Document 71mq3LgDZ6x0z0XqyKo8zL1n6

FRICTION MATERIALS STAF OS INSTITUTE, INC., E. 210 Rd 4, PARAMUS, N.J. 07652 * PLAINTIFF'S FYWro < MINUTES OF THE MEETING of the ' ASBESTOS STOP? COMMITTEE Friday, June 1, 1973, at 9:30 A.M. at the Institute Office, E. 210 Route 4, Paramus, N.J. tEBERS PRESENT I. H. Weaver, Chairaao. H. Wagner * Z. E. Feierabend Raybestos-Kanhattan, Inc. Carlisle Corporation Abex Corporation OTHERS PRESENT S. B. McGinnis (for J. C. Henning) World Bestos Company U. Jacko (for W. Spurgeon) Bendlx Corporation D. E. Stone Bendlx Corporation R. C. Wyatt Maremont Corporation r* W. 3. Gustafson E. W. Drlslane ' Karemont Corporation - Friction Materials Standards Institute, Inc. MEMBERS NOT PRESENT J. C. Henning T. Bell _ W. Spurgeon World Bestos Company E. K. Porter Co. - Bendlx Corporation The eeetlng was called to order by l . Weaver, Chairman, at 9:30 A.M. MINUTES OF PREVIOUS MEETING The Secretary read'a summary of the Minutes of the Meeting held February 16, 1973. These minutes had been released and a motion for their acceptance had been obtained. Upon motion duly made, seconded and unanimously passed, it was RESOLVED: To accept the minutes of the February 16, 1973 meeting as distributed. LABELING At the February 16, 1973 meeting, the Secretary was directed to distribute Information on typical CAUTION labels now in use. The purpose of this distribu tion was so that the Committee Members could review what is available and would be in a position to propose label specifications to meet the 0SHA requirements. 0ne center suggested that the sire of the labeling used should be of sufficient size to be noticeable on a large carton and should be commensurably smaller but Minutes of Che Asbestos Study Committee Meeting -2- June 1, 1973 still noticeable on s smaller package. One member was using an insert with a CAUTION label stuffed into the package. The use of imprinted CAUTION labels on the carton is desirable because it is essentially a one-time tooling cost. The use of separate labels is a continuing added direct expense. Most members now using separate gummed labels will eventually go over to imprinting the carton when ordered. -. . In what must be a response or s reaction by others, many customers are now asking Members about how much percentage of asbestos Is in the brake linings. ' This could be a reaction on the customer's part as to whether they would have to put control practices in their factories because of the asbestos that is contained in brake lining. To meet the true spirit of the OSHA regulations, manufacturers doing subsequent drilling, grinding or cutting of asbestoe contain^ lAg'STafcgitittlnge should use the care that OSSA suggests. One mesfeer felt that where he was shipping drilled ground lining sets that he would not have to imprint these small cartons with the OSHA CAUTION label. Other members are simply putting the OSHA CAUTION labeling on everything. When it was suggested that the Committee should take a position on this labeling requirement, the neiifiersnof the Committee were referred back to the Resolution that was made on February lb, 1973. This absolution soil, in effect, that OSHA labeling practices should be adhered to where asbestos containing materials do not liave asbestos fiber completely locked in or where subsequent operations may be per formed. The question concerning the drilled and ground set is: While it Is unlikely that subsequent operations will he performed, is it possible that they may be performed? . After a lengthy discussion it was decided that no resolution concerning recoamended"CADTIOII labels would be proposed. Rather, the Secretary Is directed to send to the Uesbershlp copies of typical labels now in use. It was called to the Secretary's attention that his yellow Bulletin of March 30, 1973 was in error. In that notice it stated, "Avoid breathing dust". The word ing should have been, "Avoid creating dust". This error will be called to the attention of the Membership. - The Chairman brought up another point as regards labels. There is a sign that can be posted in the factory where there are restrictions concerning asbestos dust in the atmosphere. This is a standard sign for placing in the factory which says: "CAUTION - Asbestos dust hazard; avoid breathing dust; wear assigned protective equipment; do not remain in area unless your work requires