Skin carcinogenicity of condensed asphalt roofing fumes and their fractions following dermal application to mice.

Condensed roofing asphalt fumes, generated at 316 degrees C, were collected by cold trap condensation and fractionated by preparative high performance liquid chromatography. Chemical classes in each of the fractions (A-E) were identified by gas chromatography/mass spectroscopy. The fractions, various combinations of fractions, the raw and heated asphalt, the neat asphalt fume and the reconstituted asphalt were tested for carcinogenicity, and three fractions were tested for cocarcinogenicity and tumor promotion with benzo[a]pyrene (BaP). The skin application carcinogenesis bioassay was conducted by twice weekly application of test materials in 0.05 ml of acetone/cyclohexane (1:1) for 104 weeks to 40 groups of male C3H/HeJ mice (30/group). Fractions were applied at a mass in proportion to their amount in the neat asphalt fumes. In addition, the neat asphalt fume was tested on Sencar mice to determine if this strain was more susceptible to the carcinogenic effects of the fumes. Condensed neat asphalt fumes produced similar and statistically significant increased tumor yields of papillomas and carcinomas in both strains as compared to respective vehicle controls. Recombination of all fractions resulted in a tumor response similar to neat asphalt fumes. Among individual fractions, C was most potent, followed by B. The other single fractions were without significant tumorigenic activity. Combinations containing fractions B and C were most active among the mixtures that were assayed and no evidence of enhancement of tumorigenesis in the mixtures was found. No significant cocarcinogenic or tumor promoting activity was observed with fractions A, D, or E and BaP. Raw unheated asphalt produced a few tumors in C3H mice, but no tumors were seen when raw asphalt heated to 316 degrees C, with the fumes permitted to escape, was applied.