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THE RAYBESTOS DIVISION *5 OF RAYBESTOS'/VVANHATTAN. inc. " Iwi^ic* * (! - & * *0**C t *11 t <*. f v*o* I 0*! l(VOHOW> C c . Bridgeport.Conn. Dec. 12, 1934 ' I AY6CST0S UNtriCS f C 6'<^ L***d So* A I Wove* S*l Stock Molded Sled Siac* Sl*f Edit CoM (d|f Move* Vco Move* F. w. He*n Ovir MoMfd $C|**(AII MoMvd L****l ** Mono Wove* Sef~c*<s D*e Sfr*>J Comotrued LA**< Trimmiiioe li^n--rod CLUTCH FACINGS Wove* Molded Setme*Ul RAkC SCtviCC STATION COUiF'mCviT 0*m* Lethe Dr*Ui*i e*d Co*Ate*i^i*8 Moc**ei Rveli*c Michwft Hem OwIt R***<e' Semi AvtemeK Rvitr L***f Cvtle' Wheel Fv*e Pedei Otwcstor* MydretHitiel Ait JkU ReH***i Sifici rake U**f G#mden i I BAXES Aolpmod^lf ImOirttnoJ. Soeoei WICKS e*e 8v*r Od SlOM ivCTS TeWtr 6'*tt S#ai Brass BACKINCS ikr $Hrm Stock A%0etto Bed e*6 Suck w** I*levied M<k Titled Pact**! Cemotttrd Fan BELTS Cab MATS MOSC * A v I v_J( I Not. . Cm wW,iiHi m.u CCmo HNi i* Hon Cmn iic^>i10. Hot. **u>' Hot. ***.*-tIiO.HO W.0O. Hot. HHi| Hot. lir. E.E. Jeffords, Gen.,]Jgr. , General Asbestos & Rubber Division, Ecrth Charleston, S. C. Uy dear "Jeff": Enclosed find copy of Report on Effects of Asbestos Dust on the Lungs and Dust Suppression In the Asbestos Industry, by E. R. A. 1/erewether, end el so Report on Conferences between Employers and Inspec tors concerning f'ethods for Suppressing Dust In Asbestos Textile Factories. If you already have copies of these pamphlets, will you klicly return the enclosed, so ne may pess them on to some one else? Tery truly yours, SS-G. C**lC M'Ck V*** Cll 004G 30-/ L*. r a*: HOME OFFICE Croxcu Ccpyifki Rtitrxti r' . . REPORT ON ** v# -V'^sfe' V*'***' - - -v EFFECTS OF ASBESTOS ON THE LUNGS - :/, S ' . . and : .'DUST SUPPRESSION. IN 'DUST - *i'! '' \ , wl . THE-^^v, ;: \ ASBESTOS. INDUSTRY , - . * V*' - ^r -' * PART -L Occurrenceof Pulmonary Fibrous usd other . ; Pulmonary Affection* in Atbcttot Worker* . .. PABT IL Processes giving rite to dust and method* for- it* suppression * :. ,J . ** * ; ___ ^E-1U A. MERPAVETHER. -M.D.- rT- . .. Hil. la*r*etart faanct AND , C. w. price ,11.11. Iwfmnr at K*tf>r*ri r*i>. , ; T` *" " ^* ' * ^ w ' ` **r`*'* * \ ' :.'S"X .V; L ::4vv::-. , --.... .hues'. f * . * .1 ' * ,.v t .*.. s . l> : iv. t t I .. r?. Ur *p.- V t iv- r*i: :" . 'A. ... 1 . .s' * ' * ` LONDON: PRINTED AND PUBLISHED BY HIS MAJESTY'S STATIONERY OFFICE. . To be purchased directly from H.M. STATIONERY OFFICE at Ox following addresses: .Ad astral Hcnuc, Kingaway, London, W.C.J; ISO, George Street, Edinburgh; York Street, Manchester; I, St. Andrew's Crescent, CardiS; IJ. Donegal! Square Wot, Belfast; ' .' . or through any Bookseller. " V*':] J4.106T' 1930 ' Price If. .v). Net I: PLAINTIFF'S IJ EXHIBIT- U--- V -r CH .0004 -%<fr 1 . . I *4 HOME OFFICE / Crova Cefjrifkl Rntrvtd REPORT ON EFFECTS OF ASBESTOS DUST ON THE LUNGS u-nd DUST SUPPRESSION IN THE ASBESTOS INDUSTRY PART L PA FT II. Occurrence of Pulmonary Fibrosis and other Pulmonary Affections in Asbestos Workers Processes giving rise to dust and methods for its suppression BY E. R. A. MEREWETHER, M.D. II,M, Madnal l^nrour of Kwhsrin AND C. W. PRICE ILU. ln;iiMirii^ Inftvtar I'aattfin LONDON: PRINTED AND PUBLISHED BY HIS MAJESTY'S STATIONERY OFFICE. To be purchased directly from H.M. STATIONERY OFFICE at the following addrtuo: Adastral House, Kingsway, London, W.C.J; >30, George Street. Edinburgh; York Street, Manchester; I, St. Andrew's Crescent, Cardiff; IJ, Donegall Square West, Belfast; or through any Bookseller. JS-** 193 Price lUl. Net CONTENTS. / Fait l I. IVTAOPPCTIOV t, Erran or IaiiTsr Doit vrow tb Lvvqb........................................................................... The Haioro ol Aobostoe -- -- ........................................................................ a. Soon or m lovovTioiTtoar ................................................................... ...................... The Pope Is tins ot risk ................................................................................................ BoltcUoo of Worker* (or Eaaaiaation........................................................................... The Clinical Eiamiuetiob and Standards adopted..................................................... a^iognokic Cjuoiuliiu of tbi Loon ... ... . . ... 4. Eavuti or ru Ikqviiy.............................................................................. ftiliofinoii Thci Pulmonary fibrotii of Aibnloi Workers ... -- The Aihwfas H^-li^s The loci droc of Palmooory Fibrosis io Asbestos Workers ... ...................... tITsell of Age end Length of Esoplo/meoi ... .................................. Effoa of Work ifi Different Pruxun ............................................................... Belatire Dustiness of Various AshcoUn i'mccaeea............................................. Cooceot ration of Dust sud Lcngtk of Exiowra arrets jry lu produce Pibnaii DisoMrmert producod by Lite Aftluntos Fibroeis............................................. Progress ood Duration of the Diieam.................................................................. Aioncislini of the Asbestos Fibroeis vitb TulffiOuiry Tuberculosis............. Sum** 17 ... ... ~ -................... -- -- ... -- A Factpis mtuiisivo m PtncrT BoDvirior or ru Aiiotqi Pimmis ... ft. Pisrvmn ftlauvnia............................................................................. 7. Tu Ovtuooi PSOB ft ft ft ft 7 7 ft ft ft V 9 10 11 It 13 1ft 16 16 10 17 17 U|r eCtQPt. PstT II. 1. IVTftOUVCTIQJl ... ... ... -- %. PlftMlIO. .............. VeutiUUuo ..................................... .......................... Separation of Processes .................................................. A Dociimaj or Psocbui sod Psivpriri Huivus ... Tkxtilkm .................................................... {) Yam and Cloth........................ ........................ Opening ......................................................... Cording .............................................................. Stripping end Grinding ........................ Cord Side Wools Trulocnt ............ . Spiunicg ood Doubling ... ....................... Warping, Wiudiug .................................. Plaiting and llrsdmg .................................. WcSTiDg ......................... ........................ Cli/th ** Picking," Efcamiuiug, ilsjuurjug 1ft 1ft 19 to to to to to to tt 13 t4 14 74 tt tft to  . * 3 NOB-TtOTU-B ............................................. Fibaruiag #r Opaaiag (I) Killbeard, Papar, Bbaata ud Tilai ........................ A () InJulnUae Malarial# ud Artidai................................... Goapoailioni ........................ ........................ Cuaolidatad Bbaala .............................................. Bartnci ud Blab* ........................................................ Kmummi ............... (d) Inti ud Quiet TJninf ... -- n. (<) Packing ud Jointing*......................................................... (/} Anhui* in red Elaalria Cudartcr* ........................ JOactrodc* ................................................................... Catli and Wiring ................................... -- Fiald-Oait Wrapping ........................ -- (p) Miaca'li nan in ............. ... _ Koeldad Qooda ... ... _ ... _. A Ct*kio or Wooxa, Macaiatar aap {Ucxi ... A. 8CMJUIT aao Baacnuroroanoid Non on Exjuoit Tsmunn m Aaaarroa YToao ... / PaOl M H t 1T 1T IT IT II II II II II 10 10 10 10 10 Id 11 14 it I This Report was laid before Parliament on the 24th March, 1930, but has not been published as a Command Paper. if- s 4 The Right Eon. J. R. Civkm. M.P.. Hi* Majesty's Secretary of State for the Home Department. Home Office, llth March, 1GS0. Sin, I submit herewith s Report by Dr. E. R. A. Merewether and hfr. C. W. Price On their inquiries into the health conditions of the asbestos industry. Dr. Merewether's investigations on the medical side are of great scientific value. They establish the facts that the inhalation of asbestos oust over a period of years results in the development of a serious type of fibrosis of the lungs, that the development of the disease varies in direct proportion to the length of the exposure to das:, and that susceptibility to the disease is not affectea either by age or sex. The remedy for these conditions is to be found, as in the cose of so many industrial diseases, in the suppression of dust. The aocond part of the Report indicates that this point has only recently beeu appreciated. In the non-textile section of the industry, no serious difficulties arise as regards the application of exhaust ventilation. For the textile section, it is evident that a good deal of experimental work will have to be carried out before completely successful ventilating appliances are evolved effectively to remove all the dust. I have the honour to be. Sir, Your obedient Servant, GERALD BELLEOUSE, f. H.H. Chief Inspector of Factories. 4 Report on Effects of Asbestos Dust on the Lungs and Dust Suppression in the Asbestos Industry. PARTI. THE OCCURRENCE OF PULMONARY FIBROSIS AND OTHER PULMONARY AFFECTIONS IN ASBESTOS WORKERS. 1.--Introduction. This Report is upou the data obtained iu an extensive investigation daring the years 1028 and 1020. The inquiry was initiated by. the Factory Deportment of the Home Office following the discovery iu February. 1928, of a case of non-tubercular fibrosis of the lung* in an asbestos worker, of sufficient severity to necessitate treatment in hospital (Seiler's Cose'). l'rior to this, this Department had knowledge of only two deaths of aslwstor. workers, about whom there was expert opiuion that the inhalation of sbeto dust bad at leas; contributed to, if not caused, the fatal outcome. The first of these, now referred to as the "Montague Murray Case," occurred in 1900, but all that is known concerning it is contained in the evideuce given by Dr. Montague Murray in 1900, before the Departmental Committee oil Compensation for Industrial Diseases'. In this case post mortem examination confirmed tfic clinical diagnosis of extensive noa-tubercular pulmonary fibrosis. The second (Cooke's Case*) occurred in 1924. Here, although Cooke' and Stuart McDonald' were of the opinion that the luugs showed a progressive dust fibrosis together with a chronic tuberculous infection, the etiological relationship between the inhalation of asbestos dust and fibrosis of the luugs would have been strengthened by the absence of a tuberculous infection. An early survey of the industry iu lUlOrll by the Department did not dis close any evidence of the existence of a serious health hazard in the industry, but some experiments os animals conducted in 1912 by Professor J. M. Beattie of Sheffield Univenitv for the Department showed that the inhalatiou of asbestos dust will cause a mild degree of fibrosis. When, therefore, investigation of Seiler's Case showed that other industrial and infective causes of fibrosis could be definitely excluded, the necessity of deciding whether the supervention of this disease in an asbestos worker was an exceptional occurrence, or evidence of i grave health risk in the industry, was apparent and the investigation referred to was undertaken. 2.--Errxcn or Ibutont Dost Upon the Loncs. The most important local effects which may follow the inhalation of dust include pulmonary and bronchial catarrh, asthma, bronchitis, fibrosis of the lungs, and secondary changes, such as emphysema, local or diffuse. These changes in the longs, which may be looked upon ms a measure of the efforts of the living tissues to repel or incarcerate the irritant particles of dust, necessarily cause interference with the general efficiency of the lungs. The impairment of functional capacity may be slight or severe, and temporary or permanent, de pending on tne variety of dust, and on other factors, such as concentration of dust and length of exposure. Moreover, individuals whose lungs have been affected os the result of the inhalation of tome dusts, show an increased susceptibility to the supervention of respiratory infections, such as tuberculosis or pneumonia. Fibrosis of the lungs is recognised to be the most important lesion caused by the inhalation of dust, and thn proneness of workers with a dust fibrosis to be affected with pulmonary tuberculosis has been shown to bo the main cause of the increased mortality rate from the latter disease in certain dusty occupa tions. <iu * s / 6 This triad--exposure to dust, fibrosis of the lungs, and bigb mortality rato from pulmonary tuberculosis--was fouDd to be oomroou to a number of large and important industries, and in all of them the dust incriminated was free crystalline silica (SiOt). These features were not observed, however, in other industries in which, while there was exposure to siliceous dust, the silica was found to exist in the combined form as a silicate and not in the free condition. Thus, shortly, free silica came to be regarded as the pre-eminent cause of induatrial fibrosis of the lungs and as a notable factor m the production of the rrm-mt mortality rate from pulmonary tuberculosis in certain industries. Whilst the pulmonary fibrosis produced by free silica (Silicosis) has been, and is being, minutely investigated, the potentialities, as fibrosis producers, of dust other th*n free silica have not been fully explored, although it appears certain that aome other inorganic dusts can, and some cannot, produce fibrosis under the conditions met witn in industry. That a aerious, even fatal, degree of fibrosis can be produced bv some of other dusts has not lyyn generally appreciated, altnough Dadliam in a thoughtful paper* has drawn attention to this point, in reporting a fatal case of pulmonary fibrosis caused by dust of an ortbodase basalt containing no free silica. Tie Nature of Atbettot.--The fibrous minerals commercially known as asbestos fall into the latter group, the silica being combined with metallic bases, mainly magnesium or iron and, to a less extent calcium, sodium or aluminium. Tbe term u a collective name applied to a variety of silicate minerals which differ from each other in chemical composition and physical properties but resemble one another in their finely fibrous nature and flexibility. Their value depends on tbo facility with whica they can be split up into long and flexible fibres for spinning ana weaving, on their resistance to heat and acids, and on their insulating properties with respect to heat and electricity. Varieties of asbestos possess these.characteristics.in differing degree. Practically speaking, all that goes under the name asbestos in commerce is either fibrous serpentine, or a fibrous mineral of the hornblende group, of which the most important are crocidolite, amosite and trcmolite. Serpentine asbestos or chryeotile is essentially a hydrated silicate of magnesium, containing little iron and practically no calcium. The hornblende varieties contain less mag nesium and usually more calcium, aluminium and iron--crocidolite and amosite being mainly silicates of iron. 3.--Scon or^THx Ikvxsticxtion. Asbestos is very largely used in industry, being an important constituent of maav different products. The diversity of industries concerned made it essential that tome restriction of the field of investigation should be decided upon. The manufacturing processes affected fall more or less sharply into two groups (1) those in which there is exposure to pure asbestos or asnest06 mixed with a very email percentage of cotton or other vegetable fibre, and (2) those in which there ia exposure to a mixture of dusts, of wttich asbestos is but one. The former group comprises, in the maiu, the textile branch of the industry, a branch manufacturing insulating materials from practically pure asbestos, and some preliminary processes in other branches. The latter group includes a number of processes in which tbe proportion of asbestos in the dust evolved ranges from a negligible Quantity upwards. Since it is impossible to evaluate the effect on the lungs of mixed dusts, of which asbestos dust is only one component, until the action of asbestos dust itself was determined, the examination of workers for the purpose of this enquiry was restricted to workers employed in processes included iu group (1), in other wordu, to workers as nearly os possible exposed to the influence of pure asbestos dust. Furthermore, the effects of previous exposure to other irritant dusts, such as that of free silica, had to be excluded. 