The Pneumoconioses

The Pneumoconioses C. S. MORROW, M.B., CH.B. (EDIN.), F.A.C.P.* A. C. COHEN, M.D., F.A.C.P.** CLASSIFICATION GENERALLY caused by mineral dusts, the pneumoconioses are divided into two groups: (1) the harmless or inert, and (2) the harmful or active. 27 The inert pneumoconioses are pulmonary dust conditions that are not associated, despite intrapulmonary dust deposition, with significant disease nor with clinical evidence of respiratory distress. Examples of these conditions of dust storage are the pneumoconioses due to such dusts as gypsum, cement, and the oxides of tin, iron and barium. Since these dusts, when inhaled for years, throw shadows of themselves on the chest roentgenogram, the inert pneumoconioses must be considered in the radiographic differential diagnosis of the harmful ones. The harmful pneumoconioses are pulmonary diseases responding to dust deposition by a specific inflammatory process of the lung, which is essentially a fibrogenic reaction; in addition, respiratory distress due to impaired pulmonary function may occur. These diseases are chiefly caused by the dusts of free silica or silicon dioxide, beryllium, bauxite and asbestos, which is a combined silica or silicate. As the pneumoconiosis due to coal dust does not satisfy either definition, it was not placed in either group. Coal dust causes a mongrel pneumoconiosis in which a significant fibrogenic reaction attributable to its particles is lacking but which is potentially harmful since respiratory distress may occur. Termed coal workers' pneumoconiosis, it will be discussed more fully under the section on pathologic features. This paper will concern itself chiefly with coal workers pneumoconiosis and the dust diseases due to silica, diatomaceous earth (a form of silica), beryllium, bauxite and asbestos, the most common of the silicate dust diseases.

INCIDENCE

The present incidence of clinical dust disease is unknown; its past incidence may be estimated. Statistics, abstracted from Public Health

* Chief, Pulmonary Disease Section, Veterans Administration Hospital, WilkesBarre, Pennsylvania. ** Chief, Tuberculosis Service, Veterans Administration Hospital, Butler, Pennsylvania. 171

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Bulletin No. 259, are available as to the number of workers exposed to dust hazards in 1940. 16 In tabular form, with regard to silica, coal and silica, and silicate dusts, these figures are as follows: Silica Coal and silica Silicate TOTAL. "

. . . .

1,140,000 639,000 1,433,000 3,212,000 workers

The figure on silicate dust probably includes not only asbestos workers but also talc and mica workers. In 1948 Mayer and Rappaport 16 estimated, on the basis of data ohtained from literature of the previous 20 years, the percentages of clinical disease due to the previously mentioned dusts: Silica 25 to 30 per cent Coal and silica. . . . . . . .. 15 to 20 per cent Silicate. . . . . . . . . . . . . .. 10 to 12 per cent

Based on these figures, the incidence of clinical disease in this country due to these dusts can be approximated at 500,000 workers. The statistics given do not include workers in the beryllium and bauxite industries, since the corresponding pneumoconioses were only discovered in relatively recent years. Incomplete data are available on berylliosis and bauxite disease. In a registry of cases of beryllium disease in the United States kept at the Massachusetts General Hospital, Hardy 9 in 1956 reported there were approximately 500 cases. With regard to bauxite fibrosis, only a small number of cases has been reported. From all of this information, it can be seen that silicosis is the most frequent of the pneumoconioses. A more recent evaluation of the prevalence of silicosis might be of interest. In a study of its prevalence in 22 states in this country from 1950 through 1954, Trasko 25 found that silicosis was still an occupational disease of considerable importance. Offered as one explanation for this finding is the lack of universal application of dust control measures. FACTORS IN PNEUMOCONIOSIS

The development of a pneumoconiosis, inert or active, rests upon a number of variable factors, all of which form the basis of the ideal occupational history. Acting independently but having a reciprocal relationship, these factors may be divided into those relating to the dust itself and those pertaining to the individual. To be discussed under dust factors are: (1) the particle size of a dust suspended in the atmosphere; (2) the presence of a mixture of dusts in the atmosphere; (3) the atmospheric concentration of a dust; (4) the duration of dust exposure; and (5) the ability of a dust upon deposition in the lung to provoke pulmonary disease.

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Individual factors to be considered are as follows: (1) inherent variation in individual susceptibility to dust inhalation and deposition; and (2) the health of the individual. Dust Factors

