Sister-chromatid exchanges in association with occupational exposure to ethylene oxide

Sister-chromatid exchange (SCE) frequencies in employees potentially exposed to ethylene oxide (ETO) were compared with those in unexposed control groups. Three worksites where the previous environmental control of ETO was known to have differed were chosen. Within these worksites, subjects were categorized into high potential exposed, low potential exposed and control groups. An additional community control group was obtained. Blood samples for chromosome studies of peripheral lymphocytes were drawn at several time points over a period of 24 months. The effects on SCE of age, sex, smoking habits and reader variation were considered. Worksites I, II and III, respectively, represented increasing levels of exposure. At Worksite III large differences among groups persisted over 24 months. At Worksite II, the SCEs in the high potential exposed workers were higher than those in the other groups. At no time was the low potential exposed group at Worksite II statistically significantly higher in mean SCE than the worksite controls. No consistent differences among groups were noted in Worksite I.     

Biological monitoring of workers in the rubber industry. I. Chromosomal aberrations and sister-chromatid exchanges in lymphocytes of vulcanizers

To evaluate the possible genetic consequences of the industrial exposure among the vulcanizers of a rubber plant we measured the in vivo levels of chromosomal aberrations and sister-chromatid exchanges in peripheral lymphocytes of 34 vulcanizers and in an adequate control population. The observed chromosomal aberration frequencies were 1.9 +/- 1.4 aberrations/100 cells in the exposed group and 2.1 +/- 1.5 aberrations/100 cells in the controls. No difference was found between the two groups for the mean value of sister-chromatid exchanges (5.2 +/- 1.3 in the exposed, 5.2 +/- 0.7 in the control group). Cigarette-smoking was clearly associated with increased sister-chromatid exchange frequencies both in the exposed and in the control groups, while chromosomal aberration frequencies were not correlated with smoking habits.     

Chromosome aberrations and sister-chromatid exchange frequencies in pathology staff occupationally exposed to formaldehyde

Past studies have shown that formaldehyde is mutagenic in microbial tests and Drosophila and causes chromosomal aberrations in cultured mammalian cells. Chromosomal analysis of bone marrow cells and spermatocytes from exposed laboratory animals has failed to show any genotoxic effect. Information on individuals occupationally exposed is limited and there is no evidence to date that formaldehyde can induce chromosome damage at occupational levels of exposure. This study examines the chromosome aberration and sister-chromatid exchange frequencies in lymphocytes from a group of 6 pathology workers and 5 unexposed controls. No detectable differences could be found between the groups in either chromosomal aberration induction or sister-chromatid exchange frequencies.     

Chromosome aberrations in workers of nuclear-power plants

The frequencies of chromosome aberrations in 135 workers from nuclear-power plants were compared with those in 135 age-matched controls. A total of 135,000 cells was scored. The frequencies of dicentric chromosome were 1.67 × 10⁻³ in the exposed group and 0.49 × 10⁻³ in the control group and those of chromosome-type deletion were 3.33 × 10⁻³ and 1.10 × 10⁻³, respectively. The frequencies of all types of chromosome aberrations in the exposed subjects were higher than those in the control group, but no significant trend of dose-dependent increase was observed when only the exposed group were considered. Poisson regression analysis, with both exposed and control included, showed that there was a significant association of chromosome aberration with radiation dose and the duration of work, but not with age, smoking habit and alcohol intake. It was also found that recent exposure to radiation, within the last 5 years, had contributed more to the observed chromosome aberration than earlier exposure.     

