Chromosomal analysis in vinyl chloride exposed workers: Comparison of the standard technique with the sister-chromatid exchange technique

A group of 21 workers occupationally exposed to vinyl chloride and 6 controls were examined for the presence of chromosomal aberrations or sisterchromatid exchanges in their peripheral lymphocytes. These people comprised a second sampling from a group of exposed workers and controls first examined 18 months earlier. The vinyl chloride exposed workers showed levels of chromosomal aberrations elevated above those of the controls, but there was only a slight increase in sister-chromatid exchanges (per cell or per chromosome) and this increase was not statistically significant. Sister-chromatid exchanges (SCEs) were also examined from in vitro cultures of lymphocytes exposed in G₀/early G₁ and late G₁/early S phase to vinyl chloride, both with and without metabolic activation. There was no increase in SCEs in vitro without metabolic activation but there was a marked increase with metabolic activation and this increase was shown to be independent of cell-cylce phase. It thus was apparent that the small increases of SCEs in workers were not due to the inability of vinyl chloride to induce SCEs in human lymphocytes but were probably because of low exposures and SCE levels could have returned to normal relatively quickly after exposure. The present study suggested that the analysis of longer-living conventional chromosomal aberrations appeared to be a more sensitive monitor of exposure to vinyl chloride in exposed workers than the estimation of SCEs; however, it should be noted that in a 3rd sampling taken 24 months later the exposed workers had chromosomal aberration levels similar to the controls.     

Cytogenetic monitoring of industrial populations potentially exposed to genotoxic chemicals and of control populations

Currently the most applied technique for monitoring biological effects of exposure to genotoxic chemicals in industrial workers is the measurement of chromosome aberrations in peripheral blood lymphocytes. In the Shell petrochemical complex in The Netherlands cytogenetic monitoring studies have been carried out from 1976 till 1981 inclusive, in workers potentially exposed to a variety of genotoxic chemicals, i.e. vinyl chloride, ethylene oxide, benzene, epichlorohydrin, epoxy resins. Average exposure levels to these chemicals were well below the occupational exposure limits. Results of these studies indicate that no biologically significant increase in the frequencies of chromosome aberrations in the exposed populations occurred compared with control populations. Our experience with this methodology has shown that the results of chromosome analyses are difficult to interpret, due to the variable and high background levels of chromosome aberrations in control populations and in individuals. It is concluded that the method is not sufficiently sensitive for routine monitoring of cytogenetic effects in workers exposed to the low levels of genotoxic compounds.     

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.     

Chromosomal aberrations in lymphocytes of employees in transformer and generator production exposed to electromagnetic fields and mineral oil

The objective was to study the risk of cytogenetic damage among high voltage laboratory workers exposed to electromagnetic fields and mineral oil. This is a cross sectional study of 24 exposed and 24 matched controls in a Norwegian transformer factory. The exposure group included employees in the high voltage laboratory and in the generator soldering department. Electric and magnetic fields and oil mist and vapor were measured. Blood samples were analyzed for chromosomal aberrations in cultured lymphocytes. In addition to conventional cultures, the lymphocytes were also treated with hydroxyurea and caffeine. This procedure inhibits DNA synthesis and repair in vitro, revealing in vivo genotoxic lesions that are repaired during conventional culturing. In conventional cultures, the exposure group and the controls showed similar values for all cytogenetic parameters. In the DNA synthesis- and repair-inhibited cultures, generator welders showed no differences compared to controls. Among high voltage laboratory testers, compared to the controls, the median number of chromatid breaks was doubled (5 vs. 2.5 per 50 cells; P<0.05) the median number of chromosome breaks was 2 vs. 0.5 (P>0.05) and the median number of aberrant cells was 5 vs. 3.5 (P<0.05). Further analysis of the inhibited culture data from this and a previous study indicated that years of exposure and smoking increase the risk of aberrations. We conclude that there was no increase in cytogenetic damage among exposed workers compared to controls in the conventional lymphocyte assay. In inhibited cultures, however, there were indications that electromagnetic fields in combination with mineral oil exposure may produce chromosomal aberrations.     

The effect of three triterpene acids and sporidesmin on the enzyme activities of rat liver plasma membranes.

Vinyl chloride and vinyl benzene (styrene) are mutagenic in microbial tests, in Drosophila, in yeast, and in mammalian cells. Reports from various countries have shown an excess of chromosomal aberrations in the lymphocytes of workers exposed to vinyl chloride monomer when the workers were compared with controls. Workers occupationally exposed to styrene also revealed a clear increase in the rate of chromosome aberrations in their lymphocytes. Both chloroethylene oxide and styrene oxide, the primary biotransformation products of vinyl chloirde and styrene respectively, bind covalently to cellular macromolecules. Vinyl chloride is a carcinogen in both animals and man. Styrene is currently being tested in animals. These findings, the demonstration of mutagenic response via microbial and other test systems and with observations of significant excesses of chromosomal aberrations among workers exposed to these agents, raise scientific and health oriented concern about the possible genetic risks of vinyl chloride and styrene to man.     

