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Occurrence, Genotoxicity, and Carcinogenicity of Regulated and Emerging Disinfection By-Products in Drinking Water: A Review and Roadmap for Research
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.
... Up to now, approximately 600 DBPs [5,6] with a high chemical diversity have been identified, and only 18 DBPs of them have been regulated by the US Environmental Protection Agency, the European Union and the World Health Organization [7]. However, 74 DBPs classified as emerging pollutants [8]. ...
... Several studies on the toxicology, genotoxicity, carcinogenicity, and mutagenicity of DBPs have revealed that DBPs are responsible for serious health complications, including bladder cancer, miscarriage, birth defects, etc. [8]. Furthermore, they are persistent, difficult to biodegrade and have the ability to accumulate in organisms. ...
... Humans can be exposed to THMs through different ways, whether directly from drinking water or as through the volatilization of DBPs during cooking, bathing, showering, etc. [8]. ...
Increasing water scarcity caused by population growth, climate change, pollution from natural and anthropogenic sources, etc. is likely to impact the occurrence of water-associated infectious diseases. Nowadays, access to clean and safe water is a growing concern worldwide. Therefore, disinfection of drinking water is a vital step in public treatment systems as it ensures the removal of various contaminants, including pathogenic microorganisms (protozoa, viruses, bacteria, and intestinal parasites) that give rise to waterborne diseases. Nevertheless, undesirable disinfection byproducts (DBPs) are formed during disinfection as a result of reactions between chemical disinfectants and natural organic matter (NOM), and/or anthropogenic contaminants, and/or bromide/iodide that are present in the raw water. The chemical complexity and heterogeneity of matters in the raw water makes the characterization and the mechanism of DBPs formation quite difficult and ambiguous regardless of the previous hundreds of studies on DBPs generation. As chlorination is still the most economic and most often used disinfection method, and beside chlorination, the application of chlorine dioxide is becoming more widespread, this paper investigates the possible DBPs generated using chlorine and chlorine dioxide with highlighting their adverse health effects. It overviews the reactions of those disinfectants with inorganic and organic compounds. It is important to note that in order to better understand the performance of disinfectants in water treatment, further investigations on the mechanisms of them with inorganic and organic compounds found in water are critically needed.
... Disinfection by-products are reactive and potentially carcinogenic chemical substances that are formed when chlorine reacts with natural organic matter in drinking water. Trihalomethanes (THMs) is the class of by-products that is found at the highest concentrations in chlorinated drinking water, and several substances are genotoxic and rodent carcinogens [6]. Two of the most common THMs induce aberrant crypts and large intestine carcinoma in carcinogenesis studies of rats, which are anatomically and functionally analogous to colorectal cancer tumors in humans [7,8]. ...
... Similarly, in the Spanish case-control study where brominated THMs were associated with increased risk of colorectal cancer in men, no association was observed with total THMs, and an inverse Downloaded from https://academic.oup.com/jnci/advance-article/doi/10.1093/jnci/djad145/7238786 by guest on 08 August 2023 association was observed with chloroform [20]. Similar differences have been found in experimental studies and suggest that not all individual THMs are equally toxic [6]. The proportion of individual THMs in different disinfection by-product mixtures depend on a number of factors, including the levels of bromine in the raw water, which highlights the complexity and the challenges associated with studying health effects of mixtures. ...
... The three brominated THMs are all genotoxic in standard test systems after glutathione S-transferase theta 1 (GSTT1-1) biotransformation. Although chloroform is not genotoxic, it induces tumors in rodent carcinogenicity bioassays [25] presumably through pathways involving cytotoxicity and regenerative cell proliferation [6]. Interestingly, bromoform and bromodichloromethane, which are also the disinfection by-products that have been the most consistently associated with increased colorectal cancer risk in humans, have been shown to produce aberrant crypts and tumors of the large intestine in rats [7,8]. ...
Background
Colorectal cancer is the third most common malignancy worldwide, and it is strongly linked to lifestyle and environmental risk factors. While several drinking water disinfection by-products are confirmed rodent carcinogens, there is still inconclusive evidence for human carcinogenicity, including colorectal cancer.
Methods
We assessed the association of long-term exposure to Trihalomethanes (THMs, the most prevalent disinfection by-products in chlorinated drinking water) with incidence of colorectal cancer in 58,672 men and women in two population-based cohorts. Exposure was assessed by combining long-term information of residential history with drinking water monitoring data. Participants were categorized according to no exposure, low exposure (<15µg/L) and high exposure (≥15µg/L). Incident cases of colorectal cancer were ascertained using the Swedish National Cancer Register.
Results
During an average follow-up of 16.8 years (988,144 person-years), 1,913 cases of colorectal cancer were ascertained (1,176 and 746 men and women, respectively). High drinking water THM concentrations (≥15 µg/L) was associated with increased risk of colorectal cancer in men (hazard ratio, HR: 1.26, 95% confidence interval, CI: 1.05 to 1.51) compared to no exposure. When assessing subsites, the association was significant for proximal colon cancer (HR: 1.59, 95% CI: 1.11 to 2.27) but not distal colon cancer or rectal cancer. In women, we observed overall no association of THMs with colorectal cancer.
Conclusion
These results add further support to that disinfection by-products in drinking water may be a possible risk factor for proximal colon cancer in men. This observation was made at THM concentrations lower than in most previous studies.
... Review of the occurrence, carcinogenic potential, and genotoxic potential have been done in many studies more than 30 years since DBPs found in drinking water at 1974 by Rook and others. The listed of Table 2 about the summary occurrence, carcinogenicity and genotoxicity of regulated DBPs (THMs and HAAs) and also for unregulated DBPs (Nitrosamines) [19] The presence of DBPs in drinking water is an important concern for human health because it causes serious problems due to continuous exposure and the ability of DBPs to increase the risk of developing cancer in the human body, disorders of the liver, kidneys and the nervous system and reproductive system [20]. The variety of DBPs that exist today is influenced by how DBPs were formed, so the diversity and complexity of their impacts on the environment and humans need to be studied properly. ...
... Summary of THMs, HAAs and Nitrosamine occurrence, genotoxicity, and carcinogenicity[19] Potential carcinogenicity of kidney, intestine, liver; central nervous and reproductive disruption; bladder, colon, rectal, or pancreatic cancer [2]. Potential carcinogenicity of stomach, liver, bladder, esophagus, lung, breast and brain[2]. ...
The reaction between chlorine and organic matter in water treatment processes formed a new product called disinfection by products (DBPs). Natural organic matter is the main precursor of the DBPs formation. Trihalomethanes as the most found DBPs in drinking water and N-Nitrosamine as one of kind DBPs from contaminated water. Those compounds are predicted to be carcinogenic for human being. This critical analysis goal is to investigate the potential formation of DBPs in water treatment and analysis the potential health risk to find the best strategies for reducing the DBPs formation. It presents a comprehensive literature review of research to understand the formation of DBPs especially Trihalomethanes and N-Nitrosamine in water treatment. Then investigation the health risk potential of trihalomethanes an N-Nitrosamine. Trihalomethanes always formed during the disinfection process. Trihalomethanes have the high can endanger human health because of the potential of cytotoxicity, genotoxicity, and lead to toxicity. N-Nitrosamine generally come in a lower concentration than Trihalomethanes but give higher health risk. Establish DBPs concentration limits is very important to protect the health of humans who consume water. Prevention of the formation of DBPs compounds by removing organic precursors in the water and adding advanced treatment after the disinfection process.
... Our data suggests that exposure to brominated THMs, but not chloroform, increases the risk of CLL, which could be expected given their different mechanisms of action and toxicological potential [26,27]. Brominated THMs are more cytotoxic than chloroform in addition to being also genotoxic and mutagenic when tested under a wide range of experimental conditions (including human cells) [28,29]. On the other hand, some animal data have observed that chloroform may have an inhibitory effect on certain tumors [30,31]. ...