7 Tkt Ptrpulation at Riik.--The gross number of worker* who nay be exposed to the inhalation of asbestos dust to any extent is unknown, end, owing to the great variety of processes concerned, there ere insuperable difficulties in ascertaining this neure. Nor, in fact, would enlighteument on this point be of any particular value. It is otherwise, however, with respect to the figure representing the number constantly exposed in the course of their daily work to the influence of pnre or almost pure dust. Some information on this point is very desirable to check the adequacy of the sample of workers examined, and to envisage the problem confronting the industry. While ouly a rough approximation is possible, it is believed that about 2,200 is the present number of persons in tnis country exposed in their daily work to the inhalation of asbestos dust, either pure or aomixed with a small proportion of cotton. It should not be overlooked that this figure does not include the considerable number of workers exposed to the influence of mixed durts of which asbestos is but one, and commonly not more than 20 per cent, of the mixture. Of these 2,200, the sample examined uuiubcred 303 (excluding 11 for reasons referred to Inter) or 10.5 per cent. S$bction of Worktrt for Examination.--The selection of workers for examination was not left entirely to chance, since it was early evident that the proportion of those employed 1(5 years and upwards in the industry was very smell; therefore, in each factory those longest employed were preferred, since the importance of including a sufficient sample of this group is evident. Regard was paid to the other end of the scale so as to obtain information as to the length of exposure to dust necessary before effects are manifested, and also to the particular process on which the worker was engaged. By balancing the component groups of the sample in this way as the enquiry proceeded, it was felt that the maximum i-'T.rr.^tion would be obtained in the shortest time. _ ___ _______ It follows, therefore, that iu respect of length of exposure to ksbesta* dust, the component groups of the sample do not bear the same relationship_*&-*h. other as the corresponding groups of the industry under review. The sub joined Tables will make tnis clear. Table 1 shows the distribution according to length of employment (not necessarily in one factory) of 775 workers, the total number engaged on those processes in several factories. Table 2 shows the sample of 3G3 workers distributed in the tame way. Tablz 1. Tauu 3 Yuri aplojtd. NuaUr. 0-4 ................ 9-9 ................ 10-14 ................ 1S-18 ............... to ud orir Touli 4*3 too ft) ii 17 77ft YirftfiUgi of Tout ll'9 in *-* i-i ** too Yura sploytd 0-4 ................ ft-9 ................ 10-14 ................ 19--10 ................ SO t&d e*r TouJs NuttUr. 99 141 S4 ts ** 363 Parcsauga cl Total ' 4<ft SB'S Ml 7*7 ft *9 100 The enormous preponderance numerically of workers employed under five years is striking, as also is the very low percentage of workers employed 10 years or longer. Comparison of the two tables shows that the effect of the method of selec tion of workers for examination ie that the number examined in each successive five years employment group is a progressively greater proportion of the total number which could have been examined in each particular group. A4 it / N With * solitary exception all those examined were at work on the day of examination. Tk* Clinical Examination and Standard) adcrpttd.--The nature and purpoee of the inquiry were explained to each worker whom it was proposed to examine, individually, and his or her co-operation obtained. Each in dividual'* previous industrial history, subsequent to leuving school, was noted iii detail. This was essential in order to exclude, especially, the elect of pre vious work in any of the numerous processus involving exposure to free silica dust, and, to a less extent, the effect of other dusts. Similarly, the in dividual's medical history was scrutinised from childhood onwards, to determine the physical level on entry into the industry and any subsequent changes. Particular attention was paid to account* of pulmonary ailments, some of which, like asthma and bronchitis, are common enough amongst the general population, yet are also non-specific sigu* of irritation caused by the inhalation of dust, whilst others, like influenza and pneumonia, are occasionally followed by a degree of pulmonary fibrosis. War service, if any, was gone into, especially as to whether there was any history of the worker having been a gas casualty at any time. The family and personal history in respect of pulmonary tuber culosis was enquired into, and also at to any close association with known coses of this disease in friends or relatives. In approaching the pertinent subject of symptoms, great care was taken to avoid leading questions, especially in eliciting information as to the existence of any undue shortness or breath. The actual details of the physical examiiintiun do not call for comment, inasmuch as they followed the usual lines of a detailed examination of the chest, witL observations of tlie general health and of the condition of the upper air passages. Inference must be made, however, to the standard of normality adopted in assessing the state of the lungs. The appraisement of any departure from the normal necessarily presupposes the existence of such a standard. Every clinician has sttaii^' experience, his own clear conception of uie"uahnai _ but. it is not often that be niiaxi* uccvaia'i'j~ ii'uT state in *Q~rrr ny words, in fact it seems scarcely possible to do so, and this for eVerkj reasons; the heart and lungs function efficiently within wide limits of applied strain, and, although vestiges of past disease may be present and apparem oc examination, they will be unimportant if they will never tax the organism beyond these limits, are non-progressive and do not predispose to other disease. Age itself lias recognisable effects, but for this reason alone, the chest cannot be considered abnormal. , There is obvious disparity between the standard of physical fitness required for an air pilot and that required for life insurance at ordinary rates; in dividuals reaching either standard cau be classed as " normal," yet many attain ing the latter standard have never approached the former. Thus, within limits, various gradations of normality may be distinguished, and correspondug standards constituted without inaccuracy, the precise status of any standard being determined by the purpose for which it is established. For toe purjiaee of this enquiry the standard adopted has been that evinced in any large group of persons living under similar environmental conditions, apart from work in dusty occupations, os those of the group being considered. This is neither a high standard nor a very low ttaudard. hut the average stan dard of normality displayed amongst the industrial population of this country. Radiographic Examituilion o) thr f.vngt.--In addition a careful radiographic examination of the chest was mode in many (133) cases, the necessity for which in investigations into the effects of dust upon the lungs has been emphasised repeatedly by various authorities It was not, of course, feasible to obtain technically sufficient radiograms of all the workers examined, derived as they were from factories scattered over the country, some in districts remote from a radiological centre. The mode of selection was dictated by the needs of the situation, with the object of elucidating material points germane to the investigation, e.g., the elucidation of complicating affections, in measuring the O 9 s extent And progress of the lesions end locating the point el which the earliest radiographic eigne appear, and ^ntllj as a check upon the human factor presented by the examiner himself "' 4.--Results or thk Inquiry. To anticipate, examination of the data collected in this investigation leads tn the conclusion that the inhalation of asbestos dust over s period of years results in the development of a serious type of fibrosis of the lungs. Asbestoris--the Pulmonary Fibrosis of Asbestos Workers.--It is helpful to visualise fibrosis of the lungs as it occurs in asbestos workers as the slow growth of fibrous tissue (scar tissue) between the air cells of the lung wherever the in haled dust comes to rest. While new fibrous tissue is being laid down like a spider's web, that deposited earlier gradually contracts. This fibrous tissue is not only useless as a substitute for the air cells, but with continued inhalation of the causative dust, by its invasion of new territory and consolidation of that already occupied, it gradually, and literally, strangles the essential tissues of the longs. In common with other essential organs of the body the lungs have a large reserve of tissue for use in emergencies and to permit of a diminution of functional capacity due to advancing age or disease. For this reason, and because fibrosa: of the lungs is essentially a local disease, it is only when the fibrosis progresses to the extent of obliterating this reserve, that undue short ness of breath on any extra effort draws the worker's attention to the fact that bis health is not what it ahould be. The other symptoms of the disease such as cough are equally unassuming, and are readily ascribed to some common and trivial cause. From this point the progress of the disease ia more rapid, since it is now encroaching on the remaining sound tissue of the lungs, already only just suffi cient to maintain him in his ordiuary daily activities. Ultimately, if no acute respiratoiy infection has precipitated a fatal termination, a stage is reached when the lungs can do little more than maintain life, and the shortness of breath becomes extreme. In its main clinical features, therefore, the disease resembles silicosis, as might be expected. It differs from silicosis, however, in the mode of distri bution of the fibrous tissue in the lungs, in its more rapid development, in its radiological features, and, there is some reason for believing, in a lessened susceptibility to the supervention of pulmonary tuberculosis, the liability to which disease is so definitely an added hazard in silicosis. The Asbestos Bodies.--In the lungs of those exposed to asbestos dust, angular particles derived from asbestos,' and spicules of asbestos" are found on microscopical examination, and also numbers of peculiar bodies described by Cooke and Hill' and Stuart McDonald*. They are yellowish brown in oolour, of elongated, bead-like form, often with bulbous ends. Cooke* and Roodhouse Gloyne* independently demonstrated a mineral oore in these bodies, evidently derived from the asbestos fibre. Stewart and Haddow" have also demonstrated their presence in the sputum of asbestos workers. These bodies have not been found to occur in any other human affection. They have bran found in the sputum within a comparatively short time after exposure to asbestos dust, and in the absence of clinical or radiological evidence of pulmonary fibrosis, their presence cannot be taken at present as indicating anytning more than previous inbalation of asbestos dust. The Incidence of Pulmonary Fibrosis in Asbestos Workerv--The extent of the risk to health associated with exposure to asbestos dust under present indus trial conditions may now be considered in detail. Of the 374 workers of both sexes examined, 105 were found to have a diffuse fibrosis of the lungs attributable to the inhalation of dust. Ten of these, and one other in which there were earlier signs of the same condition, have been excluded from further consideration, inasmuch that it was felt that previous work in other dusty occupations, such as quarrying, and ooal mining, may have been the prime or a contributory factor in the development of the pulmonary lesions found. ill* s i * 10 Thus, 95 of 363 worker*, or 20.2 per cent, showed a definite fibrosi* due to duet. As additional 21 were found with precursivesign* o' ihuaii but these ire given no weight in the general conclusions, which ire derived solely from examination of the 65 cnee of definite fibrosis. Of the 133 radiographed, 82 presented radiograpbical *ign* of a diffuse fibroeit, and in a further 25 there were suggestive radiological change* not definitely diffmm fibroaia. In 10 of the former group and 3 of the latter the changes were poasibly referable to prior work in other dusty occupations or to other cause, and they are therefore excluded, leaving 52 cases of fibrosis and 22 with signs suggestive of early changes in the lungs due to asbestos,--sufficient radiological confirmation. What inferences should be drawn from these figures 1-^Certainly not that 26.2 per cent, or roughly 1 in 4 of those at present exposed to asbestos dust in their daily work have fibrosis of the lung*. As mentioned previously the sample examined is loaded with a greater proportion of worker* employed 5 years and over than obtains in these sections of the industry at the present time (Tables 1 and 2 above), and as shown in Table 3 below the incidence of fibrosis iucreases with the length of employment. Therefore in order to obtain an approxima tion of the general incidence rate of fibrosis in these sections of the industry a correction moat bo applied on this account. Applying the rates shown in Trble 3 to the figures in Toole 1, it appears that the general incidence rate of fibrosis of the lung* amongst those employed in these sections of the industry is rather less than 1 in 6. or, excluding those employed under 5 yean, rather less thau 1 in 3. Further corrections would have been necessary if the sample had included an undue proportion of workers from the more dusty processes, but this was found not to be the case. Also no correction is required on account of differing age distribution since, as will be seen later, the incidence of fibrosis is unaffected thereby. Sex has no effect. These general incidence rates are convenient merely os affording a rough indication of the inherent risk associated with exposure to asbestos dust at the present time. They have no permanent value either as an index of the general risk of fibrosis in the industry from year to year, or as a measure of the risk in any particular factory or group of employees. This must be so since not only will the distribution of workers in the industry according to process and length of employment vary from year to year in accordance with trade develop ments, but the increasing application of methods for the suppression of dust will have a cumulative effect in reducing the fibrosis incidence rato in future vears. I Efiteti of Ago and Length of Employment.--Table 3 show* the distribution of the workers examined according to length of employment, and Table 4 their distribution according to age, together with the incidence rates of fibrosis in Mrh C&S. Txbls 3.--Incident* of Fibrotit relative to Length of Employment. Y*rt Eaplojsd. KuaUr 0-4................ 3-0................ JO-1* ................ 33-19 ................ to ABtl o*r ... ToiaIi 0 1*1 4 n *i 3(3 Chu ( Fibre*!*. Artrtfi (< io yurt. Numb*r. Group Of Group Uaa Utidiui per CAMS ttCk of Fibrosis. 0/ tuuu of Fibrosis. 0 * 36 *s 30*3 36*0 3*1 344 40*4 u 33-6 41*9 *3-3 17 00*9 Ui *3-1 a t* s 30-1 41*4 4| Group. Up to 19 90-19 ................ 