Experimental cancer studies of chlorinated by-products

Dichloroacetic acid and trichloroacetic acid as disinfection by-products in drinking water are endocrine-disrupting chemicals

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) are two typical non-volatile disinfection by-products (DBPs) found in drinking water. Increasing evidence has demonstrated that they show reproductive toxicity. However, whether they might have endocrine disrupting properties remains largely unknown. To discover this, we treated male mice or pregnant mice with 0, 1-, 102-, 103-, 104-, or 5 × 104-fold maximal concentration level (MCL) of DCAA or TCAA in drinking water. In male mice, the levels of testosterone in serum and androgen receptor (AR) in testis were declined with ≥ 103-fold MCL of DCAA (26.4 mg/kg/d) or TCAA (52.7 mg/kg/d). In pregnant mice, miscarriage rates were increased with ≥ 104-fold MCL of DCAA (264 mg/kg/d) or ≥ 103-fold MCL of TCAA. The levels of FSH in serum were increased and those of estradiol and progesterone were reduced with ≥ 103-fold MCL of DCAA or TCAA. The protein levels of estrogen receptors (ERα and ERβ) in ovary were reduced with ≥ 102-fold MCL of DCAA (2.64 mg/kg/d) or TCAA (5.27 mg/kg/d). Exposure to some certain fold MCL of DCAA or TCAA also altered the protein levels of ERα and ERβ in uterus and placenta. Exposure to 5 × 104-fold MCL of both DCAA and TCAA showed the combined effects. Therefore, both DCAA and TCAA could be considered as novel reproductive endocrine disrupting chemicals, which might be helpful for further assessment of the toxicological effects of DCAA and TCAA and the awareness of reproductive endocrine disrupting properties caused by DCAA and TCAA in drinking water.

A case report of toxic hepatitis caused by chloroform in automotive parts manufacturer coating process

Background

Several cases of chloroform-induced hepatotoxicity have been reported worldwide, but only 2 cases have been reported in Korea. We encountered a case of toxic hepatitis due to chloroform exposure in February 2022 and report the diagnosis process and clinical findings.

Case presentation

A 38-year-old employee in charge of the coating after washing (degreasing) at an automotive parts manufacturer complained of jaundice and was diagnosed with acute toxic hepatitis. After the initial diagnosis, he continued to work, his symptoms worsened, and he was hospitalized for 8 days. Liver ultrasonography (elastography) revealed acute hepatitis. The washing agent contained chloroform, which was not listed on the materials safety data sheet, and the concentrations of chloroform in the workplace were up to 4.7 times the time-weighted average.

Conclusions

This patient showed typical toxic hepatitis with chloroform; further follow-up studies are required. Both employers and workers should be aware of information on toxic substances and take precautions to avoid exposure.

Formation of nitro(so) and chlorinated products and toxicity alteration during the UV/monochloramine treatment of phenol

The UV/monochloramine (UV/NH₂Cl) process is an emerging advanced oxidation process (AOP) to remove organic contaminants in water treatment with radicals including hydroxyl radicals (HO^•), reactive chlorine species (RCS) and reactive nitrogen species (RNS). This study investigated the formation of nitro(so) and chlorinated products and toxicity alteration during the UV/NH₂Cl treatment of phenol. RNS and/or RCS induced the formation of nitro(so), chlorinated and polymeric compounds during phenol transformation by UV/NH₂Cl. These compounds dramatically increased the cytotoxicity to Chinese hamster ovary cells after 20 min UV/NH₂Cl treatment, which was 10 times higher than that after 24 h chloramination. The increase of cytotoxicity in UV/NH₂Cl was primarily attributable to 4-nitrosophenol, and the cytotoxicity followed the order of 4-nitrosophenol >> 4-nitrophenol > 2,4,6-trichlorophenol > 2,4-dichlorophenol > phenol. 4-Nitrosophenol was significantly generated by the combination of ^•NO and phenoxy radical, where the maximum conversion rates of phenol to 4-nitrosophenol increased from 4.9% to 62.4% when pH increased from 5 to 10. The highest conversion rate was at pH 10 because the ^•NO concentration increased with increasing pH from 5 to 10 in UV/NH₂Cl, as verified by the electron paramagnetic resonance (EPR) analysis. Nitrophenols were also detected at much lower concentrations than 4-nitrosophenol, which were mainly formed by the oxidation of 4-nitrosophenol and the combination of ^•NO₂ with phenoxy radicals. RCS was responsible for the formation of chlorinated products mainly through Cl^• addition and the reactions of Cl^•/Cl₂^•- with phenoxy radicals. Also, RCS and RNS significantly enhanced the formation of carbonaceous (i.e., chloroform and chloral hydrate) and nitrogenous disinfection byproducts (i.e., chloropicrin and dichloroacetonitrile) in UV/NH₂Cl. This study indicates that the UV/NH₂Cl treatment significantly increased toxicity and validates the roles of RNS and RCS in producing toxic nitro(so) and chlorinated products.

