ArticleLiterature Review

Occurrence, Genotoxicity, and Carcinogenicity of Regulated and Emerging Disinfection By-Products in Drinking Water: A Review and Roadmap for Research

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Abstract

Disinfection by-products (DBPs) are formed when disinfectants (chlorine, ozone, chlorine dioxide, or chloramines) react with naturally occurring organic matter, anthropogenic contaminants, bromide, and iodide during the production of drinking water. Here we review 30 years of research on the occurrence, genotoxicity, and carcinogenicity of 85 DBPs, 11 of which are currently regulated by the U.S., and 74 of which are considered emerging DBPs due to their moderate occurrence levels and/or toxicological properties. These 74 include halonitromethanes, iodo-acids and other unregulated halo-acids, iodo-trihalomethanes (THMs), and other unregulated halomethanes, halofuranones (MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] and brominated MX DBPs), haloamides, haloacetonitriles, tribromopyrrole, aldehydes, and N-nitrosodimethylamine (NDMA) and other nitrosamines. Alternative disinfection practices result in drinking water from which extracted organic material is less mutagenic than extracts of chlorinated water. However, the levels of many emerging DBPs are increased by alternative disinfectants (primarily ozone or chloramines) compared to chlorination, and many emerging DBPs are more genotoxic than some of the regulated DBPs. Our analysis identified three categories of DBPs of particular interest. Category 1 contains eight DBPs with some or all of the toxicologic characteristics of human carcinogens: four regulated (bromodichloromethane, dichloroacetic acid, dibromoacetic acid, and bromate) and four unregulated DBPs (formaldehyde, acetaldehyde, MX, and NDMA). Categories 2 and 3 contain 43 emerging DBPs that are present at moderate levels (sub- to low-mug/L): category 2 contains 29 of these that are genotoxic (including chloral hydrate and chloroacetaldehyde, which are also a rodent carcinogens); category 3 contains the remaining 14 for which little or no toxicological data are available. In general, the brominated DBPs are both more genotoxic and carcinogenic than are chlorinated compounds, and iodinated DBPs were the most genotoxic of all but have not been tested for carcinogenicity. There were toxicological data gaps for even some of the 11 regulated DBPs, as well as for most of the 74 emerging DBPs. A systematic assessment of DBPs for genotoxicity has been performed for approximately 60 DBPs for DNA damage in mammalian cells and 16 for mutagenicity in Salmonella. A recent epidemiologic study found that much of the risk for bladder cancer associated with drinking water was associated with three factors: THM levels, showering/bathing/swimming (i.e., dermal/inhalation exposure), and genotype (having the GSTT1-1 gene). This finding, along with mechanistic studies, highlights the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer. More than 50% of the total organic halogen (TOX) formed by chlorination and more than 50% of the assimilable organic carbon (AOC) formed by ozonation has not been identified chemically. The potential interactions among the 600 identified DBPs in the complex mixture of drinking water to which we are exposed by various routes is not reflected in any of the toxicology studies of individual DBPs. The categories of DBPs described here, the identified data gaps, and the emerging role of dermal/inhalation exposure provide guidance for drinking water and public health research.

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... Trihalomethanes (THMs), the most common of the DBPs, were first discovered in the 1970s, 3 and hundreds of DBP species have since been identified. 4 The types of by-products formed when water is treated depend on many factors, including the specific disinfection processes used (e.g., chlorination, ozonation, chloramination, use of chlorine dioxide), levels of naturally occurring organic material and anthropogenic compounds, and other characteristics of the raw water such as temperature, pH, and bromide concentration. 4 Brominated compounds are formed when bromide levels in the source water are high, and reports from water utilities have suggested increasing levels of brominated THMs in the United States. ...
... 4 The types of by-products formed when water is treated depend on many factors, including the specific disinfection processes used (e.g., chlorination, ozonation, chloramination, use of chlorine dioxide), levels of naturally occurring organic material and anthropogenic compounds, and other characteristics of the raw water such as temperature, pH, and bromide concentration. 4 Brominated compounds are formed when bromide levels in the source water are high, and reports from water utilities have suggested increasing levels of brominated THMs in the United States. 5 Three chemical classes of DBPs are regulated in the United States: total THMs (TTHMs) (chloroform, bromoform, bromodichloromethane, and chlorodibromomethane), haloacetic acids (HAAs), and oxyhalides; 6 the European Union regulates bromate and TTHMs. ...
... 12 As reviewed by Richardson et al. although ingestion is important route of exposure, for some volatile chemicals, inhalation or dermal absorption may also be important. 4 Brominated THMs have been shown to be mutagenic when activated by glutathione S-transferase theta 1 (GSTT1), in contrast to chloroform, which is not activated to a mutagen. 4 Early epidemiologic studies suggested that exposure to chlorinated drinking water was related to bladder cancer risk, 13 an association that was confirmed in later studies, including the most recent meta-analysis. ...
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Background: By-products are formed when disinfectants react with organic matter in source water. The most common class of disinfection by-products, trihalomethanes (THMs), have been linked to bladder cancer. Several studies have shown exposure-response associations with THMs in drinking water and bladder cancer risk. Few epidemiologic studies have evaluated gene-environment interactions for total THMs (TTHMs) with known bladder cancer susceptibility variants. Objectives: In this study, we investigated the combined effect on bladder cancer risk contributed by TTHMs, bladder cancer susceptibility variants identified through genome-wide association studies, and variants in several candidate genes. Methods: We analyzed data from two large case-control studies-the New England Bladder Cancer Study (n/n=989 cases/1,162 controls), a population-based study, and the Spanish Bladder Cancer Study (n/n=706 cases/772 controls), a hospital-based study. Because of differences in exposure distributions and metrics, we estimated effects of THMs and genetic variants within each study separately using adjusted logistic regression models to calculate odds ratios (ORs) and 95% confidence intervals (CI) with and without interaction terms, and then combined the results using meta-analysis. Results: Of the 16 loci showing strong evidence of association with bladder cancer, rs907611 at 11p15.5 [leukocyte-specific protein 1 (LSP1 region)] showed the strongest associations in the highest exposure category in each study, with evidence of interaction in both studies and in meta-analysis. In the highest exposure category, we observed OR=1.66 (95% CI: 1.17, 2.34, p-trend=0.005) for those with the rs907611-GG genotype and p-interaction=0.02. No other genetic variants tested showed consistent evidence of interaction. Discussion: We found novel suggestive evidence for a multiplicative interaction between a putative bladder carcinogen, TTHMs, and genotypes of rs907611. Given the ubiquitous exposure to THMs, further work is needed to replicate and extend this finding and to understand potential molecular mechanisms. https://doi.org/10.1289/EHP9895.
... Water disinfection is a necessary public health intervention to prevent waterborne infections. However, unintended disinfection by-products (DBPs) are formed during chemical disinfection processes [1]. DBPs occur in complex mixtures, and their relative concentrations depend on the characteristics of organic matter in the raw water, the treatment and disinfectant used, and the length and condition of the distribution system [2][3][4]. ...
... We aimed to provide insights to estimate exposure to a wide range of DBPs in drinking water in Barcelona (Spain), by (1) describing occurrence in tap and bottled water; (2) developing statistical models to predict non-regulated DBPs based on routinely monitored parameters in the public water supply; (3) evaluating the effect of domestic filters on tap water concentrations; and (4) exploring the use of DBPs in urine as biomarkers of exposure though drinking water. Findings are potentially applicable for exposure assessment in epidemiological studies to evaluate health effects associated with non-regulated DBPs. ...
... Moreover, our results of high brominated DBPs and THM concentrations are consistent with previous studies that found higher bromide concentrations in water to cause the formation of mainly brominated THMs and reduced formation of HAAs [30]. These results are of high importance, because brominated DBPs are reportedly more cytotoxic and genotoxic than chlorinated species and therefore there is a need to minimize the formation of brominated DBPs [1]. The median THM (42 µg/L) and HAA (18 µg/L) levels in this study compared to a study conducted in 2010 (median THM = 85 µg/L, median HAA∼35 µg/L, respectively) suggest that concentrations of these two DBP classes halved in Barcelona [29]. ...
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Background Knowledge about human exposure and health effects associated with non-routinely monitored disinfection by-products (DBPs) in drinking water is sparse. Objective To provide insights to estimate exposure to regulated and non-regulated DBPs in drinking water. Methods We collected tap water from homes (N = 42), bottled water (N = 10), filtered tap water with domestic activated carbon jars (N = 6) and reverse osmosis (N = 5), and urine (N = 39) samples of participants from Barcelona, Spain. We analyzed 11 haloacetic acids (HAAs), 4 trihalomethanes (THMs), 4 haloacetonitriles (HANs), 2 haloketones, chlorate, chlorite, and trichloronitromethane in water and HAAs in urine samples. Personal information on water intake and socio-demographics was ascertained in the study population (N = 39) through questionnaires. Statistical models were developed based on THMs as explanatory variables using multivariate linear regression and machine learning techniques to predict non-regulated DBPs. Results Chlorate, THMs, HAAs, and HANs were quantified in 98–100% tap water samples with median concentration of 214, 42, 18, and 3.2 μg/L, respectively. Multivariate linear regression models had similar or higher goodness of fit (R2) compared to machine learning models. Multivariate linear models for dichloro-, trichloro-, and bromodichloroacetic acid, dichloroacetonitrile, bromochloroacetonitrile, dibromoacetonitrile, trichloropropnanone, and chlorite showed good predictive ability (R² = 0.8–0.9) as 80–90% of total variance could be explained by THM concentrations. Activated carbon filters reduced DBP concentrations to a variable extent (27–80%), and reverse osmosis reduced DBP concentrations ≥98%. Only chlorate was detected in bottled water samples (N = 3), with median = 13.0 µg/L. Creatinine-adjusted trichloroacetic acid was the most frequently detected HAA in urine samples (69.2%), and moderately correlated with estimated drinking water intake (r = 0.48). Significance Findings provide valuable insights for DBP exposure assessment in epidemiological studies. Validation of predictive models in a larger number of samples and replication in different settings is warranted. Impact statement Our study focused on assessing and describing the occurrence of several classes of DBPs in drinking water and developing exposure models of good predictive ability for non-regulated DBPs.
... 1,13 The EPA drinking water maximum contaminant level (MCL) for nitrate (10 mg/L NO 3 -N) was set to protect against infant methemoglobinemia, an acute condition, 14 but other adverse health effects have been observed at exposure below this level. 1 DBPs, including haloacetic acids (HAAs), trihalomethanes (THMs), and oxyhalides (bromate and chlorite), are formed in drinking water supplies due to use of chlorine and other disinfectants (ozone, chlorine dioxide, chloramines, etc.), which react with organic compounds in the water to form DBPs. 2,15 Exposure can occur through ingestion, inhalation, or dermal absorption. Although more than 700 DBPs are known, only HAAs, THMs, and oxyhalides are currently regulated by the US EPA. ...
... Although more than 700 DBPs are known, only HAAs, THMs, and oxyhalides are currently regulated by the US EPA. 2,15 Epidemiologic studies have linked elevated exposure to DBPs with bladder and colorectal cancers, though evidence is strongest for bladder cancer. 2,15,16 The Agricultural Health Study (AHS) is a prospective cohort that enrolled pesticide applicators and their spouses in North Carolina (NC) and Iowa (IA), with the goal of assessing health risks associated with pesticide and other agricultural exposures. ...
... 2,15 Epidemiologic studies have linked elevated exposure to DBPs with bladder and colorectal cancers, though evidence is strongest for bladder cancer. 2,15,16 The Agricultural Health Study (AHS) is a prospective cohort that enrolled pesticide applicators and their spouses in North Carolina (NC) and Iowa (IA), with the goal of assessing health risks associated with pesticide and other agricultural exposures. 17 The AHS is unique in that most of the participants live on farms and rely on private wells for their drinking water. ...
