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450* *i?.Xrr. Asbastos Information Association/North Ameriicuaa 22 East 40th Street New York, N. Y. 10016 212-689-3378 dj> December 27, 1972 Gentlemen: Attached for your information are two recent medical papers of considerable importance with regard to asbestos-health. The first, the "Report of the Advisory Committee on Asbestos Cancers to the Director of the International Agency for Research on Cancer," presents in question and answer format the joint professional opinions of nearly three dozen of the world's top asbestos-health experts on various aspects of this problem. This report is secheduled to be released shortly. Until then, however, despite the wealth of valuable information contained therein, we have been asked to keep it "semi-confidential," which means that itshould not be given wide distribution even within your own companies, and certainly should not be distributed to those outside the industry. The second paper is entitled "Mortality in Relation to Occupational Exposure in the Asbestos Industry." It is a study of 1,400 retired United States asbestos manufacturing workers, and while the results indicate an excess of asbestos related disease among the cohort, the rates are by no means as high as those reported by Selikoff in his various studies. Sincerely, Matthew M. Swetonic Executive Secretary Enclosures (2) 2- - CC: A. E. Alpine G. M. Armstrong James Armstrong A. A. Cross Hugh Dawson-Walker J. Hall S. Holmes Wilfred Howard . Michael F. Howe/ H. M. Jackson * Art Neilson S. Monoky P. V. Pelnar, M. D. F. L. Pundsack Ivan Sabourin Hans Weill, M. D. G. W. Wright, M. D. I. C. Campbell J. A. Gossip Martin Sendecki George P. Vogel Mike Donovan C.. Nelson Codding R. C. Carter Lyman Field - Certain-teed Products Corporation - American Asbestos Textile Corporation - Bendix Corporation - Cape Asbestos Company., Ltd. - Hill & Knowlton (UK) Limited - GAF Corporation - Turner Brothers Asbestos - Asbestos Information Committee (England) - Turner & Newell - Johns-Manville Corporation - Fireman's Fund Insurance Company - Certain-teed Products - Institute of Occupational & Environmental Health - Johns-Manville Corporation - Johns-Manville Legal Counsel - Tulahe University - St. Luke's Hospital - Q.A.M.A. - Q.A.M.A. - Congoleum Industries Inc. - Ertel Engineering - Johns-Manville Corporation -Jim Walter Research Corporation - Johns-Manville Corporation - Rogers, Field, Gentry, Benjamin & Robertson /v . '"V AIA/NA MEMBER COMPANIES E. C. Bratt George Barge H. Randolph Brown j. D. Christian A. H. Fay j. K. .Whittaker W. E. ^Gatewood A. R. .Hooker J. H. |larsh C. G. Morgan C. A. Neumann J. L. Rainey J. W. Rawlings Kurt Schwarz F. J. Solon, Jr. Wes Sauerland S. D. Weaver Paul Weiner J. R. Stetson H. K. Porter Atlas Asbestos Company ^ ,j Uvalde Rock Asphalt Company Cassiar Asbestos Corporation, Ltd. National Gypsum Company Nicolet Industries, Inc. Certain-teed Products Corporation The Flintkote Company Raybestos-Manhattan North American Asbestos Corporation........- Kentile Floors Inc. American Asbestos Textile Corporation Union Carbide Corporation Supradur Manufacturing Corporation Johns-Manville Corporation Jim Walter Corporation Cement Asbestos Products Company GAF Corporation Congoleum Industries, Inc. / AIA/NA ENVIRONMENTAL CONTROL SUB-COMMITTEE E. M. Fenner Ike Weaver Frank Zimmerman W. J. Dickson W. Fassuliotis Ralph Lanz John Myers Wes Sauerland - Johns-Manville Corporation - Raybestos-Manhattan - National Gypsum - Flintkote Company - GAF Corporation - Nicolet Industries, Inc. - Union Carbide Corporation - Jim Walter Corporation AIA/NA LEGAL COUNSEL Bradley Walls - Burns, VanKirk, Jube & Kafer AIA/NA PUBLIC RELATIONS COUNSEL Jack Steinberg Mike Isser Tony Federico C. L. Forbes - Cunningham & Walsh - " " -" " AIA/NA ENVIRONMENTAL CONTROL CONSULTANT C. L. Sheckler RECEIVED JAN 8 1973 Medical P.cseatch Council icfcrcncc JCk/Y 212-8 / Pneumoconi " search Unit Llandcuigh !- PoiUii tii, Gliimorfjan Icicphcnc Penarth 7037C1 h th December, 1972 Dear I enclose the Report and Roccii:;mcndat ions of the Advisory Committee as submitted to Hr. J. Hi.Qginson. Ilr. G. V.'right, Division of Medicine, St. Luke's Hospital, 11313 Shaker boulevard, Cleveland, Ohio AA 101 , L'SA Your?; sincerely Cl J. C. V.'AGNTCR Secretary of the Advisory Committee \ REPORT OF TILE ADVISORY COMMITTEE OR ASBESTOS CANCERS TO THE DIRECTOR OF THE INTERNATIONAL 'AGENCY FOR liESBARCH ON CANCER The meeting van held at the International Agency for Research on Cancer, Lyon, France on 5th and 6th October, 1972. The Committee consisted of three panels - Epidemiology, Pathology, Physics and Chemistry. Epidemiology Panel Dr. If. Bccklako McGill University, Department of Epidemiology & lien 3775 University Street, Montreal 110, Quebec, Canad: Dr. Jl. Bohlig Chefar/.t der Strahlcnabteilung dos Stadtischen, Krenkenhausos Ludenscheid, 588 Ludcnsc.lieid, Germany Dr. N. Day Unit of Epidemiology and niostatisti.es, Internation, Agency for Research on Cancer, 150 Cours Albert 'J"no: 69OOD, Lyon, France. Prof. P. C. Elmos Department of Therapeutics raid Pharmacology, Queen'. University of Bel fasti Institute of Clinical Scif.nc Grosvenor Road, Del fast, BT12 Gl'J, N. Ireland, UK. Dr. J. C. Gilson Medical Research Council, Pneumoconiosis Unit, 'Linn Hospital, 1'enarth, Glamorgan, Vales, UK. (Chairman) J)r. J. Lepoutre Medical Department, K.V. Eternit, Kapel 1 c-cp-den-Eo Belgium. Prof. J. C. McDonald McGill University, Department of Epidemiology A He- 3775 University Street, Montreal 110, Quebec, Canoe Hr. C. E. Kossiter Medical Research Council, Pneuwoconios.is Unit, Liar Hospital, Penorth, Glamorgan, Vales, UN. Dr. 11. Sakabe Dr. I. J. Solikoff Department of Industrial Physiology, Ministry of La National Institute of 1 ndu.-r-t rial Health, 2051 Kizukisumioyof-hi-Clio, Kawasaki, Japan. Department of Medicine, 'fount Sinai School of Medic Fifth Avenue and 100th Street, New York, N.Y. JCJA. Dr. G.K. Sluis-Cremer Scutii African Medical Research Council, National JnM.iiute for Oeruj a 1 i oral Disco.-.os, P.0. Bore Johannesburg, 51. Africa. R- Dr. V. Smither Cape Asbestos Co. bid., 11li Park Street, l.oiuliv.i V; England, 1.1,. Dr G. Vright Division of Medicine, St. Luke's Hospital, 113U Boulevard, Cleveland, Ohio -WlO! USA. Pat hoi ngy. Panel . Dr. A. C. Allison Clinical Research Centre, Vatford Road, Harrow, Middlesex, 11A1 3UJ, UK. Hr. G. Bci-ry Medical Research Council, Pneumoconiosis Unit, LI and Hospital, Pcnarth, Glamorgan, Vales, UK. Dr. P. Bogovski Unit of Environmental Carcinogens, International Age for Research on Cancer, 150 tours Albert Thomas, 690 Lyon, Prance. Dr. M. Kanncrstein Pathology Department, Barnert Memorial Hospital Cent 6C0 Broadway, Paterson, N.J. 0751^, USA Prof. V.T.E.McCanghcy School of Pathology, Trinity College, University of Dublin, Dublin 2, Eire. Prof. D. Magner Canadian Tumour Reference Centre, Department of Pathology, University of Ottawa, Ottawa. Ontario, KJN 6r.'p, Canada. Prof. 11. Otto Dirccktor dcs Pathologischen Tnstituts dcr Stadt Krankcnnnstaltcn Beurhausstrase 0, liG Dortmund, V. Germany. Dr. H. T. Plantcydt Stic.h Li ng Si reeklaborator ium ''Zee! and" , Noorepoortpi c Mid'dcl burg , Netherlands. Dr. M. Stanton Department of Health, Education and Vclfuro, Nation:: In.stitutp of Health, Dcthosda, MU 2001'i , USA. Dr. J. C. Vagner Medical Research Council, Pneumoconiosis U:iii, Elam Hospital, Pcnarth, Glamorgan, Vales, UK. (Chairman. Prof. S. Vatauabe Department of Pathology, National Cancer Centre, Re; Institute, l'sukiji, 5-1-1, Chuoku, Tokyo, Japan. Prof. I. Vobstcr Medical Research Council. South Africa, National Res; Institute for Occupational. Diseases, P.0. Eon -'jVoL!, Johannesburg, South Africa. Physics'- and Chemistry Panel 1)1'. E. Lc Bouffant Lahoratoire du Centre D1Etudes et Recherche.