Synergistic cytotoxicity of binary combinations of inorganic and organic disinfection byproducts assessed by real-time cell analysis

Chlorine, chlorine dioxide, and ozone are widely used as disinfectants in drinking water treatments. However, the combined use of different disinfectants can result in the formation of various organic and inorganic disinfection byproducts (DBPs). The toxic interactions, including synergism, addition, and antagonism, among the complex DBPs are still unclear. In this study, we established and verified a real-time cell analysis (RTCA) method for cytotoxicity measurement on Chinese hamster ovary (CHO) cell. Using this convenient and accurate method, we assessed the cytotoxicity of a series of binary combinations consisting of one of the 3 inorganic DBPs (chlorite, chlorate, and bromate) and one of the 32 regulated and emerging organic DBPs. The combination index (CI) of each combination was calculated and evaluated by isobolographic analysis to reflect the toxic interactions. The results confirmed the synergistic effect on cytotoxicity in the binary combinations consisting of chlorite and one of the 5 organic DBPs (2 iodinated DBPs (I-DBPs) and 3 brominated DBPs (Br-DBPs)), chlorate and one of the 4 organic DBPs (3 aromatic DBPs and dibromoacetonitrile), and bromate and one of the 3 organic DBPs (2 I-DBPs and dibromoacetic acid). The possible synergism mechanism of organic DBPs on the inorganic ones may be attributed to the influence of organic DBPs on cell membrane and cell antioxidant system. This study revealed the toxic interactions among organic and inorganic DBPs, and emphasized the latent adverse outcomes in the combined use of different disinfectants.     

海水淡化超滤-反渗透工艺沿程溴代消毒副产物变化规律

研究了海水淡化超滤-反渗透(UF-RO)工艺沿程有机物和溴代消毒副产物(Br-DBPs)变化特征.该海水中含有较高浓度的Br-(45.6~50.9 mg·L-1)和较多的芳香类化合物[比紫外吸收值SUVA为3.6~6.0 L·(mg·m)-1];色氨酸类芳香族蛋白质、富里酸类有机物和溶解性微生物代谢产物是海水中主要的荧光特征有机物.UF-RO工艺进水海水经Na Cl O消毒后,DBPs的种类和浓度显著增加,且增加的主要为Br-DBPs,其中三溴甲烷(CHBr3)占总三卤甲烷(THMs)的70.48%~91.50%,二溴乙酸(Br2CHCO2H)占总卤乙酸(HAAs)的81.14%~100%,二溴乙腈(C2HBr2N)占总卤乙腈(HANs)的83.77%~87.45%.UF膜对THMs、HAAs和HANs的去除率分别为36.63%~40.39%、73.83%~95.38%和100%.RO膜可以完全去除HAAs,但是对THMs不能完全去除.进水海水的抗雌激素活性为0.35~0.44 mg·L-1,氯消毒后增加了32%~69%.海水淡化UF-RO系统生成的DBPs和其他生物毒性物质最终被截留到了UF浓水和RO浓水中.     

Occurrence and formation of disinfection by-products in the swimming pool environment: A critical review

Disinfection of water for human use is essential to protect against microbial disease; however, disinfection also leads to formation of disinfection by-products (DBPs), some of which are of health concern. From a chemical perspective, swimming pools are a complex matrix, with continual addition of a wide range of natural and anthropogenic chemicals via filling waters, disinfectant addition, pharmaceuticals and personal care products and human body excretions. Natural organic matter, trace amounts of DBPs and chlorine or chloramines may be introduced by the filling water, which is commonly disinfected distributed drinking water. Chlorine and/or bromine is continually introduced via the addition of chemical disinfectants to the pool. Human body excretions (sweat, urine and saliva) and pharmaceuticals and personal care products (sunscreens, cosmetics, hair products and lotions) are introduced by swimmers. High addition of disinfectant leads to a high formation of DBPs from reaction of some of the chemicals with the disinfectant. Swimming pool air is also of concern as volatile DBPs partition into the air above the pool. The presence of bromine leads to the formation of a wide range of bromo- and bromo/chloro-DBPs, and Br-DBPs are more toxic than their chlorinated analogues. This is particularly important for seawater-filled pools or pools using a bromine-based disinfectant. This review summarises chemical contaminants and DBPs in swimming pool waters, as well as in the air above pools. Factors that have been found to affect DBP formation in pools are discussed. The impact of the swimming pool environment on human health is reviewed.     

Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts

The reclamation and disinfection of waters impacted by human activities (e.g., wastewater effluent discharges) are of growing interest for various applications but has been associated with the formation of toxic nitrogenous disinfection byproducts (N-DBPs). Monochloramine used as an alternative disinfectant to chlorine can be an additional source of nitrogen in the formation of N-DBPs. Individual toxicity assays have been performed on many DBPs, but few studies have been conducted with complex mixtures such as wastewater effluents. In this work, we compared the cytotoxicity and genotoxicity of wastewater effluent organic matter (EfOM) before and after chloramination. The toxicity of chloraminated EfOM was significantly higher than the toxicity of raw EfOM, and the more hydrophobic fraction (HPO) isolated on XAD-8 resin was more toxic than the fraction isolated on XAD-4 resin. More DBPs were also isolated on the XAD-8 resin. N-DBPs (i.e., haloacetonitriles or haloacetamides) were responsible for the majority of the cytotoxicity estimated from DBP concentrations measured in the XAD-8 and XAD-4 fractions (99.4% and 78.5%, respectively). Measured DBPs accounted for minor proportions of total brominated and chlorinated products, which means that many unknown halogenated compounds were formed and can be responsible for a significant part of the toxicity. Other non-halogenated byproducts (e.g., nitrosamines) may contribute to the toxicity of chloraminated effluents as well.     

Formation of regulated and unregulated disinfection byproducts during chlorination and chloramination: Roles of dissolved organic matter type, bromide, and iodide

Algal blooms and wastewater effluents can introduce algal organic matter (AOM) and effluent organic matter (EfOM) into surface waters, respectively. In this study, the impact of bromide and iodide on the formation of halogenated disinfection byproducts (DBPs) during chlorination and chloramination from various types of dissolved organic matter (DOM, e.g., natural organic matter (NOM), AOM, and EfOM) were investigated based on the data collected from literature. In general, higher formation of trihalomethanes (THMs) and haloacetic acids (HAAs) was observed in NOM than AOM and EfOM, indicating high reactivities of phenolic moieties with both chlorine and monochloramine. The formation of haloacetaldehydes (HALs), haloacetonitriles (HANs) and haloacetamides (HAMs) was much lower than THMs and HAAs. Increasing initial bromide concentrations increased the formation of THMs, HAAs, HANs, and HAMs, but not HALs. Bromine substitution factor (BSF) values of DBPs formed in chlorination decreased as specific ultraviolet absorbance (SUVA) increased. AOM favored the formation of iodinated THMs (I-THMs) during chloramination using preformed chloramines and chlorination-chloramination processes. Increasing prechlorination time can reduce the I-THM concentrations because of the conversion of iodide to iodate, but this increased the formation of chlorinated and brominated DBPs. In an analogous way, iodine substitution factor (ISF) values of I-THMs formed in chloramination decreased as SUVA values of DOM increased. Compared to chlorination, the formation of noniodinated DBPs is low in chloramination.     

Disinfection byproduct regulatory compliance surrogates and bromide-associated risk

Natural and anthropogenic factors can alter bromide concentrations in drinking water sources. Increasing source water bromide concentrations increases the formation and alters the speciation of disinfection byproducts (DBPs) formed during drinking water treatment. Brominated DBPs are more toxic than their chlorinated analogs, and thus have a greater impact on human health. However, DBPs are regulated based on the mass sum of DBPs within a given class (e.g., trihalomethanes and haloacetic acids), not based on species-specific risk or extent of bromine incorporation. The regulated surrogate measures are intended to protect against not only the species they directly represent, but also against unregulated DBPs that are not routinely measured. Surrogates that do not incorporate effects of increasing bromide may not adequately capture human health risk associated with drinking water when source water bromide is elevated. The present study analyzes trihalomethanes (THMs), measured as TTHM, with varying source water bromide concentrations, and assesses its correlation with brominated THM, TTHM risk and species-specific THM concentrations and associated risk. Alternative potential surrogates are evaluated to assess their ability to capture THM risk under different source water bromide concentration conditions. The results of the present study indicate that TTHM does not adequately capture risk of the regulated species when source water bromide concentrations are elevated, and thus would also likely be an inadequate surrogate for many unregulated brominated species. Alternative surrogate measures, including THM3 and the bromodichloromethane concentration, are more robust surrogates for species-specific THM risk at varying source water bromide concentrations.     