Aqueous chlorination of herbicide metribuzin: Identification and elucidation of "new" disinfection by-products, degradation pathway and toxicity evaluation

A widely used herbicide, metribuzin, was evaluated for degradation, mineralization and disinfection by-products (DBPs) formation during aqueous chlorination. In addition, to assess the toxicity effects of chlorination on metribuzin solution the following tests were performed: acute toxicity using Artemia salina nauplii; cell viability using MTT assay; estrogenicity using a re-engineered Bioluminescent Yeast Estrogen Screen (BLYES) and a constitutively bioluminescent strain (BLYR); mutagenicity and developmental toxicity using Q(SAR) methodology. Metribuzin at 10 mg·L^-1 was degraded by chlorination, achieving 93% of removal at 30 min of reaction. TOC analysis showed that the herbicide does not suffer complete mineralization, even after 24 h of contact with free chlorine. Seventeen DBPs were detected and their structural formulae were elucidated by high resolution mass spectrometry. Toxicity effects for chlorinated solutions increased when compared to the unreacted metribuzin solution. DBPs were more toxic to Artemia salina nauplii, increasing around 20% on nauplii mortality. It was also observed high estrogenicity to human receptors in BLYES assays and mutagenic and developmental toxicant effects to animals and humans in Q(SAR) methodology, suggesting that DBPs are potentially more toxic than the precursor metribuzin. Metribuzin solutions at 10 mg·L^-1 showed equivalent 17-β-estradiol values ranged from 0.061 to 6.71 µg·L^-1 after to be chlorinated at different reaction times.

Metabisulfite as an Unconventional Reagent for Green Oxidation of Emerging Contaminants Using an Iron-Based Catalyst

In this work, contaminants of emerging concern were catalytically degraded in the homogeneous phase with the use of unconventional green reagents. Three reagents, namely, sulfite, metabisulfite, and persulfate, were tested and compared with conventional hydrogen peroxide in the degradation process activated by Fe-TAML. The latter is a biodegradable, homogeneous tetra-amido macrocyclic ligand catalyst containing iron(III). Metabisulfite showed the highest efficiency among the three tested reagents, and its reactivity was similar to that of H₂O₂. However, metabisulfite is a safer and cleaner reagent compared to H₂O₂. A comprehensive study of the activity of metabisulfite with Fe-TAML was carried out toward the oxidative degradation of eight contaminants of emerging concern. The catalytic process was tested at different pH values (7, 9, and 11). Metabisulfite showed the highest activity at pH 11, completely degrading some of the tested micropollutants, but in several cases, the system was active at pH 9 as well. In particular, metabisulfite showed the best efficiency toward phenolic compounds. A preliminary study on the reaction mechanism and the nature of the active species in the Fe-TAML/metabisulfite system was also conducted, highlighting that a high-valent iron-oxo species might be involved in the degradation pathways.

Comparison of DNA damages in blood lymphocytes of indoor swimming pool lifeguards with non-lifeguards athletes

Chlorination has been used as a major disinfectant process for swimming pool water in many countries. The purpose of this study is to compare the DNA damage of the blood lymphocytes in indoor pool lifeguards with non-lifeguards athletes. We performed a study in which the participants were Gonabad's lifeguards. We chose 30 participants (15 male and 15 female) for each group. We collected vein blood samples from each participant in both exposed and control group. The lymphocytes were isolated from the whole blood by ficoll, and the cell viability was determined by the trypan blue. The alkaline Comet assay was also performed on lymphocytes in order to measure the DNA damage. All the parameters indicated that the DNA damage was significantly greater in lifeguards group than control group (p < 0.001). Also, the results revealed a statistically significant higher level of DNA damage in females as evident by an increase in the tail length (μm) [8.97 ± 4.21 for females as compared to 4.32 ± 1.33 for males (p = 0.001)], tail DNA (%) [4.18 ± 1.27 for females as compared to 3.14 ± 0.94 for males (p = 0.016)] and tail moment (μm) [0.68 ± 0.53 for females and 0.26 ± 0.14 for males (p = 0.010)]. There was also a significant positive correlation between DNA damage and the duration of work (P < 0.001).

Ingested Nitrate, Disinfection By-products, and Kidney Cancer Risk in Older Women

BACKGROUND

N-nitroso compounds formed endogenously after nitrate/nitrite ingestion are animal renal carcinogens. Previous epidemiologic studies of drinking water nitrate did not evaluate other potentially toxic water contaminants, including the suspected renal carcinogen chloroform.

METHODS

In a cohort of postmenopausal women in Iowa (1986-2010), we used historical measurements to estimate long-term average concentrations of nitrate-nitrogen (NO3-N) and disinfection by-products (DBP) in public water supplies. For NO3-N and the regulated DBP (total trihalomethanes [THM] and the sum of five haloacetic acids [HAA5]), we estimated the number of years of exposure above one-half the current maximum contaminant level (>½-MCL NO3-N; >5 mg/L). Dietary intakes were assessed via food frequency questionnaire. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) with Cox models, and evaluated interactions with factors influencing N-nitroso compound formation.

RESULTS

We identified 125 incident kidney cancers among 15,577 women reporting using water from public supplies >10 years. In multivariable models, risk was higher in the 95th percentile of average NO3-N (HRp95vsQ1 = 2.3; CI: 1.2, 4.3; Ptrend = 0.33) and for any years of exposure >½-MCL; adjustment for total THM did not materially change these associations. There were no independent relationships with total THM, individual THMs chloroform and bromodichloromethane, or with haloacetic acids. Dietary analyses yielded associations with high nitrite intake from processed meats but not nitrate or nitrite overall. We found no interactions.

CONCLUSIONS

Relatively high nitrate levels in public water supplies were associated with increased risk of renal cancer. Our results also suggest that nitrite from processed meat is a renal cancer risk factor.

