Document 7OJ5rEGkzJM0Q3z4oDnwejkY8

404 0. A. SANDER 1. Nine per cent of 869 diatomite workers showed changes consistent m, Wlla diagnosis of pneumoconiosis, while 9.3 per cent had chest films with doubtf changes. $ 2. When individuals' with previous dust exposures or missing occupation!, histories were excluded from the positive and doubtful groups, presumptive diSg noses of diatomite pneumoconiosis were made on 8.3 per cent of the employ'll examined, and diagnoses of borderline or doubtful stages on 6.9 per cent. ;ij 3. Of 286 employees with experience of five years or over in the diatomf industry, 22 per cent were diagnosed as positive. 4. The prevalence of abnormal chest films was particularly high in e ployees who had worked for over five years in the mills, about half of whom h a positive diagnosis. 5. Exposures in the quarries were less hazardous, only one of 25 employi with more than five years of exposure had a pneumoconiosis diagnosis. No employees showed confluent changes. 6. Symptoms of respiratory distress or dysfunction correlated poorly wil the x-ray changes, except with confluent lesions. I 7. Workers with massive confluent lesions showed reduced pulmonary vent latory function, but those with only linear or nodular changes showed no c< sistent pattern of disturbed function by these tests. 8. No evidence was obtained to indicate that tuberculosis, histoplasmosis; coccidioidomycosis are related to either the linear-nodular or confluent lii changes in employees studied.-Clinioaliv-actiy-e-tuberc\ilosis-was-not-found-iira workers with confluent x-ray changes. It should be noted that Smart and And son97 had found nine active cases in these groups several years earlier, but tb were not limited to the confluent cases. In regard to environmental control, it was agreed after all data had correlated that the maximal allowable concentration for crude or amorp diatomite could safely be placed at 20 million particles per cubic foot, but w: atmospheric concentrations for cristobalite-containing dust should be kept und 5 million particles per cubic foot of air. It was recommended that preplacemero and periodic medical observations continue, including chest x-ray films and function studies. _In the writer's opinion,, this--w.as_on&-of-the_most-complete-and-cohcllii occupational 'disease surveys made by the United States Public Health..Sef* thus far. The suggested x-ray classification is an unusually realistic one warrants study for its possible application to other dust diseases of the lungs. -E.-COAL--W-ORKISRS!-IiN-EUM0GON-I0,SIS~('A'NTH'R`AeOSILlCOSIS'i~XNTSl The lung changes associated with coal mining vary markedly owing to!t|| great differences in amount of quartz dust to which coal miners are exposed aloip " Anthracosilicosis among hard coal miners, V. S. Pub. Health Bull. No. 221, 1935. 1 PULMONARY DUST DISEASES 405 ;he coal dust. At one extreme are the advanced cases of anthracosilicosis of coal miners who have had high-grade quartz-dust exposure.99 At the . extreme are the minimal micronodular x-ray changes in coal trimmers (ship .|s) attributed to pure coal-dust exposure (less than 1 per cent silica).100 iically all hard or anthracite coal lies between quartz veins, as does some V bituminous coal also. Most soft coal mines also have had another source of tfedust exposure: the sand used on the rails to improve the traction of the >%ocomotives. In general, it may be stated, however, that soft coal miners ``ad considerably less free silica exposure than have hard coal miners and ifhave very little, especially the sorters and loaders who do not work under- su the past, coal dust itself generally was thought to be innocuous. As a Jr of fact, it was considered by many to have beneficial properties, in that ded to prevent tuberculosis. However, after World War I, the increasing use Jlst x-ray films revealed roentgen abnormalities in the South Wales soft coal ners that in many cases differed from the characteristic silicosis pattern. The |"reticulation" began to be used for the fine lacelike pattern seen in so .jpTminers and trimmers. Compensation for silicosis in coal miners, under the piemen's Compensation Act, was first granted in Britain in 1931. During otld'War II there was a tremendous increase in cases certified for compensation, ^illarly since the Act was revised in 1943 to include a disabling form of liiioconiosis, which was not recognizable as silicosis. f--1938--the--Industrial--Fulmonary^-Committee -of .the Medical Research oil began its investigations in South Wales to determine the nature of the .disease found in coal miners. An x-ray survey was carried out in sixteen ||fby Hart and Aslett,101 and pulmonary changes were found that resembled Jf!is by x-ray, but differed from it in many .ways. It was recognized from this Wthat many coal miners had advanced and disabling disease, and that a iS|. hazard existed, especially in the anthracite mines, but to some extent also '^bituminous mines. A special Pneumoconiosis ResearchiTJnit was set up in in Cardiff to make more detailed studies of the epidemiology of the disease o.-try to find "safe dust levels" to which men may be exposed without develop- rfdus pneumoconiosis. ikyjas-realized-eaFly~by-Eletcher102.and.his.staff..at.ihe._Unit.that.there was Agreement on methods of x-ray classification of the pneumoconioses, and 3ttle progress toward a better understanding of the dust diseases could be ctfd' until a system of classification was devised that wouldvbe:-acceptable i&dMlly-.-Such a_ classification was set up and has been widely accepted ^IT:'Gough, Pneumoconiosis of coal workers in Wales, Occupational Men., 47"8fP97TI947)T 'K?P. A. Hart and E. A. Aslett, Chronic pulmonary disease in South Wjes coal miners: e'dical studies: B. Medical survey, Special Rept. Series 243, Med..Research Council,: BIB, M. S. 0., 1942. . M. Fletcher, Classification oi roentgenograms in pneumoconiosis, Arch. Ind. Hygi SNational Med., 11, 17 (1955). :