Late progression of radiographic changes in Canari chrysotile mine and mill exworkers

Our plain-English summary of Late progression of radiographic changes in Canari chrysotile mine and mill exworkers, by J.R. Viallat, C. Boutin, J.F. Pietri, et al (Archives of Environmental Health, 1983).

The study

• Authors: J.R. Viallat, C. Boutin, J.F. Pietri, J. Fondarai
• Journal: Archives of Environmental Health
• Published: 1983;38(1):54-8
• Cited by: 26 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. 001705).

Abstract

The present radiological status of 133 exworkers (mean age: 58 +/- 0.7 yr) of the chrysotile mine of Canari (Corsica) was compared to that recorded in 1965, when the mine was closed. The mean time since first exposure is 27 +/- 0.4 yr, and the mean time since termination of asbestos exposure equals 16 +/- 0.3 yr. This study showed an evolution of radiographic changes: in 1965 only 14% of the subjects had grade 1/1 or more parenchymal fibrosis, and 6% had bilateral pleural lesions; in 1979 these percentages reached 40% and 27%, respectively. Subjects who had a given parenchymal change in 1965 (e.g., 1/1 grade lesions) were older and had a more intensive dust exposure and tobacco consumption than exminers who developed the same parenchymal changes much later. A progression of parenchymal changes was observed in 39% of the subjects with normal findings in 1965, and in 63% of the subjects with grade 1/1 or more changes in 1965. Those who progressed (46% of the cohort) were older, had a longer exposure, and a more intensive dust exposure and cigarette smoking than nonprogressors.

In plain English

The authors compared chest X-rays of former Canari chrysotile mine and mill workers in Corsica taken in 1965, when the mine closed, with X-rays from 1979. Workers were exposed to rather pure chrysotile ore for an average of 11 years. Surveys in 1962 and 1963 found about 29 to 282 fibers per ml, depending on working conditions. Parenchymal (lung-tissue) changes of grade 1/1 or more were seen in 18 of 133 subjects (14%) in 1965 and in 69 of 170 (about 40%) in 1979. Bilateral pleural changes were seen in 9 of 133 (6.5%) in 1965 and in 46 of 170 (27%) in 1979. Among the 133 with 1965 films, 46% showed parenchymal progression. That included 39% of those with normal (0/0) films in 1965, 60% of those graded 0/1 to 1/0, and 10 of 16 (63%) of those graded 1/1. Progressors were older, had longer and more intense dust exposure, and smoked more than nonprogressors. The authors suggested that progression may depend on dust exposure and, to a lesser extent, age and tobacco consumption, besides individual factors.

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: Follow-up study of a cohort of former workers, comparing chest X-rays taken when exposure ended (1965) with X-rays taken in 1979
• Who was studied: Former workers of the Canari asbestos mine and mill in Corsica, which operated from 1948 to 1965. The authors traced 240 exworkers and had complete records for 170. Of these, 133 had X-ray films from 1965, when the mine closed. The 1979 figures in the tables cover 170 subjects.
• Exposure: Chrysotile ore described as rather pure. Surveys made in 1962 and 1963 found very high dust levels, approximately 29 to 282 fibers per ml depending on working conditions. Mean exposure time was 11 years. The authors also used a dust-weighted time exposure, in which years of exposure were multiplied by job-based coefficients from 0.1 (outside the mine and mill) to 6.
• Main results:
  • In 1965, 18 of 133 subjects (14%) had parenchymal changes of grade 1/1 or more.
  • In 1979, 69 of 170 subjects had parenchymal changes of grade 1/1 or more. Table 4 gives this as 41%; the text gives 40%.
  • Bilateral pleural changes were present in 9 of 133 subjects (6.5%) in 1965 and in 46 of 170 (27%) in 1979.
  • Between 1965 and 1979, parenchymal radiographic changes progressed in 46% of the 133 subjects.
  • The share who progressed differed by 1965 grade: 39% of those graded 0/0 and 60% of those graded 0/1 to 1/0.
  • Among the 16 subjects graded 1/1 in 1965, Table 6 shows 10 (63%) moving to grade 1/2 or more by 1979. The text attributes 63% to the whole group graded 1/1 or more. Table 6 also lists 2 subjects already graded 1/2 or more in 1965 who were in that category in 1979.
  • Progressors were older than nonprogressors (mean age in 1979 58.9 vs 56 years, p less than 0.05). They had longer exposure (13.4 vs 9.6 years, p less than 0.05), higher dust-weighted time exposure (35.3 vs 27, p less than 0.001) and higher tobacco consumption (25.7 vs 18.2 cigarette pack-years). Time since first exposure was similar in the two groups.
  • The authors compared subjects who already had a given parenchymal grade in 1965 with those who reached it only by 1979. The earlier group was older and had higher dust-weighted exposure and smoking, but these differences were not statistically significant in that comparison. With a different grouping (grade 1/1 or more), the difference in dust-weighted time exposure was significant: 44.7 in the 1965 group vs 36.2 in the 1979 group, p less than 0.05.
• The authors' conclusion: The authors suggested, as a possible explanation of the range of patterns they observed, that asbestos-induced lesions progress at different rates. In their suggestion, progression depends on dust exposure and, to a lesser extent, on age and tobacco consumption, besides individual factors.
• Limitations the authors state:
  • Time since first exposure and length of exposure were too uniform in this cohort to separate subgroups, because the mine was open for only 17 years.
  • For pleural changes, the difference between subjects affected by 1965 and those affected only by 1979 was not statistically significant because of the small numbers (9 and 46).
  • Unilateral pleural changes cannot be specifically attributed to asbestos exposure. The authors found 9.5% unilateral pleural changes in a control group in their earlier study.

Mines named here

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

• Canari mine, Corsica

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos Exposure, Parenchymal Fibrosis, Bilateral.

Related studies

• Radiographic changes in a group of chrysotile miners and millers exposed to low asbestos dust concentrations — S. Cordier, G. Theriault, et al. (1984)
• Lung function and radiographic change in chrysotile workers in Swaziland — M. McDermott, M.M. Bevan, et al. (1982)
• Mortality in the chrysotile asbestos mines and mills of Quebec — J.C. McDonald, A.D. McDonald, et al. (1971)
• The health of chrysotile asbestos mine and mill workers of Quebec — J.C. McDonald, M.R. Becklake, et al. (1974)
• Non-malignant consequences of decreasing asbestos exposure in the Brazil chrysotile mines and mills — E. Bagatin, J.A. Neder, et al. (2005)
• Lung function profiles in the chrysotile asbestos mines and mills of Quebec — M.R. Becklake, G. Fournier-Massey, et al. (1976)

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