Document DD2GJV5pkYa9xN7pn8136Rr8o

400 0. A. SANDED asbestosis does not tend to progress after exposure is stopped or markedly reduced. Advanced asbestosis usually is associated with considerable emphysema and commonly leads to right heart strain and failure. C. BAUXITE PNEUMOCONIOSIS (SHAVER'S DISEASE) A new occupational fibrosis of the lungs was recognised for the first time in 1942 by Dr. Cecil G. Shaver,M Niagara Peninsula Sanatorium, St. Catherines, Ontario. It is essentially a diffuse interstitial fibrosis and marked associated emphysema, with a complete absence of any nodular fibrosis. It has been found only in workers exposed to the fumes resulting from the fusion of bauxite in the manufacture of artificial aluminum abrasives. Bauxite is a natural hydrated aluminum oxide (Al-Oj) containing small amounts of silica and iron. When it is fused by heating at a high temperature in open electric furnaces, a crystalline artificial corundum results. This process gives off dense white fumes containing from 40 to 60 per cent aluminum and 30 to 45 per cent amorphous silica. Particle size ranges of the fume are remarkably small-- from 0.5 y down to .02 y--and scan be visualized only with the electron micro scope. Workers with the heaviest exposures have been the overhead crane oper ators and those who shovel the mix into the furnaces. In the early stages there are no symptoms or clinical signs.-The early x-ray pattern "is characterised by indefinite granular or lacelike shadows, particularly in the upper lobes, resembling early tuberculous infiltration. Ae the pathological changes progress, involvement Of the lower lobes occurs. The'shadows may remain granular or may assume an irregular nodular pattern. The root shadows usually are enlarged and increased in density. Emphysema usually is present and may be extreme, with large emphysematous blebs. Spontaneous pneumothorax has occurred in numerous cases and resulted in the death of several of these workers. The main symptom of those with advanced disease is shortness of breath. This may be sudden and extreme at the time the pneumothorax occurs. Most cases have developed in a rather short period of exposure: from two to five years. Approximately 50 cases had been discovered in the Niagara Palls area up to about five years ago. No tuberculosis was found in any of them. Since better fume control measures have been instituted, no new cases have come to light. It is of interest that no cases of the disease were recognised until 1942, even though the fusion process had been used since 1914. The only explanation for this is the tremendous increase in production of the artificial abrasives during the war years. The precise causative factor in the fume has not been positively identified. Heretofore, aluminum and amorphous silica had been thought to be innocuous. Also, extremely fine particles of any dust, less than 0.5 y in sire, had been thought to have no significance in the development of lung fibrosis. It wbs believed that "C. G. Shaver and A. R. Riddell. Lung rhange* associated with the manufacture of alumina abrasives, J. Ind. Hyg. Toxicol, 29, 1(5 (IM7).