The five factors in this group are of importance for various reasons in the development of pneumoconiosis. The first four determine the amount of dust deposited in the lung. The second factor, the presence of a mixture of dusts, may in addition influence the toxic properties of a dust. With regard to the fifth factor, the ability of a dust to cause pulmonary disease, several pOEsible explanations are mentioned. The particle size of a dust is inversely proportional to the amount of dust deposited in the lung. Spherical particles greater than 10 microns are seldom Eeen in the alveoli of the lung, as they either settle out of the atmosphere or are filtered out by the respiratory tract. Particles less than 3 microns can reach the alveolar spaces in large numbers. An example of such a particulate aerosol is silica. It exists in two structural forms, each of a different size: (1) quartz particles, which are crystalline and of micronic size (1 to 3 microns); (2) the particles of diatomaceous earth (deposits of skeletons of small prehistoric aquatic plants) which are amorphous and of submicronic size (about 0.1 micron). Both types can provoke a pathologic reaction which varies with the size of the particle. The typical nodular fibrosis of silicosis is caused by the micronic quartz particles, while a linear or non-nodular pulmonary fibrosis is the reaction to the submicronic particles of diatomaceous earth. With regard, then, to the fibrogenic action of silica, there apparently is no lower limit of effective size. In contrast to silica is asbestos whose flexible fibel'S even of relatively gigantic size are capable of reaching the air spaces. Fibers as long as 100 microns can be found lodged in the respiratory bronchioles. In addition, apparently only fibers longer than 10 microns are harmful, with those approximating 100 microns the most dangerous. The presence of a mixture of dusts may affect not only the amount of dust deposited in the lung but also the toxicity of the inhaled dust. These effects may be illustrated by tvvo examples. With regard to the first effect calcined gypsum, the inert dust, when suspended in the air with quartz dust, causes a flocculation of dust particles. These conglomerations not only settle out of the air rapidly but also, if inhaled, are large enough to be filtered out of the inspired air by the respiratory tract. Exemplif~ngan effect of altered toxicity is a mixture of powdered aluminum metal and silica particles. The metallic dust forms a rather stable coating over the silica particles which prevents or retards, in the experimental animal if not in man, injury to thelung tissue. The atmospheric concentration of dust is directly proportional to the amount of dust deposited in the lung. It has been ascertained, tentatively at least, that with certain atmospheric concentrations of even a harmful

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dust the lung will probably not be injured, but that above these concentrations it may be damaged. In view of this knowledge, standards of dust concentration in the atmosphere have been introduced in the form of the conception maximum allowable concentration (M.A.C.) of a dust. This indicates the maximum concentration of the dust in the atmosphere considered safe for daily exposure of eight hours over long periods of time. Table 1 shows the M.A.C. of various harmful dusts,! values which are subject to change if warranted by additional experimentation and clinical observation. With respect to silica, the table shows that, the higher its concentration in a dust mixture, the lower is the M.A.C.of the mixture. Omitted from the table have been other danger figures with regard to beryllium: (1) exposure to 25 micrograms per cubic meter of air for any period of time, however short, is considered hazardous; and (2) since cases of berylliosis have occurred in the neighborhood of a beryllium plant as the result of contamination of the atmosphere outside the plant, the limit of concentration in the outside atmosphere has been set at 0.01 micrograms per cubic meter as the average monthly concentration.! The duration of exposure to a dust, which is also a determinant of the amount of dust deposited in the lung, necessary to provoke a pneumoconiosis varies with the type of dust disease and may be exemplified by those due to beryllium and silica. Only a short intensive exposure to beryllium may be necessary to produce a dust disease. 8 In contrast, much longer periods are required with silica: exposure to moderate concentrations of silica will cause a pneumonoconiosis to appear in 10 to 15 years; with heavy exposure, however, the time will be considerably less-only about two years. Knowledge based on clinical observation and animal experiment points to the harmful properties of such dusts as silica, asbestos and beryllium. It is difficult to determine the precise toxicity of an inhaled Table 1 MAXIMUM ALLO'V ABLE CONCENTRATION OF HARMFUL DUSTS IN AIR MAXIMUM ALLOWABLE DUST

CONCENTRATION

Beryllium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.0* Silica: High (above 50% free silica) . . . . . . . . . . . . . . .. 5.0 Medium (5 to 50% free silica) 20.0 Low (below 5% free silica) . . . . . . . . . . . . . . . .. 50. 0 Asbestos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.0

•

* Beryllium concentration is expressed in micrograms per cubic meter. The other dusts are expressed in particles per cubic foot of air.

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dust in man, because the aerosol may consist of a mixture of dusts and because the duration of exposure and the amount deposited in the lung cannot be exactly ascertained. Various theories have been offered in explanation of the toxic action of these dusts. It has been suggested that berylliosis may be the expression of an allergy to beryllium. 26 With regard to the action of silica, a chemical theory, which is only one of several, has been proposed. This assumes that minute particles of silica are dissolved in tissue fluid to form silicic acid, which acts as a toxin to cause a fibrogenic reaction. 'fhere are other hypotheses with regard to all the dusts but not one has been proven. Individual Factors

Not only the dust factors but also individual factors are of significance in the development of pneumoconiosis. The influence of the factor of individual variation, consisting as it does of various intangibles, is difficult to predict. On the other hand, the influence of the factor of personal health status, which takes into consideration discernible disease, may be predictable. With respect to individual variation, it has been observed that the pulmonary response to deposition of a toxic dust varies in different individuals under similar environmental conditions. In some individuals a pneumoconiosis will develop; in others, it either will not develop or it will be less severe. Metabolic and genetic factors, efficiency of nasal filtration, physiologic peculiarities of the lung and of its lymphatic drainage system, physiologic response to climatic factors and others-all have been given as explanations, but none appears to have been substantiated. The health of the individual, particularly that of his respiratory tract, probably plays a significant role. For example, such conditions as chronic bronchitis and pulmonary emphysema by adversely affecting the selfcleansing mechanisms of the respiratory tract will probably hasten the development of pneumoconiosis. The self-cleansing mechanisms of the respiratory tract include trapping of particles above 10 microns in the nasal filters; precipitation of dust particles of similar size in the mucus between the hairs of the cilia in the tracheobronchial tree; and phagocytic action, described later, on dust particles below 10 microns in the alveoli. PATHOGENESIS