-, des Charbotmages do France, Verneui 11 -cn-l!al 1 atve, BP N CO " Creil, France. Mr. G. V. Gibbs McGill University, Department of Epidemiol ogy A Rea .3775' University ft root , Montreal 110, Quebec, Cured Dr. S. Holmes Mr. A. Morgan Asbestos;)..': Research Council, c/o Turner Bros. Ash-: Co. Etd. P.0: Bax A0, Rochdale, England, UK. # Atomic Energy Research Er.tabl i shment, Health Rhyme Medical Division, Building 3^/| t Harwell, Berks., England, UK. Physics nnd Ciifr.ilMiry Panel. (Continued) Dr F. D. Pooley Department of Mineral Exploitation, Ur.i ver.si ly Col Itof S. Wales and Monmouthshire, Newport J!oad, Cardiff Wales, UK. Dr. S. Spoil Johns Manvillc Research and Engineering Centre, P.0. 159 Manvillc, Nov Jersey, USA. Dr. V. Timbrel. 1 Medical Research Council, Pneumoconiosis Unit, bland' Hospital, Pcnarth, Glamorgan, Wales, UK. Dr. 11. du Toil Governnent. Mining Engineer's Division, Department of Mines, P.0, llox 1132, Johannesburg, South Africa. Mr. W. II. Walton Institute of Occupational Medicine, Roxburgh Place, Edinburgh EH 8 9SU, (Chaii man) Scotland, UK. The panels met in a separate session and at the final session (Chairman Dr. Gilson) prepared this report to the Director of .the International Agency for Rose on Cancer. TERMS OF RTPK'RP.XCB 1.. The Committee was to report on the present evidence relating exposure to asbestos dust to cmictrs, especially that obtained since the r.ecting of the U1CC Working Croup on Asbestos Cancers in ltyGU. 2. The Committee vns to make recommcndations for further research and indi.cat pi'iorities for work of immediate and long-term value. CO-ORDINATION OF INTI'ENATIONAb C.O-OITRATIO:,' Folloving the meeting of the UICC Working Group on Asbestos and Cancers in 190'j , a Sub-Committee of the UICC. Commi ssion on Geographical Pathology and Environmental Carcinogens (ChniDr. J. Higginson) vns formed to co-ordinate vorlc required to achieve the recommendations. the In April. 1.970 agreements hc.tveon the UICC and/.IARC led to the winding uj) of the UJCC liuh-Co; ,.:;i 11 ee and the IARC taking on responsi hil i ty for th.c Sub committee's work and extending it by supporting certain projects on asbestos cancers in several countries. The Agency has done this as part of their vide;* programme of investigating environmental carcinogens. Common memberships betve the UTCC Sub-Committee and the Committee advising the 1AHC ensured cor.tinuity of policy. In October 1972 the 1ARC hold an internalional Conference with 137 participants from 20 countries to review all the evidence relating asbestos will cancers. Subsequently the Advisory Committee prepared its report. This is divided into two sections. First, a general review in the form of answers to a number of important general questions about the relation of asbestos to canc.c. of different sites and, secondly, recommendations for further research. GENERAL )LEVTEV.T 1 1. Arc all major commercial types of asbestos able to cause lung carcinoma? Yes. Since 196'i the: evidence of a causal relationship has been increased by cpidcmiological studies showing exposure-response relations for Die incidcnc of lung carcinomas. The production of lung carcinomas in certain animals by a) types of asbestos supports this conclusion. The epidemiological evidence in n.- howevor, shows -that, there are clear differences in risk with typo of fibre and nature of exposure^ H. .Is there evider.ee "of an increased risk of lung carcinoma at low levels of exposure to a.shestos, such as have been encountered by the general population urban areas? The evidence of an exposure-response relationship based in part on past & measurements and in part on Die typo of job within the industry suggests that excess lung carcinoma risk is not detectable when Die occupational exposure ha been low. These low occupational exposures have almost certainly been much greater than that to the public from general air pollution. 3 Since )cjG-i has the evidence relating mesotheliomas changed? past exposure to asbestos and r The evidence, has been great ly strungfhened by further prospective a.ud retrospective: mortality studies in many countries of populations exposed to a; There is evidence that all commercial typos of asbestos except anthophv11i D' 1 responsible. JJvidcncc for nn important difference in risk in different e 1 (I) (II) occupations-and with the type of asbestos has increased. The risk is greatest vith croo.idol ite, less with amositc and apparently Jess with chrysotilo. h'itii amositc and chrysotilo there appears to be a higher risk in u-.anuf act-in-i r.p than in mining and milling. There is also evidence from population studios that a proportion of cases of mesothelioma have no known association vith exposure to asbestos. 4. Is there evidence of an increased risk-of r.iesothclial cancel's at low levels of exposure to asbestos, such as have been encountered by the general population in urban areas? . There is evidence of an association of mcsothelial tumours vith air pollution in the neighbourhood of croci do] ite" nines and of factories using mixtures of asbestos fibre types. The evidence rclaies to conditions many years ago. There is evidence of no excess risk of mesotheliomas from asbestos air pollution v.-hich has existed in the neighbourhood of chrysolite and amosilc nines. There are reported diffcrcncos on incidence of mesothelioma betveen urban and rural areas, the causes of vhich have not been established. There is no evidence of a risk to the general public at present. 5>. Since 1964 has the evidence changed on the importance of other factors such as cigarette smoking, vexes, oils and trace elements as contributory facie to the'cancer risks? The evidence has accumulated indicating: (I) Cigarette smoking is an important factor enhancing the lung carcinoma risk in asbestos-exposed vorkors, in boLh men and women. Asbestos workers have specially strong grounds for giving up smelling to protect their health. ko association has hern demonstrated Vc-tveen c.i.garctie smoking and mesotheliomas. (II) Animal experiments designed thu?. far to test the" importance of vaxos find oils as contributory factors in the production of Mesothelioma have shown these; contaminants are iitljtv;) -a bo relevant. (3) From animal experiments there nre no good clues suggesting that trace elements are likely to be a major factor in the production of asbestos cancers. 6. Vhat other types of cancer are related to exposure to asbestos? Prosjiec.tive .surveys of occupational groups exposed to asbestos have in general shown a small excess risk of some other types of cancers (in addition to bronchial and mcsotholial), especially those of the gastro-intestinal tract. The excess of these tumours is relatively small compared with that for bronchial cancer. Evidence for an association with ovarian tumours has not been supported by the first largo mortalitv survey of women previously exposed to asbestos. 