Document Vj0rDjzoMEVndeRb1aMQQGVYZ

FILE NAME: Visible Dust (VDT) DATE: 1938 July DOC#: VDT023 DOCUMENT DESCRIPTION: Journal Article - Industrial Medicine I V' Medical Prcas and Circular Supplement, July 20, 1938 INDUSTRIAL MEDICINE SY M PO SIU M No. 3 , 1938 9 Co ntents: H istory o f Industrial Medicine , nr T. M. Line, iLA * BCtf.(Oxon), M.R.CP, Lees in Indnstnai Medicine, University of Bristol. t Medicine's Contribution to Industry -- -- --By LmMAito P. Locam ay, M.D* M edial Officer, M essrs. Boot Pure D ree Co* Ltd, Nottingham; Chairman, Association o industrial M edial Officers. The Factory Clinic Ey Dokaio 5t* wa*t, H O , SLR .C F* M edial Officer. L C 1. Metals, L td .; Honorary Secretary, Association of Industrial M edial Officers. Dusts and the Lungs By E . R. A. M nrw rcnn*. M .D, M .R.CP, h rriw M t d w , One of ILM . Medical Inspectors of Factories. Occupational Cancer and Dermatitis By W. J. O'OotiOVAM, O.B.H. M.D, M .R.CF* Ptiysidan, DermstotOKtai Depertmcnt, London Hospital: Physician, Sinn Department, S l Pant's Hospital fur Urological and Side Diseases. London. Industrial Plumbism By Rohalo E. Lame. M-SULond.}, M.fLCP.fLond-X Hen. Assistant Physician, Salford Royal Hospital; M edial Officer, The Chloride Electrical Storage Co* Ltd* Manchester. Industrial Accidents and So-called Neuroses in Industry By Miu a is Cut-m x. M.D* F.R.C.S* Professor of M edial Industrial Psychology. London School at Hygiene and Tropical Medicine: Lecturer m Psychonetiroies, London Hospital. rT..rjcKiL e; iSteaSamu W 4 6 J Tie Medical P ig s asp CmcmA 5cfpt.piext_____________ ri if elaborate X-ray plant is "needless and un- cnnomic and is one oa cae way* in which wlustrinl medial je rrie s can be adversely riticised both by the emriorer and die medical >roteaston as a whole. /*,, X '' Voluntary Caaaedaaon This particular aspectof the raqpcy doctor's viirk has been intenoootily left to die bsL It 5 not infrequently the case that his most effeeive work is carried oat in the privacy of his unsuiting room. The worker who is worried ibout his health, who any be emotionally upset cause his imtnediato superior is a bully, or ivlxi wants information m one o f a dozen other irablcms, should be able ts find in the medical ifBcer an adviser who d a guide sm through its difficulties, either by adjusting the position vithin the factory >-^br advising him to con sult his own private medical practitioner and it the same time offering his hdp in coilax>ration. There is ootHng worse dan a feei ng of disappointment. a d frustration in one's work. Discontent is a major cause of indus trial unrest and strikes which hare affected many thousands of otherwise harpy and con tented workers have arisen as a result of the [>eny. failure of .onerperson." In modem psychotherapy, the Scientific way if dealing with a nan s also the humane and understanding wav ana h-iinarntr and underHanding are wanted badly not oaiy in indus try but throughout the world to-day. The wnpe for this trpe o f mrdiral work in industry s great and era piny a part of fundamental mporiance in the fueae development of the niatth services of this coorntry. And now une word in conclusion. We have discussed very briefly some of the measures carried out by the industrial medical officer and have shown hou^they bear on the work of the factory ch.Ucf At the present day, however, there are probably not more than two or three hundred doctors engaged in this type of work in the country and it is estimated that of these only some fifty or sixty are employed in a whole-time capacity. It is obvious there fore that only a small percentage of industrial workers--anu very often those employed in large and enlightened firms--have such facili ties offered to them. If it is conceded that (he work which has just been described is of importance in the general health schemes of the nation then the problem within industry becomes one of considerable urgency. Whether the work should be undertakes by far-sighted employers now or whether ft should be left to the State to develop and con trol must be a nutter of opinion and of poli tics. The important dung is that die work'is there waiting to be done: There are those who firmly believe that the future-prosperity of the nation depends on the health and happiness of the individual work man. If tin's b so how can we as doctors take our part? The problem, I believe, a primarily one for the medical profession, and in par: therefore for the industrial medical officer. What can be learned in .the factory clinic to day will most surely become the acceptec practice throughout industry in the future am it properly developed cannot fail to contribute successfully to the problem of national fitness which