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Human Health Risk Assessment <br /> Former Mobil Oil Bulk Plant 04-343 <br /> 500 East Grant Line Road <br /> Tracy, California <br /> 3.2 BENZENE v <br /> Benzene is an aromatic hydrocarbon C with a molecular weight 0 78.11 and is found in <br /> Y { �6) g <br /> gasoline in concentrations ranging from approximately 1 percent to 5 percent (JAT, 1989). It <br /> is a clear, colorless liquid with a very characteristic odor. An odor threshold of approximately <br /> 1.5 ppm (4.9 mg/m3) has been reported (ATSDR, 1989). The physicaa! and chemical properties <br /> of benzene are summarized in Table 3-4. <br /> Because benzene is volatile and lipid-soluble, it can be absorbed into the body through <br />' inhalation, ingestion, or dermal contact and may be stored in fatty tissues (Sandmeyer, 1981). <br /> Metabolism of benzene occurs primarily in the liver, but may also recur in bone marrow <br /> (ATSDR, 1987). <br /> The majority of scientific evidence suggests that benzene toxicity is p.-,)duced by one or more <br />' metabolites of benzene, rather than the compound itself (Klaassen et F i., 1986; IARC, 1982). <br /> Benzene is initially oxidized by mixed function oxidase enzymes located in the liver and bone <br /> marrow to form hydroxylated benzenes such as phenol (Snyder, 198^'). Humans exposed to <br /> benzene through inhalation eliminate benzene unchanged in exhaled a and as a metabolite in <br /> urine (Teisinger et al., 1952; Srbova et al., 1950; Nomiyama and No aiyama, 1974). <br />' Numerous investigators have found significant increases in chromosornal aberrations of bone <br /> marrow cells and peripheral lymphocytes from workers exposed to "enzene (IARC, 1982). <br /> Benzene also induced chromosomal aberrations in bone marrow cells of rabbits, mice, and rats <br />' (Kissling and Speck, 1973; Meyne and Legator, 1980; Anderson and Richardson, 1979). Other <br /> effects possibly linked to benzene exposure include adverse faproductive outcome, <br /> cardiovascular, renal, neurological, psychological, immunological. ophthalmological and <br /> gastrointestinal effects (API, 1986). <br /> A number of case studies and epidemiologic investigations have indicated the causal association <br /> between inhalation of benzene and leukemia in humans (Aksoy et al.. 1974; Infante, 1977a, <br /> 1977b; Rinsky et al., 1981; Ott et a1., 1978; Wong et al., 1983). Workers exposed to <br /> concentrations of 10 to 40 ppm of benzene for less than one year h:;ve shown mild cytopenic <br /> 30-0136-11 <br /> 3-9 <br /> i <br />