Enhanced excretion of thioethers in urine of operators of chemical waste incinerators

In vivo studies on genotoxicity of pure and commercial linuron

The ureic herbicide linuron [3-(3, 4-dichlorophenyl)-1-methoxy-1-methylurea] (CAS 330-55-2) was investigated for genotoxicity in a series of in vivo experiments. Since human exposure to herbicides is not only to the active principles, but also to all the chemicals present in the commercial formulation, we tested both pure and commercial linuron. Groups of rats were treated with gavage containing different doses of the herbicide (pure compound or commercial formulation) for 14 days. The doses were 150, 300 and 450 mg/kg b.wt. for the pure compound and 315.8, 631.6 and 947.4 mg/kg b.wt. for the commercial formulation (47.5% of linuron). Faeces and urine were collected at regular intervals. Urine specimens were analysed for their mutagenic metabolites, thioethers and D-glucaric acid content. Faeces extracts were tested for mutagenicity. Linuron's ability to cause DNA damage and cytogenetic effects was also investigated after treating groups of rats once with different doses of pure or commercial linuron. DNA single-strand breaks were assessed in rat liver using the alkaline elution technique and the single-cell microgel electrophoresis assay (SCGE: 'comet' assay), and in rat testes cells with the SCGE assay. Micronuclei induction was analysed in rat bone marrow erythrocytes. Results obtained were mainly negative when the excretion of mutagenic metabolites in urine and faeces of animals treated with the pure compound or with the linuron-based commercial formulation were monitored, whereas an increase in the urinary excretion of thioethers and D-glucaric acid was observed in rats treated with the commercial formulation. No increase in the frequency of micronucleated polychromatic erythrocytes was observed in the treated animals. However, linuron affected the viability of hepatocytes isolated from animals treated with higher doses. This cytotoxicity was accompanied by the induction of DNA single-strand breaks in the liver, as seen by the alkaline elution assay. The potential of pure linuron to induce in vivo DNA damage was confirmed with the microgel-electrophoresis technique ('comet' assay). Cytotoxicity was also seen in rat testes cells. However, no indication of DNA damage was visible.

Biological monitoring of genotoxic hazard in workers of the rubber industry

Biological monitoring of genotoxic hazard in the rubber industry was performed in 19 male workers and 20 age-matched controls in a local health unit in northern Italy. Peripheral blood lymphocytes were analyzed for the presence of DNA damage (single-cell microgel-electrophoresis, or comet assay) and for cytogenetic parameters (sister chromatid exchanges and micronuclei frequency, and proliferative rate index). The following bioassays were performed in urine samples: a) mutagenicity test and concentration of thioethers as markers of exposure, and b) excretion of D-glucaric acid and 6-beta-hydroxycortisol (related to 17-hydroxycorticosteroid excretion) as indicators of the inductive status of the microsomal enzyme system (phase-I). The exposed subjects showed statistically higher mean values of 17-hydroxycorticosteroids and micronuclei and lower values of 6-beta-hydroxycortisol than controls, when taking cigarette smoking into account. The comet assay showed higher values for migration distance in exposed subjects than controls, although the differences were not significant at a p-value of 0.05. These findings suggest that industrial exposure in the rubber processing industry may cause genetic damage and may modify the activity level of some enzymes; these results should be considered with caution due to the small number of subjects enrolled.

The potential of exposure biomarkers in epidemiologic studies of reproductive health

