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

Assessment of genotoxicity biomarkers in gasoline station attendants due to occupational exposure

Gasoline station attendants are exposed to numerous chemicals that might have genotoxic and carcinogenic potential, such as benzene in fuel vapor and particulate matter and polycyclic aromatic hydrocarbons in vehicle exhaust emission. According to IARC, benzene and diesel particulates are Group 1 human carcinogens, and gasoline has been classified as Group 2A "possibly carcinogenic to humans." At gas stations, self-service is not implemented in Turkey; fuel-filling service is provided entirely by employees, and therefore they are exposed to those chemicals in the workplace during all working hours. Genetic monitoring of workers with occupational exposure to possible genotoxic agents allows early detection of cancer. We aimed to investigate the genotoxic damage due to exposures in gasoline station attendants in Turkey. Genotoxicity was evaluated by the Comet, chromosomal aberration, and cytokinesis-block micronucleus assays in peripheral blood lymphocytes. Gasoline station attendants (n = 53) had higher tail length, tail intensity, and tail moment values than controls (n = 61). In gasoline station attendants (n = 46), the frequencies of chromatid gaps, chromosome gaps, and total aberrations were higher compared with controls (n = 59). Increased frequencies of micronuclei and nucleoplasmic bridges were determined in gasoline station attendants (n = 47) compared with controls (n = 40). Factors such as age, duration of working, and smoking did not have any significant impact on genotoxic endpoints. Only exposure increased genotoxic damage in gasoline station attendants independently from demographic and clinical characteristics. Occupational exposure-related genotoxicity risk may increase in gasoline station attendants who are chronically exposed to gasoline and various chemicals in vehicle exhaust emissions.

[Cancer risk evaluation in individuals occupationally exposed to organic solvents]

OBJECTIVE

To evaluate the frequency of micronuclei (MNs) and influence of GSTM1 and GSTT1 gene polymorphisms as biomarkers of cancer risk in car painters (n=152) compared to unexposed individuals (n=152).

METHODS

Molecular epidemiology study, cross-sectional analysis of gen and environment interaction. The evaluation of MN and genetic polymorphisms was determined by molecular tests in lymphocytes from subjects involved in the study.

RESULTS

It was determined that the frequency of MNs is 1.6 higher in the exposed group compared to the reference group (1.39 ± 0.92 versus 0.87 ± 0.78, p<0.0001). There was no increase in the frequency of MNs associated with the polymorphisms in GSTM1 and GSTT1.

CONCLUSIONS

The increase of MNs in car painters serves to alert the increased risk of cancer in this population exposed to organic solvents. These results can be used in Occupational Epidemiological Surveillance Programs, as a prevention strategy and policies to regulate and control the use of solvents at a national level and in other countries with a large informal sector of individuals exposed to these chemicals to reduce the risk of cancer.

Environmental Tobacco Smoke in Occupational Settings: Effect and Susceptibility Biomarkers in Workers From Lisbon Restaurants and Bars

Environmental tobacco smoke (ETS) has been recognized as a major health hazard by environmental and public health authorities worldwide. In Portugal, smoke-free laws are in force for some years, banning smoking in most indoor public spaces. However, in hospitality venues such as restaurants and bars, owners can still choose between a total smoke-free policy or a partial smoking restriction with designated smoking areas, if adequate reinforced ventilation systems are implemented. Despite that, a previous study showed that workers remained continuously exposed to higher ETS pollution in Lisbon restaurants and bars where smoking was still allowed, comparatively to total smoke-free venues. This was assessed by measurements of indoor PM2.5 and urinary cotinine, a biomarkers of tobacco smoke exposure, demonstrating that partial smoking restrictions do not effectively protect workers from ETS. The aim of the present work was to characterize effect and susceptibility biomarkers in non-smokers from those hospitality venues occupationally exposed to ETS comparatively to non-exposed ones. A group of smokers was also included for comparison. The sister chromatid exchange (SCE), micronucleus (MN) and comet assays in whole peripheral blood lymphocytes (PBLs) and the micronucleus assay in exfoliated buccal cells, were used as biomarkers of genotoxicity. Furthermore, a comet assay after ex vivo challenge of leukocytes with an alkylating agent, ethyl methanesulfonate (EMS), was used to analyze the repair capacity of those cells. Genetic polymorphisms in genes associated with metabolism and DNA repair were also included. The results showed no clear association between occupational exposure to ETS and the induction of genotoxicity. Interestingly, the leukocytes from non-smoking ETS-exposed individuals displayed lower DNA damage levels in response to the ex vivo EMS challenge, in comparison to those from non-exposed workers, suggesting a possible adaptive response. The contribution of individual susceptibility to the effect biomarkers studied was unclear, deserving further investigation.

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.

A Quantitative Meta-Analysis of the Relation between Occupational Benzene Exposure and Biomarkers of Cytogenetic Damage

BACKGROUND

The genotoxicity of benzene has been investigated in dozens of biomonitoring studies, mainly by studying (classical) chromosomal aberrations (CAs) or micronuclei (MN) as markers of DNA damage. Both have been shown to be predictive of future cancer risk in cohort studies and could, therefore, potentially be used for risk assessment of genotoxicity-mediated cancers.

OBJECTIVES

We sought to estimate an exposure-response curve (ERC) and quantify between-study heterogeneity using all available quantitative evidence on the cytogenetic effects of benzene exposure on CAs and MN respectively.

