Document dnaG0aK2gnBGjL4xadammb6QQ

o {-^ s & e* t-- MINERAL PURE CONTEST: OP HUMAN ^LONG TISSUE^ASJIN INDEX OP PAST EXPOSURE TO ASBESTOS TYPES A. J. Rogers Commonwealth Institute of Health The University of Sydney, NSW, 2006 Presented at International Academy of Pathology XT7 International Congress 15 October, 1982 \ C"J or-o 73 O 1--- C/I ABSTRACT Prolonged occupational exposure to high levels of asbestos may result in an increased .incidence of clinical cases of asbestosis, bronchogenic cancer and mesothelioma. The diagnosis of these diseases and the association with asbestos as an aetiological factor is usually-made from a knowledge of the patient's occupational history. Often such evidence is weak or may be entirely absent. Quantitative analytical microscopic examination of the asbestos content of the lung provides information for an estimation of degrees of past exposure to asbestos. The range of values of asbestos found in the lungs of the unexposed Sydney community, cases of bronchogenic cancer, and cases of mesothelioma are presented. A reasonable association is found when fibre levels are matched against past occupational history, often however the lung fibre levels provide the missing evidence of association with asbestos exposure. The data provided by such examinations has been most valuable in supplementing and substantiating evidence used for epidemiology and compensation purposes. LAM 025894 ABS-006272 MTNFFAT. FIBRE content of human lung tissue as an index " OF PAST EXPOSURE TO ASBESTOS TYPES The pathological observation of Accumulated dust in lung tissue as an aid in confirmation of pneumoconiosis and some environmentally induced malignancies has been attempted with various levels of success since the start of this century. Historically major surveys of mineral content of lung tissue has been conducted in - South African gold-mines (notable work by Watkins-Pitchford 1916) - British coal mines (Nagelschmidt 1950s) - Badham in 1936 investigated the lungs of N.S.W. coal, metalliferous and sandstone miners. \ For asbestos exposed individuals, the observation of "curious bodies" in the lungs of asbestotics produced interest from Cooke in the 1950s who by microscopic examination and XBD linked these bodies with the dust generated from the asbestos process. His major^pathological concern was "Are the curious bodies diagnostic of pulmonary asbestosis"? (Cooke 1929). The extrapolation of this comment to other asbestos related diseases resulted in the development of numerous semi-quantitative techniques for the examination of asbestos bodies resident in the human lung. lam 025895 ABS-006273 - . Specimen examination may . "be "based on preparations of , - . . - sputum ^rur- smears of incised lung . - .: :! - histological sections - micro-incineration of histological sections - chemical and enzymatic digestions. Each technique varies in its sensitivity, reproducibility and correlation^ with actual asbestos content of the lung. The Australian Mesothelioma Surveillance Programme was faced with the situation of implementing techniques to quantify past asbestos exposure by recording a detailed occupational history from the patient with confirmation of the asbestos exposure obtained by examination of residual asbestos in the lung. Many methods available in the literature were quantitatively unsuitable for our purposes although each possessed many good analytical aspects. With funding provided by the New South Wales Bust Diseases Board, eighteen months were spent in developing, testing and modifying a suitable technique (the results are currently awaiting publication in the journal "Analytical Chemistrjr"). The methodology is designed around the following steps: 1. Chemical digestion of the lung tissue using sodium hypochlorite 2. Dispersal of the residual mineral fragments using detergent 5. Concentration of the residue on membrane filters 4. Preparation of the filters for microscopic analysis 5. Quantitative examination of the mineral residues LAM 025896 - light microscopy - quantitative counting and sizing (Differential Interference Contrast X 500) - Transmission Electron Microscopy - additional Information on asbestos types by use of EDAX. ABS-006274 ; ^ ; . The interpretation of results obtained using the method has been Waite difficult since non-occupationally exposed individuals accumulate in their lungs low levels of mineral fibres from natural and man made :r _ .... " %. . .' ................... ... 'airborne contamination. . .' ... ............ ,, ... Comparison of the actual results obtained from other authors is of little value since the percentage of instances in which bodies are found and their quantitative levels varies considerably with the . analytical technique used in the investigation, the amount of lung tissue examined and the experience, diligence and persistence with which fibres are sought. For investigators using the most sensitive techniques it is obvious that the presence of asbestos fibres and asbestos bodies appears to be almost ubiquitous in the general population. ^ Baseline Population To develop baseline data, thirty matched pairs of lung cancer and control specimens (Australian bom males, Sydney residents age >40) were selected from 430 consecutive necropsy and 64 resected lung samples. Statistical comparison of the mineral fibre levels found ^in the two groups indicated there was no difference in fibre level distribution between groups when tested at the 95$ level of confidence. Using this information the two groups of matched pairs could be regarded as coming from the same homogeneous population and the results combined to form the basis for levels in the male Sydney population. It was found that 95$ of the sampled population contained less than 190,000 fibres per gram of dry tissue and less than 100,000 asbestos bodies per gram of dry tissue. On a semi-quantitative scan 83$ of the lungs contained some mineral fibres. LAM 025897 ABS-006275 TABLE 1. Mineral Fibre Levels Determined in Combined Patients and Controls Uncoated Fibres Fibre count/g dry tissue Percentage Cumulative $ Not detected <50 i io3 50- 99 i 105 100- 149 x 103 150- 199 x 105 200 - 249 x 103 31.696 42.1^ 15.096 8.896 1.736 - '"'V 31.696 ' 73.7% 89.5# 98.3$ IOO.O56 IOO.O96 Coated Fibres (Asbestos Bodies) Fibre count/g dry tissue Percentage Not detected <50 x 103 50- 99 x io3 100- 149 x 103 150- 199 x 103 200- 249 x lo3 68.496 29.896 I.856 - Cumulative 56 68.4$ 98.296 98.2$ IOO.O96 IOO.O96 IOO.O96 \ f TABLE' 2. Grade of Mineral Fibre Detected in Lung Tissue S Grade Uncoated fibres/g dry tissue Coated fibres/g dry tissue I normal*.population II] elevated amphibole mj- asbestos exposure -nr| increased incidence . rj[ asbestosis mesothelioma 0- 149 x io3 150- 299 x 103 300- 599 x 105 600- 1199 x 103` > 1200 x io3 0- 99 x 103 100-199 x i03 200-399 x 103 400 - 799 x 1o3 > 800 x 103 LAM 025898 ABS-006276 Comparison of this data to patients with known occupational exposure to asbestos indicated a geometric progression of lung fibre burden categories (Table 2). f ' ........... . >9 \ . , ' ' , .i ' . . .r- * i: .* .--...V;, > . , The interpretation of individual cases of degree of asbestos lung burden against this baseline data provides interesting information. Samples referred by Outside Pathologists and N.S.V. Dust Diseases Board \ Twelve cases were submitted on the basis of suspected asbestosis or lung cancer due to asbestos exposure; fifty-eight percent (7/l2) of the samples had higher than normal levels of fibre. Of these 7 three had extremely high levels of fibre in the lung.- .Due to the limited data available on the occupational history and medical diagnosis of these samples, it cannot be considered feasible for further analysis of these samples other than to say they come from a higher exposed group than the normal population. Medical officers of the N.S.V. Dust Diseases Board submitted seven cases of lung cancer for lung fibre analysis. Six of the seven had elevated lung fibre content and these fitted fairly well with the recorded history of occupational exposure to asbestos, hence assisting in confirmation of evidence for compensation purposes. Samples Obtained from Cases of Mesothelioma lam 025899 The first 27 completed confirmed cases of mesothelioma from the Australian Mesothelioma Surveillance Programme were examined for the presence of asbestos fibre in lung tissue by light microscopy: 44T& (12/27) bad fibre levels same as normal population range 26$ (7/27) had fibre levels slightly elevated c.f. normal population * 30$ (8/27) had fibre levels in excess 3* normal (3x - 12,000x). ABS-006277 3 .u & 5* "in ;> *." % 6U S|. " a 'y?l ;V.J Relating the fibre levels determined by light microscopy to the \ evidence of exposure to asbestos as provided in the detailed occupational history, a reasonable association between the two factors was obtained V, * \ * - .* -.a---* (Table 3)* However, one false positive was detected and five false negatives were detected, indicating the need for caution in the interpretation of aetiology of individual cases. Most interesting was the point that 26* of the cases provided no evidence of asbestos exposure from occupational history or elevated asbestos levels in the lung. The U.K. Pneumoconiosis Panel's record is that approximately 3096 of the U.K. mesothelioma cases also have no available evidence of asbestos exposure. TABLE 3* Association Between Lung Fibre Load and Occupational History Mesothelioma Cases Evidence of past asbestos exposure Normal range (Light Microscopy) Fibre count Top normal to 2x normal LAM 025 3x Normal .