM, and TBM have significant spatial variance, while DBCM and THM concentrations do not. The temporal analysis revealed that the highest THM concentration occurred in April, both in tap water and in finished water, which was also shown by temporal cluster analysis. The lowest THM concentration occurred in seasons with relatively lower temperature in all sampling sites. The results provide important information for environmental protection agencies and health care centers with emphasis on months with higher THM risk.

Degradation of dichloroacetonitrile by a UV/peroxymonosulfate process: modeling and optimization based on response surface methodology (RSM)

Response surface methodology (RSM) was utilized to model and optimize the dichloroacetonitrile (DCAN) degradation process by UV/PMS. A quadratic function between DCAN degradation efficiency and three factors including dosage of PMS, UV power and retention time was obtained. The model fitted very well according to high the value of R² (0.9919) and Adj-R² (0.9814). Additionally, the analysis of variance showed the influence of factors on degradation efficiency followed: retention time > UV power > dosage of PMS. Finally, the optimum conditions were suggested under this model. The degradation efficiency reached the maximum value of 96.2% with the optimum conditions: dosage of PMS = 0.2 mM, UV power = 7.95 W, retention time = 80 min.

Response surface methodology (RSM) was utilized to model and optimize the dichloroacetonitrile (DCAN) degradation process by UV/PMS.

Presence and seasonal variation of trihalomethanes (THMs) levels in drinking tap water in Mostaganem Province in northwest Algeria

Background

The use of chlorine to disinfect water, produces various disinfection byproducts such as trihalomethanes (THMs). These compounds are formed when free available chlorine reacts with natural organic matter in raw water during water disinfection. Epidemiologic studies have shown an association between long-term exposure to THMs and an increased risk of cancer, all of them are suspected of having carcinogenic effects.

Aim

The aim of this study was to determine the presence of THMs in the drinking tap water of Mostaganem Province (Algeria) in order to assess the seasonal variation in trihalomethane levels in tap water and to identify the season of high risk to the consumer.

Methods

This analytical study was conducted in Mostaganem Province, Algeria in March, July, September and December 2015. Primarily, we proceeded to collect 30 samples from different areas of Mostaganem Province which were marked with a higher level of residual chlorine for the year 2015; secondly, we utilised the HS-SPME method for determination of trihalomethanes in drinking tap water over a period of four months. For comparison of trihalomethanes values, we used ANOVA.

Results

The results obtained show variability in total THM concentrations from one district to another, with a maximum of 198 μg/l recorded in the Achaacha district during July, but the lowest value 07.84 μg/l is noted at Salamandre city during the same period, noting that these values decrease progressively during the winter period.

Conclusion

Our drinking tap water samples include a large quantity of THMs with different concentrations, where the dibromochloromethane and the bromoform constitute the major portion of THMs.

Assessment, modeling and optimization of parameters affecting the formation of disinfection by-products in water

This study focused on (a) the development of a screening methodology, in order to determine the main experimental variables affecting chlorinated and brominated disinfection by-product (DBP) formation in water during chlorination experiments and (b) the application of a central composite design (CCD) using response surface methodology (RSM) for the mathematical description and optimization of DBP formation. Chlorine dose and total organic carbon (TOC) were proven to be the main factors affecting the formation of total chlorinated DBPs, while chlorine dose and bromide concentration were the main parameters affecting the total brominated THMs. Longer contact time promoted a rise in chlorinated DBPs' concentration even in the presence of a minimal amount of organic matter. A maximum production of chlorinated DBPs was observed under a medium TOC value and it reduced at high TOC concentrations, possibly due to the competitive production of brominated THMs. The highest concentrations of chlorinated THMs were observed at chlorine dose 10 mg L(-1) and TOC 5.5 mg L(-1). The formation of brominated DBPs is possible even with a minimum amount of NaOCl in the presence of high concentration of bromide ions. Brominated DBPs were observed in maximum concentrations using 8 mg L(-1) of chlorine in the presence of 300 μg L(-1) bromides.

