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PLAINTIFF'S EXHIBIT U.S. TREASURY DEPARTMEl T KZNBT UOUGESTHAU. J. fcmfarr PUBLIC HEALTH SEP.VICE BUCK I. CtmtONC. fw* Cnml I EFFECTS OF THE INHALATION OF |j ASBESTOS DUST ON THE LUNGS ij OF ASBESTOS Y/ORKERS j| sr A LANZA AuuUni Mtiieal DineUr william j. mcconnell . AttitlenS UtHtai DirttUr AKD J. WILLIAM FEHNEL Ckmui . LittnfliUx Lift Inturuut Ca> BZFBINT No. IHi non w PUBLIC HEALTH DEPORTS VO. H,m.Uuun <IM (*oi-U3 ' !i t_>- f r . ./ * / 4- EFFECTS OF THE INHALATION OF ASBESTOS DUST ON TILE LUNGS OF ASBESTOS WORKERS . A PrtllraUu7 Sledr ' By A. Z. LaXxa, Attitlatu Medical Dirtdtr, Wtccum J. McCox.veia. AttitU ant Altdicai Dirtttar, and J. Wilujui Fcuku. Ctumui, Mttrapaltian Ufa Intlinnet Cf. ZXTBODUCTION' In 1939 the Metropolitan Lifo Insurance Co. was approached by officials representing tho esbesios industry in tho United States, who were desirous of ascertaining whether asbestos dust was an occupa tional baxard in their establishments and, if so, what was the nature of this hazard and what should be done to prevent or control it. About this timo several articles bad appeared in English medical journals describing a pneumoconiosis due to asbestos dust. While in one or two isolated instances the occurrence of`this type of pneumo coniosis had been described in American journals, the industry itself appeared to be quite uninformed of the existence of any ouch occupational disease. The hazard of silica dust, with special reference to the lungs, has long been appreciated, and a great deal of study~arid researeh has boon applied to the problem (in the metal mining e:id certain other industries) in Great Britain, the United States, the British Do minions, and in other countries. The nature of the ejects of silica dust expressed in the term "sSkosis", with the resultant extraor dinary predisposition to pulmonary tuberculosis, is well known. Those ejects have been associated with the inhalation of dust con taining free silica in varying amounts. The effects upon the pul monary tissue of dusts containing combined silica--silicates--are still a fertile field for investigation, but evidence is accumulating that certain of these dusts produce pathological results quite distinct from true silicosis. The name "asbestosis" has been applied to the pneumoconiosis caused by asbestos dust and it will be so used in this report. Chem ically, tho asbestos of commerce is a hydrated magnesium silicate consisting primarily of silica (combined silica) 44.1 percent, mag nesia 43 percent, and water 12.9 percent, while ferrous iron and nickel an present in small quantities. This commercial variety of uwi*-M ' , x '* loi ters or asbestos dust os lttsgs _. . * * r. - . j ' | 1 , :. !' asbestos most commonly encountered is design 'ed as clirysotile and is ono of U>e four varieties of the mineral * roentino, is which it usually occurs in seam*. . It should bo borne in mind that silicosis (a. i presumably asbes- losio) dorclops very slowly, taking from 5 to 15 and even 20 or 25 years to becomo established. This rato of progress is influenced mainly by the dosage of silica which the lungs receive, and this dos age,' in turn, depends upon threo variables--tho amount of silica in the dust, the quantity of dust in tlic air, end tho length of exposure. Individual idiosyncrasy might bo included as a fourth variable; howover, little is known of the variations in susceptibility iu those exposed to dust. It might well bo assumed that similar variables would influence the occurrence of nsbestosis. In places where asbestos is mined or fabricated in North America there does not appear to be prcecnt the clear-cut clinical picture which is so uncseapable in communities with a true silicosis hazard, such ee herd-rock mining communities. It may be that some of the asbestos plants oro of too recent origin for the typical effects of a silicate dust to become manifest, but this would not sppiy to the older mines or to ail of the fabricating plants. Tbs industrial health sorties of tho Metropolitan life Insurance Co. undertook the following investigation during the period from October 1029 to January 1031, which included: ' 1. A Study of dust conditions in asbestos mines and mills in Canada and in fabricating plants along the Atlantic Seaboard in tbs United States. 