METHODS

We carried out a systematic literature review and summarized all available data of sufficient quality using meta-analyses. We assessed the heterogeneity in slope estimates between studies and conducted additional sensitivity analyses to assess how various study characteristics impacted the estimated ERC.

RESULTS

Sixteen CA (1,356 individuals) and 13 MN studies (2,097 individuals) were found to be eligible for inclusion in a meta-analysis. Studies where benzene was the primary genotoxic exposure and that had adequate assessment of both exposure and outcomes were used for the primary analysis. Estimated slope estimates were an increase of 0.27% CA [(95% CI: 0.08%, 0.47%); based on the results from 4 studies] and 0.27% MN [(95% CI: -0.23%, 0.76%); based on the results from 7 studies] per parts-per-million benzene exposure. We observed considerable between-study heterogeneity for both end points (I2>90%).

DISCUSSION

Our study provides a systematic, transparent, and quantitative summary of the literature describing the strong association between benzene exposure and accepted markers of genotoxicity in humans. The derived consensus slope can be used as a best estimate of the quantitative relationship between real-life benzene exposure and genetic damage in future risk assessment. We also quantitate the large between-study heterogeneity that exists in this literature, a factor which is crucial for the interpretation of single-study or consensus slopes. https://doi.org/10.1289/EHP6404.

Occupational benzene exposure and the risk of genetic damage: a systematic review and meta-analysis

Background

Benzene, an important component of organic solvents, is commonly used in industry. Meanwhile, benzene is a human carcinogen leading to leukemia. Although the links between benzene and various types of genetic damage indicators have been evaluated in several studies, but their results remain inconsistent. So we conducted a meta-analysis, and to explore the influence of low concentration benzene exposure on workers’ genetic damage indicators using 3.25 mg/m³ as the boundary value, in order to provide a basis for improved prevention and control of the harm from benzene exposure to the occupational population.

Methods

We conducted a search of five databases, including Pub Med, Web of Science, China National Knowledge Infrastructure (CNKI), Wan Fang Data and Chongqing VIP, to identify relevant articles up to December 25, 2018. Two researchers independently extracted and evaluated the data according to the inclusion and exclusion criteria of the literature. The imported articles were managed by Endnote X7, and the data were extracted and sorted by Excel 2013. We utilized Stata 12.0 software to perform the meta-analysis in the present study.

Results

A total of 68 eligible articles were finally included for the synthetic analyses. The meta-analysis results showed that occupational benzene exposure led to significantly increased Micronucleus (MN) frequency, Sister chromatid exchange (SCE) frequency, Chromosome aberration (CA) frequency, Olive Tail moment (OTM), Tail moment (TM), Tail length (TL), and Tail DNA% (T DNA%) compared to the control group (P < 0.05), and the pooled effect value estimates were 1.36, 0.98, 0.76, 1.06, 0.96, 1.78, and 1.42, respectively. Subsequent analysis of the effect of low concentration benzene exposure on genetic damage found significantly increased MN frequency increased compared with the control group (P < 0.05).

Conclusions

Occupational benzene exposure can affect multiple genetic damage indicators. Even at an exposure concentration lower than 3.25 mg/m³, benzene exposure has genotoxicity. These data provide an important scientific basis for the further revision of occupational disease prevention strategies. At the same time, increased attention should be focused on the health monitoring of the occupational population exposed to benzene, and health management should be strengthened to improve the health of the occupational population.

Integrative study of cell damage and cancer risk in gas station attendants

Gas station attendants are potentially exposed to carcinogenic substances. This study aimed to evaluate chronic occupational exposed gas station attendant's according to genetic parameters and its relationship with cancer predisposition. Forty gas station attendants were recruited and paired with 40 control subjects. Thousand cells from each subject were analyzed counting the number of pyknotic (PYC), karyolitic (KYL), karyorrhetic (KHC), condensed chromatin (CC), binucleated (BN), basal cells (BC), Nuclear buds (Nbud), and differentiated cells (DIFF). More 2.000 differentiated cells were analyzed counting micronucleated (MNi) and nuclear buds (NBud). We observed a statistical increase in BC and decrease in DIFF (p < 0.05). PYC, CC, KYL, MN, NBud were statistically increased (p < 0.05). All in all, our data showed elevated DNA damage, chromosomal instability, and cell cycle disturbing in our group of gas station attendants. It is a clear risk for their health in future and could be classified as a cancer predisposition.

Utilização de biomarcadores de genotoxicidade e expressão gênica na avaliação de trabalhadores de postos de combustíveis expostos a vapores de gasolina

Resumo Introdução: a avaliação de uma exposição mensura sua intensidade, frequência e duração, podendo detectar danos precoces que, se ignorados, podem evoluir para um quadro nocivo. Nos campos da saúde ambiental e ocupacional, os biomarcadores de genotoxicidade tem sido largamente utilizados para essa avaliação. Objetivo: identificar, descrever e discutir os principais bioindicadores de genotoxicidade e seu uso conjunto com técnicas de avaliação de expressão gênica em estudos de exposição ocupacional ao benzeno em postos de revenda de combustíveis (PRC). Métodos: revisão bibliográfica de trabalhos publicados entre 1995 e 2015. Resultados: as técnicas identificadas foram: ensaio cometa, estresse oxidativo, micronúcleos, aberrações cromossômicas, polimorfismos, adutos de DNA e proteínas, fatores epigenéticos e expressão gênica. Foi observado que testes de danos genéticos e epigenéticos são utilizados em frentistas de PRC que participam de programas de saúde do trabalhador ou de pesquisas, embora um baixo número de publicações sobre o tema tenha sido identificado. Esse fato talvez possa ser explicado pelos poucos países onde a profissão persiste e pelas limitações para o desenvolvimento de pesquisas nesses países. Conclusão: os bioindicadores de genotoxicidade e as técnicas de expressão gênica são úteis na detecção de dano precoce desta exposição ocupacional e devem ser avaliados em conjunto.

