Gasoline pump mechanics had increased frequencies and sizes of micronuclei in lymphocytes stimulated by pokeweed mitogen

Derivation of an occupational exposure limit for benzene using epidemiological study quality assessment tools

This paper derives an occupational exposure limit for benzene using quality assessed data. Seventy-seven genotoxicity and 36 haematotoxicity studies in workers were scored for study quality with an adapted tool based on that of Vlaanderen et al., 2008 (Environ Health. Perspect. 116 1700-5). These endpoints were selected as they are the most sensitive and relevant to the proposed mode of action (MOA) and protecting against these will protect against benzene carcinogenicity. Lowest and No- Adverse Effect Concentrations (LOAECs and NOAECs) were derived from the highest quality studies (i.e. those ranked in the top tertile or top half) and further assessed as being "more certain" or "less certain". Several sensitivity analyses were conducted to assess whether alternative "high quality" constructs affected conclusions. The lowest haematotoxicity LOAECs showed effects near 2 ppm (8 h TWA), and no effects at 0.59 ppm. For genotoxicity, studies also showed effects near 2 ppm and showed no effects at about 0.69 ppm. Several sensitivity analyses supported these observations. These data define a benzene LOAEC of 2 ppm (8 h TWA) and a NOAEC of 0.5 ppm (8 h TWA). Allowing for possible subclinical effects in bone marrow not apparent in studies of peripheral blood endpoints, an OEL of 0.25 ppm (8 h TWA) is proposed.

Induced cytotoxic damage by exposure to gasoline vapors: a study in Sinaloa, Mexico

Gasoline is a blend of organic compounds used in internal combustion engines. Gasoline-station attendants are exposed to gasoline vapors, which pose a potentially mutagenic risk. According to the International Agency for Research on Cancer, exposure to gasoline and engine exhaust is possibly carcinogenic to humans. We determined the frequency of micronucleus and other nuclear abnormalities, such as pyknotic nuclei, chromatin condensation, cells with nuclear buds, karyolytic cells, karyorrhexis, and binucleated cells in buccal mucosal smears of 60 gasoline-station attendants and 60 unexposed controls. In addition, we explored if factors such as smoking habits, alcohol consumption, and worked years exert an additional synergistic cytotoxic effect. There were statistically significant higher frequencies (p < 0.05) of nuclear abnormalities among exposed attendants compared to the controls. No statistical significant (p > 0.05) additional effect of lifestyle habits such as smoking and alcohol consumption or worked years on the cytotoxicity was observed. The results showed that from the beginning exposure to gasoline vapors increased the frequency of nuclear abnormalities in buccal epithelial cells. Our results provide valuable information on cytotoxic damage for an early pre-symptomatic diagnosis.

Cytogenetic biomonitoring in petrol station attendants: A micronucleus study

Background:

Benzene, which is a major organic product, on chronic exposure can result in many malignant disorders, and therefore exposure to gasoline vapors is classified by the International Agency for Research of Cancer as possible carcinogenic to humans. Petrol station attendants are chronically exposed to petroleum derivatives through inhalation of petrol during vehicle refuelling.

Aim:

This study is aimed to investigate cytogenotoxic damage in exfoliated buccal cells obtained from petrol station workers and control subjects using micronucleus (MN) test.

Materials and Methods:

This study was carried out on 30 petrol station attendants working at different petrol stations located in Indore. The control group consisted of 30 healthy subjects who were not exposed to benzene. Buccal cell samples were collected at the end of the work shift. Slides were stained and were evaluated to determine the MN frequencies. Exposure monitoring was performed by the detection of phenol excreted in the urine. Urinary phenol measurements were performed following the colorimetric quantitative determination method of Yamaguchi and Hayashi.

Results:

Variations in MN frequencies were seen in control and petrol bunk attendants.

Conclusion:

The MN test in exfoliated epithelial cells seems to be a useful biomarker of occupational exposure to genotoxic chemicals. Phenol is the principal metabolite of benzene. Therefore, phenol concentration in the urine of exposed workers can be used as a biomarker of external exposure.

Risk of leukemia as a result of community exposure to gasoline vapors: a follow-up study

OBJECTIVES

To assess the temporal and spatial relationship of risk for total leukemia and AML (acute myelogenous leukemia) among community residents of an area in northeastern (NE) Pennsylvania (PA) affected by the Tranguch Gasoline Spill which occurred in the early 1990s.

