Date of Graduation
The specific aims of the present investigation were to determine the genotoxicity and potential carcinogenicity of WFC of Type I and Type III roofing asphalt by using different genetic endpoints in mammalian cells in vitro and in rat in vivo. Morphological transformation studies in cultured BALB/c-3T3 cells indicated that at concentrations that allow less than 50% survival, neither of the WFC, with or without the hamster liver S9 activation system, significantly increased foci formation in BALB/c-3T3 cells. The conventional and immunofluorescent staining MN assays showed that both types of WFC caused a significant increase in the frequency of MNC and that 70% of MNC induced by WFC of roofing asphalt carried kinetochore-positive MN. A separate MN study with fractions of roofing asphalt WFC also indicated that the numbers of MNC in cultures treated with the WFC and fractions B, C, D, and E were significantly higher than those in the control culture, and that the slopes of the linear regressions for fractions B and C were greater than those for the WFC and fractions D and E. A clear dose-response of BNC also was induced by the WFC and fractions B and C. DNA adduct study in rat-lung-cell system showed that both WFCs caused DNA adduct formation in rat lung cells in a similar dose-related manner. Under the conditions studied, however, neither Type I nor Type III WFC induced DNA adducts in WBCs. This study, therefore, has demonstrated that although WFC from both types of roofing asphalt do not induce cell transformation in BALB/c-3T3 cells, these WFCs do have an ability to induce MN in vitro in V79 Chinese hamster lung cells. The damage appear to be due to spindle-fiber damage during cell division, in addition to chromosome breakages. The appearance of binucleated cells provided an additional evidence of numerical chromosomal aberrations. Fractions B and C are the most genotoxic components of roofing asphalt WFC. The covalent binding to target DNA in lung cells is integral to the genotoxicity of the roofing asphalt WFC.
Qian, Hongwei, "Genotoxicity studies of roofing asphalt fume condensates in mammalian cells." (1998). Graduate Theses, Dissertations, and Problem Reports. 9608.