Carcinogenicity of by-products of disinfection in mouse and rat liver

A literature survey of all volatiles from healthy human breath and bodily fluids: the human volatilome

This paper comprises an updated version of the 2014 review which reported 1846 volatile organic compounds (VOCs) identified from healthy humans. In total over 900 additional VOCs have been reported since the 2014 review and the VOCs from semen have been added. The numbers of VOCs found in breath and the other bodily fluids are: blood 379, breath 1488, faeces 443, milk 290, saliva 549, semen 196, skin 623 and urine 444. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been included in a single table with the source reference(s) for each VOC, an update on our 2014 paper. VOCs have also been grouped into tables according to their chemical class or functionality to permit easy comparison. Careful use of the database is needed, as a number of the identified VOCs only have level 2-putative assignment, and only a small fraction of the reported VOCs have been validated by standards. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces and breath. However, the lack of compounds from matrices such a semen and milk compared to breath for example could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from milk and semen compared to a large number for breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. by collecting skin sebum (with dissolved VOCs and semi VOCs) onto glass beads or cotton pads and then heating to a high temperature to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this work will not only be a useful database of VOCs listed in the literature but will stimulate further study of VOCs from healthy individuals; for example more work is required to confirm the identification of these VOCs adhering to the principles outlined in the metabolomics standards initiative. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.

Inorganic chloramines: a critical review of the toxicological and epidemiological evidence as a basis for occupational exposure limit setting

Inorganic chloramines are not commercially available, but monochloramine is produced in situ for disinfection or for use in chemical synthesis. Inorganic chloramines are also formed when free chlorine reacts with nitrogen containing substances, e.g. ammonia and urea, present in chlorinated water sources. Occupational exposure may, therefore, occur in e.g. swimming pool facilities and the food processing industry. Monochloramine is soluble and stable in water and the dominating inorganic chloramine in chlorinated water sources. No clinical effects were seen in healthy volunteers given monochloramine in drinking water during 4 or 12 weeks in doses of 0.043 or 0.034 mg/kg bw/day, respectively. Limited data indicate that monochloramine is weakly mutagenic in vitro but not genotoxic in vivo. One drinking water study indicated equivocal evidence of carcinogenicity in female rats but not in male rats and mice. No reproductive or developmental effects were shown in rodents in the few studies located. Dichloramine is soluble but unstable in water. In the only study located, mild histological effects in kidneys, thyroid and gastric cardia were observed in rats administered dichloramine in drinking water for 13 weeks. Trichloramine is immiscible with water and evaporates easily from water into air. Therefore, the primary exposure route of concern in the occupational setting is inhalation. Occupational exposure to trichloramine has been demonstrated in indoor swimming pool facilities and in the food processing industry where chlorinated water is used for disinfection. Exposure-response relationships between airborne levels and self-reported ocular and upper airway irritation have been shown in several studies. Exposure to trichloramine may aggravate asthma symptoms in individuals with existing asthma. The risk of developing asthma following long-term exposure to trichloramine cannot be evaluated at present. No data on genotoxic, carcinogenic, reproductive or developmental effects were located. The toxicological data for mono- and dichloramine are insufficient to recommend health-based occupational exposure limits (OELs).As regard trichloramine, the critical effect is judged to be irritation observed in several studies on pool workers, starting at approximately 0.4 mg/m³ (stationary sampling). Based on these data, a health-based OEL of 0.1 mg/m³ (8-h time-weighted average) is recommended. This corresponds to 0.2 mg/m³ for stationary measurements in swimming pool facilities. No short-term exposure limit (STEL) is recommended.

Transcriptome analyses unravel CYP1A1 and CYP1B1 as novel biomarkers for disinfection by-products (DBPs) derived from chlorinated algal organic matter

Disinfection by-products (DBPs) are generated during chlorination of drinking water. Previous studies demonstrate that DBPs are cytotoxic, genotoxic and associated with an increased risk of human cancer. However, the molecular basis of DBPs-induced toxic effects remains unclear. Here, we chlorinated samples of algal-derived organic matter (AOM) and sediment organic matter (SOM) from a local drinking water reservoir. Chemical properties, toxicities and transcriptomic profiles of human Caco-2 cell exposed to AOM and SOM were compared before and after chlorination. We analyzed chlorination-caused distinct gene expression patterns between AOM and SOM, and identified a set of 22 differentially expressed genes under chlorination of AOM that are different from chlorinated SOM. Consequent network analysis indicates that differential CYP1A1, CYP1B1, ID1 and ID2 are common targets of the upstream regulators predicted in the AOM group, but not the SOM group. Through experimental validation and data integration from previous reports related to DBPs or environmental stressors, we found that CYP1A1 and CYP1B1 are specifically up-regulated after chlorinating AOM. Our study demonstrates that the two CYP1 genes likely act as novel biomarkers of AOM derived DBPs, and this would be helpful for testing drinking water DBPs toxicity and further monitoring drinking water safety.