Cytogenetic analysis in workers occupationally exposed to nickel carbonyl

Chromosomal aberration and sister-chromatid exchange (SCE) base-line frequencies and SCE frequencies induced by 10 ng/ml mitomycin C (MMC) were analysed in cultured peripheral lymphocytes of 65 workers occupationally exposed to nickel carbonyl Ni(CO)4. The subjects were divided into 4 groups: (1) control; (2) exposed to nickel carbonyl (= exposed); (3) cigarette smokers; (4) smoking-exposed. The results show that there are no significant differences in chromosomal aberration frequencies, breaks or gaps, between the various groups. However, the SCE base-line frequency of the smoking-exposed group, with an average of 7.7/cell, was significantly higher than that of the control group, with an average of 6.5/cell (P less than 0.01), and also than that of the exposed group with an average of 5.9/cell (P less than 0.01). Similarly, the SCE frequency induced by 10 ng/ml MMC in the smoking-exposed group which averaged 15.5/cell was significantly higher than that of the control group (average of 13.2/cell (P less than 0.05], and also than that of the exposed group with an average of 12.3/cell (P less than 0.01). Under our experimental conditions, it may be that the level of exposure was not high enough to elicit an increase in chromosomal aberrations and SCE frequencies in the non-smoker exposed group. The fact that an increase in SCE frequencies was only found in the smoking-exposed group implies that the two factors, smoking and exposure to nickel carbonyl, are jointly responsible for the result.     

Chromosomal aberrations in humans as genetic endpoints to assess the impact of pollution

The chromosomal aberration assay with peripheral blood lymphocytes has been used routinely during the last three decades to survey exposure of humans to various genotoxic agents. A large number of biomonitoring studies are based on this genetic endpoint. A great deal of data exists on occupational, life-style or medical exposure situations but less evidence of the validity of the assay is available with regards to environmental exposure. In the present paper we report our investigations on the impact of pollution in two different populations using chromosomal aberrations in human peripheral blood lymphocytes as a biomarker of chronic exposure to heavy metals and dioxins/furans for a long period and as a biomarker of acute exposure to accidentally released vinyl chloride in the air. In order to study genotoxic effects (chromosomal aberrations) of heavy metals and dioxins/furans, 52 exposed individuals from a polluted area were compared to 51 matched controls from a distant non-industrialized area. A statistically significant increase was observed in the frequency of chromosomal aberrations in peripheral blood lymphocytes from the exposed population (1.90% aberrant cells vs. 1.11% for the controls). In the case of the vinyl chloride accident, chromosomal aberrations were analyzed in peripheral blood lymphocytes from 29 potentially exposed and 29 non-exposed individuals (matched controls). The exposed group showed a statistically significant increase in the frequency of aberrant cells (1.47% vs. 1.07% for 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.     

The effect of age and low-dose irradiation on the chromosomal aberration frequency in human lymphocytes

The effect of age and of low-dose irradiation on the base level of chromosomal aberrations in lymphocytes was studied in two human groups: control one (128 people) and exposed in past to uncontrolled low-dose irradiation (283 people). In exposed group the frequencies of all types of chromosome aberrations were higher comparing to control group. For the investigation of the age response of the number of chromosomal aberrations three statistical approaches were used: correlation analysis of individual data, correlation analysis of mean frequencies of chromosomal aberrations for 10 years intervals, comparison of 3 age groups (young, middle age and old). In control group the significant increase of the level of chromosomal aberrations with age was found only when six 10-year intervals were analysed. In exposed group significant age increase of chromosomal aberration frequency (particularly due to double fragments) was observed with all 3 approaches. Low-dose irradiation of people is supposed to cause the functional defects of repair systems, controlling the level of genetic damages and they accumulate more intensive through age.     

Lymphocyte proliferation kinetics and genotoxic findings in a pilot study on individuals chronically exposed to arsenic in Mexico

In the search for early biological markers to detect genetic damage, a pilot study on a hydroarsenicism-exposed group was designed. Blood and urine samples were taken from 11 individuals chronically exposed and from 13 individuals with lower exposure to the metal. Lymphocyte cultures for cytogenetic studies and HGPRT assay were done with coded peripheral blood samples, while arsenic levels and the “rec assay” in B. subtilis were determined in urine samples. The highly exposed group excreted greater amounts of As, nevertheless the rec assay showed negative results. An interesting finding is that the cell-cycle kinetics exhibited a significant difference between the groups studied, the average generation time (AGT) was longer in the highly exposed group. The percentages of chromosomal aberrations and the frequencies of sister-chromatid exchanges were similar in both populations, although complex aberrations were more frequent in the highly exposed group, which also showed a higher average variation frequency in the HGPRT assay, but the 2 latter observations were not statistically significant. The lag in lymphocyte proliferation could mean an impairment of the immune response due to arsenic exposure.     