90-39 ... 40-49 ............. 90-49................ #0 sad e.i ... Total* s II TaOU 4.--Incident! of I'ilrvtit reiolivt to Apt. hooUr Cam* of Fibroci*. Ivor*g* / tsploymcol is fun NuaUor. Croup 01 Croup loo* lacidaoc* pr auu cut. of Fibrooi*. Of CAM of Fib rodi. M 140 0 14 11 _ 9*3 II 9*7 100 90 90 -0 1 ist 47 91 in 11-3 ii u 1M e-7 i- 14 9 C4-1 ISO 19*3 MS e te-t vs 1JS These tables indicate the outstanding importance of length of employment (and hence length of exposure to dust), and the negligible effects of age, on the production of fibrosis. Thus age groups 30/39 and 50/59 (Table 4) have incidence rates of SO per cent, and 37.9 per cent, respectively, not a wide difference, since the groups include workers in various processes exposed to different concentrations of dust. Moreover, tho average length of employment in these two groups, excluding the cases of fibrosis, is almost identical, but considerably leu than the average length for all the cases of fibrosis (13.5 years). It appears from the same Table that no special susceptibility to the development of fibrosis is shown by young persons, unless it is considered that the figure of 8.7 years, the average length of employment of the cases of fibrosis in age group 20/29, has been shortened by increased susceptibility of ages under 20. As, however, the average age of this group at cases of fibrosis is 29.7 years, and also because the establishment of fibrosis docs not necessitate immediate retirement from work, this is largely discounted. Column 4 of Table 4 also shows a genera] irregularity which, in itself, points strongly to the negligible effects of age in the production of fibrosis. Turning to the effects of length of employment a very different picture is seen. Table 3 shows that after 5 years' exposure, the incidence rate mouats rapidly, and after 10 yean increases almost in geometrical progression. Effect of Work is different Proctute.--There are insuperable difficulties in ascertaining trustworthy figures of the precise incidence of fibrosis amongst workers in particular asbestos processes. This is the mult of the common practices in the industry of housing mapy processes in one room, and of workers transferring from one process to another. These two factors, the influence of dust from neighbouring processes, and* prior work in other asbestos processes, operate to obscure the effects due to work in any one process. By distributing the-workers, however, according to the process in which each has been longest employed and grouping similar processes together, it is possible to draw certain broad conclusions at to the relative effect of work in different processes. In this way groups were obtained as follows:-- (1) Crushing, opening, disintegrating and mixing. (2) Carding. (3) Spinning, twisting, doubling, plaiting, etc. (4) Insulating mattress making. (5) Weaving and associated processes. (6) Miscellaneous processes and remaining unclassified workers. The outstanding point brought out in this way is the relatively very low incidence rate of fibrosis in group 3 (termed " spinners '' for convenience) as compared with each of the other groups. There is some indication also that amongst " spinners " the disease takes longer to develop. Study of the radio grams, also, reveals further indications confirmatory of this. Moreover, estima tions of the dust content of the air in the neighbourhood of these processes and in that of others in the various groups show that the evolution of dust in group 3 is also relatively low (Table 5). Id fsrt. the history, and the medical and radiological feature* of the caae* of fibrosis together with the result* of comparison of the duit count*, all con tribute in degree to the new that with comparatively low concentration of dust in the neighbourhood of a proots*, the resulting cases of fibrosis amongst the worker* in that process .are longer in developing and remain longer in a milder stage. It follow*, therefore, that in *uch case* the rate of accumulation of dost in the lung ha* not greatly exceeded the rate of elimination, and a further point of great practical importance emerges, namely, that in order to prevent the full development of the disease amongst asbestos workers within the spaoe of an average working lifetime, it is necessary to reduce the concentra tion of is the air of the workrooms to a figure below that pertaining to pinning at the time over which these esses were exposed. Not only does group 3 show the lowest incidence of fibrosis, but it forms the largest individual group in these sections of the industry--about one third. Relative Dustiness of Variant A tbetlot Procestet.--While tome reference here to the varying amount of dust evolved by the different processes is necessary, the causation of these difference* and methods of suppression of dust are dis- in Part II of this Report. Different asbestos processes do cause the evolution of different amounts of dust into the air of the workrooms, and, under present conditions, the difference between the least dusty and the most dusty processes <"( very pronounced. In some processes the production of asbestos dust is insignificant; in s second group dust is continuously evolved but in relatively low concentration, as in spinning; in a third group the evolution of dust is continuous and in high con centration, at in dry doth weaving; and in a fourth group much dust is dissi pated in bursts of short duration, as in emptying the fibre from settling chambers by hand into bags. Some additional data were obtained by means of a limited number of determinations of the dust content of the air at the breathing level of opera tives engaged in various processes, with the aid of the Owens' Jet Apparatus. The figures in Table 5 which were calculated -from some 50 determinations, give a rough idea of the general dustiness of the processes concerned, and also of the effect of localised exhaust ventilation and damping in reducing the concentration of 'dust in some of them. The counts in other processes arc expressed proportionately to the spinning, plaiting and braiding group, taken as unity. It will be seen from this Table that the dustiest ptooesscs are opening (with old fashioned teasers), sieving (with no local exhaust ventilation), and shovelling or otherwise handling asbestos fibre,' with a comparative ficurc of 2.34. The heaviest count* of all were found in this group, in sack filling by hand in a settling chamber. The comparative ^figure here was 0.64, but the record was denso, with much clumping togetherrof the dust particles, with the result that the total dust count arrived at was undoubtedly too low. Next in order is dry doth wearing without the spplication of lor*lived exhaust ventilation, with a figure of 1.95. This is undoubtedly a dusty process, and although local exhaust ventilation reduces the count at the breathing levei of the weaver, much dust still escapes into the workroom. Weaving doth wet. not merely damp, reduces the dust count to a remarkable degree. Column Table 5.--Rtlatiot Dustinest of various Processes and Effects of Localised Exhaust Ventilation and Damp Methods in suppressing Dust. Weaving. * Spinning Braiding. PUiting. iiUtti Weal sbauat wotiU lien. ni Cord tog. vith Uni nkiBit vwotil- IsO*. tTi CUtfc Dry. Without fence 1 rxha lilt mntil* linn. at With local aihei'st wntiU linn. M) WoC CM bod Dr*, with local riliinit mtil> lion. *e> IV* L m 1Ja Ureas Making. Dry. viOtout fence) vahauat ventil ation. P) Dr,.* with cihauit vrntiU lion. en with nhauii v*ntil atlOA. noi 0 pacific and hasdlific fibre, without local sbeuit vcntil* olios. Oil i i*n i-m 1-06 ai J`U IS fefe *34 k Mu.l Ucoiia*d it Um work hoachw UU1 paciij ftl VMiiUUu ( Um uunaa >kia|| work. / 13 7 for band (i.e., narrow) weaving, wet, is not Accurate sioce the figure ho* beta niied by duet from a neighbouring dry doth loom. Mattress making without any precaution*, auch a* exhaust ventilation, or damping floors, IeMm and doth, follow* next with a figure of 1.83 (See footnote Table 5). Application of exhaust ventilation, and damping reduces the figure considerably, out it may be that the figures in columns v and 10 are too low, einn> counts for some subsidiary processes, such as buttoning, sewing, and cutting out, are not available. It will be observed that carding, although essentially a very dusty process, produced a comparative figure of only 1.17. This is due in part to partial enclosure of the working porta of the carding machine, but is mostly the result of the application of local exhaust ventilation. Moreover, the figure does not take into account the extremely dusty operation of stripping. Relative to the comparative numbers for tho other different processes, the figure of 1 for spinning, plaiting and braiding is probably rather too high, owing to contamination by dost from neighbouring and mom dusty processes. Samples of asbestos vary much in chemical coustitutiou and physical pro perties, end of the three main varieties, chrysotile, crocidolitc, and amosite, the latter two, in the opinion of experienced workers, usually give rise to more dust than chrysotile in the textile manufacturing processes. No evidence was found to indicate that any one of the three varieties is more, or less, poteut than the others in producing fibrosis, other factors, such as oonoeutrstiou of dust, being equal. A peculiarity of the asbestos fibre is that it first fragments longi tudinally, and apparently this process can go on indefinitely, tinoe there is no ultimate fibre comparable to a vegetable fibre such os cotton. Concentration of Diut and Length of Exyotvrt Ntctua.ru to Product Pibrorii.--From the data so far examined it seems clear that nbroeis of the lungs is a definite occupational risk amongst asbestos workers os a class. Furthermore, it appears that the risk falls most heavily on those longest em ployed and on those engaged in the mom dusty processes. Some farther consideration of these two important factors, length of em ployment and concentration of dust, is desirable. Obviously, to some extent, they an interdependent, since, assuming that a specific quantity of asbestos dust most be to produce a generalised fibrosis, the fibrous will result from exposure for a period of time varying with the concentration of dust in the air breathed. Siaisoa" reports the case of ao asbestos mill worker iu South Africa, exposed for 12 months to a very dusty atmosphere, who died from a rapid tuberculosis; sections of the lungs showed, sport from the changes due to tuber culosis, a moderately marked fibrosis. * Burton Wood sad Page" report the case of on asbestos spinuer, employed 15 months, who died from a generalised tuberculosis, 8 months after ceasing work. In this cose a little fibrous tissue was generally to be seen surrounding the ssbesloe fibres found in the lung tissue, but them was no gross fibrils. It seems probable, therefore, although further research is very necessary, that not only is u certain minimal quantity of the dust required for the production of s generalised fibrosis, but that inhala tion of the dust in high concentration results in the production of a more marked degree of fibrosis in a shorter time, than when the concentration is low. Investigation of this important matter--concentration of dust and length of exposure necessary to produce fibrosis--from the clinical side is beset with difficulties, one of the most confusing being that the existence of a clinically recognisable diffuse fibrosis is quite compatible with continued work in the industry, and, therefore, the coses of fibrosis discovered in such an investigation at this are in various stages of the disease, with the result that the point at which they first became recognisable clinically cannot be ascertained. Despite this, some confirmation of the hypothesis that the length of ex posure to asbestos dust uei-essary to produce liorosis varies inversely with il.c concentration of the dust in tlic air, within certaiu low and high limits, may be obtained. 7M 4T / 14 Table 6 show* the average age and length of employment of the cates of fibroaii is the group* of processes previously dealt with (p. 11) Tabu 6. pTM Cmu of Fibroou. Avar**. A(. Arertgi Lifigti of Eplo7*t l. Oriukiss. psaisg, duisUf muciog L Cardiff - ...................................................... 1. fipUsiftg. toinittf, doubling, pUiti&g. Aft. a MiUnaa wkia|...................................................... a ud MMcitUd praeoHi ................ 0. praeMa md retuiDiDg clfiftwl rlui*. Tt*U............. ...................... 43*1 1M 37*0 38 l 43* 411 10*0 131 ia-7 130 11-7 13* J 111 The much longer average period of employment of the cater of fibrosis in group S as compared with the other groups will be noted. There is also least exposure to curt in group 3. It teems, therefore, that is this group a longer period elapsed before the fibrosis developed, or that it progressed less rapidly. This is the more apparent if the incidence rates of fibrosis amongst workers employed in the processes in group 3 are compared with the corresponding rates for workers employed in the more dusty processes comprised in groups 1, 3, 4, 5, t*lron together. These rates are set out in Tnble 7. TaBU 7Comparison between At Incidents Batts oj Bibrvsis amongst Workers employed in Group 3 (less dusty prottssts) and As Incidence Bates amongst Workers employed in Groupe I, !, V, 5, taken together {more dusty processes). Tia&i ZuriOTin. (U. * a-a 10-14. 13-18. si1 J i 1ft w S i tft ft H Z a CmtJ * X tffc1mml X X .> s= <3 2 afts 10m e * 2 W Z <5 Vft is w 1 . 0 i 3= z <3 ti 2m X 3D ad o*ar. 4 u0 .unft s <3 4 si2Xe Group 3 ... Groupa 1, t, 4, 3 (t*ka logithor). 30 47 P.r cut. 0 40 Fr MfiL 0 0*0 30 Par CftBl 0 1*1 11 0 00 31 33-7 43 it 40*9 14 Fr CtfiL 4 16*4 0 P.r ate 4 0-7 1 17-1 13 u 4-S Group 9 gpiftftiftfi, tUuo deuMiog, plaitiftg. U. Creep* dnokUc,oul,cardisg, iMUmi mokiog pod vtaviog wd ivr'*H pi It will be seen that, after 5 years' employment, the rates are consistently much higher amongst those employed in the more dusty processes, and, whereas the rate it high from about 5 years onwards in the more dusty processes, it is not until about the 15th year of employment is reached in the less dusty processes that the rate for the latter becomes high, and approximates to that reached after about 5 years' employment in the more dusty processes. Exposure to different concentrations of dust, together with the effect of cite recognition of the cases of fibrosis in different stages of the disease, also afford an explanation of the widely differing lengths of employment of in dividual ease.