Biomarkers of genetic damage and inflammation in blood and bronchoalveolar lavage fluid among former German uranium miners: a pilot study

Former East German uranium miners who are known to have been exposed to radon are estimated to be at high risk for lung carcinogenesis. Among these miners over 200 occupationally caused lung cancer cases are expected to occur each year, resulting in a total of 7,000-24,000 excess lung cancer cases in the coming years. It is still unknown whether there is a correlation between biomarkers and the exposure of the uranium miners to ionizing radiation that might enable us to trace those miners with high lung cancer risk. The primary aim of this pilot study was to test the possibility of performing a biomarker study in this unique cohort of former uranium miners in spite of several limitations that had to be taken into consideration when comparing them with healthy controls, such as old age, age-dependent diseases and potential confounding artefacts from dissimilar smoking patterns. The second aim was to test a range of biomarkers for DNA damage and inflammation in leukocytes and bronchoalveolar fluid for their ability to detect biological effects. In this cohort of miners we found an increased frequency of chromosomal aberrations in blood lymphocytes and an increased prevalence of both fibronectin and tumour necrosis factor alpha in the bronchoalveolar fluid.

p53 mutations and codon 213 polymorphism of p53 in lung cancers of former uranium miners

PURPOSE

There is a high prevalence of G-->T transversions of p53 in lung cancers of smokers. One study has reported a special "hotspot" mutation at codon 249 of p53 in lung cancers of former uranium miners. The aim of our study was to look for mutational spectra of p53 in former German uranium miners with lung cancers.

METHODS

We investigated 16 patients with lung cancer who had worked as uranium miners in Germany and 13 lung cancer patients without a mining history of the same region. By means of the polymerase chain reaction and sequencing we looked for mutations in exons 5 7 of the p53 gene.

RESULTS

We could not find any suggestion of hotspot mutations. The only G-->T mutation in former uranium miners was detected in the only nonsmoker. In 3 patients (19% of the total) we found a codon 213/3 polymorphism.

CONCLUSIONS

The results indicate that G-->T transversions do not seem to be very common mutations in p53 in lung cancers probably caused by radiation. Therefore, p53 may be mutated early in lung cancer development if radiation exposure is a critical factor in carcinogenesis. In accordance with studies of thyroid cancer patients in the Chernobyl region, our results may indicate an overrepresentation of codon 213/3 polymorphism in p53 in radiation-caused cancers.

European Consensus Statement on Lung Cancer: risk factors and prevention. Lung Cancer Panel

This article is based on discussions of the lung cancer panel at the Hohenheim Consensus Meeting organized by the World Health Organization and the German Ministry of Health in November 1996. Panel members were international experts in the field of diet and cancer who discussed specific questions relating to lung cancer risk factors and prevention.

Elevated DNA single-strand breakage frequencies in lymphocytes of welders exposed to chromium and nickel

DNA damage (alkaline filter elution) and sister chromatid exchange (SCE) frequencies were measured in lymphocytes of 39 welders and 39 controls. The welders showed a significantly higher rate of DNA single-strand breakages and significantly elevated SCE values. These results are not in accordance with those of a former study in which only DNA-protein cross-links were measured. The different results may be explained on the basis of different exposure levels for chromium(VI) and nickel. Both methods are not specific but sensitive enough to measure genotoxic damage after occupational exposure to chromium(VI) and nickel in the range of threshold values for the workplace on a collective basis. Additionally, the results indicate that DNA single-strand breakage and DNA-protein cross-links show different increases depending on the exposure levels for chromium and nickel.

DNA single strand breakage, DNA adducts, and sister chromatid exchange in lymphocytes and phenanthrene and pyrene metabolites in urine of coke oven workers

OBJECTIVES

To investigate the specificity of biological monitoring variables (excretion of phenanthrene and pyrene metabolites in urine) and the usefulness of some biomarkers of effect (alkaline filter elution, 32P postlabelling assay, measurement of sister chromatid exchange) in workers exposed to polycyclic aromatic hydrocarbons (PAHs).

METHODS

29 coke oven workers and a standardised control group were investigated for frequencies of DNA single strand breakage, DNA protein cross links (alkaline filter elution assay), sister chromatid exchange, and DNA adducts (32P postlabelling assay) in lymphocytes. Phenanthrene and pyrene metabolites were measured in 24 hour urine samples. 19 different PAHs (including benzo(a)pyrene, pyrene, and phenanthrene) were measured at the workplace by personal air monitoring. The GSTT1 activity in erythrocytes and lymphocyte subpopulations in blood was also measured.

RESULTS

Concentrations of phenanthrene, pyrene, and benzo(a)pyrene in air correlated well with the concentration of total PAHs in air; they could be used for comparisons of different workplaces if the emission compositions were known. The measurement of phenanthrene metabolites in urine proved to be a better biological monitoring variable than the measurement of 1-hydroxypyrene. Significantly more DNA strand breaks in lymphocytes of coke oven workers were found (alkaline filter elution assay); the DNA adduct rate was not significantly increased in workers, but correlated with exposure to PAHs in a semiquantitative manner. The number of sister chromatid exchanges was lower in coke oven workers but this was not significant; thus counting sister chromatid exchanges was not a good variable for biomonitoring of coke oven workers. Also, indications for immunotoxic influences (changes in lymphocyte subpopulations) were found.

CONCLUSIONS

The measurement of phenanthrene metabolites in urine seems to be a better biological monitoring variable for exposure to PAHs than measurement of hydroxypyrene. The alkaline filter elution assay proved to be the most sensitive biomarker for genotoxic damage, whereas the postlabelling assay was the only one with some specificity for DNA alterations caused by known compounds.