is being so modi discussed at the present'time. 1 DUSTS AND THE LUNGS WITH PARTICULAR REFERENCE TO SILICOSIS AND ASBESTOS1S i By E. R .A . M OEW ETHER, M.D., MJLC.P., BAtutiSTOt-AT-L\w i t o t l IL1L Xt&aH tnspanon *t F c a m Sixes the birth of tie human race dust has erted its baneful effect on civilisation. Some < tiur prehistoric curators <cd because of it, and countie are the deaths which have "crurral since. To-tfcr. the effects of dust on ilie human mechanist alone one of the major problems of the age. Two questions at mice obtrude -.heneehes. Way, after so long, is it still a major praties, and what is the present position ? Ta rise firs: we can only excuse ourselves by pomring out that dusts ar legion in variety, ,,ney m in many ways o h different organs and different Individuals. Their actions are often subtle and insidious, and irretrievable damage is done before the person most concerned even appreciates the attack. Scientific appreciation o f the poten tialities of the different dusts and mixtures of dusts, assessment of their effects, determinetion of appropriate preventive measures and the means of carrying them out, have alt had to wait upon advances in many collateral sciences before wen the full scope of the pro blem could be appreciated. Chemistry, 'physics.  nt The IIkdjcu. Pie s.s asp Cuculak SciM jatesr pathology, bacteriology, clinical medicine,radiology, petrology, microscopy, sociology ami general education have all had to Jx ar a part before the foundations couldJ>e iai<l. Whar then ha* been achieved? Not much, we may say, if man has been busy at this pro blem for 2Q0 years or more, but when one realises that the general state of human know ledge has been such that it was not possible until within the last 100 years to advance be yond the appreciation that dust was harmful, then that the foundations have been truly bid is not an inconsiderable achievement. Ir is not passible within the limits of this paper to survey all the pioneer work which has contributed to this in the past 50 years, even if the writer was competent to do so. The complications and ramifications of the subject and the labyrinths into which inquirers are forced to pendrare, make a critical survey a matter for a team of experts- It is possible, however, to consider the pro blem from the point of view of any one or us who wishes to know what principles emerging from all this work will help him to do the best for his patients, and to advise inquirers of die risks which may be associated with exposure to dust With some diffidence,* therefore, an attempt will be made to set out some rough practical jjenendisatipnr-'riiich may be of help in this way: We are constantly, exposed to dust, but generally if only causes temporary incon venience and is quickly disposed of. The effects on the human body depend on the nature of the dust and, if inhaled, also on its concentration in the air breathed, the median size of the particles, and the existing condition of the chest and lungs. No simple and accurate classification of dusts has yes been evolved, but certain broad distinctions can be made which are useful. Thus we have.:-- (1) Dusts which are systemic poisons, aslead, arsenic, manganese, trinitrotoluene and many others. (2) Irritant or corrosive dusts, as lime, arsenic, chromic acid, the bichromates and many others in varying degrees. (3) Allergic dusts, exposure to which may result in the development of a hyper sensitive state, and cause on- further minimal exposure asthma, rhinitis, urticaria, etc Usually these are due to foreign proteins in the dust, but not always, as, for example, workers with chromic arid and the bichromates who may become hyper sensitive to these chemicals. (4) Carcinogenic .o r cancer-producing dusts, as the dust of pitch, of radioactive materials and of certain ores. (5) Dusts which carry infections such as anthrax, monflia, actinorayces and other fungi. , , f? (6) Non-toxic inorganic dusts, the dusts we commonly think of as " dust." Although dusts belonging to aQ the* groups, except the first, may affect the iunw in some cases seriously, it is the last group which is the most important on thi account, because in it are included all those dusts which exert deleterious effects on the essential put. monary tissues. Included In this group are a great varietr of dusts differing in their physiol and chemi cal characteristics, and these characteristics play an important rale in determining the nature of the local effects produced when in haled into the longs. Although much work has been done on this aspect, however, it is. not yet possible to classify themembers of this group so that the effects of any particular dust may be prognosticated from its