it; breathing asbestos dust may be hazardous to your health". Information on the availability of these signs will be sent to the Membership. EPA EMISSIONS STANDARDS FOR ASBESTOS While the new EPA emsslons standards appear to be reasonable, there Is some difficulty in interpretation. For example, the standards are not simply "No visible ecssions". but (1) if the control equipment does not meet the air clean ing requirements in the regulations, do visible emissions are permissible, or (2) one could even have visible emissions if they verc using a collector with the specifications - recommended by the EPA. In other words. If you have the EPA's recommended collector you could possibly have visible emissions and still be complying with the.EPA1 requirements. It goes without saying, that interprexation. of the requirements by individuals in the different EPA regions may vary quite a bit. - *- ---J --or collector Is not as efficient ' Minutes of the Asbestos Study Comdctee Meeting -> June 1, 1973 as the dry-bag collector. If an EPA Enforceneat Officer sees a vapor from the stack where a wet collector is vised, the-source best be able to prove there is no asbestos being discharged. In ocher words, it can be inferred that if a source has wet collectors they may more likely be cited for visible emissions. While it Is apparent that the EPA*s emissions standards promote the dry collec tion of asbestos In bags, many problems have been indicated with these collectors. One of the problems was repeated fires in the collection system. Another member stated that he too had this problem until cigarette smoking was banned In the . factory. Since discontinuing smoking in the factory, he claims they have not had more than one or two fires in the last 25 years. Another member said that may be, hut they have had a Ho Smoking rule for many years and they still have fires. This party blames the fires on the incentive program where the workers receive a bonus for exceeding certain work standards. This promotes the caking of heavier-cuts with grinding wheels and creates sparks which apparently promote the fires In the system. The operation that has not had any fires for the past 25 years does not have an incentive system and does not permit smoking in the work place. Where the vet collectors are now in use, apparently the EPA is permitting their use as complying with the requirements. At thir point, the disposal of the materials picked up by the collectors was ' brought up. One member sent the dust to a pelletizing machine. In tnis.process they add 5Z-10Z cement to the pelletizer. A volume reduction in the order of 3 to l was developed. The pellets are taken by truck and dumped as land fill. While the pellets could be broken down into a powder, if they receive reasonable handling they can be readily moved from the pelletizing machine to the land fill operation. It is this member's intention to Install a vacuum system from the collecting arees to go to a central pelletizing machine. One member described his handling- of dust from (1) a central collector, to (2) a screw conveyor, to (3) a truck, and to (4) the land fill. The workers In this case use respirators. The pelletizing operation not only reduces the transportation ccst by three times but eliminates the need for a watering truck and an individual o wet down the land fill. However, the costs of this pelletizing equipment are substantial. A manufacturer of pelletizing equipment is Ferro Tech Inc., 1231 BanksviHe Road, Pittsburgh, Pa. 15216. Several members men cloned that in dealing with the EPA Regional Offices they were having difficulties deciding what was a "new source" and what was an "existing source". Also, where one manufacturer adds one machine to an existing collection system he may not be in compliance without getting a Waiver of Compliance. Appar ently the EPA will not give a Waiver of Compliance that will take more than 12 months to complete. An applicant must give the steps to be taken and the schedule to be met. When each date arrives, the applicant must advise EPA concerning completion of that stage of the schedule. One member felt that we should review the EPA source report form to get a better understanding of what they were calling for. Page one or the report would be used for each factory. As there would most likely be several points of emission, page 