If all the dust and individual factors are unfortunately favorable for the development of pneumoconiosis, what happens in the lungs? Under these circumstances, since the dust-inert or harmful- is usually disseminated ,videly and symmetrically through the lungs, the happenings are similarly distributed. In the removal of dust particles from the alveoli, the phagocytes play a primary role. Known as dust cells, they apparently originate in the alveolar walls. After ingestion of the particles, some of the phagocytes

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move to the bronchi and are expectorated through bronchial ciliary reaction and cough. Others enter the lymphatic vessels and are transported to the lymphoid tissue of the lung and the tracheobronchial or hilar lymph nodes. From these nodes they may travel to abdominal lymph glands and scalene nodes, which are accessible to biopsy. Summers23 concluded that strong confirmatory evidence of silicosis can be obtained by x-ray diffraction analysis of the scalene nodes. Still other phagocytes enter the interstitial tissue surrounding the alveoli. As the result of prolonged deposition of high concentrations of dust, these processes are intensified. With regard to the lymphatic system, the lymphoid tissue and hilar lymph nodes may become so obstructed with particulate material that other particles accumulate within the lymphatic vessels. In the case of an inert pneumoconiosis, as well as in the coal workers' hybrid pneumoconiosis, either no reaction or a minimal connective tissue reaction occurs. If the dust is harmful, however, a pathologic reaction ensues in the lung and hilar lymph nodes. In all the harmful pneumoconioses, the fibrogenic reaction is collagenous. PATHOLOGIC FEATURES

There are various degress of severity of the harmful pneumoconioses; these degrees will be referred to as stages through this paper. Use of this term however, does not necessarily mean that one stage must follow the other, but this, of course, may occur. Silicosis and Diatolllite Fibrosis

As mentioned, silicosis usually develops as a result of exposure to silica dust for about 10 to 15 years; with heavy exposure to silica, it may appear in two years-the so-called rapid silicosis. The disease is in the nature of a diffuse nodular fibrosis. Miliary nodulation is seen in the early stages of the disease. Larger nodules are noted in its later stages. These nodules, rounded and whorled, 3 to 5 mm. in diameter and rather discrete, differentiate silicosis from all the other pneumoconioses, The fibrotic reaction not only involves the lungs but also the hilar nodes, which become enlarged. There are in addition two types of modified or pigmented silicoses, siderosilicosis and anthracosilicosis. In both, the reaction to silica is modified by the contaminant dust, which is iron oxide in the former and coal dust in the latter, in that there is a combination of linear and nodular fibrosis. In either case, vvhen the percentage of silica is high, nodulation is more likely to be seen. In siderosilicosis, which occurs in hematite miners, the lung is colored reddish-brown by the oxide. In anthracosilicosis, which affects miners who extract coal from silica-bearing rock, as found in the mines of northeastern Pennsylvania,* the lung is black, owing to deposition of coal dust particularly in the scar tissue. It should be

* The Veterans Administration Hospital, Wilkes-Barre, is located in this part of Pennsylvania.

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pointed out that siderosis, as seen in electric welders of ferrous metals, is a benign pneumoconiosis due to deposition of iron oxide alone. It has been observed for many years that silicosis may progress even after exposure to silica dust has ended. Various explanations have been given. One, sounding quite reasonable, has been suggested by Gross and his associates. 7 They have shown by a photographic method that there is probably a migration of silica out of the whorled nodules to unaffected portions of lung where, presumably, new nodules are formed. Complicated pneumoconiosis or progressive massive fibrosis is due to conglomeration of nodules, the result of fibrosis of intervening lung tissues between these nodules, over large areas of lung. It is seen in both silicosis and modified silicosis, the conglomeration being unilaterally or bilaterally disposed. Infection is usually held responsible for the conglomerate masses. A high percentage of them are considered tuberculous. 5 • 27 That the incidence of pulmonary tuberculosis is increased in silicosis has been known for many years. This has been explained as due either to an increased susceptibility to tuberculosis lO or to a deleterious effect of the dust reaction on pre-existing tuberculous foci. 21 This infection may exist in the form of the conglomerate mass characteristic of the silicotic lung, the so-called silicotuberculosis; or as a chronic infection similar to that of non-silicotic pulmonary tuberculosis, known as tuberculosis with silicosis. In both instances, it is generally difficult to recover tubercle bacilli from the sputum unless there is cavity formation. As has been implied, not all conglomerate masses are of tuberculous origin, and cavitation may occur not only in those that are tuberculous but also in those that are not. In the former case the cavity is caused by the infection, while in the latter case it is regarded as ischemic in origin. Experience with anthracosilicosis at the Veterans Administration Hospital, Wilkes-Barre, Pa., has shown that ischemic cavitation is not an unusual occurrence. IS Clinical differentiation between the two types of cavity can usually be made by examination of the sputum for tubercle bacilli. Other complications of silicosis are emphysema and cor pulmonale. The former is the result of compensatory and obstructive mechanism involving the alveoli; the latter is considered due to pulmonary hypertension secondary to anoxia and vascular changes resulting from pulmonary fibrosis and emphysema or fibrosis alone. The chief cause of mortality is pulmonary insufficiency, with or ,vithout cor pulmonale and tuberculosis. It should be mentioned that there is no convincing evidence that the incidence of carcinoma of the lung is increased in silicosis. Diatomite fibrosis is a form of silicosis caused by the submicronic silica particles of diatomaceous earth. 'l'he length of exposure before the disease becomes manifest is between one and three years. The lung is the seat of linear or non-nodular fibrosis, and the hilar nodes are enlarged. The incidence of pulmonary tuberculosis is apparently not increased.

