Radiographic abnormalities among asbestos-cement workers. An exposure-response study

Our plain-English summary of Radiographic abnormalities among asbestos-cement workers. An exposure-response study, by M.M. Finkelstein, J.J. Vingilis (The American Review of Respiratory Disease, 1984).

The study

• Authors: M.M. Finkelstein, J.J. Vingilis
• Journal: The American Review of Respiratory Disease
• Published: 1984;129(1):17-22
• Cited by: 49 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. 000535).

Abstract

We studied the development of small irregular opacities and bilateral pleural thickening in a longitudinal study of 181 asbestos-cement workers. The relationships between the 32-yr risks of developing abnormalities and cumulative exposure to asbestos dust could be described with log-normal curves. Smokers had higher risks of both abnormalities than did nonsmokers. In this cohort, men leaving asbestos exposure had a risk of radiographic progression similar to men continuing in exposure, and men with abnormal radiographs had higher mortality rates than did men with normal ones.

In plain English

This historical prospective cohort study followed 181 production workers, hired before 1960 and employed at least 9 years, at an Ontario factory making asbestos-cement pipe and board from chrysotile and crocidolite asbestos, silica and cement. A single certified reader coded their chest X-rays for small irregular opacities and bilateral pleural thickening, and the authors related these to estimated cumulative asbestos exposure. Overall, 28% of the men had small irregular opacities of Category 1/1 or more and 22% had bilateral pleural thickening of Category A or more. Risk rose significantly with exposure for small irregular opacities. The trend for pleural thickening was weaker. Smokers had about three times the risk of nonsmokers for both abnormalities. In 50 matched pairs, men who left exposure progressed about as often as men who stayed (small opacities: 15 of 50 versus 19 of 50), and the difference was not statistically significant. By 25 to 27 years after first exposure, men with bilateral pleural thickening had double the death rate of men without it. The authors estimated that their exposure figures were accurate only to within a factor of 3 to 5.

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: Historical prospective (retrospective) cohort study using life-table analysis of serial chest radiographs
• Who was studied: 181 male production workers at an Ontario asbestos-cement factory, hired before 1960, employed 9 years or more with at least 12 months in asbestos exposure (186 were eligible; 5 were excluded)
• Exposure: Mixed dust from manufacture of asbestos-cement pipe and board made from chrysotile and crocidolite asbestos, silica and cement. Cumulative asbestos exposure was estimated with an extrapolation model and grouped into categories 50 fiber-years per milliliter wide, the highest being 200 fiber-years per milliliter or more (mean 250). No silica exposure estimates were available.
• Main results:
  • Overall, 28% of the men were recorded as having small irregular opacities of Category 1/1 or more
  • Overall, 22% of the men had bilateral pleural thickening of Category A or more
  • Smokers were at consistently higher risk than nonsmokers (never smokers plus ex-smokers) of developing both abnormalities, with a relative risk of about 3, which was statistically significant
  • Men older than 50 at 18 years from first exposure had a relative risk of about 1.5 for both abnormalities, but this was neither statistically significant nor consistent across exposure categories
  • There was a significant exposure-risk trend for small irregular opacities
  • The exposure trend for bilateral pleural thickening was much weaker than for small opacities and approached statistical significance only when men lost to follow-up were included
  • S-shaped log-normal curves provided adequate fits to the 32-year cumulative probabilities of abnormality versus exposure
  • Among 50 matched pairs, 15 of 50 men who terminated exposure had progression of small irregular opacities, compared with 19 of 50 men who continued in exposure
  • For bilateral pleural thickening, 14 of 50 men who terminated exposure progressed, compared with 12 of 50 who continued in exposure. Neither comparison of discordant pairs approached statistical significance.
  • At 25 to 27 years after first exposure, men with bilateral pleural thickening had a mortality rate double that of men without it
  • For 26 men with pathologic material, agreement between the pathologists and the radiographic reader was generally quite good
• The authors' conclusion: The authors concluded that, in this cohort, radiographic abnormalities were related to dust inhaled during the dusty earlier years of operation, and that continued exposure to the lower later dust levels had no measurable effect in this small group. They considered it probable that measures taken after damage becomes evident will not substantially affect the course of the disease, although slowing of deterioration by terminating exposure is conceivable.
• Limitations the authors state:
  • Radiographs were interpreted by a single reader because of financial constraints
  • Cumulative exposure estimates came from an extrapolation model and are accurate only to within a factor of 3 to 5
  • No quantitative silica exposure measures were available, so small rounded opacities and asbestos-silica interaction were not analyzed
  • Small numbers led to broad confidence intervals for the 32-year cumulative probabilities
  • The study was too small to distinguish additive from multiplicative smoking effects or to study smoking cessation
  • Film quality was somewhat variable
  • The curve fitting assumed zero risk at zero exposure, which is only an approximation
  • The effect of removal from exposure could not be studied directly, because most workers had been transferred from exposure when abnormalities developed; an indirect matched-pair approach was used instead

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Bilateral, Pleural Thickening, Cumulative Exposure, Asbestos Exposure.

Related studies

• Pulmonary function in asbestos cement workers: a dose-response study — M. Finkelstein (1986)
• Lung function in relation to radiographic changes in asbestos workers — S. Zedda, G. Aresini, et al. (1973)
• Spirometric impairments in long-term insulators. Relationships to duration of exposure, smoking, and radiographic abnormalities — A. Miller, R. Lilis, et al. (1994)
• Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers — K. Jakobsson, A. Rannug, et al. (1995)
• Risk and significance of chest radiograph and pulmonary function abnormalities in an elderly cohort of former nuclear weapons workers — M.A. Mikulski, P.G. Hartley, et al. (2011)
• Radiographic asbestosis is not a prerequisite for asbestos-associated lung cancer in Ontario asbestos-cement workers — M.M. Finkelstein (1997)

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