Document G55kXwxZMMd0mDgXKZOwVxZQv

^CO Fifth Avenue Pittsburgh 13, Pa, REPORT OF ' FHEXIMIEARr TJST IIT7ESTIGATICN FOR ' ASBESTOS T2XTHS INSTITUTE JUKE, 1947 By W.C.L, Hereon Bead Engineer June Id, 1947 Industrial Hygiene Foundation of Acsrica, Inc. By John F. McMahon lianaging Director / '/ "7 REPORT of PRELIMINARY DUST SURVEY for ASBESTOS TEXTHE INSTITUTE June, 19^7 OBJ ECT OF INVESTIGATION This project vas a preliminary investigation of the asbest03is problem in textile plants of cambers of the Asbestos Textile Institute, with the immediate object of defining the specific nature and the magni tude of the problem in all ite 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 facts upon which this report is based 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 -extended at all plants. Dr. C. Richard Valmsr, Medical Director of 3jptrlal Hygiene Foundation, participated in visits to throe plants nnd development of the medical concepts of this report. The problem is seen to be composed of three aspoct9 which are discussed in three sections of the report and summarized herewith, as ENGINEERING, MEDICAL, and PHYSICAL TESTING. 00462o Preliminary Dust Survey for Asbestos Textile Institute Juns, 194-7 o Engineering;, -- Mechanical methods vere 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 two exceptions. It is proposed to prepare formal detailed descriptions of these methods for gener al distribution to renters 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 asbestosis. 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, throe 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 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 ag practical. Physical Testing (Dust Counts, etc.) -- The "maximum permissible du3tdne&jrw' for asbestos is comnonly taken to be five million particles per cubic foot, iis 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 some workers after a long working life (greater than 20-25 yearn). Scientific evidence is obscure on this point. It is recommended, therefore, that studies be initiated aimed to develop another G04S2G  Preliminary Bust Survey for Actc3tos Textile Institute June, 19^7 yardstick, because it is suggested that vhen control bolov five million is attained, present du3t count methods may net properly measure the remaining hazard. A detailed summary of recommendations for a long-tern investigation is given at the end of this report. 4r"`! G04627 .MX Preliminary Dust Surrey for As bee too Textile Institute, June, 19^7 t X - EN0IH2EHN0 PPZSEI7T STATUS OF DUST CCKTROL Practically all plants visited have had one or more dust count sur veys node of their operations and these data were available for the present study. In addition, a few samples vere taken by the investigator in moot plants. These records vere studied and a range of concentrations Judged to bo 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. figures for carding room dustiness indicate .that with reasonably good i|3sure and exhaust of the machines, concentrations well 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 wide variation in dustiness, ranging from two to eight million, but the volume of data arc not 004625 * Prcli ir.ary lust Survey for Asbestos Textile Institute, June, 19V7. co K< CUKm CO Cm J3 If D E O O Q 6* fe p 2 W O *5". cr. W 5 fc, O e2 e* z w 0 w a 0 to w A H 3 0 pH tH O 0*^3 J-i >HJ -p e-. -h c ?0 p0 CD sO 7 r- ? K' 01 ph CV 0 A 1 pH rr--i pM 1 1 co P-- -J- 1a r- A 111 A pH 0 1 1 "1 ITS CU A O CO co w Om pH pH cu. 1 1 1 1 1 0 fr\ A A H pH A '-r TK *7 c a i1 CU 1 CO r1t -3* c-- JO 1 cu cu OO co pH pH 111 l cu CU CU fl A CU 14 W A O ,< * .r cu A 1 1 cu t 1 1 H cu pH cu pH K> 1 pHf> pH cu OS pH 1l A -3* t-- A CO 1>1 AAA 1 H* A 1 1 CU 1 p( CU cr e*- OJ iA 1 VO 0 rH A t-- 11 1 A pH A (M l1 HH AAA A 111 1 pH pH pH " A 11 OJ -3- VO 11 CU CU CU 1 r"4 t t-- CU cu 1 1 Ht cu ex? cc rt H pH 0g 22 p pM to w c<3 tr A c. to C fO V. CO CO pH a -pH c <3 P r4 pH h A *3 O to a > O tj O J.< H c M cl 0 c U <3 3 pH 4> CU pH (U O A CO ^ 5 004620 Preliminary Duot Survey for Acbcctos Textile Institute, June, 19^7. 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 tho available data of marked differences between this operation and mule spinning. There is a similar wide variation in data for twisting (two to eight million), but there is sene justification in those data for the opinion widely held that this is one of tho 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 tho campling procedure. If the largo inpinger is main tained in one location and there io a strand breakage in that immediate vicinity, the resulting whipping duot 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 million obtained in Plant A reflect highly efficient vet weaving methods there employed. Concentrations less than four to five million are readily attainable by local exhaust methods as indicated by the results in ocveral plants. The data for spooling and winding operations are included for com pleteness, but reflect miscellaneous operations and conditions. The dust re ported,!* often due to the effect of other machinery in the eame room. These conalw||tcns therefore affect the reliability of these data, as in the case of opordtiono in the preparation room. 004530 Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7. 