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4400 Fifth Aver.ua Pittsburgh 13, Fa, REPORT CF ' IBEUMISAHr DUST INVESTIGATION FOR ` ASBESTOS TEXTILE EJSTXIUTS JUNE, 1947 By W.C.L. Hereon Head Engineer Juno 18, 194? Industrial Eygiena Foundation, of Africa, Inc. By John F. McMahon ~ Managing Director '/ REPORT of PEELE'UTJARr EUST SURVEY for ASBESTOS TEXTILE INSTITUTE June, 19^7 t OB JEC T OP I K V 5 3 TIOAT ION Thia project vag a preliminary investigation of the agbesto3is problem in textile plants of members of the Asbestos Textile Institute, with the immediate object of defining the specific nature and the magni tude of the problem in all its phases. From such a definition, the char acter of a long-term project could be outlined. An original objective of most immediate importance was to facilitate the exchange of information between member companies on successful methods of dust control and other wise to promote a general improvement in that field. SUMMARY The facta upon which this report is baaed were obtained on visits, during the pact three months, to all plants of Institute members (except one, who wished the visit postponed to a later date). Complete cooperation wauaextended at all plants. Ur. C, Richard Walmer, Medical Director of lapltrial Hygiene Foundation, participated in visits to three plants and dPdevelopaent of the medical concepts of this report. The problem is seen to be composed of three aapocts which are discussed in three sections of the report and summarized herewith, as ENGINEERING, MEDICAL, and PHYSICAL TESTING. 004620' Preliminary Dust Survey for Asbestos Textile Institute June, 1947 . o Engineering;, -- Mechanical methods were seen in U3e in one or core plants which effected practical dU3t control in all operations, bringing dust concentrations down to five million or lower with one or too exceptions. It is proposed to prepare formal detailed descriptions of these methods for gener al distribution to members of Asbestos Textile Institute. Medical Suvervlslon of Workers, Only five plants have had any medical x-ray surveys of employees. In the others, therefore, there is a serious lack of information as to the incidence of asbestosi3. The lack is more serious, in a sense, because in cost of these plants no compensable cases of asbestosis have occurred to draw attention of top management to the problem. While the medical survey conducted by one plant recently shows only about three per cent of the employees with asbestosis, too other plants appear to have about 20 per cent of their employees affected. Medical supervision of workers in this industry is of utmost inportance for the protection of both employee and employer, not to mention other considerations. Therefore, it is strongly recommended that each plant insti tute a program of medical and x-ray examinations of all exposed workers as early as practical. Physical Testing (Dust Counts, etc.) -- The "maximum permissible ** for asbestos is commonly taken to be five million particles per cubic foot. 4&le represents good attainment in the dust control program. It is enphasiaed, however, that dust elimination to this extent docs not positively in sure that no asbestosis will develop in sons workers after a long working life (greater than 20-25 years). Scientific evidence Is obscure on this point. It is recommended, therefore, that studies be initiated aimed to develop another C04S2G ' - Preliminary Pust Survey for Asbestos Textile Institute, June, 191*7 CJ * yardstick, because it is suggested that vhen control bolGv five million is attained, present du3t count methods cay net properly measure the remaining hazard. A detailed summary of recommendations for a long-tern investigation is given at the end of this report. CO "Atoao0 7; .. lVi Prolir.ir.ary Bust Surrey for Ao tec too Textile Institute, June, 19^7 . 4 . I - E If Q I H 5 E R IN 5 PSESETIT STATUS OF DUST CCHTROL Practically all plants visited have had one or nore dust count stirveyo node of their operations and these data were available for the present study. In addition, a few samples were taken by the investigator in most plants. These records were studied and a range of concentrations Judged to be most representative selected for the summary given in Table I. Where relative ly extreme values appear it is an indication, of too fev data to permit a closer estimate. Figures in the last column are selected to indicate the magnitude of readily attainable dust concentrations with duet control measures now in common use; or Judged to be most typical of an operation where no special dust control measures are employed, e.g., ring spinning. Discussion, of Concentrations The available dust count data for operations in the preparation room are highly variable and reflect the poorer accuracy in sampling inherent in operations that are intermittent and miscellaneous in