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INDUSTRIAL HYGIENE FOUNDATION OF AMERICA, INC. 4400 Fifth Avenue Pittsburgh 13, Pa. REPORT OF PRELIMINARY DUST INVESTIGATION FOR ASBESTOS TEXTILE INSTITUTE JUNE, 1947 By WiCL Hemeon Head Engineer June 18. 1947 Industrial Hygiene Foundation of America, Inc. By John F. McMahan Managing Director PLAINTIFF'S EXHIBIT 6 REPORT of PEEUMUlARr DUST SURVEY for ASBESTOS TEXTILE INSTITUTE Juno, 1947 OBJECT OF INVESTIGATION This project was a preliminary Investigation of the ashestosls 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 othervise to promote a general Improvement In that field. SUMMARY The facts upon which this report Is based were obtained on visits, during the past three months, to all plants of Institute members (except one, who wished the visit postponed to a later date). Complete cooperation was extended at all plants. Dr. C. Richard Valuer, Medical Director of Industrial Hygiene Foundation, participated In visits to three plants and In development of the medical concepts of 'tills report. The problem is seen to be composed of three aspects which are discussed in three sections of the report and summarized herewith, as Hihik 1 MEDICAL, and PIQTSICAL !ISTZN(r. Preliminary Dust Survey for Asbestos Textile Institute June, 1947 2. Engineering, -- Mechanical methods vere seen In vise In one or more plants which effected practical dust control In all operations, bringing dust concentrations down to five million or lower with one or two exceptions. It Is proposed to prepare formal detailed descriptions of these methods for gener al distribution to members of Asbestos Textile Institute. Medical Supervision 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 asbestosls. The lack Is more serious, in a sense, because in most of these plants no compensable cases of asbestosls 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 asbestosls, two other plants appear to have about 20 per cent of their employees affected. Medical supervision of workers In this industry is of utmost im portance 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 dustiness" for asbestos is commonly taken to be five million particles per cubic foot. This represents good attainment in the dust control program. It is em phasized, however, that dust elimination to this extent does not positively In sure that no asbestosls will develop in some workers after a long working life N (greater than 20-25 years). Scientific evidence is obscure on this point. It is recommended, therefore, that studies be initiated aimed to develop another Preliminary Dust Surrey for Asbestos Textile Institute, June, 19^7 yardstick, because It Is suggested that vhen control below five million Is attained, present dust count methods may not properly measure the remaining hazard. A detailed summary of recommendations for a long-tern investigation Is given at the end of this report Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 h. I- ENQIHEEBINQ PRESENT STATUS OF POST CONTROL Practically all plants visited have had one or more dust count sur veys made of their operations and these data were available for the present study. In addition, a fev samples vere taken by the Investigator In most plants. These records vere studied and a range of concentrations Judged to be most representative selected for the stannary 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 vlth dust control measures now In common use; or Judged to be most typical of an operation vhere no special dust control measures are enployed, 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. The figures for carding room dustiness Indicate that vlth reasonably good enclosure and exhaust of the machines, concentrations veil below three million are obtainable. Four of the plants visited exceed the five million limit materially. All the data for mule spinners exposure Indicate a vide variation in dustiness, ranging from two to eight mUllcrf, but the volume of data are not c Preliminary Dust Survey for Asbestos Textile Institute, June, 1947. H3 O #-* S2Of g K" 4 *o O V r-l a tf\ K> 11 K> -s- r-l H rr-l H 1vO O' - a 1 1 CO 1 Jt ITi Jt OI . irv 8 HO CO CO H rl CQI CQ> 0 IT 1 K\ K> HH 1 K' r*> w < 1 CO 1 1 CM S' ir\ OO 1t- in CO H i-l O 111 01 Oi cu OI Oi OI co .1? OI J- (Tv (*, 1 CM 1 1 1 r-l OI r-l OI rl ro W 1 r- lf\ CO r-- Ha t 1 r-l tc\ K> ITS 01 OI C\ H IT\ O 1 1 1 i OI 1 01 IC\ rl OI in 1A C3 01 1 VO f- H 1 irv 0 T\ rl H r-l 1 K> CM K> tf\ lA (X) 1 1 1 1 1 H H H H r-* m -J* VO OI .a- < . 1 1 1 1 CM OI OI r-l OI 99 d H 0 2d 2d P <H rl tfl fcp I* al *24 & g O a Ad ep CO CO d 0 (H 9 Pa P ^-1 a 50 n d r-l -rl 1* 63d 0 a) O 2 5 Preliminary Duet Survey for Asbestos Textile Institute, June, 1947. 