In this study, 350 vehicles in 20 different models were examined in one of Tehran's Automobile Technical Inspection Centers. The laboratory tests indicate that longtime exposure to benzene has destructive effects on the blood cells, especially the bone-marrow cells. The concentration levels of benzene caused by the emission of gasoline vapors from fuel tanks doors were measured by PhoCheck EX5000 during a 5 to 15-minute interval for each car. The results indicate that the concentration of

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... e caused by the emission of gasoline vapors from the fuel tanks door of the domestic cars was 10 times higher than the imported cars. In most of the imported cars, the amount of benzene in the three measured areas was negligible. This is due to the use of new technology and adaptation of strict environmental standards by the manufacturing country.