character. These figures are, therefore, considered much less reliable than those for other departments. Dbe figures for carding room dustiness indicate .that with reasonably good lijg&osure and exhaust of the machines, concentrations well below three million are obtainable. Four of the plants visited oxceed the five million limit materially. All the data for mule spinners exposure indicate a wide variation in dustiness, ranging from two to eight million, but the volume of data arc not 004525 Prc ll.nlr.ery Dust Survey for Asbestos Textile Institute, June, 191*7. ^RESENT STATUS OF DUST C0KT30L IN DIFFERENT PLANTS: DESCRIBED IH. TERMS OF AVERAGE HIST COUiifS rH Si 1O-t o ftj; u >+> 4-> * -rt C ?o +> O CD o S c*- ro>-1 roi a O r IPj to t*--1 J* trHot *? rH rH 1 r- prH CO vO OS IP -d- --J CM t P Ht o o cm- oIpt to 1 CrHO 1 CrHO rtHo rtHo ! to Vw -7 u i to dr r- ?o dr dr J co t ri-sf CO orH rOH CM dr CM trp*i ^Cvt fci W O o i *{ *-L -? CDi -S1t H CV CJ CM 1 ' 4-1 I CVJ IP t H f tot -Hfv t-i CO1 r-i to tO IP l CJ O<S H* rf\ -d* J i H OJ Ai CM IP 1 (P oorHir VO IP 1 p1- f-41 IP rrHt rOl C1J rl to1 to 1 H IP 1 H P rHl 1 tP1 ' 1 t sot CM* CM CJ OJ rH 1 1 CM CM t i CM CO cl c pH vcH *0H d u eJ P. o M Ch ca5aHo, rHo 3 A 2 cao- t$ c *H *tfHoi *C>J *iH to wAH >cl -0) W a fo rH C rH O T5 oa P4 HH A* o os * CO ^ 5 004620 Preliminary Da at Survey for Asbestos Textile Institute, June, 19^+7. . -3 6, great enough to yield a good average. Concentrations for ring spinning vary frees one to five million although there is no strong indication in tho available date of marked differences between this operation and nule spinning. There is a similar wide variation in data for twisting (two to eight Billion), but there is sore justification in those data for the opinion widely held that this Is one of the dustier operations in the finishing end of the Bill. It is believed that occasional high values in both ring spinning and twisting reflect in sore cases the oaapling procedure. If the largo iupinger is main tained in one location and there is a strand breakage in that Immediate vicinity, the resulting whipping duct will bo reflected in that single cample and would not, therefore, be representative of the worker's exposure. Dustiness in weaving operations reflects the use of water for dU3t control in somo plants and exhaust systems in others. The lowest concentra tions of one to two Billion obtained in Plant A reflect highly efficient vet weaving methods there employed. Concentrations less than four to fivo million, are readily attainable by local exhaust methods as indicated by the results in oeveral plants. _ The data for spooling and winding operations are included for com pleteness, but reflect niscellaneouo operations and conditions. 'Hie dust re- portodjte often due to the effect of other machinery in the same room. These considpjiticns therefore affect the reliability of these data, as in the case of operations in the preparation room. 004630 Preliminary Duct Survey for Asbestos Textile Institute, June, 19^7. 7 EXISTED FJST CC?TT?0L PRACTICES The following discussion of duct control practices in the industry is merely an outline. To he useful to those who are responsible for the engineering in each plant, they will need to he set forth in the form of detailed specifications describing detaila of construction, specifications for sheet metal contractors, for purchase of fans of proper capacity and for design and operation of dust collectors. Preuaration Highly variable practices prevail in different plants and the mis cellaneous character of operations within a single plant cakes it impractical to formulate mny general statements. However, it cay ho said that such con trol as is realized results fron the use of ccdem equipment that is well en closed and which usually incorporates pneumatic conveyors with ceiling con densers, The large movement of air involved in pneumatic transport serves the useful additional purpose of preventing the escape of dust from the primary equipment, Discharge of stock from ceiling condensers into bins, stock boxes, or feed hoppers is a dust usually not under control. The blending operation is another source which is often not satisfactorily controlled. With the oxcepticn of these two comcm operations, most of the dust control procedures re quired vill be more or less specific for each plant. Carding Ao has been noted, reduction of dustiness in carding to concentra tions of three million or less is easily attained by good enclosure of the machine ana carefully designed exhaust. Moreover, experience of several 004631 ProUrinary Dust Survey for Asbestos Textile Institute, Jure , 131*7. 