METHODS

Standardized incidence ratios (SIR) were calculated for total leukemia and AML among 625 residents affected by the gasoline spill in relation to both PA and local county cancer incidence rates. The risk of total leukemia and AML among the gasoline exposed population was evaluated for the period prior to the spill, 1985-1989; during the time surrounding the spill, 1990-1994; and for a period subsequent to the spill, 1995-2001.

RESULTS

The incidence of total leukemia and AML was significantly elevated subsequent to the spill for the entire period 1990-2001 and was highest for the period 1995-2001, whether comparison was made to PA or local county leukemia rates. Based on comparison to PA rates, the SIRs for total leukemia and AML were 7.69 (95% CI=1.58-22.46) and 11.54 (95% CI=2.38-33.69) for the 1995-2001 period, respectively. Prior to the spill, 1985-1989, and during the period of the spill, 1990-1994, no cases of leukemia were identified among the affected residents.

CONCLUSIONS

These results suggest a possible association between chronic low level benzene exposure and increased risk of leukemia among residents of the Tranguch Spill Site in NE PA. Our study provides additional support to the growing body of evidence implicating low level benzene exposure and cancer risk. We recommend that other communities contaminated with gasoline vapor through leaking underground storage vessels be monitored for elevated risk of leukemia.

The IARC october 2009 evaluation of benzene carcinogenicity was incomplete and needs to be reconsidered

I have been familiar with the toxicological and epidemiological literature on benzene since I was a member of the NIOSH Benzene Task Force in 1975. I also am familiar with the procedures of IARC Monographs meetings from past participation, and as observer I applied this experience to the Monograph 100 F review. In October of 2009, a Working Group (WG) of the International Agency for Research on Cancer (IARC) met in Lyon, France to evaluate the available evidence for site-specific cancer to humans for 33 chemical agents and related occupations previously categorized by IARC as human carcinogens. Generally, review and discussion of the epidemiological cancer literature related to benzene was limited due to the enormous amount of material needing to be covered since the last full monograph meeting on benzene in 1981, and because 32 other chemicals and occupations were also being evaluated. Moreover, among the 33 chemicals and occupations reviewed, there was some inconsistency in the use of studies for evaluating various cancers. In some situations, consideration could have been given to the inclusion of relevant unpublished, but readily available study results. Discussion and synthesis of the animal cancer studies and mechanistic data related to specific cancers also were limited. IARC's conclusion that there is sufficient evidence for benzene to cause acute non-lymphocytic leukemia only was based on an incomplete review. IARC should schedule another monographs meeting dedicated to a complete and full review and discussion of all potential cancers related to exposure to benzene and to benzene-containing mixtures.

Biomonitoring of oral epithelial cells in petrol station attendants: comparison between buccal mucosa and lateral border of the tongue

Owing to the influence of geno- and cytotoxicity on chemical carcinogenesis, studies have demonstrated that petroleum derivatives are able to induce genetic damage and cellular death with conflicting results so far. The aim of the present study was to comparatively evaluate DNA damage (micronucleus) and cellular death (pyknosis, karyolysis and karyorrhexis) in exfoliated oral mucosa cells from gas petrol attendants using two different anatomic buccal sites: cheek mucosa and lateral border of the tongue. A total of 23 gas petrol attendants and 23 health controls (non-exposed individuals) were included in this setting. Individuals had epithelial cells from cheek and lateral border of the tongue mechanically exfoliated, placed in fixative and dropped in clean slides which were checked for the above nuclear phenotypes. The results pointed out significant statistical differences (p<0.05) of micronucleated oral mucosa cells from gas petrol attendants for both oral sites evaluated. In the same way, petroleum derivate exposure was able to increase other nuclear alterations closely related to cytotoxicity such as karyorrhexis, pyknosis and karyolysis, being the most pronunciated effects as those found in the lateral border of the tongue. No interaction was observed between smoking and petroleum exposure. In summary, these data indicate that gas petrol attendants comprise a high risk group for DNA damage and cellular death. It seems that the lateral border of the tongue is a more sensitive site to geno- and cytotoxic insult induced by petroleum derivates.