physical and chemical characteristics. Of chemical characteristics, solubility or in solubility and the* presence or not of the silica radicle, and of physical characteristics, speri lie gravity, fragility and whether of a fibrous character or not, arc ait believed to have an important Influence on the action of the dust when inhaled. In spite of die'many difficulties resulting from lack of knowledge, certain generalist.dons can be made which are helpful in prac tice, and that, after.,all, is what is required. : if knowledge is to be of practical value as well as-of academic interest. In the fine place, that healthy lungs can cope effectively with appreciable quantities oi dust, but that a& Inorganic dusts, if inhaled in concentration over a period of time, are harm ful, is such an obvious proposition that its importance is liable to be overlooked. The longs, in common with other essential organs of the body, have a large reserve, 10 permit of effective reaction to the demands of disease or of advancing age or of any emer gency, and it is only when this reserve is seriously encroached upon that clinical signs of embarrassment appear. Moreover, the filtering action of the nasal vibrisss and inssages, aided by the moist and ciliated mucous membrane of the upper respiratory tract, to gether with the imiefarigabie efforts of the i/vhefial cells (" dust ceils ") in seizing upon he intrusive dost and transporting it into the lymphatic drainage system, are more than ade quate to cope with the normal average of air borne dust ami with intermittent abnormal concentrations. It stands to reason, however, that the masi effect of daily exposure to a heavy concents* don of even a totally inert dust will wear oat even the most well disposidoned and resp0"* sive mechanism: dust will collect In the 33:53 Tins Medicai. Paess .ccd Gtt e r m SemaatE-vr xiU and sinuses, dliated epithelium :^ped and replaced progressively with less jd.. .a * ----*--1 less efficient cells, become choked and intermittent and uncoa- inflammatory comiitions nay interfere the lymplndc drainage and cause further - .^ feras*r^ 5 % sii.JssVi'` don of dust, and over-action of less areas u>* result in localised etnphy- Ultimately, therefore, such heavy and iiuous exposure to a dust which with less sure is inert, will, however, result in per lai changes and loss of efficiency, which ue manifest in course of time as a chronic hide tendency. It is not easy to deter- to what extent heavy and continuous Re to such inert dusts m j shorten life, rsome intermittent disability does result it be gainsaid. Thus, the generality of dneis lias an excess liability to chronic hills ami other affections of the- upper -atory tract, cement and basic slag |ers nave an excess incidence of upper atory tract affections, and die latter also cesr liability to pneumonia, is mechanical choking ap effect of ex- e over a period to heavy concentrations of organic dust can be demonstrated dime- m young persons with ease after ex- e tor x month or two, i.t, before it is ile for permanent changes to have red. A very slight, but appreciable, dif- impairmenr of the percussion note--less chat associated with diffuse fibrosis---will tsl, and. ou auscultation sticky rales will ard, particularly when, die amplitude of ariou is increased. -*se. effects are not spedile to particular but are common to all inorganic dusts 0/ roup. Neither are they due to any sped- ion of the dust on the lung parenchyma ; ire simply mechanical mass effects of the tad, given the chance, the lungs will dis- r>{ harmlessly in most cases the greater rdon of the dust, leaving no permanent is effect. cme, therefore, to the useful genendi- that inorganic dusts which exert no a* ic action on die lung parenchyma are :3 :ul tn the lungs only because of the mass . .fU - - f conwderaMji exposure to heavy con- tions. Tltis is important because there * '^ .." -^0 insuperable difficulties in preventing '"Oft??? ^conditions, and the Factories Act. 1937, cognisance of it in enacting (Section 47) tty of dust practicable those em- exert com 'iawlTge that many dusts are much ffiSS&S?