Asbestos and airflow limitation

Our plain-English summary of Asbestos and airflow limitation, by Z. Mohsenifar, A.J. Jasper, T. Mahrer, et al (Journal of Occupational Medicine., 1986).

The study

• Authors: Z. Mohsenifar, A.J. Jasper, T. Mahrer, S.K. Koerner
• Journal: Journal of Occupational Medicine.
• Published: 1986;28(9):817-20
• Cited by: 15 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. 001183).

Abstract

To assess the effect of asbestos on the airways, researchers studied 45 shipyard workers who were lifelong nonsmokers and had asbestos-related abnormalities seen on their chest roentgenograms. Patients with interstitial lung disease, bronchial asthma prior to asbestos exposure, recurrent pneumonias, or significant cardiovascular disease were excluded from the study. In addition to chest films, they had spirometry performed before and after bronchodilator inhalation, lung volumes, diffusing capacity, and arterial blood gases. Forced vital capacity and forced expired volume in one second were normal in all patients. Maximum midexpiratory flow rates (MMFR) were abnormal (MMFR less than 75% of predicted) in 13 patients (29%). Therefore, 29% of lifetime nonsmokers with asbestos exposure exhibited evidence of small airways dysfunction. An abnormal MMFR in these workers may be due, in part, to asbestos exposure and could conceivably indicate a population at risk for pulmonary fibrosis and/or obstructive airways disease.

In plain English

The authors examined 45 male shipyard workers from Long Beach, California, who had never smoked and had asbestos-related changes on chest X-rays. They were drawn from about 400 shipyard workers evaluated from 1980 to 1984. Most had been exposed mainly to chrysotile asbestos, for an average of 17 years. All had pleural plaques, and none showed interstitial lung disease on X-ray. Forced vital capacity (FVC), the FEV1/FVC ratio and diffusing capacity were normal in all 45. However, maximum midexpiratory flow rate, which the authors used to detect small airways obstruction, was below 75% of predicted in 13 of the 45 (29%). These 13 had significantly lower FVC and FEV1/FVC than the other 32, although their values were still normal. The authors wrote that the abnormal results were not readily explained by or correlated with exposure history or other variables. They noted that about 15% of nonsmoking, symptom-free Burbank residents in an earlier population study had such values. The authors concluded that small airways dysfunction in asbestos workers may be partly independent of smoking and may indicate increased risk of future parenchymal asbestosis or obstructive defects.

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 clinical study of lung function in referred workers, with no internal control group. A separate published population study was used for comparison.
• Who was studied: 45 lifetime nonsmoking shipyard workers from Long Beach, California, referred by the Department of Labor. They were drawn from about 400 shipyard workers evaluated from 1980 to 1984. All were male (OCR reads 'make'), with a mean age of 53 plus or minus 11 years. All had pleural plaques and none had interstitial changes on chest X-ray.
• Exposure: Occupational asbestos exposure in shipyards, mostly chrysotile, for a mean of 17 plus or minus 8 years. 19 workers reported heavy exposure and 26 moderate exposure. Exposure was primary (working directly with asbestos materials) in 9 and secondary in 36.
• Main results:
  • Pleural thickening was grade 1 in 32 patients, grade 2 in 10 and grade 3 in 3.
  • 30 of the 45 patients reported breathlessness on moderate exertion, and 22 reported cough and sputum.
  • All 45 had a normal FVC (mean 98 plus or minus 14% of predicted). FEV1/FVC (mean 80 plus or minus 4%) and diffusing capacity (mean 106 plus or minus 18% of predicted) were also normal in all patients.
  • 14 subjects had mild hypoxemia (low blood oxygen) on room air, and 12 had a slightly elevated alveolar-arterial oxygen difference.
  • Maximum midexpiratory flow rate was abnormal (less than 75% of predicted) in 13 of the 45 patients (29%).
  • Of the 13 with abnormal flow, ten had been exposed on a moderate, secondary basis. The remainder had heavy primary exposure; their exact number is lost in the OCR.
  • Two of the 13 had a normal midexpiratory flow rate after inhaling a bronchodilator (isoetharine).
  • Compared with the 32 patients with normal midexpiratory flow, the 13 with abnormal flow had significantly lower FVC and FEV1/FVC (P less than .01).
  • Using a less sensitive cutoff for abnormal flow (Kuperman and Riker), 9 of the 45 patients still showed small airways dysfunction.
  • The small airways dysfunction was not readily explained by or correlated with exposure history or other clinical, X-ray or lung function variables.
  • The authors compared their 29% with data from an earlier study by Rokaw et al. In the nonsmoking, asymptomatic subset of that study's Burbank population, about 15% had flow below 75% of predicted.
• The authors' conclusion: The authors concluded that small airways dysfunction in asbestos workers may be at least partly independent of smoking. They added that it may indicate an increased risk of future parenchymal asbestosis and/or obstructive ventilatory defects.
• Limitations the authors state:
  • The authors noted that the definition of a normal midexpiratory flow result is not perfectly clear, because different authors use different reference methods.
  • The authors noted that the bronchodilator response seen in one patient could reflect ordinary airway hyperreactivity unrelated to asbestos exposure.
  • The authors stated that follow-up studies would be needed to find out whether these early abnormalities progress.

Topics

Medical terms in this study, explained in our Lexicon: Interstitial Lung Disease, Asbestos Exposure, Chest X-Ray, Spirometry, Diffusing Capacity (DLCO), Pulmonary Fibrosis.

Related studies

• Asbestos exposure, cigarette smoking, and airflow limitation in long-term Canadian chrysotile miners and millers — R. Bégin, R. Boileau, et al. (1987)
• Airflow Limitation Increases Lung Cancer Risk in Smokers: The Lifelines Cohort Study — Y. Du, G. Sidorenkov, et al. (2022)
• Respiratory morbidity in a population of French dental technicians — S. Radi, J.C. Dalphin, et al. (2002)
• Evaluation of respiratory effects in miners and millers exposed to talc free of asbestos and silica — D.H. Wegman, J.M. Peters, et al. (1982)
• Longitudinal pattern of reported respiratory symptoms and accelerated ventilatory loss in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1996)
• Lung function impairment as a guide to exercise limitation in work-related lung disorders — J.E. Cotes, J. Zejda, et al. (1988)

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