2. Physical examinations of asbestos workers, including X-ray films. ' 3. A study of dust exhsust systems designed to eliminate tabestoe dust. Data on the fabricating plants only are included in this study and are designated in the report os plants A, B, C, D, and . This is e preliminary report. A more extensive study of the asbestos industry is now under wey. . BUST STCBtZS j " Ajiparaivs end nuihedt of sampling.---Both the tmpinger (1) and .^tho electric precipitator (2) were used for the collection of air samples jf for dusts at the breathing levels and iu close proximity to the workmen. '* Both of these forms of apparatus ore adapted for this work, os they . am transportable, easily set up and adjusted for the taking of the i sir samples at the proper level, and am extremely efficient, i i The impiager collects the dust by aspirating the air and than : | impinging it onto fiat surface covered by e liquid in a container. I The liquid used was dietflled water, containing 50 percent alcohol to I i ii 9i itt i 1 l V. V t l I i i zrrxcrs or assssros dost ojt 7W- uxnsos $ prevent the solution of tome of the dusts, p: ieularly ny silics which might be present. The impiugcr was ic ated bp an electri cally driven rotary pump and tire rate of air sa pled was measured by means of a rcsistnneo typo of flow meter with an inclined manome ter for measuring the pressure difference. Each sample represents the dust collected from a volume of ICO cubic feet of sir. Tlio electric precipitator is designed upon tho Cottrell precipitator principle used for recovering dusts and fumes commercially. This principle depends on electrifying tho dust particles by making them pus through an oleotrostuiic field and thus eaukiug them to sottle out upon a sheet of celluloid. Tlio electrostatic held is set up by means of a transformer operating from the lighting lines on 120 volts, alternating current. Air is drawn through tho apparatus by a small rotary fan, run by a motor, the quantity being measured by a flow meter. ( Samples of dust brushed from beams and pipe lines near the cdling alsowere secured for chemical analysis. All samples were shipped to the"Industrial hygiene laboratory of the Metropolitan Co., and the dust, counts were mode according to the metlx*Is accepted by the. United States Bureau of Mines end the United State* Public Health Scrvico (1). Particles in size up to 300 microns in the greatest diameter were counted. -. Chemical analyses were made for total (free and combined) silica according to the accepted standard method of JTiUcbrud (3). In the first plant studied (A) only particle* 10 microns and under in size were counted. It ha* been demonstrated repeatedly that no silica particles exceeding 10 microns (a micron equals one-millionth part of a motor or ono-thousandth part of a mfilimotcr) in greatest diameter enter the lung tisau ; for this reason, the larger particles usually ore not considered when determining dust counts. Later, as it appeared from some of the published articles (4) (English) that asbestos particles much larger in size were found in lung tissue, it was decided to count all particles and make differential count* of all those 10 microns and under.1 Total particles per cubic foot and the corresponding weight of the dust in milligrams were obtained. Since no relationship between the dust counts end tho corresponding weights was found, the weights arc not included in the tabulations in tliis report. Table 1 shows by plants end by departments the maximum sad minimum dust counts in million particles per cubic foot of air. Although the counts in plant A are of particles iu microns and under, > Sampiai aaUaau* kr knk Om Tr*n- as* ika ttmuu pnSkttaw van analit ta aSSluaa, WaaPaipprppka at Ikapt 4mt mitbm --n nkiras kr kafes pMaoa* apaaaanaaa vlttalaaun- aWapmaacar. ika aattfaS saMdaa katas aananS vttkanilaa. S~vt*Lb,aatkaitSma(ST pcmI PiOTwmO, a an aapy ap nkmlaaa aka artpaat partial# an tp. Sr k *s aT Buu'i (0 taaais>>ata paakaUMw paraa. Wa lapaaukw at ika taaaUaa la ka saaaanS Ok UU naa kiiraaal an ` 4 unni cur xsncrros dust ox t. h luvoi ad is tho oilier plants are for all particle*, direct comparison is possible, as in no sampto taken were the nv:.ibcr of particle* 10 microns and under less than 04 percent of th<- whole. ` . TaSU 1.