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Complications are emphysema, cor pulmonale, and episodes of spontaneous pneumothorax. Coal Workers' Pneullloconiosis

This form of pneumoconiosis, as seen in the coal miners of South Wales, has been the subject of much study by the British. The time exposure before the disease becomes manifest is usually about 20 years. Analysis of the coal dust to which these miners are exposed shows that it is unusual for a sample to contain more than 1 per cent free silicia. 12 This is in contrast to the relatively high percentage of silica inhaled by those miners who develop anthracosilicosis. What is the pathologic picture in coal workers' pneumoconiosis? Is this pneumoconiosis due to coal dust or both silica and coal dust? Neither appears to be agreed upon. Gilson and Kilpatrick 6 point out that it is pathologically distinct from silicosis: In the coal workers' lungs, a large quantity of coal dust is collected around respiratory bronchioles in foci, surrounding which are small areas of emphysema; the dust is held in a fine network of reticulin fibrils, fibrosis being scanty. From this description, it can be seen that it is not only distinct pathologically from silicosis but also from anthracosilicosis. It would then appear that coal is the sole pneumoconiotic agent. Pemberton 19 also believes that coal, not silica, is the causative agent, but not because of the morphologic features just described. He states that the deposition of coal dust plays no part in the pathologic or clinical manifestations and that it is merely dust inhalation that produces the chronic bronchitis, emphysema, and bronchospasm seen in high incidence in bituminous coal workers. He prefers the designation "chronic bronchitis of coal workers" to that of "coal workers' pneumoconiosis. " In contrast to this view on etiology is the opinion voiced by King and his associates.l 3 They estimated both total and silica dust in lungs of miners with coal workers' pneumoconiosis and in silicotic lungs of tin miners and granite workers. Finding both more total dust and more silica dust in the coal workers' lungs than in those of the silicotics, they concluded that both total dust and silica contributed to the pneumoconiosis of coal workers. With this findings, why isn't marked collagenous fibrosis present in coal workers' pneumoconiosis unassociated with infection? This question remains unanswered. Whether coal dust alone or both silica and coal dust are responsible for this disease, it is a disease, whatever the terminology. Since the expression, coal workers' pneumoconiosis, is well-established, its use will be continued in this paper. Complicated pneumoconiosis or progressive massive fibrosis occurs in coal workers' pneumoconiosis as it does in silicosis. Once again the formation of large fibrotic conglomerate masses is seen, apparently the result of infection. Here again a large percentage of these masses are considered tuberculous-and on the basis of much evidence, bacteriologic, histologic, and epidemiologic. 2 , 6, 11 Once more, other complications are

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ischemic cavitation, emphysema, and cor pulmonale. The incidence of carcinoma of the lung is not increased. Asbestosis

This disease usually develops after about 15 years exposure to asbestos, which is a hydrated mangesium silicate. With the fibers of asbestos quite large, phagocytosis plays only a minor role in their distribution through the lungs, it being impossible for a single phagocyte to engulf a fiber over 20 microns long. For this reason, the lymph channels are not directly affected by the pathologic process, and involvement of the hilar nodes is slight. The fibrosis, rarely nodular, is seen particularly in the basal portions of the lungs. The pleura are affected early and become thick, with many adhesions obliterating the pleural space. Asbestos bodies, which are noted in the air spaces, are believed to be formed by the deposition of protein and iron salts on the surface of asbestos fibers. These bodies are segmented masses with bulbous ends and vary in color from yellow to orange-brown. They may be found in the sputum, and it is sometimes thought that this finding is diagnostic of the disease. That this thought is in error is made obvious by the fact that, in the pneumoconioses due to other silicates, particularly talc, "asbestos bodies" may be seen in the lung and sputum. The incidence of tuberculosis is increased. 17 Similarly, the incidence of carcinoma of the lung has been found to be higher than in the non-asbetotic population. s , 15, 17 Other complications are bronchiectasis, emphysema, and cor pulmonale. The mortality is chiefly due to pulmonary insufficiency, with or without cor pulmonale, cancer of the lung and tuberculosis. Berylliosis