Ames and random amplified polymorphic DNA tests for the validation of the mutagenic and/or genotoxic potential of the drinking water disinfection by-products chloroform and bromoform

Chloroform and Bromoform are two abundant trihalomethanes found in Algerian drinking water. The investigation of the mutagenic hazard of these disinfection by-products was studied by Ames test as prokaryotic bioassay to show their mutagenic effects. For this, Salmonella typhimurium TA98 and TA100 strains were employed. Both chloroform and bromoform showed a direct mutagenic effect since the number of revertant colonies gradually increase in dose-dependent manner with all concentrations tested with the two bacterial strains and these were both in the absence and presence of S9 metabolic activation. The genotoxic hazard was also studied by random amplified polymorphic DNA test on the root cells of Allium cepa as eukaryotic bioassay. DNA extracted from the roots of the onion were incubated at different concentrations of chloroform and bromoform and then amplified by polymerase chain reaction. This was based on demonstrating a major effect of disappearance of bands compared to roots incubated in the negative control (distilled water). The results showed that these two compounds affected genomic DNA by breaks although by mutations.

Adsorption of metribuzin from aqueous solution using magnetic and nonmagnetic sustainable low-cost biochar adsorbents

Switchgrass biochar (SGB) was made by fast pyrolysis in an auger-fed reactor at 425 °C with a solid residence time of 60 s in the pyrolysis zone during bio-oil production. Magnetic switchgrass biochar (MSGB) was prepared by iron oxide precipitation onto the biochar surface using an aqueous Fe³⁺/Fe²⁺ solution followed by NaOH treatment. Both the SGB and the MSGB were characterized by FTIR, SEM, SEM-EDX, TGA, pH_pzc, elemental analysis, and surface area measurements. Batch sorption studies of metribuzin from aqueous solutions were carried out at different pH values, adsorbate concentrations, and temperatures. The adsorption of metribuzin onto both biochars was highest at a pH of 2. Adsorption isotherms were evaluated from 25 to 45 °C using the Freundlich, Langmuir, Redlich-Peterson, Toth, Sips, Koble-Corrigan, and Radke-Prausnitz adsorption models. Langmuir adsorption capacities at pH 2 were Q ⁰_SGB ~ 151, 223, and 205 mg/g and Q ⁰_MSGB ~ 155, 205, and 155 mg/g at 25, 35, and 45 °C, respectively. Low-cost magnetization of the biochar occurred without significant loss of absorption capacity, enabling facile separation of slurried biochar from liquids following contaminate absorption. Graphical abstract ᅟ.

Biofiltration of Chloroform in a Trickle Bed Air Biofilter Under Acidic Conditions

In this paper, the application of biofiltration is investigated for controlled removal of gas phase chloroform through cometabolic degradation with ethanol. A trickle bed air biofilter (TBAB) operated under acidic pH 4 is subjected to aerobic biodegradation of chloroform and ethanol. The TBAB is composed of pelleted diatomaceous earth filter media inoculated with filamentous fungi species, which served as the principle biodegrading microorganism. The removal efficiencies of 5 ppm_v of chloroform mixed with different ratios of ethanol as cometabolite (25, 50, 100, 150, and 200 ppm_v) ranged between 69.9 and 80.9%. The removal efficiency, reaction rate kinetics, and the elimination capacity increased proportionately with an increase in the cometabolite concentration. The carbon recovery from the TBAB amounted to 69.6% of the total carbon input. It is postulated that the remaining carbon contributed to excess biomass yield within the system. Biomass control strategies such as starvation and stagnation were employed at different phases of the experiment. The chloroform removal kinetics provided a maximum reaction rate constant of 0.0018 s^-1. The highest ratio of chemical oxygen demand (COD)_removal/nitrogen_utilization was observed at 14.5. This study provides significant evidence that the biodegradation of a highly chlorinated methane can be favored by cometabolism in a fungi-based TBAB.

Modelling the regional variability of the probability of high trihalomethane occurrence in municipal drinking water

The regional variability of the probability of occurrence of high total trihalomethane (TTHM) levels was assessed using multilevel logistic regression models that incorporate environmental and infrastructure characteristics. The models were structured in a three-level hierarchical configuration: samples (first level), drinking water utilities (DWUs, second level) and natural regions, an ecological hierarchical division from the Quebec ecological framework of reference (third level). They considered six independent variables: precipitation, temperature, source type, seasons, treatment type and pH. The average probability of TTHM concentrations exceeding the targeted threshold was 18.1%. The probability was influenced by seasons, treatment type, precipitations and temperature. The variance at all levels was significant, showing that the probability of TTHM concentrations exceeding the threshold is most likely to be similar if located within the same DWU and within the same natural region. However, most of the variance initially attributed to natural regions was explained by treatment types and clarified by spatial aggregation on treatment types. Nevertheless, even after controlling for treatment type, there was still significant regional variability of the probability of TTHM concentrations exceeding the threshold. Regional variability was particularly important for DWUs using chlorination alone since they lack the appropriate treatment required to reduce the amount of natural organic matter (NOM) in source water prior to disinfection. Results presented herein could be of interest to authorities in identifying regions with specific needs regarding drinking water quality and for epidemiological studies identifying geographical variations in population exposure to disinfection by-products (DBPs).