Cytogenetic investigation in lymphocytes of people living in cadmium-polluted areas

Chromosome aberrations were analyzed from peripheral lymphocyte cultures of 21 men and 19 women who had been exposed to environmental cadmium, and 11 controls (9 men and 2 women). The average cadmium level in the urine of the Cd-polluted group was 3.32 micrograms/l for men and 3.83 micrograms/l for women. There were significant differences in chromosome aberration frequencies between the Cd-polluted and non-polluted groups. The number of individuals with relatively high aberration frequencies (greater than or equal to 5%) in the Cd-polluted group was greater than in the controls. Individuals with a high cadmium content in urine (greater than or equal to 3 micrograms/l) had higher aberration frequencies and more severe aberration types in comparison with the low-cadmium group (less than 3 micrograms/l). There were significant correlations between chromosome aberration frequencies and urinary cadmium content (r = 0.463). The linear regression equation was determined. Considering the conflicting results in other published reports, it is hard to say that the conclusion that cadmium only acts synergistically to enhance the mutagenicity of other compounds present in the environment is correct. According to our study, environmental cadmium cannot only induce chromosome aberrations but also increases the chromosomal aberration frequencies and the frequency of severe aberration types.     

Cytogenetic biomonitoring of workers from laboratories of clinical analyses occupationally exposed to chemicals

A cytogenetic monitoring study was carried out on a group of workers in clinical analysis laboratories to investigate the risk of occupational exposure to chronic low levels of chemicals.Thirty-four clinical laboratories have been involved in the study. In these laboratories, toxicants and analytical procedures utilized have been characterized. The individual occupational exposure of workers was assessed by use of a questionnaire concerning the chemical substances utilized. About 300 different chemicals have been identified.Cytogenetic analyses (chromosomal aberration and micronucleus tests) were carried out on a strictly selected group of 50 workers enrolled from these laboratories and compared to 53 controls (healthy blood donors) matched for gender and age.The exposed group shows a significantly higher frequency of genetic damage than the control group. Both chromatid and chromosome aberration frequencies in workers appear significantly higher than in controls. Similarly, comparison between micronucleated cells rates of exposed and unexposed groups show significantly higher frequencies of binucleated cells with micronucleus (BNMN) and of total micronuclei (MN tot) in workers than in controls.     

Cytogenetic biomonitoring of workers from laboratories of clinical analyses occupationally exposed to chemicals

A cytogenetic monitoring study was carried out on a group of workers in clinical analysis laboratories to investigate the risk of occupational exposure to chronic low levels of chemicals.Thirty-four clinical laboratories have been involved in the study. In these laboratories, toxicants and analytical procedures utilized have been characterized. The individual occupational exposure of workers was assessed by use of a questionnaire concerning the chemical substances utilized. About 300 different chemicals have been identified.Cytogenetic analyses (chromosomal aberration and micronucleus tests) were carried out on a strictly selected group of 50 workers enrolled from these laboratories and compared to 53 controls (healthy blood donors) matched for gender and age.The exposed group shows a significantly higher frequency of genetic damage than the control group. Both chromatid and chromosome aberration frequencies in workers appear significantly higher than in controls. Similarly, comparison between micronucleated cells rates of exposed and unexposed groups show significantly higher frequencies of binucleated cells with micronucleus (BNMN) and of total micronuclei (MN tot) in workers than in controls.     

The Database for Analysis of Quantitative Characteristics of Chromosome Aberration Frequencies in the Culture of Human Peripheral Blood Lymphocytes

The data on spontaneous chromosome aberration rates in cultures of human peripheral blood lymphocytes obtained in the past 30 years have been collected to form a database. The database contains the results of analysis of more than 330 000 metaphases in lymphocytes from more than 1200 subjects. The frequency of aberrant metaphases in the control group has been estimated at 0.0213 ± 0.00085. No differences between sexes have been found with respect to either the total chromosome aberration rate or the rates of individual aberration types. The total chromosome aberration rate did not depend on age; however, it has been found that the number of fragments increased and the number of exchanges decreased with age. Smoking has been found to increase the frequency of chromosome aberrations in individuals with occupational hazards, but not in those who are not occupationally exposed to radiation or chemicals. Alcohol consumption increased the frequency of paired fragments, whereas the frequencies of other aberrations did not differ from the control values.     

