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trccuTivt ornces UUnnKet incense Keasbey & Mattisox Compaxy manufacturers or asbestos and magnesia products simcc ibts Ambler, Pennsylvania March 8, 1943. K&M No. 2831 W. W. F. Shepherd, Ksq., Turner & Newell Ltd., Spotland, Rochdale. Lear Mr. Shepherd: Subject: Dr. Leroy U. Gardner's Asbestos Dust Experiments. Further to this subject, I now hare pleasure in handing you herewith photostat copy of Dr. Gardner's letter of February 24, 1943 to Mr. Vandiver Brown, and also copy of the "Outline of Proposed Monograph on Asbestosis." I have found this outline to be extremely interest ing. It brings out a number of important new develop ments, but we feel that reference to the question of cancer susceptibility should be omitted from the report since it is inconclusive. I v/ould appreciate receiving any comments which you may have to make concerning the enolosed outline, and also will forward you the final report as soon as received. ours sincerely, em: ck Fuel. First Follow Second Follow KEASBEY & MATTISON COMPANY 060 06 00109 The Saranac Laboratory FOR THE STUDY OF TUBERCULOSIS OP THE EDWARD L TRUDEAU FOUNDATION Saranac Lake, N.Y. February 24, 1943 I V li:al fi.'pr Mr. Vandiver Erovm Johns-Nanville Corporation 22 East 40th Street New York, New York Dear Mr. Brown: ,,. . I have at last succeeded In analyzing nost of our vpr^^tlnous experimental data end assessing the results. I realize 'that; this should have been oompleted before this, but the emergency has left me short-handed in the Laboratory and also necessitated my doing a good deal of extra traveling. I hope that the sponsors of our study of asbestosls will be oharltable and realize that the work has far exceeded its original scope. We have done over 40 different experiments, many of then divided into several parts, which Involved exposure of animals for 1 to 3 years to various duets. The business of preparing micro scopic sections and chemically analyzing the tissues on more than 600 animals has been a Job in Itself. My time for studying sections and analyzing data has been so limited that we are behind our sched ule. T have still not had time to write a full report of this work which w-ill of necessity be monographic. However, for the benefit of the contributors, I am submitting a table of contents and an an notated outline to indicate conclusions and the line of argument that will be developed. The latter Itself occupies 15 pages, but I hope they will find it sufficiently interesting to read. I shall work on the final manuscript as I have opportunity. There are a few.experiments still in progress which should be completed by the tine we are ready for them. A'he work on methods.of dust determination, I consider important enough to in clude in the study. The question of cancer susceptibility now seems more significant than I had previously Imagined. I believe I can obtain support for repeating it from the cancer research group. As it will take two or three years to complete such a study, I believe it would better be omitted from the present report. If li should become possible to make this study, I hope that I amy count on some of your members to supply me with enough pure, long fibre asbestos for the purpose. 060 06 00091 Mr. Vandiver Brown -2- February 24, 1943 Naturally, I shall welcome any critloism that you or any of the other contributors would care to offer. Should any of then want to dlsouss details, 1-would be pleased to meet with them. May I take this opportunity to thank all the sponsors through you for the support that we have had. Sincerely yours, LUG: ?.3H Leroy U. Gardner, M. D. Director 060 06 00092 OUTLINE OF PROPOSED MONOGRAPH ON ASBEST03I9 Saranac Laboratory Study underGrant from Aebestoe Association PART I HUMAN A3BESTOSIS 1 Human Pathology - a Btudy of 2S autopsy oases^Illustrated 2 X-ray Patterns in Asbestosls, Illustrated 3 Ash and Mineral Values In Hunan Asbestosls 4 Complications of Asbestosls (a) Susceptibility to Infection 1 Tuberoulous 11 Non-Tuberculous 111 Cancer of the lung 5 Disability, causes and comparison with silicosis 6 Diagnosis . (a) History of adequate exposure (b) X-ray film pattern (c) Physical examination (d) Asbestosls bodies In sputum, their significance i Dr... :........................................................... . 