Article
We describe drinking water sources and water quality for a large agricultural cohort. We used questionnaire data from the Agricultural Health Study (N = 89,655), a cohort of licensed pesticide applicators and their spouses in Iowa (IA) and North Carolina (NC), to ascertain drinking water source at enrollment (1993–1997). For users of public water supplies (PWS), we linked participants’ geocoded addresses to contaminant monitoring data [five haloacetic acids (HAA5), total trihalomethanes (TTHM), and nitrate-nitrogen (NO3-N)]. We estimated private well nitrate levels using random forest models accounting for well depth, soil characteristics, nitrogen inputs, and other predictors. We assigned drinking water source for 84% (N = 74,919) of participants. Among these, 69% of IA and 75% of NC participants used private wells; 27% in IA and 21% in NC used PWS. Median PWS nitrate concentrations (NO3-N) were higher in IA [0.9 mg/L, interquartile range (IQR): 0.4–3.1 mg/L] than NC (0.1 mg/L, IQR: 0.1–0.2 mg/L), while median HAA5 and TTHM concentrations were higher in NC (HAA5: 11.9 µg/L, IQR: 5.5–33.4 µg/L; TTHM: 37.7 µg/L, IQR: 10.7–54.7 µg/L) than IA (HAA5: 5.0 µg/L, IQR: 3.7–10.7 µg/L; TTHM: 13.0 µg/L, IQR: 4.2–32.4 µg/L). Private well nitrate concentrations in IA (1.5 mg/L, IQR: 0.8–4.9 mg/L) and NC (1.9 mg/L, IQR: 1.4–2.5 mg/L) were higher than PWS. More private wells in IA (12%) exceeded 10 mg/L NO3-N (regulatory limit for PWS) than NC (<1%). Due to the proximity of their drinking water sources to farms, agricultural communities may be exposed to elevated nitrate levels.
... As an outstanding public health achievement, disinfection has been an essential process in drinking water treatment plants with the aim of preventing waterborne diseases (Richardson et al., 2007;Li and Mitch, 2018;Kali et al., 2021). However, the reactions between disinfectants (e.g., chlorine) and natural organic matter (NOM) can give rise to the formation of undesired disinfection byproducts (DBPs) (Gallard and von Gunten, 2002;Deborde and von Gunten, 2008;Hu et al., 2020;Richardson and Kimura, 2020). ...
... In previous epidemiological studies, drinking water DBPs have been verified their association to some health concerns, such as bladder cancer and spontaneous abortion (Nieuwenhuijsen et al., 2000;Villanueva et al., 2007;Yang et al., 2019b), thus they have received considerable attention over the past several decades. Over 700 halogenated DBP species have been identified to this day (Richardson et al., 2007;Shah and Mitch, 2012;Dong et al., 2019;Yang et al., 2019a;Liu et al., 2020), but they accounted for only 30-50% of the total organic halogen (TOX) in chlorinated drinking water (Krasner et al., 2006;Hua and Reckhow, 2007), and the DBPs responsible for chlorination-related health risks remain veiled to a large extent. Hence, pinpointing new drinking water DBPs, especially toxicitydrivers, is deemed an important research topic for safeguarding drinking water. ...
... As summarized in Table S7, HHBNs showed higher cytotoxicity than regulated THMs, HAAs, and bromate (the cytotoxicity of chlorite has not been reported yet) and lower cytotoxicity than HANs in CHO cells. It should be noted that the regulated DBPs and HANs practically showed significantly higher concentrations (μg/L level) in drinking water than HHBNs (ng/L level) (Richardson et al., 2007;Li et al., 2021). ...
Article
Halogenated aromatic disinfection byproducts (DBPs) exhibited similar total organic halogen levels in chlorinated drinking water samples as compared with aliphatic ones, and they predominantly accounted for the overall toxicity of the samples. Among the reported halogenated aromatic DBPs, halonitrophenols (HNPs) have received particular attention in recent years due to the relatively high risk in drinking water. In this study, a new group of halogenated aromatic DBPs were detected and then proposed to be halohydroxybenzonitriles (HHBNs) by employing the ultra-performance liquid chromatography/tandem mass spectrometers. Thereafter, the specific HHBN species in drinking water were theoretically speculated and then thoroughly identified with standard compounds. Their occurrence in drinking water was investigated, their cytotoxicity was evaluated, and their stability in the presence of chlorine was assessed. Seven newly identified HHBNs, including 3,5-dichloro-4-hydroxybenzonitrile, 3,5-dichloro-2-hydroxybenzonitrile, 5-bromo-3-chloro-4-hydroxybenzonitrile, 5-bromo-3-chloro-2-hydroxybenzonitrile, 3,5-dibromo-4-hydroxybenzonitrile, 3,5-dibromo-2-hydroxybenzonitrile, and 3,5-diiodo-4-hydroxybenzonitrile, showed 100% detection frequency in the collected drinking water samples with concentrations up to 36 ng/L. HHBNs exhibited significantly higher cytotoxicity in Chinese hamster ovary cells than regulated DBPs (e.g., trihalomethanes and haloacetic acids), which might be contributed by their cellular uptake efficiency and nucleophilicity. The seven HHBNs were proved to undergo transformation during chlorination following pseudo-first-order decay with half-lives in the range of 9–63 h. More importantly, in comparison to HNPs, which showed relatively high toxicity and strong stability among the halogenated aromatic DBPs, HHBNs presented comparable concentration-cytotoxicity contribution (50%) and slightly weaker stability (43%), suggesting that HHBNs should be a new group of DBPs of concern in drinking water.
... Disinfection is an essential process for drinking water supplies in order to prevent waterborne diseases (Postigo et al. 2018). An unintended consequence of disinfection processes (e.g., chlorination, chlorine dioxide, chloramination, ozonation, UV, and UV/H 2 O 2 ) is the formation of disinfection by-products (DBPs), many of which are potentially toxic and are known as the possible or probable human carcinogens (Richardson et al. 2007;USEPA 2019). As of now, 100 + DBPs were characterized while 600 + others can be formed in the supply water (Richardson et al. 2007; Richardson and Postigo 2012;Richardson and Kimura 2016). ...
... An unintended consequence of disinfection processes (e.g., chlorination, chlorine dioxide, chloramination, ozonation, UV, and UV/H 2 O 2 ) is the formation of disinfection by-products (DBPs), many of which are potentially toxic and are known as the possible or probable human carcinogens (Richardson et al. 2007;USEPA 2019). As of now, 100 + DBPs were characterized while 600 + others can be formed in the supply water (Richardson et al. 2007; Richardson and Postigo 2012;Richardson and Kimura 2016). Among the chlorinated and ozone-chlorinated systems, the unknown DBPs were reported to be in the range of 54.9-56.6% ...
... Some of the effects of DBPs were higher bladder and colorectal cancers risks, miscarriages, low birth weights, Responsible Editor: Guilherme L. Dotto pre-term deliveries, and cardiac irregularities (King and Marrett 1996;Savitz et al. 2006;Richardson et al. 2007;USEPA 2019). To protect the human health, different regulatory agencies have published regulations or guideline values for few DBPs including THM4 (chloroform [TCM]; bromodichloromethane [BDCM]; dibromochloromethane [DBCM]; and bromoform [TBM]), HAA5 (monochloroacetic acid [MCAA], dichloroacetic acid [DCAA], trichloroacetic acid [TCAA], monobromoacetic acid [MBAA], and dibromoacetic acid [DBAA]), bromate (BrO 3 ), and chlorite (ClO 2 ) (USEPA 2016;Health Canada 2019;WHO 2017). ...
Article
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Disinfection is an essential process for drinking water supplies resulting in the formation of unintended disinfection by-products (DBPs), many of which are potentially toxic and are known as the possible or probable human carcinogens. As of now, 100⁺ DBPs were characterized while about 600⁺ others can be formed in the supply water. To protect the human health, many regulatory agencies have set the guideline values for several DBPs. Removal of halide ions and natural organic matter prior to disinfection is an important step to reduce DBPs, and the associated exposure and risks. To date, many publications have reported various methods for halide removal from drinking water. The most review about halide removal technologies, associated challenges, and future research needs was published in 2012. Since then, a number of studies have been published on different methods of halide removal techniques. This paper aims to review the state of research on halide removal techniques focusing on the development during the past 10 years (2012–2021). The techniques were clustered into six major groups: adsorption, ion exchange, coagulation, advanced oxidation, membrane separation, and combined techniques. The progress on these groups of technologies, their advantages, and limitations were examined, and the future research directions to produce the safe drinking water were identified.
... Method of Characteristics (MoCs) reduces Equation (2) to an ODE along the advection characteristics line whose slope is dt dx i ; see the blue line in Fig. 3. By the definition of advection, we find that dxi dt = v i (t) for that line. ...
... Algorithm 2: EPANET's Lagrangian time-driven method to solve advection-reaction PDE for each hydraulic time-step Input: Hydraulic parameters (e.g., velocities, flow rates), pipe's length, and adjustment tolerance (τadj) Output: Chemical concentrations in each pipe 1 if It is the first hydraulic time-step then 2 Pipe is considered as one segment with initial concentration equal to the upstream node's concentration 3 else 4 Segments are ordered in the direction of the flow 5 end if 6 while t ≤ Ts do 7 Apply reaction to each segment 8 Calculate volume entering each downstream node, which equal pipe's flow rate times time-step 9 if volume is larger than last segment's volume then 10 Last segment is distroyed 11 Segment before the last one contributes its volume 12 else 13 Last segment's volume is decreased by the volume contributed 14 end if 15 Update concentrations at nodes according to entering volumes and demands 16 if difference between concentrations of the upstream node and the first segment ≤ τ adj then 17 Update first segment's size by the inflowing volume 18 else 19 Create new segment with the upstream node's concentration 20 end if 21 Obtain the average of the segments' concentrations to represent the whole pipe's concentration at time t 22 t = t + ∆t 23 end while ...
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Chlorine is a widely used disinfectant and proxy for water quality (WQ) monitoring in water distribution networks (WDN). Chlorine-based WQ regulation and control aims to maintain pathogen-free water. Chlorine residual evolution within WDN is commonly modeled using the typical single-species decay and reaction dynamics that account for network-wide, spatiotemporal chlorine concentrations only. Prior studies have proposed more advanced and accurate descriptions via multi-species dynamics. This paper presents a host of novel state-space, control-theoretic representations of multi-species water quality dynamics. These representations describe decay, reaction, and transport of chlorine and a fictitious reactive substance to reflect realistic complex scenarios in WDN. Such dynamics are simulated over space- and time-discretized grids of the transport partial differential equation and the nonlinear reaction ordinary differential equation. To that end, this paper (i) provides a full description on how to formulate a high fidelity model-driven state-space representation of the multi-species water quality dynamics and (ii) investigates the applicability and performance of different Eulerian-based schemes (Lax-Wendroff, backward Euler, and Crank- Nicolson) and Lagrangian-based schemes (method of characteristics) in contrast with EPANET and its EPANET-MSX extension. Numerical case studies reveal that the Lax-Wendroff scheme and method of characteristics outperform other schemes with reliable results under reasonable assumptions and limitations.
... THMs are particularly known for causing effects associated with DNA damage and several abnormalities, such as hepatotoxicity, nephrotoxicity, and teratogenicity (Zhang et al., 2012). For example, brominated THMs could be highly cytotoxic to placental trophoblasts (Richardson et al., 2007), and developing of an effective method for removing THMs from drinking water is of the highest importance. ...
Article
AC-supported nanoscale zero-valent iron composites (nZVI/AC) exhibit significant environmental implications for trihalomethanes (THMs)-contaminated water remediation. To improve the adsorption and degradation capability of AC, herein, a composite (nZVI/[email protected]) consisting of AC, reduced graphene oxide (RGO), nanoscale zero-valent iron (nZVI), and silver (Ag) was synthesized and characterized using several techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The analysis of textural and morphological structures showed that a tightly-attached RGO film, amorphous iron, and weak crystal silver nanoparticles with a size of 20–30 nm were evenly immobilized on the support. Specific surface area increased by 19.12% after supporting RGO, while it decreased after supporting nZVI and Ag due to the partial blockage of micropores. The Fe surface was concurrently coated by iron oxides (Fe2O3, FeOOH) and Ag. THMs were eliminated through multilayer reaction processes. The values of the adsorption constant (KF) of chloroform (CHCl3), dichlorobromoethane (CHBrCl2), dibromochloroethane (CHBr2Cl), and tribromomethane (CHBr3) adsorbed by nZVI/[email protected] increased by 34.4, 33.7, 81.6, and 67.3%, respectively, compared to pristine AC. THMs with more Br atoms exhibited better removal efficiency and adsorption capacity, along with a higher oxidation degree of the Fe surface. CHBrCl2 and CHBr2Cl mainly decomposed into chloromethane (CH3Cl) and dichloromethane (CH2Cl2), and CHBr3 and CHCl3 primarily degraded into dibromomethane (CH2Br2) and CH2Cl2, respectively, along with generating Cl⁻ and Br⁻. Conclusively, THMs-contaminated water could be remediated by coupling AC pre-enrichment and the reactivity of nZVI/Ag.
