Document b2rvkZEbd735v6eqdymLEK7k

FILE NAME: CERAMICS (CER) DATE: 1936 July DOC#: CER013 DOCUMENT DESCRIPTION: Journal Article - Industrial Pulmonary Disease Due to the Inhalation of Dust [J olt 4, 18 JOLT 11,1836 ierivatives bohydrate ; proteins itic tissues. IO N insure the immediate iblets. N . J ., U . S . A . DN, Ltd. Mjndon, S. W. I O ffices: 7, Adam Street, Apbt.ph i, W.O.2. / Telegrams: Lancet, Raxd, London. . Telephone: Teuflb B ab 7228 and--722B. No. I I .. op Vol.IL , 1936. No. 3889. Vol. CCX X I. . LONDON, SATURDAY, JU LY 11, 1936. . Pp. 112--Pnce 1 ? V A nnul Subscription : Founded 1823. Published Wexelt. Ragistared at a Newspaper'. W in d B la. Abroad O Ita. 0X FO B D MEDICAL publications. DemySTO. P p.x + 358. ItsSdd,PeC ogfago THE NATURE AND TREATMENT*-- '-'''*^ 8 n Paob s * " " A STHMA, HAY FEVER AND MIGRAINE. T H S H Y G I E N E OP The c hange i n wo me n (Tho CUouoUrio) Br I S A B E L Jb M S L I E B U T T O N , MJB. (Author of The Hygiene of MAnlago ") Crown 8to. 5e. net. 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Saturday to 1 p.m. T sh p ta ,. ..............1 3 6 O O W C R 8 T R E E T , L O N D O N , W .C .1 . - Puaucavir.WESTOEifT.LoHDOif.** Teb phone :M ueuu 7758 (3 lines). [July 11,193 ' d for regular relief salts, th e tri-basic acidity b u t never 1 indigestion ; also istipation. Calsoma ot readily tire o f it. London, W .l i the exhausting rvous irritation ility, restlessness, :iated with the i U SE or thrice daily. !7 c c i f r-- -- JG CO . LTD. 4DON, W.C.I ickness NDON W .C.l] THZ LANCZT] ADDRESSES AND O R IG IN A L [jolt 11, 1936 ARTICLES INDUSTRIAL PULMONARY DISEASE DUE TO THE INHALATION OP DUST SVITH SPECIAL REFERENCE TO SILICOSIS * The distribution of diameter, size, or thickness of ftoi-et m one sample w a s : median diameter O'56 u 5 per cent, less than 0 2 fi, 43 per cent, less than O Sil 98 per cent, less th an 2 fi. ^ B t E. L. Mid d l e t o n . M.D. Edia., D.P.H. H.M. MEDICAL INSPECTOR OP FACTORIES The modem development of the industry has a comparatively short history. The history of the disease asbestosis is correspondingly short. The In the first lecture the characteristics of th e disease known as sflxcosis were outlined, and it was pointed out th a t the essential lesion is the fibrous nodule Certain of the occupations in which the disease occurs ere referred to, and it was found they involved exposure to dust of free silica, as flint or quartz In some occupations free silica was the only im portant constituent of the dust j in others it was mixed with other dusts, and m the case of granite, which contains large and variable proportions of silicates, there appeared a tendency to the formation of a linear or diffuse type of fibrosis. This type of fibrosis was waa de8cr*hed by Dr. Montague . 14 wa? man employed 13 or 14 years m th e industry. the first 10 years in the card-room. an d he w as the last survivor of 10 workers in th a t room. T h at was in 1899. The diagnosis was verified q7 , P t ' ^Jd n ay after post-mortem examination sections of th e lungs made about 1925, from this case,- show " asbestosis bodies." Fahr > described a case of asbestosis in 1914. Merewether " records the few cases published in the literature between th a t tim e and 1924, when Cooke ' described a case which has been followed by an incidence of several in each successive year. seen m the radiogram of a sagger-maker, in the industry The man was 65 years of age and had been employed in sagger-making for 53 yeare, . and he would be exposed to dust of fireclay a t his work. A radiogram taken five years le*er showed n o d d a tio T 36 Shad0,rS b ut n evidence of J)' now P4*? on the consideration of some industrial processes in which the workers are exposed *fl,WUSV 0f 6dl.Catea'. that . Chemically c o p i e d sihca. From the point of view of health by far- the most important of the silicates is asbestos. Asbestos Asbestos is a commercial term applied to a group **ssesw5S the common property of finely c h r a t i W ^ r ' ,The. mo8t important varieties are ' j 11141* . 0* magnesium with little iron, amount*1T d amo81*e- " heetes of iron w ith smaller -- ` Process. Cardin* D oabia*. Spinning. j W eartn* (cloth). j ! ._ .7 We*r i n * (brake-Unin*). S 9 Win dinar. 10 n Plfti,,tin*. 12 'Mattress 13 *. ,, l i i Banin*. IS r Dlsintegratin*. IS I Ma lin* sections. jIS Plpemakin*. 50 ! Total.* t l (12) - 215 () 200 IS) < 335 (0) ! 325 (9) 1 95 (3) 210 (g) 185 (5) 440 (13) 170 (5) . 205 (6) ltU W 430 (12) 450 (13) 2320 (66) 320 (9) 230 (3) 325 (9) .215 (R) dp^l th l In tJT icaI aamples of * / bres can ^ separated to an extreme rom .-- br" t u E leTel o* worker; o.a. _ n m l a lr.o l the loiuri^f oi fineness, while retaining considerable o t e ^ S i i e c a ^ 0Perty ? adm tb material S K cloth! 8 d dl 8pun mto yam > 4nd woven ^into During the last ten yeare an extensive literature . from < W ? * 5 received in this cou try, chiefly W ince ^ ^ y' Rhoderie, and he clpS lock and ? . the rude iorm conaisting of the crushed include is t a tJ S L ^ UentAPrC*^*8 " ita anuiacture Pinnine a,nd <>Pmng the fibre, carding, and mix'inp ^he textile materials, or grinding has been produced on this subject, and it will suffice for th e present purpose to mention briefly some of th e features in which this disease diffre from silicosis. Clinically, th e signs of asbestosis are slight in the early stages. The striking symptom is dyspnoea of gradually increasing intensity as the disease pro li,' ' .y.,; ' %.k : oi insulating slabs *ub* hi the manufacture gresses. The radiographic appearance is typically . th a t of a fine ty p e of fibrosis of the lungs occupying W rounded or an frm " b" 4f * fibres and sm all particles a d e by WataoS8?141 h*Pe- The follow ing counts w ere * v i i e t i ^ f " " P1 theo in a factory w here es of asbestos were being used (see T able). distribution o ? " d 0 diametr. " d the percentage , h'S u an d o s V "oo ,,Waa 3240 54 P " centflees t h S - . TThhe b J ? . ! , Per cent, le u *thhaan? 