060 06 00093 (2) PART II Experimental Aabeatoale 1 Methods (a) Inhalation exposure to plant duata. (b) Injection Into lungs through trachea of pure minerals (o) Injection of pure minerals into other organs. 2 Species Susceptibility Man, guinea pigs* rabbits, cats, white mice and rats, dogs. 3 Peculiar Characteristics of Asbes.tosls (a) Unusual locallzalon of chrysotlle fibre In lungs. (b) Hate of resultant tissue reaction more rapid than to ouartz. (c) Reaction to chrysotlle not progressive after exposure ceases; again the reverse of the situation in silicosis (d) Asbestosls Bodies 1 Composition and methods of formation. 11 Occurence In different species. Ill Formation does not parallel development of fibrosi lv Gradual disappearance after exposure ceases. 4 Comparative Effects of Different Asbestlform minerals. (a) Canadian Chrysotlle. (b) Arizona Chrysotlle, low iron. (c) Crocldollte 1 Bolivian specimen, stiff and elastic. . li South African, soft and flexible. (d) Anthophylllte (e) Amoslte. (f.) Tremolite. 5 Effects of Control Minerals (a) Grannular Serpeatine, same ohemical composition as chrysotile. (b) Glass Wool, a synthetic silicate fibre. (c) Brucite, a fibrous magnesium hydroxide almost free of silica i 6 Chemical Composition of Asbestlform minerals In Relation to Irritation. (a) Nothing In composition correlated with relative lrritatl capacity. (b) Preliminary acid treatment 1 Hydrochloric aoid 11 Carbonic aoid ? X ic - c? 060 06 000^4  (3) (c) Effects of Aluminum 7 Physloal Properties in Relation to Irritation (a) Length of fibre (b) Effeot of Crushing (o) Heat treatment 8 Nature and Significance of Aabeatosls Body (a) Formation (b) Protective effect preventing further Irritation (o) Ultimate solubility in tissue 9 Theories of Action of Aabestiform Minerals (a) Chemical - reasons for considering invalid (b) Meohanical - experimental demonstration of. 10 Complications r (a) Infection, tuberculosis and other varieties (b) Cancer of lung - experimental data suggestive but not proven 11 Disability 12 Essential Features of Hazardous Exposure (a) Nature of dust - fibrous component and size factors (b) Atmospheric Concentrations - probably lower than for quartz i Inadequacy of standard lmpinger sampling method ' which does not collect the dangerous fibres li Electrostatic precipltatafsampllng preferable but method must be modified (c)'Duration of Exposure 13 Recommendations for a New Standard of Safe Atmospheric Con centrations of Asbestos Dust (a) The Quasi-official standard of 4 to 5 million particles per cu; ft. (b) Work upon better method of sampling ,, (c) Necessity for comparison of results with X-ray findings in employees 14 Prevention (a) Chemical means not practical 060 06 00095 (4) 1 Acidosis neoeasary to dissolve fibre in lungs worse than Asbestosis li Aluminum Therapy inapplicable ill Chief reliance still upon dust prevention with speoial emphasis upon the fibrous components P X ^ Ip ", Cc S' 080 06 00096 -I- ASBESTOSIS - ANNOTED OUTLINE INDICATING RESULTS PART I - HUMAN-ASBESTOS!8 1 Human Pathology and X-ray Patterns - Description Based upon 23 human autopsies 2 Ash ^nd Mineral Values In Human Lungs. 3 Complication of Asbestosls (a) Susceptibility to Infeotion 1 Tuberoulous- High lnoldenoe in English experience not duplicated In surveys of American Plants. Available autopsy statistics deceiving because of sel ection of material. 11 Non-Tuberoulous- The sane reason probably applies should be checked, by analysis of ab senteeism among asbestos workers. Ill Cancer of Lung Ditto, but there are now on record 10 cases of. lung cancer In asbestos workers. Compared to the total number of autopsies on asbestosls, this incidence Is excesslvf . No such frequency has been discovered In silicosis $r other forms of pneumoconio sis except^the Sohneeberg miners of radio active ores. The evidenoe is `suggestive but not conclusive that asbestosls may precipitate the development of cancer In susceptible individuals. 