... On the one hand, this freshly produced BDOM would strongly influence its binding properties to heavy metals and thus their fate, mobility, and toxicity in aquatic environments; especially, the algal-derived polymeric component increases the coagulation and sedimentation rates of colloidal material and associated metals, and thus brings hidden potential dangers to benthic healthy [25,26]. On the other hand, after long-term biodegradation, progressive accumulation of algal-derived recalcitrant DOM, as disinfection by-product precursor compounds, is transformed into trihalomethanes and haloacetic acids (i.e., carcinogenic and mutagenic disinfection byproducts), which inevitably leads to increased costs of drinking water supply systems [27][28][29]. In addition, during the decay of cyanobacteria blooms in lake ecosystems, cyanobacteria toxins are introduced into water and could directly threaten human health [30,31]. ...
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Cyanobacterial blooms caused by phytoplankton Microcystis have occurred successively since 1980 in Lake Taihu, China, which has led to difficulty collecting clean drinking water. The effects of cyanobacterial scum-derived dissolved organic matter (DOM) on microbial population variations and of algal-derived filtrate and algal residual exudative organic matter caused by the fraction procedure on nutrient mineralization are unclear. This study revealed the microbial-regulated transformation of DOM from a high-molecular-weight labile to a low-molecular-weight recalcitrant, which was characterized by three obvious stages. The bioavailability of DOM derived from cyanobacterial scum by lake microbes was investigated during 80-d dark degradation. Carbon substrates provided distinct growth strategy links to the free-living bacteria abundance variation, and this process was coupled with the regeneration of different forms of inorganic nutrients. The carryover effects of Microcystis cyanobacteria blooms can exist for a long time. We also found the transformation of different biological availability of DOM derived from two different cyanobacterial DOM fractions, which all coupled with the regeneration of different forms of inorganic nutrients. Our study provides new insights into the microbial degradation of cyanobacterial organic matter using a fractionation procedure, which suggests that the exudate and lysate from degradation products of cyanobacteria biomass have heterogeneous impacts on DOM cycling in aquatic environments.
... Conventional water treatment by coagulation-sedimentation-filtration-disinfection, the most widely used drinking-water treatment process in China, can remove 10-60% of dissolved organic matter (DOM) 3,4 . However, disinfection by-products (DBPs) formed during the chlorine-based disinfection process are associated with adverse health outcomes (for example, bladder cancer) [5][6][7][8][9] and represent a long-term public health problem with regard to drinking water 10 . ...
Article
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The quality of drinking-water supplies is of fundamental importance to public health and sustainable development. Here, we provide a spatial assessment of the tap-water quality across mainland China. We examine natural and anthropogenic origins of low quality as well as its association with public health risks. By quantifying key indicators, including total organic carbon, ionic conductivity and disinfection by-products (DBPs), we find that precipitation is a crucial factor driving the change of organic matter content and ionic conductivity of tap-water, especially for arid and semi-arid regions. Although the concentration of DBPs is closely related to the organic matter content, the occurrence of highly toxic DBPs is more subject to anthropogenic factors such as economic development and pollution emission. We show that nanofiltration is an effective point-of-use treatment to reduce the adverse effects of DBPs. The present results highlight the potential health hazards associated with low-quality drinking water, suggesting that countries and regions experiencing rapid socioeconomical development might face high levels of DBP toxicity and should consider adoption of sustainability solutions.
... Chlorination, one of the most widely adopted disinfection methods in drinking water and wastewater treatment, plays a critical role in protecting people from waterborne dis-known or suspected to be toxic ( Plewa et al., 2017 ;Sedlak and von Gunten, 2011 ;von Gunten, 2018 ). Although more than 700 DBPs have been identified to date, these typically contribute less than 50% to the total mass balance of halogenated compounds that are formed ( Richardson et al., 2018( Richardson et al., , 2007Richardson, 2003 ). Toxicological and epidemiological studies have demonstrated that the toxic effects of chlorinated water can only partially be accounted for by the commonly known halogenated DBPs, suggesting the relevance of other, so far unrecognized DBPs ( Chuang et al., 2019 ;Han et al., 2021 ;Li and Mitch, 2018 ). ...
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Despite the widespread occurrence of phenols in anthropogenic and natural compounds, their fate in reactions with hypochlorous acid (HOCl), one of the most common water treatment disinfectants, remains incompletely understood. To close this knowledge gap, this study investigated the formation of disinfection byproducts (DBPs) in the reaction of free chlorine with seven para-substituted phenols. Based on the chemical structures of the DBPs and the reaction mechanisms leading to their formation, the DBPs were categorized into four groups: chlorophenols, coupling products, substituent reaction products, and ring cleavage products. In contrast to previous studies that investigated the formation of early- stage chlorophenols, the primary focus of this study was on the elucidation of novel ring cleavage products, in particular α, β-unsaturated C4-dialdehydes, and C4-dicarboxylic acids, which, for the first time, were identified and quantified in this study. The molar yields of 2- butene-1,4-dial (BDA), one of the identified α, β-unsaturated C4-dialdehydes, varied among the different phenolic compounds, reaching a maximum value of 10.4% for bisphenol S. Mo- lar yields of 2-chloromaleic acid (Cl-MA), one of the identified C4-dicarboxylic acids, reached a maximum value of 30.5% for 4-hydroxy-phenylacetic acid under given conditions. 2,4,6- trichlorophenol (TCP) was shown to be an important intermediate of the parent phenols and the C4-ring cleavage products. Based on the temporal trends of α, β-unsaturated C4- dialdehydes and C4-dicarboxylic acids, their formation is likely attributable to two separate ring cleavage pathways. Based on the obtained results, an overall transformation pathway for the reaction of para-substituted phenols with free chlorine leading to the formation of novel C4 ring cleavage products was proposed.
... Moreover, to achieve control of Legionella proliferation, the national and international directives point out several disinfection strategies, based on chemical disinfectants (i.e., chlorine dioxide, monochloramines, and hydrogen peroxide) and physical treatments [i.e., ultraviolet (UV) light and hot temperature treatments]. All of them have shown some advantages and disadvantages (Mcdonnell and Russell, 1999;Richardson et al., 2007;Lin et al., 2011;Mancini et al., 2015;Girolamini et al., 2019). However, some authors have shown how these treatments, especially the use of chemical disinfectants, could select resistant strains and introduce some changes in the bacterial genome. ...
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... Yallop and Clutterbuck, 2009). Whatever the reason, increased DOC concentrations in reservoirs used for drinking water supply are a problem for water companies because they are associated with discoloration (and, hence, consumer complaints) and because they can result in the formation of chlorination by-products such as trihalomethanes (THMs) which are known to be carcinogenic (Richardson et al., 2007). Long term trends in POM concentrations at the tidal limit follow a similar pattern to those for DOM with a peak ...
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The precursors of commonly known DBPs have been widely investigated, yet few studies have paid attention to the typical compositions of AOM-related DBP precursors at molecular-level. Hence, in this study, we established the potential relationships by linking AOM molecular formulas or properties with the formation potentials of typical CX3R-type DBPs (i.e., dichloroacetonitrile (DCAN), trichloroacetone (TCP) and trichloromethane (TCM)) by regression analysis and Spearman’s correlation analysis. By the results of significant and strong correlations between AOM molecules and DBP formation potentials, the typical precursors of DCAN or TCP were observed to be the molecules with relatively high O/C (0.5-0.8) and low H/C (0.9-1.8) ratios, while different precursors of TCM were obviously determined. Compared to the aliphatic and vascular plant-derived polyphenol compounds, the phenolic and highly unsaturated aliphatic compositions were prone to generate DCAN and TCP in chlorination. Besides, the H/N and O/N ratios of precursors of DCAN distributed around a straight line, namely, H/N = 1.86 O/N + 1.23. Such findings will provide new insights into the specific precursors at molecular-level and be beneficial to the development of effective controlling strategies for these AOM-related DBPs.
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Haloacetic acids (HAAs) are a type of disinfection byproducts commonly found in drinking water with carcinogenic, mutagenic, or teratogenic risks to humans. Currently, the analytical methods of trace HAAs are either labor-intensive or very expensive. We herein propose a facile multiple-step extraction strategy for HAAs analysis with common ion chromatography (IC). This study is based on a fundamental water chemistry principle that HAAs become protonated featuring positive logKow values (> 0.34) under pH < pKa but deprotonated featuring negative logKow values (< -2.37) under pH > pKa. By taking advantage of the species and property switches, HAAs can be extracted and enriched into methyl tert-butyl ether first at pH < 0.5 and then back-extracted into neutral water and enriched again. Equally important, interfering anions in IC chromatogram are eliminated because they have negative logKow values. Verification results show that HAAs were enriched by 11.4 times in average while interfering anions were almost eliminated (> 99%). Although similar to USEPA Method 552.3 in method detection limits (0.033~0.246 μg/L), recoveries (70%~110%), and relative standard deviations (< 9.91%), this method took ≤ 70 min to run a batch of samples without derivatization, which takes over 2 h. The methodology may be applicable to other pollutants that also have contrasting Kow values at different pH.
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Pathogen contamination of water has a massive impact on global human health. In particular, viruses pose unique challenges to water treatment techniques due to their small size and presence in water as both individual virions and when absorbed onto larger particles. Low-energy water treatment processes such as media filtration are not capable of completely removing viruses owing to their small size. Hence, less sustainable processes with high chemical or energy consumption such as chemical disinfection, ultraviolet irradiation, and membrane filtration are usually required. To overcome high energy and/or chemical requirements for virus treatment, designs for sustainable fiber filters fabricated from minimally processed natural materials for efficient virus (MS2) and bacteria (E. coli) removal are presented in this work. These filters were created by functionalizing readily accessible natural fibers including cotton, silk, and flax with a simple aqueous extract containing cationic proteins from Moringa oleifera seeds. The proposed filters offer a comprehensive low cost, low energy, and low environmental impact solution for pathogen removal from water with removals of >7log10 (99.99999%) for viruses and bacteria.
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Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.
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Due to its potential applications in decentralized water treatment systems, electrochemical synthesis of H2O2 for water decontamination has been widely investigated in recent years. In this study, it is found that the anodic oxidation of the residual H2O2 in the presence of Cl⁻ can be an efficient electrochemical disinfection technology to guarantee the microbiological safety of the treated water. H2O2 can be oxidized by HOCl generated at the anode to form singlet oxygen (¹O2). ¹O2 has been recognized as an important disinfectant in solar disinfection (SODIS) but it has not yet been reported in electrochemical disinfection. The generation of ¹O2 was directly confirmed by the detection of ¹O2 monomol emission using a near infrared imaging system. The concentration of ¹O2 can reach up to 1.64 pM in the anodic oxidation of H2O2 with Cl⁻. ¹O2 plays an important role in Escherichia coli (E. coli) inactivation, and HOCl only plays a subordinate role in the presence of 1 mM H2O2 due to its low concentration. For example, by adding up the inactivation of E. coli by sole H2O2 and micro-concentration HOCl together only attribute to about 2 log in 60 min but ¹O2 itself can account for about 3 log. Besides, the formation of the chlorinated disinfection by-products (Cl-DBPs) was mitigated considerably benefited from the fast reduction of HOCl by H2O2. These findings have potential implications for H2O2-based decentralized water treatment systems and provide a novel strategy for electrochemical disinfection because electrochlorination is having the same problems that chlorination has.
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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.
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Copper water pipelines are widely used in water distribution systems, but the effects of solid copper corrosion products (CCPs) including CuO, Cu2O and Cu2(OH)2CO3 on the generation of iodinated trihalomethanes (I-THMs) during chloramination remain unknown. This study found that the formation of I-THMs during chloramination of humic acid (HA) was inhibited by the presence of CuO and Cu2O, but promoted with the addition of Cu2(OH)2CO3. The negative effect of CuO and Cu2O is mainly exerted by promoting the decay of both NH2Cl and HOI. Although Cu2(OH)2CO3 also accelerated the decomposition of NH2Cl and HOI, it was found that the complexes formed between Cu2(OH)2CO3 and HA facilitated, through carboxyl functional groups, the reaction between HA and HOI, leading to an enhancement of I-THM generation during chloramination, which was further confirmed by model compound experiments. Additionally, this study demonstrated that the effects of solid CCPs on I-THMs generation during chloramination were solid CCP- and HA-concentration dependent, but almost unaffected by different initial I⁻ and Br⁻ concentrations. This study provides new insights into the health risks caused by the corrosion of copper water pipelines, especially in areas intruded by sea water.