Mutagenicity and genotoxicity of drinking water in Guelma region, Algeria

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

Virus adsorption of water-stable quaternized chitosan nanofibers

The burden of unsafe drinking water is responsible for millions of deaths each year. To relieve this burden, we are in search of an inexpensive material that can adsorb pathogens from drinking water. In this pursuit, we have studied the natural carbohydrate, chitosan. To impart virus removal features, chitosan has been functionalized with a quaternary amine to form quaternized chitosan N-[(2-hydroxyl-3-trimethylammonium) propyl] chitosan (HTCC). HTCC can be electrospun into nanofibers with the non-ionogenic polyvinyl alcohol (PVA), creating a high surface area mat. High surface area is a major requirement for effective adsorption processes. HTCC is antiviral and antimicrobial, making it a good material for water purification. However, HTCC dissolves in water. We have explored the parameters to crosslink the nanofibers with glutaraldehyde. We have imparted water stability so there is a maximum of 30% swelling of the fibers after 6h in water. The water stable fibers retain their ability to adsorb virus, as shown for an enveloped and nonenveloped virus. HTCC now has the potential to be incorporated into a microfiltration membrane that can remove viruses. This could create an inexpensive, low pressure filtration membrane for drinking water purification.

Fluid intake and risk of bladder cancer in the Nurses' Health Studies

Increase in fluid intake may reduce bladder cancer risk by decreasing the contact time between carcinogens in urine and bladder epithelium. However, this association has not been examined in a large cohort of women. The association between total fluid intake and bladder cancer risk in two large prospective women's cohorts with 427 incident bladder cancer cases was examined. Detailed information on total fluid intake was collected by repeated food frequency questionnaires over time. Multivariable relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated by using Cox proportional hazards regression models. Results from the two cohorts were pooled together using the random-effects model. Using the average values from the earliest two dietary assessments and lowest quartile as reference, a suggestive inverse association was observed between total fluid intake and overall bladder cancer risk (RR: 0.83, 95% CI: 0.61-1.12, p-value for trend: 0.08), and invasive bladder cancer risk (RR: 0.47, 95% CI: 0.23-0.97, p-value for trend: 0.04). Among heavy cigarette smokers, women with the highest quartile of total fluid intake had a 38% decrease in bladder cancer risk (RR: 0.62, 95% CI: 0.41-0.93, p-value for trend: 0.02). The findings suggested that total fluid intake may reduce bladder cancer risk for female smokers, as well as reduce the risk of invasive bladder cancer.

Genotoxicity of drinking water disinfection by-products (bromoform and chloroform) by using both Allium anaphase-telophase and comet tests

Genotoxic effects of bromoform and chloroform, disinfection by-products of the chlorination of drinking water, were examined by using mitotic index (MI), mitotic phase, chromosome aberrations (CAs) and comet assay on root meristematic cells of Allium cepa. Different concentrations of bromoform (25, 50, 75 and 100 μg/mL) and chloroform (25, 50, 100 and 200 μg/mL) were introduced to onion tuber roots. Distilled water was used as a negative control and methyl methansulfonate (MMS-10 μg/mL) as positive control. All obtained data were subjected to statistical analyses by using SPSS 15.0 for Windows software. For comparison purposes, Duncan multiple range tests by using one-way analysis of variance were employed and p < 0.05 was accepted as significant value. Exposure of both chemicals (except 25 μg/mL applications of bromoform) significantly decreased MI. Bromoform and chloroform (except 25 μg/mL applications) increased total CAs in Allium anaphase-telophase test. A significant increase in DNA damage was also observed at all concentrations of both bromoform and chloroform examined by comet assay. The damages were higher than that of positive control especially at 75-100 μg/mL for bromoform and 100-200 μg/mL for chloroform.

An optimized analytical method for the simultaneous detection of iodoform, iodoacetic acid, and other trihalomethanes and haloacetic acids in drinking water

An optimized method is presented using liquid-liquid extraction and derivatization for the extraction of iodoacetic acid (IAA) and other haloacetic acids (HAA9) and direct extraction of iodoform (IF) and other trihalomethanes (THM4) from drinking water, followed by detection by gas chromatography with electron capture detection (GC-ECD). A Doehlert experimental design was performed to determine the optimum conditions for the five most significant factors in the derivatization step: namely, the volume and concentration of acidic methanol (optimized values  = 15%, 1 mL), the volume and concentration of Na2SO4 solution (129 g/L, 8.5 mL), and the volume of saturated NaHCO3 solution (1 mL). Also, derivatization time and temperature were optimized by a two-variable Doehlert design, resulting in the following optimized parameters: an extraction time of 11 minutes for IF and THM4 and 14 minutes for IAA and HAA9; mass of anhydrous Na2SO4 of 4 g for IF and THM4 and 16 g for IAA and HAA9; derivatization time of 160 min and temperature at 40°C. Under optimal conditions, the optimized procedure achieves excellent linearity (R(2) ranges 0.9990-0.9998), low detection limits (0.0008-0.2 µg/L), low quantification limits (0.008-0.4 µg/L), and good recovery (86.6%-106.3%). Intra- and inter-day precision were less than 8.9% and 8.8%, respectively. The method was validated by applying it to the analysis of raw, flocculated, settled, and finished waters collected from a water treatment plant in China.