*! -ssfrfaoasivvce:; we Kknnow that the china aflcr engaged in the trivial operation of removing the minute burrs from china by means of a toy size abrasive wheel and a paste of dint and water, may die in middle life of an intense diffuse tjbrosis of the lungs due to the dine dust.' ' What is the distinguishing characteristic of a dust so potent? The researches of many able tnen all point to the same factor--the presence of the silica radide in the dust. Silica may be present, of course, either " free " as silicon dioxide, SiO , or combined " with many bases as silicates. Proof has been piled upon proof incriminat ing the free silica in so many dusts encoun tered industrially, such as quartz, Sint, sand stone, ganister, etc.; and this, together with evidence of the relatively innocuous character of some common silicate dusts, such as day, have combined to establish the unhappy pre eminence of silica in the free state in this con nection, and to overshadow the possibility that some silicate dusts may be harmful. ' Until a few years ago, therefore, the im pression was widespread that dusts containing free silica were dangerous, and dusts contain ing silica only m the combined state were harmless. Since, however, there is now con clusive proof that one group of silicates, to wit asbestos, are equally as dangerous as tree silica, the above view is not strictly accurate, and we are led to the following generalisa tions: all. dusts containing free silica are dangerous ; dusts containing silica only m the combined form are reiativdy harmless, with the exception of the asbestos group and possibly also other light silicate dusts in which the partide form is fibrous or plate-like and comparatively large. The asbestos group of minerals are mainly silicates of magnesium and iron, and to a less extent calcium*; the particles are elongated anti fibrous, and can split up longitudinally and fray out to an indefinite extent, thus aiding their retention in the bronchioles. It seems likely that this physical characteristic of asbestos, which tends to- immobilise the partides in the lungs, may point to one dis tinguishing attribute of the dangerous sili cates: there seems to be no other feature which will explain-, for.am plerwhy asbestushas disabling and lethal potentialities, whereas a le has not, yet chrysolite asbestos and talc are both magnesium silicates. For practical purposes, therefore, far as present knowledge goes, the dusts which cause serious local effects on the lungs and which may and often do cause disablement and death, are those containing free silica and asbestos : other dusts are harmless in this respect unless, as has been said so happily, " inhaled in insulting concentrations." * Air K n i M * F ew d U M * , ( M o , Iim. ; S iiir a n and A D M OiMAtan. History it W w n ia l Im pam n *. Matin ai Sri. Hojlrti X - .1, p. 4. n tta k u rc k IJ. ; si-W-""rTTv*-- TXV The Medical Px esj ako Cieculae ScprtiaiEST H i siliceous dusts and asbestos also differ from other dusts in that they cause a .diffuse fibrosis of the longs, silicosis and^ssbestoais respectively: that is to say that they irritate and destroy the essential long tissues and ex cite the formation and the proliferation of ordinary scar or fibrous tissue, due, it is gener ally believed, to the very slow solution of the silica. This scar tissue is nbt only useless lumber but also, if there is much of it, exerts secondary harmful effects by blockage of the lymphatic drainage system, `interference with the proper aeration of the blood, production of strain on the right side of the heart, block ing and distortion' of bronchioles by contrac tion of the fibrous tissue, production of localised emphysema, and definitely acts as a bait for the tubercle bacillus. The dust particles must be small, very small, to be dangerous, since they must be. small enough to float in the air and small enough to get past the outer defences of the lungs, at least as far as the smaller bronchioles; There? fore, an industrial process which does not pro-'' ject dust particles into the air in sufficient number and^of^uch size and weight that they will remain floating for a considerable time cannot be dangerous in this way. With the silica dusts the dangerous particle size range is up to 10 microns, with the lighter asbestos dust it is much greater, extending even up to 200 microns. The majority of the particles, however, which get into and sa y in the lungs are much smaller in each case---up to 5 microns in the case of silica dust and up to about SO microns in the ease of asbestos. That is to a y , that the dust p arad e which are in visible to die naked eye are the. important ones: this leads us to the practical point that if a silica or an asbestos process produces visible dust in the air,, then the invisible dust is cer tainly in dangerous concentration. The silicotic .fibrosis is laid down in nodules, whereas that of asbestos is laid down as a cob web. This distinction is important since it is reflected in the typical radiographic appear ances. The explanation lies in the different physical and chemical characteristics of the dusu. The smaller and more stimulating silica particles are taken up by " dust ceils" and. hurried away from the alveoii into the lymphatics and towards the many minute lymph nodes at the junctions of