Document JmXYD4Y6pMmJ008QJO06KmEB

FILE NAME Allied Signal Bendix ASB DATE 1975 Dec 11 DOC ASB013 DOCUMENT DESCRIPTION Bendix Engineering Staff Report - Health Hazards of Asbestos THE BENDIX CORPORATION CORPORATE ENGINEERING STAFF SOUTHFIELD MICHIGAN TET 1-9-76 PLAINTIFF'S BDX 50 HAZARDS OF ASBESTOS = A REVIEW OF THE MEDICAL LITERATURE 8 Prepared By Jacob W. Tawiah December 11 1975 UOT spp me, a ol . EXECUTIVE SUMMARY HAZARDS OF ASBESTOS A. CURRENT MEDICAL KNOWLEDGE 1. Nature of Asbestos Diseases Present medical knowledge associates asbestos with three primary diseases Asbestosis Bronchogenic lung Cancer and Mesothelioma a rare form of cancer All three diseases affect the lungs and in the case of mesotheliona the abdominal cavity may also be affected Asbestosis can cause death but it is not always fatal bronchogenic cancer is fatal and mesothelioma is the most deadly of them all Is there a safe exposure level There is general agreement that the risk of developing one of the asbestos diseases is positively correlated with the intensity and duration of exposure to asbestos dust ; intensity However there is no conclusive proof of a safe threshold level of exposure If and when such a threshold level is determined present indications are that it will vary from type of asbestos fiber to type of asbestos fiber from occupation to occupation and fror disease to disease What is the relationship between asbestosis and lung cancer There are reported cases of lung cancer victims showing symptoms of asbestosis but if an individual does not smoke asbestosis does not lead to lung cancer The medical evidence is that asbestosis do occur irrespective of one's smoking habits while an excess risk of lung cancer has thus far been only associated with cigarette smokers 4 What are the relative risks following exposure to only one variety of asbestos All commercial forms of asbestos cause asbestosis bronchogenic cancer and mesothelioma However the risk is greatest with crocidolite less with amosite and perhaps still less with chrysotile 5 What is the mechanism of disease causation in asbestos diseases Existing evidence appear to indicate that extracellular processes and the physical features of fibers constitute a major part of the causation of the lung diseases associated with exposure to asbestos dust The of fiber diameter appear to be the controlling factor in the causation of disease -2- The association of asbestos cancer with cigarette coupled with the physical nature of the process of disease smoking causation . as present studies indicate perhaps permits the speculation that asbestos fibers or other fibers of similar physical dimensions once in the lungs act only as a mechanical confactor in enhancing retention , inhibiting clearance and modifying the distribution of inhaled insol- uble cigarette smoke particles which are proven to be carcinogenic It may be inferred therefore that other insoluble particulate matter of similar physical dimensions as asbestos may be equally cocarcino- genic as asbestos 6. What other causes of mesothelioma are there There have been reported cases of mesothelioma that cannot be linked to asbestos but there are no known other cuases of the diseast other than exposure to asbestos dust 7 Can asbestos cause other diseases Yes There is ample evidence of an association between pleural plaques and all types of exposure to asbestos and to all types of asbestos fiber Asbestos is not the only cause of plaques but it is the rost common 33 8 Is it possible to detect asbestosis early enough to permit a cure With regular ray examinations it is possible to detect asbestosis to at least permit its control llowever the of asbestos diseases is estimated to be about 20 the onset of latent period years 19 COMMENTARY There is no doubt that the inhalation of substantial amounts of asbestos can lead to increased rates of various types of lung disease including two forms of cancer The medical literature is full of solid evidence linking asbestos to disease Eliminating the emission of asbestos dust into the working environment appears to an obvious way of dealing with the problem This however may not be the most feasible approach in light of economic consider ations It then becomes necessary to examine what other alternatives exist There is strong evidence to indicate that all the diseases associated with asbestos is exacerbated by cigarette smoking In fact the evidence is that there is