--Afoa'ieum and nuiuaiwm (fv rmini* in wiftfton particles per cubic foot / air, bn plant and department Plast A nw* PltsiC | MatD nut c Pumuiin MRUm Xum* Mura* beral STAram* toftaka parti* rter aaarr Matte? CUlM total Mum* Ural UK* I tafean Miiiiaa l*sri cu* per UIhC tot a atr NU*urmW> cam* pirn taaca MftlJas |Wll* T*r cae total ur Num* Ur at Mm* luu MiRtaa ur uf t.Mli pin cubic f rr total mate MT total MRUaa hnt* cin ftef cubic total atr mi air _________ Crrt ream....--.......... JtMC llWM ipiMUf Mate tfMMMC......... Wranas--.......... ... Tea crrwt meat....... Uaid*! mm Mad aad ddU|M.MMNM HmetuOed k ipusial H-mj t i tletod8U!. 4 -- to* UMh t H-i 0> to 5i S 1 ItoUii 3 in- iW DfM j ---------- \ -- aa ~T "itoio" Ft" i P>4to r MtoiHi S H-N -- 'tesfuea IraUiwa smia*. Whereas the dust in the preparation room is practically all .due to asbestos, the contrary is tho caso in the other deportments. In the carding, spinning, and wearing rooms asbestos comprises about 25 percent of tho material used. On special jobs the percentage of asbestos may be higher, but in general the figure quoted is approxi mately correct, the other material consisting principally of cotton. In the insulating departments of plant A, asbestos is bat 5 ptrcsnt of the total material used. In ths molded brake-lining and dutch division of plant D, asbestos comprises about 25 percent of the total material Tho actual exposure to asbestos dust, therefore, is consid erably less than is indicated in the dust counts in table 1. COKStTIOKS IK TSt PLANTS The processes in these plant* were very similar to those in cotton mills in general. For illustration, the process in the preparation room of plant B is here detailed at length: ' Asbestos is received in bags. These art emptied upon the floor and theSsbcstos is shoveled into pug mills and run for about 5 minutes in order to crush end open the fibers. From there ths asbestos is shoveled into trucks and wheeled to hoppen with either horizontal or vertical openers, similar to those used in textile mils. After passing through the opener, the material is discharged into trucks. Waste manufacturing material is first run through a garnet machine and ir7xcn or asusros bust os u.e lvsos 5 discharged into truck*, which aro wheeled to the openers, and the material is fed into these in the same manner is the new material. After being discharged from the opener, tho ateriel is put onto a vibrating or shaking screen, where the long f.-ers are picked off by a suction hood and blown into a bin to be used again in textiles. The short fibers falling through the screen are cither sold as such or usc'd in making an asbestos cement. , ' The cotton is received in boles, opened, and also run through vertical openers. It is discharged into trucks. The filled trueks from tli* vertical nr.il hnrixontnl openers containing either the ssbestoe fiber, the cotton, or tho wasto material are taken to separate storage bins. As needed, these materials arc weighed and dumped onto tho floor in proportion to the mixture desired, and iho resulting mixed materials are then passed through a mixing picker. As this mixture is discliergcd from tho picker, it is sprayed with a light mineral oil. The material is then taken by a mechanical conveyor to Lite storage bin in the eard room. Two of theso mixing pickers discharge onto this conveyor system, while s third maehino is equipped with s suction doviee which eonvet's the material to a stonge bin in the card room. Tho object of tho two systems is to facilitate tho handling of two grades of material at tho same time. Tho third machine is not equipped with an oil spray. Tho object of the oil spray is pri marily to entrap the email asbestos fibers and hold them enmeshed in the cotton fiber throughout the processes of carding, spinning, end weaving. Incidentally,, it is apparent that it also diminishes the amount of dust. The material is saturated with about 4 percent of oil at this point; but by tho time it reaches the looms, the oQ had diminished to leu than 1 percent. - While mineral oil was used in the preparation room of plant C, it apparently was not as efficacious as in plant B. In plant oil was not used, nor wss there any attempt at humidification or any eystem of dust exhausting. Carding machines were fed by hand. In plant A there was a humidifying, ventilsting, and heating system, while plant B depended on natural humidity. In