Associated health risk assessment due to exposure to BTEX compounds in fuel station workers

OBJECTIVES

The purpose of this review study was to assess the risk of exposure to BTEX compounds in gas station workers and operators.

CONTENT

The main components of BTEX compounds are Benzene, Toluene, Ethyl benzene and Xylene. Petroleum, coal large quantities in crude oil and its products are the most important sources of BTEX compounds. These compounds have both high solubility (found in surface and underground waters) and evaporate quickly. Gas stations are one of the most important sources of emission of these compounds in communities. Workers who work in these places have a lot of exposure to these compounds. Exposure to these dangerous compounds can cause many problems for workers. This study was a narrative review article. According to different databases: PubMed, Web of Science, Springer, Cochran and Science Direct, 451 articles were retrieved. 55 full-text articles entered into the analysis process. Finally, 32 articles were selected in this study. The search was restricted to English-language papers published between 1 February 1995 and 13 August 2022. The results of our study showed that the carcinogenic risk (ILCR) for gas station workers in Bangkok (1.82 ∗ 10-4 - 2.50 ∗ 10-4), Shiraz (6.49∗10-7 - 1.27 ∗ 10-5), Brazil (1.82 ∗ 10-4), Ardabil (390∗10-6 ± 1884 ∗ 10-6) and Johannesburg (3.78 ∗ 10-4) was high. The non-cancer risk for oil industry workers of Dilijan (Iran) who were exposed to toluene was also reported in the range of 10-6∗176. The health of gas station workers is affected by exposure to BTEX and gasoline vapor emissions. According to the result this study, BTEX compounds cause genotoxic changes, chromosomal and genetic abnormalities.

SUMMARY AND OUTLOOK

Genotoxicity at high levels in gas station workers can cause cancerous and non-cancerous risks. Improving the production process of diesel fuel and gasoline in refineries, using periodical examinations of workers and operators at gas and fuel stations, using Euro 4 and 5 fuels, and replacing worn out cars can play an important role in reducing the emission of BTEX compounds and thus reducing health risks and carcinogenic.

Genotoxic Effects on Gas Station Attendants in South-southeastern México due to Prolonged and Chronic Exposure to Gasoline

Background

Gasoline, a complex mixture of volatile organic compounds is classified as possibly carcinogenic to humans. Gasoline station attendants, consistently exposed to its hazardous components, may face genotoxic effects. This study aimed to assess the influence of varying work shift durations on DNA damage in gasoline station attendants.

Methods

Ninety individuals from three locations in southern México were studied. Peripheral blood mononuclear cells (PBMCs) were isolated, and DNA damage was assessed using the comet assay. Demographic, occupational, and lifestyle data were collected. Statistical analyses included t-tests, ANOVA, and Pearson correlation.

Results

Significant differences in DNA damage parameters were observed between exposed and unexposed groups. The impact of tobacco, alcohol, and exercise on DNA damage was negligible. Extended work shifts (12 and 24 hours) showed heightened DNA damage compared to 8-hour shifts and the unexposed group. A novel finding revealed a modest but significant correlation between DNA damage and job seniority.

Conclusion

The study highlights the intricate relationship between occupational exposure to gasoline components, DNA damage, and work shift lengths. Extended shifts correlate with heightened genotoxic effects, emphasizing the importance of personalized safety measures. The significant correlation between DNA damage and job seniority introduces occupational longevity as a determinant in the genetic health of gasoline station attendants. This discovery has implications for implementing targeted interventions and preventive strategies to safeguard workers' genetic integrity throughout their years of service. The study calls for further exploration of unconsidered factors in understanding the multifactorial nature of DNA damage in this occupational setting.

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.

The effect of exposure to crude oil on the immune system. Health implications for people living near oil exploration activities

