Document Lg7pN4bO9zErwGwMrJnbm0zGX

isillTUTE OF OCCUPATIONAL' AND ENVIRONMENTAL HEALTH MONTREAL, CANADA Asbestosis -- A Diagnostic Enigma A Personal View / f 77 H. C. Lewinsohn,^WB., B.Ch., D.l.H. ^ . &02049 IOEH Code 457 1 10 11 12 13 82 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 (hat removal from further exposure will pre vent the direct and indirect complications. Regulations to control the asbestos industrv in the United Kingdom were made in 1931 1 The evidence upon which they were based was gathered in 1929 bv Merewcther and Price, the former a medical inspector of factories (who later became senior medical inspector) and the latter an engineering inspector of factoricsT Mercwether selected for his studies the textile branch of the industry (a branch manufacturing industrial textiles for insula tion, friction and packing material applications', and some prelimi nary processes in other branches- Lach individual's previous in dustrial history, subsequent to leaving school, was noted in detail. Mcrewether considered this to be essential in order to exclude people whose previous work may have been in any of the numerous processes involving exposure to free silica and other efusts. Mercwether's investigations led him to state: "To sum up, therefore, it appears probable that concentration of dust and length of exposure as factors in the production of fibrosis are in terdependent within certain limits. While it scvms necessary for fr<vn 1 H A IfiHusif 1.1! HmhIuiIs ivi k!'t'h(l.ilr' ljk 1h' .uHhnf \ fyrMMit .mH'.-ns x K u U-m* r NVi n!i.3t 1.1 n ini HX> OxiLviuw Dt fiumlKill (. \ ftiiMl Cop: iul<* I , 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 i!, 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 rn 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 cumulatis'e dust exposure over any given period of time Because of the limitations of the 1931 regulations, and because the regulations applied to manufacture hut not usage of products, the hoped tor reduction in cases of asbestosis in the U K. did not occur at a national level. The Senior Medical Inspector's Advisory Panel on Asbestos, in its report to the minister of labor in 1967' gave the following reasons for the increasing incidence of asbestosis: (at The clinical criteria for diagnosis have changed since the* 1920 s. (M taggers, the total of whom was not known, tended to be excluded from the process to which the 1931 regula tions applied. !c) There kid been an increase in overall consump tion of asbestos and a rising population of exposed workers (d) Medical supeivision of workers in the1 asbestos industry (originally recommended by Metewetherl had not been extended to workers in new processes as these were introduced. Journal of Occupational Metlicme/Vol 19, No. S/September 1977 UCC 024120 , 607 020296 AU2050 Comparison Between Meiewether's findings in 1929 and Prevalence ot Asbestosis in 1975.' No. of VtJO Employed 09 10 H IS 19 20 & Over Tot#f* No. Closed Le*tnsohrt 19?5 No. cf ' ClSM wl as 0 66 3 82 t 1093 IS Group Inctdenc* S 0 125 -- *5 49 0 77 no. Euni'ned 230 84 23 21 363 1929 Na. of Cam Dia^nowd 3b 2t IS It Si (Hir & astesiosis tr> iec;p! of lrd>>|.'^i injunes cr^` are ir I3.'S hgures t3 cases wiift mo't lhan 20 yiry t.sy&Jr* **(* frsl etpo?eS be'yt 1933 fTab'.t *VJ Group Inc >dentt % L5 5 32 1 53.5 80 9 26.2 The Advisory Panel did record, however, that although they were inclined to accept 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 1969, new regulations known as the Asbestos Regulations 1969 wcte made in the U K, and they took effect in May 1970.1? 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 Note 13 iRevTA1 Technical Data Mote 13 states that where the dust concentra tion is less than 2 fibres 'ml, H\1 Factory Inspectorate will 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 limit of 100 t'ibres 'ml during a working life time, the dust level should not exceed an annual average of 2 fibres'mf .'.50 years x 2 f/ml = 100 f. yearsml.. 50 years v 4 f.'m! = 100 f. years/mf. etc. 'Adequate' Occupational Exposure History !n the determination of an adequate occupational exposure history it is necessary to ascertain the type of asbestos fibre m use. There are four main varieties in commercial use, namely: Chrysotile -- white -- 95% world production. Crocidolite -- blue -I 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 complicated by tire development of carcinoma of the lung, and the risk of this complication is multiplied many times by cigarette smoking. Before discussing the t liniral features of asbestosis, one further difficulty in obtaining an adequate occupational exposure history requires reference. Merewether attempted tn quantify the dusti ness in the textile branch of the industry but was only able to pro duce a rough guide. The respirability of asbestos dust, because it is composed of fibres and not of spherical or uniform particles, depends upon its aerodynamic behavior whit h is related to fibre diameter and falling speed. It was not until suitable instruments became available in tlte late 1940's and early 1950's that routine environmental monitoring could be introduced into industry. The British Occupational Hygiene1 Sot iety made use of dust measure ments and clinical data from a Rochdale asbestos textile factory in its first attempt to set "Hygiene Standards foe 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 BOHS 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 as the earliest physical signs due to the effects of asbestos exposure. !n the medical surveillance of asbestos workers in Britain we are now concerned with two populations for follosv-up, namely, those people who have worked in the industry when dust mea surements were not made and when variable dust control mea sures svere 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. 