Chest
Volume 106, Issue 4, October 1994, Pages 1061-1070
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Clinical Investigations: Occupational/Environmental
Airways Obstruction From Asbestos Exposure: Effects of Asbestosis and Smoking

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Objective

To define the apparent steps in developing airways obstruction vs restrictive lung disease in men exposed to asbestos for more than 20 years who had never smoked vs cigarette smokers.

Design

Physiologic signs of asbestosis were studied in cross-sectional age-matched groups of never, current, and ex-cigarette smoking workers.

Setting and participants

The study included 8,720 asbestos-exposed construction and shipyard workers in the United States.

Measurements

FVC, FEV1, FEF25–75, and FEF75-85 were measured by spirometry and total lung capacity (TLC) by planimetry of standard chest radiographs and adjusted for height, age, and duration of cigarette smoking and expressed as percentage of predicted. TLC minus FVC yielded RV. We compared means and mean residuals (measurement minus group mean) expiratory flows and lung volumes in 1,146 men with pulmonary asbestosis age matched to 1,146 without asbestosis who had similar durations of asbestos exposure and to 370 men without asbestos exposure. Next, flows and volumes were regressed against the International Labour Office (ILO) profusion scale of irregular opacities on chest radiographs (PIO) and the duration of asbestos exposure for 1,777 never smokers (NS), 4,550 current smokers, and 2,393 ex-smokers.

Results

Asbestos exposure in NS men decreased expiratory flows and increased TLCs compared with unexposed NS men. Further reductions in flows and FVC and increases RV/TLC with radiographic asbestosis were not statistically significant. As the PIO increased from 1/1 to 3/3, obstruction and air trapping increased significantly but TLC did not.

Conclusions

Asbestos exposure reduced flows and produced air trapping after 20 years in workers who never smoked. Smoking increased these abnormalities.

Section snippets

Methods

The 1,146 men with asbestosis and the 1,146 age-matched asbestos-exposed comparison men were from 8,720 workers studied at 47 sites across the United States from California to Florida. The asbestos exposed men (ILO profusion 0/0 and 0/1) were individually matched for age to men with asbestosis (ILO profusion 1/0 to 3/3) in each smoking category using a computer algorithm. A few current and ex-smokers, older than 65 years, were matched to the next youngest or oldest individual if the match pool

Results

There were 1,146 white men in both asbestos-exposed and asbestosis groups. Each group included 119 who had never smoked cigarettes, 722 current cigarette smokers, and 305 ex-smokers. Groups were compared as means and their pulmonary functions as mean percent predicted horizontally for the effect of asbestos and vertically for effect of smoking (Table 2).

Progressive Functional Impairment From Asbestosis

Asbestos without personal cigarette smoking caused progressive asbestos lung disease. Its course has been approximated from these observations. Analysis by difference in means, differences in residuals (observation minus group mean), and by regression agreed that physiologic abnormalities worsened as asbestosis was recognized and increased in severity on radiographs. First, with asbestos exposure alone, was reduced flow in small airways suggesting obstruction with air trapping as the earliest

ACKNOWLEDGMENT

We are grateful for the assistance of Robert G. Fraser, M.D., Professor of Radiology, University of Alabama, Birmingham, School of Medicine, and Daniel Powers, M.D., Los Angeles, as radiologists and “B” readers. Each read several hundred chest radiographs.

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    Presented, in part, at the Annual meeting, American Thoracic Society, Cincinnati, May 16, 1989.

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