Radiographic changes in a group of chrysotile miners and millers exposed to low asbestos dust concentrations

Our plain-English summary of Radiographic changes in a group of chrysotile miners and millers exposed to low asbestos dust concentrations, by S. Cordier, G. Theriault, S. Provencher (British Journal of Industrial Medicine, 1984).

The study

• Authors: S. Cordier, G. Theriault, S. Provencher
• Journal: British Journal of Industrial Medicine
• Published: 1984;41(3):384-8
• Cited by: 8 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. 000530).

Abstract

Radiographic changes in 342 Quebec asbestos miners exposed to low levels of asbestos dust for an average period of 20 years were studied. Their estimated cumulative exposure ranged from 7 fibres per cubic centimeter X years (f-y/cc) to 300 f-y/cc. Of these workers, 2.1% showed a small opacity score of 1/0 or more and 2.7% showed pleural changes. No linear relationship could be established between small opacity score and any index of exposure to asbestos. Pleural changes were related to age. A referent group of office workers within the same mining industry showed a prevalence of 2.1% (1/48) for small irregular opacities 1/0 or more, and for pleural changes.

In plain English

This study looked at chest X-rays of 342 male workers at a chrysotile asbestos mining and milling company in the Thetford Mines region of Quebec. The men were first employed between 1954 and 1969 and had at least five years of exposure. Their estimated cumulative exposure ranged from 7 to 300 fibre-years per cubic centimetre. Five readers, who did not know the men's jobs or exposures, classified the films, and 331 films were read by all five. Pooling four readers, 2.1% of the men had small irregular opacities of grade 1/0 or more and 2.7% had pleural changes. These changes showed no statistically significant link with duration of exposure or cumulative exposure. In a multivariate analysis the only significant association was between pleural change and age. A fifth reader, whose readings were analysed separately, recorded 24.0% and 8.8%. That reader's opacities were associated with average exposure and smoking. Among 48 office workers used for comparison, the four readers found 2.1% for both kinds of change. The authors concluded their data tend to confirm a 2% risk of radiographic changes below 300 f-y/cc in mining. They noted that imprecise exposure estimates cannot be ruled out as a cause of some negative 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 radiographic (X-ray prevalence) study of a group of exposed workers, with a comparison group of office workers; films read blind by five readers using the ILO U/C 1980 classification
• Who was studied: 342 male workers of a company operating a chrysotile mining complex in the Thetford Mines region of Quebec (Lake Asbestos), first employed 1954 to 1969 with at least five years of exposure. Workers with more than six months in another asbestos mine or factory, or more than one year in another non-asbestos mine, were excluded. 331 radiographs were read by all five readers. The comparison group was 48 office workers (29 from other mines and 19 from Lake Asbestos).
• Exposure: Chrysotile asbestos dust in mining and milling. Estimated cumulative exposure was 7 to 300 fibres per cubic centimetre x years (f-y/cc), with exposure starting 10 to 27 years before the study. Exposure was estimated from yearly fibre concentrations at seven job locations.
• Main results:
  • Among the 331 workers, the pooled four readers found small irregular opacities of grade 1/0 or more in 2.1% and pleural changes in 2.7%.
  • According to the four readers, radiographic changes showed no association with duration of exposure or with cumulative exposure. Age, smoking and time since first exposure seemed to show an association, but none reached statistical significance.
  • In multivariate analyses (age, smoking, asbestos exposure) of the four readers' results, the only significant association was between pleural change and age (p less than 0.03).
  • Of the seven workers with opacities of 1/0 or more, the authors reported that five smoked one pack of cigarettes a day. One was a non-smoker whose cumulative dust index (262.6) was among the highest in the group.
  • The fifth reader, analysed separately, recorded 24.0% small irregular opacities and 8.8% pleural changes among the exposed workers.
  • In the fifth reader's results, small opacity score was significantly associated with average level of exposure and with smoking. Prevalence of opacities rose sharply above an average exposure of 10 f/cc.
  • In the 48 office workers, the four readers found one worker with small opacities and one with pleural changes, a prevalence of 2.1% for each. The authors described this as close to the exposed group. The fifth reader recorded 13 of 48 (27.1%) with small opacities and four (8.3%) with pleural changes.
• The authors' conclusion: The authors concluded that the four readers' results on exposure and radiological change were essentially negative. They stated that their data tend to confirm an estimate of a 2% risk of radiographic changes after exposure to less than 300 f-y/cc in the mining industry.
• Limitations the authors state:
  • Imprecision in estimating exposure levels could be responsible for some of the negative findings.
  • No past dust measurements were available for the open pit or the office, or for different tasks at the same location.
  • Objective evaluation of radiological changes is difficult. One of the five readers gave results far outside the range of the others.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Lake Asbestos of Quebec, Black Lake, Quebec

All asbestos mines

Topics

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

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

Related studies

• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part III. Radiographic findings — H.E. Amandus, R. Althouse, et al. (1987)
• Development of radiographic abnormality in chrysotile miners and millers — G.M. Eyssen (1980)
• Prevalence of radiographic asbestosis in crocidolite miners and millers at Wittenoom, Western Australia — W.O. Cookson, N.H. De Klerk, et al. (1986)
• Late progression of radiographic changes in Canari chrysotile mine and mill exworkers — J.R. Viallat, C. Boutin, et al. (1983)
• Lung function and radiographic change in chrysotile workers in Swaziland — M. McDermott, M.M. Bevan, et al. (1982)
• Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort — S. Lin, X. Wang, et al. (2014)

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