Document V33z1gZRaeQ35Gdq7yOkOme4Z

J.951 *1U kh4 * t Ft4 ~u t. im C, tud B^S 4 U -J2 Ar Pneumoconiosis Due to Diatomaceous Earth. CLINICAL AND X-RAY ASPECTS IrcfcjU. "uutaJWt/w*. BrtUi4 'ortr. _ _ J: saitar t r. M lift. i JUnu^ -r- Pnlmii <t vttt. Jto M ***--" I *4 (Mi W "Ef<t Tnfl for u -- otter* ft tka NMMl* J 01 t/mm"1 Old 1MN ** 4 Wl / ism REGINALD H. SMART, M. D., Clinic*! Pxofmor o( Medicine Univenity oi Southern Calilornii, Lo Aagele* WALTER M. ANDERSON, M.D.. Plant Phy.ici.n John.-Manvillc Product* Corporation, Lompoc, California ( t ntIL recently a reasonable doubt has been entertained that diatomaceous earth was . , capable of producing disabling pneumoeo- ~ niosis in human workers. In 1935 Belhtker1 concluded that up to that time, serious pneu moconiosis in man due to the inhalation of kicsel- guhr had not been observed. Actually, three yean prior Legge and Rosenerantz* had reported x-ray evidence of a rather high incidence (68.5%) of "pneumoconiosis due to silica" among a selected group of Mexican worken exposed to diatomaeeous earth. In their paper they classified the x-ray findings under the heading* of "Pneumoconiosis: very early; early; moderately advanced; and ad vanced," but did not define these terms or de scribe the x-ray appearance of the lesions seen on the chest films. The objective of the survey was to determine whether there was an increased incidence of tuberculosis in these Mexican work ers, but no mention of tuberculosis found was made in the final tabulation. No statement was made concerning the incidence of disability, al though, of the 118 workers examined, one was recommended for hospital care and five others for "a change of job." The present investigation was undertaken without benefit of the films made by Legge and Rosencrantx who deserve credit for first calling attention to this problem. We who later observed the x-rays of men work ing in this plant, failed to aee nodular "silicosis'* ns designated in the title of Legge and Roseaentntz' paper. However, we did observe the linear pulmonary change# and also the coalescent lesions which will be described later in this paper. It whs only upon realizing that the inhalation of diatomaceous earth and its processed products causes a different type of reaction in the lungs PrMil4 Mm EWtttftOi Anwil Meeting f tiw WctTttM (xnuirTwtAL MentfAi AMACtATto*. April 34. I0S1. U( Angel*** than does quartz, that we began to make some progress in the understanding of this disease. In 1943 Nordmann* reported six autopsies on individuals employed in the kieselguhr industry in the Luneburger-Heide deposits in Germany. These men had all been engaged in dusty oper ations for periods varying from two to 16 yean. Typical nodular silicosis was reported in each - case. It is probable that the typical silicosis ob served by Nordmann was due to the high quartz (30%) content of this particular deposit.' On x-ray examination of a number of fullers earth workers, Middleton4 in 1936 reported only two cases of slight fibrosis. In 1947 Martin* and his co-workers examined 32 workers exposed for many yean to heavy concentrations of diatomite dust with only three showing mild linear changes. In 1948 Vfgliani and Mottura* reported "several cases of advanced silicosis among worken em ployed in the manufacture of filter candies." In their paper the statement la made that "Gard ner's opinion given in 1940 that amorphous silica is less silicosis-produeing than crystalline silica had contributed largely to the widespread opinion that diatomite dust is not very dangerous to human beings." Gardner's opinion was arrived at after dusting a series of animals with crude diatomaceous earth for a considerable period of time. (At that time he reported haring con siderable difficulty in maintaining high concen trations of dost in the dusting chambers when the humidity was relatively high.) We wish to reiterate that these observations of Gardner have been verified by our clinical experience. We have observed men exposed only to crude distomaeeoas earth (some of them underground) for long periods of time (20 to 25 yean) whose chest x-rays have shown only linear changes, and who have no discernible clinical pulmonary disability. Why then is there this wide difference of opinion concerning (he toxicity of diatomite? There would seem to be At least two possible explanations for this divergence. The first might be the varying composition of natural diatomite deposits as found the world over. In addition to the possibility of contamination of diatomite earth with other minerals such as quartz, clays, etc., it should be emphasized that diatomite de posits are of two general types. Deposits found on the shores of the seas are known as marine diatomite. Material found on the floors of ex tinct inland lakes is classified as fresh water diatomite. There seem to be significant differ* ences in the toxicity for humans of these two different varieties