no excess risk of bronchogenic cancer in asbestos workers who do not smoke In this case it appears that asbestos is merely a catalyst to the causation of bronchogenic cancer and the primary carcinogen is cigarette smoke An alternative solution to the problem that perhaps would be economically attractive to all concerned may thus be a requirement that workers in the asbestos industry be smokers This option becomes even more attractive when recognition is taken of the fact that existing evidence even though inconclusive at this time indicates that other fibers with certain physical dimensions below cm diameter irrespective of chemical composition swy have the same effect as asbestos eee me ee -3- In the self interest of Bendix the apparently physical nature of the mechanism of disease causation of asbestos fibers should be carefully considered in our search for alternate material for our brake lining composition P.S SEE ATTACHMENT A FOR SUPPORTING DETAIL AND BIBLIOGRAPHY OF THE MEDICAL LITERATURE REVIEWED ATTACHMENT _A , HAZARDS OF ASBESTOS - A REVIEW OF THE MEDICAL LITERATURE ASBESTOS DISEASES Three primary diseases are known to be caused or induced by the exposure to and inhalation of asbestos fibers in industrial environments They are asbestosis bronchogenic lung cancer and mesothelioma an extremely rare form of cance which affects the lining of the pleural lung cavity or the peritoneal abdominal cavity Asbestosis This is the most common of the three asbestos diseases It is one of the lung diseases classified as pneumoconioses Among others are silicosis from crystalline silica dust byssinosis from cotton dust talcosis from tale and anthracosis from coal dust Asbestosis is a malignant fribotic lung condition which shows a high of occurrence in populations exposed to asbestos dust if the centration is high or the duration of exposure is long 1,2 frequency dust con- When an asbestos fiber is inhaled into the body and it is not capture and eliminated by the normal cleansing mechanisms two different actions can occur It can be encapsulated with rich protein - in which case it is then referred to as an asbestos body or ferruginous body Dr. it can remain in a naked uncoated For all intents and purposes the asbestos fiber if coated is harmless On the other hand if the fiber remains in a naked state in the lung then an almost uncontrolled growth of cells may begin resulting in the formation of collagen or scar tissue When collagen forms in the lungs it alters the normal tissue so that it no longer functions properly When this biological reaction occurs the body's vital capacity is greatly reduced and the oxygen dioxide exchange function within the lungs is altered The overall effect is poor ventilation and labored breathing which are signs of asbestosis Other physical symptoms of asbestosis are rales - unusual sounds produced in the chest cavity and finger clubbing 3a nume 38 Asbestosis has been shown in is not necessarily always fatal studies to cause death but it . All the commercially significant varieties of asbestos chrysotile amosite crocidolite and anthophyllite have been shown to cause asbestosis 4-9 However there is considerable evidence to suggest that the risk is greatest with crocidolite less with amosite and perhaps still less with chrysotile 11 12 While exact response relationships are not well established there is general agreement that there exists a positive correlation between intensity of exposure and the frequency of occurrence of asbestosis He + wenn eM moe mene, -2- Studies workers of risk indicate that pulmonary fibrosis is augmented in asbestos cigarette smoking 13 It has also been shown that the death from asbestosis may be increased by cigarette smoking Bronchogenic lung Cancer A high frequency of bronchogenic cancer greater than that expected on the basis of the general male population has been shown to be manifested among persons who trial settings 15-18 who have had exposure to asbestos in Studies 19-25 have shown that all of asbestos can give rise to an excess of bronchogenic cancer indus- types under some circumstances It has been forcefully demonstrated that the risk of bronchogenic cancer is greatest with crocidolite less with amosite and perhaps still less with chrysotile Evidence from studies using dust exposure assessments has generally shown that the excess risk of bronchogenic cancer is related to dose and duration of exposure Perhaps the most