thee*passages, and from thence to the large ones at root of the lung. Unfortunately, many phagocyte succumb and drop their hostile passengers on the way for others to collect the debris, until ultimately, with continued exposure to the dust, the traffic along the lymphatics becomes very congested and at the cross-roads com plete stoppages occur; here we get accumu lations of parades of silica and dead phago cytes, and slowly the'silica dissolves and, in course of cf ac^nodules of- fibrous appear. This explains many things; for ex ample, that healthy lungs can dispose of quite a lot of dust, even silica, for so long as thetraffic can be kept moving no serious effects will result; again, it explains the ill-effects of any antecedent Illness which has damaged the lungs permanently, even if locally; the 01cffects of a coincident infection, for that con gests the traffic in the lymphatics still more; and the danger of a bte infection when silico sis has developed generally and the lymphatic system is already grossly damaged. Also dear are the causal factors underlying the produc tion of massive sQicosis, in which a m of fibrous tissue, the size of a hen's egg, or larger, and constating of. lunumeiabfe small nodules tightfy packed together, appears. * Moreover, the obstruction of the lymphatic drainage by the silicotic nodules accounts also for the great retention of ordinary carbon and other dst in the silicotic lung.* In asbestosis, the course of affairs is dif ferent. With the longer, awkward and often frayed-out asbestos fibres, transportation into the lymphatics is impossible, and Gardner and Cummings have shown that the fibrosis com mences around the-smaller bronchioles where the asbestos particles felt up and become im mobilised. la some way or another, the silica is dissociated and dissolved out and diffuses into the neighbouring tissues, and the fibrous tissue is formed in radiating strands. The lymphatic system does not, therefore, bear the first brunt of the attack, and it may be that the longer potency of the system aids the cobweb like formation o f the fibrous tissue. Within a few weeks of the lodgment of the fibres, the curious beaded and dubbed asbestosis bodies, which- ate altered asbestos fibres, begin to appear. Sines the fibrous tissue formed is the result of the solution of the silica, the extent of the fibrosis, which will develop in any given case, Is limited by the amount of silica immobolised and retained in the lungs : therefore, an post mortem examination one sect all grades of simple silicosis from a few scattered nodules up to massive silicosis occupying over haif of the lungs. Knowledge of the pathology of these two diseases, together with inquiry into Che length of exposure to the dust and the dustiness of the process concerned in any.given case, gives one such an appreciation of the symptoms, signs and clinical course of these diseases ilia: the alleged difficulties in diagnosis mostly vanish. Needless to say, fibrous tissue takes time tc develop, and also the less the concentration oi the dust in the air breathed, the longer ex posure to the dust will be required befon Tilt Medical Press a.vd C ir c u la r Sumzanurr so sts develops to such an extent as to cause Sects appreciable by the patient. is tree that cases of so-called " acute" >>5 and similar cases of asbestosis, due to sure to intense concentrations of dust, occurred with a' fatal outcome in less but usually 15 or more years for the disease to develop, de ling on rbe concentration of dust in the air. this country the average duration of em- ,-ment of a series of 311 cases -who died of without tuberculosis was 35.1 years, ^ - i the average in the different industries ged from 39 2 years in the pottery indtu- to 92 years in the manufacture of scour- powders.. As the effects of additional pre- rive measures become apparent, which also :i matter of years, the average duration of pioyment in fatal eases increases pari pom . "race these diseases are not infections, they - " dry" diseases during most of their use, and since the eari I k symptom is rtnuss of breath, on slight extra exertion, i to the mechanical interference of the rims with the proper aeration of the blood, . se diseases are. slow, silent and insidious, ugh, such as there Is during the devciop- :-nt of the disease, is a slight; dry, morning ugh, which may well be ascribed by the __rj~I_f_. dent to too much smoking. The shortness -- breath, occurring in the ew lyritfj, may also - '- yyyrqqtagpiJ^g^ie put down to getting old too soon and little anion paid to it, except perhaps to move om an upper to a ground floor flat because unting the stairs becomes inconvenient. We have, therefore, as symptoms a little dry lorning