* of fibrosis, which ranged from 5 years to over 30. While no definite cose of fibrosis clearly due to asbestos dust was found amoDgst workers with less than 5 years exposure, the possibility of such cases occurring with 4 15 ' exposure to high concentration* of duit cannot be ruled out. Three cue* were found with 3, 3) and 4^ year* work in aabeslos, respectively, but iu eacn there wu previous exposure to other du*u (eee p. 10). Support for thi* view is provided by (11 Professor Beattio's experiment* previously mentioned, which demonstrated that the lunge of guinea-pig* ex posed for 43 and 07 hour* to asbestos dust showed " definite cellular pro $ liferation, though not eery extensive, and thi* is certainly a preliminary Huge in the production of fibrosis (2) Simeon's case mentioned above, and his report in the nm paper on the lung* of a guinea-pie exposed by hlavrogordato to asbestos dust for 100 hour* during s period of 56 day*. On the death of the animal (from causes other than asbestosis) some 32 months later, sections of the lungs showed a (light generalised fibrosis. Iu commenting on the amount of fibrosis found, he states that " a comparison between the huuiun coses and the experimental anitnal showed that the fibrosis was more rapid and extensive in the human cases than in the experimental animal," and again ` the amount of fibrosis in two of the human cues was quite rapid, and if due to the presence of asbestos dust, the initial rate of production was rapid when compand with present day non-infective silicosis on the Band (3) datu from Uii* investi gation, in which 21 of the 3G3 worker* showed signs suggestive of commencing fibrosis (p. 10). Of these 12 had been employed for less than 7 years, and 0, for between 4 and 5 years. To sum up, therefore, it appears probable that concentration of dust anu length of exposure as factors in the production of fibrosis an interdependent within certain limit*. While it seems necessary for the production of generalised fibrosis of the lungs that a definite minimal quantity of dust must be inhaled, the lower the concentration of dust iu the air breathed, the longer the lapse of time before the fibrosis is fully developed, and within a certain limit, the higher the concentration of dust, the soouer the fibrosis becomes fully developed ana the more intense the involvement of the lung tissue. If this hypothesis is correct, and the evidence points to it, the practical inferences are of very great importance, since it follows that the application of measures resulting in the redaction of the eoneeutration of dust in the air in the neighbourhood of dusty asbestos processes will cause, firstly a great in crease in the length of time before workers develop a disabling fibrosis, and secondly, the almost total disappearance of the disease, as the measures for the suppression of dust are perfected. Disablement produced by the Asbestos Fibrosis.--Regarding the amount of disablement produced by the development of pulmonary fibrosis in asbestos workers,--for a number oi years this is surprisingly slight, even more so *hav is generally the case in silicosis. This is partly due to the character of the disease, and partly to the nature of Jthe work, which in tbo majority of these processes does not involve much physical exertion. The affected person may, and often does, continue at work with occasional intermissions, latterly, due to exacerbations of bronchitis, until the condition is advanced, although he suffers increasing inconveniences from shortness of breath, on exertion. Some times a terminal broncho-pneumonia, or other acute infection, commences while still at work, and there is no long period of invalidism. There is no doubt but that fibrosis of the type produced by asbestos can of itself lead to complete disablement and to a fatal termination; and this in the absence of a superadded tuberculous infection. Particulars have been collected up to the eud of 1921) of 10 cases in which on advanced degree of the asbestos fibrosis without tuberculosis was the primary cause of death. In 9, the cause of death was verified by post mortem examination and in the 10th, repeated clinical, radiological and sputum ex aminations confirmed the diagnosis. In on 11th cose, post mortem examination showed that a lobar pneumonia had superveued upon lungs already the seat of a moderate degree of the asbestos fibrosis. With one exception, all these deaths occurred in the years 1927-29. The length of exposure to asbestos dust in these varied between 9 and 24 years. >u It is not suggested that these few faulitiee, in which the cause of death ha* been verified by strict enquiry, ere euy criterion of the true effect of the disease on mortality rate* of asbestos worker*. Other* ere known to have occurred in which the existence of the uabesto* fibrosis he* been determined in life, but no poet mortem examination he* been poeaible. Proars** and Duration of tin Ditto**.--The rate of progreu end duration of the disease varies within wide limit*. With continued exposure to high concentration* of du*t, the fibroei* may be folly developed in from 7 to 0 years, end may cauae death after about 13 year* exposure, exceptionally in e snorter period. On the other hand, with exposure to less concentrations of dust, the period of maturation of the fibrosis may be exleuded to 16, 20 or 26 yean. There ere definite indications, derived from the industrial historic* end ex amination of worken, that a diminution in the concentration of dust in the air breathed, either by change of employment from a higlily dusty process to one less dusty, or the effect ox methods taken for tho suppression of dust, result* in a prolongation of thi* period of maturation of the fibrosis, except in the late stages of the disease. While this is so, the existence of a clinically re cognisable degree of the asbestos fibroei* in any individual ie an additional adverse factor in the prospects of recovery from any acute infection of the lungs, such as pneumonia or broncho-pueumonia. Association of tks Asbsstos I'ibrorit tcith Pulmoiiury Tuberculosis.i-A* previously mentioned (p. 6). ailiousis, the fibrosis of the lungs due to the inhalation of free silica dust, has an unhappy association with pulmonary tuberculosis, in that there is a much increased liability to the supervention of the latter disease amongst sibooties. It is of importance, therefore, both from the point of view of the individual worker, and in its bearing upon the scope of the preventive measure required, to euquire. whether there ie a similar liability attached to the asbestos fibrosis. ' It will be remembered that in this investigation the examination of workers was restricted to those at work at the time of the examination, and. therefore, a number of advanced cases of fibrosis, and a number of cases of pulmonary tuberculosis--with or without an asbestos fibrosis in addition---who had either given up work or who were oil work temporarily, will have been missed. Moreover, tfie supervention of a tuberculous infection on a lung already the subject of fibrosis produces an increase in symptoms, previously unnoticed or disregarded, and induces the worker to seek medical advice. Be is then appropriately advised to give up his dusty employment, migrates from the in dustry, and may or may not accept sanatorium treatment. Thus there tends to be a drift of such cases from the fibrosis producing industry. In fact, during the course of the investigation, information was obtained of a number of persons, previously employed in asbestos, who were either at home or in eanatoria, suffering from chest complaints. Precise information as to the incidence of pulmonary tuberculosis amongst asbestos workers cannot be obtained therefore, in the absence of periodical medical examinations in the industry, without prolonged enquiry involving the search of the records of local sanatoria, tracing workers known to have ceased work in asbestos, and examination of death certificates, and of the sickness records of firms, where these are kept. Nevertheless, with these reservations, the data obtained in this investigation did not disclose any outstanding susceptibility to pulmonary tuberculosis, either amongst asbestos workers as a class, or amongst the cases of fibrosis. - Summary.--The outcome of thisTnvestigation is to establish the existence of a definite occupational risk in the asbesUw industry. This takes the form of a distinct type of fibrosis of the lungs, resembling silicosis in its main clinical aspects, but differing from that disease in the mode of distribution of the fibrous tissue in the. lungs, in its radiological features, in the enhanced rate of development under average condition* in this country, and as far os the evidence goes, in a lower susceptibility to the supervention of pulmonary tuberculosis.* The asbestos fibrosis results from the inhalation of asbestos dust, the proximate causes being concentration of dust in the air breathed and length * Tba uxadical and radiological data obuiowl Id ihia iuvoati^aliwo will U puUUbaU alaawbara. s 17 f axpoeure to it. Thu* the incidence rale ie higheel in the most dusty pronrt uDongtl those longest employed. Age end sex heve no apparent infliiimw on the production of the disease. $__FACToee Drmitinimc thx PaxexNT Bicocnition of ths Asbestos Fissobib. It is of interest to consider why it is that this disease has only recently ^Uncled end beoome e problem in tfr* industry, elthough esbettos was Jmown to, end worked by the ancients. Many factors contribute to this position, some dependent on the nature of the disease, aome on the phenomenal expansion of the industry, others on the advance of medical science. While has been known and spasmodically worked for hundreds of jeers, it is only in the past 40 years or so that it has been commercially exploited to any extent. Not only that, bnt it is leu than SO years since the groat expan sion of the industry commenced. Even after a number of years of steady expan sion. the industry is still comparatively small, and the workers employed in the essentially dusty processes relatively few. The insidious onset and unobtrusive signs and symptoms of the in its earlier course, its covert advance by imperceptible stages, its points of Tcsemblance latterly to fibroid tuberculosis, with which infection it is sometime; associated, and the migration of those affected from the industry, have all com bined to delay its recognition as an entity, and to obscure the causal agent. Knowledge of the effects of specific dusts upon the lunga has been greatly extended in the past 20 years, but research has been mainly concerned with the more important and widespread risk associated with the dusts containing free ailica, and enquiry into the effects of other dusts had to wait upon thou investi- -gutions. 6.--Paxvumvx Mxaeubxb. The necessary preventive measures include, first, thou directed specifically towards the suppression and control of the dust evolved in manufacturing pro cesses, which are examined in Part II of this TVp"r_t -directed towards those employed in the industry. These latter include the control of the disease by periodical TMHi|~*l examina tion of the workers, by which those unfitted by health reasons are prevented from entering the industry, and cases of fibrosis and pulmonary tuberculosis are detected at the earliest possible moment. Tbe ultimate and only reliable test of the effectiveness of the preventive measures adopted in the industry will be found in the statistics derived from the records of periodical medial examina tion of the workers. } They also include tbe education of the individual, os in other dangerous trades, to a sane appreciation of the risk, and to his personal responsibility in the prevention and suppression of dust. The protection afforded by respirators is only partial, and .there is a real danger that the use of them may give a tense of false security. (just floating in the air contains a majority of particles of the order 2*. and under, .many being only 0.5* (n Vse inch) in size. In practice, the discomfort of constant wear, and difficulty in speech, etc., render workers very -unwilling to dm this form of protection for any length of time. Since, however, a high class respirator will trap a proportion of the large par ticles which can enter the lung, they cannot be said to be valueless, but can only be recommended as a aecond line of defenoe, and not in substitution for other preventive measures apecifically directed to the control of dust as as possible to its point of origin. Under very exceptional circumstances there may oe scope for tbe use of the efficient type of breathing apparatus, comprising a mask or helmet with a long tube, enabling the wearer to breathe pure air from a distance. 7.--Tnt Outlook. From consideration of the nature of the processes in the asbestos industry and other relevant matters, it is felt that the outlook for preventive measures is igood. That is to say that in the space of a decade, or thereabouts, the effect of - 18 energetic application of preventive measures should bo apparent, in * great.reduc tion in the incidence of fibrosis. , . .. : V*- An immediate temporary rue in the incidence rate u probable, duetto tbe sccumul&Ud damage, partly a legacy of the war years, but with the passing of the peak, a steady foil should ensue. ?...-i Much generous assistance has been received from many sources during the count of this investigation; these are gratefully acknowledged elsewhere. Special thanks are due, however, to Dr. E. w. Twining of Manchester-and Dr. Nt Tattersall of Leeds for their indispensable expert assistance in t|ie elucidation of the radiological features, to Dr. W. E. Cooke, Professor M. J. Stewart^'ind Dr. Roodhouse Gloyne, whose researches in the same field are well known,- and to Dr. I. M. D. Grieve for information from an unpublished study of a group of aabestos workers. "* .`i .4 (' Tj0%. > 4- Rviunces. 1. Seiler, H. E.. Brit. Med. Jnl., 1928, II, 982. i 2. Departmental Committee on Compensation for Industrial Diseases. .i (a) Minutes of Evidence, Appendices and Index, 1907. ,Cd.:S49C, p. 127. (5) Report. 1907. Cd. 3495, p. 14. 8. Cooke, W. E.t Brit. Med. Jnl., 1824, II, 147. 4. Cooke. W. E., Brit. Med. Jnl. 1927, II. 1024. t. McDonald, Stuart, Ibid. p. 1025. <- 6. Badhom, C., Studies in Industrial Hygiene, No. 13, Report of the Director- General of Public Health, New South Wales, 1927. ''' 7. Cooke, W. E., and Hill, C. F., Jnl. Royal Micros. Soc. 1827, 232' .* 8. Cooke, W E.. Brit. Med. Jnl., 1929, II, 578. , 9. Gloyne. S. Roodhouse, " Tubercle ", 1929 X 404 10. Stewart, M. J., and Haddow, A. C., Jnl.'Path. and Boot., 1929 XXXII, ........ 172 - , jj*.--r.-AI a.1 11. Simaon.F. W;; Brit. Med. Jnl., 1923 I. 885. ' -12. "Wood, "W. Burton, and Page, D. S., " Tubercle ", 1930, XI,'" ' - part ii. r'.v Pbocxsbxs Gmnc Risk to Dost and Mxthodb job its Sbtmixssjon! 1.--Introduction. The asbestos industry has developed greatly in recent years and continues to expand rapidly, mainly because of the demands of the motor, electrical, engineering and building industries, and of the increasing attention now paid to the insulation of steam plant to promote fuel economy. . Asbestos products may, for convenience, be divided into seven main groups TutiUt. (a) Yarn and cloth. Non-TtxtiUt. (b) Millboard, paper,' asbestos-cement sheets, tiles, and other build ing materials, sheet material of rubber or bituminous mixtures.contain ing asbestos. (c) Insulation materials and articles. !