Document jgJQ5ex5DB5KdaOEe2gr0L9kN

I THE DISEASES OF OCCUPATIONS DONALD HOWTEK c.b.c.. o.*t, m.u.. r.R.c.r. C--mmitii* Phyutimm 7%f Ltmdm Hmpiltt A <? A M* v-*k' & frjk / S T O O I 1670 LITTLE, BROWN AND COMPANY BOSTON DOW 06953 IS T 0 0 1671 TJir. PNEUMOCONIOSES 1009 V- Mk -- 1t . rinduKft iung*i-daily dun n&blitb Kenm. jotrola a, me the rad. voune 1 iium **e ate d,\r e wiuvii inhalot. mother. >r not u ;.,x i'j'untt ith Mitcmt* at Timmins, Ontario, hersthin* Aluminium i'ouucr (non an Ki;wrinicnt*l Treatment Chamber . win mf t*. II. It*. JmtH (a) Afthcttoe * :,i* the name given to a scries of miners!* composed of silicate* -u >iiitii and iron. It is sometimes referred to as earth flax, atone flax .,,:.;ti otra. It is silky and fibrous in form, and this fibrous structure nutty of the characteristics of esbeitorii, the disease caused by of ti,c uusc A -bestoais is a more serious disease even than sili- !:i -.l.iition tn this asbestos workers face the risk of cancer of the . -.-.u oi imxitiiclioma of the pleura and peritoneum both of which are , <tw fatal tii'vasc*. !o<aory of Asbestos < N a mull scale, asbestos was made into cloth at least 3,000 year* ago, .i..:us t'450 a.c.) relates how the Romans mined it in the Italian Alps t :J Mountains, using it for enshrouding corpses before cremation to r...t rosy collection of the aahes for burial. They named it emieetkmt, .. iiltout miasma, undefiled or incorruptible. Pliny (a.i>. jo) refers : niv to diiflcultics in the weaving of asbestos, but also to the use of . "!** to avoid the inhalation of dust. Strabo (30 s.C) and Plutarch refer to the wicks of the lamps of the vestal virgins as atbetf, the . .icnci-ble, inextinguishable or inconsumable. It is stated that Charie* :rx possessed a tablecloth made of it, which was cleansed by passage DOW 06954 b lU U I1672 IOIO THE DISEASES OP OCCUPATIONS through fire. Uwcttr, although the occurTtnce of asbestos b widespr. throughout the world, it ia only line* about 1*90 that it hat been used industrial purpose*. In 1M0 the annual world production was only tom, a figure which had risen to aoo,ooo tons by 1920 2nd nearly 3.500,1 a tom by 1967. ' %: and Varieties Canada produces *5 per cent of the world's asbestos. The remaim comes from Italy, Cyprus, Finland, Russia, South Africa, Australia, X* Zealand, the United States of America and Pertr. The term asbestoi r collective name applied in commerce to a variety of silicat* minerals h: differ from each other in chemical composition and physical properth but resemble one another in their finely fihroua nature and Eeribilit Their value depends on the facility with which they can be split in' long and short flexible fibres, their resistance to adda and their insular* properties with respect to heat and electricity. Most of the asbestos commerce ia fibrous serpentine, especially chrysotOe, 3Mg0.aSi0rill1f This has the longest and strongest fibres and can be spun. Asbestos ; derived nNo from the lmmblende (amphibole) group of minerals, of nhic the most important are emcidotite and amoaite. These consist of fibm tr short for spinning, but more stable chemically and more resistant to acit and heat than chrysolite. The hombtende varieties contain leas magnruu? and usualty more aluminium and iron, crocidolite being mainly a silica: of iron, NaKc^SiO^KeSiO,. It is also known aa 4/ve s4rrfar, an silusiw t its prevalent cotour, and as Cap* blue, because formerly it was mined eri in Cape Province, South Africa. Amoaite, (MgFe)O.SiO,, which occurs i workable qtiantities only in the Union of South Africa, ia named from th initial letters of Asbestos Mine of South Africa, the title of the mine tvher it was first worked. Other varieties are actinolhe, CaO.jjMgFeJO^SK). and tremolite, CaO.3MgO.4SiO,. #* Use* Capable of being spun into jam and woven into cloth orefmixing cement, rubber, resin, pfastici or graphite, it provides the engineering automobile, shipbuilding, electrical, building, chemical and other trade*: with a variety of useful products. These include a wide nagt of tamlatieii product* for pipe tagging, aa well as flat and corrugated cement sheets for building work, and also roofing shingles, cements, tflea and paints. Wool-asbestos fibre is even used in the filter pads of certain types* ' of respirator! From modest beginnings in a small disused Austrian paper; ^ mill in t*93 the asl>catos-ccmcnt industry has constantly expanded so that! by 19*7 it was estimated that over too.ooo people were employed in it.-^K' Tn 191a an Italian engineer built the first machine for making tcunlrui asfwstns-ccment pipes. In 50 years the demand for such pipes for >r*e ia* domestic installations, water mains and sewerage has greatly expanded in at least 40 countries, fn bnke linings and clutvli facings the asbesto* DOU 06955 S T O O I 1673 1| -2 IK rXKlMOCOMOSES (Oil r. *** -*k 'V? - is tr * *; wire thread*. A>bc*to* is made into acid-roi'ting chemical pans, valve packings, ga*kct. jointing steam pipe's end is used for coating the bulkhead* Long*fibred asbestos, which can lie spun and far fire-fighting suits, firemen's hdmets. slieeu boiler uttrcw wand for the coverings of as a flux. Domestic uses indude plastic doer board*, own dosha, table and cooking matt, made with asbestos asphalt for mad surfacing, many of these industries $t highly mobile and dWtri* number of small addition there is a vast ` smdcr ofM* ii TowrscSr* cntHususia btexposed intermittently h*W? concentrated aJ*c%tt Just. la Seutk Africa adwstua is obtained cast and deep Driffing and espbwives are rock is hard and rrnTTexcaration when it is milled to remove the borf rock and the fibrous *fo4* is partiaiiy teased nut *97-v/5 Mure it is packed into bags, tthnv labour is cheap some of Ac wparation of rock front fibre idone by SunJ withtaa ccoobnbniinngg zjajmer (fig. &)) usually i>v ,, | v *?* . > iV f''*'1 *" - ** * - V *'.