Document O134QZ7qOnvL0GQbomK3Kern1

kkCO Fifth Avcr.ua Pittcturgh 13, Pa. PLAINTIFF'S EXHIBIT GF-807 REPORT CF PRELEEXAHY LUST lir/ESTICATICN FOR ' ASBESTOS TEXTILE IIJSTITUTS JUTE, 1947 By V/.C.L. Ktraon Head Engineer Jur.o 18, 194? Industrial Hygiene Foundation of America, Inc. By _____John F. McMahon Managing Director f' -A REPORT of PRELIMINARY RUST SURVEY for ASBESTOS TEXTILE INSTITUTE June, 19-'iY OBJECT OF INVESTIGATION This project was a preliminary investigation of the asbest03is problem in textile plants of nsnbers of the Asbestos Textile Institute, with the immediate object of defining the specific nature and the magni tude of the problen in all its phases. Fron such a definition, the char acter of a long-tern 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 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 v&a extended at all plants. Dr. C. Richard VJalmer, Medical Director of Ia$uetrial Hygiene Foundation, participated in visits to three plants nnd in development of the medical concepts of this report. The problen is seen to be composed of three aspects which arc discussod in three sections of the report and summarized herewith, as ENGINEERING, MEDICAL, and PHYSICAL TESTING. 00i62j Preliminary Dust Survey for Asbestos Textile Institute June, 19^7 Engineering. -- Mechanical methods vere seen in use in one or more plants which effected practical du3t 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 asbestosi3. The lack is more serious, in a sense, because in most 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, two other plants appear to have about 20 per cent of their employees affected. Medical supervision of workers in thi3 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, Shis represents good attainment in the dust control program. It is em phasized, 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 00452-5 U Preliminary Dust Survey for Asbestos Textile Institute, June, 1947 yardstick, because it is suggested that vhen control "below five million is attained, present du3t count methods nay net properly measure the remaining hazard. A detailed sumary of recommendations for a long-tern investigation is given at the end of this report. 004627 * Preliminary Bust Survey for Asbestos Textile Institute, June, 19^7 I - ENGINEERING FP2SSI?T STATUS OF DUST 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 feu samples vere taken by the investigator in cost plants. These records vere studied and a range of concentrations Judged to to 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 vith dust control measures now in common use; or Judged to be nost 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. Die figures for carding room dustiness indicate.that with reasonably good occlosure and exhaust of the machines, concentrations veil belov three million are obtainable. Four of the plants visited oxceed the five million limit materially. All the data for mule spinners exposure indicate a vide variation in dustiness, ranging from two to eight million, but the volume of data are not G04S25 Preliminary Duat Survey for Asbestos Textile Institute, June, 19V7. fsw-: A. cC_O< E--r o E cj gC*4 P- to fac 2 wo cr; 6* OH:; oo < oc=. ten* S3 E-> o ZM eCO aw 8 04 <-4 3 O r-l >-1 o p< jz u > *> *J El -r4 C ?o <-> a (S o X r> tO o1 r-l a a CQ t rH tr--i rH 1 1 CO r- -d* in r1i to -d vO o\ m -d to rH 1 OJ 1 w\ M v-- rw -7 O Ex< w O .< -4 .( r* o o in o* i o K*1 CO H CO rH i1( to fO rH 1 K-\ tO 11 cu i 00 ntt -d JO tl OJ OJ 0 o rH O rH ii1t OJ OJ OJ Ha GO -d OJ -d m 1 i OJ 1 t i rH OJ H OJ H tO I1 Ha rH OJ ON 1 to -d- o- m CO 1it to to m l -d* tn 1 OJ i H OJ m C- OJ i i NO in o H in rH 1i l in H H rOl OJ i H r< fO n in in 1iii H H rH to ll OJ 1 -d* VO 1i OJ i OJ OJ rH f1 tf\ cu 1 c*~ t OJ OJ 1 1 J- 1 OJ oc: CO c cCO H cc h c2 V CO w c3 tr ex. c.- rY CO C fO cl C H co co *H 4-> Tc-< rt C rJ H p. T? o >-4 o rH ty c o rH > <1 O TJ oc u c; 3 0) Ct th P o * a ce ;s 5 004620 Preliminary Dust Survey for Acbcstos 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 otrong indication in tho available data of narked differences between this operation and cole spinning. There is a similar wide variation in data for twisting (two to eight million), but there is sera 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 sore cases the sampling procedure. If the largo impinger ia main tained in one location and there is a strand breakage in that immediate vicinity, the resulting whipping dust will be reflected in that single cample end would not, therefore, be representative of the worker's exposure. Dustiness in weaving operations reflects the use of water for dU3t control in some plants and exhaust systems in others. The lowest concentra tions of one to two million obtained in Plant A reflect highly efficient vet weaving methods there employed. Concentrations le3S 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 came room. These considerations therefore affect the reliability of these data, as in the caso % of operations in the preparation room. 004550 Preliminary Duct Surrey for Asbestos Textile Institute, June, 147. 