of diatomaceous earth, as will be discussed later. The other explanation may lie in the differences in the manufacturing processes of diatomaceous earth products in various parts of the world and at different times. In this in dustry, significant changes in monufactaring methods have occurred during the past 30 years. Until recently there has been a failure to co ordinate the changes and advances made in the manufacturing processes with comprehensive in dustrial medical studies. These studies should include (1) the mineralogy, petrography, chem istry. x-ray diffraction analyses and particle siz^ distribution of the products involved: (2) ex haustive engineering studies of the industrial operations, working environment and atmos phere: (3) complete medical studies of the work ers themselves, including epidemiological sur veys correlating work history with x-ray, clinical, and cardiorespiratory function studies of the employees, and also with pathological studies of human tissue; and Anally (4), experimental studies on animals with the various diatomaceous earth products. Industrial Uses and Processes 'T'he diatomaceous earth industry is a compara tively recent one, although diatomaceous earth has been used in various wavs since the days of the Roman Empire. In 1870 Nobel invented dynamite which consisted of diatomaceous earth saturated with nitroglycerin. This stimulated the search for diatomaceous earth in Europe, where some rather impure deposits have been worked for the past 60 or 70 years. The largest and best known deposits on this continent are on the Pacific Coast, and have been producing since the turn of the century. Today diatomaceous earth has many uses, some of whfeh are filtering aids, insulation, fillers and extenders, abrasives and polishes, and in ceramics and building materials. In California, where the American diatomaceous earth industry* is chiefly located, it was only after a clinical survey and preliminary animal studies that we began to appreciate the complexity of this problem. In the California industry a majority of workers are exposed to at least three or four qualitatively different types of silica, some of which are apparently quite toxic. Furthermore, there are differences in Cat* I. White male. age 52 years, worked 14 years in quarries. No Symptoms or physical signs. Film shews second degree linocr fibrosis. Cos* 2. Mesican malt, ege 41 years. Worked four yttrs ai tunnel tiln holpor and piling brick, end 21 years in the laboratory. X-ray unchanged sinco 1440 and shows third dogroo tinaar fibrosis, indefinite nodulation, and hilar enlargement. Tuberculin, ceccidioidin end histopUtmin skin tests all positive. Serology for eoccidioidas nagotivo. Sputa and stomach washes repeatedly nega tive on culture end animal Inoculation. VentBatery pulmonary function tests only slightly Impaired. Patient suffered subacute bacterial endocarditis in I4S0 end coronary thrombosis in 1451 from which ho has made good recoveries end is new well and working. '.'y-i&izt&z J ..1^0 *V . rV"-****'* ",**<T*,*'" 'MS-S ::>25T "wi-T-tt; iJt.I . Fig. 3-A. Cm 3. Fig. 3-B. M*iicn *g* 27 y*rt. Woik*d on* y*r <> pck*r nd ( y*n * i*p driver in mitt; 1h* y*n * ch-miit in l*beriory. No tymptomi, d*livrd oi h*Hhy child in I9SI. Skin tutt with coccidieidin, hhto- plmin *nd fubtrculin (tint nd i<ond ilrvngih P.P.B* nd 10 mg. O.T.) *11 g*tiv*. Not* tn 3-4 lh* dv v*lopm*M of mottling in mid-lung fitldt which tiimiUtci tub*rclout infUtrlion. particle nizes within the various products which may be of considerable importance in the patho genesis of this disease. Crude diatomaeeous earth and one of its products known as '`natural pow ders" are apparently much less toxic, clinically, than some of the other forms. The rapidly pro gressive, coalesceut lesions with resulting early disability as reported by Vigliani and Motturs, and which were also seen in California before the inauguration of adequate dust control, were in all probability due to intense exposure to one of the more toxic forms of crystalline silica. This toxicity as previously mentioned may be related not only to the type of crystalline silica, but also to particle size. A similar situation has been ob served in other silica industries, i.e., bauxite fume pneumoconiosis,T and in men exposed to intense concentrations of very small particles of quartz such as have been reported by Sander* and Vorwald.