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Dangerous Dust: The Silicosis Hazard in American Industry

by Leonard Greenburg, M.D.

Executive Director, Division of Industrial Hygiene, New York State Department of Labor

December 1936

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It will be observed that the tuberculosis rate for grinders and polishers in this ax factory was twelve times that of the other employes of the factory and that the ax factory district had a tuberculosis rate of 200 as compared with 150 for the state as a whole. This table also shows that the contribution of tuberculosis deaths from a local industry or group of industries may adversely affect the mortality rate of a general population group. In other words if the high incidence of tuberculosis associated with certain occupations could be reduced, a reduction might be expected in the general tuberculosis rate for the entire area.

The most valuable silicosis data come from detailed studies in selected industries, but only a few such studies have been made. The U. S. Public Health Service through its publication has made available the greater part of this knowledge in the United States. Among the industries in which the dust hazard has been studied in detail are: the scouring powder industry, granite stone cutting, and silverware.

Some brands of scourit1g powder contain quartz as the abrasive agent, which may constitute 75 percent or more of the finished product. The quartz is usually very Enely pulverized in order to prevent scratching; hence the dust is potentially very dangerous. Dr. Eugene S. Kilgore of San Francisco writing in the lournal of the American Medical Association summarizes his experience with cases of silicosis arising in this industry. In one case which resulted after eleven months of occupational exposure, the patient experienced marked shortness of breath in attempting to climb one flight of steps. Dr. Kilgore cites the cases of six employes who worked from ten to twenty-seven months in this industry, five of whom were dead from silicosis at the time of his publication. This occupation may be regarded as one of the most serious types of exposures, closely paralleling quartz rock and quartz sand grinding. Several years ago cases of silicosis were reported among New Jersey workers engaged in grinding and pulverizing sand. This pulverized material is almost identical with that used in the making of scouring powder and the sand pulverizers were found to develop silicosis after about two years' exposure.

According to the best available studies, approximately one to two years represents the shortest time required for the development of silicosis. It is conceivable for the disease to develop in a shorter period when exposure to pure quartz dust is encountered but clear cut evidence on this question is lacking.

In 1922 F. L. Hoffman in cooperation with the National Tuberculosis Association published the first study of the dust hazard among Barre granite workers. In 1929 after several years of study the U. S. Public Health Service brought out an exhaustive report on the same problem. This study includes determinations of the quartz content in the dust, the actual clustiness of the atmosphere, as determined for workers at different tasks, morbidity and mortality statistics of workers engaged at various occupations and X-ray studies of the lungs of workers.

Normal X-Ray

X-ray of a normal chest;
a worker not exposed to dangerous dust

X-Ray Showing Silicosis

The creeping shadow of silicosis
in a doomed worker's lungs

Barre, Vt. is the center of the granite stone industry. Blocks of granite are taken from the quarries, cut to dimensions, surfaced, carved and lettered. This material is used for building purposes and for tombstones. The average quartz content of Barre granite is 35 percent. The Public Health Service study showed that the dust content of the air varied from five to forty-eight million particles per cubic foot, depending on the particular industrial process studied.

IN the following table which presents the findings of l this study the workers are grouped in four classes according to dust exposure. The table presents average dust exposures, the period of time in years required to produce early and advanced silicosis and the tuberculosis deathrate for each group. The relationship between the amount of dust, the time required for the production of silicosis and tuberculosis is obvious.

Group Average Dust Count Years to Develop Silicosis (Early) Years to Develop Silicosis (Advanced) Tuberculosis Deathrate per 100,000
A 48 2 5 1950
B 35 4 7 1280
C 20 4 9 230
D 5 10 ---- ----



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