7- Is there evidence of an increased risk of cancer rcsul ti.ng from asbestos fibres present in vat or, beverages, food or in the fluids used for the adm.i r.i stmt-ion of drugs? Such evidence as there' is does not indicate any risk. 8. Is there evidence of a risk of lung fibrosis from low levels of exjiosuro to .asbestos such as have been encountered by the general population in urban areas' There is at present no evidence of lung damage by asbestos to the general public. The amount of asbestos in the lungs of members of the general public . is very small, compared to those occupationally exposed'. It is greatest whore asbestos is mined or worked and lowest in rural areas. 9. Mas the relat ionshi p between ,-fsbosLos exjiosuro and the development of pi email plaques been established? Pleural jil agues have been associated with past exposure to all commercial _ types of .ashes l os. Put additional factors, other than asbestos itself, arc involved. The plaques may remain fibrous'or become calcified. Not all jilcu.-u' plaques are associated with asbestos. Projects which the Pane is rated high in priority arc marked *; those which will require close co-operation bcWcen the Panels are marked / . RPl'PEMTOI-OCtY The Panel agreed tliat as bestos rcl ated cancers occur in several sites in the body. The incidence of the different cancers varies with a number of definable factors and for oilier reasons, such ns competing causes of death.' Epidemiological studies will usually provide information on more than one type of cancer. Research directed at only a single type may, on occasions, be useful but in -general the inevitable uncertainties, in some, cases in the differential diagnosis of, for example, peripheral lung carcinomas and pleural mesotheliomas, and between peritoneal mesotheliomas and other-intra-abdominal cancers will require that more than one type is st.udicd at the same time. The Panel recognised that -some of the epidemiological projects could only be pursued if there was close co-operaiion between epidemiologists, pathologists, physicists and chemists, and others, because their success will depend upon the development of-improved techniques, some of which arc referred to in the recommendations of the other two Panels. PROJECTS (l) Kurther development of objective methods for early detection and surveil1 a of effects caused by asbestos. Topics for pnrticuliir study include : (a) Immunol og ic.al techniques for screening for fibrosis \- and neoplasia. (b) Kunctional tests of changes in the peripheral airways. (c) Detection of pleural thickening. - (cl) Asses.-m-:u t. of the rpoci f :i c.i t y of- small irregular opnei tics in tin: chest radiograph n:-:`defined in the 1L0 U/C Classification (2 971 > > (e) Tests of the uscfillness of different techniques of chest radiography, including the use of 100 ir.m films. (f) Development of statistical, procedures for analysis and presentation of serial observations. (2) revaluation of the usefulness of early detection in the prevention of progressive fibrosis and asbestos cancers, also in the identification of hazardous conditions. Routine health surveillance of industrial populations ------------------------------------" " should should bo designed to .assist epidemiological studios nnd/includc measurement an recording of environmental dust levels. Surveillance of new entrants could be particularly valuable. Arrangements should be made to register workers so that their morbidity and mortality experience can be. studied even after cessation (if exposure to asbestos. (3) Assessment of excess cancer risks following exposure to only one typo of fibre. (a) Chryrot.i 1 e: The much higher cancer risk reported for chrysotile textile voj-kors compared with mine and mill workers requires explanation. Haw much is explicable bv differences in size of past airborne fibres and/dustiness? There is need to make more use of past dust, records for relating to indices of disease. (b) Amosito: The excess lung carcinoma and mesothelioma risk is apparently much greater in the manufacturing and application sections of the industry than in the mining and milling of fair; typo of fibre. Uhat'nrc the important factors in this reported difference? (c) Creel del i 1 : Further studies are required in occupational group; exposed only to croc idol i to or cuosito or cliry.vot.il o in the manufacturing and npp'ii cat ion parts of the industry to establish more clearly differences in risks due to different fibres. * / (/j) Studies of the n-iount and typo of asbestos in the lungs of cases of ! mesotheliomas (if possible by cell type) in (a) national survey of liicsotholio;;ias, (b) representative samples of cases arising in groups with a definable past exposure. * (5) Studies of secular changes i:i incidence of pleural .and peritoneal mesotheliomas nationally and internationally. * (6)'Epidemiological studies to investigate the association between past exposure to .asbestos and cancer of sites other than lung, pleura, and peritoneum. (7) Studies of secular trends in the asbestos content of the lungs in the general population. / (8) Studios to relate amount .and type of asbestos in tbo lung .and estimates of past dust exposure and interval since last exposure. (9) Experimental and epidemiological studios-to investigate possible differences of effect of continuous low and intermittent high exposure to asbestos. (10) Opportunities afforded by intereurrent deaths should be used to interrelate radiographic appearances, lung pathology, respiratory function, dust content, and type in asbestos workers. Standardised techniques and classification recommended by the Panels should Le used. (11) Investigate the prognostic significance and actjological factors in the development of calcified and uncalcifi.ed pleural plaques in different environments. (l?.) Investigate tale-exposed groups in mining and manufacturing to cstnbl i any differences in morbidity or mortality which might, bo related to the amou and sh.-ipc-of tire fine respirable particles. (lj) bevel opr lent of cost/benef j t analysers to study the; health, safety, social `and economic, in l orrol at i ons of the use of asbestos. paimoi.qcv a.vd i"-:r>r-:n'irr::\TAL PAThoior.y Tlic Panel reviewed the progress made oil the 1 9^1 U] CC rccommendat i oils. It was agreed that considerable progress had been made on the majority of the recomtncndations. Some require further study, or modification of previous methods of investigation; these are included in the list of rccoinmendationr. that follows. The recommendations are divided into three categories, morbid anatomy and histology, clinical rc.senrch, and experimental studies. PROd?:CTS Morbid Anatomy and Histology 1. Asbestosis * (l) Purther cons; i. deration should be given to methods foi' deterniuing t)ie amounts, types and structural features of asbestos in tissue. A SubCommittee should he established with members of the Pii.'/sics and Chemistry Panel, .and others to accelerate- work on this problem. (2) The methods for assessing the severity of asbcsto.vis (see. paper should be tested for consistency by different observers. 