A review of the volatiles from the healthy human body

A compendium of all the volatile organic compounds (VOCs) emanating from the human body (the volatolome) is for the first time reported. 1840 VOCs have been assigned from breath (872), saliva (359), blood (154), milk (256), skin secretions (532) urine (279), and faeces (381) in apparently healthy individuals. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been grouped into tables according to their chemical class or functionality to permit easy comparison. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces. Careful use of the database is needed. The numbers may not be a true reflection of the actual VOCs present from each bodily excretion. The lack of a compound could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from blood compared to a large number on VOCs in breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. collecting excretions on glass beads and then heating to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this database will not only be a useful database of VOCs listed in the literature, but will stimulate further study of VOCs from healthy individuals. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.

A comparative toxicity evaluation of Escherichia coli-targeted ssDNA and chlorine in HepG2 cells

In this study, a comparative assessment of the effectiveness of ssDNA and chlorine as disinfectants for treating water contaminated with Escherichia coli (E. coli) was investigated on the basis of cytotoxicity and genotoxicity. The gene targets addressed for the ssDNA based inhibition method were marA (multiple antibiotic resistance) and groL (essential gene Hsp60) in E. coli. Based on the maximum log reduction in E. coli cell numbers when compared to no ssDNA control, groL-1 was chosen as the optimized ssDNA for gene silencing-based inactivation. For toxicity assessment, HepG2 cells were exposed to extracts corresponding to concentrations of 0.2, 1, 5, 25 and 50 mL water/mL medium of chlorine doped water and 1, 10, 100, 300 nM of ssDNA. Compared with ssDNA, HepG2 cells exposed to extracts of chlorine doped water for 24 h showed higher cytotoxicity, caspase 3/7 levels, DNA damage, micronuclei frequency, and decreased cell viability. Water doped with chlorine was found to be more toxic than that by ssDNA when exposed to HepG2 cells. The results of this study provide a scientific basis for comparative evaluation of new and conventional disinfection methods by taking into consideration the outcome of cytotoxicity and genotoxicity assessments.

Biological Basis of Differential Susceptibility to Hepatocarcinogenesis among Mouse Strains

There is a vast amount of literature related to mouse liver tumorigenesis generated over the past 60 years, not all of which has been captured here. The studies reported in this literature have generally been state of the art at the time they were carried out. A PubMed search on the topic "mouse liver tumors" covering the past 10 years yields over 7000 scientific papers. This review address several important topics related to the unresolved controversy regarding the relevance of mouse liver tumor responses observed in cancer bioassays. The inherent mouse strain differential sensitivities to hepatocarcinogenesis largely parallel the strain susceptibility to chemically induced liver neoplasia. The effects of phenobarbital and halogenated hydrocarbons in mouse hepatocarcinogenesis have been summarized because of recurring interest and numerous publications on these topics. No single simple paradigm fully explains differential mouse strain responses, which can vary more than 50-fold among inbred strains. In addition to inherent genetics, modifying factors including cell cycle balance, enzyme induction, DNA methylation, oncogenes and suppressor genes, diet, and intercellular communication influence susceptibility to spontaneous and induced mouse hepatocarcinogenesis. Comments are offered on the evaluation, interpretation, and relevance of mouse liver tumor responses in the context of cancer bioassays.

In vitro toxicity of surface water disinfected by different sequential treatments

The in vitro toxicity of extracts of Hanjiang water disinfected by different sequential treatments was evaluated. Hanjiang water was disinfected using ozone, chloride dioxide or chlorine as the primary disinfectant followed by chlorine as the secondary disinfectant. HepG(2) cells were exposed to extracts corresponding to concentrations of 0.2, 1, 5, 25 and 125 mL water/mL medium. Compared with control, HepG(2) cells exposed to extracts of raw water and all disinfected water for 24h increased oxidative stress level, DNA damage and micronuclei frequency, and decreased cell viability. Water disinfected by Cl(2)+Cl(2) had the highest DNA double-strand breaks. All disinfected water and raw water increased micronuclei frequency via clastogenic and aneugenic effects. Oxidative stress induced DNA strand breaks and micronuclei frequency and therefore reduced cell viability either in disinfected water or raw water. Compared with raw water, water after disinfection increased DNA strand breaks, decreased cell viability and changed oxidative stress potential. Compared with chlorination, sequential treatment using O(3) or ClO(2) as primary disinfectant followed by chlorine disinfection reduced chlorinated by-products, DNA double-strand breaks and cell viability, but did not decrease micronuclei frequency and other DNA damage such as DNA single-strand break, alkali liable sites and incomplete excision sites. Sequential treatments did not significantly reduce in vivo toxicity of disinfected Hanjiang water.