Biomonitoring of urinary aromatic amines and arylamine hemoglobin adducts in exposed workers and nonexposed control persons

The renal excretion of arylamines in occupationally exposed and nonexposed subjects was measured by a gas chromatography-electron capture detector method. Additionally, in the occupationally exposed persons hemoglobin adduct levels of arylamines were determined by a liquid chromatography-electrochemical detector method, together with the individual acetylator status. The aromatic amines aniline, p-toluidine, 2-naphthylamine, and 4-chloro-o-toluidine were detected in the urine of nonsmoking subjects who were not occupationally exposed to arylamines. Significantly higher concentrations of aniline, o-toluidine, m-toluidine, 2-naphthylamine, and 4-methyl-1,3-phenylenediamine could be observed in the urine of smoking control persons in comparison to nonsmokers. Comparison of smokers and nonsmokers in a group of workers primarily exposed to aniline and 4-chloroaniline revealed significant differences (P < 0.05) in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 2-naphthylamine. The slow acetylators in this group produced significantly more hemoglobin adducts of aniline and 4-chloroaniline than did the fast acetylators. In slow acetylators among the smoking workers there was a significant increase in the formation of 4-aminodiphenyl hemoglobin adducts and in the renal excretion of 4-chloroaniline and m-toluidine. The results indicate that there are influences of smoking habits and acetylator status on the levels of arylamine hemoglobin adducts as well as urinary arylamine concentrations. Hemoglobin adducts seem to be good parameters for monitoring aniline and 4-chloroaniline exposure at the workplace, especially if the acetylator polymorphism can be taken into account. 4-Aminodiphenyl hemoglobin adducts might be good parameters for monitoring individual smoking habits. The determination of urinary arylamine concentrations provides additional information concerning acute exposures to aromatic amines.

32P-postlabeling analysis of DNA adducts in different populations

Blood samples were obtained from different populations exposed occupationally or by lifestyle habits to polycyclic aromatic hydrocarbons (PAH). DNA adducts were determined by 32P-postlabeling assay either in white blood cells (WBC) or lymphocytes. The level of DNA adducts ranged from 1.5 per 10(9) nucleotides in one of the control groups up to 7.1 per 10(9) nucleotides in one group of PAH-exposed workers. Comparison of the adduct thin layer chromatography (TLC) profiles revealed individual variation in both pattern and level of DNA adducts. Significant differences of adduct levels were detected between one group of PAH-exposed coke-oven workers and the corresponding control group. Only a weak influence of the smoking habits on the amount of adducts was detectable in occupationally exposed or unexposed individuals.

Nasal cancer in leather workers: an occupational disease

Nasal cancer has a number of causative agents; exposures to most of the established nasal carcinogens occur in the workplace. An increased risk of nasal cancer has been ascertained in shoe-making and shoe-repairing, but the results for leather goods manufacture and leather tanning don't provide adequate evidence of carcinogenicity. Findings from two epidemiological studies carried out in Italy (a case/control study and a case/series report) add further information on this issue. The case/control study was performed in the provinces of Siena (Tuscany), Verona and Vicenza (Venetia) including 96 cases and 378 controls. A significant increased risk (Odds Ratio: 6.8; 90% C.I. = 1.9-25) of sinonasal cancer was found for the employ in the whole leather industry; Odds Ratio of 8.3 (C.I. = 1.9-36) and 5.0 (C.I. = 0.92-28) were associated with shoe-making and leather tanning. The case/series report is based on 110 patients accepted in some Italian hospitals during last three years (1990-1993): 26 cases had worked in the leather industry; adenocarcinoma is the most frequent type observed. Chromium salts and natural tannins are indicated as possible aetiological agents.

DNA-protein cross-links and sister chromatid exchange frequencies in lymphocytes and hydroxyethyl mercapturic acid in urine of ethylene oxide-exposed hospital workers

The lymphocytes of 25 hospital workers exposed to ethylene oxide and of a standardized control group were investigated for DNA damage (measured by alkaline filter elution) and sister chromatid exchange (SCE) frequencies. Additionally, the excretion of hydroxyethyl mercapturic acid (HEMA) in the 24-h urine of ten workers and ten control persons was determined. The peak levels of ethylene oxide in air during the first 8 min after opening of the sterilization unit were measured. Peak levels of ethylene oxide in the air of up to 417 ppm after opening of the sterilization unit were detected. In the alkaline filter elution assay we found significantly reduced elution rates in the exposed workers, indicating DNA-protein cross-links. The reduction of the elution rates through HVLP filters correlated significantly with the exposure classification (low, medium, high) (r = -0.45, P < 0.05) and the ethylene oxide peak level after opening of the sterilization unit (r = -0.42, P < 0.05). The SCE frequencies in the standardized control group were significantly elevated. With respect to (n = 78) historic control SCE values of our institute, the SCE values of the disinfectors were not significantly elevated (6.54 vs 6.27). The ethylene oxide-exposed workers did not have a greater percentage of high-frequency SCE cells. The mean HEMA concentration in the urine of the exposed workers was significantly elevated, but there were wide variations in HEMA concentrations and no correlation to ethylene oxide exposure. We conclude that the alkaline filter elution assay may be a sensitive parameter for ethylene oxide-exposed workers.(ABSTRACT TRUNCATED AT 250 WORDS)

Sister chromatid exchange frequencies in lymphocytes of oral cancer patients seem to be influenced by drinking habits

Sister chromatid exchange (SCE) values were determined in the lymphocytes of 24 oral cancer patients before therapy and in the lymphocytes of 24 control persons standardized with respect to sex, age and smoking habits. Oral cancer patients showed significantly elevated SCE values (mean 7.82 versus 6.42). In both groups the highest SCE values were found in the subgroups with the highest alcohol consumption. A significant correlation between SCE and gamma-glutamyltranspeptidase (GGT) values by Spearman correlation analysis was detected in the combined group (cancer patients and control persons) (n = 32, r = 0.40, P = 0.023). The SCE values in the oral cancer patients were weakly correlated (Pearson) to DNA adduct levels (n = 22, r = 0.39, P = 0.068) and DNA single-strand breakage frequencies (n = 12, r = 0.56, P = 0.054) in lymphocytes. The correlation (Pearson) between SCE values and DNA strand breakage values in lymphocytes was significant (n = 10, r = 0.67, P = 0.036) in smoking cancer patients. The increase of SCE values with respect to alcohol drinking habits underlines epidemiologic findings that alcohol is an important co-carcinogen in many cancers, especially in oral cancers. Because of the influences on SCE and adduct levels in lymphocytes, alcohol drinking habits should be controlled as broadly as possible in biomarker studies.