Photodegradation of haloacetonitriles in water by vacuum ultraviolet irradiation: Mechanisms and intermediate formation

Photodegradation of haloacetonitriles (HANs), highly carcinogenic nitrogenous disinfection by-products, in water using vacuum ultraviolet (VUV, 185 + 254 nm) in comparison with ultraviolet (UV, only 254 nm) was investigated. Monochloroacetonitrile (MCAN), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), and dibromoacetonitrile (DBAN) were species of HANs studied. The effect of gas purging and intermediate formation under VUV were examined. The results show that the pseudo first order rate constants for the reduction of HANs under VUV were approximately 2-7 times better than UV. The order of degradation efficiency under VUV and UV was MCAN < DCAN < TCAN < DBAN. The degradation efficiencies of individual HANs under VUV were higher than those of mixed HANs, suggesting competitive effects among HANs. Under nitrogen purging, the removal rate constants of mixed HANs was much higher than that of the aerated condition by 34.4, 34.9, 10.1, and 3.8 times for MCAN, DCAN, TCAN, and DBAN, respectively. The major degradation mechanism for HANs was different depending on HANs species. Degradation intermediates of HANs such as 2-chloropropionitrile, 2,2-dimethylpropanenitrile, and fumaronitrile were produced from the substitution, addition, and polymerization reactions. In addition, chlorinated HANs with lower number of chlorine atom including MCAN and DCAN were found as intermediates of DCAN and TCAN degradation, respectively.

Evaluation of genotoxic effects caused by extracts of chlorinated drinking water using a combination of three different bioassays

Potential genotoxic effects of chlorinated drinking water now are of a great concern. In this study, raw water, finished water, and tap water from a water plant in Wuhan, China were collected in two different sampling times of the year (January and July). Genotoxic effects of water extracts were evaluated using a combination of three different bioassays: SOS/umu test, HGPRT gene mutation assay, and micronucleus assay, which were separately used to detect DNA damage, gene mutation, and chromosome aberration. The results of three different bioassays showed that all water samples in January and July induced at least one types of genotoxic effects, of which the DNA-damage effects were all detectable. The levels of DNA-damage effects and gene-mutation effects of finished water and tap water in January were higher than those in July. Chlorination could increase the DNA-damage effects of drinking water in January and the gene-mutation effects of drinking water in both January and July, but did not increase the chromosome-aberration effects of drinking water in both January and July. Our results highlighted the importance of using a combination of different bioassays to evaluate the genotoxicity of water samples in different seasons.

Assessing the human health impacts of exposure to disinfection by-products--a critical review of concepts and methods

Understanding the public health implications of chemical contamination of drinking water is important for societies and their decision-makers. The possible population health impacts associated with exposure to disinfection by-products (DBPs) are of particular interest due to their potential carcinogenicity and their widespread occurrence as a result of treatments employed to control waterborne infectious disease. We searched the literature for studies that have attempted quantitatively to assess population health impacts and health risks associated with exposure to DBPs in drinking water. We summarised and evaluated these assessments in terms of their objectives, methods, treatment of uncertainties, and interpretation and communication of results. In total we identified 40 studies matching our search criteria. The vast majority of studies presented estimates of generic cancer and non-cancer risks based on toxicological data and methods that were designed with regulatory, health-protective purposes in mind, and therefore presented imprecise and biased estimates of health impacts. Many studies insufficiently addressed the numerous challenges to DBP risk assessment, failing to evaluate the evidence for a causal relationship, not appropriately addressing the complex nature of DBP occurrence as a mixture of chemicals, not adequately characterising exposure in space and time, not defining specific health outcomes, not accounting for characteristics of target populations, and not balancing potential risks of DBPs against the health benefits related with drinking water disinfection. Uncertainties were often poorly explained or insufficiently accounted for, and important limitations of data and methods frequently not discussed. Grave conceptual and methodological limitations in study design, as well as erroneous use of available dose-response data, seriously impede the extent to which many of these assessments contribute to understanding the public health implications of exposure to DBPs. In some cases, assessment results may cause unwarranted alarm among the public and potentially lead to poor decisions being made in sourcing, treatment, and provision of drinking water. We recommend that the assessment of public health impacts of DBPs should be viewed as a means of answering real world policy questions relating to drinking water quality, including microbial contaminants; that they should be conducted using the most appropriate and up-to-date data and methods, and that associated uncertainties and limitations should be accounted for using quantitative methods where appropriate.