2 would be completed for each stack or collector that emits asbestos. If a manufacturer wished to make an addition or modification in his plant with equipment that might put asbestos into the atmosphere, he must file with the EPA. On page 1 of the report he would cross off the words "Source Report" and type in either "Application to Construct a New Source", or "Application to Modify Exist ing Source". In reviewing page 2 of the report under "Process Description", vsone questions came up as to how to complete this section. One metier who had worked on this report with the EPA said you should enter here the type of ' 'Minutes of the ' Asbestos Study ConrdLi -e Meeting -4- June 1, 1973 machinery used without quantifying. Another member indicated that the EPA insisted that he list the type of equipment and the nunbers of each piece of equipment. If the EPA specifically said to list the nunbers and types of equip ment in this section it was suggested that they would have said so on page 2 of the report. The question of putting down the numbers and types of equipment could become very cumbersome where a manufacturer wished to move a grinding machine from a location with one collector to another location where it would be hooked into another collector. The member who filed with the EPA worked on reports In 2 different Jurisdictions: New York and Tennessee. He Indicated that at neither location did he enter the number of pieces of equipment on this form. (Since the' meeting he called to advise that the application filed in Tennessee without quantities was accepted by .the EPA. His application In New York State had not been either accepted or rejected as of June 4. 1973.) It would appear that Regional Offices are not in agreement as regards quantification of the equipment under the M?rbcess'Descrlption.M .... _ . The question came up concerning Interpretation of question 3, the "Amount of Follucant." In many factories a sec of dry mix brake blocks could emit into a collection system at the mixer, at the briquette press, at the cut-off . wheels, at grinding, at drilling, and at inspection and boxing. The problem is that this Is the same original asbestos which entered the process and (sight be counted 6-8 times. So, lq effect, a factory taking In on* million pounds of Mb..tc/ili5i|S|p,?S'dnlSe,'Sa!ictfoSsaTStai. t"rn* 7"*^lc appear Chat eight mi 11 log pounds of asbestos is going Into the operation. From the wording of the form. It would appear that this is exactly what the EPA wants. However, another member was told that this In not what the EPA wants. Be suggests that If a factory takes In one million pounds of asbestos Into the process that it should not report In total more than one million pounds of asbestos. If he had 10 different emission points, he would divide the one million pounds of asbestos by 10 to give the "amount of pollutant." Again, their apparently has been a difference In Interpretation from different Regional Offices of the EPA. On page 3 cf the report, under "Waiver of Compliance," it was stated that Sections 2a and Zb did not have to be completed unless EPA specifically requests this information. INSTITUTE SEMINAR ON SAFETY AND HEALTH At the February 16, 1973 meeting, suggestions were made that the Institute consider the sponsoring of a seminar for members associated with plant-operations. The Institute indicated it would be willing to sponsor such a seminar if suffi- . dent interest developed. A question was raised as to whether this seminar would apply only to asbestos. The Secretary indicated that such a seminar would apply to any field of interest but it should be related to problems that can be tied into State and Federal regulations. Among the topics suggested for a seminar were the following: - Air sampling and asbestos concentration determination. The pulmonary function test and X-Ray. Possible extension to Include noise and heat stress. Cooperation between management and workers in meeting the regulations. Asbestos bag opening machinery. * Minutes of the Ashes toe Study Comn_ -ee feting -5- Juae 1, 1973 Ihe Secretary was directed to make up a list of subjects which night interest the lieoership and to canvass the menbers as regards their interest. la addition to the agenda iters to suggest to the Membership, it was suggested that the canvassing letter ask if an individual from that