Experimental Study on the Pathological Changes in Lung Tissue Caused by Zinc Stearate Dust

Abstract

Pathological changes in lung tissues of Sprague Dawley rats after single intratracheal administration of 1 mg, 5 mg or 10 mg of zinc stearate were examined to ascertain whether lung fibrosis such as that described in Uotila's case report is caused by exposure to this dust. The results obtained were as follows: 1. The lungs of rats administered 1-10 mg of zinc stearate did not show any evident formation of dust foci or proliferation of collagen fibers after nine months, whereas such changes were evident in the rats administered 10 mg of quartz. 2. The hydroxyproline content of the lung, as an indicator of collagen fiber formation, was significantly less in the zinc stearate groups than in the rats ad-ministered 10 mg of quartz. 3. The Zn content of the lung tissues increased soon after the administration of the dust and then decreased rapidly. The incresed dust content of whole lungs of rats administered 10 mg of zinc stearate was 641 pg after week and 53 pg after nine months. From the above results, it was considered that zinc stearate by itself might not always act as a severe chemical irritant or a main facter in fatal pneumoconiosis.