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INTSIIXAT10 NAL C ONFERENCE on the BIOLOGICAL EFFECTS OF ASBESTOS Roport on Proceedings by Dr. VT, TAYLOR Department of Social Medicine, Queen's College, Dundee. November, 1964. A 1 790'r UCC 007833 CONTENTS , I, Occurrence and the Major Use of Asbestos II. The Incidence of Asbestos and the Association of Asbestosis and Intra-thoracic Tumour. l III. Environmental Asbestos Exposure IV. Research Matters Arising from Asbestos Conference V. Clinical Criteria -- Asbestosis and Radiological Appoarar.cos, ' VI. Colleagues Working in Asbestos Reaoarch Fiold VII. References . . foS0. l 3 4 6 S 0 10 UCC 007834 T. ` Occurrence and the Major Use of Asbestos o'.i.t Serpentine "p.vsotile Asbestos p**---r 1 CROC IDOLITE I jjMOSXTE Amphibolos l ir TREMOLITE ACTINOLITE The important members of those groups are: ;) c'TtVSCTriS - X7hite asbestos, a hydrated magnesium silicate yith the formula (3MgO 2Si0g SH^O), Sp.g. 2.55 with a long fibre of tubular structure. - i f^orTiiOLTTE - Blue asbestos (Xa^O 3FoO Fo,,03 SSi0o H20). Sp.g. 3.37 vith a high resistance to acids and alkalies. ) .'.if OS ITS - Whitish-fawn, forrous magnesium silicate (l.5*IgO 5,5FoO r.SiO^ H^O), Sp.g. 3.45 ''11 ` ~ the Ampkibolcs all have 8 silica units with 7 mineral units and 1 wator molecule. UCC 007835 A 5 790 r' _ 0- - thoao throo countries producing CIS pci* cent af the world production, and eleven countries, including Finland, providing the redlining 15 per cent of the world production. .. There arc many industrial uses for the manufactured products from asbestos minerals which follow from the chemical inertness and high thermal insulation properties of asbestos fibre. Because it is important to ascertain whether a clinical case has been exposed during a lifetime to asbestos in ar.v form, it is necessary to know tho industrial applications in detail. The following list includes the major usos:- 1. . 2, 3. 4. 5. fl. 7. Asbestos Mining. Asbestos Textile Manufacture (woven and non-woven), mattresses, curtains, safety-suits, pipe covers, filter presses etc, Asbestos Cement Products (sheets, partitions etc.) Asphalt and Vinyl asbestos floor covor'ings. " Roof coverings (in spray form). Clutch and Brake Linings in the Automobile Industry. Fillers for paints, caulking compounds, and in plastic rosins. - Thero are now over 3.000 industrial applications recorded. The hazard from Asbestos Bust arises in Industry in many environments; (a) Ship broaking and demolition yards, (b) Ship yard maintenance (dockyards). (c) Ship building yards. (d) Sawing, drilling and grinding of asbestos products in brukolining works, (0) Sawing, grinding, levelling of asbestos sheets. . (f) '/caving mills, especially in screening and preparation rooms, picking, stacking, carding, spinning, winding and weaving. _ (g) Spraying buildings to roduco fire risk. (h) Tho bagging of asbestos products - Insulation materials. (1) Demolition and renewal of pipe lagging in all industrial works. UCC 007836 II. The Incidence of Asbestosis and the Association of Asbestos and Intrg-Thoracic Tumour At this confcrcnca, the need for further epidemiological studies or. .asbestos in ail countries was stressed. There was wide divergence in iho fow epidemiological studies presented an the incidence of asbestosis, and this was even more apparent in tho figures presented from Canada, South Africa, the States and tho United Kingdom, on the association of asbestos with intra--thoracic neoplasms. In this respect, the Ministry of Labour, through the Factory Inspectorate^^ appear to be ahead, in that they havo been collecting mortality data since 1924, With the size of sample now presented, the figures from England and Wales would appear to be tho most roliablo of all the countries represented at this conference. In summary these arei Year 1924-1947 1924-1355 1924-1063 TABLE I Asbestos is (unc ompiic ated) 128 365 584 ' Ashesiosis j. (latra-thoracic tumour) 22 65 143 The proportion of asbestosis death certificates which also record a thoracic tumour, has risen in both sexes disproportionately to the number of uncomplicated asbestosis, so that currently over 50 per cent of males dying with asbestosis have also a neoplasm. Even when viewed against the