* Properly to understand this disease, it is neces sary to have a basic understanding of the min eralogy, chemistry, and manufacturing processes. Diatomaeeous earth is an amorphous form of silicon dioxide (Si03) and always exists in the form of an opal which is an amorphous hydrated milieu (Si0-.nH-0) or silica and water in chemi cal combination. The manufacturing processes are brieAy as follows: The deposit is explored by test holes to deter mine the location of strata of commercially valuable diatomite, and quarry areas are laid out by use of data thus obtained. Top soil is re moved and crude diatomite is taken out by power shovel and hauled to storage bint. These are actually large shafts or "glory" holes. A tunnel runs from the bottoms of the "glory" holes to the processing plant Crude diatomite is drawn out of the holes through specially designed gates into mine cars. An electric locomotive hauls the can through the tunnel to the processing plant Three types of powders are made: (1) natural. (2) calcined, and (3) flux-calcined. The natural powder is manufactured by drying; milling and air-classifying the diatomite. In the air-classify ing operation impurities are removed as waste. The finished product is packed in 50-pound multi wall paper bags. The ealdned product is made by passing the dried, milled, and airdassifled diatomite through a rotary kiln at temperatures in the neighborhood of 1800* F. The flux-cal cined product is made in the same way except that the diatomite is mixed with a flux or soda ash (sodium carbonate) before it is placed In the rotary kiln. After calcined and flux-calcined products leave the rotary kilna they are again milled, air-classified,'and delivered to packer bins. Coarse and over-size particles removed in the air-classifying operation go to waste. A number of other products are prepared by mixing diatomite with other materials in a me chanical mixer, in an area known as the mortar plant. Weighed amounts of the various ingredi ents are dumped into the mixer and after a def inite period of time the charge is dropped into a bin below the mixer. It is then packed into multiwall paper bags. Various types of bricks containing diatomite mixed with other materials such as clays, asbestos, etc., and heated to high temperatures are also made in this area. -t id ' rj -- -**72 MW. ; 2-18 W msi?-' :&*?/ . . P9 4*A. Casa 4. ' Fi$. 4-8. Some of these manufacturing processes, re sult in rather important physico-chemical changes in the original crude diatomaceous earth. The production of natural powders removes the water held in physical combination or adsorbed by the porous diatoms, but it does not remove the water held in chemical combination. As a result, finished natural powders are still true opals. The simple calcination process produces a slightly different product. Keating the natural powders to 1800* F causes a physico-chemical reaction with the formation of email amounts of Whit* mala, ayi SI yaara. Warbad t and a kali yaart a> a piclar. Adviiad, and lift industry at tlma af Tint film (4-a). No dyapnaa than. All skin taala cam* plately aa^atrra up to 10 mf. O.T. Many sputum ipacimans and itMutk waakaa nafativa an cultura aad animal iaacuUtiaa. Films 4-b lad 4- show martad praynuiat afar cassation of aapaturo. Saaara dyspnaa aa*, fdawsuy function tasts show martad impairmant. Nata location of daasa fibrosis in pariUsr ami in Fip. 4>e aad 4-d, also bullous amphysama in basas and antara-suparior limy fialds. Rf.44X Casa 4. fi*. 4-0. ' VOL a d: cry^ tiss mat for tall Gai bal. a: cor cal 45' arr by tw an di be \v lo jc h: ei tl b i: c d \ i 1 Vou 21, No. 11 INDUSTRIAL MEDICINE and SURGERY Page SIS a different form of silica known as cristobalite, a crystalline silica somewhat more toxic for animal tissue than quartz. Flux-calcination produces a much greater per cent of cristobalite with the formation of a trace of another form of crys talline silica, tridymite, which, according to Gardner,10 is more toxic for tissue than is cristo balite. Some sodium silicate is also formed as a result of flux-calcination. Calcined powders contain 1% to 3% of criatobalite, whereas fluxcalcined powders contain approximately 30 to io'.'c cristobalite and about 1% of tridymite. Thus crude diatomaceous earth, originally amorphous in form, may be partially converted by various manufacturing processes into at least two forms of crystalline silica, and also into small amounts of sodium silicate. Inasmuch as several different products are manufactured and a num ber of these are of heterogeneous composition, we can expect the clinical, radiological, and patho logical manifestations to be variable. The ma jority of the men employed in this industry have had exposures to many or all of the differ ent products, and if pneumoconioses develop, they are apt to be of complex type. . It should be noted that great advances have been made by the manufacturers in dust control in recent years- Like all dusty trades, employee comfort requires continuous efforts to minimize dust, regardless of pathogenicity. With the ad vent of modern methods of dust control, exhaust ing and filtering, working conditions have im proved greatly in this industry. Thus, many of the findings herein reported may have arisen some yean ago under lew favorable circum stances than now exist. Until the studies sug gested above can be completed. It is impossible to relate degree of exposure to incidence of demonstrable disease. We