Volatile organic compounds from feces and their potential for diagnosis of gastrointestinal disease

Little is known about the volatile organic compounds (VOCs) in feces and their potential health consequences. Patients and healthcare professionals have observed that feces often smell abnormal during gastrointestinal disease. The aim of this work was to define the volatiles emitted from the feces of healthy donors and patients with gastrointestinal disease. Our hypotheses were that i) VOCs would be shared in health; ii) VOCs would be constant in individuals; and iii) specific changes in VOCs would occur in disease. Volatile emissions in health were defined in a cohort and a longitudinal study. Subsequently, the pattern of volatiles found in the cohort study were compared to that found from patients with ulcerative colitis, Campylobacter jejuni, and Clostridium difficile. Volatiles from feces were collected by solid-phase microextraction and analyzed by gas chromatography/mass spectrometry. In the cohort study, 297 volatiles were identified. In all samples, ethanoic, butanoic, pentanoic acids, benzaldehyde, ethanal, carbon disulfide, dimethyldisulfide, acetone, 2-butanone, 2,3-butanedione, 6-methyl-5-hepten-2-one, indole, and 4-methylphenol were found. Forty-four compounds were shared by 80% of subjects. In the longitudinal study, 292 volatiles were identified, with some inter and intra subject variations in VOC concentrations with time. When compared to healthy donors, volatile patterns from feces of patients with ulcerative colitis, C. difficile, and C. jejuni were each significantly different. These findings could lead the way to the development of a rapid diagnostic device based on VOC detection.

Use of a medium-term liver focus bioassay to assess the hepatocarcinogenicity of 1,2,4,5-tetrachlorobenzene and 1,4-dichlorobenzene

1,2,4,5-Tetrachlorobenzene (TeCB) and 1,4-dichlorobenzene (DCB) are important environmental contaminants that have been used extensively for a variety of industrial applications. Limited data are available in the literature regarding the carcinogenicity of TeCB. DCB has been shown to cause renal adenocarcinomas in rats and hepatic adenomas and carcinomas in mice at high doses in a 2-year study. In the studies presented here, we report that TeCB can promote the formation of preneoplastic foci and DCB cannot in a medium-term initiation/promotion assay. These results suggest that TeCB is a liver tumor promoter and that DCB is not at fairly low doses (0.1 and 0.4 mmol/kg per day).

The effects of subacute and subchronic oral exposure to cis-1,2-dichloroethylene in Sprague-Dawley rats

Cis-1,2-dichloroethylene was administered daily by corn oil gavage to male and female Sprague-Dawley rats at the following dose levels: 1.0, 3.0, 10.0 and 22.0 mmol/kg/day for 14 days. Doses gavaged during the 90-day subchronic study were 0.33, 1.00, 3.00 and 9.00 mmol/kg/day. There were no compound-related deaths or histopathological changes demonstrated. Significant increases in relative liver weights were seen after 14- and 90-days of treatment in both sexes. This study demonstrates some indication of toxicity at subacute and subchronic exposure levels as low as 0.33 mmol/kg/day. Implications of liver abnormalities were demonstrated at an exposure level of 1 mmol/kg/day while kidney abnormalities (relative weights) were demonstrated at an exposure level of 0.33 mmol/kg/day.

Haloacetonitriles: metabolism, genotoxicity, and tumor-initiating activity

Haloacetonitriles (HAN) are drinking water contaminants produced during chlorine disinfection. This paper evaluates metabolism, genotoxicity, and tumor-initiating activity of these chemicals. The alkylating potential of the HAN to react with the electrophile-trapping agent, 4-(p-nitrobenzyl)pyridine, followed the order dibromoacetonitrile (DBAN) greater than bromochloroacetonitrile (BCAN) greater than chloroacetonitrile (CAN) greater than dichloroacetonitrile (DCAN) greater than trichloroacetonitrile (TCAN). When administered orally to rats, the HAN were metabolized to cyanide and excreted in the urine as thiocyanate. The extent of thiocyanate excretion was CAN greater than BCAN greater than DCAN greater than DBAN much greater than TCAN. Haloacetonitriles inhibited in vitro microsomal dimethylnitrosamine demethylase (DMN-DM) activity. The most potent inhibitors were DBAN and BCAN, with Ki = 3-4 X 10(-5) M; the next potent were DCAN and TCAN, with Ki = 2 X 10(-4) M; and the least potent inhibitor was CAN, with Ki = 9 X 10(-2) M. When administered orally, TCAN, but not DBAN, inhibited hepatic DMN-DM activity. The HAN produced DNA strand breaks in cultured human lymphoblastic (CCRF-CEM) cells. TCAN was the most potent DNA strand breaker, and BCAN greater than DBAN greater than DCAN greater than CAN, which was only marginally active. DCAN reacted with polyadenylic acid and DNA to form adducts in a cell-free system; however, the oral administration of DBAN or DCAN to rats did not result in detectable adduct formation in liver DNA. None of the HAN initiated gamma-glutamyltranspeptidase (GGT) foci when assayed for tumor-initiating activity in rat liver foci bioassay.(ABSTRACT TRUNCATED AT 250 WORDS)