steadily rising incidence of lung cancer in the population as a whole, /2 \ there seems little doubt that the increase is a real one. Soiikoff, 1 in the New York area, and using data from the Asbestos Workers Union (total population 632) for the period 1942-1962, has recorded 45 deaths, 42 of these duo to carcinoma of the bronchus and 3 to pleural neoplasms (mesothe lioma), giving a death rate 6.8 times highor in asbestos iaggers than in the general U.S. white, male population. In the studies among asbestos workers in this series, it is interesting to note that cancer of tho stomach-, colon and rectum was throe times as frequent as expected, thus focussing attention on tho relationship between industrial asbestos exposure and carcinoma of the gastro-intestinal tract. Whilst x-raying tho large New York series, Selikoff(' s)' noticed a high incidence of ploural calcification amongst asbestOB insulation workers, and tho suggestion mudo at this conference) is that asbostoois is perhaps tho most common cause of pleural calcification in industrial conn triers at present, especially if bilateral. Of 1,120 pipe Iaggers examined!' /TABLE II ... . 4:790 UCC 007837 i TATiT.K II Radiological Examination of Pine Loggers Lapsed Time Since Onset of Exposure Number Examinad. C-r ; . Calcific ration <10 00 -00 20 - 20 10 - 10 121 57.9 194 3 <1.5 77 10.4 379 1.1 He concluded that lapsed tine, since onset of exposure, is more important than total exposure. The common sites of pleural plaques- ..re diaphragm, costal margins, anterior and posterior-mediastinal, pericardium, inter-lobar fissures and even lung apices. Many plaques were missed in the early days, (o.g. those are obscured by rib shadows). Tiro modifications of procedure have now brought many more calcifications to lights . " (1) Oblique views aru always tulcen -,,v.a and Left) (2) A highor penetration Icilovoltago is used if usbestosis * is suspected. Pleural calcifications appearto be uncommon before 15 years interval or lapsed time following first exposure. An average figure is 20 years. Ill, Environmental Asbestos Exposure This conference high-lighted a maxim well recognised in Industrial Health but insufficiently stressed in medical teaching - the importance of taking a dotailed occupational history. Many cases in papers describing pleural calc ificatiou and pleural and peritoneal neoplasms could find at first, no association with asbestos. Careful histories, however, revealed chance environmental exposure to asbestos many years previously. Iluddew^"*' in 1929, reported asbostos bodies in a nan not employed in asbestos, but living near an asbestos factory. At this conforonce Thomson^*31^ 2reported the results of 500 autopsies in Cape Town and '500 in Miami, Florida. The result* wore similar in the two cities. 30 por cent of males and 0 per cent of females showod asbestos bodies. In 0 por cent of tho males tlioro war. the possibility of occupational origin, but in B0 por cent of the positive tho presence of asbestos was regarded as tho result of contamination of the urban atmosphere. The origin of tho asbestos fibres was thought to be brake and clutch lining disintegration, but this has now been disproved and the problem remains unsolved, V/hat is now required is a base line so that A 1 7 903 future trends may he accurately followed. The arton- of the problem nay be n arger UCC 007838 f Sor-rvr wo appreciate uu present* Among 3,312 ru} cd .;* in area around an asbestos nine ir. Eir.laad, i&vilaoto^f found 459 cases of pleural calcification. In a control area, withoux, an asbestos nine, no cases were found among 7,101 persons x-rayed. In this respect, concern r,ay be felt for certain job categories. Pipe insulation vor-cers undoubtedly share their exposure with other.trados 7 electricians, plumbobs, sheet-metai workers, boiler nakera, fitters and oven foromen. Perhaps tho supervising engiuoer ox- architect should bo oxaniuud. In Loifast, where there are no asbestos factories, Elmos*' 7).'found 42 cases of pleura. l . mesothelioma in a population of 3/4 million in the period 1949-1963 (l'i years). Between 19C6 and 1923, 1,CC0 tons per year of boiler conposition (S5 per cent asbestos) was imported for shipbuilding purposes and it is thought that the latent period