Document gbE7yYy7zbGnGKkv8kvbKNRq9

i r't 1 r- .* i $r- - *. - . .... I* CAHIDII II a,5&/o& v - >**/. . kl -C -.'JV * ^ w 9+ . . *. 7-' * x-*-,. '' .'.>* :t.A. ;'-- ../* ET ASBESTOS AND HEALTH IN T969/$^Sff7 eS'/c^c^ - r^*rr-> tT>-^r*^r^V r-'i v- GEORGE W. WRIGHT r - v \v ' Y - -V.- Y r* . wfrC r * '^*53- - -.<f AJ Hiprlalad from Avtafour Rjrtmmw o RjuarruToir Dmin^^v ^mV ,.! 4 , . N*r. VoL 200, No.* *2t7l"' * `i ? * I OaSjL I ' "'* * f* * .K-.' ".* * -,\- ;:- " .' ^ -;. * ; - v-t*.?v v . `j^.v v* j .-r -..*/ '.. :>.'V . ;' ;:yj&k:. . " * . fc`jr?* ^ .. T-. ..V '`J.r-H >* V * '*. -J^-- ! T~ ' r * / ' : - ; ~J.\- r^T-: YTY-." ' - ;...5*l-`!f-"0 " .. \ '*j f&. 1 *' 2 <" > . --r w-- t <r-* ay- *-- *vy ASBESTOS AND HEALTH IN 19691-* GEORGE W. WRIGHT Although a group of materials referred to asbestos, it is imperative that the character of generically by the term "asbestos" have been the exposure in terms of concentration, sire, and known and used, to a small extent, far back in types of fibers be known. This sort of data is antiquity, widespread and abundant use of scant or often nonexistent at present with these fibers did not begin until the last quarter respect to exposure of humans. of the nineteenth century, with further augmen Pulmonary fibrosis: In 1907, Murray (2) re tation of production during the first half of the ported the first cases of diffuse pulmonary twentieth century. There are six distinct varieties fibrosis discovered among a group of persons of asbesti/orm fibrous minerals. Among some of who had experienced substantial and prolonged these, there are striking differences in chemical exposure to respirable-sized asbestiform 'fibers. and physical composition (I). Most commonly Subsequently, the term "asbestosis" was applied produced is chrysotile, a member of the ser to this reaction. Traditionally, asbestosis has pentine family. The amphiboles are subdivided connoted this kind of reaction and its sequelae into crocidolite (blue asbestos), amosite, an- with regard to altered pulmonary and cardio thophyllitc, trcmolitc, and actinolite. All are vascular function. Recently, the term has been silicates, crystalline in nature, and characteris corrupted to include such manifestations as tically are divisible into very small fibrils. pleural thickening, pleural plaques, aDd even the Chrysotile and antbopbyllite contain much simple presence of ferruginous bodies. Resolution larger amounts of magnesium than either of the use of the word asbestosis must be ob crocidolite or amosite, and the last two contain tained to bring clarity to scientific reporting. much more iron than the others. The crystalline Murray's report revealed the paradox of a life structure and surface properties, which may be saving agent possessing the capacity for human of importance in the biologic reaction, are also harm. At first, the conditions under which this strikingly different among the varieties of biologic reaction came about seemed to be re asbestos (1). In view of the great variation of stricted to those created during fabrication, chemical and physical properties, it is most un conditions limited to textile manufacturing at safe to predict that the biologic reactions of one that time. In 1930, Merewether and Price O variety of asbestos will be mimicked by another demonstrated that asbestosis posed a major in terms of either actual consequences or mech threat to the health of workers in the asbestos anisms. To interpret the biologic actions of textile trade. It is now known that in any of the several trades in which persons experience pro 'From the Department of Medicine, St. Luke's Hospital. Cleveland, Ohio. 'Presented before the Medical Session, aa part of Section 3A, at the annual meeting of the Ameri can Thoracic Society. Miami Beach, Florida, May 25, 3909. longed exposure to a high concentration of respirable-sized asbestiform fiber, it is probable that aome of them ultimately will develop pulmonary fibrosis. In response to the report of Mcrewrthcr and American Review or Resets.* - < Disease, Volume 100, 1909 467 4 PLAINTIFF'S i EXHIBIT /3BS(3)_ 9 4GS CEonoE w. wniairr s Price, the fabricators of asbestos-containing their experience with population exposure and products took substantial measures to reduce pulmonary fibrosia during the past 30 years. It the concentration of airborne fibers in the fac will be of interest to learn how their findings tories. The report of Bayers and Dreesen (4) in compare to those of the United Kingdom. A 1939 further stimulated the introduction of provisional TLV expressed in conccntri'-jcn of such corrective measures, especially in factories respirable-sized asbestos fibers haa been v". re of the UJ5. and in mines and mills of Canada cently in the United Kingdom, and a alight!v dif where 95 per cent of the free world's asbestos ferent value been established in the OK. was produced. Regrettably, substantial numbers (6, 7). Whether these are proper for all varieties of persons exposed to asbestos in their occupa of asbestos and all settings in which human ex tion have never come under a protective occu posure might occur is debatable. There ia con pational hygiene program. Insulation applicators siderable evidence to suggest tbit chrysotile and Gome individual or small business fabrica penetrates to the deep lung spaces less readily tors fall into this category. and is cleared from the lung more readily than The preventive efforts that were applied led to either aznosite or crocidolite (8). Also, chrysen considerable improvement in the factories, mills, tile causes less pulmonary fibrosia in experimental and mine environments and a subsequent less animals than amosite or crocidolite (9). ening of the occurrence and severity of pul With regard to the prevention of pulmonary monary fibrosis. Unfortunately, the relaxation fibrosis, one would conclude in 1969 that in of precautions governing occupational health, many settings the measures taken have not been common under the stresses of World War II, adequate, and there are populations that have seriously interfered with many health protection had little or no protection at all. The knowledge programs, includmg that for the safe use of required to protect all workers is not available asbestifonn fibers. As a result, the protection of at present, and its development is oDe of the workers using asbestos in mining and milling urgent tasks of the immediate future. Neverthe - and especially in factory settings has not been as less,.an important step haa been taken toward good as it might otherwise have been. further defining the conditions necessary for the Until quite recently, the threshold limit prevention and ultimate abolition of significant value (TLV) for environments containing as pulmonary fibrosis in persons exposed to as bestifonn fibers suggested tentatively by Sayers bestos fiber. and Dreesen (4) in 1939 haa served as a guide. Bronchogenic cancer: Although in 1935 Data entirely adequate for the purpose were not Lynch and Smith (30) reported bronchogenic available in 1939, and it has taken years to recog cancer in 2 patients with asbestosis, it was not nize this inadequacy and to obtain the informa until 1947 tiat the possibility of this second tion upon which to base a more meaningful TLV. biologic influence of asbestos fiber was seriously Fortunately, one of the major users of asbestos raised, when Merewether (11) demonstrated in the production of textiles and textile products bronchogenic cancer in 13 per cent of autopsies has pursued for many years a program of en of persons who had asbestosis arising from em vironmental and population monitoring that ployment in the textile trade. Eight year? later, now provides