Document BR7qEENzxgLw4bMQYLo7dxvNE

FILE NAME Owens Corning OC DATE 1935 Jan 4 DOC OC002 DOCUMENT DESCRIPTION US Treasury Dept Report - Effects of the Inhalation of Asbestos Dust on the Lungs of Asbestos Workers U.S. TREASURY DEPARTMENT HENRY MORGENTHAU Jx Secretary PUBLIC HEALTH SERVICE HUGH S. CUMMING Surgeon General INHALATION EFFECTS OF THE OF ASBESTOS DUST ON THE LUNGS OF ASBESTOS WORKERS ee BY e A. J. LANZA e Assistant Medical Director we WILLIAM J. McCONNELL ere Assistant Medical Director wes AND teee J. WILLIAM FEHNEL Chemist Metropolitan Life Insurance Co. a ee REPRINT No. 1665 FROM THE PUBLIC HEALTH REPORTS VOL 50 No. JANUARY 4 1985 Page 1-12 | CORNING FIBERGLAS CORP | LEGAL & PATENT DEPT REC'D SEP 15 1941 REC'D UNITED STATES GOVERNMENT GOV GOVERNMENT ERNMENT PRINTING OFFICE : WASHINGTON 1985 er PLAINTIFF'S EXHIBIT a For mal by the Superintendent of Documents Washington D. eo ne ec ; uwaane STATEfiINTERNATIONAL .t EFFECTS OF THE INHALATION OF ASBESTOS DUST ON THE LUNGS OF ASBESTOS WORKERS oan <n A Preliminary Study % By A. J. LANZA Assistant Medical Director WILLIAM J. MCCONNELL Assist ant Medical Director and J. WILLIAM FIENEL Chemist Metropolitan Life Insurance Co. INTRODUCTION In 1929 the Metropolitan Life Insurance Co. was approached by officials representing the asbestos industry in the United States who were desirous of ascertaining whether asbestos dust was an occupational hazard 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 time several articles had 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 such occupational disease refrenc The hazard of silica dust with special reference to the lungs has long been appreciated and a great deal of study and research has been applied to the problem in the metal mining and certain other industries in Great Britain the United States the British Dominions and in other countries The nature of the effects of silica dust expressed in the term silicosis with the resultant extraor- dinary predisposition to pulmonary tuberculosis is well known These effects 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 silicates still a fertile field for investigation but evidence is accumulating that certain of these dusts produce pathological results quite distinct from true silicosis asbestosis pneumoconiosis pneumoconiosis The name asbestosis has been applied to the pneumoconiosis caused by asbestos dust and it will be so used in this report Chem- . ically the 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 are present in small quantities This commercial variety of t _ S ni mai stations ardua lolil ena Sihe ngte dor| EFFECTS OF ASBESTOS DUST ON THE LUNGS 2 encountered is designated as chrysotile and asbestos most commonly of the mineral serpentine in which it is one of the four varieties usually occurs in seams silicosis and presumably asbes- It should be borne in mind that 15 and even 20 or 25 ! tosis develops very slowly taking from 5 to of progress is influenced to become established This rate receive and this dos- *mainly _g years by the dosage of silica which the lungs amount of silica in three variables age in turn depends upon dust in the air and the length of exposure ~ the dust the quantity of included as a fourth variable idiosyncrasy might be in those Individual little is known of the variations in susceptibility however well be assumed that similar variables exposed to dust It might would influence the occurrenicsemoifneadsbeosrtofsaibrsicated in North America In places where asbestos the clear clinical picture there does not appear to be present with true silicosis hazard ,. which is so unescapable in communities a be that some of the mining communities It may of a such as hard of too recent origin for the typical effects plants are would asbestos manifest but this not apply to the silicate dust to become =~ older mines or to all of the fabricating plants the Metropolitan Life Insurance The industrial health service of during the period from CCo.o. undertook the following investigation * October 1929 to January 1931 wihn iacshbeisntcolsumdiendes aand nd mills in Canada United 1. study of dust conditions Atlantic Seaboard in the in fabricating plants along the . and workers Sta2t. ePshysical examinations of asabestos sbestos workers including ray 3. study of dust exhaust systems designed to eliminate asbestos extensive included in this study and the fabricating plants only are are Data on A B C D and E. This is a designated in the report as plants of the asbestos industry are extensive study preliminary report A more asbestos is now under way =, cf oF ee "| ., ot Oo, DUST STUDIES| a we ace ates 8 ' . and methods of sampling the impinger 1 and collection Apparatus used for the of air samples the electric precipitator 2 were and in close proximity to the workmen for dusts at the breathing levels are adapted for