Tribromomethane Research Articles

Sunlight enhanced the formation of tribromomethane from benzotriazole degradation during the sunlight/free chlorine treatment in the presence of bromide

The coexistence of free chlorine and bromide under sunlight irradiation (sunlight/FC with Br−) is unavoidable in outdoor seawater swimming pools, and the formation of brominated disinfection byproducts could act more harmful than chlorinated disinfection byproducts. In this study, benzotriazole was selected as a model compound to investigate the degradation rate and the subsequent formation of disinfection byproducts via sunlight/FC with Br− process. The rate constants for the degradation of benzotriazole under pseudo first order conditions in sunlight/FC with Br− and sunlight/FC are 2.3 ± 0.07 × 10−1 min−1 and 6.0 ± 0.7 × 10−2 min−1, respectively. The enhanced degradation of benzotriazole can be ascribed to the generation of HO•, bromine species, and reactive halogen species (RHS) during sunlight/FC with Br−. Despite the fact that sunlight/FC with Br− process enhanced benzotriazole degradation, the reaction results in increasing tribromomethane (TBM) formation. A high concentration (37.8 μg/L) of TBM was detected in the sunlight/FC with Br−, which was due to the reaction of RHS. The degradation of benzotriazole was notably influenced by the pH value (pH 4 − 11), the concentration of bromide (0 − 2 mM), and free chlorine (1 − 6 mg/L). Furthermore, the concentration of TBM increased when the free chlorine concentrations increased, implying the formation potential of harmful TBM in chlorinated seawater swimming pools.

Degradation of prometryn during UV/persulfate process: Kinetics and disinfection by-product formation

Prometryn is one of the commonly used triazine herbicides and is also widely used for algae removal in aquaculture. This study investigated the degradation kinetics of prometryn via UV/persulfate (PS) oxidation and confirmed its adherence to pseudo-first-order kinetics, with a calculated rate constant (kobs) of 0.2358 min−1. The impact of PS concentration, water matrix (including background ions of Cl− and Br− and natural organic matter (NOM)), and solution pH on prometryn degradation were assessed. Results indicated an increase in prometryn degradation with raising concentrations of PS, Cl−, and Br−, especially evident at a PS concentration of 400 μm where complete degradation was achieved. Conversely, degradation decreased with increasing NOM concentration and pH. Radical scavenging experiments affirmed the promotion of prometryn degradation in UV/PS by both HO• and SO4−•, with SO4−• contributing over 70 % of the total free radical contribution. Evaluation of disinfection by-product (DBP) formation revealed trichloromethane (TCM) as the predominant DBP in non‑bromine water and tribromomethane (TBM) in bromine water. Thus, this study offers a theoretical foundation for UV/PS degradation of triazine herbicides in aqueous environments. The obtained results hold significance for controlling DBPs in subsequent water treatment processes, ensuring the provision of safe drinking water to the public and meeting the sustainable development goal 6.

Phytotoxicity of trihalomethanes and trichloroacetic acid on Vigna radiata and Allium cepa plant models.

Disinfection by-products (DBPs) are a concern due to their presence in chlorinated wastewater, sewage treatment plant discharge, and surface water, and their potential for environmental toxicity. Despite some attention to their ecotoxicity, little is known about the phytotoxicity of DBPs. This study aimed to evaluate the individual and combined phytotoxicity of four trihalomethanes (THMs: trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM) and their mixture (THM4)), and trichloroacetic acid (TCAA) using genotoxic and cytotoxic assays. The analysis included seed germinationtests using Vigna radiata and root growthtests, mitosis studies, oxidative stress response, chromosomal aberrations (CA), and DNA laddering using Allium cepa. The results showed a progressive increase in root growth inhibition for both plant species as the concentration of DBPs increased. High concentrations of mixtures of four THMs resulted in significant (p < 0.05) antagonistic interactions. The effective concentration (EC50) value for V. radiata was 5655, 3145, 2690, 1465, 3570, and 725 mg/L for TCM, BDCM, DBCM, TBM, THM4, and TCAA, respectively. For A. cepa, the EC50 for the same contaminants was 700, 400, 350, 250, 450, and 105 mg/L, respectively. DBP cytotoxicity was observed through CAs, including C-metaphase, unseparated anaphase, lagging chromosome, sticky metaphase, and bridging. Mitotic depression (MD) increased with dose, reaching up to 54.4% for TCAA (50-500 mg/L). The electrophoresis assay showed DNA fragmentation and shearing, suggesting genotoxicity for some DBPs. The order of phytotoxicity for the tested DBPs was TCAA > TBM > DBCM > BDCM > THM4 > TCM. These findings underscore the need for further research on the phytotoxicity of DBPs, especially given their common use in agricultural practices such as irrigation and the use of sludge as manure.