are presenting our clinical experience from six Pacific coast plants (three in Cidifomia, two in Nevada, and one in Oregon) that are current ly processing diatomaceous earth. The present clinical study makes no attempt to determine the incidence of morbidity or mortality in the workers employed in these plants. Such a study would Involve the analysis of thousands of work histories, clinical records and chest x-ray films. A thorough study of such data is being under taken as a joint project of the U.S. Public Health Service, the state Health Departments, and the three operating companies. One of us (.RMS.) has been consultant to these manufacturers for several years and has had an opportunity to do detailed clinical and laboratory studies on ap proximately 100 workers. The authors have re viewed the work histories and chest films on sev eral hundred additional employees. In 1945 Dr. Leroy U. Gardner made .a survey jf the industry and since then an intensive effort has been made to secure post-mortem examina tions on deceased persons who were ever em ployed in these plants. Twenty-two pathological -"laminations have been made since 1933. The pathological data are being correlated with in dividual work histories, chest Aims and clinical and laboratory studies, and will be reported in a later paper. Dr. Gardner instituted a number of animal experiments with various diatomaceous products in 1945. This work was completed and' reported in 1949" by his successor. Dr. Vonvsld. who is currently conducting additional animal experiments with these materials. It has seemed desirable to record our clinical and x-ray obser vations in these workers, after a brief resume of the pathological findings observed in the human cases. Pathology, We abe indebted to Dr, Wm. H. Carnes, of the w Department of Pathology, Stanford Univer sity School of Medicine, for the following brief summary of the pathological changes observed in the lung tissues of 20 workers* employed in this industry: . "The basic pattern of the pathological reaction to diatomaceous earth, described by Gardner in his note on the first seven cases of this series, has been present in aU subsequent cases. This consists of a diffuse thickening of the pulmonary framework which is accentuated in the perivascu lar sheaths and contiguous alveolar walls. The thickening is due mainly to increased cellulsrity and is accompanied by more or less increase in delicate collagenous fibrils. There are conspicu ous numbers of small multinuclear cells. Vari able numbers of dust-laden phagocyte* lie in the alveolar spaces. In IS cases this has been the only type of pulmonary alteration directly referable to dust. "The rest of the cases have shown focal coales cence of the lesions to verious extent. The coa lesced lesions have varied from about 1 cm. in diameter to massive sizes, occupying the greater part of a lobe. The latter have been concentrated chiefly in the upper lobea and in the apices of the lower lobes. The coalescence is accompanied by extensive necrosis and. in the older lesions, by marked thickening and. hyalinization of col lagenous fibers. All four cases in which death seemed attributable to the pneumoconiosis have had extensive lesions of this character. '"The tracheobronchial lymph nodes have shown marked enlargement by massive accumulations of dust-laden phagocytes in those cases with ad vanced pulmonary lesions nnd in soms of them Only tour ( thee* palfeau 4M *lr*ctly < vacMtsfiwixl earth wimnatocic. Twn eO*T will, whs 4iW tots ha4 caalctccnt pulmonary laafeas MW mltV wrth O.E. pnoumocontoai*. 4 to* at the** ah* M awattt aiSmiia. tThta WM lariaborsts* hr th* MuMlimtl bipt**T > w*a w> Wy hltUIxii t4 dMWttil tu*y u MMbM4 by Or. Cmw.1 Th* other MDlem H*4 unImm mt ttw rriup with imp t IS* Hines. Tw* mm t wtryml mkimi I"" eulmoeary nwniwi Mil far (ll ehnnie tuna atoms as* (2) inimmiwii. *fl palfaau wh* ; tiH arise. OlS*r Mias ( inti worst Mnwy Oiramtass twa: cannery inufSctoaey ana; lubeiuule*t*. miliary two. thth.aio aw rue* tuead aneurysm two Ihiatia ena. attr-wwaVrutla anaii p*pie*r ana: auburn* haatcrml aiutocardltia ani caraiaama e( the oaaphatua ana: akull fracture ana. fig. 5-A. Cat* S. Fif. S I. M*iic*n mil*, *9* 41 ytn. W#it*l til yttn in tflihid* qunrrint tnA i'9k* y**rt in qvarriot w*nhguu. T*l*n off work in 1944 boctut# of bilt*r*l uppr (un^finM Infiltration thouykt i b* tubrc*loii* (Fif. S-b). Skin t*sh far fabarculetU potitiv* but otliari nayaliv*. Many ipaeimant tpirta **d itomach laaafu nafalira an cuHura and animai inoculation. Employ** in sanatorium on* y**r and off" work anotlwr y*r and a half. Minimal polar* to dust iinca rotum to work. Not* d*v*!opm*i)t of mauivo coaloHanc* and ompbyMRia tine* 1944. Wotltr now bat dyipnoa and mark*d impairment of function t*t. focal areas of necrosis have occurred like those in the conglomerate lesions of the lungs. "There has been a conspicuous absence of some of the cardinal