a more up-to-date experience Doll (12) reported a frequency of lung cancer (5, 6). These studies demonstrate that pulmo of ten times the expected rate in textile workers nary fibrosis can be minimized when adequate exposed for at least 20 years, during the period protective measures are instituted, and that the between 1922 and 1953. This experience has been concentration of airborne" fibers must be the confirmed in the textile trade by Newhouse (13), focal point of attention even though the tech Enterline and Kendrick (14), and Mancuso nology of such monitoring may be new, difficult, and El-Attar (15). More recently, Sclikoff and and expensive. The U. S. Public Health Service, co-workers (16) reported a frequency of bron which began extensive studies into the problems chogenic cancer eight times that anticipated in of asbestos and health in 1901,' together with a group of insulation workers employed for asbestos producers and manufacturers in the more than 20 years who utilized a substantial U.S. and Canada are at this time examining portion of their time removing old or applying * Cralley, L. J.: Personal rommunica'.. - new insulation that contained asbestos. This -rposure 30 yean. It heir finding* Kingdom. A *nir*tion of been set re- i slightly difin the U. r all varieties h human exIhers ia con it chrysotile i leas readily readily than ilso, ehryso experimental 9). f pulmonary '9G9 that in ave sot been is that have le knowledge aot available : ODe of the e. Nevertheaken toward sary for the if significant wsed to as- . h in * 1935 jronchogenic ; it was not this second ras seriously lemonstrated of autopsies lg from emyears later, lung cancer rtiJe workers r the period nee has been rbouse (13), d Maneuso Selikoff and cy of bronitieipated in oployed for substantial or applying restos. This . j i J i | i j , I : I j , | * j I . PLAINTIFF'S I EXHIBIT i L52XM1 ASBESTOS AND HEALTH IN 1P0 4G9 aeries of reports suggests that ashestiform fiber* persons exposed for 20 or more years. This indi play an undetermined role in the augmented cates a heavy and prolonged exposure to asbestos frequency of bronchogenic cancer in some cate . for these two types of worker. Knox and as gories of worker*. In none of these categories, sociates (5), in a continuation of the study of however, has there been a full exposition of other textile workers previously reported by Doll substances which coexist with asbestos in the (12), show that the incidence of lure cancer ' environment and to which the worker has been decreases with progressively smaller total ex exposed (5, 6, 17, 18). It is possible, therefore, posures to asbestos fibers. Newhtauie ;3), also that coexisting materials possessing carcino in an asbestos textile population, has shown genic potential might be implicated. It would be that the occurrence of pulmonary cancer differs prudent to explore this possibility thoroughly markedly with total exposure. She reports no before accepting asbestos per se as the carci increase of the incidence of bronchogenic nogenic factor. cancer in a low to moderately exposed group, In asbestos textile mills, the exposure involves whereas in a heavily exposed group the inci primarily two varieties of asbestos, chrysotile and dence was augmented eightfold. Both groups erocidolite. In some factories, oil has been were from the same textile mill and were similar applied to the fibers before final processing. with respect to duration of exposure and the Moreover, in the process of "opening" the length of time of observation. Enterline and fibers, a strong possibility exists that traces Kendrick (14) demonstrated a stronger rela of metals known to have carcinogenic in tionship between lung cancer and employment fluences may have been added to the fibers in the asbestos textile trade than exists in the (19-21). less dusty manufacturing of asbestos building Insulation workers have been exposed not products or building materials. In a series of only to chrysotile and amosite but also, espe studies, Maneuso and El-Attar (15) suggested cially in shipyards, to erocidolite. The nature that cancer risk is lower with lesser exposures of their work, as they remove old insulation and to asbestos. From these observations, the in apply new in various places, exposes these ference strongly favors a dose relationship be workers to many nonasbestos substances, some tween bronchogenic cancer and whatever effect of which may be hydrocarbons adsorbed onto asbestos fibers may ultimately be shown to have the asbestos fiber. The exposure history of in in its causation. sulation workers is seriously lacking as to specific The question of whether the carcinogenic details of all of the materials that they may role of asbestos is related to the specific kind of have inhaled in addition to asbestos. fiber is more difficult to answer. For this pur Of the numerous questions which could be pose, populations having long-term exposure to posed concerning the relationship of asbestos only one variety of fiber are needed. Virtually and bronchogenic cancer, the following three all fabricating processes use more than one are of immediate practical importance: (/) Is variety within the same premises at any one the influence dose-related 7 () Is it related to lime or have used more than one variety at variety of asbestos? (5) Does the relationship various times. Populations restricted to mining involve eocareinogenesisT Some evidence bear and milling in the production of asbestos fiber ing upon these questions is now available, but lend themselves best to a study of the effects in no instance is it complete. of a single kind of fiber, and it is to these Data concerning the question of dose rela populations that one mu6t look for an answer to. tionships do exist. The type of work related the influence of a single variety of fiber. most strongly to the development of bronebo- Kiviluoto and Meurman (22) showed that genic cancer has been in the textile and the exposure during the production of anlhophvl- insulation applications trades; the worker, in lite in Finland carries with it a threefold to most instances, has been employed in either fivefold increased risk of bronchogenic cancer trade for 20 or more years. Merewethcr and for those in the age group older than 45 years Price (3), and Selikoff and associates (21) re with more than 10 years of exposure. At this port an incidence of asbestosis (pulmonary time, there are no published data with respect fibrosis) in these groups of 80 per cent among to the frequency of bronchogenic cancer m the PLAINTIFF'S exhibit 470 GEORGE W. WBI0HT crocidolite or amosile production areas of South The considerable variation in the lung Africa, the only place in the world where ap cancer incidence between populations of dif preciable amounts of these types of fiber are produced. A verbal report* from South Africa suggests that the frequency is somewhat higher than anticipated is the general population of that country. Data from these regions will be fering types of employment may be solely related to dosage, but it may also be the result of differing cocarcinogens. Gross and associates (26) produced a higher than anticipated fre quency of pulmonary cancer in rata erpoe*- to awaited with great interest. In 1058, Braun and chrysotile. They attributed this variance, from Truan (23) reported a study of the frequency the experience of others, to Be related to t-id- of lung cancer in workers of the mines and tamination of the chrysotile fibers by nickel, mills producing only chrysotile in the eastern cobalt, and chromium caused by the wear of part of Quebec, Canada. From the data avail the metal components of the mill used in pre able to