Document 6BMjGqpOajNkmDbONLrrj7q4R

FILE NAME: Electrical Insulation (ELEC) DATE: 1965 DOC#: ELEC011 DOCUMENT DESCRIPTION: Article from Scientific Journal /}/>/) & Section IV . H um a n E xposure to A sbestos: C o m m u n ity Studies OCCUPATIONAL AND NONOCCUPATIONAL EXPOSURES TO ASBESTOS W. C. Hueper National Cancer Institute, Bethesda, Md. Numerous reports by many investigators from various countries estab- sh the fact that an occupational or nonoccupational inhalation of dust f different chemical and physical types of asbestos results in the develop- lent of asbestosis of the lungs which, depending upon the type of expos- re, may be designated as an occupational, neighborhood or household # neumoconiosis. Since 1935 an increasing amount of epidemiologic, clinical nd pathologic evidence, moreover, incriminates this health hazard as one f the environmental sources of cancers of the lung ( table 1 ), and more cently also of mesotheliomas of the pleura and peritoneum, although >me commercially interested parties and their medical guardians and pro ctors still prefer for their own reasons and motives, to deny the existence ' these dangerous and usually fatal sequelae of a respiratory contact with ;bestos dust. The obvious fallacy of such allegations is well demonstrated r the remarkable and progressive rise in the number of cases of asbestosis id of cancers of the lung, pleura, and peritoneum reported from various untries during the past two decades. It is shown also by the increase publications noting the first observations on the occurrence of asbestosis id asbestos cancers from several countries during the past decade (Den- irk, Sweden, Belgium, Finland, Japan).1~<i Both occupational diseases e definitely not as rare and in fact, have become less so in recent times, has been claimed by several industrial parties.7 There was, for instance, an estimated total of about 700 cases of asbes- sis in Germany in 1946 among a total of approximately 8,000 employees the asbestos industry.'1" Wegelius- found 125 cases of asbestosis of the ig in a roentgenologic examination of 476 asbestos workers of one com- ny in Finland. Of 132 asbestos workers examined by Bhme,1-'13 29 per it showed radiologic evidence of asbestosis. The morbidity rate of as- stosis in members of this worker group rose, moreover, with the duration employment, being five per cent in workers exposed to asbestos for less in three years; 56 per cent for those employed for five to ten years, and per cent for those with over 10 years' exposure. A similar morbidity e of 80 per cent among English asbestos workers with over 20 years employment, was reported by Merewether and Price14 in 1930. Noro4 ed an asbestosis attack rate of 65 per cent in 167 asbestos workers died roentgenologically. It is remarkable that no large-scale observations the incidence, morbidity and mortality rates of asbestosis and asbestos cers have been published from the giant American asbestos industry. 184 2 ' T able 1 Carcinomas of the Lung in Asbestotics: Reported Cases O fS Hueper: Exposures to Asbestos Country USA CO Number IO Sex M 34 F 1 Age 37-69 Av. 50 Exposure time Latent period 5-36 Av. 20 6-36 Av. 23 Lag period 1-30 Site* Histtyoploegtical LL 26 UL 2 *" 4 CO t o co a <; < H *-rH Canada England Germany Finland Italy France Switzerland Total o rH CO CO M 10 M 106 F 32 M 44 F 7 48-65 Av. 57 32-76 Av. M. 55.2 F. 44.6 Av. 54 35-71 Av. 52 CM r - i 46-54 Av. 49 tot--4 r 4 CO S CM CO r4 s H 240 M 197 32-76 F 41 c- 2-33 Av. 22.5 1-45 Av. 16 3-34 Av. 15 17-26 Av. 29 1-45 T <> CM rr 14-34 Av. 25 16-45 Av. 23 4-45 o N CO 4-16 Av. 11 9-20 Av. 3 LL 4 UL 1 LL 22 UL 4 ______ ; m 05 < S 16 R 24 A 6 <0 CM CM H a C-- o CO 1r --4 LL 53 UL 7 H to TOj* 0 5 CO < CO 05 < *LL-Lower Lobe; UL-Upper Lobe. tS - Squamous Cell; R - Round Cell; and A - Adenocarcinoma. 