... Among the 700 DBP identified, THMs and haloacetic acids are the most prevalent chlorination by-products, and have consequently been used in epidemiological studies as surrogates of total DBPs. However, there are other DBPs more toxic [32] such as haloacetonitriles, haloacetamides, or halonitromethanes [28,33,34]. Thus, a possible synergism or additive effect among the different DBPs in drinking water can be suspected and future studies should evaluate more completely the potential effects of combined exposures. ...
Background
Chronic lymphocytic leukemia (CLL) etiology is poorly understood, and carcinogenic chemicals in drinking and recreational water are candidates.
Objective
To evaluate the association between drinking-water exposure to trihalomethanes (THMs) and nitrate as well as lifetime swimming pool attendance and CLL.
Methods
During 2010–2013, hospital-based CLL cases and population-based controls were recruited in Spain, providing information on residential histories, type of water consumed and swimming pool attendance. Average THMs and nitrate levels in drinking water were linked to lifetime water consumption. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using mixed models.
Results
Final samples for residential tap water analyses and swimming pool attendance analyses were 144 cases/1230 controls and 157 cases/1240 controls, respectively. Mean (SD) values for average lifetime residential brominated THMs and chloroform in tap water (μg/L), and ingested nitrate (mg/day) were 48.1 (35.6), 18.5 (6.7) and 13.7 (9.6) respectively in controls; and 72.9 (40.7), 17.9 (5.4), and 14.1 (8.8) in CLL cases. For each 10 μg/L increase of brominated THMs and chloroform lifetime-average levels, the ORs (95% CI) were 1.22 (1.14, 1.31) and 0.54 (0.34, 0.87), respectively. For each 5 mg/day increase of ingested nitrate, the OR of CLL was 0.91 (0.80, 1.04). The OR of lifetime pool users (vs. non-users) was 2.38 (1.61, 3.52). Upon performing annual frequency of attending pools analysis through categorization, the second and third categories showed an ORs of 2.36 (1.49, 3.72) and 2.40 (1.51, 3.83), respectively, and P-trend of 0.001.
Impact statement
This study identifies an association of long-term exposure to THMs in drinking water, at concentrations below the regulatory thresholds and WHO guidelines, and swimming pool attendance, with chronic lymphocytic leukemia (CLL). These unprecedented findings are highly relevant since CLL is an incurable cancer with still unknown etiology and because the widespread exposure to chlorination by-products that remain in drinking and recreational water worldwide. Despite the demonstrated carcinogenicity in animals of several chlorination by-products, little is known about their potential risks on human health. This study makes a significant contribution to the search for environmental factors involved in the etiology of CLL and to the evidence of the health impact of these high prevalent water contaminants.
... In the literature, disinfection by-products are often referred to as by-products from the reaction of biocides/disinfectants with organic/inorganic matrix. This definition is mainly based on aqueous applications [3]. The place and time of formation (during the application phase, after application, or at a later point in time ) have not yet been further considered and defined in the literature. ...
... Consequently, compared to the same reaction mixture in an aqueous solution, alternative reaction may occur in a non-aqueous setting, leading to divergent results concerning the resulting DBPs. No studies investigating DBP formation under conditions of surface disinfection could be identified in the literature [3]. In a recently published review of the use of ozone for disinfection during the Covid crisis, it was found that masks could become damaged by repeated disinfection with ozone and that the polymer bonds could be degraded. ...
Disinfectants and preservatives used as biocides may contain or release active substances (a.s.) that can form by-products with the surrounding matrices during their application which may be released into the environment. Over the past 40 years, several hundred of these so-called disinfection by-products (DBPs) have been detected after applications of biocides used for disinfection. Due to intensive research and further development of analytical capabilities, many new DBP classes, such as iodinated DBPs (I-DBPs), halonitromethanes (HNMs), haloacetamides (HaAms), or halomethanesulfonic acids were detected worldwide in various matrices and applications. Due to the possible hazards and risks for humans and the environment, frequently occurring DBP classes, such as trihalomethanes (THM), haloacetic acids (HAA) and nitrosamines (NDMA), have already been included in many legislations and given limit values. In the European Union, biocides are assessed under the Biocidal Products Regulation 528/2012 (BPR) regarding their efficacy, potential hazards, and risks to human health and the environment. However, the available guidance for the environmental risk assessment (ERA) of DBPs remains vague. To identify knowledge gaps and to further develop the assessment scheme for the ERA of DBPs, a literature search on the multiple uses of biocides and their formation potential of DBPs was performed and the existing process for ERA was evaluated. The results show knowledge gaps on the formation of DBP in non-aqueous systems and DBP formation by non-halogen-based biocidal active substances. Based on the literature research on biocides, a possible proposal of grouping a.s. to consider their DBP formation potential is presented to simplify future ERAs. However, this also requires further research. Until then, a pragmatic approach considering the DBPs formation potential of the active substances and the identified knowledge gaps need to be established for the environmental risk assessment of DBPs in the EU.
Graphical Abstract
... The carbonyl-containing compounds are typical volatile organic compounds and ubiquitouslypresent inthe environment (Yao et al. 2017). Low molecular weight carbonyl-containing compounds, such as formaldehyde and acetaldehyde, were classified by Richardson et al. as toxic and carcinogenic (Richardson, et al. 2007). They have further classified acetaldehyde among the compounds that have toxic properties of human carcinogens. ...
... Aldehydes are formed in drinking water during water disinfection processes as disinfection by-products (DBPs) upon the use of disinfectants such as ozone, chlorine, chloramines or chlorine dioxide. These disinfectants react with organic matter that are naturally occurring in water producing DBPs (Richardson, et al. 2007). A significant increase in the concentration of carbonyl compounds in treated water was observed as the time of reaction of Cl2 and ClO2 with aldehyde precursors increased (Dabrowska et al. 2005). ...
The kinetics of removal of Acetaldehyde (A,Al), Benzaldehyde (B.al),2-Butanone (2-But), Acetophenone (A.Ph) and Benzophenone (B.Ph) from their aqueous solution by adsorption onto powder of Iraqi Porcelanite rocks was investigated. The results were treated by non-linear pseudo-first order (PFO) and non-linear pseudo-second order (PSO) models, the latter model was better fitting with experimental data. Furthermore, the non-linear treatment indicates that the time periods of the operation is longer than that estimated from direct observation, hence the quantity of adsorption at equilibrium will be greater than observed directly. Another advantage of non-linear treatment not mentioned before is deducing kinetic model best fitting with data by expecting the equilibrium time of the process depending on the data pointsof initial time period. The obtained kinetic parameters were correlated with some molar parameters using multi-variable linear regression which show that molar polarizability has a promotional effect upon kinetic adsorption parameters, while molar volume and hydrophobicity have a demotion effect. The kinetic investigation was extended to include diffusion Boyd', and Weber-Morris models. The results showed that A.Al and 2-But had a film diffusion kinetic determining step, the remaining compounds show a non-diffusional (local adhering) like behavior.
... Les quatre principaux représentants de cette famille de composés sont le trichlorométhane, le dichlorobromométhane, le dibromochlorométhane et le tribromométhane. La toxicité de cette famille de composés est clairement établie au travers d'intenses recherches effectuées les trente dernières années [52]. En France, la somme des quatre principaux THMs de l'eau de consommation ne doit pas excéder 100 µg/L [40]. ...
... Pour autant, cette contrainte des sous-produits de désinfection ne doit pas faire oublier la nécessité d'une désinfection rémanente des réseaux AEP. De nombreuses maladies telles que la dysenterie, le choléra et la fièvre typhoïde ont été fortement atténuées grâce à sa mise en place [52]. Un équilibre est donc à trouver dans la dose de chlore utilisée. ...