6. great enough to yield a good average. Concentrations for ring spinning vary from one to five million although there Is no strong indication In the available data of maried differences between this operation and mule spinning. There Is a similar vide variation In data for twisting (two to eight million), but there Is some Justification In these data for the opinion widely held that this Is one of the dustier operations In the finishing end of the mill. It Is believed that occasional high values in both ring spinning and twisting reflect In some cases the sampling procedure. If the large lmplnger la main* talned In one location end there Is a strand breakage in that Immediate vicinity, the resulting whipping dust will be reflected In that single sample and would not, therefore, be representative of the worker's exposure. Dustiness In weaving operations reflects the use of water for dust control In seme plants and exhaust systems in others. The lowest concentra tions of one to two million obtained In Plant A reflect highly efficient vet weaving isthods there employed. Concentrations less than four to five million are readily attainable by local exhaust methods as indicated by the results In several plants. The data for spooling and winding operations are Included for com pleteness, but reflect miscellaneous operations and conditions. The dust re ported is often due to the effect of other machinery In the same room. These considerations therefore affect the reliability of these data, as In the case of operations In the preparation room. if Preliminary Dust Surrey tar Asbestos Textile Institute, June, 19^7. 7. EXISTING HJST CONTROL HACTICES The following discussion of dust 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 be set forth In the form of detailed specifications describing details of construction, specifications for sheet metal contractors, for purchase of fans of proper capacity and for design and operation of dust collectors. Preparation Highly -variable practices prevail In different plants and the mis cellaneous character of operations within a single plant males it impractical to formulate many general statements. However, it may be said that such con trol as is realized results from the use of modem equipment that is veil en closed and which usually Incorporates pneumatic conveyors with celling 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 celling 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 ex ception of these two ccaaon operations, most of the dust control procedures re quired will be more or lass specific for each plant. Carding As has been noted, reduction of dustiness In carding to concentra tions of three million or less Is easily attained by good enclosure of the nachine and carefully designed exhaust. Moreover, experience of several ProUrinary Dust Survey for Asbestos Textile Institute, June, 1947. 8 companies proves that it does not Interfere seriously vlth manufacturing operations nor vith quality of roving produced. Our Investigations Indicate the superior advantages of having side walls of the enclosure of wood to facilitate snail clearance by rubbing con tact at the edge of the main cylinder, thus avoiding excessive air infiltra tion at that point. Wood covers have the advantage of resistance to crushing, which was evident in Installations with sheet metal covers. Connection of the enclosure to the exhaust system by means of cham bers of ample dimensions, l.e., large cross-sectional area is of major im portance to avoid localized high air velocities close to the webbing in the main cylinder. Ms detail was not always observed. In view 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 from the machine was 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 Set A 1500 cfm B 2200 cfm E 3800 cfm G 51+00 cfm H 2000 cfm It is apparent from this investigation that 2000-2500 cfm per set of breaker and finisher cards is ample exhaust capacity if the system is properly designed. Preliminary Suet Survey for Aebeetoe Textile Institute, June, 1947 9 All five of the systems described In the table serve their, purpose satisfactorily from the vievpoint of operation, but it does not mean that they vould be. equally satisfactory to others. Thus the plant vlth high ex haust capacity (C) has a unique Interplant tunnel connection, so that excess heat from another plant supplies replacement air vlthout added cost, for heat, or vlnter discomfort. Plant H controls dust by completely housing each pair of cards in a spacious rocm, exhausted at a rate of 2000 cfm. Sidewalls are easily remov ed for repairs. Most plants vould not prefer this arrangement. As far as the dust count data can show, the card room of Plant B with 2200 cfm. is equal if not superior to that of Plant E with 38OO cfm, a recently installed system. The fundamental features of best card dust control systems observed are as follows: 1. Wood enclosure with hingeing 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". 