185 186 Annals New York Academy of Sciences It is an axiom of sound public health practice that protective and pre ventive control measures, to be rational and effective against environmental health hazards, must be based on adequate information on the sources and types of exposure of the causative agent involved and on the population groups affected. For such an assessment of the potential scope of an en vironmental health hazard of occupational and nonoccupational implica tions, it is necessary to determine the distribution pattern of the agent from the site of its original occurrence and production through the sites and types of its subsequent industrial and commercial uses to the homes of the ultimate consumers. It is, moreover, essential to ascertain the various types of products into which the causative agent might be incorporated and the purposes for which such products might be used. It is important furthermore to investigate the existence and degree of environmental pol lution of the plant area as well as of the plant vicinity and the zones along ;he routes of transportation of such materials. When some or all of such lata have become available, a sound factual basis is provided for a com)etent epidemiologic investigation of the workers employed in mines and actories producing, using and handling the causative agent, and of the nembers of various trades and occupations having primary and associated ontact with it, as well as of members of the general population sustaining n incidental exposure to it. Past experiences have shown that only through uch comprehensive and painstaking epidemiologic procedures are any worthwhile, factual data on the existence and scope of occupational and elated environmental health hazards obtained. The continued insistence f some industrial parties that reliable decisions on such aspects can be ased on what is called deceptively "sound clinical impression" often terely reflects an objectionable desire to escape from an unpleasant situaon into a wishful dreamland in which profits are properly protected ?ainst ju st compensation claims. A brief presentation of the sources and types of occupational and non:cupational exposures to asbestos and of the various occupational and moccupational population groups having such contacts, therefore, may irnish a proper foundation for the subsequent discussions of the biologic nctional and anatomic effects associated with and produced by the in flation of asbestos dust. The immediate importance of such data is indi ted by the fact that the world production of asbestos has increased from 0 tons in 1880, to 330,000 tons in 1925, to 446,000 metric tons in 1938, over 2,000,000 tons in 1958, and that it is still rising ( figure 1). The rin producing country is Canada, while the principal consuming country the United States of America, which consequently should have the largest mber of individuals exposed for occupational and nonocuppational reasons an inhalation of asbestos dust from an increasing number of sources d from a growing number and variety of products. WORLD PRODUCTION ASBESTOS IN METRIC TONS Hiieper: Exposures to Asbestos 187 * Latent period 2 0 fears F igure 1. World production of asbestos and asbestosis carcinoma of the lung. Since, of the different types of asbestos, chrysotile represents approxi mately 95 per cent of the total asbestos produced, contact with this type of asbestos furnishes the chief cause of asbestos pneumoconiosis and cancer in most countries, and especially in the U.S.A. which maiinly produces, im ports, processes and uses chrysotile.1' 15Contact with other types of asbestos, particularly amosite and crocidolite, is of comparatively minor and regional importance for occupational reasons because these varieties of asbestos are mainly mined in South Africa and preferably consumed in Great Britain, and represent only a relatively small fraction of the total amount of asbestos produced and used. The exposure data to be given apply, therefore, mainly to chrysotile, although according to Lanza'" 17 all three types of asbestos elicit the same