People who reside near oil exploration activities may be exposed to toxins from gas flares or oil spills. The impact of such exposures on the human immune system has not been fully investigated. In this review, research investigating the effects of crude oil on the immune system is evaluated. The aim was to obtain a greater understanding of the possible immunological impact of living near oil exploration activities. In animals, the effect of exposure to crude oil on the immune system depends on the species, dose, exposure route, and type of oil. Important observations included; hematological changes resulting in anemia and alterations in white blood cell numbers, lymph node and splenic atrophy, genotoxicity in immune cells, modulation of cytokine gene expression and increased susceptibility to infectious diseases. In humans, there are reports that exposure to crude oil can increase the risk of developing certain types of cancer and cause immunomodulation.Abbreviations: A1AT: alpha-1 antitrypsin; ACH₅₀: hemolytic activity of the alternative pathway; AHR: aryl hydrocarbon receptor; BALF: bronchoalveolar lavage fluid; COPD: chronic obstructive pulmonary disease; CYP: cytochrome P450; DNFB: 2, 4-dinitro-1-fluorobenzene; G-CSF: granulocyte-colony stimulating factor; IFN: interferon; IL: interleukin; 8-IP: 8-isoprostane; ISG15: interferon stimulated gene; LPO: lipid peroxidation; LTB₄: leukotriene B₄; M-CSF: macrophage-colony stimulating factor; MMC: melanomacrophage center; MPV: mean platelet volume; NK: natural killer; OSPM: oil sail particulate matter; PAH: polycyclic aromatic hydrocarbon; PBMC: peripheral blood mononuclear cell; PCV: packed cell volume; RBC: red blood cell; ROS: reactive oxygen species; RR: relative risk; T_H: T helper; TNF: tumour necrosis factor; UV: ultraviolet; VNNV: Viral Nervous Necrosis Virus; WBC: white blood cell.

Evaluation of some biological parameters of gasoline station attendants in Damascus, Syria

Introduction

Gasoline is a blend of organic compounds used in internal combustion engines. gasoline station attendants (GSA) are exposed to gasoline vapours, which promotes oxidative stress through the production of ROS, which can damage biological structures with the formation of new metabolites which can be used as markers of oxidant/antioxidant imbalance. This is a comparative cross-sectional study. This study aims to evaluate some biological parameters as indicators of toxicity as a result of exposure to gasoline in workers at gas stations in Damascus.

Methods

Blood samples were collected from GSA (n = 30) and non-exposed (NE) (n = 30) with no history of occupational exposure, and the following markers of oxidative stress were analysed: malondialdehyde (MDA), advanced oxidation protein products (AOPP), catalase activity (CAT), CBC, ALT and AST.

Results

We have found that the levels of MDA, AOPP, CAT, RBC and Hgb in GSA were significantly higher than NE (p = 0.000, p = 0.02, p = 0.002, p = 0.018 and p = 0.015 respectively). On the other hand, there were no statistically significant (p > 0.05) in HCT, MCV, WBC, PLT, ALT and AST between the two groups. In the GSA group, there was no effect of the smoking habit and the number of years of work on biological parameters, but alcohol consumption habit had a clear effect on increasing both levels of MDA and CAT (P = 0.021 and P = 0.036 respectively), in comparison to the non-consumers of the alcohol group. The results from our study showed that chronic gasoline exposure may result in long-lasting oxidative stress, as demonstrated by the presence of statistically significant correlations between gasoline exposure and levels of biomarkers (MDA, AOPPs, Catalase activity).

Conclusions

the early identification of these biomarkers can be very useful to promote programs on health protection and prevention for those populations more susceptible to the adverse effects of gasoline exposure.

Genotoxic risk in occupational exposure to petrol and its amelioration by vitamin C and vitamin E

Petrol contains mixture of mutagens and carcinogens which have potential health risk after prolonged occupational exposure. We have compared genotoxicity and its amelioration in blood samples from 70 petrol pump attendants, working in congested area of the Ahmedabad city, India and similar number (n = 70) of Control samples from office workers dwelling in less polluted areas of the city. The cytokinesis-block micronucleus assay showed highly significant frequencies of micronucleus in Exposed than in the Controls. The sister chromatid exchanges were also significantly increased while the cell cycle proliferative index was significantly decreased in the Exposed individuals than the Controls. Addition of standardized doses of vitamin C and vitamin E in the lymphocyte cultures (in vitro) significantly improved all the biomarkers. The long-term occupational petrol exposure causes genotoxic effects and use of vitamins C and E for protection should be further explored in randomized controlled studies.

Assessment of oxidative stress among refueling workers in an Egyptian setting

BACKGROUND

Unlike developing countries, in Egypt, gasoline is dispensed at dedicated stations by gasoline filling workers. This leads to high levels of exposure to the aromatic compounds in gasoline [principally benzene, toluene, ethyl benzene, and xylene (BTEX)] with the consequences of adverse health effects including oxidative stress.

OBJECTIVE(S)

To assess oxidative stress and trace metal levels among Egyptian gas filling workers.

METHODS

A cross-sectional study was conducted among 50 gasoline filling station workers (exposed group) and a matched group of 50 clerical workers (non-exposed group). Trace metal levels (Cu, Zn, Fe, and Mn) and the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured in sera of all enrolled participants using atomic absorption spectroscopy. BTEX levels were assessed in the environment of the studied gas filling stations using the MIRAN IR system.