55 ^u ddiiaammeetteerr.. W t w e c TM o . rf the " five counts was hotion of"lenitbJ # and the Percentage distri- "l 87 to 92 W* * " 8 *c I less th a n 1 pt, the whole of both long elds, and more dense a t . th e oases. The individual shadows are minute, lobulated, superimposed b ut not tending to form * massive coalescence, an d th e lung fields present a v veiled or ground-glass appearance. A ebeiwctftriotic feature is th " shaggy " outline of the heart shadow -s T he nodular shadows seen in silicosis are not present in uncomplicated asbestosis. ' . ... Post mortem, th e appearance oi the lungs is quite ' unlike th a t in silicosis. Pleural adhesions are usually extensive an d dense, b u t the surface of the pleura shows no nodnlation and nodules-are not seen or felt on th e cu t surface of th e lung. The consistence delivered before the Royal S&O*,Wta ^ E 0DL ^ ^ t 3 of the whole lung is increased, and large areas m ay show .fibrous condensation, which is tough- rather ' , th a n hard as in sOioosis. P arts of the long least . affected by the fibrotic change are often congested THE LANCET] DR. E . L. MIDDLETON : INDUSTRIAL PULMONARY DISEASE or pneumonic. Emphysema is notably localised in m onary and mediastinal lymphoid tissues, and pro lore -are n< of china-c areas and bullous in form, usually a t the anterior voked an early and rapid multiplication of fibroblasts. and lower margins, and a t the extreme apices a The German workers quoted by Gloyne M suggested ^ __.'-.workers ; ^industry in Con honeycomb-like patch of emphysematous b u lls may th a t the silicate is broken down into silica in the "nojinjury to hea be seen. A partial pneumothorax is present in some tissues. Beger and Giese took a similar view and hatr re s p ira to ry cases. explained th e slower action of silicates compared Histological examination of the lung reveals the w ith free silica in th a t way. EoppenhSfer " points ?Xhr. Chown, lat ^vgHorium a t Tehidy, most characteristic features of the disease. There is o u t th a t the magnesium and iron are dissolved out generalised fibrosis and the alveolar walls show and are replaced by alkalis which combine w ith the ,, f i w k n . Two o: ' " .radiogram from a i diffuse thickening." Everywhere in th e pulmonary silica. The silica th en undergoes solution. Fow- . no -inclusive sigi tissue are to be seen fibres of apparently unaltered weather " records th e result of chemical analysis of --- ae.f hOom, linear, ar. asbestos, isolated and in clumps, and the th e lunge in a fata l case of asbestosis, in which the J%gram of a man, a " asbestosis bodies " so well described by Gloyne * am ount of ash, in excess of w hat would be present '-geolosis, Showed th and Beger.'1 in normal lungs, was wholly accounted for as silica. "-extremely fine xl Asbestosis bodies have been found in the sputum He drew the tentative conclusion th a t the asbestos scum and a t the ri pnioeii. not of ail b y Stew art and Haddow,** Simeon and Strachan," had undergone decomposition in th e lung with '/radiogram of ai Page,** and others and by exploratory lung puncture deposition of SiOt and removal of th e metallic oxides. _ ifpr.J9 year* in tl (first suggested by S. A. Henry). The presence of asbestosis bodies in the faeces was described by . Sillim anite * J_axpoaed to dust o: '(SStunercle bacilli ir Gloyne." This is anhydrous aluminium silicate, with the ^evidence of mottlii In th e five-year period, 1930-34, a to ta l of 50 deaths were certified in which asbestosis is mentioned as a cause of death. In addition 4 deaths must be added in which asbestosis was known to he the cause of death, although it is not mentioned on the certificates. These 54 cases occurred in the five consecutive years in th e following numbers : 8, 9, 7, 15, and 15. There is therefore no evidence of diminution in numbers. Of the 54 deaths 31 were females and 23 were males The average age of the females was 32-6 yean and of the males 46-7 years. The seasonal incidenee was irregular, being highest in January and October, with 8. each; next in order are February and June with 6 each; March, August, and December with 5 each; May with 4 ; April, July, and September with 2 each; and November with 1. In 13 cases asbestosis was given as the only cause of death : 8 females, 5 males. In 24 cases tuberculosis was also present (44-4 per cent.): 16 females and 8 males. Broncho-pneumonia was present in 6 cases (11 per cent.): 4 females and 2 males; cardiac disease or cardiac failure in 4 cases : 1 female and 3 males; cancer of the lung in 3 cases: 2 females and 1 m ale; lobar pneumonia in 2: both males; and bronchitis and nephritis, 1 each : both males. In 43 deaths from asbestosis in the four years from June, 1931, to June, 1935, the periods of employment in the industry ranged from 10 months in distintegrating, to 23 years on weaving; the average duration of employ ment for the 43 fatal cases was just under 10} years. * The relationship between asbestosis and tuberculosis has been discussed by Merewether 11 and has been com mented on by numerous writers. The general experience is th at tuberculosis is by no means an infrequent accompani ment of asbestosis, while the opinion is general that it is less frequent than with silicosis. In the present series of 54 fatal cases of asbestosis, tuberculosis was present in 24 (44-4 per oent.). In a series of 67 fatal eases collected by the Factory Department11the number with tuberculosis is 26 (38-8 per oent.). In 100 cases collected by Burton Wood and Gloyne " there were 21 (21 per cent.) with tuberculosis. Only 26 of their series were fatal, and, in view of the higher proportion found with tuberculosis in the fatal groups, it may be that active tuberculosis is more frequent as a terminal complication than as a -oonoomitant disease during earlier stages. The difference in the reaction of the tissues to silica and asbestos has been demonstrated by experi m ent. Gninea-pig experiments made by Gloyne with asbestos showed th a t injection of the dust was n o t followed b y An acute inflammatory reaction ; a similar observation was made by Policard." Gardner and Cummings 11 found th a t asbestos was concentrated in the respiratory bronchioles and their lateral alveoli, and fibrosis was first manifested after 600 days' exposure. Quartz, on th e other hand, pene trated to the terminal alveoli of the lung, was rapidly concentrated by m igrating phagocytes in the pul formula Al,SiO,. I