Genotoxicity of benzene and its metabolites

The potential role of genotoxicity in human leukemias associated with benzene (BZ) exposures was investigated by a systematic review of over 1400 genotoxicity test results for BZ and its metabolites. Studies of rodents exposed to radiolabeled BZ found a low level of radiolabel in isolated DNA with no preferential binding in target tissues of neoplasia. Adducts were not identified by 32P-postlabeling (equivalent to a covalent binding index <0.002) under the dosage conditions producing neoplasia in the rodent bioassays, and this method would have detected adducts at 1/10,000th the levels reported in the DNA-binding studies. Adducts were detected by 32P-postlabeling in vitro and following high acute BZ doses in vivo, but levels were about 100-fold less than those found by DNA binding. These findings suggest that DNA-adduct formation may not be a significant mechanism for BZ-induced neoplasia in rodents. The evaluation of other genotoxicity test results revealed that BZ and its metabolites did not produce reverse mutations in Salmonella typhimurium but were clastogenic and aneugenic, producing micronuclei, chromosomal aberrations, sister chromatid exchanges and DNA strand breaks. Rodent and human data were compared, and BZ genotoxicity results in both were similar for the available tests. Also, the biotransformation of BZ was qualitatively similar in rodents, humans and non-human primates, further indicating that rodent and human genotoxicity data were compatible. The genotoxicity test results for BZ and its metabolites were the most similar to those of topoisomerase II inhibitors and provided less support for proposed mechanisms involving DNA reactivity, mitotic spindle poisoning or oxidative DNA damage as genotoxic mechanisms; all of which have been demonstrated experimentally for BZ or its metabolites. Studies of the chromosomal translocations found in BZ-exposed persons and secondary human leukemias produced by topoisomerase II inhibitors provide some additional support for this mechanism being potentially operative in BZ-induced leukemia.

Micronucleus induction in human B and T lymphocytes separated by an immunomagnetic technique

Micronuclei were induced in human lymphocytes by mitomycin C or gamma radiation. After the incubation the cells were separated in B- and T-cells by an immunomagnetic method, i.e., Dynabeads. The cultures were stimulated by PHA. The effect of different incubation times (60-110 h) as well as different doses of mitomycin C (0-100 nmol/l) and gamma radiation (0-2 Gy) at an incubation time of 72 h were studied. There were significantly higher frequencies of micronuclei in B- than in T-cells, when micronuclei were induced by mitomycin C. This was not found with gamma radiation, probably because of a cytotoxic effect of this agent on the B-cells.

Lack of correlation between environmental or biological indicators of benzene exposure at parts per billion levels and micronuclei induction

Despite growing concern for possible carcinogenic effects associated with environmental benzene exposure in the general population, few studies exist at parts per billion (ppb) levels. We investigated the existence of a relationship between airborne/biological measurements of benzene exposure (i.e., personal/area sampling and unmodified urinary benzene/trans,trans-muconic acid; t,t-MA) and micronuclei induction (cytochalasin B technique) among exposed chemical laboratory workers (n=47) and traffic wardens (n=15). Although urinary t,t-MA (106.9+/-123.17 microg/L(urine)) correlated (R(2)=0.37) with urinary benzene (0.66+/-0.99 microg/L(urine)), neither biological measurement correlated with environmental benzene exposure (14.04+/-9.71 microg/m(3); 4.39+/-3.03ppb), suggesting that, at ppb level (1ppb=3.2 microg/m(3)), airborne benzene constitutes a fraction of the total intake. Traffic wardens and laboratory workers had comparable numbers of micronuclei (4.70+/-2.63 versus 5.76+/-3.11; n.s.), similar to levels recorded in the general population. With univariate/multivariate analysis, no association was found between micronuclei induction and air/urinary benzene exposure variables. Notably, among the personal characteristics examined (including age, gender, smoking, drinking, etc.), high body mass index correlated with micronuclei induction while, among females, use of hormonal medication was associated with less micronuclei. Thus the present study provides no evidence that ppb levels of environmental benzene exposure appreciably affect micronuclei incidence (against the background of other relevant factors). However, this should not be taken as an argument against efforts aiming to reduce environmental benzene pollution.

The use of non-tumor data in cancer risk assessment: reflections on butadiene, vinyl chloride, and benzene

The estimation and characterization of a cancer risk is grounded in the observation of tumors in humans and/or experimental animals. Increasingly, however, other kinds of data (non-tumor data) are finding application in cancer risk assessment. Metabolism and kinetics, adduct formation, genetic damage, mode of action, and biomarkers of exposure, susceptibility, and effects are examples. While these and other parameters have been studied for many important chemicals over the past 30-40 years, their use in risk assessments is more recent, and new insights and opportunities are continuing to unfold. To provide some perspective on this field, the ILSI Risk Science Institute asked a select working group to characterize the pertinent non-tumor data available for 1,3-butadiene, benzene, and vinyl chloride and to comment on the utility of these data in characterizing cancer risks. This paper presents the findings of that working group and concludes with 15 simple principles for the use of non-tumor data in cancer risk assessment.