cough, a little shortness of breath on :tra exertion, a little " tightness of the chest " >d, with asbestosis cases more than silicosis les, slight pallor with a tinge of cyanosis of ie lips. The finer, more diffuse, fibrosis of 'wstosis is much more effective in musing elective aeration of the blood and ultimately icreased strain on the right side of the heart, <an silicosis. As .the disease progresses, the vntness of breath increases until it is present yen at rest and in the late stages is very ilitressmg: " colds go to the chest " and there ru intermittent attacks of bronchitis; there is am from adhesions and attacks of dry learisy; emphysematous bulbs may burst, losing partial pneumothorax, which is not lacommon in both diseases. In advanced ,i-*!- - **. ubestosis, bronchiectasis due to dragging and distortion by the fibrous tissue Is quite a corn- '* '.V men concomitant, and also the pericardium may be so anchored and dragged upon as to increase materially the dyspncca. Occasionally (more commonly with ashes !- \*tSA Kis) deatii may occur from heart failure with v-n masarea and a nutmeg liver, owing to back a'sm* --**'_**3?. pressure 'i aurosis. on the heart from the extreme As a rule, however, cases are carried off by some infection" which the remaining sound lung tissue is quite insufficient to cope with; not uncommonly tins is a Sow grade broncho pneumonia, but indue .-afar a lobarpneumonia -may precipitate death, and the commonest of all intercurrent and terminal infections is tuberculosis. Some 60 per cent, of sdicoties die from silicosis- with tuberculosis and about 30 per cent, of fatal cases of asbestosis are also associated with tuberculosis. It is not known exactly why this should be, but a superadded tubercular infection is the supreme risk for silicotics and is an added risk for cases of asbestosis. Tuberculosis may appear at any stage, and then the symptoms and signs of that disease tend to mask those of the pneumoconiosis. Wasting; fever and haemoptysis are- not signs of uncomplicated silicosis and asbestosis, although lens of weight does occur very late in both dtsrasrs. The signs of uncomplicated- silicosis and ' asbestosis are by no means obtrusive, and mostclinicians form their own conceptions of them. As would be expected from the pathology, there is a very slight diffuse impairment of the percussion note, which some clinicians recog nise more as a ' slight diffuse resistance on percussion rather than impairment of note. The uniform bilateral character of this change is misleading since it is easy to miss it entirely, there being no normal area for com parison. It must be admitted that it is some what of* a strain attempting to detect this alteration except in advanced cases: it must be detested quickly or appreciation soon dulls and doubt occurs; rapid light percussion, how ever, usually reveds it, and comparison with a normal chest of similar build will restore one's appreciation when duffed, as is likely to happen if two or three eases appear consecu tively amongst a group of workers for examination, Naturally, also, the cheat move ment is restricted, and the breath sounds more distant--usually but not always---and the inspiratory murmur thin and higher pitched. - As already mentioned, these are silent diseases, and therefore the presence of adven titious sounds are indications of temporary superadded intercurrent infections, except in cases with concurrent tuberculosis and those with the bilateral and mainly basal bronchiec tasis seen in very advanced asbestosis. The presence of tuberculosis gives the usual indications, but may make recognition of the dust fibrosis more difficult. Usually, however,. one can determine what may be described as the oasis of tuberculosis m the desert of the diffuse fibrosis. Silicosis and asbestosis may, of course, develop in lungs already diseased, and their occurrence in emphysematous chests :s perhaps the most confusing. The writer  xvi 'T kK MOJICA!. P sESS AXO CntCnAK SC?XStEKT has seta one case in which asbestos existed conjointly with silicosis. Radiographic examination should newer be omitted and. as that great pioneerxWatkinsPitchtord hid down a number of years ago, radiograms must be " technically satisfactory," or doubt and confusion is certain. The value of the radiogram is in confirming the results of occupational and clinical investigation and in estimating the stage of the disease and presence of complications. Both diseases result in the production of abnormal radiographic' shadows, and these shadows reflect the underlying pathological process to a sufficient extent as to make if worth while considering them from this angle. Thus, following exposure to silica but before the formation