7. EXISTING FJST CONTROL 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 fora 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 makes it impractical to formulate cany general statements. However, it cay ho said that such con trol as is realized results from the use of modem equipment that is well en closed and which usually incorporates pneumatic conveyors with ceiling con densers. The largo 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 ex ception of these two common operations, most of the dust control procedures required,Tvill be noro or less specific for each plant. Cardl nrr 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 machine and carefully designed exhaust. Moreover, experience of several G 0 4 6 31 Preliminary Dust Survey for Asbestos Textile Institute, Jure, 1947. 8 companies proves that it docs not interfere seriously with manufacturing operations nor vith quality of roving produced, Cur investigations indicate the superior advantages of having side- walls of the enclosure of wood to facilitate erall clearance by rubbing con tact at the edge of the rain cylinder, thus avoiding excessive air infiltra tion at that point. Wood covers have the .advantage of resistance to crashing, vhich vss evident in installations vith sheet ratal covers. Connection of the enclosure to the exhaust system by means of cham bers of ample dimensions, i.e., large croes-sectional area is of major im portance to avoid localized high air velocities close to the webbing in the main 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 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 A i.y B 20 B Air Exhausted Per Sot 1500 cfa 2200 cfm 3800 cfa 5400 cfa 2000 cfa \ tt 1 1 1 It is apparent froa this investigation that 2000-2500 cfa per set of brcaicer and finisher cards is ample exhaust capacity if the system i3 properly designed. 004S32 Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 9 All five of the systems described in the table serve 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 cfa. Sidewalls are easily romoved for repairs. Most plants would not prefer this arrangement. As far as the dust count data can show, the card room of Plant B vith 2200 ctn is equal if not superior to that of Plant 2 with ?SCO cfa, a recently installed system. The fundamental features of best card dust 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. K Duct branch not over 5"> preferably V*. No blaet gate dampers in branch line. Exhaust influence over comb, cither by extension of main cover or by separate hood3. 7, Exhaust space under machine, not over V 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 q>ace between the ring doffers and the main cylinder. 004633 Preliminary Dust Surrey for Asbestos Textile Institute, June, 19^7 One plant has installed ventilation for their ring spinning frames which 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* Tire did not permit demonstrating to our o\m 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 volume of air exhaust is insufficient to effect a true local ex haust action, and if it is effective it rust, therofore, be an effect of sirple dilution. Twin tinft Interest in control of dust fron twisters is widespread in the in dustry and Plants A and B have installed an exhaust syaten 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 / * j; (k> (,(.<:- 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 for Foster winders was developed many years ago and is veil known. The tendency to elimination of this machine makeo the problem one of little practical interest now. In moot plants, dust fron other equipment, such ao opinning arid twisting which are commonly in the some room, ia of greater importance than that from winding operations. 0045 3 4 Preliminary Dust Survey for Asbestos Textile Institute, June, 19^7 11* Weaving One plant hao a superior method of suppressing duct in weaving by vet methods and dust cotint records indicate a complete suppression of dust. v , i.. It involves a water spray head counted 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 core effective than the system eoffion in several plants wherein 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 inrerativefor cpecial properties of the cloth. One of the best exhaust arrangements includes an exhaust opening directly under the warp at the rear of tho harness frame with a slot exhaust opening carried by the lay bean, tho latter connected to the stationary part of tho exhaust system, either by flexible hose arrangement or by an all natal 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 polnwp)** of sufficient importance to require emphasis. . Special care should be ei(Jpp|sed in the fabrication to avoid sharp projections on the inside that " vfe- create points of lodgement for fibers. Secondly, it must be designed to pro vide adequate transporting velocities* Velocities below 2000 fja, in the experience of tho industry, cay permit settlement of material and gradual clogging* Therefore, allowing a margin of safely, the deoi^i should provide for velocities of 3000 fpra. 004S35 Preliminary Bust Survey fcr Asbestos Textilo 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 oxhauat systems. The use of dampers in branches to