Document OEexGYNjEBBMx1E8eGRJx1axX

1230* January 28, 1959 U TO i Hr. J. S. Sullivan Vinnsboro Kills FROM: Frederick V. Sands Industrial hygienist SUBJECT: Asbestosis I have just received a reply to qy letter to la*. John F. Knox, Chief Medical Officer, Turner Brothers Asbestos United, Rochdale, England. : I am attaching one copy of the two letters I re* ceived. Tou will, X think, be interested in a number of the ccrrvcta be made. I refer particularly to the lack of a standard in gland for asbestos dust concentrations in the atroeacere, his eoesests on the dnst 4wg taeh^que, and his resrics os methods of control. Perhaps, after yen, John ilezznder, Hr. Uhk, end Doctor Yells have reviewed this material.* it might be verth re* questing further elaboration on sasaa of these points. FYS :iS Encloeure* o:;:: 19 COP* OF LETTS FROM Dr. John. ?. Knox North Beightons Lowerfold Rochdale, England January 20, 1959 Mr. F. W. Sands United States Rubber Company New York 20, New York Dear Mr. Sands: I was most interested to hear from you and to learn your experience of the manufacturing hazards of asbestos. The condition of asbestcsis is one about which it is impossible to be can-egoric. TkeTe are many considera tions to be taken into account, and standards of radiology and clinical examination cannot be said to .be universally agreed. Similarly, with re^rd to the working environment, safe st*--daidg bv any specific -_gthr>d nf nrst. counting cannot be said to have been established. There is considerable difference also in the experience of operatives in the different manufact uring processes. Some jobs involve intermittent exposure ci varying degrees of severity while others - especially in textile operations - involve a whole day working in an atmosphere with a measurable dust ^cncentratiom. In the interests of brevity, I will take it for granted that yen are familiar with the exneriaen+.fli g work on particle si2e in relation to asbestosis. This was heavily in favour of the production of fibrosis hr the inhalation of_the fibres microns in lenrch causing irritation of the resnirancrr bronchioles. While agreeing vich the import- am.ee of fibre length in the etiology, I crusader that the retention in the lung of fibres too long for phagocytosis -mich later undergo changes into asbestosis bodies in or around the alveoli to be a highly significant natter. It is the later changes which cotrmr in these bodies from 15 yetars and upwards which seen to be most strongly related tc the genesis of aubas-- tesis in workers. If this is so, it does account for the long incubation period, and places emphasis on the effect of general bodily states, es pecially infections (including tuberculosis; and cardiac insufficiency. If these factors are operative at a tine wasn the inhaled fibres are breaking up and exerting a fibrogenic effemt then the lung is less able to withstand their effects. This conception nay help ycu to -mnderstand wry j'Ji are experieuroing trouble at this time. In the medical rare of the exposed workers, it should be realised that symtons of amber o-sis may precede radiological signs atm also, that the early radiologic: 1 changes suggesti-re but not .ntlcgnomenic of asoestosis, may be crese" n without any clinical eviienic=e of the condition. Long observation ever ; ^mths, or even 7% s, may be required before a case cam be considered ' ,c rave been ertabl -shed. Cf course, if there is considerable suspicir: . that fibres!* cf he lunr ray be present, further exposure to dust" is 1 .shly undesirable, Tnfortu=.-elr* in is net possible in sera individuals tn change the vrrkia? area--wither-rc psychological ill effect* or social sr-ban -assment in the aha nee of a definite diagnosis. Ir. these early cases nn is likely -.ban ulmonary f-jnenien studies of the tyne now bcir.= >' -alcped by the thy? tlogisns vi.-- zr, when we might 7 0001120 2 condition as due to heavy previous exposure' and provided that the working area has been significantly improved further exposure to minute concentra tions night be considered permissible. At the risk of stressing points cf which you are no doubt aware already, I would say that there are four general lines of attack on the dissemination of dust (1) enclosure of the process if possible and partial enclosure with exhaust if not possible; (2) dust extraction, as close' to the point of production as possible, with casting to lead the dust laden air to an efficient filter bag unit; (3) wetting of the process or if this is impracticable, damping is most helpful; (4) frequent air changes in the workroom. It is sometimes considered desirable to use an oil and water emulsion to with the fibre before opening in order to diminish dust emission later. There has to be a combination of several of these methods in workrooms where a variety of processes Is being conducted and sometimes more than one method in one process, e.g* ssming and exhaust with weaving. In every case experiments have to be conducted with each tjpe of machine to get the best results. Up till now I have avoided mention of cast counts about which thtere is a wide difference of opinion between the United States and Great Britain. No permissible dust concentration figure is written into our factory regu lations emd therefore we do not hesitate to use whatever new methods of dust courting are developed* The Governors Factory Inspector may con sider aay area unsatisfactory and demand improvement wither; consideration of an actual rest count figure. The instrument in use here fer mist counting is the tbsur^l rrecinitator and there are already several tonifications of* this In usa. Vben lengthy sailing periods are required vs prefer the Ottney instrument nwly U.S. dust gcninHTjff _ _rogat with vtffr 7 -m four? ilg is the Greanhurr--Smith. Ve have attempted, to find a factor uf ccrrelatiom between between this instrument and the tiercel precipitator art as they operate cm different principles this is net reslly possible. As far as we have been able to compare the results of the tvs instruments the Greenberg-- Smith gives rermts vastly lover in aim-Hs-- situations than the th^-rmal ci pitator. It is in the particle size range front to 2 mimes that the thermal pracipisator finds the greatest c=3er of particles x the counting slide and it is likely that the'Qreenburg-Scith. does not rsv*c as many here owing to the lower power cf the micros.