plant E the carding machines wore equipped with s dust-exhaust system, bnt it was not efficiently used. In plant C cording was done in 2 buddings, 1 of which was equipped with an air-conditioning system, and in both buildings the machines had exhaust equipment. ' Two plants, B and C, had artificial humidity installations in their pinning rooms. In tho former the temperature was 76* F., relative humidity 78 percent. One plant, C, had a humidification system in tbs twisting department and also in tht weaving department, where the relative humidity wss 76 percent with a dry-bulb temperature of 69* F., si compand with a relative humidity of 44 percent in the weaving room of plant A. '6. ZTTZCZS OT ASBESTOS D"ST OX THi. UTXGS Aside from plant E, it would Appear that the !ust hazard was not excessive except in the preparation rooms of pi its B and C. The dust counts arc interesting, too, when considers ; in the light of tho permissible standard for granite dust, established by tho United States Public Health Service (7), namely, shout 10 million particles (10 microns and undor) per cubic foot. However, we are'not justified in assuming that because available information suggests that asbestosis is a milder diseaso clinically than silicosis, the threshold of permissible dust counts is higher. Asbestosis appears to bo patho logically different from silicosis, and tho experience ao far docs not werrnnt an attempt to define a standard of dustiness for asbestos dust. non coxtbol Various measures, such ss oiling, humidification, and local exhausts, tended to reduce the dust. Nevertheless, it was evident that they were only partly successful. If it is expected to control dustiness in these plants, find reliance must rest upon properly constructed exhaust equipment. In plant C in ono department an experimental installa tion was set up. In spite of aomo obvious faults, this equipment, on tbo basis of comparative dust counts, reduced the dust by SO percent and with further alterations will probably be 75 percent effective. In this esse such a reduction seemed quite satisfactory. It is noither practicable nor economically desirable to install sueh equipment as will nuke tho air entirely dust free. The normal defensive mechanism of the body takes care of a fair amount of atmospheric pollution. It is when the body is exposed to an excessive amount of dust that this defense mechanism breaks down. The application of exhaust equipment to textile machinery involves considerable difficulty, especially where the construction of the plant is such that it is not possiblo to apply down-draft suction to the looms. It is desirable to install exhaust apparatus in any plant on an ex perimental basis first, and then check its efficiency by dust counts. This practice will mult in saving a needless expenditure of money. ran:csx zxaasranoxa . . X-ray films wero made of 120 persona (108 men, IS women) working in asbestos plants in the United States. All but five of these were given physical examination. The cases were eelected more or lass at random from among those having more than 3 years of employ ment in the industry. It was soon obvious that the early diagnosis of osbestosis must rest to a large extant on X-ray pictures of the cheat. As in the early stages of silicosis, the clinical symptoms of the asbestos workers were usually indefinite and inconclusive. The interpretations of these films are based on the readings of one com petent roentgenologist, but they have been reviewed by several Oi- ASUtifOS OS 1'ii <\JXC& ol/icrs experienced in this field. Tlio differences f opinion were of r. minor nature, and there was general agreement i to interpretation. The films were read conservatively, taking into n ount the physical examination and the age of the individual, ai were classed ns positive only when there was no major disagreement. All examiners were guided by their experience in silicosis and other types of pneu moconioses. The films olasscd ns negative for asbestosis were further subdivided into doubtful and negative. Only time can tell whether the individuals classed as doubtful are progressing toward a dcfinil e asbestosis. Particular attention waa foouased on th preenc or absence of indications of tuberculosis, and in this respect all tho reviewers of the fiims were in accord. With tho unhappy experience of silicosis