5. No blast gate dampers in branch line, 6. Exhaust influence over comb, either by extension of main cover or by separate hoods. 7. Exhaust space under machine, not over 4W duct. ^ 8. Enclosure and exhaust of feed hopper, not over 4" duct. TWo installations include an exhaust branch to prevent the escape of dust originating in the apace between the ring doffers and the main cylinder. Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 10. Spinning One plant has Installed ventilation for their ring spinning frames vhich 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 frame. Time did not permit demonstrating to our own satisfaction vhether a measurable improvement had been effected or not. This should be done by a series of dust measurements vith exhaust an and off. The volume of air exhaust is insufficient to effect a true local ex haust action, and If it Is effective It must, therefore, be an effect of simple dilution. Twisting Interest in control of dust from 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. Here again the operators believe a marked improvement has resulted. Dust count data is needed that will measure the degree of improvement. Winders Cop winders have been exhausted in Plants A and B with reports of beneficial reduction in dustiness. We do not have quantitative data on this point. The exhaust arrangement far Foster winders was developed many years ago and is well known. The tendency to elimination of this machine makes the problem one of little practical interest now. ^ In most plants, dust from other equipment, such as spinning and twisting which are commonly in the same room, is of greater importance than that from winding operations. Preliminary Dust Survey for Asbestos Textile Institute, June, I9U7 11 Weaving One plant has a superior method of suppressing dust In veaving by vet methods and duet count records Indicate a complete suppression of dust. It Involves a vater spray head mounted above the varp at the rear of the harness vith a mechanical screw arrangement for constant movement of the spray head transversely to the varp, Thoj believe It to be more effective than the system common In several plants vhereln the varp Is passed over vetted rolls. It Is apparently not practical to recommend 100 per cent vet veaving throughout the Industry, Moreover, ve are satisfied that It Is practical to control dust In this operation by local exhaust, vhere dry veaving Is consider ed imper&tivefor special properties of the cloth. One of the best exhaust arrangements Includes an exhaust opening directly under the varp at the rear of the harness frame vith 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 evlvel Joint. Duct Work The actual arrangement of duct vork and exhaust fan present no un usual problems vhere good practice In sheet metal fabrication Is followed. lVo points are of sufficient importance to require emphasis. Special care should be exercised. In the fabrication to avoid sharp projections on the Inside that create points of lodgement for fibers. Secondly, It must be designed .to pro vide adequate transporting velocities. Velocities below 2000 fpm, in the experience of the Industry, may permit settlement of material and gradual clogging. Therefore, allowing a margin of safely, the design should provide for velocities of 3000 fpm. 6 Preliminary Dust Survey for Asbestos Textile Institute, June, 19U7 12, The problem of distribution of planned air flows to the different branches of the system Is of Importance In the design of all dust exhaust systems. - The use of dampers In branches to adjust air flows Is avoided In the best systems. Their function In effecting balance between branches Is best attained In the original design. Design procedures to. effect this ob jective are available but will not be elaborated at this point. Dust Collectors , Five plants In the survey esploy the well-known burlap dust house for filtering air from various exhaust systems. The favored filtering area Is determined on the basis' of one square foot for each air flow of 2 cftn. Most arrangements are such as to permit cleaning by whipping with a bamboo pole or a buggy whip by men who remain on the clean air side of the filter cloth. In one system, the men are required to enter the dust side for clean ing purposes, and finalcleaning Is carried out once weekly with the use of a central station vacuum cleaner. Practices In different plants are variable as to frequency with which the burlap filter Is freed of Its dust load by whipping. While these duet collectors work well, we are not prepared to recom mend them to the exclusion of seme commercial -types of filters having automatic shakers', Several engineering elements enter Into the design of a