adjust air flows is avoided in the best aystecs. Their function in effecting balance between branches is best attained in the original design, resign procedures to effect this ob jective are available but vill not be elaborated at this point. Dust Collectors Five plants in the surrey employ the well-known burlap dust house for filtering air from "various exhaust systems. The favored filtering area is determined on the basis of ono square foot for each air flew of 2 ofn, Mo3t arrangements are such as to permit cleaning by whipping vith a bamboo polo or a buggy whip by men vho remain on the clean air side of the filter cloth. In one system, the men 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 are variable as to frequency with which the burlap filter is freed of its dust load by whipping. While these dust collectors work well, ve are not prepared to recom- mend them to the exclusion of some commercial types of filters having automatic shaker*. Several engineering elements enter into the design of a dust collect- or s involving principally a proper estimate of pressure drop in all ele- nento of the system and especially that through the filter proper (lack 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 increaso over a period 00463 r O Preliminary Eust Survey for Aotcst03 Textile Institute, June, 19^7 13 of weeks, the system operation will suffer. Apparently, goes of the older commercial flat tag type of collectors did exhibit that difficulty. Modificaticr.3 in the design of such units have, however, been incorporated in more recent models and thoce difficulties say have been eliminated. Two plants employ commercial collectors of the flat bag or envelope type. Another plant uses a cloth tube commercial collector and al3o one whose filtering element i3 of paper, which is replaced at intervals of several weeks. A study of operating details of these cecnercial collectors is indicated in this study, including considerations of original coat and operating coat. / Recirculation Several plants return air fron 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 recontaninaticn 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 involjsif in dust, Control represent a tremendous problem as to heat loss and 3S.. ` boilo capacity which cannot be pasced over lightly. 0046b3 Preliminary Duet Survey for Asbestos Textile Institute, Juno, 19 Ik II - MEDICAL PRESENT MEDICAL FACILITIES Aim PRACTICES Every plant has connections with 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 veilestablished schedule of periodic medical examinations. Half of the plants have no positive information as to the incidence of asbestoois among their workers. The situation is these respects is in dicated in Table H. TABLE H. PRESENT PRACTICES Aim FACILITIES AS TO MEDICAL X-FAY SXAMEwvi'ICNS IN VARIOUS HANTS Plant A B C D E T" pV Ct H I J Recent X-ray1 Survey Made Yes No Yes Yoe No No No Yen No YC3 Periodic X-ray Examinations Made No No , No No No No No Yes ' No No Have Own X-ray Machine Yes No : ,.ft. No No No No `No Yes No Yea ^Within last few years, and results available to plant or it3 plsycician G04536 Preliminary Dust Survey for Asbestos Textile Institute Juno, 1917 15 ESTIMAT'D Ii:C2Di::CS 0? ASEESTCSIS The incidence of asbestosis among enployees of those plants where employees vere examined in recent years, shows a marked variation as indicat ed by the following: Plant A lias recorded cases disposed as asbestosis to the extent of about 20 per cent, and in the past nine years lias compensated, on tho average, two cases per annua. Total textile employment about 100. Plant C on tho basis of a recent systematic survey, estimates asbestosis incidence to bo about three to-four per cent. Plant S has results from an incomplete survey in which four cases vere found among those volunteering for examination with a total textile em ployment of around 150, They have compensated one case in about 10 years. Three more are pending. Plant 5 with a textile employment of 3^0 finds five or six cases annually that the physician believes show early changes due to asbestos. Plant J has counted potential coses of asbestosis amounting in number about 20'per cent, comparable with Plant A. ****/ She other plants have conducted no systematic x-ray surveys of their own and have no information as to incidence among their enployees. None of these has had cases requiring compensation. While we have no complete data on history of employment and labor turnover in tho several plants, it is apparent that there is, at least super ficially, a marked inconsistency in this picture. Also, it is clear that CO 4 Prcli.cir.ary Dust Surrey for Asbestos Textile Inatituto, Juno, 19 47 16. a serious lack of information prevails generally on this aspect of the problem. The story in North Carolina i3 vorth special mention. This state instituted 10 years ago, a ays ton of periodic medical examinations for all vorkors in dusty industries and, hence, all usbestos textile workers have been 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 aobest03io they have the authority to effect this change. They also see to it that vorkors who should recoive vorixan*s compensation due to dis abling asbestools are processed. So far as vo have been able to ascertain neither ovont