Combined exposure to 3-chloro-4-dichloromethyl-5-hydroxy-2(5H)-furanone and microsytin-LR increases genotoxicity in Chinese hamster ovary cells through oxidative stress

The disinfection byproducts 3-chloro-4-dichloromethyl-5-hydroxy-2(5H)-furanone (MX) and microcystins-LR (MC-LR), which are common contaminants in drinking water, often occur together in water sources in areas with high gastrointestinal tract cancer risks. While often studied alone, combination effects of these compounds are unknown. Here, we examine combined genotoxic responses to mixtures of MX and MC-LR using the Ames test, a cytokinesis-block micronuclei assay, and the comet assay with analysis for interactions by fractional analysis. We also evaluated a possible mechanism of genotoxicity by examining effects of the compounds on markers of oxidative stress. MX and MC-LR administrated jointly at noncytotoxic concentrations demonstrated significant interactions in the Ames test, the micronuclei assay, and the comet assay showing responses greater than those expected for additivity. Moreover, coexposure to MX and MC-LR significantly increased luciferase antioxidant response element activity, intracellular superoxide dismutase, catalase, glutathione, and reactive oxygen species production. In comparison with exposure to either compound alone, the mixtures of MX and MC-LR caused a less than additive effect on oxidative stress. Taken together, these results indicate that MC-LR exacerbates MX genotoxicity in low-dose combined exposure. This interaction may be enhanced by oxidative stress in the combined exposures.

Application of the International Life Sciences Institute Key Events Dose-Response Framework to food contaminants

Contaminants are undesirable constituents in food. They may be formed during production of a processed food, present as a component in a source material, deliberately added to substitute for the proper substance, or the consequence of poor food-handling practices. Contaminants may be chemicals or pathogens. Chemicals generally degrade over time and become of less concern as a health threat. Pathogens have the ability to multiply, potentially resulting in an increased threat level. Formal structures have been lacking for systematically generating and evaluating hazard and exposure data for bioactive agents when problem situations arise. We need to know what the potential risk may be to determine whether intervention to reduce or eliminate contact with the contaminant is warranted. We need tools to aid us in assembling and assessing all available relevant information in an expeditious and scientifically sound manner. One such tool is the International Life Sciences Institute (ILSI) Key Events Dose-Response Framework (KEDRF). Developed as an extension of the WHO's International Program on Chemical Safety/ILSI mode of action/human relevance framework, it allows risk assessors to understand not only how a contaminant exerts its toxicity but also the dose response(s) for each key event and the ultimate outcome, including whether a threshold exists. This presentation will illustrate use of the KEDRF with case studies included in its development (chloroform and Listeriaonocytogenes) after its publication in the peer-reviewed scientific literature (chromium VI) and in a work in progress (3-monochloro-1, 2-propanediol).

Reexamination of total fluid intake and bladder cancer in the Health Professionals Follow-up Study Cohort

It has been hypothesized that high fluid intake may reduce contact time between carcinogens and bladder epithelium and consequently reduce carcinogenesis. Epidemiologic studies examining fluid intake and bladder cancer have been extremely inconsistent, ranging from strong inverse to strong positive associations. The authors reevaluated the association between fluid intake and bladder cancer among 47,909 participants in the prospective Health Professionals Follow-up Study over a period of 22 years. During follow-up (1986-2008), 823 incident bladder cancer cases were diagnosed. Information on fluid intake was collected by using the food frequency questionnaire at baseline and every 4 years thereafter. Cox proportional hazard regression analysis was used to adjust for risk factors for bladder cancer. Total fluid intake was inversely associated with bladder cancer when the analysis was based on the baseline diet (relative risk = 0.76, 95% confidence interval: 0.60, 0.97), comparing the highest total daily fluid intake quintile (>2,531 mL/day) with the lowest quintile (<1,290 mL/day) (P(trend) = 0.01). However, no association was detected when the analysis was based on recent diet or cumulative updated diet. The updated analysis for total fluid intake and bladder cancer was attenuated compared with the original findings from the first 10-year follow-up period.

Synergistic effect of the combination of immobilized TiO2, UVA and ozone on the decomposition of dichloroacetic acid

The performance of a heterogeneous photocatalytic ozonation system (TiO(2)/UVA/O(3)) was evaluated on the degradation and mineralization of dichloroacetic acid as a contaminant in aqueous solutions by means of a planar reactor. The commercial product "Pilkington Active™ glass" was used as the immobilized TiO(2) photocatalyst and it was irradiated by near UV light in this study. The synergistic interaction between ozone and the photoactivated TiO(2) surface was discussed and highlighted. Furthermore, the influences of initial concentration and temperature on the degradation rate of dichloroacetic acid and the ozone consumption level during the oxidation process were investigated. The concentrations of dichloroacetic acid and chloride anions produced during degradation were measured using ion chromatography. The mineralization of dichloroacetic acid was evaluated by Total Organic Carbon (TOC) measurements. The degradation of dichloroacetic acid by photocatalytic ozonation showed good agreement with the kinetics of first-order reactions with respect to dichloroacetic acid.

Mutagenic analysis of six disinfection by-products in the Tk gene of mouse lymphoma cells

Drinking water must be disinfected prior to its distribution for human consumption. This water treatment process generates disinfection by-products (DBPs), formed by the interaction of the disinfectant with organic matter, anthropogenic contaminants and inorganic (bromide/iodide) matter naturally present in source water. Due to the potential genotoxic/carcinogenic risk of these DBPs, we have investigated the mutagenic potential of six of such compounds on the thymidine kinase (Tk) gene in the well-validated mouse lymphoma assay (MLA). The MLA quantifies a wide range of genetic alterations affecting the expression of this gene in L5178Y/Tk(+/-)-3.7.2C cells. In this study we selected six emerging DBPs, corresponding to three different chemical classes: halonitromethanes (bromonitromethane and trichloronitromethane), halogenated acetaldehydes (tribromoacetaldehyde and chloral hydrate) and hydroxyfuranones (mucobromic and mucochloric acids), each class including one chlorinated and one brominated form. The results showed that after 4h of treatment, only mucobromic acid increased the frequency of mutant colonies, with a higher proportion of small colonies, which would indicate a clastogenic potential. This is the first study reporting mutagenicity data in mammalian cells for the six selected DBPs.

