Malignant mesothelioma and duration of asbestos exposure: correlation with tissue mineral fibre content

Our plain-English summary of Malignant mesothelioma and duration of asbestos exposure: correlation with tissue mineral fibre content, by V.L. Roggli (The Annals of Occupational Hygiene, 1995).

The study

• Author: V.L. Roggli
• Journal: The Annals of Occupational Hygiene
• Published: 1995;39(3):363-74
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Among 441 cases of malignant mesothelioma in the author's files, there were 324 for whom reliable information was available regarding the duration of exposure to asbestos. Included were 298 pleural and 26 peritoneal mesotheliomas. The mean duration of exposure to asbestos was 23 +/- 14 years for all cases, and was not different for the pleural and peritoneal groups. Lung tissue was available for analysis of mineral fibre content in 94 cases. Linear regression analysis showed a significant correlation between duration of exposure and asbestos bodies per gramme of wet lung as determined by light microscopy, and between duration of exposure and total uncoated fibres (5 microns or greater in length) as well as commercial amphibole fibres per gramme as determined by scanning electron microscopy (P < 0.05). Individuals with direct exposures had on average higher asbestos contents than patients with indirect exposures. Furthermore, for each duration of exposure, shipyard workers had on average higher asbestos contents than non-shipyard workers (P < 0.05). Mesotheliomas are associated with a wide range of durations of exposure to asbestos and pulmonary asbestos burdens, and there is a rough correlation between duration of exposure and pulmonary commercial amphibole content.

In plain English

This study reviewed 441 cases of malignant mesothelioma in the author's files and found 324 (298 pleural, 26 peritoneal) with exposure duration information from patient interviews. Mean exposure duration was 23 plus or minus 14 years, with no statistical difference between pleural and peritoneal cases. Four men with pleural mesothelioma had less than 1 year of exposure. Lung tissue was available in 94 cases; asbestos bodies were counted in 93 and fibre types analysed in 84. Longer exposure correlated with higher lung counts of asbestos bodies and of commercial amphiboles (amosite and crocidolite) (r=0.31 for each), and less strongly with total uncoated fibres (r=0.22). Chrysotile, non-commercial amphiboles and non-asbestos mineral fibres showed no significant correlation with duration. Direct handlers of asbestos had higher lung asbestos levels than bystanders, and shipyard workers had higher levels than non-shipyard workers. The author concluded that mesotheliomas occur across a wide range of exposure durations and lung burdens, with a rough correlation between duration and commercial amphibole content. Individual variation was too great to predict one person's lung burden from duration, and exposure intensity was not known.

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: Case series of pathologically confirmed malignant mesotheliomas from the author's files, with exposure histories and, in a subset, lung tissue fibre analysis by light and scanning electron microscopy
• Who was studied: 324 of 441 malignant mesothelioma cases in the author's files (298 pleural, 26 peritoneal) had information on exposure duration. 94 of these also had lung tissue analysed: 85 men and nine women, mean age 61 plus or minus 10 years (range 31 to 87), 89 pleural and five peritoneal. The article does not state where the patients came from or the study dates, beyond the author's affiliation (Durham Veterans Administration and Duke University Medical Center, North Carolina).
• Exposure: Duration of occupational or household asbestos exposure, taken from patient interviews. Exposures were grouped as direct (handling asbestos materials) vs indirect (bystander or household contact), and as shipyard vs non-shipyard. Lung fibres were classified as commercial amphiboles (amosite, crocidolite), non-commercial amphiboles (tremolite, anthophyllite, actinolite), chrysotile, or non-asbestos mineral fibres.
• Main results:
  • Mean duration of asbestos exposure for all 324 cases was 23 plus or minus 14 years.
  • Mean exposure duration was 23 plus or minus 14 years for pleural cases and 24 plus or minus 11 years for peritoneal cases. The difference was not statistically significant (P greater than 0.05).
  • 51 of 298 pleural cases (17%) but only 1 of 26 peritoneal cases (4%) had 5 years or less of exposure (P = 0.056 by Fisher's exact test).
  • Four of the 324 cases had less than 1 year of exposure. All were men aged 39 to 65 years with the epithelial type of pleural mesothelioma.
  • Of the 94 cases with lung tissue, asbestos bodies were counted by light microscopy in 93, and fibre types were analysed by scanning electron microscopy in 84.
  • In the lung-tissue group, asbestos bodies and commercial amphibole fibres per gramme of wet lung correlated significantly with duration of exposure (r = 0.31, P less than 0.01).
  • Total uncoated fibres per gramme of wet lung correlated less strongly with duration of exposure (r = 0.22, P less than 0.05).
  • Median asbestos body, commercial amphibole and total uncoated fibre counts were substantially greater in people with direct exposure than in those with indirect exposure (P less than 0.001).
  • Shipyard workers had greater median values than non-shipyard workers. The difference was statistically significant for commercial amphiboles and total uncoated fibres (P less than 0.05) but not for asbestos bodies (P = 0.09). This held even though mean exposure duration was 4 years shorter for the shipyard workers.
  • Asbestos bodies and commercial amphiboles per gramme correlated significantly with duration within each of the four exposure groups (shipyard, non-shipyard, direct, indirect). The one exception was commercial amphiboles in the direct-exposure group (P greater than 0.10).
  • For each duration of exposure, shipyard workers had higher asbestos body counts than non-shipyard workers.
  • Non-commercial amphibole, chrysotile and non-asbestos mineral fibre content showed no significant correlation with duration of exposure in any exposure category.
• The authors' conclusion: The author concluded that mesotheliomas are associated with a wide range of exposure durations and lung asbestos burdens. The author also concluded that there is a rough correlation between duration of exposure and lung content of asbestos bodies and commercial amphibole fibres, and stated that this was shown for the first time in a large series of patients with mesothelioma.
• Limitations the authors state:
  • Individual variation was too great for the regression lines to accurately predict a single person's asbestos burden from exposure duration.
  • No information on intensity of exposure was available.
  • Continuous and intermittent exposure could produce different lung burdens even with the same duration and intensity.
  • Brake repair workers were classed as direct exposures even though they are exposed to low levels of fibres 5 micrometres or longer.
  • Exposure histories depend on patients remembering exposures from decades earlier.
  • Tissue fibre analysis correlates poorly with chrysotile exposure.
  • People differ substantially in how efficiently they clear dust particles from their lungs.
  • Fibre content varies from site to site within the lung.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Asbestos Exposure, Peritoneal Mesothelioma, Asbestos Bodies, Amphibole Group, Scanning Electron Microscopy (SEM), Mesothelioma.

Related studies

• Correlation between the tissue response and asbestos fiber content — A.G. Heppleston (1974)
• Correlation between fibre content of the lung and disease in east London asbestos factory workers — J.C. Wagner, M.L. Newhouse, et al. (1988)
• Correlation between fibre content of the lungs and disease in naval dockyard workers — J.C. Wagner, C.B. Moncrieff, et al. (1986)
• Correlation between fibre content of lung and disease in east London asbestos factory workers — R.M. Rudd (1989)
• Mineral fiber content of lung tissue in patients with environmental exposures: household contacts vs. building occupants — V.L. Roggli, W.E. Longo (1991)
• An examination of the fibrous mineral content of asbestos lung tissue from the Canadian chrysotile mining industry — F.D. Pooley (1976)

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