新型溴代苯酚类消毒副产物的氯化降解机制

最近,13种新型极性卤代苯酚类消毒副产物在氯化消毒后的饮用水中被发现,它们按结构被分成4组,分别是二卤-4-羟基苯甲醛、二卤-4-羟基苯甲酸、二卤水杨酸和三卤苯酚.为研究它们在氯化消毒过程中的降解机制,选取了其中的4种全溴代种类,即3,5-二溴-4-羟基苯甲醛、3,5-二溴-4-羟基苯甲酸、3,5-二溴水杨酸以及2,4,6-三溴苯酚,利用UPLC/ESI-tq MS中的前体离子扫描,多反应监测和子离子扫描,鉴定了这几种消毒副产物在氯化消毒过程中的中间产物以及终产物,并根据这些中间产物和终产物与消毒时间的关系推测了其降解路径.结果表明,除了3,5-二溴水杨酸相对较稳定外,其余3种消毒副产物在氯化消毒过程中不稳定,通过取代、水解以及氧化等过程最终降解为卤乙酸等脂肪族小分子消毒副产物.在降解过程中有许多中间产物被检测并鉴定出来,其中包含一组具有五元环结构的新型消毒副产物(三卤代-羟基环戊烯二酮).     

Carbonaceous and nitrogenous disinfection by-product formation in the surface and ground water treatment plants using Yellow River as water source

This work investigated the formation of carbonaceous and nitrogenous disinfection by-products (C-DBPs, N-DBPs) upon chlorination of water samples collected from a surface water and a ground water treatment plant (SWTP and GWTP) where the conventional treatment processes, i.e., coagulation, sedimentation, and filtration were employed. Twenty DBPs, including four trihalomethanes, nine haloacetic acids, seven N-DBPs (dichloroacetamide, trichloroacetamide, dichloroacetonitrile, trichloroacetonitrile, bromochloroacetonitrile, dibromoacetonitrile and trichloronitromethane), and eight volatile chlorinated compounds (dichloromethane (DCM), 1,2-dichloroethane, tetrachloroethylene, chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene and 1,2,4-trichlorobenzene) were detected in the two WTPs. The concentrations of these contaminants were all below their corresponding maximum contamination levels (MCLs) regulated by the Standards for Drinking Water Quality of China (GB5749-2006) except for DCM (17.1 μg/L detected vs. 20 μg/L MCL). The SWTP had much higher concentrations of DBPs detected in the treated water as well as the DBP formation potentials tested in the filtered water than the GWTP, probably because more precursors (e.g., dissolved organic carbon, dissolved organic nitrogen) were present in the water source of the SWTP.     

加氯消毒过程中纯细菌物质生成消毒副产物研究

按照UFC方法对水体中3种常见细菌Acinetobacter junii、Staphylococcussciuri和Escherichia coli进行纯细菌加氯消毒处理,同时考察水中溴离子对纯细菌物质生成DBPs的影响.结果表明,3种细菌均为DBPs前体物,加氯消毒生成的DBPs除水合三氯乙醛(CHD)外,生成的三卤甲烷(THMs)物质主要为氯仿(TCM),卤乙腈(HANs)物质主要为二氯乙腈(DCAN).氯仿的生成量与细菌物质TOC浓度无明显关系,但HANs和CHD生成量均随细菌TOC浓度增大而增加.其中革兰氏阳性细菌Staphylococcus sciuri生成的DCAN和CHD比革兰氏阴性细菌Acinetobacter junii和Escherichia coli生成的要高,说明细胞壁的化学组分可能是DCAN和CHD生成的影响因素之一.Escherichia coli细菌反应液中溴离子(Br-)存在时,除生成CHD、TCM及DCAN外,THMs和HANs中的溴代种类CHBr3随Br-增多而持续增加,相反TCM持续减少.当Br-浓度为4mg.L-1时,TBM浓度增至最高127.9μg.L-1;HANs和CHD生成量随Br-浓度增加先有所增加,随后持续降低至低于检测限;Br离子存在时THMs为主要DBPs种类.     