-suc'e used. A fisre cf 5 milli-om particles per cubic foot (173 particles per c.c.> would be at indication of relatively good conditions as judged by the thermal preCuiiacor. The absolute safety of such a standard for a definite number cf years exposure has not been determined. - - of the maier 0f years 2t*=t by an cpermiTe in on area ---sz namard has mm: tc recommend it where practices Tq +>,e of two asoestos firms is this count--, nrrt dealing ,-^T' ine terti_s ssc^oniSof tie^veri~itthise ^riodtfoorlit- ^ ITCC uurseualilklyelets`fs.ss* knCTLheedreaandrelcrev*t rernaouidgh aTltheeml_srt^nvm* fjovbos-kon --*1 -j the^ a1 rT- `-Iso vdti from , sii^ea^ ^-^,XXX J Imam masks should, as Vl*g--tng - which not take kisrfly to the v%ri of interns.tmemt exposure -.. warm vi ocurg verk such -imnerotected --nr. vxkers mo Vtrsti-musjusly, It u the field themr gr-satest tat, Cose at?* 0J ^w j .t '11".) if  3 There la a difference between working conditions in the U.S. and Great Britain in that we are not permitted to re-circulate air which has been through the filter bag units and therefore these are in separate chambers* Ve have such faith in our own arrangements that we regard this as unnecessary in the interest of works hygiene* With regard to actual methods of dust extraction, I am not A competent authority but in general terms fiberising and mixing are best dealt with by methods of enclosure* Flyer Spinning is regarded as the least' dusty process here and is not required to be ventilated* Ring Spinning is ventilated and such processes as pirn winding and doubling are rendered safe by damping rollers. Weaving is carefully ventilated and also damped where this is appropriate. A small article on this subject is awaiting publication at present and 1 shall send you a reprint when aveilahle* 1 enclose with the corres pondence, a short memorandum on the subject of asbestosis research* It is useful sanetimes to set down, in & series of simple propositions, just what we are attempting to accomplish in our efforts to control a hazard* You mention in your letter that x-ray films have been referred to Dr. Pendergrass for his opinion. He may certainly be regarded as a leading authority and I have read his work on this subject with great interest and profit* He states in "Silicosis and Asbestosis* edited by Lanza (1933), "With regard to the radiological classification of asbestosis, I should Include only two states, asbestosis moderately advanced and asbestosis markedly advanced* I feel certain that the roentgenologic diagnosis of the clinically early stage of asbestosis is not entirely reliable." His recent pronouncements on this subject suggest that his views have not altered significantly from this. When we are considering the early case,* I think this is a most important matter to bear in mind. In fact I occasionally find radiological appearances in new entrants to the industry suggestive of early asbestosis although they have never been exposed. If there are any specific points on which I can give further help perhaps you would be good enough to let me know. With kind regards. Tours sincerely, Joizi ?. Knox, M.B., Chief Medical Officer 00 01 <l C> <-w COPT OP LETTER FROM Dr, John, F. Knot North Belghtons Loverfold Rochdale, England January 21, 1959 Dear Hr. Sands, You will find my formal reply enclosed. On re-reading it, I feel it might be helpful to add a few points for your personal interest. An article was published in the British Journal of Industrial Medicine Vol. 12, P. 81, 1955, by Dr. B. Doll on the mortality from lung cancer in asbestos workers. This gave figures for a factory with which I am associated. It represents what I should call the results of working in the *bad old days," and makes the point that things are better now. The Regulations under which we operate now were introduced in 1931 and there is evidence from the figures that the incidence both of asbestosis and lung cancer has declined since then (F. 85, 86). Further statistical studies involving larger numbers of operations which are not yet published demon strate this fully. These show mortality rates equal to those of Great Britain as a whole. There is a substantial literature on the subject of asbestosis, but the subject is often treated as if it were an unchanging entity. Ve have noted a more benign type in recent years with a longer incubation period. The complications are less numerous and less deadly. I think the work of S. R. GIotb# arid >L J. Stews-rc. in this country was very good on the pathological side and you will find numerous references to it in the literature. The work of Dr. K. Lmch of South. Carolina also is strikingly good but he leans more heavily cn the purely _ physical*theory than ve do over here. There is some difference in the ! results of the experimental work between the D.S. and G.B. This is j to be noted in the publications from the Saranac lab in 1951 (Vorvald et al) * and those of E. J. King (Thorax Vol. 1, So. 3, Sept, 1946). j Articles with which I have bees associated and vrich contain soma discussion are -- Knox & Beattie, Mineral ooatent of the ltsg3, and distribu tion of particles and fiberrf'in A.M.A. Arch, cf Indust. Byj,,, July 1954, Vol. 10, P.P. 23-36. Like silicosis, on which there has been a fantastic amount of work done all over the world, we have not achieved finality in asbestosis. With the number of biological, chemical, physical, climatic, and statistical problems Involved this is not to be wondered at. One thing Z know - there is a gratifying reduction in the number cf oases when a good measure of duJt oontrol is aohieved and this is possible of achievement. With kind regards, Tr=*s sincerely, Jei- F, Enox -- 0r, 0-I