Early effects of asbestos exposure on lung function

Our plain-English summary of Early effects of asbestos exposure on lung function, by G. Jodoin, G.W. Gibbs, P.T. Macklem, et al (The American Review of Respiratory Disease, 1971).

The study

• Authors: G. Jodoin, G.W. Gibbs, P.T. Macklem, J.C. McDonald, M.R. Becklake
• Journal: The American Review of Respiratory Disease
• Published: 1971;104(4):525-35
• Cited by: 111 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. 001362).

In plain English

This study examined lung function in 24 men, aged 35 to 45 on October 31, 1966, from the largest Quebec chrysotile asbestos mining company, with chest X-rays read as normal. They came from an earlier random sample of Quebec mine employees. Exposure was estimated as a dust index: estimated average dust concentration times years of exposure (corrected to a 40-hour week), summed over each job held. Eleven men with an index below 110 were compared with 13 above it. Symptoms were generally infrequent and mild; only 3 men had bronchitis. Static lung compliance (how easily the lungs stretch) was 36 per cent lower in the more exposed group (P less than 0.005). Maximal elastic recoil pressure was 36 per cent higher, but was not reported as significant. Other differences were small; diffusing capacity showed no change. In five more exposed men, expiratory flow was lower at all lung volumes despite greater driving pressure. The authors concluded the findings suggest asbestos dust is another cause of small airway disease. They noted smoking could not be ruled out for some airway findings.

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 current workers divided into two exposure groups, with detailed lung function and lung mechanics testing
• Who was studied: 24 men employed by the largest Quebec asbestos mining company. They were selected from 171 workers aged 35 to 45 years (on October 31, 1966) whose chest radiographs were read as normal. Those 171 came from an age-stratified random sample of 1,069 men studied in 1967 to 1968, out of 6,180 employees of the Quebec asbestos mining companies. Service ranged from six months to 24 years. Lung mechanics were measured in 23 of the 24 men.
• Exposure: Dust exposure in Quebec chrysotile asbestos mines and mills. Each man's exposure was expressed as a dust index. For each job he had worked on, the estimated average dust concentration during working hours (millions of particles per cubic foot) was multiplied by years of exposure (corrected to a 40-hour week), and these products were summed. Indices ranged from very low (less than 10) to medium (110 to 310); none were in the high range. The less exposed group (index below 110, n = 11) had a mean index of 31 and mean exposure of 13 years. The more exposed group (index above 110, n = 13) had a mean index of 161 and mean exposure of 21 years. The more exposed group's average concentration was about 8 million particles per cubic foot (lowest 5.4). No man in the less exposed group averaged above 3.5.
• Main results:
  • Static lung compliance was 0.245 litre per cm H2O in the less exposed group and 0.157 in the more exposed group, a 36 per cent difference that was significant (P less than 0.005). Maximal elastic recoil pressure was 28.3 versus 38.4 cm H2O (+36 per cent); this difference was not marked as significant.
  • Five men in the higher exposure group had maximal elastic recoil pressure above 35 cm H2O, compared with one man in the low exposure group. Most subjects' static elastic properties fell within the normal range.
  • Other group differences were generally small (under 20 per cent). The more exposed group had lower lung volumes (vital capacity 4.05 versus 4.37 litres, -7 per cent). It also had larger FEV1/FVC (81 versus 78 per cent) and larger maximal midexpiratory flow (3.91 versus 3.49 litres per second). The authors described these as changes in the direction of restrictive disease.
  • Of the measurements plotted against dust index, only static compliance appeared to show a consistent relationship with dust exposure. Vital capacity and single breath diffusing capacity did not.
  • In 5 more exposed subjects (13, 17, 18, 19 and 21), FEV1 and FEV1/FVC were within normal limits. Even so, maximal expiratory flow was less throughout the range of lung volume despite greater driving pressure. The authors took this to suggest intrabronchiolar or peribronchiolar rather than interstitial changes.
  • Diffusing capacity showed no change between groups (single breath diffusing capacity at rest 31.9 in both groups).
  • Respiratory symptoms differed little between the groups and were generally infrequent and mild. Only 3 men in the total sample had bronchitis, and one man (in the least exposed group) had basal crepitations.
• The authors' conclusion: The authors concluded that, in men with normal chest films, asbestos dust exposure produced measurable effects on lung mechanics before symptoms, radiographic changes or other lung function changes appeared. They stated that the findings suggest exposure to asbestos dust is another cause of obstructive disease of small airways.
• Limitations the authors state:
  • The authors could not say with certainty that the high upstream resistance in subjects 13, 18, 19 and 21 was unrelated to cigarette smoking. All four had smoked 15 or more cigarettes a day for 20 years or more.
  • Static recoil measurements cause some subject discomfort and demand high cooperation. The authors said it would be unrealistic to use them to monitor exposed workers.
  • Frequency dependence of compliance was not measured. The authors said it would have been of interest for small airway disease.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure.

Related studies

• Ethnic differences in lung function: evidence for proportional differences — C.E. Rossiter, H. Weill (1974)
• Lung function impairment as a guide to exercise limitation in work-related lung disorders — J.E. Cotes, J. Zejda, et al. (1988)
• The relative importance of clinical, radiological and pulmonary function variables in evaluating asbestosis and chronic obstructive airway disease in asbestos workers — G.M. Regan, B. Tagg, et al. (1971)
• The health of chrysotile asbestos mine and mill workers of Quebec — J.C. McDonald, M.R. Becklake, et al. (1974)
• Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1993)
• Low exposure to asbestos. Gas exchange in ship pipe coverers and controls — R.L. Murphy, E.A. Gaensler, et al. (1972)

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