8 companies proves that it docs not interfere seriously vith manufacturing operations nor vith quality of roving produced. Cur investigations indicate the superior advantages of having side- vails of the enclosure of vood to facilitate srall clearance "by rubbing con tact at the edge of the main cylinder, thue avoiding excessive air inflitre. - tion at that point. Wood covers have the.advantage of resistance to crushin; vhdeh vas evident in installations vith sheet netal covers. Connection of the enclosure to the exhaust systea by means of chan ters of ample dimensions, i.e,, large croes-aectional area is of major in- portance to avoid localized high air velocities close to the vetoing in the rain cylinder. This detail vas not alvays observed. In vlev of similar degrees of success, Judged by dust counts, be- tween various installations, the best criterion of superior design, as to de tails of exhaust fron the machine vas in the relative economy respecting volume of air exhausted per machine. Our observations indicated rather ex treme variations as indicated in the following table of exhaust rates per carding set in five representative plants: Plant Air Exhausted Per Sot G B *: U`\ 1500 cfn 2200 cfn 3800 cfn 5U00 cfn 2000 cfn v \ It Is apparent froa this investigation that 2000-2500 cfn per set of breaker and finisher cards i3 ample exhaust capacity if the systea i3 properly designed. 0046 Preliminary Dust Survey for Asbestoo Textile Institute, June, 1947 All five of the systems described in the table servo their purpose satisfactorily from the viewpoint of operation, but it docs not mean that they would be equally satisfactory to others. Thus the plant with high ex haust capacity (G) has a unique interplant tunnel connection, so that excess heat from another plant supplies replacement air without added cost, for heat or winter discomfort. Plant H controls dust by completely housing each pair of cards in a spacious rocn, exhausted at a rate of 2000 cfm. Sidewalls are easily remov ed for repairs. Most plants would not prefer this arrangement. \ As far as the dust count data can show, the card room, of Plant B with 2200 efia is equal if not superior to that of Plant S with 3SCO cfa, a recently installed system. The fundamental features of best card dU3t control systems observed are as follows: " 1. Wood enclosure with hingoing arrangement. .2 Liberal clearance between worker rolls and curve of cover permitting -air passage at low velocity. 3* large chamber connection on cover, to duct. 4. Duct branch not over 5", preferably 4'*, No blast gate dampers in branch line. . Exhaust influence over comb, either by extension of main cover or by separate hoods. 7. Exhaust space under machine, not over 4" duct. .8 Enclosure and exhaust of feed hopper, not over 4" duct. Two installations include an exhaust branch to prevent the escape o dust originating in the q>ace between the ring doffers and the main cylinder. 00463S Prelirir.&ry Dust Surrey for Asbestos Tc-xtile Institute, June, 19 b7 ' SdI inr* < u <v^ One plant has installed ventilation for their ring spinning frames vhioh management believes has reduced dust in this operation. It consists in a series of exhaust openings under the frame, near the floor, running the length of each frare. Tire did not permit demons trating to our enm satisfaction whether a measurable improvement had been effected or not. This should be done by a series of dust measurements with exhaust on and off. The volure of air exhaust is insufficient to effect a true local ex haust action, and if it is effective it rust, therofore, be on effect of sirpie dilution. Twisting Interest in control of dust fron twisters is widespread in the in dustry and Plants A and B have installed an exhaust system like the one de scribed for the spinning frames in Plant A. Hero again the operators believe a marked improvement has resulted. Dust count data is needed that will measure the degree of improvement. Winders K* " i " ; , is.*-1-* - -iov' Cop winders have been exhausted in Plants A and B with reports of benefjiiol reduction in dustiness. We do not have quantitative data on this point* The exhaust arrangement for Foster winders was developed many years ago and io veil known. Hie tendency to elimination of this machine makes the problem one of little practical interest now. In most plants, dU3t fron other equipment, such as opinning and twisting which are commonly in the same room, is of greater importance than that fron winding operations. 