Cytogenetic damage in plastic industry workers exposed to polyvinyl chloride

Cytogenetic investigations on peripheral blood lymphocytes of 40 workers exposed to polyvinyl chloride in the plastic industry were undertaken. These were compared with an equal number of occupationally unexposed and matched controls in relation to age, sex and smoking habits. The mitotic index (MI), chromosomal aberrations (CA), sister chromatid exchanges (SCE) and satellite associations (SA) were analysed. All the parameters showed a significant increase (p <0.01) in the exposed sample compared with the controls, viz MI, 3.64-6.30, CA 1.02-3.77, SCE 3.40-7.83 and SA 5.57-12.05. The occurrence of the DG type of satellite association B was highest and that of 3D type lowest. The frequencies of all the parameters increased with the duration of exposure, but MI declined after 15 years of exposure.     

Cytogenetic effects in workers occupationally exposed to tobacco dust

Tobacco dust mainly contains nitrosamines, which are readily absorbed by the body tissues like skin, respiratory epithelium, and mucous membrane of mouth, nose and intestines. Exposure to tobacco dust is known to affect the respiratory tracts in humans. In the present study, cytogenetic effects of exposure to tobacco dust are evaluated in 154 male tobacco factory workers and 138 age and sex matched controls by analysing chromosomal aberrations in their peripheral blood lymphocytes. The workers were in the age group of 20-55 years and were employed in the tobacco processing factory for 1-32 years. Heparinised blood samples were collected from workers and control subjects and lymphocyte cultures were carried out by using standard technique. Slides were prepared and 150 metaphases were screened for each sample for various structural and numerical types of abnormalities. A statistically significant increase was observed in the frequencies of chromosomal aberrations in non-smoking and smoking exposed groups when compared to the respective controls. An increase in the frequencies of chromosomal aberrations was also observed with increase in years of service in the exposed subjects.     

Occupational exposure to bidi tobacco increases chromosomal aberrations in tobacco processors

In India, workers engaged in processing of tobacco for the manufacture of bidis (the indogenous substitute for cigarettes) are chronically exposed to tobacco flakes and dust via the cutaneous and nasopharyngeal routes. Hence, workers in a tobacco processing factory were monitored for chromosomal aberrations (CA) using peripheral blood lymphocytes as the test system. Cytogenetic analysis revealed a significant increase in deletion fragments and chromatid gaps in the exposed group. The frequency of aberrant metaphases and the proportion of individuals with CA were significantly higher in workers than in controls, indicating that occupational exposure to tobacco imposes considerable genotoxicity among tobacco processors.     

Cytogenetic biomonitoring of a floriculturist population in Italy: micronucleus analysis by fluorescence in situ hybridization (FISH) with an all-chromosome centromeric probe

Flower production in greenhouses associated with a heavy use of pesticides is very wide-spread in the western part of the Ligurian region (Italy). The formation of micronuclei in peripheral blood lymphocytes is a valuable cytogenetic biomarker in human populations occupationally exposed to genotoxic compounds. In the present study we investigated the micronucleus frequency in peripheral blood lymphocytes of 52 floriculturists and 24 control subjects by use of the cytokinesis-block methodology associated with fluorescence in situ hybridization with a pan-centromeric probe that allowed to distinguish centromere-positive (C+) and centromere-negative (C-) micronuclei. The comparison between floriculturists and controls did not reveal any statistically significant difference in micronucleus frequency, although an increase was observed with increasing pesticide use, number of genotoxic pesticides used and duration of exposure. An increase in C+ as well as in C- micronuclei and in the percentage of C+ micronuclei with respect to the total number of micronuclei was detected in floriculturists, suggesting a higher contribution of C+ micronuclei in the total number scored. The percentage C+ micronuclei was not related to the duration of exposure or to the number of genotoxic pesticides used, but a higher percentage (66.52% versus 63.78%) was observed in a subgroup of subjects using benzimidazolic compounds, compared with the floriculturist population exposed to a complex pesticide mixture not including benzimidazolics. These results suggest a potential human hazard associated with the exposure to this class of aneuploidy-inducing carcinogens.     