The nature of chromosomal aberrations detected in humans exposed to benzene

Benzene is an established cause of human leukemia that is thought to act by producing chromosomal aberrations and altered in cell differentiation. In several recent studies increased levels of chromosomal aberrations in peripheral blood lymphocytes were correlated with a heightened risk of cancer, especially hematological malignancies. Thus, chromosomal aberrations may be a predictor of future leukemia risk. Previous studies exploring whether benzene exposure induces chromosomal aberrations have yielded mostly positive results. However, it remains unclear whether the chromosomal aberrations induced by benzene occur in a distinct pattern. Here, we thoroughly review the major chromosome studies published to date in benzene-exposed workers, benzene-poisoned and preleukemia patients, and leukemia cases associated with benzene expose. Although three cytogenetic markers (chromosomal aberrations, sister chromatid exchanges, and micronuclei) are commonly examined, our primary focus is on studies of chromosomal aberrations, because only this marker has so far been correlated with increased cancer risk. This review surveys the published literature, analyzes the study results, and discusses the characteristics of effects reported. In most studies of currently exposed workers, increases in chromosomal aberrations were observed. However, due to the relatively small number of affected individuals and variability in the reported aberrations, firm conclusions cannot be made about the involvement of specific chromosomes or chromosome regions. Further, in leukemia cases associated with benzene exposure, there is no evidence of a unique pattern of benzene-induced chromosomal aberrations in humans. Leukemia cases associated with benzene exposure are, however, more likely to contain clonal chromosome aberrations then those arising de novo in the general population.

Genotoxicity biomonitoring in regions exposed to vehicle emissions using the comet assay and the micronucleus test in native rodent Ctenomys minutus

Exposure to motor vehicle emissions represents an important concern for possible long-term health effects. The present report describes: 1) the application and verification of the alkaline comet assay in Ctenomys minutus to detect the possible genotoxicity of automobile emissions; 2) a comparison of the comet assay results with peripheral blood micronucleus (MN) assay results performed in the same animals; and 3) the identification of agents involved in the responses and in the seasonal variation of the effects. Ctenomys minutus (Octodontidae-Rodentia) were captured in two different fields from both sides of RS/030, a highway on the coastal plain of the Brazilian state of Rio Grande do Sul. Reference animals were obtained from a nearby field that was about 3 km distant from any road. By the end of this study, 123 rodents (73 females and 50 males) were live-trapped. Our results indicate that there was an increase in cells with DNA damage for C. minutus environmentally exposed to automobile emissions, as demonstrated by the alkaline comet assay, but there was no increase in micronucleated cells. The alkaline comet assay showed age and gender differences in the response. The comet assay results suggest that adult females are the principal population affected by air pollutants from vehicle emissions. Chemical data were also collected from areas exposed to automobile exhaust and these indicated that elevated levels of hydrocarbons, metals, and NO(2) were associated with the elevated levels of damaged cells observed in the wild rodent C. minutus. Our results agree with previous data on engine and fuel components, where weak increases in damage for native rodents exposed to emissions have been observed. Other larger, controlled studies are needed to better understand how the metabolism of C. minutus affects its response to emission exposure.

Lymphocyte DNA damage in bus manufacturing workers

To study the effect of occupational exposure, smoking, and drinking on lymphocyte DNA damage in bus manufacturing workers, 346 employees (106 women and 240 men) from six job categories (welders, mechanics, painters, and assembling, auxiliary and managerial workers) in a bus manufacturing factory in Guangzhou were included. Significant differences of tail moment among the six job categories were found (P=0.003) with adjustment for age and gender. Smoking increased tail moment significantly (3.14 (2.89-3.40) versus 2.79 microm (2.63-2.97), P=0.023). Analysis of covariance showed that occupational exposure (P=0.001) and smoking (P=0.019) had significant effect on tail moment after adjusting for all factors, whereas age and gender had no effect on DNA damage. Stratified analysis showed that painters (P=0.002), auxiliary workers (P=0.011), and mechanics (P=0.044) had larger tail moments than managerial workers after adjusting for age, gender, smoking, and drinking.

