Document R5KyngVLdVXGmOMEpgGpwNgX

57 Asbestosis -- A Diagnostic Enigma A Personal View H. C. Lewinsohn, M.B., B.Ch., D.f.H. Although the carcinogenic properties of asbestos are pres the production of generalized fibrosis of the lungs that a definite ently attracting a good deal o( attention, asbestosis is still the minimal quantity of dust must be inhaled, the lower the con earliest lung disease resulting from exposure to it and its inci- centration of dust in the air breathed, the fonger the lapse of time dence in an exposed population i_the most useful indicator of before the fibrosis is fully developed, and within a certain limit, the the degree of dust control exercised over a period of time. The diagnosis of asbestosis depends upon: (1) An adequate higher the concentration of dust, the sooner the fibrosis becomes fully developed and the more intense the involvement of the lung occupational exposure history. (2) Physical'signs of pulmonary tissue." fibrosis. (3) Progressive radiological changes. (4) Confirmatory He went on to hypothesize that, in the light of the above measurements of altered lung function. reasoning and the evidence which pointed to it. th- application of Asbestosis is a clinical entity and is readily diagnosed when dust control measures would cause "firstly, a great increase in the alt the above-mentioned criteria are met. Problems in length of time before workers develop a disabling fibrosis, and diagnosis are encountered when one or more of the diagnostic secondly, the almost total disappearance of the disease, as the criteria listed above cannot be substantiated. At the present measures for the suppression of dust are perfected." time every effort is made to diagnose the disease in its early The improvements made in the British manufacturing industries stages in the hope that removal from further exposure wilt pre after the 1931 Asbestos Industry Regulations took effect may be vent the direct and indirect complications. said to have occurred slowly and progressively from 1931 on wards and although much was achieved before World War II. the Regulations to control the asbestos industry in the United major advances in dust control probably took place in the 1930's.* Ouring the years of World War II regulations were relaxed and Kingdom were made in 1931.'- The evidence upon which they conditions in factories deteriorated. One of the problems in quan- were based was gathered in 1929 by Merewether and Price, the. ,,_4jf;jn'g dust exposure data is how to take account of the effect of termer a medical inspector of factories' (who later became senior historic events on working hours and working conditions. There is medical inspector and the latter an engineering inspector of fac- no way at present of analysing the effects of depressions, booms tories.-' .Merewether selected for his studies the textile branch of and other socio-economic phenomena when attempting to mea the industry :a branch manufacturing industrial textiles for insula sure cumulative dust exposure over any given period of time. tion. friction and packing material applications), and some prelimi ^Because of the limitations of the 1931 regulations, and because nary processes in other branches. Each individual's previous in the regulations applied to manufacture but not usage of products, dustrial history, subsequent to leaving school, was noted in detail. the hoped for reduction in cases of asbestosis in the U.K. did not Merewether cons'dered this to he essential in order to exclude occur at a national level. The Senior Medical Inspector's Advisory people whose p-evious work mav have been in any of the Panel on Asbestos, in its report to the minister of labor in 1%?* numerous p.*oes-es involving exposure to tree silica and other gave the following reasons for the increasing incidence of dusts. asbestosis: (a) The clinical criteria lor diagnosis have dunged Merewether's investigations led him to state: "To sum up. since the t920`s (b) taggers, the total of whom was not known, therefore it appejrs probable that concentration of dust and tended to be excluded from the process to which the 1931 regula length of exposure ax factors in tlx* production of fibrosis are in tions applied, fc' There had been an increase in overall consump terdependent within certain limits. While it seems necessary for tion of asbestos and a thing population of exposed worker*, (d: f..*n In I n.lu.irV l:-l K'wsiiX. ex Th* 41th*** i.Mp**'* fc4*b*M*u Mnhv.un Ifts C<w(y*.|<r O' CSO^bll Medical supervision of workers in the asbestos industry (originally recommended bv Meresvether) hid not been extended to workers in new proven.-. a> these were,inirwiiuted. ASBESTOS INFORMATION AbSOJUT.v Journal of Occupational Medicme/Vol. 19. No. 9/Septenibsr 1977 11774455 Jefferson D-wis hwy. Suite 509, Crystal Arlitiffloit, V.t. 2: 607 ASARCO ELP 0004117 I 4 1 CoRipftrittfl Menwilhtf's findtoft id 1929 and PrtvaUnca of Aib*s(stt< in 1975.* If*. *1 Ym* Empitr*4 0-9 to - 14 IS - 19 20 0r Uttk N*. Cqwwd 73/ u M IZ 1033 1973 1*3. fl Cauf CvWIW i 0 j. t htidwo \ 012S -- 45 49 0J7 Ortj Citn <t r*t d IMirtiroi txi BeHit ft muM m in 1915 t3 cmm anth mr pan JO jmo wt Cf* Vst ngmst Wars 1933 tttfto Mt ft*. Etxniiwd 230 14 28 21 3C3 . M Om CHiffwud 35 11 IS 12 95 C/ IftCWiAC* n 155 32.1 535 109 2(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 betow 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 (Rev.).1' Technical Data Note 13 states that where the dust concentra tion ts less than 2 fibrcs/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 iibrcs-'ml during a working life time. the dust level should not exceed an annual average of 2 fibres'ml .'