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.nalirUTE OF OCCUPATIONAL AND ENVIRONMENTAL HEALTH MONTREAL, CANADA W Code 4 5/1 10 11 12 13 82 Asbestosis -- A Diagnostic Enigma A Personal View /_ '177 H. C. Lewinsohn,tft.B., B.Ch., D.I.H. AO'2043 Although the carcinogenic properties of asbestos are pres ently attracting a good deal of attention, asbestosis is still the earliest lung disease resulting from exposure to it and its inci dence in an exposed population is the most useful indicator of the degree of dust control exercised over a period of time. The diagnosis of asbestosis depends upon: (1) An adequate occupational exposure history. (2) Physical signs of pulmonary fibrosis. (3) Progressive radiological changes. (4) Confirmatory measurements of altered lung function. Asbestosis is a clinical entity and is readily diagnosed when all the above-mentioned criteria are met. Problems in diagnosis are encountered when one or more of the diagnostic criteria listed above cannot be substantiated. At the present time every effort is made to diagnose the disease in its early stages in the hope that removal from further exposure will pre vent the direct and indirect complications. > Regulations to control the asbestos industry in the United Kingdom were made in 1931.' The evidence upon which they were based was gathered in 1929 by Merewcther and Price, the former a medical inspector of factories (who later became senior medical inspector! and the latter an engineering inspector of fac tories.2 Merewcther selected for his studies the textile branch of the industry (a branch manufat turing industrial textiles for insula tion. friction and packing material applications', and some prelimi nary processes in other branches Each individual's previous in dustrial history, subsequent to leaving si hool. was noted in detail Merewcther considered this to be essential in order to exclude people whose previous work mav have been in anv of the numinous processes involving exposure to (roc situ a and other dusts. Mercwether's investigations lid him to state: "To sum up. therefore, it appears probable (hat concentration of dust and length of exposure as iai tors in tin' produi lion of fibrosis are in terdependent within certain limits While it seems necessary for lium IRA lMt1usUt.il l`i..luils |t-1 K<h-M.iL- l.'k 1h .uithnf's .til l'ess is K nltesim M.irth.in.m lo 100 Q.iLvm*** Hi IimtoIkjII IN' 0<>M1 Cnp ul*4 HiMtiqij.wlt'fN Journal of Occupational Ucdicine/Vol 19, No 5/Septembei 1977 ^ the production of generalized fibrosis of the lungs that a definite minimal quantity of dust must be inhaled, the lower the con centration of dust in the air breathed, the longer the lapse of time before the fibrosis is fully developed, and within a certain limit, the higher the concentration of dust, the sooner the fibrosis becomes fully developed and the more intense the involvement of the- lung tissue." He went on to hypothesize that, in the light of the above reasoning and the evidence which pointed to it. the application of dust control measures would cause "firstly, a great increase 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 are perfected " The improvements made in the British manufacturing industries after the 1931 Asbestos Industry Regulations took effect may be said to have occurred slowly and progressively from 1931 on wards and although much was achieved before World War II, the major advances in dust control probably took place in the 1950's.1 During the years of World War II regulations were relaxed and conditions in factories deteriorated One of the problems in quan tifying dust exposure data is how to take account of the effect of historic events on working hours and working conditions. There is no way at present of analysing the effects of depressions, booms and other socio-economic phenomena when attempting to mea sure cumulative dust exposure over any given period of lime Because of the limitations of the 1931 regulations, and because the regulations applied to manufacture but not usage of products, the hoped for reduction in cases of asbestosis in the U K. did not occur at a national lexel Tin* Senior Mednal Inspector's Advisory Panel on Asbestos, in its report to the minister of labor in 19674 gave the following reasons for the increasing incidence of asbestosis: <a> Tito clinical criteria for diagnosis have changed since the 1920's (b1 Laggers. the total of whom was not known, tendid to be excluded from the process to which the 1931 regula tions applied, (cl Tliere liad been an increase in overall consump tion of asbestos and a rising population of exposed workers, (d) Medical supeivision of workers in the asbestos industry (originally recommended by Merewcther) Kid not been extended to workers in new proi esses as tliese were introduced. 