**! mn. but sometime* juu accompanied Wby ;i!W><r tulao. I mil recently large xuoanttufa*beto fibre escaped ism liw sir from the mines and da so Uut not only the miners : "i -< ..J 2 -t ad milter* hut tiic whole 'wpubuon of the mining towns rod the surrounding country* dJs have been exposed. From the sir a cloud of a*Iwtos dust cat be seen over the small mining tmwhipo. ft was Customary 390---Csbhfaut hammer w mlnn in Cnsli >CW.a*. to transport asbestos from the mines to the factories in jute bags. Sometimes s bey who did tide tafatg t Junkcy wagon would sleep on the asbestos bags during pert of the journey. This exposure of a whole aeries of tnnapoct workers could be eliminated by using sealed impervious bags. Work in Factories For the manufacture of asbestos textiles raw asbestos in crude and core lona is imported into Crest Britain and stored in seeks in opes abed*. DOW 6956 101* T11B DISEASES OF OCCUPATIONS Th aadoi are carried to rotary mil! am! opened. tm or threo it time, by had. Tht crashing pmct* i dusty. Tho material than pomca by vacuum action Into a closed-in machine which deliver* ITocculent. toft, fibroin material, free from grit For tin manufacture of yam and cloth, cotton la often incorporated with the fibre before canline. The cardin* machine consists of lance, fast-running cylinders, covered with innumer able minute wire point* to m*ttre that tlie fibre* are laid parallel. From the end of thia machine the material i* received at a diver nr rope. Strippine the cardine machine* (fie* 400) and cleanine the cylinden with a wire brush was a very dusty occupation before modem types of exhaust ven tilation were applied locally. Spinning, doubling and wcavine follnw the process of cardine. Dry weaving is usually practised. for wet weaving has the disadvantage of rustine errtain fitting* on the machinery. For non textiles. such as mill-lnvirds, a wet process is employed. Fibred asbestos is mixed with city, cement and water, and run through a series of sedimen*s-^g^atfaMiTjlia m secure the finest of the pulp. Thia passes along the machine ' *? OWolwori. becoming drier and more douehv on its way, until it is * " rolTed out upon a cylinder. From this it is cut. removed and Wthc drying-room. SuKwjuvnt operations, such as sawing, grind3$??figFr&rn'ng am! polWu'ng, give rise to much dust. Insulating mattresses ***"'' "hire made almost entirely hv hand from lengths f n*lesto* doth, and are ! t i i r ftHeand tv- > 9. vat CO --4 P* O wl O w! ar d* <T O' u -^4 4T- J r 1 t ^ '** 4*0.~t<tipoin* *i Aihnlswtdlist Machine hrf.-ne m<*!rm (vw nf 1-ahswst VcTUi!*(in u nppIirU t-ieaCy (/* tmftMf / ffiilnl /IWrit tmi I.U.1 f1 0A/ 69s7 IS T 0 0 1675 llll. l*Ni:i:MOC()MUMi.S ioij . . ...... . a..* .............. w by hand, scoop or shovel, levelled Jy Ix'uting fw f.WwstvHI (iuOJk ul - in'.to* factories are iiM-tl in the Hiaiiufacliirv of ..j-.wer units diii*. car* and domestic stoves, lv 1 i .i,.'.l.l trad. tmn with their helper*. 'Hivsc men sometime* red i..4:-ri.l wool. they mix With water and ap|wy on the *}ot i,,; .: .;* mixture i* wet. or tStey use prefabricated block* or mattresses repure cutting. >-wii< or shaping to nuke tlutn tit. 'Hie material* .n .. ...rfiij- r<uicii*ttiii'l.cu uikctt they leave the factory and relvuM.* >utne . handled by stmt-men and transport worker*. Hot water pipe* ^..pper aiid other metal* are instated hv co.cring them with asbestos. 4i,, jiijv* are similarly treated with a*botna, wire and cvmvnt. The jub . and it U carried out in shipbuilding. in factory . and private house*. At or.e time the asbestos was applied v,t i,t now pietahrivated material* shaped to the job are used dry, the o.'i(iatk >..nu,e them up to the required length* a* he gm-a on with hi* ..rk. It t<<iiow that die new method produce* dust whereas the old :-.:ttimd d.J not. lluilding worker*, interior decorators and nuny other* *..e ^ov.'to* materials Klcctririaiis, piumiicr*. fitter* and painter* :..av nor* iti eoulir.ed space* and may create du*t cutting or drilling theac t...,r,r;..N in ti.e course of their work. Mot aslvesW** material* are coated { u. tii juitit or saiidwici.cd iK-twecn other substance* so tiut they do not j .n-Ni!.: a continuing risk until the huiiding or installation is Jer.;whcd. -'iK-stH rooting and brake lining* unhappily cause some general .:r.k"'phcric pollution, and certain uses such as the lining of duct* for air vondktioning with soft asbestos and the u*e of unsealed cciiing tiles cause fir.tinunn* pollution of the air of odice and factory building* where people ntk all day. Asbestos in Fire Protection In i</6t the Pari* Metro, a* a result of a tire in which H3 people died, ciwng.d fiom vat iron brake blocks to asbestos*resin blocks. The tire had '.mu started by metallic dust, causing a short circuit. Asbestos*resin brake Mocks have hevn used l*v the London Underground for this and other r.as..r.* ever since. In 1933 when the Quttn Mary was being built, mock cd'ir.s were constructed and ignited to test different materials, and it was then that aslte*tos*ba>cd board established its supremacy in fire protection. Today advstos insulation board is increasingly used for compartment wall* where targe number* of people congregate, for example in elfieca, >:o:cs, schools, hospitals and multi*storcy fiats. Asbctos*ccmcnt sheets, widely employed for sidc-cladding and roofing are weather-proof and will roi: the surface spread of flame. Asbestos textiles are used for furnace nrc curtains and other types of fire shield, of which the thestre fire safety curtain is one. Wherever workers are exposed to greet heat or to the risk p.0.-33* DOW 06958 91911001'9'i ! r ;^ - tor* DISEASES OF TUP. OtXITAT IONS M hot metal splashes !e use of protectrre clothing i* desirsble. For this Purpose alumini/cd 2'besfos textile materials have been developed. In a major fire steel g:rdrr prove surprisingly vulnerable and their distortion mar wnt the c"!;apr of floor*. `Hieir resistance to fire can t*e enhanced by treating tfirm with a-InMos spray. TTiis forms a homogeneous coating and ha* the advantage of adding but little weight (Ilrown, ir/iyj. Historical Summary The danger* of aslwsto* remained for long unsuspected. They came to light wi?i a somewhat disconcerting suddenness. The first case of ashestosia known in Great Hritain was observed in 1900. snd described by Mtirray in 1907. 'Hie man had worked on a anting machine for fourteen year* and was the last survivor of ten men who had worked in the card room, the others all having died altout the age of thirty with lung disease.. Me died in Charing Cross Hospital at tlie age of thirty-four, and neefttpsy revealed extensive diffuse pulmonary fibrosis. Although the lungs were found to contain asIxMos Ivwlics. a diagnosis was made of typical fibroid plithisis. DifTicultiv* *f certification delayed further action and cases of ashestosis continued to occur. Sjurcial attention was drawn to the disease by Cooke (192**. Hot it was the case published by Sleler in P)Jl which j^jQgaaal to establish an unctjuivocal relationship Iwtween asbestos and ^gMsMnary fihr*is which precipitated the in|uiry leading to the Report of l3%&ei.SOfiifewr'.h"er and Trice O930). Reports of a heavy incidence of ashestosis rwrre then mail** in some (U-rman factories, especially in 1 >r* den (Kriigvr and others, 1 ijt r) and Iferlin (fb rbis and L'ckn, tots). In Great Hritain the report by Mcrew ether and Trier lit! to safety measures being adopted in factories and t the workers being kept undvr medical surveillance. Hut although improvements in dust cortr"! were eflcctivc in most of the aabostnx textile factories rew cases are still being diagnosed by the I'anels of the Ministry of Soci;:! Security. Furthermore wr now know that many people with aslx-stmis or mesothelioma had contact with asbestos only outside industry either through Jiving near a mine or a factor}* or through dusty clothes being brought home from work. The story of mesothelioma of the pleura and reritmteum i* related on p. 1019. Thirty Cases in One London Factory between toto and tot* thirty-seven worker* in asbestos all from one factory attended the Oot-patirrt Department of the Iguidon Hospital; twenty-five were woven ami twelve were men. Of these, thirty were judged to le suffering from n!