t occurs as rock of great density, imported from India, and it is used as a refractory m aterial. The broken surface shows masses of prismatic crystals in the form of fibres, which do not appear to be capable of division into extremely fine fibres like asbestos, but they tend to fracture and, when crushed, to be reduced to powder. The pro cesses of m anufacture include crushing, grinding, and sieving th e rock, usually after it has been calcined, and considerable quantities of dust are given off. The results of exposure to the dust of sillimanite are of special interest, because of th e fibrous form of th e mineral, in which it resembles asbestos." Few persons are employed in the industry a t present. At a factory where 15 men are employed, 13 of the workers were examined clinically and radiologically, and a complete occupational history was taken, with the assistance of my colleague Dr. Henry, and the cooperation of the employers. None of the work had any previous exposure in a dusty occupation. The ages ranged iron'. 24 to 50 years, and the duration of employment in the industry from 1} to 16 years. From examination of the 13 radiograms it was evident th a t no striking changes had occurred in the lungs of the men examined. In 4, employed respectively 16, 11, 7, and 5 years, there was some flight change which might be due to dust. This was not supported by clinical evidence, except that in the first there was slight bronchial catarrh. In 3 others, slight changes found might have been due to antecedent disease. In au the others hilum shadows were increased in extent or density, and in 4 of them there were also increase of the linear shadows and of the pulmonary reticulum. The num bers are too small to support any final conclusion, b u t w ithin th e lim its of the material of th e investigation i t does n o t appear th a t dust of sillimanite is highly injurious. I t cannot be said, however, th a t injury to health would not be caused by longer exposure, or th a t it m ight not become apparent after a lapse of tim e from the period of exposure. C h in a -cla y . China-clay, or kaolin, is hydrated silicate of alu minium, HAltSi,0. I t is formed by the decom position of felspar, b y th e removal from it of silicate of potassium through th e action of water containing carbon dioxide. The largest production of chinaclay in th e world is in Cornwall, where it occurs in deep pits from which it is washed with water under pressure. There is exposure to d u st in shovelling th e clay after i t has been dried in th e kilns. China.-cliy is an im portant ingredient in china and earthenware pottery, and it is used in the manu facture of paper, cotton-cloth, paint, soap, and a large number of other commodities. jS xT hese radiolog ftyfanim al experin -China-clay alone ftw fth the formati the alveoli, whi 1caused the of the siljco nund '* h; m a r inJSi t substance Talc -.^ frjn .its compact or soapsti $ & * * * H.Mg.Si.O ,,.taAIIer for paper ^fdreesing, and as a' 1 ua***rie switehboa pipes. A f ich chalk. g -J tn w e ther ' era TOo dust of French < : " dis-rubber works, f .^Hefound that while t if presence of a d ^p ftb e lungs with ur . examination and otl / iff yr* exposure, o: A"* 0had resulted. The suggestion i i^Bces seen reallv re -ifffiether with any : he presence of a d_ "u t made 6o far sblement after < Examination of 1 ( ranging from b previous conclui Hi ** described i employed for fi\ bber factory wher. J^radiographic pje; " in the ri; mey of righ shadows ---- through t ith e reticular ah< ^practically no " case seems t ' lions infection liological appear [jxtly 11, 1930' ' . ihoid tissues, and pro^ plication of fibroblast ! by Gloyne " suggest* town into silica in the ik a similar view and of silicates comps Koppenhofer ** point iron are dissolved o i l /hich combine w ith the irgoes solution. Fowl of chemical analysis oa isbestosis, in which thq w hat would be presen accounted for as silici. usion th a t the asbestos on in th e lung with U of the metallic oxide lite linm silicate, w ith the s rock of great densit is used as a refractor face shows masses ofl i of fibres, which do nof sion into extrem ely fine 7 tend to fracture an l to powder. The proj u d e ' crushing, grinding ifter i t has been calcined of dust are given ofl ie dust of sillimanite of the fibrous form. -.sembles asbestos. Fe industry a t present. J are employed, 13 of ' Uy and radiologicaUy, ory was taken, with _, Henry, and the coSperatio f workers had any prev in. The ages ranged i cion of employment in ' From examination of hat no striking changes 1 . examined. In 4, employ -ears, there was some s i j to dust. This was e, except that in the itarrh. lei 3 others, ' n due to antecedent di tvs were increased in ex there were also increa pulmonary reticulum. mil to support any . lim its of the material? not appear th a t dust] a rm I t cannot be a a lth w ould n o t be can ^ .at it m ight n o t becofl tim e from th e period* -clay hydrated silicate of js formed b y th e deooj removal from it of silic iciaon of w ater coat ;est production of m w all, w here it occu w ashed w ith w ater un xre to dust in shove ried in the kilns, cant ingredient in m d it is used in the ms doth, paint, soap, modifies. firr LiXCET] PB. E. L, ariPDIETOK i grDPSTRIAX. PULMONABY DISEASE [JULY 11, 1938 61 There are no satisfactory data regarding the effects of china-clay on the human lungs, b u t am ongst both workers a n d . management, engaged in th e industry in Cornwall, there is a general belief th a t uo injury to health follows exposure to th e dust an d that respiratory disease is not unusually prevalent. type in th e rig h t lung. It resembles the reaction w ith tubercle and china-clay Ihorel described in 1896 a case of talc pneumo coniosis ^ which he designated SpecksUirdungt. Sand described the case of e woman who had worked for several yean m an atmosphere of tele dust. Post mortem the Dr. Chown, late medical superintendent of the sana torium at Tehidy, kindly let me see X ray films of 4 clayworkers. Two of them showed tuberculosis only. A radiogram from a third man, aged 37, in whom there were lung showed the presence of much tele dust but with out great reaction. This case wee reported