The current context of sustainable development drives operating services in charge of water distribution to reduce water loss, whilst ensuring a high-quality service to users. Thus, EPANET 2, software from the US EPA, the American Environmental Protection Agency, distinguishes itself as a decision-making and patrimonial knowledge optimization tool and turns out to be an add-in tool to mapping lead by GIS softwares. Its operating inputs cover up amongst others yields optimization, both a rural and urban issue, through sectorisation decision-making, renewal strategy of an ageing heritage, pressure management and map errors corrections. Distribution systems are inherently oversized both to face unexpected demand and to enable a legally compliant fire-fighting system, against a backdrop of uncertain demographic forecasting. Within the Cher Sologne Indre Service from Veolia Water Company, whose communes in contract are mainly rural, this oversizing often reaches extreme proportions. This trend originates in the unforeseen population drop, typical of the southern part of the French region Centre-Val-de-Loire. CFD (Computational Fluid Dynamics) modeling notably enables the highlighting of the consequences of rurality on networks; including the effects of their much branched typology. The conventional key indicators encompass pressure, velocity and of course water age. Last but not least, this third indicator, enabling the quantification of water stagnation within pipes and tanks, is somehow constrained. Thus, an innovative indicator for the practice of the Beauce Cher & Loire Centre, free chlorine, aims at counterbalancing the limits of water age. At its stage of development, the developed chlorine modeling method produced some good results concerning the distribution system in the French town of Argenton-sur-Creuse located in the Indre Département. Taking into consideration the wall and temperature impacts, the method however could be applied as a tool to characterize the chlorine decay within other distribution systems. Its first goal being disinfection management of rural networks; the “chlorine method”, opens-up some new prospects in species modeling, such as total trihalomethanes determination.
... Several epidemiological studies have found a clear association between chlorinated water consumption and an increase in cancer in the population. According to IARC (1999aIARC ( , 1999b, TCM and BDCM are classified as possible carcinogens in humans (2B) mainly linked to bladder cancer (Villanueva et al. 2017(Villanueva et al. , 2021, although they have also been linked to stomach and colon cancer (Richardson et al. 2007;Genisoglu et al. 2019). In Europe, 5% of bladder tumours are associated with THMs in water (Evlampidou et al. 2020). ...
Trihalomethanes (THMs) are generated in the drinking water treatment plant, due to the reaction of the halogenated disinfection compounds with the natural organic matter (NOM). They are related to health problems both from the point of view of cancer development and other important diseases. This study aimed to assess the quality of tap water in Madrid in terms of prevention and control of THMs risks in the supply water treated by Canal de Isabel II (CYII) in a total of 108 samples throughout 2015 to 2020, to distinguish the problems of the different 21 districts or types of buildings, the seasonality and to estimate the risk of exposure to THMs from tap water in the population of Madrid. The variables considered include year, seasonality, district of Madrid and sampling point. The concentrations of THMs detected in all samples were within the current legal limit (100 µg/l). Chloroform was the compound with the highest contribution to the sum of THMs. A decreasing trend in THMs concentrations was observed over the years of the study related to the removal of NOM and the use of chloramines. THM levels were higher in the central area than in the peripheral districts and the lowest concentrations were detected in summer. Regarding risk assessment, the results of the non-carcinogenic risk indicate that there is no potential risk from tap water consumption for the adult population. For the carcinogenic risk, only water samples with THM concentrations between 50 and 75 µg/l could constitute a risk for high consumers.
... However, current disinfection practices rely on strong oxidants or harsh conditions 4,5 , leading to a high carbon footprint and unpredictable health risks (e.g. carcinogenic byproducts 6,7 and microbial resistance 8,9 ). Most of these technologies require a large-scale infrastructure and extensive maintenance, and therefore cannot be easily deployed in rural areas with inadequate electric power 10,11 . ...
Water disinfection is conventionally achieved by oxidation or irradiation, which is often associated with a high carbon footprint and the formation of toxic byproducts. Here, we describe a nano-structured material that is highly effective at killing bacteria in water through a hydrodynamic mechanism. The material consists of carbon-coated, sharp Cu(OH)2 nanowires grown on a copper foam substrate. We show that mild water flow (e.g. driven from a storage tank) can efficiently tear up bacteria through a high dispersion force between the nanotip surface and the cell envelope. Bacterial cell rupture is due to tearing of the cell envelope rather than collisions. This mechanism produces rapid inactivation of bacteria in water, and achieved complete disinfection in a 30-day field test. Our approach exploits fluidic energy and does not require additional energy supply, thus offering an efficient and low-cost system that could potentially be incorporated in water treatment processes in wastewater facilities and rural communities.
... High brominated THM concentrations in the water and air were also found in a study by Tardif et al. (2016), though only chlorinated pools were surveyed. The presence of brominated THMs in significant proportions could require vigilance as it was shown that brominated DBPs are more genotoxic than chlorinated ones (Richardson et al., 2007) and recent studies have linked them to potential health issues Rivera-Núñez & Wright, 2013). ...
Disinfection by-products (DBPs) are formed in the water in swimming pools due to reactions between disinfectants (chlorine, bromine, ozone) and the organic matter introduced by bathers and supply water. High concentrations of DBPs are also reported in the air of indoor swimming pools. Based on a robust multisampling program, the levels and variations of DBPs in the air (trichloramine [TCAM] and trihalomethanes [THMs]) and water (THM) were assessed, as well as their precursors (total organic carbon, water temperature, pH, free, and total chlorine) and proxies (CO2 and relative humidity) in four indoor chlorinated swimming pools. High-frequency sampling was conducted during one high-attendance day for each pool. This study focused on parameters that are easy to measure in order to develop models for predicting levels of THMs and TCAM in the air. The results showed that the number of bathers had an important impact on the levels of THMs and TCAM, with a two-to-three-fold increase in air chloroform (up to 110 μg/m³) and a two-to-four-fold increase in TCAM (up to 0.52 mg/m³) shortly after pools opened. The results of this study for the first time showed that CO2 and relative humidity can serve as proxies for monitoring variations in airborne THMs and TCAM. Our results highlight the good predictive capacity of the developed models and their potential for use in day-to-day monitoring. This could help optimize and control DBPs formation in the air of indoor swimming pools and reduce contaminant exposure for both pool employees and users.
... Two subsets of carbonaceous DBPs (C-DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs), have been demonstrated to be the largest classes of DBPs formed in drinking water treatment plants (Krasner et al., 2006) and are regulated by the US Environmental Protection Agency (USEPA, 2006) and the European Union (The European Parliament and the Council of the European Union, 2020). Other subsets of DBPs, including nitrogenous DBPs (N-DBPs) such as haloacetonitriles (HANs), haloacetamides (HAMs), and halonitromethanes, are not yet regulated but are thought to be substantially more cytotoxic and genotoxic to humans than C-DBPs (Bond et al., 2011;Komaki et al., 2014;Richardson et al., 2007;Wagner and Plewa, 2017). Because fire alters DOM characteristics and its concentration in runoff, the DBP precursors present downstream from a wildfire are thought to be substantially different and present at different concentrations than those from unaffected areas. ...
We investigated short (first post-fire precipitation)- and long-term (11-month) impacts of the Caldor and Mosquito Fires (2021 and 2022) on water quality, dissolved organic matter, and disinfection byproduct (DBP) precursors in burned and adjacent unburned watersheds. Both burned watersheds experienced water quality degradation compared to their paired unburned watersheds, including increases in dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and DBP precursors from precipitation events. DBP precursor concentrations during storm events were greater in the Caldor Fire's burned watershed than in the unburned watershed; precursors of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and haloacetamides (HAMs) were 533 µg/L, 1,231 µg/L, 64 and 58 µg/L greater. The burned watershed of the Mosquito Fire also had greater median concentrations of THM (44 µg/L), HAA (37 µg/L), HAN (7 µg/L), and HAM (13 µg/L) precursors compared to the unburned watershed during a storm immediately following the fire. Initial flushes from both burned watersheds formed greater concentrations of more toxic DBPs, such as HANs and HAMs. The Caldor Fire burn area experienced a rain-on-snow event shortly after the fire which produced the greatest degradation of water quality of all seasons/precipitation events/watersheds studied. Over the long term, statistical analysis revealed that DOC and DON values in the burned watershed of the Caldor Fire remained higher than the unburned control (0.98 mg C/L and 0.028 mg N/L, respectively). These short and long-term findings indicate that wildfires present potential treatment challenges for public water systems outside of the two studied here.
