Airway disease in non-smoking asbestos workers

Our plain-English summary of Airway disease in non-smoking asbestos workers, by K.H. Kilburn, R.H. Warshaw, K. Einstein, et al (Archives of Environmental Health, 1985).

The study

• Authors: K.H. Kilburn, R.H. Warshaw, K. Einstein, J. Bernstein
• Journal: Archives of Environmental Health
• Published: 1985;40(6):293-5
• Cited by: 33 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. 001220).

Abstract

Ninety-seven non-cigarette-smoking white male insulators from the midwestern United States had significantly reduced forced expiratory volume in 1 second (FEV1.0) (P less than .0017) and forced expiratory flow from 75 to 85% of expired volume (FEF75-85) (P less than .042) when compared to a reference population of Michigan male nonsmokers. There were parenchymal opacities with a profusion of 1/0 or greater in 7 and pleural changes in 13 of these 97 nonsmokers. Asbestos, in the absence of cigarette smoke effects and other diseases, appears to decrease airflow, probably by the distortion of small airways (less than 2mm) by peribronchiolar fibrosis. This stiffening of the lung parenchyma protects midflow (FEF25-75) as the fibrosis increases the lung's radial traction on airways larger than 2 mm. This observation contributes to the natural history of physiological impairment due to asbestos disease.

In plain English

This study measured lung function in 416 white insulators exposed to asbestos in six midwestern US cities, focusing on the 97 who had never smoked cigarettes. The workers completed a respiratory questionnaire, had chest X-rays read by a certified "B" reader, and did breathing tests (spirometry). Results were compared with Michigan men of the same smoking category, adjusted for age and height. Compared with Michigan nonsmokers, nonsmoking insulators had significantly lower FEV1, the air blown out in the first second (adjusted difference minus 0.221 litres, p 0.0017). They also had significantly lower airflow near the end of breathing out (FEF75-85, p 0.042). Their forced vital capacity was 0.124 L smaller, but that difference was not statistically significant. Of the 97 nonsmokers, 7 had irregular lung opacities graded 1/0 or greater, 13 had pleural changes, and 21 (21.6%) reported chronic bronchitis. Self-reported exposure intensity did not predict X-ray or breathing-test abnormalities. The authors concluded that the study adds to evidence that asbestos alone produces a small-airway lesion that can be measured physiologically. They noted that none of the nonsmokers had severe asbestosis.

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 study comparing questionnaire, chest X-ray and spirometry findings in asbestos insulators with a reference population of Michigan men, using comparisons specific to each smoking category
• Who was studied: 416 white insulators exposed to asbestos, from Cleveland, Akron, Dayton and Youngstown (Ohio), Detroit (Michigan) and South Bend (Indiana). Of these, 97 had never smoked cigarettes, 172 were ex-smokers and 147 were current smokers. The nonsmokers were aged 19 to 69 years (mean 40.0), were actively employed, and were analyzed in detail. Study dates are not given.
• Exposure: Work as asbestos insulators. No fiber type is named. Exposure intensity was measured only by self-report on the questionnaire.
• Main results:
  • Nonsmoking insulators had significantly lower FEV1 than Michigan nonsmokers (age- and height-adjusted difference minus 0.221 L, standard error 0.070, p 0.0017). Their FEV1 was 92.4% of predicted.
  • Nonsmoking insulators had significantly lower terminal airflow (FEF75-85) than Michigan nonsmokers (adjusted difference in log FEF75-85 minus 0.101, standard error 0.049, p 0.042). Their FEF75-85 was 92.4% of predicted.
  • In nonsmoking insulators, forced vital capacity was 0.124 L smaller (p 0.14) and mid-flow (FEF25-75) was slightly greater than in controls. Neither difference was statistically significant.
  • 7 of the 97 nonsmokers had parenchymal irregular opacities with a profusion of 1/0 or greater.
  • 13 of the 97 nonsmokers had pleural changes.
  • 21 of the 97 nonsmokers (21.6%) had a history of chronic bronchitis.
  • Self-reported exposure intensity did not predict either radiographic or spirometric abnormality.
  • Current smokers and ex-smokers were compared with Michigan smokers and ex-smokers. Even after this subtraction of the smoking effect, they still had greater average decreases in FEF75-85 and FEV1 than the nonsmoking insulators.
• The authors' conclusion: The authors concluded that asbestos, without cigarette smoke effects, appears to decrease airflow, probably by distortion of small airways by peribronchiolar fibrosis. They stated that the study adds to the evidence that asbestos alone produces a small airway lesion that can be measured physiologically.
• Limitations the authors state:
  • None of the nonsmokers had severe asbestosis (profusion 2/2 or greater). The authors said more subjects with more severe asbestosis are needed to complete the analysis.
  • The only measure of exposure intensity was self-reported by questionnaire.

Topics

Medical terms in this study, explained in our Lexicon: Insulator, FEV1, Fibrosis, Parenchyma.

Related studies

• Airway obstruction in asbestos-exposed shipyard workers: with and without irregular opacities — K.H. Kilburn, R.H. Warshaw (1990)
• High prevalence of reversible airway obstruction in asbestos-exposed workers — S. Delpierre, M.J. Delvolgo-Gori, et al. (2002)
• Does asbestos exposure cause airway obstruction, in the absence of confirmed asbestosis? — J. Ameille, M. Letourneux, et al. (2010)
• Does asbestos exposure (asbestosis) cause (clinical) airway obstruction (small airway disease)? — A. Miller, W.N. Rom (2010)
• Adverse effects of asbestos exposure and smoking on lung function — X. Wang, E. Yano, et al. (2006)
• Association between increased small airway obstruction and asbestos exposure in patients with asbestosis — X. Yang, Y. Yan, et al. (2018)

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