2. Carej noma * / (l) An investigation of whether reduction of asbestos exposure to levels below tlio.se producing asbestosis also abolishes excess risk of carcinoma was considered important. (2) A comparison of lung carcinomas in persons occupationally exposed to asbestos and those not so exposed, including both cigarette smokers and non-smokers;, in respect of sites of origin and cytology of tumours and presence or absence of asbe.stonis, would be of value. (1) ThcIn!.er:i:-.t ional Panel of Pathologist.1.; and National Panels 2 established following the 19.6^ Meeting liave r-ervod a useful purpose. It is recommended that panels be established in other countries and membership of the International Panel be extended. The main purposes of these Panels is to ensure uniformity of diagnostic criteria and recording of histological types of diffuse mesotheliomas. Collaborative study of histology slides in National Panels is-recommended. The diagnosis of mesothelioma can be made by exfoliative cytology of the pleural fluid. If the cytological diagnosis is made by a competent cytoloyist, biopsy may be unnecessary. (2) To improve consistency of diagnosis there is an urgent need for a Comprehensive Atlas on mesotheliomas, or alternatively, for inclusion of an enlarged section on mesotheliomas in the now edition of the V.110 Monograph on Tumours of the Lung. Criteria for diagnosis by exfoliative cytology .and a description of the fine structure of mesotheliomas should be included. C.1 ini cal P'-rearch , * / (l) Monitoring by immunological methods of populations exposed to asbestos should be investigated to ascertain whether it is possible to recognize those who are developing, or will develop, tumours. .(2) The use of chromatographic methods for the study of irmcopolysar.clo.. and other tumour-associated substances in pleural fluids .shoul d be explored. Sensitive methods might be developed and applied to identify secretory products of mesotheliomas in blood and urine. The Intel-national Panel consists of: Ur. M. Kannerstoin (USA), Prof. D. Mag nor(Canada), Ur. L. Meuri.ian (Finland), Prof. V.T.F. McCauphey (Lire), Prof. li. Otto (KUC,), hr. H. T. PIc-ydt (Nethei lav..!,-.), Pr. IN lio.il-.-nh, (GUli), Prof. I.. Sant i (Italy), Prof. 1. Webster (South .'Crica), and Ur. J.C.Vagner (lit) as Secretary. Great llritain, .South Africa, United States, Canada, Netherlands. KurMirr Experimental >1 i os * (1) Information ir. required about the role of fine particles, e.-pociai 1 influence of fibre sire;, in the induct ion of tumours. These studies should he extended to include fibres other then asbestos. A Sub-Committee shoul'd be established to review the need for, and arrange the distribution of standard samples of asbestos and other fibres; in addition to the lll'CC llofcrencc Semples;. / (2) The fete of inhaled particles of various sixes, shapes and chemical compositions, should be studied to detenuinc. more precisely the quantities and sites of initial deposition, change within the body and later retention. The feasibility of increasing fibre elimination by various methods should be explored. Studies should be made of means of reducing the f5brogenicity and carcinogenicity of fibres already retained in the lungs. (3) The use of cell and organ culture, including mesothclial tissue from man and other species, should be further .investigated with a view to developing Methods of screening dusts'for fibrogenic and.carcinogenic properties <M Further studi cs should bo carried'out to determine the nature of the combined effect on tumour... induction when animals are exposed to asbestos dust and cigarette smoke, metal:; or oilier chemical carcinogens, including those which act syst.omically .such as nitrosaminos. (3) Inhalation experiments should be extended to test various types of fibre; of special interest are forms of c.hrysotilc and crocidolitc including the finer grade materials. (G) It \.v.s felt that studies of the pathological effects of asbestos on species other than rodent:.: would be of value. (7) The effect of long-term ingestion of fibre's of various sixes, shapes and chemical compositions should be studied. . (0) The effects, of fibre:; and associated metal s on the Metabolism of target organs should bo investigated. PHYSICS AND Cin'Ml STP.Y The Panel reviewed the progress wade on the 196^ UICC Recommendations. Tne propo.sal s for the prcpai'ation and characterization of the UICC reference samples of asbestos had been satisfactorily implemented', and the Panel recommended that a list of references to papers featuring the samples .should be distributed to investigators in-this field. Considerable progress had been wade on methods of identifying the: type of fibre in tissues but a quantitative method when several types of fibres were present had yet to be developed. The Panel discussed the further -contribution that physical and chemical studies can make to research on the biological effects of .asbestos and other fibrous materials. Of especial interest are the effects of fibre size and shape on the retention of material in the lungs, the site of deposition, the migration of fibres v.-j.thiri the body, and their carcinogenic or other biological, activity. The following recommendations were made: */ < / PROJECTS 1. Materials for cvnorimental work a) Supplies of asbestos from relevant sources should be obtained where there is evidence of variation in geological form, trace element content or significant biological findings. b) Small samples of various fibrous materials should- be prepared for studies on the influence of fibre size and shape on carcinogenicity. For this purpose the samples should he milled to different degrees of fineness. c) For investigations on the influence of particle shape and size, on the inhalation and subsequent fate of asbestos fibres a chrysotilo and an nwphibole * of fibre length greater than the UICC samples should be prepared. 2. Mei hods * a) There is on urgent need for the quantitative assessment, size: analysis and characterization of particles and fibres in the lungs .and other organs. Pctails of available i.k thuds .should be circulated, international comparisons an.lei t , met ho.-ls ; i a in1, i r.!j zed and new t rim i quo;: devel op"d. b) Mo methods arc at present available for the. preparation of fibres in narrow ranges' of diameter and length in sufficient 'quantities for inoculation experiments. Techniques for those purposes are urgently required, especially in view of the advantages such graded samples could provide fox* investigating the influence of these, physical, factors on the carcinogenicity of fibres of different materials. c) Since the degree of dispersion of fi.bi'cs (e.-pecial 1 y chrysot i 1 o) used in inoculation studies may have a marked influence on their carcinogenicity, methods are required for quantifying dispersion. d) Inhalation studies require precise control of the characteristics of the dust clouds. Improved methods of dispensing fibrous dusts in such investigations need to be developed. c) Methods are available for collecting the important size, fractions of dust clouds in inhalation studios when the particles arc of compact shape. Similar methods must be developed for fibrous particles. f) The present membrane filter methods of measuring the levels of airborne asbestos dust require standardizatjon. This should be done by iuter-laboratory trials on a continuing basil.. Particle counting by electron microscopy should also be developed. Gravimetric assessment methods and the automation of particle counting should bo explored. 