Document 4vLn6oVo1ey3vNo7QN6MJ20N

-o Thezfcrd Mines, Ilarch Mr. D.A. Macleod, Chier Inspector, Silicosis Branch, Workmen's Compensation Board, 700 West*37th Avenue, Vancouver 13, B.C. r PLAINTIFF'S i EXHIBIT FK-88 ] Dear Mr. Macleod letter of March 18th. I acknowledge receipt and thank you for your From the medical point of view, asbestos fibers of 10 microns or more in length are more liable to produce asbestos is than fibers below 10 microns in length. This was proved by a certain number of post mortem examinations but I do not think that there are enough data on hand to make that absolutely certain. And that brings me to the reason why I count all particles greater than 5 microns in length, if the length is three times the width, instead of counting only the particles of 10 microns or more in length. The only reason is to be on the safe side. It is to be noted that for our reports, we count all dust particles including rock dust which accompanies asbestos dust. Identification of fiber particles is only done, for the time being, for per sonnel information. As our Quebec law do not specify the percentage of asbestos fibers allowable in the permissible dust concentration for the asbestos industry, which is 5 millions particles per cubic foot of air, we cannot emphasize too much on the size of the fiber particles. Work is being done in order that the present law be amended and that in the permissible dust concentration it specifies what percentage and v/hat size of asbestos fibers are allowable. If you need any more informations on this subject please do not hesitate to write again. Date ............. trp.LZpr?... Official Reporter KATHY RYLaNDSHOLN* ASBESTOSIS* by A. ; . ^aN2a Chairman, Institute qf Industrial Medicine New York University Post-Graduate Medical School In opening my discussion of asfcestosis, I would like to say-that while it has been' presumably described by Herodotus in 450 B.C., the disease as we now know it is very new. It was first reported in England in 1900 and a comprehensive report was made in that country by Dr. Merewether (Chief Medical Inspector of Factories") and Dr. Price in 1950. The first cases in the United States were described by Lynch and Smith of Charleston, South Carolina in 1930. During 1930 and 1931, Drs. Lanza and McConnell of the Metropolitan Life Insurance Company conducted the first study of Asbestosis in the United States and Canada. This study included the mines in Canada and nearly all the fabricating plants in the United States. The reports of this study were published by the United States Public Health Service in 1935. Asbestosis, I would like to point out, is the only silicate dust capable of producing disability and death that does so to any marked or appreciable extent. The total number of persons involved -in the industry probably does not exceed 12,CC0 and as far as can be borne out by clinical experience, tuberculosis Is not a factor in this disease. Ever since the survey was started in 1930 the industry has carried on strenuous measures to control the dust in mine, mill and factory with a very marked degree of success. It would seem, therefore, there will never be available the clinical experience of asbestosis that has been a marked feature of silicosis in various industries throughout the world. I would also like to point out that the experience with asbestosis in England appears to differ sharply with that in Canada and the United States. The authorities in Great Britain regard asbestosis as a very serious disease, much more so than silicosis, and they seem to be convinced that cancer of the * A paper read before the Fourth Conference of McINTYRZ RESEARCH FOUNDATION on Silicons, held in Noranda, Quebec, January 23th-30th, 29S2. lungs is a frequent sequela. This is not the experi ence in either Canada, or in the United States. A great deal of information is available from, the medical departments of the various industries that have for a long time maintained constant roentgenographic examinations of'asbestos' worker1! wnicnT" coupled with the efforts at dust*control,'may explain the difference in clinical findings. As far as we have been able to ascertain, there does not seem to be any undue prevalence of cancer among asbestos workers in this country and, as some of the mines and fabricating plants have been working extensive ly for over thirty years, it would seem that if cancer was a frequent complication of exposure to as bestos dust, this fact would have become evident long ago, especially as the medical supervision of asbestos workers is both thorough and comprehen sive. I have, within the last couple. of months, spent several days with Dr. Kenneth Smith in Asbestos reviewing a great many films covering a period of- a number of years and I understood him to say that he had seen only one case of cancer of the lungs during that time. Dr. Cartier at Thetford has found only a very small number of cases of cancer of the lungs in the asbestos clinic in Thetford. I would like to emphasize that none of us can afford to he too dogmatic in discussing these oc cupational diseases and because the experience in one country indicates one set of results, it does not necessarily follow that the same results are to be found in other countries. There are many circum stances and environmental conditions that may differ markedly and, unless all these divergent factors are known, comparisons can be made only with the greatest of caution. It is quite possible that the asbestos fibers themselves in various parts of the world may differ in their structure and com position and hence produce different pathological results when inhaled. We have recently learned to appreciate the importance of this phase of dust disease of the lungs in connection with the effects of the inhalation of diatomaceous earth. Diato- maceous earth is chemically identical with crystal line silica, but the amorphous form of silica pro duces quite a different pathology' in tie lungs than does crystalline silica. In these dust diseases the matter of dosage aiso is important ar.d ur.iess the seriousness of the exposure in terms c: cost ir. the inspired air can be determined with some degree of accuracy, one cannot compare one set of conditions with another without running the risk of serious error. The matter of asbestos as a carcinogenic agent deserves, and will receive, continuing extended study both in Canada and the United States. In dustrial physicians have been alerted to be on the lookout for lung cancer among asbestos workers. Some years ago the late Dr. Gardner of-Saranac first ascribed the action of asbestos fibrosis in the lung to the larger particles rather than smaller ones. This is exactly opposite to the effect of silica where it has been demonstrated that the smaller the particles the more active they are in producing pulmonary fibrosis. Dr. Gardner was also of the opinion that the action of the asbestos fibers was mechanical rather than chemical which again is in contradistinction to the action of silica. However, some of the persons who have studied asbestosis are not in complete agreement with this and it is probable that the factor of asbestos particle size in' producing puim.or.ary fibrosis wiil receive further extena'ea study. Tuberculosis does not appear to be a factor :r. asbestosis ar.d there :s general scrcemenr or. this both in Car.aca ar.c the United States. Certainly there is nothing in the clinical observations on asbestos workers comparable to the experience with tuberculosis seen among industrial workers exposed to silica dust. Aluminum prophylaxis has not been tried la the asbestos industry. The result of the work of Smith, Wooton and King published in THORAX, in June 1951 indicates no amelioration"'of asbestosis in experimental animals as has been evidenced for silicosis. To summarize: Hand in hand with continuing efforts to control air borne dust in mine, mill and factory goes a well developed and thorough medical supervision of asbestos workers, together with a research program involving not only experimental animals, but also clinical studies including pulmon ary function evaluation tests (Saranac) on selected cases of asbestos workers showing roentgenograpnic evidence of asbestosis.