[Experimental silicosis. Evaluation of the silicogenic properties of apatites and phosphorites]

White rats were intratracheally injected with 50 mg of apatite or phosphorite dust. The animals were killed 3, 6 and 10 months after the injection. Fibrogenic properties were evaluated on the basis of biochemical and histopathological studies. It was found that the dusts under examination after 3 months of experiment induced a statistically significant increase of wet and dry lungs weight, of hydroxyproline and lipids content in the lungs, and intrathroacic lymph nodes as compared with the control group. After 3 and 10 months, a further but statistically insignificant increase of hydroxyproline content in lungs and of wet lung weight was observed, as compared with animals in the 3--months experiment. The obtained values of fibrogenic action indices for apatite and phosphorite dusts were quite similar to the values obtained in animals injected with inert dust of titanium dioxide. They were 4--5 times lower than the indices obtained after administrating the river sand--a dust of strong fibrogenic properties. Histopathological studies primarily revealed inflammatory changes in bronchial and peribronchial tissue, and focal emphysematous changes, whereas no features of a progressive development of fibrous changes in lungs. The MAC values of 6 mg/m3 for phosphorite dust of 8 mg/m3 for apatite dust--were suggested.