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(1) Background : The products of guanine oxidation in DNA and RNA excreted in urine are 8-oxo-7,8-dihydroguanine (8-oxoGua), 8-oxo-7,8-dihydroguanosine (8-oxoGuo), and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo). Despite intra and inter-individual variability, it is possible to identify situations that significantly increase the levels of these compounds when comparing urinary concentrations of some workers to those of the general population. (2) Methods : urines from gasoline pump attendants (58 from Saudi Arabia and 102 from Italy), 24 workers of a fiberglass reinforced plastics plant, 17 painters and 6 divers were analyzed by HPLC/MS-MS. To test the individual variability, two subjects provided daily samples for one month, and 132 urine samples from the general population were analyzed. (3) Results : We summarized the results for each biomarker, and found the following were statistically higher than in the general population: 8-oxoGua in fiberglass and Italian gasoline workers; 8-oxodGuo in fiberglass and both Saudi Arabian and Italian gasoline workers; 8-oxoGuo in fiberglass workers, both Saudi Arabian and Italian gasoline workers, and painters after the working shift. (4) Conclusions : these results confirm that both 8-oxodGuo and 8-oxoGuo are valuable biomarkers for occupational exposures to dangerous chemicals and seem to suggest that 8-oxoGuo, related to RNA oxidation, is a suitable biomarker to evaluate short term, reversible effects of occupational exposures even within the health-based limit values.

(1) Background: The oxidized guanine derivatives excreted into urine, products of DNA and RNA oxidation and repair, are used as biomarkers of oxidative damage in humans. This study aims to evaluate oxidative damage in gasoline pump attendants occupationally exposed to benzene. Benzene is contained in the gasoline but it is also produced from traffic and from smoking. (2) Methods: Twenty-nine gasoline pump attendants from two major cities of Saudi Arabia and 102 from Italy were studied for urinary 8-oxo-7,8-dihydroguanine (8-oxoGua), 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo), and S-phenyl-mercapturic acid (SPMA) for benzene exposure and urinary cotinine for smoking status assessment by liquid chromatography-tandem mass spectrometry. Airborne benzene was also assessed in the Italian group by gas-chromatography with flame ionization detector (GC-FID). (3) Results: The results suggest that high levels of benzene exposure can cause an accumulation of SPMA and bring about the formation of the oxidation biomarkers studied to saturation. At low exposure levels, SPMA and oxidation biomarker levels were correlated among them and were associated with the smoking habit. (4) Conclusions: The study confirms the association between benzene exposure and the excretion of nucleic acid oxidation biomarkers and enhances the importance of measuring the smoking habit, as it can significantly influence oxidative damage, especially when the exposure levels are low.