features of typical silicosis, name ly, the focal, discrete, hyaline nodules and the whorled pattern, of the collagenous fibers. Only one case has shown these typical features of silicosis and his lung ash, unlike the others ana lyzed, contained a high proportion of quartz." Chest X-ray Menrfeiiationi Tt should be emphasized that the majority of 1 men employed in this industry have chest x-rays which show no recognizable abnormalities. Most of the employees, whose films we will show, have been in this work for periods ranging from 15 to 25 years. There are, however, a few notable exceptions. The workers who have developed pul monary x-ray changes ean be divided roughly into two groups: (1) those having pneumoconio sis of linear type, and (2) workers with coales ced or massive lesions. Linear exaggeration and generalized mot tling: The largest number of men whose x-rays showed abnormal chest changes were classi fied as having simple linear exaggeration of the finer bronchovascular pattern of the lungs. We have divided these changes into three groups ac cording to the classification of Sampson and Gardner,11 and have designated them as first, second, and third stsge linear fibrosis or pneu moconiosis for which we use the symbols: F,, P-, and P*. The first stage, or P., has been called "the stage of imagination" or that degree of linear exaggeration of the terminal bronchovascular markings which is just barely recogniza ble on the film and Is often debatable. Stereo scopic films of the very best quality are necessary in order properly to evaluate these pulmonary changes. The second stage, or P*. is a definite linear thickening of the finer bronchovascular structures which is seen stereoscopically to ex tend well out towards the periphery of the lung fields but falls short of "cross-hatching," or "reticulation." and is not at all auggestive of nodulation. The third stage, or P,, has been de scribed as verging on first degree nodulation* or the so-called S, (first stage aillcosis), and some have considered these two groups as syn onymous. However, in this condition there seems to be a place for the designation third degree linear pneumoconiosis (P4), for, when "nodula tion" ocean in this disease, the so-called nodules are seldom as discrete or well defined as is seen in classical silicosis due to quarts. In associ ation with these "linear" changes we have also frequently seen diffuse changes best de scribed as "cross-hatching," "reticulation" or "fine mottling." At times this simulates a fine ground-glass appearance, especially at a distance, but on closer examination is seen to have a fine lacy-like character. Gardner12 described this type of x-ray appearance as a "diffuse mottling" and likened it to the roughened appearance of the external surface of orange peel. We prefer to designate it as a fine mottling, which may be /v*.>V W* . the point of tremendous contraction of the dense opacities towards the hila with the development of concomitant bullous emphysema in the ex treme apices and bases of the lungs. As in Shaver's disease, spontaneous pneumothorax is not infrequent and we have seen it in 10 work ers, and in four of these it was bilateral, ll was either the immediate or a contributory cause of death in three of 20 patients who have died. As might be expected, extensive pleural scars and adhesions are usually seen in the instances of massive coalescent fibrosis. The diaphragms al though flattened are tented, distorted, and markedly restricted in their motion. In some instances the diaphragms are drawn upward by the extreme contraction of the fibrosis and the extensive pleuritis, in others the diaphragms are depressed by the severe emphysema in the bases. /2-/3-5I Clinical Aspects T inear lesions: The workers with linear fibro sis rarely have respiratory symptoms and can be compared to instances of pneumoconio sis due to so-called "inert dusts." Often the R* S-C. greater portion of dust exposure in the linear cases has been out of doors and to crude localized to the itpice* or infraciavicular zones, diatomaceous earth and natural powders. Many of >r may be more generalized in distribution. the men with longexposures in the industry have Amor*3 believes that reticulation "represents the chest x-rays that show only slight evidence of next stage in the slow-progressive advancement linear pulmonary fibrosis (Pi). However, we towards definite nodulation." However, in this occasionally have seen men with prolonged ex disease we have seldom seen reticulation or fine posure to crude diatomaceous earth and natural mottling progress to nodulation even after the powders whose chest films have shown progres lapse of many years. Furthermore, we have seen sion to a third stage (Ps) linear type fibrosis. reticular fibrosis progress to the stage of coales Only rarely do they have respiratory symptoms. cence without passing'through a recognizable Recently have we had opportunity to