Genotoxic and cytotoxic effects of 4-aroyl-1-nitrosohydrazine-carboxamides on O6-alkylguanine-DNA alkyltransferase-positive and -negative human cell lines

Five different representatives (I-V) of a new class of bifunctional alkylating agents, the 4-aroyl-1-nitrosohydrazinecarboxamides ("nitrososemicarbazides"), were evaluated for their potential interaction with DNA and for their cytotoxic activity in vitro to O6-alkylguanine-DNA alkyltransferase-positive (Mer+) and -negative (Mer-) human cell lines. The HeLa MR cell line (Mer-) showed up to 20-fold higher sensitivity at IC50 (dose that inhibits colony formation by 50%) to agents I-V than did the HeLa S3 cell line (Mer+) in a colony-formation assay. These data were compared to those obtained by treatment of the two cell lines with carmustine, a currently used antitumor drug. In Mer+ cells comparable results to those with carmustine were obtained with compounds III, IV and V; in Mer- cells compounds I and II showed nearly the same effects as carmustine. Whether compounds I-V produce DNA strand breaks and/or DNA-protein cross-links was investigated using an alkaline filter elution technique. In this assay all compounds produced DNA single-strand breaks; no correlation could be detected between the strand breakage frequency and cytostatic, mutagenic and antitumor activity.

Concentrations of benzene in blood and S-phenylmercapturic and t,t-muconic acid in urine in car mechanics

Different parameters of biological monitoring were applied to 26 benzene-exposed car mechanics. Twenty car mechanics worked in a work environment with probably high benzene exposures (exposed workers); six car mechanics primarily involved in work organization were classified as non-exposed. The maximum air benzene concentration at the work places of exposed mechanics was 13 mg/m3 (mean 2.6 mg/m3). Elevated benzene exposure was associated with job tasks involving work on fuel injections, petrol tanks, cylinder blocks, gasoline pipes, fuel filters, fuel pumps and valves. The mean blood benzene level in the exposed workers was 3.3 micrograms/l (range 0.7-13.6 micrograms/l). Phenol proved to be an inadequate monitoring parameter within the exposure ranges investigated. The muconic and S-phenylmercapturic acid concentrations in urine showed a marked increase during the work shift. Both also showed significant correlations with benzene concentrations in air or in blood. The best correlations between the benzene air level and the mercapturic and muconic acid concentrations in urine were found at the end of the work shift (phenylmercapturic acid concentration: r = 0.81, P < 0.0001; muconic acid concentration: r = 0.54, P < 0.05). In conclusion, the concentrations of benzene in blood and mercapturic and muconic acid in urine proved to be good parameters for monitoring benzene exposure at the workplace even at benzene air levels below the current exposure limits. Today working as a car mechanic seems to be one of the occupations typically associated with benzene exposure.

DNA strand breakage and DNA adducts in lymphocytes of oral cancer patients

In lymphocytes of 12 oral cancer patients (and two control groups) the frequencies of DNA single-strand breaks and DNA-protein cross-linking were determined by alkaline filter elution. We found elevated DNA elution rates, which must be interpreted as an increased strand breakage frequency. There were significant correlations between the DNA strand breakage frequency and smoking habits. Using the 32P-postlabelling assay we determined the DNA adduct level in lymphocytes of 23 oral cancer patients (and two control groups). No significant influence of smoking habit on the DNA adduct level could be detected. There was a significant correlation between the DNA adduct level and the gamma-glutamyltranspeptidase (GGT) value, suggesting systemic influences of alcohol drinking habits on the adduct level.

Genotoxic effects of subacute treatments with wood dust extracts on the nasal epithelium of rats: assessment by the micronucleus and 32P-postlabelling

Human exposure to wood dust has been epidemiologically linked to a number of enhanced incidences of various neoplasias, including those of the nose. Among different suspected woods, long-term exposure to the dust of beech (Fagus silvatica) is strongly associated with development of these tumors. Experimentally, it has been shown that a simple alcoholic extract of beech wood dust is mutagenic toward some bacteria and tumorigenic on mouse skin. For the present study, different groups of male Wistar rats were treated with aqueous, ethanol, or methanol extract of untreated beech wood dust via nasal drip at three concentrations for 48 h. Animals were killed 24 h after the last treatment and the nasal tissues were isolated to be examined for possible induction of micronuclei and DNA adducts. A clear dose-dependent increase in the number of micronuclei (P < 0.01) was observed after treatment of rats with each alcoholic extract of wood dust. In contrast, no DNA adducts could be detected with these extracts using the 32P-postlabelling technique. No increased number of micronucleated cells was found with solvents alone or with aqueous extract of dust. These data might support the early hypothesis that wood dust per se contains some in vivo genotoxic and thus possibly carcinogenic components extractable by an alcohol.