significant conditional factor asso- ciated with the excess risk of bronchogenic cancer related to indus- trial exposure to asbestos is the requirement of cigarette smoking Existing evidence indicates that smokers do not show any excess risk of bronchogenic cancer regardless of their exposure to asbestos 26 27 * The biological mechanisms involved in the development of bronchogenic cancer and mesothelioma are not yet clearly established However evidence based on studies thus far conducted on this subject permits reasonable speculation on a probable course of events In a study conducted by M. F. Stanton 28 of the Laboratory of Pathology National Center Institute Bethesda U.S.A. various structural forms of asbestos fibrous glass and aluminum oxide were tested for carcinogenicity on the pleura lung of rats Results from all three materials indicate that carcinogenicity is related primarily to fibrous structure rather than to physicochemical properties A comparison of the dimensional distribution of fibers in those samples of asbestos and glass producing high and low tumor incidence indicate that carcinogenicity may be related to fibers below 2.5 m micron in diameter and between 10 to 80 ym in length Another study by V. Timbrell ofof the MRC Pneumoconiosis Unit Llandough Hospital Penarth UK concluded that extracellular processes and the physical features of fibers appear to constitute a major part of the etiology causation of the lung diseases associated with exposure to asbestos dust including the cancers The biological exposures which different types of asbestos fibers produce when inhaled seem to be governed largely by the aerodynamic properties of the fibers The physical characteristics of the fibers which form the basis of these suggested explanations are fiber diameter fiber length and fiber morphology the central parameter being fiber diameter -3- Further evidence supporting the thesis of physical processes as etiological causation mechanisms of asbestos cancers is provided by Dr. Edward A. Martell of the National Center for Atrospheric Research In two articles 30,31 published in 1974 and 1975 Dr. Martell asserted and provided evidence to support the following Airborne 210 is concentrated on small Aitken particles which accumulate on tobacco trichomes Tobacco curing and the combustion of trichomes in burning cigarettes produce insoluble particles of high 210pb radioactivity which are inhaled and deposited in the bronchi of smokers The subsequent ingrowth of 210 results in high local alpha irradiation which may account for bronchial cancer among smokers The significance of this finding is that coupled with the cited evidence of the physical nature of the causation of asbestos cancers and other related facts the suspected carcinogenicity of asbestos or fibers of an appropriate physical dimensions may be subject to reinterpretation It has been observed by Selikoff et al 26,27 that bronchial carcinoma deaths among asbestos workers who smoke cigarettes are about eight that expected for cigarette smokers in general whereas there were times no excess bronchial carcinomas among asbestos workers who did not smoke It thus follows that asbestos is not a primary carcinogen It is indeed a cocarcinogen It may be concluded therefore that it is likely that an accumulation of the small asbestos fibers or other similar fibers in the lungs of the workers acts only as a mechanical cofactor in enhancing retention inhibiting clearance and modifying the distribution of inhaled insoluble emitting radioactive particles from cigarette smoke which are proven to be carcinogenic Mesothelioma Mesothelioma is the third asbestos disease It is an extremely rare form of cancer which affects the lining of the lung cavity and of the abdominal cavity Mesothelioma is by far the most serious of the three diseases because at the present time once it is diagnosed it is inevitably fatal -- there is no known treatment Death usually occurs within 18 months after diagnosis Although there are reported cases or mesothelioma that can not be linked to asbestos asbestos remains the prime suspect as the carcinogenic agen 04- According to P. C. Elmes 32 the tumor usually starts in the pleura lung but a small proportion starts in the peritoneum abdomen Jc either case pain is usually the first symptom followed later by breathlessness and loss of weight The time course of the disease is short averaging 13-14 months for the pleural