1974,1 states. "139 new cases of asbestosis were recorded by DHSS during the year. These con tinued to retied conditions in past years when the long-term etfeds of asbestos dust on the Health of Workers was not fully ap preciated. The latent period for this disease is such that annual figures cannot yet he 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 be completely resolved, but such evidence as there is allows certain standards to be set in the hope of reducing the risk and providing a base-line for further study. (B.O.H.S. 19681. Physical Signs of Pulmonary Fibrosis Where exposure is known, the presence of asbestos bodies and fibers in sputum is or little importance, since their presence simply confirms exposure and tlieir absence does not indicate freedom from disease. The presence of basal rales (crepitations or crackles! and finger clubbing have long been accepted as important clinical findings in conjunction with a history of asbestos exposure. The British Occupational Hygiene Society's Committee on Hygiene Standards, in dtetr publit atmn 'Hygiene Standards for Chrysotile Asbestos Dust' considered hasal rales as the "key symptom." The crackles are < haras teristically of high piti h amt occur in ondinspiratton. persisting after coughing and most prominent in the dependent areas of the lungs. It is important to establish tfv.it the i r.u kies are persistent .and not due to otlxu diseases resulting m pulmonary fibrosis. . Until it is possible (o record tong sounds amt preserve graphic records site proseme or absent e ot these fine craikles remains a 60S UCC 024121 Asbestosis/Lewmsohn 'r E ,,;!vi--. ' K sign vvi-iii h w ill hi1 t-lu iti'il in ditfi-rr-nt u u\ - bv rlilterent ,,hsriv,-rs .ii i i ii i !m>' to (lie r|U.ilit\ oT ttirir stelhn'iiipe-,. till' ill'lliv'ol pre-hyi n-wix tmm whiih they sutler and tf*' ability of it*- patten' tn bn-atlv in ,1 t uritrolled manner Progressive Radiological Changes X-ray tix hnologv anil i UomIi. ,11 ions of pneumoi oniiii'' have {hanged i onsirli'r.itjl. during the It -Hi sears since Morewether surveyed worker', m the asbestos textile industry The radiological criteria which I*' used to diagnose asbestosis are not defined in his report Radiological change' considered '-igniiVant in the diagnosis ot asbestosis bv the BOMS Committee were mi reased general opacity of the lower lohi". btu'iing of if s' cardiac outline, pleural thickening and adhesions Isolated areas of calcification, un connected with the above change' were not considered as necessarily or probably axbo'totic in this series It appears likely that Morewether and the BOHS Committee were concerned with relatively far-advanced disease. The BOHS Committee recognised the onset ot the disease to be gradual and hence difficult to deune All the features of the disease may occur to varying degree and indeed, the severity of the alteration of the separate features maw well he related to the type of past dust exposure. Thus the particular set of criteria used to decide whether asbestosis is present or absent will vary. Various systems of classification have been used to attempt to standardize the description of radiological opacities. The Interna tional Labor Office's 1959 Classification1' was, until recently, the most widely used but had certain difficulties with regard to asbestosis The classification was recently modified by a UICC working group and extended to include irregular opacities such AS occur in asbestosis as well as other abooima'ities.' The HO UC In ternational Classification of Radiographs of Pneumoconiosis. 1971/ is designed to describe "persistent radiological opacities in the lung fields provoked bv mineral dust" and to allow1 them to be categorized according to size and shape and to indicate their pro fusion or extent in the lung be-ds A set of standard films i&sstrat ing all categories is issued by the ILQ. Confirmatory Measurements of Alter'd lung Function Lung function tests have three main uses, namely. (a! To establish base-line values in order to assess lung function, periodi cally using each worker as his 'her awn control, (bl To confirm the clinical and radiological diagnosis 'c t To assist in the assessment of disability in established disease. It is not proposed to discuss ia' and let but merely to describe briefly the value of lung function tests in confirming the diagnosis. According to Bader et af in asbestos workers vital capacity reduc tion precedes category 2 or 3 radiological changes bv 10 to 15 years; the latter changes do not occur until 20 years ol exposure. After 30 years of exposure, the incidence of functional and radio graphic abnormalities is approximately the same The tests most readily used according to Becklake et <il.11 arc.' those of ventilatory rapacity, which include measurement of the FFVi, FVC and FLVFVC'V Lung volumes and gas transfer should.be measured in all sus pected cases to obtain confirmatory evidence of pulmonary fibrosis General Remarks An atUxnpt has been made to indicate that asbestosis is not an e.isv inmiilinn to diagnose It requires ultimate knowledge of the industry am! tf*- use of it' piodu. Is The sum is shared by Flmos who. in relation to a partnulai < ase wtw h he diagnosed as asbestosis of nonm iiipatu'nnl origin, lias subsequently published an account of the autopsy endings indicating that h>s diagnosis was incorrect The diagnosis established at autopsy in this case was chronic at live fibroi .isrntjx tuberc