3. Julialat ion 5-Indies Considerable information is now. avai lnbl e on the deposition, retention and migration of particles of compact shape. I Keecntly developed methods, especially radio-active tracer techniques, should he used to obtain similar knowledge for fibrous particles. This- information is needed to identify the biologically important size fraction ami to help int er;n elation of epi bemiol eg i cal and pathological studies. h . Oacnnat.ional and onvi ronmr-ntal studies The use of both fibre counts and gravimetric methods for a;;sc s.sing nsboslo dust concentrations should be encouraged. Data collected over an extended y>eri will be particularly valuable in identifying the parameter:-, of the dust which c be correlated with epidemiological evidence on the health hazard. 5* Physics and Cher.ii stry Panel * It is recommended that an international Panel be established to assist in implementing these recommendations. The Panel would periodically review requirements for materials for experimental work; provide guidance on physical and chemical problems; and arrange national and international standardization trials n iourne.l cT Gecupr.oO.i.xl i..c-ciicuia December 1S72 Vof. In'T-io 12 lation to Occupational 5 Asbestos Industry Philip EnU-rliiie, Ph.D., Pierre De- Coufle, Sc.D., and Vivian llen- detson, M.Sc. M oiuihtv estimates inr large- oc cupational or industrial groups can be made by relating counts iii population census returns to counts based on death certificates, for a gwe-n occupation, (his would consist of a count ui (icrsons in that occupation as enumerated in a national population census combined with counts of persons with the same occupation as it appears on death cer tificates. From time to time government publications are issued based on com bining these two sources of information, and mortality lales are* shown for a wide vaiicty of occupational and industrial groupings. Fcr mmole, mortality ra'es by occupation v. tm publisher! f.r the year 1951 for England in Wales m the Registrar General's Decennial Sup plement on Occupational .Mortalitv and for the United States for the >car ll)50 in a series of publications issued be the US Department of Health. Education, and Welfare.1 2 In addition to these govern ment publications, life insurance com panies publish data cr. rnortaliie for various occupation and industry groups based on their evperience with individual and group policyholders. ' While- such data point !' eiccupan.nw and industries whose workets have an unusual mortjlitv experience. thes arc- of limited me- in assessing the- health (.-fleets of particular oicupatn.n..i esposuiex since the* du nut usual!-. per mi! sub divisions b', type of i-'.powee or ex posure levels Moreover, occupational f mi |M-- ! ) ; -.i itn It. r. -l i !i* i* VI-*> i Ms >s.:v Ml iv:-tt,k:, n, I) <.o*rf!* is 11. iv\ \*. fii* N, JI Ir.'liiiut , ( h VN*J*fi:>! ,.!* !< I * >t *<*! il I t..;'.. Ihc :. ... i (Mr |-ili 5VNI.iik`. I\l !".' I'trs-i .it |i>< .in i! V. iI i !.<*,.< ( ;m iinsi-c. \.i. Ifun. imm. '.1. . ! :,,'J mortality estimates which combine cen sus re-turns with death certificates are of ten questionable due to differences in the wav occupation is defined in preparing these two documents. w hile data published bv life insurance com panies only relates to mortality ex perience while life insurance policies arein force. A recent review of data from these two sources for a particular oc cupation provides some ide-j as to their value anci limitations.4 Probably a more useful approach to studying mortality for a particular oc cupation is to identify groups of persons in that occupation and follow them fcr a long period of time, observing their mor tality regordk-s of whether they con tinue* in 'he occupation of interest or not. This has the advantage of using a singledefinition of an occupation and of per mitting observations on deaths which occur after employment in a particular occupation has ceased but which may be related to some environmental factor in that occupation. A large number of such studies have been reported on in recent ^ears. Those include long follow up studies of uranium mineis, stcclwatkt-rs. asbestos miners, asbestos in sulators, asbestos products workers, gasvvo.kers, and rubber workers' " To he most useful this tvpo of study should int lurie rstima'.es of exposures and sh-ju'd allow- a sufticientlv long tollow-up |i;-nod for any c'lects of ex posure on mortality to lie observed Such sludie. are u- uallv time consuming and expensive since !h--v uquue (raring large numbr-is o; individual. as they move through a vanetv of jobs and ry-r-graphir locations and establishing liic fart ot Ji-atii .'.nd causes of death. Nevi lihiTess. lor mon> health conditions vvhi-re death is a likely outcome, they an- a valuable means for evaluating the im portance of a particular exposure and can assist in the setting of environmental standards. In an earlier paper, we reported on (he mortality experience at ages 65 and ovoi of a group of men who completed their working lifetime as production or main tenance-service employees in the asbestos industry.'- These were men who retired with an industry pension and who were nearly all exposed to asbestos dust in varying degrees in the course of then employment. The average duration of employment in the asbestos industry for these men was 25 yea is with a range from 3 to 51 years. Historic dust levels, measured with a migot impingc-r, were sometimes in excess of 50 million particles per cubic foot of air. for each of these retirees it was possible, by combining personnel records with asbestos dust level estimates for each job and time period, to reconstruct their asbestos dust ex posure history and, for each man. to assign a measure of his cumulativeasbestos dust exposure at the time of retirement. It was found that this timeweighted measure of asbestos dust ex posure was directly related to respiratory cancer, with the excess ranging from 1.7 times expected for men in the lowest ex posure group to 5.6 expected for men in the highest Separation of the effects of duration of exposuie from the effects of aveiage dust level on respiratory cancer moitaiiiy showed tiiat the contribution*, of each was about the same am! that a limc-vwtgkled measure or asbestos dust appealed to be an appropriate me.liod for predicting respiratory cancer clleclv Ties is a report on additional data arising lion. the same study. Tbo cohort upon which this study was based con- Joiitnai el Cctxjini'un! b'ed ctoc V;t. -i:-. le'OcCCtitl'-ir 197? 897 Tiltt 1. -- rJ.Mifir7 fro'-i t.'r? V.* I i;... iwj* Dfjth Ce.i.'lCitci rz`. of Dicker 31. KT!*-- Kl'R.ttH l.Kt S:? Sr'? 