them at that time, they found no evidence paring the fiber for administration to their ani of an augmented frequency of bronchogenic mals. Crallcy and associates (19,20) showed sub cancer in this group of employees. Although the stantial amounts of these trace metals in the period of observation was only five years and the group was diluted by short-term exposures, it contained more than 1,700 persons employed asbestos fibers used commercially. Miller and as sociates (27) have shown that bento (a) pyrene plus asbestos augments the yield of pulmo longer than 20 years, all of whom had had at nary tumors produced by bento (a) pyrene least five years of exposure and 930 of wham lone. Harington and associates (28) raised the were older than 55 years of age. The data would possibility that adsorbed hydrocarbons occur have been more meaningful if arranged in terms ring natively or picked up in storage and of total exposure and time from beginning of ex handling may play a role in coc&rcinogenesis. posure. Nevertheless, if an excess of lung cancer As reviewed in 1969, the role of asbestos in equivalent to that seen in the settings referred augmenting the incidence of bronchogenic can to previously in this paper did actually exist cer appears to be dose-related, may be dependent in this population, it seems likely it would upon the specific category of fiber, especially in have been found. This same population is now relation to the degree of effect, and appears to being restudied after a much longer period of be that of a coearcinogen. observation and in a more adequate way. Vigliani and associates (24) have found evi dence of an-augmented frequency of cancer of the lung and pleura in a group of 288 persons, previously compensated for asbestosis arising from all occupations, wbo died between 1943 and 19G7. In a subgroup of 32 miners exposed to chrysotile only, there was no augmentation of the rale of cancer of lung and pleura. Al though these studies suggest that chrysotile has little or no carcinogenic influence, more ex tensive and refined epidemiologic data are needed before reaching that concluaios. The possibility that the carcinogenic role of asbestos is solely that of a cocarcinogen is very strong. The data of SelikofT and associates (25) are especially pertinent in this regard, in that not a single bronchogenic eaDccr has been found in an insulation worker wbo waa a ooncigarctte smoker, even though the exposure to asbestos experienced by the nonsm-iters was the same as that of those who smokca and did develop lung cancer. Mesothelioma; Subsequent to the earlier re ports linking occupational exposure to asbestos and bronchogenic cancer, there were several suggestions that tumors of the peritoneal and pleural meso(helium might be similarly linked. Interest in this phenomenon remained dormant, however, until Wagner (29), in 1959, reported 20 cases of pleural mesothelioma associated with the Northwest Cape region of South Africa. He suggested that these were related to exposure to crocidolite asbestos because 14 of the persons were born or bad 6pent their early youth-near Kuruman, where crocidolite production : one of the major industries. This observation prompted an intensive search for all mesothe liomas in South Africa. Gilson (30) plotted the number and distribution of the South African coses up to 1962 and demonstrated a striking concentration of caaes in the Northwest Cape. Although almost none was found to occur elsewhere in South Africa, the inference that the concentration of mesotheliomas coincided with the sole source of crocidolite in South Africa 'Webster, 1.: Personal eommunicati'- would not be warranted. A substantial quantity tJhy .'l.'*./ id the lung rlions of dif ay-be solely J^tie result tsd associates sidpated fre ts* exposed to ariance, from dated to eona* by nickel, the wear of 1 used in pre) to thdr aniI) showed sub metals in the Miller and as . .xo (a) pyrene Id of pulmo'-o (a) pyrene ' 28) raised the arbons occurstorage and rcinogenesis. of asbestos in ichogenic canr be dependent especially in nd appears to the earlier reTe to asbestos were several oeritoneal and nilarly linked, ined dormant, 1959, reported issoeiated with Jth Africa. He to exposure to if the persons . ly youth near iuetion is one observation r all mesothe0) plotted the Boutb African ted a striking 'rthwest Cape, and to occur trenee that the coincided with South Africa intial quantity * PLAINTIFF'S J EXHIBIT ASBESTOS AND HEALTH IN 1M9 of crocidolite haa been produced for a period of It is apparent that the overwhelming number of many yean, hundreds of miles away in the eases thus far being related to asbestos are eastern Transvaal, the same area in which amo- diagnosed on the baais of biopsy alone. Further site and chrysolile asbestos are produced (31). study will be needed to demonstrate whether Investigator* in other parts of the world mesothelioma is being over or under diagnosed. have examined the distribution of mesotheliomas If one accepts that some kind of direct or and the frequency of mesothelioma in popula indirect relationship between ast-vtos and tions occupationally exposed to asbestos, with mesothelioma exists, does it involve a specific the result that a strong relationship between ex variety of fiber? The data from the UK. and posure to asbestos fiber and the presence of United Kingdom does not lend itself to resolving i mesothelioma has been indicated. Most of the this question because chrysolile, amosite, and k cases outside South Africa, where mining and crocidolite are involved in the insulation workers' milling are implicated, have been reported in exposure, and chrysotiJe plus crocidolite in that the United Kingdom and, to a lesser degree, in of the textile manufacturing employees. If one the UK. In spite of a thorough search, no examines the mining and milling exposures to mesotheliomas have been found associated with the specific variety of fiber, interesting facts anthophyllite asbestos production in Finland emerge. Kiviluoto and Meurman (22) did not (22), and few are reported in France (32), find a single mesothelioma in a large popula where the subject has probably not been tion of miners and mill workers exposed only to thoroughly investigated. In the United King anthophyllite. This group worked for three dom, the association has been with populations months or more between the period of 1935 of insulation workers and asbestos textile manu and 1967. Although others have stressed the facturing factories (33). In the UK, the rela long period of time required for mesothelioma tionship has been shown predominantly with development, one would think that if anthopbyl- insulation workers (16) and, to a lesser degree, lite by itself is implicated, at least one case with textile manufacturing employees (15). Re would have been found by now in a \ setting cent study of the distribution of mesotheliomas known to cause asbestosis and a somewhat aug in Canada will be commented upon later. mented frequency of bronchogenic cancer. In a In most of the studies to date, the question study of the distribution of mesotheliomas in has been raised as to whether the population Canada, McDonald and co-workers (35) were at risk with respect to mesothelioma is to be unable to show excess frequency in the geo found outside as well as inside the factory or graphic area where chrysolile, but no other place of work. There has been a plethora of - variety of asbestos, is produced. speculation by students of the problem that The South African distribution of mesothe often has been accepted as fact or interpreted as liomas is unusually interesting. Webster (3G) such by lay writer*. These dramatic speculations