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Dissolved black carbon (DBC), the water-soluble component of black carbon, which is formed by incomplete combustion of fossil fuels or biochar, takes up about 10% of dissolved organic matter (DOM) in river water. However, the distribution of DBC in water environment especially in source water is not clear and as an important component of DOM, whether DBC can produce disinfection byproducts (DBPs) like other DOM during disinfection remains unknown. In this study, the DBC concentrations in seventeen source water samples from East China were measured. The concentrations of DBC in the source water samples ranged from 60-270 μg/L, which were positively correlated with UV254 absorbance and chemical oxygen demand. The levels of DBC in wet season were higher than that in dry season. The average concentrations of DBC in different types of source water samples followed the order of reservoir > canal > lake > river. DBC could only be removed by 20% during the simulated coagulation, and further generate different categories of DBPs during chlorination, among which the concentrations of haloacetic acids (HAA) were the highest. The results indicated that DBC widely distributes in source water and is an important precursor of HAAs and THMs during chlorination.
Article
The presence of emerging contaminants, such as pharmaceuticals and personal care products (PPCPs), in aquatic environments has received increasing attention in the last years due to the various possible impacts on the dynamics of the natural environment and human health. In global terms, around 771 active pharmaceutical substances or their transformation products have been detected at levels above their respective detection limit. Additionally, 528 different compounds have been detected in 159 countries. Seeking to overcome potential ecotoxicological problems, several studies have been conducted using different technologies for PPCPs removal. Recently, the use of macro, microalgae, and aquatic macrophytes has been highlighted due to the excellent bioremediation capacity of these organisms and easy acclimatization. Thus, the present review aims to outline a brief and well-oriented scenario concerning the knowledge about the bioremediation alternatives of PPCPs through the use of macro, microalgae, and aquatic macrophytes. The characteristics of PPCPs and the risks of these compounds to the environment and human health are also addressed. Moreover, the review indicates the opportunities and challenges for expanding the use of biotechnologies based on algae and aquatic macrophytes, such as studies dedicated to relate the operational criteria of these biotechnologies with the main PPCPs removal mechanisms. Finally, algae and macrophytes can compose green and ecological biotechnologies for wastewater treatment, having great contribution to PPCPs removal.
Chapter
Disinfection byproducts (DBPs) form after the reaction of natural and anthropogenic organic matter and other inorganic substances present in water with the disinfectants used to inactivate pathogens. This chapter provides insights into the most common DBP classes regarding their chemical properties, environmental occurrence, and the most suitable methodologies for their reliable determination in water. It includes the halogenated DBP classes trihalomethanes, haloacetic acids, haloacetaldehydes, halobenzoquinones, haloacetonitriles, halonitromethanes, haloacetamides, and the non‐halogenated DBP class nitrosamines. Liquid‐liquid extraction is the most widely used extraction method due to its simplicity, low cost, and effectiveness in simultaneously extracting various DBP classes. Linearity is obtained in most analytical approaches with the internal standard calibration method. Known DBPs represent only a small fraction of the halogenated material formed during the disinfection process. The development of target multi‐class methods is encouraged to obtain valuable information at once for many DBPs, minimizing economical and lab‐effort resources.
Article
Objectives : The formation characteristics and fate of haloacetamides (HAcAms), nitrogenous disinfection by-products (DBPs), were evaluated for each process in a drinking water treatment plant (DWTP) located downstream of the Nakdong River in summer and winter. In preparation for the gradually strengthening rules for DBPs, it was intended to be used as basic data for operating DWTPs. Methods : Seven HAcAms were monitored from the raw water to the clean water in the summer (Jul.∼Aug.) and winter (Dec.∼Jan.) at a large DWTP (180,000 m 3 /day) located downstream of the Nakdong River. Liquid-liquid extraction (LLE) method was used for sample extraction and GC-MS/MS was used for HAcAms analysis. Results and Discussion : The concentrations of HAcAms formed by the pre-Cl 2 treatment in the DWTP in summer and winter were 9.4~27.2 µg/L and 1.4~3.5 µg/L, respectively, and were 7.7 times higher in summer than in winter. The HAcAms/TOX concentration ratio was 0.09~0.14 in summer compared to 0.01~0.02 in winter, and the HAcAms composition ratio among DBPs formed by the pre-chlorination increased rapidly in the summer. Five species of DCAcAm, BCAcAm, TCAcAm, DBAcAm, and BDCAcAm were formed in summer by the pre-chlorination, and five species of DCAcAm, BCAcAm, DBAcAm, DBCAcAm, and TBAcAm were formed in winter. The composition ratio of di-HAcAm species accounted for 91% and 66% in summer and winter, respectively, and the DCAcAm concentration was highest compared to other HAcAms species. In the batch biodegradation experiment, it was evaluated that the biodegradation of the HAcAms species was easy, and in the laboratory scale BAC process experiment (water temp. 20℃, EBCT 10~30 min.), di-and tri-HAcAms removal rate were 75~99% and 85~100%, respectively. In summer and winter, the removal rates of HAcAms in the BAC process of the DWTP were 81% and 54% on average, respectively. The HAcAm detection concentrations in the clean water ranged from 1.7 to 2.4 μg/L in summer and 0.7 to 1.2 µg/L in winter, which was twice as high in summer as was compared to winter. Conclusion : The formation concentration of HAcAms was higher than in winter by pre-chlorination, but it was easily removed in the BAC process in summer. However, in winter, the formation concentration of HAcAms was low by pre-chlorine treatment, but the removal rate in the BAC process was as low as 54%. The main removal process and mechanism of HAcAms in the DWTP were the BAC process and biodegradation. In a lab-scale BAC process simulation, a removal rate of more tthan 95% removal efficiency could be expected with the increase of EBCT to 30 minutes when HAcAms was highly formed in summer.
Article
This study systematically quantified the impacts of different operation conditions, e.g., pH, chlorine dosages, contact times, and temperatures towards the disinfection by-product (DBP) formation, integrated toxicity, and structural changes in seawater natural organic matter during seawater chlorination. Higher concentrations of total DBPs were found under longer contact times, higher chlorine dosages, higher temperatures, and lower pH. The concentration of tribromomethane, the most abundant DBP, was found lowest at pH 10. Monobromoacetic acid, dibromoacetonitrile, and dibromoacetaldehyde were the three main contributors to integrated cyto- and geno-toxicity, stressing the need to monitor DBPs based on their contributions to integrated toxicity, regardless they are regulated or nonregulated. The concentrations of total organic chlorine remained stable under different conditions, while those of total organic bromine increased with increasing contact times, chlorine dosages, and temperatures, but with decreasing pH, indicating the changes of toxicity in chlorinated seawater compared to drinking water or groundwater. Changes of ultraviolet absorbance at 254 nm and fluorescence excitation emission matrix values are useful indicators for monitoring the concentrations of high molecular weight adsorbable organic bromine and total organic halogen under all operating conditions.
Article
Halobenzoquinones (HBQs) have been reported as an emerging category of disinfection byproducts (DBPs) in drinking water with relatively high toxicity, and the previously reported HBQs include 2,6-dichloro-1,4-benzoquinone, 2,3,6-trichloro-1,4-benzoquinone, 2,6-dichloro-3-methyl-1,4-benzoquinone, 2,6-dibromo-1,4-benzoquinone, 2,6-diiodo-1,4-benzoquinone, 2-chloro-6-iodo-1,4-benzoquinone, and 2-bromo-6-iodo-1,4-benzoquinone. In this study, another HBQ species, 2-bromo-6-chloro-1,4-benzoquinone (2,6-BCBQ), was newly detected and identified in drinking water. The occurrence frequency and levels of 2,6-BCBQ were investigated, and its cytotoxicity was evaluated. Since the formed 2,6-BCBQ was found to be not stable in chlorination, its transformation kinetics and mechanisms in chlorination were further studied. The results reveal that 2,6-BCBQ was generated from Suwannee River humic acid with concentrations in the range of 4.4–47.9 ng/L during chlorination within 120 h, and it was present in all the tap water samples with concentrations ranging from 1.5 to 15.7 ng/L. Among all the tested bromochloro-DBPs, 2,6-BCBQ showed the highest cytotoxicity on the human hepatoma cells. The transformation of 2,6-BCBQ in chlorination followed a pseudo-first-order decay, which was significantly affected by the chlorine dose, pH, and temperature. Seven polar chlorinated and brominated intermediates (including HBQs, halohydroxybenzoquinones, and halohydroxycyclopentenediones) were detected in chlorinated 2,6-BCBQ samples, according to which the transformation pathways of 2,6-BCBQ in chlorination were proposed. Besides, four trihalomethanes and four haloacetic acids were also generated during chlorination of 2,6-BCBQ with molar transformation percentages of 1.6–13.7%.
Article
Halogenated disinfection byproducts (DBPs) are an unintended consequence of drinking water disinfection, and can have significant toxicity. XAD resins are commonly used to extract and enrich trace levels of DBPs for comprehensive, nontarget identification of DBPs and also for in vitro toxicity studies. However, XAD resin recoveries for complete classes of halogenated DBPs have not been evaluated, particularly for low, environmentally relevant levels (ng/L to low µg/L). Thus, it is not known whether levels of DBPs or the toxicity of drinking water might be underestimated. In this study, DAX-8/XAD-2 layered resins were evaluated, considering both adsorption and elution from the resins, for extracting 66 DBPs from water. Results demonstrate that among the 7 classes of DBPs investigated, trihalomethanes (THMs), including iodo-THMs, were the most efficiently adsorbed, with recovery of most THMs ranging from 50-96%, followed by halonitromethanes (40-90%). The adsorption ability of XAD resins for haloacetonitriles, haloacetamides, and haloacetaldehydes were highly dependent on the individual species. The adsorption capacity of XAD resins for haloacetic acids was lower (5-48%), even after adjusting to pH 1 before extraction. Recovery efficiency for most DBPs was comparable with their adsorption, as most were eluted effectively from XAD resins by ethyl acetate. DBP polarity and molecular weight were the two most important factors that determine their recovery. Recovery of trichloromethane, iodoacetic acid, chloro- and iodo-acetonitrile, and chloroacetamide were among the lowest, which could lead to underestimation of toxicity, particularly for iodoacetic acid and iodo-acetonitrile, which are highly toxic.
Article
Background: Disinfection byproducts (DBPs) and N-nitroso compounds (NOC), formed endogenously after nitrate ingestion, are suspected endometrial carcinogens, but epidemiological studies are limited. Objectives: We investigated the relationship of these exposures with endometrial cancer risk in a large prospective cohort. Methods: Among postmenopausal women in the Iowa Women's Health Study cohort, we evaluated two major classes of DBPs, total trihalomethanes (TTHM) and five haloacetic acids (HAA5), and nitrate-nitrogen (NO3-N) in public water supplies (PWS) in relation to incident primary endometrial cancer (1986-2014). For women using their PWS >10y at enrollment (n=10,501; cases=261), we computed historical averages of annual concentrations; exposures were categorized into quantiles and when possible ≥95th percentile. We also computed years of PWS use above one-half the U.S. maximum contaminant level (>½ MCL; 40μg/L TTHM; 30μg/L HAA5; 5mg/L NO3-N). Dietary nitrate/nitrite intakes were estimated from a food frequency questionnaire. We estimated hazard ratios (HR) and 95% confidence intervals (CI) via Cox models adjusted for age, endometrial cancer risk factors [e.g., body mass index, hormone replacement therapy (HRT)], and mutually adjusted for DBPs or NO3-N. We evaluated associations for low-grade (cases=99) vs. high-grade (cases=114) type I tumors. We assessed interactions between exposures and endometrial cancer risk factors and dietary factors influencing NOC formation. Results: Higher average concentrations of DBPs (95th percentile: TTHM ≥93μg/L, HAA5 ≥49μg/L) were associated with endometrial cancer risk (TTHM: HR95vsQ1=2.19, 95% CI: 1.41, 3.40; HAA5: HR95vsQ1=1.84, 95% CI: 1.19, 2.83; ptrend<0.01). Associations were similarly observed for women greater than median years of PWS use with levels >½ MCL, in comparison with zero years (TTHM: HR36+vs0y=1.61, 95% CI: 1.18, 2.21; HAA5: HR38+vs0y=1.85, 95% CI: 1.31, 2.62). Associations with DBPs appeared stronger for low-grade tumors (TTHM: HRQ4vsQ1=2.12, 95% CI: 1.17, 3.83; p-trend=0.008) than for high-grade tumors (TTHM: HRQ4vsQ1=1.40, 95% CI: 0.80, 2.44; p-trend=0.339), but differences were not statistically significant (p-heterogeneity=0.43). Associations with TTHM were stronger among ever HRT users than non-HRT users (p-interaction<0.01). We observed no associations with NO3-N in drinking water or diet. Discussion: We report novel associations between the highest DBP levels and endometrial cancer for our Iowa cohort that warrant future evaluation. https://doi.org/10.1289/EHP10207.