kinds of biologic reactions. Occupational A ctivities, P rocesses and P roducts w it h Asbestos H azards Asbestosis and asbestos cancer hazards related to an inhalatory exposure to asbestos exist not only for asbestos workers proper engaged in the direct and regular production, processing, handling, and using o f asbestos-con taining materials, but also for the large number of individuals who may sustain such contacts on an incidental basis. Such persons may be em ployed permanently or temporarily in or near operations where asbestos and asbestos products are produced or handled and where they inhale, 188 Annals New York Academy of Sciences T able 2 Asbestos Sites of asbestos cancers Exposure stigmata Rec ogni z ed--Lung Chronic fibrosing pneumonia involving first lower lobes (asbestosis), asbestos bodies in sputum, asbestos warts of skin (fingers) Compounds of economic importance Chrysotile, amphibole, amosite, crocidolite, tremolite containing magne sium, aluminum, calcium, iron, silica. Operations and products with contact to asbestos for producers, processers, users, consumers, residents Asbestos rock mining, loading, shipping, crushing, milling, asbestos spin ning, weaving, mixing, cutting, pressing, molding, plastering, cementing, spray ing of steel construction, undercoating of automobiles, insulating pipes, etc., clothes, cloths, sheets, blankets, curtains, brake linings, yarns, cords, ropes, twines, ribbons, artificial snow, filler in rubber goods, plastics and roof coat ings, filter cloths, filter pads, filter paper, artificial wood, tiles, shingles, cardboards, wall boards, partitions, panels, paper, clutch facings, clapboard, pipe coverings, pipes, insulation blocks, insulation jackets, gaskets, pump pack ings, electric wire insulation, structural heat insulation, facings of acoustical building materials, catalyst supports in sulfuric acid production, putties Population groups with occupational and environmental exposure to asbestos Occupational groups Nonoccupational groups Asbestos rock miners, loaders, truckers, crushers, m illers, asbestos s p i n n e r s , weavers, electrical ap pliance and wire manufacturers, ma sons, carpenters, heating equipment workers, rubber workers, shingle and tile manufacturers, building material manufacturers, f i l t e r i n g material manufacturers, molders of asbestos products, asbestos-asphalt makers, putty manufacturers, asbestos cement makers, asbestos paper, cardboard ind brake-lining producers, asbestos 'elt insulation workers, a s b e s t o s sound insulation workers, asbestos nsulators, pipe coverers, asbestos ube wrappers, asbestos cork insulaion workers, construction workers, lutomobile makers, garage attendants Residents in vicinity of asbestos processing and textile mills inhaling plant effluents polluted with asbestos dust, and individuals living and work ing along roads on which asbestos is trucked; inhabitants of houses with asbestos insulation. Hueper: Exposures to Asbestos 189 therefore, air polluted with asbestos dust (repairmen, maintenance men, engineers, mechanics, laboratory technicians, office workers, medical per sonnel, truckers, railroad workers, yardmen, construction workers, ship yard workers, automobile plant and garage employees, etc.)-18"2'1 The total number of individuals in the United States having manifest, suspected and possible, but often unsuspected contact with asbestos, should run between 50,000 and 100,000. The duration and degree of exposure to asbestos in members of this group, however, must vary considerably and their relative liability to asbestosis and asbestos cancer consequently will also show distinct differences. The recent estimate as to the total number of about 50,000 asbestos workers employed in the United States, Canada, England, and several other European countries made by Braun and Truan24 must be considered an optimistic understatement which tends to minimize the actual scope of the health hazard associated