RESULTS

All the measured trace metal levels and antioxidant enzyme activities were significantly lower among the exposed workers than among the non-exposed workers. All trace metals decreased significantly in relation to SOD activity among the exposed workers, whereas only Zn and Cu decreased in relation to SOD and GPx activity among the non-exposed workers. The exposed workers did not comply with the use of the required personal protective equipment (PPE) to avoid the dangerous effects of BTEX exposure. Among BTEX components, benzene exceeded the allowable Egyptian TLV in the studied gasoline stations (110.4 mg/m3 versus 1.6 mg/m3, respectively). The hygienic effect (HE) of the BTEX pollutant mixture exceeded the allowed borderline HE in Egypt although it did not show a significant correlation with different oxidative stress biomarkers and trace metals.

CONCLUSION

Exposure to BTEX at gasoline filling stations lowers the levels of antioxidant enzyme activities and trace metals due to the strong hygienic effect of BTEX. Individual protection using the proper PPE should therefore be enforced. Research assessing the need of providing refueling workers with supplements of necessary trace metals and antioxidants is warranted.

Environmental Assessment and Evaluation of Oxidative Stress and Genotoxicity Biomarkers Related to Chronic Occupational Exposure to Benzene

Environmental and occupational exposure to benzene from fuels is a major cause for concern for national and international authorities, as benzene is a known carcinogen in humans and there is no safe limit for exposure to carcinogens. The objective of this study was to evaluate the genotoxic effects of chronic occupational exposure to benzene among two groups of workers: filling station workers (Group I) and security guards working at vehicles entrances (Group II), both on the same busy highway in Rio de Janeiro, Brazil. Sociodemographic data on the workers were evaluated; the concentration of benzene/toluene (B/T) in atmospheric air and individual trans,trans-muconic acid (ttMA) and S-phenylmercapturic acid (S-PMA) were measured; oxidative stress was analyzed by catalase (CAT), glutathione S-transferase (GST), superoxide dismutase (SOD), thiol groups (THIOL) and malondialdehyde (MDA); genotoxicity was measured by metaphases with chromosomal abnormalities (MCA) and nuclear abnormalities, comet assay using the enzyme formamidopyrimidine DNA glycosylase (C-FPG), and methylation of repetitive element LINE-1, CDKN2B and KLF6 genes. Eighty-six workers participated: 51 from Group I and 35 from Group II. The B/T ratio was similar for both groups, but Group I had greater oscillation of benzene concentrations because of their work activities. No differences in ttMA and S-PMA, and no clinical changes were found between both groups, but linearity was observed between leukocyte count and ttMA; and 15% of workers had leukocyte counts less than 4.5 × 10⁹ cells L^-1, demanding close worker's attention. No differences were observed between the two groups for THIOL, MDA, MCA, or nuclear abnormalities. A multiple linear relationship was obtained for the biomarkers MCA and C-FPG. A significant correlation was found between length of time in current job and the biomarkers C-FPG, MCA, GST, and MDA. Although both populations had chronic exposure to benzene, the filling station workers were exposed to higher concentrations of benzene during their work activities, indicating an increased risk of DNA damage.

Genotoxic effects of occupational exposure to benzene in gasoline station workers

Benzene, a hazardous component of gasoline, is a genotoxic class I human carcinogen. This study evaluated the genotoxic effects of occupational exposure to benzene in gasoline stations. Genotoxicity of exposure to benzene was assessed in peripheral blood leucocytes of 62 gasoline station workers and compared with an equal numbers of matched controls using total genomic DNA fragmentation, micronucleus test and cell viability test. An ambient air samples were collected and analyzed for Monitoring of benzene, toluene, ethyl benzene and xylene (BTEX) in work environment and control areas. DNA fragmentation, micronucleus and dead cells percent were significantly higher in exposed workers than controls. Level of benzene, Toluene, Ethyl benzene and xylene in the work environment were higher than the control areas and the permissible limits. Gasoline station workers occupationally exposed to benzene are susceptible to genotoxic effects indicated by increased DNA fragmentation, higher frequency of micronucleus and decreased leukocytes viability.