7. EXISTING DUST CC?IT?0L PRACTICES The following discussion of duGt 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 fom 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 mhos it impractical to formulate niny general statements. However, it cay bo said that such con trol as is realized results from the use of nedem 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 bc::es, or feed hoppers is a dU3t usually not under control. The blending operation is another source which i3 often not satisfactorily controlled. With the ex ception of these two common operatior.3, most of the dust control procedures re quired vill be noro or less specific for each plant. Cardins As has been noted, reduction of dustiness in carding to concentra tions of three million or less is easily attained by good enclosure cf the machine and carefully designed exhaust. Moreover, experience of several 004631 Pro Urinary Dust Survey for As tea too Textile Institute, Jure, 13UT. 8 companies proves that it decs not interfere seriously vith manufacturing operations nor vith quality of roving produced. Our investigations indicate the superior advantages of having side- valla of the enclosure of wood to facilitate small clearance by rubbing con tact at the edge of the rain cylinder, thuo avoiding excessive air infiltra tion at that point. Wood covers have the .advantage of resistance to crushing, which va3 evident in installations vith sheet ratal covers. Connection of the enclosure to the exhaust syeten by neans of chan- bero of ample dimensions, i.e., large cross-sectional area is of major in- portar.ee to avoid localized high air velocities close to the webbing in the rain cylindor. This 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 rachinc 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: ^ _P_l_a_n_t ^ ^ A 1 f/3 B S*. E G H ' f'-"\ Air Exhausted Per ' Set 1500 cfn 2200 cfn 3800 cfa 5^00 cfn 2000 cfn I1 j II' \| \ \ It Is apparent from this investigation that 2000-2500 cfn per set of breaker and finisher cards i3 ample exhaust capacity if the system is properly desired. C04S32 Preliminary Dust Surrey for Asbestos Tortile Institute, June, 19^7 9 All five of the systems described in the table serve their purpose satisfactorily fron 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 fron 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 20C0 efrn. Sidewalls are easily remov ed for repairs. Most plants would not prefer this arrangement. As far as the dust count data can chow, the card room, of Plant B with 2200 cfm is equal if not superior to that of Plant 2 with 3SCO cfa, 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 aid curve of cover permitting air passage at low velocity, 3. large chamber connection on cover, to duct. 4. Duct branch not over 5", preferably V*. 5. No blast gate dampers in branch line. 6. Exhaust influence over comb, cither by extension of main cover or by separate hood3. 7. Exhaust apace under machine, not over V duct. 8. Enclosure and exhaust of food hopper, not over 4" duct. Two Installations include an exhaust branch to prevent the escape of dust originating in the qpace between the ring doffers and the main cylinder. 004633 Preliminary Dust Survey for Asbestos Textile Instituto, Jure, 19U7 One plant hag installed ventilation for their ring spinning frames which management believes hag 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 ovn satisfaction whether a measurable improvement had been effected or not. Thi3 should be done by a series of dust measurements with exhaust on and off. The volume of air exhaust is insufficient to effect a true local ex haust action, and if it is effective it must, therofore, be an effect of simple dilution. Twin tin it 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. Hero again the operators believe a marked improvement has resulted. Dust count data is needed that will measure the degree of improvement. Winders ' ; . lA.i'--' h l'wv' Cop winders have been exhausted in Plants A and B with reporto of benefieial reduction in dustiness. We do not have quantitative data on this point. Tho exhaust arrangement for Foster winders was developed many years ago and la veil known. The tendency to elimination of this machine makes tho problem one of little practical interest new. In moot plants, dU3t from other equipment, such as spinning and twisting which arc commonly in the same room, is of greater importance than that from winding operations. G04S34 Preliminary Dust Survey for Asbestos Textile Institute, Juno, 19^7 11 Weaving One plant has a superior method of suppressing dU3t in weaving 'ey vet methods and dust count records Indicate a complete suppression of dust, v. ,U It involves a water spray head mounted above the warp at the rear of the harness with a mechanical screw arrangement for constant movement of the spray head transversely to tho warp. They believe it to be Bore effective than the system. Corson in several plants vherein the warp is passed over vetted rolls. It is apparently not practical to recommend 100 per cent vet weaving throughout tho industry. Moreover, wo are satisfied that it is practical to control dust in this operation by local exhaust, where dry weaving is consider ed ir.perctivefor apecial properties of the cloth. One of the best exhaust arrangements includes an exhaust opening directly under the warp at the rear of the harness frane with a slot exhaust opening carried by tho lay bean, the latter connected to the stationary part of tho exhaust systen, either by flexible hose arrangement or by an all metal swivel Joint. Duct Work Tho actual arrangement of duct work and exhaust fan present no un usual problems where good practice in sheet metal fabrication is followed. Two pointjare of sufficient importance to require enphasis. . Special