by Devoto and Cesabianchi.1' 1 C unning h am ex am in ed a man employed for nine yean grinding talc, and found evidence no conclusive signs of tuberculosis, showed only increase of hilum, linear, and reticular shadows. The fourth radiocram of a man, aged 49, with no definite signs of tuber* culosis, showed the whole of both lung fields covered with extremely fine mottling, most marked in the middle of pneumoconiosis. Dreen e n * described the results of an investigation into working conditions in a tremolite talc-mine and mill and the efiects on the health of the workers exposed to the dust. Those employed over five yean (the longest wee 16 yean) and exposed to very- zones end at the right base. The film suggests a pneumo coniosis, not of silicotic typ_. Later, Dr. Chown sent me n radiogram of another clay-worker, aged 40, employed for 19 years in the " d r y " or kiln, where he would be iixposed to dust of china-clay. He had tuberculosis with rulicrcle bacilli in the sputum. The radiogram shows evidence of mottling of silicotic type. These radiological appearances recall th e results of animal experiments obtained by K ettle," in which china-clay lore produced only cellular reaction with the formation of plaques of dust an d cells in high concentrations of dust showed first stage pneumo coniosis. The appearances wen those of a fine, diffuse bilateral nbrosia. The ebaoges did not cause disability. Dreessen and Dalla Valle144 carried out a further surrey of two talc-mining and manufacturing plants in Murray County, Georgia. Clinical and radiological examinations showed th at 16 mill-workers out of 33 exposed to high concentration of dust and 6 of 13 miners had pneumoconiosis. In 4 of th e most seriously affected cases evidence of pulm onary infection was present. tlio alveoli, while china-clay w ith dead tubercle bacilli caused the formation of fibrotic tissue in the . M ica form of the silicotic nodule. Siegmund has suggested th a t a tuberculous process may influence the changes which occur in mineral substances in the tissues. A group of widely distributed rock-forming minerals, two of which, muscovite and phlogopite, are im portant commercially. Muscovite is a silicate of aluminium w ith potassium. -It'is used, on account of its trans Talc and French Chalk parency and its resistance to fixe, for windows of stoves and lanterns. Ground mica is used in the In its compact form the mineral talc is known as m anufacture of paper, wall-paper, and paint and as a steatite or soapstone. I t is a hydrated magnesium lubricant an d absorbent. Phlogopite is magnesium silicate Hs^fgjSi.Oj,. In powder form it is used as aluminium silicate. I t is almost exclusively used for a filler for paper, soaps, and paints, and for leather electrical purposes. Dust is produced especially in dressing, and as a lubricant. I t is also used in making the processes of sawing, grinding, and finishing. electric _switchboards a n d ' for heat insulation of Ferguson * examined 12 workers exposed to mica stcam-pipes. A fine granular variety is known as dust. In only 5 was the exposure as much as five years French chalk. ' ' and these complained of cough and dyspnoea, the symptoms Merewether " examined 11 workers who were exposed . being slight except in one men, aged 59, who hod been to i.ust of French chalk in the tyre department of an employed 32 years. He had well-marked pulmonary india-rubber works, for periods varying from 10 to 32 years. fibrosis and emphysema, and another, employed eight Iefound that while the radiographic appearances suggested years, had quite definite fibrosis. Three m.w were tho presence of a developed, diffuse, interstitial fibrozi* examined radiologicaUy.. The radiogram of one man, of the lungs with under 10 years' exposure, the clinical employed 32 years, showed fibrosis, larcelv peribronchial examination and other factors indicated th at even e 'ter in type, chiefly in the middle zones, with increased hilum >'e"f* exposure, only e peribronchial increase of fibrous shadows and, a t one or two points, nodule formation. tissue had resulted. The other two radiograms showed increased hilum shadows with increased linear striation and fine, Hifh. shadows The suggestion is th a t the radiographic appear in the middle zones. Ferguson, with a reservation regard ances seen really reflect th e actual dust in th e lungs, ing the smaU numbers, concluded that dust of mica may together with any associated congestion, ra th e r than be- capable of causing pulmonary fibrosis. the presence of a diffuse fibrosis. The few exam ina tions made so far did not disclose any appreciable Sericite , vean ment after exPsules ranging from 9 to 32 . -A- mineral of widespread occurrence, sericite is of interest in a study of the etiology of silicosis because of 13 additional workers, w ith expo res ranging from months to 40 years, supported the previous conclusion.** of its frequent association with quarts in rooks, exposure to th e dust of which has caused th e disesse. I t is a hydrous silicate of aluminium and potassium ZaneUi described the case of a woman of 27 who had a for ^vyearn in the tyre department of Th toi7! where she wee exposed to clouds of dust. pietures showed an early tuberculous in m t*1 right subclavicular region, decrease in rMiiprren<?r ot right compared with left due to increase "trih .T ? *"adoT* V"1 nodular formations uniformly field thl**1 *lsru8h the right lung. In the left lung were 5.etlpular shadows were accentuated, but there practically no " nodules." (H,KAl,(SiO,),) and is produced in the decomposition ~ of potash felspar. I t occurs in two forms--silky, talc-like plates and minute needles. The occurrence of sericite in the gold-bearing banket of th e Witw atersrand was described by Watkina-Pitchford an d Moir.1** T hey thought i t " almost certain th a t a ' ' large proportion of the bright white images seen by polarized light in a silicotic-lung section o tS o n d origin are produced by sericite." Mavrogordato1,7 included : .. ,case seems to show th a t the interaction of a rad: S ectio n with the silicate dust produced lologieal appearance of " nodules " of infective " intractable silicates, e.g., sericite," as a possible facto r in th e