In many occupational settings, the ambient environment is a sink of various contaminants that emerge from point and nonpoint sources and causes direct exposure to workers. Such exposures in petroleum-related occupations usually result from routine transportation, distribution, accidental spills, improper handling and use, and leaching of petroleum hydrocarbons products; there are also many other ways by which humans are exposed to these chemicals [1]. Many of the aromatic organic solvents, such as toluene, ethyl benzene, xylene, etc., are common components of petroleum products, most of which have already been confirmed as carcinogens, e.g., benzene 2, 3 and 4. Benzene is considered to be one of the possible causes of morbidities among automobile workshop mechanics as well as in automobile painters [5]. Among many other environmental sources, benzene mostly arises from fuel vapors and gasoline (range, 1.8–3.7%) and from solvents used for degreasing or as diluents at work areas of automobile mechanics [6]. Most exposures to organic solvents occur during the maintenance of various engine parts [7]. Such solvents, after being absorbed into the intercellular fluid, may enter main bloodstream and get distributed throughout the body [8]. Benzene affects blood production by affecting the bone marrow. In Korean industries, an excessive risk of hematopoietic diseases because of relatively high past exposure to benzene has been reported [9]. Apart from direct occupational exposure, nonoccupational population around chemical factories and other occupational sites may also undergo indirect exposure [10]. Thus, occupational exposure hematotoxicity [11] and other blood disorders such as blood cancer (leukemia), aplastic anemia, and dysplastic bone marrow conditions are common results of exposure to aromatics such as benzene [12], screening of which can be done easily by complete blood counts.