4 Disability Clinical experience suggests that truly disabling asbestosls is manifested' by less striking X-ray changes than a corresponding degree of silicosis. Such disability in asbestosls is due to disease within the lungs and not to secondary heart disease. As In silicosis, associated pulmonary infection increases the amount severity of the dust fibrosis with resultant accentuation of disability. There la urgent need for a careful physiological etudy of pulmonary function in asbestosls of varying severity. Undoubtedly, there are many diagnosable cases with no significant disability. 5 Diagnosis depends upon three factors. (a} History of adequate exposure, usually 6 to 6 years', some times longer, at work where both the concentration and character of the "asbestos" dust are hazardous. vc - ic 1; L') 060 06 00097 (b) Evidence of disease-tin a characteristic X-ray pattern. (c) A physical examination which reveals certain characteristic signs and nay reveal evidences of disability if present. (d) Asbestosls bodies in'the sputum are confirmatory when the -' previous factors are: all positive.' However, the bodies nay be absent,-' particularly in the absence of bronchitis'.'*# infection. : Asbestos!.) bodies unsupported by other evidence do not make} a diagnosis. Occasional ones have been found in about 15 v autopsy specimens of/persons with no known exposure and no fibrosis, probably'of inon-occupational origin. . V'-'H ':.:0 HART II Experimental Asbestosls I . Methods v' ' WMi.. (a) Inhalation Exposures .to Plant Duajfc ." Specific fibrosis'in'?;}, lungs, but no changes elsewhere. (b) Injections of - Suspension's of Purei ;Minerals into Trachea Similar results. .. iv <.,v,v v"' r':- : -/ (c) Injection of .Suspensions of Pure'Mineral into other organs Fibres dissolved; no asbestosls bodies; tissue reactionvcorv fined to phygocytosia and'encapsUlationA- Compare' the `Ar--' asbestos Cfitta of hunan-:subjects -V;.:'.';-'- rV 'sjra... II Species Susceptibility hri-: -AAAAAA ..... - \: Unlike free silica,1 asbAefslftAoSs:;doAAeAs. AnoAtf ''ApMroAd/ uce itsTspecific effeci .in any organ of any: species.}6f.-animal.'':;v:It;}eauses fi'brosis"only; J ........A- Guinea Pig 2+ 3+ - '*> -'-v ''White :-Mouse 0 - Rabbit JL -VO <* + Z vsrv snail atVPl' iaL_aabeatoa ^bodies) '*' PoS:-- `'r-0 ."4 - -' - *-<> wsm III Peculiar Characteristics .-'of Asbestosls j (a) Locallzation"of-fibrous jtalnerals of crranular dust partioles'iAMS? " V'dlffere`''from ISII, ,* AVv-?*.$r.&*,-I 'M'f 060 06 00098 -3- 1 Fibres like ohrysotile having a certain degree of flexibility and elasticity accumulate within the finest air tubes; granular dust is carried further on and is widely scattered through the ' terminal air spaces. (b) Rate of tissue reaotlon to asbestos la ouoh more rapid than to an active dust like quartz. Evidences of formation appear as soon as sufficient concentration of fibres has localized 'in epeolfio areas; with quartz, there is a latent period of months. (c) Reaction to asbestos does not progress on cessation of expos ure. Young scar tissue that may have formed, contracts and becomes more dense but the area of Involvement decreases in size. In silicosis, the .young nodules become larger after exposure oeases. (d) , Asbestoeie Bodies are a specific concommitant of this form of pneumoconiosis. They are due to a deposit of protein and iron upon the surface of Inhaled fibres. In guinea pigs'they form after about 60 days of oontact with the tissue. They are abund ant in man and guinea pigs, (See paragraph 2 above) but much larger in the former probably because the larger sized air tube admit larger fibres. In cats,- rabbits and mice, there is an atypical coating of a few of the fibres after much longer resi dence in the lunge; in rata and dogs no bodies could be dis covered. > From paragraph 2 it is apparent that their occurence does not parallel development of fibrosis. In lung injection experiment), the bodies have developed nnff-t after fibrosis ia-udall-advanced. The number of bodies seems to decrease several years after exposure ceases. i/ Comparative Effects of Different Asbestosls Minerals (a) Canadian Chrysotlle - highly irritating. (b) Arizona Chrysotlle (low In iron) equally irritating and pro duces Just.