Sister chromatid exchange (SCE) and micronucleus (MN) frequencies in lymphocytes of gasoline station attendants

Peripheral blood lymphocytes from 22 men with low average exposure (229 micrograms/m3 = 0.72 ppm) to benzene and 19 control men were investigated for Sister Chromatid Exchange (SCE) frequency. The majority of the men (21 exposed, 19 controls) were also investigated using the micronucleus assay (MN). The exposed subjects were employed at 10 different gas stations in or near the city (Bari/South Italy). SCE frequencies were significantly related with age and smoking habits, on the contrary no relation was observed between SCE and length of employment (SCE = 7.41 + 0.03.age (*) + 0.0001.length of employment (n.s.) + 0.03.cigarette consumption (*); F = 4.87; p < 0.01; (*) significant; (n.s.) non-significant). MN frequencies were significantly increased in relation with length of employment; but no relation was observed when age and smoking habits were taken into consideration (regression model: MN = 18.03 + 0.006.age (n.s.) + 0.32.length of employment (*) - 0.1.cigarette consumption (n.s.); F = 4.138; p < 0.05).

Determination of diesel genotoxicity in firebreathers by micronuclei and nuclear abnormalities in buccal mucosa

Diesel or its derivatives could have aneuploidogenic and/or clastogenic activity. Hence, the genotoxicity of diesel gases has been studied, considering exposure to them as potentially carcinogenic. The results obtained by different authors suggest the need to know the effects of direct and chronic exposure to diesel in humans, as in the case of the street workers called 'firebreathers' who fill their buccal cavity with diesel and then spread it to a burning torch many times during the day in order to give a 'dragon show' for 5 h a day and 6 days a week. The buccal samples of eight firebreathers were collected, processed and scored according to the criterion established by Tolbert et al., 1992 and then compared with positive and negative control groups. The results revealed that diesel was not micronucleogenic although it induces some nuclear abnormalities.

Comparison of DNA damage in peripheral blood and spleen lymphocytes using the single-cell gel assay

The alkaline single-cell gel (SCG) or 'comet' assay has been applied to the detection of DNA damage from a number of chemical and biological factors in vivo and in vitro. In the past, a number of cell types has been used with peripheral blood lymphocytes being the most readily accessible. This study was designed to determine whether lymphocytes sequestered in the spleen might prove more sensitive to DNA damage than those in the peripheral circulation. This would result in a more effective SCG assay. Baseline DNA length to width ratios for peripheral blood and splenic lymphocytes did not differ significantly from each other (1.27 and 1.21, respectively). Neither did ratios of lymphocytes from the two sources, sampled 20 and 48 h after injection with 100 mg/kg methyl methanesulfonate (MMS) (3.81 and 3.62 at 20 h, respectively; and 1.96 and 2.21 at 48 h, respectively). Recovery from MMS damage at 168 h postinjection was also not different in the two groups of cells (1.13 and 1.16, respectively). However, an examination of cell profiles of DNA damage showed that splenic lymphocytes had a significantly higher percentage of damaged cells (63.33%) than did peripheral blood lymphocytes (40.67%) 48 h postinjection. Of the hypotheses proposed for this difference, the most likely seems to involve the different proportions of B- and T-lymphocytes present in the peripheral blood and the spleen. Since the difference between peripheral blood and splenic lymphocytes was seen only at 48 h postinjection, the use of splenic lymphocytes in the SCG assay is not advantageous under most circumstances.

SCE analysis in peripheral blood lymphocytes of a group of filling station attendants

Petroleum derivatives constitute a complex mixture of chemicals which contain known genotoxicants. Thus, chronic occupational exposure to such derivatives may be considered to possess genotoxic risk. Service station attendants are workers exposed to petroleum derivatives and, as consequence, biomonitoring studies designed to evaluate the genetic risk are required. Here we present the data on sister chromatid exchange (SCE) frequencies, proliferation rate index (PRI) and cells with high frequency of SCE (HFC) from a group of 42 attendant workers. In addition, data from a group of 45 unexposed (controls) are presented. The results obtained indicate that there are no significant differences in SCE values between the exposed workers when compared to the non-exposed individuals. The only difference is found when smoking habit is considered, the smokers having significant increases in the SCE frequency. There is a slight increase in the HFC frequency of the occupationally exposed group but the difference did not attain statistical significance.

Biomonitoring study of a group of workers potentially exposed to traffic fumes

Risk assessment of environmental pollutants is concerned with the identification of compounds in the environment that might be hazardous to human health: measuring exposure levels, measuring cellular damage and then estimating the probability of harm occurring. The feasibility of such a comprehensive approach has been explored in this study of two groups of workers, one of which may be occupationally exposed to exhaust fumes. No statistically significant difference in cellular damage, as measured by the lymphocyte micronucleus assay, was found between these two groups of workers, although clear differences in exposure levels to volatile organic compounds were detected. A number of other factors identified in the study did show clear effects on micronucleus frequency.

