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Rcpeint*4 fram Tka Jamraai af tka American Medical A/aae*atiau AmgmM if, I9JJ. I'aL tOt, ff. HJ and $H ETIOLOGY OF SILICOSIS A. J. LANZA, M.D. Auuttat MoficaJ Director, Uctrapolitu Life Insurance CmwpaAj NEW YOUC The Committee on Pneumoconiosis and the Com mittee on Standards of the American Public Health Association, at a joint meeting in November, 1932, adopted the following definition of silicosis: Silicosis is a disease doe to breathing air containing silica (SiOt) characterized anatomically by generalized fibratie changes and the development of miliary nodniation in both lungs, and clinically by shortness of breath, decreased chest expansion, lessened capacity for work, absence of fever, increased susceptibility to tuberculosis (some or all of which symptoms may be present) and by characteristic x-ray findings. The disease is divided arbitrarily into first, secood and third stages for convenience of description and possible compensa tion purposes. I wish to make clear that in this discussion we are concerned with true silicosis and not with other forms of pneumonoconiosis due to the inhalation of dusts containing combined silica in the form of silicates or of organic dusts. Numerous dusts will produce a pneu monoconiosis demonstrable by x-rays; but just as these other dust diseases of the lung differ in their exciting cause, so do they differ in the pathologic changes that characterize them. Silicosis is an important disease because it is widespread in industry, and, because, as a result of the peculiar susceptibility to tuberculosis which it induces, it is attended by a high rate of mortality. DUST The primary cause of silicosis, then, is free silica, inhafed in the form of dust. Extensive research and experimentation have dearly demonstrated that this kgfsrt tkt Scetitt t ___ _______ PvUic Bcaltfc u the Eighty-Fowth Amoral S--'no of Medical AnocinioB. 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