Genetic toxicology of vinyl chloride--a review

Impacts of nano/micro-plastics on safety and quality of aquatic food products

The spread of nano/microplastics (N/MPs) pollution has gained importance due to the associated health concerns. Marine environment including fishes, mussels, seaweed and crustaceans are largely exposed to these potential threats. N/MPs are associated with plastic, additives, contaminants and microbial growth, which are transmitted to higher trophic levels. Foods from aquatic origin are known to promote health and have gained immense importance. Recently, aquatic foods are traced to transmit the nano/microplastic and the persistent organic pollutant poising hazard to humans. However, microplastic ingestion, translocation and bioaccumulation of the contaminant have impacts on animal health. The level of pollution depends upon the pollution in the zone of growth for aquatic organisms. Consumption of contaminated aquatic food affects the health by transferring the microplastic and chemicals. This chapter describes the sources and occurrence of N/MPs in marine environment, detailed classification of N/MPs based on the properties influencing associated hazard. Additionally, occurrence of N/MPs and their impact on quality and safety in aquatic food products are discussed. Lastly, existing regulations and requirements of a robust framework of N/MPs are reviewed.

A comprehensive review on assessment of plastic debris in aquatic environment and its prevalence in fishes and other aquatic animals in India

The presence of meso, macro, and microplastics (MPs) in aquatic environments has raised concerns due to their potential risks to aquatic as well as human life. Though plastics are considered to be inert in nature, MPs with toxic additives and accumulated contaminants have harmful ecological effects. Reports of absorption of MPs by internal tissues and toxicity in vital organs such as lung cells, liver, and brain cells have proved its serious health hazards. The study of plastic debris in the aquatic environment deserves special attention due to its ecotoxicological impact. This review presents a detailed account of the assessment of plastic debris in marine as well as freshwater environments. The formation of MPs and their sources, sampling, isolation, identification and characterization methods adopted, and the prevalence of MPs in aquatic life are discussed. To the best of our knowledge, the present article is a first-ever comprehensive review covering the entire of India. Our review finds that, so far, very few studies have been carried out, and there is a paucity of information, especially on the prevalence of plastic debris in the freshwater environment, fish, and other aquatic animals in India. While major studies have been done at various coastal locations in the southern part of India and a few studies in the rest of India, south-eastern states remain neglected. Toxicological studies on various life forms, including humans, are lacking. The present review also fills the gap in our knowledge of the various locations studied across India and can guide future research.

Dynamics of chlorinated aliphatic hydrocarbons in the Chalk aquifer of northern France

The Chalk aquifer used for drinking-water production in the southwest of the Lille European Metropolis is threatened by the presence of chlorinated aliphatic hydrocarbons (CHCs), their concentrations in groundwater regularly exceeding the regulatory limits for drinking water in France. This hinders its use for drinking-water production. Understanding the dynamics and spatial distribution of CHC in the aquifer is a key factor for resource sustainability. For that purpose, an intensive monitoring was undertaken in several well fields and at different depths over eight years. To assess a possible migration and/or degradation of the compounds, the water column in several wells was sampled at various depths with passive samplers. Furthermore, CHC degradation mechanisms were investigated with compound-specific carbon-isotope analysis. The CHC concentrations and their distributions in the area depend on past and current industrial activity, causing plumes emphasized by pumping in the wells, such plumes being multi-source with no identified origin in most wells. In the south area of Les Ansereuilles, reductive dechlorination of tetrachloroethylene from a former industrial laundry highly impacted the surrounding area with its main degradation product cis-1,2-dichloroethylene. The same area is also affected by tetrachlroroethylene from several industrial laundries, textile factories and dyeing industries with also an anaerobic degradation. In the northern part of Les Ansereuilles, tetrachloroethylene, trichloroethane, trichloroethylene and 1,1-dichloroethylene were found as primary products, whereas cis-1,2-dichloroethylene appears to be an anaerobic degradation product of TCE. The other well fields (Houplin-Ancoisne, Seclin and Emmerin) are less impacted by CHC pollution, and it was shown that no CHC degradation occurred in the wells. However, the stratification of CHCs in the well-water columns, their constant concentration values over time caused by the large amount of available CHCs, and the minor degradation occurring in wells are of concern for water operators in the future.