in mind, it wus felt that a great deal of care should bo devoted to ascertaining, if possible, whether or not asbestosis pre disposes to tuberculous infection. The eases of asbestosis were divided into two classes, first stage and second stage. Tho first stage embraces those who show by X-ray examination definite lung pathology sufficient in extent to warrant a diagnosis of pneumoconiosis, but who havo no definite symptoms. Tho second-stage cases exhibit more extensive lung pathology and also definite symptoms. All tlicso individuals 1 were actively engaged in factory work, and it was not practicable to make any distinction on tho basis of wprking ability or disability. Had any individuals been found who exhibited extensive pulmonary involvement and marked physical disability or total disability, they would have been classified as third stage, but no such eases were found. Of the total of 12G X-ray examinations, 4 were diagnosed as sccomi-dcgrcc asbestosis, 03 os first degree, 30 as doubtful, and 20 as negative. There is a definite increase in the percentage diagnosed as positive in relation to tho years of exposure, as shown in table 2. Small numbers mako it impossible to determine how far the factor of age enters into this increase. Table 2.--Classification of casts by yean of exposure ' Years oJ upoauro Percentkce positive Positive Number Doubtful Negative 87 13 6S so 30 Voder i years...................................................................... . o 17 10 67 38 <3 3 12 20 * Part time. * 1 sot continuous. . 1 Ooe asbestos worker (second slago) roared of bU owe accord, become of old age. id yean previous to ebb study, but is still active about bis garden. _ EFFECTS OF ASBESTOS OUST OK THE 1 UKGS Of the 64 persons given physical examination .nd diagnosed as having positive asbestosis, only 8 were entirely fr from symptoms, while 10 out of 37 with doubtful and 7 out of 20 .th negative diag noses were free from symptoms. Dyspnoea and cougii were the symptoms most complained of, but nono of these eases exhibited the 'urgent or evident type of "short wind" scon in true silicosis. Several of tho.se classed as negative stated that they were "short winded" and wore so recorded, but too much emphasis should not be placed on statements of subjective symptoms. During the progress of the study, pliy*ioiiiti.i who were practicing in the ci.mniunitic* where asbestos workers lived were questioned and stated that they did not find an unusual amount of tuberculosis among these workers. The contrast between this state of affairs and that found in a community with a silicosis hazard is noteworthy. Tho incidence of tuberculosis (based upon X-ruv films) is given in table 3; 40 of tho 67 examined had less than 15 years of employ ment in tho industry- . Table 3.--Incidence of tuberculosis # Positive Doubtful Negative 71 lt 0 C7 30 20 i Thi< cue wax dU;acsel a& probably active oo lbe X-ray finding*. Tablo 4 gives information as to physical signs of chest trouble. Table 4.--Chest findings Positice Doubtful XeS(ire Phyxlm) siirns of ehost trouble..................................................... 123 JO 57 No phy.'lcti ...................................................................... . 31 2S 13 3 2 0 07 3S 2a At tent fi 'it tKevo r.o xvltltncc ttvcuiUrl with A.%ir#tosi*. 2 of the* not ft<4<v>:nre>l wliii uiunl *ieus found with asbestos!*. > 6 of these not Miociated with usual signs of asbestosis. What significance, if any, can bo attached to the presence of "asbestos corns" on the hands of workers appears doubtful, as IS percent of the positives (12 out of 64) and 15 percent of tho others (doubtful, 7 out of 37, negative, 2 out of 20) showed such corns. Each roentgenologist who reviowed the X-ray films called attention to tho fact that these films indicated a very unusual incidenco of enlargement of tho heart. It is probable that tills is a compensatory enlargement due to the additional work put upon tho heart in efforts *& OJr* Aoiu'.c>rO.S 1>CST OX THE LL GS 9 . ko pump blood through the fibrosed lungs. It is p siblo that not . sufficient attention has been paid to the oficcts of tho teumocoaioscs upon tho heart. . Many workers had changed from ono department another and from one plant to anothor during their years of employment in tho asbestos Industry. Sinco only tho amounts of dust