dust collect or system. Involving principally a proper estimate of pressure drop In all ele ments 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 N operate properly. If the basic resistance of the filter, l.e., that Immediate ly after shaking the cloth. Is subject to a constant Increase over a period Preliminary Duet Survey for Asbestos Textile Institute, June, 19^7 13. of veeta, the system operation will suffer. Apparently, some of the. older commercial flat hag type of collectors did exhibit that difficulty. Modifi cations In the design of such units have, however, been Incorporated In more recent models and those difficulties may have been eliminated. Two plants employ commercial collector's of the flat bag or envelope type. Another plant uses a cloth tube commercial collector and also one whose filtering element Is of paper, which Is replaced at intervals of several weeks. A study of operating details of these commercial collectors Is indicated In tills study. Including considerations of original cost and operating cost. Recirculation Several plants return air from the dust 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 where there Is obvious ly leakage of dust through the filter and consequent ^contamination of the air Inside the plant. The practice is generally frowned upon where dusts that are hazardous to health are being handled. We believe there are certain circumstances where the practice might be permissible provided adequate safe guards are Incorporated In operating procedures. The large volumes of air Involved In dust control represent a tremendous problem as to heat loss and boiler capacity which cannot be passed over lightly. Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 14 II - MEDICAL PRESENT MEDICAL FACILITIES AND PRACTICES Every plant has connections vlth a local specialist In radiology vho Is employed for diagnostic work on an .Irregular basis. Three have their own x-ray machines used by the local specialist, but only one has a wellestablished schedule of periodic medical examinations. Half of the plants have no positive Information as to the Incidence of asbestosis among their workers. The situation Is these respects Is In dicated In Table H. TABLE H. PRESENT PRACTICES AMD FACILITIES AS TO MEDICAL X-RAY EXAMINATIONS IN VARIOUS HANTS Plant A B C D E F G H I J' Recent X-ray1 Survey Made Yes No Yes Yes No No No Yes No Yes Periodic X-ray Examinations Made No No No No No No No Yes No No Have Own X-ray Machine Yes No No No No No No Yes No Yes ^Within last few years, and results available to plant or Its physician Preliminary Dust Survey for Asbestos Textile Institute June, 1947 15 ESTIMATED INCIDENCE OF ASHBSTOSIS Tho Incidence of asbestosIs among employees of those plants vhere enqiloyees vere examined In recent years, shows a marked variation as Indicat ed by the following: Plant A has recorded cases diagnosed as asbestosla to the extent of about 20 per cent, and In the past nine years has cca$ensated, on the average, two cases per annum. Total textile employment about 400. Plant C on the basis of a recent systematic survey, estimates asbestosis Incidence to be 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 vlth a total textile em ployment of around 150, They have compensated one case In about 10 years. Three more are pending. Plant H vlth a textile employment of 300 finds five or six cases annually that the physician believes shew early changes due to asbestos. Plant J has counted potential cases of asbestosis amounting In number to about 20 per cent, comparable vlth Plant A. 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 cases requiring compensation. \ While ve have no complete data on history of employment and labor turnover In the several plants, it is apparent that there is, at least super ficially, a marked inconsistency In this picture. Also, It is clear that Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 16 a serious lack of information prevails generally an this aspect of the problem* The story in North Carolina Is vorth special mention. This state Instituted 10 years ago, a system of periodic medical examinations for all vorkers in dusty industries and, hence, all asbestos textile workers have been x-rayed and clinically examined for a longer period, on a periodic basis, than any other asbestos textile plant in this group. If the state examination finds that workers should discontinue their employment because of rapidly developing asbestosls they have' the authority to effect this change. They also see to It that workers who should receive workman's cccrpenaatlon due to dis abling asbestosls are processed. So far as we have been able to ascertain neither event has occurred to any employee of the two North Carolina asbestos plants in this group. These observations suggest that