Short term in vivo method for prediction of the fibrogenic effect of different mineral dusts.

The effect of intratracheal introduction of different metal and mineral dusts and the change in activity of pulmonary acidic phosphatase have been studied as a function of time (72 h, 2 weeks, 1, 12, 20 months). The activity and localization of acid phosphatase were compared with the degree of pulmonary damage caused by dusts. The degree of fibrosis was determined on the basis of the composition of cells and fibres, according to Belt and King's classification. Due to the membrane-damaging effect of DQ 12 silica and mixed dusts (enargite and porphyry rock dusts) an increase in acid phosphatase activity of macrophages could be observed at the end of the first month. At the same time non-fibrogenic or only mild fibrogenic dusts (bentonite, corundum, scarnic rock dust) caused a decrease or disappearance of tissue acid phosphatase activity. It has been stated that there is a very close correlation between the change in pulmonary acidic phosphatase activity and the progression of pulmonary fibrosis due to exposure to mineral dusts. The above investigations have been most useful in predicting the subsequent effect of rock patterns, emphasizing at the same time the importance of in vivo long term experiments.