Applied gradient boosting decision tree algorithms for accurate prediction of trihalomethanes: A case study in dual-sources drinking water distribution system in metropolitan

The complex hydraulic environment in dual-source drinking water distribution system (DWDS) in metropolitan puts water safety in an unknown situation, which requires systematic water quality monitoring and controlling to reduce the water risk during water distribution process. Given that, this study conducted a one-year sampling of trihalomethanes (THMs) and identified the hydraulic junction area in a real dual-source DWDS. For efficient prediction of THMs, several predictive frameworks were established via mechanistic algorithms and machine learning (ML). The results indicated that Gradient Boosting Decision Tree (GBDT) algorithm achieved higher interpretability and generalizability in describing the relationship between various of features with R2 reaching 0.903, 0.908, 0.945 and 0.959 for trichloromethane (TCM), bromodichloromethane (BDCM), dibromomonochloromethane (DBCM) and tribromomethane (TBM), respectively. Shapley additive explanations (SHAP) analysis of GBDT models further identified water temperature, residual chlorine, water supply distance, and pH were key features affecting THMs formation in practical DWDS. Furthermore, the spatio-temporal distribution of THMs was simulated by GBDT models and identified the region might be exposed to high risk of the THMs. The simulation results indicated that the DBCM and TBM were more likely to form in the region nearly to DWTP-X, whereas in the region nearly to DWTP-Y, the TCM and BDCM were the dominant THMs species due to differences in raw water characteristics. Undoubtedly, this study provided novel insights into utilizing ML models to predict THMs levels in dual-source DWDS in the metropolitan.

Photodegradation of halogenated organic disinfection by-products: Decomposition and reformation

In this study, the photodegradation of 33 different DBPs (trihalomethanes, haloacetic acids, haloacetaldehydes, and haloacetonitriles) and TOX with low pressure UV light and the subsequent reformation of DBPs with chlorine and monochloramine were investigated. Results indicated that photodegradation followed the order of TOI > TOBr > TOCl, and treated surface water with low SUVA254 background did not impact the photodegradation of highly UV susceptible DBPs such as triiodomethane (TIM), diiodobromomethane (DIBM), tribromomethane (TBM). The mass balance results of chloride, bromide and iodide showed that the main photodegradation mechanism of TOBr and TOI was dehalogenation supported by halide releases (i.e., Cl−, Br− and/or I− ion). In addition, the photodegradation removal effect was higher, when brominated DBPs formation was high. Although low pressure UV light effectively removed halogenated organic DBPs, subsequent use of disinfectants (Cl2 and NH2Cl) reformed photodegraded DBPs, and the overall DBPs concentrations were increased, which suggested that the released Br− and I− ions will reform DBPs in distribution systems, with oxidants present or added (e.g., booster chlorination) in distribution systems. This study showed that although UV photodegradation will reduce halogenated organic DBPs in distribution systems, especially more toxic iodinated and brominated DBPs, it will be a more effective technology towards the end of the distribution system or a point of entry solution rather than in distribution system with post-disinfection and residence time.