Article
Since 1974, more than 800 disinfection byproducts (DBPs) have been identified from disinfected drinking water, swimming pool water, wastewaters, etc. Some DBPs are recognized as contaminants of high environmental concern because they may induce many detrimental health (e.g., cancer, cytotoxicity, and genotoxicity) and/or ecological (e.g., acute toxicity and development toxicity on alga, crustacean, and fish) effects. However, the information on whether DBPs may elicit potential endocrine-disrupting effects in human and wildlife is scarce. It is the major objective of this paper to summarize the reported potential endocrine-disrupting effects of the identified DBPs in the view of adverse outcome pathways (AOPs). In this regard, we introduce the potential molecular initiating events (MIEs), key events (KEs), and adverse outcomes (AOs) associated with exposure to specific DBPs. The present evidence indicates that the endocrine system of organism can be perturbed by certain DBPs through some MIEs, including hormone receptor-mediated mechanisms and non-receptor-mediated mechanisms (e.g., hormone transport protein). Lastly, the gaps in our knowledge of the endocrine-disrupting effects of DBPs are highlighted, and critical directions for future studies are proposed.
Article
N-Nitrosodimethylamine (NDMA) is a commonly identified carcinogenic and genotoxic pollutant in water. In this study, we prepared Ru catalysts supported on carbon nanotube (Ru/CNT) and studied the electrocatalytic reduction of N-nitrosamines on Ru/CNT electrode in a three-electrode system. The results show that Ru-based catalyst exhibits a high activity of 793.3 μmol L-1 gCat-1 h-1 for electrochemical reduction of NDMA. Reaction mechanism study discloses that the electrocatalytic reduction of NDMA is accomplished by both direct electron reduction and atomic H* mediated indirect reduction pathways. Further product analysis indicates that NDMA is finally reduced to dimethylamine (DMA) and ammonia. The reduction efficiency of NDMA strongly relies on cathode potential, initial NDMA concentration and solution pH. To verify the universality of Ru/CNT electrode, electrocatalytic reduction of three dialkyl N-nitrosamines with different alkyl groups was performed and Ru catalyst has high catalytic activities for the three N-nitrosamines, while the catalytic efficiency differs with their structures. Simultaneous electrochemical reduction of the three N-nitrosamines indicates that the reduction rates of N-nitrosamines follow the same order in the multiple-component system as that in the single-component system. Catalyst recycling results demonstrate that after 5 consecutive recycling runs Ru/CNT electrode remains almost identical catalytic activity to the fresh catalyst, manifesting the high catalytic stability of Ru/CNT electrode.
Article
Dibromoacetonitrile (DBAN) and dichloroacetonitrile (DCAN) are haloacetonitriles (HANs) produced as by-products of chloramine disinfection of drinking water and can cause neurotoxicity. The molecular pathways leading to HAN-induced neuronal cell death remain unclear. The nuclear factor erythroid 2–related factor 2 (Nrf2) is an important regulator of oxidation reactions. We explored the role of the sequestosome 1 (p62)–Kelch-like ECH-associated protein 1 (Keap1)–Nrf2 pathway in DBAN- and DCAN-induced mouse hippocampal neuronal (HT22) cell injury. DBAN and DCAN reduced cell viability, increased lactate dehydrogenase release rate, and promoted apoptosis. Over the same treatment time, DBAN at lower concentrations caused cell injury, suggesting that DBAN is more cytotoxic than DCAN. DBAN and DCAN triggered oxidative stress by reducing intracellular glutathione and increasing reactive oxygen species concentrations. DBAN and DCAN activated the Nrf2 pathway. Furthermore, Nrf2 inhibitors (all-trans retinoic acid) attenuated DBAN- and DCAN-induced toxicity, whereas Nrf2 activators (tert-Butylhydroquinone) achieved the opposite effect. This indicates that activation of the Nrf2 pathway mediates DBAN- and DCAN-induced cell injury. Notably, the expression of p62, a noncanonical pathway that mediates Nrf2 activation, increased, whereas the expression of Keap1, another regulator of Nrf2, decreased. We noted that high p62 expression activated the Nrf2 pathway, and p62 was regulated through Nrf2, forming a positive feedback loop. N-acetyl-L-cysteine, a mercaptan substance, protected against DBAN- and DCAN-induced toxicity and inhibited the Nrf2 pathway. In summary, Nrf2 pathway inhibition and mercaptan supplementation prevent DBAN- and DCAN-induced HT22 cell injury, accordingly, targeting them is a potential approach to preventing HAN-induced neurotoxicity.
Article
In China, rapid growth is raising concerns about the impacts of industrial pollution on drinking water and health. A recent study identifies concentrations of disinfection byproducts as a possible culprit in high levels of bladder cancer.
Article
Dissolved organic matters (DOM) have important effects on the performance of surface water treatment processes and may convert into disinfection by-products (DBPs) during disinfection. In this work, the transformation of DOM and the chlorinated DBPs (Cl-DBPs) formation in two different full-scale surface water treatment processes (process 1: prechlorination-coagulation-precipitation-filtration; process 2: coagulation-precipitation-post-disinfection-filtration) were comparatively investigated at molecular scale. The results showed that coagulation preferentially removed unsaturated (H/C < 1.0 and DBE > 17) and oxidized (O/C > 0.5) compounds containing more carboxyl groups. Therefore, prechlorination produced more Cl-DBPs with H/C < 1.0 and O/C > 0.5 than post-disinfection. However, the algal in the influent produced many reduced molecules (O/C < 0.5) without prechlorination, and these compounds were more reactive with disinfectants. Sand filtration was ineffective in DOM removal, while microorganisms in the filter produced high molecular weight (MW) substances that were involved in the Cl-DBPs formation, causing the generation of higher MW Cl-DBPs under post-disinfection. Furthermore, the CHO molecules with high O atom number and the CHON molecules containing one N atom were the main Cl-DBPs precursors in both surface water treatment processes. In consideration of the putative Cl-DBPs precursors and their reaction pathways, the precursors with higher unsaturation degree and aromaticity were prone to produce Cl-DBPs through addition reactions, while that with higher saturation degree tended to form Cl-DBPs through substitution reactions. These findings are useful to optimize the treatment processes to ensure the safety of water quality.
Article
Nitrification and biofilm growth within distribution systems remain major issues for drinking water treatment plants utilizing chloramine disinfection. Many chloraminated plants periodically switch to chlorine disinfection for several weeks to mitigate these issues, known as "chlorine burns". The evaluation of disinfection byproduct (DBP) formation during chlorine burns beyond regulated DBPs is scarce. Here, we quantified an extensive suite of 80 regulated and emerging, unregulated DBPs from 10 DBP classes in drinking water from two U.S. drinking water plants during chlorine burn and chloramination treatments. Total organic halogen (TOX), including total organic chlorine, total organic bromine, and total organic iodine, was also quantified, and mammalian cell cytotoxicity of whole water mixtures was assessed in chlorine burn waters for the first time. TOX and most DBPs increased in concentration during chlorine burns, and one emerging DBP, trichloroacetaldehyde, reached 99 μg/L. THMs and HAAs reached concentrations of 249 and 271 μg/L, respectively. Two highly cytotoxic nitrogenous DBP classes, haloacetamides and haloacetonitriles, increased during chlorine burns, reaching up to 14.2 and 19.3 μg/L, respectively. Cytotoxicity did not always increase from chloramine treatment to chlorine burn, but a 100% increase in cytotoxicity was observed for one plant. These data highlight that consumer DBP exposure during chlorine burns can be substantial.
Article
Chlorine disinfection of saline wastewater effluents rich in bromide and iodide forms relatively toxic brominated and iodinated disinfection byproducts (DBPs). Ultrasonication is a relatively new water treatment technology, and it is less sensitive to suspended solids in wastewaters. In this study, we examined the effects of ultrasonication (in terms of reactor type and combination mode with chlorination) on the DBP formation and toxicity in chlorinated primary and secondary saline wastewater effluents. Compared with the chlorinated wastewater effluent samples without ultrasonication, ultrasonic horn pretreatment of the wastewater effluent samples reduced the total organic halogen (TOX) levels in chlorination by ∼30%, but ultrasonic bath pretreatment of the wastewater samples did not significantly change the TOX levels in chlorination, which might be attributed to the higher energy utilization and decomposition extent of organic DBP precursors in the ultrasonic horn reactor. Moreover, the TOX levels in the chlorinated samples with ultrasonic horn pretreatment (USH–chlorination), simultaneous treatment (chlorination+USH) and subsequent treatment (chlorination–USH) were also significantly reduced, with the maximum TOX reductions occurring in the samples with ultrasonic horn pretreatment. A toxicity index was calculated by weighting and summing the levels of total organic chlorine, total organic bromine and total organic iodine in each treated sample. The calculated toxicity index values of the chlorinated wastewater effluent samples followed a descending rank order of “chlorination” > “chlorination+USH” > “chlorination–USH” > “USH–chlorination”, with the lowest toxicity occurring in the samples with ultrasonic horn pretreatment. Then, a developmental toxicity bioassay was conducted for each treated sample. The measured toxicity index values of the chlorinated wastewater samples followed the same descending rank order.
Article
Many drinking water treatment plants in the U.S. have switched from chlorination to chloramination to lower levels of regulated trihalomethane (THM) and haloacetic acid (HAA) disinfection byproducts (DBPs) in drinking water and meet the current regulations. However, chloramination can also produce other highly toxic/carcinogenic, unregulated DBPs: iodo-acids, iodo-THMs, and N-nitrosodimethylamine (NDMA). In practice, chloramines are generated by the addition of chlorine with ammonia, and plants use varying amounts of free chlorine contact time prior to ammonia addition to effectively kill pathogens and meet DBP regulations. However, iodo-DBPs and nitrosamines are generally not considered in this balancing of free chlorine contact time. The goal of our work was to determine whether an optimal free chlorine contact time could be established in which iodo-DBPs and NDMA could be minimized, while keeping regulated THMs and HAAs below their regulatory limits. The effect of free chlorine contact time was evaluated for the formation of six iodo-trihalomethanes (iodo-THMs), six iodo-acids, and NDMA during the chloramination of drinking water. Ten different free chlorine contact times were examined for two source waters with different dissolved organic carbon (DOC) and bromide/iodide. For the low DOC water at pH 7 and 8, an optimized free chlorine contact time of up to 1 h could control regulated THMs and HAAs, as well as iodo-DBPs and NDMA. For the high DOC water, a free chlorine contact time of 5 min could control iodo-DBPs and NDMA at both pHs, but the regulated DBPs could exceed the regulations at pH 7.
Article
Microcystis aeruginosa (M. aeruginosa, blue-green algae) blooms frequently in drinking water reservoirs and subsequently causes the formation of disinfection by-products (DBPs) after disinfection, which may pose a potential health risk. In this study, the formation of N-nitrosodimethylamine (NDMA) was evaluated from algal organic matter (AOM) including extracellular organic matter (EOM) and intracellular organic matter (IOM) during the disinfection process of chlorination, chloramination, or ultraviolet (UV) irradiation. The effects of a variety of factors, including reaction times, disinfectant dosages and pH, on the NDMA formation by three different disinfection methods were investigated. Additionally, this study evaluated the nitrogen sources involved in NDMA formation during chloramination of EOM and IOM using ¹⁵N-labeled monochloramine. The results showed that the NDMA formation by three different disinfection methods were ranked in the order of chlorination > UV irradiation ≈ chloramination and the specific yield from EOM was greater than that from IOM regardless of disinfection method. The yields of NDMA firstly increased and then plateaued as time prolonged during the chlorination and chloramination of AOM. Similarly, the NDMA formation from EOM was firstly increased and then remained constant with the increase of the disinfectant dosage, while it was gradually increased for IOM. The solution pH highly influenced the NDMA formation during chlorination and chloramination, while exhibited a little impact under UV irradiation. Moreover, fluorescence excitation-emission (EEM) analysis confirmed that soluble microbial by-product-like (SMPs) in EOM and IOM were the major precursors in algal-derived organic matter that contributed to the NDMA formation. Chloramination of EOM and IOM using isotope ¹⁵N-labeled monochloramine indicated that the nitroso group of the formed NDMA originates mainly from EOM and IOM of algal cells.
