In general, the carcinogenic potential of
petroleum-derived materials is related to the
polycyclic aromatic hydrocarbon (PAH) content. Thus it has been assumed that liquids which boil below the PAH distillation range (i.e., below approx. 370 degrees C (700 degrees F) would not be carcinogenic. Several early studies supported this conclusion but were of relatively short duration. Several recent and more rigorous studies have shown that repeated application of certain
petroleum-derived materials boiling between approximately 177-370 degrees C (350-700 degrees F) (i.e., middle distillate fuels) can produce
tumors in mouse skin. The current studies assessed the tumorigenic potential of a series of middle distillates which varied with respect to boiling range, composition, and source of blending stocks. All of the samples produced evidence of weak tumorigenic activity which was characterized by low
tumor yields and long median latencies. However, the majority of the
tumor yields were significantly different from the control. There were no apparent differences in response among the samples. Thus the various parameters examined did not substantially influence
tumor outcome. In particular, there was no association of tumorigenic activity with aromatic
carbon content; this finding, coupled with evidence that PAH levels were low, suggested that the tumorigenic responses were not PAH-dependent. In addition to the
tumors, there was evidence of non-neoplastic dermal changes including
hyperplasia. These may have contributed to the tumorigenic responses; however, the actual mechanism of
tumor induction is unknown.