Lung Tumours in Rats after Intratracheal Instillation of Dusts

Abstract
Intratracheal instillation of several non-fibrous dusts induced tumour rates of between 3 and 65% in female Wistar rats. Diesel soot showed a relatively high tumourigenic potency. However, carbon black with a high specific surface area and an extremely low PAH content was just as carcinogenic. The surface properties of elemental carbon seem to be much more effective than dusts from iron oxides, titanium dioxide and silicon carbide. There are indications of a rat specific ‘overload carcinogenesis’, but this term may oversimplify a mechanism which does not seem to exist in hamsters. Polyvinylpyridine-N-oxide inhibited the development of severe siltcosis after treatment with quartz DQ 12 and prolonged the life-span; the total tumour incidence and especially the rate of malignant tumours increased. This supports the assumption that benign lung tumours, which seldom occur in humans are, in animals, precursors of malignant tumours and should be combined for toxicologic evaluation. Relatively low masses of man-made mineral fibres from silicon carbide and glass induced tumours and confirmed the conclusion from earlier experiments that there is an s reaction of the serosa and lung tissue to mineral fibres.

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