607 HCfc H n9H9oc A U 2 050 Ho of tun Employed 09 10 - H IS 19 20 t 0*1 Totals *0if oi J3 uses *ith mo** Comparison Between M?te*ether'$ Findings in 1929 and Prevalence of Asbestosis in 1975.` tmmtohn 1975 He. Erposed Hi of C*i Certified w ts 66 8? 1033 1 0 3 t S Croup Incidence S 0125 -- 45 49 077 Ho. Eumined 230 84 28 21 383 M*reeth*r 1929 Ho ol Cases Ow; nosed 36 27 15 i; M in tec*.;' o> trd-sV' ore*' are tv iJfS Inures 20 yean r*>x.'e * lrst etpesed Oe'y* 1933 ftjfc'r IV) Croup Incidence \ 156 37 1 53 6 80 9 26 2 The Advisory Panel did record, however, th.it although they were inclined to .ircept the growing use of asbestos as the most probable explanation of the increase in cases, "conversely there is no evidence pointing to a decrease in the attack rate in the in dustry as a whole although there is such evidence in certain im portant asbestos using factories." In 1%9. new regulations known as the Asbestos Regulations 1969 were made in the UK. and they look effect in May 1970. These regulations recognized two things, among many others, namely, the importance of their application to both manufacture and usage of asbestos products and the acceptance of a level of dustiness below which there was no hazard to health The latter principle was acknowledged by the publication of "Hygiene Stan dards for Airborne Asbestos Dust Concentrations for Use with Asbestos Regulations 1969" in Technical Data Mote 13 .Rev I." Technical Data Mole 13 states that where the dust concentra tion is less than 2 fibres'ml. HM Fat tory Inspectorate svill not seek to enforce the substantive provisions of the Regulations This figure is derived from the simple assumption that in order to ac cumulate an exposure I'mit of 100 fibres'ml during a working life time. the dust level should not exceed an annual average of 2 fibres ml .*.50 years x 2 f'ml = 100 f. years'ml , 50 years x 4 tVml = 100 f years'ml etc. 'Adequate' Occupational Exposure History In the determination of an adequate occupational exposure history it is necessary to ascertain the type of asbestos fibre in use. There are four main varieties in commercial use. namely: Chrysotile -- white -- 95% world production. Crocidolitc -- blue -) Arposite -- brownish -1 5% of world production Anthophyllite -- brownish -) It is accepted that all varieties of asbestos can give rise to asbestosis Asbestosis might he compile ated by the development of carcinoma of the lung, and the risk of this complication is multiplied many times by cigarette smoking Before discussing the clinical features of asbestosis. one further difficulty in obtaining an adequate occupational exposure history requires reference. Merewether attempted to quantity the dusti ness in the textile branch of the industry but was only able to pro duce a rough guide The respirabilitv of asbestos dust, because it is composed of fihres and not of spherical or uniform particles, depends upon its aerodynamic behavior which is related to fibre1 diameter and falling spevd. It was not until suitable instruments became available1 hi tile late 1940's and early lOIO's tint routine environmental monitoring could be mtnxluied into industry. The Bril ish Occ upjtion.il Hygiene So< iety made use of dust measure 608 ments and clinical data from a Rochdale asbestos textile factory in its first attempt to set "Hygiene Standards <nr Chrysotile Asbestos Dust" in 1968. Prior to this the only standard' recorded was in the U S A and was 5.000.000 asbestos particles per cubic foot as mea sured by means of the midget impinger. The BOMS Standard recommended a cumulative dust exposure limit of 100 fibre years per cubic centimeter. This would allow a 1% risk of developing basal rales, which were considered zs the earliest physical signs due to the effects of asbestos exposure. In the medical surveillance of asbestos workers in Britain we are now concerned with two populations for follow-up. namelv. those people who have worked in the industry when dust mea surements were not made and when vat table dust rontrol mea sures were taken and those who have entered since May 1970 when new improved conditions were demanded by new- regula tions and when environmental monitoring could he added to the data for epidemiological evaluation HM Chief Inspector of Fac tories in his Annual Report. 