reports that before the end of 1968, 179 cases have further compounded an already difficult of mesothelioma were agreed upon as meeting matter for those responsible for public protec acceptable criteria. Of these, the history of ex tion as well as those responsible for the health posure was known in 148 patients, and in 24 i of employees. Controversial or paradoxic issues there was no asbestos exposure. Fiftv-one pa about mesothelioma and asbestos deserve a tients had been exposed during the mining and l more complete discussion than is possible in this milling of crocidolite in the Northwest Cape paper. Among the controversial features about only. An additional 52 patients with mesothe the relationship of asbestos exposure to meso lioma, not exposed occupationally, were as i thelioma of the pleura and peritoneum are the sociated in some way with residence in the following. Northwest Cape. Sluis-Crcmmcr (31) has in There is a lively controversy among patholo dicated that about 20 per cent of all crocidolite gists regarding the requirements for establish production in South Africa actually comes from ing the diagnosis of primary mesothelioma (34). mines located in the Transvaal, a few hundred Not only is there a question ~wjth respect to miles from the Northwest Cape. He also indi the histologic criteria, but even more important, cated that although the exposure mev have been the necessity for establishing by autopsy somewhat less intense in these mines than in whether the tumor is prims r. -r secondary. those of the Northwest Cape, it neverthelea was 472 OEOROE W. TnuanT hiph. The writer'* inquiries confirm this and Tbe question of whether there is a tolerable indicate further that the mines of the Trans exposure or threshold limit value for asbestos vaal have been in operation for as many yean without contracting an enhanced risk of de as those in the Northwest Cape. The mechanism veloping mesothelioma has been raised by the for obtaining data regarding mesothelioma finding of what, on first inquiry, seemed to be in the Transvaal crocidolite area is identical minor exposures to the fiber in nonoeeupati^r-sJ to that for the Northwest Cape. Because not a settings ss a background for same of tbe cases single ease of mesothelioma has been discovered of mesothelioma reported in South Africa i.iff) from the crocidolite mines or surrounding cam- and the United Kingdom (33). Although origi munities of the Transvaal, although 51 eases nally it had been thought that there were many have come from the crocidolite mines and 52 such examples of mesothelioma developing out additional eases from the neighboring commu side an occupation or occupation-associated en nity in the Northwest Cape producing exactly vironment, better and more complete exposure the same kind of fiber, the contention that histories reduced this proportion greatly. At crocidolite per se causes mesothelioma becomes present, 80 per cent or more of the mesothe difficult to accept. Suia-Crtunmer (31) pointed liomas thus studied in the United Kingdom out this paradox in 1954. Webster (36), in his and South Africa have been shown to have an current report on asbestos exposures in South occupational or paraoccupational association Africa, likewise calls attention to this disparity. with asbestos fiber. The level of this exposure It is of equal interest that only 3 cases of is substantial. Most cases occurring outside mesothelioma have been reported as originat actual "on the job occupational exposure" occur ing from the Transvaal, these being from the through an exposed worker living on the same amosite asbestos mines (36). No cases of premises, who brings fiber into the home on his mesothelioma have been reported from the clothing, or through contamination of the chrysolite mines of the Transvaal. On the basis environment surrounding an industrial opera of what is known about the number of tion which has cast airborne fiber into tbe persons employed, the intensity and duration of atmosphere for years and thus exposed persons exposure, plus - lapse time, one would expect living or working in such a neighborhood. This far more than 3 cases of mesothelioma if was especially exemplified in the Northwest amosite bad the same potential as the factor Cape region of South Africa where roads were musing mesotheliomas in the Northwest Cape. The dosage and particle site have not been sufficiently different in the Northwest Cape and Transvaal to explain the striking absence made of asbestos-bearing waste rock, where women were employed in hand cobbing or in gleaning asbestos fiber from the waste heaps, and where the mill disseminated blue fiber quite or minima] occurrence of mesotheliomas in widely around its location. There is reason to the Transvaal. believe that these various types of exposure The discovery of such a striking concentra have been substantial in tbe population thus tion of mesotheliomas in the Northwest Cape suggests the need for a thorough study of the differences between this region and other areas of South Africa in terms of possible etiologic factors. That something other than, or in ad dition to, asbestos plays a role in mesothelioma involved during the past 40 years. With respect to neighborhood or panioccuns- tional exposure to asbestos in the UK., it is of interest that Borrow and co-workers H7) called attention to the fact that none of tr.cir scries of mesothelioma, gleaned from a com formation seems inescapable. Tbe geology and munity medical practice, fell into this eate^ climate of the Northwest Cape differs con siderably from that of the Transvaal. Trace metals, chemicals, or oils adsorbed ODto asbes tos may be factors. If crocidolite is impli cated, it is likely to be in tbe role of & co carcinogen, some additional agent providing the gory of exposure. Is it reasonable to believe that the cases of mesothelioma in which no occupational or paraoccupational asbestos exposure can be dis closed, amounting to les than 20 per cent of those reported from the United Kingdom and difference between the experience of the North South Africa, in fact represent a reaction to west Cape and the Transvaal. Much more study the casual exposures which might be experi needs to be made of this aspect. -- enced by the public at large7 In the United is a tolerable rfor asbestos I-risk of deraieed by the seemed to be noeeupationa] e of the eases h Africa (36) hhougb origire were many weloping outassociated co ilete exposure i greatly. At the meaotherd Kingdom u to have an ' J association this exposure rring outside txjsure" occur od the same : home on his tion of the istrial opereber into the Dosed persons jorhood. This ie Northwest *e roads were rock, where ebbing or in waste heaps, oe fiber quite is reason to of exposure sulation thus paraoeeupae U5., it is workers (37) rone of their Tom a eom0 this eate- tbe cases of onal or paracan be dia per cent of kingdom and reaction to t be expert1 the United ASBESTOS AND Kingdom, where an intensive search for meso thelioma has been pursued actively during the These structures have been assumed by many to past four jeara, fewer than 100 cases thus far represent coated asbestos fibers and, therefore, have been discovered in perrons who have not to indicate an exposure to the inhalation of as had a known substantial exposure to asbestos bestos fiber, hence a higher riak of developing (33). If one adds to this a portion of the 132 mesothelioma. Several facts mlLitat- '.gainst eases about which there was no information, this conclusion. ~ the number of perrons who have not had a The coated fibers found in the hir..