this work as they Both of these forms of apparatus and adjusted for the taking of the are transportable easily set up extremely efficient ee air samples at the proper level and are aspirating the air and then impinging The impiitngoenrtocoallfelcatts stuhrefacdeusctovbeyred by a liquid in a caolncothaoilnetro entr 50 percent iTmhpiengilnigquid used was distilled water containing eee me SRT FELT AN aS ale DCE. Ghia pla Met et NEN inig at bis : EFFECTS OF ASBESTOS DUST ON THE LUNGS 3 prevent the solution of some of the dusts particularly any silica which might be present The impinger was actuated by an electri- cally driven rotary pump and the rate of air sampled was measured by means of a resistance type of flow meter with an inclined manome- ter for measuring the pressure difference Each sample represents the dust collected from a volume of 100 cubic feet of air precipitator The electric is designed upon the Cottrell precipitator principle used for recovering dusts and fumes commercially This particles principle depends on electrifying the dust by making them pass through an electrostatic field and thus causing them to settle out upon a sheet of celluloid The electrostatic field is set up by means of a transformer operating from the lighting lines on 120 volts alternating current Air is drawn through the 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 ceiling also were secured for chemical analysis All samples were shipped to the industrial hygiene laboratory of the Metropolitan Co. and the dust counts were made according to the methods accepted by the United States Bureau of Mines and the United States Public Health Service 1 Particles in size up to 360 microns in the greatest diameter were counted Chemical analyses were made for total free and combined silcasilica according to the accepted standard method of Hillebrand 3 In the first plant studied A only particles 10 microns and under in size were counted It has been demonstrated repeatedly that no silica particles exceeding 10 microns a micron equals millionth part of a meter or thousandth part of a millimeterin greatest diameter enter the lung tissu; for this reason the larger particles usually are not considered when determining dust counts Latears it appeared from some of the published articles 4 English that asbestos particles much larger in size were found in lung tissue it was all decided to count all particles and make differential counts of 10 microns and under those Total particles per cubic foot and the corresponding weight of the dust in milligrams were obtained Since no relationship between the dust counts and the corresponding weights was found the weights ; are not included in the tabulations in this report plants Table 1 shows by and by departments the maximum and minimum dust counts in million particles per cubic foot of air Although the counts in plant A are of particles 10 microns and under Samples collected by both the impinger and the electric precipitator were counted In addition microphotographs of these dust particles were anlarged by being projected a scresca ren an with a lantern- slide projector the enlarged particles being measured with ruler Knowing the antire anlargement by actual measurament It was ossy to calculate the original particle size 5 By the use of Hasan's 8 Joga libmic micrana probability paper the logarithms of the function to be measured in this cas ae plotted as ordinates against the probability of occurrence as abecisuse *@, ie word OKT a orn FSS Fa aed AROSHAW ) Sl Soe 4 EFFECTOSF ASBESTOS DUST ON THE LUNGS anidn the other plants are for all particles direct comparison is as in no sample taken were the number of particles 10 EP possible and under less than 94 whole microns percent of the oe e . .. .. fs. . . 1S Doge nthe cubic foot FP Maximum TABLE and minimum dust counts in million particles per . of air by plant and department ar) . | rat | Plant A Plant B Plant Plant | Plant TH : Motoo Million |Million Millas | e e | Nam- Num Nuo partic Million Num Million . Num Millas of Milion Milion Department pari under | t partpier ber plas part of ber of cles ber of ber of plas cod O 83.30- PA cubic cuhic | Flee cubic cuble PALL 10 per | | | | | t | | cubic foot of cubic foot of of of ples ples foot Flee foot plas taken taken taken | foot of Ale Biz taken ae foot air ME air |. air CEA Preparation 8] IH 9 2 88 en 0 i 43 MEA Card room . spinning 3] keln $ 4h 6 | 844-154 844-154 2. afew ewan 88 % Ring spinning ea frame nning....ssce. DOANN I Mulespinning .. Twisting . Felt department Sheet insulating DOANN Sah! se 30 Yh}... 