1974.' states. "139 new cases ot asbestosis wore recorded by DHSS during the year These con tinued to reflect conditions in past years when the long-term ef fects of asbestos dust on the Health of Workers was not tullv ap preciated The latent period for this disease is such that annual figures cannot vet be expected to reflect improved conditions fol lowing the introduction of new legislation in 1970" What constitutes an adequate occupational history? There is in sufficient evidence available from industry to enable this question to he completely resolved, but such evidence as there is allows certain standards to he set in tin1 hope of reducing the risk and providing a base-line lor further study iB.O H.S 196BI. Physical Signs of Pulmonary Fibrosis Where exposure is known, the presence of asbestos bodies and fibers m sputum is of little importance, since their presence simplv confirms exposure and llxer absence does not indicate freedom from disease The presence of basal rales (crepitations or crackles: and linger clubbing liave long b(>en at cepted as important clinical findings in < oii|unction with a history of asbestos exposure The Briteh Occupational Hygiene Sotiely's Committix1 on Hygiene Standards, in their publu alien 'Hygiene Standards for Chrysotile Asbestos Dust' considenxf hasul rales as the "key symptom" The crat kies are < liar,u tenstu ally of high pin li and act ur in endmspiration. ()er\isting after toughing and most prominent in the dependent areas of the lungs It is important to establish that the xtaikles are persistent and not due to oilier diseases resulting in pulmonary fibrosis. . Until it is possible to ret iml lung sounds and preserve graphic nx ords. tlx1 present e or absent e ol lliese fine i r.u kies remains a Asbcdnsi'l/lewinsrihn 1 1 n ' ** Mv*,n w i,i< h v% ill h- du a^d m HiH.'hmM w .n * hv rl*M<r<nt oh^'iv.'rs .111 tt!*nv; l tin* nl liven MrlhoM opes iht* o' pfe-.!)vi ih'-'s liom which 11v'\' sullrr ,iml il** alnlilv ot p.Uit'n' lo Imalhr in a contri>!l\l m.mni'f Progressive Radiological Changes K-rav tix hnolngv and i I.ismIu atmns ol pneumoi omosus have (handl'd i r >ris iri* o! j l > iluiuig llv past -lb \i,ar'> since Mc'iewethor surveyed workers in the ,-,.be-tn. textile mdu-ttv Thi' radiotogu al i ntcfia which lx' used to diagnn-e ashe-tosis are not dclined in ho report Radiological change- considered significant in the diagnosis ot a-hestosis bv the BOHs Commit',>v wore increased general opacity of the lower lobe- b'irring of the cardiac outline pleural thickc'ning and adhesion- Isolated areas of calcification, un connected with the abuse change-, were not con-ideced as necessarily or probable asbe-totK in this senes It appears likelv that Morcwether and the BOHS Committee svere concerned with relatively tar-advanced disease. The BOHS Committis- recognized the onset of the disease to be gradual and hence difiicult lo detine All the' feature- of the disease may occur to sarsing degree and indeed, the severity ot the alteration of the separate feature' mas svell be related to the tvpe of pa-t dust exposure Thus the particular set ot critena used to decide wlrether a-be-tosps is present or absent will vary Various system- of classification have been used to attempt to standardize the description of radiological opacities The Interna tional Labor Oftice s 1950 Classification'- was. until recently, the most widely u-ed but had certain dibit ulties with regard to asbestosis The tla-sifu anon svas recently modified by a LMCC working group and extended to include irregular opacities such as occur in asbestosis as well a- other abnormalities ' The ILO UC In ternational Classification of Radiograph- of Pneumoconiosis 1971 ' is designed to de-cribe ' persistent radiological opacities in the lung held- provoked bv mineral du-t" and to allow them to be categorized according to size and shape and to indicate their pro fusion or extent in the lung field- A set of standard film- illustrat ing all categories is issued bv the ILO. Confirmatory Measurements of Alter-d Lung Function Lung function te-ts have three main uses, namely (a1 To establish base-line values in order lo as-e-s lung (unction, periodi cally using each worker as his her own control, ib' To confirm the clinical and radiological diagnosis (c' To assist in the assessment of disability m established disease. It is not proposed to dr-cu-s la' and lc' but merely to describe briefly the value ot lung function lest- in confirming the diagnosis According to Bader et al" in asbestos workers vital capacity reduc tion precede- category 2 or 5 radiological changes bv 10 to 15 years; the latter change- do not meur until 20 >ears ot