member company would attend, where the meeting should be held, and when the meeting should be held. It was indicated that a meeting in the late fall would be desirable and such locations as Chicago, Detroit, Pittsburgh and Paramus were suggested. When the Secretary has prepared a questionnaire it will be submitted to Mr. k Feierabend for his review prior to distribution to the Membership. The actual. agenda will be drafted after the' members have Indicated their preference. The question vss raised as to whether outside speakers would be latvolved and it was suggested that we were not interested in a comaei .lal pitch as the meeting. Johns-Manvilie had indicated an Interest in approaching such seminar with the idea of promoting their HEAP (High Energy Air Filter) pollution control equip ment. It was suggested that perhaps it might be worthwhile to have outsiders make presentations concerning asbestos bag openiig equipment, pelletizing, collection, etc. This will have to be worked ou: at a future Committee meeting. Drake and Clutch Emissions Generated luring Vehicle Operation This particular study was run by Bendix Research Laboratories aider sponsorship of the E?A. 'A paper was presented to the S.A.E. by Dr. M. Jacko and Mr. R. DuCharse of Bendix, and Mr. J. Somers of the EPA. The actual report to the EPA is a massive document explaining every test procedure and every method of collection used in the study. A technical paper was presented by these 3 gentlemen at the SAE Meeting in Detroit in May, 1973. The study essentally centers on how. much asbestos is being put into the atmosphere from brake linings and clutch facings. As Dr. Jacko was in charge of this investigation he discussed the paper at our meeting. He advised that a condensed version appears in the magazine AUTOMOTIVE ENGINEERING. Among the points that Dr. Jacko made was that there were problems where a brake on one side was enclosed and the other brake was open to the regular atmosphere. Modifications had to be made involving cooling of the outside of the shroud so that there would not be too great a temperature difference from the left side to the right side. This was more of a problem with the disc brakes on the fronts. Actually with the necessary cooling, there was hardly any difference between the drum brake rears side to side. Among the items discussed in the paper were how much asbestos is used in friction materials. It is indicated that there are about 103 million pounds of asbestos in the friction materials which are used in the United States each year. There apparently are some differences of opinion as regards how much asbestos is Involved but it generally falls in the 90-120 million pound range. Actually, the amount Subject to wear is about 66-2/3Z of the actual lining that gets on to the brake (after grinding). Uhen asbestos is being used in brake linings it is discarded in one of three ways: It gets deposited on the surfaces of the brake, such as on the caliper, and around the wheel cylinders. (This Is surface debris). Additional material is collected on the lining surfaces, in the rivet holes, and on the brake drum. (This is called sump debris) Additional material becomes airborne and is collected on membrane filters. (This is called airborne debris). It is this latter airborne debris that the research ers are seeking Co quantify. Based on the samples that were collected, the conclusions were that more than 99.7Z of the asbestos in the brake lining is converted to other products. By ..extrapolating the data that they were able to develop on a passenger car the researchers indicate that a total of 5060 pounds of asbestos is put into the % Ilinutes of the Asbestos Study Committee Meeting -67 June 1, 1973 atnosphere. This airborne asbestos emission is 3.2Z of.the-total asbestos esitted from all automotive brake lininps end clutch facings In the U.S. A question arose as to what happens to the asbestos debris that drops out. Does it eventually get Into the atnosphere? It was Indicated that based on the study of ocher saterlals that apparently there have been build-ups such as lead along the sides of turnpikes. This material apparently goes Into the earth's surface and whether It is picked up again Is dependent on ocher factors such as the proximity to streams, etc. A gentleman, from Ford Motor Company was also to present a paper to