Document MJ3xK203QQdDdogVxDROEZmDV

Asbestosis -- A Diagnostic Enigma A Personal View H. C. Lewinsohn, M.B., B.Ch., O.I.H. 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 dinical 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 Merewether and Price, the former a medical inspector of factories (who later became senior medical inspectori and the latter an engineering inspector of fac tories -' Merewether 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. Each individual's previous in dustrial historv. subsequent to leaving school, was noted m detail Merewether 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 dusts Merew ether s investigations fed 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 seems necessary for fr*im TRA JnrtuKfn.fi Pf/xlm !* ltd Rohftlp UK Thf .iiitKix v iwwrt .irtrtfOAA iv tidvhi>x.tn<>-MjnhdtUn Inc OwjVK.iti* im f).iicv*w Df n untfKill c.srnwii . lournal of Occupational Medicine/Vol 19. No. 9/September 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 bec omes fullv developed and the more intense the involvement of the lung tissue " He went on to hypothesize that, in the light ot the above reasoning and the evidence which pointed to it the application of dust control measures would cause ''firstly, a great increase m 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 mav he said to have occurred slowly and progressively trom 1931 on wards and although much was achieved before World War II the maior advances in dust control probably took place in the 19S0's 1 During the years of World War II regulations wore 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 oi time Because of the limitations of the 1931 regulations and because the regulations applied to manufacture but not usage of produi ts the hoped for reduction in cases of asbestosis m the U K did not occur at a national level. The Senior Medical Inspet tor's Advisory Panel on Asbestos, in its report to the minister of labor in 1967* gave che following reasons for the increasing mi idem e of asbestosis: (al The clinical criteria for diagnosis have i hanged since the 1920's, fbl Laggers. the* total of whom svas not known tended to be excluded from the process to whuh the 19II regula tions applied, (cl There had been an inc rease in overall i onsumption of asbestos and a rising population of exposed workers `d' Medical supervision of workers in the asbestos industry 'originally recommended bv Merewetherl had not been extendi-d to workers in new processes as these were, mtrodui ed 409677 0005 607 Cawpwixn fctwaan Wwisuttur'l Radian la 1929 nd PrtmlHct at AAaxtoin la 1975* to. C / Tm'i 0-9: : 10 - W. IS 19 S'. - ' 2B4 0*\ ' Tdik Uatanki l* m, * . ***** nt: y > -."i . ' M' at-v.- im r Crw* lacWm % a.m --. 45 -ax ; 49 077 ' - EmM - u 24 - 7 V - ; IM. - mravector 1929 Hi. *t ten 36 27 15 17 95 *0^r cases tf asoesios'S wi recent of Induslrul knurws Benefit are nduOeO m the 1975 figures 3 uses '!" more than 20 fears e*posue *er first eioosed before 1933 tTabie *vi Grotto ittcidonce % 156 32 1 S36 809 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 were made in the U K. and they took 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 bv the publication of "Hygiene Stan dards for Airborne Asbestos Dust Concentrations for Use with Asbestos Regulations 1969" in Technical Data Note 13 (Rev.).11 Technical Data Note 13 states that where the dust concentra tion is less than 2 fibres/ml. HM 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 fibresfml during a working life time. the dust level should not exceed an annual average of 2 fibresfml .*.SO years x 2 f/ml = 100 f. years/ml., 50 years x 4 f/ml = 100 f. years'mf. 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. Crocidolite -- blue -I Amosite -- brownish -i 5% of world production. Anthophyllite -- brownish -) It is accepted that all varieties of asbestos can give rise to asbestosis. Asbestosis might be complicated 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 difficultv m obtaining an adequate occupational exposure history requires reference. Merewether attempted to 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 iibres and not of spherical or uniform particles, depends upon its aerodynamic behavior which is related to fibre diameter and falling speed It was not until suitable instruments became available in the late 1940's and early 1950's that routine environmental monitoring could be introduced into industry. The British Occupational Hygiene Society made use of dust measure 608 ments and clinical data from a Rochdale asbestos textile Mi lory -n its first attempt to set "Hygiene Standards iot Chrysolite Asbestos Dust" in 1968. Prior to this the only standard recorded wax in the USA. and was 5.000.000 asbestos particles per < uhn loot as mea sured by means of the midget impinger The BOHS Standard recommended a cumulative dust exposure limit oi 100 tibre 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 In the medical surveillance of asbestos workers in Britain we are now concerned with two populations for lolloxs -up namely those people who have worked in the industry when dust mea surements were not made and when variable dust control mea sures were taken and those who have entered since May 1970 when new improved conditions were demanded hv new regula tions and when environmental monitoring could be added to the data for epidemiological evaluation. HM Chief Inspixlor of Fac tories in his Annual Report. 