Addition of Shewanella oneidensis MR-1 to the Dehalococcoides-containing culture enhances the trichloroethene dechlorination

Dehalococcoides is able to completely dehalogenate tetrachloroethene (PCE) and trichloroethene (TCE) to ethene (ETH). However, the dechlorination efficiency of Dehalococcoides is low and result in the accumulation of toxic intermediates. In this study, Shewanella oneidensis MR-1 (S. oneidensis MR-1) was added to the Dehalococcoides-containing culture and the complete TCE to ETH dechlorination was shortened from 24 days to 16 days. Dehalococcoides-targeted 16S rRNA gene and two model reductive dehalogenase (RDase) genes (tceA and vcrA), responsible for dechlorinating TCE to vinyl chloride (VC) and VC to ETH respectively, were characterized. Results showed that S. oneidensis MR-1 has no effect on the cell growth while the RDase genes expression was up-regulated and the RDase activity of Dehalococcoides was elevated. The mRNA abundance of vcrA increased approximately tenfold along with the increased concentration of vitamin B₁₂ (cyanocobalamin). Interestingly, the addition of S. oneidensis MR-1 increased the concentration of vitamin B₁₂ by affecting the microbial community structure. Therefore, the addition of S. oneidensis MR-1 might have a positive effect on regulating the activity of RDase of functional microorganisms and uptake of vitamin B₁₂, and further provided a practical vision of chloroethene dechlorination by the Dehalococcoides-containing culture.

Immunotoxic effects of an industrial waste incineration site on groundwater in rainbow trout (Oncorhynchus mykiss)

The discharge of organic waste from the petrochemical industry into the Mercier lagoons caused major groundwater contamination. The objective of this study was to determine the immunotoxic potential of three groundwater wells at increasing distance from the incinerator dumping site (1.17, 2.74 and 5.40 km). Rainbow Trout were exposed to increasing concentrations of water from three groundwater wells for 14 days. Immunocompetence was characterized by phagocytosis, mitogen-stimulated proliferation of lymphocytes, cell cycle analysis and apoptosis. A significant increase in innate (phagocytosis) and specific immune response (B lymphocyte proliferation) was observed in trout exposed to water collected from the well at 2.74 km. However, phagocytosis activity was suppressed in groups at 1.17 and 5.40 km. The proportion of lymphocytes in S phase was significantly increased in groups at 2.74 and 5.40 km, while lymphocytes in G0/G1 phase were decreased in all three exposure groups. Additionally, dexamethasone (DEX)-induced apoptosis of lymphocytes was significantly reduced in the group at 2.74 km, which suggests decreased lymphocyte turnover. Furthermore, the ratio of DEX-induced apoptosis/apoptosis was lower in the groups at 2.74 and 5.40 km. In summary, our experiments have shown that exposure to the mixture of organic compounds present in Mercier groundwater modulates phagocytosis and cell proliferation, disrupts the cell cycle and reduces the ratio of DEX-induced apoptosis/apoptosis. It is concluded that groundwater collected in the vicinity of an incinerator containment field could impact immunocompetence in fish.

Predicting carcinogenicity of diverse chemicals using probabilistic neural network modeling approaches

