Environmental pleural plaques in residents of a Quebec chrysotile mining town

Our plain-English summary of Environmental pleural plaques in residents of a Quebec chrysotile mining town, by A. Churg, L. DePaoli (Chest, 1988).

The study

• Authors: A. Churg, L. DePaoli
• Journal: Chest
• Published: 1988;94(1):58-60
• Cited by: 7 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. 000895).

Abstract

We report four cases of pleural plaques found at autopsy in individuals who resided in or near the chrysotile mining town of Thetford Mines, Quebec, and who had never been employed in the chrysotile mining and milling industry. Three of these patients were farmers, and one was a road construction worker. Lung asbestos content of these cases was compared with that of a group of nine persons living in the same vicinity who did not have pleural plaques. The plaque group was found to have an equal chrysotile content but about a fourfold elevation in median tremolite content, a statistically significant increase. Fiber sizes were the same in both groups. Also, one plaque case had an elevated level of relatively long titanium oxide fibers. These observations suggest that environmental pleural plaques in this region of Quebec are probably caused by exposure to tremolite derived from local soil and rock and that other types of mineral fibers such as titanium oxide may occasionally also be the cause of such lesions.

In plain English

This study examined autopsy lungs from people who lived in or near Thetford Mines, Quebec, a chrysotile mining town, but had never worked in the chrysotile mining and milling industry. From cases received between 1980 and 1986, the authors compared four men with pleural plaques with nine residents without plaques. Three of the men with plaques were farmers and one was a road construction worker. A fifth plaque case, a carpenter with a very high lung level of amosite, was excluded. The authors counted and identified fibers in the lung tissue by electron microscopy. The plaque group had a median tremolite concentration of 8.0 million fibers per gram of dry lung, against 1.2 million in the group without plaques. This difference was statistically significant. Chrysotile levels and fiber sizes did not differ between the groups. One plaque case had an elevated level of fairly long titanium fibers. The authors concluded that these plaques were probably caused by tremolite from local soil and rock. They added that a role for chrysotile could not be completely ruled out.

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: Autopsy case series with a comparison group: lung fiber content of four people with pleural plaques compared with nine people without plaques from the same area
• Who was studied: Residents of Thetford Mines, Quebec, or the neighboring regions who had never worked in the chrysotile industry, autopsied 1980 to 1986. There were 18 such cases. Four women whose husbands had worked in the industry were excluded, and one plaque case with high amosite levels was also excluded. That left 4 plaque cases (all men, aged 70 to 80) and 9 controls without plaques (five men and four women, mean age 60).
• Exposure: Non-occupational (environmental) exposure in a chrysotile mining area, measured as concentrations and sizes of chrysotile, tremolite and titanium fibers in lung tissue. All four plaque cases had jobs likely to generate dust from soil or rock. None of the controls had similar jobs.
• Main results:
  • Median tremolite concentration was 8.0 (range 1.2 to 26.8) x 10^6 fibers per gram of dry lung in the plaque cases, compared with 1.2 (range 0.2 to 20.7) x 10^6 in the cases without plaques (p less than 0.03).
  • Chrysotile concentrations were similar in the two groups: median 0.9 (range 0.1 to 5.3) x 10^6 fibers per gram of dry lung in plaque cases and 1.3 (range 0.2 to 3.8) x 10^6 in cases without plaques, not significant. Chrysotile and tremolite fiber sizes were the same in both groups.
  • Plaque case 4, a farmer with a relatively low tremolite level, had an elevated level of titanium fibers (1.7 x 10^6 per gram of dry lung). The median was 0.2 x 10^6 in the cases without plaques and 0 in the other three plaque cases, and their titanium fibers were generally much shorter.
• The authors' conclusion: The authors concluded that environmental pleural plaques in this region of Quebec are probably caused by exposure to tremolite from local soil and rock. They added that other mineral fibers, such as titanium oxide, may occasionally also cause such lesions.
• Limitations the authors state:
  • Because so few cases were available, cases and controls could not be matched demographically.
  • Chrysotile tends to accumulate poorly in lung tissue, so a role for chrysotile could not be completely ruled out.
  • The exact source of the tremolite exposure was uncertain.
  • Any conclusions about titanium fibers causing plaques are speculative.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile, Pleural plaques and thickening, Tremolite.

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Quebec Chrysotile, Autopsy, Chrysotile, Thetford Mines, Tremolite, Mineral Fiber.

Related studies

• Respiratory cancer in chrysotile textile and mining industries: exposure inferences from lung analysis — P. Sebastien, J.C. McDonald, et al. (1989)
• Radiological survey of past and present vermiculite miners exposed to tremolite — J.C. McDonald, P. Sebastien, et al. (1986)
• Chrysotile, tremolite, and malignant mesothelioma in man — A. Churg (1988)
• Tremolite/chrysotile ratios — G. Scansetti, G. Piolatto (1987)
• Fiber burden and patterns of asbestos-related disease in chrysotile miners and millers — A. Churg, J.L. Wright, et al. (1993)
• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)

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