... The causes of human cancer include food additives, medicines, pesticides, chemical fertilizers, and hair dye [1,2]. The majority of mutagenic substances either affect the DNA of somatic cells, which may result in the emergence of cancer, or they may affect the DNA of reproductive cells, which may result in the accumulation of mutant genes in the community, which damages the reproductive cells and causes problems with fertilization and the emergence of mutations in future generations [3]. As genetic mutations are usually associated with cancer, various studies have revealed a connection between mutagenesis and the development of cancer. ...
The purpose of this study was to determine the possible mutagenicity of hair dye using the auxotroph’s methionine Proteus Mirabilis as a test. The Ames test was employed to identify reverse mutations in auxotroph’s P. Mirabilis treated with hair dyes. The results demonstrated a significant increase (P< 0.05) in reverse colonies of auxotroph’s P. mirabilis treated with 250 and 500 mg/mL of hair dyes in comparison to the negative control. Reverse mutations in the metE gene of the auxotroph’s P. Mirabilis were identified using DNA sequencing and polymerase chain reaction. The results confirmed the presence of the metE gene at a percentage of (100%) in all isolates treated with hair dyes at 250 and 500 mg/mL. Using BLAST software, the metE gene’s sequence was compared to the gene sequence of a standard isolate. Point mutations in the DNA of the metE gene altered protein translation, according to a genetic study of metE gene isolates treated with hair dyes. Finally, point mutations in the metE genes were identified using amino acid translation analysis of auxotroph’s P. mirabilis isolates treated with hair dyes. Point mutations in the metE gene cause many amino acids to be converted to methionine, which enables auxotroph’s P. mirabilis to grow without the need for methionine from an external source. The study found that the test for identifying mutagens in hair dyes was simple to use and cheap. It has also shown high efficacy in altering the amino acid and nitrogenous base sequences in the metE genes, thus their effect on methionine synthesis.
... However, for organic matter, particularly environmental contaminants and artificial chemicals, halogen elements are important elements and their chemical and toxicological properties cannot be overlooked. [6][7][8] Moreover, the application of HRMS in environmental pollutants and anthropogenic organics is increasing, 8,9 and the ability to more accurately interpret large amounts of data is essential. Therefore, we adapted the van Krevelen diagram and the other indexes with halogen elements for the analysis of organic matter with complex constituents. ...
The traditional van Krevelen diagram, the nominal oxidation of organic carbon, and several aromaticity indexes generally considered C, H, O, N, P, and S factors, or just C, H, and O. However, these evaluated methods may provide incorrect interpretation for high-resolution mass data of organics containing halogen elements. Therefore, we adapted the van Krevelen diagram and the other indexes with halogen elements and verified with 2235 model organics. The results demonstrated that the modified van Krevelen diagram and the adjusted indexes were more accurate for the analysis of mass data, either in the compound classification or in the evaluation of oxidation state of organic matter.
Background
Advances in drinking water infrastructure and treatment throughout the 20 th and early 21 st century dramatically improved water reliability and quality in the United States (US) and other parts of the world. However, numerous chemical contaminants from a range of anthropogenic and natural sources continue to pose chronic health concerns, even in countries with established drinking water regulations, such as the US.
Objective/Methods
In this review, we summarize exposure risk profiles and health effects for seven legacy and emerging drinking water contaminants or contaminant groups: arsenic, disinfection by-products, fracking-related substances, lead, nitrate, per- and polyfluorinated alkyl substances (PFAS) and uranium. We begin with an overview of US public water systems, and US and global drinking water regulation. We end with a summary of cross-cutting challenges that burden US drinking water systems: aging and deteriorated water infrastructure, vulnerabilities for children in school and childcare facilities, climate change, disparities in access to safe and reliable drinking water, uneven enforcement of drinking water standards, inadequate health assessments, large numbers of chemicals within a class, a preponderance of small water systems, and issues facing US Indigenous communities.
Results
Research and data on US drinking water contamination show that exposure profiles, health risks, and water quality reliability issues vary widely across populations, geographically and by contaminant. Factors include water source, local and regional features, aging water infrastructure, industrial or commercial activities, and social determinants. Understanding the risk profiles of different drinking water contaminants is necessary for anticipating local and general problems, ascertaining the state of drinking water resources, and developing mitigation strategies.
Impact statement
Drinking water contamination is widespread, even in the US. Exposure risk profiles vary by contaminant. Understanding the risk profiles of different drinking water contaminants is necessary for anticipating local and general public health problems, ascertaining the state of drinking water resources, and developing mitigation strategies.
Background
Pathogenic viruses have been abundant and diverse in wastewater, reflecting the pattern of infection in humans. Human feces, urine, and perhaps other washouts that frequently circulate in sewage systems may contaminate wastewater with SARS-CoV-2. It’s crucial to effectively disinfect wastewater since poorly handled wastewater could put the population at risk of infection.
Aims
To emphasize the presence and spread of SARS-CoV-2 in sewage (wastewater) through viral shedding from the patients to detect the virus in the population using wastewater-based epidemiology. Also, to effectively manage the transmission of SARS-CoV-2 and reduce the spread of the virus in the population using disinfectants is highlighted.
Methods
We evaluated articles from December 2019 to August 2022 that addressed SARS-CoV-2 shedding in wastewater and surveillance through wastewater-based epidemiology. We included the papers on wastewater disinfection for the elimination of SARS-CoV-2. Google Scholar, PubMed, and Research4Life are the three electronic databases from which all of the papers were retrieved.
Results
It is possible for viral shedding to get into the wastewater. The enumeration of viral RNA from it can be used to monitor virus circulation in the human community. SARS-CoV-2 can be removed from wastewater by using modern disinfection techniques such as sodium hypochlorite, liquid chlorine, chlorine dioxide, peracetic acid, and ultraviolet light.
Conclusion
SARS-CoV-2 burden estimates at the population level can be obtained via longitudinal examination of wastewater, and SARS-CoV-2 can be removed from the wastewater through disinfection.
Light emitting diode (LED-UV)/chlorine disinfection can replace UV/chlorine disinfection in wastewater treatment plants and water supply plants. Halonitromethanes (HNMs) are a class of novel nitrogenous disinfection by-products, which are characterized by higher cytotoxicity and genotoxicity than regulated disinfection by-products. Herein, the impact factors and pathways of HNMs formation from aspartic acid (ASP) were investigated during LED-UV265/chlorine disinfection. The results showed that three types of chlorinated-HNMs (Cl-HNMs) were found during LED-UV265/chlorine disinfection, and their concentrations increased first and then declined as the reaction progressed. Cl-HNMs yields increased with increasing LED-UV265 intensity, free chlorine dosage, and ASP concentration, which declined with increasing pH (6.0–8.0). Meantime, the important impact of the coexisting ions contained in water matrices on HNMs formation from ASP was observed during LED-UV265/chlorine disinfection. It was found that copper ions (Cu2+) promoted Cl-HNMs formation. Furthermore, when bromide (Br−) appeared during LED-UV265/chlorine disinfection, nine types of HNMs were detected simultaneously. Moreover, Br− not only converted Cl-HNMs toward brominated (chlorinated)-HNMs and brominated-HNMs but also showed a marked effect on HNMs concentrations and species. Subsequently, the possible pathways of HNMs formation from ASP were proposed during LED-UV265/chlorine disinfection. At last, it was proved that the formation trends of HNMs obtained in the real waters were similar to those in simulated waters. This work elaborated on the influence factors and pathways of HNMs formation, which is conducive to controlling the HNMs produced during LED-UV265/chlorine disinfection.
Dichloroacetonitrile (DCAN) is a common biotoxic disinfection by-products (DBPs) of chlorine. The current detection methods for DCAN are tedious and heavily instrument-dependent, which is not suitable for on site detection....