Article
With the increased use of microplastics in modern society, tonnes of various microplastics (MPs) end up in natural and engineered water systems if not properly handled. Being a class of organics, the role of MPs during the disinfection of water treatment systems is still unclear at this stage. In the current experimental study, the formation of 6 typical disinfection by-products (DBPs) was investigated using varying concentrations of polypropylene (PP) MPs under various aquatic chemistry conditions and disinfectants. All investigated DBPs were detected, during the chlorination of PP, with an average CHCl3 concentration of 378 μg/g, and other DBPs, including CHCl2Br, TCA, DCAN, 1,1-DCP, and TCNM, were present in less than 60 μg/g, on average. When PP coexisted with Suwannee River Fulvic acid (SRFA), a suppression of DBP formation was observed with a 56% net reduction compared with a condition of PP alone. The dynamic balance of being a DBP precursor, or a scavenger, by absorbing the organics of PP is subjected to aquatic chemistry. Increasing the pH decreases the HOCl concentrations, reducing the PP oxidation capacity and DBP formation. As salinity increases, the aggregation of PP can reduce the reaction sites on the surface of PP and enhance the adsorption of SRFA, hence lowering the formation of DBPs.
Article
This study demonstrated the remarkable potential of electrolytic system type for industrial reverse osmosis concentrate (ROC) treatment on effluent quality and energy requirements. Following their individual system optimization, the required current density decreased from 20 mA cm⁻² for the batch system during 4 h of electrolysis, to 5 mA cm⁻² for a continuous-flow system (CFS) without effluent recirculation (CFS-A), and 3 mA cm⁻² for a CFS system with a rear (CFS-B) or front (CFS-C) buffer tank for effluent recirculation (R = 1). The final or effluent chemical oxygen demand (COD) and NH4⁺−N levels were 31 and 0.4 mg L⁻¹ (Batch), 24 and 0.56 mg L⁻¹ (CFS-A) and 5.7−8.1 and 0.24−0.34 mg L⁻¹ (CFS-B or -C), respectively. Besides the highest pollutant removal, the optimized CFS-B and -C systems also achieved the highest treatment capacity and energy efficiency, and the lowest effluent toxic organic byproduct levels due to the homogeneous diffusion characteristic of CFS systems, and the reutilization of long-lived active chlorine species (ACS) oxidants in CFS-B/C electrolytic effluent. As compared with the optimized CFS-B system, the optimized CFS-C system at an identical recirculation ratio further achieved the lowest effluent ACS level due to the ACS consumption in the front buffer tank (rather than direct discharge in the CFS-B system) and lower flow rate into the electrochemical cell (than that in the CFS-B system), and was finally recommended for future engineering implementation.
Article
During the COVID-19 pandemic, the use of chlorine-based disinfectants has surged due to their excellent performance and cost-effectiveness in intercepting the spread of the virus and bacteria in water and air. Many authorities have demanded strict chlorine dosage for disinfection to ensure sufficient chlorine residual for inactivating viruses and bacteria while not posing harmful effects to humans as well as the environment. Reliable chlorine sensing techniques have therefore become the keys to ensure a balance between chlorine disinfection efficiency and disinfection safety. Up to now, there is still a lack of comprehensive review that collates and appraises the recently available techniques from a practical point of view. In this work, we intend to present a detailed overview of the recent advances in monitoring chlorine in both dissolved and gaseous forms aiming to present valuable information in terms of method accuracy, sensitivity, stability, reliability, and applicability, which in turn guides future sensor development. Data on the analytical performance of different techniques and environmental impacts associated with the dominated chemical-based techniques are thus discussed. Finally, this study concluded with highlights of gaps in knowledge and trends for future chlorine sensing development. Due to the increasing use of chlorine in disinfection and chemical synthesis, we believe the information present in this review is a relevant and timely resource for the water treatment industry, healthcare sector, and environmental organizations.
Chapter
The assessment of drinking water quality is one of the main applications of UV–visible spectrophotometry. From the quality of resources to tap water, UV sensing is used for the characterization of water resources (freshwater or groundwater) and drinking water even during rainfalls or floods, for water treatment assistance or as early warning system in the case of accidental or intentional contamination. On the other hand, UV measurement is more and more considered as a surrogate parameter for the monitoring or the prediction of disinfection by-products. Finally, UV spectrophotometry remains a good tool for the chemical characterization of drinking water either in the distribution system or packed in bottles.
Article
Dibromoacetonitrile (DBAN) is a disinfection byproduct (DBP) and linked with cancer in rodents, but the mechanism of its carcinogenicity has not been fully elucidated. We recently reported that DBAN induced inhibition of nucleotide excision repair (NER). In this study, we investigated if glutathione (GSH) is involved in the DBAN-induced inhibition of NER. Human keratinocytes HaCaT were pretreated with L-buthionine-(S,R)-sulfoximine (BSO) to deplete intracellular GSH. BSO treatment markedly potentiated the DBAN-induced NER inhibition as well as intracellular oxidation. The recruitment of NER proteins (transcription factor IIH, and xeroderma pigmentosum complementation group G) to DNA damage sites was inhibited by DBAN, which was further exacerbated by BSO treatment. Our results suggest that intracellular GSH protects cells from DBAN-induced genotoxicity including inhibition of DNA damage repair.
Article
In this study, the formation of iodinated trihalomethanes (I-THMs) was systematically evaluated and compared for three treatment processes - (i) chlorination, (ii) monochloramine, and (iii) dichloramination - under different pH conditions. The results demonstrated that I-THM formation decreased in the order of monochloramination > dichloramination > chlorination in acidic and neutral pH. However, the generation of I-THMs increased in the dichloramination < chlorination < monochloramination order in alkaline condition. Specifically, the formation of I-THMs increased as pH increased from 5 to 9 during chlorination and monochloramination processes, while the maximum I-THM formation occurred at pH 7 during dichloramination. The discrepancy could be mainly related to the stability of the three chlor (am) ine disinfectants at different pH conditions. Moreover, in order to gain a thorough insight into the mechanisms of I-THM formation during dichloramination, further investigation was conducted on the influencing factors of DOC concentration and Br⁻/I⁻ molar ratio. I-THM formation exhibited an increasing and then decreasing trend as the concentration of DOC increased from 1 to 7 mg-C/L, while the yield of I-THMs increased with increasing Br⁻/I⁻ molar ratio from 5: 0 to 5: 10. During the three processes mentioned above, similar I-THM formation results were also obtained in real water, which indicates that the excessive generation of I-THMs should be paid special attention during the disinfection of iodide-containing water.
Article
Water disinfection can generate water disinfection byproducts (DBPs). Iodoacetic acid (IAA) is one DBP and it has been shown to be an ovarian toxicant in vitro and in vivo. However, it is unknown if prenatal and lactational exposure to IAA affects reproductive outcomes in female offspring. This study tested the hypothesis that prenatal and lactational exposure to IAA adversely affects reproductive parameters in F1 female offspring. Adult female CD-1 mice were dosed with water (control) or IAA (10, 100, and 500 mg/L) in the drinking water for 35 days and then mated with unexposed males. IAA exposure continued throughout gestation. Dams delivered naturally, and pups were continuously exposed to IAA through lactation until postnatal day (PND) 21. Female pups were euthanized on PND 21 and subjected to measurements of anogenital distance, ovarian weight, and vaginal opening. Ovaries were subjected to histological analysis. In addition, sera were collected to measure reproductive hormone levels. IAA exposure decreased vaginal opening rate, increased the absolute weight of the ovaries, increased anogenital index, and decreased the percentage of atretic follicles in female pups compared to control. IAA exposure caused a borderline decrease in the levels of progesterone and follicle-stimulating hormone (FSH) and increased levels of testosterone in female pups compared to control. Collectively, these data show that prenatal and lactational exposure to IAA in drinking water affects vaginal opening, anogenital index, the weight of the ovaries, the percentage of atretic follicles, and hormone levels in the F1 generation in mice.
Article
BACKGROUND: Sodium chlorate occurs when drinking water is disinfected by chlorine dioxide. We studied the effects of sodium chlorate in rats and mice to identify potential toxic or carcinogenic hazards to humans.
Article
The object of the present study is to verify the suitability of using chlorine dioxide as a preoxidant in the Water Treatment Plant of La Presa (Manises) and El Realón (Picassent), in order to minimize the trihalomethanes formation. To prove the effectiveness of chlorine dioxide, on the trihalomethanes precursors removal by oxidation, many controls and analytics have been done on the two water treatment plants. On the other hand, this study also shows the chlorine dioxide generation method used, as well as its high disinfection efficiency, higher than the chlorine.
Article
It has been known for many years that ozonation of natural water produces polar organic compounds such as aldehydes and carboxylic acids, presumably from the oxidative fragmentation of higher molecular weight natural organic compounds such as humic and fulvic acids. Until lately, few studies have been reported that show how aldehydes are produced in actual treatment plants that use ozone. This paper reports the results obtained in the first phase of a study of several treatment plants in the United States and one in Canada that use ozonation. Some of the plants are full scale, others are pilot scale units that are being tested prior to design and construction of full scale units. The portion of the study reported here was carried out during 1990 and early 1991.
Article
The occurrence of the carcinogen chloroform in chlorinated drinking water has been shown to arise from reaction of this disinfectant with so-called humic substances which are found varying quantities in natural waters. Disinfection with chlorine dioxide is one alternative to chlorination as it does not result in the formation of chloroform or other trihalomethanes. However, knowledge of the identities and quantities of all but a few of the reaction products of humic substances with chlorine dioxide and chlorine is rather incomplete as well. A research project to define the chemistry of disinfecting drinking water with chlorine, chlorine dioxide and mixtures thereof in the presence of the model substance humic acid has been in progress for some time. The paper presnts an interim report that deals with kinetics, oxidant demand and formation of the toxic reaction products CHCl//3 and ClO//2** minus ion in the pH interval 6. 0-9. 5. These data may be of interest in reconciling maximum permissible dosages of disinfectant with the need to maintain disinfectant residuals at the tap.
Article
Mammalian cell asays can provide toxicological information that may be more relevant to human risk asessment than commonly used microbial tests. Rapid, semi-automated, quantitative mammalian cell cytotoxicity and genotoxicity assays were developed to analyze drinking water disinfection by-products (DBPs). These assays employ 96-well microplates; selected DBPs were analyzed with cultured Chinese hamster ovary (CHO) cells. The concentration of the DBPs that repressed 50% of CHO cell growth with a 72 h exposure was calculated as the %C1/2 value. Using these values the rank order (from highest to lowest cytotoxicity) was bromonitromethane, dibromonitromethane, tribromonitromethane, bromoacetic acid, dibromoacetic acid, and tribromoacetic acid. Genotoxicity analyses of the DBPs were conducted using the single cell gel electrophoresis (SCGE) assay. This assay detects genomic DNA damage at the level of the individual nucleus. Using SCGE genotoxic potency the rank order was bromoacetic acid> dibromonitromethane>>bromonitromethane>dibromoacetic acid>tribromoacetic acid. The relative cytotoxicity and genotoxicity of these agents were compared with Salmonella typhimurium. Studies of specific DBPs in mammalian cell systems are important to compare the toxicity of these hazardous water contaminants. Such knowledge is necessary for risk assessment and to assist in the formulation of public regulatory policies that protect the environment and the public health.
Article
This research evaluated a chlorine gas-solid sodium chlorite chlorine dioxide (ClO 2) generation system at the Roanoke County (Va.) Spring Hollow Water Treatment Facility and monitored concentrations of the oxidant and its by-products within the facility and distribution system. Project objectives were to (1) document changes in ClO 2, chlorite ion (ClO 2-), and chlorate ion (ClO 3-) concentrations throughout the facility and distribution system following raw water ClO 2 pretreatment; (2) evaluate ClO 2- removal by the postfiller granular activated carbon (GAC) contactors; and (3) determine distribution system ClO 2 concentrations associated with odor complaints. The average raw water ClO 2 dose was 0.4 mg/L, and overall ClO 2 - removals by GAC averaged 63% but declined markedly with increasing throughput volume. Distribution system ClO 2- concentrations were generally <0.2 mg/L and decreased with increasing distance from the treatment facility; ClO 3- never exceeded 0.1 mg/L. ClO 2 was measured at low concentrations (0.017-0.17 mg/L) in the distribution system, and a measured concentration of 0.03 mg/L was found at the home of one customer who complained of odors.
Article
This article reviews the use of the Ames Salmonella assay for assessing the mutagenicity of water produced by various treatment processes. Although chlorination is the most common means of disinfection in North America, chloramines, chlorine dioxide, and ozone have been shown to produce water that is less mutagenically active. Granular activated carbon (GAC) removes mutagens preferentially compared with parameters such as total organic carbon. In the absence of GAC, postchlorination typically increases mutagenicity. Inconsistent interstudy results with respect to the effects of ozone and metabolic activation (S9) and the capacity of GAC point to the role of raw water characteristics in the determination of treated water mutagenicity. In the case of ozone, dosage and contact time may also be important.
