Some Current Concepts of the Pneumoconioses

Home , Bagassosis, Berylliosis, Byssinosis, Suberosis

GONZALO E. APONTE, M.D.

Jefferson Medical College, Department of Pathology, Philadelphia, PA 19107

ABSTRACT Selected aspects of the pneumoconioses are briefly reviewed. Coal-workers pneumoconiosis is a complex disease involving multiple pathogenetic factors which can modify the outcome considerably. The development of diffuse pul monary fibrosis in some patients may be determined by immunologic mecha nisms. The risk of neoplasia from occupational exposure to asbestos is great, and the tumors develop irrespective of the extent of pulmonary fibrosis. Chrysotile fibers can be identified frequently in the lungs of urban dwellers without occupational exposure. Chronic berylliosis is truly a systemic disease, and its manifestations include hyperglobulinemia, decreased tuberculin re activity, hyperuricemia and hypercalciuria. The extrinsic allergic pneumonias, secondary to the inhalation of various dusts of vegetable origin, are thought to develop from the deposition of immune complexes within pulmonary blood vessels.

Coal-Worker’s Pneumoconiosis (CWP) paired by disorders such as chronic bron The pathogenesis of coal-workers pneu chitis and fibrocystic disease of the pan moconiosis is complex and not fully under creas; the latter by alveolar proteinosis and stood. It appears that the coal in the dust idiopathic pulmonary microlithiasis. In can serve as the primary etiologic agent, 1969, Buechner and Ansari2 described a but other factors which often play import new variant of acute silicosis in sandblasters ant modifying roles include (1) the silica which they termed silicoproteinosis. There content of the dust, (2) air pollution by were four patients who developed, within agents such as hydrocarbons and nitrogen an average of 4 years after exposure, a oxides, (3) cigarette smoking, (4) co rapidly fatal disease characteristic of acute existent tuberculosis and (5) constitutional silicosis clinically but with histopathologic factors, such as an associated impairment changes of alveolar proteinosis. in the mechanism whereby the respiratory The characteristic lesion in the simple tract clears itself of foreign particles. This (uncomplicated) type of coalworker’s pneu mechanism has two components— (1) mu moconiosis is a multifocal, avascular nodu cociliary “escalator” action of tracheobron lar fibrosis. The reacting cells most prob chial epithelial cells and (2) alveolar clear ably originate from the alveolar membrane ance. The former may be significantly im and not from the blood.3 Coal dust itself 2 2 0 APONTE stimulates the production of some reticulin dose-tumor response curve are crucial ques fibers, but the amount of collagen produced tions which remain unanswered. depends largely on the silica content. Pro An even more important problem is the gressive massive pulmonary fibrosis devel extent of non-occupational exposure through ops in a minority of cases and acid-fast environmental pollution or other sources. bacilli have been demonstrated in about 40 That this can be significant was suggested percent of such patients. Experimentally, by epidemiologic studies reported from simple CWP can be converted into the South Africa in I96020 and from London in massive progressive type by the synergistic 1965,9 in which a significant number of effects of virulent or avirulent tubercle cases of mesothelioma were found to occur bacilli or nonfibrogenic dusts. It is likely, in persons with only “family” or “neighbor but not yet proved, that the “conversion hood” exposure. The subsequent frequent factors” are immunologic.3 demonstration of asbestos bodies in the It is well known that patients with rheu lungs of urban dwellers did not settle the matoid arthritis and co-existent lung dis question since it was not proved that their ease are prone to develop multiple periph cores were invariably asbestos. The search, eral pulmonary nodules which resemble with the light microscope, for asbestos fibers histologically the subcutaneous rheumatoid and fibrils in digested sections of lungs has nodules, as well as a diffuse type of pul yielded positive results in nearly 50 percent monary fibrosis.14 The association with of the cases. The technique, however, is pneumoconiosis, described as Caplan’s syn hampered by a high incidence of back drome, has been noted in coal workers, ground contamination and by the fact that foundry workers and boiler scalers, as well the fibrils less than 1 ¡x in diameter, which as in a few cases of asbestosis. More re are more characteristic of chrysotile asbes cently, the analogue of Caplans syndrome tos (the type most prevalent in the USA), has been reported in a sandblaster with are less numerous and more difficult to scleroderma.22 identify. Specific identification requires techniques such as electron microscopy and A sbestosis electron microprobe analysis. Two studies The risk of malignant neoplasm from oc which utilized the former method have cupational exposure to asbestos is consider been reported recently by Selikoff and asso- able. Among asbestos insulation workers in ciates16 from New York and by Pooley and New York City,15 about one in five deaths others12 from London. In both, a high inci is due to lung cancer and one in 10 to dence of asbestos fibers was found in the mesotheliomas, gastrointestinal neoplasms lungs of urban dwellers. The former group or cor pulmonale. There is a predominance of investigators also has found chrysotile of lower-lobe origin in asbestos-associated asbestos in about 33 percent of samples of lung cancers. Some, but not others,4 have 17 widely used drugs, including antibiotic also found a higher incidence of peripheral agents.11 Precisely what all this means in tumors and of adenocarcinomas. These neo terms of disease for persons who are ex plasms occur with increased frequency even posed non-occupationally perhaps will be in workers with little or no radiologic evi determined by future quantitative studies. dence of pulmonary fibrosis; and the few reported data indicate that the asbestos Berylliosis content of the lungs is quite small (0.6 per The use of beryllium in the United States cent or less).16 Whether or not there exists has increased 500-fold during the past 20 a threshold dose and the nature of the years. Chronic berylliosis, which also can CURRENT CONCEPTS OF THE PNEUMOCONIOSES 221