do ven phase of nodulation. Nevertheless, we have on tilatory pulmonary function studies (spirograms, tare occasions seen workers whose fibrosis can be timed vital capacity, and maximal breathing best described as nodular although the nodules capacity), which will be reported in a later paper. have fuz2y, ill-defined borders and are less dis In the individuals having linear fibrosis we . crete than in quartz silicosis. occasionally have observed localized x-ray Massive os confluent lesions: As in sili changes that simulated super-imposed infection. cosis, we not infrequently have seen massive Only rarely has it been possible to Isolate a opacities develop. These are usually preceded specific bacterium, even after using the most by diffuse, fuzzy, localized mottling, as de sensitive bacteriologic techniques available. In scribed above, rather than by generalized nod sueh cases tuberculin skin tests have usually hat ulation. We have seen coalescence of these 111- not always been positive. When infiltrative or Uefined, fuzzy "mottles" in both the absence and localized mottled lesions have appeared in the the presence of demonstrable infection. Insofar chest films of men showing linear fibrosis of its this disease is concerned, we disagree with minor degree. (Pt, Ps), these infiltrates, which Pendergrass** when he implies that coalescence we formerly had presumed due to tuberculous always denotes associated infection, either con infection, have often shrunk or contracted comitant, or pre-exiating and healed. This will somewhat, especially if exposure to diatooitc be discussed later. The confluent opacities are ceased. usually limited to the infraciavieular and mid In the few patients who have later developed zones of the lungs. The opacities have a ten frank tuberculosis, St has been extremely difficult dency to be localized in the postero-superior seg to demonstrate tubercle badUi before the advent ments of the lobes. These opaque coalescent of cavitation. When cavitation occurs, the re lesions have rarely occurred after comparatively sponse to treatment is poor and not unlike that a short periods of exposure (two to three years), seen in silico-tuberculosis. This is true in spite and sometimes have been noted to become mas of intensive treatment with sanatorium care, sive, and to increase rapidly and occasionally for chemotherapy and collapse procedures. How months (as long as three years) after cessation ever, infiltrates that later underwent cavitation of exposure. They have sometimes progressed to and were proved to be due to. tuberculosis. U U m fj n IY li I 1 ra il'<f 31 il I s *: .. X`- VOL. 2 r -< .. f>T^C%V>r-.*V/V- ; v r*-. * S/ m^-IJL?W -1 Fig. s-a. CeSO 4. FI*. -8. could not be readily distinguished is their pre-cavitary stage from uncomplicated confluent lesions. We have apparently seen a greater in cidence of acute pulmonary infections such as pneumonia and pneumonitis than in the general population, which may be due to the associated emphysema. Furthermore, acute pneumonic processes do not always completely resolve and may leave extensive fibrous scars. Physical find-' ings on chest examination were not abnormal un less infection or emphysema was present COALSSCEXT LESIONS: Of the men whose films showed only linear pulmonary fibrosis, the great majority have pursued a benign course as de scribed above. However, we occasionally have seen individuals who developed linear pulmonary fibrosis that was progressive, and showed a great tendency towards confluence or coalescence and was followed by marked pulmonary, disability and occasionally death. These men often had dyspnea, cough, dull chest pain, and sometimes cyanosis and polycythemia. If expectoration was present, it was usually scant and when combined with gastric washings has been negative for tubercle bacilli on repeated culture and animal inoculation, unless frank tuberculous cavitation was present. Dyspnea was the outstanding symp tom and may develop early and be out of pro portion to what is seen on the x-ray. It was the chief cause of disability. The vital capacity and maximal breathing capacity were diminished, and the breath-hoiding time was shortened. Spirograms showed marked prolongation of ex piration. Unless manifest tuberculosis was pres ent. fever and night sweats were absent and the blood sedimentation rate was usually consistent ly normal, even in the absence of polycythemia. (Polycythemia was rare and usually mild.) Al- Meiicen mala, <{< SO years. Worhed ll'/j yeers ia fix Mcimn lad vmlwiiu end four yeats ia tin labora tory. Tuberculin tlrla torts posittvs, others Mfitm. Developed right spontaneous pneumotharaa In ltdl (Fig. 4-e). Pieced in senetorium but sputum esd gestric lavages negetive te ell tests. Employee left senaterium sflsr ana yaar and resumed nemdusty jab altar tv* years. Infiltration Sncroosod (Fig. t-b| ead sputum become positive in IMt. Patient con fined to sanatorium post