<f) Brake and dutch linings, s) Packing and jointings. (f) Asbestos-covered electric conductors--electrodes, wiring, coils for electric machinery. cables and (g) Miscellaneous, induding moulded electrical and other goods, tetc. Some factories make both textile and non-textile goods. So-called " fiberired " asbestos, i.e., opened or broken-up material in a' fine flock-hke / 19 condition, is manipulated, nnmi^ with other msterisli, in large quantities in the feelories included in groups (a), (f>), end (e), end to e much smeller extent in some of the other factories end workshops. (0) Asbestos yarn is woren into cloth for insulation mattress coverings, in* suleting wrappings, filtering materiel, fire curtains, fire-smothering blankets end fire-resisting clothing, Narrower woven materiel is produced for belting for conveyors, brake linings end insulating tape. Some asbestos cloth is rubber-proofed for use intne manufacture of steam packings and jointings. Besides its mein use for weaving, asbestos yarn is braided and plaited for use as packing, and also for insulating material. Spools of yarn are supplied to factories in which electric cable or' electrodes are made, and polished thread for the completion of incandescent mantles. * (1) Asbestos millboard and paper are manufactured from pulp containing . short fibre asbestos, by a wet method, like ordinary millboard and paper. Asbestos-cement sheets, tiles, gutters, pipes, etc., for building and similar pur poses are made from wet mixtures of Portland cement and short fibre asbestos. A synthetic composition sheet is made from a rubber mixing, for use as jointing. Bituminous mixings containing asbestos are made for switchboard panelling, and other mixings for floorings. (e) Insulation materials include flberited asbestos; " magnesia/' so-called containing about 15 per cent, of fiborized esbestos and 85 per cent, of magnesia, and other finely divided mixtures composed partly of fiberized asbestos, used os insulating cements or plasters; fiberized asbestos stiffened into thick sheets, like mats, for lining bulkheads of ships; shaped sections and slabs, moulded from fiberized asbestos or mixtures containing it, or built up of corrugated asbestos paper so as to enclose air cells; mattresses, made of asbestos doth and filled with fiberized asbestos, magnesia, or other filling. (d) Brake and dutch linings are chiefly prepared from impregnated and heat-treated asbestos doth, but also from moulded asbestos material. (#) Plaited and braided asbestos yarn, proofed asbestos doth and com position sheet are used in making packings and jointings. {/) Electrodes for wdding work are plaitod with asbestos yarn or covered with a paste containing asbestos. Some electric cable and wiring required to withstand beat are plaited with asbestos yarn; field coils for'electric'machinery may be wrapped with asbestos tape. (p) Miscellaneous manufactured ortides or products, composed wholly or partially of asbestos, indude, in addition to moulded electrical and other goods, asbestos putty and powder, robber hose plaited with asbestos yarn, and many others. Apart from manufacture, certain work is carried on in premises subject to the Factory and 'Workshops Acts, as well as in other premises, which involves use or manipulation of asbestos or product! containing it. The insulating of boilers, pipes, engines, and parts of ships is the most important. Much of this work is done on board ship by contractors who employ a considerable outdoor staff. 2.--Paxsfisxs. The factories and workshops included in (a) to (p) number at least 160, of which 18 are textile factories. This total is based on lists supplied by the District Inspectors. It does not indude the large number of works where there is incidental nse of asbestos packing and jointing, asbestos-covered electric cable, or other finished goods, required for completing other manufactures. There is only one works in which the employees concerned with asbestos exceed 500. There are many small premises in wnich but s few employees, in some cases only one or two, are employed. A small " asbestos " aepartment is found in a number of important factories. Textile departments are usually well housed in modern buildings. A few of the older textile factories have been improved recently by the addition of modern buildings. In one case a badly housed small concern is in process of removal to newly constructed premises. The asbestos-cement sheet factories are modern premises of large floor area, lofty and spacious, in the main, tingle storey buildings. The cable and electrode factories are also modern and generally suitable. t so Some small work*, more particularly those engaged in making boiler com position!, are unsatisfactory. A few are mere open-sided sheds. Such premises are difficult to keep clean. Some works are congested with plant and stocks of material. This moy result from inadequate accommodation or a temporary falling-off in the demand, but effect on cleanliness is bod. The dust evolved in manufacturing pro cesses is more didicult to control if the premises are unsuitable, particularly if crowded with plant or material. Cleaning is not easily accomplished and the dust is more concentrated. Ventilation.--The arrangements provided tor ventilating asbestos works ary as in other industries. Dust removal systems, where used, effect a measure of general ventilation. A number of workrooms in textile 'factories are ventilated by plenum systems, the air eupply being wormed in winter. Over head extracting propeller fans are but little used now and would be unsuitable. In one mattress making room extraction fans connected to large overhead hoods re used. Extraction by downward displacement, the air being drawn through openings in the floor, or near floor level, has not been met with, but bos been considered for some weaving rooms. This system, if designed of a capacity sufficient to effect a high standard of general ventilation, would tend to reduce the dust in the general atmosphere at breathing level, and, with other safeguards, be a possible alternative to localised exhaust ventilation. It could not be success ful without efficient beating, owing to the rapid change of sir entailed. Separation of Procurer.--In many works several processes are carried on in the same room. In the absence of effective means of preventing escape of dust into the air, many workers are subjected to a risk from which they would other wise be immune, or to a greater risk than that arising from their own work. In a few textile factories crushing and opening plants are placed close to spinning and carding machines. Spinning frames are installed close to looms and wet and dry weaving are carried on close together. In non-textile premises there is more effective separation of dusty work and processes from non-dusty. 3.--Dxscbotion or Pxocxsbxs and Paxvumvx Miasobxs. A complete account of manufacturing methods is not attempted. Attention is mainly directed to the dust-producing processes, n description of which, in broad outline, has been deemed necessary to make clear the circumstances under which exposure to dust arises, and the character and object of the remedial measures already in use or here recommended. Somewhat important changes are on foot which, it is confidently hoped, will greatly reduce exposure to dust in certain hitherto dusty processes. On the other hand, certain developments, e.g., speeding up of textile machinery, and the increased use of ashestos in various industries, may intensify the dust problem, if adequate measures to deal with the dust are not taken. Textiles . (a) Yam and Cloth. The manufacture of asbestos yarn and cloth proceeds on the whole like that of other textiles, but there are some important differences. Fiberized and other asbestos materia] is freely handled in various operations, in gathering "waste," and in cleaning. Exposure, in somo degree, to asbestos dust, is common throughout all the factories, but steps have been taken, extending over many years, to deal with dust produced at various points, though the necessary degree of efficiency has, generally speaking, not been reached. Exhaust ventila tion plants used in the best-equipped asbestos factories for removing dust appoar to be as efficient as those used in other textile industries, and to have been applied over a wider field. As regards other safeguards against dust, e.g., substitution of mechanical methods for handwork for feeding the machines in preliminary operations, efficient enclosure of machines, and vacuum methods of cleaning, little development has been made. Opening.--Asbestos, suitable for yarn, has usually to be crushed, and in all cases . opened (" fiberiied ") before it is ready for carding. These prepara tory processes arc effected by .machinery, but entail much handwork. Separat ing (to remove iron) and graoing or sieving follow crushing, but precede opening. Material for yarn u not usually treated in disintegrator*, but in moil factories those are ued for nberizing waste asbestos yarn, etc. Crushing flatteos out aad breaks op the mineral without damaging the fibres. It is accom plished either is a large edge runner, or in a small pan mill of the mortar mixing type. The material is emptied upon the floor dose to the machine, the contents of eerersl *A sometimes being spread on the floor to obtain a rough " mixing." The crushed material is either takeu from the machine by band, or discharged through a bottom delivery slide, usually filled into tacks or ships and, if necessary, weighed on a portable weighing machine. A few edge runners discharge upon abort inclined lattices and the material falls automatically into the sack or skip. Edge runners give rise to dust of considerable amount where short fibre is crushed; Hate are and have exhaust applied. This is always neces sary. Pan are not and also give rise, to dust, though less in amount. Handwork, e.g., sack emptying and filling, mixing, shovelling and feeding machine pans or lattice feeds, gives rise to dust, sometimes ol considerable nmount, and is done without exhaust. Application of exhaust draught would be facilitated if feeding were done from a higher level so that sacks might be emptied under enclosed conditions, i.e. in a sack emptying apparatus. Automatic delivery and reversible bagging lattices eliminate dust produced in band filling of aacks, but require to be efficiently enclosed with exhaust draught applied. An open travelling band passing round an electro-magnet is used for separating Irae iron, the asbestos being delivered to an elevator. Enclosed apparatus should be adopted. Enclosed rotary sieves (rotaries) or long oscillating frame sieves are used for roughly grading crushed material. Rotaries should be mechanically fed and the asbestos collected under enclosed conditions (not always done) and exhaust applied to the machine enclosures, otherwise unnecessary dust is created. Some oscillat ing sieves are very open, the material being allowed to fall on the floor, and being filled into sarin by hand. Very dusty conditions are then inevitable. Efficient enclosure with exhaust draught applied and, to avoid hand filling, automatic delivery and bagging lattices, also enclosed and exhausted, as used in some cases, are generally practicable. Crighton openers, enclosed centrifugal machines, are used for opening crushed asbestos, preparatory to carding. Careful mixing or blending of crushed material is effected by spreading it evenly in layers on the floor over e considerable area--cotton may be added at this stage if required--and when feeding, taking a vertical cut through the mass. Admixture with a small proportion of cotton may also be achieved by blowing it into the feed opening. The opened material is delivered upon a lattice and collected either in a large container or in sacks, automatic bagging lattices being used, in some cases. Mechanical feeding under enclosed conditions, with exhaust draught applied to feeding lattices or other conveyors, should be adopted. Hand feeding gives rise to dust, from sack empty ing, shovelling and particularly mixing on the floor. Mixing is a great hindrance to elimination of hand work; it is asserted that poor yarn results if it is not done and that machine mixing has been' tried and gave less satisfactory results. If retained, it should be done at a higher level than the opener, under a large exhausted canopy and the mixture fed at a series of chutes. Delivery lattices should be well enclosed and exhaust applied,as now done in some cases; otherwise dust is evolved. Opened material sot required at once, may be stored in open bins in the workroom, involving emptying and filling sacks or skips, which necessarily cause dust. This storage in bulk ahould be avoided; alternative arrangements might be adopted which avoid dust. Some material, e.g., long fibre waste from later processes, is opened at enclosed lattice-fed teasers or willeys, not infrequently of primitive design, worn out, and emitting much dust, notwithstanding that a fan is an integral part of the machine. These old machines should not be for aslwstos opening. Dust may be emitted at feed points of modern machines, particularly when the feed is irregular. Exhaust is necessary at the feed lattice for this reason and also because feeding itself causes dust. The material is either discharged upon a lattice for immediate collection, or blown into a chamber. The standards suggested for Crighton machines should be adopted. / St Hopper " feed* ore largely used with openLug machines; the hopper lipi ere about 3 f**1 6 inches above floor level. Much dust is produced in shovelfeeding as it is difficult to avoid scattering at the lip. An enclosed lattice, fed at or just below floor level,with localised exhaust applied to the enclosure is more satisfactory. Single disintegrators, or two or three machines tn series are used tor break ing up textile or other asbestos waste, more rarely for opening crushed asbestos. Present arrangements for preliminary hand sorting of waste are unsatisfactory; it should be accomplished at a covered bench, suitably exhausted. Whereas in some cases, the indraught at the disintegrator feed openings caused by the rapid rotation of the rotor is not sufficient to remove dust, and because, at any rate, as soon as it is stopped, escape of dust may result from reversed air currents, exhaust should be applied here also. Disintegrated material is blown into chambers, a blower fan being in some * connected to the delivery of the machine to create a stronger draught. Air pressure in the chamber is relieved in diflerent ways, the sides may be covered with tacking, allowing much dust to escape, a " relief balloon " connected, or exhaust applied. Chambers connected with disintegrating and teasing machines vary in size, some are little more than a large box, others are more roomy. Some, but not all, are separated from the workroom. They are entered for emptying, the material being filled into socks or skips by band after the machine is stopped or the flow of material diverted to another chamber. Work in chambers is very dusty and its elimination is most desirable. (See page 26.) Carding.