0 Spa1r7 me RN 21645-7 6-10 6-10 8 - hp 11645-7 DOANN 410-2 | ( 44 03-10 03-10 03-10 15 3 - 3 110}+-10M DOANN ce H OPPS EEO ees Ste DN SEES Se Sans Snneen DOANN H ace celeccwcce|ccwccce|sceccccna|scccnns|ccnncces[onncccalacccccves Molded brake band and clutch a lecc cee e|-cacccec|concecclecnccncc|scnennc[ocacccnce 2354 2354 + Included in spinning Includes broad loom weaving Whereas the dust in the preparation room is practically all due to asbestos the contrary is the case in the other departments .In the carding spinning and weaving rooms asbestos comprises about 25 percent of the material used On special jobs the percentage of asbestos may be higher but in general the figure quoted is approximately correct the other material consisting principally of cotton In the insulating departments of plant A asbestos is but 5 percent of the total material used In the molded lining and clutch division of plant D asbestos comprises about 25 percent of the total material The actual exposure to asbestos dust therefore is considarably less than is indicated in the dust counts in table 1 IN THE PLANTS CONDITIONS 1 The processes in these plants were very similar to those in in cotton millsin For illustration the process in length preparation general the of planBtis here detailed at emptied floor Asbestosis receivedin bags es These are are upon the room and the asbestosis shoveled into pug mills and run for about 5 minutes in order to crush and open the fibera From there the asbestos is shoveled into trucks and wheeled to hoppers with either horizontal After for vertical openers similar to those used in textile mills passing through the opener the material is discharged into trucks Waste fi machine tan ma mecfin mhiawie me ep ntorial in fast mercer thmuch a2 zemet zemet machine and ; H oF ae a Cyd . MIetme r * A ary ty Lu i R 9 ned + eae EFFECTS OF ASBESTOS DUBT ON THE LUNGS er discharged into trucks which are wheeled to the openers and the material is fed into these in the same manner as is the new material After being discharged from the opener the material is put onto a vibrating or shaking screen where the long fibers 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 either sold as such or used in making an asbestos cement The cotton is received in bales opened and also run through vertical openers It is discharged into trucks The filled trucks from the vertical and horizontal openers containing either the asbestos fiber the cotton or the waste material are taken to separate storage bins As needed these materials are weighed and dumped onto the floor in proportion to the mixture desired and the resulting mixed materials are then passed through a mixing picker As this mixture is discharged from the picker it is sprayed with a light mineral oil storage The material is then taken by a mechanical conveyor to the bin in the card room Two of these mixing pickers discharge onto this conveyor system while a third machine is equipped with a suction device which conveys the material to a storage bin in the card room The object of the two systems is to facilitate the handling of two grades of material at the same time The third machine is not equipped with an oil spray The object of the oil spray is primarily to entrap the small asbestos fibers and hold them enmeshed in the cotton fiber throughout the processes of carding spinning and 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 the time it reaches the looms the oil had diminished to less 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 E oil was not used nor was there any attempt at humidification or any system of dust exhausting Carding machines were fed by hand In plant A there was a humidifying ventilating and beating system while plant B depended on natural humidity In plant E the carding machines were equipped with a exhaust system but it was not efficiently used In plant C carding was done in 2 buildings 1 of which was equipped with conditioning system and in both buildings the machines had exhaust equipment Two plants B and C had artificial humidity installations installations in their spinning rooms In the former the temperature was 76 F. relative humidity 78 percent One plant C had a humidification system in the twisting department and also in the weaving department where the relative humidity was 76 percent with a bulb temperature of 69 F. as compared with a relative humidity of 44 percent in the weaving room of plant A. i bs RAR . 