Occupational styrene exposure and chromosomal aberrations

Results from a study on the clastogenicity of styrene in vivo are reported. The chromosomes in cultured blood lymphocytes from ten men occupationally exposed to styrene and 5 controls were examined. Styrene-exposed men showed an increase in the rate of chromosomal aberrations. The incidence of aberrant cells ranged from 11 to 26% in the lymphocytes of the exposed subjects and was 3% or less in those of the control group.     

Cytogenetic analysis in lymphocytes from radiation workers exposed to low level of ionizing radiation in radiotherapy,CT-scan and angiocardiography units

Ionizing radiation is known as a classical mutagen capable of inducing various kinds of stable and unstable chromosomal aberrations. The percentage of cells with chromosomal aberrations was analyzed in peripheral blood lymphocytes of occupationally exposed workers in radiotherapy, CT-scan, angiography and healthy controls. The incidence of all types of aberrations (gap, acentric fragment, dicentric and ring) in exposed subjects were higher than those observed in healthy controls (P = 0.0001). However, the frequency of aberrant cells with dicentric and ring chromosome in exposed subjects were not significantly different from those in controls. To see whether there is a significant difference in the incidence of chromosomal aberrations among three groups, they were compared for all types of observed aberrations. No significant difference was found between radiotherapy and CT-scan groups (P = 0.838). The percentage of aberrant cells observed, for angiography groups were significantly higher than radiotherapy (P = 0.0001) and CT-scan (P = 0.0001) group. Taken together these data suggest that the cumulative effects of low level chronic exposure to ionizing radiation is higher for those who occupationally exposed in angiography.     

Influence of different occupations with possible mutagenic effects on reproduction and level of induced chromosomal aberrations in peripheral blood.

In a group of 200 dysfertile couples (400 persons), the possible role of different occupations in failures of reproduction was assessed. These couples were examined from different points of view, classical genetic examination (pedigree, kayrotype, etc.) included. The suspected genotoxic effects in the personal history were checked also by testing the level of induced chromosomal aberrations. A significantly increased level of induced chromosomal aberrations was detected in 37 persons, i.e., 9.3% of the whole group under study. The average level of induced aberration in these subjects was 6.8%, as opposed to the control group (fertile and dysfertile persons without any unusual exposure to mutagens) with a mean of 1.58% aberrant cells in peripheral blood. Most of the occupations with demonstrated genotoxic effects involve daily contact with chemicals of different types. In some persons also intensive therapy in the recent past had genotoxic effects.     

Influence of different occupations with possible mutagenic effects on reproduction and level of induced chromosomal aberrations in peripheral blood

In a group of 200 dysfertile couples (400 persons), the possible role of different occupations in failures of reproduction was assessed. These couples were examined from different points of view, classical genetic examination (pedigree, kayrotype, etc.) included. The suspected genotoxic effects in the personal history were checked also by testing the level of induced chromosomal aberrations. A significantly increased level of induced chromosomal aberrations was detected in 37 persons, i.e., 9.3% of the whole group under study. The average level of induced aberration in these subjects was 6.8%, as opposed to the control group (fertile and dysfertile persons without any unusual exposure to mutagens) with a mean of 1.58% aberrant cells in peripheral blood.Most of the occupations with demonstrated genotoxic effects involve daily contact with chemicals of different types. In some persons also intensive therapy in the recent past had genotoxic effects.     

The genotoxic risk of underground coal miners from Turkey

A cytogenetic monitoring study was carried out on a group of workers from a bituminous coal mine in Zonguldak province of Turkey, to investigate the genotoxic risk of occupational exposure to coal mine dust. Cytogenetic analysis, namely sister chromatid exchanges (SCEs), chromosomal aberrations (CAs) and micronucleus (MN) tests were performed on a strictly selected group of 39 workers and compared to 34 controls matched for gender, age, and habit. Smoking and age were considered as modulating factors. Both SCE and CA frequencies in coal miners appeared significantly higher than in controls. Similarly, there was a significant increase in the frequency of total micronuclei in exposed group as compared to control group. The effect of smoking on the level of SCE and MN was significant in the control group. A positive correlation between the age and the level of SCE was also found in controls. The frequencies of both SCE and CA were significantly enhanced with the years of exposure. The results of this study demonstrated that occupational exposure to coal mine dust leads to a significant induction of cytogenetic damage in peripheral lymphocytes of workers engaged in underground coal mining.     