Knockout and transgenic mice in glutathione transferase research

Glutathione transferases (GSTs) are a multigene family of ubiquitously expressed, polymorphic enzymes responsible for the metabolism of a wide range of both endogenous and exogenous substrates, play a central role in the adaptive response to chemical and oxidative stress, and are subject to regulation by a range of structurally unrelated chemicals. In this review, we present a current summary of knockout mouse models in the GST field, discussing some of the issues pertaining to orthologous proteins between mice and humans, the potential confounding issues related to genetic background, and also cover new transgenic models in the increasingly important area of humanization.

Polymorphisms in GSTT1, GSTZ1, and CYP2E1, disinfection by-products, and risk of bladder cancer in Spain

BACKGROUND

Bladder cancer has been linked with long-term exposure to disinfection by-products (DBPs) in drinking water.

OBJECTIVES

In this study we investigated the combined influence of DBP exposure and polymorphisms in glutathione S-transferase (GSTT1, GSTZ1) and cytochrome P450 (CYP2E1) genes in the metabolic pathways of selected by-products on bladder cancer in a hospital-based case-control study in Spain.

METHODS

Average exposures to trihalomethanes (THMs; a surrogate for DBPs) from 15 years of age were estimated for each subject based on residential history and information on municipal water sources among 680 cases and 714 controls. We estimated effects of THMs and GSTT1, GSTZ1, and CYP2E1 polymorphisms on bladder cancer using adjusted logistic regression models with and without interaction terms.

RESULTS

THM exposure was positively associated with bladder cancer: adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were 1.2 (0.8-1.8), 1.8 (1.1-2.9), and 1.8 (0.9-3.5) for THM quartiles 2, 3, and 4, respectively, relative to quartile 1. Associations between THMs and bladder cancer were stronger among subjects who were GSTT1 +/+ or +/- versus GSTT1 null (P(interaction) = 0.021), GSTZ1 rs1046428 CT/TT versus CC (P(interaction) = 0.018), or CYP2E1 rs2031920 CC versus CT/TT (P(interaction) = 0.035). Among the 195 cases and 192 controls with high-risk forms of GSTT1 and GSTZ1, the ORs for quartiles 2, 3, and 4 of THMs were 1.5 (0.7-3.5), 3.4 (1.4-8.2), and 5.9 (1.8-19.0), respectively.

CONCLUSIONS

Polymorphisms in key metabolizing enzymes modified DBP-associated bladder cancer risk. The consistency of these findings with experimental observations of GSTT1, GSTZ1, and CYP2E1 activity strengthens the hypothesis that DBPs cause bladder cancer and suggests possible mechanisms as well as the classes of compounds likely to be implicated.

Assessment of the cytotoxicity and genotoxicity of haloacetic acids using microplate-based cytotoxicity test and CHO/HGPRT gene mutation assay

Haloacetic acids (HAAs) are the second most prevalent class of disinfection byproducts found in drinking water. The implications of HAAs presence in drinking water are a public health concern due to their potential mutagenic and carcinogenic effects. In the present study, we examined the cytotoxic and genotoxic effects of six common HAAs using a microplate-based cytotoxicity test and a hypoxanthine-guanine phosphoribosyltransferase (HGPRT) gene mutation assay in Chinese hamster ovary K1 (CHO-K1) cells. We found that their chronic cytotoxicities (72h exposure) to CHO-K1 cells varied, and we ranked their levels of toxicity in the following descending order: iodoacetic acid (IA)>bromoacetic acid (BA)>dibromoacetic acid (DBA)>chloroacetic acid (CA)>dichloroacetic acid (DCA)>trichloroacetic acid (TCA). The toxicity of IA is 1040-fold of that of TCA. All HAAs except TCA were shown to be mutagenic to CHO-K1 cells in the HGPRT gene mutation assay. The mutagenic potency was compared and ranked as follows: IA>DBA>BA>CA>DCA>TCA. There was a statistically significant correlation between cytotoxicity and mutagenicity of the HAAs in CHO-K1 cells. The microplate-based cytotoxicity assay and HGPRT gene mutation assay were suitable methods to monitor the cytotoxicity and genotoxicity of HAAs, particularly for comparing the toxic intensities quantitatively.

DNA damage induction by two halogenated acetaldehydes, byproducts of water disinfection

Drinking water contains disinfection byproducts, generated by the interaction of chlorine (or other disinfecting chemicals) with organic matter, anthropogenic contaminants, and bromide/iodide naturally present in most source waters. One class of these chemicals is the halogenated acetaldehydes (HAs), identified in high quantities when ozone is used as primary or secondary disinfectant. In this study, an analysis of the genotoxic potential of two HAs, namely tribromoacetaldehyde (TBA) and chloral hydrate (CH) has been conducted in human cells (TK6 cultured cells and peripheral blood lymphocytes). The comet assay was used to 1) measure the induction of single and double-strand DNA breaks, 2) evaluate the capacity of inducing oxidative DNA damage, and 3) determine the DNA repair kinetics of the induced primary genetic damage. In addition, chromosome damage, as a measure of fixed damage, was evaluated by means of the micronucleus test. The results of the comet assay show that both compounds are clearly genotoxic, inducing high levels of DNA breaks, TBA being more effective than CH. According to the comet results, both HAs produce high levels of oxidized bases, and the induced DNA damage is rapidly repaired over time. Contrarily, the results obtained in the micronucleus test, which measures the capacity of genotoxic agents to induce clastogenic and aneugenic effects, are negative for the two HAs tested, either using TK6 cells or human peripheral blood lymphocytes. This would indicate that the primary damage induced by the two HAs is not fixed as chromosome damage, possibly due to an efficient repair or the death of damaged cells, which is an important point in terms of risk assessment of DBPs exposure.