21a yom ae Ra MPRA 8 By 4 Be Ped | oes 4 1 ? ptt se ERTS LF arO s eESPe ATER Nt Poh . ope a # PBS, 9, 4 6 EFFECTS OF ASBESTOS DUST ON THE LUNGS . Aside from plant E it would appear that the dust hazard was hot [3 The te" excessive except in the preparation rooms of plants and dust counts are interesting too when considered in the light of th United ) particles wae. permissible standard for gran7 ite ndaumsetlyesatabboluitsh1e0d mbiyllitohn e States Public Health Service js justified 7 microns and under per cubic foot However we are not asbes E:4~ 10 that because available information suggests that threshold of 3. in assuming disease clinically than silicosis the 'tosis is a milder Asbestosis appears to be patho permissible dust counts is higher far does not logically different from silicosis and the experience so asbestos asbestos to define a standard of dustiness for warrant an attempt fod ACH wee. dust DUST CONTROL an et sutee., exhausts Ea? Various measures such as oiling humidification and local that ss tended to reduce the dust Nevertheless it was evident they exhauexshaus experimental were only partly successful If it is expected to control dustinessexhaus final reliance must rest upon properly constructed eer these plants an installs 22% equipment In plant C in one department equipment c tion was set up spite of some obvious faults this percent =: the basis of comparative dust counts reduced the dupsetrcbeynt50effective 2% be and with further alterations will probably 75 2 reduction seemed quite satisfactory It is neither In this case such a desirable to install such equipment =: practicable nor economically mechanism normal defensive mechanism will make the air entirely dust free The | mechanism of the body takes care of a fair amount of atmospheric pollution is when the body is exposed to an excessive amount of dust - defense mechanism breaks down involve The application of exhaust equipment to textile machinery involve where the construction of the plant fi Oa cisonssuicdhertahbalteitdiisffnioctulptoysseisbpleecitaollaypply down suction to the loom It is desirable to install exhaust apparatus in any plant on an count 3 basis first and then check its efficiency by dust count perimental will result in saving a needless expenditure of money This practice a. PHYSICAL EXAMINATIONS ee working A films were made of 126 persons 108 men 18 women working _ ray - in the United States All but five of these wer G in asbestos plants examination The cases were selected more or less given physical those having more than 3 years employ at random from among obvious that the early diagnos ment in the industry It was soon of of asbestosis must rest to a laorfgesielxitceonsits otnhercaliy nicapliscytmuprteosms tUhe chest As in the early stages the asbestos workers were usually indefinite and inconclusive The of these films are based on the readings of one con con interpretations have been reviewed by petent roentgenologist but they EFFECTS OF ASBESTOS DUST ON THE LUNGS 7 others experienced in this field The differences of opinion were of a minor nature and there was general The films were read agreement as to interpretation conservatively taking into account the physical ee subdivided into doubtful and whether the individuals classed negative Only time can tell as doubtful are progressing toward & definite asbestosis Particular attention or absence of indications was focussed on the presence reviewers of the of tuberculosis and in this respect all the films were in accord With the of silicosis in mind it was felt that a great dealunohfacpaprye esxhpoeurlidenbcee devoted to ascertaining if possible whether or not asbestosis disposes to tuberculous infection ; pre- The cases of asbestosis were divided into two and second stage classes first stage The first stage embraces those who show by ray examination definite lung pathology sufficient in extent to warrant a diagnosis of pneumoconiosis but who have no definite symptoms The second cases exhibit more extensive lung pathology and also definite symptoms extensive pulmonary involvement and marked or total disability they would have been classifipehdysaiscatlhidridsasbtilaigtey but no such cases were found Of the total of 126 ray examinations 4 were second asbestosis 63 as first diagnosed as negative degree 39 as doubtful and 20 as There is a definite increase in the in relation to the percentage diagnosed as positive years of exposure as shown in table 2. Small ennutmebresrisntmo atkhies iitncirmepaossesible to determine how far the factor of age TABLE Classification of cases by years of exposure . Years of exposure years... ee. Over 18 30 to 18 years 5 Cnder Cnder years eee Cnder & years Total axamined es . eeeee. . . peeee : . oes "2 tima 4. gs . 9 One asbestos worker second stage retired of to this study but is still active about his bis garden . own Percentage Number Debuu - Positive | Debuu { Negative 6889 6889 6889 6889 - 27856 27856 . 27856 27856 1 3 P 16 a : 13 3 a 2 .o "20 1 not continnom fy Feta old egs sccord because of old egs old egs 10years Se, 8 EFFECTS OF ASBESTOS DUST ON THE LUNGS Of the 64 persons given physical examination and diagnosed as having positive asbestosis only 8 were entirely free from symptoms while 10 out of 37 with doubtful and 7 out of 20 with negative diagnoses were free from symptoms Dyspnoea and cough were the symptoms most complained of but none of these cases exhibited the furgent or evident type of short wind seen in true silicosis Several of those classed as negative stated that they were short winded and were so recorded but too much emphasis should not be placod on statements of subjective symptoms During the progress of the study physicians who were practicing in the communities 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 The incidence of tuberculosis based upon ray films is given in table 3 40 of the 67 examined had less than 15 years of employment in the industry TABLE Incidence of tuberculosis Poullive | Doabthl | Negative Tuberculosis baalo~ 954 Tuberculosis active -08 2 ee rer eeee Total . 