Toxicology and Industrial Health 2007; 23: 167–175 http://tih.sagepub.com Introduction Benzene is a volatile organic compound (VOC) and a major component of vehicular pollution (Sterling, 1984). It is present as gas in both exhausts and evapora- tive emissions from automobile fuels (Sterling, 1984). Persons occupationally exposed to urban air pollution from road traffic such as traffic policemen are highly exposed to benzene (Crebelli et al., 2001). Several epi- demiological studies have demonstrated harmful effects of benzene on human health (Aksoy, 1985; Rothman et al., 1996). For example, benzene exposure has been shown to increase the risk of developing leukemia, lymphoma, aplastic anemia, pancytopenia and chromosomal aberrations (Aksoy, 1985, 1989; WHO, 1993; Snyder, 2000). Benzene has been classified by International Agency for Research on Cancer as a human carcinogen, and the carcinogenic effect may occur even at low-level exposure (IARC, 1982). Occupational benzene exposure from vehicular sources in India and its effect on hematology, lymphocyte subsets and platelet P-selectin expression MR Ray a , S Roychoudhury b , S Mukherjee a and T Lahiri b a Experimental Hematology Unit, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata 700 026, India b Department of Neuroendocrinology, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata 700 026, India Benzene exposure from vehicular sources and its health impact are relatively unexplored in India. We have investigated in this study hematology and lymphocyte subsets of 25 petrol pump attendants, 25 automo- bile service station workers and 35 controls matched for age, sex and socioeconomic conditions. The participants were non-smoking males of Kolkata (former Calcutta) in eastern India. Compared with con- trols, the workers had 3.8- times more trans,trans-muconic acid in urine, suggesting higher level of benzene exposure. The exposed subjects had decreased erythrocyte, hemoglobin, lymphocyte and platelet levels, but increased neutrophil, band cells, RBC aniso-poikilocytosis and target cells. In addition, CD4+, CD8+ and CD19+ cells were decreased by 37, 20 and 47% respectively, but CD 16+ 56+ NK cells were increased by 20%. P-selectin expression on platelet surface of the workers was significantly elevated (P  0.05), indicating upregulation of platelet activity. In summary, the study revealed high level of ben- zene exposure from vehicular sources in India, and the exposed subjects had hematological and immunological alterations. Toxicology and Industrial Health 2007; 23: 167–175. Key words: Benzene; hematology; immunology; India; vehicular pollution Address all correspondence to: Manas Ranjan Ray, Ph.D., Experimental Hematology Unit, Chittaranjan National Cancer Institute, 37, S. P. Mukherjee Road, Kolkata 700 026, India Tel: +91-33-2476 5101; Fax: +91-33-2475 7606 E-mail: manasrray@rediffmail.com © 2007 SAGE Publications 10.1177/0748233707080907