exposure. After 30 years of exposure', the incidence of functional and radiographic abnormalities is approximately the' same The tests most readily u-ed according to Beiklake et alare those of ventilatory capacity winch include measurement of the Ft Vi. FVC and FtV fVC% Lung volumes and ga- transfer should.be measured in all sus pected cases to obljm confirmatory evidence of pulmonary fibrosis. General Remarks An attempt ha- been made to indicate that asbestosis is not an Journal of Occupational Mcdicinc/Vol. 19. No 9/September 1977 easy rnndtlMin In ili.ir.no-e It reqia*,-- intimate know ledge of the' indu-lrv and tlm u-e ot it- ptodu: t- 1 he view w -lured by Limes wlio in relation to a partu ul.ir < a-o vvlm h he diagnosed as a-bc-to-i- of nnniM i upatmnal origin, ha- subsequently published an account of tin' autop-v ending- indicating th\t tvs diagnosis was incorrect The diagno-i- established at autopsy in this case was chrnrvc active1 fihroe asenu- tuberculosis." Asbestosis i- nor a-clear-cut entity except in the advanced stages of di-ea-e and very oticn a mistaken diagnosis can be made winch, if communicated to the individual concerned beto'e all diagnostic avenue's have been explored and tlx> disease con firmed, can load lo p-vcliolog.c a! stress and breed ill-will in a com munity It is sound practice in the' United Kingdom to discuss all xu-poeted ca-e- with the Members ot tlie Pneumoconiosis Medi cal Panel and to accept tlx'u judgment with regard to diagnosis There may be a few people vvho have some, but not all diagnostic criteria, vvho are not considered to be suffering from asbestosis. Many of tliese cases are elderly and on the verge of retirement. They are symptom-free, then earning capacity ts not affected and they are unable to find alternative work it they have to change jobs. Furthermore the dust condition- which probably produced the slight changes in their x-rays should no longer exist and they should now be employed in conditions where the Asbestos Regulations. 1909 ensure their safety. Unless they develop symp toms. or clinical findings indicate doiinitv changes."there does not appear to be any need to take further action The first indication of deterioration must elicit a rapid response leading to immediate further investigation, diagnosis and appropriate compensation. In the interpretation of lung function test results it should be borne in mind that there is a wide range of "normality" for most available measurements made and it is thus important to establish for each individual worker a "normal" base-line value prior to ex posure and to observe deviation from the base-line in order to assess deterioration of lung function during his working lifetime. The measurement of FLVi. and FVC. is a simple procedure and the test equipment available i- robust transportable and dependable. The use of lung function tests m the future in the surveillance of asbestos workers is obvious and should form an essential part of any preventative medical programme. Physiological tests alone cannot prove the diagnosis of asbestosis. but merely the abnormal pattern of lung function which characterises difiuse pulmonary fibrosis from any cause. In combination with occupational history, physical signs and radiological changes tlicy give confirmatory evidence of the presence of the disease and assist in assessing its seventy. They are e-sential in the investigation of suspected asbestosis. A number of points arise a- a result of the increasingly wide spread use of the ILO U C Classification of rad ographs. TFie com monest changes recorded by mu-t observers aie in category 1 and relate to irregular small opacities. It would appear that the presence of irregular small opacities in smokers can significantly affect the interpretation of x-rays and that in the older age group these changes can also occur.u The significance of category 1 (irregular small opacities in asbestos workers working in low dust concentrations!, unless demonstrated to be related to cumulative dust exposure when re viewed on a serial basis, cannot yet be determined. There is no clear-cut dividing line between early change and disease. The diagnosis of asbestosis should not be made purely on the basis of a slight alteration in radiological appearance and m the absence of serial review radiographs, a history of asbestos exposure (including A02C5 1 609 *-mc knowledge of dust levels and fibre type) and confirmatory clinical findings of pulmonary fibrosis. Many workers who have been exposed to asbestos never de velop any x-ray changes and only some develop asbestosis. It