occurrence of silicosis. . B a d h am I0* suggested th at the fine type of fibrosia `' of W estern Australian miners is probably related to- ~ 62 the ujjcet] , DB. E. I,. KTDDLETOK t ZKSDETBIAI. PDUIONABY DISEASE [toly 11, 1936 sericite which is found in quantities greater than quartz in eome of th e mines. . I t was not, however, until W . R. Jones published his paper in 1933 on Silicotic L u n g s: The Minerals they Contain,1" th a t sericite became familiar to everyone interested in th e aetiology of silicosis. By petrological methods, he found th e mineral, sericite, m rocks and materials which had given rise to sili cosis, and in th e lungs of 29 men who had died from the disease. Although quartz was also present it was subordinate in amount to sericite, especially in number of particles. ' In the South Wales coal-mines and the gold-bearing quartz-conglomerate of South Africa, abundant sericite was shown to be present. The experience a t the Broken HOI mines in New South Wales was cited to show that rocks with a low quartz content, but with fibrous silicate minerals, produced cases of silicosis. The physical property of sericite fibres, by which they remain suspended in the atmosphere, was demonstrated to show the opportunities for inhalation of tbe mineral. The only industries in this country in which it appears th a t workers are exposed to dust of sericite without uncombined silica are those connected with the production of china-clay and manufactures in which it is'used. The evidence a t present available is insufficient to allow of a definite statem ent regard ing the occurrence of pulmonary disease amongst these workers, as no systematic examinations have been carried out. The opinion of employers and workers in the china-clay industry is against the view th a t a high incidence of such disease is prevalent, and medical evidence is negative apart from the cases already mentioned. Certain pulmonary changes have been produced by silicates, and, apart from asbestos, individual cases of fatal disease have occurred in which the dust of silicates seemed to be the cause. The disease, however, did not show the radiological or patho logical signs which are characteristic of silicosis. This was the experience in South Africa in workers exposed, in a quarry, to dust of norite,11" and in New South Wales w ith an orthoclase basalt,111 and in th e Great Cobar mine. D r. Badham al60 described a fine type of fibrosis amongst the miners of Broken Hill, and of Western Australia and Tasmania. Identity of H arm ful D usts K e ttle 1U utilised the interstitial method for deter mining the tissue reaction to various kinds of dust, and the influence on th e local lesion of infection w ith tuberculosis. In these experiments " activ e" and " inert " dusts were distinguished. Colloidal amor phous silica caused necrosis; w ith crystalline silica necrosis was delayed, and rite characteristic lesion w as produoed in 2 or 3 weeks. Dust from a South African gold-mine caused lesions which differed scarcely, if a t all, from those caused by amorphous silica. Shade from A1tofts and Great Mountain collieries gave the characteristic reaction of silica, though modified by the high admixture of inert material. Kaolin had all the attributes of a soluble form of silica, while the leeion produced by asbestos mimicked th a t of crystalline silics b u t tbe central ooagulum was more pronounced. The lesion produoed by carborundum was remarkable for its quieeoenoe, and non-sOioeous dusts characteristically showed quiescence. Following inoculation with tubercle bacilli the " active " dusts ware: all compounds of silicon except carborundum--Le., colloidal, amorphous, and crystalline silica, gold-mine dust, shale, lrmdin and asbestos. . A method was introduced by K e ttle 111 for adminis tration to experimental by the tracheal route of dust suspended in liquid. By this method u< no substance other than silicon derivatives was found which caused m ore th an a m oderate degree of fibrosis of th e lung, certainly n o t enough to interfere with its function, and no other constituent of ordinary dust which could influence unfavourably a pulmonary infection. All forms of crystalline silica appeared to be capable of producing th e disease, and th e closest reproduction of sim ple silicosis in m an, so far obtained, occurred in guinea-pigs some 600 days after the introduction of a single dose of finely powdered flint into th*ir lungs. According to G ard n er111 th e reaction to dust may be divided into five general p h ases: (1) early diffuse parenchymatous disease; (2) linear perilymphatic proliferation; (3) beading of th e tru n k s ; (4) enlarge m ent of th e mediastinal lym ph nodes; and (5) late chronic proliferation and nodule formation in the finer connective tissues of the pulmonary parenchyma. Different phases of this picture are accentuated by various types of pure dust. Silica produces all of them. P ure fibrous asbestos produces generalised fibrosis involving primarily the finer connective tissues of th e pulm onary framework. H e 111 found th a t silicon carbide (carborundum) excited a moderate degree of parenchymatous reaction and some linear fibrosis. The o th e r common industrial dusts gener ally set up a reaction th a t is characteristically linear, with more or less diffuse changes in the parenchyma b u t no nodule formation. B eger117 expressed th e view th a t the action of dust is due to free silica, w hether it contains quartz or silicates. H e explains th e findings of W. R. Jones by th e slow solution of sericite, which he does not consider free from danger, though only the dissolved silica is the cause of the disease. * Siegmund u * 111 produced positive results by the intravenous injection of quartz. Typical sihcotic lesions were produced in the liver, spleen, and other organs by dusts containing quartz, but not with quartz-free dust. Silicates produced the ' changes only after ten m onths; th e delayed action is explained as due to dissolving o ut of *silica. The fibrosis increased w ith a decrease in size of the quartz particles. Experiments with colloidal silica produced tbe greatest change. Giese170 h ad obtained sim ilar results by injecting quartz into the