Zebrafish embryo toxicity of 15 chlorinated, brominated, and iodinated disinfection by-products

Disinfection to protect human health occurs at drinking water and wastewater facilities through application of non-selective oxidants including chlorine. Oxidants also transform organic material and form disinfection by-products (DBPs), many of which are halogenated and cyto- and genotoxic. Only a handful of assays have been used to compare DBP toxicity, and researchers are unsure which DBP(s) drive the increased cancer risk associated with drinking chlorinated water. The most extensive data set employs an in vitro model cell, Chinese hamster ovary cells. Traditionally, most DBP research focuses on the threat to human health, but the effects on aquatic species exposed to DBPs in wastewater effluents remain ill defined. We present the developmental toxicity for 15 DBPs and a chlorinated wastewater to a model aquatic vertebrate, zebrafish. Mono-halogenated DBPs followed the in vivo toxicity rank order: acetamides > acetic acids > acetonitriles ~ nitrosamines, which agrees well with previously published mammalian in vitro data. Di- and tri-halogenated acetonitriles were more toxic than their mono-halogenated analogues, and bromine- and iodine-substituted DBPs tended to be more toxic than chlorinated analogues. No zebrafish development effects were observed after exposure to undiluted or non-concentrated, chlorinated wastewater. We find zebrafish development to be a viable in vivo alternative or confirmatory assay to mammalian in vitro cell assays.     

Do DBPs swim in salt water pools? Comparison of 60 DBPs formed by electrochemically generated chlorine vs. conventional chlorine

Disinfectants are added to swimming pools to kill harmful pathogens. Although liquid chlorine (sodium hypochlorite) is the most commonly used disinfectant, alternative disinfection techniques like electrochemically generated mixed oxidants or electrochemically generated chlorine, often referred to as salt water pools, are growing in popularity. However, these disinfectants react with natural organic matter and anthropogenic contaminants introduced to the pool water by swimmers to form disinfection byproducts (DBPs). DBPs have been linked to several adverse health effects, such as bladder cancer, adverse birth outcomes, and asthma. In this study, we quantified 60 DBPs using gas chromatography-mass spectrometry and assessed the calculated cytotoxicity and genotoxicity of an indoor community swimming pool before and after switching to a salt water pool with electrochemically generated chlorine. Interestingly, the total DBPs increased by 15% upon implementation of the salt water pool, but the calculated cytotoxicity and genotoxicity decreased by 45% and 15%, respectively. Predominant DBP classes formed were haloacetic acids, with trichloroacetic acid and dichloroacetic acid contributing 57% of the average total DBPs formed. Haloacetonitriles, haloacetic acids, and haloacetaldehydes were the primary drivers of calculated cytotoxicity, and haloacetic acids were the primary driver of calculated genotoxicity. Diiodoacetic acid, a highly toxic iodinated DBP, is reported for the first time in swimming pool water. Bromide impurities in sodium chloride used to electrochemically generate chlorine led to a 73% increase in brominated DBPs, primarily driven by bromochloroacetic acid. This study presents the most extensive DBP study to-date for salt water pools.     

我国地表水中典型DBPs的暴露水平及生态风险

氯消毒过程中可能生成有毒有害的副产物,会对水生态系统和环境健康产生直接和间接的次生危害.三卤甲烷（THMs）和卤乙酸（HAAs）是地表水中检出率最高的消毒副产物（DBPs）,其毒性效应受到广泛关注.本文检索整理了三氯甲烷（TCM）、三溴甲烷（TBM）、二氯乙酸（DCAA）和三氯乙酸（TCAA）在我国地表水暴露浓度和对水生生物的毒性效应浓度,了解我国重点流域地表水环境中TCM、TBM、DCAA和TCAA的浓度水平,分别利用急、慢性毒性数据推导预测无效应浓度（PNEC）,并使用风险商（RQ）和概率生态风险评价法（PERA）对我国重点流域水环境中TCM、TBM、DCAA和TCAA进行多层次生态风险评估.结果表明,我国地表水环境中TCM、TBM、DCAA和TCAA暴露浓度范围为n.d.~51μg/L.以致死和生长、繁殖等为测试终点的急、慢性毒性数据,构建物种敏感度分布（SSD）曲线,推导出TCM、TBM、DCAA和TCAA的PNEC值分别为0.586,0.857,0和44.880mg/L;0.006,0.064,0.956和0.012mg/L.基于急、慢性毒性数据计算出的RQ小于1.我国重点流域中TCM和TCAA对1%的水生生物造成生长、繁殖等慢性毒性影响的概率分别为78.86%和20.61%,存在潜在的生态风险.     