Production and characterization of monoclonal antibodies to N7-phenylguanine

N7-Phenylguanine, a base adduct possibly formed after arylation of DNA by benzene oxide, the first reaction metabolite during benzene metabolism, was synthesized in our laboratory and used as reference for the production and characterization of monoclonal antibodies. 2-Hydroxymethyl-7-phenylhypoxanthine, a molecule structurally similar to N7-phenylguanine, was coupled by a linker molecule to different carrier proteins. The resulting conjugate was used to immunize BALB/c mice, the spleen cells of which were fused with mouse P3X63-Ag8.653 myeloma cells to obtain monoclonal antibodies. Several hybridoma lines were cultivated in defined media and characterized as to sensitivity and specificity by an enzyme-linked immunosorbent assay (ELISA). Competitive ELISA demonstrated that all antibodies showed a very high affinity for N7-phenylguanine but had a lower affinity towards various other samples including N7-chlorophenylguanines and C8-, N2-and O6-phenylguanine. As little as about 20 pg N7-phenylguanine could be detected with one of the most sensitive antibodies, CE6/G11, with a colorimetric end point while the detection limit could be lowered to about 10 pg N7-phenylguanine when a fluorescent end point was used. The detection limit of other methods used to determine N7-phenylguanine so far is 10 ng for gas-chromatography/mass-spectrometry and 1 ng for high-pressure liquid chromatography. Thus the use of specific monoclonal antibodies seems to be the most sensitive method for the detection of N7-phenylguanine.

[Polychlorinated biphenyls (PCBs) and reproduction disturbances]

A review of the impact of chlorinated biphenyls (PCBs) on reproduction is presented. PCBs are able to pass the placenta; accumulation in offspring is mainly achieved by breast feeding. Disturbances of fertility and embryotoxicity were detected in animals; teratogenicity without maternal toxicity was only observed in mice. In animal experiments disturbances of fetal and postnatal development were detected as well as in human studies. Neurotoxicity was observed even at low-level exposures in monkeys, which are most comparable to humans because of the development of the same clinical symptoms. Technical PCBs which are dominating in occupational and environmental exposure until now must be judged as toxic for reproduction: dermal exposure (especially in accidents) should be considered as an important route of exposure beside inhalation. Work to list possible PCB exposure risks and to develop ways to reduce these risks are necessary now.

Studies on guanine adducts excreted in rat urine after benzene exposure

Investigations with [14C]benzene indicate the formation of base adducts in vivo. Experiments to separate adducts from urine of [14C]benzene-exposed rats suggest the excretion of eight labeled compounds different from benzene metabolites. In order to obtain information about their structure we synthesized N7-, O6-, C8- and N2-phenylguanine. With regard to their chromatographic properties we compared these phenylguanines with products obtained by alkylation of guanine by metabolites of unlabeled and 14C-labeled benzene in vivo with HPLC with UV detection and liquid scintillation counting. Furthermore GC/MS and ELISA techniques were used to detect N7-phenylguanine. Phenylguanines could not be identified in collected DNA fractions. The labeled compounds detected in urine of [14C]benzene-exposed rats also showed deviations from the HPLC elution patterns of our reference substances. Even N7-phenylguanine, formerly suspected to be a urinary metabolite of benzene in the rat, could not be detected with these refined HPLC methods. With GC/MS a compound was found in trace amounts in concentrated rat urine samples, which had a similar fragmentation pattern to N7-phenylguanine. These data could not be confirmed by a sensitive immunological assay (ELISA). No N7-phenylguanine was detected in purified rat urine samples. The results suggest the excretion of a hydroxylated phenylguanine which may be formed in liver or bone marrow DNA by highly reactive hydroxylated intermediates. The OH group might be lost because of the high temperatures during GC/MS measurements. A hydroxy group at the phenyl-ring of N7-phenylguanine will cause other elution properties in HPLC compared to N7-phenylguanine.

Investigations of the frequency of DNA strand breakage and cross-linking and of sister chromatid exchange frequency in the lymphocytes of patients with multiple myeloma undergoing cytostatic therapy with melphalan and prednisone

An investigation was made of 17 patients with multiple myeloma using the method of alkaline filter elution for the detection of DNA damage and the determination of sister chromatid exchange (SCE) frequency in peripheral lymphocytes during a course of chemotherapy with melphalan and prednisone. We were able to detect elevated SCE frequencies in pretreated patients that approximately doubled during the therapeutic cycle. An appreciable level of DNA cross-linking was detected by alkaline filter elution; DNA cross-linking scarcely increased during a course of chemotherapy. The increase in the SCE frequency during the first therapy cycle was even greater in the case of patients with newly diagnosed multiple myelomas. The results obtained by alkaline filter elution and measuring SCE frequencies suggest that these techniques are suitable as methods in molecular epidemiology, especially if applied to persons who are chronically exposed to cytostatic drugs. Whether or not the methods could be valuable in evaluating therapy response needs further investigation.

Incidence of bladder cancer in a cohort of workers exposed to 4-chloro-o-toluidine while synthesising chlordimeform

Between 1982 and 1990 seven cases of bladder cancer were detected in a group of 49 workers who were synthesising chlordimeform from 4-chloro-o-toluidine. Latency periods ranged from 15 to 23 years. The incidence of bladder tumours in this group was significantly higher than that of the cancer registers of the former GDR, Saarland, and Denmark by factors of 89.7, 53.8, and 35.0 respectively. This provides further evidence that monocyclic aromatic amines such as 4-chloro-o-toluidine may be carcinogenic in humans.

Concentrations of tetrachloroethene in blood and trichloroacetic acid in urine in workers and neighbours of dry-cleaning shops

Tetrachloroethene concentrations in blood and trichloroacetic acid concentrations in urine were determined--primarily over the course of a week--for 29 persons living in the vicinity of dry-cleaning shops. The mean levels of tetrachloroethene increased during the week. In some neighbours concentrations were exceeding the German biological threshold limit value for tetrachloroethene (1000 micrograms/l blood), persisting over the whole week in one case. The concentrations of tetrachloroethene in blood depended on the floor and the construction type of the building where these people were living, but not of the type of system used in the dry-cleaning shops. 5 of 12 dry-cleaners were found to have tetrachloroethene levels exceeding the German biological threshold limit value, some of them by a considerable amount.