The genotoxic risk of underground coal miners from Turkey

A cytogenetic monitoring study was carried out on a group of workers from a bituminous coal mine in Zonguldak province of Turkey, to investigate the genotoxic risk of occupational exposure to coal mine dust. Cytogenetic analysis, namely sister chromatid exchanges (SCEs), chromosomal aberrations (CAs) and micronucleus (MN) tests were performed on a strictly selected group of 39 workers and compared to 34 controls matched for gender, age, and habit. Smoking and age were considered as modulating factors. Both SCE and CA frequencies in coal miners appeared significantly higher than in controls. Similarly, there was a significant increase in the frequency of total micronuclei in exposed group as compared to control group. The effect of smoking on the level of SCE and MN was significant in the control group. A positive correlation between the age and the level of SCE was also found in controls. The frequencies of both SCE and CA were significantly enhanced with the years of exposure. The results of this study demonstrated that occupational exposure to coal mine dust leads to a significant induction of cytogenetic damage in peripheral lymphocytes of workers engaged in underground coal mining.     

Cytogenetic analysis of peripheral blood lymphocytes in workers exposed to vinyl chloride

In the present study, the method of cytogenetic analysis of peripheral blood lymphocytes was used to examine 43 workers exposed to vinyl chloride monomer (average exposure 11.2 years) and 22 subjects selected from the same locality (control group). A total number of 8650 metaphases were analysed. All cytogenetic parameters examined were increased in the exposed group as compared to the control group and 3 parameters, chromatid breaks, percentage of aberrant cells and breaks per cell, were significantly increased (P less than 0.001).     

Chromosomal aberrations in patients with primary biliary cirrhosis

Summary Chromosomal aberrations in untreated lymphocyte cultures, bleomycin (BLM)-induced aberrations and sister chromatid exchanges (SCE) in the peripheral blood lymphocytes of 11 patients suffering from primary biliary cirrhosis (PBC) and 14 matched control individuals were analysed. The lymphocytes of the PBC patients had on average a lower mitotic index (2.3) compared with controls (3.5) in the untreated cultures. The mean baseline rate of aberrations of the cultured lymphocytes of the patients was 5.3 aberrations per 100 metaphases (%); this was significantly different (P=0.0291) from that of the controls with a mean of 2.3%. In lymphocytes of the patients and controls, most of the aberrations observed took the form of gaps; there was an almost equal breakage rate in both groups (0.5% and 0.4%, respectively). The average number of mitoses with aberrations in the PBC patients studied was double that of the controls (4.9% and 2.3% respectively, P=0.0323). The mean number of the BLM-induced aberrations was 54.0% and 27.7% for the lymphocytes of the patients and controls, respectively. The mean number of the aberrant mitoses in the BLM cultures was 6 times higher than that of the untreated cultures for both groups, 25.7% and 14.6% respectively (P=0.018). The chromosomal distribution of baseline and induced aberrations was not random. The PBC patients had a mean number of 8.7 SCE per mitosis, which was significantly higher than the SCEs in the controls (6.3 SCE per mitosis; P=0.0156). The evidence suggests that the chromosomes of the lymphocytes of PBC patients may be less stable than those of the control individuals in this study.     

Leather tanning workers: chromosomal aberrations in peripheral lymphocytes and micronuclei in exfoliated cells in urine

A cytogenetic study was performed on workers of a leather tanning industry. Two different approaches for the biological monitoring of the individuals were used: chromosomal aberration analysis in peripheral lymphocytes and the frequency of micronucleated cells exfoliated in urine samples. 26 men working in the sections considered to present a greater risk were included in the study. Controls were 20 men that were not exposed to chemicals. The percentage of abnormal cells was higher in workers than in controls. Smokers showed higher values of chromosome breaks than non-smokers in both groups. These differences were not statistically significant. The percentage of cells with chromatid and chromosome gaps in workers and controls was different (p less than 0.01). A slight but not significant increase in the mean percentage of micronuclei was observed in the exposed group. We conclude that exposure to chemicals during leather tanning did not produce genotoxic effects measured by chromosomal aberrations in peripheral lymphocytes and micronuclei in urine in this group of workers.     

Cytogenetic damage in the buccal epithelium of Brazilian aviators occupationally exposed to agrochemicals

The frequency of micronuclei in both buccal cells and peripheral blood lymphocytes is extensively used as a biomarker of chromosomal damage and genome stability in human populations. We examined whether prolonged exposure to complex mixtures of pesticides leads to an increase in cytogenetic damage. The exposed group comprised 50 agricultural aviators, mainly from Central and Southeast regions of Brazil, who had inhaled agrochemicals for more than 10 years without personal protection equipment; the control group consisted of 17 men from the same regions, without indication of exposure to pesticides, There were three times higher frequencies of micronuclei (P < 0.05) and 2.5 times higher frequencies of binucleated cells in the aviators when compared to controls. However, cytotoxic alterations such as broken eggs and karyorrhexis did not present statistically significant differences between the exposed and control groups. Therefore, diverse agrochemicals used to combat pests in agriculture possess genotoxic effects in the oral mucosa of the agricultural pilots, as showed in this study.