Document O1yEm420erVXojw04ZwGpkbj

A I A ): exposure to high coaoealrationi of dust cannot be ruled out. Three cases were found will 3, 3J and 4| ^ein work in asbestos, respccliisi/, hut iu ***'B there *u previous exposure la ether dusts (tee p. 10). Suptxvr. for Uu view le provided by (1) Professor Beeuiu'e cxperuueoti previously mentioned, which aeao&tlreted that the lung* of guinea-pigs ex posed fur 43 end VS hours to asbestos duel allowed "definite cellular pro liferation, though not very extensive, and ihie ie certainly a preliminary stage in the production ef fibrosis (3) Simeon`t otee mentioned above, and hu report in the tame paper on the lunge ef a guinea-pig exposed by Jiavrogwdato to asbestos duet for 100 hour* during a period of St days. On the death of the animal (from suae* other than aabatosis) tome 32 month* later, aectiaai of the lunge ahawed a alight generalised fibrotis. In commenting on the amount of fibrosis found, ha elate* that " a comparison between the human cue* and the experimental showed the fihroeie was more rapid and extensive in the human cases then in the experimental animal,** aud again * the amount of fihroeie in two of the human cuee area quite rapid, and if due to the pretence of asbestos dual, the initial rate of production u rapid when compared with present day sou-infective ailicoei* on the Sand (3) data from Ihie investi gation, in which 21 of the 3C3 workers showed elgtu suggestive of oouimeaeiog hbro*ie (p. 10}. Of these 12 had been employed for less than 1 year*, and 6, for between 4 and 5 jean. To rum op, therefore, It appears probable that concentration of duel and length of exposure ae factors in the production of fibrosis are interdependent within certain limits. While it warms neceasejy for the production of generalised fibrosis of the lunge that a definite minimal quantity of dust must be inhaled, the lower the oouumtration of dust in the air breathed, the longer the lapse of tixue before the fibrosis it fully developed, and within a certain limit, the higher the concentration ef dust, the toouer the fihroeie homines fully developed and the more intense the inrolmoment of the lung tissue. If this hypothesis is comet, and the evidence points Lu at, the practical inferences are of rtrj great importance, aince it follow* that the application . of measures resulting in the reduction of the concentration of dust in the air in the neighbourhood of dusty asbestos processes will cause, firstly a great in crease in the length of time before workers develop a disabling fibrosis, and secondly, the almost total disappearance of the disease, as the measures for the suppression of dust ar* perfected. piiablmrui produced by lit Jtbutei Fibretit.--Begirding the amount of disablement produced by the development of pulmonary fibrosis in tsbeitos workers,--for a number of years thi* u surprisingly alight, even more so then is generally the esse in sihoosu. This is partly due to the character of the disease, and partly to the nature of 4the work, which in tho majority of these proaesaei does not involve much physical exertion. The affected person may, end often does, continue at work with occasional inlcrmiasioaa, latterly, due to exacerbations of bronchitis, until the coadition is advanced, although he suffers increasing^ incouvenieneei from shortneai of breath, on exertion Some times a terminal broncho-pneumonia, or other acute infection, commence* while still at work, and there is no long period of invalidism. There is so doubt but that fibre*is of the type produced by asbestos an of itself lead to complete disablement and to a fatal termination, and this in the absence of a muperadded tuberculous infection. Particulars have been collected up to the end of 1020 of 10 cates in which an advanoed degree of the aihqUa fibrosis without tuberculosis was the primary cause of death. In 0, the muse of death was verified by post mortem examination and is the 10th, repeated clinical, radiological and sputum ex aminations confirmed the diagoosis la an 11th case, post mortem examination showed that a lobar pneumonia had auperveued upon lunge already the scat of a .moderate degree of tie asbalm fibrosis With one exception, all these deaths occurred in the years 1927-20 The length of exposure Us asbestos dust in,these cases varied between 9 and 24 years tu s, '-s jn -y & n j -lt ->r fa K