Investigations of the frequency of DNA strand breakage and cross-linking and of sister chromatid exchange frequency in the lymphocytes of female workers exposed to benzene and toluene

Peripheral lymphocyte DNA damage as measured by the method of alkaline filter elution and the frequency of sister chromatid exchange (SCE) in lymphocytes was investigated for a group of 20 female workers of a shoemaking plant who were exposed to benzene and toluene, primarily below the German threshold limit value of 5 and 100 p.p.m. respectively; the results were compared with those from a control group. In the female workers significantly raised (P less than 0.05) SCE values were found. The relative DNA elution rate through polycarbonate filters was significantly increased (P less than 0.001). The elution rate through polyvinylidene fluoride (HVLP) filters showed a tendency to increase (P = 0.052), which must be interpreted as indicating increased DNA strand breakage. The SCE rates of the female workers were significantly correlated (P less than 0.01) with the relative DNA elution rate through HVLP filters. There was no correlation with the actual benzene and toluene uptake measured by personal air monitoring. Four months after cessation of work, DNA strand breakage decreased significantly (P less than 0.05) in blood samples of six reinvestigated female workers.

Investigations of the frequency of DNA strand breakage and cross-linking and of sister chromatid exchange in the lymphocytes of electric welders exposed to chromium- and nickel-containing fumes

A total of 39 electric welders exposed to chromium and nickel were compared with 18 controls standardized for age, smoking habits and sex with respect to the frequency of sister chromatid exchange (SCE) and of DNA strand breakage and cross-linking (measured by the method of alkaline filter elution) in their blood lymphocytes. A significant correlation was found between the frequency of SCE and of individual DNA strand breakage and the concentration of chromium in the urine. Less DNA from the welders than from the control group was eluted through the two filter types used (polycarbonate and polyvinylidene fluoride filters). This must be interpreted as resulting from the presence of DNA-protein cross-links, which has the secondary effect of leading to a relative reduction in the measurable frequency of strand breakage amongst the welders. The present results are in good agreement with in vitro and in vivo investigations that confirm the importance of DNA-protein cross-links for the carcinogenic effect of chromium.

Mutagenic activity of some newly synthesized cytostatic 1-(2-chloroethyl)-4-arylacyl-1-nitrososemicarbazides in the Salmonella/mammalian microsome assay

Five experimental anti-leukemic agents, 1-(2-chloroethyl)-4-arylacyl-1-nitrososemicarbazides, were synthesized and tested for genotoxicity in the Salmonella/mammalian microsome assay. No strong mutagenic activity could be detected when tested with the S. typhimurium TA98. A clear dose-dependent base-pair-substitution mutagenic activity was observed with each compound when the tester strain TA100 was used with or without metabolic activation. The genotoxicity of the unsubstituted substance was similar to that of the known mutagenic cytostatic drugs, lomustin and carmustin, and was stronger than the mutagenicity of each substituted derivative.

Release of mutagens after chemical or microbial degradation of beech wood lignin

The microbial or chemical degradation of lignin from untreated samples of beech wood dusts (Fagus silvatica) resulted in the release of different mutagenic responses in the Salmonella/mammalian plate incorporation assay. In the first experiment using chemical degradation of lignin, dust samples were pre-extracted using acetone-water; the lignin portions were degraded into simpler compounds which were further fractionated on a Sephadex-LH20 column. The compounds isolated from the second phase of Sephadex, representing substances with a 3-4 ring structure and/or those of the same molecular weight, were highly mutagenic towards Salmonella typhimurium TA100 in the presence of metabolic activation. These substances were also active to some extent in strain TA1537 both in the presence and absence of Aroclor-induced rat liver homogenates. In contrast, no direct- or indirect-acting mutagenicity was found when testing with strains TA97 and TA98. Strain TA1535 responded positively only to direct-acting mutagens in the fraction tested. The mutagenic fraction was found to be toxic to the cells when tested in a histidine-rich medium. Repurification of this mutagenic fraction, using silica-gel column chromatography, revealed much higher mutagenic activity than the test material towards strain TA100. In the second pilot experiment, Phanerochaete chrysosporium and Chaetomium globosum, which are known for their ability to degrade lignin, were each incubated with wood dusts in a mixture of physiological saline and nutrient broth for either 3 or 30 days. Significant mutagenic activity was observed with the dust extract after incubation with Ph. chrysosporium but not with Ch. globosum which is a known degrader of beech lignin. These results are discussed regarding hypotheses on the carcinogenicity of beech wood dusts.

Comparative carcinogenicity of cigarette mainstream and sidestream smoke condensates on the mouse skin

The direct carcinogenic effects of sidestream (SS) and mainstream (MS) smoke condensates of a filtered commercial brand of blond cigarettes were compared using a lifetime mouse skin tumorigenicity assay on female NMRI mice. Each cigarette was smoked by a smoking machine under the standard conditions, and the separately collected SS and MS smoke condensates were extracted with acetone/methanol as described elsewhere. These were tested for carcinogenicity on an area of 1-1.5 cm shaved skin of mice on the lower back. The mice were treated with half of each dose (5, 10 or 15 mg) twice a week, for only 3 months. No substance was used as promoter or as an additional initiator of carcinogenicity. No statistically significant difference was found when the life spans of MS-treated and untreated animals were compared. In contrast, the life spans of SS-treated mice were significantly (P less than 0.01) shorter than those of MS-treated animals or those of all three negative control groups together. The observed carcinogenic effects were based on tumours and lesions found only on the site of application of the test material. Of 210 mice (effective number, 129) serving as the negative controls, 3 developed skin lesions but no tumours. Of 210 MS-treated mice (effective number, 177), 7 developed tumours (4 malignant and 3 benign) and 35 had a uniform type of precancerous skin lesions. The numbers of tumours or lesions were not increased dose-dependently. Of 210 SS-treated animals (effective number, 182), 30 developed tumours (16 malignant and 14 benign) and 56 had a uniform type of precancerous skin lesion. The initiation of these latter lesions was found to be dose-dependent (P less than 0.001). The SS-treated animals developed two to six times more skin tumours than the MS-treated mice. Comparing the negative controls with the MS- or SS-treated animals, the overall carcinogenic effect observed was statistically significant. Comparing the MS- with SS-treated animals, the overall carcinogenic effect of SS was much higher than that of MS (P less than 0.001).

