Airway function in lifetime-nonsmoking older asbestos workers

Our plain-English summary of Airway function in lifetime-nonsmoking older asbestos workers, by R. Bégin, A. Cantin, Y. Berthiaume, et al (The American Journal of Medicine, 1983).

The study

• Authors: R. Bégin, A. Cantin, Y. Berthiaume, R. Boileau, S. Péloquin, S. Massé
• Journal: The American Journal of Medicine
• Published: 1983;75(4):631-8
• Cited by: 68 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001706).

Abstract

Previous studies of lung function in asbestos workers have documented airflow limitation in many of the workers, but the specific influence of asbestos exposure could not be clearly differentiated from the effects of the cigarette smoking habit. In this study, airway function was evaluated in lifetime-nonsmoking, long-term workers of the mines and mills of Québec. The 17 asbestos workers in this study had worked for an average of 28 years in the mines and mills of the local asbestos industry and did not have any other respiratory industrial dust exposure. They did not have a history of previous pulmonary disease and did not meet the usual diagnostic criteria for chronic bronchitis, emphysema, or asthma. Seven of the workers met the diagnostic criteria for asbestosis and 10 workers did not. The latter group of workers did not differ from a matched control group except in terms of a higher isoflow volume (p less than 0.05). The workers with asbestosis, however, had a restrictive pattern of lung function, increased isoflow volume, and increased upstream resistance at low lung volumes (p less than 0.01). Lung biopsy in three of the patients with the disease demonstrated peribronchiolar alveolitis and fibrosis with obliteration and narrowing of the small airways. These data on lifetime-nonsmoking, long-term asbestos workers provide further evidence of small airway obstruction associated with asbestos exposure and independent of the smoking habit. This airflow limitation was observed predominantly in workers with a restrictive pattern of lung function associated with peribronchiolar alveolitis. The lifetime-nonsmoking asbestos workers without restrictive patterns of lung function had minimal dysfunction of the peripheral airways.

In plain English

This study measured lung and airway function in 17 older men who had worked an average of 28 years in the chrysotile asbestos mines and mills of Quebec's Eastern townships. Each had smoked fewer than 20 cigarettes in his lifetime. Seven met diagnostic criteria for asbestosis and 10 did not. They were compared with 16 lifetime nonsmokers without industrial exposure, matched by age, height and sex. Workers without asbestosis did not differ from controls except for a significantly higher isoflow volume, which was also raised in workers with asbestosis. Workers with asbestosis had lower lung volumes and diffusing capacity, more rigid pressure-volume curves, and higher upstream airway resistance at low lung volumes. Standard flow-volume measurements did not differ significantly between groups. Lung biopsies from three workers with asbestosis showed inflammation and fibrosis around narrowed small airways, with asbestos fibers and ferruginous bodies. The authors concluded that, without smoking, long-term chrysotile dust inhalation causes minimal small-airway dysfunction before asbestosis is recognized. They concluded that significant airway obstruction afterward is associated with the disease process around the small airways.

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: Cross-sectional comparison of lung function in lifetime-nonsmoking asbestos workers, split into those with and without asbestosis, against matched control subjects; open lung biopsy in three workers
• Who was studied: 17 lifetime-nonsmoking asbestos workers (smoked fewer than 20 cigarettes in their lifetime), average age 57 (range 47 to 70), seen at the Centre Hospitalier Universitaire de Sherbrooke, Quebec, over two years. 7 had asbestosis (Group C) and 10 did not (Group B). Controls were 16 normal lifetime nonsmokers with no industrial exposure or pulmonary disease, matched by age, height and sex (Group A).
• Exposure: Canadian chrysotile asbestos only, in the mines and mills of the Eastern townships of Quebec. Average 28 years (range 7 to 35). The authors describe the workers as heavily exposed in the 1940s to 1960s. An exposure index was based on company work records and a 0 to 3 dust estimate.
• Main results:
  • Workers with and without asbestosis did not differ in years of asbestos dust exposure: 28 plus or minus 2 years in Group B and 27 plus or minus 5 years in Group C. Their exposure index was also similar: 47 plus or minus 7 in Group B and 49 plus or minus 8 in Group C.
  • Workers with asbestosis (Group C) had significantly higher rales scores and chest X-ray scores than workers without asbestosis (Group B). They also had lower total lung capacity, vital capacity and carbon monoxide diffusing capacity.
  • There were no significant differences in lung volumes or diffusing capacity between controls (Group A) and workers without asbestosis (Group B).
  • Maximal expiratory flow rates taken directly from the flow-volume curve did not differ significantly between the three groups.
  • Isoflow volume was significantly higher in both asbestos worker groups (B and C) than in controls (p less than 0.05). Closing volume did not differ.
  • Workers with asbestosis (Group C) had significantly more rigid pressure-volume curves (p less than 0.01) and higher flow rates at high lung volumes (p less than 0.05). They had higher upstream resistances at volumes equal to or below 60 percent of predicted total lung capacity (p less than 0.05). Groups A and B did not differ on these measures.
  • In the seven workers with asbestosis, the authors found three- to fourfold increases in upstream resistance at low lung volumes. This obstruction was not severe enough to significantly reduce the usual spirometric measures, including the FEV1/FVC ratio.
  • Open lung biopsies from three workers with asbestosis showed inflammatory cells and fibrosis around small airways, which were distorted and narrowed. Asbestos fibers and ferruginous bodies were seen in all biopsies.
  • 9 of the 10 workers without asbestosis, and 5 of the 7 with asbestosis, had no symptoms of chronic cough and sputum production.
• The authors' conclusion: The authors concluded that, in the absence of smoking, long-term chrysotile asbestos dust inhalation causes minimal dysfunction of the peripheral airways before asbestosis is clinically recognized. They concluded that significant airway obstruction is thereafter associated with the peribronchiolar disease process, which also restricts lung volumes.
• Limitations the authors state:
  • Upstream resistance was not measured at lung volumes below functional residual capacity, because esophageal pressure measurements below that volume are uncertain.
  • The authors stated that whether this process adds to or multiplies the effects of smoking was not answered by this study.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Habit, Emphysema, Biopsy, Fibrosis.

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• Morphologic features and function of the airways in early asbestosis in the sheep model — R. Bégin, S. Massé, et al. (1982)
• Pulmonary function of nonsmoking female asbestos workers without radiographic signs of asbestosis — X.R. Wang, E. Yano, et al. (1998)
• Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)
• High prevalence of reversible airway obstruction in asbestos-exposed workers — S. Delpierre, M.J. Delvolgo-Gori, et al. (2002)

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