Association between occupational exposure to benzene and chromosomal alterations in lymphocytes of Brazilian petrochemical workers removed from exposure

We aimed to investigate the association between chronic exposure to benzene and genotoxicity in the lymphocytes of workers removed from exposure. The study included 20 workers with hematological disorders who had previously worked in the petrochemical industry of Salvador, Bahia, Brazil; 16 workers without occupational exposure to benzene served as the control group. Chromosomal analysis was performed on lymphocytes from peripheral blood, to assess chromosomal breaks and gaps and to identify aneuploidy. The Kruskal-Wallis test was used to compare the mean values between two groups, and Student's t test for comparison of two independent means. The frequency of gaps was statistically higher in and the exposed group than in the controls (2.13 ± 2.86 vs. 0.97 ± 1.27, p = 0.001). The frequency of chromosomal breaks was significantly higher among cases (0.21 ± 0.58) than among controls (0.12 ± 0.4) (p = 0.0002). An association was observed between chromosomal gaps and breaks and occupational exposure to benzene. Our study showed that even when removed from exposure for several years, workers still demonstrated genotoxic damage. Studies are still needed to clarify the long-term genotoxic potential of benzene after removal from exposure.

Comet assay based DNA evaluation of fuel filling stations and automobile workshops workers from Khyber Pakhtunkhwa province, Pakistan

BACKGROUND

Fuel filling stations workers and automobile workshops mechanics are consistently exposed to gasoline hydrocarbons during their occupation, this may cause DNA damage. Objective of this study was to evaluate the level of DNA damage in subjects occupationally exposed to these hydrocarbons.

METHODS

Comet assay was performed on blood lymphocytes of exposed subjects to assess the probable DNA damage. 100 cells per individual were scored and graded by comet tail length. Exposed group consisted of 98 subjects (age 25.4 ± 7.2 years), of which 68 were CNG/Petrol filling men and 30 were automobile workshop workers, selected randomly from different service stations and automobile workshops of populated and adjacent cities of Peshawar, Mardan and Nowshera of Khyber Pakhtunkhwa province, while control group included 92 subjects (age 26.7 ± 11.8 years) were also from the same areas.

RESULTS

Significantly high level of DNA damage was found in the subjects exposed to gasoline hydrocarbons as compared to control subjects (173.2 ± 50.1 and 61.0 ± 25.0, P = 0.001, respectively). Period of exposure and use of tobacco also showed considerable effects (P < 0.05) on DNA damage, while effect of age and daily working hours on total comet score (TCS) were non-significant (P > 0.05).

CONCLUSIONS

The results of our study concluded that petroleum hydrocarbons have the potential to cause DNA damage in the exposed subjects. The study also suggested that protective strategies should be implemented by the concerned authorities to minimize exposure to fuel hydrocarbons.

Evaluation of genotoxic effects of benzene and its derivatives in workers of gas stations

The search for reliable biomarkers of human exposure to benzene and its derivatives is still subject of research. Many of the proposed biomarkers have limitations ranging from the low sensitivity to the wide variability of results. Thus, the aim of our study was to assess the frequencies of chromosomal abnormalities (CA) and sister chromatid exchanges (SCE) in workers of gas stations, with (cases, n = 19) and without (local controls, n = 6) risk of exposure to benzene and its derivatives, comparing them with the results from the general population (external controls, n = 38). The blood dosages of benzene, toluene, and xylenes were measured in all participants. Blood solvent levels were compared with the findings obtained in cytogenetic evaluation and a research protocol which included data of the workplace, lifestyle, and health of the individuals. We did not detect the presence of benzene and its derivatives and did not find chromosomal damage that may be associated with the gas station activity in cases. Moreover, although we found an association of increased SCE and the working time in the local controls, the values found for SCE are within normal limits. Thus, our evaluation of SCE and CA reflected the levels of benzene and its derivatives observed in the blood. We believe, therefore, that SCE and CA may actually constitute possible tests for the evaluation of these exposures. However, we believe that further studies, including individuals at risk, are important to confirm this assertion.

Monitoring of gas station attendants exposure to benzene, toluene, xylene (BTX) using three-color chromosome painting

BACKGROUND

Chronic exposure of BTX (benzene, toluene, xylene) may lead to progressive degeneration of bone marrow, aplastic anemia and/or leukemia. In Brazil there is no self-service fuel in gas stations and attendants fill the fuel themselves. Due to this they are chronically exposed to high concentration of BTX. Occupational exposure to benzene has been associated with increased chromosomal aberrations in peripheral blood lymphocytes. Fluorescence in situ hybridization (FISH) using whole chromosome painting (wcp) probes allows the rapid detection of chromosomal aberration. In the present study three-color wcp probes for chromosomes 1, 2 and 4 were used for monitoring 60 gas station attendants.