004834 Preliminary Dust Survey for Aotcatoa Textile Institute, June, 19VT 11 Weaving One plant haa a superior method of suppressing duct In weaving 'ey wet methods and dust count records indicate a complete suppression of dust. * , I, It involves a water spray head counted above the warp at-the rear of the harness with a mechanical screw arrangement for constant covenant of the spray head transversely to the warp. They believe it to be core effective than the Bystem eomon in several plants wherein the warp is passed over wetted rolls. It is apparently not practical to recommend 100 per cent vet weaving throughout the industry. Moreover, wo are satisfied that it is practical to control du3t in this operation by local exhaust, where dry weaving is consider' s. ed ir.rerativefor special properties of the cloth. One of the best exhsuct arrangements includes an exhaust opening directly under the warp at the rear of the harness frame with a slot exhaust opening carried by the lay beam, the latter connected to the stationary part of the exhaust system, either by flexible hose arrangement or by an all metal swivel Joint. Duct Work The actual arrangement of duct work and exhaust fan present no un usual problems where good practice in sheet metal fabrication is followed. Two noin^pppa of eufficient importance to require emphasis, . Special care should be e^pofsed in the fabrication to avoid sharp projections on the inside that " TWi; - creato points of lodgement for fibers. Secondly, it must be designed to pro vide adequate transporting velocities. Velocities below 2000 fpm, in the experience of tho industry, may permit settlement of material and gradual cloggingi Therefore, allowing a margin of safety, tho deoi^i should provide for velocities of 3000 fpm. 004535 Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 12. The problem of distribution of planned air flews to the different branches of the system is of importance in the design of all dust oxhaust systems. The use of dampers in branches to adjust air flows is avoided in the best aystens. Their function in effecting balance between branches is best attained in the original design. Design procedures to effect this ob jective are available but vlll not be elaborated at this point. Dust Collectors Five plants in the survey employ the veil-known burlap dust house for filtering air fron various oxhaust systems. The favored filtering area is determined on the basis of one Bq.uare foot for each air flew of 2 cfn. Most arrangements are such as to permit cleaning by whipping with a bamboo polo or a buggy whip by men who remain on the clean, air side of the filter cloth. In one system, the con are required to enter the dust sido for clean ing purposes, and final cleaning is carried out once weekly with the use of a central station vacuum, cleaner. Practices in different plants arc variable as to frequency with which the burlap filter is freed of its dust load by whipping. While these dust collectors work well, we are not prepared to recom mend them to the exclusion of some commercial types of filters having automatic shakers*: Several engineering elements enter into the design of a dust collect* -- . .. * or syelj|* involving principally a proper estimate of pressure drop in all ele- nente of the system and especially that through the filter proper {back pressure. If the pressure drop estimate in the filter is incorrect, the system will not operate properly. If the basic resistance of the filter, i.e., that immediate ly after shaking the cloth, is subject to a constant increase over a period Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 3-3 of weeks, tho oystem operation, will suffer. Apparently, sons of the older commercial flat tag type of collectors did exhibit that difficulty. Modifl- . caticr.3 in the design of such units have, however, been incorporated in more recent models and those difficulties nay have been eliminated. Two plants employ commercial collectors of the flat bag or envelope type. Another plant uses a cloth tube commercial collector and also one whose filtering element i3 of paper, which i3 replaced at intervals of several weeks. A study of operating details of these commercial collectors is indicated in this study, including considerations of original cost and operating cost. / Recirculation Several plants return air from the duct collectors to the workroom to conserve heat in the cold weather. We are not prepared at this point either to condone or to condemn this practice except in cases whore there is obvious ly leakage of dust through the filter and consequent recontaolnation, of the air inside the plant. The practice is generally frowned upon where dusts that are hazardous to health ere being handled. We believe there are certain circumstances where the practice night be permissible provided adequate safe guards are incorporated in operating procedures. Tho large volumes of air involyrtr In dust, control represent a tremendous problem as to heat loss and boilfl% capacity which cannot be passed over lightly. 