The excretion of chlorophenylmercapturic acid, chlorophenols and a guanine adduct in the urine of chlorobenzene-treated rats after phenobarbital pretreatment

Chlorobenzene (CB) was administered to male Wistar rats. Twenty-four-hour urine samples were collected over a period of 7 days. p-Chlorophenylmercapturic acid, chlorophenols and a guanine adduct were determined by chromatographic methods. The excretion pattern of p-chlorophenyl-mercapturic acid did not seem to be significantly affected by phenobarbital. To analyze for the chlorophenols and guanine adducts, diluted urine was subjected to cation exchange chromatography using UV-detection. Fractions were found containing chlorophenols and a compound showing chromatographic properties similar to those of the synthetic N7-phenylguanine. The results of the HPLC analyses suggested the presence of a guanine adduct excreted on days 1 and 2 and between days 4 and 6 post-administration. There were no compounds detected which were identical with p-, m- or o-isomers of N7-chlorophenylguanine. The excretion of p- and m-chlorophenols by phenobarbital-pretreated animals was twice as high as that in untreated rats. A 4-fold increase was detected for o-chlorophenol. It is assumed that it is mainly direct hydroxylation that can be induced by phenobarbital. Dehalogenated phenolic metabolites may be capable of covalent binding to DNA.

Cancer epidemiology of woodworking

The literature published between 1965 and 1989 on the cancer epidemiology of woodworking in furniture industries and carpentry shops in 17 countries is reviewed. Included are some unpublished data obtained through personal communication with epidemiologists or collected from doctoral dissertations. Of 5,785 cases with sino-nasal cancers, about 23% were found to be woodworkers. Dusty jobs, especially wood processing using high-speed machines, are mainly associated with the enhanced incidence of nasal adenocarcinomas. The latency periods of the latter tumors ranged from 7 to 69 years in five European countries. A variety of neoplasias of the respiratory, digestive, and urinary tracts as well as the hemopoietic and lymphatic systems, including Hodgkin's disease are reported to be significantly associated with occupational exposure to wood dust. These data suggest that the exposure to some types of wood dust might cause a systemic rather than local neoplastic disorder.

Urinary and faecal excretion of pyrene and hydroxypyrene by rats after oral, intraperitoneal, intratracheal or intrapulmonary application

The urinary and faecal excretion of pyrene and 1-hydroxypyrene after oral (53.4%), intraperitoneal (3.1%), intratracheal (30-37%) and intrapulmonary application (0.003%) to rats has been determined by means of gas chromatography/mass spectrometry and the excretion rates were found to depend on the mode of application. With regard to the low urinary excretion rates, 1-hydroxypyrene seems not to be very suitable as a biological marker for PAH exposure to man.

The mouse-skin carcinogenicity of a mutagenic fraction from beech wood dusts

A life-time mouse-skin carcinogenicity assay was conducted using female NMRI mice to evaluate the possible direct carcinogenic activity of a mutagenic fraction isolated from beech wood dusts. The samples of untreated beech wood dusts were extracted with methanol at pH3 and were purified from the inhibitory compounds toxic to bacteria, using silica-gel column chromatography. The fraction obtained after passing through the column was tested for mutagenicity in the Ames assay employing Salmonella typhimurium TA100 in the presence of Aroclor-treated rat-liver-S9. Using acetone as the vehicle, this mutagenic fraction was tested for carcinogenicity on an area of 1-1.5 cm shaved skin of mice on the lower back. The mice were treated with half of each dose, twice a week, for only 3 months. The total doses applied per week were 2.5, 5, 7.5 or 10 g equivalent dust/mouse. No substance was used as promoter. No statistically significant difference was found when the life spans of treated and untreated animals were compared. The observed carcinogenic effect was based on tumours and lesions found only on the site of application of the test material. Of 210 mice (effective number, 129) serving as the negative controls, three developed skin lesions but no tumours. Of 280 treated animals (effective number, 188) 34 developed different types of tumours and 20 had a uniform type of precancerous skin lesion. Of 34 tumours observed 21 were originated from the skin, 12 from the mammary glands beneath the site of application, and one was a lymphoma. Comparing the negative controls with the treated animals, the overall carcinogenic effect observed was dose-dependent and statistically significant. Excluding the mammary tumours and a lymphoma found beneath the site of treatment, the overall induction of skin tumours was still significant. However, the dose-dependent increase in the number of skin tumours alone was not statistically significant. These results suggest that beech wood dust contains mutagenic and carcinogenic constituent(s).