three yuan, receiving pneame peritoneum refills, streptomycin, PAS aad Isoaland. Sputum remains pesitlve althaugh cavity is smaller but not closed. Pulmooery function tests ska* only slight impairment. Fig. 6-C. 1T Hr- iri&i 'M.G. //-28-W; 4ti VOL. 21, No. U INDUSTRIAL MEDICINE and SURGERY Pope S17 though infection may play a role in the patho genesis of confluent lesions, we have seldom been able to prove it clinically or pathologically, and m many instances we feel it has been excluded .oth on clinical and laboratory examination, and ..ccasionally by post-mortem studies as will be discussed later. Persons having confluent opacities in the infradavicular or mid-lung fields frequently have de veloped marked bullous emphysema particularly in the pulmonary apices and bases. This was al ways associated with shrinking and contraction of the coalescent lesions. The emphysema oc casionally has resulted in spontaneous pneumo thorax which rarely has been the immediate >ause of death. Unlike the cases of simple linear ribrosis, we have often seen marked progression or increase in the confluent lesions for months and even as long as three years after dust ex posure had ceased. This progression has oc curred in many patients where active infection has been excluded as will be described herein after. In other instances the progression has appeared to halt, especially if the employee was removed from exposure. In these latter cases there often has been some apparent improve ment in the dyspnea. Physical examination revealed markedly im paired resonance over the coalescent areas which usually were located posteriorly. Bronchial breath sounds with fine rales were frequently noted over these opacities. The emphysematous areas gave the usual findings of hyper-resonanee and diminished breath sounds with prolonged ex piration. Although Legge and Rosencrantz re ported finding a rather high incidence (7%) of clubbed fingers, we have never seen frank dubbing of the fingers in our patients. Cor pulmonale has been an important compli cation, especially in those patients with massive coalescent disease. Of 20 workers* who died from one cause or another it was a contributory cause of death in 10. It is a prominent feature in several of the patients who are still under observation. One of us (R.H.S.) has been consultant for several years to four plants processing only fresh water diatomite, and although all workers are x-rayed annually, we have never seen coa lescent lesions develop among these men. The diatomite is subjected to flux-calcination in only one of these plants, but a number of men have been employed there for over 10 years. We have also observed that linear pulmonary x-ray change are found among these workers very in frequently. snd then are only of minor degree (P,). The explanation for this apparent lesser toxicity of fresh water diatomite is not known. The Role of infection f'OALESCENT lesions: Intra-dermal skin tests with histoplasmin, coccidioidin and tuberculin were frequently negative. In several cases hav ing massive coalescent lesions, repeated tests to full dosage with tuberculin (P.P.D. and O.T.) jyere consistently negative. Repeated acid-fast cultures and animal inoculations of combined specimens of sputum and stomach washings have been negative in most of the cases of confluent disease. However, a total of nine patients have developed frank pulmonary tuberculosis, several with cavitation, and a number of these are now in sanatoria. In only one other patient were we able to demonstrate consistently any 'Xne ww mi 9fcuia< i> tm itm rtiwuj u ktx Mr wbml Sarlar life. Rg. 4-0. Cam A. Fig. 4-E. Page Si* INDUSTRIAL MEDICINE and SURGERY November, 19St other micro-organism in the sputum even after intensive study. This was a Friedlander's bacil lus and was thought to be a saprophytic infection during life, and also later at post-mortem exami nation. Fungous cultures of the sputum have been consistently negative. Whenever coccidioidin skin tests proved positive, blood serological stud ies (complement fixation and precipitins) were done and these have always been negative. One worker with coaiescent disease gave a history of Brucella infection and the skin test and blood agglutination were positive. At necropsy no evi dence of brucellosis was discernible in the lungs or elsewhere. In our experience the clinical, laboratory, x-ray, and pathological evidence does not indicate that concomitant infection plays a significant part in the pathogenesis of the coa lesces form of this disease. INFF.CTION IN THE NON-COALESCENT FORMS OF the disease: In workers having linear, reticular or generalized mottled types of fibrosis we have occasionally seen localized apicai or sub-apicai infiltrates which were radiologically compatible with tuberculosis. Tuberculin skin tests have usually, but not always, been positive in these cases, but bucteriologic studies of the sputum and gastric contents