0? :o sisted of .ill men retirin'.; during the years 1941 through 1967 and deaths occurring among these men through 1969. Such a study could lie conducted almost en tirely using industry records, except that where deaths occurred official copies of death certificates needed to be obtained. Included in this study were three lands of retirees: those who retired normally at age 65. those who retired before age 65 for personal reasons but lived to age 65. and men who retired prior to age 65 because of a disability but who lived to be 65. The observed mortality among these men was compared with an ex pected molality based upon the ex perience ot the entire US white-male population living the time-age intervals that characterized the retired population. Inclusion of disabled retirees improves comparability with the US white-male population since the l.tiler also include'men unable to work for health reasons. The modified life-table method was ired for computing the expected number of deaths. This method is widely usid and was described in an earlier report.' There were a total of I .-192 men in this stud) who reached age 65. Of these, complete exposure and job histories were available tor 1,-164. Table 1 shows the vital status as of December 31, 1969, of the 1,464 men for whom complete ex posure and job histories were available and the success we had in locating death certifir ati>. As might he expected for an oider age group, trie mortality rate was high, with deaths occurring in well over half of the cohort. Tor only 20 out of the total 622 deaths could a death cer tificate not be located Table 2 shows observed and expected deaths and standardized mortality ratios (SMR's) fur selei led causes of death for the 1,4(34 men for whom complete job and exposure data could he obtained. The expected value of the SMR. where observed and expected deaths is the same, is 100 and (levnations tioin UK) are percentage deviations from expected mortality. As noted above, expected deaths were based upon the mortality experience of the entire US white-male population living at the same ages and time periods as the cohort under stud) It is not know n how much NMR's for individual causes of death might be changed had all death curtiiic.ites been found. It is unlikely, rioweve:. that (here would be much of an increase lor any single cause and no attempt has been made to allocate the 20 unlocated death certificates to a cause of death group ings. All death certificates were coded according to the Seventh Revision of the International Classification ot Dis eases by a regular coder from the National Center tor Health Statistics. In this typo of study the coding procedure is important it comparability with US TzMf 2. -- Obicrvr.l, Fi?ocl.d lUMai, s.id Si.iKN tar Si.!,'red Cruorv ol F>ra Matos l.'!iri.'-s irofi l.c It .Nil'). 19'.j l'.'.T :, fdir..*:! ISr;-:r. I,'.?. Cdill t\ [*:! t AM CiJ.75 Cav.-'r CiO/iit ti(.; !fr-n : , ;!;:* :r?i i" *' S . }: 2. !. ,,.-t i).... . hr O' t lMi !i) Tf -t-, ,*ui r.. ... r*. i ..V .in ! : I-..' e?? IV i Itc J!?4 V? 4`.' 9 i') ?ir Ss ll * (.< . 1 v.} 3 '> S n u !R V\ U ?0 114 14/ i ; n. b ' s lib4! Vt ii' I ivl 1 DO mortality data is to he maintained. Num bers in parentheses in l,it>!e 2 corre spond to the lntemation.il Cla-Mlicatmn of Disease rubrics. Table 2 shows that these men who retired from the asbestos mdustrv and reached age 65 had an overall morialiiy rate 14.5% higher than all US males living, at the same ages and time periods. This excess is due almost entirely to can cer anil diseases of the respiratory system. For cancer, the greatest .excess was in cancer of the respiratory system, but with some excess also in cancer of the digestive system. For respiratoe/ disease, the excess was due entirely e, pneumonoconiosis and pulmonary fibrosis ol which 1C deaths were due to asbestosis (ISC 523.2). Since the ex pected number of death; in these latter two categories is extreme!',- small, SMR's were not calculated. Of the 1,464 retirees whose mortality experience is shown in Table 2. a total of l,026 had worked as production workers while 436 lud been classified as main tenance-service workers. Inc latter con sisted largely of trade-related jobs such as machinist, painter, electrician, pipe fitter. mThv right, etc These mainte nance-service jobs constitute a distinct grouping, and there was relatively little movement between these trade-ieiated jobs and production jobs during the course of employment. Table 3 shows the standardized mor tality ratios for selected causes of death for these two groups of retirees. Actual numbers used in calculating these ratios appear in the Appendix. It is clear from Table 3 that the mortality experience of these two groups of men subsequent to retirement was quite different. Whiie the same general pattern of excess appears in both groups, with high death rates for respiraloi) cancer and diseases of live respiratory system, cancer mortality rjtes are greatly exaggerated for the men who had . w orked in maintenance-service jobs, fo'i all causes the excess mortality for production workers was onlv 10.. w hereas for mamlenanc e-serv ice workeis the excess was 24.3%. for re-piMlniy earner the excess for pm dm lion workeis was 7.1.7"., while lor m,iiulen.iiu e-serv ice workers it vv.i' 32116",. . Considerably higher raies also appear among niaintenaru e-w'v u e winkers lor cancer of the o.geslive system and tor re-.i.lu.il la.icoi'. lor other causes rates for m.iinli iuiu e 852 Ucilali'.y and f,r.|iuyti:r tu Aihcyloi/fn'.ciline. CcCcjfic and Ht'ituVrson t3h!c }. -- S'.!Jii.voir-'d :'*l lot Cn: ot Pc..!:i r.**ui;. tfc.u tiu.M/, .'r.u iv .J Jv- u iy '*;*. v.; V'..,l. C; : cf C;;!'i 5*.* .-2 f.'j ' y V vr.'.fpiTie P'51*:-- ** S* *:;f 1; C2."CM i1.*: .'32' C-(:`3 R',;; ty/j'i \lv 1-j) A!t Sr-;-.-;s ti:7 J-O h*:-'! : (O! a:: cw.r rwi i j*r-* Y-.'V c . i'1:-`I-' tuhd-r-i Pa Yf ;u cv'i Ci.'.e-. !1C 7 i:-1 ll?.t PV< 173 7 4.1 S Vr. 9 75 6 SI 7 10- s tis.t 9' ! i?r.7 155 * in I'-? $ :?o; 9 i-Ms 96 4 75 S service workers are not remarkable, while lor. the respiratory disease anti, other heart diseases (including cor pulmonale) rales were somewhat lower than for production worki rs. Regarding respiratory diseases, there were a total of IB deaths coded a. due to asbcslosis. as noted in Table 2. Seventeen ot these were in the gmup of 1,02b production workers anti only I in the -!3B main tenance-service workers. Il these and other deaths from pnenmunoconiosis are exclud'd respiiatorv i.'iea<e death rates are not much different in the two groups. 'reduction and maintenance-sere ice workers appeared to be similar in most other respects. Retirements occurred at about the same lime so that dnierences in mortality for respiratory cancer and asbestosis do not reflect changes in diagnostic fashions associated with mor tality in various periods. Of the produc tion workers, (i.-Cu had retired due- to a disability whereas only -I.T'i of the maintenancr-seivice .workers had reined for this reason. Thus, the Ivghei death rate for the maintenance-service group was apparently not due to gieater disability at time of retirement. The mean age at death fur men dying of respiratory' cancer was about live same in the two groupr.--72.S vs 71.3 tor production and maintenance-service workers respec tively. Smoking histories were available for only 373 of the total l.-ib-l retirees representing 2b1' production workers and 10-1 maintenance-service workers. These were available in only the most recent retircmeriis but probably give a fairly good pictuie c.r the smoking habits of the whole gmup. There was essen tially no difference in the smoking habits ot the production as compared with the maintenance-service woikers. Of the 269 production workers. 