with work in asbestos. The numerous occupations and products associated with the production and utilization of asbestos provide a vivid illustration of the wide scope of the industrial health problem related to this mineral (TABLE 2). Asbestos Ore Mining and Milling Miners, sorters or dressers of asbestos ore in open pit mines, but partic ularly in underground mines, are exposed to the inhalation of rock dust containing asbestos. Similar exposures exist for the loaders of the mined rock and for the truckers and railroad personnel who haul the material and deliver it to the crushing mill.25The crushing and screening of asbestos rocks (comminuation), carried out in the mills for separating the asbestos fibers from the adherent rock, is associated with the production of a great deal of dust and thus entails a heavy exposure to asbestos unless stringent technologic precautionary measures are taken for protecting the workers employed in these mills. The amount of dust produced in these operations and escaping from the mill buildings can, moreover, cause a marked pollu tion of the intraplant and periplant environment with asbestos dust and thereby create not only an intraplant asbestosis hazard for workers em ployed in the yard and offices located on the premises but also a periplant hazard endangering individual and animals working and living in the vicin ity of such plants (industrial neighborhood and household hazard).28' 14 Reports on the occurrence of asbestosis and asbestos cancer among asbestos miners and millers which are on record from Canada, the United States, and South Africa15' 18-24-11-11" demonstrate the existence of the typical health hazards associated with these occupations in asbestos. Asbestos Cement Production and Consumption The greatest quantity of asbestos of all grades is used in the manufacture of a variety of asbestos cement and plaster products, such as asbestos cement proper which may be applied like ordinary m ortar or plaster, or ? 190 Annals New York Academy of Sciences which may be sprayed on walls; insulating material for the covering of pipes, boilers, cables, conduits and ducts; siding shingles, roofing shingles, tiles, flat and corrugated sheets, wallboard, clapboard and automobile undereoating.25-7 The production, processing and commercial use of these materials often entail for workers engaged in such activities, a distinct exposure to asbestos-containing dust. Reports in the more recent medical literature attest to the existence of distinct occupational health hazards from such exposures by noting the occurrence of asbestosis and asbestos cancers in asbestos cement and plaster makers, mixers, and sprayers, in sulators, laggers and pipe coverers, especially those employed in shipyards, and masons.-':l-'J,MO-4, -'>,-4V,-47' 7,1"''`7'4a The circumstances under which asbestos cement products are used in the human economy make it likely that they nay create asbestos health hazards of an associated type for other workers as well as in homes where asbestos insulating is used.2"-30 Manufacture of Asbestos Textiles Asbestos alone or in combination with other vegetable or animal fibers tnd synthetic plastics is employed extensively in the manufacture of hreads, yarns, wicks, cords, ropes, tapes, cloths, sheets, blankets, and imilar products which in turn are used widely in industry (automobile, airraft) as friction materials, brake linings, fireproof safety clothing, curains, life jackets, and similar articles, clutch facings, lagging cloths, and askets. During the preparation of the asbestos fibers and in the fabricaion process of textiles from asbestos (carding, stripping, mixing, bobbing, pinning, and weaving), the workers become exposed to asbestos dust re used into the air, although the absolute amounts of this have greatly een reduced during recent years by proper technologic measures in modern :xtile plants.4"-30 Whether the introduction of such protective procedures as succeeded in totally eliminating asbestotic hazards for the workers nployed in such plants, however, remains to be seen because of the often datively long latent period which may elapse before asbestosis may be>me symptomatically manifest even after workers have left such hazardis operations.