--Considerable developments have taken place in recent years. One or two important new cardrooms have been started. Many new machines, including some of foreign construction, have been installed. The machines, of large overall dimensions, arc of the roller and clearer type. Modern cards are of high class construction and fitted with two doBei cylinders supported on a carriugo, which con be racked iulo or out of position. For fine yarns, a breaker and a finisher, constituting a set, is used, connected by lattioea, lap sliver from the former being antomstickily fed to the finisher card. In cases where the sliver is collected in cans, a Derby aoubler is used for prepar ing laps for finisher cards. Single marhinre and breaker cards are equipped with hopper lattice feeds supplied from skips or socks, handfuls being dropped in, and shaken sport as fed, or the sack emptied into the hopper. The asbestos falls intermittently upon a creeper feed which conveys it to the " licker-in " feed rollers, between which point and the doffer the material is under enclosed conditions. The material is combed from the open doffera of finisher cords, as a web or '* sheet ", the aheets from the two doffers usually being combined at a con denser, and the resulting sliver yarn wound into spools. Occasionally, combed web is collected without being condensed, the condenser carriage being with drawn. In other aarding, the sliver may be obtained os a lap. Admixture with cotton is usually accomplished by carding the two materials together, a cotton lap being mounted above the creeper feed, and the cotton fed through the feed rollers with the asbestos. The evolution of dust at cards is inevitable and a fine dust cloud may be observed in most cardrooms. Suppression of dust cannot be realised unless machines are maintained clean and in satisfactory repair, and there is elective enclosure of various parts. Above all, localised exhaust must be applied at well-defined points of dust emission, and improved stripping arrangements pro vided. Wide spacing of machines is also desirable. The upper parts of modern machines are usually provided with well made wooden covers and the lower ports are enclosed below in metal. The frames are well enclosed at the tides. A hinged metal cover, fitted in some coses, pre vents escape of dust produced by movements of the feed lattice. A curtain of fabric is less satisfactory. In older types, particularly, the wooden covers may not fit satisfactorily, the cylinders may not Oe truly aligned with the frame and other defects may account for side escape of dust, not controllable by exhaust. Such defects should be remedied. Creeper feeds, doffers and condensers and connecting lattices between breaker and finisher cards are not enclosed. Dust is evolved at doffer combs and at creeper feeds / S3 Loc*lid exhaust ventilation *u first applied to carding *chn*Jmany year* ago. Methods and apparatus have since been gradually improved and more powerful exhaust draugliU are now used. One Urge firm have much eubce&s by alandardiaing their practice as regard* point* of application of exhaust draught, design of air guide*, size of branch duct* to air rude* and duct velocity. Exhaust u applied at (a) the presser at the creeper TMe<>; (6) feed roller at lirlrer.it>; (e) top ol cylinder; (d) each dofler, air guides or hoed* being fitted at these point* with connecting branch duct*. Muff couplings, used on branch pipes f*cilit*t cosy disxn&Dtliog- Branch pipe liies nod duct velocities are liberal The improvement realised by applying powerful exhaust at each of the point* mentioned, at all of which evolution of dust is important, ahow* that this practice abould be followed generally and gives point to the view expressed by some occupiers that cardiog can be carried on practically d.ust-free. Apart from the above case, exhaust is applied in nearly all cases to the cylinders; in a moderate proportion to the creeper feed; in a few,.to one dofler--the top, and in one or two only, to the bottom dofler. But, apart from dust-emitting points not provided for, the results may be inadequate. _ Carding machines are occasionally installed and put into use without exhaust, this should never be done. Efficient results are not possible unless the exhaust draught is applied as closely as possible to the dust-producing points. Transverse air guides, with branch ducts connected at each end, are apparently more efficient than pyramidal hoods of the usual type. Ducts of adequate diameter and high duct velocities are essential. The usual air guide for the cylinder, provided to effect removal of dust both during carding, and stripping and grinding (though proved inadequate for stripping) is placed a little above an opening in the crown of the cover. Two branch ducts, as above, and in addition a larger central branch duct (for nse during stripping) are connected to it. The shallow space below the bade of the air guide is closed up during carding by a wooden hinged piece--thrown back for stripping--and the dual produced at the cylinder is prevented from escaping by inflow of air from the room, at the front. The dust-laden air is withdrawn at the side ducts. In stripping, inflow of air carrying some of the stripping dust takes place from below the lifted cylinder cover; the central branch duct, kept dosed br a blast gate during cardiDg, is then folly opened to provide a greater air volume. In one factory, a circular dofler deaning brush runs continuously above the dofler comb. A pyramidal exhaust hood is provided, but much dust escapes; unless fully efficient exhaust is devised an alternative to this cleaning, if really necessary, should be found. The collection of combed web, previously referred to, is done without exhaust end dust is produced. Collection might be effected by exhaust draught as applied for removing side waste at condensers. Notwithstanding the use of covers for card lattice feeds dusty conditions are produced and exhaust draught should be applied at this point also. Strijrping and Grinding.--Card " stripping " or cleaning is done when tht machine is opened out for grindinc, which follows cleaning and takes place at each machine about onoe a week, but shorter and loneer intervals also obtain. In one important factory the two processes are combined in one operation. Roller and clearer cards must be opened out, i.e.. the lattice feed and breast, and con denser and dofler carriages are drawn back, the cylinder covers are raised, and the various small rollers, which are cleaned nnd ground at a special maebine, removed. The cylinder is first cleaned, with the dofler carriage drawn back; the carriage is then replaced and the doflers, run at a greatlv increased speed, cleaned in turn. Cleaning takes about ten minutes and is usually done in working hours, but in one case, at least, after. The men press their " strickles *' or fiat hand brushes about 12 inches long covered with card clothing, against the wireoovered surfaces. Much of the debris is heavy and falls to the floor. Dust is evolved in a dense cloud, some being removed at the cylinder exhaust hood. In one oase floor openings, beneath the machine, are connected to the exhaust. Present exhaust arrangements are altogether inadequate, particularly so as regards the bottom dofler. Much dust is therefore carried into tht general atmosphere of the room. The cleaners wear respirators or " helmets." In a. few cases, more effective measures are taken, e.g.. the opened-out machiDe is almost entirely enclosed with high canvas-covered screens. In the * 14 worlu where deaaiag Like* place after working hours, as auxiliary exhaust system, with a hood for the bottom doffer, is brought into use. Grinding which takes several hours, it an automatic process effected by abrasive covered rollers driven by the machine. -Tbe small amount of dust produced is chiefly of a metallic character. In tbe factory where griodiDg and cleaning are combined, the doffer exhaust arrangements are first re-connected. Much less dust is evolved and appears to be dealt with more effectively. This firm consider that hand (trickling before grinding should not be allowca. Their methods may, however, not be generally applicable. A little strickling may be necessary after grinding to remove small pieces of d&ria. Tbe trade recognise that present conditions are not satisfactory and experi ments are being 'made with tbe object of developing improved appliances. In ODe case a revolving brush is being tried, with independent exhaust draught applied by flexible connection';' it is said to give promise of success. Tbe brush is narrower than the band strickle and less dust is evolved at a particular moment. In another case, a vacuum fitting is under consideration. Previous use of vacuum tripping was given up because of rapid erosion of tbe metal pipe bends and other parts. Unless effective dust suppression is realised for stripping, all workers, other than strippers, should be excluded while it is in progress and for some time afterwards, and tbe room well ventilated. Tbe machine fur cleaning and grinding the smaller rollers, which gives rise to much dust, should be fitted with efficient exhaust arrangements--a straight forward matter--and as completely enclosed as practicable to collect the heavier ddbris, precautions which ore not always taken. The machine is either installed in the carding room, or in a room adjoining. Independent machines should be provided to deal with rollers of different lengths, otherwise inconvenient adjust ments, liable to be neglected, have to be made. Card Side Waste Treatment.--The irregular " selvedge " of carded fibre, separated at the two sides of tbe finishing card, being unsuitable for sliver yarn, is removed by auction draught to a " aiae-end *' machine, which prepares it for further use. The material is blown upon perforated cylinders, the air escaping at the tide and the material being discharged on the floor. The process produces dust, particularly when the feeding is irregular, the air then having a free path between the cylinders. Tho material should be delivered under suction ana not under pressure, a " pressure " maebino being unsuitable. Spinning and Doubling.--Yarn is spun at flyer or ring frames which may cany up to 80 spindles, 40 on each side. Much piecing is required owing to the comparative weakness of the fibre. A fine metal tbread is spun with asbestos, for brake linings and oertain other purposes. Mule spinning is not practised in this country. A large amount of doubling is carried on. Spinning, more particularly ring spiuning, gives rise to dust, continuously produced by tbe " ballooning ' out of the fibre owing to the rapid rotation of tbe spindles, which may run at speeds of 1,700 revolutions per minute; and intermittently, when tbe yarn breaks. Doubling is less dusty than spinning. While the amount bears no comparison with that produced in carding, and is 1* than that from dry weaving, the workers are continuously exposed to some dust, .more in some factories than in others, doubtless due to differences in working methods or materials. Exhaust draught for its removal has not been applied hitherto, but experiments in one factory have been so far successful that the firm are prepared to equip all spinning and doubling frames with exhaust ventilation plant, embodying (i) exhaust ducts parallel with the frames, above the tin rollers, with shaped hoods at intervals, each to deal with a small group of spindles, and (ii). for more effective-concentration of the draught, panelling for the ends and lower parts of the frames beneath the spindles, capable of being easily removed when necessary. Such safeguards may require somewhat wide application unless special general ventilation is provided. Warping.--Warp beams arc prepared in the usual way from creeling frames, a small evolution of dust occurring at the frames and beaming machines; localised exhaust ventilation could hardly be applied effectively. A partilionedoff space, mechanically ventilated crosswise, with extraction at low level would effect improvement. ss s Winding.--Many winding machine* ere used, varying from makeshift types of primitive construction, at which the practice tuay obtain of boldingthe yarn in the hand, to modern universal winden for winding " cheeses." Dust may be evolved to some extent, particularly in connection with the above practice, which could be eliminated. Application of exhaust draught will then probably not be necessary, except in particular cases. Plaiting and Braiding.--Plaiting and braiding, also carried on in engine packing nd electric cable factories, end done at machines of normal design, cause tome evolution-of dust,`except where the yarn is impregnated with "grease." While the amount of dust is sometimes less tbaD in spinning, Uie difference i* not material. But there is perhaps less exposure of the operative under ordinary working conditions and precautionary measures other than localised erhsns: ventilation may suffice. Wtarring.--Looms vary greatly in size and general arrangement. As maDy as 140 looms msy be found in a single room, but this is cxccptioual. The clear p&oe between machines may sot exceed IB inches. Some looms are independently driven by electric motors. Cotton warp or weft is sometimes used. Tnin doth, fur mattress covers, filters, clothing, etc., is woven from a single warp team at a simple type of loom. Belting looms, for thick belting and brake lining material are complicated, several warp beams, Arranged in tandem under tbe loom, or is some other convenient way, being required. These looms are narrow, but often very long. Tape looms are also narrow, unless several tapes are woven together when several shuttles, in line, working in unison, are used. Cloth is beamed at tbe front in tbe usual way, but belting may be led under the loom, and coiled high above it, at tbe back. Most wearing is " dry," but some weaving is done wet, either warp or weft, and occasionally both being wetted. Wet weaving is accomplished more easily and a closer weave obtained, but rusting of beald fittings, and the subse quent drying entailed and the less satisfactory appearance of the material are disadvantages. Thoroughly dry fabric is required for brake linings and rubberproofed material, and wet woven cloth may be strongly objected to on this account. Considerable evolution of fine dust occurs in dry weaving as a result of (a) the forward movement of the slay in " beating up," this source being close to tbe operative, (b) tbe repeated contacts of tbe rising and falling warp threads with their neighbours, this source being the most important from a quantitative standpoint, (c) the disturbance of " dust " or " fluff " od machine parts, especially those in motion. A fine dust cloud may be observed behind the bealds above the warp threads. Much less dust is produced in wet weaving. Some " dry *' looms are now fitted with localised exhaust usually applied to deal with dust evolved by both (a) and (6), in some cases (a) only. (a) A flat horizontal " hood " is fitted in front of the operative, just above the clotb, the opening facing towards the healds; (4) either an upright pyramidal hood, placed transversely, or horizontal flat hoods, one on each side facing each other, are fitted dose behind the bealds. The second arrangement is the more elective for narrow looms, as the " scissors-like " action of the warp threads appears to displace most of the dust to tbe sides. The exhaust draught has effected some improvement, but all the dust is not removed, especially that produced by (l). It may be impracticable to apply the draught to all dust-producing points behind the healds, particularly at long looms, but greater success would have been achieved with more powerful draught and larger air displacements, as is now being recognised. The methods described for dealing with the dust created by (4) must be less successful at doth looms of ordinary width. A few such looms in one factory have recently been equipped with large " bonnet " hoods, fitted transverselv, close down over the machine, covering the slay, reed and healds. The hoods are of hemispherical section, with extensions over the shuttle boxes. An internal electric light fitting, aDd binged sections, facilitate working. A powerful draught, suitably applied, should prevent escape of dust, generated within. In another case, experiment is said to have shown that a transverse inclined hood facing the operative, placed just below the warp near the front of the loom, ran be more effective for reducing dust concentration in the air breathed, than present arrangements, and the new design is to be substituted. / 16 Application of efficient dust removal arrangements to weaving is clearly difficult. The expedient of installing individual machines or small groups of machines in suitably ventilated small rooms or cubicles, os suggested under *' Warping " does not appear to bave been tried, but migbt be considered if localised arrangements are not sufficiently effective. Long narrow sheds, for a single line of looms, ventilated os suggested, migbt be a possible .alternative. Cloth Picking, Examining, Measuring.--There operations involve running out the rolls of cloth and tend to produce a small amount of dust. If carefully done, so that very little dust is created, other precautions may be unnecessary. Non-Tixtilxs. Fiberized asbestos is not used in some of the non-textile factories and exposure to asbestos dust may be slight or even negligible. Dust is evolved in factories or departments where such material is prepared for subsequent use, or for sale, ana also in departments where fiberized material or dry mixtures containing it ore manipulated in preliminary manufacturing processes. Again, finishing processes, involving abrading or cutting at high speed, may be a source of dust, but such dust may contain only a small percentage of asbestos. The application of exhaust draught, where suggested in the following description or processes, is in most coses a straightforward problem, comparable with many others met with in non-textile factories, e.g., woodworking and grinding, where machinery similar to that described is used. Fibtrixiug or Opening.