blood stream, and negative results were obtained w ith dusts free from silica. Stfiber," 1 on th e suggestion of Dr. C. K. Drinker, used the lym phatic glands as a rapid means of deter mining th e toxicity of dusts. The cellular response of th e lym ph nodes to dusts of flint (99 per cent, free silica) an d B arre granite (26-5 per cent, free silica) was peculiar in th e appearance of " silica-cells,'' while some silicates, including asbestos, did not have th is effect. Using th is m ethod, Drinker, Field, and D rin k erin found th a t after 10 or 12 days th e changes produced by two samples of sericite were similar to those of finely ground flint. H aynes,1" as a result of inhalation experiments on guinea-pigs, concluded th a t th e m ost deadly of all dusts was precipitated silica. Less dangerous, b u t all producing fibrosis, were th e following, arranged in order of decreasing to x icity : flint, slate, aluminium hydroxide, precipitated chalk, magnesium carbonate, and carborundum. The harm ful effects of soluble silica may be neutralised by simultaneous adminis tration of basic dusts suoh as aluminium hydroxide or magnesium carbonate, though the latter are harmful when inhaled alone. Robson w as struck by th e fact th a t th e incidence of silicosis was higher' amongst the underground Si xhe zaxcetJ liners in certaii K the men emplo. g th e dust in the funderground m Egassy atmosphe: experiments to tth e etiology of experiment* we: fctute. ' Rabbits jfcof irritating ga [degenerative lesi ^dilute irritating muced no fi weeks; dih [silica dust gave [to an acute puli ^nodules in th e ai od in the lymp] : Perrott, Babe ixides of nitroge averaging 260 p: and Jones m fou of from 100 to 9( "' In several anti of silicosis nine-air were ta ng, and wer I case did i t ex >conoentratio sthan 3 or 4 1'figure, nea: oxide, was i ficient ventilat . eeeitoxea; M21er and Say ' nta in which : nsion was i ' guinea-pigs. *] absorption, prolif M forpfnm respon peritonea] cavity Uaaoe. This was ntated calcium fjTpoate), and cemec s U calcium comp ^ ^ o o n t of inject I. active moven extensive are: &** p v e n by s. frcarborundum (car jjfferric oxide), a r t ' n, collected froc Mferatire reacti it continued to sr injection, tb< Jd i t seemed like] re resulted. Tw 'response. " c and chert i ores) gave ile tb e hist i were not as os, they wei Sfirentiation of ~ l [ju l y 11, 1838 atives was found degree of fibrosis interfere w ith , tent of ordinary ibly a pulm onary' silica appeared .e, and th e closest a, so far obtained, days after the ly powdered flint tion to dust may : (1) early diffuse ar perilym phatic in k s; (4) enlarged e s ; and (5) late formation in the nary parenchyma. -e accentuated by a produces all of { duces generalised : finer connective' rk. H e 114 found excited a moderate ] a and some linear .' trial dusts gener.cteristically linear, 1 in the parenchyma bat the action ofj it contains quarts! Qgs of W. R. JonesJ which he does not only the dissolved cive results by the Typical silicotic r, spleen, and othe irtz, b u t n o t witl duced the change d action is explain ; ilica. T he fibrosis size of th e . qu oidal silica produce results by injecting in d negative result" m silica. f D r.C . K. Drinke apid means of deter] The cellular response flint (99 per cent (26-5 per <*nt. fre< once of " silica-cells.i bestos, did not hay] , Drinker, Field, ana r 12 days th e chang sericite were sin halation experiment the most deadly / ca. Less dangeroc he following, arrangi flint, slate, aluminio nagnesium carbonati iu l effects of solubj umultaneous admin aluminium hydroxfd ough the latter " ict th a t the incidenj gst the undergro o ::sS-S<&if' \ - ; > - - \ - * ' ' . v - ' / * 1-.V ;' " . if A'Vlff1. -- - - '.r j'- TEL UKCR] V DB. E . L. M IDDLETON: INDUSTRIAL PULMONARY DISEASE [ j u r r ll) 1936 63 miners in certain gold-mines in Ontario, th a n am ongst the men employed in the crusher-houses, although the dust in the latter was greater in am ount. The underground men suffered from headaches in the gassy atmosphere after blasting, an d this suggested experiments to ascertain the effects of mine-gas on the (Etiology of silicosis. W ith Irw in an d King 1,4 experiments were carried out a t th e B anting Insti tute. Babbits were exposed to th e inhalation of irritating gases (NO, and SO ,), these produced degenerative lesions and predisposed to p n eu m o n itis; dilute irritating gases combined w ith sericite dust produced no flbrotic changes in an exposure of 40 w eeks; dilute irritating gases com bined w ith silica dust gave rise, in periods of 13 weeks o r more, to an acute pulmonary silicosis w ith typical silicotic nodules in the alveoli, in th e lym phatic aggregations, and in the lymphatic glands. Perrott, Babcock, Betting, and J o n e s 1,4 found oxides of nitrogen in .mine drift air in concentrations averaging 250 parts per million. Gardner, Howell, and Jo n e s1,4 found sulphur dioxide in concentrations of from 100 to 900 parts per million. In several anthracite mines in South Wales, where cases of silicosis had occurred, tw enty samples of m<oe-air were taken a t the working faces, ju s t after blasting, and were tested for nitrogen peroxide.15T In no case did it exceed 90 parts per million, an d even this concentration could not have been present for mure than 3 or 4 minutes after each shot. An excep tional figure, nearly 200 parts per million of nitrogen tetroxide, was found in another series illustrating deficient ventilation. . an ordinary dried long does not contain more than 0*2 per cent, of silica (that is, total silica). Sladden1,1 concluded th a t fibrosis of an important extent, clearly contributory towards death, is usually present when the silica content of the lungs exceeds I yer cent, of the dried lung substance. When the silica exceeds 1'8 per cent, the fibrosis associated is, with practically no exception, vety severe and sufficient in itself to lead to death. The 60 -ccts on which this conclusion was based included hard-heading workers in coal-mines, coal-hewers, coal-trimmers, stonemasons, and others. Badham and Taylor u *_described a method for chemical analysis of longs, and the results of analyses of th e h u g s of 31 