Effects of key reaction parameters on the reductive dechlorination of chloroform with Pd/Fe0 bimetal in aqueous solution

In this study, bimetallic Pd/Fe(0) particles were synthesized and employed to reduce chloroform in aqueous solution. The investigation emphasized on the effects of some key reaction parameters including Pd/Fe(0) dosage, pH, oxidation-reduction potential (ORP) and presence of anions on the reductive dechlorination reaction. The experimental results showed that high Pd/Fe(0) dosage, low initial pH and low ORP benefited the reductive dechlorination of chloroform. The ORP values in the aqueous chloroform solution bubbled with different gases of N(2), O(2) and air varied significantly and the efficiency of chloroform degradation under different atmospheres followed an order from high to low as N(2) > air > O(2). The experiments also demonstrated that SO(4)(2 -) and NO(3)(-) ions inhibited the dechlorination reaction significantly, while H(2)PO(4)(-) ion had no significant influence on the dechlorination.

Mode of action considerations in the quantitative assessment of tumour responses in the liver

Chemical carcinogenesis is a complex, multi-stage process and the relationship between dose and tumour formation is an important consideration in the risk assessment of chemicals. Extrapolation from empirical dose-response relationships obtained in experimental studies has been criticized, as it fails to take into account information on mode of action. Strategies for incorporating mode of action information into the risk assessment of chemical carcinogens are described, with a focus on hepatic cancer. Either toxicokinetic or toxicodynamic processes can be addressed. Whilst the former have been the focus of more attention to date, for example by using physiologically based modelling, there is increasing interest in the development of mode of action-based toxicodynamic models. These have the advantage that they do not require extreme assumptions, and may be amenable to paramaterization using human data. This is rarely if ever possible when using conventional dose-tumour response relationships. The approaches discussed are illustrated using chloroform as a case study. This compound is converted to a cytotoxic metabolite, phosgene, by CYP2E1 in liver and/or kidney. Cytotoxicity results in proliferative regeneration, with increased probability of tumour formation. Both physiologically based toxicokinetic and toxicodynamic models have been developed, and it is possible to use probabilistic approaches incorporating, for example, data on the distribution of hepatic CYP2E1 levels. Mode of action can provide an invaluable link between observable, experimental data, on both toxicokinetics and toxicodynamics, and chemical-specific risk assessment, based on physiological approaches.

Drinking water quality: an in vitro approach for the assessment of cytotoxic and genotoxic load in water sampled along distribution system

An in vitro approach was performed to assess the quality of drinking water collected at two treatment/distribution networks located near the source (Plant #1) and the mouth of River Po (Plant #2). The water was sampled at different points of each distribution network, before (raw water) and after the chlorine dioxide disinfection, and in two points of the pipeline system to evaluate the influence of the distribution system on the amount and quality of the disinfection by-product. Cytotoxicity and genotoxicity of water extracts were evaluated in human peripheral lymphocytes and Hep-G2 cells by the use of the micronucleus (MN) test and Comet assay. Raw water samples of both plants induced cytotoxic effects, but not the increases of MN frequency in Hep-G2 cells and in human lymphocytes. Increases of DNA damage in human leukocytes was detected by Comet assay for raw water of Plant #2 at concentration > or = 0.25 Leq/mL. The disinfection process generally has reduced the toxicity of water samples, even if potential direct DNA-damaging compounds have been detectable in drinking water samples. The proposal approach, if currently used together with chemical analysis, can contribute to improve the monitoring drinking water.

Application of key events analysis to chemical carcinogens and noncarcinogens

The existence of thresholds for toxicants is a matter of debate in chemical risk assessment and regulation. Current risk assessment methods are based on the assumption that, in the absence of sufficient data, carcinogenesis does not have a threshold, while noncarcinogenic endpoints are assumed to be thresholded. Advances in our fundamental understanding of the events that underlie toxicity are providing opportunities to address these assumptions about thresholds. A key events dose-response analytic framework was used to evaluate three aspects of toxicity. The first section illustrates how a fundamental understanding of the mode of action for the hepatic toxicity and the hepatocarcinogenicity of chloroform in rodents can replace the assumption of low-dose linearity. The second section describes how advances in our understanding of the molecular aspects of carcinogenesis allow us to consider the critical steps in genotoxic carcinogenesis in a key events framework. The third section deals with the case of endocrine disrupters, where the most significant question regarding thresholds is the possible additivity to an endogenous background of hormonal activity. Each of the examples suggests that current assumptions about thresholds can be refined. Understanding inter-individual variability in the events involved in toxicological effects may enable a true population threshold(s) to be identified.

