Document Jkd7nV9Bmd4ry3GdrVQV4e8v

7toa*T7 4,1033 2 asbestos most commonly encountered is designated as chryBOtHe and is one of the four varieties of the mineral serpentine, in which it usually occurs in seams. It should be borne in mind that silicosis (and presumably asbestosis) develops very slowly, taking from 5 to 15 and even 20 or 25 years' to become established. This rate of progress is influenced mainly by the dosage of silica which the lungs receive, and this dos age, in turn, depends upon three variables--the amount of silica in the dust, the quantity of dust in the air, and the length of exposure. Individual idiosyncrasy might be included as a fourth variable; however, little is known of the variations in susceptibility in thoso exposed to dust. It might well be assumed that similar variables would influence the occurrence of osbestosis. In places where asbestos is mined or fabricated in North America there does not appear to be present the clear-cut clinical picture which is so unescapable in communities with a true silicosis hazard, such as hard-rock mining communities. It may be that some of tho asbestos plants are of too recent origin for tho typical effects of a silicate dust to become manifest, but this would not apply to tho older mines or to all of the fabricating plants. The industrial health service of the Metropolitan Life Insurances Co. undertook the following investigation during the period from October 1929 to January 1931, which included: 1. A study of dust conditions in asbestos mines and mills in Canada and in fabricating plants along the Atlantic Seaboard in the United States. 2. Physical examinations of asbestos workers, including X-ray films. 3. A study of dust exhaust systems designed to eliminate asbestos dust. Data on the fabricating plants only are included in this study and are designated in the report as plants A, B, C, D, and E. This is a preliminary report. A more extensive study of the asbestos industry is now under way, DUST STUDIES Apparatus and methods of sampling.--Both tbo impingor (1) and the electric precipitator (2) were used for the collection of air samples for dusts at the breathing levels and in close proximity to tho workmen. Both of these forms of apparatus ore adapted for this work, as tlioy are transportable, easily set up and adjusted for tho taking of tho air samples at the proper level, and are extremoly olficiont. The impinger collects the dust by aspirating the air and then impinging it onto a flat surfaco covorod by a liquid in a container. The liquid used was distilled water, containing 50 percent alcohol to