Robust global models capable of discriminating positive and non-positive carcinogens; and predicting carcinogenic potency of chemicals in rodents were developed. The dataset of 834 structurally diverse chemicals extracted from Carcinogenic Potency Database (CPDB) was used which contained 466 positive and 368 non-positive carcinogens. Twelve non-quantum mechanical molecular descriptors were derived. Structural diversity of the chemicals and nonlinearity in the data were evaluated using Tanimoto similarity index and Brock-Dechert-Scheinkman statistics. Probabilistic neural network (PNN) and generalized regression neural network (GRNN) models were constructed for classification and function optimization problems using the carcinogenicity end point in rat. Validation of the models was performed using the internal and external procedures employing a wide series of statistical checks. PNN constructed using five descriptors rendered classification accuracy of 92.09% in complete rat data. The PNN model rendered classification accuracies of 91.77%, 80.70% and 92.08% in mouse, hamster and pesticide data, respectively. The GRNN constructed with nine descriptors yielded correlation coefficient of 0.896 between the measured and predicted carcinogenic potency with mean squared error (MSE) of 0.44 in complete rat data. The rat carcinogenicity model (GRNN) applied to the mouse and hamster data yielded correlation coefficient and MSE of 0.758, 0.71 and 0.760, 0.46, respectively. The results suggest for wide applicability of the inter-species models in predicting carcinogenic potency of chemicals. Both the PNN and GRNN (inter-species) models constructed here can be useful tools in predicting the carcinogenicity of new chemicals for regulatory purposes.

Estimation of a safe level for occupational exposure to vinyl chloride using a benchmark dose method in central China

OBJECTIVES

The aim of this study was to estimate a benchmark dose (BMD) for chromosome damage induced by vinyl chloride monomer (VCM) in VCM-exposed workers in central China and validate the published results in Shanghai.

METHODS

VCM-exposed workers who had been exposed to VCM for at least one year (n=463) and matched subjects not exposed to VCM or other toxins (n=273) were asked to participate in this study. Micronucleus (MN) frequency based on the cytokinesis-block micronucleus assay (CBMN) was used as a biomarker for chromosome damage induced by VCM exposure.

RESULTS

The MN frequency in the VCM-exposed workers was significantly higher than that in the control group, and multivariate Poisson regression suggested that gender, smoking status and VCM exposure were the significant factors influencing the risk of increased MN frequency. When subjects were further stratified according to gender and smoking status, the results showed that female VCM-exposed workers were more susceptible than the males to the risk of increased MN frequency. The MN frequency of smokers was significantly higher than that of nonsmokers in the control group. Our study also suggested that there was a strong dose-response relationship between VCM CED and the increased risk of MN frequency in the total group, males and females. The BMDL(10) was found to be 630.6, 670.2 and 273.7 mg-year for all VCM-exposed workers, males and females, respectively.

CONCLUSIONS

These results invite further scrutiny of the current VCM occupational exposure limits and warrant further study of the risk of VCM genotoxicity and carcinogenicity.

Evaluation of cell types for assessment of cytogenetic damage in arsenic exposed population

BACKGROUND

Cytogenetic biomarkers are essential for assessing environmental exposure, and reflect adverse human health effects such as cellular damage. Arsenic is a potential clastogen and aneugen. In general, the majority of the studies on clastogenic effects of arsenic are based on frequency of micronuclei (MN) study in peripheral lymphocytes, urothelial and oral epithelial cells. To find out the most suitable cell type, here, we compared cytogenetic damage through MN assay in (a) various populations exposed to arsenic through drinking water retrieved from literature review, as also (b) arsenic-induced Bowen's patients from our own survey.

RESULTS

For literature review, we have searched the Pubmed database for English language journal articles using the following keywords: "arsenic", "micronuclei", "drinking water", and "human" in various combinations. We have selected 13 studies consistent with our inclusion criteria that measured micronuclei in either one or more of the above-mentioned three cell types, in human samples. Compared to urothelial and buccal mucosa cells, the median effect sizes measured by the difference between people with exposed and unexposed, lymphocyte based MN counts were found to be stronger. This general pattern pooled from 10 studies was consistent with our own set of three earlier studies. MN counts were also found to be stronger for lymphocytes even in arsenic-induced Bowen's patients (cases) compared to control individuals having arsenic-induced non-cancerous skin lesions.

CONCLUSION

Overall, it can be concluded that MN in lymphocytes may be superior to other epithelial cells for studying arsenic-induced cytogenetic damage.