>o:'i*is. Seven of these died; and in four nevmpsy showed t'>.*t the a*lv*tni* was complicated by pulmonary tuber* C'llmb. Many had worked in mrc th.. one department of the same factory but the pric*tvf KT*!;v*?ons in order of frequency were as follows; spirimv, weaver, d?-:*:tegr.'0r, m:xer, matt'rss maker, card cleaner, store* k'x-pvr. slab tn.-'u *, p-v'c* ami m.tchinio, The average length of exposure bvf'Te l.e on*vt of ymptotn* was seven years. Of the patients who died. . t . * .*> DOW 06959 S T O O I 1677 or |L lit s 'luetimi UWVil outing i lfF. PNETMOCOMoistei tuiy m .- - wrvvr w..n been c\poM\i tor eighteen mnnt!.> j:.J ur.mher . -v.rvi.i.pvf i.u hid been <t work fur nineteen \ear.. in cmv* ;i (re d h*r.g interval between removal from exposure and the onset of m: the longest such interval was eight year*. Symptom* Tiie presenting symptom was dyspneta. This was early, cnn-picuoua irS tlvint iml nf proportion to the signs fount! in the chest. It nearly ilnaxt uMnciutcd with non-productive cough, aa many aa eighteen eaaca hat me little or no sputum. Hemoptysis never occurred in the absence of pulmonary tuberculosis: it was found in three case*. In sixteen cases pain occurred between the shoulders, under the scapula or behind the sternum; it was never mure than slight, In two cases a diagnosis of acute pleurisy had :-<vn made during the period of employment in asbestos, but in no case had j ph-ur,tl ctfusion occurred. A history of laryngitis was obtained in three tiH-. and of conjunctivitis m taro. Warts on the fingers had been present it one time in thirteen caeca and had subsequently disappeared. It is untile, a Iwavier and thicker fibre than chrysolite, which may, in some upentions, penetrate the stun and form a com or mrt. Histologically the lesion sivows extreme keratosis (Aidcn and I lowed, 1944). Physical Signs *l*hc patients were usually well nourished. Clubbing of the fingers was present in six case*. Cyanosis was occasionally noticed, hut was only slight. Mumination of the chest showed limitation of the respiratory excursion no Salt sides. The percussion note was never seriously impaired, hut slight Julinow was sometimes found at the base*. The breath sounds were uvular, and auscultation sometimes revested scattered, medium, creptunt rites, often with a metallic tone, and situated especially at the basics. Added sounds were absent on repeated examination in ten cases. For ii intis reasons the condition is not unilateral, and therefore displacement of the lieart and other mediastinal structures was not found. Tiie tubercle '.'.u;illu was found in the sputum of five of the above thirty cases, and luur of thoc died. Asbestos Bodies In tho Sputum Thirteen case* slmwcd asbestos bodies in tho sputum. These art cdJcn-ycIIow structures of elongated bead-like form, often with bulbous nuis (Conke and Hilt, 1947). The appearance of fully formed bodies has hern compared to beads on a necklace. The beads vary in size and make up an irregularly segmented body. These bodice have been found to vary in ivngth from ao to over aoo microns. An asbestos fibre forms the central core in each body (Gloyne, 1929). They are best seen with sa oil immersion lens, snd show up clearly without staining as golden-yellow structures (fig. 43s). They can be stained by hematoxylin. TTw demonstration of asbestos bodies in the sputum has not proved to be a useful diagnostic technique 0UJ 06960 ,ei TIIE DISKAMEM OF OCCUPATION'S Fro. 40t.~AtbrMua LwsJie* in the sputum magnified t,ooe diameter* because so many patients in industrial communities have some asbestos in their lungs which are otherwise normal. Therefore the presence of asbestos bodies in the sputum indicates that the patient has been cap*sed to nsltestm dust at some time in the pas* n!y, and as a solitary positive finding is certainly n*t an indication of a!ero.:. In fact, one London Hospital patient with sputum due to broncho-pneumonia apparently released ast*vstos bodies more readily at the height of tfie illness, the numbers in the sputum diminishing a rite inflammatory condition resolved. Asbestos Bodies In the Lungs at Necropsy In a ease of asbestos!* necropsy may show targe numbers of asbestos bodies in the lung sections Iwth in alveolar spaces and within the thickened alveolar waits. They arc readily demonstrated in smears of fluid scraped from the cut surface of the lung. In astscstosia the presence of a*lc*toa !*odiv* may be demonstrated in the hilar lymph node* also. It is important to emphnsiae that asbestos lx>di< are seen more often in the absence o? atbvstosis. In many of these cases the number of asbestos bodies is smalt; ft. -s m arc thirty standard pirenchyt of &-----it h oo ccn --< orx O occ O thi "I cn set CO ret. asbestos recogni* in thelu ation sp Radlog The Inrilto inasbe? fine as : opaettit obviott* thicken the finlimits apicso< in defii asbestr seen ir Plewr Rv nodu!; which sre US tendo' lateral laterj' cotnn thick, in o\ DOUI 06961 Till: I'NKL'MOCONKWKS 1017 t a rouit ti.v ,,rc k.x r-uMy dcmot>traivd, but hy examining thick H\iin:;> ;'lung i;.* ir identification * facilitated, `llic^e section* .rc tii.nv r.r.cri-:. i;> t!mkiH>, I>dne approximately six time* a* truck a* <u:.datd M-ctim**; in a.Mitinn to viMiaiiaing a greater volume of lung pormchtiiu tin-re i !>* likvliiuwwJ of a*lw*t< Ixxlic* Uing knocked out ul the section* wi..*n the parafiin block* arc cut. At The lawidon Hospital it has been pnNuhle to identify asbestos todies in tltc lung* in 30 to 40 per cent of routine adult nccrojwie*. Lung* of such ease* nuy contain only one or two a>in-xtoa bodies per section; generally there i* a negative occupational history, but many of these patients have lived and worked in the Eat End of Iamdnn for tinny years. Since other structures may Hipcnorfy resemble aslwstos bodies it i* valuable to identify them with greater certainty. The heat resistant property of asbestos is utilised when xviions of lung are incinerated by heating to 600* C. which effectively removes the lung parenchyma. Surprisingly the characteristic shell of the i>bcstna body remains intact *0 the* these structures are still readily recognizable. In fact, since the incineration removes the carbon deposits in the lung too, many more asbestos bodies are revealed in the poat-incincr- atien specimens (Smith, 1967). Radiographic Appearances The fibrosis in ashestosis is much more diffuse than that due to silica. In