Progression of asbestos effects: a prospective longitudinal study of chest radiographs and lung function

Our plain-English summary of Progression of asbestos effects: a prospective longitudinal study of chest radiographs and lung function, by R.N. Jones, J.E. Diem, J.M. Hughes, et al (British Journal of Industrial Medicine, 1989).

The study

• Authors: R.N. Jones, J.E. Diem, J.M. Hughes, Y.Y. Hammad, H.W. Glindmeyer, H. Weill
• Journal: British Journal of Industrial Medicine
• Published: 1989;46(2):97-105
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000103).

Abstract

From an original prospective cohort of 244 current and ex-workers in two asbestos cement plants, longitudinal radiographic data covering ten years were available for 165 and lung function data covering about six years for 150. Estimates of average and cumulative dust exposure were available for each participant, all men. Radiographic progression (onset or worsening) was assessed by comparing earliest and latest films side by side. Annual changes in lung function were computed by fitting regression lines to all the data points. Small opacities (ILO category 1/0 or higher) were found in 16% of initial films, and progression of small opacities occurred in 13% of film pairs. Average and cumulative dust exposure were each significant determinants of the initial presence of small opacities, and were determinants of the progression of both parenchymal and pleural abnormalities. There was greater likelihood of progression if an abnormality was initially present, and a greater likelihood of progression in the plant that had systematic use of some crocidolite. Initial levels of lung function were related to smoking, exposure to dust, and initial radiographic status. Mean annual declines in lung function were modest (FVC-0.017 l/y, FEV1-0.020 l/y) and were related to smoking but not exposure to dust, initial radiographic status, or radiographic progression. Both plants used mainly chrysotile asbestos and exposure levels declined severalfold after 1960. Our findings suggest a waning effect of the larger remote dust exposures on recent annual change in lung function. This accords with human and experimental pathology data showing the relatively low resistance of chrysotile fibres to chemical alteration and clearance.

In plain English

This prospective study followed men from two New Orleans asbestos cement plants that used mainly chrysotile asbestos. Plant 2 also systematically used crocidolite in its pipe production area. Of 244 men aged 44 to 59 in 1970, 165 had usable chest X-ray pairs covering about ten years, and 150 had repeated breathing tests. Small opacities (ILO category 1/0 or higher) appeared on 16% of first films. During follow up, 51 of 165 men (31%) showed progression of at least one abnormality, and 13% of film pairs showed progression of small opacities. Dust exposure was a determinant of progression of both parenchymal (lung tissue) and pleural abnormalities. Progression was more likely when an abnormality was already present, and more likely at plant 2. Average yearly declines in lung function were modest (FVC 0.017 litres per year, FEV1 0.020 litres per year). These declines were related to smoking but not to dust exposure or X-ray findings. The authors concluded that the findings suggest a waning effect of the larger, earlier dust exposures on recent lung function change. They could not separately analyse the effect of fibre type.

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: prospective longitudinal cohort study, with repeated chest radiographs (about ten years) and lung function tests (1973 to 1980)
• Who was studied: 244 men, current and ex-workers at two asbestos cement plants in New Orleans, aged 44 to 59 in 1970. 167 were examined in the 1980 round, 165 had satisfactory first and latest film pairs, and 150 had serial spirometric data.
• Exposure: Individually estimated dust exposure: average exposure in millions of particles per cubic foot (mppcf) and cumulative exposure in mppcf-years, based on midget impinger particle counts. Chrysotile was the primary fibre in both plants, with systematic use of crocidolite in the pipe production area of plant 2.
• Main results:
  • Small opacities (ILO category 1/0 or higher) were found on 16% of initial films, and progression of small opacities occurred in 13% of film pairs.
  • 51 of 165 men (31%) showed progression of at least one abnormality (small opacities, pleural thickening or pleural calcification).
  • Average and cumulative dust exposure were each significant determinants of the initial presence of small opacities, and were determinants of progression of both parenchymal and pleural abnormalities.
  • Progression was more likely if an abnormality was initially present, and more likely in the plant that systematically used some crocidolite (plant 2).
  • For small opacities, there was a significant dust exposure and progression relation among men with an initial parenchymal abnormality, but not among men without one. Plant 2 workers had a higher probability of progression.
  • Initial levels of lung function were related to smoking, dust exposure and initial radiographic status.
  • Mean annual declines in lung function were modest: FVC 0.017 litres per year and FEV1 0.020 litres per year (printed with hyphens for decimal points in the scanned text).
  • No significant effect on any lung function test was found for any continuous exposure variable, or for initial radiographic status or radiographic progression. Smoking was a significant determinant of declines in spirometric tests.
• The authors' conclusion: The authors concluded that their findings suggest a waning effect of the larger, remote dust exposures on recent annual change in lung function.
• Limitations the authors state:
  • Exposure durations fell within a relatively narrow range because of the age 44 to 59 entry criterion. The authors said this may explain why they could not detect independent effects of duration of exposure and time since first exposure.
  • Because most plant 2 participants had worked in the pipe area, a separate analysis of fibre type effect was not possible.
  • The authors considered that the difference from their earlier follow up of this cohort might arise from attrition (loss of participants).
  • Some men counted as progressors may have X-ray changes mainly reflecting smoking. The authors said this would reduce the power to detect lung function effects of other variables.
  • The study did not directly show changes in annual rates of lung function decline.

Topics

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

Medical terms in this study, explained in our Lexicon: Chest X-Ray, Asbestos-Cement, Crocidolite, FEV1, Chrysotile, Pathology.

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