of 40 years has now produced the ir.tra-thoraoic tumours in Belfast. A positive history of exposure to asbestos at work- was obtained in 32 of tho 42 cases of pleural mesothelioma. Newhousef' s') found S3 cases of mesothelioma from hospital records in London, 10 between (1917 - 1350 ) and 73 betveon (1950 - 1903). Tho interval between first exposure and terminal illness ranged from 10 to 55 years with a moan of 37 years. A history of exposure to crocidolite was obtained in 53 per cent of cases and throe main types of exposure wore recognised! (1) Asbestos textile works * (2) Laggers or pipe insulators (3) Exposure to dusf brought home by relatives (4), Of the 33 patients with mesothelioma, with no positive occupational history and no. relatives living at hone who worked with asbestos, 11 lived within half a milo of an asliostoa factory, Of the 33 casos found in London, 62 had pleural mesothelioma, an.l in 21 the tumour was peritoneal in origin. Enticknap and Smithcr' ' .in 54 years (1958 - 1934) saw 52 cases cf asbostosis at necropsy. Nineteen (36 per cent) had lung tumours and fourteen (27 per cent) had abdominal tumours, nine of which appeared to originate in .the peritoneum. The lapsed tine following exposure varied from 20 to 46 years and exposure time varied from 10 months to 32 years. The interesting feature of the peritoneal tumours associated with 'ndustrial exposure to asbestos was that associated lung- fibrosis and pulmonary changes are below average in severity (disability 10 - 30 per cent) and in some of those cases 'here was insufficient lung disability to qualify for asbostosis certification (4 cuss*). It was also suggested that the incidence of peritoneal tumours veil bo very much higher but for: (r.) The hortor life span of the soveroly affected worker vhutv du.su pathology predominates. ' 1 1 ifficult differential diagnosis from other forms Io"iiijuI neoplasm, i.o. Carcinoma of stomach, I'.v.r.-ies and many unclassified cases of liii-.our. ' A ; 79 I 0 UCC 007839 IV, Hosoarch '.'ntti'rs Ari s 1 n1-: from Asbestos C or.for' (1) In future work, the exact y/ne of asbestos dust'must bo idontifiod, There is insufficient data correlating typo of duet and subsequent ' 'pathology. Animal experiments must be conducted with standard dusts. Tho exact significance of particle sine is not known. Originally it was thought that only coarse ' fibres were responsible for lung . changes but the conference felt that ulira-raicroscopic particles will also produce fibrosis (less than 2 microns). The JI.A.C. 5 miliion/ra is not now accepted. This conference made it clear that industry should aim at 1 million/m3 maximum and accept this figure with reservations until our icnowlodge in this field is extended (3) Tho pathogenesis of asbestos is unknown. The following scheme - ' asbestos fibre - macrophages -j lysis -) sclerosis fibrosis -> carciaogoncsis is thought to bo an immunity reaction associated with 1 gammaglobulin. Tho reaction is not now regarded as explosive in nature hut is a slow, insidious, low grade, progressive fibrosis with early fibrotic changes around the bronchioles. There is thickening of bronchiole walls and of the pleura. In its early phase the lesion is not obstructive. Finally there is the formation of the asbestos body, a forriton (iron-protein complex) surrounding the fibre and is laid clown in concentric rings. Tatar tho asbestos body becomes fragmented. Asbestos bodies are difficult to find, will require polarisod light, may not be characteristic of asbestos only, and may contain metals other than iron. Small birefringent bodies seen ir. lung tissue have always been accepted as asbestos, but caution is now required in interpretation. Electron-microscope studies are now proceeding at Cambridge, The conclusions are (a) that all asbestos bodies so identified may not bo due to asbestos, and (b) that thoro is difficulty finding asbestos parti clos less than 10 micron without tho necessary techniques. i \ i) Asbestos fibres may migrate from tho lung and have been found in spleen and liver. This migration may explain the presence of gastro intestinal malignancies, but again, fibres may be swallowed direct (ingestion of bronchial secretions). (-) There doca appear to be a direct correlation between asbestos dust exposure time and tumour formation. There is, however, strong evidence reported by T'agner in a large series of cases cf mesothelioma that crocidolito is more dangerous than chrysctilo. In Xorth Anori. a however, chrysotilo has boon associated with peritoneal tumour's. There have boon no cases reported from South Africa of tumour format L..