silicosis it occurs in the form of numerous more or lea isolated foci, hut in ashestosis as a fine network throughout the lungs. In radiognphs it is so tine as to resemble ground glass or fine cobweb (plate XVI). I lomogeneuus opacities of this nature arc seen at both bases, and may later become more obvious a a tine punctate stippling. The inter-iobar pleura is usually thickened, and there is a shaggy outline to the heart shadow. Ultimately the line punctate mottling can be observed to have spread beyond the limit* of iIk lower zone to the middle and even the upper zone, but the apices usually remain free. This fine, diffuse, punctate mottling stands out in definite contrast to the nodulstion seen >,, silicosis. In feet, in sdvanced i>betu*i* tl degree of sltadowing present would have little significance if seen in silicosis (Timmermans, 2931). Pleural Plaques Ilcural plaques are frequently present in asbettusis. They may he nodular or smooth and are composed of very firm, white hystlne material which may be focally calcified. They have a characteristic distribution and are usually confined to the parietal pleura. The usual sites are the central tendons of the diaphragms and in parallel lines over the ribe of the postern* lateral chest wall, but plaques may be present also behind the remum just lateral to the middin*. Plaques* with the same distribution, are more commonly seen in patients without ssbcsiesis. However, examination of thick, unstained lung sections reveals small numbers of asbestos bodies in over So per cent of these cases. On microscopy pleural plaques srs S T O O I 1679 1 DOW 06962 IS T 0 0 1680 rotX TIIE DISUSES OF OCCUPATIONS composed of hyilme, acelTufar fibrous time aranged parallel to the pleural surface: they often contain variabte sited foci of calcification which when extensive may be visible on chest X-ray. Films such as these may be misinterpreted unless the possible presence of calcified plaques is home in mind (Hourihane, Ixssof and Richardson, 1966). Respiratory Fraction Testa These tests are of little value in the detection of early the individual case unless serial readings over previous years are available. The pattern of functional impairment includes low tots! tung volume, low vital capacity without evidence of airways obstruction, tow pulmoMiy compliance and low diffusing capacity. The extent of the diffusion defect is the best estimate of disability. Williams and Hugh Jones (l)4o) reported: abnormalities in diffusing capacity for carbon monoxide, before X*ray changes had occurred in factory workers. However other workers hire found this test less sensitive than X-rays of the chest in the early detection of ashestons. -A -SVa-" ' ~ C, the length of time which may elapse between exdust and a fatal termination is only one-half of that in siBrr words, in asbestosis the fibrosis develops more rapidly. With exposure to high concentrations of dust, the fibrosis may be ' fully developed in seven years, and may cause death after about twelve years' exposure t* compared with thirty-five years for all cases of silicosis. The shortest length of exposure to asbestos dust which has ultimately caused death is eighteen months. Since about 1930, as conditions in the factories improved, and tulwrrculo-is declined, the onset nf asbestosis became delayed so that now it requires an average of 17 years' exposure to develop. It must !w rcmcmfwred that the existence of a clinically recognimble degree of alet<n fibrosis in any individual is an additional adverse factor in the prognosis of any acute infection of the lungs such as pneu monia nr broncho-pnenmoni.t. Pathology of Asbestosis At necropsy pleural adhesions are extensive snd dense, and there are often thick siibpleursl plaques of fibrous tissue. I.arge arm of the lung are tough owing to the presence of tihmus tissue: emphysema is extensive but usually Incaliml to the lower and apical parts of the lungs. There are tww views regarding the mode of development of asbestosis. According to the ore. the action of the dust is chemical; the other view supposes that the asN-sv** fibres art mechanically. Experiments carried out at the Saranac lalroratnries do nt support the chemical theory, since aluminium hydroxide w hich nrutru'ircs *he t"X?c action of quarts does not prevent sslwstosis. Moreover, .-s!es**s fibres shorter than ao microns were found to be r-!.itivf!y innocuous, whereas if the action were chemical an increase in DOW 06963 THIS I'NI-XMOCONIOSKS potency *<hi!4 Imv Iwrcn expectc4wiU redaction in panicle tin I-ehrv j micron*. it in the of ulus. A comparison of the effect af ast>cto fiber* 15 microns long with those 2*5 micron* *>110 {King and *2htj, 1940) thawed that rabbit* receiving the loos fibres developed a nodular mkulio formation comparable with experimental silimtic nodules; aniti.Js receiving the short fibres developed a diffuse iatentiual miculia horns* Incidence of Associated Psimeett^ Tuborcoioats Precise information as to the incidence of pulmbosrjr tuberculous asregst asbestos workers cannot be obtmnsd, but the Factory Department figures for 1935 russ*** * lem dose aasocistinn between osbotooia and tuberculoaia than it the ease with silicosis and tuberculosis. Thus among yi deaths fmm silicosis the disease was accompanied by tuberculosis in r<i per cent, whereas among eighty-two deaths from asbestos** only 36 per cent showed associated tuberculosis. Later, with the decline oftuberculosis, these percentage figures loth for isbcstotis and silicosis have become lea*. #t Association with Carciaocns of th Lung. The first recorded case erf-carcinoma of the lung associated with adnwiua was described by Lyneh and Smith (1935). By 1955. according to Doll, a total of ot eases had been reported. We luw already seen (p. Ni.h) tlut Doll (>93;) reached the conclusion that asbestos worker* faced a risk of cancer of the lung ten times as great as that in the general population; and tlut McCullough (1959) collected particulars of a series of 365 patients with asbestos!* among whom 18 per cent had cancer of the lung. Dut tiic carcinogenic eifecu of asbestos are evidently not confined to the lung*, for Kcal (1960) found e high incidence of peritoneal carcinoma in women with asbestos!