uJosis." Asbestosis is not a -clear-cut entity except in the advanced stages of di'V.i'i- and very often a mistaken diagnosis can be made which, if communicated to the individual concerned before all diagnostic avenues have been explored and the disease con firmed. c an lead in psycbolrvga a! stress and breed ill-will in a com munity' ft is sound practice in the limit'd Kingdom to discuss all suspected cases with the Members oi the Pneumoconiosis Medi cal Panel and to accept their turfgment with regard to diagnosis. There may be a few- people- who have some, but not all, diagnostic criteria, who ,ee not considered to be suffering from asbestosis. Many of these cases are elderly and on the verge of retirement. They are symptom-free, their earning capacity- is not affected and they are unable to find alternative work if they have to change jobs. furthermore, the dust conditions 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, 1969 ensure their safety. Unless they develop symp toms. or clinical 'findings indicate definite 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 home 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 FEVi, and FVC. is a simple procedure and the test equipment available is robust, transportable and dependable. The use of lung function tests in the future in the surveillance of asbestos workers is obvious and should form an essential part of any preventative medical programme. Physiologica! tests alone cannot prove the diagnosis of asbestosis. but merely the abnormal pattern of lung function which characterises diftuse pulmonary fibrosis from any cause. In combination with occupational historv, physical signs and radiological changes tfiey give confirmatory evidence of the presence of the disease and assist in assessing its seventy. They are essentia! in the investigation of suspected asbestosis. A number of points arise as a result of the increasingly wide spread use of the FLO U C Classification of tachographs. The com monest changes lecordert by rno-t observers ate 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.'1 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 basts of a slight alteration in radiological appearance and in the absence of serial review radiographs, a history of asbestos exposure (including Journal of Occupnttonal Mtdictne/Vol. 19, No. 9/September 1977 UCC 024122 AQ2G5 ! 609 s-srne knowledge of dust levels and fibre type) and confirmatory clinical findings of pulmonary fibrosis. ! Many workers who have been exposed Ip 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 healthy 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 known whether the improved methods of examination available permit the detection of the disease at a stage where fur ther progression can be prevented if exposure ceases. The disease is now almost certainly diagnosable at an earlier stage than 46 years ago in Merewether'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 job habits and it is unusual to find him working in one firm or one job 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 load to the eradication of this complication of asbestosis." 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 Meresvether's finding of 2t>.2% in 1929. (Table). This reduction has been achieved by conscientious effort on the part of management to eliminate the disease. In recent years there has been a grosving 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 be lost from the hazards of fire and most kinds of energy conservation, transportation and industry would be unable to function effectively. References 1. The Asht-sto' Industry Regulations. (SR & O 1911 No. 11-10), 1931 2. Men-wrlher ERA and Price CW: Report on Elfectsof Asbeslns Dust on the lun^s and Dust Suppress,on in the Asbestos Industry. Part 1. Oc currence of Pulmonary Fibrosis and nthcr Pulmonary Affections in Asbestos Workers H M S O . London. 1930 3. British Occupational Hygiene Society; Committee on Hygiene Stan dards: Hvgiene standards tor chrysotile asbestos dust. Ann Orcup Hyg 11:47. 1968 4. Problems arising from the use of Asbestos. Memorandum of the Senior Medical Inspector's Advisory Panel London: H.M.SO 1967. 5. Department oi Employment 1974. Annual Re|X>rt 1974. H.M. Chief In spector of Factories London. HMS.O. fCrrtnd 6322). 6. International labour office meeting of experts on the international classification of radiographs of the pneumoconioses. Occup Safety Hkb 9:2, 19S9. 7. U1CC'Cincinnati classification of the radiographic appearances of pneumoconioses A co-operative study by the UICC committee Chew 58:57. 1970. 8. International Labour Office. International Classification of Radiographs of Pneumoconioses. HO U'C Classification 1971: 1972. 9. Bader ME, Bader RA. Teirstein AS et at: Pulmonary function and radio graphic changes in 598 workers with varying duration of enposure lo asbestos. \fr. Sinai I Med 37:492. 1970. 10. Becklake MR Fournier-Massey G, McDonald 1C et al: Lung function in relation to chest radiographic changes in Quebec asbestos workers. Bull Physiqpaih Resp 6:637-659, 1970 11 Elmos PC: Incorrect diagnosis of asbestosis. Postgrad Med I 50:250 251. 1974, 12 The Asbestos Regulations. London; H.M.SO.. (1969 No. 690! 13 Department of Employment Hygiene Standards for Airborne Asbestos Dust Concentration for Use wish Asbestos Regulations. Technical Data Note 13 iRev.l. 1969, 14, Amandus HE, Lapp NL, lacobsen C, and Reger RB: Significance of irregular small opaotics in radiographs of coalminers in the U S A. Bril I In dur.tr Med 13:13. 1976 15. Berry G. 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. A0205 610 Asbestosis/Lewinsohn UCG 024123