--Fibcrizing is almost exclusively confined to works in groups (&) and (c). Much of the work is done under less supervision than in textile factories and unsatisfactory machinery is more common! Primitive teasers (" devils ") are used in several mattress-making works, and chamber work is also an unsatisfactory feature (sec p. 22). In some asbestos-cement sheet factories, crushed material, from edge runners, falls into worm conveyors below, which transfer it automatically to disintegrators. In one Urge works, the process is being entirely enclosed; the material from the edge runners, which are lattice-fed, will be discharged upon is conveyor and raised by an elevator to large overhead storage hoppers, fitted with automatic bagging lattices. Localised exhaust draught will be applied at feeding and delivery points, where dust might escape. Chambers have beeu eliminated in some large works, with beneficial results. The material, after being disintegrated or opened, is fan-handled, and blown to a hopper fitted with bottom rotary delivery valves, the air being re-circulated. The material is bagged at lattices. Direct supply to a manufacturing point is uunther improvement now being tried. Such pneumatic conveyance should be practicable in many cases. Localised exhaust at feeding and discharge points of these systems is necessary. Vacuum methods for filling sacks may also be practicable. If chambers are retained, the necessity for entering them might be avoided, by providing chambers of small front to back dimensions fitted with low doors, at which sack filling would be done, localised exhaust ventilation being applied over the doors. (b) Millboard, Paper, Sheets and Tiles. The wet mixtures for millboard, paper, and asbestos-cement products ore prepared in e beater, as used in paper mills. Dry fiberized asbestos is emptied into the beater trough, the sacks being shaken to some extent. Evolution of dust occurs before the material becomes mixed with the circulating water. Occa sionally a sack is emptied before the water is turned on. Several sacks are required for a charge and the process is repeated a number of times daily. Precautions are not taken at present but the dust might be avoided by (<i) mechanical feeding under enclosed conditions, os appears to be done in some foreign works, (6) applying exhaust draught, (t) feeding in small quantities and in such a way that the material is wetted at once. Finishing processes od asbestos-cement sheets include sawing to size, corru gating, pressing and drilling, carried on in some factories with the material ao moist os to prevent dust, and this practice should be adopted generally. Otherwise much dust is produced iu wi11^. uwiug to the rapid cutting speed, and localised exhaust is necessary though not applied. Similarly, turning, filing and smoothing of dry asbestos-cement pipes, at lathes, may require exhaust to remove the dust produced. Synthetic composition sheeting, sometimes made in a rubber department, it produced from dough consisting of fiberized asbestos and rubber, mixed with talent in kneading machines-. Dust is produced iu feeding the mixer with asbestos, done in an open manner by band, from sucks or skips, the sacks being shaken out, or from an open lattice feed. Subsequent processes are dust-free. Exhaust should be spplied at the feeding poiut. (c) Insulation Materials and Articles- Compositions.--" Magnesia," the most important insulating composition, is produced on a large scale by the principal manufacturers, by enclosed methods with pneumatic conveyance of the mixture to automatic sack fillers. Weighing and feeding the fiberized asbestos gives rise to dust for which exhaust is neoessary. Fiberized asbestos or magnesia " is a component of many iusulating com positions which may also contain clay, kiesclguhr, fossil meal, flax, hemp or jute waste and other materials. The proportion of asbestos in die final product varies widely. In many small works the materials are mixed " dry," by baud, in on open manner, involving sack emptying and filling, shovelling and weigh ing. Enclosed rotary mixers could a be used for such work with exhaust applied at feeding points an tcrial discharged and bagged under enclosed conditions. It hand work is retained, exhaust should be applied. Consolidated Sheets.--Large sheets resembling thick mats, built up of layers of fiberized asbestos, are consolidated with silicate of soda, sprayed on in manu facture. The sheets may be backed on one face with millboard, or supplied without a backing, lacing fnced when fixed with millboard ur os)lestos-cement sheets. The sheets are produced of the required size and shape at work benches, or built up on the table of a machine, capable of slow reciprocating movemeut, and fed from a hopper above. In the former case, the fiberized material is taken in handfuls from skips and spread out in the forms, the surplus being scraped away and falling about at the sides of the work benches, and on the floors, a considerable quantity being scattered. Dust, produced in manipulating the dry fibre, before treatment with the silicate of 6odu, is lurgely avoided at the machine. Efficient localised exhaust should be applied to the hand process with improved bench arrangements, to prevent scattering. Band sawing of piled sheets, causes evolution of much dusi, owing to the considerable depth of cut. Localised exhaust alone, not yet applied, may prove insufficient. Sections und Slabs.--Moulded insulation is made chiefly iu two forms, sec tions--semi-cylindrical and moulded hollow to suit various pipe sizes--and slabs, which are rectangular and solid. These products are usually moulded wet, either by hand or machinery, from a paste or cream, prepared in a mixing machine nr tank. Feeding of dry material involves evolution of dust which might be avoided by one of the methods suggested for feeding beaters in millboard making. Sections are made at one factory by a dry process, at a machine indifferently enclosed. Feed hoppers, filled from skips, deliver the asbestos to iutcmal lattices which in turn supply a travelling liana, at which the section is rolled by hand. Revolving brushes which clear the lattice and spread the material evenly on the band give rise to much dust, and dust is produced at the hoppers, and in rolling ana brushing away superfluous material. Exhaust draught, not hitherto applied, is to be provided at the exposed brush and the machine is to be more effectively enclosed. An enclosed " feed " is also necessary. The sections and slabs are trimined to size with circular or baud saws. Much dust is produced and exhaust draught is cuinninuly applied, but is in some cases inefficient. Circular saws used in some cases in pairs, for trimming ends in one operation, can be fitted with exhaust hoods above and below the benches. ml band saws can be enclosed below the tables atid inverted hoods fitted, the exhaust drought being applied as for woodworking machines. Efficient arrangeindpls should te readily practicable for all sawing work here. \:liattrtuts.--Mattresses are manufactured by practically all firms who produce insulation requisites, though only occasionally by some. Mattresses for large contracts are made in tbo contractors' premises, their outdoor stofl taking necessary measurements and preparing rough plans. A mattress has sometimes to be made on site. Mattress making involves, broadly speaking, the sequence of processes associated with the making of domestic mattresses. The work is almost eutirelv hand work'. Lengths of asbestos cloth for covers are cut out on a wide bend) and sewn op, by treadle or power driven machines, to an extent depending on the method of filling. Large mattresses may be sewn along one side only or both aides may be seamed and filling done from Doth ends. Before filling, covers arc turned inside out. Supplies of filling material, which usually, but may not, contain fiberized asbestos, are brought, in sacks or skips, from chambers, or taken from open bins, in the room, kept supplied from the thantbers, or from sacks, of material supplied by outside firms. Pilling is dope by hand, scoop or shovel, and quantities way be weighed. The end filling of long double-seamed mattresses, referred to above, necessitates the workmen mounting on the bench to empty the material from skips into the openings. After filling, the mattress is levelled, nr beaten, to make tnc filling lie evenly within, the hand or a fiat wooden beater being used. Finishing processes include final tewing, stubbing or buttoning, fixing ou hooks, etc. Some dust is produced at the cutting out bench, in opening out the roll of doth, and at the sewing machine, but far more in taking material from bins or sacks, in weighing, filling and levelling. Beating of the doth produces asbestos dust, the amount of which is largely increased if the filling contains asbestos. The work is largely done without regard to the necessity for suppressing dust. All benches are entirely open. Localised exhaust draught ia not applied. One firm have improved conditions considerably by the followiug pre cautions:-- (a) Keeping floors and benches damp aud spraying covers before filling. Hose connections and spray fittings are proviacd. (b) Suh-<livision of department into several independent workrooms. (r) Exdusion during filling of all workers not to employed, the exduded workers proceeding; to another section. (d) Mechanical ventilation of each room by cross ventilation, embody ing plenum supply (warmed when necessary) at one side and low level extraction at the opposite side, the air being changed between 10 and 20 times per hour. (t) Enforcement of use, by fillers, of respirators. These precautions do not include application of localised exhaust ventilation, without which mattress filling and beating must involve some risk of inhalation of dust. For small mattresses, a wide double-sided canopied bench with exhaust draught applied at gratings along the centre line might be used, the fillin'* material being supplied within the canopy. Such a bench may not perhaps be practicable for the making of large mattresses but the possibility should be explored. Otherwise at least the precautions referred to above should be adopted. (d) Brake and Clutch Linings. Before being impregnated, the dry asbestos cloth, known as " grey," may be calendered at squaring rolls and in all cases the coils are eased out to separate them a little, so ensuring thorough treatment by the liquid. A little dust is produced in these operations but insufficient to render special precautionary measures necessary. Other preparatory work on " grey " arises in the making of special linings. Lengths of cloth are lightly hammered to ring shape, in templates, then cut with chisel or shears and the radial edges sewn together at a wire-stitching machine, as used in book-binding. Dust occurs in hammering and stitching. A canopied bench fitted with localised exhaust arrangements might be provided and the machine placed under exhaust draught. Dry impregnated materia] is shaped and finished mainly by power-driven ' machines, e.g. knives, circular and guillotine, cutting presses, hydraulic squeezing presses and band saws. Cutting and sawing expose ends of wire and leave rouge edges; trimming and smoothing, done on grinding wheels and linishers, are necessary to obtain exact sire and fiuish. All the operations, except squeezing, produoe waste, and dust is created in some. The dust is heavy and stickv and less likely to fly about than dry asbestos dust. Tbe amount is considerable at sawing and grinding machines and localised exhaust draught, to remove it, has been applied--in some rasa; with much success--and is always necessary. Inverted hoods are fitted at band saws, iusl below the tables, tbe dust being drawn through the small openings in the tame guides. A powerful draught is essential. Grinding and finishing wheels include, iii addition to ordiuary single-disc machines, two-disc and vertical spindle segmental grinders, used for flat liuings. The hoods by which the draught is applied to all these types are similar to those applied to the same machines when used for metal grinding. The position is similar as regards linishers, a hood being fitted in line with and at the back: of the band. A baffle plate to prevent dust being carried past the hood by the high linear speed of the band is a necessary uddition. Special linings and anti-friction bushes are moulded from disintegrated impregnated waste. Some dust is created in the filling of moulds and elficient localised exhaust draught msy be necessary. The articles are shaped and finished as just described. Bushes are turned and bored in lathes, with production of waste and dust, bnt exhaust draught is not at present applied though possibly necessary. (e) Packing and Jointings. Engine packing is either (a) " cloth " packing built, up from cloth, usually rubber proofed on both sides, handling of which does uot cause dust, and (4) rope " packing made from yarn, at braiding and plaiting machinery, as used in textile factories, (o) Negligible amounts of dust may arise at the spreading machine, from the unprooi'ed cloth, and, in building up, from material proofed on one side only. (4) " Cheeses " of yarn are first rewound on bobbins for tbe braiding and plaiting machines. Simple winding mechanisms are used. Some little dust is produced; special preventive measures will usually not be necessary. Flat packing, known as " grummet," is made, on a small scale, from asbestos yarn, threaded on a needle ana wound in and out by hand, as balls of wool are wound. This apparently insignificant process causes sufficient dust to cover in a short time the hair and dothing of the workers and should be doue at a canopied bench provided with localised exhaust arrangements. (1) Asbestos-covered Electric Conductors. EltciTodti.--Electrodes are either wrapped with yarn, the usual method, or passed through paste containing asbestos fibre, yarn being wrapped upon this coating. The former method is usually uchieved by a small high speed stranding machine fitted with a flier carrying the spools or bobbins of yarn, the wire travelling axially through the flier. Treatment with consolidating liquid, straightening anil cutting to length follow, all done at the stranding machine. Alternatively, single electrodes may be wrapped by a simple winding mechanism, hand-operated or power-driven. Paste-covered electrodes are also made singly at small extruding machines, a flier for feeding the yarn being fitted behind the extruder. After drying, a short length of the covering at one end is ground away, leaving-, the bare metal ncceasarv for making electrical contact in the bolder, when in use. Small abrasive wheels, almost entirely unclosed, are used. Small amounts of dust arc projected from fliers, though insufficient prob ably to require the adoption of special precautions. Much dust is produced in grinding ends and efficient exhaust ventilation is essential ; present apparatus, where provided, is capable of improvement. The process would be unnecessary if bared ends were left in manufacture, and experiments directed to this desirable end are being made and give promise of success. s so Preparatory processes iu paste making include (i) dry grinding of fiberized asbestos by suiali vertical disc grinding wheel*, fed at tbe uiulre Iron: a hopper above and discharged from the periphery into a box below, aud (ii) hud mixing of tbe ground materials at a bench, involving emptying out of dry material into pans. Das: is produced, the amount being considerable iu gnudiug. Little precaution is taken. The processes might be accomplished under almost entirely enclosed conditions, efficient exhaust draught beiug applied , ut points where dry material is exposed, e.g., in feeding. Rewinding of yarn is sometimes necessary aud primitive arrangements may be used, the practice referred to ou page t!4 being followed, mid as a considerable amount of dust is produced, the practice should he given up. Cable and Wiring.