Formation and estimated toxicity of trihalomethanes and haloacetic acids from chlorination of nonylphenol-containing water: Effect of chlorine and bromide concentration, contact time, and pH

The presence of nonylphenol (NP), an endocrine-disrupting chemical (EDC), in water sources can form toxic chlorination disinfection by-products (DBPs) during the water disinfection process using chlorine. This study investigated the formation of trihalomethanes-4 (THM4) and haloacetic acids-5 (HAA5) as regulated DBPs during the chlorination process of NP-containing water. The effects of chlorine dose, bromide concentration, pH, chlorine contact time, and the presence of NP in real natural water on THM4 and HAA5 formation were investigated. The increase of chlorine dose increased all of the THM4 and HAA5 formation especially chlorinated DBPs (Cl-DBPs), including trichloromethane (TCM) (0.140 %) and dichloroacetic acid (DCAA) (0.722 %) when the chlorine concentration was 5 times higher than NP. However, the increase of bromide concentration increased the formation of brominated DBPs (Br-DBPs), reaching concentration yields of 1.615 % for tribromomethane (TBM) and 0.421 % for dibromoacetic acid (DBAA), but decreased the chlorinated (Cl-DBPs formation). Similarly, the increase of chlorine contact time and pH increased the DBPs formation significantly especially Br-DBPs. The TBM and DBAA concentration yields reached 1.615 % and 0.676 %, respectively, when chlorinated at pH 9 and reached 0.653 % and 0.751 %, respectively, when chlorinated for 168 h. The addition of NP in natural water also raised the hydrophilicity of dissolved organic matter (DOM), indicated by the decrease of specific ultraviolet absorbance (SUVA) value, which enhanced the formation of certain species including THM4 and HAA5. Based on toxicity calculation, the regulated DBPs formed were cytotoxic rather than genotoxic.

Using UV–Vis differential absorbance spectra of tropical peat water DOM fraction to determine trihalomethanes formation potential and its estimated cytotoxicity

Absorbance differential spectra could be utilized to identify dissolved organic matter (DOM) characteristics such as the disinfection by products (DBPs) formation. This research purposed to establish the relationship between absorbance differential spectra and trihalomethanes-4 (THM4) formation potential, as well as the estimated cytotoxicity of tropical peat water DOM percentage. The ion exchange resin was used to separate the DOM components from peat water. In addition, the UV–Vis spectrum was examined between 200 and 700 nm. The hydrophobic-acid (HPOA) fraction contains the highest concentration of dissolved organic carbon (DOC), THM4 production potential, and calculated cytotoxicity. On the other hand, the hydrophilic-neutral (HPIN) fraction has the lowest potential THM4 production. The UV–Vis absorbance spectra of all DOM fractions showed a comparable peak at 277 nm. The differential spectra of 277 nm (ΔA277) indicated a significant association with DOC concentration (99.6 %), trichloromethane (TCM) creation (86.6 %), total-THM4 (TTHM4) (81.3 %) formation, THM4 estimated cytotoxicity (89.7 %), and a moderate correlation with bromodichloromethane (BDCM) formation (55.6 %). Meanwhile, ΔA277 had a poor correlation with brominated THM4 formation potential (chlorodibromomethane (CDBM): 2.59, tribromomethane (TBM): 2.78 %). The absorbance differential spectra might be employed as a surrogate measure for the peat water DOM fraction and its precursor properties to form THM4 during the chlorination process, as well as its estimated cytotoxicity.

Removal assessment of disinfection by-products (DBPs) from drinking water supplies by solar heterogeneous photocatalysis: A case study of trihalomethanes (THMs)