RESULTS

Blood tests were done and interviews were conducted for each worker. For searching for possible associations between the clinical characteristics and the frequency of chromosomal aberrations the workers were divided into two groups (≤ 10 chromosomal abnormalities per 1,000 metaphases and > 10 chromosomal abnormalities per 1,000 metaphases).The studied workers had a low median age (36 year), albeit long period of BTX exposure (median was 16 years). Low prevalence of smoking and moderate consumption of alcoholic beverages were found in this population. The cytogenetic analysis showed 16.6% (10/60) of workers with a high frequency of chromosomal abnormalities (>10 chromosomal abnormalities per 1,000 metaphases). Translocations were the most frequently observed chromosome aberration. The statistical analysis revealed highly significant differences in skin color (p = 0.002) and a weak significant differences in gender (p = 0.052) distribution between the two groups.

CONCLUSION

16.6% of the studied population showed elevated frequencies of chromosomal abnormalities, which is highly likely to be correlated with their exposure to BTX during their work. Therefore, further studies are needed for better characterize the work associated damage of the genome in gas station workers. It is necessary to better understand the risks that these workers are exposed, so that we can be effective in preventing diseases and maintaining the health of these workers and possibly the offspring.

Wider action plan and multidisciplinar approach could be a wining idea in creation of friendly environment

Herein, we proposed planning of wide transdisciplinary actions, which bring a solution for economic activity such as transportation, strongly related to pollution output with possible repercussions on climate change and public health. To solve logistics problem by introduction of common intermodal policy, and creation of more friendly transport solution, it is possible to obtain sustainable development, climate change prevention, government policy, and regulation which are all related to human health and creation of health-supportive environment. This approach permits environmental and biological monitoring same as economic results measurement by key performance indicators. This approach implementing emerging scientific knowledge in environmental health science such as genetic epidemiology aimed at understanding how genomic variation impacts phenotypic expression and how genes interact with the environment at the population level with subsequent translation into practical information for clinicians as well as for public health policy creation.

Determination of genetic damage and urinary metabolites in fuel filling station attendants

Fuel (diesel and petrol) constitutes a complex mixture of volatile flammable liquid hydrocarbons among them benzene (BZ), toluene (TOL), and xylene (XYL) are considered to be the most hazardous, predominantly BZ because of its carcinogenic potency. Exposure to these compounds may have an impact on the health of the exposed subjects. Hence, genotoxicity and quantitative analysis of these compounds was performed in blood and urine samples of 200 workers exposed to fuel in filling stations and compared to controls. The level of genetic damage was determined by micronucleus test (MNT) in buccal epithelial cells (BEC) and chromosomal aberrations (CA) assay in peripheral blood lymphocytes (PBL) of fuel filling station attendants (FFSA) and compared to a matched control group. Urine analysis for BZ and its metabolites, phenol (Ph), trans, trans-Muconic Acid (t, t-MA), and S-Phenyl Mercapturic Acid (S-PMA) was done in all the study subjects. The results of our study revealed that exposure to BTX in petrol vapors induced a statistically significant increase in the frequency of micronuclei (MN) and CA in the exposed subjects than in controls (P < 0.05). There was a significant rise in the levels of urinary BZ, Ph, t, t-MA, and S-PMA in the exposed subjects. Our study highlights the significance of MNT, CA, and urinary metabolites as potential biological exposure indices of genetic damage in FFSA. This study suggests the need for regular monitoring of FFSA for possible exposure to BTX as a precautionary and preventive step to minimize exposure and reduce the associated health risks.

Biomonitoring of DNA damage and cytotoxicity in individuals exposed to cone beam computed tomography

OBJECTIVES

The aim of the present study was to evaluate DNA damage (micronucleus) and cellular death (pyknosis, karyolysis and karyorrhexis) in exfoliated buccal mucosa cells from adults following cone beam CT exposure.

METHODS

A total of 19 healthy adults (10 men and 9 women) submitted to cone beam CT were included.

RESULTS

No significant statistically differences (P > 0.05) in micronucleus frequency were seen before and after cone beam CT exposure. In contrast, the tomography was able to increase other nuclear alterations closely related to cytotoxicity such as karyorrhexis, pyknosis and karyolysis (P < 0.05).

CONCLUSION

In summary, these data indicate that cone beam CT may not be a factor that induces chromosomal damage, but it is able to promote cytotoxicity.

Assessment of occupational cytogenetic risk, among petrol station workers

The focal aim of this study was to assess the frequency of chromosomal aberrations (CA) including chromatid type aberrations (CTA) and chromosomal type aberrations (CSA), micronucleus (MN) and XRCC1 399 Arg/Gln polymorphism in the peripheral blood lymphocytes of 27 petrol pump workers and same number of controls to explore the possible cytogenetic risk on occupational exposure to petrol vapors. The exposed subjects and controls were classified into two groups based on their age (group I < 40 years; group II > 40 years) apart from the classification of the exposed subjects based on their exposure duration (> 8 and < 8 years). CTA and MN frequency were significantly higher in petrol pump workers (p < 0.05) with longer work duration. CTA was found to increase with age in the exposed subjects as well as controls, with exposed subjects showing a statistically higher degree. This effect was not observed in MN. A significantly higher frequency of MN was observed in the smoking petrol pump workers than in control smokers (p < 0.05). No association was found between smoking and CA in both subjects. The study on XRCC1 399 Arg/gln polymorphism in petrol pump workers demonstrated very less difference in allele frequency compared to controls. In conclusion, these datas indicate that petrol pump workers under risk group should be monitored for any long-term adverse effects of the exposure.