Solution structure of duplex DNA containing the mutagenic lesion 1,N(2)-etheno-2'-deoxyguanine

We have used high-resolution NMR spectroscopy and molecular dynamics simulations to determine the solution structure of DNA containing the genotoxic lesion 1, N (2)-etheno-2'-deoxyguanosine (epsilonG), paired to dC. The NMR data suggest the presence of a major, minimally perturbed structure at neutral pH. NOESY spectra indicate the presence of a right-handed helix with all nucleotides in anti, 2'-deoxyribose conformations within the C2'-endo/C1'-exo range and proper Watson-Crick base pair alignments outside the lesion site. The epsilonG residue remains deeply embedded inside the helix and stacks between the flanking base pairs. The lesion partner dC is extrahelical and is located in the minor groove of the duplex, where it is highly exposed to solvent. Upon acidification of the sample, a second conformation at the lesion site of the duplex emerges, with protonation of the lesion partner dC and possible formation of a Hoogsteen base pair. Restrained molecular dynamics simulations of the neutral-pH structure generated a set of three-dimensional models that show epsilonG inside the helix, where the lesion is stabilized by stacking interactions with flanking bases but without participating in hydrogen bonding. The lesion counterbase dC is displaced in the minor groove of the duplex where it can form a hydrogen bond with the sugar O4' atom of a residue 2 bp away.

Effect of different Thai traditional processing of various hot chili peppers on urethane-induced somatic mutation and recombination in Drosophila melanogaster: Assessment of the role of glutathione transferase activity

Four different Thai traditional chili peppers, namely bird pepper (Capsicum frutescens), red chili spur peppers (Capsicum annuum), green bell peppers and sweet pepper (C. annuum) were investigated for their antimutagenic properties. Each chili was prepared in three formulations commonly used for chili food processing; raw paste (chili ground in water), pickled in vinegar or stir-fried in palm oil. Each sample was tested for its antimutagenic effect against urethane by using the somatic mutation and recombination of wing hair of Drosophila melanogaster as an indicator. Three-day-old larvae, trans-heterozygous for two genetic markers, multiple wing hairs mwh and orrigon (ORR;flr3), were exposed to urethane alone or in combination with each chili formulation. The various processing methods for chilies differentially extracted the antimutagenic chili components. The specific chili as well as the method of processing influenced the observed antimutagenic properties against urethane. This suggested each chili contains a unique complex mixture of many antimutagens. Co-treatment and pre-treatment experiments showed that both direct and indirect protective mechanisms are involved in an 'activation' process to give antimutagenesis effects. An association between antigenotoxicity and glutathione transferase activity could not be established.

DNA single strand breaks in peripheral lymphocytes associated with urinary thiodiglycolic acid levels in polyvinyl chloride workers

The association between vinyl chloride monomer (VCM) exposure and DNA damage has been established. However, the relationship between individual exposure and DNA single strand breaks was limited. Since environmental monitoring may not reflect the actual exposure, a useful marker of exposure is needed to assess the individual exposure. In our previous study, we have found a high correlation between air VCM level and urinary thiodiglycolic acid (TdGA) at the commencement of the next shift. Here, we further used comet assay to evaluate the relationship between urinary TdGA levels and DNA single strand breaks in polyvinyl chloride monomer (PVC) workers. Urinary TdGA levels (n=26) at the commencement of the following shift were analyzed. Ten of the 26 workers also had personal air sampling for air VCM exposure. Questionnaires were administered to obtain epidemiological information including detailed history of occupation and lifestyles. Workers experiencing air VCM level greater than 5 ppm had higher tail moment and tail intensity (%) than those experiencing VCM exposure between 1 and 5, or <1 ppm, respectively (P < 0.05). The results also revealed that level of DNA single strand breaks, including tail moment and tail intensity, were increased with urinary TdGA level. The dose-response relationship of urinary TdGA level and DNA single strand breaks was particularly significant among the workers with 4 mg/g Cr of urinary TdGA level, which is equivalent to 5 ppm air VCM level. We concluded that air VCM exposure greater than 5 ppm could induce DNA damage. Further sensitive assay should be developed for the diction of DNA damage when air VCM exposure below 5 ppm.