Solar heterogeneous photocatalysis was used to remove trihalomethanes (THMs) from drinking water. THMs, mainly trichloromethane (TCM), tribromomethane (TBM), bromodichloromethane (BDCM) and dibromochloromethane (DBCM) are one of the main class of disinfection by-products (DBPs). THMs were determined by HSGC-MS with detection limits (LODs) ranging from 0.5 μg L−1 to 0.9 μg L−1 for TCM and BDCM, respectively. Results show that a great proportion of THMs present in water are finally transferred to air as a result of their high volatility in the order TCM > BDCM > DBCM > TBM. The use of band-gap semiconductor materials (TiO2 and mainly ZnO) used as photocatalysts in combination with Na2S2O8 as electron acceptor and sulfate radical anion (SO4•-) generator enhanced the photooxidation of all THMs as compared to photolytic test. The time required for 50% of THMs to disappear (DT50) from water calculated for the most effective treatment (ZnO/Na2S2O8) were 12, 42, 57 and 61 min for TCM, TBM, BDCM, and DBCM, respectively. Therefore, solar heterogeneous photocatalysis can be considered as an interesting strategy for THMs removal, especially in sunny areas like Mediterranean basin.

Association of blood trihalomethane concentrations with asthma in US adolescents: nationally representative cross-sectional study.

BackgroundPopulation studies show that the use of swimming pools is associated with the risk of asthma and allergic diseases among children. Our objective was to explore the associations between blood trihalomethane (THM) concentrations and asthma among US adolescents, and assess to what extent the association is modified by active tobacco smoke exposure.MethodsWe included 2359 adolescents aged 12–19 years with measured blood concentrations of chloroform (trichloromethane (TCM)), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (tribromomethane (TBM)) from the National Health and Nutrition Examination Survey 2005–2012. Logistic regression models were fitted to assess the odds ratios for the association of blood THM concentrations (three or four categories) with the risk of self-reported current and ever (lifetime) asthma.ResultsBlood DBCM concentrations were associated with a higher risk of ever asthma among all adolescents (OR 1.54 (95% CI 1.07–2.21), comparing the extreme exposure categories). The relationship was stronger among adolescents exposed to tobacco smoke (OR 3.96 (95% CI 1.89–8.30), comparing the extreme exposure categories). We also found positive relationships between blood brominated THM concentrations (sum of BDCM, DBCM and TBM) and risk of ever asthma and between blood DBCM and brominated THM concentrations and risk of current asthma among adolescents with tobacco smoke exposure. The relative excess risk of ever asthma due to the interaction between high blood DBCM and brominated THM concentrations and tobacco smoke exposure was 1.87 (95% CI 0.30–3.43) and 0.78 (95% CI 0.07–1.49), respectively.ConclusionsExposure to THMs is associated with a higher risk of asthma in adolescents, particularly among those exposed to tobacco smoke.

Mechanistic insight for DBP induced growth inhibition in Vigna radiata via oxidative stress and DNA damage

Chlorination is important to the safeness of recouped water; though it shows concern about disinfection by-products (DBPs) formation and its toxic effects. DBPs generation mostly specified by category of disinfectant utilized and naturally occurring organic matter present in the water pre and post disinfection. Plants are exposed to diverse stresses of environment across their lifespan. Reactive oxygen species (ROS) perform significant roles in preserving ordinary plant growth and enhancing their tolerance towards stress. This study is focused on the generation and elimination of ROS in apical meristematic growth and responses in Vigna radiata towards DBPs exposure. Phytotoxic and genotoxic effect of selected DBPs, TCAA (trichloroacetic acid), TCM (trichloromethane), TBM (tribromomethane) revealed concentration-dependent root length inhibition, germination index, vigour index, tolerance index, root/shoot ratio with higher EC50 value for TCM (6000 mg/L, 50.26 mM) over TCAA and TBM (1850 mg/L, 11.32 mM; 4000 mg/L, 15.83 mM). DNA laddering assay demonstrated DBP induced DNA damage to be concentration-dependent too. The concentration-dependent increase in the lipid peroxidation, H2O2 generation for each DBPs examined with highest oxidative stress for TCAA over TBM and TCM at fixed concentration illustrates that possible mechanism behind observed toxicity may be via ROS. Its regulation by antioxidative defense enzymes activities can be attributed to observed decline in these enzymes (catalase, ascorbate peroxidase, guaiacol peroxidase) activities with increasing concentration again where TCAA found more significantly affected than TBM and TCM over control. Results thus provide a useful understanding of the mechanism of DBP induced phytotoxicity and genotoxicity in V.radiata.