1974.' states. "119 ness cases of asbestosis were 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 fullv ap preciated. The latent period for this disease is such that annual figures cannofyet be expected to reflect improved conditions fol lowing the introduction of nexv 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. (BOH 5. 1968' Physical Signs of Pulmonary Fibrosis Where exposure is known, the presence of asbestos hrxfies and fibers in sputum is of little importance, since their presence simply confirms exposure and their 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 their publication `Hygiene Standards lor ChrysotileAsbestos Dust' considered basal rales as the key symptom " The crackles are characteristically of high pitch and occur in endinspiration. persisting after coughing and most prominent m the dependent areas of the lungs. ft is important to establish that the crackles are persistent and not- due to other diseases resulting in pulmonary nhrosis Until it,is possible to record lung sounds and pre-sr-rvg--graphic records, the presence or absence of these fine crackles remains a Asbestosis/lewinsohn 409677 0006 : i\r xun whi< h will bo Hh iKkI n ditforont w,iv< bv ihtieronl m i. <>r<iim> to tlx* quality ot ttwir stolhnst ijm*s tlv dkn*r o |>M*shvi irom which they *aitU*f and llv* ahilitv ot iho fiaiHMit lo hriMtho in a controlled manner Progressive Radiological Changes X rav ti\ hnologv and r la-sifications of pneumoconiosis have i h.iniseri mnsiderablv during the past 46 vears since Merevvether survevrd workers in the asbestos textile industry This radiological criteria w hich he used to diagnose asbeslosis are not defined in his report. Radiological changes considered significant in the diagnosis of ashestosis bv the BOHS Committee were increased general opac itv of the lower lobes, blurring of the cardiac outline pleural thickening and adhesions. Isolated areas of calcification, unconnec ted with the above changes, were not considered as necessarily or prnbablv asbestotic in this series It appears likelv that Merewether and the BOHS Committee were concerned with relatively far-advanced disease The- BOHS Committee rec ognized the onset of the disease to be gradual and hence difficult to define. All the features of the disease mav occur to varying degree and. indeed, the severity of the alteration of the separate features may well be related to the type of past dust exposure. Thus the particular set of criteria used to decide whether asbestosis is present or absent will varv Various systems of classification have been used to attempt to standardize the description of radiological opacities. The Interna tional Labor Office's 1959 Classification* 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 m asbestosis as well as other abnormalities ' The ItO'UC In ternational Classification of Radiographs of Pneumoconiosis. 1971 " is designed to describe "persistent radiological opacities in the lung fields provoked by mineral dust" and to allow them to be categorized according to size and shape and to indicate their pro fusion or extent in the lung fields A set of standard films illustrat ing all categories is issued by the ILO. Confirmatory Measurements of Altered Lung Function Lung function tests have three main uses, namely ta> To establish base-line values in order to assess lung function, periodi cally using each worker as his/her own control, (hi To confirm the clinical and radiological diagnosis, (cl To assist in the assessment of disability in established disease. It is not proposed to discuss (at and (cl 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 vears: the latter changes do not occur until 20 years of exposure After 30 vears of exposure, the incidence of functional and radiographic abnormalities is approximately the same. The tests most readily used according to Becklake et al 10 are those of ventilatory capacity, which include measurement of the FEVi FVC and FEV/FVCV Lung volumes and gas transfer should be measured in all sus pected cases to obtain confirmatory evidence of pulmonary fibrosis General Remarks An attempt- has been made to indicate that asbestosis is not an easv condition to diagnose It require- intimate knowledge ot the industry and the use oi its products The view i- -hared bv Elmewho in relation to a particular r a-e which he diagnosed as asbestosis of nomx cupational origin has subsequently published an account of the autopsy finding- indicating tfvtt his ci-agnosis was incorrect The diagnosis established at autopsy in this case was chronic active fibrocaseous tuberculosis 11 Ashestosis is not a clear-cut entity exiept in the advanced stages of disease 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. can lead to psychological stress and breed ill-will m a com munity It is sound practice in the United Kingdom to discuss all suspected cases with the Members of the Pneumoconiosis Medi cal Panel and to accept their |udgment with regard to diagnosis There may be a few people who have some, but not all. diagnostic criteria, who are not considered to be suffering from asbestosis Many of these cases are elderly and on the verge ot retirement They are symptom-free, their earning capacity is not affected and they are unable to find alternative work it thev have to change jobs. Furthermore, the dust conditions which probably produced the slight changes in their x-ravs 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 detinue 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 