Micronucleus-centromere assay in workers occupationally exposed to low level of benzene

Benzene is a well-known carcinogen that induces chromosomal instability, including chromosome aberration and aneuploidy. In order to assess aneugenic effect of low-level benzene, micronucleus-centromere assay using specific probes for chromosomes 7 and 9 was performed in workers occupationally exposed to low-dose benzene at a petroleum refinery. A micronucleus-centromere assay using a pan-centromeric probe was also performed to determine the origin of benzene-induced micronucleus (MN). Frequency of aneuploidy of chromosomes 7 and 9 was significantly higher among workers compared to the unexposed control group. Poisson regression analysis revealed that aneuploidy frequency of chromosome 7 or 9 was significantly associated with benzene level after adjusting for confounding variables such as age, smoking, alcohol intake, and duration of work (p = .042). Additionally, frequencies of MN and centromere-negative micronuclei (MNC-) were significantly higher in benzene-exposed workers compared to controls, while frequency of centromere-positive micronuclei (MNC+) was similar in both groups. In conclusion, aneuploidy of chromosomes 7 and 9 could be a useful biomarker to assess the effect of low-level benzene exposure, and benzene-induced MN originates from chromosome breaks rather than chromosome non-disjunction.

Effect of gene polymorphisms and ethanol consumption on micronucleus frequency in human reticulocytes: a preliminary study

OBJECTIVE

Results from previous studies suggest that alcohol consumption can be genotoxic on peripheral lymphocytes. The aim of our study was to examine the association of alcohol consumption and its genotoxic effect on hematopoietic stem cells in vivo.

METHODS

We investigated 156 healthy Japanese males in a cross-sectional study. Lifestyles, including alcohol drinking behavior and cigarette smoking status, were investigated by means of a self-completed questionnaire. Polymorphisms of ADH1B and ALDH2 were identified by PCR-restriction fragment length polymorphism (RFLP) analysis. The presence of micronuclei in transferrin-positive reticulocytes (MN-RET) was detected with a single-laser flow cytometer. Associations between the genetic polymorphisms, lifestyle factors, and MN-RET frequency were statistically analyzed.

RESULTS

We found a significant difference in the mean frequencies of MN-RET between habitual drinkers and non-habitual drinkers (P = 0.043), and between the ALDH2*1/*1 and ALDH2*2/*2 genotype (P = 0.015). The ADH1B*2 and ALDH2*2 haplotype was estimated to have a significantly higher influence on MN-RET frequency than the ADH1B*2 and ALDH2*1 haplotype (P = 0.00035), and the frequency of alcohol consumption played a significant role in MN-RET frequency on the background of the ADH1B*2 and ALDH2*1 haplotype (P = 0.012).

CONCLUSION

The results of our study suggest a possible association between the ADH1B and ALDH2 polymorphism and the genotoxic effects of alcohol drinking on hematopoietic stem cells.

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.

Toxicity and genotoxicity of wastewater from gasoline stations

The toxicity and genotoxicity of wastewater from eight gasoline stations in Brasília, Brazil's capital city, was studied by assessing chromosomal aberrations, chromosomal malsegregation and the mitotic index in Alliumcepa root cells, and the occurrence of micronucleus and nuclear abnormalities in peripheral erythrocytes of tilapia fish (Oreochromis niloticus). The content of gasoline station effluents was also analyzed based on several physico-chemical parameters. None of the wastewater samples was genotoxic to A. cepa root cells, although cell proliferation was significantly inhibited, especially at the highest concentrations. Likewise, no micronuclei were observed in O. niloticus peripheral erythrocytes, even after exposure to high concentrations, but there was an increase in the number of nuclear abnormalities and fish mortality. These results show that although the effluent from gasoline stations is processed by an oil/water separation system before being discharged into the main sewage system, the wastewater still contains toxic compounds.

Effects of lifestyle on micronuclei frequency in human lymphocytes in Japanese hard-metal workers

OBJECTIVE

The risks of cardiovascular disease, cancer, and other major causes of mortality are largely attributable to lifestyle factors such as smoking, alcohol drinking, hours of working and sleeping, physical activity, diet, and stress. Earlier studies have suggested that an unhealthy lifestyle is also associated with increased lymphocyte sensitivity to mutagens, oxidative DNA damage level, and leukocyte DNA damage. In order to explore the genotoxicity of unhealthy lifestyle, we evaluated the effect of overall lifestyle as well as some individual lifestyle factors on micronuclei (MN) frequency in cultured human lymphocytes.

METHOD

The study was conducted among 208 healthy adult (19 to 59 years) male Japanese hard-metal workers. The subjects were divided into groups according to their self-reported good, moderate, and poor lifestyles based on their responses to a questionnaire regarding eight health practices (cigarette smoking, alcohol consumption, sleeping hours, working hours, physical exercise, eating breakfast, balanced nutrition, and mental stress), the presence or absence of each of which was summed to obtain a health practice index (HPI: range 0-8). Peripheral blood was taken and the cytokinesis-block micronuclei (CBMN) assay was performed.

RESULTS

Total lifestyle quality as measured by the HPI was strongly negatively associated with MN frequency in cultured human lymphocytes (p<0.01). Nutritional imbalance, lack of regular exercise (<2 times per week), insufficient sleep (< or =6 h per day), and overtime working (> or =9 h per day) each contributed significantly to higher MN frequency (all p<0.05). In the smoker group, a significantly higher MN frequency was only found in heavy smokers (p<0.05). On the other hand, mental stress, eating breakfast, and alcohol drinking had no effect on MN frequency.