00453 Preliminary Dust Survey for Asbestos Textile Institute, Juno, 1947 14 II - MEDICAL PRESENT t'SDICAL FACILITIES AND PRACTICES Every plant has connections with a local specialist in radiology who is employed for diagnostic work on an irregular basis. Throe have their ovn x-ray machines used by the local specialist, but only one has a veilestablished schedule of periodic medical examinations. Half of the plants have no positive information as to the incidence of asbestoois anong their workers. The situation Is these respects is in dicated in Table H. TABLE II. PRESENT PRACTICES AND FACILITIES AS TO MEDICAL X-FAY EXAMIilATICNS IN VARIOUS PLANTS Plant Recent X-ray1 Survey Made A Yea B No C Yes D Yos E T~ No F r' - No Ct No H Yen I No J YC3 Periodic X-ray Examinations Made No No , No No No No Ho Yes No No Have Cvn X-ray Machine Yes /' * No ([-, l.f *. No No ` No No 'No Yee No J 11 1L1 Yes Vlthin last few years, and results available to plant or its pliycician 0046 J3 'AJ Prcllmlnary Dust Survey for Asbestos Textile Institute Juno, 19^7 15 ESTIMATED INCIt^CS OF AS23STCSIS The incidence of asbestosis among employees of those plants where employees vere examined in recent years, shews a marked variation as Indicat ed hy the following; ' Plant A has recorded cases diagnosed as astestosis to the extent of about 20 per cent, and in the past nine year's lias compensated, on tho average, two cases per annua. Total textile employment about 400. Plant C on tho basis of a recent systematic survey, estimates asbestosis incidence to bo about three to four per cent. Plant D has results from an incomplete survey in which four cases vere found among those volunteering for examination vith a total textile em ployment of around 150, They have compensated one case in about 10 years. Three more are pending. Plant 5 vlth a textile employment of 300 finds five or six cases annually that the physician believes show early changes duo to asbestos. Plant J has counted potential cases of asbestosis amounting in number about 20 per cent, comparable with Plant A. 'iArj T The other plants have conducted no systematic x-ray surveys of their own and have no information as to incidence among their employees, None of these has had caecs requiring compensation. Vhilc ve have no complete data on history of employment and labor turnover in the several plants, it is apparent that there is, at least ouper- ficially^ a marked inconsistency in this picture. Also, it is clear that 004 Q M Preliminary Dust Surrey for Asbestos Textile Institute, Juno, 19 47 16. a serloua lack of Information, prevails generally on this aspect of tho problem. The story in North Carolina i3 worth special mention. This state instituted. 10 years ago, a system of periodic medical examinations for all workers in dusty industri03 and, hence, all asbestos textile workers have boon x-rayed and clinically examined for a'longer period, on a periodic basis, than any other asbestos toxtile plant in this group. If the state examination finds that workers should discontinue their employment because of rapidly developing acboot03is they have tho authority to effect this change. They also see to it that workors who should recoive workman's compensation due to dis abling asbestools are processed. So far as we have been able to ascertain neither ovent has occurred to any employee of the two North Carolina asbestos plants in this group. These observations suggest that there may well be a marked divergence in medical procedures, interpretations, and attitudes respecting the diagnosis of asbestosis. There is a very urgent need for a concerted cooperative nodical effort to develop improved diagnostic procedures and uniformity of Interpre tation* Preliminary Dust Surrey for Asbestos Textile Institute, June, 19^7 17 IMPOKKKCi: OF JEEICDIC MEDICAL EXAMINATIONS One of the most important elcnents of a program of protecting health of workers in dusty occupations is the periodic medical examination. The lack of scientific information regarding all aspects of asbestosis is serious. This cannot be over-emphasized. The obvious procedure to help overcome this deficiency is to employ every tool new available that will threw norc light on tho. facte. The importance of the periodic nodical x-ray examination can per haps boot bo emphasized by stating that dust count investigations cannot, in the present state of knowledge, give us assurance as to tho extent of cur suc cess in eliminating tho hazard. #. Regular examinations cerve to protect the worker by giving early in dication of health impairment due to dust, and permit intelligent action to be taken to avoid further serious health deterioration. This is particularly true if the detection is early enough and there is no progression to late stage aebestosis. More important, for the long term, the accumulation of factual in formation regarding the health status of exposed workers, statistically inter preted in relation to dustiness studies and to mechanical developments in dust controirW^ttipcent, will eventually indicate when the battle of aebestosis con trol i*`^being won. This aspect of the problem is elaborated in the following section, . The inventory provided by such a medical program is Just as important to intelligent action in this