care should be eJfarclBed in tho fabrication to avoid sharp projections on the inside that create points of lodgement for fibers. Secondly, it Bust be designed to pro vide adequate tiunsporting velocities. Velocities below 2000 fpn, in the experience of the industry, cay permit sottlement of material and gradual clogging. Therefore, allowing a margin of safety, the design should provide for velocities of 30C0 fpra. G04S35 Preliminary Dust Survey fcr Asbestos Textile Institute, June, 19*+7 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 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 vill not be elaborated at this point. Dust Collectors Five plants in the survey employ the vcll-kncwn burlap dust house for filtering air fron various exhaust systems. The favored filtering area is determined on the basis of ono square 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 systen, the men are required to enter the dust side for clean ing purposes, and final cleaning is carried out once weekly with the use cf a central station vacuum cleaner. Fractice3 in different plants are variable as to frequency with which the burlap filter i3 freed of its duct load by whipping. While these dust collectors work well, we are not prepared to recom mend them to the exclusion of eons 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 tlirough the filter proper (tack 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 0046 r 0 Preliminary Dust Survey for Asbcat03 Textile Institute, June, 19^7 of weeks, the oysten operation will suffer. Apparently, soae of the older commercial flat tag type of collectors did exhibit that difficulty. Modifi cations In the design of such units have, however, teen incorporated in more recent models and thoce difficulties may have teen 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 coat and operating C03t. Becirculation / 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 vhore there is obvious ly leakage of dust through the filter and consequent recontamination of the air inside the plant. The practice is generally frevned upon where dustc 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 boilor capacity which cannot be passed over lightly. 004637 Preliminary Dust Survey for Asbestos Textile Institute, Juno, 1947 14 II - MEDICAL PRESENT I-SDICAL FACILITIES AND PRACTICES Every plant has connections vith a local specialist in radiology vho 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 vellestablishcd schedule of periodic medical examinations. Half of the plants have no positive information as to the incidence of asbestosis among their vorkers. The situation i3 these respects is in dicated in Table H. TABLE H. PRESENT PRACTICES AND FACILITIES AS TO MEDICAL X-PAY EXAMINATIONS Hi VARIOUS PLANTS Plant A B C D E F Cr H I J Recent X-ray"*Survey Made Yes No Yes Yos No No No Yes No Yes Periodic X-ray Examinations Made No No No No No No No Yes No No Have Cvn X-ray Machine Yes * No No No No No ` No Yes v!- No Yes ^Within last few years, and results available to plant or its plsycician G04S30 Prcl.lr.~tnary Dust Survey for Asbestos Textile Institute June, 19^7 15 estimated iNcuircs OF AS2ESTCSIS The incidence of asbestosis among employees of those plants where employees were examined in recent years, shows a narked variation as indicat ed by the following: Plant k has recorded cases diagnosed as asbestooi3 to the extent of about 20 per cent, and in the past nine years tea compensated, on the average, two cases per annua. Total textile employment about 400. Plant C on the basis of a recent systematic survey, eotiaates asbestosis incidence to bo about three to four per cont. riant D has results from on incomplete survey in which four cases were found among those volunteering for examination with a total textile em ployment of around 150. They have compensated one cese in about 10 years. Three more are pending. Plant H vith a textile employment of 3CO finds five or six cases y\ annually that the physician believes show early changes due to asbestos. Plant J has counted potential cases of asbestosis amounting in number to about 20 per cent, comparable with Plant A. The other plants haw conducted no systematic x-ray aurvoys of their own and have no information as to incidence among their employees. None of these has had caee3 requiring compensation. While we 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 G04830 Preliminary Dust Survey for Asbestos Textile Instituto, Juno, 194T 16. a serious lack of information prevails generally on this aepoct of tho problem. The story in North Carolina i3 vortli special mention. This stato instituted 10 years ago, a system of periodic medical examinations for all vorkors in dusty industrio3 and, hence, all asbcsto3 textile workers have bocn x-rayed and clinically examined for a`longer period, on a periodic basis, than any other asbestos toxtile plant in. this group. If the stato examination finds that workers should discontinue thoir employment because of rapidly developing asbootosio they have tho authority to effect this change. They also eee to it that vorkors who should recoive workman's compensation due to dis abling asbestosis are processed. So far as wo have been able to ascertain neither ovont has occurred to any employee of the two North Carolina aabectcs plants in this group. These observations sugge3t that there nay well be a marked divergence in nodical procedures, interpretations, and