No increase in micronuclei frequency in cultured blood lymphocytes from a group of filling station attendants

Service station attendants are workers that are definitely exposed to petroleum derivatives. Taking into account that this exposure has been considered to possess genotoxic risk, here we present data on the biomonitoring of a group of 50 service station workers and 43 controls. Micronuclei (MN) from peripheral blood lymphocytes has been considered as the genetic endpoint to be studied and, in addition, data on the concentration of aromatic hydrocarbons at the workplace, urinary metabolites and differential white blood cell count have also been analysed. The results obtained indicate no significant differences between petrol station attendants and controls, when the effects of petrol exposure were investigated by differential white blood cell count and analysis of MN frequencies in phytohaemagglutinin-stimulated lymphocytes. Regarding the urinary metabolites, a significant increase in the phenol level was found in the exposed workers.

Genetic effects of petroleum fuels: cytogenetic monitoring of gasoline station attendants

Workers in the petroleum distribution trades experience relatively high-level exposures to fuel vapours whose consequences have not been fully elucidated. In this study, the possible relationship between occupational exposure to petroleum fuels and cytogenetic damages in peripheral lymphocytes was investigated. Twenty-three male, non-smoking workers from the area of Rome were enrolled in the study, together with age-paired controls with no occupational exposure to fuels. Peripheral lymphocyte cultures were set up for the analysis of structural chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei (MN) in cytokinesis-blocked lymphocytes. Frequencies of CAs, SCEs and MN were compared between exposed and control groups, and evaluated in relation to blood lead level (as an indicator of engine exhausts exposure) for the whole group under study, and to yearly averaged exposure to benzene (8-h time weighted averages, as determined by repeated personal sampling) for fillingstation attendants only. Both CAs and SCEs were slightly increased in station attendants: 1.97 versus 1.46 aberrations per 100 cells, and 4.73 +/- 0.15 versus 4.48 +/- 0.11 SCEs/cell in exposed and control individuals, respectively. The difference between cumulative CA rates in the exposed and control populations was of borderline statistical significance (p = 0.066). However, when the exposed population was dichotomized for benzene exposure, a significant (p = 0.018) correlation of CAs with benzene exposure was found. The analysis of SCE data highlighted a significant increase of cells with more than 6 exchanges (HFCs), corresponding to the 75 degrees percentile of the overall distribution, in fillingstation attendants (relative risk (RR) = 1.3, 95% CI = 1.1-1.5) in comparison with controls. In the pooled population, the frequency of HFCs showed a statistically significant upward trend at increasing blood lead levels (chi 2 for trend = 27.8, p < 0.0001). A complex relationship between SCEs and benzene exposure was observed, with an increased frequency of HFCs in the medium exposure intensity class (RR = 1.5, 95% CI = 1.2-1.7), and no difference for exposure to higher benzene levels (RR = 1.0, 95% CI = 0.9-1.2), compared to reference subjects. Finally, the analysis of MN in both phytohemagglutinin- and pokeweed-stimulated cell cultures did not show significant excess of MN in binucleated lymphocytes of exposed workers with respect to the age-paired controls.

Relationship between locations of chromosome breaks induced by vinyl chloride monomer and lymphocytosis

The distribution of vinyl chloride monomer (VCM)-induced chromosome breaks was studied in cultured lymphocytes of subjects occupationally exposed to this gas. In the examined subjects, the mean group value of chromosome aberrations is 6.5% and for sister chromatid exchange (SCE) frequencies, the mean value per cell is 7.9. These values are significantly higher than in the control population. Occupational exposure to VCM caused lymphocytosis together with disturbances of mitogenic activity in lymphocytes stimulated by phytohaemagglutinin. The results of G-banding showed that sites of chromosome breakpoints caused by VCM can be related to the lymphatic tissue disorders.

DNA single strand break analysis in mononuclear blood cells of petrol pump attendants

DNA single strand breaks, including DNA adducts that lead to alkali-labile sites, were measured in peripheral mononuclear blood cells of 35 petrol pump attendants by alkaline filter elution. Blood samples from petrol pump attendants were taken on Monday and Friday. Additionally, DNA single strand breaks of smoking and non-smoking control persons were examined. For the smoking (n = 12) and the non-smoking controls (n = 20) a mean normalized elution rate of 1.49 +/- 0.52 (mean value +/- 95% confidence interval) and 1.32 +/- 0.28, respectively, was obtained. The difference between smoking and non-smoking controls was not statistically significant (U test). An increase in DNA single strand breaks from Monday to Friday was detected for non-smoking petrol pump attendants with a daily working time of more than 4 h at the pump station. Their mean normalized elution rate increased from 1.08 on Monday to 1.89 on Friday. This difference was statistically significant (P < 0.05; Wilcoxon test for paired data), although the 95% confidence interval was large on Friday (0.43 on Monday; 1.23 on Friday). However, no significant increase was found for non-smoking petrol pump attendants who were on duty for less than 4 h per day at the pump station. No statistically significant increase in DNA single strand breaks could be detected for smoking petrol pump attendants whether they were pumping gasoline for more or for less than 4 h per day.