-',~:'4,'' Exposure conditions in the asbestos textile industry itil rather recent times, definitely demonstrate that asbestos textile work 's (spinners, carders, weavers) were subject to a distinct asbestosis and bestos cancer hazard.33"38-12-13-53-54-59' 72-"-73-74-20-"-TM Periplant hazards for the population living in the vicinity of such plants ay ensue if the effluents of exhaustive ventilation equipment are released to the environmental air without previous removal of their asbestos nstituents. Miscellaneous Asbestos Products Asbestos is being made into floor tiles by blending it with other mateils, such as asphalt, plastics, and similar chemicals. It is used for seals, Hueper: Exposures to Asbestos 191 packing material for pumps and joints, for making paper, filter material, circuit breakers, molds, and many other articles, whose total number Selikoff et a ir' have estimated to run at about 3,000 different items. While not all contacts with asbestos and asbestos products are associated with exposures to asbestos dust and thus may result in the development of pneumoconiosis and cancers of the lungs, pleura and peritoneum or less often of asbestos warts of the skin,77''" there can be little doubt that such health hazards are connected with the production, processing and handling of many of them. Their existence, however, may often not be known, rec ognized and appreciated by members of the medical profession, not ade quately familiar with industrial practices and products. Protection of Asbestos Workers by Workmen's Compensation Laws Asbestos workers of several countries, acquiring as the result and in the course of their regular employment asbestosis of the lung with or without a complicating respiratory cancer, are covered by provisions of workmen's compensation laws. These occupational diseases must moreover, in some countries be reported to governmental agencies (Germany, Great Brit- ain) it seems, however, that this type of protection applies in Great Britain to only some types of occupations but not to others. The conditions on this m atter differ distinctly in the different states of the United States, where each state has its own compensation acts differing from each other to a considerable degree concerning the type of coverage and the length of the mandatory time-clause. Compensability of asbestosis was denied, for instance, in North Carolina in 1937 in a suit against the Carolina Asbestos Company by the Industrial Commission. In an appeal, this decision was confirmed by the Supreme Court of North Carolina. Legal provisions furnishing presumably adequate protection of asbestos workers against the health hazards peculiar to their occupation at the present time still leave much to be desired in many states. C o n c l u s io n s (1) The enormous rise in the production and industrial use of asbestos during the past 50 years has resulted in markedly widened exposure to asbestos dust for a greatly increased number and variety of workers. Some of them, moreover, sustain such contacts incidentally either when being employed in various capacities in operations where asbestos products are processed, used, or handled or when working in plant areas in which an environmental pollution of the a ir with asbestos exists.84' 80 (2) The harmful effects of such growing exposures to asbestos during the past two decades are reflected not only in a growing number of reports on the occurrence of asbestosis and asbestos cancer in a variety of asbestos workers but also in the fact that such reports originate from a rising 192 Annals New York Academy of Sciences number of countries in some of which such observations were made