cases and six months for the peritoneal Even though the evidence 26 is not conclusive it appears cigarette smoking aggravates the occurence of mesothelioma that The causation of this disease in so far as it relates to the role of asbestos is similar to bronchial cancers as previously described Ft ae, a REFERENCES Merewether E.R.A. and Price C.W. Report on the Lungs and Dust Suppression in the Asbestos Stationary Office London 1930 Effects of Industry Asbestos Dust on Her Majesty's 2 Sayers R.R. and Dreesen W.C. Asbestosis American Journal of Public Health 29 205 1939 3" Manville Corporation Asbestos and Health Environmental Facts Asbestos March 1974 3b Selikoff I.J. Churg J. and Harmond E.C. The Occurrence of Asbestosis Among Insulation Workers in the United States Ann N.Y. Acad Sci 132 139 1965 4 through 9 were presented at LARC Conference on Biological Effects of Asbestos Lyon France 1972 McDonald J.D. Asbestosis in Chrysotile Mines and Mills Cremer G.K. and duToit R.S.J. Amosite and Crocidolite Mining and Milling as Causes of Asbestosis 4 Ahlman K. et al Anthophyllite Mining and Milling as a Cause of Asbestosis Smither W.J. and Lewinsohn H.C. Asbestosis in Textile Manufacturing Cooper W.C. and Miedema J. Asbestosis in the Manufacture of Insulating Materials Enterline P.E. and Weill H. Asbestosis in Asbestos Cement Workers Timbrell V. Conference on 1969 The Inhalation Pneumoconiosis of Fibers Proceedings of the International Dept. of Mines Republic of South Africa . 10b Report of the Advisory Committee on Asbestos Cancers the Director of the International Agency for Research on Cancer October 6 1972 11. Wagner J.C. and Skidmore J.W. Asbestos Dust Deposition and Retention in Rats Ann N.Y. Acad Sci 132 77 1965 12. Wagner J.C. Asbestosis in Experimental Animals British Journal of Industrial Medicine 20 1 1963 13. Weiss W. Cigarette Smoking Asbestosis and Pulmonary Fibrosis Arves Rev. of Respiratory Diseases 104 223 2271971 meee), REFERENCES PAGE 2 14. Auerbach O. et al Smoking Habits and Age in Relation to Pulmonary Changes Rupture of Aveolar Septums Fibrosis and Thickening of Walls of Small Arteries and Arterioles New England Journal of Medicine 269 1045-1054 1963 15. Doll R. Mortality from Lung Cancer in Asbestos Workers British Journal Industrial Medicine 12 81 1955 16. Selikoff I.J. J. Churg and E. C. Hammond Asbestos Exposure and Nuopinsia 17 Elmes P.C. and J.J.C. Simpson Insulation Workers 1940-66 Brith J. Ind Med 28 226-236 1971 in Belfast - Mortality 18 Newhouse M.L. A Study of the Mortality of Workers in Asbestos Factory Brit J. Ind Med 26 294-301 1969 19 through 26 28 29 32 and 33 were presented at LARC Conference on Biological Effects of Asbestos Lyon France 1972 19. McDonald J.C. Cancer in Chrysotile Mines and Mills 4 20. Webster I. Malignancy in Relation to Crocidolite and Amosite * 21. Meurman L.O. et al Mortality and Morbidity of Employees of Authophyllite Asbestos Mines in Finland 22. Newhouse M.L. Cancer Among Workers in the Asbestos Textile Industry 23. 24 Selikoff I.J. et al Cancer Risk of Insulation Workers in the United States Bohlig H. and Hain E. Cancer in Relation to Environmental Exposure 25. Pooley F.D. Mesothelioma in Relation to Exposure 26. Selikoff I.J. and E.C. Hammond Relation of Cigarette Smoking to Risk of Death of Asbestos Disease Among Insulation Workers in the United States - : 27. Selikoff I.J. E.C. Hammond and J. Churg Asbestos Exposure Smoking and Neoplasia Journal of Amer Med Assoc 204 106-112 1968 28. Stanton M.F. Some Etiological Considerations of Fiber Carcinogenesis 29. Timbrell V. Physical Factors as Et'ological Mechanisms rh REFERENCES . PAGE 3 30. Martell E.A. Radioactivity of Tobacco Trichomes and Insoluble Cigarette Smoke Particles Nature 249 5454 215-217 May 17 1974 31. Martell E.A. Tobacco Radioactivity and Cancer in Smokers American Scientist 63 404-412 August 1975 32. Elmes P.C. The Natural History of Diffuse Mesothelioma 33 Jones J.S.P. and G. Sheers Pleural Plaques EXPLANATORY NOTES 1. Because the three major types of asbestos differ chemically and physicaltlheyy also differ in biological effect in animal experiments The significance of this difference in relation to human health is uncertain Current knowledge indicates that crocidolite the type least used in the United States is most clearly associated with health hazards for people This is the concensus of a panel of nine medical experts appointed by the British