collected at the time of this survey in tho various departments nro known, thero is no way of knowing tho averngo amount of dust in tho atmosphero inhaled by these pcoplo over tho years of thoir employment. Conse quently, ll Is not possible to eorrelatu individual Ouaci with dotlnita amounts of dust exposuro. ' INSURANCE CLAIMS To throw light on tho relationship between asbosfosis and pulmo- nary tuberculosis, an analysis of death claims and total and per manent disability claims was made in regard to companies carrying group insurance and having nvailablo figures. Thero wero 2,000 lives involved, with a total exposuro of 7,010 lifo . years. The death claims aro so small in number that reliable con clusions cannot be rcnched from any subdivision of tho figures. The same is true of tho sickness claims under health insurance. The number of claims for respiratory diseases is high in.'wo of the plants studied but low for the others, as compared with tho Metropolitan experience of 1927. However, during the latter part of 1028 and tho first part of 1929 thero was on epidemic of influenza. The records of one establishment (plant B) showed that 6 of 36 death claims and S of 10 permanent and total disability claims were listed ns duo to pulmonary tuberculosis. This appeared to be an in ordinate amount of tuberculosis from this plant. However, many of the employees were Negroes, und also tuberculosis claims are gener ally high in tliis section of the country. .Realizing the difficulty in . diagnosing pneumoconiosis and tho tendency to confuse it with tuberculosis, these claims were studied individually. Tho physicians who luid treated tho individuals were interviewed, and tho hospital and sanatorium records, including nvailnblo X-ray films, were investigated, with the following results: Death claims: 1. A typist, not exposed to dust; died of pulmopary and intestinal tuberculosis. 2. Colored male, ago 27; worked in asbestos 1 year and S months; died of pulmonary tuberculosis following a hemorrhage; was in sanatorium 10 months. Also had a four plus Wasscrmann. No evidence of asbestosis. 3. Colored male, ago 32; worked in asbestos plant 1 year and 7 months; died of pulmonary tuberculosis after 1 month in hospital. Cavitation both lungs; no evidence of asbestosis. . 'i /* i r r t tt i. r l f r 10 El-'FLCIS or ASOFSTCS i> ON liU LUNGS i. Colored umlc, ago 34: worked in ns -stos plant 2 yours and 0 months. llis physician believes thi: .vs a case of uncom plicated tuberculosis. Wes not innate c tiospital or sanatorium. No information could be obtained on t i other two cases. Total anti permanent disability claims: 1. Mule, employed in asbestos plant 3 years. His physician states that lie first enme under his ebservatiou with nn old cstab.- ' lished ease of tuberculosis about 2 years after asbestos employ ment started. Also had tuberculosis of the kidney and cervical glands. ... 2. Mule, employed in asbestos plant S months. ITis physician states finding of old fibroid tuberculosis with tubercle bacilli In sputum. No X-ray available; but according to physician, as bestos bodies were found in sputum. 3. Mnlc, 10 years' employment. Two physicians who treated birn at different times ore now inclined to believe this man is not tuberculous, but iias nsbestosis. 1. White male, was reexamined at lime of investigation. Ilis physician reports well nourished, husky looking, good color, no cyanosis; no clubbing of finger^; diminished expansion; incessant cough; X-rav shows fine mottling disseminated through both lungs. No evidence of tuberculosis. Probably a second stage nsbestosis. 5. White male, 13 years in asbestos plant. Is now in sanato rium. An interesting,*ease. His physician states that lie has ex tensive nsbestosis and pulmonary tuberculosis; cavity in right lung; sputum loaded with tubercle bacilli and asbestos bodies; believes tuberculosis long antedated osbestosis. This patient is progressing in a satisfactory manner. It was not possible to locate tho other threo cases of total and permanent disability who had been diagnosed os having pulmonary tuberculosis. On tho basis of the information obtained, tho deaths in death-claims cases eppear to be due to uncomplicated tuberculosis; threo of them were Negroes, who were probably tuberculous at tLe time their employment in the asbestos plant commenced. Of tho S disability claim eases, 1 was uncomplicated tuberculosis and 2 wore uncomplicated asbestosis who were put on disability because of a mistaken diagnosis of tuberculosis. In this same com munity we know of one death duo to uncomplicated asbestosis in an individual with many yoars' employment in the industiy.3 conclusions 1. Prolonged exposuro to asbestos dust caused a pulmonary fibrosis of a type different from silicosis and demonstrable on X-ray films. Clinically, from this study, it appears to be of a type milder than silicosis. 