To further the development and application of exposure markers in field investigations in reproductive epidemiology, we have synthesized recent examinations of the issues surrounding exposure measurements in reproductive epidemiology. The specific goals of this paper are to define exposure biomarkers and explore their potential uses, particularly as screening tools. The tests for glucaric acid, thioethers, mutagenicity, and porphyrin patterns meet the general criteria for useful exposure screens. For certain xenobiotic agents, these tests accurately differentiate exposure levels, as demonstrated in occupational and environmental epidemiologic studies. As urinary screens, they are noninvasive and applicable on a large scale with current laboratory techniques. For short-term exposure, glucaric acid, thioethers, and mutagenicity tests are useful. Porphyrin patterns may measure cumulative effects as well as current exposure levels. The usefulness of these tests in epidemiologic studies of environmental effects on reproductive health has yet to be studied. To do so, the battery must be standardized for pregnant women, and test results must be correlated with measured adverse reproductive outcomes, such as gestational length and birthweight. This correlation is particularly important because maternal exposure rather than fetal exposure is being measured. The extent to which xenobiotic chemicals cross the placental barrier may vary greatly depending on the type of exposures, timing in pregnancy, and maternal detoxification capability. Without better exposure measures, epidemiologic studies of reproductive health probably will not successfully identify xenobiotic fetotoxic agents in the environment. However, with an adequate battery of nonspecific exposure biomarkers, prospective studies of environmental effects on pregnancy outcomes might be possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary screening for potentially genotoxic exposures in a chemical industry

Mutagenic activity, measured by the bacterial fluctuation assay and thioether concentration in urine from workers at a chemical plant producing pharmaceuticals and explosives, was determined before and after exposure. Of 12 groups only those exposed to trinitrotoluene (n = 14) showed a significant increase in mutagenic activity using Salmonella typhimurium TA 98 without any exogenous metabolic system. The same strain responded only weakly when the S-9 mix was used; with Escherichia coli WP2 uvrA no effect of exposure was observed. Urinary thioether concentration was higher among smokers than among non-smokers, but occupational exposure had no effect. Urinary mutagenicity testing may be a useful tool for screening potentially genotoxic exposures in complex chemical environments.

Effects of methyl methacrylate on non-protein thiols and drug metabolizing enzymes in rat liver and kidneys

Male Wistar rats received methyl methacrylate monomer (MMA) i.p. in olive oil 1.0 g/kg body weight on 3 successive days. The weight of the livers and kidneys, and the body weights did not differ from their controls. On the fifth day after treatment, hepatic NADPH-cytochrome c reductase, 7-ethoxycoumarin 0-deethylase and the 2,5-diphenyloxazole hydroxylase exhibited maximal decreases in activity (25%, 58%, 36%, respectively) without any coincident effect on the total amount of cytochrome P-450 hemoprotein itself. One week later these activities had returned to control levels. The enzymatic changes in the kidneys were smaller in magnitude, and they were also reversed sooner. A single i.p. dose of MMA (2 g/kg body weight) caused elevation of serum alanine aminotransferase activity. A tenfold increase of the excretion rate of urinary thioethers was also discovered. The hepatic reduced glutathione (GSH) was depleted in 3 h to 20% and the GSSG to half of the value in controls. In kidneys, the GSH was decreased to 48% in 3 h before an apparent phase of overrecovery. At the end of the 24 h observation period, cytochrome P-450 concentrations were somewhat decreased in the liver. The GSH contents showed dose and time-dependent reversible decreases in isolated hepatocytes when incubated for 2 h in a medium containing MMA at the nominal concentrations of 0, 2, 5, or 10 mM. None of the treatments affected either the content of cytochrome P-450 or the viability of the liver cells.

Urinary excretion of thioethers among low-tar and medium-tar cigarette smokers

The urinary excretion of thioethers was studied among smokers of medium-tar cigarettes (16.3 mg/cig.) and low-tar cigarettes (5.4 mg/cig.). The test persons (26 smokers and 11 nonsmokers) were healthy young men in the military service. The smokers had an increased excretion of thioethers into the urine (P = 0.002 with Mann-Whitney U-test) when compared with the nonsmokers. No differences in the amount of urinary thioethers were detected between the low-tar and medium-tar cigarette smokers. The smokers (varying from 2.0 to 8.5 mmol/mol creatinine) had more individual variation than the nonsmokers (varying from 1.5 to 4.5 mmol/mol creatinine). Furthermore, the individual variation in the group of low-tar cigarette smokers did not markedly differ from the individual variation of medium-tar cigarette smokers.