the SAE meeting concerning asbestos particulate emissions Into the atmosphere. Ho paper was available at this time. There were some questions concerning procedures and a source of data on the Ford paper, but In any event the paper Indicated a lower total asbestos emission than the Bendix paper. These two papers should serve as source information when' others are attempting to quantify the asbestos emitted latr the atmosphere from brake linings and clutch facings. OTHER ITEfS Tht topic if OSHA Inspection? md enforr^rart was brought up briefly and the members indicated that no new actions had been taken by OSUA as regards enforce ment concerning the asbestos standards. The Asbestos Information Association (AIA) is to put out a Compliance Manual concerning control practice. This Is still preliminary and there is no advance copy available at this time. ****** There being no further business brought to the attention of the Committee, upon motion duly made and unanimously passed, it was RESOLVED: to adjourn. Adjourned: at 2:30 F.M. E. H. Drislane Secretary I t s i ( l 1 if 'r i ! t I t I l .v T f \Vh. oi lor.,* info rat.due to; c by the*: lost ic'jr fib rouy. protec: r in their hydroxk The : from bc into the other 0 nutcerr. reaction in^agree As& intratra maiercJ 3Vl M.*i The ascafter in; rather v. treattaer which rt that thebv Bein' Two and react In the c: assuntrd in this p capable ? is merely untenable 12. Girt d'antarse.** II Ecer too Brrer. VORWALD ET AL__ STUDIES uF ASBESTOSIS 39 Pnortrnve Acriox or Aukimm Cr'wroirx&s When eciloitlal aluminum hvdrnxide h.-.ii hern .-.dried to a Mt*pciiNinu of long fiber chrvsotiie prior to imcrtinr rht~ >..'pcn>tm imratrarlu-.n'.A into rats, the aluminum compound did not prevent the irritation oi tissue due to chrvsotiie. I: anything. the acute mtiaiuinatory response evoked by the injected fibrous mineral was accelerated. One month after the last injection of the rittst suspension the bronchiolitis was becoming fibrous. King and his associates also found that aiuminiuti failed to protect pulmonary tissue front the irritation caused hv ad>estn> fillers in their experiments metallic aluminum tva* u?cd iu>u;iil nf tlic hydroxide. Formation or Assurors Eonir.s The iron in the coating of the asoestosis body apj>ears to be derived from blood or tissue elements and not, as lias been suggested, from the mineral fiber. After two kinds of chryn*ile were injected sitltcutnitrnusly into the groin of a guinea pig--one kind containing 2 per cent and the other 0.2 per cent ferric oxide--the asbestosis bodies were equally numerous at both sites of injection and showed no difference in their reaction to prussiai; blue, the reagent which stains iron. This finding is in agreement with that of Giroux.15 Tiisct Rcactiox re Ascesrests Booits Asbestosis bodies recovered from human lung tissue and injected intratracheallv into guinea pigs failed to produce a fibrous reaction. The material ior injection was obtained Lv digesting with sodium hypochlorite solution ii:e lung t:.:;r.e remove-! at autopsy from an aiLostoj worker. The asbestosis bodies (.mid be seen in tiie guinea pigs for at least a year after injection. This experiment shows that the asbestosis body has a rather resistant coating which is not destroyed by moderate hypochlorite treatment, which may he maintained in vivo for a year or longer and which renders the fiber incapable of producing fibrosis, it thus apoears that the coating is a protective mechanism. This thought was expressed by Beintker as early as 1934.'1 THEORY OF IRRITANT ACTION Two hypotheses have been proposed to explain the tissue irritation and reaction caused by asbestos fibers: the chemical arid the mechanical. In the chemical theory, which is hased on experience with quartz, it is assumed that the asnestos minerals dissolve in the body fluids and tha: in this process ti;c:r bases are leached away to leave silica in a form capable of irritating tissues. According to tins hypothesis asbestosis is mereiv an ir.diree: iiiicu.-is. Several tacts make the chemical theory untenable: Intratracheal Injection of brume fillers, which had a siiica 12. Giroux. Nf: Arr.ur.sote exacrimentaic: vileur ritl-.ugnonomqu.' ilu "corps d'armante.'' Laval nu-d. S:239, 19aj. 12. Beintker. E.: Cbcr die .