--? of the discoverable substantial exposure, but in whom public have not been proved to be asbestos a mesothelioma has developed, is less than 200. fibers. When they are found in persons who I This number is such a minuscule proportion have experienced a heavy exposure to the in of the adult population from which the eases halation of asbestos fiber, it is reasonable to were gleaned that it becomes difficult to en assume that the bulk of these bodies do tertain the view that the asbestos fibers that represent asbestos fiber. It has been shown, may be in the air and respired in a casual fashion by the public at large pose a genuine carcinogenic threat. If one postulates that there are respirable sized fibers of asbestos in the ambient air breathed by the general public, the strikingly rare occurrence of mesothelioma not related to occupation strongly suggests that there is a tolerable level of airborne asbestos fiber which does not cause an undue risk of development of mesothelioma. The findings of Newbouse (13) and McDonald and associates (35), which indicate that a genuine occupational exposure to asbestos has been tolerated without evi dence of an increased risk of developing a mesothelioma, suggest that the tolerable level however, that other materials which are fibrous in nature will produce bodies of an identical appearance (41). Cralley and as sociates (42) have listed 20 mineral materials that are fibrous in cature and that may be widely disseminated in the environment of the general public. Because of the numerous other types of fibers that may, and almost cer tainly do, gain access to human lungs wbere they become coated with an iron-protein com plex, Gross and co-workers (43) suggested the term ferruginous bodies for these structures and suggested that they be called asbestos bodies only when it is known with certainty, or can be presumed on the basis of known is substantial. The evidence strongly favors the exposure, that the central fiber of the body is concept' that the casual exposure of the gen in fact asbestos. This would appear to be a far eral public has not exceeded such a level in more accurate designation and scientific atti the past. tude than to insist on calting all of these ' Ferruginous (asbestos) bodies. In epite of the bodies asbestos bodies whether or not they foregoing considerations, additional develop ments have caused some investigators to suggest that an epidemic of mesotheliomaa will occur among the general public in the near future (38). This apprehension is bssed on the finding of Thomson and associates (39), confirmed by several others, that structures identified as being similar to asbestos bodies (commonly seen in persons known to have an intensive exposure to asbestos fibers) are found in 25 per cent or more of the adult general public by direct examina tion of lung tissue or of the juices pressed from such tissue. The frequency of occurrence of these bodies in the lungs of the genera! uublie appar ently depends upon the volume cf lung tissue examined and the intensity with which the are known to be such. The literature concerning ferruginous bodies has become quite large, and sweeping infer ences from their presence in the general pop ulation have been made (33, 44). Without attention to the necessary quantitative and qual itative factors, it has been predicted that the experience of the general pubbe with respect to mesothelioma will parallel that which has thus far been disclosed in certain very specific occupational and paraoecupatiooal settings. A number of facts indicate a great need for cau tion before arriving at such a serious con clusion. To transfer the experience of a specific occupational or paraoccupational population to search is made, because Utidjiar --d co-workers the general public requires evidence that the (40) report that in their sen- ->st 300 per exposure of the public does, in fact, eorre- 474 OEOHQE W. WBIOUT pond to those populations in which an in ruginous bodies is necessary before any mean creased risk of mesothelioma is said to exist. ingful interpretation of their importance for This is especially true now that it has been the general public ean be made. demonstrated that there are some occupational The finding of ferruginous bodies in a large populations in which the exposure to asbestos proportion of the general population has led fiber exceeds many fold that of the general public to the contention that the augmentTM: use of and in which no evidence of an unusual asbestos in the manufacture of prod icts has mesothelioma risk was found (13, 22, 35). What greatly increased the degree to which -je gen is the present situation in this regard 7 eral public has been exposed to tbs fiber. As indicated in foregoing discussions, con This assumption has been based upon the clusions with regard to the relationship be simple statistic of asbestos consumption, with tween mesothelioma and asbestos fiber per se, no attention being paid to bow the fiber is even in an occupational setting, are rather un used nor the degree to wbieb its ultimate certain at this time. The roles of types of fiber, fabricated form would lend itself to dissemi cocarcinogcnesis, and dosage are so far from nation of fiber among the public (30). Al being clear in these special occupational set though it is possible that augmented consump tings as to give little assurance that they can be tion of asbestos fiber led to a greater output transferred in any meaningful way to the of these fibers from factories into the air sur nonoccupstional related or general public popu rounding the factory, this does not constitute a lations. gencralixed public environmental exposure. Although a scant number of ferruginous Tabershaw (45) has pointed out that asbestos bodies has been demonstrated in lungs from is used for the most part in fabrication of the general public, there has been no demon materials that are unlikely to become air stration that these are in fact the result of borne. It is not widely appreciated that the ' exposure to asbestos fiber rather than to one bulk of the products using asbestos actually or more of the many other materials known bind the fiber firmly in the product, aDd there to be capable of producing ferruginous bodies. is subsequently very little opportunity for re At this time, the determination of whether the lease of this fiber except by slow wear of the fibrous core of a ferruginous body is in fact products. asbestos is extraordinarily difficult and quite The estimated consumption of asbestos fiber beyond the means of other than the most in the UI3. has increased from 125,OCX) short sophisticated laboratories. In spite of this, the tons in 1918 to 720,000 in 1905; most of the necessary investigation must be done before increase occurred after 1940* Once the fiber, the contention that all ferruginous bodies in the in the form of a product, is put into place, general public are in fact asbestos fibers can it is not released except by gradual wear, which be accepted. in most examples is minimal. During factory Quantitative estimates indicate that the processing, the public at large is not exposed. number of ferruginous bodies found in the During the use of certain products, such as lungs of the general public is a small fraction insulation removal and application, fibers are of the number found in the lungs of those released and those in the immediate vicinity, who had been occupationally exposed. If one workmen and public, may be expo'-d. This accepts the contention that ferruginous bodies category of product can be thought of as reflect asbestos exposure, one must conclude having fibers that are "loosely bound," in con that the general public has had far less ex trast to such products ss asbestos cement or posure than those