Distribution Characteristics of Disinfection By-Products and the Effects of Booster Chlorination in Long-Distance Water Supply Systems

It is difficult for waterworks that add chlorine into finished water once to maintain sufficient residual chlorine at unfavorable points of the pipe network that supply water for large areas of coverage. Therefore, booster chlorination was employed for a long-distance water distribution system. The study was performed in H City with a water supply system serving about 400 km2 of downtown and rural areas. The purpose of this work is to obtain the distribution characteristics of disinfection by-products (DBPs) in the booster chlorination disinfection pipe network through uniformly distributed sampling analysis. The results showed that detected DBPs include trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and tribromomethane (TBM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), dichloroacetonitrile (DCAN), bromochloroacetonitrile (BCAN), and trichloronitromethane (TCNM). The concentrations of the regulated DBPs were found to be lower than the standard limits specified in the Sanitary Standard for Drinking Water (GB5749-2006). Before booster chlorination, the average concentrations of the DBPs mentioned (expressed as mean±deviation) were (8.08±3.34), (9.77±2.91), (7.38±4.82), (2.65±2.02), (2.95±3.26), (6.02±6.06), (3.13±2.48), (1.61±2.05), and (0.15±0.10) μg·L-1, while afterwards, they were increased to (10.30±4.55), (11.73±3.60), (8.23±5.22), (2.95±2.45), (3.29±3.60), (8.15±7.58), (3.31±2.61), (1.33±2.04), and (0.12±0.06) μg·L-1, respectively. Trihalomethanes (THMs) and haloacetic acids (HAAs) increased by 6.32%-26.60% and 5.32%-42.71%, respectively, after booster chlorination. In addition, raw water quality and seasonal changes had a certain impact on the occurrence of DBPs. The levels of DBPs in summer were generally higher than those in spring or autumn. According to the analysis of DBP formation potential of source water, finished water, and tap water, it was found that the risk of DBPs exceeding the standard limit may exist in the water supply system of H City; therefore, further optimization of the treatment process should be considered to ensure water quality.

Experimental and simulation investigations of UV/persulfate treatment in presence of bromide: Effects on degradation kinetics, formation of brominated disinfection byproducts and bromate

Bromide (Br−), which is omnipresent in water bodies, can not only affect the degradation kinetics of target pollutants but may also form undesired byproducts (such as bromate (BrO3-) and brominated disinfection byproducts (Br-DBPs)) through sulfate radical (SO4∙-)-based advanced oxidation processes (AOPs). This study found that Br− significantly suppressed the degradation of diethyl phthalate (DEP) based on the ultraviolet (UV)/persulfate (PS) treatment and was efficiently converted into reactive species (radicals and free bromine) by the SO4∙- or hydroxyl radical (HO) generated in the UV/PS system. These reactive bromine species could, in turn, brominate the phenolic degradation intermediates of DEP as well as natural organic matter (NOM), yielding Br-DBPs, including tribromomethane (TBM), which was observed when Br−, DEP and/or NOM coexisted in this UV/PS system. However, the Br-DBPs were a short-lived form of bromine during the transformation of Br– and were degraded by the excessive oxidants (e.g., SO4∙- and HO). Instead, Br− was eventually transformed into BrO3-, with free bromine acting as the requisite intermediate. The BrO3- formation initially showed a delay before increasing monotonically. In general, raising the PS dosage and the initial Br− concentrations enhanced both the maximum concentration of TBM and the formation of BrO3-, while increasing the amounts of DEP and NOM facilitated the former and inhibited the latter. The maximum concentration of TBM increased while the formation of BrO3- was suppressed with increasing pH from 5.0 to 8.0. In addition, through simulating the steady-state concentration of radicals, it was found that the contribution of bromine atom radical (Br) towards oxidizing free bromine to BrO3- was far greater than those of SO4∙- and HO. The findings demonstrate the potential negative effects of Br− on SO4∙--based AOPs, which need to be considered when this technology is applied in practice.