of nodules of fibrous tissue, all that is seen radiographically is accentuation of the linear markings and increased root shadows; these are not characteristic of silicosis since they occur with, eeposure to many harmless dusts, and also irrespective of any special exposure to dust at ail; they are within normal limits in the absence of ether signs of intrathoraric disease, and no diagnosis of silicosis or of adverse effects of exposure to dust can be made on these appearances. This stage is followed by the appearance of nodular shadows, discrete and fairly uniform in appearance, diffusely scattered, over both lung fields; this reflects the underlying patho logical condition in silicosis and therefore is strong contributory evidence in the diagnosis of that condition. In between the discrete mottling the lung lights up well, the white and dark areas being nicely contrasted. This is important as this contrast is not evident iu a typical radiograph of asbestosis. As the silicosis progresses many changes in the picture may be seen, the nodules become larger, may aggregate into large masses, and areas of increased transiuceacy indicating associated load emphysema may appear. Increased density of the discrete nodular shadows may even be so pronounced as to suggest calcification and also, of course, quite commonly indications of an active tuberculosis process may show. The co-existence of a tubercular infection at any stage modifies the picture in many ways and may obscure the diagnosis especially if, when first seen, the tubercular infection is well developed and the associated silicosis not so well developed. The general effect is to soften, agglomerate and biur over the silicotic mottling, even remote from the original focus. The more evident this softened, blotted and blurred appearance is, the more certain one can be--provided the original mottling is associated with silicosis--of a co-existent tubercular infection, even if the sputum is repeatedly negative. The radrograghied appearances of silicosis are classified in `different ways, but the essen tial point m the radiographic diagnosis of silicosis is the presence of typical nodular mottling. To form a sound opinion on the radtographical appearances of the lungs of an in dustrial worker, it will be agreed, is often a matter o f extreme difficulty or impossible. Apart from shadow's caused by diseases affect ing equally the non-industrial population, which may cause confusion, such as diffuse carcinomatosis, tuberculosis--chronic miliarv or other manifestations--eta, the inhalation ot mixed dusts produces variations in the picture; thus, silicosis in the potter tends to vary radio graphically from silicosis in the sandblaster, which again differs from silicosis in the granite worker; the mixer of boiler insulating materials exposed to ashesras fibre, ground up pitchers (fired earthenware body), kieseiguhr, ground up bricks and other organic and in organic dusts,' shows a radiographical picture which can often be recognised as ratemediarej between these of silicosis and asbestosis. I Again, exposure to fine particulate metal spray (fcg. in zinc metallisation), iron oxide, fine particles projected during electric welding, fine metal partides from shot blasting, and gross exposure to talc, or cement dust--in the absence o f added fiint-y-causcs diffuse mottling la the radiographic pictures in some variety, which is very contusing as in one of these examples does the picture indicate the exist ence of a true diffuse fibrosis in the lung parenchyma. A point of some help l* to regard with grave suspicion a picture in which a diffuse.fish net appearance instead of a diffuse discrete Modulation can be identified, since considerable exposure lo some harmless dusts produces this appearance. In asbestosis, also, the underlying patho logical process suggests the typical radiographical appearances. he diffuse fine cobweb fibrosis in its de veloped stage results in the production of a diffuse fine cobweb- mottling, which at the ordinary distance from the viewing box looks like a tine pinhead mottling; the result of this is that the whole film lights up very badly, and compared with a typical film of sflicosb. the absence of the dark areas between the shadows is striking. This lias been aptly described by Burton Wood as the Hground glass appearance." Typically it is very uniformly distributed and denser towards the bases. As the fibrosis increases, becomes denser and contracts, the typical pinhead mottling tends to disappear u the bases, but there is so difficulty then m interpreting the shadows as the result of gross and massive fibrosis. The obscuration of the pericardial and diaphragmatic outlines witl Ac " shaggy ~ - --4- Th i Medical Pitias aso O bcvlak Sum xsttK T rvn - -- wS*1 - `r i ^ S ^ ^ d i " `T ^ P 7 * ~.