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 Physiological tests alone cannot prove the diagnosis of asbestosis. but merely the abnormal pattern ot lung function which characterises diffuse pulmonary fibrosis from any cause In combination with occupational history, physical signs and radiological changes they give confirmatory evidence of the presence of the disease and assist in assessing its severity. Tfiey are essential in the investigation of suspected asbestosis A number of points arise as a result of the increasingly wide spread use of the ILO U/C Classification of radiographs The com monest changes recorded by most observers are 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 basis of a slight alteration in radlqlogical appearance and in the absence of serial review radiographs, a history of asbestos expu-ure tint ludmg- Joutnal of Occupational Medicine/Vol. 19. No. 9/September 1977 409677 0007 609 Mtm,. km >w l < 1 gi' ! <hi''l levels and fibre type' and < nnitrmat < >t v ilinuai timfmg' oi pulmonary Mm>sis Mam worker' who have heeiv expos'd to asbestos nev"r devclop .mv \ t,i\ changes and nnlv miiiic develop asbestosis It is not hjmmIK nMtlM'd In suggest to a symptom-trev. oth<,r\vi>r liealthv individual th.U he or she is Mibenng from an incurable diet disc.iM1 with a (ontumiiani cancer risk, it there e not dehnite pn>.>t It the disease is "definitely sus|hk. led" then the individual ks a right b * know tr> c ease exposure and lr> seek < om|>ensat h m It in tv it vet know n whether the improved methods ofwarn mat ion .nailable ; vrimt the detect inn ot the disease at a stage whore turther progression tan he proven it'd it exposure teases. The disease is now almost tortamlv dugnosabk* at an earlier Mage than 46 wars ago m Merewether's time The disease will probably pro gress m tb* more advanced cases oven when exposure to asbestos dust has ceased The British worker has changed his job habits and it is unusual to tmd him working in one firm or one job for as long as 20 vears. W**oov)<. is j p/vwnMb/e r/eease -- it now remains to prove whether lung t an< er and mesothelioma are preventable bv the Ntme mean* With regard to lung cancer the eradication of the < igarette hahit will undoubtedly also lead to the eradication of this (nmpj .idun of asb<*str)sis.' * In a largo asbestos textile factory m Rochdale the prevalence of asbiMosis has been reduced in 1975 to 0.77% among the current labour torce compared with Merewether's finding of 26.2% tn 1929 Table' This reduction has been achieved bv conscientious eftort on the part ot management to eliminate the disease In recent wars there has been a growing awareness among workers m industry ol their role in the prevention of occupational disease and when enlightened management takes advantage of this new willingness to t ooperate then useful practical measures follow Confrontation is not the wav 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 evervthing means a great deal, the work man no matter how willing he mav be to do so. cannot protect himself The world c annot do without asbestos at the present time as it lurin', an twsontial < ompoivnt m mam M>|>hiNtn ated 'Og'ni**fMg tion and evervein devices Without ashiM.*' m<ve l*w> w on Id undouhtedlv-he 1M tn im tin* hazards ni two .\n I on st knnU >r energ\ < nosercution transportation and mdieav would ho unable .o turn tier ethxtivek References ) riw AdV'tns indudn Regulations SR A l) HH) V. 1140 I'ltl 2 MerrwrMher ERA and Pm < CW Ro|*irt on {itui In t A'ls-Mo' DuM on Jungs .ind Dint Suppression m toe A'h*si*i' indti'P. PaM 1 () ( unrru e m Pulmonary Fkhimh and other Pulmonary Atir< tn *Ms m A'Ixmo' Workers HMSO London 19 til \ RmIinH Oh ujMlional Mvgione Sck ietv Committee on fbgienr sun- dirds Hygiene standards tor chrvsotile asbestos dii't A:'' * ><. ..> thi* 11 47 (968 4 Prnhk*ms arising from the use oi Asbestos \\emot andnni ot the Senior Medic a! Inspector's Advisory Panel london H M $ O 5 Department of Employment 19-4 Annual Report 19*4 H M Chiei tn- '|Vt tor oi Factories London HMSO :Cmnd 61226 International lahrvjr oilier meeting ot e\|'K,flN on the international classification of radiographs of the pneumcx'omoNCs Omm s.ireo H//hS 2 J9i9 7 UlCC'Cine innati slassiiication of the radingrajxhu ajj>Mr.m<.os oi imeumcxoniosps A co-operative study hv the UlCC r omnvttee f 'hevf 58 57 1970 ft International Labour Oftice International Classifu atmn of RarlmgrajifiN oi Pneumrxoniosev (LO U C Classiticatirjn 1971 19-2 9 Rader ME. Bader RA. Teirstem AS et al Pulmnnan tun< t*m and radio- graj>hr( ( hanges in 598 workers with varying Hurafion oi <>>jN)sure to aNhiwtos \fi Smai / \ferf 37 492. 1970 10 flecklake MR. Fourmer-Mass<v C McDonald 1C et at lung iiimt.on m relation to chest rjdiographti change'm QueNu ast>-\ti>N workers 8u(f P/oMMfHfh Resp 6'637-659 1970, 11 Times PC lncoru*ct diagnosis oi ashestnsix Pustgrar/ \fi-rf / 50 25U- 251 19*4. 12 The AshesUr'- Regufations London HMSO \. f>90 H Deputment ot Employment Hvgieno Standard' i < k Airborne AshevtON Dvist Concentration tor Us<* with Asht'stos Regulation' Te< hnu a1 Data Note 1 i tRev.*. 1969 14 Amandus HE. Lapp NL lacobsen C. and Reger RH Sigwi.<ane >>' irregular 'mall opacities in radiographs ot coalminers in the L's A Hnt ! m dour \/erf 13'13. 1976 15 Berry C, Nr*whoue ML. and Turok M Combrnr-rJ afe< r j asf>>NloN exjvoNiire and sm<iking on mortality trom lung i.im or n ia< lurv worker' I dm el 2 476-4,9. 1972 Asbestosis lewmsohn 409677 0008 AtHcleS -. .*.* v? , 409677 0001