-: where the exposure was to ariosi to only, but one tumour (peritoneal) has been reported by oclilxff with amasite. The natural asbestos minerals an mined, always contain .mineral oil (up UCC 007840 4 ; 7 9| i ; .. ; r.-v I >. i \ C 1 *.ll K' rt . 'fork ill tllO ci 1 < :Vi i i: I - J I :``U! i'h vr iViniy !!,:o rvreh Institute v l>i". Ifurr ingtor.). _ ' r i s : i :u- idem: o of br.onehinl c ri i' c i j -. pleural mesotheliomas, poritoneal tumours one! possibly guciro-.ntv... oiiiai ne,linr.iicy might bo explained by tho fact that tho asbestos workor is now in the so-ctllad "tumour formation period", i.o. 20 -- 40 years following tho first exposure. If this is the pathology with asbestos fibre, then*wo shall require to look closely at fibre glass, a later development, now in production 10 -- 12 years in Scotland. Personnel exposed to this fibre will not have arrived at the tumour formation period for a further 10 - 12 years in Scotland, but in Germany, where tho fibro glass process originated, a production time in the region of 20 years is reported. (S) There,are large differences both in morbidity and mortality of asbestos in the surveys in different parts of tho world. These discrepancies may be explained by the different chemical nature of tho minerals, but there is f.t the same-tine, an urgent need to standardise radiological findings and histology. * (0) Therewore ton many small surveys presented at this conference without the required statistical control. In overall epidemiological study is urgently required. (10) In malignant tissue arising from asbestos, tho characteristic lung histology is not easily interpreted. The loose, fibrous tissue is not particularly malignant-looking. Tho fibrous tissue is infiltrated with clefts lined with capillary and alveolar pseudo-epithelium, the whole picture being difficult to distinguish from adenocarcinoma. (11) In tho experience of tho M.M.C. Pneumoconiosis Unit, there is evidence that chest disease in asbestos workers detected by moans of x-raya is more serious than pneumoconiosis or silicosis with similar radiological findings. (12) Tho average age at death when tho asbestos hazard was first recognised (1907) was 33 years. In 103-i, the average age at death is 57 years. It must, howovor, ho recognised that heavily exposed people are dying in 1034 in their CO's and IC's. (13) There are two groups ef asbestos workers in which the risk of asbestos and malignancy is high; (a) pipe luggers and demolition vor . rs, where . tho exposure will bo constant over many years, and (b) asbestos sprayer where tho atmospheric concentration of asbestos is very high. (14) Thero is a vast improvement in dust control in largo manufacturing works whore the asbestos hazards are now recognised ana controlled, and : whoro preventive measures will eventually reduce tho ; .icin'; i m; iii <- asbestosis, ,Snail uni tu. how..vr.j*, are still not duut free and ur.. ..cl- ;oct to environmental control. In this respect, tho effect of the "................. ", combined with long working hours at that UCC 007841 A i 79 12 -3- V, Clinical Criteria - Asbe3tosis Throughout tho conference there wore many referpnces to signs and symptoms of asbostosis. Those are:- 1, ' 2. 3. 4. 5. 6. 7. 8. ' 9. 10, Vaguo chest pains - a very curly symptom , Dypsnooa - may bo first clinical symptom Unproductive cough or bronchitis in an otherwise hc-.Ithy subject, with no previous cheat history. Loss of energy and generally off-colour. Early symptom, There is little or no tendency to asthma. Lung function tests are not of great value in the early stages, other than, to ostablish a base lino, e.g. pre-employment examinations. Basal r.les - early sign. Finger chubbing - noted in about 20 per cent of cases, Pleurisy nay bo first indication of asbostosis, with or without associated neoplasm. Saoumonia may also bo first indication, as in S. Peritoneal tumours may often come to light (a) Vague abdominal pain in any quadrant of abdomen (b) Abdominal discomfort, Indigestion is an early symptom and an employee complaining of vague discomfort is seen by the Factory M.O. (c) Ascites. Patient may report fer a slimming diet, as happened in one case. Rad iolofrlcal Anpc qranc o s 1. Basal distribution and commonly bilateral is characteristic of asbostosis. ' . 