Association of hepatitis virus infection, alcohol consumption and plasma vitamin A levels with urinary 8-hydroxydeoxyguanosine in chemical workers

Urinary 8-hydroxydeoxyguanosine (8-OHdG) DNA adduct has been used as a biomarker in epidemiological studies. However, the determinants for urinary 8-OHdG have not been clearly identified. We tested urinary 8-OHdG levels in 205 male workers who had been exposed to vinyl chloride monomer (VCM). Epidemiological information was obtained by an interviewer-administered questionnaire. Hepatitis B surface antigen (HBsAg) and anti-hepatitis C antibody (anti-HCV) were also determined by immunoassay. Plasma antioxidants including Vitamins A and E, alpha- and beta-carotenes were assayed by high performance liquid chromatography. Median of urinary 8-OHdG level was 9.8 ng/mg creatinine (range, 1.4-60.1). Multiple linear regression analysis showed that alcohol drinkers had higher urinary 8-OHdG than those who did not, but there was no dose-response between the amount of alcohol consumption and urinary 8-OHdG. Workers with positive HBsAg, anti-HCV and elevated plasma Vitamin A level were independently associated with higher levels of urinary 8-OHdG, whereas age, smoking, body mass index, plasma alpha- and beta-carotenes, Vitamin E levels, or VCM exposure did not show such an association. The results suggest that active inflammation of hepatitis B and C, alcohol consumption and higher Vitamin A level can induce oxidative stress. Thus, we conclude that potential determinants need to be considered in epidemiological studies when urinary 8-OHdG is used as a biomarker.

Antimutagenic properties of bell and black peppers

The wing Somatic Mutation And Recombination Test (SMART) in Drosophila melanogaster was used to study the modulating action of bell pepper (Capsicum annuum) and black pepper (Piper nigrum) in combination with the alkylating agent methyl methanesulfonate (MMS) and the promutagen agent ethyl carbamate (EC). Larvae trans-heterozygous for the third chromosome recessive markers multiple wing hairs (mwh) and flare-3 [flr(3)] were fed genotoxins alone or in combination with each of the two spices. Genetic changes induced in somatic cells of the wing's imaginal discs lead to the formation of mutant clones on the wing blade. Our results showed that bell pepper was effective in reducing the mutational events induced by EC and MMS and black pepper was only effective against EC. Pretreatment of 2-day-old larvae with the spices for 24 h followed by a treatment with EC and MMS was only effective in reducing mutations induced by EC. Suppression of metabolic activation or interaction with the active groups of mutagens could be mechanisms by which the spices exert their antimutagenic action.

Genetic toxicology of a paradoxical human carcinogen, arsenic: a review

Arsenic is widely distributed in nature in air, water and soil in the form of either metalloids or chemical compounds. It is used commercially, as pesticide, wood preservative, in the manufacture of glass, paper and semiconductors. Epidemiological and clinical studies indicate that arsenic is a paradoxical human carcinogen that does not easily induce cancer in animal models. It is one of the toxic compounds known in the environment. Intermittent incidents of arsenic contamination in ground water have been reported from several parts of the world. Arsenic containing drinking water has been associated with a variety of skin and internal organ cancers. The wide human exposure to this compound through drinking water throughout the world causes great concern for human health. In the present review, we have attempted to evaluate and update the mutagenic and genotoxic effects of arsenic and its compounds based on available literature.

