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The process streams refined from petroleum crude oil for use in petroleum products are among those designated by USEPA as UVCB substances (unknown or variable composition, complex reaction products and biological materials). They are identified on global chemical inventories with unique Chemical Abstract Services (CAS) numbers and names. The chemical complexity of most petroleum substances presents challenges when evaluating their hazards and can result in differing evaluations due to the varying level of hazardous constituents and differences in national chemical control regulations. Global efforts to harmonize the identification of chemical hazards are aimed at promoting the use of consistent hazard evaluation criteria. This paper discusses a systematic approach for the health hazard evaluation of petroleum substances using chemical categories and the United Nations (UN) Globally Harmonized System (GHS) of classification and labeling. Also described are historical efforts to characterize the hazard of these substances and how they led to the development of categories, the identification of potentially hazardous constituents which should be considered, and a summary of the toxicology of the major petroleum product groups. The use of these categories can increase the utility of existing data, provide better informed hazard evaluations, and reduce the amount of animal testing required.

Varying doses of TCDD ranging from 25 to 1000 mug/kg were administered to the larval and adult forms of the American bullfrog, Rana catesbeiana. Doses of TCDD as high as 1 mg/kg failed to have any significant effect upon survival or completion of metamorphosis in tadpole and doses of up to 500 mug/kg had no effect on survival of adult frogs. Histopathological examination of various tissues from the metamorphosed tadpoles and adult frogs failed to show any abnormalities.

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