is not morally justified to suggest to a symptom-free, otherwise feallhy individual that he or she is suffering from an incurable dust disease with a concomitant cancer risk, if there is not definite proof. If the disease is "definitely suspected" then the individual has a right to know, to cease exposure and to seek compensation. It is not yet kno.vn whether the improved methods of examination available permit the detection ol the disease at a stage where fur ther progression can be prevented if exposure ceases. The disease is now almost certainly diagnosahlc at an earlier stage than 46 years ago in Merewother's time. The disease will probably pro gress in the more advanced cases even when exposure to asbestos dust has ceased. The British worker has changed his |ob habits and it is unusual to find him working in one firm or one |ob for as long as 20 years. .Asbestosis is a preventable disease -- it now remains to prove whether lung cancer and mesothelioma are preventable by the same means. With regard to lung cancer the eradication of the cigarette habit will undoubtedly also lead to the eradication of this complication of asbestosis.1' In a large asbestos textile factory in Rochdale the prevalence of asbestosis has been reduced in 1975 to 0.77% among the current labour force compared with Merewether's finding of 26.2% in 1929. (Table). This reduction his been achieved by conscientious effort on the part of management to eliminate the disease. In recent years there has been a growing awareness among workers in industry of their role in the prevention of occupational disease and when enlightened management takes advantage of this new willingness to cooperate, then useful practical measures follow. Confrontation is not the way to better health. Elimination of occu pational disease depends upon joint consultation and sensible ap plication of the most reliable and practicable preventive measures, implementing Legge's aphorism that unless and until the employer has done everything, and everything means a great deal, the work man, no matter how willing he may be to do so. cannot protect himself. The world cannot do without asbestos at the present time as it forms an essential component in many sophisticated engineering production and everyday devices Without asbestos, more lives would undoubtedly he lost from the (vizards of fire and most kinds of energy conservation, transportation and industry would be unable to function effectively. References 1. The Asbestos Industry Regulations. (SR & O 1911 No 1140). 1931 2 Meresvother ERA and Price CW Report on Effects of Asbestos Dust on the Lings and Dust Suppression in the Asbestos Industry Pjrt 1 Oc currence ol Pulmonary Fibrosis and other Pulmonary Aiiections in Asbestos Workers IIMSO London. 1930 3 British Occupational Hygiene Society: Committee on Hygiene Stan dards: Hygiene Standards for chrysolite asbestos dust. Ann Or ( up Hyg 11 47. 1968 4 Problems arising from the use of Asbestos Memorandum of the Senior Medical Inspector s Advisory Panel London- H.M.S.0. 1967. 5 Department of Employment 1974 Annual Report 1974 H M Chief In spector of Factories: London. H M S O (Cmnd 6322). 6 International labour ollice meeting of experts on the international classification of radiographs of the pneumoconioses Occup Safety Ulth 9:2. 1959 7. UlCC'Cincinnati classification of the radiographic appearances of pneumoconioses A co-operative study by the UlCC committee Chest 58:57. 1970 8. International Labour Office International Classification of Radiographs of Pneumoconioses. ILO U'C Classification 1971: 1972. 9. Bader ME. Bader RA. Teirstein AS et at Pulmonary function and radiographic changes in S98 svorkers with varying duration of exposure to asbestos Mr Sinai / Mod 37:492. 1970. 10 Becklake MR. Fournier-Massey C. McDonald |C et al Lung function in relation to chest radiographic changes in Quebec asbestos workers. Bull Phvsioparh Rosp 6:637-659. 1970. 11 Elmes PC: Incorrect diagnosis of asbestosis Postgrad Med I 50.250251. 1974. 12. The Asbestos Regulations. London: H M S O . (1969 No. 690) 13 Department of Employment Hygiene Standards for Airborne Asbestos Dust Concentration for Use with Asbestos Regulations Technical Data Note 13 (Rev.l. 1969 14 Amandus HE. Lapp NL. lacobsen C. and Reger RB Significance of irregular small opacities in radiographs of coalminers in the U S A. Brit I Induitr Med 13:13. 1976. 15. Berry C. Newhouse ML. and Turok M Combined effect of asbestos exposure and smoking on mortality from lung cancer in factory workers. Lancet 2:476-479. 1972. AU2G52 610 Asbestosis/Lewinsohn