occur from non-occupational neighborhood ease, develops in persons who work with exposure, develops in only a small percent aluminum abrasives. The fumes contain of those exposed, but the factors which de about 7 percent silica, but typical silicotic termine individual susceptibility are un nodules have not been found in the re known. It is truly a systemic disease inas ported cases and the etiology of the pul much as high concentrations of beryllium monary changes remains obscure. have been found in almost every organ, ex Most cases of pulmonary disease follow cept perhaps the brain, whether or not the ing exposure to aluminum have appeared > tissue shows histopathologic changes. The in the European medical literature. The metal can also be detected in tissue sections particles of aluminum metal powder usually by laser microprobe and emission spec- are larger than 5 /i, but smaller ones ap V troscopy.13 Pulmonary fibrosis characteristi- parently are present in sufficient concen „ cally is most marked in the upper lobes, tration to become a hazard in selected in although the average beryllium content is stances. The pulmonary lesion is an inter > not greater in the upper lobes than in the stitial fibrosis similar to that seen in bauxite others. lung, the most severe changes being located Four additional findings which deserve near the pulmonary hila. * mention because they are relatively fre- Silica does not play a role in the patho > quent include (1) decreased tuberculin re genesis of the massive pulmonary fibrosis activity (without increase in the incidence which may develop in some carbon-elec- * of tuberculosis),19 (2) hyperglobulinemia trode makers. The lesions are thought to in about 40 percent, (3) hyperuricemia,5 result from the additive effects of carbon apparently due to decreased renal clearance dust and low-grade tuberculosis infection. * rather than increased production, and (4) The inhalation of dust from fiberglass *, hypercalciuria (20 percent),19 associated in fewer instances with hypercalcemia or renal plastic reportedly has produced pulmonary " stones, or both. reactions in human beings, and the irritant is calcium carbonate. Other Mineral Dusts Silver-polishers lung was first described Many other types of pneumoconiosis sec- in 1945. The dust inhaled contains iron ’ ondary to mineral dusts have been recog- oxide and metallic silver. The latter com ^ nized,1’18 but there is no space here to re bines with tissue proteins and stains the view them adequately. Silica or silicates tissues black. * are the principal cause of the pulmonary Stannosis results from prolonged inhala fibrosis after occupational exposure to tion of dust or fumes of tin oxide. The graphite, fuller earth, talc and Kaolin particles are deposited in the alveolar septa, ' (china clay), as well as in arc-welder’s subpleurally and around bronchioles and *. lung. blood vessels, but do not elicit much fibrosis. The pulmonary lesions from hematite are Acute exposures to fumes containing cad 1 due to silica modified by the presence of m ium can produce fatal pulmonary edema j iron. It resembles the pneumoconiosis of and chemical pneumonia. The changes in coal workers and involves the upper lobes ' 1 most severely. The serum concentration of cases of chronic exposure consist of moder » inorganic iron is elevated in some patients. ately severe perivascular fibrosis and infil The complications include bronchiectasis, tration with lymphocytes. Proteinuria is a ‘ tuberculosis, and pulmonary carcinoma, common finding and the urine contains t Bauxite lung, also known as Shaver’s dis complexes of cadmium and protein. -V 222 APONTE «r ^ Extrinsic Allergic Pneumonias lung. Relapses are frequent and are prone «, The concept of “extrinsic allergic pneu to occur at variable periods of time after monias”1’ 6>7’10 encompasses most of the