have nearly always been negative. Most of these lesions, formerly pre sumed tuberculous, have remained stationary or regressed without treatment. However, in a few instances they have progressed, with the sub sequent development of open tuberculosis. Four patients with tuberculous cavitation responded, at first somewhat encouragingly, to sanatorium treatment. The cavities closed by "blocking," and sputum specimens became negative for a time but subsequently reverted to positive. On the x-ray films these cavities although dosed temporarily by "blocking," (not the most de sirable form of cavity closure), later re-opened. Nevertheless,.we have never previously observed even temporary- "blocking" of tuberculous cavi ties complicating nodular quartz silicosis. Two patients in the necropsy series died of miliary tuberculosis, and another has recently died of progressive phthisis. Dr. Gardner examined the tissues of the patients with miliary disease snd was of the opinion that the pneumoconiosis did not predispose to the tuberculosis. Our consult ing pathologists have not yet reported on our most recent death from tuberculosis. Other complicating infections which we have identified (one each of actinomycosis and chronic lung abscess) have been considered as inter current infections, and as not contributing etio logically to the pneumoconiosis. However, one can not say that the pneumoconiosis did not pre dispose to, or aggravate the infections. Conclusions 1 the inhalation of diatomaceous earth may * produce a distinct type of pneumoconiosis. 2. The inhalation of crude diatomaceous earth and natural powders over a long period of time may produce s benign type of linear pulmonary fibrosis, leading to few if any symptoms and no demonstrable disability. 3. The calcined and fiux-calcined powders may occasionally produce a rapidly progressive pul monary fibrosis or granuloma with massive coa- 1essence, bullous emphysema, extensive pleuritij, cor pulmonale, and not infrequently spontaneous J pneumothorax. 4. Massive coaiescent pulmonary lesions oc casionally have developed is persons whose intra- dermal skin tests were completely and repeatedly negative to full dosage of standardized tubercu lin, and in these cases we have been unable to identify tuberculous infection either during life or at post-mortem with the most sensitive boc- ^ teriologic and histologic techniques that were available. ._ 5. When tuberculosis is superimposed on dia- tomaceous earth pneumoconiosis the infection often pursues a benign coarse nntii cavitation supervenes, then the course seems to be slowly downhill in spite of modern treatment including collapse procedures snd chemotherapy. 6. Fresh water diatomite appears to be much kss toxic for workers engaged in processing this material, even when it is subjected to flux- calcination, than are marine diatomaceous earth products. . ' <1136 W. 6th St, Los Angelos.) References X. Seamen. E.t "Dl Baaktioa **n KuiMbnlaasM *vd di* lll--f *M ziwlmiink* Vlwthtwt ink. SS4. 14*. ItU. L Uses. X. T_ and Ramxauias. Z.< "Oknwltwi and Statin aa Sttaaai* Vr IMataaucaaaa fillian.** Am. J. M. Snti. tZ. 10M. 1MZ. S. NaaaMAM*. M.I "D/ Staabkiasa d# XitMifumabtit**.' VMtat AraA, ML US. IZ4Z. . tXSMIwr. E. L. (ISIS): "Zmdaatrial Pubnanary Pheaie Du# la fahalaaioa at teat wttk Spatial Baferaa* to SIHtmka* Idaan. t 1*. IMS. TOtat iinmianiliartiaa aa tka aSaat at anaad tint. FaDar'a Eartk SHIaatiai Pranatiata at tka IatamtUoaal Caali ina at Canaan, Amu tMnMakn t. IMS. LL.O. Ganava, . 134. ^ f. MaanK. VaUAVa aaS Ckavkcc: "Caanrftatiaa a ratndt tit itaaoa aiSeaUaaa tt da aa preaaatioa dnn* rinduatti*' fraantie da la till** taaalla." La Madlada Ctimt, t. ZZf, INI. I. Vtsuuti aad Maittnui -glatimamun Eattb SMtaala.*. Brit. J. Maet. S, 1M. p. IU.IU. 1P4S. ' t. tun. C. C- aad Hanna. A. la Inn* Ckuia . aiatad nrltk tfea Vuiiultn at Alumina AknUm." /. /nddat. Nap. A TaaiaaL, 1*1144, IMS. S. Saxon. 0. A.! Fcronal connmaicatioa. i. Ttawau, A. i.i ranannl aammnnlaatinn. liStikW. L. V. (19SS) I Ttfcilapy ad Fnaoi AAJ(A. 111. lies. 1L Ganna*. L. D. aad liSNM, H. L.i "Toortk Sana** Lakaiaiaay Symptom* aa SlRcaai*.'* Saaaaaa Lake, Nan Yaffc,- (IMS), pp. 1S1 aad ltd. ? IS. Gaapan. L. U.i -ladoatiy, Tabartnlaai*. SPldoalt. aad flumptnatiUn.** WaHanal Tabaiaaloaia Aaaoa. Naw Yatk <H4S>. p. Tl. .,, 13. Aaaa. Aayava J.l ~Aa ay Atlaa ad SOamia." lad M. WUSaaa * Wllklaa Co. Baltlmata, 1*43. p. tOk. i 1*. Tkaanaian. E. L.: -SlUcaaia aad Aakaataa.** Editad W A. I. Laum. Oadatd Utlvanity Fm, Mam Teik. IMS, Mt U4. m. m If. Vaawata, A. J.: "Olatomaaaana Zutk Fmatmlak. Pmeaadlac* ef tha Ninth laUrnatioaal Coaprtat aa ladua- rial Madiaiaa. Jaka Wrfukt O Saaa Ltd.. BNatoL 1*40. . he pa T the p more or by the r of evalue trial and added to The p; avoided tha case violate t and his j approves that the nent dia evidence evaluate to deter percents basis, r basis. 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