persons. They showed th a t the pathological findings varied markedly and without any constant relationship to the silica content of th e lungs. In 4 cases without exposure to dust, th e lungs contained an average of OT23 per cent, of silica in the dried tissue. McNally 141 reached the conclusion th a t the silica content of the normal lung was 0T13 per cent, of dried tissue. In a series of eight lungs from worker exposed to dust the percentage of silica varied from 0-24 in a machinist to 2-60 in a granite-cutter, while a 6tone.quanym an's lung gave 0-50, a stone-cutter's T40, and a zinc-miner's 109. Fowweather ,4` found in the lungs of 5 normal adnlts between the . ages of 23 and 65, a silica contentfrom 0-12 to 0-20 per cent., with an average of 0163 per eens. He found no obvious connexion between the amount of . in th e lungs and the amount of fibrosis. PERITONEAL RESPONSE TO VARIOUS DUSTS Miller and S ayers1,4 carried o u t a series of experi ments in which a small am ount of dust. (0'2 g.) in suspension was injected into th e peritoneal cavity k The response could be dsstified as absorption, proliferative, or inert reaction. In tbe abtorpiion response the dust disappeared from the peritoneal cavity w ithout the production 'o f scar tissue. This was given w ith calcite, lim estone, pre cipitated calcinm carbonate, gypsum (calcium 'sul phate), and cement. I t will be noted th a t these are a j calcium compounds. In th e inert reaction th e amount' of injected dust was unaltered, b u t there "as active movement, by the action of phagocytes, over extensive areas of the peritoneum. T his reaction was given by soapstone (talo or french chalk), carborundum (carbide of silicon), jewellers' range * oxide), anthracite and bitum inous coal, and Mb. collected from a smoke stack effluent. In th e ,\n.lJtTaUr.e a c t i o n the nodules produced b y the a h t. * increase in size up to 112 days and . " J***0" ,.th e maximum duration of th e tests, v 11>emed likely th a t scar tissue would u ltim ately thi* -m ttit*d. Two samples of pure quartz produced onnrt*^0n5' " dm * " (a w aste product containing iimiSL ckert from t t e concentration of lead ?ve * " " tf" response. m "* " * histological variations in tb e three * . Z J ? r* tnot " tr *k" K * th e well-marked gross din,.'"I' they were sufficiently distinctive to perm it group,ntlon oi dnsts into the same three CHEMICAL ANALYSES OF LUNGS *nadv*Ve A rcher144 suggested th a t chem ical. letern.,-1117 . ProTe to be the deciding facto r in whetherln' ,n absence of a typical fibrosis, ,fRard#,l r ? ot tuberculosis of th e lung m ay be as due to occupation. In their experience A series of 44 analyses of lungs was carried out "T P- L. Sutherland xor the Committee on Industrial Pulmonary Disease. There were 21 stone masons in this group, and in these the average content of total silica in the dried long tissue was 1-23 per cent. In a group of 13 sandstone-quarrymen the average silica content of the dried lungs was 1-72 per cent. The highest silica figure in this series, 7 04 per cent., was found in the lungs of s miner, aged 61, who had worked on gani6ter and coal, in the same mine, for 49 years. Both lungs were the seat of carcinoma, and small silicotic nodules and some consolidation were present. Kecent work by Belt, Irwin, and TT.'ng m*howa th a t the proportion of silica varies in different portions of the lungs of persons who have not been exposed to a dust hazard. They found that in normal adults' ' lungs the " silica '' content averaged about 151 mg. ' per c e n t.; and 217 mg. per cent, in persons over 52 years of age. The tracheo-bronchial glands of most adults contained from twice to 20 times as much silica as the corresponding lungs. I t is generally found th at the proportion of total silica in a normal adult lung is between 0-1 and 0-2 per cent, of the weight of dried lung. T h e re . appears to be no constant relationship between the * am ount of fibrosis and the proportion of ni*** in . altered lungs. The presence in such lungs of large , amounts of other dusts appeals to be accompanied by : - t retention of silica. . ... - During the time after the exposure tp dost has ceased and before death, the amounts, relative. ' 'proportions, and even the character of the.minerals become altered by the action of the tissues.144 ' . . A - Tideswell144examined s series of silicotic lungs with :$ a view to determining the form in which th e silica \ occurred and particularly to attem pt to estimate the hydrated silica. He found th at approximately 5 per - cent, of the to tal silica in the lung examined was present in a readily soluble form. V /X 6 4 THE L U iCET] I | * DK. E . L . MIDDLETON : INDUSTBIAL PULMONARY DISEASE [JULY 11, 1936 TTin;. and D olan1,1 have shown th a t silica reaching the blood stream, either by absorption from th e gut or by solution in th e lung, is rapidly excreted in the urine. Soluble silica injected into th e blood is quickly eliminated in the urine. There appears to be a low kidney threshold for silica. No significant differences were found in th e silica level in th e blood of normal and sQiootic persons. ' Removal of silica from th e lungs b y continued activity of phagocytes is recognised, and the presence in the sputum of dust-laden cells long after exposure to the source of dust has been frequently observed. B e lt1*' observed th a t an edematous sta te of the tissue favoured the activity and migration of dust laden 11 several months after the exposure to dust inhalation had ceased. Conclusions Certain conclusions regarding th e etiology of 6ilicosis may be drawn from th e consideration of the occupations in which the disease occurs. _ (1) Where silicosis has been caused, th a t is, the nodular form of pulmonary fibrosis, exposure to the inhalation of silica in the uncombined 6tate appears to have been present. _ (2) W ith a dust-bloud of moderate concentration, the disease develops 6lowly and the nodules of fibrous tissue appear a t certain situations in the lungs. This occurs-in grinders of metal, workers on sand stone, and in pottery workers. _ (3) When the dust contains a very high proportion of free silica, and is in a fine sta te of division and the concentration of particles in the atmosphere is high, the disease tends to develop rapidly. In 6uch cases th e fibrosis retains the nodular form and develops a t the usual sites, b u t it appears also in other parts of the structure of the lungs. This has been seen in flint-grinding, sand-blasting, and abrasive-soap manufacture. . (4) When the dust of free silica is inhaled mixed with certain other kinds of dust in im portant amount, the arrangement and distribution of the resulting fibrous tissue may be modified. Such modifications have been found in workers in coal-mines and haematite-mines. ... (5) When the inhaled dust consists of silica combined with bases, as silicates, some degre of change in the pulmonary tissue appears to resu. In this respect asbestos dust is unique am ongst 6ili.