Formation and detoxification of reactive intermediates in the metabolism of chlorinated ethenes

Short-chain halogenated aliphatics, such as chlorinated ethenes, constitute a large group of priority pollutants. This paper gives an overview on the chemical and physical properties of chlorinated aliphatics that are critical in determining their toxicological characteristics and recalcitrance to biodegradation. The toxic effects and principle metabolic pathways of halogenated ethenes in mammals are briefly discussed. Furthermore, the bacterial degradation of halogenated compounds is reviewed and it is described how product toxicity may explain why most chlorinated ethenes are only degraded cometabolically under aerobic conditions. The cometabolic degradation of chlorinated ethenes by oxygenase-producing microorganisms has been extensively studied. The physiology and bioremediation potential of methanotrophs has been well characterized and an overview of the available data on these organisms is presented. The sensitivity of methanotrophs to product toxicity is a major limitation for the transformation of chlorinated ethenes by these organisms. Most toxic effects arise from the inability to detoxify the reactive chlorinated epoxyethanes occurring as primary metabolites. Therefore, the last part of this review focuses on the metabolic reactions and enzymes that are involved in the detoxification of epoxides in mammals. A key role is played by glutathione S-transferases. Furthermore, an overview is presented on the current knowledge about bacterial enzymes involved in the metabolism of epoxides. Such enzymes might be useful for detoxifying chlorinated ethene epoxides and an example of a glutathione S-transferase with activity for dichloroepoxyethane is highlighted.

Increased lymphocyte sister chromatid exchange frequency in workers with exposure to low level of ethylene dichloride

The genotoxicity of low-level exposure to ethylene dichloride (EDC) and vinyl chloride monomer (VCM) in humans is not clear. We used lymphocyte sister chromatid exchange (SCE) frequency as a parameter to investigate the genotoxicity of low level EDC and VCM in VCM-manufacturing workers. The SCE frequency was determined for 51 male workers with exposure to VCM and/or EDC and for 20 male workers devoid of such exposure. Epidemiological data were obtained by questionnaire, and included history of smoking, drinking, and any medication taken, as well as a detailed occupational history. Personal- and area-sampling and analysis were conducted in order to calculate the time-weighted average (TWA) contaminant-exposure level corresponding to different job categories. Moderate EDC exposure around 1 ppm corresponded to a significantly greater SCE frequency than was the case for the low EDC exposure group (p<0.01). However, VCM exposure of similar level was not associated with increased SCE. We conclude that EDC may cause genotoxicity at a relatively low level of exposure.

Etheno-adduct-forming chemicals: from mutagenicity testing to tumor mutation spectra

During the past 25 years, ethenobases have emerged as a new class of DNA lesions with promutagenic potential. Ethenobases were first investigated as DNA reaction products of vinyl chloride, an occupational carcinogen causing angiosarcoma of the liver (ASL). They were subsequently shown to be formed by several carcinogenic agents, including urethane (ethyl carbamate), and more recently, to occur in various tissues of unexposed humans and rodents. The endogenous source of ethenobases in DNA is thought to be a lipid peroxidation (LPO) product. Initial studies on metabolic activation, mutagenicity and carcinogenicity moved to the analyses of the formation of ethenobases in vivo and to the determination of their promutagenic properties. Quantification of etheno adducts in vivo became possible with the development of ultrasensitive techniques of analysis. To study the miscoding properties of ethenobases, the initial assays on the fidelity of replication or of transcription were replaced by site-directed mutagenesis assays in vivo. Ethenobases generate mainly base pair substitution mutations. With the advent of new techniques of molecular biology, mutations were investigated in the ras and p53 genes of tumors induced by vinyl chloride and urethane. In liver tumors induced by vinyl chloride, specific mutational patterns were found in the Ki-ras gene in human ASL, in the Ha-ras gene in hepatocellular carcinoma (HCC) in rats, and in the p53 gene in human and rat ASL. In tumors induced by urethane in mice, codon 61 of the Ha-ras gene (liver, skin) and of the Ki-ras gene (lung) seems to be a characteristic target. These tumor mutation spectra are compatible with the promutagenic properties of etheno adducts and with their formation in target tissues, suggesting that ethenobases can be initiating lesions in carcinogenesis. Another recent focus has been given to the repair of etheno adducts, and DNA glycosylases able to excise these adducts in vitro have been identified. The last two decades have brought ethenobases to light as potentially important DNA lesions in carcinogenesis. More research is needed to better understand the environmental and genetic factors that affect the formation and persistence of ethenobases in vivo.

