Assessment of the utility of the micronucleus test for petroleum-derived materials

The micronucleus test is a commonly used in vivo assay for chromosomal dama ge and is an integral part of many mutagenicity testing strategies. The pre sent report describes an assessment of the micronucleus test for the detect ion of mutagenic potential of petroleum-derived materials. To this end, stu dies were conducted with catalytically cracked clarified oil (CCCO). This m aterial contains high levels of polycyclic aromatic constituents (PAC) and is a very potent inducer of mouse skin tumors. CCCO is also active in the S almonella assay and other in vitro tests. As CCCO is the most potent of the various petroleum-derived materials in other assays, it was assumed to be the most easily detectable in the micronucleus test. CCCO was tested in sta ndard mouse micronucleus tests utilizing oral and intraperitoneal injection for test material administration. All of these studies were negative, alth ough DMBA, tested at roughly equivalent levels based on potency in the Salm onella assay, produced statistically significant increases in micronucleus frequency. In a second series of studies, aromatic fractions of CCCO were p repared and tested at up to acutely toxic levels. Results of these studies were also negative. Finally, another petroleum-derived material which is ca rcinogenic and contained PAC was tested in the micronucleus assay. It also produced negative results. Thus, it was concluded that petroleum-derived ma terials do not produce clastogenic effects in vivo in the mouse micronucleu s test, despite the fact that some pure polycyclic aromatic hydrocarbons ar e quite active in this assay. (C) 1999 Elsevier Science B.V. All rights res erved.