has occurred to any employee of the-two North Carolina astec tea plants in thia group. These observations suggest that there may well be a marked divergence in radical procedures, interpretations, and attitudes respecting the diagnosis of astestosis. There is a very urgent need for a concerted cooperative nodical effort to develop improved diagnostic procedures and uniformity of interpre tation* Preliminary IXmjt Survey for Asbestos Textile Institute, June, 19^7 17 IMPORTANCE OF PERIODIC MEDICAL EXAMINATIONS One of the most important elements of a program, of protecting health of workers in dusty occupations is the periodic medical examination. The lech 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 more light on the, facts. The importance of the periodic medical x-ray examination can per haps boot bo emphasized by stating that dust count investigations cannot, in the present stato of knowledge, give us assurance as to the extent of cur suc cess in eliminating tho hazard. Regular examinations cervc to protest 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 contro;*4alpc6nt, will eventually indicate when the battle of asbestosis con trol io^being von. 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 inventcries are to the proper conduct of business. C04 Preliminary Dust Survey for Asbestos Tortile Institute, June, 19U7 18 Use question as to whether a plant should purchase its cvn x-ray equipment is an economic one involving consideration of cost of local outside nodical and x-ray facilities and of loss of employee tine in travel, etc. Diagnostic Panel To further the objective of improvement and uniformity in diagnostic procedures, a nodical section of the program is proposed in the fom of a MEDICAL AS2E3ICSIS PAIHL to be composed of outstanding medical non in this field, and of the physician designated by each company as the ono responsible for its 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 cones from exchanges of scientific experiences and information. The panel would neet, 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 Walter's services vould be-available for the organization and other details. C04642 Preliminary Duct Survey for Asbestos Textile Institute June, 19^7 19^ STATISTICAL STUPES OF MEDICAL KEC0PI3 There are two very important questions concerning the physiological nature of aobc3t03 that have not yet been answered by any published investi gation: 1, . What is the expectation of acbestosis 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 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 ashesto3is after exposure cv 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 on these questions. Hone of the plants visited during this inquiry have sufficiently extensive and systematic records to provide satisfactory. answes to these A**' qtuwptcn*, but the medical department of Metropolitan Life Insurance Company, 3t~- 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 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 with state lav have x-rayed workers in this, and other dusty industries, alno3t 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 renters in North Carolina, ve already have assurances of their full cooperation in any investigations, and although vo have not discussed the natter vith then directly as to details, there is every reason to suppose that the desired information vould te node available to us for the purposes described. In addition, a general x-ray and medical survey of workers in one or tvo plants vith a long history of high order of dust control vould be of great value for this purpose. G04644 Preliminary Bust Survey for Asbestos Textile Institute June, 19^7 21 HI - PHYSICAL SIGNIFICANCE OF LUST COUNTS Correlation between development of osbest03is 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* However, to be useful for preventive purposes, theseprocedurcs have to be extx&ed into the past vhorever data is availab.e This was tho proced ure employed in the studies of the U.S,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 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 sen employed* A statistical comparison of the two sets of data investigators to the conclusion that now cases of asbestosis would not occur if dust control measures were undertakento ensure that ncTduat exposures exceeded five million particles per cubic foot (measured in the sane manner) Preliminary Dust Surrey for Asbe3t03 Textile Institute, June, 15^7 22 APPPAISftl CP HHXSCED IaJST FAZAPD Haring reached a degree of dust control represented by the dust count Unit of.five million, it is then proper to ask: "What degree of assurance is afforded toy existing knowledge that aetoe3tosis will not, in fact, develop in the future if dustiness is kept toelcw that level?" If there are factors, at present unknown, that will indicate a need for still letter dust control,what will that limit toe? The information available does not permit complete assurance that 11 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 assurances be sought or a new yardstick of accomplishment be found for ac curately measuring any remaining hazard in the dust zone below fire 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 duct counting techniques to tho measurement