-as many asbestoeie bodies as the Canadian product with over 11 times as much iron. (c) Crocldollte - The South African blue asbestos is known to cause asbestosls. Only a limited supply of this material in pure form was available, most of it was used earlier in the work in non-productive experiments. For the later-critical Injection tests into the lungs, a Bolivian variety was substitute^ be cause of Its high purity. Its fibres were much stralghter, stiffer and more elastic than the cottony South African variety. Perhaps because of these peculiarities, It has not given reactions comparable to chrysotlle. It produced asbestosls bodies but did not localize in the terminal air tubes nor cause any fibrosis. Tests now being repeated with a typical South African crocldollte with physical characteristics simulating chrysotlle. ^ - L (c (jo) 060 08 00099 (d) Anthoohylllte - stiff, straight fibres - atypical asbestosis bodies forms slowly but no localization or fibrosis in lunge J'*V! (e) Anoslte - Ditto. (f) Araphlbole - Ditto. (g) Tremollte - Ditto but very few asbestosis .bodies Observation being continued. V Control Mineral (a) Granular Serpentine of same chemical composition as chrysotile is inert causing no fibrosis in lungs or other organs, -it attraote iron from the lungs but' of oourse, no "bodies" develop (b) Glass Wool(a synthetic silicate) fibres are not inhalabl'e from,, air-borne suspensions, apparently because of their stiffness v;' (the diameter is not responsible as some used were less .than':!!? 1 micron thick) Qn injection into the lungs, they do not ' localize in the air .tubes but are widely scattered. They cause' no fibrosis. After 3 or 4 months in eontaot with lung fluid,-' a few glass fibres take up iron but remain smooth. They never show the swollen ends and lateral projections of the true "4-^ asbestosis bodies. . ! ;,. (c) Bruclte of interest beoause it is a fibrous mineral practically free of silica (o.9^). Crystallographioally the arrangement of its $g and OH groups in each unit oell is similar to that in chrysotile. The sample used also contained about 16/ iron, pro bably from contaminating magnetite. The fibres are stiff and needle like. Observations not yet completed but after 2 months in the lungs, typical asbestosis bodies develop but there is as yet no fibrosis. fj-'he fibre are scattered .through the lung instea of being.localized Inside the terminal air tubes and tissue reactlon'.occurs around, Instead of within the tubes. VI Chemical Composition in Relation to Irritation (a) Nothing in the following chemical compositions can be cor related with variations in capaolty to provoke tissue reaction. (See Table Next Page) i I 3-(o - Is W 060 06 00100  # wSSmjEJK.l. s..>^Cral*w0P Chrys Crooid- otile ollte nhviiite 5 i Qg 37.43# 2.35# 34.99# 16.27# 0 .. O 4.29# .laOi . ! aj 0 0.36# . 1.02# 0.05# 0.79# *<10 . 38.77# 12.25# 57.43# ^^!i46.23# 55 f04# m66.20# ' r 0.90# *f@m> 0^51# "^3.06#'r* i;'7._21# ^6.70% 0 33.83# 0 ***<&**.-.'0 ~mk . 0.25# 0.44# i:09#' 1; 69# 4* 0.56# ` 0.46# *88* 2.01# ' 12122#'- F' 4145# ol40#&% 29 .'54# 6.29# " 23I29# ^20!62# *.W.99#'v2&^ 0 0.29 _ 6,92 Si.0 0.08 0.57 c>as<1050 4.30 0.02 ` >105 14.92 2.56 0.52 0.15 0.62 2.42 0:33 0.40 6.78 ' -'O'.91 -^%'h O'.IO 0.12v' ^' 0.99 ' 0.16 ** 0.66 ' 0.32 ^'0.34 ` 0l53^'^` 1.51 '' 3.59 ''&&&''2i7& v'26.66^%$ (b) Acid treatment of ohryeotlle 1 One hour In dilute or concentrated HCL does not alter"ap pearance of fibre but after such treatment it rapidly-.'diar solves and disappears on injeoting into living tissues'.' , . /, v/-VwV ; ' 4 . ' 'r:' ii Treatment with CO2 bubbled through water or lung Juiced suspensions of chrysotile fibres causes partial solution with liberation of silica and magnesia. 