CONCLUSIONS

Taken together, these findings indicate that poor lifestyle habits significantly increase MN frequency in human lymphocytes.

Chromosome aberrations in workers exposed to organic solvents: Influence of polymorphisms in xenobiotic-metabolism and DNA repair genes

Organic solvents are widely used as diluents or thinners for oil-paints, gasoline and other organic mixtures. We evaluated chromosome aberrations (CAs) in lymphocytes of 200 workers exposed to organic solvents and 200 referents and the influence of polymorphisms in xenobiotic-metabolism (CYP2E1, GSTM1 and GSTT1) and in DNA repair genes (XRCC1(194) Arg/Trp, XRCC1(280) Arg/His, XRCC1(399) Arg/Gln and XRCC3(241) Thr/Met). Polymorphisms were determined by PCR-RFLP. Poisson regression analysis indicates a significant CA frequency increase in exposed workers, representing a higher risk in relation to the matched referent (RR 2.15, 95% CI 1.21-1.53, p<0.001). The CA frequency in exposed workers was influenced by the polymorphic genotypes: GSTM1 null (RR 1.33, 95% CI 1.31-1.69, p<0.001), XRCC1(194) Arg/Trp, Trp/Trp (RR 1.23, 95% CI 1.08-1.40, p<0.001) and by the wild genotypes CYP2E1 C1/C1 (RR 1.20, 95% CI 1.05-1.37, p<0.001), GSTT1 positive (RR 1.49, 95% CI 1.31-1.69, p<0.001), XRCC1(280) Arg/Arg (RR 1.44, 95% CI 1.26-1.64, p<0.001) and XRCC1(241) Thr/Thr (RR 1.54, 95% CI 1.34-1.76, p=0.001). We contribute to the follow-up predictive value of individual susceptibility biomarkers and their CA frequency influence during occupational organic solvent exposure. We provide tools for surveillance and prevention strategies to reduce potential health risks in countries with a large population of car painters not using protection devices and limited organic solvents use control.

Multipronged evaluation of genotoxicity in Indian petrol-pump workers

Petrol (gasoline) contains a number of toxicants. This study used human biomonitoring to evaluate the genotoxic effects of exposure to benzene in petrol fumes in 100 Indian petrol-pump workers (PPWs) and an equal number of controls. The study was corroborated with in silico assessments of the Comet assay results from the human biomonitoring study. An in vitro study in human lymphocytes was also conducted to understand the genotoxicity of benzene and its metabolites. In a subset of the population studied, higher blood benzene levels were detected in the PPWs (n = 39; P < 0.01) than the controls (n = 18), and 100-250 ppb benzene was also detected in air samples from the petrol pumps. PPWs had higher levels of DNA damage than the controls (P < 0.01). In addition, the micronucleus assay was performed on lymphocytes from a subset of the subjects, and the micronucleus frequency for PPWs was significantly higher (n = 39; 14.79 +/- 3.92 per thousand) than the controls (n = 18; 7.54 +/- 3.00 per thousand). Human lymphocytes were treated in vitro with benzene and several of its metabolites and assayed for DNA damage with the Comet assay. Benzene and its metabolites produced significant (P < 0.05) levels of DNA damage at and above concentrations of 10 microM. The metabolite, p-benzoquinone, produced the greatest amount of DNA damage, followed by hydroquinone > benzene > catechol > 1,2,4,-benzenetriol > muconic acid. This study demonstrates that, using sensitive techniques, it is possible to detect human health risks at an early stage when intervention is possible. possible.

Association of the NQO1, MPO, and XRCC1 polymorphisms and chromosome damage among workers at a petroleum refinery

Benzene is a leukemogen, and exposure to benzene is an occupational hazard in the petroleum refining industries. The effects of genetic polymorphisms in the NQO1 (rs1800566), MPO (rs2333227), and XRCC1 (rs25487) genes on benzene-induced chromosome abnormalities were assessed in 108 benzene-exposed workers and 33 office workers. The mean benzene exposure for exposed workers was 0.51 ppm for full-shift workers, and the time-weighted average ranged from 0.004 to 4.25 ppm. The frequencies of micronuclei (MN) and chromosome aberrations (CA) were significantly higher in workers exposed to benzene than unexposed controls. Exposed workers with the T/T genotype for NQO1 showed significant 1.9-fold (95% CI = 1.5-2.3) and 2.6-fold (95% CI = 1.7-3.9) increases in MN and CA frequencies, respectively, compared to controls with C/C and C/T genotypes, after adjusting for age, smoking status, and alcohol intake. Among exposed workers, subjects with the combination of MPO G/G and XRCC1 Arg/Gln or Gln/Gln showed a significantly higher CA frequency compared to those with the combination of MPO G/A or A/A and XRCC1 Arg/Arg genotypes. These results indicated that the genotoxicity induced by a chronic benzene exposure is modulated by genes involved in both DNA repair and benzene metabolic pathways.

Benzene's toxicity: a consolidated short review of human and animal studies

A large population of humans is exposed to benzene from various occupational and environmental sources. Benzene is an established human and animal carcinogen. Exposure to benzene has been associated with leukaemia in humans and several types of malignancies in animals. The exact mechanism of benzene-induced toxicity is poorly understood. It is believed that benzene exerts its adverse effects by metabolic activation to toxic metabolites. Certain benzene metabolites are genotoxic and mutagenic. This consolidated short-review is composed of human and animal studies to summarize the adverse effects of benzene with special reference to molecular mechanisms involved in benzene-induced toxicity.