Comparing three Australian natural organic matter isolates to the Suwannee river standard: Reactivity, disinfection by-product yield, and removal by drinking water treatments

Water treatments that provide efficient removal of organic and inorganic disinfection by-product (DBP) precursors across variable natural organic matter (NOM) sources are desirable. Treatments that effectively remove inorganic DBP precursors such as bromide, which significantly shift the speciation of DBP formation towards more toxic DBPs, are of particular interest and have been less investigated.This study characterised NOM isolated from three major drinking water sources in Southeast Queensland (SEQ), Australia, and compared it to the International Humic Substances Society (IHSS) Suwannee River NOM isolate (SR) in terms of DBP precursor removal treatments and DBP formation. Each NOM isolate was used to make synthetic water samples with otherwise identical water quality parameters, that were treated with enhanced coagulation (EC) or EC followed by; anion exchange (MIEX® resin), powdered activated carbon (PAC), granular activated carbon (GAC) or silver impregnated activated carbon (SIAC), to investigate the removal of DBP precursors (bromide and DOC), minimisation of DBPs, as well as the change in specific chlorine demand. EC/SIAC treatment was the most effective method of DBP control studied, due to the efficient simultaneous NOM and bromide adsorption of the SIAC (99 ± 1% bromide removal regardless of NOM source). This treatment also resulted in >92% removal of each of the measured DBPs across all NOM sources, with the exception of DBAN and 1,1-DCP, which achieved >80% removal across all NOM sources. Increases in tribromomethane (TBM) and dibromoacetonitrile (DBAN) formation were observed after all other treatment/NOM-isolate combinations, due to increased Br:DOC ratio after treatment, whereas chlorinated DBPs were generally well-controlled by all treatment/NOM-isolate combinations. Differences in reactivity of the individual NOM isolates were found to be related to both the origin of the isolate and the treatment employed, however, bromide removal capacity for each treatment was independent of NOM source.

Trihalomethane yields from twelve aromatic halogenated disinfection byproducts during chlor(am)ination

As the first identified category of disinfection byproducts (DBPs), trihalomethanes (THMs) have received continuous attention. Previous studies have demonstrated that the transformation of aromatic halogenated DBPs during chlor (am)ination resulted in the formation of THMs, which may occur in both water treatment plants and drinking water distribution systems. In this study, THM yields from aromatic chlorinated/brominated DBPs during chlorination and aromatic iodinated DBPs during chloramination were investigated. The trichloromethane (TCM) yields from 3,5-dichloro-4-hydroxybenzaldehyde, 3,5-dichlorosalicylic acid, 2,6-dichloro-4-nitrophenol, and 2,4,6-trichlorophenol were in the range of 0–11.4%, 0–8.4%, 0–6.4%, and 0–17.8%, respectively. The THM4 (TCM, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM)) yields from 3,5-dibromo-4-hydroxybenzaldehyde, 3,5-dibromosalicylic acid, 2,6-dibromo-4-nitrophenol, and 2,4,6-tribromophenol were in the range of 0–12.9%, 0–27.0%, 0–8.6%, and 0–29.4%, respectively. The TCM and triiodomethane (TIM) yields from 3,5-diiodo-4-hydroxybenzaldehyde, 3,5-diiodosalicylic acid, 2,6-diiodo-4-nitrophenol, and 2,4,6-triiodophenol were in the range of 0–5.2%, 0–7.0%, 0–2.2%, and 0–10.6%, respectively. After 72 h, TCM yields from aromatic chlorinated DBPs were generally higher than that from their brominated analogues; TBM yields from aromatic brominated DBPs were significantly lower than TCM yields, BDCM yields, and DBCM yields; and among aromatic halogenated DBPs, 2,4,6-trihalophenol had the highest THM yields while 2,6-dihalo-4-nitrophenol had the lowest THM yields. Moreover, the results revealed that alkaline conditions and higher temperatures favored the THM yields from the twelve aromatic halogenated DBPs during chlor (am)ination, and chlorine/monochloramine dose affected the yields and speciation of THMs from the aromatic halogenated DBPs.