Spatial and seasonal variability of tap water disinfection by-products within distribution pipe networks

Gradually-changing shocks associated with potable water quality deficiencies are anticipated for urban drinking-water distribution systems (UDWDS). The impact of structural UDWDS features such as, the number of pipe leaking incidences on the formation of water trihalomethanes (THM) at the geocoded household level has never been studied before. The objectives were to: (i) characterize the distribution of water THM concentrations in households from two district-metered areas (DMAs) with contrasting UDWDS characteristics sampled in two seasons (summer and winter), and (ii) assess the within- and between-household, spatial variability of water THM accounting for UDWDS characteristics (household distance from chlorination tank and service pipe leaking incidences). A total of 383 tap water samples were collected from 193 households located in two DMAs within the UDWDS of Nicosia city, Cyprus, and analyzed for the four THM species. The higher intraclass correlation coefficient (ICC) values for water tribromomethane (TBM) (0.75) followed by trichloromethane (0.42) suggested that the two DMAs differed with respect to these analytes. On the other hand, the low ICC values for total THM levels between the two DMAs suggested a large variance between households. The effect of households nested under each DMA remained significant (p<0.05) for TBM (not for the rest of the THM species) in the multivariate mixed-effect models, even after inclusion of pipe network characteristics. Our results could find use by water utilities in overcoming techno-economic difficulties associated with the large spatiotemporal variability of THM, while accounting for the influence of UDWDS features at points of water use.

Mutagenicity and genotoxicity of drinking water in Guelma region, Algeria

In this study, a battery of genotoxicity assays for monitoring drinking water was performed to assess the quality of the water resulting from the treatment plants. Five different types of samples were collected: raw water (P1), treated after pre-chlorination (P2), treated after decantation (P3), treated post-chlorination (P4), and consumers' taps (P5-P12). This study aims to evaluate the formation/occurrence of mutagenic and/or genotoxic compounds in surface drinking waters treated with chlorine disinfectant, during four seasonal experiments: summer, autumn, winter, and spring between 2012 and 2013 by bacterial reverse mutation assay in both Salmonella typhimurium TA98 and TA100 strains with or without metabolic activation system (S9 mix) and Allium cepa root meristematic cells, respectively. All of water samples, except at P1, P2, and P5 in summer; P1 in autumn; and P1 and P3-P12 in spring without S9 mix, and at P1 and P2 in summer and P6 and P8-P12 in spring with S9 mix, were found to be mutagenic in S. typhimurium TA98. However, only P11 and P12 in winter were found to be mutagenic for TA100 without S9 mix. The tested preparations in Allium anaphase-telophase test revealed a significant decrease in mitotic index (MI) and a simultaneous increase in chromosome aberrations (CAs) compared to the control. The bridge, stickiness, vagrant chromosomes, and disturbed chromosome aberrations were observed in anaphase-telophase cells. Physicochemical analysis, trihalomethanes (THMs), romoform (CHBr3), chloroform (CHCl3), bromodichloromethane (CHBrCl2), and dibromochloromethane (CHBr2Cl) levels in water samples were also determined. The results show also that this short-term battery tests are applicable in the routine monitoring of drinking water quality before and after distribution.

The formation potential of haloacetonitriles in the Dez River water, Iran

The formation potential of haloacetonitriles (HANsFP) from chlorination of raw water of the Dez River in Iran was determined. Samples were collected before treatment at an intake of a water treatment plant. Tests were carried out to determine the effect of the reaction time (5-120 h), water pH (4-10), total organic carbon (TOC) content (2-8 mg L(-1)), chlorine dosage (3-25 mg L(-l)), water temperature (5-30 degrees C) and usual coagulants on HANsFP in the Dez River water. Increasing chlorine reaction time up to 80 h led to the remarkable increase in HANsFP and after that the HANsFP was gradually increased. Over 90% of the HANs was formed during 80 h reaction time. Linear relationships were found between the HANsFP and the chlorine dosage. The result showed that the HANsFP increased by increasing TOC content up to 6 mg L(-1), while further increases in the TOC level did not lead to any significant changes in the HANsFP level. The acidic water pH resulted in the highest HANsFP. An increase in water temperature enhanced the HANsFP; this factor should be considered for tropical waterworks. The ferric chloride had a high efficiency for the removal of HANsFP (72%). Overall, the Dez River water had a high potential for forming the HANs (approximately 17 microg L(-1)).

Health risk assessment of exposure to organic matter from the use of reclaimed water in toilets

To estimate the carcinogenic and non-carcinogenic risks of six volatile organic compounds (VOCs) found in reclaimed water used for flushing toilets, a probabilistic health risk assessment based on Monte Carlo simulations was used. Before Monte Carlo simulations, the contaminant volatilization model was applied to estimate the concentration of the pollutants in air. Moreover, a questionnaire was used to acquire daily exposure time and the Batch Fit tool of Crystal Ball software was applied to find the best-fitting distribution of a part of the input parameters. The risk analysis indicated that the health risks from six VOCs were lower than the negligible risk level (1 × 10(-8)) in all cases, and the health risk for females was slightly higher than that for males. Overall, exposure to organic pollutants in reclaimed water during toilet flushing does not currently pose a significant carcinogenic risk to humans. In this study, we want to provide some information on the health risk from reclaimed water used for toilet flushing in China and hope that it will be useful to promote the application of reclaimed water in water-deficient areas.