954 -08 1 et examined 954 -08 4) This case was diagnosed as probably active on the ray Bndian Table 4 gives information as to physical signs of chest trouble Table Chest findings chest . . . ....... ....... cress -eeee examined Physical signs of No physical signs Not trouble 11... ....... ....... Total Total SP .... esas woae - of * At least 6 of these showed no evidenos associated with asbestosis 12 these not associated with usual algas found with asbestosis 6 of these not associated with usual signs of asbestosis Positive | Doubtful Negative 12 a 3 C 9 a7 3 13 3 9 ) soot oe . and What significance if any can be attached to the presence of asbestos corns on the hands of workers appears doubtful as 18 percent of the positives 12 out of 64 15 percent of the others doubtful 7 out of 37 negative 2 out of 20 showed such corns Each roentgenologist who reviewed the ray films called attention to the fact that these films indicated a very unusual incidence of enlargement of the heart It is probable that this is a compensatory enlargement due to the additional work put upon the heart in efforts EFFECTS OF ASBESTOS DUST ON THE LUNGS 9 to pump blood through the fibrosed lungs It is possible that not sufficient attention has been paid to the effects of the pneumoconioses upon the heart Many workers had changed from one department to another and from one plant to another during their years of employment in the asbestos industry Since only the amounts of dust collected at the time of this survey in the various departments are known there is no way of knowing the average amount of dust in the atmosphere inhaled by these people over the years of their employment Consequently it is not possible to correlate individual cases with definite amounts of dust exposure INSURANCE CLAIMS To throw light on the relationship between asbestosis and pulmo- nary tuberculosis an analysis of death claims and total and permanent disability claims was made in regard to companies carrying group insurance and having available figures There were 2,099 lives involved with a total exposure of 7,019 life- years The death claims are so small in number that reliable con- clusions cannot be reached from any subdivision of the figures same is true of the sickness claims under health insurance The The number of claims for respiratory diseases is high in two of the plants studied but low for the others as compared with the Metropolitan experience of 1927. However during the latter part of 1928 and the first part of 1929 there was an epidemic of influenza The records of one establishment plant B showed that 6 of 36 death claims and 8 of 10 permanent and total disability claims were listed as due to pulmonary tuberculosis This appeared to be an inordinate amount of tuberculosis from this plant However many of the employees were Negroes and also tuberculosis claims are generally high in this section of the country Realizing the difficulty in diagnosing pneumoconiosis and the tendency to confuse it with tuberculosis these claims were studied individually The physicians who had treated the individuals were interviewed and the hospital and sanatorium records including available ray films were investigated with the following resulta Death claims intestinal 1. A typist not exposed to dust died of pulmonary and intestinal tuberculosis 2. Colored male age 27 worked in asbestos 1 year and 8 months died of pulmonary tuberculosis following a hemorrhage was in sanatorium 10 months Also had a four plus Wasser- mann , No evidence of asbestosis ve . ' 7 3. Colored male age 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 - 10 EFFECTS OF ASBESTOS DUST On the LUNGS 4. Colored male age 34 worked in asbestos plant 2 years and physician 6 months His believes this plicated tuberculosis Was not was a case of uncom- inmate No information could be of hospital or sanatorium ! obtained on the other two cases Total and permanent disability claims * * ; 1. Male in asbestos plant 3 years His physician employed states that he first came under his observation with an old estab- lished case of tuberculosis about 2 years after asbestos employ- ment glandsstarted Also bad tuberculosis of the kidney and cervical glands - 2. Male employed in asbestos plant 8 months His physician states finding of old fibroid