*, lie showed that during the period 1948-58, twenty-three women were admitted, to The London Hospital with a'bestosis; fifteen of these had subsequently died, four with carcinoma of tiie lung, nine with carcinomatosis peritonei; of tbe letter, one was cer tainly ovarian in origin, and this was possibly the primary site in four ctliers, but in the remaining two no primary site could be found. Mesothelioma of tbe Pleura and Peritoneum The ides of an association between mesothdiomo end exposure to abc*tns came from Cape Province, South Africa aed.wm suggested by Wagner, Slvggs and Marchand in 1960. They found their cbm in the a-botus hill* west of Kimberley where communities lead to duster round the mine workings. Schools have been built closets mounds of asbestos on which children played. There was ahntadw la the sir, in houses and in the streets. Within thief yesra rteytD&ttd a pedants with mesothdiome, nearly all of whoa had evidence ef exposure a oroddolit* often non-occupationaL By contrast, then eta no itpcnod asm from the vicinity ef smoeite workings. They recorded 31 asm ef diffuse pleural IS T 0 0 1681 1 OOU] 6 964 IS T 0 0 1682 1020 TITE DISEASES OF OCCUPATIONS mesetheSoraar Histological proof of asbestosi* woo present in eight of these ew Prior to this work only occasional cam of thh condition had been uwo itri with asbes'nsis. In 1946 Wyero published the first case of mesothelioma of the pleura to be diagnosed in an asbestos worker in Crest Britain. Up to February 19^5 the total number of cases diagnosed in the British Wen was t''o (Gilson, In contrast to the averaee latent interval of twenty years Iwtwrcn the first exposure to asbestos am! the development of carcinoma ot the lung, the interval between the first exposure ami the onset of symptom* from mesothelioma may vary from between *5 and 50 year* with an average of 33 years. While some patients give a rtory of continuous exposure to asbestos over many years, a stem* ficant proportion give a history of only transient exposure sometime* amounting to a few weeks only, many years before. Such parents may show little or no evidence of fifjrosis of the lungs but do show large or small quantities of a!*etos Ndie* in the lung parenchyma. Some of these latter case* show identical amount* of asbestos in the lung to that olwetved in many patients living in the Ka*t End of I/indon. This raises the ques tion of whether minor degrees of community contamination by asbestos are capable of giving rise to mesothelioma. In Factory, Shipyard and Community fourihane (19*4) examined tissues and records of S3 cases of meso thelioma from the files of the pathology department of the London Hospital. Fifty-six *f these were pleura!, and 27 peritoneal tumours. Occupational and resident:;!! historic* were obtained from the relative* of 76 of these cacs by Nc\v!inu*e and Thompson (1965). Forty out of 7* gave s history of occupational or domestic exposure to asbestos. Only 9 of 76 control patients suffering from other diseases gave such a history. Among th'rc with no evidence of occupational or domestic exposure, onethird lived within half a ri;V of a l.i-ge as'*etK factory. Seventeen cases of mesothelioma were :nvr**:*mted in the Merseyside area. Exposure to asbestos was confirmed in 14. Eleven rv,:cnt* gave clear historic* of hand ling asbestos as laggets, !o?!er makers and ship repairers. Two ferrule patient* had been sorters of ucd *4c'.:ng (Owen, 19*4). Mesothelioma occur* with equal frequency in the two sexes, which i in contrast to the striking male preponderance in carcinoma of the long. The condition i* invariably fatal in month* rather thsn rear*. Symptoms and Sign* of Mesothelioma 'Hie principal symptom i* dyspmea, usually rapidly increasing, and it may be associated wit!; pain in the ehest, cough and harmoptyvi*. The signs are thn*c of rlcur.il e'lusion usually with complete collapse of the lung. Tire fluid remove*! i* *!raw-cloourcd and sometime* bloodstained. Cytologies! examination hn\v malignant cells. Metastase* are rare bit they may occur as generalised lymplindenopathy, small nodule* in the sulKut.--evu* tissues ov>-- vk anl chest nr nodules on the tongue. should been DOW 06965 * 9 ol :tory. , one* ol t W ' of handfemale ^theliom* i to the ition * asing. pl\i. 'Hi*-* ap*c ol the loodstalned. arc rare but in the the tongue- THE I'NEliMOCONIOSKS X-ray* *: the she-: vwy r.:...vive il.hkcmng ol' the pleura ar.d sometime* a tunMKir wl.uh ;..eJv in-.ca*e*. The tiuivl i<t course i* *wn ard ><xurnmr a loti.Lied cdusior. i present. Tlachcning uf ti.c oi>.hj..e ;i.vure n.av be *rcn. I himaielv ii;c p.cural cavity Ixoaw* chutcrstcd. A progres* ..vriy enlarging mediastinal tumour i* common, Thoracoseopy Usually the** tumour nodules on 1te thickened pleura with the lung oeUapanl acd immobile. Thoracos.opic plcurad bioptj thnolJ bo Uriod m method afdiagnari*. Morbid Anatomy of Mesothelioma Mesothelioma i an uncommon primary tumour of the Ktnul surface*, arai may occur in the pleura, peritoneum or pericardium. TIar ;*.Vural and *.r;:-)r.vl tumours, either alone nr tocviixr, are the most frequent, .*tl.*vi~is aii or any cmht nation of the three may <xvur. Heura] incai- tia-Iionu* arc m.i>i\e white tumour* wiiieh tend to surround the inns .preading to involve the fissure* ami main pleura, upacc ami to cause' , l\ritnm*al `..mour* usually involve all surface* of the aUiotuinal c.v.ty. I 'u..i.y :!.e distribution of toiuoi.r is uneven, will, a main nuu perhaps involving the greater omentum and witiv discrete or confluent r.iaiulo elsewhere. IVrsistentiy recurring e:fu*ion or ascites may >iccur. !.\n*.ph Male UKt-'taM'* are enmimat but discrete ruetastase* within ; v..;. organs are not seen. 'Hie liver may lie clnselv invented by t..rrw.r with d.siorv.on and even erosion of i:* eujisuie, but ail the tumour ecu i* in continuity unit ti-at in t..e peritoneal cavity. Mesothelioma* t,r.J to !. a mive.i histological picture consisting ol epithelial pattern* in uane areas .mu spindlc-cvil tihroRutou* tumour in nihef*. V3'- 4M? I*;.'y. : ..;V> O 01 oo co Preventive Measure* I;; mining wet rock drilling is imjvrutive. Hand sobbing - ..h! Ic rcpl..sit; hv crushing in enclosed machine*. Asbestos muU not !'e dumped carelessly aiiout the mine working* and town*. *rran*port Iv e..rrie,t out i*v the use of strung imprrvbaa* hagv lu tlie tactorie* i! <*reaf Hr:tditt ;on has Ux*n effective in controlling the xverity f the diw *e but case* do still occur. In factories and teMilc mills tiw princsple of h<-ily applied v\..a.>t ver.tiiation must Ik* vnfnrvcd to prevent the waj'v asln-stos dut into the air of any room in whie'n work is done. Hat'd ticai.ing of ilie cylinders of carding machine* i* prohibited while any oth -r jHfson is prexnt. nor may it lur Uor.c by iond MricUc* or otlwr hand tools, 'oimh1 cleaning cyllrdm. filling inaularing raanrvsMO Md chatulvrs containing iuose uleiloi sbmdd be provided with art ..ihient apparatus by mean* of which they can breathe air free loan du*. v.pprosun of d..st lr. the cleaning of carding mac'.iiiws 1* beat ensured by d.c uc oi * reducing brush fitted with a cover and connected tu a portable ioswuiu cleaner >:'g. 403). Ily the um of ,hwevirin mald:ies, liandiitig .< .ld he reduced to a minimum. In one laaory, >;inning i.-aincs iur* 1<cc:i tutaily enclosed in penpt* with an ingenious device widch penaiti 00Ul 06966 *18911001S Fw. 4W.