.30 years x 2 f/mt = 100 f. vears/ml.. 30 years x 4 f/ml "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: Chrysotiie -- white -- 95% world production. Crocidolite -- blue ) ' Amosite -- brownish ) 5% of world production. Anthophyllite --; brownish -) It is accepted that all varieties of asbestos can give rise to asbestosis. Asbestos* 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 difficulty in obtaining an adequate occupational exposure history requires reference. Mcrewethcr attempted to quantify the dusti ness in the textile branch of the industry but was only able to pro duce a rough guide. The respirabitity of asbestos dust, because it is composed of fibres 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 1930`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 tevtle factory in its first attempt to set "Hygiene Standards for Chrv-v.ile Asbestos Dust" in 1968. Prior to this the only standard reeord-.d was in the U.S.A. and was 5.000.000 asbestos particles per cub:, foot as mea sured by means of the midget impinger. The BOSS Standard recommended a cumulative dust exposure limit of iro fibre years per cubic centimeter. This would allow a 1% risk of developing basal rales, which were considered as the earliest pivsical signs due to the effects of asbestos exposure. In the medical surveillance of asbestos workers in 3-itain we are now concerned with two populations for follow-up. namely, those people who have worked in the industry when dust measurements 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 by new regula tions and when environmental monitoring could b* .:dded to the data for epidemiological evaluation. HM Chief Inxjvx tor of Fac tories in his Annua! Report. 1974.' states. "139 new ca-es 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 \va> not tullv ap preciated. The latent period for this disease js such that annual figures cannot yet be expected to reflect improved conditions fol lowing the introduction of new legislation in 1970 ` What constitutes an adequate occupational historv * There is in sufficient evidence available from industry to enable this question to be completely resolved, but such evidence as ttvo is allows certain standards to be set in the hope of rcdjcinq the risk and providing a base-line for further study. (B.O.HS. 19h8s. Physical Signs of Pulmonary Fibrosis Where exposure is known, the presence of asbestos bodies and fibets in sputum is of little importance, since their pre-vtice simply confirms exposure and their absence does not indk ite freedom from disease. The presence of basal rales (crepitation:- or crackles) and finger dubbing have long been accepted as impo-tant clinical findings in conjunction with a history of asbestos exposure. The British Occupational Hygiene Society's Committee on Hvgicne Standards, in their publication `Hygiene Standa-ds for Chrysotiie Asbestos 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 in the dependent areas of the fungs. It is important to establish that the crackles are persistent and not due to other diseases resulting in pulmonary fibrosis. Until it is possible to record lung sounds and preserve graphic records, the presence or absence of these fine crackles remains a Asiestosis/lewinsahn ASARCO ELP 0004118 J T it subjective sign which will be elicited in different wavs by different observers accords* to the quality of their stethoscopes. the decree of presbvc jsviv from which they suffer'and the ability of the patient to breathe in a controlled manner. Progressive Radiological Changes X-rav technology and classifications of pneumoconioses have changed considerably during the past 46 years since Merewether surveyed workers in the asbestos textile industry. The radiological criteria which he used to diagnose asbestosis are not defined in his report. Radiological changes considered significant in the diagnosis of asbestosis by the BOHS Committee were increased general opacitv of the low er lobes, blurring of the cardiac outline, pleural thickening and adhesions. Isolated areas of calcification, un connected with the above changes, were not considered as necessarily or arobably asbestotic in this series. It appears likeh that Merewether and the BOHS Committee were concerned with relatively far-advanced disease. The BOHS Committee recognized the onset of the disease to be gradual and hence difficult to define. All the features of the disease may 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 vary. Various' systems of classification have been used to attempt to -Standardize-the description or rauiulugicai opacities. The Interna tional tabor Ofi:ce`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 asbestos-s as well as other abnormalities/ The tt.O.'UC In ternational Class *'ication of Radiographs of Pneumoconiosis. 