persons in occupations us floor tile which actually incorporate the fibers ing asbestos fiber. That some persons with and bind them very tightly. The quantity of known occupational exposure to asbestos fiber asbestos fiber used for "loosely bound" products, appear to have but few ferruginous bodies including insulation (figure 1), has increased complicates an interpretation of 'ruantitative from 39,000 only to 55,000 short tons between measurement of ferruginous bodies, it is clear 1920 and 1965.' that much more comprehensive and reliable The commercial grade of fiber indicates the data with regard to the dymur.es and the kind of products in which it will be used quantitative and qualitative a:'-~".' of fer * Pundaack, F.: Personal communication ASBESTOS AND HEALTH IK 1909 PLAINTIFF'S EXHIBIT /sasc/) r any nusnortuM for U. S. A. IMPORTS CHRYSOTILE ON l_Y grin-a large Son' has led rated use of products has licli the gen a this fiber, d upon the mption, with the fiber is its ultimate : to dissemie (30). AJrd eonsumpcuter output the air sur * - constitute a d exposure, that asbestos lbrieation of become airted that the stos actually ct, and there unity for re wear of the I I Fic. 1. Amount of ehrysotile asbestos (short tons) used in the TJ. S. during 1930 to 19G5, according to the grade of fiber. Longest fibers are grade 3 and shortest are grade 7. "Loosely bound" products include insulation and other materials that may release fibers during use, installation, or removal. -sbestos fiber 125,000 short most of the ee the fiber, t into place, I wear, which iring factory : exposed, acts, such as n, fibers are iate vicinity, rpoaed. This ought of as rad," in con 's cement or ite the fibers quantity of ad" products, lie increased tons between indicates the ill be used stioa. That most of the augmentation of consump tion of ehrysotile has been in grades 4, 6, and 7 (especially 7) is shown in figure 1. Grade 7 goes predominantly into asphalt and vinyl floor tile which usually has a life of 20 to 25 years or more before it is changed, as a result of decoration alterations rather than wear. The bulk of grades 4 and 6 goes into asbestos cement products, especially asbestos cement pipe, in which the replacement time is indefinite--systems now in use are more than 30 years old. Air contamination does not occur from this source. Although there may be some weathering of asbestos cement shingles and siding, the rate of wear is very alow. It can readily be seen that although there has been an augmented utilization of asbestos fiber, tbe largest fraction of it haa gone into strongly bound products designed to last many years. Tbe wear from these products is also far less than tbe total product by the time the ma terial is discarded. Asbestos forms an essential part of friction materials. Concern has been e.rr\re*sed that the public is exposed to large quantities of asbestos fiber liberated by the wear of automobile brake linings. This is unwarranted. The amount of asbestos fiber used in friction material in the UjS. was estimated at 33,000 tons, less than 5 per cent of the total in 1965.* Studies of the ma terial released during the use of brakes (46) demonstrated that the high heat of frietion destroys the asbestos converting it to an amorphous material no longer having the char acteristics of asbestos. Of the total materials removed from brake linings durirr their use, less than 5 per cent appears as actual asbestos. The amount of asbestos fiber released by normal friction material wear must be small indeed. . The fibers that might be released from all kinds of wear either become intimately bound with the soil or are captured in either rain water or in water used for cleansing. Ultimately the fibers are distributed predominantly where water ia distributed. A study of river water has shown that asbestos fiber is almost universally present although in quite amall amcuuts. Bow \ - PLAINTIFF'S EXHIBIT /&SO) 476 OEonoE w. Tnuoirr TABLE 1 of fibers in the genera) environment as a result Amount or Comutrcial Talc Used rom Various of wear. It is obvious from these data that Products in thx D.B. (Short Tons in 1967) commercial talc provides a potent source at Total U_S. consumption OrArnica Paint Hoofing Insecticides Paper Refractories Rubber Toilet preparations Other 820,000 220,000 163,000 72,000 69,000 45,000 41,000 81,000 28,000 167,000 least equivalent to that of asbestos for supply ing respirable-sized fibers that could produce ferruginous bodies. It is difficult to eonec'-r of a better way of having fibers inhaled than the use of cosmetic talcum powders. In tre gard, it is of interest that Avril and Champeix (49) found no ferruginous bodies in 138 autopsies in France. It is claimed that the cosmetic talcum in France has no fibers.* The Total O.S. consumption of asbestos in 1965 was extent to which other mineral or vegetable 720,000 abort tons. fibers known to be present in the environ ment of the general public may contribute much of this comes from wear of products and to the production of ferruginous bodies is as how much from leaching of soil is of course yet unknown. not determined. The concept that asbestos is Data have been reported recently by Sclikoff indestructible is fallacious, and the belief that and Hammond (50) showing that the frequency it accumulates on the surface of streets and of occurrence of ferruginous bodies is essen other places seems ill-founded. tially the same in lungs obtained by autopsy in The possibility that sources of fiber other 1934 as in 1967, a finding difficult to reconcile than commercial asbestos may lead to ferrugi with the contention that the augmented use of nous bodies must be considered. Talc is a asbestos during the past 35 years has greatly form of magnesium silicate that exists in sev- enhanced the exposure of the general public * era! forms, has large industrial use, and com to asbestos fiber. It also raises the question of monly is contaminated by fibrous substances whether the fibers in these ferruginous bodies such as tremolite and even chrysotile. It should are in fact asbestos. A similar study in Grest be noted that talc production has been shown Britain failed to demonstrate any ferrugi to cause pulmonary fibrosis and possibly in nous bodies in lung samples obtained at ne fluence the development of bronchogenic can cropsy in 1936 or in lung samples from fe cer (47). As shown in table 1, the consumption males autopsied in 1946 (51). Although they of commercial talc in the U.S. exceeds that may have been fewer than now, there surely for asbestos. Attention to some of the products must bsve been potent sources for the dissemi made suggests that the opportunities for air nation of both tale and asbestos in Great borne talc dissemination may have been aug Britain before 1936 and 194G. mented to an even greater degree than has The previous findings provide little or no asbestos. Cralley and associates (48), in an evidence to suggest that an epidemic of assessment of 22 cosmetic talcum powders mesothelioma among the public at large is to purchased in the U.S., found that an average be expected. In a more positive way, th- data of 20 per cent of the particles were fibers. from South Africa indicate that during the past These fibers are fully capable of producing five or six years the number of new cases of ferruginous bodies in the experimental animal. mesothelioma have been rather constant at It is of interest to note that the amount of approximately 20 per year, and in Great commercial talc that ultimately finds its way Britain (33)* only a moderate increase has into toilet preparations is far in excess of the been shown. amount of asbestos used in the manufacture