Increased frequency of micronuclei in lymphocytes of Swedish chimney sweeps

Forty-five Swedish chimney sweeps and 49 controls were investigated with micronuclei stimulated by phytohemagglutinin and pokeweed mitogen and by analysis of lymphocyte subgroups and neutrophilic leukocytes. There was a statistically significant effect among sweeps with respect to both micronuclei variables and neutrophilic leukocytes. The effect on lymphocyte micronuclei was most prominent in pokeweed mitogen-stimulated cells, which may imply that the T4 lymphocytes were preferentially damaged by the occupational exposure.

Micronuclei and mitotic index in B-, T4- and T8-cells treated with mitomycin C and gamma-irradiation

Lymphocytes were treated in vitro with mitomycin C and gamma-radiation at different doses (0-250 nmol/l and 0-2 Gy, respectively). After incubation in RPMI 1640 medium and stimulation with phytohemagglutinin for 72 h, the lymphocyte subgroups T4 (CD4), T8 (CD8) and B (CD19) were separated by an immunomagnetic method and analyzed for the presence of micronuclei. With mitomycin C the highest levels were found in T4- and B-cells. When micronuclei were induced by irradiation the T4-cells showed the highest frequencies and the B-cells the lowest. The outcome of B-cells with gamma-irradiation was probably due to a pronounced cytotoxic reaction in this cell type, which could be measured as a decrease in mitotic index.

No significant increase in sister-chromatid exchanges in cultured blood lymphocytes from workers in a large oil refinery

In order to assess the potential genotoxic effects of occupational exposure to petrochemicals, the incidence of sister-chromatid exchanges (SCE) in cultured lymphocytes was studied. Blood samples were taken from 233 individuals (184 exposed and 49 worksite controls) in an oil refinery and from 47 community control persons. The data showed a non-significant elevation of SCE frequency in occupationally exposed workers when compared to non-exposed individuals. The mean SCE frequency per cell ranged from 7.55 +/- 0.55 in blood of lube oil blending and canning (LOBC) workers to 9.13 +/- 0.71 in catalytic cracking and water treatment (CCWT) workers. The control values were 6.2 +/- 0.67 and 7.21 +/- 0.45 in the community and worksite individuals, respectively. Furthermore, the SCE frequencies were influenced neither by age nor by smoking.

The frequency of micronuclei with X chromosome increases with age in human females

The rate of micronuclei counted on lymphocyte cultures from five healthy female donors, 27-80 years old, increased with age. Using pXBR1 probe, specific for the alphoid DNA of the X chromosome, the presence of this chromosome was investigated by FISH (fluorescence in situ hybridization) in both micronuclei and metaphases. Both X aneuploidy and frequency of X chromosome per micronuclei increased with age. However, this overinvolvement of X chromosome was not sufficient to explain the overall increase of micronuclei with age, suggesting that autosomes are also involved. Thus, the higher increase of X than autosome aneuploidy in lymphocytes may result from both an excess of X chromosome losses and a better survival of cells with a monosomy X.

B- and T-lymphocyte micronuclei in chimney sweeps with respect to genetic polymorphism for CYP1A1 and GST1 (class Mu)