there may well be a narked divergence in medical procedures. Interpretations, and attitudes respecting the diagnosis of asbestosls. There Is a very urgent need for a concerted cooperative medical, effort to develop improved diagnostic procedures and uniformity of Interpre tation Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 17 IMPORTANCE OF HBKEOPIC MEDICAL EXAMINATIONS One of the most Important elements of a program of protecting health of workers In dusty occupations Is the periodic medical examination. Hie lack of scientific Information regarding all aspects of asbestosls Is serious. This cannot be over-emphasized. The obvious procedure to help overcome this deficiency Is to employ every tool now available that will throw more light on the facts. The Importance of the periodic medical x-ray examination can per haps best be emphasized by stating that dust count Investigations cannot. In the present state of knowledge, give us assurance as to the extent of our suc cess In eliminating the hazard. Regular examinations serve 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 end there Is no progression to late stage asbestosls. 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 control equipment, will eventually Indicate when the battle of asbestosls con trol is 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 business. Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 18, The question as to whether a plant should purchase its own x-ray equipment is an economic one involving consideration of cost of local outside medical and x-ray facilities and of loss of employee time 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 form of a MEDICAL ASHESTOSIS PANEL to be composed of outstanding medical men in this field, and of the physician designated by each company as the one responsible for its medical and diagnostic work. The composition, ae 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, and consider the sig nificance of x-ray films and other clinical data brought to the group by each participating physician. Dr. C. Richard Valuer's services would be available for the organization and other details. 6 Preliminary Dust Survey for Asbestos Textile Institute June, 1947 19. STATISTICAL STUDIES OF MEDICAL RECORDS Hiere are two very important questions concerning the physiological nature of asbestos that have not yet been answered by any published investi gation: 1. - What is the expectation of asbestosls in workers exposed more than 15-20 years to low concentrations of asbestos dust? Among the 500*od& workers who composed the subjects in the U.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 the conclu sions that could be drawn. 2. Is there a progression to advanced asbestosls after exposure oi* an Individual has been discontinued or has been reduced to very low 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 throw valuable light on these questions. None of the plants visited during this inquiry have sufficiently extensive and systematic records to provide satisfactory answers to these questions, but the medical department of Metropolitan Life Insurance Company, under Dr. A. J. Lanta, 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. 6 Preliminary Duet Survey for Asbestos Textile Institute, June, 1947 20. The most outstanding store of information Is In the records of the Division of Industrial Hygiene of the North Carolina Department of Health vho, In accordance vlth state lav have x-rayed workers In this, and other dusty Industries, almost annually for the. past 10 years. A study 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 their full cooperation In any investigations, and although we " have not discussed the matter with them directly as to details, there Is every reason to suppose that the desired Information would be 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 would be of great value for this purpose. N Preliminary Dust Survey for Asbestos Textile Institute June, 1947 21 HI - PHYSICAL SIGNIFICANCE OF DUST COUNTS Correlation, between development of asbestos is and some pertinent measure of dustiness, e.g., dust counts, can be developed by periodically observing and recording data on both aspects -- periodic medical examinations of exposed workers together with the periodically measured dust exposure of each. However, to be useful for preventive purposes, theseprocedures have to be exfcdaded Into the past wherever data Is avallab.e This was the proced- 1 ure employed in the studies of-the U.3,Public Health Service In North Carolina plants (Public Health Bulletin No. 24l, 1938)* The main value of dust counts In asbestos plants Is to obtain data on dust concentrations that can be compared with that study, and thus lead to conclusions as to probability of development of asbestoels In the