-N*W to iw b rtwL___ M ----- f -- work pradoer* dust. Since menthcTtoim Mem* to be x*b clitctljfefwa^, *. om* with my sun*!! exposure* to xherte* system eTeointret byKUimt the import ami use of what hi probably the most daftfteroo* fom-ef nhnto*. croefc'oltfc or Hue asbestos, ha* been advocated. Tn 1967 Brfthh Rail announced that asbestos wa* no longer used * inrniUtionm rsitaf carnsfr* because of po*iMe danger to men *n the workshop* what panelling was removed, and cta* fibre was used instead. The British Li __ fio. jot.--IVfflVe Vacuum Apparatus for cfemMf AsV*m < an*:se Machine. .Vote the Revolvme Rrv*h t;"r.! with c A\r' afHi cnsmctH t*a Vacuum Cleaner ptfmmi at frn$ .CaMmifM Hf m .('*** /#**> /ih **, t+J$t OOLJ 06967 S T O O I 168b t ii In rr* fccM. thd*~ THE P.NKLMOCONIOSB8- il] A,brw* Industry ha* proposal that all asbestos libra shipped to Great gnum shaH.be packed in duMproof bags, and that all blue asbestos shall t addition's shipped on padeta which can bs handled mechanically. la July 1966 at Buxwonh, Derbyshire, a feed enquiry by the Ministry of Hewing sad Local Government mealed diet a firm using asbestos in the manufacture of brake linings and dutch facings bed dumped its waste is dnusnl quarries for about 4a years. At first tffere were no houses in the .v --wilisfr virility nf 1T11 quarry used, tipping wee dene from open ferries ^ aad tbedaaK.ema net bagged, in July 1964. space in the first quarry had became exhausted and tipping was transferred to another quarry only 60 raids from the neatest house; By July 1966 contractors were tipping aye tans monthly and the conditions under which this was done were totally unsatisfactory. Asbestos dust formed *$ per cat of the material dumped md although this was bagged, sometimes e hag would fiUl from e ferry and remain on the ground split open and unearned. Themanufacturing firm had disdained responsibility for the waele aace.it hftd ldt tilth gstta. Although pubSc health inspectors hnd'vS&edrfht tafte- regulady..the nuisance persisted. From what we now know of the etiology of mao is dear that uncontrolled tipping of asbestos waste such ae in the tillage of Buxworth should be sternly repressed. a v< Draft Asbestos Regulations, 1968 These tong>awaitcd draft regulations, to supersede those of 1931, have been issued and circulated to interested panics for criticism. They will mw apply to alt factories, building operations, civil engineering work, >hipbuiiding and ship-repairing; and particularly to lagging and delagging, which are known to be dangerous operations not previously covered. Any praens in which asbestos dust is liable to be given oilto a dangerous extent will be carried out either under an cthauw draught,iwhteh util effectively prev ent the escape of asbestos dust into theeirof the workpieceerfceerat equally safe way. If this ta not possible, workers mutt be given protective clothing and approved respiratory-protective equipment. Any person undertaking a process in which crocidolitc ta used win have to notify the district inspector nf factories. But the Factories Act cannot protect priests users. We know that inhalation of dun from such activities aa awing or sanding material containing aabestoe presents the haaard'of'mefigmat mesothelioma outside aa welt aa inside industrial situstfenc. It scene not unreasonable, therefore, to insist that materials containing asbettoesfould he dearly marked to show this, so that adequate preceatfena can be taken by the users. For instance, amateur handymen sowing materials containing asbestos could easily wear a lightweight dun meek, and either work tut of Joon or in a well ventilated room, Mcaawhjfemany doctors have nfced wthheesthsebrotthee. cporomppeortisees aopfpaeswb.nttoeainadrfeceasawuaTalqZwweetarsatnbas nayakeatnhaaarsnhSipraolf VV'-a. f: .. ( '. i DOW 06968 % S T O O I 1686 1014- Tins DISEASES OF OCCUPATIONS fibres neb m glass wool, rock woo) or stag wool, which hen metal fwhsrewt 8rt*prooflng properties hot not the fibmgeftic or careinogenlg effects on the lung*. Ie tt certain that the properties of asbestos justify the risks of-aabestosis, arcinoma of the lung and mesothelioma which are entailed by its use? .............-- Case yji Ashetfas spinner txpanre to athestat dnttfarfbeyran--ashestam. A. P-, woman, aged ay, had worked from 1914 to' 1939 In the miinn^ QnwnTTivTii */f m ptKmws "wu wnnr up pninbiivii new. duat was poor. In 19x8 she suffered from a dry cough, aad in 1930 from shortness of breath and occasional pain in the right side of the cheet on breathing. On rxmsmmafnm: five warts on fingers, the largest 3 by t mm. No clubbing of fingers. Pyeptwea, but no eyinneis. Apes heat not die* ptaced, and heart sounds normal. There was diminished' movement of the base of the right tung, with alight dullness, diminished breath sounds and extensive creaking pleuritic sounds. A few crepitations at both bases. No sputum. X-ray showed the heart to be normally situated, and there were fine homogeneous opacities resembling Si1' ground glam at the bases of both lungs, tn 1935 the shortness of hreath waa worse; there was a dry cough. On examination there were no warts on the fingers, and the physical signs in the chest were un changed. Cate 38. Ashestm tariff and nearer expanrt tn athettm dintfar three yean --latent interval nf teenty-free yean--deathfrom nmpeettim paraplegia, temadary tartinama af spine; primary eartimma affang; ashettmis. M. G, a married woman, aged 43, L.II. Reg. No. 41149/1947. t9tf-2ii Iwtween the ages of fifteen and eighteen she worked carder and weaver in an a`>vstos factory. It ia not known wltether she cleaned the carding machines with a steel handbrush, but this method was in Use at the time. Sh- gave up the work owing to sitonneas of breath. ty yean: site hsd frequent brief snacks of breathlessness some* rimes with cough but waa not disabled. idyean: at the age of twenty*seven she married, and Tatar hsd one miscarriage but no further pregnancy. She remained active, doing 0 the duties of a housewife. Four months: sudden onset of aching pain in the back of the neck without any apparent precipitating factor. The pain radiated to both Itouldeis and to I'oth aides of the chest, waa continuous and severe enough to interfere with sleep. It remained for some time practically unchanged, but had gradually increased in severity during sit weeks. Three rrrehs: *!ic Wt uo<eat!y on getting out of hed in the morning and since then she lud K-come progressively weaker am! m*re un* DOW 06969 IS T 0 0 1687 - ISC My tlx kltkh UT rcre un- " ikrtt \tan tit, M U9.f|)47* worsej u s whether iht ,, t this method ! ta shortness of sneis Hint* JP&d later hod one gjKlciKv, doing all Lback of the neck L radiated to both buous and severe ?S*etinie practically during six weeks, I in the morning ' and more ua- ; i ii; I'XKUMOCOMO.Sli.'t K-35 steady <>it l.ir leg*. There Here uecasiutuu involuntary tniuei.iciit* rtf the I cs u.muUv ilesion uf the knev* wit!. planur llexion <-i' the ankles, OceaMond puruMhesiie of the leg*. I (cxiuncy of micturition. Uowcls open rvgtilarly. da txaminutium: temperature 99* F. IHjbc 11 a. Respiration a a. A unuut distressed woman, in considerable pain. Furred moist tongue. Xu pallor. Xt enlarged lymph glands or trdema. Regular pulse. Apex beat 1 inch lateral to mid-clavicular line. Dlond-prcssure 130,90. lleatt hn.uN iMtrmal. There wax miw impairment of resonance and diminution uf breath sound* wiilt coarse crepitation* at the (uses of . With lungs. 