Crude mineral oil contains benzene as a natural constituent of approximately 0.1%. - GreenMedInfo Summary
Benzene: standards, occurrence, and exposure.
Am J Ind Med. 1985;7(5-6):375-83. PMID: 4003400
The national occupational standard values for benzene are 10 ppm for Australia, 10 ppm for Denmark, 10 ppm for Finland, 10 ppm for Japan, 10 ppm for The Netherlands, 10 ppm for the United States, and 5 ppm for Sweden; in the Federal Republic of Germany the technical guideline value is 8 ppm. Crude mineral oil contains benzene as a natural constituent of approximately 0.1%. Gasoline in Sweden may contain 4-5% benzene by volume. The 8-hour time-weighted average (TWA) exposure levels of Swedish petroleum refinery workers vary between 0.1 to 1 mg benzene/m3 in air. The exposures of benzene in various other occupations were measured and described. Other environmental exposures to benzene may have their origin in pyrolysis, such as tobacco smoking and burning of substances such as polyvinylchloride.