Probabilistic analysis of risks to US drinking water intakes from 1,4-dioxane in domestic wastewater treatment plant effluents

The risks of 1,4-dioxane (dioxane) concentrations in wastewater treatment plant (WWTP) effluents, receiving primarily domestic wastewater, to downstream drinking water intakes was estimated using distributions of measured dioxane concentrations in effluents from 40 WWTPs and surface water dilution factors of 1323 drinking water intakes across the United States. Effluent samples were spiked with a d8 -1,4-dioxane internal standard in the field immediately after sample collection. Dioxane was extracted with ENVI-CARB-Plus solid phase columns and analyzed by GC/MS/MS, with a limit of quantification of 0.30 μg/L. Measured dioxane concentrations in domestic wastewater effluents ranged from <0.30 to 3.30 μg/L, with a mean concentration of 1.11 ± 0.60 μg/L. Dilution of upstream inputs of effluent were estimated for US drinking water intakes using the iSTREEM model at mean flow conditions, assuming no in-stream loss of dioxane. Dilution factors ranged from 2.6 to 48 113, with a mean of 875. The distributions of dilution factors and dioxane concentration in effluent were then combined using Monte Carlo analysis to estimate dioxane concentrations at drinking water intakes. This analysis showed the probability was negligible (p = 0.0031) that dioxane inputs from upstream WWTPs could result in intake concentrations exceeding the USEPA drinking water advisory concentration of 0.35 μg/L, before any treatment of the water for drinking use.

Occurrence of disinfection by-products in tap water distribution systems and their associated health risk

The concentrations of trihalomethanes (THMs), including chloroform, bromodichloromethane, dibromochloromethane, and bromoform, and haloacetic acids (HAAs; monochloroacetic acid, monobromoacetic acid, dibromoacetic acid, dichloroacetic acid, and trichloroacetic acid) were measured in tap waters passing through water distribution systems of six water treatment plants in Seoul, Korea, and their associated health risks from exposure to THMs through ingestion, dermal contact, and inhalation were estimated using a probabilistic approach. The concentration ranges for total THMs and HAA5 were 3.9-53.5 and <LOD-49.5 μg/L, respectively. Among DBPs, chloroform, bromodichloromethane, dichloroacetic acid, and trichloroacetic acid were the most frequently detected. Spatial and seasonal variations in concentrations of THMs and HAAs in the six water distribution systems were significant (P < 0.001).The mean lifetime cancer risks through ingestion, dermal contact, and inhalation during showering ranged as 7.23-10.06 × 10(-6), 2.19-3.63 × 10(-6), and 5.22-7.35 × 10(-5), respectively. The major exposure route to THMs was inhalation during showering. Sensitivity analysis showed that shower time and shower frequency had a great impact on the lifetime cancer risk by the exposure to THMs in tap water.

Spatio-temporal variability of non-regulated disinfection by-products within a drinking water distribution network

The non-regulated disinfection by-products (NrDBP) targeted in this study include four haloacetonitriles (trichloroacetonitrile (TCAN); dichloroacetonitrile (DCAN); bromochloroacetonitrile (BCAN) and dibromoacetonitrile (DBAN)); one halonitromethane (trichloronitromethane, better known under the name chloropicrin (CPK)); and two haloketones (1,1-dichloro-2-propanone (11DCPone) and 1,1,1-trichloro-2-propanone (111TCPone)). This study provides a detailed picture of the spatial and temporal variability of these NrDBP concentrations throughout a drinking water distribution system located in a region with major seasonal climate variations. The results obtained show that the concentrations of the investigated NrDBPs varied significantly according to time and location. The average concentrations of TCAN, DCAN, CKP and 111TCPone were significantly higher in summer. Surprisingly, the average concentrations of 11DCPone were significantly higher in winter. For BCAN and DBAN, the average concentrations observed in winter were higher, but not in a statistically significant way. On the other hand, the four HANs, CPK and 111TCPone generally had spatial profiles involving an increase of the concentrations along the network according to increasing water residence times, whereas 11DCPone overall had a profile where concentrations increased at the beginning of the network, followed by a drop in the concentrations towards the ends of the network. In spite of certain disparities in the individual spatio-temporal variation profiles, strong correlations were generally observed between NrDBPs, and trihalomethanes (THMs) and haloacetic acids (HAAs). Therefore, THMs and HAAs could be good statistical indicators of the presence of NrDBPs in the drinking water of the system under study.