'llic aitdomcn, including digital examination uf rectum and vagina, slwwcj nothing abnormal. Nervous Intern; an anxious hut co-operative lady. Cranial nerves normal. Cppcr limb* normal, lamer Iu1m--approximately symmetrical spastic paralysis with brisk relieves, ankle cionus and extensor ptanur response*. Abdominal re lieve* absent, and some weakness of lower trunk musculature, host of... sensation to pin-prick, postural sense and vibration up to the level of Oft. Intetfigalhtu: catheter urine: trace of albumin; deposit; calcium ' oxalate crystals; culture sterile. Blood count: hxmnglobin X9 per cent, red blood cells 4,7*0.000 per c.mm., colour index 0*94, platelets 355.000 per c.mm., white blood cells and differential count normal. Cerebrospinal iluid: clear, colourless fluid, under normal pressure, rising unevenly on jugular compression to 300 mm., and falling similarly; no increase in ceils, protein 500 mgm. per cent, Lange 111.311. Wassermann reaction negative. X-ray o: chest: lung markings heavy throughout, excessive fine interlacing lwdow* at bases, no nodulation. X-ray of spine--tlie body of 1)4 is smaller than iu neighbours, especially in vertical height, and is mottled. The pedicles are not visible. Pn-grtu: while in hospital the pain continued without much, alteration. In the middle of the second week she suddenly developed severe pain in the left chest, became dyspnrsic, collapsed, pale and evanosed. Some relief was obtained from morphine and oxygen. This was followed by fever up to tot*S* F., with rapid respiration rate and two further attacks of cheat pain. Electrocardiogram at this time showed absent Q and inverted T in lead 3 with right axie deviation, the rate being 180, She became steadily weaker and died 3} weeks after admission. .Xttrapty: Professor Dorothy Riasell mode the necropsy(L.H.P.M. 381/1947), uf which the following is a summary. StcwJary tareixoma of thoracic vtrltir* ixtadixg epidural spate, I`rimary eartinama of lung. Atbettom, Dark greyish-black reticular fibrosis throughout both lungs, es pecially lower lobes and right middle lobe, with conspicuous sub- . bold 6970 S T O O I 1688 I 1 THE DISEASES OF OCCUPATION* - pleural Iftww foy cm. deep). Arm (j.x j.X. * emj.of pel**nr* . aiuiwm bwmli plwn of mesial aspect of left upper lob* Orar"f* yellow pleural efTmimt, left *j me.). A few fibrous pleural tdhaiom over pnetcrior surface of left lunf and mesial aspect of right upper lobe. Secondary carcinoma of hilar glands, moat marked right nd one 01 Mpowv nwvinnnw CsOf--conurj Qranovni w |mw m|mmmA wraw*"^ * ^) bodka of and to 4th thoracic wrtehna Collar of growth tadidht-'.- j dura oner 4th and 5th thoracic tegmenta. Patchy softening of ^Hul ;. j. cord at this ImL Nodule (t cm. diam.) of secondary carcinoma in * *' mesial surface of left perietal cortex. Secondary carcinoma in aupn*claricufar {Ms Swollen red pulp "> apleww. A.-wen-nourished/.. ,,i. edentalouo now--a. Mitntnfir. longs: conaptcuooa anatomocrag bands- of fibrosis containing numerous asbestos bodies^ often in dumps, and associated with foreign body giant-cella. Similar me beneath pleura of lower lobes; few marked* and interrupted over middle lobe. Com gcation end emphysema of residual tong tissue; many macrophages and occasional asbestos bodies in alveolar spaceae Lifi'ssffir- War similar changes, together with in-defined, inSJtrtttng tubular,' *- columner-cdled and polygonal trabecular earrinomn-beneath meSsl"^>'`^'*~ pleura, apparently arising from bronchus. Gland from right kihm: focus of secondary polygonst-certed carcinoma; anthracosta and a few collections of asbestos bodies. Right end left tnpeaclavicnlar gloria: extensive secondary carcinoma. Fifth thoracic segment with dura: ft* -';^^dS^^tcmic secondary carcinoma of epidural tissues, not penetrating dura. " Permeation of many vein*. Engorgement of pial veins. Ill-defined wedges of tscfacmic softening in N>th lateral columns of spinal cord extending into corned pyramidal tracts, and a few smaller simitar fod in anterior and pmrerior column*. Thoracic rtftthree j-j with inter* tertrbral Use: extensive osteoclastic and osteoplastic secondary card* noma of spongwaa and pervwteum. Considerable necrosis of medullary tissue. Ijft parietal errthrum: nodule of secondary carcinoma {*, r. superficial cortex. Splttn: slight myeloid reaction in pulp. (b) Tale Talc is a hydrated magnesium silicate, j Mg04Si0rH,0. The purest deposits occur in association with dolomiteand magnesian limestone, where the talc owes Ha origin to the hydration of the magnesium silicate mineral* which were formed during the earlier metamorphism of the carbonate rocks. Talc mining h carried out mainly in the United States of America and Manchuria. The largest deposit Hi Europe is on the northern slept of the Pyrenees. Uses Talc b the first mineral man encounters upon entering the world, for H is the main constituent of talcum powder and of toilet powders in general. It is soft and lias a greasy feel, and on that account the massive impure DOUl 06973 S T 0O I 1689 ' gltn/j; i daw.* ts* line dune .111-Ucfirvcd r spinal cord similar fuci J tri/A A/rrr.dary card* i of medullary carcinoma in .The puma tone, where its minerals the carbonate of America slope of the world, for it sn is general, ive impure TilK I'XEUMOCONIOSEft- inayr' uiwUntv lu '.wen called tUuitU or toufttme. This is the Frtntk tUmlk used-'' be Uilr ir marking eUelu IVrliapo *jO per cent of all the talc pnwluccd is oarheu-d in the form of an ifr.paipslde powder. Nearly half the total output is u*-d in tlir manufacture of paint and distemper. In ceramics, tak i* used for the manufacture of tiles, electrical porcelain, table-warsand refractories Nearly sy per cent of talc production goes into the manufacture of paper in which the mineral serves for lilting and glazing better than kaolin. It ia widely used aa a dusting agent for rubber tyres, rubber gloves, fun and for packing parachutes to prevent rotting from moistuiu. Workmen who handle it for such purposes often call it pesmer* Pneumoconiosis in Talc Mining and Milling <* InNcw York State, disabling pneumoconiosis occurred in 14*5 per cent of the workcra in Use talc mining and milling industry. The dust contained far, straight, needk-tike fibres. The tak libmsie was associated with an iaemsed susceptibility to tuberculosis (Stegal and others, 1943), Marked radiological changes were found in nine out of thirty-foor men employed*... ' ia a talc null in Norway for periods tasting from seven to twenty-four yean; there was less disablement than would have been expected from the X-njfc- ` appearances (Druusgaard and Skjelbred-Knudaen, 1949). A Case proved by Necropsy The first ease of this type proved by necropsy to occur in Great Britain a published by McLaughlin and otben in 1949. Tlie man was fifty-ofa year* of age and had worked in a rubber-tyre factory since he left school at fourteen years of age. The only industrial dust to which lie was exposed wa tlut of talc. For two years he had complained of increasing dyspmza, which was partly due to heart failure arising from rheumatic carditis with aortic incompetence. 