Determination of S-phenylmercapturic acid in the urine--an improvement in the biological monitoring of benzene exposure

In an inhalation study rats were exposed to different doses of benzene, ranging from 1 to 500 p.p.m. The urine was sampled during the inhalation period of 8 h and for 24 h after exposure. S-Phenylmercapturic acid (S-PMA) in the urine was determined by amino acid analysis. Phenol was measured by gas chromatography/mass spectrometry. In both cases the correlation between benzene uptake and the excretion of the urinary metabolites was significant at the level of P = 0.01. The same significant correlation (P = 0.01) was demonstrable after i.p. administration of benzene at doses between 0.7 and 140.0 microliters/kg body weight. In the case of two collectives of workers who were exposed to air concentrations of up to 0.15 p.p.m. for 8 h and of up to 1.13 p.p.m. for 12 h respectively, the amount of S-PMA in the first urine samples after the shift was significantly higher than in samples collected at the beginning of the shift (P = 0.01). In the first collective the mean values and the standard deviations of the S-PMA concentrations in the samples at the beginning of the shift were 12.0 +/- 16.7 compared with 48.5 +/- 64.5 micrograms/g creatinine at shift end. In the second collective they were 25.1 +/- 25.1 compared with 70.9 +/- 109.2 micrograms/g creatinine. The level of significance of the difference between the concentration values of S-PMA at the beginning and end of the shift was P = 0.01. The phenol concentration did not differ significantly. These results suggest that S-PMA can be regarded as a useful indicator for monitoring individuals and collectives exposed to benzene at levels even less than 1 p.p.m.

Comparative bone marrow clastogenicity of cigarette sidestream, mainstream and recombined smoke condensates in mice

The chromosome-damaging effects of cigarette sidestream (SS) and mainstream (MS) smoke condensates and a mixture of these were compared in 8-week-old NMRI mice by intraperitoneal administration. Each filtered commercial brand of cigarette was smoked by a smoking machine under the standard conditions, and the separately collected SS and MS smoke condensates were extracted with acetone/methanol as described elsewhere. The extracts were tested before and after treatment of animals with an enzyme inducer (Aroclor 1254) or inhibitor (Metyrapone). Increased formation of micronuclei within polychromatic erythrocytes (PCEs) of femural bone marrow 30 h after injection of the extracts was regarded as being due to a clastogenic effect. Regardless of the type of smoke extract injected, the increased formation of micronuclei was found to be dose dependent. The SS smoke condensate induced approximately 29% more micronuclei than the MS smoke condensate, the difference being significant (P less than 0.01). The overall clastogenicity of a 1:1 mixture of SS and MS smoke condensates was not substantially different from the activity of either SS or MS smoke condensate alone. Pretreatment of animals with Aroclor clearly enhanced the differences between the number of micronucleated PCEs caused by SS versus MS smoke condensate; SS smoke condensate induced 50% more micronuclei than did MS smoke condensate (P less than 0.001). Pretreatment of mice with Metyrapone did not modify appreciably the induction of micronuclei by either type of smoke. These results are discussed with reference to our previous data involving inhalation experiments and the recent issue of passive smoking.

Investigations on metabolism and carcinogenicity of 1,1,2-trichloroethane

Two groups of male and female Sprague-Dawley rats (50 animals/group per sex) were treated with either 15.37 or 46.77 mumole of 1,1,2-TCE in DMSO/rat for 2 years. The animals were treated once a week by s.c. injection of test compound in the skin of neck. Two groups of controls received either DMSO or no treatment at all. The incidence of benign mesenchymal and epithelial tumors was not significant when compared with either DMSO-treated or untreated controls. The animals treated with 46.77 mumole 1,1,2-TCE significantly developed sarcomas when compared with the untreated controls. In a further experiment, either 40 mumole or 160 mumole 1,1,2-TCE was injected into male Wistar rats and the metabolites, TdGA and HEMA, were determined in 24-h urine samples. Comparative studies were carried out giving equimolar amounts of chloroethanol and 2-chloroacetaldehyde diethyl acetal. Analysis of the metabolites showed that no detectable HEMA was excreted in urine after treatment of rats with 1,1,2-TCE or chloroethanol. TdGA was excreted in urine much more among chloroacetaldehyde-treated animals than among 1,1,2-TCE- or chloroethanol-treated rats.

Urinary and faecal excretion of chrysene and chrysene metabolites by rats after oral, intraperitoneal, intratracheal or intrapulmonary application

The urinary and faecal excretion of chrysene and its phenolic metabolites after oral, intraperitoneal, intratracheal, and intrapulmonary administration to rats have been studied by means of gas chromatography/mass spectrometry. The metabolite profile was found to depend on the mode of excretion and on the route of administration. In all cases the oxidation of chrysene in the 1,2- or 3,4-position predominates, whereas oxidation in the 5,6-position (K-region) seems be a minor pathway.

Biomonitoring of benzene exposure by trace analyses of phenylguanine

From preliminary experiments it was known that radiolabelled benzene and some of its metabolites during its metabolic activation process produce different in vitro DNA-phenyladducts in mitoplasts. As we reported previously at least one of these adducts, N-7-phenylguanine, is excreted in the urine of rats in measurable amounts, probably through an excision-repair mechanism after an inhalation experiment. Now we found, after i.p. application of benzene in the urine of rats, a compound separated by cation-exchange chromatography that behaves like a synthesized N-7-phenylguanine reference substance with respect to its retention index and the UV-absorption. This finding could be confirmed by HPLC-measurements with reversed-phase carrier materials. Silylation and gas chromatographic/mass spectrometric (GC/MS) separation of the fraction, which contains the phenylguanine, revealed that these fractions contain further phenyl adducts. Furthermore we studied the time-dependent excretion of the DNA-base adduct. Surprisingly the excretion dropped to zero on the fourth day and showed a new increase thereafter.

Urinary excretion of acrylonitrile and its metabolites in rats

Quantitative analysis of the dose-dependent urinary excretion of acrylonitrile and its metabolites was carried out in male Wistar rats following inhalation exposure of the animals to 1, 5, 10, 50 and 100 ppm acrylonitrile for 8 h. Quantitative analysis of acrylonitrile in urine was performed by gas chromatography. The urinary metabolites cyanoethyl mercapturic acid, S-carboxymethyl cysteine and hydroxyethyl mercapturic acid were measured by a modified amino acid analysis, and thiodiglycolic acid by GC-MS. The excretion pattern of the compound and its metabolites was dependent on the exposure level; it is concluded that urinary determination of the unmetabolized acrylonitrile and two of its metabolites, cyanoethyl mercapturic acid and thioglycolic acid, may be useful for biological monitoring of industrial exposure.