Comparative cancer risk assessment of THMs in drinking water from well water sources and surface water sources

This research evaluates the lifetime cancer risks from trihalomethanes in Tehran's drinking water. The Trihalomethanes were measured in seven different water districts. Sixty-three samples were taken from tap water across the city for 7 months. The samples were analyzed for trihalomethanes using US EPA method 524.2. The average concentration of total trihalomethanes in different districts were between 0.81 and 9.0 μg/L, and the highest concentrations were detected in district 2 at 19.5 μg/L. Total lifetime cancer risks assessment from exposure to trihalomethanes in drinking water (ingestion, inhalation, and skin routes) were performed for people living in different districts in Tehran. The lifetime cancer risk was 7.19 × 10(-5) in district 2 (a more affluent neighborhood) where mostly surface water sources is used to supply drinking water and 9.38 × 10(-6) in district 7 (a less affluent neighborhood) which is mainly supplied with well water sources. Based on the population data, the total expected lifetime cancer cases from exposure to trihalomethanes are 104, 108, 81, 81, 41, 27, and three for districts 1 through 7, respectively. The average lifetime cancer risk was 4.33 × 10(-5) which means a total of 606 lifetime cancer cases for the entire province of Tehran. The highest risk from THMs seems to be from the inhalation route followed by ingestion and dermal contacts.

Spatial variations of human health risk associated with exposure to chlorination by-products occurring in drinking water

During disinfection, chlorine reacts with organic matter present in drinking water and forms various undesirable chlorinated by-products (CBPs). This paper describes a study of the spatial variability of human health risk (i.e., cancer effects) from CBP exposure through drinking water in a specific region. The region under study involves nine drinking water distribution systems divided into several zones based on their characteristics. The spatial distribution of cancer risk (CR) was estimated using two years of data (2006-2008) on various CBP species. In this analysis, trihalomethanes (THMs) and haloacetic acids (HAAs) served as surrogates for CBPs. Three possible routes of exposure (i.e., via ingestion, inhalation and dermal contact) were considered for each selected compound. The cancer risk assessment involved estimating a unit risk (R(T)) in each zone of the selected distribution systems. A probabilistic analysis based on Monte Carlo simulations was employed. Risk assessment results showed that cancer risk varied between systems, but also within individual systems. As a result, the population of the same region was not exposed to the same risk associated with CBPs in drinking water. Unacceptable levels (i.e., R(T) > 10(-4)) for the estimated CR were determined for several zones in the studied region. This study demonstrates that a spatial-based analysis performed to represent the spatial distribution of risk estimates can be helpful in identifying suitable risk management strategies. Suggestions for improving the risk analysis procedure are also presented.

Seasonal variation effects on the formation of trihalomethane during chlorination of water from Yangtze River and associated cancer risk assessment

For the system of water samples collected from Yangtze River, the effects of seasonal variation and Fe(III) concentrations on the formation and distribution of trihalomethanes (THMs) during chlorination have been investigated. The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA. The results indicated that the average concentration of THMs (100.81 microg/L) in spring was significantly higher than that in other seasons, which was related to the higher bromide ion concentration resulted from the intrusion of tidal saltwater. The total cancer risk in spring reached 8.23 x 10(-5) and 8.86 x 10(-5) for males and females, respectively, which were about two times of those in summer under the experimental conditions. Furthermore, it was found that the presence of Fe(III) resulted in the increased level of THMs and greater cancer risk from exposure to humans. Under weak basic conditions, about 10% of the increment of THMs from the water samples in spring was found in the presence of 0.5 mg/L Fe(III) compared with the situation without Fe(III). More attention should be given to the effect of the coexistence of Fe(III) and bromide ions on the risk assessment of human intake of THMs from drinking water should be paid more attention, especially in the coastland and estuaries.

Formation of disinfection byproducts in typical Chinese drinking water

Eight typical drinking water supplies in China were selected in this study. Both source and tap water were used to investigate the occurrence of chlorinated disinfection byproducts (DBPs), and seasonal variation in the concentrations of trihalomethanes (THMs) of seven water sources was compared. The results showed that the pollution level for source water in China, as shown by DBP formation potential, was low. The most encountered DBPs were chloroform, dichloroacetic acid, trichloroacetic acid, and chlorodibromoacetic acid. The concentration of every THMs and haloacetic acid (HAA) compound was under the limit of standards for drinking water quality. The highest total THMs concentrations were detected in spring.

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

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