problem, as. material Inventories are to the proper conduct of busincc3, , C04 4fft .4 J Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 18 The question as to './hother a plant should purchase its own x-ray equipment is an economic one involving consideration of cost of local outside nodical and x-ray facilities and of loss of employes tins in travel, etc. Diagnostic Panel To further the objective of improvement and uniformity in diagnostic procedures, a medical section of the program is proposed in the fom of a MEDICAL ASBE3I0SIS PAIEL to be composed of outstanding medical men in this field, and of the physician designated by each company as the ono responsible for it3 medical and diagnostic work. The composition, as to outside medical personnel, of this panel would be determined by its objectives: the assembling of the best possible medical brains and the mutual education in diagnostic procedures that comes from exchanges of scientific experiences and information. . The panel would meet, perhaps semi -annually j and consider the sig nificance of x-ray films and other clinical data brought to the group by each participating physician. Dr, C. Bichard Maimer*a services would be-available for the organization and other details. JV-.-v- C 0 4 6 4 o u Preliminary Duet Survey for Asbestos Textile Institute Juno, 19^7 19^ * STATISTICAL STUDIES OF MEDICAL KSC0PS3 There are two very important questions concerning the physiological nature of asb03t03 that have not yet been answered by any published investi gation: 1 . What is the expectation of aabestosis in workers exposed core than 15-20 years to low concentrations of asbestos dust? Among the 500-odd workers who composed the subjects in the IT.S. Public Health Service study, there were abnormally few who had been exposed for more than 15 years and practically none over 20 years. These facts seriously affected tire conclu sions that could be drawn, 2, Is there a progression to advanced asbestosis after exposure ov an individual has been discontinued or has been reduced to very lew levels, due to action of dust deposits from earlier exposure? This question is of very great importance to intelligent medical supervision of workers in these plants. It is virtually certain that statistical investigations of existing records would threw valuable light an these questions. Hots of the plants visited during this inquiry have sufficiently extensive and systematic records to provide satisfactory.answeis to these quocptcu*, hut the medical department of Metropolitan Life Insurance Company, under Dr. A, J. Lanza, have x-rays of a number of men obtained in the early 1930's which could provide the nucleus of some useful information, depending on how many of the original Group are available for re-x-ray, . 004643 Preliminary Du3t Surrey for Asbestos Textile) Institute, June, 19^7 ' 0 The moat outslanding store of information is in the records of the Division of Industrial Hygiene of the North Carolina Department of Health vho, in accordance with otate law have x-rayed workers in thla, and other dusty industries, almost annually for the past 10 years. A atudy of these records would undoubtedly cast much light on the question of progression. Through officials of the company members in North Carolina, we already have assurances of thoir full cooperation in any investigations, and although ve have not discussed tho natter with then directly as to details, there is every reason to suppose that the desired information vould he made available to us for the purposes described. In addition, a general x-ray and medical survey of workers in one or two plants with a long history of high order of dust control vould be of great value for this purpose. % 004644 Prcllr.irj.zy Bust Survey for Asbestos Textile Institute June, 19^7 21 HI - PHYS I C A L significance of fust counts Correlation between development of asbestosis and son pertinent measure of dustiness, e .g., dust counts, can "be developed by periodically ob serving and recording data on both aspects -- periodic radical examinations of exposed workers together with the periodically measured dust exposure of each. However, to be useful for preventive purposes, theseprocedurc3 have to be QXtesied into the post vhorever data is availab.e This was the proced ure employed in the studies of the U.S,Public Health Service in North Carolina plants fPublic Health Bulletin No, 2kl, 1936). The main value of dust counts in asbestos plants is to obtain data on dust concentrations that can be compared with that study, and thuc lead to conclusions as to probability of development of asbestosis in the particular plant being studied. In that study, dustiness of different occupations was measured in the usual manner, and also the incidence of asbostosis by medical and x-ray examinations of the men employed* A statistical comparison of the two sets of data I* the investigators to the conclusion that new cases of asbestos is woulfeyfrafalv not occur if dust control measures were undertakento ensure that nefduat exposures exceeded fivo million particles per cubic foot (measured in the same manner). 