Article
N-nitrosodimethylamine (NDMA) is a carcinogen known to be present in various foods and industrial products. The US Environmental Protection Agency has established a 10 -6 cancer risk level for NDMA of 0.7 ng/L. NDMA has been found in the effluents of various water and wastewater plants, but its formation mechanism is not yet understood. This study evaluated NDMA formation during various water and wastewater treatment processes including chlorination and chloramination, ozonation, and ion exchange. On the basis of the limited results obtained in this study, NDMA appears to be a by-product of the chloramination of water and wastewater, with the level of NDMA formed directly related to the *chloramine dose. In the waters tested, NDMA did not form on contact with free chlorine or ozone. Contact of one water with typical levels of amine-based polymer did not form any measurable NDMA levels (<2 ng/L). Batch testing was conducted with four strong-base anion exchange resins contacted with untreated groundwater and with buffered deionized water. Results showed that some resins might leach or form NDMA and the level of NDMA produced is a function of the chemical functional group on the surface of the resin.
Article
Objectives and methods—Chlorination has been the major disinfectant process for domestic drinking water for many years. Concern about the potential health eVects of the byproducts of chlorination has prompted the investigation of the possible association between exposure to these byproducts and incidence of human cancer, and more recently, with adverse reproductive outcomes. This paper evaluates both the toxicological and epidemiological data involving chlorination disinfection byproducts (DBPs) and adverse reproductive outcomes, and makes
Article
Chloroform, generally regarded as a non-genotoxic compound, is associated with the induction of liver and/or kidney tumors in laboratory mice and rats. In particular, chloroform produced renal tubule tumors in low incidence in male Osborne-Mendel rats when administered by corn-oil gavage or in the drinking water. There is a lack of data on intermediate endpoints that may be linked to renal cancer development in this strain of rat, in contrast to mice. Specifically, evidence linking chloroform-induced liver and kidney tumors in mice with cytotoxicity and regenerative cell proliferation is very strong, but weak in the rat. In the present study, kidney tissue from a carcinogenicity bioassay of chloroform in Osborne-Mendel rats was re-evaluated for histological evidence of compound-induced cytotoxicity and cell turnover. All rats treated with 1800 ppm (160 mg/kg/day, high-dose group) in the drinking water for 2 years and half the rats treated with 900 ppm (81 mg/kg/day) had mild to moderate changes in proximal convoluted tubules in the mid to deep cortex indicative of chronic cytotoxicity. Tubule alterations specifically associated with chronic chloroform exposure included cytoplasmic basophilia, cytoplasmic vacuolation, and nuclear crowding consistent with simple tubule hyperplasia. Occasional pyknotic cells, mitotic figures in proximal tubules, and prominent karyomegaly of the renal tubule epithelium were present. These alterations were not present in control groups or at the 200-ppm (19 mg/kg/day) or 400-ppm (38 mg/kg/day) dose levels. This new information adds substantially to the weight of evidence that the key events in chloroform-induced carcinogenicity in rat kidney include sustained cellular toxicity and chronic regenerative hyperplasia.
Article
Cancer risk assessment methods for chemical mixtures in drinking water are not well defined. Current default risk assessments for chemical mixtures assume additivity of carcinogenic effects, but this may not represent the actual biological response. A rodent model of hereditary renal cancer (Eker rat) was used to evaluate the carcinogenicity of mixtures of water disinfection by-products (DBPs). Male and female Eker rats were treated with individual DBPs or a mixture of DBPs for 4 or 10 months. Potassium bromate, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone, chloroform, and bromodichloromethane were administered in drinking water at low concentrations of 0.02, 0.005, 0.4, and 0.07 g/l, respectively, and high concentrations of 0.4, 0.07, 1.8, and 0.7 g/l, respectively. Low and high dose mixture solutions comprised all four chemicals at either the low or the high concentrations, respectively. Body weights, water consumption, and chemical concentrations in the water were measured monthly. All tissues were examined macroscopically for masses and all masses were diagnosed microscopically. Total renal lesions (adenomas and carcinomas) were quantitated microscopically in male and female rats treated for 4 or 10 months. A dose response for renal tumors was present in most treatment groups after 4 or 10 months of treatment. Treatment with the mixture produced on average no more renal, splenic, or uterine tumors than the individual compound with the greatest effect. This study suggests that the default assumption of additivity may overestimate the carcinogenic effect of chemical mixtures in drinking water.
Article
There is widespread potential for human exposure to disinfection byproducts (DBPs) in drinking water because everyone drinks, bathes, cooks, and cleans with water. The need for clean and safe water led the U.S. Congress to pass the Safe Drinking Water Act more than 20 years ago in 1974. In 1976, chloroform, a trihalomethane (THM) and a principal DBP, was shown to be carcinogenic in rodents. This prompted the U.S. Environmental Protection Agency (U.S. EPA) in 1979 to develop a drinking water rule that would provide guidance on the levels of THMs allowed in drinking water. Further concern was raised by epidemiology studies suggesting a weak association between the consumption of chlorinated drinking water and the occurrence of bladder, colon, and rectal cancer. In 1992 the U.S. EPA initiated a negotiated rulemaking to evaluate the need for additional controls for microbial pathogens and DBPs. The goal was to develop an approach that would reduce the level of exposure from disinfectants and DBPs without undermining the control of microbial pathogens. The product of these deliberations was a proposed stage 1 DBP rule. It was agreed that additional information was necessary on how to optimize the use of disinfectants while maintaining control of pathogens before further controls to reduce exposure beyond stage 1 were warranted. In response to this need, the U.S. EPA developed a 5-year research plan to support the development of the longer term rules to control microbial pathogens and DBPs. A considerable body of toxicologic data has been developed on DBPs that occur in the drinking water, but the main emphasis has been on THMs. Given the complexity of the problem and the need for additional data to support the drinking water DBP rules, the U.S. EPA, the National Institute of Environmental Health Sciences, and the U.S. Army are working together to develop a comprehensive biologic and mechanistic DBP database. Selected DBPs will be tested using 2-year toxicity and carcinogenicity studies in standard rodent models; transgenic mouse models and small fish models; in vitro mechanistic and toxicokinetic studies; and reproductive, immunotoxicity, and developmental studies. The goal is to create a toxicity database that reflects a wide range of DBPs resulting from different disinfection practices. This paper describes the approach developed by these agencies to provide the information needed to make scientifically based regulatory decisions.
Article
Dichloroacetate (DCA), a by-product of water chlorination, causes liver cancer in B6C3F1 mice. A hallmark response observed in mice exposed to carcinogenic doses of DCA is an accumulation of hepatic glycogen content. To distinguish whether the in vivo glycogenic effect of DCA was dependent on insulin and insulin signaling proteins, experiments were conducted in isolated hepa- tocytes where insulin concentrations could be controlled. In hepa- tocytes isolated from male B6C3F1 mice, DCA increased glycogen levels in a dose-related manner, independently of insulin. The accumulation of hepatocellular glycogen induced by DCA was not the result of decreased glycogenolysis, since DCA had no effect on the rate of glucagon-stimulated glycogen breakdown. Glycogen accumulation caused by DCA treatment was not hindered by inhibitors of extracellular-regulated protein kinase kinase (Erk1/2 kinase or MEK) or p70 kDa S6 protein kinase (p70 S6K ), but was
Article
Dichloroacetic acid (DCA) is a chlorination byproduct found in finished drinking water. When administered in drinking water this chemical has been shown to produce hepatocellular adenomas and carcinomas in B6C3F1 mice over the animal's lifetime. In this study, we investigated whether mutant frequencies were increased in mouse liver using treatment protocols that yielded significant tumor induction. DCA was administered continuously at either 1.0 or 3.5 g/l in drinking water to male transgenic B6C3F1 mice harboring the bacterial lacI gene. Groups of five or six animals were killed at 4, 10 or 60 weeks and livers removed. At both 4 and 10 weeks of treatment, there was no significant difference in mutant frequency between the treated and control animals at either dose level. At 60 weeks, mice treated with 1.0 g/l DCA showed a 1.3-fold increase in mutant frequency over concurrent controls (P = 0.05). Mice treated with 3.5 g/l DCA for 60 weeks had a 2.3-fold increase in mutant frequency over the concurrent controls (P = 0.002). The mutation spectrum recovered from mice treated with 3.5 g/l DCA for 60 weeks contained G:C→A:T transitions (32.79%) and G:C→T:A transversions (21.31%). In contrast, G:C→A:T transitions comprised 53.19% of the recovered mutants among control animals. Although only 19.15% of mutations among the controls were at T:A sites, 32.79% of the mutations from DCA-treated animals were at T:A sites. This is consistent with the previous observation that the proportion of mutations at T:A sites in codon 61 of the H-ras gene was increased in DCA-induced liver tumors in B6C3F1 mice. The present study demonstrates DCA-associated mutagenicity in the mouse liver under conditions in which DCA produces hepatic tumors.
Article
The brominated trihalomethanes (THMs) are mutagenic and carcinogenic disinfection by-products frequently found in chlorinated drinking water. They can be activated to mutagens by the product of the glutathione S-transferase-q (GSTT1-1) gene in Salmonella RSJ100, which has been transfected with this gene. To evaluate this phenomenon in humans, we have examined the genotoxicity of a brominated THM, bromoform (BF), using the Comet assay in human whole blood cultures exposed in vitro. No differences were found in the comet tail length between cultures from GSTT1-1 F versus GSTT1-1 ‐ individuals (1.67 K 0.40 and 0.74 K 0.54 mm/mM, respectively, P J 0.28). The high variability was due to the relatively weak induction of comets by BF. Combining the data from both genotypic groups, the genotoxic potency of BF was 1.20 K 0.34 mm/mM (P J 0.003). GSTT1-1 is expressed in red blood cells but not in the target cells (lymphocytes), and expression within the target cell (as in Salmonella RSJ100) may be necessary for enhanced mutagenesis in GSTT1-1 F relative to GSTT1-1 ‐ cultures. To examine this, we exposed Salmonella RSJ100 and a control strain not expressing the gene (TPT100) to the most mutagenic brominated THM detected in Salmonella, dibromochloromethane (DBCM), either in the presence or absence of S9 or red blood cells from GSTT1-1 F or GSTT1-1 ‐ individuals. S9 did not activate DBCM in the non-expressing strain TPT100, and it did not affect the ability of the expressing strain RSJ100 to activate DBCM. As with S9, red cells from either genotypic group were unable to activate DBCM in TPT100. However, red cells (whole or lysed) from both genotypic groups completely repressed the ability of the expressing strain RSJ100 to activate DBCM to a mutagen. Such results suggest a model in which exposure to brominated THMs may pose an excess genotoxic risk in GSTT1-1 F individuals to those organs and tissues that both express this gene and come into direct contact with the brominated THM, such as the colon. In contrast, those organs to which brominated THMs would be transported via the blood might be protected by erythrocytes. Such a proposal is reasonably consistent with the organ specificity of drinking waterassociated cancer in humans, which shows slightly elevated risks for cancer of the colon and bladder but not of the liver.
Article
Aberrant crypt foci (ACF), identified as putative precursor lesions in the development of colon cancer, were induced by brominated trihalomethanes (THMs) administered in the drinking water of rats. To investigate whether ACF induced by THMs could be promoted by a diet high in saturated animal fat, male F344/N rats were exposed to 0.5, 0.7, 0.9 or 1.1 g/l of trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and tribromomethane (TBM), respectively, in drinking water. All animals were fed a Purina 5001 diet with half receiving the normal 4.5% fat feed and half receiving feed supplemented with 19% animal fat. After 26 weeks of treatment, colons were excised and examined for ACF. No difference in ACF was noted between animals fed a normal or high fat diet and exposed to TCM, BDCM or DBCM. However, animals exposed to TBM and fed a high fat diet showed a significant and near two-fold increase in ACF when compared to TBM exposed animals fed a normal diet.
