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1 <br /> Human Health Risk Assessment <br /> Former Mobil Oil Bulk Plant 04-343 <br /> 500 East Grant Line Road <br /> Tracy, California <br /> r <br /> 3.1.6.1 Lead <br /> Before 1985, regular octane gasoline contained organic lead (leaded gasoline) at a concentration <br /> of approximately 300 ppm. In 1985, the U.S. EPA (EPA, 1986) restricted lead concentration <br />' in gasoline to 35 ppm, with a further reduction to 7 ppm as of Januani 1986 (Bradley, 1986). <br /> The concentration of alkyl lead vapors from gasoline constitute a sm 0l relative percentage in <br /> ' air. The quantity of tetraethyl-lead in gasoline vapor is not toxicologically significant in acute <br /> exposure (Carrol and Abel, 1973). <br /> ' 3.1.6.2 Other Octane Improvers <br /> With the regulation of alkyl lead compounds and benzene, a variety of proprietary and <br /> nonproprietary octane enhancers (also referred to as oxygenates), such:?; methanol, ethanol, tert- <br /> ' butyl alcohol (TBA) and methyl-tert-butyl ether (MTBE) have been introduced to boost octane <br /> ratings to their desired levels (Bradley, 1986). The oxygenates are not likely to contribute <br /> significantly to the acute toxicity of the gasoline mixture due to their relatively low inherent <br /> toxicity and percent by volume. <br /> ' 3.1.6.3 Ethylene Dichloride <br /> ' To prevent accumulation of lead deposits in automotive engines, scavenging agents are added <br /> to gasoline. Humans repeatedly exposed to low levels of ethylene dichloride (EDC) <br /> demonstrated liver and kidney dysfunction, neurological changes, anoro:da, and epigastric pains <br /> (NIOSH, 1976). EDC has been found to be mutagenic in vitro mutagenic tests (Nylander et al., <br /> 1978). The National Cancer Institute (NCI) considers it to be carcinogenic by gavage in rats <br /> and mice and recommends that exposure levels be kept as low as feasible (NCI, 1978). Maltoni <br /> et al., (1980) could not confirm the carcinogenicity of EDC through inhalation studies in <br /> ' Sprague-Dawley rats or Swiss mice. Pregnant female rats exposed to -100 ppm of EDC showed <br /> extensive maternal toxicity and decreased fecundity. Pregnant rats exposed to 100 ppm, and <br /> pregnant rabbits exposed to 100 or 300 ppm EDC did not produc, abnormal offspring <br /> ' (Rao et al., 1980). <br /> ' 30-0136-11 <br /> ire 3-8 <br />