Water and human health issues are intertwined within a changing urban setting. There is a momentum of societal demand to act on the aging drinking water pipe infrastructure to protect human health and at the same time to devise control options that will promote further the well‐being and quality of urban life in the developed world. The main objective of this work was to critically review the main challenges, opportunities, and risks associated with drinking water's current and emerging pressures as exerted on human health in urban centers of middle‐ and high‐income countries. Discussion about drinking‐water distribution systems did not focus on their portion extending from the water meter to the home tap, i.e. the premise plumbing system characteristics. One city does not hold a single water quality metric that remains constant because it changes in the urban space and time. Bigger urban centers will be differentially more complex to address water and health risks because of their numerous neighborhoods (district‐metered areas, DMA) being spread apart geographically in large distances. The water and health issues are multidisciplinary in nature and demand the close cooperation among health scientists, engineers, environmental scientists, social scientists, economists, and policymakers to address each city's unique risks.
Residual disinfectants react with various natural organic matter in distribution networks (DNs) to form disinfection by‐products (DBPs), which are a public health concern. The regulated DBPs in various jurisdictions are trihalomethanes, haloacetic acids, bromate, and chlorate, which are mostly associated with chlorine. Owing to this, several alternative disinfectants, such as chloramines, ozone, and chlorine dioxide are also used. Although the use of alternate disinfectants has reduced the formation of regulated DBPs, these disinfectants have gathered much attention by introducing another cluster of DBPs known as unregulated DBPs (U‐DBPs). Many U‐DBPs are potentially toxic, mutagenic, and/or carcinogenic. This study reviews the models for predicting the spatiotemporal variation of U‐DBPs and analyzes their variability in DNs in the provinces of Quebec, and Newfoundland and Labrador, Canada. The findings show that limited predictive models are available for U‐DBPs compared to regulated DBPs. The concentrations of haloacetonitriles, chloropicrin, and haloketones significantly differed along the DNs based on the distance traveled and/or residence time. Similarly, temporal variability was significant in different seasons and in various weeks in summer but not significant by days from Monday to Friday. The formation of U‐DBPs can be controlled by source water protection, use of advanced treatment, alternative disinfectants, etc.
The use of seawater as a source for potable water supply after desalination, and in once‐through industrial cooling is a common practice in many parts of the world that have limited fresh‐water resources. A disinfectant (commonly chlorine) is added to the seawater to control biofouling in desalination or cooling systems. The added chlorine reacts with bromide and other compounds present in seawater to produce a wide range of chemical oxidants. Regrettably, reactions between the residual oxidants and natural organic matter present in seawater lead to the formation of halogenated organic compounds that have detrimental effects on human health and the environment. Of particular note is the fact that brominated forms of disinfectants are more effective in producing halogenated organic by‐products than chlorinated forms. In this article, the kinetics of residual oxidants decay and formation of halogenated disinfection by‐products (DBPs) in seawater is discussed and explained in detail. A kinetic model is developed, which includes rate constants for all base reactions and stoichiometric coefficients for all halogenated (DBPs) formed by these base reactions. The model is calibrated using experimental results to obtain the different kinetic rate coefficients.
The Crow River, a tributary of the Mississippi River in Minnesota, U.S.A., that is impacted by agricultural activities and municipal wastewater discharges, was sampled approximately monthly at 12 locations over 18 months to investigate temporal and spatial variations in N-nitrosodimethylamine (NDMA) precursor levels. NDMA precursors were quantified primarily by measuring NDMA formed under the low chloramine dose uniform formation conditions protocol (NDMAUFC) and occasionally using the high dose formation potential protocol (NDMAFP). Raw water NDMAUFC concentrations (2.2 to 128 ng/L) exhibited substantial temporal variation but relatively little spatial variation. An increase in NDMAUFC was observed for 126 of 169 water samples after lime-softening treatment. A kinetic model indicates that under chloramine-limited UFC test conditions, the increase in NDMAUFC can be attributed to a decrease in competition between precursors and natural organic matter (NOM) for chloramines and reduced interactions of precursors with NOM. NDMAUFC concentrations correlated positively with dissolved nitrogen concentration (ρ = 0.44, p < 0.01) when excluding the spring snowmelt period and negatively correlated with dissolved organic carbon concentration (ρ = -0.47, p < 0.01). Overall, NDMA precursor levels were highly dynamic and strongly affected by lime-softening treatment.
The U.S. Environmental Protection Agency (EPA) is cons i dering a regulatory revision of the Disinfectant and Disinfection Byproduct Rule (DBPR) with a goal of limiting nationwide exposure to DBPs of emerging health concern. The occurrence of four brominated haloacetic acids (HAAs), which are generally more toxic in in vitro assays than the five currently regulated HAAs and are candidates for future regulation, were surveyed in 4924 public water systems under EPA's fourth unregulated contaminant monitoring rule (UCMR4). Using UCMR4 data, this study evaluated the nationwide occurrence of nine HAA species and the potential for two regulatory scenarios (the mass sum of all nine HAA species, HAA9, or just the six brominated HAA species, HAA6Br) to control nationwide exposure to the most toxic HAAs. Neither HAA9 nor HAA6Br approaches were effective for identifying water systems that exhibit high HAA exposure, assessed as additive cytotoxicity, because they are more specific to the HAA species that form at high concentrations rather than the species that are most toxic. However, the effectiveness of HAA6Br is highly sensitive to the relative toxicity of one HAA compound, monobromoacetic acid, which has the highest in vitro toxicity among HAAs but also the lowest occurrence and about which little is known regarding in vivo health risks. In contrast to HAA9, systems with high HAA‐associated additive toxicity tend to share similar treatment and disinfectant characteristics as systems with high HAA6Br concentrations. Systems with high source water bromide and total organic carbon were far more likely to use chloramines as a disinfectant residual compared to other systems, but were no more likely to adopt organic precursor removal technologies (biofiltration, granular activated carbon, and ion exchange) than other systems, on average.
Increasing operating temperature has been recommended for controlling opportunistic premise plumbing pathogens (OPPPs) growth in buildings. However, tradeoffs with operation and both disinfectant residuals and disinfection byproducts (DBPs) are not...
In this study, the photodegradation of 33 different DBPs (trihalomethanes, haloacetic acids, haloacetaldehydes, and haloacetonitriles) and TOX with low pressure UV light and the subsequent reformation of DBPs with chlorine and monochloramine were investigated. Results indicated that photodegradation followed the order of TOI > TOBr > TOCl, and treated surface water with low SUVA254 background did not impact the photodegradation of highly UV susceptible DBPs such as triiodomethane (TIM), diiodobromomethane (DIBM), tribromomethane (TBM). The mass balance results of chloride, bromide and iodide showed that the main photodegradation mechanism of TOBr and TOI was dehalogenation supported by halide releases (i.e., Cl-, Br- and/or I- ion). In addition, the photodegradation removal effect was higher, when brominated DBPs formation was high. Although low pressure UV light effectively removed halogenated organic DBPs, subsequent use of disinfectants (Cl2 and NH2Cl) reformed photodegraded DBPs, and the overall DBPs concentrations were increased, which suggested that the released Br- and I- ions will reform DBPs in distribution systems, with oxidants present or added (e.g., booster chlorination) in distribution systems. This study showed that although UV photodegradation will reduce halogenated organic DBPs in distribution systems, especially more toxic iodinated and brominated DBPs, it will be a more effective technology towards the end of the distribution system or a point of entry solution rather than in distribution system with post-disinfection and residence time.