*rr iVl* , heart are outstanding at this stage. No dis tinctive gradations in the radiographic appearantes <( the asbestos fibrosis have beta, I'tnerailv accepted as yet, and there is estrone difficulty in evaluating such stages. . ^ The eaect of a supcradded tnbereubr in jection is, as with silicosis, to obscure the .typical mottling, and to render the identifica tion ot the asbestosis element more difficult, more so than in thecase o silicosis. The main features of the radiographic appearances of asbestosis.are, therefore: (1) .general lack of ttanslucency ; (2) diffuse bi lateral pinhead molding, denser at the bases --the ground-glass appearance; and (3) pro gressive obscuration of the diaphragmatic and pericardial outlines-"with the " shaggy heart" The latter is rare in radiograms of simple silicosis. It will be agreed that distinctive radiographic appearances are very strong contribu tory evidence in diagnosis, but that many borderline and difficult cases will be sent for -opinion. This being so, a personal collection uf radiogrnphs of cases, ht which the occupa tional and case histories together with- the post-mortem findings are known, 3 of the utmost value for comparison. In diagnosis, weight should always be given to all three aspects: ( 1) occupational history --nature -of, coucentrat!9xs;of and length of exposure to the dust, remembering that the dusty job may have been many years pre viously ; <2) dinical signs and symptoms; (3) radiographic appearances. With regard to disability in uncomplicated silicosis or asbestosis :.the amount of disability produced obviously depends on the extent of the fibrosis, and the nature of the nan's work. Usually the disaoiliry is remarkably slight until the disease is advanced, and there is no long period of invalidism; the advent of tuber culosis or of some other acute infection quickly doses the scene, since the margin of unaffected and fully functioning lung tissue is too small to cope with added strains of this nature. Treatment is obviously symptomatic and preventive of further infections; if supcradded infections are avoided, life in fair comfort may continue for many years, even in developed cases. The Sbrasts does not develop further after the. retained silica has. exerted .all its potential action, bat in asbestosis the secondary mechanical and other sequels which occur in cases with dense basal fibrosis are an added danger. In this slight survey only some of the more practical, points which appeal to the writer have been stressed. The literature on (he subject of the pneumoconioses is now very extensive and no reference has been made to much invaluable work. A'few recent publica tions only are arbitrarily selected and recom mended below as bring encyclopedic in range and eminently readable, and by acknowledged authorities. of AaaofcA ta& SSOmtm a t AKM M antara. H uttry a4 Ik ta w l Invariante. iW kmi S e ria . B attuta So . 1 P lm taufc. P * . C A A , ^bdjSajtjuida mA HafttL^itqliaiiit, B n ttra (4) Ottta. l i n m , M IA _ 4(J> CleaimeecevhLal SNa t , HBiaiiiaaatit*r J .u__r_t___TVa__a_it_a_a_.__n_o_t_c_h_. ilc O --HU1 Booh Go--i u . l l Yo r* and London, J9KL (4) Da*. Blaulnta, AC. C t a ra iu k Hod. u s . l a t a , -* ---Ck'. .-t- - **j*cai OCCUPATIONAL CANCER AND DERMATITIS By W. J. O'DONOVAN, O.B.E., M-D,, M-R.CP. B iu nu alil. L a llan H w ittl: rty nn io. Shin St ?**fi Soa^icai lor Urolafia I and Shin Oiaouaa. ' ' '-** *'*"* j A^-. g g p ^*HE consideration of cancer of the skin that w occupational origin cannot be a dis- tussion of the causing cause of cancer, for cancer of the skin occurs both in employed and amongst, the unemployed. It occurs in those engaged in modern industry anti in'those en raged m domestic occupations, but m some industries its occurrence is so regular and so frequent that one can properly a y that, but lor the patient's occupation in this industry, the cancer would not have occurred, so that it may be said to be produced by the skin haaard *t A * trade and the more abstract question of the causing cause is left for further research. The registration of deaths was pnt on an organised basis in this country in 1237, but, as regards industrial medicine, death certificates provide no statistics of the necessary facts for coming to any conclusion on this matter. They do not give us the requisite information as to the victim's former employment. Death certi ficates supply no due 33 to the technical pro cess on which a nan may have been antece dently engaged. There is no cross-reference either to cases in his family, grandparents, parents, brothers or sisters. -~v. - T7. * -.-f