Prevalence of pleural calcification in persons exposed to asbestos dust, and in the general population in the same district

Our plain-English summary of Prevalence of pleural calcification in persons exposed to asbestos dust, and in the general population in the same district, by M. Navrátil, F. Trippé (Environmental Research, 1972).

The study

• Authors: M. Navrátil, F. Trippé
• Journal: Environmental Research
• Published: 1972;5(2):210-6
• Cited by: 25 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. 002429).

Abstract

It is of interest whether pleural calcification is primarily the result of long years of exposure to asbestos dust or whether there are factors other than exposure to dust. We have investigated persons working for a long period in a plant processing asbestos products (chrysotile), persons without occupational exposure to dust but living in the vicinity of the plant, and consanguineous relations of patients with pleural calcifications. We have also studied a large population above the age of 40, in the district in which the plant is situated. Comparison of the groups disclosed that prevalence of pleural calcifications was closely related to opportunity for exposure to asbestos dust either occupationally or by family or neighborhood contact, as contrasted with the unexposed population. The prevalence in the group with direct or indirect asbestos exposure was 5.3, 5.8, 3.5%; whereas in the unexposed population it was 0.34%. These results indicate that asbestos is primarily responsible for pleural findings, but that some pleural disease may be the result of the other factors, still not known. The identification of other causes is hampered by the long period which need elapse from the onset of the process to the radiological appearance of the pleural change.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This Czechoslovak study used chest X-ray surveys in district N, home to factory A, which used mainly Soviet and Canadian chrysotile, to compare pleural calcification across groups. Among about 800 workers employed there over 10 years, 42 had pleural calcifications (5.3%), counted over 16 years; 23 also had X-ray signs of asbestosis. Among 155 neighbors who never worked there, 9 (5.8%) had them, five of whom were also workers' blood relatives; among 114 blood relatives, 4 (3.5%). Of 8133 district residents over 40 not working at the plant, 36 (0.44%) had pleural calcification, but 8 had worked at the factory before World War II. The other 28 gave 0.34% among 'the remaining 8097', which equals 8133 minus all 36 cases, not minus only the 8. Each exposed group had more cases than expected from the general population (workers: 42 against an expected 2.75). The authors reported these differences as statistically significant at the 1% level. The authors concluded that chrysotile exposure is associated with pleural changes and outweighs any unknown factor, while some cases without known exposure remain unexplained.

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: Epidemiological X-ray survey comparing the prevalence of pleural calcification in groups with occupational, neighborhood or family asbestos contact and in the general population of the same district
• Who was studied: District N, Czechoslovakia. About 800 workers of factory A employed more than 10 years (755 in the 1971 survey). 155 neighbors of the factory over age 20 who never worked there. 114 blood relatives of employees over age 20. 8133 district residents over age 40 not working in plant A, examined in area X-ray surveys in 1970 and 1971.
• Exposure: Chrysotile asbestos, mainly Soviet and Canadian, used in a factory processing asbestos products. Exposure was direct (factory work), neighborhood air pollution, or household contact with workers who may have brought home contaminated work clothes.
• Main results:
  • Factory workers employed more than 10 years: 42 had pleural calcifications (5.3%). 23 of them also had X-ray signs of asbestosis, and 19 had pleural calcification only.
  • Neighbors of the factory: 9 of 155 (5.8%) had pleural calcifications. Five of these 9 were also blood relatives of employees.
  • Blood relatives of employees: 4 of 114 examined (3.5%) had pleural calcifications.
  • General population over 40: 36 of 8133 (0.44%) had pleural calcification.
  • Of those 36 cases, 8 had worked in factory A before World War II. The 28 with no history of direct or indirect asbestos exposure gave a rate of 0.34% among what the article calls the remaining 8097 examined. That figure is 8133 minus all 36 cases, not 8133 minus the 8 previously exposed.
  • Observed against expected cases, based on the unexposed general population: workers 42 against 2.75; neighborhood group 9 against 0.53; family group 4 against 0.39.
  • The difference in prevalence between the general population group and each of the other three groups was statistically significant at the 1% level.
  • Among the factory workers, most pleural calcifications were first found at ages 51-60 and 61-70.
  • No signs of tuberculosis were found in any person examined, in any group.
• The authors' conclusion: The authors concluded that exposure to chrysotile asbestos is associated with pleural changes and that its influence is far greater than any other supposed unknown factor. They also concluded that some cases of pleural calcification occur without known asbestos exposure and that the cause of these has not been clarified.
• Limitations the authors state:
  • Blood relatives of employees were difficult to investigate, and some had moved to other regions. More than 90% were traced.
  • The authors could not say whether the cases without asbestos exposure had the same causes as in other series where asbestos exposure could not be identified.
  • The authors state that identifying other causes is hampered by the long delay between the start of the process and the pleural change appearing on X-ray.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Calcification, Chrysotile, Occupational Exposure, Asbestos Exposure.

Related studies

• Decreasing prevalence of pleural calcifications among Metsovites with nonoccupational asbestos exposure — C. Manda-Stachouli, Y. Dalavanga, et al. (2004)
• The calcification of fibrous pleural lesions produced in guinea-pigs by the injection of chrysotile asbestos dust — J.M. Davis (1971)
• Pleural calcification, pleural mesotheliomas, and bronchial cancers caused by tremolite dust — S. Yazicioglu, R. Ilçayto, et al. (1980)
• Pleural calcification associated with exposure to chrysotile asbestos in southeast Turkey — S. Yazicioglu (1976)
• Metsovo lung: pleural calcification and restrictive lung function in northwestern Greece. Environmental exposure to mineral fiber as etiology — S.H. Constantopoulos, J.A. Goudevenos, et al. (1985)
• Metsovo lung outside Metsovo. Endemic pleural calcifications in the ophiolite belts of Greece — S.H. Constantopoulos, P. Theodoracopoulos, et al. (1991)

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