Hematological changes among Beninese motor-bike taxi drivers exposed to benzene by urban air pollution

Exposure to high-concentration of benzene in polluted air has been associated with bone marrow deficiency, aplastic anemia and leukemia. However, epidemiological studies have reported conflicting data following human exposure to benzene levels below 1 ppm (that is, 3.2 mg/m3). Therefore we investigated the influence of outdoor air benzene on peripheral blood cells among exposed motor-bike-taxi drivers (MBTD) in which specific IgG antibodies against reactive benzene metabolites, such as hydroquinone (HQ) and para-benzoquinone (p-BQ) are identified and quantified for further use as biomarker of exposure. We compared 144 MBTD with 30 unexposed age and sex-matched controls. The mean age ± SD (95 % CI) were: MBTD 39.5 ± 7.82 (38.2- 40.7) and village residents 40.3 ± 10.56 (39.1-43.0). Personal benzene exposure was assessed using GABIE diffusive samplers. The levels of specific IgG antibodies to HQ and p-BQ were determined by ELISA. The peripheral blood cells were counted by an automated analyzer. Benzene, Toluene and Xylene levels were much higher in MBTD in comparison to the control group. Benzene exposure levels ranged from 0.012 to 0.550 ppm in MBTD. Their average exposure level per one week was 0.126±0.206 ppm. Accordingly, MBTD had significantly higher levels of specific IgG antibodies to HQ and p-BQ compared to the controls (p< 0.001). WBC, lymphocytes, eosinophils and platelets were significantly decreased in MBTD, whereas RBC and other blood cel