Mutagenicity assay in Salmonella and in vivo sister chromatid exchange in bone marrow cells of mice for four pyrazolone derivatives

Phenylbutazone (PB), oxyphenbutazone (OPB), antipyrine (AP) and dipyrone (DP) are four important pyrazolone derivatives mainly used as anti-inflammatory, antipyretic and analgesic drugs. At present these are the most widely used pyrazolone derivatives throughout the world. The widespread use of these drugs are of great concern for human health problems. In the present study these four drugs were tested in mutagenicity assays in Salmonella strains TA97a, TA98, TA100 and TA102 using a plate incorporation assay both with and without S-9 mix and for in vivo sister chromatid exchanges (SCE) in bone marrow cells of mice. The first three drugs were negative in all the tester strains but dipyrone showed a weak mutagenic activity at higher concentrations in all four strains both with and without metabolic activation. In the in vivo SCE assay in male mice, all four drugs showed a statistically significant increase in SCE in bone marrow cells when compared with control.

Assessment of vinyl chloride-induced DNA damage in lymphocytes of plastic industry workers using a single-cell gel electrophoresis technique

DNA damage and the formation of stable carcinogen-DNA adducts are considered critical events in the initiation of the carcinogenic process. This study was carried out to assess whether exposure of plastics industry workers to the vinyl chloride monomer (VCM) for different periods of time would cause DNA damage, using the single-cell gel electrophoresis (SCGE) technique. Levels of DNA damage was assessed by both extent of DNA migration and numbers of DNA damaged spots in the peripheral blood lymphocytes from 32 plastics workers with different periods of exposure to VCM; they were evaluated by comparison with a group of non-exposed individuals. It was found that plastics workers who were exposed to VCM for different periods of time showed significantly increased levels of DNA damage compared with the non-exposed subjects. There was a significant correlation between the severity of DNA damage and duration of exposure. However, no significant correlation was found between the age of all subjects and DNA damage. Concentrations of VCM in the air inside the factory were found to be significantly higher than values in non-exposed areas, despite being lower than the threshold limit value (TLV). Our results encourage the application of SCGE as a sensitive, simple, fast and useful technique in the regular health screening of workers occupationally exposed to VCM (even at concentrations below the TLV) to assess the possibility of any DNA damage.

Metabolic activation of vinyl chloride by rat liver microsomes: low-dose kinetics and involvement of cytochrome P450 2E1

The metabolism and pharmacokinetics of vinyl chloride (VC) have been extensively studied in rodents and humans, but the maximum velocity (Vmax) and Michaelis constant (K(m)) for the activation of VC by microsomal monooxygenases in vitro have not yet been determined. Using a new sensitive assay, the epoxidation of VC by rat liver microsomes (adult Sprague-Dawley) at concentrations from 1 ppm to 10(6) ppm in the gas phase was measured. In the assay, the reactive VC metabolites chloroethylene oxide and 2-chloroacetaldehyde were trapped with excess cAMP, yielding, 1,N6-etheno-cAMP (epsilon cAMP) which was quantitated by HPLC fluorimetry. The trapping efficiency of electrophilic VC metabolites by cAMP was close to 10%. The specificity of the method was confirmed by purification of epsilon cAMP on an immunogel. The VC concentration in the gas phase was measured by GC/flame ionization detection, while in the aqueous phase it was calculated from the partition coefficient between air and the microsomal suspension. Activation of VC by rat liver microsomes followed Michaelis-Menten kinetics with K(m) = 7.42 +/- 0.37 (+/- SD) microM and Vmax = 4674 +/- 46 pmol.mg protein-1.min-1. Inhibitor studies and immunoinhibition assays showed that VC was activated by cytochrome P450 (CYP) 2E1 down to 1 ppm in the air phase. Based on the metabolic parameters determined, the uptake of VC by rats in vivo can be accurately predicted.