tuberculosis with tubercle bacilli in sputum No ray available but according to physician as- bestos bodies were found in sputum 3. Male 10 years employment . Two physicians who treated him at different times are now inclined to believe this man is not tuberculous but has asbestosis 4. White male was reexamined at time of investigation His physician reports well nourished busky looking good color no cyanosis no clubbing of fingers diminished expansion incessant cough ray shows fine mottling disseminated through both lungs No evidence of tuberculosis . Probably a second stage asbestosis in 5. White male 13 years asbestos ' plant Is now in . sanato- rium An interesting case His physician states that he has tensive asbestosis and pulmonary tuberculosis cavity in ex- right lung sputum loaded with tubercle bacilli and asbestos bodies believes tuberculosis long antedated asbestosis This patient is progressing in a satisfactory manner : It was not possible to locate the other three cases of total and permanent disability who had been diagnosed as having pulmonary tuberculosis On the basis of the information obtained the deaths in claims cases appear to be due to uncomplicated tuberculosis three of them were Negroes who were probably tuberculous at ; the time their employment in the asbestos plant commenced Of the 8 disability claim cases I was uncomplicated tuberculosis and 2 were uncomplicated asbestosis who were put on disability because of a mistaken diagnosis of tuberculosis In this same com- munity we know of one death due to uncomplicated asbestosis in an individualwith many years employment in the industry _ CONCLUSIONS silicosis 1. Prolonged exposure to asbestos dust caused a pulmonary fibrosis of a type different from silicosis and demonstrable on ray films Clinically from this study it appears to be of type milder than enlargement cardiad ae - 2. Cases of definite cardiad enlargement were frequently / frequently found to * Personal communication 7 EFFECTS OF ASBESTOS DUST ON THE LUNGS it 3. A EFFECTS to tuberculosis to predisposition predisposition predisposition predisposition asbestos asbestos was not not due indicated this study study in this , indicated Asbestosis observed observed in series cases had not resulted resulted in marked marked disability disability disability case case . asbestosis add to the mortality mortality 6. not practicable practicable dust content content . dust in the air the asbestos be amount dust asbestos plants studied can RECOMMENDATIONS It is recommended It recommended recommended recommended seriously face the That the problem dust dust control in physically physically asbestos asbestos plants employees be examined That new employees employees and rejected for including ray examination examination pneumoconiosis employment they they show tuberculosis tuberculosis employees pneumoconiosis examined but 3. That every employes years this examination examination preferably every year examination to include X ray The authors wish wish aided The making this express their sincere thanks to officials and emstudy possible especially the officials extent aided ployees of asbestos companies who extent ployees and every facility facility cooperated Dr. Pancoast Pancoast the University University securing data also and Dr. valuable advice in interpreting Pennsylvania interpreting films for and his interest Meriwether Meriwether United United States States Health Service and Dr. surgeon V. Meriwether United United States surgeon surgeon Picher of Okla whose inter- H. Fellows Fellows of New York Dr. Dr. Paul Quebec Snoke Lancaster Pa Dr. H. Stevenson of Danville Danville Canada Canada Dr. L. U. Gardner Gardner undertaken Donald Saranac Saranac Saranac Laboratory Laboratory Laboratory who have undertaken undertaken 12 EFFECTS OF ASBESTOS DUST ON THE LUNGS through animal experimentation with the aid of a grant from the Metropolitan Life Insurance Co. REFERENCES 1 Greenburg Leonard and Bloomfield J. .: The impinger dust sampling apparatus as used by the United States Public Health Service Pub Health Rep vol 47 no 12 Mar. 1932. Reprint no 1528 7 2 Drinker Philip and Thomson Robert M Determination of suspensoids by alternating precipitators Jour Ind Hyg vol VII no 6 June 1925 , 3 Hillebrand W. F The analysis of silicate and carbonate rocks United States Geological Survey Washington D. C. Bull 422 4 Cooke W. E Pulmonary asbestosis Brit Med Jour Dec. 3 1927 5 Green H A photomicrographic method for the determination of particle size of paint and rubber pigments Jour Franklin Institute 1921 pp 192 637 6 Whipple G. C Vital statistics John Wiley and Sons New York 1925 P. 451 ] . 7 Russel A. E. Britten R. H. Thompson L. R. and Bloomfield J. J The oe health of workers in dusty trades II Exposure to siliceous dust granite industry Pub Health Bull No. 187. 1929 -- et 6 erateore a Cm