7'..!.'' (c) Colloidal allumlna does not neutralize'the`effects of asbestoi as it does quartz. On injecting chrysotile suspended in . . aluminum hydrate solution, fibrosis and asbestos bodies dev elop at the usual rate. It remains to demonstrate whether the fibres`become coated with a layer of aluminum raonohydrate as has been proved in the case of quartz. If they have, the coal does not affeot their capacity to irritate tissue. VII Physical Properties In Relation to Irritation of Lung Tissue - V : (a) Length of Fibre Short chrysotile fibres under 3 microns are practically inert.' ' 20 to 50 micron fibres cause typical fibrosis. ' The effects of longer ones could not be tested for teohnloal' reasons. , (b) Crushing completely destroys the fibrous structure of ' chrysotile. With loss of structure, all,capacity to irritate disappears. vy} ' - 'VlXb " <0(} 060 06 001,01 (c) x- Heat - At .ignition ..jenperatwrtxwater'Asjdrlyeii^pf^bttt^thef^te. . :ibra*itruotur ;le preservedi^Flbrea beo6mer'extreiqely>brltti,<j`,Jj' i' The physical change -.altera..typical locali2atTon';wi'thin `thef|^|?s; lungs, no fibrosis .deyelopsp-reaotion.`limited to'phyagooytOBlB^ No asbestosls bodies `-'formed. VIII Nature and Significance of Asbestosls Bodies'* - - .* (a) Bodies, probably result ;from depositionJof <:lron\and organic - v' matter'on a slowly ^dissolving il'lbre'iof,|aflbeatosi\^ The souroe . of the iron Is more "likely .to^be^the Aung `tissue ^han `the mineral Itself as ythe ^eoatlngsisjJ^stlAeiihe'avyXoh^flbrous .'.';*? minerals of low Iron ;content^ppohi'tho8e;|h`lBhl-ln'Iron. . :2'$V: (b) The effect of asbestosls body|fprmation?la.^eflUBed to be pro-'li/ tectlve although .-it 'has not;tbeen>jpo8SiblejitO;.l8olate 'a large enough quantity ofrthese'r.ptx^dJiiufqs^ri^iml^WcAv'forn for'C'rlSi' purposes of teat.'..The, smoothjrqtuide'di^nde^l^es'ehted by the ^0 bodies would not 'be nebhanleAlly^wlta1{aing^^S^^M-;f :i .;; - - >; *v (c) If they were capable of caualhgklrrltatlon^ftheXfibroals in.the ' lungs should progress after exposure^beasesjwhich'it does not.i;- - i-1-' ' (d) The gradual disappearance of ibodies .(and,'tiibre8) ;long after exposure'polnts. to ultimate solubility irr'tissue fluids. A ' -V . ........W;. .y ... M iy:. * " (e) The bodies are probably a fortuitous boncomnltant rather than" a cause of fibrosis. , *"r IX Theories of Irritant Action of Asbestlform Minerals (a) Chemical These experiments do not confirm the theory that asbestosls la merely a form of silicosis resulting from free silica liberated in the solution of a silicate molecule. If this were true asbestos,like quartz_,phould cause fibrosis in any organ of any species for the experiments have shown that injected asbestos dissolves In these locations. However, it does not. c.^uoe such reaction in any location but the lungs'of &e species. (b) Mechanical Irritation We are proposing the theory of mechanical Irritation which is manifested only in the lungs because this organ is the only one whose normal physiological functions involve a high degree of mobility. Experiments designed to prove the necessity for notion In this tissue have failed for technical xeasons. For this theory to be applicable,-it ie'necessary that'the fibres be concentrated in the fl/fe termlnal'alr. tubes1. It has been shown that only ohryaotlle of .the asbestlform minerals thus fa? nas the proper physical characteristicsIto insure'such localization. It is also essential. that;-the .fibre shall persist long enough before It dissolves in thellungV of speoles like mice, rats,+ dogs. It apparently diesoiyea'Jso rapidly that it exerts no Irritation. Similarly..rapid^olutlon may explain In part, the lack of fibrosis.in organslother than the lungs. ' : ' : .- .1 U - ' (. (q) . in U'./ . * . 