particular plant being studied. that study, dustiness of different occupations was measured In the usual manner, and also the Incidence of asbestosls by medical and x-ray examinations of the men employed. A statistical comparison of the two sets of data led the Investigators to the conclusion that new cases of asbestosls would probably not occur If dust control measures were undertakento ensure that no dust exposures exceeded five million particles per cubic foot (measured In the same manner) Preliminary Duet Survey for Asbestos Textile Institute, June, 1947 29, APPRAISAL OF RSDPCED JUST HAZARD Saving reached a degree of dust control represented by the dust count limit of five million, it is then proper to ash: 'Vhat degree of assurance is afforded by existing knowledge that asbestosis 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? Die information available does not permit complete assurance that five million 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 assurances be sought or a new yardstick of accomplishment be found far ac curately measuring any remining hazard in the dust zone below five million for the elimination of future asbestosls depends upon the degree of control ^effected now. Measurement of Duetineas One basis of uncertainty as to applying present conventional dust counting techniques to the measurement of asbestos dust hazards below the five million level is summarized in the question -- are the fibers of asbestos the causative agent or the non-fibrous "cubical" particles that look like those of other Industrial dusts? The non-fibrous particles in most textile operations couprise 80-95 per cent of the total dust seen in dust counting. While it is proven that asbestos dust is the cause of asbestosls, there is no certain Information as to vhat shape or size of dust is the causative factor. The correlation studies of the U.S.Public Health Service Preliminary Duet Survey for Asbestos Textile Institute, June, 19U7 23 employed, conventional dust count techniques vhlch, In effect, related Incidence of asbestosls to the number of nan-fibrous particles of a size ranging from one to five or 10 microns. For Illustration, suppose the causative dust element Is something different, e.g., fibers that are less than 50-60 microns long, and less 1-2 microns in diameter. The conventional dust count method would be satis factory only'If there were a fairly constant ratio between the two types of dust; It would. In that case, provide an adequate. Index. Pret'tTirfnagr Studies on Qualities of Asbestos Dust With a view to eventual development of supplementary methods for measuring asbestos dust concentrations bh a weight basis, we have conducted 8erne preliminary studies directed to the colorimetric determination of total silica In the 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-mlcroscoplc particles and fibers. Another aspect of the dust examination problem an which preliminary work has been done Involved studies with the electron microscope. We posed the two following questions: 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 non-fibrous or are they bundles of fibers? Preliminary Dust Survey for Asbestos Textile Institute, June, 1947. 24 2. Secondly -- since the limit of resolution of the microscope lenses used In dust 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, sane of which are reproduced In the attached Figure. They demonstrate first, that the cubical particles seen by a low power light-microscope are in fact bundles of fiber resembling a life- size handful of partially opened fibers. 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 dust counting microscope. \ 6 N /* THIS CIRCLE 1 MICRON DIAMETER Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 25. They also showed sane fibers a few microns In length whose diameter Is only 0,01-0.02 microns, although the commonest particles are bundles of fibers about 0.1 micron in width. In addition to the light these observarlons throw on the sub* microscope character of asbestos dust, they are cited to Indicate the other qualities that might be pertinent to evaluation of dust exposure, to supple ment the dust count technique now In use. Preliminary Dust Survey for Asbestos Textile Institute June, 1947 26 INHERENT DUSTINESS OF STOCK In Investigations of the type being presently considered, a primary aim must be to develop Improvements in dust control with the rninimnin of waste motion 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, combined with the few tests we performed ourselves, provide numerous Instances of variation, the cause of which Is not apparent. We undertook recently to measure the amount of dust In the roving of different manufacturers by suspending a measured quantity of roving In alcohol, then making a dust count In the same maimer as with