'Hie X-ray film sliowcd nodular shadows distributed over both lung fields. At necropsy, throughout the lungs there were grey nodule* which Sod coalesced in some places, especially in the lower lobes* Microscopically the nodules showed whorling, but this had not the typfml appearance of silicosis. Within the nodules were fibre-tike structures from 19 to 90 microns in length, arranged singly tnd in dumps; the nort-fibroua particles apparently had been eliminated. Some of the fibre-like structures te similar to asbestos bodies, sad the appearances suggested that talc pneumoconiosis and ssbestosk are similar dismissand that the former may be caused only by the fibrous nrietka of afeJlfaeseoe Is mor* actively - fibmgenic than talc, and this might bo doo m.tbs.higher pnapertssn ef fares in asbestos. >'**$?>* --v;; (r) Soridto . ... ficrfcitt is of geological rather than coamehM importance It is a variety of the mica known as muscovite, Kt0.3AIt0v.68i0rzI 1,0. It oecura m minute shreds or in very thin veins and is a secondary mineral formed by hydrotbermal alteration of silicates such ss the felspars. It forms scscular cry stals and has been suggested aa a causa of pulmonary disease by Mav- (i9fa)Bsdham (19*7) and Jones (1933}. Sacs it occurs in many v> DOUI 06972 IS T 0 0 1690 < THE DISEASE* u*T ^ ^ with ipiem withe hnp of miners with ificoaiw*It ta Mwidwimaterial tnljr ni hit t**bj tt*df Iwen found to ttuw progr--ire fihrmis of the fang*i p3w*Wf th fibnn (wricks m-M hm tk ifM cainni by VosS about 19*0 the mmcihofthe Lura outside the geological worhhbwt wAtyw a gretdeamnd far mrfaag-high-grsda rrfnawia>.r" , oCwkfnumliiii. high tcnrpernuw thrTitntml; tjiwtt tad riSmarifeiMgiifki fiw* tfwiu thuicttriwd etfMin, resistance ti* which* render the 1 electric and forging ft OnHitt Pncwsit 9VUVTWHIG- pifWIBI V when-calcined, but, unlike crushed. When fused in a fomneta* t,j4^ C, aBBmaahe'b1 partly nr wlmlly into muRhc. Glrtner (1997} auggeated that dot bet may be related to t!te histological change?, with tha formation of araaS irreguln nodules, found in a portion of fang of a furnace worker, and reported by Gartner and ran Mtrwyck (1947). fn the examination of sixteen workers exposed tn duct of calcined Mllimantte, Henry and Middleton (1936) fovnd radiographic changes but no disability, and no aigna or aymptoma which * could be related to the dost exposure. (e) Glasa Wooi Fibrou* rfm*, fihrt flma orgtm nasCfcia manufactured aiBcata utad in imlwry for sound ami lieat {mutation, air fiftrstforV a IQtar ta mta> bonded laminate*, and a* an inert bate foctectiJe manufacture or pocking proceww*. rnfia'atiou of fibre glam dot does not eaima pncomoceniamfc. Schepem (1759) showed in three animal apedaa thnt tha duet, when ' inhaled, behave* a biologically inert substance. In dt produced by dm machining of plas**ic materials containing a glass wool war tha working atmosphere may contain pertidee of glass wool fromaboutjto ao/r ia length. There particle* may be inhaled by the workmen butdeepfee their physical fimilarity to aabnaot parifchntheinfem rridriAdbt fflUmah <C rl tin tong* ft*u(te or d doced (Gardner, 194s). The' Iawrerer, cstne irritation of the akbi, conjoncdne end tipper respiratory tr;.t. Implantation of splinter* of gbea wool In the. region of the nail fold of rite finger may produce paronychia sometimes with eccondary malfnmuti'in of tfte nail (McKenna, Smith and Maclean, 1958). Away from the nail fold fibres of spun gliue wool may produce wane on the DOW 06973 S T O O I 1691 nnrrxKt^iocoNJWKjr Smpt*. Th* panicles will penetrate normal-clothing hut wo^Wn under* < clothing trap provide sum -pfotsciian. ss map harrier cmnu for th* ujniirl iksuTh*. skin irritation disappears following a both and a change-*- f clothing. Gtaee wool dose not itself<aaecdcnraiitb. However, oil* used m lubricant* in th* tranipuktkm of the fibre map cause oil folliculitk. - Lftnrac hi th* plastic*-industry an-epoxy resin map be added to tho taka oralas binders far the ghee Shewfilling material. Should denradfin- ^TT ~ dbn oecur it it caus*d noc bp the gtoa fibre Ut by tho epozy resin. . XOM-riHCVI SILICATES'" In the absence of quartz and of fibrous structure, silicate mi <) MknMicas are complex afnmiinsum ritkerae cosnbiaed with cither doeu 111 >ptriiowi o*iron>.Th*more common arc muscovite, K.O.jAljO^"* asior2U,o, biotitc. (Kig.Mgr.j/AiFeysiO,)*. and (Kl^Mfi^KStOJb. Muscovite, or whit* mice, ia transparent and colourless in tliin sheets - ind is disungubhed by its highly perfect dear-age. It is (UK decomposed bp sulphuric acid. The name b derived from Muscovy in Russia, where the mineral waa in early use as window glass. In commercial deposits the ,n>u!s van imi a few inches to a foot or so in diameter and up to two :;! in thickness. They are referred to as Aooftt of mica tweause they can hr cleaved into shecu almost u easily m separating th* pages of a honk. India supplies 70 per cent of the world total of sheet mica. Large quantities f muscovite are mined in the United Sates of America, but only a smalt-' percentage is of I*t-quality, the rest being used as ground mica. PMnga' pile, or amber mica, b mined in Canada and .Madagascar. It is difficult to ditfcifiubt* fmm muscovite, except that it is decomposed bp sulphuricarid. Riotite varies in colour, being either brown, black or dark green, and even in thin sheets, in contrast to muscovite, k has c smoky colour and la spotted with impurities. For thb reason h b rarely toed in sheet form but *is employed as ground mica. Usoa Owing to in transparency and heat imhlanua, muscovite b used far the chimney* of oil-lamps, for peep holes in stove doote, ovens, furnaces snd optical lanterns, and b then often wmid Iringl-- tons, after binglam,. which b a semi-transparent form *C gelatin. No other mineral has better cleavage, flexibility or elasticity; h bpoerible to roO a sheet of muscovite a thousandth of aa inch in thkkncm into a cylinder quarter of an inch in diameter, and its elasticity would enable the sheet to flatten out again quite DOU) 06974