060 06 00102 -7- The fibres must be long enough so that they cannot be completely ' surrounded by.phagocytic cells which'would prevent contact of thes round, broken"ends with the delicate cells supporting the air tube Observation has demonstrated that these conditions are realized in guinea pigs treated with long fibre chrysotile and fibrosis result With the other asbestiforn minerals that have been' tested, some or all of the prerequisite were lacking and no fibrosis developed. (c) If the irritation were chemical, fine serpentine which has th same chemical composition as chrysotile should have also caus fibrosis. The crushed chrysotile sh'oudl have been more activ than intact fibres, because of the greater surfaoe areas ex posed to body fluids. On the assumption that ohrysotlle, lik ouartz, becomes coated with a very thin layer of aluminas on treatment with colloidal aluminum hydroxide, capacity .to causi fibrosis should be destroyed if the aotion were chemical but such i$ not the case. (d) Tvie heavy cQating resulting from as'oestosis body formation ap parently does stop tissue reaction but here the effects are probably mechanical for reasons cited. (e) Heat sufficient to alter chemical structure d estroys power to Irritate but it also altera essential physioal characterist that affect' localization of the fibres in the lungs. X Complications (a) Susceptibility to Infection dt/iii i Tuberculous - Asbestos behaves like most other mineral^ in this respect and not like ouartz which specifically lncreas native susceptibility to the tubercle bacillus. This in fection may spread for a time but then heals. The resultan fibrosis accentuates that oaused by the mineral fibre. li Non-Tuberculous - of no greater frequency than in animals inhaling dusts of other kinds. Occasional epidemics of pneumonia occur in our dust rooms, but these are due to methods of housing rather than to dust; they also occur in unexposed animals. ill'*- Cancer of Lungs No experiments wereAdealgned to elucidate this point but certain evidence suggests that asbestosis nay actually favor development of tumors in susceptible species. 1 In guinea pigs, rabbits,' rats, cats and dogs dung tumors are rare. 2 When these species were subjeoted to 2 to 3 years in halation of asbestos dust, the incidence of lung tumor was not inoreaaed. .S -y- . *W-' ... Vv . ` " <rL(o - Ua-Cl) ::rw - 4 l',iuU.- .. *->. 060 06 00103 -8- 3 Some strains of white nice do develop tumors without . . apparent cause. > 4 such a strain of white mloe was unintentionally used in three Inhalation experiments with asbestos. 5 Of 11 mice Inhaling long fibre asbestos for 15 to 24 month 8 developed malignant tumors In their lungs and 6 of them had tumors in other organs. The lnoldenoe rate la excessive. 6 Of 22 mice inhaling short fibre asbestos for not longer th 12 months only 3 developed lung tumors. Rate 13.6# 7 As controls, we have only the experience with mloe In othe: dust experiments. For short periods. there were 51 mice exposed to 4 othpr kinds of dust for 10 to 12 months, lnoldenoe of lung tumoj 1.9#. For long periods. there were 143 mice exposed to 4 dlfferer kinds of dust, Including pure quartz, 23 to 31 months. Fox all this group of mice the average Incidence of lung tumor was 13.8#: the highest rate (25#; was In a subgroup exposed to flint dust'. Thus the incidence of lung cancer in the long fibre asbestos mice was over 16 times the average for mice Inhaling other dusts for comparable periods and over 3 tines the maximum for any other'group Mice exposed to the practically inert short fibre asbestos showed fewer lung tumors although 7 times more than those in short exposur to other dusts. rA'hese observations are suggestive but not conclusive evidence of a cancer stimulating aotlon by asbestos dust. They are open to several criticisms. The strain of mice was not the same In the asbestos experiment as in many of the others cited; apparently the former were unusually susceptible. Not enough animals survived In the dust for longer thjin the 15 months apparently necessary to produce many-tumors, -`-here were no unexpoeed controls of the same strain and age and no dimilar controls exposed to other dusts. It is hoped that this experiment can be repeated under properly controlled conditions to determine whether asbestos actually favors cancer.pf the lung. XI Disability Cannot be determined in animals. T^e accidental deaths were from the same causes net with In all our dust inhalation experi ments. h.Xki -( ^ ($) 060 06 00104 c: 3 I V I r XII Essential (a) In the duet. Granular material"and crushed fibre are -- Inert diluents. 