Trihalomethanes (THMs), as the most common species of disinfection byproducts in chlorinated water, have been associated with hypertensive disorders in pregnancy. However, there is sparse epidemiological evidence regarding the possible link between THMs exposure and hypertension in general adults. In the present study, we aimed to characterize the associations between THMs exposure and hypertension in general adults. We performed cross-sectional analyses of 15,135 adults from the 1999-2018 National Health and Nutrition Examination Survey. In the general US adults, the median blood concentrations of the chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (TBM) were: 4.80 pg/mL, 0.71 pg/mL, 0.44 pg/mL and 0.71 pg/mL, respectively. And adults in the highest tertile of blood TBM and DBCM had odds ratios of 1.20 (95 % confidence intervals: 1.02, 1.42) and 1.15 (1.01, 1.30), respectively, for hypertension, compared with adults in the lowest tertile. Also, significant positive associations between blood brominated THM concentrations (sum of TBM, BDCM and DBCM) and prevalent hypertension were observed. In addition, significant interactions with BMI were demonstrated for Br-THMs (P for interaction = 0.017). Our study provides epidemiological evidence supporting a positive association between blood THMs and hypertension by using the nationally representative data, highlighting the need for further investigations to deepen our findings and elucidate the underlying mechanisms.
The nonwoven PET fabrics are chemically, mechanically and thermally treated fiber aggregate without weaving, knitting or braiding, which could be used as a base to make polyurethane (PU) synthetic leather through a series of processing. Our research systematically compared the photoaging behaviors of pure non-woven PET base fabric (NPET-P) and PU synthetic leather (nonwoven PET-base fabrics with PU coating, NPET-U), and their possibilities for microplastic fibers (MPFs) generation and chemical transformation in water. NPET-U was photoaged to a higher oxidation degree with higher O/C ratios and more distinct changes in chemical structures. The amount of MPFs released from NPET-U (1.98 × 107 g/fibers) was significantly lower than that from NPET-P (4.76 × 107 g/fibers) after 360 h light irradiation (p value<0.05) with a slower degradation rate and delayed MPFs release. The lengths and diameters of released MPFs from NPET-U varied within a smaller range than that from NPET-P exposed to UV light irradiation. Natural sunlight aging of fabrics for 365 days was found to be equivalent to approximately 85.3-127.2 h UV aging in the laboratory, which indicated the lab accelerated experiments was extraordinarily intense to simulate natural sunlight aging. Furthermore, abundant calcium and sulfur-contained chemicals were detected in original fabrics and the leachate of 360 h light-aged fabrics using the inductively coupled plasma optical emission spectrometer (ICP-OES). The organic components of the leachate were separated according to their molecular weight with the changes of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and the UV response over aging time. UV stimulation aggravated the role of plastic polymers as disinfection by-product (DBP) precursors. Nevertheless, although NPET-U could produce more nitrogen-contained chemicals, it had similar formation potentials of nitrogen-containing DBPs as NPET-P. The discussion lucubrated the potential risks of the production of MPFs and chemical release in the leachate with regard to combined plastic pollution.
Proper control/removal of disinfection byproducts (DBPs) is important to drinking water safety and human health. In this study, a membrane-less electrochemical system was developed and investigated to remove DPBs through integrated adsorption and reduction by granular activated carbon (GAC)-based cathode. Representative DPBs including trihalomethanes and haloacetonitriles at drinking water concentrations were used for removal experiments. The proposed system achieved >70% removal of most DBPs in a batch mode. The comparison with control tests under either open circuit or hydrolysis demonstrated the advantages of electrochemical treatment, which not only realized higher DPBs removal but also extended GAC cathode lifetime. Such advantages were further demonstrated with continuous treatment. High dechlorination and debromination efficiencies were obtained in both batch (82.2 and 94.3%) and continuous (79.3 and 87.6%) reactors. DBPs removal was mainly contributed by the electrochemical reduction and adsorption by the GAC-based cathode, while anode showed little oxidizing effect on DBPs and halide ions. Dehalogenated products of chloroform and dichloroacetonitrile were identified with toxicity reduction. The energy consumption of the continuously operated system was estimated to be 0.28 to 0.16 kWh m-3. The proposed system has potential applications for wastewater reuse or further purification of drinking water.
With the increase of algal blooms worldwide, drinking water resources are threatened by the release of various algal toxins, which can be hepatotoxic, cytotoxic, or neurotoxic. Because of their ubiquitous occurrence in global waters and incomplete removal in conventional drinking water treatment, oxidation/disinfection processes have become promising alternative treatment options to destroy both the structures and toxicity of algal toxins. This Review first summarizes the occurrence and regulation of algal toxins in source water and drinking water. Then, the transformation kinetics, disinfection byproducts (DBPs)/transformation products (TPs), pathways, and toxicity of algal toxins in water oxidation/disinfection processes, including treatment by ozonation, chlorination, chloramination, ultraviolet-based advanced oxidation process, and permanganate, are reviewed. For most algal toxins, hydroxyl radicals (HO•) exhibit the highest oxidation rate, followed by ozone and free chlorine. Under practical applications, ozone and chlorine can degrade most algal toxins to meet water quality standards. However, the transformation of the parent structures of algal toxins by oxidation/disinfection processes does not guarantee a reduction in toxicity, and the formation of toxic TPs should also be considered, especially during chlorination. Notably, the toxicity variation of algal toxins is associated with the chemical moiety responsible for toxicity (e.g., Adda moiety in microcystin-LR and uracil moiety in cylindrospermopsin). Moreover, the formation of known halogenated DBPs after chlorination indicates that toxicity in drinking water may shift from toxicity contributed by algal toxins to toxicity contributed by DBPs. To achieve the simultaneous toxicity reduction of algal toxins and their TPs, optimized oxidation/disinfection processes are warranted in future research, not only for meeting water quality standards but also for effective reduction of toxicity of algal toxins.
2,6-dichloro-1,4-benzoquinone (DCBQ) has been identified as an emerging disinfection byproducts (DBPs) in drinking water and has the potential to induce neurodevelopmental toxicity. However, there is rarely a comprehensive toxicological evaluation of the neurodevelopmental toxicity of DCBQ. Here, neural differentiating SH-SY5Y cells were used as an in vitro model. Our results have found that DCBQ has decreased cell viability and neural differentiation, generated higher level of reactive oxygen species (ROS), increased the percentage of apoptosis and lowered the level of mitochondrial membrane potential, suggesting the neurodevelopmental toxicity of DCBQ. In addition, antioxidant N-acetyl-L-cysteine (NAC) could significantly attenuate these DCBQ-induced neurotoxic effects, supporting our hypothesis that the neurodevelopmental toxicity may be related with oxidative stress induced by DCBQ. We further demonstrated that DCBQ-induced neurodevelopmental toxicity could promote the mitochondrial apoptosis pathway and inhibit the prosurvival PI3K/AKT/mTOR pathway through inducing ROS, which ultimately inhibited cell proliferation and induced apoptosis in neural differentiating SH-SY5Y cells. These findings have provided novel insights into the risk of neurodevelopmental toxic effects associated with DCBQ exposure, emphasizing the importance of assessing the potential neurodevelopmental toxicity of DBPs.
Iodinated disinfection by-products (I-DBPs) exhibited potential health risk owing to the high toxicity. Our recent study demonstrated that I-DBPs from Laminaria japonica (Haidai), the commonly edible seaweed, upon simulated household cooking condition were several hundred times more than the concentration of drinking water. Here, the characterization of Haidai and its leachate tandem with the formation, identification and toxicity of I-DBPs from the cooking of Haidai were systemically investigated. The dominant organic matter in Haidai leachate were polysaccharides, while the highest iodine specie was iodide (∼90% of total iodine). Several unknown I-DBPs generated from the cooking of Haidai were tentatively proposed, of which 3,5-diiodo-4-hydroxybenzaldehyde was dominant specie. Following a simulated household cooking with real chloraminated tap water, the presence of Haidai sharply increased aggregate iodinated trihalomethanes, iodinated haloacetic acids, and total organic iodine concentrations to 97.4 ± 7.6 μg/L,16.4 ± 2.1 μg/L, and 0.53 ± 0.06 mg/L, respectively. Moreover, the acute toxicity of Haidai soup to Vibrio qinghaiensis sp.-Q67 was around 7.3 times higher than that of tap water in terms of EC50. These results demonstrated that the yield of I-DBPs from the cooking of Haidai and other seaweed should be carefully considered.