Simultaneous removal of dissolved organic matter and bromide from drinking water source by anion exchange resins for controlling disinfection by-products

Anion exchange resins （AERs） with different properties were evaluated for their ability to remove dissolved organic matter （DOM） and bromide, and to reduce disinfection by-product （DBP） formation potentials of water collected from a eutrophic surface water source in Japan. DOM and bromide were simultaneously removed by all selected AERs in batch adsorption experiments. A polyacrylic magnetic ion exchange resin （MIEX） showed faster dissolved organic carbon （DOC） removal than other AERs because it had the smallest resin bead size. Aromatic DOM fractions with molecular weight larger than 1600 Da and fluorescent organic fractions of fulvic acid- and humic acid-like compounds were efficiently removed by all AERs. Polystyrene AERs were more effective in bromide removal than polyacrylic AERs. This result implied that the properties of AERs, i.e. material and resin size, influenced not only DOM removal but also bromide removal efficiency, MIEX showed significant chlorinated DBP removal because it had the highest DOC removal within 30 rain, whereas polystyrene AERs efficiently removed brominated DBPs, especially brominated trihalomethane species. The results suggested that, depending on source water DOM and bromide concentration, selecting a suitable AER is a key factor in effective control of chlorinated and brominated DBPs in drinking water.     

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.     

南水北调丹江口水库水氯(胺)化消毒副产物产生特性与消毒工艺对比

系统研究了南水北调中线工程水源——丹江口水库水在氯(胺)化消毒条件下,常规消毒副产物的产生特性,考察了消毒方式、消毒剂投加量、接触时间、p H和溴离子浓度等因素的影响,并对消毒工艺参数进行了优化.结果发现,丹江口水库水经氯化消毒可产生三氯甲烷、二氯一溴甲烷等常规含碳和较低浓度二氯乙腈、三氯硝基甲烷等含氮消毒副产物,而氯胺化消毒仅产生三氯甲烷和三氯硝基甲烷等消毒副产物(disinfection by-products,DBPs).自由氯消毒过程产生的各类型DBPs浓度约为氯胺消毒的7.5倍,短时自由氯转氯胺方式DBPs产生量介于两者之间;随着自由氯投加量增加,各类型消毒副产物均呈现增加趋势,投加量大于2 mg·L-1后DBPs增加量较少.随氯胺投加量增加,三氯甲烷生成量变化不大,投加量大于2mg·L-1后可产生三氯硝基甲烷等副产物.随反应时间延长,自由氯的衰减速率明显大于氯胺,同时消毒副产物增长量明显快于氯胺消毒.随着p H升高,自由氯消毒后三卤甲烷含量呈现增加趋势,而氯胺消毒后变化不明显.随溴离子浓度的增加,自由氯和氯胺消毒后副产物类型均向溴代DBPs转变,同时总生成量明显增加,自由氯消毒DBPs增长量明显大于氯胺消毒过程.丹江口水库水采用氯胺化消毒可以降低消毒副产物的生成风险,如采用自由氯消毒方式,水厂需根据实际常规处理工艺重点控制自由氯的投加量等参数.     

含溴黄浦江水消毒过程中溴代三卤甲烷和卤乙酸的生成特性

通过水厂出水DBPs调查和氯化培养实验探讨了黄浦江水中溴离子（Br-）在消毒过程中的迁移及对含溴副产物（溴代三卤甲烷和卤乙酸）生成的影响.结果表明,采用氯胺消毒的水厂出水中约10%的Br-迁移至Br-THMs和Br-HAAs.氯化培养时,在余氯充足的前提下增加Br-浓度,总有机溴（TOBr）和含溴副产物均增加.延长氯化...     

