Validity of new biomarkers of internal dose for use in the biological monitoring of occupational and environmental exposure to low concentrations of benzene and toluene

Exposure to low environmental levels of benzene: evaluation of micronucleus frequencies and S-phenylmercapturic acid excretion in relation to polymorphisms in genes encoding metabolic enzymes

An integrated approach based on environmental and biological monitoring, including the analysis of biomarkers of exposure [excretion of S-phenylmercapturic acid (S-PMA)], early biological effects [micronucleus (MN) frequency] and susceptibility (genetic polymorphisms), was applied to characterize benzene exposure in a group of 70 traffic policemen and 40 employees of the city of Bologna, Italy. Median personal benzene exposure was 6.55-fold higher for traffic policemen than for controls (P<0.0001). This higher exposure was confirmed by a significant, 2.53-fold higher S-PMA excretion in traffic policemen compared with that observed for indoor workers (P<0.0001). Median MN frequency was also significantly higher in policemen compared with indoor workers (P=0.001), emphasizing the genotoxic effect potentially associated with benzene exposure. With regard to biomarkers of susceptibility, the analysis revealed that high epoxide hydrolase (mEH) (predicted) enzyme activity was significantly correlated with a lower median MN frequency (P=0.003). A gene-gender interaction was observed for the glutathione-S-transferase M1 (GSTM1) genotype. The GSTM1-null genotype was associated with a significantly higher median MN frequency in men, not in women. Statistical analysis did not reveal any association between the presence of the protective allele, pushing the pathway towards benzene detoxification, and MN frequency or S-PMA excretion. Even though there are some limitations in the study, our results indicate that policemen are exposed to higher levels of benzene than individuals spending most of the time indoors. This higher exposure may contribute to DNA damage, suggesting an increase health risk from traffic benzene emission. Finally, a more comprehensive study is warranted in order to better elucidate the involvement of EPHX1 genotypes combination in benzene genotoxicity.

Benzene exposure in childhood: Role of living environments and assessment of available tools

Benzene is a widespread air pollutant and a well-known human carcinogen. Evidence is needed regarding benzene intake in the pediatric age group. We investigated the use of urinary (u) trans,trans-muconic acid (t,t-MA), S-phenylmercapturic acid (SPMA), and unmodified benzene (UB) for assessing exposure to low concentrations of environmental benzene and the role of living environment on benzene exposure in childhood. u-t,t-MA, u-SPMA, u-UB and u-cotinine were measured in urine samples of 243 Italian children (5-11 years) recruited in a cross-sectional study. Analytical results were compared with data obtained from questionnaires about participants' main potential exposure factors. u-UB, u-t,t-MA and u-SPMA concentrations were about 1.5-fold higher in children living in urban areas than in those in the rural group. Univariate analyses showed that u-UB was the only biomarker able to discriminate secondhand smoke (SHS) exposure in urban and rural children (medians=411.50 and 210.50 ng/L, respectively); these results were confirmed by the strong correlation between u-UB and u-cotinine in the SHS-exposed group and by multivariate analyses. A regression model on u-SPMA showed that the metabolite is related to residence area (p<0.001), SHS exposure (p=0.048) and gender (p=0.027). u-UB is the best marker of benzene exposure in children in the present study, and it can be used as a good carcinogen-derived biomarker of exposure to passive smoking, especially related to benzene, when urine sample is collected at the end of the day. In addition, it is important to highlight that SHS resulted the most important contributor to benzene exposure, underlining the need for an information campaign against passive smoking exposure.

Occupational exposure to gasoline and the risk of non-Hodgkin lymphoma: a review and meta-analysis of the literature

AIMS

Gasoline comprises over 500 chemicals, including the known or suspected carcinogens benzene, 1,3-butadiene, ethylbenzene and methyl tert-butyl ether (MTBE). To assess whether work in the production, distribution and use of gasoline is associated with non-Hodgkin lymphoma (NHL), we reviewed the published literature on this topic.

METHOD

English-language peer-reviewed articles were identified by keyword searches of bibliographic databases. Twenty-two cohorts and thirteen case-control studies examined the risk of NHL among persons employed in the downstream petroleum industry.

RESULT

No positive associations were found with the exception of one study. The pooled risk estimate from a random-effects meta-analysis was 1.02 (95% confidence interval (CI) 0.94-1.12). Although there were no estimates available, exposure is likely to have varied by occupation, location and time period; there was no evidence however that risk estimates varied by any of these factors. NHL is a heterogeneous disease, yet no data were reported for NHL subtypes.

CONCLUSION

In summary, there is no suggestion across an extensive literature that exposure to gasoline at the levels workers' experience in an occupational setting increases the risk of NHL.

Occupational exposure to low levels of benzene: Biomarkers of exposure and nucleic acid oxidation and their modulation by polymorphic xenobiotic metabolizing enzymes

This study investigated nucleic acid oxidation associated with exposure to benzene at low levels in 239 workers recruited among traffic policemen, taxi drivers and gasoline pump attendants of the city of Parma (Italy). Biomarkers of exposure, namely urinary t,t-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA), urinary cotinine, and urinary biomarkers of nucleic acid oxidation, namely 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydroguanine (8-oxoGua) were determined by liquid chromatography-tandem mass spectrometry. Relevant polymorphisms of NAD(P)H:quinone oxidoreductase (NQO1), glutathione S-transferases M1-1 (GSTM1), T1-1 (GSTT1), and A1 (GSTA1) were characterized by polymerase chain reaction-based methods in a subgroup of subjects. Biomarkers of nucleic acid oxidation were correlated with each other (r> or =0.32, p<0.0001) and with exposure biomarkers (r> or =0.28, p<0.0001). Multiple linear regression models including age, sex and smoking habits as independent variables demonstrated that benzene exposure is associated with oxidation damage to nucleic acid, particularly to RNA (p<0.0001) and is modulated by the NQO1 polymorphism. The study confirmed a significant modulating effect of GSTM1 (p=0.010), GSTT1 (p=0.023) and GSTA1 (p=0.048) polymorphisms on S-PMA excretion, with a significant interaction between GSTM1 and both GSTT1 and GSTA1 (p=0.006 and p=0.037, respectively).