Environmental risk appraisement of disinfection by-products (DBPs) in plant model system: Allium cepa.

The organic toxicants formed in chlorinated water cause potential harm to human beings, and it is extensively concentrated all over the world. Various disinfection by-products (DBPs) occur in chlorinated water are genotoxic and carcinogenic. The toxicity is major concern for chlorinated DBPs which has been present more in potable water. The purpose of the work was to evaluate genotoxic properties of DBPs in Allium cepa as a plant model system. The chromosomal aberration and DNA laddering assays were performed to examine the genotoxic effect of trichloroacetic acid (TCAA), trichloromethane (TCM), and tribromomethane (TBM) in a plant system with distinct concentrations, using ethyl methanesulfonate (EMS) as positive control and tap water as negative control. In Allium cepa root growth inhibition test, the inhibition was concentration dependent, and EC50 values for trichloroacetic acid (TCAA), trichloromethane (TCM), and tribromomethane (TBM) were 100mg/L, 160mg/L, and 120mg/L respectively. In the chromosome aberration assay, root tip cells were investigated after 120h exposure. The bridge formation, sticky chromosomes, vagrant chromosomes, fragmented chromosome, c-anaphase, and multipolarity chromosomal aberrations were seen in anaphase-telophase cells. It was noticed that with enhanced concentrations of DBPs, the total chromosomal aberrations were more frequent. The DNA damage was analyzed in roots of Allium cepa exposed with DBPs (TCAA, TCM, TBM) by DNA laddering. The biochemical assays such as lipid peroxidation, H2O2 content, ascorbate peroxidase, guaiacol peroxidase, and catalase were concentration dependent. The DNA interaction studies were performed to examine binding mode of TCAA, TCM, and TBM with DNAs. The DNA interaction was evaluated by spectrophotometric and spectrofluorometric studies which revealed that TCAA, TCM, and TBM might interact with Calf thymus DNA (CT- DNA) by non-traditional intercalation manner.

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 10.4μg/L in tap water samples and 3.2, 17.2, 22.7, and 10μg/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.

Validation of a robust LLE-GC-MS method for determination of trihalomethanes in environmental samples.

An analytical liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS) method was developed and validated for the determination of trihalomethanes (THMs) in environmental samples. The compounds studied were trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM). The calibration curves for the THMs showed high linearity in the range of 1-1000μgL-1. Studies of intra-day and inter-day precision, limit of detection (LOD), limit of quantification (LOQ), accuracy, and recovery were performed with low (10μgL-1), medium (40μgL-1), and high (200μgL-1) concentrations of THMs. The intra-day and inter-day precision RSD varied in the ranges of 0.17-6.95% and 0.26-15.70%, respectively. No statistical differences were observed between the analysis of the concentration of certified reference materials (CRM 4M8140-U) and the values reported by CRM, indicating the good accuracy of the proposed method. The recovery was 88.75-119.21%. The LOD and LOQ were smaller than 0.13 and 0.40μgL-1. Compared with reported LLE-GC-MS methods, the validated method had similar LOD and enhanced LOQ, precision, accuracy, and recovery. Also, the method is robust, selective to THMs, and the total time for the extraction and GC separation of THMs is about 18min. The method was useful for detecting and quantifying low concentrations of TCM (40-80μgL-1) formed by water chlorination in the presence of Microcystis aeruginosa cyanobacteria, thus demonstrating its applicability for monitoring THMs in real samples.