11 ^he long fibres must be thin enough (1-3 Microns) and short ') enough (under 50,Microns?) to be Inhaled. ` ill Very short fibred (under 3 Microns) are practically Inert. (b) Atmospheric Concentration Still under study. Apparently this factor la lower than in the case of dusts composed of granular minerals but methods of estimation are misleading. :/ i The aiverage standard Publio health'Service inpinger count In the long fibre asbestos";dust .room`was 140 million particles per cu. ft. of air. V>hi8^concentration *caused fibrosis visible to the naked eye'ln~;20 to"24:mInths. -.For comparison the average implnger ..counts."In an. experiment with pure quartz was 120 million particles per .cuT ft.'and fibrosis developed at about the sane 'rate. 11 However, implnger counts are deceptive because by this method of sampling very few .'fibres, .which are the significant elements in the dust are'."cpileoted." ill Sampling with an electrostatic precipitator is a much more efficient means of collecting . .fibres.from air-borne sus pensions. Samples from ourjlong fibre asbestos room showed that the dust in the air contained 32.5J& of fibres few of which had been collected or counted in the implnger sample. The latter sampled largely the inert granular parti- Ole9. . ' lv As ordinarily employed precipitator samples are weighed and the results expressed in mg. per cubic foot of air. There is no means of converting such values into numbers of particles particularly when these vary in size, shape and 'specific gravity. '' v Simultaneous sampling with precipitator and standard im plnger yielded the respective values of 0.65 mg and 60 mil lion particles per cublo foot of air. f. . V 1 vi 1heoretlcally the best index of hazard would be either the number or weight of fibrous elements in the dust. (plot0) 060 06 00105 , .// ` .. - -,!{ U ./ -V-W- -10(c) Duration of Exposure ^c.r - ', 1 Fibrosis visible to the naked eye after IS months exoosurV Increases in extent in subsequent 13months. ' . 11 The scan of life of our most susceptible..laboratory animal'"the guinea pig has prevented continuing Exposure longer tha three years. .In this period only.^the comparatively early : stage? of asbestosis have .been'-produced, s" With the know- ' ledge that we have gained,itfi.s probable "that more extensi' disease could have been produced with a purer long fibre : chrysotile. The long lived^apecies, -likecats, dogs are un fortunately not susceptible $ tftXIII ill 'For these reasons X-ray changes have. been, minimal and we i'"' were not able to fulfill one of the objectives of this pro-? gram. - / . ,, Recommendation for a New Standard of. Safe 'Atmospheric Concentration '$1 :-;' ../*** * ' . {.V'y6-',S '.>/*> *yV. (a) While there is no official 'standard,'''.the-'tentative one of ' -,.i 4 or 5 million particles per cubic foot ;kf.fair.is frequently . cue ted. > . (b) This is probably unreliable because it`la phased upon sampling.', with a standard implnger vhlch.we ha vei'sho'wo/.doee not collect moaf" of the fibres that are 'the' source" :of jda'zard. ` '; f" (c) We now think that a etandard .should befbase'd upon samples collected with an electrostatic precipitator;if.it is feasible to determine readily the relative proportion'.'of-fibres in such material. ; (C) Work is still in progress uponthe latt'er.point'.' (e) To be of-value the new standard would^hayeStol'be "correlated with" the'-''X-ray findings upon-'enploye'eoj'e^pbsed^tb .different concentrations of XIV Prevention of Asbestosis'' The experiments have failed .t6''`develop'`any^ffctl'eAr?cher.iical '* means of neutralizing the actlon^bf 'fibroub-/hWSst6s m 's'--' ; (a) `0 alter the :hunan>lung 'so that .it ;;wouid;i'die"oblve'yasbestos fibres rapidly like "'v creating *n acidosJ the fibrosis. (c - (c Cp (j O) "V i'-v v.. ' ' ' i! : 060 06 00106 v. ( ^ ~ ic Co (\ 0 :'.-^\^^r?.^Efi'.- -: -:y.-' - * < : ^r^TMlWf>A^i..5'' ..." '. ' . . . v .--.. -' - ^\:w;?Vvw .-v ^ i .> ---* - . . v.: ;: ;AV- , ........ y:iW^V3$?*' ' " M`- :t' ;v :t^ :\vy. ";#r ' /#!> ;!v-V*J,%nr:... ::&' . ;** .t*' 060 06 00107 060 06 00108