-ates in the prevalence and severity of the disease which it causes. The physical form of asbestos differs from th a t of all other industrial dusts. - _ (6) The fibrosis produced in the lungs by th e action of silicates differs from th a t produced by free silica, and tit types can be distinguished by radiological and histological means. _ (7) In certain states of the lungs, for example in the presenoe of tuberculosis, th e action of silicates may be modified. Mad. 77. Merewether, E . R . A ., an d P rit, C. W . : R sp. on tbe Effects of asbestos D ost on tb* L ungesnd Dost Sup pression In tb e Asbestos Industry, E h . Stationery Offloe. London, 1930. . __ 73. Cooke, W . E . : B rit. Med. Jo n r., 1 9 i. U.. H i . 79. Gardner. L. U. : Jo u r. a m e r. Med. Assoc 1933, d , 5 t i . 80. Gloyne, S. R . : T a x L m c r r , 1933.1., 1351. 81. Bearer, >P . J . : Virehowe Archly, 1933. cexc., 330. 33. S tew art, M. J .. an d H addow , a . C. : Jo n r. P ath , and S3. S i Bact. meon, . f 1 r. 939. W ., m an o d di S .. tr 173. acba n , a . S. : Ibid.. 1931, x x x jy .. 1. St. P**" R C . : am er. Jonr. Scl.,.1933, clxxxlx.. 4. 63. Gloyne. S. R . : Tubercle. 1 931,33L, 133. 86. Merewetbar. E . R . A . : ib id .. 1933, r r . . 9,109, an d 133. 37. Ann. R ep. Chief Inep. Factories, 1931, London, p. 63. S3. W ood, W . B arton, a n d Gloyne, S. R . : THZ LaxccT, 1931, 39. 90. GPollircnar.dS|,*aR. -: : Tubercle. 1930, x l , 131. B oll. d 'Histologie applique. Facult de Mdecine de L yon, 1933, vil.. 193. 91. Gardner, L . V ., a n d Cummins, D. E .: Jo n r. ot In d u it. 93. G loyne.'s'R .1;' Tubercle. 1933. xt.. 4 5 .483,330. __ 93. KoppenbOler, G. F . : Archlv. 1. Gewerbeputh. u . Gewer- 9t. FowweUher, F i s . : ^ y . , 1931. x ., 176. 93. S e ttle . E. H . : Jo u r, of P a th , an d B act., 1934. x c r rlU .,806. 96. Slesrmund. H . : Archlv. 1. Gewerbepath. u. Gewerbebyg., 97. M eriwether, E." R . A . : A nn. R ep. Chlel Insp. Factories, London. 1933, j u 63. . . ., 98. Ann. Rep. Cbiet In sp . F actories. 1931. London, p. 63. 99 Zsuelli. A. : .Talcum Pneumonoconlosii, M edians del IftToro. LU*u, 1931, K o. 1. ,, A. 100. Tborel, C. : B eltr. z. p a th . A nat. u. z. allg. P ath ., 1896. 101. National*Congress on Occupational Diseases. Turin, 1911. iSJ: Cunningbam : Dept, ot Indnst. H ys Toronto. Quoted 103. Droeeien? W*-' C.P; Jo u r, o t In d u st. H tx H J J lXv 6. 101 D reessS W .C .. an d D alla Valle. J .M .: U S . P ub. Health R ep!; W ashington. 1935, r o l .l .N o . 3. 105 Ferguson, T . : A N ote on Mice D ust and th e Lung Con dition ot Some Mica Worker*. Unpublished memo, to Comm, on I n d u it. P ulm . Di*. ot Med. Research Council. p. _, 1932. . 106. W atkim -Pitchlord. W ., an d Molr. J . : On th e N ature ot the Doubly-retracting P articles Seen In MiajotMiplc Sections ot SUlootic L ungs, SA., la s t, lo r Med. Res-. Johannesburg, 1916, No. 7. 13. 107. MarTOgordstoTA. : C ontribntlom to th e S tudy of Mlnert P hthisis. S.A. lu s t, lo r Mod. Rer . 19 6, No. 19, *. IS. 108. Bsdbam , C. : Studies In Industrial H yg.. R ep. of Pubue H ealth D ept., New S ooth Wales, Sydney, 193i. No. 13, Min. and p . 108. ' 109. Jones, W. R. : Jour, of Hyg., 19SS, xxadll.. S0i. 110. M avrogordato, A. : Studies In k rp e im e n ta J Sicotis. S.A. In st, for Mad. Res.. 1933, No. IS. p . 10. j l l . BBsUdDbKssUil.i CV/<. :. IR*e.py .' wo*f P oaow. aHmealth D ept., Kew Sooto Wales. Sydney. 1937, p. 103. 113. Settle. E; S . : Jour..Path, and.Bact.. 1933. ,397. 113. Same a u th o r: THE Lzncxt, 1934. 1.. 889. 111154.. Same a u th o r: Bull. Inst. Gardner, L. U .: Jonr. Amer. Met., 1931. xllll., <. led. Aasoc 1933. d ., Su. 116. Seme a u th o r: Amer. ReT. Tuberc.. 1933,. vU *44. 117. Beger, P. J . : Med. Klin.. 1934. x p U.. IS M is d IMS- 118. Siegmund. H .: Aerzt. Sachrerst.-2^.. 1934. zl.. 28y 119. Seme a u th o r: Arcblr. 1. Gewerbepath. n. Gewerbebyg., 118801.. GlmOkTV'Beitr. path. Anat., 1933, xelr.. 413. StUber, K athrrlna: Jour, of Indust. Hyg., 1934. __ 133. Drinker^tL K., Field, U . E., end Drinker. P . : Ibid., 1931. Ill i S t S l $ $ J .: Camd. 135 TechnJcsJPeper 4S3-.' V S . "Bureau ot`lines. 1930. 136. Bull. 367, UB. Bureau of Mines. 1937. 137. Haldane, J . S . : Rep. ot Mining Res. Lab., Unlr. o. 133. O U s r^ N v ^ a h ^ S a y e tlR . R - : V S . Pub. Health Rep-. 130. * : J1 - 131. S l z i n S , A . F . : i h n e L a n ck t* 1933. 11.. 133. 133. Med. Jonr. ot Australia, 1933, x t 311. S- M ed ... AcJcnowUdpmtnli.--I t is a pleasure to acknowledge the help and advice of many colleague and friends in the preparation of these lectures. My thanks ere due to the rinrnmittoo on Industrial Pulmonary Disease for permission to use unpublished material, and especially to the chair- .man. Sir Arthur `F a ll; to colleagues in the Home Office and the Minna Department, to members of the Silicosis 'Medical Board, as well as to many friends in this country '.and abroad, of whom mention has been made in the -text. - . w r m niflM 76. Fuhr.; Dent. mod. Woch., 1914, zl., 1346. ill: 13. w J tS & S ft: : " *d- M#i 1.34, x 173. ill: Si 'c i i f i : m * . a - oc. jo 139. B eit, T.` g f f c f m d . P ub. Health Jour.. 193*. r s .. 01. G o o l e H o s p it a l .-- L ad y Eaglerome is U rin e tbe foundation-stone of the extensions of the Gooic Bartholomew Hospital on Saturday. The extensions, which will cost about 11,000, will include a new ward, a modem operating theatre, and a laundry. Some 2500 is Already in hand.