attitudes respecting the diagnosis of asbestosis. There is a very urgent need for a concerted cooperative medical effort to develop improved diagnostic procedures and uniformity of interpre tation. G04C40 Preliminary Dust Surrey for Asbestos Textile Institute, June, 19^7 17. IMPOKEATICi: 0? TTF.ICBIC 1-EDICAL EXMffiJATlONS One of the r.03t important elements 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 aabestosis 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 more light on the. facts. The importance of the periodic medical x-ray examination can per haps best bo emphasized by stating that duot count investigations cannot, in the present stato of knowledge, give U3 assurance as to the extent of cur suc cess in eliminating the hazard. Regular examinations cervc 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 asbestosis. 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 eqplpnent, vill eventually indicate when the battle of aabestosis con trol is- being von. This aspect of the problem is elaborated in the following section, Tho inventory provided by such a medical program is Just as important to intelligent action in this problem, as. material inventcrics are to the proper conduct of business. CO 45 Preliminary Dust Survey for Asbestos Tortile Institute, June, 1947 18 The question aa to whether a plant should purchase ita cvn x-ray equipment is an econonic one involving consideration of cost of local outside nodical and x-ray facilities and of loss of enployce tine in travel, etc. PlaCTogtic Fanel To further the objective of inprovenent and unifornity in diagnostic procedures, a nodical section of the progran is proposed in the fora of a MEDICAL ASTIoICSIS PAIEL to be composed of outstanding nedical con in this field, and of the physician designated by each conpany as the ono responsible for it3 nedical and diagnostic work. The composition, as to outside nedical personnel, of this panel would be determined by Its objectives: the assenbling of the best possible nedical brains and the nutual education in diagnostic procedures that cones fron exchanges of scientific experiences and information. The panel would meet, perhaps seni-ennually, and consider the sig nificance of x-ray files and other clinical data brought to the group by each participating physician. Dr. C.' Richard Walter's services would be available for the organization and other details. C04S42 Preliminary Bust Survey for Asbestos Textile Institute June, 19^7 19. STATISTICAL STUDIES OF MEDICAL ILCOFTS There are tvo very important questions concerning the physiological nature of asbc3t03 that have not yet been answered by any published investi gation: 1, . What is the expectation of asbestosis in workers exposed core than 15-20 years to lev concentrations of aobestes dust? Among the 500-odd workers vho composed the oubjects in the U,S. Public Health Service study, there were abnormally few vho had been exposed for more than 15 year3 and practically none over 20 years. These facta seriously affected the conclu sions that could be drawn. 2. Is there a progression to advanced asbestosis after exposure oi 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 throw valuable light on these questions. Hone of the plants visited during this inquiry have sufficiently extensive and systematic records to provide satisfactory .answes to these questions, but 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. CO a n t 404 Preliminary Du3t Survey for Asbestos Textile Institute, June, 19^7 20. The moat outstanding store of information, is in the records of the Division of Industrial Hygiene of the North Carolina Department of Health vho, in accordance vith state lav have x-rayed vorkera in this, and other dusty Industries, almost annually for the past 10 years. A study of these records vould undoubtedly cast much light on the question of progression. Through officials of the company members in North Carolina, ve already have assurances of their full cooperation in any investigations, and although vo have not discussed the matter vith them directly as to details, there is every reason to suppose that the desired information vould be made available to us for the purposes described. In addition, a general x-ray and medical survey of vorkers in one or two plants vith a long history of high order of dust control vould be of great value for this purpose. G046 <( Pro Urinary Bust Survey for Asbestos Textile Institute June, 19^7 21 HI - PHYSICAL SIGNIFICANCE OF BUST COUNT'S Correlation between development of osbestosis and some pertinent measure of dustiness, e.g., dust counts, can be developed by periodically ob serving and recording data on both aspects -- periodic medical examinations of exposed workers together with the periodically measured dust exposure of each. Hcwever, to be useful for preventive purposes, theseprocedurcs have to be extooied into the past wherever data is availab.e This was the proced ure employed in the studies of the U.S,Public Health Service in North Carolina plants (Public Health Bulletin No. 2Ul, 1939). The main value of dust counts in asbestos plants is to obtain data on dust concentrations that can be compared with that study, and thuG 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 asbost03is by medical and x-ray examinations of the men employed. A statistical comparison of the two sets of data 1tho investigators to the conclusion that new cases of asbestosis would jyobably not occur if dust control measures were undertaken to ensure that no dust exposures exceeded five million particles per cubic foot (measured in the sane manner). 