004645 Preliminary rust Survey for Asbestos Textile Institute, June, 15^7 22 APPRAISAL CF RSPJCED TOST HAZARD Having reached a degree of dust control represented by the dust cotint limit of.five Billion, it is then proper to ask: "What degree of assurance is afforded by existing knowledge that asbe3tosis will not, in fact, develop in the future if dustiness is kept below that level?" If there are factors, at present unknown, that will indicate a need for still better dust control, what will that limit be? The information available dees not permit complete assurance that f t five nillion is thoroughly safe nor has information been developed permitting a better estimate of safe dustiness. It is nevertheless of the greatest importance either that such t f i assurances be sought or a new yardstick of accomplishment be found for ac curately measuring any remaining hazard in the dust zone below five million for the elimination of future asbestosis depends upon the degree of control effected now. Measurement of Dustiness On basis of uncertainty as to applying present conventional duEt counting techniques to tho measurement of asbestos dU3t hazards below the five 4Llian level is summarized in the question -- are the fibers of asbestos the c$ttSativ agent or the non-fibrous "cubical" particles that look like those of other industrial dusts? The non-fibrous particles in most textile operations comprise 80-95 P- cent of the total dust seen in dust counting. Whilo it is proven that asbestos dust is the cause of asbestosis, there is no certain information ao to what shape or size of dust is the causative factor. Tho correlation studios of the U,S,Public Health Service Preliminary Dust Surrey for Asbestos Textile Institute, June, 19^7 23 employed conventional duet count techniques which, In effect, related incidence of aabostosia to the number of non-fibrous particles of a size ranging from one -bo five or 10 microns, For illustration, suppose the causative duct element is something different, e.g,, fibers that are less than 50-60 microns long, and lass than 1-2 microns in diameter. The conventional dust count method would be satiafactory only if there wore a fairly constant ratio between the two types 0? dust; it would, in that case, provide an adequate, index. Preliminary Studies on. Quailtiea of Aobestos Eust With a view to eventual development of supplementary methods for measuring asbestos duct concentrations on a weight basis, ve have conducted some preliminary studies directed to the colorimetric determination of total silica in tho minute quantities of asbestos dust obtained in a typical atmos pheric sample. This requires development since it could provide a valuable tool for further Investigation, Sub-microscopic particles and fibers. Another aspect of the dust examination problem on which preliminary work has been 4on% involved studies with the electron microscope. We posed jg ~ jM%5? the ifciestions: * 1. Ordinary dust particles, one to three microns in diameter, com prise most of the particles in the dust count. They look like ordinary in dustrial dust and ve refer to them as "cubical" as distinguished from "fibrous" particles. The question is: are these particles in fact nen-fibrous or are they bundles of fibers? ' Preliminary Duat Survey for /i3'bcsto3 Textile Institute, June, 19^7, 24 2. Secondly -- since the limit of resolution of the microscope lenses used in du3t counting does not permit seeing particles very much smaller than one micron, one may ask if there are many fibers of great length, but of such small width that they are invisible? Samples of atmospheric dust were obtained for examination by the electron microscope, by mounting the small specimen slide used with this instrument, in the dust collecting zone of the electric precipitator. In order to eliminate very large fibers, the air being sampled was caused to pass first through a glass spiral coated with adhesive on its interior. This subjected the dust particles to centrifugal force and the largest ones would be pre cipitated out, much as they might be in the nasal passages of man. Studies with other industrial dusts employing this spiral indicate that very rarely do cubical particles larger than three to five microns suc ceed in passing through the several turns of the spiral. ' In samples obtainedvith this apparatus in a card room, having a good dust control, we obtained pictures, some of which are reproduced in the attached Figure. They demonstrate first, that the cubical particles seen by a lew power light-microscope are in fact bundles of fiber resembling a life- size handful of partially