Berylliosis may be defined as a harmful pneumoconiosis due to the inhalation of the dust of either beryllium itself or the oxide or salts of this metal. According to HardY,9 the ore of beryllium, called beryl, is not known to produce this disease. Exposure to beryllium may result in acute or chronic disease processes and various intermediate formfS. In all of them, tissues other than the lung may be involved. For example, in chronic disease, lesions may be found in the liver, kidney, spleen, lymph nodes and myocardium. This discussion will be limited to the pulmonary abnormalities, which are the principal ones. Acute disease may develop after a few months exposure, or apparently even after a short, intensive exposure to the toxic dust. The pathologic features are those of a non-specific chemical pneumonitis manifested by macrophages and variable degrees of infiltration by chronic inflammatory cells and of intra-alveolar edema. Spontaneous remission may occur as well as transition into the chronic form, but fatalities have been described. Chronic berylliosis, which may apparently occur after an exposure time of several months, is a peculiar form of pneumoconiosis that de-

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velops, as a rule, insidiously and is chronic in its course. It may develop from the acute type. It may even become manifest many years after exposure has terminated; and such an event has given rise to the expression, "delayed case." The initial pulmonary lesion is an intra-alveolar collection of phagocytes which soon undergoes central necrosis. Prominent in the reaction are foreign body giant cells. These granulomatous lesions tend to merge with one another as a fibrogenic reaction occurs. The hilar nodes are enlarged, showing varying degrees of chronic inflammation and fibrosis. The pathologic picture resembles that of sarcoidosis which cannot be differentiated from berylliosis on histologic grounds. The incidence of tuberculosis and cancer of the lung has not been found to be increased. Complications are emphysema and cor pulmonale, which represent the chief cause of mortality. Bauxite Fibrosis

!{nown as Shaver's disease,22 this pneumoconiosis occurs in workers exposed to fumes escaping from electrically heated furnaces in the processing of bauxite for the manufacture of abrasives. These fumes contain silica and aluminum oxide of submicronic size, which are believed to be responsible for the disease process. Clinical and x-ray evidence of the disease has become manifest after three years' exposure. The inhalation of fumes has been followed in a small number of cases by a non-nodular fibrosis of the lungs associated with enlarged hilar nodes, pronounced emphysema, and numerous bullae. There may be repeated episodes of pneumothorax due to rupture of the bullae. 'fhe mortality is chiefly due to pulmonary insufficiency. Table 2 PATHOLOGIC PULMONAHY CHANGES AND COMJlLICATIONR IN PNEUMOCONIOSIS DISEASE

Silicosis Diatomite fibrosis Coal workers' pneumoconiosis

PATHOLOGIC CHANGES

.

. Nodular fibrosis Non-nodular fibrosis

Dust between reticulin fibrils; sparse fibrosis

Asbestosis. . . . . . . . .. . ... Fibrosis, rarely nodular Berylliosis Acute Chronic Bauxite fibrosis

Pneunlonitis Granulomatous fibrosis N on-nodular fibrosis

COMJlLICATIONS

Enlphysema; cor pulmonale; tuberculosis; ischemic cavitation of conglomerate mass E~mphysema; spontaneous pneumothorax; cor pulmonale Emphysema; cor pulmonale; tuberculosis; ischemic cavitation of conglomerate mass F~mphysenla; cor pulmonale; bronchiectasis; tuberculosis; cancer of lung Enlphyserna; cor pulmonale Emphysema; spontaneous pneumothorax

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Table 2 has been prepared to sho\v the basic pathologic features and the complications of the pneumoconioses. DIAGNOSIS

The diELgnosis of benign and early stages of harmful pneumoconiosis is based upon t,vo criteria: (1) an adequate occupational history, and (2) a characteristic roentgenogram of the chest. 'l-'he diagnosis of later stages of harmful pneumoconiosis rests upon the two factors just mentioned and on a third criterion: clinical manifestations compatible with the dust disease itself and its complications, if present. Occupational History

Before the discussion of this subject is begun, Table 3 should be referred to for the listing of the principal industrial operations in ,vhich exposure to harmful dust occurs. Included in the list opposite beryllium is neighborhood contamination, a nonindustrial exposure mentioned previously. The occupational history should concern itself with the dust factors in particular and also with the exact type of work performed by a patient. He can be quite specific about his job, duration of dust exposure, and probably about the nature of the dust; and he undoubtedly has some conception of the atmospheric dust concentration. Obviously, he cannot furnish information regarding particle size and concentration of the dust in terms of particles percubic foot of air. Table 3 PRINCIPAL HARMFUL ])UST OPERATIONS OPERATIONS

DUST

Silica. . . . . . . . . . . . . . . .

Diaiomaceous earth Coal and silica (?) Asbestos Beryllium

Bauxite

.

Mining in silica-bearing rock; building and construction; dressing of granite; quarrying; foundry work; sandstone and flint work; sandblasting; metal grinding; ceramic and glass nlanufacturing; soap powder manufacturing Pottery glazing; quarrying; manufacturiEg of insulating materials, filter-candles, aCEorceut powders, metal polishes, and paints Bituminous mining Ascestos-products manufacturing; installation of insulating material; spinning and weaving of asbestos ,vith other textiles Extraction of metal from ore ;fluorescent lamp, * neon sign and radio tube manufacturing; fluorescent lamp salvage; various metallurgic processes; phases of atomic energy development; neighborhood contamination Manufacturing of synthetic abrasives

* The use of beryllium in fluorescent lamp manufacture has been discontinued.