Evaluation of genotoxicity in a group of workers from a petroleum refinery aromatics plant

Petroleum refinery workers are potentially exposed to a wide range of petroleum-derived hydrocarbons and chemical substances used in the manufacturing of petroleum derivatives. Benzene, toluene and xylene (BTX) are produced by distillation in the aromatics units and used as raw materials for petrol and petrochemical products. The aim of this study was to evaluate the genotoxic effects of occupational exposure to BTX in a petroleum refinery in the North of Portugal. The exposed group consisted of 48 workers from the aromatics plant and the control group consisted of 30 persons matched for various confounding factors. Chromosome aberrations (CA), micronuclei (MN), and DNA damage (evaluated by means of the comet assay) were measured in peripheral blood leukocytes. t,t-Muconic acid (t,t-MA), hippuric acid (HA) and methylhippuric acid (MHA) concentrations were measured in urine samples collected at the end of the workshift. The results suggest that occupational exposure to toluene and xylene is very low. A statistically significant increase in t,t-MA excretion was found in the exposed group although t,t-MA levels were found to be lower than the biological exposure index (BEI). Significant increases were found for CA, MN and comet tail length (TL) in the exposed group (p<0.05). No association was found between tobacco smoking and the effect biomarkers analysed. A positive association was found between CA and MN with age in the control group (p<0.05).

Lack of genotoxic effect in workers exposed to very low doses of 1,3-butadiene

1,3-Butadiene (BD), a probable carcinogen to humans, has been shown to have an ill-defined genotoxicity in occupationally exposed workers. In the present study, the influence of exposure to very low doses of BD and to cigarette smoking was investigated on some cytogenetic endpoints, namely, sister chromatid exchanges (SCE), chromosomal aberrations (CA) and cells with a high frequency of SCE (HFC), in peripheral blood lymphocytes. Twenty-seven male workers employed in a petrochemical plant and 26 matched controls were included in the study. As regards the airborne BD values, there was a significant difference between exposed (median BD value 1.5, min-max 0.2-69.0 microg/m3) and non-exposed workers (median BD value 0.4, min-max <0.1-3.8 microg/m3). Genotoxic biomarkers were not able to distinguish between the two groups. The frequency of SCE was higher in smokers than in non-smokers (p=0.001), with a positive correlation between the number of cigarettes smoked per day and both SCE (r=0.4; p=0.004) and HFC frequency (r=0.3; p=0.04). Multiple regression analysis confirmed the influence of cigarette smoking on the level of SCE and HFC, while these parameters were not affected by personal exposure to BD. Overall, the biomarkers of genotoxic effect investigated in our study were not able to discriminate between workers with a very low exposure to BD and controls, while it was possible to distinguish between smokers and non-smokers on the basis of SCE.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Biological monitoring in occupational exposure to low levels of 1,3-butadiene

Exposure to 1,3-butadiene (BD), a probable carcinogen to humans, was investigated in two groups of subjects working in a petrochemical plant where BD is produced and used to prepare polymers: 42 occupationally exposed workers and 43 internal non-occupationally exposed controls. BD personal exposure was very low but significantly different in the two groups (median airborne BD 1.5 and 0.4 microg/m(3) in exposed and controls, respectively). Similarly, BD in blood and urine, but not in exhaled air, was higher in the exposed workers than in controls (blood BD 3.7 ng/l versus <1.8 ng/l, urinary BD 2.4 ng/l versus <1.0 ng/l). These three biomarkers correlated significantly with personal exposure ( 0.283 < or = Pearson's r < or = 0.383) and between them (0.780 < or = r < or = 0.896). Excretion of urinary mercapturic acids N-acetyl-S-(3,4-hydroxybutyl)-l-cysteine (MI), N-acetyl-S-(1-hydroxymethyl-2-propenyl)-l-cysteine and N-acetyl-S-(2-hydroxy-3-butenyl)-l-cysteine (MII), chromosomal aberrations (CA), and sister chromatid exchanges (SCE) in peripheral blood lymphocytes were not influenced by occupational exposure. Our results show that unmetabolised BD in biological fluids, and particularly urinary BD, represents the biomarker of choice for assessing occupational exposure to low airborne concentrations of BD.

Utility of a routine medical surveillance program with benzene exposed workers

BACKGROUND

A medical surveillance program of benzene-exposed workers has to be established in such a way as to observe early signs of benzene-induced cytopenia, pancytopenia, or leukemia. This study evaluates the utility of routine medical survey applied to benzene-exposed workers by analyzing the hematological, immunological, and cytogenetic assay results.

METHODS

The results of a previous study of hematological, immunological, and cytogenetic assays in benzene-exposed workers (up to 15 ppm) are used to discuss medical surveillance program by defining the relationship between various benzene exposure concentrations and toxic endpoints.

RESULTS

Exposure to benzene concentration lower than 5 ppm does not produce any abnormal hematological measurements. For benzene cumulative exposure above 100 (ppm-years), some blood indices [mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), band neutrophils] show significant differences in comparison to the control group. The incidence of dicentric chromosomes was higher and the level of B-lymphocytes was lower even with workers exposed to 5 ppm of benzene; correlation with exposure indicators was not found.

CONCLUSIONS

The results suggest that peripheral blood indices, although not sensitive enough, are still the most suitable parameters in a health surveillance program applied to benzene-exposed workers. B-lymphocytes could be a promising indicator of the benzene-induced damage. Cytogenetic tests did not prove to be suitable. Further investigation of useful screening tests for health surveillance program of benzene-exposed workers is still required.