Effect of gasoline fumes on reproductive function in male albino rats

The increase in the frequency of exposure to gasoline fumes and the growing incidence of infertility among humans has been a major concern and subject of discussion over the years in Nigeria. We therefore present the reproductive effect of gasoline fumes on inhalation exposure in 40 male albino rats. The rats were randomized into five experimental treatments (T) with eight rats per treatment. T1 (control) was exposed to distilled water while T2, T3, T4, and T5 were exposed to gasoline fumes in exposure chambers for 1, 3, 5, and 9 h daily respectively for 12 weeks. Serum level of testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, oxidative stress markers in the testicular tissue, epididymal sperm health assessment, and testicular histopathology of the rats were used as a diagnostic marker of reproductive dysfunction. Significant (p < 0.05) alterations in the levels of all the reproductive hormones and oxidative stress markers assayed were observed in rats exposed to gasoline fume. Significant reductions (p < 0.05) in sperm count and percentage motility in the exposed rats were observed. Significant (p < 0.05) increased in abnormal sperm cells characterized by damaged head, bent tail, damaged tail, and without head were also observed in the exposed rats. Histopathologically, severe degenerative testicular architectural lesions characterized by alterations in all the generations of sperm cells and reduction of interstitial cells were seen in the exposed rats. Gasoline fume is thus said to interfere with spermatogenesis and impair fertility in male gonad.

Oxidative Stress and Genotoxicity of Long-Term Occupational Exposure to Low Levels of BTEX in Gas Station Workers

Atmospheric benzene, toluene, ethylbenzene, and xylenes (BTEX) can lead to multiple health injuries. However, what remains uncertain is the effect of long-term exposure to low levels of BTEX. Thus, we determined the BTEX levels in the air from the refueling and office areas in gas stations. Then we collected workers’ (200 refueling vs. 52 office workers) peripheral blood samples to analyze the serum total-superoxide dismutase (T-SOD), glutathione (GSH), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) levels. DNA damage was analyzed by the comet assay and micronucleus test in buccal epithelial cells. We found that the levels of BTEX in refueling areas were significantly higher than those in office areas (p < 0.001). The serum T-SOD and GSH of refueling workers were significantly lower than those in office workers (p < 0.001). By contrast, the serum MDA and 8-OHdG of refueling workers were significantly higher than those of office workers (p < 0.001, MDA; p = 0.025, 8-OHdG). Furthermore, tail and Olive tail moments in refueling workers were longer (p = 0.004, tail moment; p = 0.001, Olive tail moment), and the micronucleus rate was higher (p < 0.001) than those in office workers. Taken together, long-term exposure to low levels of BTEX may reduce the antioxidant ability and increase the risk of DNA damage in refueling workers of gas stations.

Overexpression of miR-221 in peripheral blood lymphocytes in petrol station attendants: A population based cross-sectional study in southern China

Benzene is a recognized environmental leukemogen, however, the mechanisms for its carcinogenesis have not been fully elucidated. Recently, miR-221, a suggested oncogene involved in a number of malignancies, has been detected with elevated expression levels in blood cells of patients with leukemia. To explore whether benzene exposure has an effect on the expression of miR-221, a population based cross-sectional study was conducted in southern China, with 97 petrol station attendants as the exposure group and 103 general residents as the control group. Plasma benzene was analyzed by using GC∖MS. miR-221 in peripheral blood lymphocytes were measured by qRT-PCR and the ΔCt value for each sample was calculated by normalizing the Ct value for miR-221 with U6 RNA (i.e., ΔCt = CtmiR-221 - CtU6). Potential confounding factors were taken into account. Pearson correlation, univariate and multivariate logistic regression were performed in statistical analysis. The results showed that the air concentrations of benzene were significantly higher in petrol stations than in control sites (P < 0.05); The levels of benzene and miR-221 in exposure group were both significantly higher than in control group (P < 0.05) and there was a significant positive correlation between the two indexes (r = 0.851, P < 0.05); An association between benzene levels and the ΔCt values for miR-221 was identified by univariate and multivariate logistic analysis (OR 0.274; 95%CI 0.117, 0.396). Our investigation indicates that benzene exposure may be related to elevated miR-221 expression in human lymphocytes.

Some Biochemical and Hematological Parameters among Petrol Station Attendants: A Comparative Study

Objective. To describe selected biochemical and hematological parameters (blood picture, liver enzymes, and kidney functions) in petrol station attendants in Mansoura city. Methods. This is a comparative cross-sectional study. The exposed group included 102 petrol station attendants. They were compared to a matched group of healthy 102 male service and office workers at the Faculty of Medicine, Mansoura University. The results of blood picture, liver enzymes, and kidney functions were compared between both groups. Results. Mean Red Blood Cells (RBCs) count, hemoglobin level, and Hematocrit (HCT) level were significantly lower in petrol station attendants than the comparison group. All other blood picture parameters showed nonsignificant difference between both groups. Liver enzymes, renal functions, serum albumin, and total protein showed statistically nonsignificant difference between both groups except for alanine aminotransferase (ALT) which was significantly higher in petrol station attendants. Conclusions. Some laboratory parameters among petrol station attendants showed changes that could be attributed to workplace exposure and should be given attention at preemployment and periodic medical examination.