004545 Preliminary Bust Survey for Asbestos Textile Institute, June, 15^7 22. APPRAISAL CF FHEUCZD LUST HAZARD Having reached a degree of dust control represented by the duct count Unit of five million, it is then proper to ask: "What degree of assurance is afforded by existing knowledge that asbestosis will not, in fact, develop in the future if dustiness is kept b9lcv that level?" If there are factors, at present unknown, that will indicate a need for still tetter dust control,what will that limit be? The information available dess not permit complete assurance that lf 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 I I 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 One basis of uncertainty as to applying present conventional duet counting techniques to tho 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 comprise 80-95 per cent of the total dust scon in dust counting. While it is proven that asbestos dust i3 the cause of asbestosis, there i3 no certain information as to what shape or size of dust is the causative factor. The correlation studies of the U.S.Public Health Service G04S4S Prclinlnaty I>-at Survey for Aabestos Textile Institute, June, 19^7 23 employed conventional dust count techniques which, in effect, related incidence of asbostosia to the number of non-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 than 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 on adequate, index. Preliminary Studies on Qualities of Aobsstos Eust With a view to eventual development of supplementary methods for measuring asbestos dust concentrations on a weight basis, wo have conducted scoj 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-microscopic particles and fibers. Another aspect of the dust examination problem on which preliminary work has been dons 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 we 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? GO 4 S 4 7 Preliminary Duot Survey for Asbestos Textile Institute,. June, 1947, 24. 2. Secondly -- since the limit of resolution of the microscope lenses used in dust counting dose not permit Geeing 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 low power light-microscope are in fact bundles of fiber resembling a lifesize 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; tho fiber is therefore invisible in the dust counting microscope. 004640 o g0-1 ow-< -I *\ THIS CIRCLE 1 MICRON DIMETER Prelinirsry Dust Survey for Aabeot03 Textile Institute, June, 19^7 25. Urey also shoved sons fibers a few nicrona in length whose dianeter is only 0,01-0.02 nicrcns, although the comonest particles are bundles of fibers about 0.1 nicron in width. In addition to the light these observarions threw on the subnicroseope character of asbestos dust, they are cited to indicate the other qualities that night be pertinent to evaluation of dust exposure, to supplenent the duct count technique now in use. 004650 Preliminary Dust Survey for Aabestoo Textile Institute June, I9U7 26 DJHEKEKT KJSTH.TS3 OF STOCK In investigations of the type being presei&ly considered, a primary ain cu31 be to develop improvements in dust control vith the minimum of vaste notion end 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 vith the fev tests we perfoxrsd ourselves, provide numerous instances of variation, the cause of vhich 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 alcoho.l, then caking a dust count in the same manner as vith 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- l 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 standardized mechanical^ahuse of roving in a small vessel while sucking a stream of air vith resulting dust as in the campling 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. C0465.1 Preliminary Du3t Survey for Asbestos Textile Institute, June, 19^7 27 OUTLITE OF D PROCEDURES FOR ASBESTC3IS UrTESTIGATICNS X. ENSE5EHIKO 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 nrenaration, miscellaneous operations 3, Wet 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. C-04652 Preliminary Duct Garvey for Asbestos Textile Institute Junc; 19^7 28 II. MEDICAL A. Institution of Periodic Medical Examinations This ia urgently recommended to all companies. Medical advice ns to organisation! procedures vill lie given by the Foundation upon request, B. Or.cnnination of a Diagnostic Panel for Asbestogis Arranged by the Foundation's Medical Director and organized to meet in Pittoburgh at suitable intervals for scientific reviev of diagnostic problem, reading of x-ray files, etc. Panel to consist of individual conpany physician or nodical consultants together with other nedical authorities to bo determined. C. Statistical Study of Existing Medical Becords Designed to find ansvors to important questions concerning radical and physical nature of aobestosic; especially concerned vitil records of State of North Carolina, Metropolitan Life Insurance Company, etc. III. PHYSICAL TESTING -- (Further Dust Studios) 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 ashestools hazard after reduction of dust to meet the present standard; to insure that effective control of duet has been attained. This is a step by step program aimed at the elimination of asbestos!# cases from the plants of Asbestos Textile Institute members. G04653