Chest
Volume 108, Issue 3, September 1995, Pages 647-655
Journal home page for Chest

Clinical Investigations: Occupational/Pulmonary Function
Emphysema in Silica- and Asbestos-Exposed Workers Seeking Compensation: A CT Scan Study

https://doi.org/10.1378/chest.108.3.647Get rights and content

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 nonsmokers, 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.

Section snippets

Subjects

The 207 patients of the study were consecutive subjects referred to our two committees in Montréal and Sherbrooke by the Workers' Compensation Board of Québec for diagnosis of possible lung disease associated with long-term exposure to mineral dusts. On request by a worker claiming possible occupational lung disease, the Board refers all claimants to the nearest committee, without any winnowing process. Their chest radiographs were read by the three-member committees in the International Labor

RESULTS

The anthropometric and clinical data presented in Table 1 documented that distribution of exposed subjects was balanced among exposure type, industry type, and smoking index (no significant differences by χ2 or ANOVA statistics). There were small differences in age, the asbestos-exposed subjects being slightly older, and those with asbestosis having restrictive lung function changes. Separate analyses of primary or secondary industry workers documented changes in the same direction, with lower

Potential Sources of Bias

Our study has the bias of a population selected on the basis of referral for possible Workman's Compensation and on the ILO category 0 or 1 chest radiographs. It is neither a cross-sectional nor cohort epidemiologic study. The criterion ILO category 0 or 1 chest radiograph was used to avoid the subjects with the most advanced silicosis, in whom emphysema is a well-accepted complication21,22 and contributes to the worker's disability. The population of this study is fairly representitive of the

CONCLUSION

In Workers Compensation Board-referred subjects with category 0 or 1 pneumoconiosis, we found a significant excess of CT scan emphysema, associated with lung dysfunction. Prevalence of emphysema was increased in those with pneumoconioses and in smokers with silica exposure. These changes contributed to the lung function impairment of these subjects. In lifetime nonsmokers, emphysema was a component of the pneumoconioses. Simple mineral dust exposure, in absence of smoking, pneumoconiosis, or

REFERENCES (34)

  • BéginR et al.

    CT scan in the early detection of silicosis.

    Am Rev Respir Dis

    (1991)
  • International Labor Organization/University of Cincinnatti. International classification of radiograph of...
  • BéginR et al.

    Computed tomography in the early detection of asbestosis.

    Br J Ind Med

    (1993)
  • Task force on occupational respiratory disease (G. Ostiguy, chairman). Health and Welfare Canada. Ottawa: Canadian...
  • SnedecorGW et al.

    Statistical methods.

    (1967)
  • AuerbachO et al.

    Relation of smoking to emphysema.

    N Engl J Med

    (1972)
  • Cited by (76)

    • Silicosis: An Update and Guide for Clinicians

      2020, Clinics in Chest Medicine
      Citation Excerpt :

      One study using chest computed tomography (CT) found emphysema in silica-exposed workers who had smoked as well as in nonsmoking workers with radiographic evidence of silicosis based on ILO classification. A paracicatricial pattern of emphysema was noted in association with confluent silicotic opacities.69 Studies in South African gold miners found evidence of a dose-response relationship between increasing cumulative silica exposure and airflow obstruction in both smokers and nonsmokers.67,70

    • Imaging of Occupational Lung Disease

      2016, Radiologic Clinics of North America
      Citation Excerpt :

      In addition, CT also better demonstrates surrounding paracicatricial emphysema (Fig. 4). Interestingly, silica has been shown to be a risk factor for the development of emphysema independent of smoking.31,32 CT scoring of emphysema and extent of air trapping have been shown to correlate with PFTs.33,34

    View all citing articles on Scopus

    Supported by MRC Canada.

    View full text