Emphysema in silica- and asbestos-exposed workers seeking compensation. A CT scan study

Our plain-English summary of Emphysema in silica- and asbestos-exposed workers seeking compensation. A CT scan study, by R. Bégin, R. Filion, G. Ostiguy (Chest, 1995).

The study

• Authors: R. Bégin, R. Filion, G. Ostiguy
• Journal: Chest
• Published: 1995;108(3):647-55
• Cited by: 59 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It has been established that coal pneumoconiosis and confluent silicosis are associated with emphysematous changes in the lungs. In the present study, we addressed the concept of emphysema in simple silicosis and asbestosis and in workers exposed to these minerals without the pneumoconiosis. The study was done on 207 consecutive workers evaluated for possible pneumoconiosis at Québec Workman Compensation Board, who had a radiographic reading of pneumoconiosis in the category 0 or 1 of the ILO scale, and in 5 control subjects. Emphysema was detected, typed, and graded on high-resolution CT scans by three independent experienced readers. Age, work experience and industry, smoking habits, and pulmonary function test results were analyzed for possible associations. The subjects were 59 +/- 1 years of age and had mineral dust exposure averaging 26 +/- 1 years; 31 were lifetime nonsmokers and the others were either ex- or current smokers. Ninety-six workers were from primary and 111 from secondary industries and did not differ in any parameter. The CT scan readings for emphysema yielded a 63% complete agreement. In lifetime non-smokers, emphysema was seen in 1 of 20 subjects without pneumoconiosis but in 8 of 11 patients with pneumoconioses. In smokers without pneumoconioses, emphysema was present in 55% of patients with silica exposure, but 29% of patients with asbestos exposure but comparable smoking (p = 0.04). Emphysema type was equally distributed among the groups except for more paracicatricial type in confluent silicosis. Regression analyses documented that age, smoking, exposure type, and presence of pneumoconiosis were significant contribution factors. In the workers without pneumoconiosis, age, smoking, and exposure type (silica) were significant. Emphysema related best with FEV1/FVC ratio, MMEF, and DCO reductions. The prevalence of abnormality of FEV1/FVC ratio was two to five times normal and that of reduced DCO two times normal. We conclude that, in our population, there was a significant excess of CT scan emphysema, associated with lung dysfunction, in those with pneumoconioses and in smokers with silica exposure. In the absence of smoking, it took a patient with pneumoconiosis to have emphysema. These changes contributed to the lung function impairment of these subjects with ILO category 0 or 1 pneumoconioses.

In plain English

This study used high-resolution CT scans to look for emphysema in 207 consecutive men referred by the Workers' Compensation Board of Quebec for possible lung disease from long-term silica or asbestos dust. It also included 5 healthy volunteers. The workers' chest X-rays had been read as ILO category 0 or 1. Three readers, who were the authors, scored the scans and fully agreed on emphysema in 63% of readings. Emphysema was seen in 94 patients. Among lifetime nonsmokers, it was found in 1 of 20 without pneumoconiosis and in 8 of 11 with pneumoconiosis. Among smokers without pneumoconiosis, 21 of 38 silica-exposed workers (55%) had emphysema, compared with 15 of 51 asbestos-exposed workers (29%). Patients with emphysema had lower lung function. The authors concluded that dust exposure alone, without smoking or pneumoconiosis, did not increase emphysema. In workers without pneumoconiosis and with comparable smoking, they found silica exposure was associated with more emphysema than asbestos exposure. They noted that the group was selected through compensation referral and that the study was neither cross-sectional nor cohort.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: CT scan study of consecutive workers referred for compensation evaluation, compared across exposure and disease groups. The authors state it is neither a cross-sectional nor a cohort epidemiologic study.
• Who was studied: 207 consecutive workers referred by the Workers' Compensation Board of Quebec to committees in Montreal and Sherbrooke, Canada. All had chest radiographs read as ILO category 0 or 1, and all were men. 111 were silica-exposed and 96 asbestos-exposed, and 31 were lifetime nonsmokers. Five healthy volunteers served as controls. Study dates are not given.
• Exposure: Long-term silica or asbestos dust exposure, measured as years of employment in a silica or asbestos dust work environment. Mean exposure was 26.5 years. Asbestos fiber types are not named. For asbestos, primary industry meant mining and milling, and secondary industry meant transformation, manufacturing, and isolation processing. For silica, primary industry meant mining, milling and stone cutting, and secondary industry meant foundry work.
• Main results:
  • The three readers' complete agreement on CT emphysema readings was 63%.
  • CT scan emphysema was seen in 94 patients.
  • Among lifetime nonsmokers, emphysema was seen in 1 of 20 without pneumoconiosis and in 8 of 11 with pneumoconiosis.
  • Among smokers without pneumoconiosis, emphysema was present in 21 of 38 silica-exposed patients (55%) and in 15 of 51 asbestos-exposed patients (29%), p=0.04.
  • In patients with simple radiographic silicosis, 58% had emphysema on CT, compared with 28% in the internal control group of asbestos-exposed workers without asbestosis.
  • In asbestosis (ILO category 1), emphysema was found in 19 of 37 (51%) in Table 2 (54% in the discussion), compared with 16 of 59 (28%) asbestos-exposed workers without asbestosis. The authors suggested an association of emphysema, airflow limitation and asbestosis.
  • In asbestos-exposed workers without asbestosis, the prevalence of lung function abnormalities suggestive of COPD was about two times normal.
  • Compared with patients without emphysema, patients with emphysema had significantly reduced diffusion capacity (8%, p=0.01), increased residual volume (13%, p=0.01) and decreased FEV1/FVC (8%, p=0.001).
  • In regression analyses, age, smoking, exposure type and presence of pneumoconiosis were significant contributing factors for emphysema.
• The authors' conclusion: The authors concluded that mineral dust exposure alone, without smoking or pneumoconiosis, did not increase the prevalence of emphysema. In lifetime nonsmokers, they found emphysema was a component of the pneumoconioses. For comparable smoking and without pneumoconiosis, silica exposure was associated with a higher prevalence of emphysema than asbestos exposure.
• Limitations the authors state:
  • The population was selected by compensation referral and ILO category 0 or 1 radiographs, and the study is neither cross-sectional nor cohort.
  • The study is affected by healthy and sick worker effects.
  • Reader agreement for emphysema was lower, possibly because the scale was new and lower grades of emphysema were read variably.
  • The comparison with pathology-based and lung function-based reference values is imperfect.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Emphysema, CT Scan, Pneumoconiosis, Silicosis, High-Resolution CT (HRCT), Habit, Pulmonary Function Test (PFT), Asbestos Exposure.

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