(3* - 12,000x) No evidence / unlikely Some evidence / possible Good evidence / probable 7 4 1 f1 51 2 ' 6 (4456) (26*) (30*) The evidence of mesothelioma induction produced by elevated total fibre count is only part of the asbestos story. Epidemiological evidence 1 clearly points to a difference in the potency of mesothelioma induction by 1 the various asbestos types, i.e. . Crocidolite ^ Amosite *> Chrysotile I (blue asbestos) (grey/brown asbestos) ' (white asbestos) i ABS-006278 y- Problems are encountered in reviewing occupational histories' V< for mesothelioma cases since , almost no information is provided on the'. ,r. :^type of asbestos encountered-by ,the.patient.... Since approximately 95$; "of asbestos usage-;is from-chirysotile, most infoxmation on amphibole exposure is not obtained from occupational history taking. The analytical electron microscope provides a technique for identification of each type of asbestos in the lung. \ Once again a study of Sydney urban males (60- 70 years of age) indicates 95$ tad fibre counts and types as follows: TABLE 4* Transmission Electron Microscope Counts >2 jjm length (normal male population) Total fibres Chrysotile Amosite Crocidolite Fibres x 10^/g dry tissue <2.0 <0.5 <0.5 41.0 The distribution of crocidolite in the Sydney unexposed population approached that found in populations in North American and in the TT.K. (Pooley et al) For the 27 mesothelioma cases: 67$ (18/27) had crocidolite levels within the range of the normal population 1)$ (3/27) had crocidolite levels 1 - 2x the range of the normal population * 22$ (6/27) had crocidolite levels >4x normal population. This data is contrary to our occupational epidemiological concepts and poses the following questions: 1. Is a high proportion of the mesotheliomas not related to'past amphibole asbestos exposure? There is some evidence being gathered by overseas studies that a fair proportion of mesothelioma cases fit into a no asbestos exposure category. lam 025901 2. rrls. the method of/predicting past : exposure .t7^e2amination,qf3^j> , residual asbestosjtypes in the lung insensitivejfor;the -?y. r.r ;..V: . >levels of - asbestos .that nay cause increased incidence 'of ' ; mesothelioma?" The high level of negative evidence produced &, from occupational history data tends to discount this approach. Future work will he based on an extension of this data to see if these trends continue. Conclusions The results obtained from detailed investigations of asbestos fibre load of lung tissue provide some basis for assisting in diagnosis of asbestos related diseases. However, the natural incidence of these diseases associated with no asbestos exposure in our population causemany anomalies in the prediction of the diagnosis and aetiology of individual cases. Conclusions may only be reached on a firm basis of clinical diagnosis, histopathology, lung fibre counts and review of the patient's occupational history by an astute experienced occupational hygienist. This work was supported by research grants provided by the New South Wales Workers' Compensation (Dust Diseases) Board. Electron microscope facilities were provided by the Director, ELectron Microscope Unit, The University of Sydney. LAM 025902 ABS-006280 References Cooke WE. Asbestos dust and the curious bodies found in pulmonary asbestosis. Brit Med J Sept 28 1929; p. 578-80. \ Watkins-Pitchford W and Moir J. On the nature of the doubly refracting particles seen in microscopic section of silicotic lungs. Rep Sth African Inst Med Res 1916; 1(Sept):000-000. Nagelschmidt G. The relation' between lung dust and lung pathology in pneumoconiosis. Brit J Ind Med I960; 17:247-59* Pooley P et al. Mineral fibre content of mesothelial tumours in North America. Inhaled Particles 7 (in press). Ibid. A pathological and mineralogical study of asbestos . related deaths in U.K. 1977* Inhaled Particles 7 \io. press). Rogers AJ. Determination of mineral fiber in human lung tissue by light microscopy and transmission electron microscopy. Analytical Chemistry (in press). LAM 025903 ABS-006281 __________Tfciy___ sUt^eJ ____ /fr~ ____ p^hCl? * K.^dt. ......t^a /? . ftrtiMitM*^(044<r C-W. A~tAtjL&QAtyts).. jl /y-'< ? --f.-*A ^ [?. i /*"? < _____ fjSZU ^ >ul" i ^ t<rf/dCi. A- ^f-yf^-/: ___puz&l__ _________________ 1 LAM 025893 ABS-006271