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The exact type of work is important, since an individual may be employed in an industrial operation posing a dust hazard, but his occupation may be such that he is not exposed to any dust. At times, in the presence of a characteristic roentgenogram, it will be found that a patient is not currently engaged in a hazardous operation. Review of his entire occupational history, however, might reveal that he had been exposed to a dust hazard in the past. In nonindustrial cases of chronic berylliosis, obviously no occupational history can be obtained. In such cases the diagnosis can be made by the combined findings of sarcoid-like lesions by microscopy and of beryllium itself by spectrographic analysis in lung tissue obtained by biopsy. With regard to duration of exposure, it should be determined in years, months, weeks, days and even hours. Inquiry as to the number of hours may appear to be a triviality, but it is not, since short exposure times to beryllium may provoke a dust disease. In addition, the duration of exposure should be correlated with the known exposure times of the various pneumoconioses. For an occupational history to be regarded as adequate, it should be concluded, if possible, that there has been exposure to a sufficiently high concentration of dust for a sufficient period of time and that this dust is capable of producing a pneumonoconiosis. Where the occupational history does not appear to be adequate, a lung or a scalene node biopsy may be helpful in establishing a diagnosis. Chest Roentgenogram

It is obvious that the roentgenogram will reflect the gross morphologic features of the various pneumoconioses. In the diagnosis of a specific pneumoconiosis, an attempt should be made to correlate its known morphologic features with the roentgenographic manifestations. Before such an attempt is made, a knowledge of these manifestations in each of the pneumoconioses is necessary. There are three points worth remembering about the roentgenogram: (1) the film must be properly exposed and developed, since the early changes of pneumoconiosis are· readily sinulated or masked by poor technique; (2) with emphysema, attenuation of the abnormal denAities of pneumoconiosis occurs so as to render them less visible; and (3) the roentgenogram is the most reliable single piece of evidence in establishing the diagnosis of a pulmonary dust condition. In silicosis, modified silicosis, and coal workers' pneumoconiosis, several patterns are visible on the x-ray film, depending upon the stage of the disease and complications. The early stages of the so-called simple or uncomplicated type of these pneumoconioses are characterized by an intensification of the pulmonary striations, diffuse and symmetrical stippling, and widening and increased density of the hilar shadows. The later stages of the simple type are marked by the appearance of discrete pea-sized nodules. Figure 36 shows the chest film of a 37 year old white

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Fig. 36. Nodular silicosis with beginning conglomeration in the right upper lobe.

man exposed for eight years to hard-coal mining through silica-bearing rock; it shows nodular silicosis with beginning conglomeration in the right upper lobe. The complicated type of pneumoconiosis is manifested by the appearance of a single· conglomerate mass or more than one. Attaining large. proportions, the conglomerate mass or masses is or are usually seen in one or both upper lobes; if bilateral, the masses are as a rule symmetrically disposed. t:~ If cavitation, whether of ischemic or tuberculous origin, occurs in the conglomerate mass, a fluid level may be seen within the cavity. A conglomerate mass before and after ischemic cavitation is shown in Figure 37. A shows the chest film of a 66 year old white man who had spent 25 years in the hard-coal mines; it shows bilateral conglomerate masses. In B, taken 12 days later, is seen a cavity, ischemic in origin, with a fluid level in the conglomerate mass on the right. Numerous examinations of his sputa by smear and culture failed to reveal tubercle bacilli. A conglomerate mass before and after tuberculous cavitation is demonstrated in Figure 38. A, shows the chest film of a 70 year old white man who had spent seven years in the hard-coal mines; it shows bilateral conglomerate masses. In B, taken almost seven years later, a left-sided

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A

B

Fig. 37. A, Complicated silicosis. B, Same case 12 days later. Cavity of ischemic origin within conglomerate mass in right lung.

cavity with a fluid level and a bilateral bronchogenic spread, both of tuberculous origin, is evident. Tubercle bacilli were recovered from his sputum by both smear and culture. Antituberculous chemotherapy resulted in regression of the diffusely scattered lesions, but the cavity remained open. Cor pulmonale, ,as in any other disease in which it occurs, is recognize by widening of the pulmonary artery, but hypertrophy of the right ventricle is identified only with difficulty or not at all. Left auricular enlargement, as seen in mitral stenosis, is not present. In diatomite fibrosis, the early stages show an increase in the pulmonary striations, possibly stippling, and hilar node enlargement. In the later stages, massive linear shadows and "hard" or dense, irregular patchy opacities are observed. In asbestosis, the chief roentgen manifestations may be divided into stages depending upon the severity of the disease. In the early stages, there is widespread stippling as well as intensification of the striation-so In the later stages, as a result of the confluence of the stippled densities, the lungs have the ground glass appearance of a diffuse haze. These features are more evident, in both stages, over the base of both lung fields. If emphysema occurs, it may so mask these changes that the roentgenogram will not reveal much of the severe anatomic abnormalities present. Contracting adhesions due to involvement of the pleurodiaphragmatic and pleuropericardial surfaces may cause marked irregularities of the shadows of the heart and diaphragm, a feature which may appear earlier than the other roentgen manifestations. The hilar lymph nodes are not enlarged. Figure 39 shows the chest film of a 52 year old colored man who had been exposed to asbestos dust in an asbestos products manufacturing

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B

Fig. 38. A, Another instance of complicated silicosis. B, Same case 7 years later. cavity within conglomerate mass in left lung and bilateral bronchogenic spread, both of tuberculous origin.