2. The low grade, interstitial fibrosis gives rise to coarse, linear markings, more common in the lower lobes on both sides, and spreading into the middle lobuo, described as "honey coTr.hing". 3. Pleural thickening (lung, diaphragm and pericardium). . 4. Tho presence of calcified plaques. 5. An uneven right border of tho heart - "the shaggy heart" sign - pericardium thickening. UCC 007842 Ai79 a 3 -9VI.__ Nam or, and Units of Colongues Uorkinff in tho Asbestos Research l-'iolil 1; Ur, J. C, Gilson U.R.C, Pneumoconiosis Research lfr.it, Glamorgan, Unios. 2. Dr. J. C. '"iiS0" 3. Dr. U. J. Saithcr (Member of the Asbestos 'Research Council) As"above The Cape Insulation and Asbestos Products Co. Ltd,, , London. (Medical Officer). r, Dr. S. Holmes (Dust sampling and counting techniques) o. Dr. C. G. Addingley . ( 'Royco1 expert) Turnor Asbestos Co. Ltd. Rochdale. British Belting and Asbestos Co.' Ltd., St, Peters Buildings, York Street, Leeds 0, Dr. Ross Hunt . (Physiologist and dust expert) As above 7. Dr. J. G. a!. Davis (Electron-microscope expert physicist) 0. Dr. J. C. McVittio University of Cambridge, Cambridge. Ministry of Pensions and National Insurance, London. . 9. Dr. U. D. Buchanan Ministry of Labour, London. 10. Dr, J, S. Harrington Chester Beatty Research Institute, Royal Cancer Jiospi 'u&l J London. 11. Dr. H. E. Ayer Public Health Service, Division of OccupationalHealth, ') Braun, D.C. Truon. T.D. (lOoC) Epidemiological Study in Lung Cane ru in .asbestos Minors. Arch. Industrial Health. 17 : C.'M-G (o) y/agner. Nl.-ws, C,A.. Mai-cb.-.r.f! f. (1 ilfiQ) 3- f Moao tiie 1 ionju and Asbestos Exposure in N.V/, Ca n; Irni'inci:, B. o, I * M, : 2GC"d7I ^`) McCftuyhloy. ff.f.E. . T/ndo. O.L., Elciss. P. (l9Gu) Exposure to Asbestos Dust and Di1iuso* Pleural ^ttsotheiiofta.. ' 2 i 1397 i'j) Uagnor, J.C. (1932) Nature. ico'ew ISO (*') V.'agnor, J.C.. Murid ay, D.E., Harrincton, J.S. (106:3) J, Path. Bact. 73 UCC 007843 A i 79 }4 1 til, References (1) Annual Report of Chief loupe.r-or of Factories for the year 1055, Her i'iajuaty',H fitaii one:," OrTiu.j. Annual Report _C : 2C6. (2) Sol iI:of 7 I..T. , Clnirnr, J. , r ,C, (lOSt) Journal of tho ' American M...ileal Assoc:,.. uien, April, p,22 (3) Asbestos Conference, l-'eV York ( 1A J * . (}) . Knddoy. A.C. (1029) Lancet - 2 ; 230-231 (O) Thoniaon, J'.G. University of Capa Town Medical Asbestos Conference (1964), . . School, Capo t Tara (6) Kivilnoto, ft. (1030) Pleural Calcification as x-ray -ign of Noil-occupational Endemic Authu;'`.y 11 ito-A,,.c.:to si; Acta Radiol, Suppl. 194 : 1-S7 (7) Elmos , P, C, ( 11-3!: ^ Tho Relationship of Exposure to Asbestos and Pleural Mali nancy in Boifuat. Asbestos Conference, New York (1964). (8) Newhouss. Ai,L. (1 96 ;) Epidemiology of Mosotholia! Tumours in tho London Area. __ Asbestos Conforencoj Nov York (1964). ' (9) EnticTmar). J.d., .`5nither. W.J. (l-R-l) Peritoneal Tumours in Asbestesis. D.J.I.M. 3l : 20 Further !!.. fore-neon - Papers un A., btern not spec i f icn.1 lv .-ofa to in (a) Lynch. K.M. , Smith, . A. (19.35) Pulmonary Asbestos!.--j Carcinoma of Lung in asbestos-silicosis. Aser. J. Cancer 24 : 56-6-1 (b) Ackerman, L.V. (195-1) Atlas of Tumour lithology. Armed Forces Institute of Pathology, Washington. (c) Doll, R. (1955} Mortality from Lung Cancer in Asbestos Workers. B.J.I.M. . - 12 : 81-W (d) Braun, D.C. Truan, T.D. (1938) Epidcniological Study in Lung Cancer ' in As bps to s Minors. Arch, Industrial Health. 17 : C-'i-i-tV',:: -'lo so tlio liORIu ana Asbestos Exposure in N,'-7. Cm.e Zruvi :ictr , 3.J.I.M. ' 17 : 200-2 (0 McCaurthley. V.'.T.E. . Undo, 0.L, , Elmos, P. (l9Gj) Exposure to Asbestos Dust and Diffuse 'Pleural Mesothelioma. ' B.U.J. 2 i i307 b> V/acner, J.C. (19-52 ) Nature. 136 : ISO (h) Warner, J.C. , Muuday, D.. . Ha rrinirton. J.3. (1962) J* Pilw*! , Duel. O'i : 73 UCC 007844 A ; 79 1