--Asbestos-covered cable and wiriug constitute a small percentage of the output of the cable factories. The yarn is braided and plaited on the conductors at machines, not reserved for " asbestos " products, similar to those previously described. Rewinding of " cheeses," as received from asbestos textile factories, is done at universal winding machines The aiuouul of dust evolved is email, and special precautionary measures are apparently not required. Field-coil Wrapping.--Field coils for electrical machinery are wound with asbestos tape by hand at ordinary work benches. The process does not give rise to appreciable quantities of dust. (g) Miscellaneous. Moulded Goods.--Some electrical insulating httiugs are moulded from varnish-impregnated fiberized asbestos, prepared after thorough drying in a mixer aud ground iu an edge ruuucr. Alternatively, impregnated scrap, ground iu a rumble.', may be used. The preparatory processes on dry or practically dry material are intermittent, and involve sack emptying, shovelling, weighing, filling and emptying shallow trays. They are carried on iu an open manner without special precautions except that as regards griudiug, hanging curtains may be used at the edge ruoner, and the scrap rumblcr is enclosed. Dust is evolved iu the processes mentioned and localised exhaust ventilation should be applied to effect its removal, with, in addition, effective enclosure of some hand work, e.g., emptying of trays into machines could be done inside a cabinet provided with internal arrangements for securing the trays aud an external handle for turning them over. Localised exhaust may be necessary for final trimming if done at abrading wheels. Moulded articles made in other trades may contain but a small proportion of asbestos, although a large quantity may be used. In one case tbe asbestos is sieved after drying, both operations being done in enclosed machines, and, in addition, dry mixing, done iu rotary machines, and paste mixing, on open rolls, as in rubber works, arc also required. Processes carried on with some risk of exposure to dust include emptying of sacks into bins, filling of trays for drying, feeding at the sieve elevator hoppers, the dry mixer, ana the rolls. Localised exhaust is applied at (a) the elevator hopper, (b) the storage chamber above an intermediate bagging ]>oint, (c) the dry mixer, and (d) the rolls More efficient arrangements appear to be desirable for (a) and (c); the feeding of the elevator might be done under enclosed conditions'if a cabinet as mentioned above were provided into which the trays could be inserted. Localised exhaust is necessary at storage bins. Final trimming of rough edges is done under efficient exhaust draught. Other processes of comparatively minor importance, e.g., asbestos putty mixing, in which there is handing and feeding of dry material in preparatory processes, will call for precautions as previously described for similar work. 4.--Sacks. In a few cases sacks of Kiilcloth or oilier closely woven material are used inside the factories. Such sacks are much to be preferred to those made of the ordinary material, which is " leaky " and gives rise to dust in handling. 5.--Ci.EANim; of Wohks. Machinery anu Sacks. Some factories are kept in a more cleanly slate than others, hut higher standards and improved methods arc desirable generally. Weekly cleaning by dry methods is general in textile factories, but is more effectively done in some s 31 jo others. cIcAuiog may tlto be done during llic week.. The .Jb* wfaidb gather* in * week render* cleaning a very daily operation. Young . riaen ny be *' <m carding machines brushing dust into the oir from the etc., b considerable amount, near other workers. Some firms have 'Mfeatcd wt frequent regular cleanings and more satisfactory methods by Jmpiag botee sweeping. Vscbbxb cleaning methods have not beeu adopted and such methods seem Befit regarded as impracticable, but this can hardly be accepted. Portable wbdb acta axe constantly used with great advantage in other classes of works, lw'wjr cable factories, by adult cleaners who keep the machines, plant, wmm pipes, etc., thoroughly clean. If vacBBB methods are not adopted, well organised daily cleaning, by adults, siiqg duap methods for floor cleaning, ahoula be the rule in textile factories, sopply with suitable hose and spray connections should be provided. Safaris produced in asbestos-cement sheet works under moist conditions may me drj and cause general dusty conditions. Cleaning should be so frequently as to prevent this. The denning under machines mich as loom* and cards entails collecting mmh of considerable value, done at prncut by hand. Vacuum collection should hrjmiihh : id principle, it is already used for removing side waste at finishing arik The sound principle of collecting card waste, through floor openings, bar keen adopted in one new factory, and might be followed in others, with tOsaitic collecting arrangements. lock deaaing is done in a few large works in rinduscd machines. involving mar risk of exposure to dust in filling and emptying, notwithstanding the parisioo of localised exhaust ventilation. A type of '' exhausted " machine fid docs not involve such work is to be preferred. 6.--SUMMAKY AND ReciiUMEKDaTIONS. Ashretns factories and workshops cover n great variety of processes. The pnma differ widely in structural features and are congested in many cases wixhnadiiaeiyor material. Processes are largely carried on in close association. Dust is produoed at many kinds of machines, in hand process work, and in simple inridmtal operations, particularly in emptying settling chambers, and in aJ ms(fling of " fiberized ''asbestos. la textile factories, pure asbestos dust is continuously produoed, iu differing amounts, at all the principal machines. Card stripping, a very dusty operation, is uuify effected by hand strickles. Hand mixing of diflereut grades and varieties, incidental in opening processes, is also dusty. Ia non-textile factories, pure asbestos dust is produced nt opening machines, in feeding machines, in making insulating mattresses (n.dusty hand process), and u) mridenul hand work. Dust, though rarely pure asbestos, is produced iu A&ithing operations, e.g., sawing, grinding and other nbrading of asbestos products. . The appropriate methods for suppression of dust may only be fully deter mined when the harmful effects of comparatively low concentrations of asbestos dus are duly appreciated. Very dusty processes will not fail to be recognised, but in processes such as spinning and weaving, in which in other textile trades special methods for dust control are not required, due precautions are also neces **ry. .The asbestos manufacturers are clearly confronted with the necessity of attaining conditions in their industry which will ensure much less dust in the atmosphere than can safely be tolerated in many comparable trades not usin'* asbestos. The principal methods for the control of dust are :-- (a) application of exhaust draught at dust-producing points; (b) substitution of enclosed mechanical methods for hand conveyance, and for dusty hand work generally; (c) effective enclosure of dust-producing machines and plant ; (<f) substitution of wet methods for dry. / 32 Each of these has its particular sphere of utility, and the particular indica tions for their adoption are put forward inter alia m the reoomendations below. RECOhlMENDATIONS. (1) Application ol Efficient Localised Exhaust Ventilation at dust-producing points. This measure, of the greatest important*: where manufacturing and incidental processes occasion escape of dust not controlled by euclosure or other measures, is necessary for :-- (a) Dust-prodvciug mwehinct, e.g -- (i) Crushing, disintegrating, teasing and other opening machines; sieving machines; fibre grinding machines; dry mixing machines; rolls fed with dry mixings. (ii) Carding machines (to suppress dust from cylinder and doITers, caused by stripping and grinding, in addition to that pro duced by carding); card side waste exhaust machines; looms for dry weaving; stripping and grinding machines; other textile machiucs, if the dust evolved renders this preventive measure necessary. (iii) Sawing, grinding, trimming, polishing and other abrading machines, used on dry asbestos products. (b) Feeding and delivery lattices, or other couveyors, at machines or other plant; feed hoppers at elevators; bagging lattices; feeding of dry material at wet mixing machines. (e) Chambers, containers. " cyclone " hoppers, or other enclosed space into which fiberized asbestos or mixtures containing it arc delivered, or pass. (d) Work benches, e.g. for mattress making, waste sorting. () Various hand operations, e.g., sack emptying and filling, weigh ing. mixing. This is the principal measure hitherto adopted, aDd is probably that most generally applicable. It has been applied to some only of the above machines, aud appliances, but not to hand work. The methods of apjdyiug the exhaust draught, and other associated factors, are becoming more effective, but there arc few fully satisfactory plants. Special difficulties remain to be overcome in some cases, e.g., looms, mixing, mattress making. If not surmounted, an alternative, viz., general ventilation of a high standard applied so as to draw the dust-laden air away from the worker, should be provided. (2) Substitution of enclosed mechanical methods for hand conveyance, and for dusty hand work'generally. This measure-- (a) avoids depositing material in clumbers, intermediate filling and emptying of sacks or skips, hand feeding of machines, and other incidental . hand work; (b) permits of final filling and weighing, under the least dusty con ditions, of materials for dispatch; (c) renders exhaust draught more effective, or, in some cases, unnecessary. It is already employed to some extent, and its further application, wherever possible, is greatly to be desired. (3) Effective enclosure of dust-producing machines and plant. (a) To prevent escape of dust not controlled by exhaust draught, or (b) to render its application more efficient. (4) Substitution of wet methods Ior dry. To reduce the dust given oil in certain processes nud work, c.g., (a) ft'ooneiderable amount of weaving; (t) mattress making, by wetting.the covers before filling, and by frequent wetting of floors and benches; (c) final tawing, and other machine processes, in asbestos-cement aheet and tile factories, before the prepared material bus had lime to dry; (d) works' cleaning, by damping floors arid benches, before brushing or weeping. This measure might be adopted to a greater extent thau at present. (5) Elimination ol certain dust-producing appliances. Certain appliances arc used i'd a few works, sometimes with a measure of precaution, but which emit much dust, difficult or impossible to control by efficient enclosure or exhaust draught. They should not be retained unless effectively modified. () exposed doffer brush at carding machines; () card aide waste exhaust machines, delivering uuder pressure. (c) certain willeys and teasers, particularly old machines. (6) Abandonment of Settling Chambers in Manufacturing Processes, to the utmost extent. (7) Effectual separation of processes to prevent unnecessary exposure to dust. New factories should be laid out to os to avoid exposing workers to risk from processes upon which they arc not engaged. Iu particular, there should be effectnal separation of-- (o) opening, cardiug and weaving, from each other, and from any other process; (b) spinning, doubling, plaiting and similar processes, from work not causing dust; (c) mattress making, from all other work; (<f) chambers, containing fiberized asbestos in bulk, and dust settling chambers and apparatus, from any workroom. Tire separation of mattress making should be adopted in existing works, and other separation referred to. as fur as practicable. (8) Wide spacing of dust-producing machines in new factories and, as fa: as practicable, in existing works. This measure would bring about permanent reduction of dust concentration in the air of the workroom as a whole, and provide improved cleaning facilities (9) Use of sacks of close texture material for internal work. (10) Efficient cleaning system with wide use of vacuum methods. (See also (4).) (11) Storage ol asbestos and other goods to be outside workrooms. (12) Exclusion ol young persons from specially dusty work. (Vote.--Particular preventive measures of a medical nature are referred to iu Part I, where also the limited value of respirators as a safeguard in this industry is briefly discussed. u Not* un Exhaunt Vkntilatiun in AsursTus TVohks. Some exhaust plants are carefully designed and reasonably efficient, but tome are ill-desigued and inefficient; others, again, do not eflcct removal of dust to a sufficient extent. The draught may not be applied as closely as possible to the dust-produciue points, or may be too weak, lhe emission of a visible dust cloud at a point where exhaust is applied is n clear indication of inadequacy. Extensive alterations of existing plants may produce serious loss of efficiency. Exhaust provision for new machinery and processes should, therefore, generally peaking, be made independently. While advantages result from dealing with many dust-produciug points, by a single exhaust plant, a number of self-contained plauts, with independent fans and settling apparatus, is ofleu more effective. Exhaust ventilation applied on a large scale entails continuous removal of a considerable volume of air from the room. The supply of fresh air must be ample or the efficiency of the exhaust ventilation may be reduced. Iu winter, the workers arc liable to bring about this result by closing windows and doors. Plenum ventilation capable of supplying the volume extracted, the incoming air being warmed, may therefore be desirable, where extensive exhaust plants are installed. Efficiency of au exhaust ventilation plant may be greatly reduced by in efficient dust-settling methods. Each fan should discharge into an independent settler. Settlers adopted in asbestos works include cyclones, large chambers connected with cyclones, large chambers enclosed with sucking or other filtering material, aud bag fillers. Cyclones and chambers are usually well separated from workrooms. Bag filters are now being commonly adopted, for small instal lations. These filters and " balloons " are sometimes placed inside workrooms, a bad practice. They are best pluced in freely ventilated rooms, effectively separated from workrooms. Filtering fabrics fur settling dust gradually become clogged; aud as this effect increases llic exhaust plant becomes more and more inefficient, the volume of air moved by the fau being reduced. Such settlers must therefore be kept clean. The usual practice is to beat the filtering material. Arrangements for. shaking bags from outside, or automatic shaking apparatus are not provided. Asbestos dust docs not appear to be so difficult to detach from suitable filtering material as some dusts, but much dust is produced iu beating. Efficient shaking arrangements, avoiding this ex|msure, should be provided if this method of fettling is retained. Some firms strongly support the view that it should be given up because of the difficulty of maintaining the exhaust plant at the highest effiriciiry. The matter merits careful consideration. In particular, the efficiency of the exhaust plant should be kept under constant observation by a responsible person. Cyclones should be of adequate dimensions. The combination of chamber and cyclone is used extensively, the fan discharging the air into the chamber, to which the cyclone inlet is connected. The efficiency of this arrangement should remain practically constant. E R. A MERETVETHER. CHAS. TV. PRICE. 14th March, 1030. m% m 41-TVtw v* r m t,