air samples, lhe 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 overcame, and the solution depends on more laboratory experimentation. Another test method which would be of value is a standardized mech anical abuse of roving in a small vessel while sucking a stream of air with resulting dust sb 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. Preliminary Duat Survey for Asbestos Textile Institute, June, 1947 OUTLINE OF RECCMfflHHED PROCEDURES FOR ASBESTOSIS INVESTIGATIONS X. ENGINEERING A. Dissemination of Existing Information Provide factual information to Institute members vlth least possible delay; prepare bulletins vlth 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 mates 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 dust house B. Development of New Techniques for Dust Control In this category, the problems for which there are no present answers: like twisting, spinning, appraisal of operation, efficiency and cost of commercial dust collectors, etc. Preliminary Dust Survey for Asbestos Textile Institute June, 19^7 28. II. MEDICAL A. Institution of Periodic Medical Examinations This is urgently recommended to all companies. Medical advice as to organizations procedures vill be given by the Foundation upon request. B, Organization of a Diagnostic Panel for Asbestosls Arranged by the Foundation's Medical. Director and organized to meet In Pittsburgh at suitable intervale for scientific reviev of diagnostic problems, reading of x-ray films, etc. Panel to consist of individual company physician or medical consultants together vith other medical authorities to be determined. C, Statistical Study of Existing Medical Records Designed to find ansvers to important questions concerning medical and physical nature of asbestosls; especially concerned vith records of State of North Carolina, Metropolitan life Insurance Company, etc. in. PHYSICAL TESTING -- (Further Dust Studies) Studies of physical and chemical characteristics of asbestos dust designed. In conjunction vith medical studies, to provide more significant Information concerning the nature of the dust exposure; to develop supplementary techniques for measuring remaining asbestosls hazard after reduction of dust to meet the present standard; to insure that effective control of dust has been attained. This is a step by step program aimed at the elimination of asbestosls cases from the plants of Asbestos Textile Institute members. \ 11 iroUBTRIAl HTGIHHE TOOTfDATIOW 0? AMIBIGA, IC. 4400 ?ifth Arena# Pittsburgh 13, Pa. July 11, 1947 Meoerandun on Plant of The Oarloek bucking Company Supplementing The Qoneral ttannrt -Pre Hainary T^st Investigation-for Asbestos Textile Institute" Of Jane, 1947 Pastiness Thie plant is designated as 0 in the general report and an appraisal of Its tastiness Is siusaarlted in that ooluan of Table 1, page 5. The difference between these mines and those of other good plants are, on the whole, not significant and we rate this plant ae erersge "good." However, this does not mean that dust control is entirely eatlsfaetory in all respeots as Indicated in the general report. There is an insnfflolsnt amber of duet counts in the coopany flies to oonstltuts an adequate record ef tastlneee. Homal variation# require a number of ooonte at each operation to prerldo n uaefal average. Oar own single duet counts taken at the tine of the visit are given below. 1 > 2 3 4 5 3 3 5 Dust {Santa At operator end of 4 carding aaehlnse (See. 1, ?, 7 and 8) 1.5 General air in aisles of twisting suehlnee 3.0 General air, along row of loomt nest winders open along the working alolee 3.1 General air in alelee of spinning frame 1.7 t> !>iat Control Praatlces Qardlng dust control Is dltoussed on pogos 7 *nd Q of th* general report. Reference Is made to the exhanet system In this -:lant vhioh scoowolishes ns good dust control ss almost nil the other "good" plants but *t exhaust rates that would not he practical for other northern plants. The dust collectors in use et this plant ere of consider-hie interest because they include tvo tyr.es not in use in eny other plant (Air ''at and Parsons) because commonly thought to he impractical* Test data on these unit would therefore he valuable. Engineering studies planned for the lone term investigation of particular interest to this plant end outlined in the general report -re dust control in preparation, tvisting and veering, and efficiency of dust collectors. ItflLflftI In the nodical section of the general rsport reference is made to the severe! conpsnlee who h*re no inferantion as to the incidence of potential ashestosia la their plant. This company is one of those *n'T therefore vish to underscore here the recommendations concerning periodic v-ray examinations discussed particularly on png* !* to 18. V.C.I. Eemeon Heed Engineer