The database for analysis of quantitative characteristics of chromosome aberration frequencies in the culture of human peripheral blood lymphocytes]

The data on spontaneous chromosome aberration rates in cultures of human peripheral blood lymphocytes obtained in the past 30 years have been collected to form a database. The database contains the results of analysis of more than 330,000 metaphases in lymphocytes from more than 1200 subjects. The frequency of aberrant metaphases in the control group has been estimated at 0.0213 +/- 0.00085. No differences between sexes have been found with respect to either the total chromosome aberration rate or the rates of individual aberration types. The total chromosome aberration rate did not depend on age; however, it has been found that the number of fragments increased and the number of exchanges decreased with age. Smoking has been found to increase the frequency of chromosome aberrations in individuals with occupational hazards, but not in those who are not occupationally exposed to radiation or chemicals. Alcohol consumption increased the frequency of paired fragments, whereas the frequencies of other aberrations did not differ from the control values.     

Stable intrachromosomal biomarkers of past exposure to densely ionizing radiation in several chromosomes of exposed individuals

A multicolor banding (mBAND) fluorescence in situ hybridization technique was used to investigate the presence inhuman populations of a stable biomarker-intrachromosomal chromosome aberrations-of past exposure to high-LET radiation. Peripheral blood lymphocytes were taken from healthy Russian nuclear workers occupationally exposed from 1949 onward to either plutonium, gamma rays or both. Metaphase spreads were produced and chromosomes 1 and 2 were hybridized with mBAND FISH probes and scored for intra-chromosomal aberrations. A large yield of intrachromosomal aberrations was observed in both chromosomes of the individuals exposed to high doses of plutonium, whereas there was no significant increase over the (low) background control rate in the population who were exposed to high doses of gamma rays.Interchromosome aberration yields were similar in both the high plutonium and the high gamma-ray groups. These results for chromosome 1 and 2 confirm and extend data published previously for chromosome 5. Intrachromosomal aberrations thus represent a potential biomarker for past exposure to high-LET radiations such as alpha particles and neutrons and could possibly be used as a biodosimeter to estimate both the dose and type of radiation exposure in previously exposed populations.     

Cytogenetic analysis of peripheral blood lymphocytes in workers exposed to benzene

In the present study, the method of cytogenetic analysis of peripheral blood lymphocytes was used to investigate 66 workers exposed to benzene, and 20 individuals selected from general population from the same locality, not exposed to particular mutagenic or carcinogenic agents (control group). Altogether, 8,600 metaphases were analysed. Frequencies of aberrant cells, including chromatide and chromosomal breaks, and chromatide and chromosomal exchanges, were scored in both groups. A very slight increase in aberrant cell frequencies (2.152% aberrant cells) was observed in the professional exposure group as compared to the control group (1.6% aberrant cells). Increased frequencies of aberrant cells were found in smokers of both the benzene-exposed and the control group. The differences were however not significant. In addition to cytogenetic examination, the workers underwent a general examination of their health condition (preventive examination). Benzene exposure seemed to have no injurious effect on the state of health of exposed workers. Biochemical and haematological tests gave normal values.     

Level of chromosome aberrations in peripheral blood lymphocytes in evacuees from the 30-kilometer zone of the Chernobyl Atomic Energy Station and residents of radioactively-polluted territories in the long term after the Chernobyl accident

Eighteen Ukrainian evacuees from the Chernobyl exclusive zone, twenty one inhabitants of radioactively contaminated areas of Belarus and twelve control donors age-matched to the exposed persons were investigated 14-15 years after the Chernobyl accident for chromosomal aberration yields detected in blood lymphocytes by fluorescence in situ hybridisation technique. Unstable aberration yields measured in both Chernobyl cohorts were close to the background frequencies. Positive age-dependence trends in control donors were determined for the all type stable aberration levels. In evacuees the tendency for diminishing the difference between them and controls for stable aberration levels with persons' age increasing was found. The total stable chromosome exchange yields in evacuees 46-55 years old and inhabitants of areas with low contamination level didn't exceed the control values, but for younger evacuees and inhabitants of sufficiently contaminated regions the statistical increase above the age relevant background meanings was detected for this end-point. The advantages of using the FISH-detectable stable aberrations and particularly the total level of stable chromosome exchanges as the end-points for retrospective biological indication of past radiation exposure in Chernobyl cohorts were discussed.     