Sandstorms, a natural meteorological event, occur repeatedly during the dry season and can accumulate large amounts of natural/anthropogenic pollutants during the deposition process, potentially introducing disinfection by-product (DBP) precursors into surface waters. In this study, the characteristics of sandstorm-derived dissolved organic matter (DOM) and its DBP formation potential were elucidated. Overall, sandstorm-derived DOM mainly consisted of low-molecular-weight, low-aromaticity, high-nitrogen organic matter, with a dissolved organic carbon (DOC) release yield of 14.4 mg-DOC/g. The halogenated DBP formation potential (calculated as total organic halogen) of sandstorm-derived DOM was comparable to that of surface water, while the normalized DBP-associated toxicity was 1.96 times higher. Similar to DOM introduced by other depositional pathways, sandstorm-derived DOM also had higher yields of highly cytotoxic DBPs (haloacetaldehydes [HALs], haloacetonitriles [HANs] and halonitromethanes [HNMs]). The average atmospheric deposition flux for DOM during the sandstorm event (50.4 ± 2.1 kg km-2 day-1) was 6.95 times higher than that of dry deposition, indicating a higher probability of contaminant input. Simultaneously, the estimation revealed that the sandstorm will increase the formation potential of toxicity forcing agents, such as HALs, HANs and HNMs, in surface water by 3.87%, 2.39% and 9.04%, respectively. Considering the high frequency of sandstorm events and the sorption of other organic pollutants by sand and dust, the impact of sandstorms on surface water quality should be of concern.
Pharmaceuticals have been considered a priority group of emerging micropollutants in source waters in recent years, while their role in the formation and toxicity of disinfection byproducts (DBPs) during chlorine disinfection remains largely unclear. In this study, the contributions of natural organic matter (NOM) and pharmaceuticals (a mixture of ten representative pharmaceuticals) to the overall DBP formation and toxicity during drinking water chlorination were investigated. By innovatively "normalizing" chlorine exposure and constructing a kinetic model, we were able to differentiate and evaluate the contributions of NOM and pharmaceuticals to the total organic halogen (TOX) formation for source waters that contained different levels of pharmaceuticals. It was found that at a chlorine contact time of 1.0 h, NOM (2 mg/L as C) and pharmaceuticals (total 0.0062-0.31 mg/L as C) contributed 79.8-99.5% and 0.5-20.2%, respectively, of TOX. The toxicity test results showed that the chlorination remarkably increased the toxicity of the pharmaceutical mixture by converting the parent compounds into more toxic pharmaceutical-derived DBPs, and these DBPs might contribute significantly to the overall developmental toxicity of chlorinated waters. This study highlights the non-negligible role of pharmaceuticals in the formation and toxicity of overall DBPs in chlorinated drinking water.
Combining dissolved organic matter (DOM) in raw water (RW) with DOM in treated wastewater (TWW) can react with chlorine and pose emerging disinfection by-products (DBPs). This study evaluated DOM based on the molecular weight (MW) size fractionation, trihalomethane, iodinated-trihalomethane, haloacetonitrile, and trichloronitromethane formation potential (THMFP, I-THMFP, HANFP, and TCNMFP) of the RW from the U-Tapao Canal, Songkhla, Thailand and the RW mixed with TWW (RW + TWW) samples. The RW and RW + TWW were treated by coagulation with poly aluminum chloride. The DOM of RW and RW + TWW and their treated water was distributed most in the MW below 1 kDa. The MWs of 3-10 kDa and 1-3 kDa were the active DOM involved in the specific THMFP for the RW + TWW. The MW of < 1 kDa in the RW + TWW resulted in a slightly high specific I-THMFP and HANFP. The MW of 1 - 3 kDa in the coagulated samples had a high specific I-THMFP. The MW of > 10 kDa in the coagulated RW + TWW was a precursor for a particular HANFP. Monitoring systems for measuring the level of TWW mixed with RW and an effective process to enhance the efficiency of traditional water treatment must be set up to produce a consumer-safe water supply.
Increased disinfection of wastewater to preserve its microbiological quality during the coronavirus infectious disease-2019 (COVID-19) pandemic have inevitably led to increased production of toxic disinfection by-products (DBPs). However, there is limited information on such DBPs (i.e., trihalomethanes, haloacetic acids, nitrosamines, and haloacetonitriles). This review focused on the upsurge of chlorine-based disinfectants (such as chlorine, chloramine and chlorine dioxide) in wastewater treatment plants (WWTPs) in the global response to COVID-19. The formation and distribution of DBPs in wastewater were then analyzed to understand the impacts of these large-scale usage of disinfectants in WWTPs. In addition, potential ecological risks associated with DBPs derived from wastewater disinfection and its receiving water bodies were summarized. Finally, various approaches for mitigating DBP levels in wastewater and suggestions for further research into the environmental risks of increased wastewater disinfection were provided. Overall, this study presented a comprehensive overview of the formation, distribution, potential ecological risks, and mitigating approaches of DBPs derived from wastewater disinfection that will facilitate appropriate wastewater disinfection techniques selection, potential ecological risk assessment, and removal approaches and regulations consideration.
Studies have shown that hypobromous acid (HOBr) produced during chlorination disinfection of tap water can react with some organic matter in water to form toxic brominated disinfection byproducts (Br-DBPs) and HOBr also plays an important role during the process of micro pollutants degradation. Hence, real-time monitoring of HOBr in water environment plays a significant role in controlling the generation of Br-DBPs and degradation of micro pollutants. Herein, a novel highly specific fluorescent probe (PBE-HOBr) for accurate detection of HOBr was constructed based on the HOBr-induced oxidation elimination of benzothiazoline moiety employing the photo-induced electron transfer (PET) mechanism. PBE-HOBr has high sensitivity and linear response to HOBr with a low detection limit of 119 nM. PBE-HOBr not only has the ability to detect endogenous and exogenous HOBr in cells and zebrafish, but also has been used to monitor the formation of HOBr in water treatment. In addition, benzothiazoline group was demonstrated for the first time to be able to be used as a new recognition receptor for developing highly specific fluorescent probes for HOBr.
Triclocarban (TCC) is an antimicrobial agent commonly used in many household and personal care products, and has been found persistent in the aquatic environment. Here we elucidate the kinetics and mechanism of TCC degradation during chlorination process by density functional theory (DFT) calculation and experimental verification. Results showed that hypochlorous acid (HOCl)/hypochlorite (OCl-) reacted with TCC via Cl-substitution, OH-substitution and C-N bond cleavage pathways. The reactivity of OCl- (2.80 × 10-7 M-1 s-1) with TCC was extremely low and HOCl (1.96 M-1 s-1) played the dominant role in TCC chlorination process. The N site of TCC was the most reactive site for chlorination. The second-order rate constants, which are determined using density functional theory (DFT) (kTCC-chlorineC, 1.96 M-1 s-1), can be separated into reaction rate constants related to the reactions of HOCl and OCl- with different isomers of TCC (TCC2 and TCC6). The obtained kTCC-chlorineC was consistent with the experimental determined second-order rate constant (kTCC-chlorineE, 3.70 M-1 s-1) in chlorination process. Eight transformation products (TP348, TP382, TP127, TP161, TP195, TP330, TP204, and TP296) were experimentally detected for chlorination of TCC, which could also be predicted by DFT calculation. Explicit water molecules participated in the chlorination reaction by transmitting the proton and connecting with TCC, HOCl/OCl- and other H2O molecules, and obviously reduced the energy barrier of chlorination.