Effect of smoking habit on the frequency of micronuclei in human lymphocytes: results from the Human MicroNucleus project

The effect of tobacco smoking on the frequency of micronuclei (MN) in human lymphocytes has been the object of many population studies. In most reports, the results were unexpectedly negative, and in many instances smokers had lower frequencies of MN than non-smokers. A pooled re-analysis of 24 databases from the HUMN international collaborative project has been performed with the aim of understanding the impact of smoking habits on MN frequency. The complete database included 5710 subjects, with 3501 non-smokers, 1409 current smokers, and 800 former smokers, among subjects in occupational and environmental surveys. The overall result of the re-analysis confirmed the small decrease of MN frequencies in current smokers (frequency ratio (FR) = 0.97, 95% confidence interval (CI) = 0.93-1.01) and in former smokers (FR = 0.96, 95% CI = 0.91-1.01), when compared to non-smokers. MN frequency was not influenced by the number of cigarettes smoked per day among subjects occupationally exposed to genotoxic agents, whereas a typical U-shaped curve is observed for non-exposed smokers, showing a significant increase of MN frequency in individuals smoking 30 cigarettes or more per day (FR = 1.59, 95% CI = 1.35-1.88). This analysis confirmed that smokers do not experience an overall increase in MN frequency, although when the interaction with occupational exposure is taken into account, heavy smokers were the only group showing a significant increase in genotoxic damage as measured by the micronucleus assay in lymphocytes. From these results some general recommendations for the design of biomonitoring studies involving smokers can be formulated. Quantitative data about smoking habit should always be collected because, in the absence of such data, the simple comparison of smokers versus non-smokers could be misleading. The sub-group of heavy smokers (> or =30 cigarettes per day) should be specifically evaluated whenever it is large enough to satisfy statistical requirements. The presence of an interaction between smoking habit and occupational exposure to genotoxic agents should be always tested.

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.

Sex chromosome loss, micronuclei, sister chromatid exchange and aging: a study including 16 centenarians

In the present study we analysed the possible effect of age, sex and smoking on the mean values of micronucleus (MN) and sister chromatid exchange (SCE) frequencies on peripheral blood obtained from 38 subjects ranging in age from 16 to 63 years and 16 centenarians. The mean number of binucleated cells with micronuclei varied in function of age and sex (as demonstrated by the analysis of covariance (F=13.13; P<0.001), particularly evident was the increment observed in women with increasing age (interaction age/sex: F=5.53; P<0.05). Smoking habits had no effects on MN frequency (F=0.36; P>0.05). Sex (F=4.18; P<0.05) and smoking habits (F=14.64; P<0.001) influenced significantly SCE per cell frequencies, but age had no effects on them (F=2.45; P>0.05). The age-associated increase of sex chromosome loss was studied using fluorescence in situ hybridisation (FISH) on interphase nuclei. The loss of Y signals was observed in approximately 10% of interphase cells from the centenarians males, that is six times more often than in the younger control men (approximately 1.6%). The frequency of X signal loss (approximately 1.7%) in young women was similar to that observed in male controls of the same age but the incidence of the X chromosome aneuploidy in centenarian females was appreciably higher (approximately 22%) than that found for the Y chromosome in males. These results were correlated with the data on MN formation and a positive correlation between the percentage of aneuploid cells (FISH) and MN values was observed (r=0.50; P<0.05).

17-alpha-ethinylestradiol and norgestrel in combination induce micronucleus increases and aneuploidy in human lymphocyte and fibroblast cultures

Oral contraceptives are highly efficient and easily administered drugs; however, it must not be forgotten that they are composed of chemical substances which can be classified as potential carcinogens. Testing of a substance for genotoxicity represents a reliable approach both to evaluate the genetic hazard and to obtain information on its possible tumorigenic (cancerogenic) properties. The present study was undertaken to evaluate through carefully planned and controlled investigations the in vitro cytogenetic effects of oral contraceptives (ethynilestradiol and norgestrel mixed in the proportion 1:5) using three different concentrations, with two different durations of treatment (48 and 72 h), on two types of human cells (lymphocytes and fibroblasts) and a series of short-term test procedures: sister chromatid exchange (SCE), micronucleus test (MN), and chromosome aberrations (CA). In addition, the FISH procedure and in vitro anaphase and metaphase preparation analyses were performed. In contrast to CA and SCE frequencies, the frequency of MN in treated blood lymphocytes showed higher values by comparison with the controls, although the difference was statistically significant only for the lowest concentration (P = 0. 016). When using pancentromeric alphoid probes, the FISH procedure gave positive signals in more than 85% of micronuclei, clearly indicating that MN may contain whole chromosomes rather than acentric fragments. Unlike the lymphocytes, the fibroblasts showed dose-dependent effects, although those treated with the highest hormone concentrations showed an increased number of highly damaged cells (cytoplasmatic vacuolization, nuclear fragmentation, etc.), a decreased number of anaphase cells, a large number of which were abnormal, and a reduction of mitotic index. In conclusion, our data confirm that hormones do not induce structural chromosome aberrations in lymphocytes and indicate that ethynilestradiol and norgestrel have an aneugenic effect on fibroblast and lymphocyte cultures; FISH analysis on micronuclei from lymphocyte cultures and anaphase preparations from fibroblast cultures support this hypothesis. Teratogenesis Carcinog. Mutagen. 20:147-159, 2000.