Comparative mutagenic and genotoxic effects of three propionic acid derivatives ibuprofen, ketoprofen and naproxen

The mutagenicity of three propionic acid derivatives, namely ibuprofen, ketoprofen and naproxen, was tested in the Ames mutagenicity assay (in strains TA97a, TA100 and TA102) and in vivo genotoxicity was tested by sister chromatid exchange (SCE) in bone marrow cells of mice. These are the anti-inflammatory drugs frequently used in different parts of the world. Mutagenicity results showed no mutagenic effects in strains TA97a, TA100 and TA102 for all three drugs. Results of in vivo SCE assays indicate that these three drugs are weakly genoxic in bone marrow cells of mice. This is the first report of the Ames mutagenicity assay for ketoprofen and in vivo SCE assay for three drugs.

Primary hepatocellular carcinoma in workers exposed to vinyl chloride: a report of two cases

BACKGROUND

Vinyl chloride (VC), an industrial toxic gas, has a dose-dependent carcinogenicity in rodents and has been responsible for multiple cases of liver angiosarcoma in humans. The aim of this study was to describe histopathologic liver alterations and to evaluate risk factors for hepatocellular carcinoma in two workers from the same plant, both of whom had primary nonangiosarcoma liver tumors and were exposed to VC.

METHODS

Clinical, biochemical, serologic, and pathologic data were reviewed at the time of hepatic resection. Clinical and biologic follow-up were available for several years before the diagnosis of hepatocellular carcinoma.

RESULTS

Liver alterations distant from the tumor site were compatible with ongoing exposure to VC in both cases. Several areas containing dysplastic hepatocytes were present in nontumoral liver in one patient. Both patients are alive after partial liver resection, and 1 has had 5 years of follow-up without recurrence.

CONCLUSIONS

Exclusion of classic risk factors for noncirrhotic hepatocellular carcinoma of the liver in both patients suggests a relationship between VC exposure and observed tumors. Systematic long term follow-up with biology and ultrasonography for workers exposed to VC may result in relatively early diagnoses of liver tumors and long term survival in some cases.

Genetic toxicology of epichlorohydrin: a review

Epichlorohydrin (ECH) is one of the more commercially important aliphatic epoxides used extensively as an industrial intermediate, a laboratory reagent, and as an insecticide. It is a volatile, colourless liquid with an ethereal odour. It behaves as an alkylating agent. Reports have shown it to cause the respiratory and dermal toxicity in animals and humans. It has also been reported to be carcinogenic in experimental models. Thus, the wide-spread use of this aliphatic epoxide is of great concern in human health problem. The purpose of this paper is to critically review and update the mutagenic and clastogenic effects of ECH based on available literature.

Comparative genotoxicity of six salicylic acid derivatives in bone marrow cells of mice

In vivo sister chromatid exchange (SCE) and chromosome aberrations (CA) were carried out for six salicylic acid derivatives in bone marrow cells of mice. Six salicylic acid derivatives, namely acetyl salicylic acid (aspirin), salicylic acid, salicylamide, sodium salicylate, diflunisal and niclosamide, were used for these experiments. Drugs were administered both intraperitoneally (i.p.) and orally by gavage. Out of these six salicylic acid derivatives tested, only diflunisal and niclosamide showed genotoxicity as measured by both SCE and CA assays. Acetyl salicylic acid and sodium salicylate showed weak genotoxicity as measured by SCE and CA, respectively, only at the highest dose tested.

Genetic toxicology of four commonly used benzodiazepines: a review

Benzodiazepines are a group of drugs which have been extensively used for their activities as an anti-anxiety, sedative, muscle relaxant and anti-convulsant. Benzodiazepines at present are the most commonly prescribed drugs. Some of these drugs are teratogenic and also carcinogenic in experimental animals. The wide human exposure to this group of drugs throughout the world is of great concern for human health. In the present review, we have attempted to evaluate and update the mutagenic and genotoxic effects of four of the most commonly used benzodiazepines, i.e., chlordiazepoxide (CDZ), diazepam (DZ), nitrazepam (NZ) and oxazepam (OZ) based on available literature.