Nitrogen-containing disinfection byproducts (N-DBPs) are highly toxic DBPs in drinking water. Though, under normal conditions, NO3- could not directly participate in disinfection reactions to generate N-DBPs, here, we first found that NO3- could promote the formation of N-DBPs in corroded iron drinking water pipes. The coexistence of corrosion produced Fe(II) and iron oxides is a critical condition for the transformation of N species; meanwhile, most of the newly generated N-DBPs had aromatic fractions. The Fe-O-C bond formed between iron corrosion products and natural organic matter promoted electron transfer for the N transformation with pyrrolic N as the intermediate N species. Density functional calculation confirmed that the coexistence of Fe(II) and iron oxides effectively reduced the Gibbs free energy for NO3- reduction. ΔG of the key rate-determining step from NO* to NOH* decreased from 1.55 eV on FeOOH to 1.35 eV on Fe(II)+FeOOH. In addition, the large decrease of cell viability of the water samples from 74.3% to 45.4% further confirmed the formation of highly toxic N-DBPs. Thus, in a drinking water distribution system with corroded iron pipes, the low toxic NO3- may increase toxicity risks via N-DBP formation.
Wildfires can release pyrogenic dissolved organic matter (pyDOM) into the forest watershed, which may pose challenges for water treatment operations downstream due to the formation of disinfection by-products (DBPs). In this study, we systematically assessed the physio-chemical properties of pyDOM (e.g., electron-donating and -accepting capacities; EDC and EAC) and their contributions to DBP formation under different disinfection scenarios using (1) ten lab samples produced from various feedstocks and pyrolysis temperatures, and (2) pre- and post-fire field samples with different burning severities. A comprehensive suite of DBPs-four trihalomethanes (THMs), nine haloacetic acids (HAAs), and seven N-nitrosamines-were included. The formations of THM and HAA showed an up to 5.7- and 8.9-fold decrease as the pyrolysis temperature increased, while the formation of N-nitrosamines exhibited an up to 6.6-fold increase for the laboratory-derived pyDOM. These results were supported by field pyDOM samples, where the post-fire samples consistently showed a higher level of N-nitrosamine formation (i.e., up to 5.3-fold), but lower THMs and HAAs compared to the pre-fire samples. To mimic environmental reducing conditions, two field samples were further reduced electrochemically and compared with Suwannee River natural organic matter (SRNOM) to evaluate their DBP formation. We found increased DBP formation in pyDOM samples following electrochemical reduction but not for SRNOM, which showed increased N-nitrosamines but decreased THMs and HAAs post-electrochemical reduction. Furthermore, this study reported for the first time the formation of two previously overlooked N-nitrosamines (i.e., nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA)) in both laboratory and field pyDOM samples, raising concerns for drinking water safety given their higher toxicity as compared to the regulated counterparts. Results from this study provide new insights for DBP mitigation during post-fire recovery, which are particularly relevant to communities that rely on forest watersheds as their drinking water sources.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 (
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.
There are still compounds to identify, and new data indicate that already known DBPs may pose additional health risks.
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.
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.
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 progressively as the treatment period was increased, and no longer occurred at 8 weeks. A shift of the liver glycogen–iodine spectrum from DCA-treated mice was observed relative to that of control mice, suggesting a change in the physical form of glycogen. These data suggest that DCA-induced glycogen accumulation at high doses is related to decreases in the degradation rate. When DCA was administered by single intraperitoneal (i.p.) injection to naı̈ve mice at doses of 2–200 mg/kg at the time of glucose challenge, a biphasic response was observed. Doses of 10–25 mg/kg increased both plasma glucose and insulin concentrations. In contrast, very high i.p. doses of DCA (>75 mg/kg) produced progressive decreases in serum glucose and glycogen deposition in the liver. Since the blood levels of DCA produced by these higher i.p. doses were significantly higher than observed with drinking water treatment, we conclude that apparent differences with data of previous investigations is related to substantial differences in systemic dose and/or dose–time relations.
The chlorinated acetic acids monochloroacetic acid MCA and trichloroacetic acid TCA are found as chlorine disinfection by-products in finished drinking-water supplies. TCA has been demonstrated to be a mouse liver carcinogen. A chronic study in which male Fischer 344 N rats were exposed for 104 wk to TCA and MCA in the drinking water is described. Animals, 28 d old, were exposed to 0.05, 0.5, or 2 g L MCA, or 0.05, 0.5, or 5 g L TCA. The 2.0 g L MCA was lowered in stages to 1 g L when the animals began to exhibit signs of toxicity. A time-weighted mean daily MCA concentration MDC of 1.1 g L was calculated over the 104-wk exposure period. Time-weighted mean daily doses MDD based upon measured water consumption were 3.5, 26.1, and 59.9 mg kg d for 0.05, 0.5, and 1.1 g L MCA, respectively; TCA MDD were 3.6, 32.5, and 363.8 mg kg d. Nonneoplastic hepatic changes were for the most part spontaneous and age related. No evidence of hepatic neoplasia was found at any of the MCA or TCA doses. The incidence of neoplastic lesions at other sites was not enhanced over that in the control group. Drinking water concentrations of 0.5 g L MCA produced a moderate to severe toxicity as reflected by a depressed water consumption and growth rate. A no-observed-effects level NOEL for carcinogenicity of 0.5 g L 26.1 mg kg d MCA was calculated. TCA at drinking water levels as high as 5 g L produced only minimal toxicity and growth inhibition and provided a NOEL of 364 mg kg d. Our results demonstrate that under the conditions of this bioassay, MCA and TCA were not tumorigenic in the male F344 N rat.
Disinfection by-products (DBPs) generated from chlorination, chloramination, ozonation, and chlorine dioxide treatment were characterized and compared. DBPs examined included four trihalomethanes, nine haloacetic acids, four haloacetonitriles, two haloketones, chloropicrin, total organic halogen (TOX), total organic bromine (TOBr), total organic chlorine (TOCl), thirteen aldehydes, and bromate. The contributions of known DBPs to TOX, TOCl and TOBr formed from using different disinfectants were given. The reaction of humic substances with small amount of free chlorine in equilibrium with NH2Cl constitutes an important pathway for the formation of TOCl during chloramination. The yields of TOBr and total aldehydes produced from using each disinfectant were found to be related to the redox potential corresponding to each disinfectant. This work makes a step toward better decisions about which disinfectant poses the lowest risk to human health.
Tribromoacetamide was isolated from the Okinawan alga Wrangelia species, and the biological activities of this compound and its analogs were investigated.
The chlorinated acetaldehydes, chloral hydrate (CH) and 2-chloroacetaldehyde (CAA), have been identified as chlorination by-products in finished drinking water supplies. Although both chemicals are genotoxic, their potential for carcinogenicity had not been adequately explored. The studies reported here are chronic bioassays conducted with male B6C3F1 mice exposed to levels of 1 g/liter CH and 0.1 g/liter CAA via the drinking water for 104 weeks. Distilled water (H2O) served as the untreated control and dichloroacetic acid (DCA; 0.5 g/liter), another chlorine disinfection by-product, was included. The mean daily ingested doses were approximately 166 mg/kg/day for CH, 17 mg/kg/day for CAA, and 93 mg/kg/day for DCA. Evaluations included mortality, body weight, organ weights, gross pathology, and histopathology. The primary target organ was the liver as the organ weights and pathological changes in the other organs spleen, kidneys, and testes) were comparable between the treated groups and the H2O control group. Liver weights were increased for all three test chemicals at the terminal euthanasia with the greatest increase seen in the CH and DCA groups. Hepatocellular necrosis was induced by all three test chemicals, and it was also most prevalent and severe in the CH and DCA groups. A significant increase in the prevalence of liver tumors was seen for all three chemicals. The strongest response was with DCA, in which 63% of the 104-week survivors had hepatocellular carcinomas (carcinomas) and 42% possessed hepatocellular adenomas (adenomas) and the combined prevalence for carcinomas plus adenoma was 75%. The corresponding prevalence rate for carcinomas, adenomas, and combined tumors were 46, 29, and 71%; 31, 8, and 38%; and 10, 5, and 15% for CH, CAA, and H2O, respectively. In addition to the tumors we evaluated the prevalence of a possible preneoplastic lesion, the hepatocellular hyperplastic nodule (nodules), a lesion which occurred in all three treated groups but not in the H2O group.