1971." is designed to describe "persistent radiological opacities in the lung fields orovoked by mineral dust" and to allow them to be categorized acco'ding to size and shape and to indicate their pro fusion or extent m the lung fields. A set of standard films illustrat ing all categories is issued by the HO. Confirmatory Measurements of Altered Lung Function lung function tests have three main uses, namely. <ai To establish base-line values in order to assess lung function, periodi cally using each worker as his'her own control, lb' To confirm the clinical and radmogical diagnosis. <c' To assist in the assessment of disability in established disease.' It is not pronosed to discuss ia and (cl but merely to describe briefly the value of lung function tests in confirming the diagnosis. According to Baser ct af in asbestos workers vital capacity reduc tion precedes category 2 or 3 radiological changes by 10 to 15 vears: the latter changes do not occur until 20 years of exposure. After 30 years o' exposure, the incidence of functional and radio-' graphic abnormalities is approximately the same. The tests mo-: readily used according to Becfclake ct at..'8 are those of ventilators' capacity, which include measurement of the FEVt. fVC and FcV FVC%. lung volumes and gas transfer should be measured in all sus pected cases to obtain contirmatory evidence of pulmonary fibrosis. General Remarks An attempt has been made to indicate that asbestosis i> not an easy condition to diagnose. It requires intimate knowledge of the industry and the use of its products. The view is shared by times who. in relation to a particular case which he-diagnosed as asbestosis of nonoccupational origin, has subsequently published an account of the autopsy findings indicating that his diagnosis was incorrect. The diagnosis established at autopsy in this case was chronic active fibtocascous tuberculosis." Asbestosis is not a clear-cut entity except m 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 in 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 judgment 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 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 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 FEVt. 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 of lung function which characterises diffuse pulmonary fibrosis from anv 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. They are essential in the investigation of suspected asbestosis. A number of points arise as a result of the increasingly wide spread use of the HO 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 afiect the interpretation of x-rays and that in the older age group these changes can also occur.'* The - significance of category 1 (irregular small opacities in asbestos workers working ,in loiv dust concentrations), unless demonstrated to be related to cumulative dust exposure svhen re viewed on a serial basis, cannot vet 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 in the absence of serial review radiographs, a history of asbestos exposure (including Journal o( Occupational Medicira/Vol. 19. No. 9/September 1977 609 ) ASARCO ELP 0004119 1 some knowledge of dust levels and fibre type) and confirmatory clinical findings of pulmonary fibrosis. Many svprkcrs svho have been exposed to asbestos never de velop any x-ray changes and only some develop asbestosis. It 4s 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 knosvn 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 diagnosahle 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 di<cute -- 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.'* 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. (Tablet. This reduction has 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 Icgge'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 tune-ion effectively. References I. The Asbestos Industry Regulations. (SJL & O 1931 No. 11401.1911. Z Meresvethcf ERA and frit CW: Report on Effect* of Asbestos Oust on the Lungs and Oust suppression in the Aslx-stos Industry. Part 1. Oc currence or Pulmonarv fihrettis and other Pulmonary Affections in Asbestos Workers. H.M.S.O.. tontlon. 19 V). 3. British Occupational Hygiene Society: Committee on Hygiene Stan dards: Hygiene standards for chrysolite asbestos dust Ann Occup Hyg 11:47. 1968. 4. Problems arising from the use of Ashestos. Memorandum of the Senior Medical Inspector's Advisory Panel London: H.M.S 0. 1967. 5. Department o> Employment 1974. Annual Rejxirt 1974. H At Chief In spector of Factories: London. H.M.S.O. ICmnJ 6112'. 6. International labour office meeting of exports on the international classification of radiographs of the pneumoconioses. Ouup Safety HUH 9:2. 1959. 7. U1CC'Cincinnati classification of the radiographic appearances of pneumoconioses. A co-operative study by the UtCC committee. Che-: 58:57. 1970. 8. International labour Office. International Classification of Radiographs of Pneumoconioses. HO LlfC Classification 1971: 1972. 9. Bader ME. Bader RA. Teirstein AS ct al: Pulmonary fijnetioo and radiograph'C change* in 598 tvnrkpjajvith varying duration of exposure to _ asbestos. Mt. Sirui / Mod 37:492. 1970. 10. 8ectlake M.R. Fournier-Massey C. McDonald IC al: Lung function in relation to chest radiographic changes in .Quebec aibe-tcn workers. Soil Phywjfuth Ketp 6:617-659. 1970. II. Eljpes PC: Incorrect diagnosis of asbestosis. Po-tgrad Mid / 50:250251. 1974. 12. The Asbestos Regulations. London: H.M.S.O. !1969 No. 6901. 13. Department of Employment. Hygiene Standard- for Airborne Asbestos Ouse Concentration fix Usc'with Asbestos Regulations. Technical Data Note 11 IRev.l. 1969. 14. Arrundus HE. Lapp NL laeobsen C. and Reger RB: Significance of irregular small opacities in radiographs of coalminers in the U.S.A. Bril I Induttr Med 13:13. 1976. 15. Berry C. Nesvhouse ML and Turok M: Combined effect of asbestos exposure and smoking on mortality from lung cancer m factory workers. Lancer 2:476-479. 1972. 610 Asbeslosis/lewinsofm ASARCO ELP 0004120