Although the study of ferruginous bodies of insulation materials. Insecticide preparations is of interest, the necessity for the central consume a larger tonnage than all of the un core to be identified and for quantitative data bound kinds of asbestos fiber put together. to be obtained in order that more meaningful Rubber, which utilizes a large amount of com conclusions be reached about their import mercial talc, may contribute to the discharge `Avril, J.: Personal communication. . )l u i result a&vdit-i that at * source it fer:supplymitf produce a ecDcejve of Jed than the In this re ad Champeix dies in 138 ed that the fibers.' The or vegetable the environv contribute bodies is as . y by Selikoff he frequency ies is esseny autopsy in . to reconcile tented use of : has greatly meral public : question of rinous bodies idy in Great \ny ferrugiined at neles froto feIthough they there surely the dissemias in Great little or no epidemic of . I large is to ay, the data ring the past sew eases of constant at d in Great increase has rnous bodies the central tilative data : meaningful heir import PLAINTIFF'S EXHIBIT , 0Z5O3) ASBESTOS AND HEALTH IN 10G9 suggests that this is an area of study with epidemiologic point of view it is proper to i diminishing returns. A direct approach to the consider these findings as evidence of asbestos more easily identifiable naked fibers contained exposure. in the lung would appear to be a more fruit Long-term implications of pleural plaques are ful avenue of search. Still better would be a a matter of interest. In general, unless the direct approach to the types and amounts of thickening of the pleura is ertci-cve, the ef fiber present in the ambient air of the various fects of this patchy thickening on various as environmental locations that are of interest pects of pulmonary function are 'rinimal or with respect to occupational, paraoccupational, absent/ There is no evidence that me presence and genera] public exposure. Although this of pleural plaques connotes anything with re would pose the disadvantage of not giving spect to the ultimate development of mesothe information with regard to long-term past ex lioma. In fact, two of the geographic areas posure, there is equally no guarantee that in which the largest concentrations of pleural ferruginous bodies truly represent the complete plaques have been reported, Finland (52) and history of past exposure. The direct approach eastern Quebec Province,* do not have a to the study of fiber populations in the ambient demonstrated excessive frequency of mesotbe- air would have the advantage of telling us JionwrTo use the presence of pleural plaques what the conditions are for the public at as a marker of previous asbestos exposure is ent. of limited value, in view of the fact that other Pleural plaquex: Attention has been directed toward another phenomenon said to be the result of past exposure to asbestos fiber. Since the first recognition that prolonged inhalation causes lead to this condition and especially in view of the fact that the absence of plaques in no way connotes the absence of absestos ex posure. of asbestos fibers might in some persons lead to diffuse pulmonary fibrosis, clinicians have been aware that areas of thickening of the pleura occur in some such ]>ersons. At times, this thickening is localized loading to the ap pearance of plaques, some of which may be calcified. The pleura effects tange all the way The relationship between asbestos and health of humans, as renewable in 1969, indicates that serious exposures to asbestos fiber can occur in certain occupational and immediately ad jacent environments. Fortunately, the con from minimal findings to extensive and bizarre, centration of asbestos fibers in these settings irregularly shaped, calcific masses. Pleura] can be controlled. Tbe environment of the in plaques with or without calcification are a sulation workers is more difficult to control matter of considerable interest at the present than the more fixed and permanent environ time. Unexpectedly, these manifestations are ment of the factory and associated neighbor often absent in persons who bave well-developed hood. An approximation of the concentration diffuse pulmonary fibrosis resulting from pro of respirable-sized asbestos fiber that can be longed exposure to asbestos fiber, and they tolerated without the risk of pulmonary fibrosis may be very extensive in persons with little or has been achieved. There is reason to believe no diffuse fibrosis. In fact, rather extensive that this concentration will also minimize the pleural plaques have been reported as being risk of pulmonary malignancy including meso common in large populations not direetly ex thelioma. Because of the Jong tune lapse as posed occupationally to asbestos, but living in sociated with the development of malignancy, or near the region where asbestos fiber is being longer periods of observation are desirable for a produced or used (52). There are, of course, final decision on this point. There is reason to other causes for pleural plaques and calcifi believe that the occupational use of asbestos cation, and, in some instances, it is unwise to fiber can achieve the same degree of safety as ascribe these findings to the inhalation of the use of explosives, radiation, and beryllium, asbestos fiber. In a geographic area where although extensive alterations may be required asbestos fiber is known to be present in con in the control of production and manufacturing, siderable concentration in the ambient air, there is every reason to believe that from an * Beeklake. M.: Personal eommuni&itjoo. * Cartier. P.: Personal communiutioc. ; PLAINTIFF'S | EXHIBIT | 112503) 478 CEOROE W. WEIGHT the containment of asbestos fiber so that cone escapes to the outside, and the proper disposal of solid wastes containing the fiber. . The risk to the general public posed by the (13) Nrwhouae, M. L.: The mortality of asbestos factory workers. Proceedings of the Inter national Conference on Pneumoconiosis, Department of Mines, Republic of South Africa, 1969, to be published. mostly intermittent exposure to the low con (14) Enterline, P. E. and Kendrick, M. A.: centrations of asbestos likely to be present is the ambient air has been exaggerated beyond the limits imposed by known facts. Research to develop the necessary additional information Asbestos dust exposures at various levels * and mortality,, Arch. Environ. Hc-ulq, (Chicago) 1967, JS, 181. (16) Maneuao, T. F, and El^Atlar, A. E.: Zsi- cinogenie risk and duration of employment upon which appropriate and realistic measures among asbestos workers. Proceedings of the for safe use of asbestos fiber can be taken should be the goal in the next few years. 2nd International Conference on the Bio logical Effects of Asbestos, 1968, in press. (16) Selikoff. I. J, Hammond, E. C, and Churg. (Received for publication July JO, JBS9) REFERENCES J.: Mortality experience of asbestos insula tion workers. Proceedings of the Inter national Conference on Pneumoconiosis, (1) Spefl, S, and Leinweber, J. P.: Asbestos Department of Mines, Republic of South minerals in modem technology, Environ. Africa, 1969, to be published. Res, 1969, t, 166. (17) Balzer, J. L, and Cooper, W. C.: The work (2) Murray, H. M.: Report of the departmental environment of insulating workers, Amer. committee on compensation for industrial Industr. Hyg. Aasn. J, 1968, t9,222. diseases, Her Majestys Stationary Office, (18) Harries, P. G.: Asbestos hazards in naval London, 1907. dockyards, Ann. Occup. Hyg, 1968,11, 135. (3) Merewetber, E. R. A, and Price, C. W.: (19) Cralley, L. J, Keenan, R. G, and Lynch, J. Report on effects of asbestos dust on the R.: Exposure to metals in the manufac lungs and dust suppression in the asbestos ture of asbestos textile products. Amer. . industry. Her Majestys Stationary OfiPee, Industr. Hyg. Aasn. J, 19G7, t8, 452. London. 