Cytogenetic biomonitoring of occupationally exposed workers to ashes from burning of sugar cane in Ahome, Sinaloa, México

Burning the sugar cane field before harvesting has a negative impact on both air and human health, however this issue had not been explored in Mexico. The objective of this work was to determine the chromosomal damage in workers from sugar cane burning fields in Sinaloa, México. To this purpose, we analyzed 1000 cells of buccal exfoliated epithelia from 60 exposed workers and 60 non-exposed controls to determine micronucleus frequencies and other nuclear abnormalities. The results indicated significant higher values of micronucleus and nuclear abnormalities such as binucleate cells, pyknosis, karyolysis, chromatin condensation and nuclear buds frequencies in the exposed subjects compared to those that were not exposed. Our data indicates that sugar cane burning, that generates polycyclic aromatic hydrocarbons, represents a genotoxic risk for workers in this important sugar cane producing area in Mexico.

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.

Occupational exposure of diesel station workers to BTEX compounds at a bus depot

Diesel fuel is known to emit pollutants that have a negative impact on environmental and human health. In developing countries like South Africa, attendants are employed to pump fuel for customers at service stations. Attendants refuel vehicles with various octane unleaded fuel, lead-replacement petrol and diesel fuel, on a daily basis. Attendants are at risk to adverse health effects associated with the inhalation of volatile organic compounds released from these fuels. The pollutants released include benzene, toluene, ethylbenzene and xylenes (BTEX), which are significant due to their high level of toxicity. In this study, a risk assessment of BTEX was conducted at a diesel service station for public buses. Using Radiello passive samplers, it was found that benzene concentrations were above recommended international standards. Due to poor ventilation and high exposure duration, the average benzene concentration over the sampling campaign exceeded the US Environmental Protection Agency’s chronic inhalation exposure reference concentration. Lifetime cancer risk estimation showed that on average there is a 3.78 × 10⁻⁴ cancer risk, corresponding to an average chronic daily intake of 1.38 × 10⁻³ mg/kg/day of benzene exposure. Additionally, there were incidences where individuals were at potential hazard risk of benzene and toluene that may pose non-carcinogenic effects to employees.

Early hematological and immunological alterations in gasoline station attendants exposed to benzene

INTRODUCTION

Elucidation of effective biomarkers may provide tools for the early detection of biological alterations caused by benzene exposure and may contribute to the reduction of occupational diseases. This study aimed to assess early alterations on hematological and immunological systems of workers exposed to benzene.

METHODS

Sixty gasoline station attendants (GSA group) and 28 control subjects were evaluated. Environmental and biological monitoring of benzene exposure was performed in blood and urine. The potential effect biomarkers evaluated were δ-aminolevulinate dehydratase (ALA-D) activity, CD80 and CD86 expression in lymphocytes and monocytes, and serum interleukin-8 (IL-8). The influence of confounding factors and toluene co-exposure were considered.

RESULTS

Although exposures were below ACGIH (American Conference of Governmental Industrial Hygienists) limits, reduced ALA-D activity, decreased CD80 and CD86 expression in monocytes and increased IL-8 levels were found in the GSA group compared to the control subjects. Furthermore, according to multiple linear regression analysis, benzene exposure was associated to a decrease in CD80 and CD86 expression in monocytes.

CONCLUSIONS

These findings suggest, for the first time, a potential effect of benzene exposure on ALA-D activity, CD80 and CD86 expression, IL-8 levels, which could be suggested as potential markers for the early detection of benzene-induced alterations.