Effects of pretreatment of male NMRI mice with enzyme inducers or inhibitors on clastogenicity of toluene

Five groups of young male NMRI mice were pretreated with IP injections of three known inducers of cytochrome P450, Aroclor 1254, phenobarbital and 3-methylcholanthrene, and two inhibitors, metyrapone and alpha-naphthoflavone, 5, 3, 2, 1, and 1 day(s) before receiving toluene, respectively. Toluene was given to animals by IP injections of two similar doses 24 h apart. Increased formation of micronuclei within polychromatic erythrocytes of femoral bone marrow 30 h after the first injection of toluene was recorded. None of the treatments with an inducer or inhibitor alone gave a significant increase in the frequency of micronucleated polychromatic erythrocytes. However, pretreatment of animals with each inducer or even inhibitor resulted in an enhanced clastogenic activity of toluene. Simultaneous injections of an inhibitor and toluene clearly decreased the clastogenicities observed. Enhancement of the clastogenicity of toluene was more evident among Aroclor -pretreated animals than among the other groups. Treatment of animals with a mixture of toluene and benzene did not result in an additive clastogenic activity of benzene. IP injection of a mixture of toluene and every xylene isomer resulted in an enhanced clastogenic activity of toluene, although xylene isomers are not found to be clastogenic.

The bone marrow clastogenicity of eight halogenated benzenes in male NMRI mice

Eight widely used halogenated benzenes, including bromobenzene (BB), chlorobenzene (CB), three isomers of dichlorobenzene (DCB) and three isomers of trichlorobenzene (TCB) were tested for acute toxicity (LD50) and clastogenicity in 8-week-old NMRI mice by intraperitoneal administration. Four doses of each chemical (up to 70% of LD50) were tested for clastogenic activity. Each compound was administered in two equal doses, 24 h apart. Increased formation of micronucleated polychromatic erythrocytes, observed in femoral bone marrow, 30 h after the first injection, was considered to be due to the clastogenic activity of the test compound. All the halogenated benzenes tested were found to be clastogenic (P less than 0.01). The highest clastogenic activities were induced by m-DCB and BB. Among the three isomers of DCB, m-DCB significantly (P less than 0.05) induced more micronuclei than o-DCB or p-DCB. No significant differences were found between the clastogenic activities of TCB isomers.

Urinary excretion of mutagens in passive smokers

Six healthy young volunteers with no history of active smoking were asked to keep on their Western diets avoiding the consumption of alcoholic beverages, excess coffee, any sort of medicament, and the known pro- and/or anti-mutagen-containing foods and drinks, 24 h before and during the experiments. They were exposed passively to cigarette smoke produced by 4 habitual smokers in an unventilated 48.6 m3 room for 8 h. The carbon monoxide concentration was 18.85 +/- 7.3 ppm during the 8-h exposure. Frameshift mutagens were isolated from 10-h urine samples using chloroform and were tested for mutagenicity in the Salmonella/mammalian microsome assay employing Salmonella typhimurium TA98. Although clearly enhanced, no significant mutagenic activity could be found with 25 ml equivalent urine/plate after passive exposure to cigarette smoke. The weak mutagenicities found were highly significant when 50 ml equivalent urine/plate was tested. No direct correlation was observed between urine mutagenicity and the urinary cotinine concentration. The results obtained are discussed with reference to inconsistent reports in the literature concerning the mutagenicity of urine after passive smoking.

Urinary excretion of mutagens in smokers of cigarettes with various tar and nicotine yields, black tobacco, and cigars

Frameshift mutagens were isolated and concentrated from smokers' urine employing a method recently described. Urine concentrates of the habitual smokers and non-smokers who smoked cigarettes with low-, medium-, and high tar/nicotine yields, RCN (Reduced Condensate and Nicotine; artificial cigarettes containing cotobacco materials), black tobacco, and cigars were tested for mutagenicity in the Salmonella/mammalian microsome assay using Salmonella typhimurium TA98. Non-smokers who smoked 5 and habitual smokers who smoked 10 cigarettes of various tar and nicotine yields excreted more mutagens in urine with low-tar cigarettes than with medium- or high-tar cigarettes. Consuming more than 10 cigarettes a day resulted in a higher urinary excretion of mutagens with medium-tar cigarettes than with high-tar cigarettes. Smoking 5 RCN cigarettes a day by habitual smokers resulted in a higher urinary excretion of mutagens than smoking 5 commercial brand of cigarettes. In contrast, smoking 10 RCN cigarettes resulted in a lower urinary excretion of mutagens than smoking 10 commercial brand of cigarettes. The highest mutagenic activity was found with the urine of a habitual black tobacco smoker. Smoking cigars by non-smokers resulted in a very weak mutagenic activity of urine.

Clastogenic effect of passive smoking on bone marrow polychromatic erythrocytes of NMRI mice

The genotoxic effect of passive inhalation of sidestream cigarette smoke on bone marrow polychromatic erythrocytes was studied using male NMRI mice. The animals were placed in individual 145.2-dm3 glass chambers resembling a room provided with normal air flow. They were exposed to the sidestream smoke of a commercial brand of cigarettes smoked by a smoking machine under standard conditions. Increased formation of micronuclei within polychromatic erythrocytes (PCEs) of femoral bone marrow 30 h after passive smoking was regarded as being due to the clastogenic effect of the smoke. Passive inhalation of the diluted sidestream smoke of a single cigarette resulted in a significant increase (P less than 0.01) in the frequency of micronucleated PCEs. This clastogenic activity was found to be dose-dependent.