Effect of hydrotreatment on the photomutagenicity of shale oil.

Dimethyl sulfoxide extracts of a parent crude and a hydrotreated Paraho shale oil were tested in Salmonella to detect the presence of direct acting mutagens, promutagens, which are converted by liver enzymes to direct acting mutagens, and photomutagens, which photosensitize Salmonella to mutation by fluorescent light. Direct acting mutagens were not detected in extracts of either shale oil. Both photomutagens and promutagens were detected in the parent crude, but only photomutagens were detected in the hydrotreated material. These results suggest that the photomutagens and promutagens were effected differently by hydrotreatment and that the two types of mutagens are to some degree different chemical entities. Both the crude and hydrotreated shale oils are reported to be carcinogenic in mouse skin, and our results of photomutation testing more closely parallel the carcinogenicity of the shale oils than do our results of testing with enzymatic activation.