Fig. 39 Fig. 40 Fig. 39. Asbestosis. (Courtesy of Dr. Henry P. Close, Veterans Administration Hospital, Philadelphia, Pennsylvania.) Fig. 40. Chronic berylliosis. (Courtesy of Dr. Harold L. Israel, The Graduate Hospital, University of Pennsylvania, Philadelphia, Pennsylvania.)

plant for nine years. The pulmonary fields show a ground glass appearance, and there is pleuritic involvement at both bases. In berylliosis, the roentgen findings vary depending upon whether the disease is acute or chronic. In acute beryllium pneumonitis, the chest roentgenogram shows "soft" patchy densities throughout both lung fields.

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With resolution of the pneumonia, the regression of the opacities is practically complete. In chronic berylliosis, the roentgenogram varies with the severity of the disease. The early stages are characterized by a wide symmetrical distribution of stippled densities. In the later stages, nodules, smaller than in silicosis, are seen as well as enlarged hilar lymph nodes. Figure 40 is a chest film of a 40 year old white woman; it shows "videspread distribution of small nodules. She had been exposed to the contaminated clothing of her husband who had been employed for five years at a beryllium plant five miles from their home-another form of nonindustrial exposure. The patient died of respiratory insufficiency, and necropsy disclosed histologic changes of berylliosis. Beryllium was found in the lung tissue. In bauxite fibrosis, the roentgenogram shows an increase in linear markings, possibly generalized stippling, and enlarged hilar nodes. Later, dense, irregular patchy opacities may be noted. Emphysematous blebs and localized areas of pneumothorax may also be visible. In benign pneumoconiosis, the radiologic signs depend upon the amount of dust stored in the lung. In the early stages, there is an intensification of the pulmonary striations with stippling throughout the lung fields. With marked deposition of dust, there is a widespread distribution of small nodules. The hilar nodes may be enlarged but not to the extent seen in silicosis. It should be mentioned that the incidence of tuberculosis or carcinoma of the lung is not increased. Table 4 shows the distribution of various pneumoconioses according to their roentgen features. Table 4 ROENTGEN MANIFESTATIONS IN THE PNEUMOCONIOSES

Stippling and increased striations .... Silicoses; coal workers' pneumoconiosis; asbestosis; chronic berylliosis; bauxite fibrosis; diatomite fibrosis; benign pneumoconioses Nodulation Silicoses; coal workers' pneumoconiosis; chronic berylliosis; benign pneumoconioses Conglomeration Silicoses, coal workers' pneumoconiosis "Soft" patchy densities Acute berylliosis "Hard" patchy densities Bauxite fibrosis; diatomite fibrosis Ground glass appearance Asbestosis

Clinical Manifestations

In harmful pneumoconiosis, if sufficiently harmful, the clinical picture either shows the features of the dust disease itself or is a composite of features of the dust disease and its complications, and this picture should be correlated with the roentgenogram. The manifestations of the dust reaction itself depend upon whether the pathologic process is acute or chronic.

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In acute beryllium pneumonitis, there is clinical evidence of a widespread pneumonia with prostration, dyspnea on limited exertion, cyanosis and an irritating cough productive of blood-streaked sputum. There is little or no fever. The disease may progress to a fatal end in several weeks. If death does not occur, there may be a gradual disappearance of symptoms and a concomitant resolution of pneumonia in the succeeding weeks and months. In some instances, there is a slow transition into the chronic form of berylliosis. In the early stages of the chronic forms of pneumoconiosis, clinical manifestations of the dust reaction may be absent. Progression to the later stages may never take place. If it does, respiratory distress manifested by dyspnea on limited exertion or even at rest, the cardinal symptom of impaired pulmonary function, becomes evident owing to pulmonary fibrosis and emphysema, or fibrosis alone. It should be pointed out that pulmonary function cannot be closely correlated with the chest roentgenogram. The accurate evaluation of disability due to pulmonary disease is based chiefly upon the results of physiologic tests. The type of pulmonary complication will have its influence on the clinical picture. Bronchitic infection, as in silicosis and coal workers pneumoconiosis, may produce wheezing, cough and an increase in dyspnea. Cor pulmonale will be preceded by distention of neck veins, enlargement of liver, and peripheral edema. An episode of spontaneous pneumothorax, as in bauxite fibrosis, may produce chest pain and marked dyspnea. Pulmonary tuberculosis, when cavitation occurs, may become manifest by cough and hemoptysis. As in tuberculous excavation, ischemic necrosis of the conglomerate mass is manifested, in the coal miner, by marked cough and tarry black expectoration. Carcinoma of the lung, as in asbestosis, may reveal itself by cough, hemoptysis, and chest pain. In general, most cases of disabling pneumoconiosis occur in elderly silicotics who present a complex clinical picture. This picture is dependent upon the presence of pulmonary fibrosis and emphysema in varying degrees; cor pulmonale; complicating infections, such as bronchitis and pulmonary tuberculosis; and degenerative changes of advancing age. 16 DIFFERENTIAL DIAGNOSIS

Generally, the differential diagnosis of pneumoconiosis is not difficult if it is remembered that the benign type and the early stages of harmful pneumoconiosis are characterized by an adequate occupational history and a characteristic roentgenogram; and that later stages of harmful pneumoconiosis may have, in addition, clinical manifestations consistent with such a diagnosis as well as those of the complications. It is of course conceivable that an individual with an adequate occupational history may develop a disease which mimics pneumoconiosis radiologically. The diagnosis of such a disease will depend on the presence of its own characteristic clinical features.