2. Cases of definite cardiac enlargement were frequently found to bo associated with asbestosis. _________-- Personal communication. 1.1 * .v'itf Oc Aol>K6TOo OX I'lll* <UXGS 11 o. A predisposition to tuberculosis due to asb tos dust was not indicated in Ibis study. 4. Asbestosis as observed in this series of cases id not resulted in marked disability in any ease. 5. i t- is not known how much, asbestosis may add to tho mortality of pneumonia and acute nontubcrculons pulmonary infections. 6. It is not practicable as yot to establish standards for tho asbestos dust content of sir. 7. The amount of dust in the air in the asbestos plants studied can bo substantially reduced. KECOUSI N DATIONS It is recommended-- 1. That the industry seriously face the problem of dust control in asbestos plants. . 2. That new employees be examined physically, including X-ray examination of the chest, and rejected for employment if they show tuberculosis or pneumoconiosis. 3.,That employees be examined physically, preferably every year, but at least every 2 years, this examination to include uu X-ray examination of tho chest. 4. That the industry sponsor studies on known eases of asbestosis, as well as studies on effects oi asbestosis on the heart and circulation. ACKNOWLEDGMENTS Tho authors wish to express their sincere thanks to all those who aided in making this study possible, especially the officials and em ployees of the asbestos companies who cooperated to the fullest extent and gave every facility for securing data; also to Dr. Pancoast, of the University of Pennsylvania, for his interest nnd valuable advice in interpreting X-rav films, and to Dr. F. V. Meriwether, of the United States Public Health Service, surgeon in charge of the United States Bureau of Mines Cooperative Clinic in Pichcr, Gkla., whose inter pretation of all the X-ray fdms listed in this report is followed. Ap preciation is also expressed to Dr. W. Atmar Smith, nnd Dr. Kenneth Lynch, of Charleston, S. C., for information and advice, particularly as to the pathology of asbestosis;4 to Dr. IV. 17. Wild, of Charleston, S. C.; to Dr. Joseph H. Wyatt, of Newark, N. J., and Dr. H. H. Fellows, of New York, for assisting in interpreting X-ray films; to Dr. Paul O. Snokc, of Lancaster, Pa.; to Dr. R. H. Stevenson, of Danville, Quebec, Canndu; nnd to Dr. L. U. Gardner and Mr. Donald E. Cummings, of the Saranac Laboratory, who have undertaken tho study of the pathological effects of the inhalation of asbestos dust * A*bc*:e*i* bodici io iputum *c.d hinz. By Koroetb M. Lyscb, M. t>.. tod W. Audit SxxtlLb, M. D Jour. Am. MoJ. Amc.. Au. 30,IMP, rol. Ci, so. &, pp. 359-641. Erx'ECXS Or' ASiiiiSrOS DUaT ON Til' LUNGS 12 . jj ftnimal experimentation, with tlie aid t a grant from the Metropolitan Life Insurance Co. REFERENCES m~Orccnburg, Leonard, and Bloomfield, J. J.: The iuipir.gcr dust sampling ap- ^ paralus as used by the United States Public Health Service. Pub. Health Bop-, vol. 47, no. 32, Mar. 18, 15)32. ' Reprint no. 152S. (2) Drinker, Philip, and Thomson, Robert M.: Determination of suspensoids by alternating-current precipitators. Jour. Ind. Hyg., vol. VII, no. 6, June 1023. (3) llilleUmml, W. Tho aimlynl* of silicntn nnd enrhnnnta rocks. Bull. 422, United States Geological Survey, Washington, D. C. (4) Cooke, W. E.: Pulmonary asbestosis. Brit. Med. Jour., Dec. 3, 1627. (5) Green, II.: A photomicrographic method for the determination of particle size of paint and rubber pigments. Jour. Franklin Institute, 1021, pp. 192, C37. (0) Whipple, G. C.: Vital statistics. John Wiley and Sons, Nc>v York, 1025, p. 451. ' (7) Russel, A. E., Britten, R. H., Thompson, L. R., aud Bloomfield, J. J.: The health of workers in dusty trades. II. Exposure to siliceous dust (granite industry). Pub. Health Bull. Ho. 1S7. 1020. o. v