Bio-Directed Fractionation of Laboratory-Generated Asphalt Fumes: Relationship Between Composition and Carcinogenicity

In the 1980's the National Institute of Occupational Safety and Health (NIOSH) sponsored mouse skin-painting bioassays of roofing asphalt fume condensates laboratory generated at 316°C. Five HPLC subfractions (designated A-E) were skin-painted individually and in various combinations. The whole fume condensates and two of the five fractions (B and C) were shown to be carcinogenic. The present study repeated the fume generation and fractionation phases of the NIOSH study using the same asphalt (bitumen), fume generation apparatus, and HPLC method. The carcinogenic fractions, B and C, were then subfractionated by cyanopropyl and silica gel column chromatography. Biological activity was tracked using the Modified Ames Assay, while relative PAC content was monitored using a newly developed fluorescence method. The results were consistent with the hypothesis that relatively high molecular weight PACs were largely responsible for the carcinogenic activity of the NIOSH fumes.