In the course of testing of fibrogenicity of industrial dust samples in rats, an unusual morphological type of the formation of strong collagen bundles of collagen fibres in coniophagic foci induced by a series of five instilled dust of low or medium fibrogenicity, expressed by the determination of collagen multiplication in the lungs. Four dust samples represented various forms of aluminium oxide (gamma Al2O3, corundum, resistex /SiO2 .Al2O3/, starting dust for the production of artificial corundum) and the fifth sample is from diorite. The findings are discussed in view of evaluating the results of intratracheal test and its improvement, particularly by the use of histopathological evaluation of the induced changes

        Key words: industrial dust - intratracheal test - corundum - gamma AL2O3 - resistex - diorite - collagen - Saturn red