1930. (20) Cralley, L. J, Kienan, R. G, Eupel, R. E, - (4) Sayers, R. R, and Dreesen, W. C.: Asbeslosis, Kinser, R. E, and Lynch, J. R.: Char Amcr. J. Public Health, 1939,19,205. acterization and solubility of metals asso (5) Knox, J. F, Holmes, S, Doll, R, and Hill, ciated with asbestos fibers, Amer. Industr I. D.: Mortality from lung cancer and Hyg. Assn. J, 1968, t9,509. other causes among workers in an asbestos (21) Selikoff, I. J, Cburg. J. and Hammond, E. textile factory, Brit. J. Industr. Med, 1968, C.: The occurrence of aabestosis among in t, 293. sulation workers in the United States, Ann. (6) Committee on Hygiene Standards of the N. Y. Acad. Sci. 19G5. lit. 139. British Occupational Hygiene Society: Hy (22) Kiviluoto, R, and Meurtnan, L.: Results of giene Standards for Cryaotile Asbestos asbestos exposure in Finlnd, Proceedings Dust, Pergamon Press, Long Island City, of Internationa] Conference on Pneumo New York. 1968. " coniosis. Department of Mines, Republic (7) American Conference of Governmental In of South Africa. 1969. to be published. dustrial Hygienists: Threshold Limit (23) Braun. D. C- and Truan. T. D.: An epi Values of Air-Borne Contaminants, demiological study of lung cancer in asbes A.C.GI.H, Cincinnati, 1968. tos miners. A.MA. Arch, lodust. Health. (8) Timbrell, V.: The inhalation of fibers, Pro 1958,17, 634. ceedings of the International Conference on (24) Vigliani, E. C, Ghetri, I, Marantana. P, and Pneumoconiosis, Department of Mines, Peroia, &.: Epidemiologies! study of Republic of South Africa, 1969, to be asbestos workers io northern Its.;, Med. published. Lavoro, 1968.69,481. -. (9) Wagner, J. C,, and Skidmore, J. W.: Asbestos (25) Selikoff, I. J. Hammond, E. C, and Churg. dust deposition and retention in rats, Ann. J.: Asbestos exposure, smoking and neo N.Y. Acad. 8d, 1965, ISt, TJ. plasia. J.AJdA. 1968. tOt, IOC. (10) Lynch. K. M, and Smith, W. A.: Carcinoma (26) Gross, P, de Treville. R, Tolkcr, E, Kas- of the lung in aabesto-silicosis, Amer. J. Cancer, 1935, U, 66. chak. M. and Bab.vak, M.: The develop ment of lung cancer in rats with pulmonary (11) Merewetber, E. R. A.: Aabestosis and car deposits of chrysolite asbestos dust. Arch. cinoma of the lung. Annual Rerort of Chief Environ. Health (Chicago). 1967, IS, 343. Inspector of Factories. 79 Her Majestys (27) Miller, L, Smith, W. E, and Berliner, S. Vi.: Stationary Office.London, 1947. Tesla for effect of asbestos on benzo (a) (12) Doll, R.: Mortality from luce cancer in pvrene carcinogenesis in the respiratory asbestos workers, Brit, J. In :ui'r. Med, tract. Ann. N. Y. Acad. Sci, 1965, lit. <S9. 1955, It, 81. (28) Harington. 1- S_ Roe. F. J. C, and Waiters. I< islity of asbestos og of the Inter Pneumoconiosis, rpublic of South winch. ' M. A.: il various level* Jjviron. Health, tar, A. .: Car > of employment roeeedingi of the ace oa the Bio1963, in press. . C, and Churg, asbestos insula- of the InterPneumoeoniosis, nublie of South . C.: The work worker*, Amer. S9, 222. izirds in naval 1968,11, 135. . and Lynch, Ji the maouiaceoducta, Amer. 28,152. . Kupel, H. E,, . J. R.: Cbarof metali aasoAmer. Induxtr Hammond, E. >si* among ind States. Ann. c. . L.: Result* of d. Proceedings on Pntumomes, Republic ublished. . D.: An epitncer in asbesodust. Health, mans. P_ and el study of t Italy, Med. and Churp, mit and neo- ncr. E. KaeThe deveJopth pulmonary dust. Arch. 3907, 16, 343. rimer. S. W.: so bemo (a) r respim ton1965. ;i*. 189. and Walter*. ASBESTOS AND HEALTH IN 1969 479 M.: Studies of the mode of action of R.: Ferruginous bodies in human lungs, asbestos a* a carcinogen, S. Air. Med. J. Arch. Environ. Health (Chicago), 19CS, 17, 1967, it, 800. 327. (29) Wagner, J. C.: Some pathological aspects of (41) Gross, P,, de Treville, R, Cralley, L. J, and ssbestosis in the Union of South Africa, Davis, J, M. G.: Pulmonary ferruginous * Proceedings of the Pneumoconiosis Con bodies. Arch. Path. (Chicago). 1968, 85, ference, 1969, Johannesburg, Little, Brown 539. and Co, Boston. 19G0. (42) Cralley, L. J, Keenan, R. C, Lynch, J. R, (30) Gilson. J. C.: Health hazards of asbestos: and Lainhart. W. 8.: Source s-.J identifica Recent studies on its biologies! effects, tion of respirable fiber*. Amer. Industr. Trans. Soc. Oceup. Med, 1965, IS, 02. Hyg. Assn. J, 1968,29, 129. (31) Sluis-Cremmer, C. K.: Asbestoses in South (43) Gross. P, CrmlJey, L. J, and de Treville, R.: Africa, certain geographical and environ "Asbestos bodies": Their nonapediidty, mental considerations, Ann N. Y. Acad. Amer. Industr. Hyg. Assn. J, 1967, 25, 541. Sd, 1965, IS!, 215. (44) Sdikoff, I. J, Bader, R. A, Bader, M. E,, (32) Cbabot, J.: Primarv tumor* of the pleura Churg, J, and Hammond, E. C.: Editorial: and cancer* of the lung and pleura related Asbestos and neoplasia, Amer. J. Med, to asbestos, Poumon Coeur, 1968, 25, 487. 1967, ii, 487. (33) Gilson, J. C.: Asbestos health hazards, recent (45) Tabcrabaw, 2. R.: Asbestos as an environ- observations in U. K, Proceedings of mental hazard, J. Occup. Med, 1968, 10, Internationa] Conference on Pneumo 32. coniosis, Department of Mines, Union of (46) Lynch, J. R.: Brake lining composition prod Soutb Africa, 1969, to be published. ucts, J. Air Pollut. Constr. Asa, 1963, IS, (34) Cluckman, J, and Hurwitz, M.: Problems in 824. the diagnosis of primary diffuse malignant (47) KJeinfeld. M, Messite. J, Kooyman. 0, and mesothelioma and its relation to asbestos, Zaki, M. H.: Mortality among talc minere Proceedings of International Conference on and millers in New York Stale, Arch. Pneumoconiosis, Department of Mines, Environ. Health (Chicago), 1967,14, 663. Union of Soutb Africa, 1959, to be pub (48) Cralley, L. J, Key, M. M, Grolb, D. H, lished. Lainhart, W. S. and Ligo, R. M.: Fibrous (35) McDonald, A. D, Harper, A, El Attar, 0. and mineral content of cosmetic talcum A, and McDonald, J. C.: Epidemiology producta, Amer. Industr. Hyg. Assn. J, of primary malignant mesotbeLial tumors 1968,29,350. in Canada, Proceedings of International (49) Avril, J, and Champcix, J.: Results of Conference on Pneumoconiosis, Department asbestos exposure in France, Proceedings of Mines, Republic of South Africa, 1969, of International Conference on Pneumo to be published. coniosis, Department of Mines, Republic of (36) Webster. 1.: Asbestos exposure in South South Africa, 1969. to be published. Africa, Proceedings of International Con (50) Sslikoff. I. J. and Hammond. E. C.: Asbestos ference on Pneumoconiosis, Department of - bodies in the New York City population in Mines. Union of South Africa, 1969, to be two periods of time. Proceedings of Inter published. national Conference on Pneumoconiosis, (37) Borrow, M, Conston, A, Livornese, L,, Department of Mines. Republic of South Moolten, S. E,, and Scbalet, N.: Africa. 1969, to be published. Mesothelioma associated with aabeatosis, (51) Poolcv, F. D.. Oldham. P. D, Chang-B.vun. JAJdA, 19G7, tOl, 587. Um. and Wagner, J. C.: The detection of (38) Thomson, J. G.: Asbestos and the urban asbestos in tissues. Proceedings of Inter dweller, Ann. N. Y, Acad. Sd, 1965, 1SI, national Conference on Pneumoconiosis. 196. Department of Mines, Republic of South (39) Thomson, J. G, Kaachula, P. R, and Mac Africa, 19G9, to be published. ~ Donald, R. K.: Asbestos as a modem (52) Raunio. V.: Occurrence of unu*-ial pleural urban hazard, S. Afr. Med. J. 1963, 57, 77. calcification in Finland, Ann. Med. Intern. (40) Ulidjian, M. D, Gross, P, and de Treville, Fean. 1966,55 (Supplement No. 47).