Ministry of Labour -- Christy R.K. and members of the panel Problems Arising from the Use of Asbestos Her Majesty's Stationery Office 1967. Wagner et al reported a high number of mesothe- lioma cases among crocidolite miners in one area of South Africa but no cases among amosite miners -- Wagner J.C. Sleggs C.A. and Marchand P. Diffuse Pleural Mesothelioma and Asbestos Exposure in the North Westerng Cape Province British Journal of Industrial Medicine 1960 22 261 By contrast chrysotile mining areas in other parts of the world have not exhibited a high incidence of mesothelioma Wagner also published experimental evidence that compared with other asbestos fibers crocidolite produces the most severe asbestosis in laboratory animals -- Wagner J.C. Asbestosis in Experimental Animals British Journal of Industrial Medicine 1963 20 1 2. Only in occupational exposure do asbestos dust levels appear great enough to become possible health hazards This point is related to dosage Ievels as pointed out by Enterline and Kendrick Asbestos dust at levels to which general populations are exposed probably is of little importance in the etiology causation of disease -~ Enterline P.E. and Kendrick N.A. Asbestos Dust Exposures at Various Levels and Mortality Archives of EnvironDental Health August 1967. In addition investigators who report called asbestos dodies in human lungs note that these findings are not related 22 - . to cause of death or indeed to any disease The comment of Thompson and Graves is representative of those in other studies But to convert the scanty of very scanty bodies which have demonstrated to be present in so many urban dwellers to the frequency present in a minimal basal asbestosis would require an increase by hundredfolds and to get a more diffuse classical asbestosia with pulmonary disability the multiplying factor might well be in many millions -- Thomson J.C. and Graves W.M. Asbestos as an Urban Air Contaminant Archives of Pathology May 1966 3. called asbestos bodies in the lung may be produced by other substances Gross et al have offered experimental proof called asbestos bodies were produced in the lungs of hamsters injected intratracheally with respirable filamentous particles composed of aluminum silicate Instead of the tim asbestos body the designation of ferruginous body is suggested -- Gross Cralley L.J. and deTreville R.T.P. Asbestos Bodies Their Nonspecificity American Industrial Hygiene Association Journal December 1967. Similar results have been reported by Davis working at Cambridge University England Davis said that hamsters were injected in the trachea and the pleura with dust from aluminum silicate glass fiber carborundum and made textile fiber In both injection sites all these foreign materials produced bodies which with the light microscope appeared very similar to asbestos bodies The basic assumption that asbestos like bodies can only be produced from asbestos has proved incorrect -- Davis J.M.G. Gross P. and deTreville R.T.P. Asbestos Bodies and Bioeffects -- A Detective Story Annual Meeting Industrial Hygiene Foundation Pittsburgh October 1967 ae =-=gs@ 4. One of the substances capable of producing ferruginous bodies in human lunga is tale which has numerous industrial uses one of the least important being the manufacture of talcum powder The United States consumes annually about 100,000 more tons of tale than asbestos As for the ubiquitous talcum powder an analysis by Cralley et al revealed that the average drug store product contains about 20 percent of respirable fibers -- Cralley L.J. Key M.M. Groth D.H. Lainhart W.S. and Ligo R.M. Fibrous and Mineral Content of Cosmetic Talcum Products American Industrial Hygiene Association Journal August 1968 5. Gross et al used electron microscopy in an effort to find chrysotile asbestos in 28 random samples of ferruginous bodies in city dwellers Chrysotile which comprises more than 90 of the asbestos used in this country has a characteristic electron diffraction pattern On the basis of the election diffraction pattern chrysotile was decisively excluded as a constituenotf the cores of all 28 ferruginous bodies isolated from lungs of urban dwellcis not occupationally exposed to asbestos This exclusion is considered highly significant because if the ferruginous bodies in the above city dwellers had been caused by the inhalation of asbestos dusts then some of the cores should logically be composed of chrysotile -- Gross P. deTreville R.T.P. and Haller M.N. Pulmonary Ferruginous Bodies in City Dwellers Archives of Environmental Health August 1969 6. An uninformed speculation frequently stated as if it were a fact is that the wearing of automobile brakes releases dangerous quantities of asbestos fiber into the air A study by Lynch of the U.S. Public Health Service has demonstrated that this statement is erroneous Lynch performed laboratory tests of automotive brake linings and found that normal wear panne eee + - we eee en ~- releases insignificant amounts of asbestos fiber into the air He concluded that the free fibers from brake lining wear appear to be an inconsequentia health factoirn urban air pollution -- Lynch J.R. Brake Lining Dicens position Products Journal of the Air Pollution Control Association 7. time factor in asbestosis cases is demonstrated by the study of Mevistic showing that clinical asbestosis takes on the average about 17 years to develop ee McVittic J.C. Asbestosis in Great Britain Annals N.Y. Academy of Sciences December 31 1965 8. Selikofeft al reported a much higher rate of lung cancer among asbestes workers who smoked than among cigarette smokers generally However they reported not one case of lung cancer among nonsmoking asbestos workers Ti authors concluded that their evidence . not lead to an extremely high risk of suggests that exposure to asbestes dees lung cancer among nonsmokers -- Selikoff I.J. Haumond E.C. and Churg J. Asbestos Exposure Smoking 4 Neoplasia Journal of the American Medical Association April 1960 A 1969 update of this study reported one case of lung cancer among nonsen o= Selikoff I. J. Hammond E. C. and Churt J. Hortality Experiences of e Asbestos Insulation Workers 1947 196p3resented at International Conference on Pneumoconiosis Johannesburg South Africa April 1969 9. That dust control measures effectively reduce the incidence of lung cancer among asbestos workers is evidenced in the continuing study by Knox Doll and Hill These investigators studied one plant in the British asbestos textile industry In 1955 the workers in this plant exhibited a high insidence of lung cancer as was reported by Doll at that time Eut in 1965 and again In 1968 subsequent to dust control measures the incidence of lung cancer among these workers was approximately the same as for the general British Donulation -- Knox J.F. Holmes S. Doll R.S. and Hill I.D. Mortality e from Lung Cancer and Other Causes Among Workers in an Asbestos Textile Factory British Journal of Industrial Medicine October 1968 10. The varying prevalence of mesothelioma in the two crocidolite mining areas of South Africa has prompted comment by Wright That something other that or in addition to asbestos plays a role in mesothelioma formation seems Inescapable o- Wright G.W. Asbestos and Health in 1969 American Review of Respiratory Disease October 1969 11. Not a single case of mesothelioma has been reported among the anthophyllite asbestos miners of Finland -- Kiviluoto R. and Meurman L. Results of Asbestos Exposure in Finland Proceeding International Conference on Pneumoconiosis Johannesburg South in Canada among all Africa 1969. Primary malignant mesothelioma is very rare segments of the population including the chrysotile asbestos miners -- McDonald A.D. Harper A. El Attar O.A. and McDonald J.C. Epidemiology of Primary Malignant Mesothelial Tumours in Canada Proceedings International Conference on Pneumoconiosis Johannesburg South Africa 1969 12. About 50 cases of mesothelioma are reported annually in Great Britain e- Gunter R. Minister of Labour Official Report to the House of Commons April 17 1967 13. Typical of the doubt involved in any diagnosis of mesothelioma is the observation of Demy and Adler The mesothelial tumors as usual were the subject of doubt debate review and review but as usual no other primary lesion was found and so they were classified as mesotheliomas ++ Demy N.C. of and Adler H. Asbestosis and Malignancy American Journal of Roentgenology July 1967. Similarly Wright comments There is lively controversy . -6- among pathologista regarding the requirements for establishing the diagnosis of primary mesothelioma Further study will be needed to demonstrate whether mesothelioma is being over or under diagnosed - Wright G.W. Asbestos and Health in 1969 American Review of Respiratory Disease October 1969 ~xxx~ G1007 we eee -- : Te ee ve pee ee - Sammaieelicahentend fe gp ee