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The simple type of pneumoconiosis may be simulated by many diseases demonstrating radiologically stippling and nodulation. The following list is not exhaustive: miliary tuberculosis, fungus infections, diffuse carcinomatosis, sarcoidosis, mitral stenosis, polycythemia vera, Hamman-Rich syndrome, scleroderma, lupus erythematosus disseminatus, periarteritis nodosa, and such oddities as pulmonary alveolar microlithiasis 4 and endogenous pneumoconiosis. 28 Complicated pneumoconiosis may be mistaken for carcinoma of the lung, particularly if only one conglomerate mass is present and there is attenuation of small opacities as a result of emphysema. The reverse may also be true, since carcinoma of the lung can occur in silicosis. Usually the problem in complicated pneumoconiosis is the determination of ,vhether tuberculosis is present. Acute beryllium pneumonitis will be confused with diffuse bronchopneumonia of viral origin if a history of exposure to beryllium is not obtained. THERAPY

The therapy of the dust diseases is disappointing, since nothing can cause the regression of a well-established pneumoconiosis, except possibly steroids in chronic berylliosis. Hardy 8 found that such therapy caused regression of roentgen changes and improvement in pulmonary function. In addition, treatment with chelating agents has been suggested as holding out promise for preventing the progression of this disease. 24 r-rhe status of aluminum therapy in the prevention and treatment of silicosis was reviewed in 1956 in a leading editorial in the Lancet. 14 It pointed out that there was much evidence that small quantities of aluminum inhaled regularly would retard, if not actually prevent, silicosis in workers subject to a dust hazard. The article commented, however, that there were apparently no adequate control studies and that, about the same time, a wider and more efficient application of methods of dust control had been instituted. It also cited a control study on the effects of the inhalation of metallic aluminum dust in patients with established silicosis and coal workers' pneumoconiosis. Sixty patients received aluminum and the other 60 an inert dust during the study; the condition of these patients was then evaluated each year up to five years. The results of this study indicated that there was no benefit from the aluminum therapy as reflected by various indices which included the roentgenogram and pulmonary function tests. It would appear that the only efficacious method of treating pneumoconiosis is to prevent it by dust control measures. These should include: (1) exhaust systems to remove dust at its source; (2) general ventilation by rapid change of air in the workroom; (3) wetting of dust by the application of water at the source of the dust; (4) substitution of dangerous

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dust by innocuous materials; (5) isolation of the dusty process; and (6) wearing of protective equipment. The therapy of the chief complications of pneumoconiosis, emphysema, bronchitis, heart failure, cancer of the lung and tuberculosis, should be similar to the treatment of these conditions in the absence of a dust disease. Several remarks with regard to tuberculosis would appear to be in order because of the increased incidence of this disease in silicosis. One of us (C.S.M.) reviewed the results of prolonged chemotherapy in approximately 25 hard-coal miners, patients at the Veterans Administration Hospital, Wilkes-Barre, Pennsylvania, with silicotuberculosis and tuberculosis with silicosis, all of whom had tubercle bacilli in the sputum. A small number of these patients were also treated by surgical procedures on the chest. The chemotherapy consisted chiefly of streptomycin administered intramuscularly 1 gram twice weekly, and isoniazid given in a daily dosage of 300 mg. The results of chemotherapy alone were poor, while those of chemotherapy plus surgery were relatively good. There were nine deaths, the majority of cardiac origin. However, there were a few instances of cavity closure in patients showing tuberculosis with silicosis. Furthermore, several patients with adequate pulmonary function had successful resectional procedures, which included one pneumonectomy. Out of this experience emerges one suggestion. As has been stated, a high percentage of conglomerate masses in both silicosis and coal workers' pneumoconiosis is of tuberculous origin. This fosters the suggestion that, when the tuberculin test is positive, antituberculous chemotherapy be instituted even though tubercle bacilli are not recovered from the sputum. The presence of such a mass, particularly when it is small but gro,ving, would seem to indicate such therapy if only to prevent its further enlargement. SUMMARY

1. The pneumoconioses are classified into two groups: (1) the inert: (2) the harmful. In the inert group are the pneumoconioses caused by such dusts as gypsum, cement and the oxides of tin, iron and barium. In the harmful group are those produced by such dusts as silica, asbestos,. beryllium and bauxite; in addition, the pneumoconiosis caused by coal dust possibly mixed with small amounts of silica should be included in this group. Silicosis is the most frequent of the pneumoconioses. 2. Dust factors and individual factors as determinants of pneumoconiosis, and the pathologic features, diagnosis and differential diagnosis of the disease have been discussed. 3. The therapy of harmful pneumoconiosis and its complications has been considered. 4. Prophylaxis through dust control measures is the only efficacious method of eliminating pneumoconiosis.

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