Unusually high level of chromosome variability in cultured human peripheral blood lymphocytes]

A cytogenetic examination carried out in the inhabitants of Seversk (Tomsk oblast) and workers of the Siberian chemical industrial complex (a complex of nuclear-chemical and fuel plants), living in the same town, revealed unusually high level of spontaneous chromosomal variability both in control and industrial groups (total irradiation doses 1.8 to 3.7 and 9.3 to 15.7 Gy, respectively). The frequencies of cells with chromosomal aberrations (estimated per 100 cells) in control and industrial groups were 4.69, 6.04, and 6.64, respectively, and the total number of aberrations constituted 6.93, 8.47 and 12.06, respectively. These frequencies were several times higher compared to the summarized literature data on the control levels. The high average aberration level was caused by the elevated proportion of chromatid-type aberrations and paired fragments. The reasons for this are unclear. The levels of radioactive background and chemical air pollution in the town were not increased.     

Chromosome painting for cytogenetic monitoring of occupationally exposed and non-exposed groups of human individuals

The suitability of a three-color fluorescence in situ suppression hybridization technique was examined for monitoring five different groups of individuals: 30 occupied in radiology, 26 occupied in nuclear medicine or radiation physics, 32 patients with breast cancer, 26 occupied with military waste disposal, all presumably exposed to low doses of radiation or chemical mutagens and a non-exposed control group (N=29). The average frequency of breaks constituting the various aberrations did not significantly differ between the groups of medical radiation appliers and the control group. However, breast tumor patients and military waste disposers, as groups, showed a higher aberration rate than did healthy controls. Stable rearrangements mainly characterized the groups of controls, tumor patients, and radiation appliers, while a higher proportion of unstable aberrations was found in the chemically exposed individuals. Individuals with an increased frequency of aberrations could be detected within each examined group, which clearly determined the average values of the whole group. With respect to interchromosomal distribution of the breakpoints constituting the found aberrations and the involvement of the labeled chromosomes in rearrangements, the observed values were very close to the expected ones in the controls. A rather similar trend of deviations from expectation was observed in all other groups. Chromosome 4 was slightly over-affected, while chromosome 2 was slightly underrepresented in all analyzed groups (except tumor patients). Rearrangements of the labeled chromosomes with the unlabeled ones exceeded expectation. In conclusion, chromosome painting if included in further attempts of human population monitoring will broaden the basis of argumentation with respect to health risks introduced by mutagen exposure.     

The effect of functional inactivation of TP53 by HPV-E6 transformation on the induction of chromosome aberrations by gamma rays in human tumor cells

The influence of expression of TP53 (formerly known as p53) on the induction of chromosome aberrations by gamma rays was examined in an isogenic pair of human tumor cell lines where TP53 expression was normal or inactivated by human papillomavirus (HPV) type 16 E6 expression. Plateau-phase cultures were exposed to 0-8 Gy gamma rays and then either immediately released by subculture or held for 24 h prior to subculture and subsequent cytogenetic analysis. Aberration frequency was determined only in cells entering their first mitosis after irradiation, and cells were sampled over a 48-h period to include cells whose progression into mitosis was delayed. While aberration frequencies were similar at early harvest times, there was evidence for a subpopulation of more heavily damaged cells in the E6-transformed cells that cycled into late mitosis. Holding cells noncycling for 24 h to allow repair of potentially lethal damage eliminated this subpopulation of more heavily damaged cells. The E6-transformed cells also had higher levels of chromatid-type aberrations and sister chromatid exchanges, consistent with an additional defect in kinetics of repair of base damage that is associated with the E6 transformation. Holding cells noncycling for 24 h eliminated the elevated levels of chromatid-type aberrations and sister chromatid exchanges. These studies demonstrate that E6 transformation of human tumor cells will influence both the frequency and types of chromosome aberrations observed after radiation exposure, and that these effects are related to the expression of potentially lethal damage.