-.;l'e>tosi`ieorr^rce.en: Bentrrlcungen tu der Arbeit ron 3eger. Virchows Aren t. pi't. Anal. 333 :527, 195-1 <0 tXDLSTHl.iL ItYGtEXE A Mi UCClT.iT10X.lt. MEDtCt.VE content of only O.CO per cent. cau.'cti typical fibrosis like that produced by the asbestos minerals: free smea r" rttcics ir-crea-e in potency as the particle site Incomes less, but a'..oiy> fibers shorter than about 10 to 20 microns arc relatively innocwui.i; aluminum hydroxide neutralnes the irritating effect of quartz but not of asbestos: serjientine iias the same chemical cnmp*'Mtion as lone hlicr chrysotiie, but it produced only an inert type <jf tissue reaction: re is a wide range in the chemical composition of the minerals which do cause asbestosis (table 19). In view of this evidence it seems more b'-cU that asbestosis is caused by an unusual mechanical irritation due to mug asbestos libers, this irritation being related to the peculiar hianicntcd structure of the fiber and the associated flexibility, which are possessed by no other foreign liodv studied. Thus, ignition of chrysnnie fliers changed their structure and made them inert, although the same fibers*, before being heated, would have produced fibrosis (table !). Further support for tiic theory of mechanical irritation is dial a.*bcaiv>is occurs in an organ of high mobility --die lung--and that a fibrous reaction can be produced by injecting , ' . ' j . Taolt 19- Analvumf or fit; r.ius Miturait ftbraui Uliuftt* AlSOfUl.................................... iapAihoif............................... A(ftOVA>Ul(g.................. ... Urttrn*........................................ Cftrr*ulii*................................ . .... .................................. 510. X 44.3 ii.A4 It V. M `A .* J>*0 4.os ICO a.;: A 7% g ^ w> % : s-a .... __ f.ZA ..... i.r* AlOt % 1.0# 1.* 0.3 0 44 o 14 lp: 3 jC CftO * rw trr; C 44 o.nt C.'*' 4.44 *to % L3 3.9 3r il # n m N..O 0.3 o.u o 52 in| ^ 5?? E.O % 0.3 0.1t 0.15 ou O.'J* 0.3" 0 ffmtJoa < lUs C. r* LO**- -- > luaC. % T..U e*4 0.44 1.3 0.3 1.00 o.r: 4 Ob 1 51 3.04 VI 4 H.J9 0 C! >*, 0.*4 *.. asbestos fibers into the peritoneum, where there is also a degree of mobility, but not by injecting them ur.u other extrapuhnonary organs such as the liver, the spleen and subcutaneous tissue. COMPLICATIONS The experimental inve'tigntinns with ashesto- minerals were con cerned primarily with the erect o: tite dust on normal tissue, but some attention was given to other phases, such as susceptibility to infection. The only experiment in which the effect of asbestos dust on a pulmonary infection was studied was the firs: inhalation experiment, carried on with King's floats dust. It ii unfortunate that, owing to the lack of adequate facilities at that time, mfccti-m >:v.cies could not be made in the other ir.halat.cn experiments aiso. - Si'sccpimiurr to Tlauci iocs I.Mrcriox The development of a tuberculous process initiated at the beginning of exoosure to dust, and also of a t-uercuious infection superimposed on an established asbestosis. was descr.bed in preceding sections of this paper. It may be stated that asbestos wh.cn classified according to the effect of a dust cn tuberculous :r.:cc::on would be placed below an active r< dust like qu infected wit process to j have no eft disease disa experiments ing the evolt process for-s (he tubercle healing to!! bacilli after years, progr the infection fibrous term the usual foe There vr. asbestos dust rather comm in guinea, pig 16 tty-39 per-- an effect of since suen ct other duati c .... . i nnat;u:on o? susceptiliilitc Owing to seems most o the various r follow each w A. \ arious r rabbit, t fibrosis q by inhahr fibers. Both inha for this state: in guinea pigs the fibrosis c Similar but 1 (table J). M of different sp 3. Long aibe ciiiolar fibt . jtm'ALiJ c . .; L.