Chlorine decay and trihalomethane formation following ferrate(VI) preoxidation and chlorination of drinking water

This paper presents the effect of preoxidation with ferrate(VI) (FeVIO42−, Fe(VI)) prior to chlorination on chlorine decay and formation of disinfection by-products in filtered raw water from a full-scale drinking water treatment plant. The rate of chlorine decay became significantly faster as the concentration of ferrate(VI) increased. Chlorine degradation followed two first-order decay reactions with rate constants k1 and k2 for fast and slow decay, respectively. Kinetic modeling established the relationships between k1 and k2 and varying dosages of chlorine and ferrate(VI). When ferrate(VI) was used as a pre-oxidant, the levels of trihalomethanes (trichloromethane (TCM), dichlorobromomethane (DCBM), dibromochloromethane (DBCM), and tribromomethane (TBM)) in water samples decreased as the ferrate(VI) concentration increased. The concentrations of these trihalomethanes followed the order TCM > DCBM ≈ DBCM > TBM.

Composition profiles, levels, distributions and ecological risk assessments of trihalomethanes in surface water from a typical estuary of Bohai Bay, China

To characterize the spatiotemporal distribution and potential ecological risk for trihalomethanes (THMs) in the surface water of a river estuary, surface water samples were collected over five consecutive months (from March to July 2016) from four sites in the Haihe River estuary of Bohai Bay. The potential ecological risks of THMs were evaluated quantitatively based on a species sensitivity distribution (SSD) model. The results demonstrate that trichloromethane (TCM) was the predominant THM in surface water of the Haihe River estuary (2.93±1.98μg/L) followed by tribromomethane (TBM) (0.42±0.33μg/L), bromodichloromethane (BDCM) (0.14±0.06μg/L) and dibromochloromethane (DBCM) (0.09±0.10μg/L). The concentration of TCM was higher in summer than that in spring, while TBM displayed the opposite trend. The TCM concentration decreased from the estuary to the adjacent sea. However, the levels of TBM and DBCM in the adjacent sea were higher than those in the estuary. The ecological risks of THMs in surface water of Haihe River were notably low, and the ecological risks of THMs in freshwater were generally higher than those in seawater. Compared with other contaminants in water and surface sediment from rivers and coastal areas, the ecological risk levels of THMs in surface water can be considered low. This study is a contribution to the progress of ecological risk assessment of THMs.

Association between exposures to brominated trihalomethanes, hepatic injury and type II diabetes mellitus

Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder in the Western world, commonly diagnosed in the majority of obese patients with type 2 diabetes mellitus (T2DM). Metabolic disrupting chemicals with short half-lives, such as those of halogenated structure (trihalomethanes, THM) have been linked with hepatic insulin resistance phenomena in animal studies. However, human studies evaluating the role of THM exposure on liver pathogenesis and T2DM disease process are scarce. The objectives of this study were to: i) determine the association of urinary brominated THM (BrTHM) levels and T2DM disease status, and ii) investigate the association between urinary BrTHM levels and serum alanine aminotransferase (ALT) concentrations, often used as surrogate markers of NAFLD. A pilot case–control study was conducted in Nicosia, Cyprus (n=95). Cases were physician-diagnosed T2DM patients and controls were healthy individuals. Liver enzymes, leptin and TNF-α were measured in sera, while urinary THM levels were measured using tandem mass spectrometry. Diabetics had higher levels of serum leptin, body mass index and ALT than the controls. Among all study participants those with serum ALT levels above the median (17IU/L) had higher mean tribromomethane (TBM) concentrations compared to those with serum ALT below 17IU/L. A significant increase in the odds of having above the median serum ALT levels [OR 6.38, 95% CI: 1.11, 42.84 (p=0.044)] was observed for each unit increase in creatinine-unadjusted urinary TBM levels, along with BMI and past smoking, after adjusting for possible confounders, such as urinary creatinine, age, sex, and leptin; no other THM compound showed a significant association with serum ALT. Logistic regression models for T2DM using the urinary BrTHM as exposure variables did not reach the predetermined level of significance. The interplay between exposures to BrTHM and the initiation of key pathophysiological events relating to hepatic injury (ALT) and inflammation (leptin) was recognized via the use of selected biomarkers of effect. Our evidence that THM could act as hepatic toxins with a further initiation of diabetogenic effects call for additional studies to help us better understand the disease process of the two co-morbidities (NAFLD and T2DM).