only recently for the first time. (3) Information on the number and variety of exposed *rrkers and on the occurrence and incidence of asbestosis and of asbes: :s cancers among them is most fragmentary in all countries, especially ir. the United States and Canada, one being the principal consumer of asbes:::s and the other the chief producer of this mineral. It is for this reason rsrrettable that the original plan of having a recent epidemiologic survi y on these aspects of asbestos production in Canadian mines and mills :: :e undertaken under the aegis of the National Cancer Institute of Cans :a was not adhered to and that this study was carried out as an industry--irminated venture which yielded highly controversial negative results.90" (4) The principal worker groups exposed to respiratory c: r.tact with asbestos are employed in the asbestos mining and milling indus:::es. in the production and commercial use of asbestos cement and plasterand their numerous secondary products, in the production and applicatior. asbestos for insulating purposes, and in the processing of asbestos ar.: its manufacture into textiles. (5) Because in many countries and states the workmen's cc:irensation laws are defective, the protection of asbestos workers against :: :upational health hazards related to respiratory and cutaneous contact w:: asbestos is inadequate. References 1. A hlborg, G. & C. J. Hansson. 1956. Asbestosen fr Sverige ny vrsessukdom. Sven. Lk. Tidn. 53: 1376-1383. 2. W egelius, C. 1947. Changes in the lungs in 126 cases of asbes:.: 5.i observed in Finland. Acta Radiol. 28: 139-150. 3. F rost, J., J. Georg & P. F. Miller. 1956. Asbestosis with pleurt. caicification among insulation workers. Danish Med. Bull. 3: 202-204. 4. Noro, L. 1946. Histology of asbestosis. Acta Path. Microbiol icand. 23: 53-59. 5. Clerens. 1950. Occupational asbestosis. J.A.M.A. 143: 489. 6. Nordvik, N. 1959. Le silicose et l'asbestose prdisposants-eli iu cancer pulmonaire? Arch. Belg. Md. Soc. Hyg. Md. Trav. Md. Lr IT: 85-99. 7. Rosato, D. V. 1959. Asbestos: Its Industrial Applications: 4` :i Reinhold Publ. Corp. New York, N. Y. 8. Wedler, H. W. 1939. Klinik der Lungenasbestos. Leipzig, Gerir.= 9. Wedler, H. W. 1943. Asbestos und Lungenkrebs. Deut. Med. ~ tchenschr. 69: 575-576. 10. Baader, E. W. 1939. Asbestos. Deut. Med. Wochenschr. 65: 407-4 "s. 11. Baader, E. W. 1951. Der Lungenkrebs als gewerbemediziniser.es Problem. Proc. 57. Tagg. Deut. Ges. Inn. Med. 12. Bhm e, A. 1959. Asbestose und Lungencarcinom. Arch. Gewer::epath. 17: 457-462; 17: 384-395. 13. Bhm e, A. 1942. Examination of workers in an asbestos far.:ry. Arch. Gewerbepath. 11: 433-452. 14. Merewether, E. R. A. & C. W. P rice. 1930. Report on Effects :: Asbestos Dust on the Lungs and Dust Suppression in the Asbestos Industry. H. M. S. O. London, England. Hueper: Exposures to Asbestos 193 15. Bowles, O. & D. I. March. 1947. Asbestos. Minerals Yearbook 1945 : 1457. Washington, D. C. 16. Lanza, A. Z. 1936. Asbestosis. J.A.M.A. 106:368-370. 17. Lanza, A. Z. 1938. Silicosis and Asbestosis: 439. Oxford University Press. London, England. 18. Bohlig, H. 1955. ber das Auftreten des Lungenkrebses bei Asbestose. Ber. I. Kongress Med.-Wiss. Ges. Rntgenologie Deut. Demok. Rep. p. 102-105. 19. Bohlig, H., G. J acob & H. Mller. 1960. Die Asbestose der Lungen: 106. Georg Thieme Verlag. Stuttgart, Germany. 20. Bohlig, H., G. J acob & H. Mller. 1962. Asbestaublunge und Tuberkulose -- neue Gesichtspunkte zur Entschdigungspflicht. Internat. Arch. Gewerbepath. 19: 434-449. 21. Bohlig, H. & G. J acob. 1958. Die Hufigkeit des Lungenkrebses bei deut schen Asbestarbeitern. Deutsch. Gesundheitsw. 13:1101-1103. 21a. CURETON, R. J. R. 1948. Squamous cell carcinoma occurring in asbestosis of the lung. Brit. J. Cancer. 2: 249-253. 22. Brugsch, H. G. & H. Bavley. 1961. Asbestosis in a worker engaged in automobile undercoating. New England J. Med. 265: 379-381. 23. Selikoff, I. J., J. Churg & E. C. Hammond. 