--i v / .i.W/h.sr wi.'a i dust like quart* but above an inert dust such as iron oxide, In animals infected witn attenuated tubercle bacilli, quart* causes the infectious process to nrogress untii t!;e animal dies 01 tui crcuinsis. Inert dust.' have n" etTeet on the infection. and the lemons usually heal ami the disease disappears. Asbestos dust is in a different category. In the experimental investigation. w hert thcmrbroui dusr^was being inhaled dur ing the evolution of the infection, there was spreading of the tuberculous process for a time, but usually the stimulus for continued proliferation of the tubercle bacilli was not sustained, the progression was arrested and healing followed. In guinea ptgs infected with attenuated tubercle bacilli after being exposed to asbestos dust for slighriy more than two years, progressive disease did not develop. The only modification of the infection was one of localization, a few baciili being retained in the fibrous terminal bronchioles and forming tubercles there, in addition to the usual foci beneath the pleura. Such tubercles healed in a few months. SescrennuTv n> XosrniKXCt;u*'> Ixrrrmix There was no specific exj'eriment concerning the effect of inhaled asbestos dust on nomuberculnus* infection. Intercurrent pneumonia was rather common among animals exposed to asbestos cia>t. the frequency in guinea nips exposed ir. thr four inhalation experiments ranging from 16 to J9 per cent. This incidental evidence suggests the possibility of an effect of asliestos dust on nonruberculous infection. .Vevertltele*s. since such epidemics are not uncommon in inhalation experiments with other dusts and even in the colony of normal animals, it is feit that the inhalation of asbestos dust does not exert a significant e::ec: on the susceptibility to nomnbrrrulnu* pulmonary infection. COMMENT AND SUMMARY Owing to the vast amount of data induced in this investigation, it seems most convenient to summarize and to state as concisely as possible the various observations which emerged from the experiments and to follow each with a brie: resirme or the evidence. A. Various species of a-rimals. including the guinea pig. the rat and the rabbit, but not the m-ui.-e a:'.d the dig. tL.t.-'ii perihrouehieiar fibrosis of the lung similar to human asbe.-tosis aitcr being exposed by inhalation or intratracheal injection to long chrysolite ti'liesios fibers. Both iniiaiation and injection experiments provide amoie support for this statement. Figure 3 .-f reveals the ceiluiar fibrosis that occurs in guinea pigs following inhalation o: long fiber a.-ficstcs; figure 9 'hows the fibrosis caused ir. the cat by inhalation of long fiber asbestos dust. Similar but less extensive fibrosis occurred also in rats and rabbits (table i). Mice ana arcs faded to respond. This variation in response of dificre::: species to identical dust exposures is still to cc accounted tor. B. Long as'nejtoi fibers are c'scmul m the production of the peribron chiolar fibrosis; snort fibers are incapable of producing this reaction.  * <2 industrial hygiene and occupational medicine Inhalation exocnments with ahc>tps <Inst suggest. and intra tracheal in lection experiment? rnnurm. mat ncrmroncmnl.-tr hhro<is is \ produced by asbestos fibers he;ween 2D anti 50 microns in length l>ut not \ by particles shorter tlun 20 microns (tallies 16 anti 1ST This indicates that the minimum length or' fiber possessing the capacity to produce the rypicai peribronchiolar fibrosis in animals is somewhere between 20 and SO microns. Tainted studies have not been earned out to determine the upper limit oi enivtive rilier length. It appears, however, that that limit will I* determined hv the i::i-.:;!nhi!ity oi the filler. C. The mode oi action ot the long asbestos fiber in the production ot asbesto.ds is primarily mcchamcai rather than chemical in nature. The evidence for tilts conclusion has been reviewed in a preceding ' section. page 30. The flexible filamented structure oi aslxtstos fibers i ! plays an essential pan in the irritating action, -nice the solid, inflexible__ fibers of uia.-s wool do not produce lii-iM-is (i g id ;). D. Typical experimental asbcuosis was produced by the inhalation ot an atmospheric suspension containing an average oi 1.5; miiliou asbestos particles per cubic foot oi air hv light ncid omi::. i wine!: less than 1 per cent consisted oi ulicrs longer than iu uuvr.ms. I In the inltahtfi n experiment with 100 per cent lall-miilcu asbestos dust containing 0.6 per cent ot fibers longer than 10 microns (table 11) . typical fibrosis was obtained (table 9). The evidence presented snows / at least that an atmospheric concentration oi asbestos dust containing ( less than 1 million f0.6 per cent X 13o miitbti l fd<er< longer than 10 '> microns per cubic iuot oi air is -arable oi producing experimental asLcst -sis ;u gv.uiea pigs. The avt.itd lower hunt >i v;:tr;i:n : .'