77.3"u were smok ers, while of the 101 maintenanceservice vvoikcrs, ~6.9"u were smokers. Table -( shows the cumulativ e asbestos dust exposures at time of retirement for these two groups of men. These were estimated based on miget irrpinger counts expressed as million particles per cubic toot ot air (mppcf). It was not always possible to very precisely Journal r.f Occupaticnil Mg:lirinc,Vci 14, No. Ic.'CcCsrtln.-r 15'? estimate the cilia level for each job. par ticularly for past pr nods, and otien diet levels could only be roughly ciassitien lobs wen: placed in one of six classes or ranges and lor calculating total exposuie mid-points of 'he range weie usid. Classes used were: no exposure (0), un der 5 mppcf (2.5), 5 to 10 mppcf (7.5), 10 to 30 mppcf (20 0), 30 to 50 mppcf (10.0), .50 mppcf or more (62.5). To compute cumulative dust exposure for each man the dust level at each job and lime period was multiplied by years at that job and summed across all jobs. 1 his total cumulative exposure can be thought ol as mppcf-ycars. Thus, if a man with a 30-year work history initially worked ten years at a job with a dust level at that time of 20.0 mppcf, ten years at a dust level of 2.5 mppfc, and ten years at a dust level of 7.5 mppcf. his cumulative exposure to asbestos dust would be: (10 x 20) + (10 x 2.5) + (10 x 7.5) or 300 mppcf years.. His average exposure level would be 10 mppcf (300 30). As Table -1 shows, the distribution of the two groups of retirees by cumulative dust exposure was quite similar. Actual means, shown in Table -l, were slightly higher tor maintenance-service as com pared with production workers. Table 5 shows SMR's for respiratory canter by cumulative dust exposure a! tune of retirement tor all retirees, for men who had worked as production workers, and for men who had worked as main tenance-service workers. Numbeis used in compiling this table appear in the Ap pendix. lor all retirees there is an almost linear relationship between asbestos dust exposure and respiratory cancer, with ratios of observed to expected deaths ranging from 1.7 in the lowest dust ex posure category to 5.6 in the highest. This relationship also exists for licith the production and the maintenance-service workers, except that at each level the SMR is higher lor maintenance-service workers and seems to increase more sharply with cumulative asbestos dust exposure. Mri respiratory cancer deaths w ere observed among the B0 production workers i,i die slid to 74`i exposure category vs I I expelled (Appendix). Al Ihe higher du'l levels lliedealb rale lor resptrulo.-y cancer among mainlen.iiire-M rvue workoix is remarkable. Of the .57 many..'rum e-service workers with a ; umuialive exposure ot 500 mnpet-year, and over (lable -5), W died ol 893 ----* Table 5. -- Stariii ri.zfi Mo: Eebos for F-.piratorr Cancer r, 1,W ef V.c-h s-d C-jndi^ve *:fcs':Pls- ficv.u: ; f'dv OMlr.j ! 'rt f--'. U:s 1: tunc; JOS1-JVS.7 i.\i fcMv.i Cv.' Tjli!. ft [AO'.i'e to Av.t'lat Dujt (n ;'s;l r:.irr! a;; Pclire:* S'.T'j Frodv :t: sn V.of'xri Sri'iic? l:nC*r# !?b IrSriJ ?:-o 4*? 5>C*0 749 7SO am e.tr l*:: : 77J.5 7=0 3 500 0 G5S6 NS 7 li.? ?2? ? occ c 4 CSC 2\i g 203 G 4N 4 l?ia 7 1030 0 Table 7. -- Ty;? cf Pstosl:$ by Type ol V.`crK-- Males 1.:*;:* ftc.tt Ire Asbsslcs hdusiry During 1S1 C7 and fol:eM*d tr*rej;h I>x:0 Who 1 V'o'J ji ot Job.- t'fjler 10 nppei Tyn< r-1 Product-on VYo<kers MunLftj.*::*Service C -"'r A*:*<*.*: c-'.. Ku-'d t ' S22 : n 3S5 .M 44 5 S3 IS5 co:<c.'U,f ' Includes cicmob'.r <2 153 all causes of which 11 or T0'u were due to respiratory cancer. Among main tenance-service workers, only respiratory cancer is highly related lo cumulative asbestos dust exposure (\ppendix). Numbers'involved are small, however, so that information is no; very con clusive for most disease categories. One possible explanation for the higher respiratory cancer rate in maintenance-service workers is the way in which their cumulative dust exposure was leceivtd. In compiling data tor ibis study, when the dust level of any job was found or estimated to be greater than 10 rnppi: t. a iiide.menl was marl" as to whether that expo-me was steads or intermittent. I here were a total ot ~f I winkers in such |ob-. and a derision as to whether the exposure was intermittent re steady was possible lor t>l7. Table h shows lioxv tins r. lassite. ation lelated tei whether the worker wjs a production or a maintenance-service worker. (Tom this, it is clear that a characteristic of the exposure of the maintenance-service workers xvas intermitiency. Exposure data for these men was difficult to estimate and was intended to relate: to average exposures over the course o; a svorking day.-Very high levels of brief asbestos dust exposure could be hidden in these data. for the jobs where dust levels ex ceeded 10 mppcl. there was also re corded the type of asbestos involved These data arc shown in fable 7 for the 701 men working in such |obx Clearly there sver** ditferenres in tire tvpe ot asbestos to v. hull pmduction workers were exposed as compand to mamtenjnce-servu e wnrkeis. On!v .V/V, ol the production wnil.eis were exposi.sl to amosi'e atid'or r me rdnhti- asbestus. whereas 71",. ol the mami"iiani e-ser- vice workers were expo-id to amosite and'or croc ido.'ite, l or cro< irlolite, the contrast is mine striking, with unlv h",. ol production workers exposed as com pares! with 6-!"-'< of maintenanc e-seiv ice workers. Discussion This analysis of the mortality ex perience of retned workers from the asbestos industry' supports findings in other studies in terms of specific health hazards associated with asbestos dust exposure. What has not been previously shown, however, is that men in main tenance-service jobs are apparently at greater risk of developing respiratory cancer than men in production |obs. Cunously, maintenance-service workers did not seem to develop asbestosis or diseases related to asbestosis as readily as production workers. The intermitiency and possible severity of their exposures may somehow account for the excess in respiratory cancer Newhouse found that severe exposures to asbestos dust, whether short or long, produces significant excesses in cancer of the lung, whereas' only long exposure produced excess deaths m m respiratory disease.11 Severe intermittent exposures might also account for the high respiratory cancer mortality found in insulation workers.* It is also possible that the type of asbestos dust is involved in the dif ferences between the mortality ex periences of production as compared with maintenance-service workers. It is generally believed that the carcinogenic properties of crocidolite are higher than chrysolite. particularly as related to malignant mesotheliomas. This could ac count for (he great excess of respiratory cancer among maintenance-service workers at every dust exposure level. One limitation on data presented here is (hat only mortality at ages 63 and over is dealt with. What might have hap pened prior to age 65 is unknown, and it is possible that many workers left em ployment lor health reasons related to dust exposure and were not available for study We have been able to check on possible biases inliodured vv gh regard to respiratory tancer In examining special tabulations ot data on coke oven vvoikeis in the steel industry, comparing SMK's for men 65 and over with those for men under 65. for a cohort of steelworkers Ironi Allegheny Counts BOO Mortality and Csposurc to Asbcstos/Cntcrlinc, DcCoude and Henderson m VIKl ?i-e ;*u s /us" uiisiij Q U|Wf **B*ia--03 P-* sat3 t* `It qsw5i2 s'^u-il ii.i.'