Metabolic polymorphisms and biomarkers of effect in the biomonitoring of occupational exposure to low-levels of benzene: state of the art

Current levels of occupational exposure to benzene, a genotoxic human carcinogen, in Western countries are reduced by two-three orders of magnitude (from ppm to ppb) as compared to the past. However, as benzene toxicity is strongly dependent on biotransformation and recent evidence underlines a higher efficiency of bio-activation pathways at lower levels of exposure, toxic effects at low doses could be higher than expected, particularly in susceptible individuals. Currently, biological monitoring can allow accurate exposure assessment, relying on sensitive and specific enough biomarkers of internal dose. The availability of similarly reliable biomarkers of early effect or susceptibility could greatly improve the risk assessment process to such an extent that risk could even be assessed at the individual level. As to susceptibility biomarkers, functional genetic polymorphisms of relevant biotransformation enzymes may modulate the risk of adverse effects (NQO1) and the levels of biomarkers of internal dose, in particular S-phenylmercapturic acid (GSTM1, GSTT1, GSTA1). Among biomarkers of early effect, genotoxicity indicators, although sensitive in some cases, are too aspecific for routine use in occupational health surveillance programmes. Currently only the periodical blood cell count seems suitable enough to be applied in the longitudinal monitoring of effects from benzene exposure. Novel biomarkers of early effect are expected from higher collaboration among toxicologists and clinicians, also using advanced "omics" techniques.

Traffic-related air pollution. A pilot exposure assessment in Beirut, Lebanon

Traffic-related volatile organic compounds (VOCs) pollution has frequently been demonstrated to be a serious problem in the developing countries. Benzene and 1,3-butadiene (BD) have been classified as a human carcinogen based on evidence for an increased genotoxic and epigenotoxic effects in both occupational exposure assessment and in vivo/in vitro studies. We have undertaken a biomonitoring of 25 traffic policemen and 23 office policemen in Beirut, through personal air monitoring, assessed by diffusive samplers, as well as through the use of biomarkers of exposure to benzene and BD. Personal benzene, toluene, ethylbenzene, and xylene (BTEX) exposure were quantified by GC-MS/MS, urinary trans, trans-muconic acid (t,t-MA) by HPLC/UV, S-phenyl mercapturic acid (S-PMA), monohydroxy-butenyl mercapturic acid (MHBMA) and dihydroxybutyl mercapturic acid (DHBMA) by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC/ESI(-)-MS/MS) in MRM (Multiple Reaction Monitoring) mode. We found that individual exposure to benzene in the traffic policemen was higher than that measured in traffic policemen in Prague, in Bologna, in Ioannina and in Bangkok. t,t-MA levels could distinguish between office and traffic policemen. However, median MHBMA levels in traffic policemen were slightly elevated, though not significantly higher than in office policemen. Alternatively, DHBMA concentrations could significantly distinguish between office and traffic policemen and showed a better correlation with personal total BTEX exposure. DHMBA, measured in the post-shift urine samples, correlated with both pre-shift MHMBA and pre-shift DHMBA. Moreover, there was not a marked effect of smoking habits on DHBMA. Taken together, these findings suggested that DHBMA is more suitable than MHBMA as biomarker of exposure to BD in humans. Traffic policemen, who are exposed to benzene and BD at the roadside in central Beirut, are potentially at a higher risk for development of diseases such as cancer than office policemen.

Comparison of BTX profiles and their mutagenicity assessment at two sites of Agra, India

In the present study, the concentrations of three volatile organic compounds (VOCs), namely, acronym for benzene, toluene, and xylenes (BTX) were assessed because of their role in the tropospheric chemistry. Two representative sites, a roadside and a petrol pump, were chosen for sample collection. VOCs were collected using SKC-activated charcoal tubes and SKC personal sampler and characterized by gas chromatograph using flame ionization detector. Among BTX, benzene had the highest concentration. At the roadside, mean concentration of benzene, toluene, o-,m-xylene, and p-xylene were 14.7 ± 2.4 μgm(-3), 8.1 ± 1.2 μgm(-3), 2.1 ± 0.8 μgm(-3), and 5.1 ± 1.2 μgm(-3), respectively. At the petrol pump, the mean concentrations of benzene, toluene, o-,m-xylene and p-xylene were 19.5 ± 3.7 μgm(-3), 12.9 ± 1.1 μgm(-3), 3.6 ± 0.5 μgm(-3) and 11.1 ± 1.5 μgm(-3), respectively, and were numerically higher by a fraction of 2. Monthly variation of BTX showed maximum concentration in winter. Inter-species ratios and inter-species correlation indicated traffic as the major source of BTX. Extracts of samples were positive in both Salmonella typhimurium tester strains TA98 and TA100 without metabolic activation suggesting the presence of direct mutagens in ambient air that can cause both frame-shift and base-pair mutation. The mutagenic response was greater for TA100 than TA98 suggesting greater activity for base-pair mutagenicity than frame-shift mutagenicity and was found to be statistically significant.