. i ..c***rj ner * -- rouace asLestosis in animais cannot be eatnu- !:h:d irom -- E. The duration oi exposure required to develop the puinmnary reaction to inhaled asbestos dust is inversely proportional to the concentration i.iii of inng fibers in the atmosphere; as the concentration is increased, the reaction develops in shorter time. The basis for this statement appears in the data of the inhalation experiment with long fiber as'oPrtos. For tlaat experiment the average concentration oi the atmosphertc dust was about -0 minion particles per cubic toot oi a:r. and size-trequenev deter: .inauons disclosed that 6.7 per cent c: the a:r-suspendeu material consisted ot fibers longer than 10 microns 'table il). Thus, hy cairu-ation. it estimated that the con- cer.trattcr. c: :ger r.oers was 2 / amuon i <> / per cent F3 mii- lion). The lung; of ar.iutais exposed to the !*>og nl-cr asbestos dust revealed t;:e pttlmi.nary reacunn devciupcd :n approximately one- hai: t:te ext.via.*: tur.c requircti for :ts dc\eiopirer.: m animals ir.naiing the bail-miii-td "reduce, tor which the cor.certrr.f.on oi the longer fibers vt. as only O.'S mu'.igr. v0/. per cent ;< '.IS timber.:. F. EstaMi*r.ed experimental asbestosii ceases to progress on discon tinuance oi du.-t exposure. Tite e:tt-.ris:tcntal investigation shows, in tact that on discontinuance o: exposure there was an appreciable ciearmg oi me mature pulmonary w. lesion ture. t fibrosi of nbr noted G. Th by fib In: typical of pro; due to H. All Ion Ai prior it ot =i`. I. Iaha ot c. the t The to thepmre sine- :: cx;> rl shows t exposut with sul dost ex: The latti dust or i of quar: iniecticr on a bat sensitive the latte inability tubercub inhaled 1 pulmoru Thii c {roup G! . :-OR:r.iLD ET .-tL.-^STlOICS or .PESTOStS -J lesions, due to contraction oi the fibrous tissue. In contrast, an imma ture tissue response, evidenced primarily In ceil'1 with little nr no fibrosis, continued to progress. It is assumed thai. I'iiowmg attainment t ai fibrotic maturity, the same process oi contractu n wy.iid ensue a> was noted tor the mature lesion. G. The formation oi uhesrosis bodies represent; a coating ot the fibers by blood and tissue elements, which results i:: loss oi ability ot the fiber to produce nbrois. Intratracheal injection oi a>l>sto>is l>odie< failed to produce the typical asbcstotic tissue reaction in experimental aumiai-. The cc--ation of progressive reaction observed soon after e\|---,:rv terminated may be due to die formation oi asbestosi> bodies. H. Aluminum hytlroxide tailed to neutralize tlie fibrosing action or the long fiber asbestos. Aluminum hydroxide added to the suspension of chrysotiie ar-i-cstos prior to intratracheal nicction did not retard or on-vent the di-vr*.... .. of ttbcstosis in rats. * I. Inhalation of a*bcs'as dust did not alter significantly the final omcMiic of experimental tu crcttiosis in two series of guinea rags cxr--e*i to the dust. The apparently mild imhicncc oi asbestos dust is in distinct c-ntrsst .to the stimulating ettect exerted by inhaied quart! on a tuberculous process.in the lung. The interpretation must remain tentative, however, since it is based on an investigation limited to two series oi guinea mg* exposed to only one kind oi asbestos, namriy. King s heats: T:.: ie - shows that when the infection was coincidental with the nmet oi bust exposure, there was tenst-omry prcgrr.--.cn cf ;r ith subsequem heaiing; wiien infection was initiated alter lii ir.usiti.s ci dust exposure, the course of the tuberculosis was r.wt appreciably abend. The latter finding is quite different from our usual experience with quarta dust or with mixed dusts containing quartz, wherein the adverse influence of quartz on a tuberculous infection is manifested r.:o- strikingly when iniection is initiated after a period of dust exposure, viz., superimposed on a background of established silicosis. As indicated above, this more sensitive test, when a. piled tn abestos dust, faded to demonstrate that the latter had an adverse inriuence on a tuberculous infection. The inability oi asbestos dust in that experiment to afreet unfavorably the tuberculous process iumish.es strong support ior the interpretation that inhaled asbestos dust has no more than a mildly unfavorable ettect on pulinor.r.rv tuberculosis. This isvev.igation \*i$ ruac possible br the generous n:.:.r.ciii support of (roup o: companies of L'.t aswr.os :rcusirr. __ i / *\>m ,A 9 .>