Genotoxicity analysis of two hydroxyfuranones, byproducts of water disinfection, in human cells treated in vitro

In general, water for human consumption is chemically disinfected, usually by adding chlorine. As well as producing safe drinking water however, the chlorine treatment, also results in a number of disinfection byproducts (DBPs). One important class of these DBPs is made up of hydroxyfuranones (HFs). In this article, we report the results of a recent investigation to assess the genotoxicity of two HFs, namely mucobromic acid (MBA) and mucochloric acid (MCA), in cultured human cells. The comet assay is used to measure the induction of primary DNA damage and to determine the DNA repair kinetics and the ability of the tested compounds to cause oxidative damage. In addition, the micronucleus (MN) assay is applied to evaluate chromosome damage. The results of the comet assay reveal that both HFs are clearly genotoxic leading to high levels of DNA breaks, and that MBA is more effective than MCA. According to the comet results, the DNA damage induced by MBA repairs well over time, but not the one induced by MCA. Furthermore, HFs produce high levels of oxidized bases. In contrast, the results from the MN assay, which measures the induction of clastogenic and/or aneugenic effects, are mainly negative for the two HFs tested, although MCA is able to increase significantly the frequency of micronuclei in binucleated TK cells, at the concentration of 10 microM.

Molecular pathogenesis and diagnostics of bladder cancer

Despite elaborate characterization of the risk factors, bladder cancer is still a major epidemiological problem whose incidence continues to rise each year. Urothelial carcinoma is now recognized as a disease of alterations in several cellular processes. The more prevalent, less aggressive, recurrent, noninvasive tumors are characterized by constitutive activation of the Ras-MAPK pathway. The less common but more aggressive invasive tumors, which have a higher mortality rate, are characterized by alterations in the p53 and retinoblastoma pathways. Several diagnostic tests have attempted to identify these molecular alterations in tumor cells exfoliated in the urine, whereas prognostic tests have tried to identify aberrations so as to predict tumor behavior and identify therapeutic targets. The future of bladder cancer patient management will rely on the use of molecular tests to reliably diagnose the presence of disease, predict individual tumor behavior, and suggest potential targeted therapeutics.

Genotoxic evaluation of two halonitromethane disinfection by-products in the Drosophila wing-spot test

Few studies on the genotoxicity of halonitromethanes (HNMs) have been done. This limited information on their potential genotoxic risk gives special relevance to the collection of new data on their potential genotoxic activity. In the present study we have analyzed the genotoxicity of two HNMs namely bromonitromethane (BNM) and trichloronitromethane (TCNM) in the in vivo wing somatic mutation and recombination test in Drosophila, also known as the wing-spot assay. This test is based on the principle that loss of heterozygosis and the corresponding expression of the suitable recessive markers, multiple wing hairs (mwh) and flare-3 (flr(3)), can lead to the formation of mutant clones in larval cells, which are then expressed as spots on the wings of adult flies. BNM and TCNM were supplied to third instar larvae (72+/-4 h-old) at concentrations ranging from 0.1 to 2 mM. The results showed that none of the three categories of mutant spots recorded (small, large, and twin) increased significantly by the treatments, independently of the dose supplied, indicating that the selected HNMs exhibit a lack of genotoxic activity in the wing-spot assay of Drosophila melanogaster. These results contribute to increase the genotoxicity database on the HNMs.

Genotoxicity analysis of two halonitromethanes, a novel group of disinfection by-products (DBPs), in human cells treated in vitro

Halonitromethanes (HNMs) constitute an emerging class of disinfection by-products (DBPs) produced when chlorine and/or ozone are used for water treatment. The HNMs are structurally similar to halomethanes, but have a nitro-group in place of hydrogen bonded to the central carbon atom. Since little information exists on the genotoxic potential of HNMs, a study has been carried out with two HNM compounds, namely trichloronitromethane (TCNM) and bromonitromethane (BNM) by using human cells. Primary damage induction has been measured with the Comet assay, which is used to determine both the repair kinetics of the induced damage and the proportion of induced oxidative damage. In addition, the fixed DNA damage has been evaluated by using the micronucleus (MN) assay. The results obtained indicate that both compounds are genotoxic, inducing high levels of DNA breaks in the Comet assay, and that this DNA damage repairs well over time. In addition, oxidized bases constitute a high proportion of DNA-induced damage (50-75%). Contrarily, no positive effects were observed in the frequency of micronucleus, which measures both clastogenic and aneugenic effects, neither using TK6 cells nor peripheral blood lymphocytes. This lack of fixed genetic damage would minimize the potential mutagenic risk associated with HNMs exposure.

Risk assessment of trihalomethanes from tap water in Fortaleza, Brazil

The cancer risks (CR) by oral ingestion, dermal absorption, and inhalation exposure of trihalomethanes (THM) from tap water of ten districts in Fortaleza, Brazil were estimated. The mean levels of THM compounds were obtained in Fortaleza tap water as follow: 63.9 microg L(-1) for chloroform (CHCl(3)), 40.0 microg L(-1) for bromodichloromethane (CHBrCl(2)), and 15.6 microg L(-1) for dibromochloromethane (CHBr(2)Cl). Bromoform (CHBr(3)) was not detected. The mean CR for THMs in tap water is 3.96 x 10(-4). The results indicate that Fortaleza residents have a higher CR by inhalation than dermal absorption and oral ingestion. The CR for CHCl(3) contributes with 68% as compared with the total CR, followed by CHBrCl(2) (21%), and CHBr(2)Cl (11%). The hazard index (HI) is about ten times lower than unity, not indicating non-cancer effects.