1964. Asbestos exposure and neoplasia. J.A.M.A. 188: 22-26. 24. Braun, D. C. & T. D. T ruan. 1958. An epidemiological study of lung cancer in asbestos miners. Arch. Indust. Health, 17: 634-652. 25. Sinclair, W. E. 1959. Asbestos, Its Origin, Production and Utilization: 512. 2nd ed. Mining Publications, Ltd. London, England. 26. W a.gler, F., H. Mller & M. A nspach. 1962. Gibt es eine endemische Asbestose? Zeitschr. Ges. Hyg. Grenzgeb. 8: 246-255. 27. Kiviluoto, R. 1960. Pleural calcification as roentgenologic sign of nonoccupational endemic anthophyllite-asbestosis. Acta Radiol. Supp. 194, p. 1-67. 28. Cordova, J. F., H. T esluk & K. P. K nudtson. 1962. Asbestosis and car cinoma of the lung. Cancer 15: 1181-1187. 29. T homson, J. G., R. O. C. Kaschula & R. R. MacDonald. 1963. Asbestos as a modern urban hazard. S. Afr. Med. J. 37: 77-81. 30. T homson, J. G. 1962. Mesothelioma of pleura or peritoneum and limited basal asbestosis. S. Afr. Med. J. 36: 759-760. 31. Walters, L. G. 1963. Industrial cancer in South Africa. Med. Proc. 9: 24-30. 32. F elice, J. R., P. A. M ller, G. J. V. A lfonzo, M. Osorio-Murga, C. E. Guedez & T. M. P arka. 1961. El problema de la asbestosis en una planta de separacin y clasificacin de fibras de asbesto. Rev. Venezol. Sanid. Asist. Soc. 26: 523-529. 33. Webster, I. 1963. Asbestosis in non-experimental animals in South Africa. Nature 197: 506. 33a. Becker, B. J. P. Personal Communication. 34. W agner, J. C., C. A. Sleggs & P. Marchand. 1960. Diffuse pleural meso thelioma and asbestos exposure in the North Western Cape Province. Brit. J. Indust. Med. 17: 260-271. 35. Cartier, P. 1955. Some clinical observations of asbestosis in mine and mill workers. Arch. Indust. Health. 11: 204-207. 36. Cartier, P. 1949. Contribution l'tude de l'amiantose. Arch. Malad. Prof. 10: 589-561. 37. Sleggs, C. A. & J. C. W agner. 1961. Diffuse pleural mesotheliomas in South Africa. S. Afr. Med. J. 35:28-34. 38. Desmeules, R., L. Rousseau, M. Giroux & A. Birois. 1941. Amiantose et cancers pulmonaires. Lav. Md. 6: 97-108. 39. Isselbacher, K. J. & H. L. Hardy. 1953. Asbestosis and bronchiogenic car cinoma. Am. J. Med. 15: 721-732. 40. T elischi, M. & A. I. Rubenstone. 1961. Pulmonary asbestosis. Arch. Path. 72: 234-243. 194 Annals New York Academy of Sciences 41. Stoll, R., R. Bass & A. A. A ngrist. 1951. Asbestosis associated with bronchiogenie carcinoma. Arch. Intern. Med. 88: 831-834. 42. A nderson, J. & F r. A. Campagna. 1960. Asbestosis and carcinoma of the lung. Arch. Envir. Health. 1: 27-32. 43. Beintker, E. 1931. Die Asbestose der Lungen. Arch. Gewerbepath. 2: 345358. 44. Nordmann, M. & H. Sonnenberg. 1960. Asbest-Zementstaub-Lunge. Arch. Gewerbepath. 18: 205-219. 45. A lvarado, L. C., J. E nriquez & D. Barron. 1960. Asbestosis - epidemio logical study in an asbestos-cement plant. Salud Publ. 11: 557-566. 46. Caprioglio, A. 1960. Inquinamento atmosferico da cemento: alterazioni polmonari nelle maestanze del cemento-amianto e nella popolazione. Ras. Med. Indust. 29: 375-379. 47. H eustis, A. E. 1963. Spraying of asbestos. Mich. Occupational Health 8: 3-5. 48. Leathart, G. I. & J. T. Sanderson. 1963. Some observations on asbestosis. Ann. Occup. Hyg. 6: 65-74. 49. Mitchell, J. 1961. Health progress in an asbestos textile works. Arch. Envir. Health 3: 37-41. 50. Postman, B. F. 1962. Dust control in the asbestos textile industry. Am. Indust. Hyg. Ass. J. 23: 67-74. 51. Luton, P. & J. Cham pfix. 1946. tude de l'asbestose. Arch. Mal. Prof. 7: 365-367. 52. H eard, B. E. & R. W illiams. 1961. The pathology of asbestosis with refer ence to lung function. Thorax 16: 264-281. 53. Gloyne, S. R. 1935. Squamous cell carcinoma of the lung occurring in as bestosis: Two cases. Tubercle 17: 5--10. 54. Gloyne, S. R. 1932-1933. The morbid anatomy and histology of asbestosis. Tubercle 14: 445-451; 493-497; 550-558. 55. Doll, R. 1955. Mortality from lung cancer in asbestos workers. Brit. J. Indust. Med. 12: 81-86. 