Epidemiological studies have shown an increased incidence of lung cancer, bladder cancer, and esophageal cancer in chimney sweeps, probably due to their exposure to PAH in soot. The work environment for sweeps has, however, improved during the last decades. It was thus important to assess whether the present exposure still may cause genotoxic effects. A further objective was to assess whether genetic polymorphisms in metabolic enzyme activities could explain some of the variation in the parameters of genotoxicity. Venous blood samples were drawn from 71 chimney sweeps and 59 control subjects. Micronuclei were analyzed in activated peripheral B- and T-lymphocytes with preserved cytoplasm. Polymorphisms for CYP1A1 and GST1 in the sweeps were analyzed by a PCR technique. The sweeps did not have higher frequencies of micronuclei in B- or T-lymphocytes than the control subjects, when allowance was made for age and smoking in a multiple regression analysis. Further, there was no association between years of active work as a sweep and any of the two micronucleus parameters. None of the sweeps had the rare CYP1A1 genotype val/val and only one individual had the m2/m2 genotype. The presence of at least one GST1 allele (GST1+) was observed in 36 subjects (51.4%). Thirteen individuals (18.6%) were of the m1/m2 or m2/m2 genotype. And among those only seven had the combined GST1- and m1/m2 genotype. No difference was observed in B- or T-lymphocyte micronucleus frequencies between sweeps with the rare CYP1A1 genotypes m1/m2, m2/m2 or ile/val compared to individuals with the m1/m1 and ile/ile genotypes. Moreover, the GST1 deficient sweeps (GST1-) did not show any altered micronucleus frequency compared to the GST1 positive sweeps. A possible reason for the lack of genotoxic effect in sweeps is the improved hygienic conditions and change in fuels, which has decreased the exposure levels for PAH. Host polymorphisms for metabolizing enzymes did not influence the micronucleus frequencies. As the sweeps did not differ from the control subjects, with respect to micronucleus frequencies, no conclusion on the importance of host polymorphisms for genotoxic risk can be drawn.

Radiation induced micronuclei in subpopulations of human lymphocytes

The micronucleus expression in T-helper, T-suppressor and B lymphocytes of the peripheral blood was studied after in vitro exposure to high (2.5 Gy and 5 Gy) and low (0.5 Gy and 1 Gy) doses of ionizing radiation. Investigations were carried out by combining the micronucleus assay with immunofluorescence staining using subpopulation specific antibodies. While in the higher dose range B cell proliferation was inhibited nearly completely-so that micronuclei could not be expressed-we found after exposure to lower doses that B cells were the lymphocyte subpopulation which was most sensitive to micronucleus induction. Among the T cell population, the T-suppressor subset revealed a higher yield of micronuclei than T-helper cells, whereas with regard to the effect of radiation on proliferative ability, T-helper cells reacted more sensitivity than the T-suppressor lymphocytes. Our studies provide insight into the effect of radiation exposure on the micronucleus expression of lymphocyte subpopulations and new information which may be useful for the further development of biological dosimetry.

Cytogenetic studies on gas station attendants

Forty-nine gas station attendants employed to pump fuel and 24 controls were studied cytogenetically. This type of worker is occupationally exposed to fuel fumes and to automotive vehicle emissions. Chromosome analysis showed a significantly higher frequency of chromosome deletions among the gas station attendants than a control group. Taking into account the relationship between clastogenicity and increased cancer risk, we may consider these workers to form a risk group.

A comparative study of micronucleus frequency in peripheral blood lymphocytes of human subjects given dietary cis, trans and saturated fat

The micronucleus test using peripheral blood lymphocytes has been used to study the clastogenic effects of saturated, cis or trans fatty acids in human volunteers. Consumption of diets rich in either saturated fats (palmitic acid), monounsaturated cis fats (oleic acid) or monounsaturated trans fats (elaidic acid) for 3 wk had no effect on either the number of micronuclei or the frequency of micronucleated cells in lymphocytes in culture. This study adds to the accumulating body of evidence to suggest that dietary intake of trans fatty acids is not especially linked to genetic damage.

Cytogenetic effects in rotogravure printers exposed to toluene (and benzene)

Comparing 21 rotogravure printers exposed to toluene (medians: time-weighted air level 150 mg/m3, blood toluene 1.6 mumole/l) and 21 unexposed controls (median blood toluene less than or equal to 0.01 mumole/l) there was a significant increase in the frequency of micronuclei (MN) in pokeweed mitogen (PWM)-stimulated peripheral blood lymphocytes in the printers, as compared to the controls (2.8% vs. 1.5%; p = 0.03; all p adjusted for age and smoking). The frequency of small MN (size ratio MN/main nucleus less than or equal to 0.03) in PWM-stimulated lymphocytes was associated with the exposure (1% vs. 0.3%; p = 0.05). Furthermore, among the exposed subjects there was an association between blood toluene and small MN (0.17% per mumole/l; p = 0.0005). Small MN in phytohemagglutinin (PHA) cultures displayed no association with any exposure parameter. However, in the printers, an estimated cumulative exposure index was weakly correlated with the frequency of total MN in PHA-stimulated cells (0.00003% per mg/m3 x year; p = 0.07). Among the printers, chromosomal breaks in PHA-stimulated cells were associated with the duration of earlier benzene exposure (0.03% per year; p = 0.01). The results of this study strongly indicate that toluene causes a clastogenic effect on the B-cells even at low exposure levels. Further, earlier benzene exposure seems to have caused chromosomal breaks in T-cells.