COMPARATIVE PATHOLOGY OF SILICATE PNEUMOCONIOSIS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 96  (1) , 149-+
Abstract
A simple pneumoconiosis with lamellar birefringent crystal was observed in animals dying in the San Diego Zoo [California, USA]. Autopsies (100) from 11 mammalian [koala, kangaroo, okapi, goat, antelope, camel, oryx, giraffe, saiga, bobcat, rabbit] and 8 avian species [rhea, ostrich, kiwi, touraco, swan, owl, crane, duck] were studied. In mammals, mild pulmonary lesions comprised crystal-laden macrophages in alveoli and lymphatics. Interstitial fibrosis was present in 20% of cases. There were no nodules. In birds, dust retention produced large granulomas around tertiary bronchi without fibrosis. Mineralogic analysis using scanning and transmission electron microscopy showed most of the crystals to be silicates. There were 90% complex silicates, with aluminum-potassium silicates comprising 70% of the analyzed particles. Electron and x-ray diffraction showed the silicates to be muscovite mica and its hydrothermal degradation product, illite clay. This mice was also present on filtration membranes of atmospheric air samples obtained from the San Diego Zoo. The amount of dust retention was related to the animal''s age, anatomic or ecologic variances, and length of stay in the San Diego Zoo. Its semi-desert atmosphere is rich in silicates, which are inhaled and deposited in the lungs. Similar mica-induced lesions are found in humans living in this region or the southwest of the USA. This simple pneumoconiosis is likely to be widespread in human populations living in desert or semi-desert climates.