Evaluation of the dermal carcinogenic potential of tar sands bitumen-derived liquids

The carcinogenic potential of Athabasca tar sands and six experimental liquids derived from crude bitumen was evaluated utilizing the mouse epidermal carcinogenesis model. Tar sands, bitumen, and untreated naphtha produced few, if any, tumors. Three thermally and catalytically cracked liquids, light (nominal boiling range: 149-316 degrees C) and heavy (nominal boiling range: greater than 316 degrees C) gas oils and gas oil blend (boiling range: greater than 316 degrees C), produced a significant number of epidermal neoplasms. A synthetic crude oil, prepared by blending naphtha and light and heavy gas oils, was moderately carcinogenic; however, the activity of this sample fell within the range of values obtained in studies of crude petroleum samples. Since the bitumen-derived streams do not differ substantially in carcinogenic potency from petroleum-derived materials of comparable boiling range and process history, industrial hygiene practices which limit exposures to levels comparable to those observed in the petroleum-refining industry should provide similar measures of protection.