opened fibers. - jp. The picture further demonstrated that there are many fibers of con siderable length, some fully 50 microns, whose other dimension is only a fraction of a micron; the fiber is therefore invisible in the duat counting microscope, 00464-3 THIS CIRCLE MICRON DIAMETERI w Q flf*t\ ig6--l* 1O<-t oMa O Etsao-t w e 9 td OEi oto ICMJ iotae. EH 8 &3 -1 < Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 25, They also shoved sons fibers a few microns in length whose diameter is only 0,01-0.02 microns, although the commonsat particles are bundles of fibers about 0.1 micron in width. In addition to the light these oboervarlons throw on the sub- nicroscope character of asbestos dust, they are cited to indicate the other qualities that night be pertinent to evaluation of dust exposure, to supple ment the dust count technique now in use. 004650 Prelird.rr.ry Dust Survey for As be 3 too Textile Institute June, 19^7 26 XyHEKEKT lUSTE^SS OF STOCK In investigations of the typo being presei^iy considered, a primary aim must be to develop improvements in dust control with the minimum of waste notion and expensive experimentation on a plant scale. At the stage of development of the industry, causes of dust are very often not obvious. An examination of dust count records made available to us, canbined with the few tests we perforce! ourselves, provide numerous instances of variation, the cause of which is not apparent. We undertook recently to measure the anount of dust in the roving of different manufacturers by suspending a measured quantity of roving in ale oho.1., then caking a dust count in th9 sane manner as with air samples. The result would be expressed in millions of particles per yard of roving or per gram, etc and would be of great advantage in relating differences in dustiness to the causative factor. Such a measurement technique would be essential in apprais[ ing the actual value of oil. We do not have sufficient data on this effort on which to draw con clusions, There are difficulties to be overcome, and the solution depends on more laboratory experimentation. Another test method which would be of value is a standardised mech- anical#gtase of roving in a small vessel while sucking a stream of air with resultj|gg duet as in the sampling for ordinary dust counts. A test of this kind, in conjunction with the dustiness index would be of value in evaluating the oiling practice, or it might take the place entirely of the procedure previously outlined. . 004651 Prelirbinary Dust Survey for Asbestos Textile Institute, June, 19^7 m 27 OUTLET OF ESCCIO-STDED PPCCEDuRSS FOR ASBEST03XS E.TF3TIGATICNS X. ENQESERINQ A, Dissemination of Existing Information Provide factual information to Institute members with least possible delay; prepare bulletins with design sketches on some or all of the several subjects listed below, to be distributed singly as ready. Additional field observations required in many cases. 1. Carding dust control; for various makes of machines 2. Dust in. preparation, miscellaneous operations 3. Vet weaving equipment 4. Exhaust for Dry weaving 5. Exhaust for winders. etc. 6. Design of duct work 7. Design of duat house B, Developcant of Hew Techniques for Dust Control In this category, the problems for which there are no present answers: like twisting, spinning, appraisal of operation, glv efficiency and cost of commercial dust collectors, etc. C04652 Preliminary PacJt. O* ;i rvey for Asbestos Textile Institute June, 19^7 II. MEFICAL A. Institution of Periodic Medical ExarJ.no.tione This is urgently recommended to all conpanieo. Medical advice aa to organizetiona procedures vill "be given by the Foundation upon request. B. Organization of a Diagnostic Panel for Aabostosis Arranged by the Foundation'3 Medical Firector and organized to meet in Pittsburgh at suitable intervals for scientific review of diagnostic problem, reading of x-ray files, etc. Panel to consist of individual company physician or nodical consultants together with other nodical authorities to bo determined. C. Statistical Stud.'/ of Existing Medical Becords Fcsigncd to find answers to important questions concerning medical and physical nature of aobestosie; especially concerned with records of State of North Carolina, Metropolitan Life ' Insurance Company, etc, III, PHYSICAL TFSTSTO -- (Further Fust Studios) Studies of physical and chemical characteristics of aGbeetos du3t designed, in conjunction with medical studies, to provide more significant information concerning the nature of the dust exposure; to develop supplementary techniques for measuring remaining asbeatoois hazard after reduction of dust to meet the present standard; to insure that effective control of duet has been attained. asbe This la a step by step program aimed at the elimination of cases from the plants of Asbestos Fertile Institute members. GG4S5