.j) iu payaa c-;,\ sa4 ; ` : 5**,; W ifJi :i,;:=o p-;c--*a p;/..isqo -- V [06 <!Z6; J'-'l'inw*!//.: Cf| '{.j I0,\ oJUijio;'; ;ci<ci;i .l.rjjfl ;! p:Hiiv;j (Pittsburgh) identified in 1933 and followed Ihiough C. K. Kcdm'md found that among coke oven workers iho SMR Inr respiratory rancor jl ages under 65 was 125.3 and at a sits 65 and over 375.9 (personal communication. May 9, 1972). Thus, the study reported here of retired employees from the asbestos industry may provide a (air estimate of risks associated with respiratory cancer at younger ages. Unfortunately, we have not as yet been able to examine in detail one of the impodant causes of death related to asbestos exposure--malignant meso thelioma. One reason for this is that the International Classification of Dis eases makes no provision for coding malignant mesothelioma and. moreover, it may not appear on the death cer- tifica tes, even if present. To study this condition requires an independent ef fort--contacting physicians, hospitals, and pathologists where mesothelioma is suspected and supplementing data recorded on death certificates. On only one of the 602 death certificates in cluded in this study was a malignant mesothelioma recorded. This was a maintenance-service worker who died at the age of 69 with a pleural mesothe lioma. His cumulative dust exposure v.-js relatively low (60 mppcf- years) and his first exposure occurred 29 years p-ior to death. There were a num ber of men not included in this study who died prior to age 65 of a malignant mesothelioma, and it is our impression that mesotheliomas in this population occurred at a considerably earlier age than respiratory cancer. We hope to report more on this in a subsequent paper, particularly as it relates to the type of asbestos to which workers were ex posed. Summary There are a number of publications which deal with mortality rates by oc cupation and which suggest effects of occupational exposures. Probably the most useful type of studies are those in volving follovv-up of the .cohorts of workers over long periods of lime with blown exposure-. This is a report on a ioilow-up study of T.T6T men who completed their working lifetime as production or main tenance-service workers in the asbestos industry and reined with an industry MotUily anti Exposure lo Asbeslos'Enicrline, OcCoisfte and Henderson pensicn churri:; tin: period 1`I4I to 1967. These rnc-u wore observed for deaths through 1969. Tire average length of em ployment in tlie asbestos industry for these men was -5 years and nearly all had exposure- to asbestos dust. In some instances these exposures were very high and cnnlinj'td ioi many years. Mortality for this cohort of men was 14.5% higher than for the entire population of US while males living at the same ages and time periods. This ex cess was due to cancer and respiratory disease. The cancer excess was chiefly clue to respiratory cancer where mor tality was 2.5 limes the expected. The respiratory' disease excess was entirely due to pneumoconiosis and pulmonary fibrosis, including asbestosis. When these retirees were1 examined in terms of whether their work experience had been as production w orkers or as maintenance-service workers, some striking differences in their mortality ex perience appeared. For production workers the excess tor all causes of death was only 10.7% w'hereas for maintenance-service workers the excess was 24.3% . For respiratory cancer dif ferences were very great, with produc tion workers having an excess of only 73.7% as compared to 32b.6% ror main tenance-service workers. While mainienanco-s-'rvice workers had a high respiratory cancer modality rale, they had a relatively low death rate from asbestosis, contributing only u.ue out of 18 deaths from asbestosis ob served in the entire study. Differences in respiratory cancer mor tality between these tw-o groups of workers were probably not due to dir lerences in time of retirement, disability at time of retirement, smoking histories, or cumulative asbe stos dust exposure. At each dust exposure level maintenarn eservice workers had a higher respiratory cancer death rate than production workers: and, overall, their, respiratory cancer death rate showed a sharper response to changes in dust levels. At the higher cumulative dust levels 30% of their deaths were due to respiratory can cer. One explanation lor the difference is the observation tfiat maintenance-service workers had m'crmilteiU asbestos dust exposures--probably at a very high level--and that this produces excesses in respiratory cancer but not great excesses in asbestosis. Other studies lend some support lo this notion. Another ex planation lies in tire ty pe of asbestos to which those tw-o groups of workers were exposed. Sixty-four percent of the main tenance-service workers with a high ex posure had been exposed to crocidolite asbestos whereas only 8% of the production workers with a high ex posure Find been so exposed. References 1. The Keg.mar General's Decennial Suppiemen!, England and Wales. 1951 Oc- ci/pariunaf X Urahr/ I'.i; [ ||. vol 1. Iter Majesty's Stationery Oiticr. London. 1958. 2. Curalnick L: Mo.-ta/tlv by Occupation and Industry Among .Veil 2U to 0-f Years of Age: United Sr,ires. 7950. Viul Stalisticv Special Cep. voi 53, no. 2. US Ucpt of lleallh. Education, anti Welijre Public Iti-alili Service, National Vital Suiis'irs Omo-in. s, n; 3. 1 Fie Actuarial Soc ie'y m Anunc.: aiul i*n Assosulion or Lire Insurance Wed-: al U:i.-clors. New York. NY. Inlv 1929 |,imt Oc cupational Slut!,'. 192S. 4. Loierlmc I'f- A P.^view ol Afo/r.iSrv Dara for American Ccutl Xti'icn. Proceeding- n' ine Inrernaiionjl Conierence on Coal Worker*' Pneumoconiosis. New York. NY, Sopl. 14, 1971. 5. Lundm Ft, Lloyd |W', Smith FW. el al: Mortality of uranium miners in relanon ro radiation ex;v.,*uie. hard-rock mining and cigarette smoking--195f) through September, 1997. Hedllh Pins 16:57l-578,'l%9. 6. Lloyd |W'. Ciucco A- Long term mortality study of steelworkers / Occup Med 11.299310, 1969. 7. McDonald |C, McDonald AD. Cibbs GW, et ak Mrirtalily irom lung cancer arid other causes in rIv:- chrysolite asbestos mines and nulls ui Quebec. Arch m iron I fea/rh, 1971. 8. SelikolT IL. Churg |, Itaminond EC: Asbestos exposure and neoplasia. IAMA VutS.22-26. PA,4. 9 Enlerline PE: Mortality among astrestos prrxlucts workers in lire United Stale*. Arm \'Y Acad Sci 132(1) I5i> U>5. 1963. 10. Doll K. 1 he c.iu-cs or death among gasv. orkers xxilh special reiercnce to cancer of the lung. Brit / IrcluUr Mvd 9 180, 1952. 11. Mancir.o IF. Oa: Co A. El-Attar A: An epidemiological approach ro the rubber in dustry--A study based on departmental ex perience / Ocriyi Med 10 213. b*r,3 12. Eniorlm" PL. DeCou;:e P. M'-ndm-nn VArt f/rfe/cmiofopic af Medy of pesp.Yuron Canct-r Among kerned Asoerrns U'crkers ro Establish Standards for Occupariortaf vfiostrres. Presented a! lb- annua! mrst-.n-.; ni (tie Ameiican -'-.i.td.-mv ol Occup-auonal Medicine. Pittsburgh. Feb 9. 1972. 13. Ness-house ML: The Morr.diry ol As/x'stos factory Workers. Pioccodings of the Intcmarionjl Contcrenrv on Pneurnoconm-is. luhannnshurg. S. Amca, 1 lJC9. Jouin.il pf Occupational f.-c-dicinc/Vnl. 14, No. )2/D';cf.rrbrr 197? 903