56. Doll, R. 1955. Etiology of lung cancer. Adv. Cancer Res. 3: 1-50. 57. Lynch, K. M. & W. A. S m ith. 1931. Pulmonary asbestosis. Am. Rev.Tuberc. 23: 643-648. 58. Lynch, K. M. & W. A. Sm ith . 1939. Pulmonary asbestosis. I. Report of bronchial carcinoma and epithelial metaplasia. Am. J. Cancer 36: 567572. 59. J acob, G. & M. Boulig. 1955. Incidence and characteristics of lung cancer in asbestos workers. Arch. Gewerbepath. 14:10-28. 60. O'Donnell, W. M. & R. H. Ma n n . 1957. Asbestos: An extrinsic factor in the pathogenesis of bronchiogenic carcinoma. Am. J. Path. 33: 610. 61. Rombola, G. 1955. Asbestosi e carcinom a pulmonare in una filatrice di amianto; spunti sui problema oncogeno dell'asbesto. Med. Lavoro 40: 242-250. 62. E nticknap, J. B. & W. J. S mither. 1964. Peritoneal tumours in asbestosis. Brit. J. Indust. Med. 21: 20-31. 63. Leicher, F. 1955. Primrer Deckzellentumor des Bauchfelles bei Asbestos. Arch. Gewerbepath. 13: 382-392. 64. E gbert, D. S. & A. Geiger. 1936. Pulmonary asbestosis and carcinoma. Am. Rev. Tub. 34: 143-146. 65. Mancuso, Th. F. & E. J. Coulter. 1963. Methodology in industrial health studies. Arch. Envir. Health 6: 210-226. 56. Merewether, E. R. A. 1947. Annual Report Chief Inspector of Factories for the Year 1947: 15-17. H.M.S.O. London, England. 37. Merewether, E. R. A. 1955. Annual Report Chief Inspector of Factories for the Year 1955: 206. H.M.S.O. London, England. 58. Lynch, K. m . & H. R. P ratt-T homas. 1955. Carcinoma of the lung in asbestosis: Report of two additional cases. South. Med. J. 48: 565-569. Hueper: Exposures to Asbestos 195 69. Lynch, K. M. & W. M. Cannon. 1948. Asbestosis. IV. Analysis of forty necropsied cases. Dis. Chest 14: 874-890. 70. Keal, E. E. 1960. Asbestosis and abdominal neoplasms. Lancet 2: 1211-1218. 71. W yers, H. 1950. Asbestosis. Postgrad. Med. J. 25: 631-638. 72. Hardy, H. L. 1952. Medical progress. Occupational medicine. New Engl. J. Med. 247: 473-483 ; 515-524. 73. Stewart, H. L., C. J. Bucher & E. H. Coleman. 1931. Asbestosis. Arch. Path. 12: 909-916. 74. Krger, E., Rostoski & Saupe. 1931. fiber Lungenasbestose. Arch. Gewer- bepath. 2: 558-590. 75. Wood, W. B. & S. R. Gloyne. 1934. Pulmonary asbestosis -- A review of 100 cases. Lancet 2: 251-254; 1383-1385. 76. S hull, J. R. 1936. Asbestos. Radiology 27: 279-288. 77. Dreessen, W. C., J. M. Della Valle, et al. 1938. A study of asbestosis in the asbestos textile industry. Publ. Health Bull. No. 241, pp. 68-69. 78. Alden, H. S. & W. H. HOWELL. 1944. The asbestos corn. Arch. Derm. Syph. 49: 312-314. 79. Dewirtz, A. P. 1930. Asbestwarzen. Arch Dermat. 161: 1-5. 80. Olliver, H., P. Morand & R. Brun. 1949. Considrations propos des granulomes cutans de l'amiante. Arch. Mal. Prof. 10: 516-517. 81. Young, J. W. 1944. The asbestos corn. Arch. Dermat. 49: 309-311. 82. Knig, J. 1960. fiber die Asbestose. Arch. Gewerbepath. 18: 159-204. 83. Merewether, E. R. A. 1933 and 1934. A memorandum on asbestosis. Tu bercle 15: 69-81; 109-118; 152-159. 84. Hueper, W. C. 1942. Occupational Tumors and Allied Diseases: 896. C. C. Thomas. Springfield, III. 85. Hueper, W. C. 1952. Occupational and environmental pulmonary cancer with special reference to pneumoconiosis. Proc. 7th Saranac Symposium on Pneumoconiosis. Saranac Lake. 86. H ueper, W. C. 1955. A Quest into the Environmental Causes of Cancer of the Lung. Public Health Monograph No. 36, PHS Publ. No. 452: 54. Washington, D.C. 87. H ueper, W. C. 1957. Environmental factors in the production of human cancer. In Cancer Vol. 1: 404-496. R. W. Raven, Ed. Butterworth & Co., Ltd. London, England. 88. Hueper, w . C. 1961. Carcinogens in the human environment. Arch. Path. 71: 237-267; 355-380. 89. Hueper, W. C. 1959. Carcinogenic studies on water soluble and insoluble macromolecules. Arch. Path. 67: 589-617. 90. P h illips, A. J. 1955-1956. Annual Report National Cancer Institute of Canada : 25. Toronto, Canada. 91. Demy, N. G. 1961. Asbestosis. J.A.M.A. 175: 530.