Article
Chloroform acts via a nongenotoxic–cytotoxic mode of action to produce cancer if given in doses and at dose rates sufficiently high to produce organ-specific toxicity. In a recent study, chloroform failed to induce cancer in male or female F-344 rats when administered by inhalation for 2 years at 90 ppm, 5 days/week. The present study was undertaken to define the concentration–response curves for chloroform-induced lesions and regenerative cell proliferation in the F-344 rat when exposed by inhalation and to correlate those patterns of toxicity with the results from the inhalation cancer bioassay. Male and female F-344 rats were exposed to airborne concentrations of 0, 2, 10, 30, 90, or 300 ppm chloroform 6 hr/day, 7 days/week for 4 days or 3, 6, or 13 weeks. Additional treatment groups were exposed 5 days/week for 13 weeks or were exposed for 6 weeks and held until Week 13. Bromodeoxyuridine was administered via osmotic pumps implanted 3.5 days prior to necropsy and the labeling index (LI, percentage of nuclei in S-phase) was evaluated immunohistochemically. A full-screen necropsy identified the kidney, liver, and nasal passages as the only target organs. This study confirmed that 300 ppm is extremely toxic and would be inappropriate for longer-term cancer studies. The primary target in the kidney was the epithelial cells of the proximal tubules of the cortex, with significantly elevated increases in the LI at concentrations of 30 ppm and above. However, only a marginal increase in the renal LI in the males was seen after exposures of 90 ppm, 5 days/week. Chloroform induced hepatic lesions in the midzonal and centrilobular regions with increases in the LI throughout the liver, but only at 300 ppm exposures. An additional liver lesion seen only at the highly hepatotoxic concentration of 300 ppm was numerous intestinal crypt-like ducts surrounded by dense connective tissue. Enhanced bone growth and hypercellularity in the lamina propria of the ethmoid turbinates of the nose occurred at the early time points at concentrations of 10 ppm and above. At 90 days there was a generalized atrophy of the ethmoid turbinates at concentrations of 2 ppm and above. Cytolethality and regenerative cell proliferation are necessary but not always sufficient to induce cancer because of tissue, sex, and species differences in susceptibility. A combination of a lack of direct genotoxic activity by chloroform, only a marginal induction of cell proliferation in the male rat kidney, and lower tissue-specific susceptibility in the female rat is apparently responsible for the reported lack of chloroform-induced cancer in a long-term inhalation bioassay with F-344 rats.
Article
Sodium dichloroacetate (DCA) is a drug with potential for treating patients with stroke and head injury. Conflicting evidence has been published on the mutagenic potential of DCA. A series of genetic tests for mutagenicity and clastogenicity was carried out on pharmaceutical grade DCA. Four types of mutagenicity test were included, with and without metabolic activation where appropriate. These studies included: (i)SalmonellaandEscherichia colimutation (Ames) tests, (ii) thymidine kinase locus forward mutation in L5178Y mouse lymphoma cells, (iii) tests for chromosomal aberrations in Chinese hamster ovary cells, and (iv) anin vivorat bone marrow erythroid micronucleus test. In each study, there was no evidence of mutagenic activity attributable to DCA. It is possible that the present test material, of pharmaceutical grade, has fewer impurities than materials studied in previous reports. These data extend, and in some cases contradict, previous published reports on DCA.
Article
Toxicology and carcinogenesis studies were conducted by administering doses of 0, 100, or 200 mg/kg tribromomethane in corn oil by gavage, 5 days per week for a period of 103 weeks, to groups of 50 rats of each sex and 50 female mice. Groups of 50 male mice were administered 0, 50, or 100 mg/kg tribromomethane on the same schedule. Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of tribromomethane for male F344/N rats and clear evidence of carcinogenic activity for female F344/N rats, based on increased incidence of uncommon neoplasms of the large intestine. Reduced survival for male rats given 200 mg/kg tribromomethane lowered the sensitivity of the group to detect a carcinogenic response. Chemically related noneoplastic lesions included fatty change and active chronic inflammation of the liver in male and female rats, minimal necrosis of the liver in male rats, and mixed cell foci of the liver in female rats. There was no evidence of carcinogenic activity for male B6C3F1 mice given 50 or 100 mg/kg tribromomethane or for female B6C3F1 mice given 100 or 200 mg/kg; male mice might have been able to tolerate a higher dose. Survival of the female mice was reduced, partly due to a utero-ovarian infection.
Article
Minimizing the inorganic by-products chlorite ion and chlorate ion in drinking water treated with chlorine dioxide is important if ClO₂ is to remain a viable alternative in potable water treatment. The use of sulfur dioxide-sulfite ion chemistry to quantitatively remove chlorite ion to below the 0.1-mg/L level is described, along with the use of free chlorine to remove the sulfur dioxide-sulfite ion. The stoichiometry and the rate law are described for pH values of 5.5 to 8.5 so that the chemistry can be applied directly in existing drinking water treatment facilities. La minimización de los subproductos inorgánicos de los iones de clorito y clorato en aguas potables tratadas con el dióxido de cloro es importante si el ClO₂ va a seguir siendo una alternativa viable en el tratamiento de aguas potables. Se describe el uso químico del ión azufredióxido-sulfito para remover cuantitativamente el ión de clorito a menos del nivel restante de 0.1-mg/L, junto con el uso del cloro libre para remover el ion azufre-dióxido-sulfito restante. La estequiometría y la ley cambio son descritas para valores pH de 5.5 a 8.5 de tal forma que la química pueda ser aplicada directamente en las plantas de tratamiento de agua potable existentes.
Article
An investigation of raw and finished waters was conducted (1) to determine whether chlorine dioxide pretreatment lowers trihalomethane (THM) and total organic halide (TOX) formation, (2) to evaluate the rate of chlorine dioxide consumption and the corresponding rate and extent of chlorite formation, and (3) to investigate the stability of chlorite in treated water and its interaction with chlorine. Results of these experiments showed that chlorine dioxide can reduce THM and TOX precursor concentrations and that when added to raw water, chlorine dioxide will not persist long enough to maintain oxidizing conditions through flocculation-sedimentation basins. Utilities should be able to meet the recommended limit of 1.0 mg/L for the sum of the residual chlorine dioxide species by not exceeding a chlorine dioxide dosage of 1.2-1.4 mg/L. Una investigatión de aguas crudas y terminadas de fué conducida (1) para determinar si pretratamiento con cloro dióxido reducé la formación de trihalométanos (THM) y haluro orgánico total (TOX), (2) para evaluar la velocidad de consunción de cloro dioxido y la velocidad y grado correspondiente de formación de clorita, (3) para investigar la estabilidad de clorita en agua tratada y su interactión con cloro. Resultados mostraron que cloro dióxido puede reducir niveles de precursores de THM y TOX y que cuando agregado a agua cruda, cloro dióxido no mantendrá condiciones oxidantes a través de cuencas de floculation y sedimentatión. Utilidades deberian ser capaces de llegar al límite recomendado de 1.0 mg/L para la suma de las especies residuales de cloro dióxido si no exceden una dosis de cloro dióxido de 1.2-1.4 mg/L.
Article
The national media have reported that the chlorination of water during treatment is responsible for the formation of potentially harmful chlorinated organic materials—notably chloroform—in the nation's water supplies. The following report by three research scientists from the Nati. Envir. Res. Ctr. of EPA describes that agency's research concerning these organohalides. The report concludes that the number of organohalides formed during the chlorination process does not constitute any immediate threat to the public health or welfare, but that more research into possible long-term effects is warranted.
Article
Despite the noteworthy genotoxic potency of many industrial wastewaters, the genotoxic hazard posed to the downstream ecosystem and its associated biota will be determined by genotoxic loading. Municipal wastewaters, although ranking low in potency, can achieve loading values that are several orders of magnitude greater than those of most industries. Although these wastewaters are generally mixtures of wastes from several different sources, the volumetric proportion of the daily discharge that is of industrial origin rarely exceeds 30%. Genotoxicity calculations for the Montreal Urban Community (MUC) municipal wastewater treatment facility indicate that over 90% of the genotoxic loading (31.1 kg benzo(a)pyrene equivalents per day) is nonindustrial in origin. Moreover, a mass balance of surface water genotoxicity for St. Lawrence river at Montreal indicates that over 85% of the total contributions from the Montreal region are nonindustrial in origin. Additional calculations for the Great Lakes, and other rivers throughout the world, provide further support of a strong relationship between surface water genotoxicity and population. Despite some information about physical/chemical properties, the identity of the putative genotoxins in municipal wastewaters and surface waters remains a mystery. Likely candidates include potent genotoxins, such as N-nitroso compounds and aromatic amines, known to be present in human sanitary wastes, as well as genotoxic PAHs known to be present in many municipal wastewaters. Calculations based on literature data indicate that human sanitary wastes may be able to account for a substantial fraction (4–70%) of the nonindustrial loading from municipal wastewaters. Similar calculations suggest that pyrogenic PAHs that enter municipal wastewaters via surface runoff can only account for a small fraction (
Article
N-Nitrosodimethylamine (NDMA) has been assessed as a Priority Substance under the Canadian Environmental Protection Act. Based upon laboratory studies in which tumours have been induced in all species examined at relatively low doses, NDMA is clearly carcinogenic, with a very strong likelihood that the mode of action for the induction of tumours involves direct interaction with genetic material. Qualitatively, the metabolism of NDMA appears to be similar in humans and animals; as a result, it is considered highly likely that NDMA is carcinogenic to humans. A Tumorigenic Dose05 (TD05) of 34 μg/kg body weight per day has been derived, based upon the benchmark dose associated with a 5% increase in the development of hepatic biliary cystadenomas in female rats in an oral carcinogenicity bioassay.
Article
There are still compounds to identify, and new data indicate that already known DBPs may pose additional health risks.
Article
This study investigated the oxidation of the oral contraceptive 17alpha-ethinylestradiol (EE2) during ozonation. First, the effect of ozone (O-3) on the estrogenic activity of aqueous solutions of EE2 was studied using a yeast estrogen screen (YES). It could be shown that O-3 doses typically applied for the disinfection of drinking waters were sufficient to reduce estrogenicity by a factor of more than 200. However, it proved impossible to completely remove estrogenic activity due to the slow reappearance of 0.1 - 0.2% of the initial EE2 concentration after ozonation. Second, oxidation products formed during ozonation of EE2 were identified with LC-MS/MS and GC/MS and the help of the model compounds 5,6,7,8-tetrahydro-2-naphthol (THN) and 1-ethinyl-1-cyclohexanol (ECH),which represent the reactive phenolic moiety and the ethinyl group of EE2. Additionally, oxidation products of the natural steroid hormones 17beta-estradiol (E2) and estrone (E1) were identified. The chemical structures of the oxidation products were significantly altered as compared to the parent compounds, explaining the diminished estrogenic activity after ozonation. Overall, the results demonstrate that ozonation is a promising tool for the control of EE2, E2, and El in drinking water and wastewater.
Article
Data were gathered on the presence of disinfection by-products (DBPs) in drinking water and on the impact of treatment processes on DBP formation and control. Thirty-five water treatment facilities were selected to provide a broad range of source water qualities and treatment processes. Trihalomethanes were the largest class of DBPs detected (on a weight basis) in this study, with haloacetic acids being the next most significant DBP fraction. Formaldehyde and acetaldehyde, by-products of ozonation, were also demonstrated to be produced by chlorination. Cyanogen chloride was found to be preferentially produced in chloraminated water. Se recogieron datos de la presencia de sub-productos de la desinfección (DBPs) en aguas de bebida y sobre el impacto de los procesos de tratamiento en la formación y control de los DBPs. Treinta y cinco plantas de tratamiento fueron seleccionadas para obtener un amplio rango tanto de calidad del agua cruda, como de los procesos de tratamiento. Los trihalometanos fueron la clase de DBPs más grande detecatada (sobre la base de peso) en este estudio, y los ácidos haloacéticos fueron la fracción siguiente más significante de DBPs. Se comprobó que los formaldehidos y los acetaldehidos, sub-productos de la ozonización, también eran producidos por la clorinación. El producto principal de la aplicación de cloraminas fue el cianuro de cloro.
Article
Dichloroacetate (DCA) is a by-product of drinking water chlorination. Administration of DCA in drinking water results in accumulation of glycogen in the liver of B6C3F1 mice. To investigate the processes affecting liver glycogen accumulation, male B6C3F1 mice were administered DCA in drinking water at levels varying from 0.1 to 3 g/l for up to 8 weeks. Liver glycogen synthase (GS) and glycogen phosphorylase (GP) activities, liver glycogen content, serum glucose and insulin levels were analyzed. To determine whether effects were primary or attributable to increased glycogen synthesis, some mice were fasted and administered a glucose challenge (20 min before sacrifice). DCA treatments in drinking water caused glycogen accumulation in a dose-dependent manner. The DCA treatment in drinking water suppressed the activity ratio of GS measured in mice sacrificed at 9:00 AM, but not at 3:00 AM. However, net glycogen synthesis after glucose challenge was increased with DCA treatments for 1–2 weeks duration, but the effect was no longer observed at 8 weeks. Degradation of glycogen by fasting decreased progressi