of asbestos dust hazards below the five $|lliGn. level Is summarized in the question. -- are the fibers of asbestos the cfi&tiiativ* 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 pern 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 as to what shape or size of duct ia the causative factor, Tho correlation studios of tho U.S.Public Health Service 004S46 Prolining*7 Duet Surrey for Asbestos Textile Institute, Juno, lS^T 23 employed conventional dust count techniques which, in effect, related incidence of asbestosia to the number of non-fibrous particles of a si2 ranging from one to five or 10 microns. For illustration, suppose the causative dust element is somethin 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 duat; it would, in that case, provide an adequate, index. Preliminary Studies on Qualities of Aobestos Dust With a view to eventual development of supplementary methods for measuring asbestos duot concentrations on a weight basis, wo have conducted some preliminary studios 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 dco%involved studies with the electron microscope. Ve posed 1, Ordinary dust particles, one to three microns in diameter, conprise most of the particles in the dust count. They look like ordinary in dustrial duat and ve refer to them as "cubical" as distinguished from `'fibrous" particles. The question io: are these particles in fact non-fibrous or are they bundles of fibers? Preliminary Duat Survey for Aabcstoa Textile Institute, June, 19^7, 2k 2. Secondly -- since the limit of resolution of the microscope lenses used in dust counting doss not permit seeing particles very much smaller than one micron, one may ask if there are cany fibers of great length, but of such small width that they are invisible? Samples of atmospheric dust vere 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 vary large fibers, the air being sampled vao caused to pass first through a glass spiral coated vith 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 obtainedwith this apparatus in a card room having a good dust control, we obtained pictures, some of which are reproduced in the attached Figure. Cxey demonstrate first, that the cubical particles seen by a lew power light-microscope are in fact bundles of fiber resembling a lifesize handful of partially opened fibers. |j|L 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. 004640 THIS CIRCLE 1 MICRON DIAMETER o &ir\ w6-i MfMO<*4 oC3 s 8toQo-4 CO 8 3 CQ W A O ICJ sM 0- H 8 S3 GO 4640 Preliminary Dust Surrey for Asbestos Textile Institute, June, 19^7 25 They also showed sons 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 observations threw on the subnicroscope 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 duct count technique new in use. 004650 Preliminary Dust Survey for Asbestoo Textile Institute Juno, 19^7 26. TUHEFEyr rusTi^ss of stock In investigations of the type being preseAly considered, a primary ain east be to^develop improvements in dust control with the minima of vasts 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, combined vith the few tests we performed ourselves, provide numerous instances of variation, the cause of which is not apparent. We undertook recently to neasure 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 sane manner as with air samples. The result would be expressed in millions of particles per yard of roving cr 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. i 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 mech- anica&g&ose of roving in a small vessel while sucking a stream of air with resultjpg dust as in the sampling for ordinary dust counts. A test of this kind, in conjunction vith the dustiness index would be of value in evaluating the oiling practice, or it might take the place entirely of the procedure previously outlined. C04651 Preliminary Dust Survey fcr Asbestos Textile Institute i June, 19^7 OUTLINE 0? ESCffC-gTSED PRCCI3TJFES FOR ASB5ST0SIS ErVESTIGATIOKS 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 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 cococrcial dust collectors, etc 004352 Prcliniinary Duct Survey for Asbestos Textile Institute June, 19'i-T II, KSD1CAL A, I:\g tituticnofPoriodic H-dies1 Fxamiratione This is urgently recommended to all companies. Medical advice aa to organizations. procedures vill be given by the Foundation upon request* B. Organization of a Diagnostic Panel for Asbestosis Arranged by the Foundation's Medical Director 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 medical authorities to bo determined. C. Statistical Study of Existing Medical Becords Designed to find answers to inportant questions concerning medical and physical nature of aobe3tosic; especially concerned vitil records of State of North Carolina, Metropolitan Life Insurance Company, etc. Ill, PHYSICAL TlSTSIC -- (Further Dust Studios) Studies of physical and chemical characteristics of asbestos dust 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 asbestosis hazard after reduction of dust to meet the present standard; to insure that effective control of duet has been attained. asbe Rifs la a step by step program aimed at the elimination of eases from the plants of Asbestos Textile Institute members. vw C04S5