re-exposure. Structural changes in the lungs 4 pulmonary reactions reported to occur after have been noted only after prolonged ex- the inhalation of vegetable dusts. The basic posure and have consisted chiefly of an mechanism is held to be the deposition interstitial pneumonia with the inflamma- ♦ within pulmonary blood vessels of immune tory cells predominantly mononuclear. Al complexes consisting of antigen in excess, though the sera of affected persons fre IgG or IgM antibody, and often also com quently contain precipitins against extracts * plement. These deposits elicit acute inflam of bagasse, these are found almost as fre- < mation with or without necrosis, in a man quently in normal unexposed persons. Al ner analogous to the pathogenesis of post though thermophilic Actinomycetes, similar * streptococcal nephritis and lupus nephritis. to those in the moldy hay which causes -* The prototype is farmers lung, which farmer’s lung, are also found in moldy first develops 6 to 10 weeks after exposure sugar cane, the precise source and nature to moldy hay containing the antigen, a of the antigen have not been identified. polysaccharide of actinomycetes. The histo Other disorders in this category include pathologic changes in the lungs vary with bird-breeder’s lung, mushroom-picker’s 1 the stage of the disease. In the early phases, lung, cheese-worker’s lung, pituitary-snuff < there is interstitial infiltration with mono lung, bible-printer’s lung, wheat weevil dis nuclear cells, predominantly lymphocytes, ease, maple-bark disease, suberosis (from but well-defined granulomas are noted in a oak bark) and sequiosis (from red wood A minority of cases (9 of 24 cases in one re dust). A recent addition is detergent-work- _ ported series ). Later, the changes resemble er’s lung,21 and the source of the antigen in sarcoidosis or berylliosis. The presence of the sensitizing detergent powder is said to ^ doubly refractile bodies, probably particles be alcalase, an enzyme from Bacillus sub- J of the inhaled material, has been noted tilis, although this has been disputed lately. in about half of the cases. Although vascu Some also include byssinosis, a hazard in litis is a common finding, the predominant the textile industry, but with less convincing ^ lesion is a non-necrotizing granulomatous evidence. The acute symptoms consist of pneumonia. This fact suggests that another shortness of breath, cough and fever, char- ” “ mechanism, involving delayed-type of hy acteristieally developing on Monday upon ,, persensitivity, may also be operative, al return to work but gradually subsiding though antigen-antibody complexes report later in the week. Continued exposure is ^ edly can produce granulomas.17 About 10 aggravated by smoking8 and gradually leads _ percent of the patients die within six years to an impairment in ventilatory capacity of diagnosis. After withdrawal from expo and irreversible pulmonary changes. How- r sure, 70 percent of survivors become asymp ever, few deaths have been recorded. Al- * tomatic and the others remain dyspneic. though antibodies to antigens of the cotton Characteristically, the dyspnea of patients plant have been found in the sera of many r with bagassosis is severe and out of propor of these patients, desensitization to these <, tion to the physical findings. In the great antigens has not been an effective form of majority of cases, recovery is complete, but therapy. It has not been shown conclusively * ~4 a few have developed chronic pulmonary that bysinnosis is primarily a reaction of t disease with reduction in the maximal hypersensitivity. A view of pathogenesis is < breathing capacity. The functional abnor that some dusts of the textile industry con malities resemble those found in farmer’s tain a substance capable of inducing bron- *

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