我国典型地区饮水中致突变性表征

报道上海,昆明,哈尔滨、沈阳、广州、武汉和深圳等城市自来水的致突变性特征,以及上述城市自来水厂源水及其氯化源水致突变性的比较研究。发现７城市自来水中均含有移码型直接致突变物。ＴＡ９８菌株是最敏感的监测菌株。另外,按水样比活性和沈集物比活性和沈集物比活性为指标,则上海,昆明,哈尔滨、沈阳、广州和武汉等６城市自来水厂氯化源水对ＴＡ９８和ＴＡ１００２菌株的致突变性均明显地高于源水,上海市尤为突出。该结果     

Characterization of disinfection byproduct formation potential in 13 source waters in China

The formation potential of four trihalomethanes (THMFP) and seven haloacetic acids (HAA7FP) in 13 source waters taken from four major water basin areas in China was evaluated using the simulated distribution system (SDS) chlorination method. The specific ultraviolet absorbance (SUVA254: the ratio of UV254 to dissolved organic carbon (DOC)), which ranged between 0.9 and 5.0 L/(mg m), showed that the organic compounds in di erent source waters exhibited di erent reactivities with chlorine. The HAA7FP of source waters ranged from 20 to 448 g/L and the THMFP ranged from 29 to 259 g/L. The HAA7FP concentrations were higher than the THMFP concentrations in all but one of the samples. Therefore, the risks of haloacetic acids (HAAs) should be of concern in some source waters. TCM (chloroform) and BDCM (bromodichloromethane) were the major THM constituents, while TCAA (trichloroacetic acid) and DCAA (dichloroacetic acid) were the major HAA species. Br-THM (brominated THM species) were much higher than Br- HAA (brominated HAA species), and the formation of Br-DBP (Br-THM and Br-HAA) should be of concern when the bromide concentration is over 100 g/L.     

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water: Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics (FQs) in synthetic marine aquaculture water were subject to sodium hypochlorite (NaClO) disinfection scenario to investigate their reaction kinetics and transformation during chlorination. Reactivity of each FQ to NaClO was following the order of ofloxacin (OFL) > enrofloxacin (ENR) > lomefloxacin (LOM) > ciprofloxacin (CIP) ~ norfloxacin (NOR) >> pipemedic acid (PIP), while flumequine did not exhibit reactivity. The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO, while humic acid was inhibitable to their degradation. The bromide ions promoted degradation of CIP and LOM, but restrained oxidation of OFL and ENR. By analysis of liquid chromatography with tandem mass spectrometry (LC-MS/MS), eight kinds of emerging brominated disinfection byproducts (Br-DBPs) caused by FQ_S were primarily identified in the chlorinated synthetic marine culture water. Through density functional theory calculation, the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms. Their formation involved decarboxylation, ring-opening/closure, dealkylation and halogenation. Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position. The piperazine ring containing tertiary amine was comparatively stable, while this moiety with a secondary amine structure would break down during chlorination. Additionally, logK_ow and logBAF of transformation products were calculated by EPI-Suite^TM to analyze their bioaccumulation. The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.     

The impact of iodinated X-ray contrast agents on formation and toxicity of disinfection by-products in drinking water

The presence of iodinated X-ray contrast media (ICM) in source waters is of high concern to public health because of their potential to generate highly toxic disinfection by-products (DBPs). The objective of this study was to determine the impact of ICM in source waters and the type of disinfectant on the overall toxicity of DBP mixtures and to determine which ICM and reaction conditions give rise to toxic by-products. Source waters collected from Akron, OH were treated with five different ICMs, including iopamidol, iopromide, iohexol, diatrizoate and iomeprol, with or without chlorine or chloramine disinfection. The reaction product mixtures were concentrated with XAD resins and the mammalian cell cytotoxicity and genotoxicity of the reaction mixture concentrates was measured. Water containing iopamidol generated an enhanced level of mammalian cell cytotoxicity and genotoxicity after disinfection. While chlorine disinfection with iopamidol resulted in the highest cytotoxicity overall, the relative iopamidol-mediated increase in toxicity was greater when chloramine was used as the disinfectant compared with chlorine. Four other ICMs (iopromide, iohexol, diatrizoate, and iomeprol) expressed some cytotoxicity over the control without any disinfection, and induced higher cytotoxicity when chlorinated. Only iohexol enhanced genotoxicity compared to the chlorinated source water.