A postmortem case control study of asbestos burden in lungs of malignant mesothelioma cases

Our plain-English summary of A postmortem case control study of asbestos burden in lungs of malignant mesothelioma cases, by S.D. Visonà, B. Bertoglio, C. Favaron, et al (Journal of Translational Medicine, 2023).

The study

• Authors: S.D. Visonà, B. Bertoglio, C. Favaron, S. Capella, E. Belluso, C. Colosio, S. Villani, T. Ivic-Pavlicic, E. Taioli
• Journal: Journal of Translational Medicine
• Published: 2023;21(1):875
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Asbestos lung content is regarded as the most reliable tool for causal attribution of malignant mesothelioma (MM) to previous asbestos exposures. However, there is a lack of studies on asbestos burden in lungs of MM patients in comparison with healthy individuals. This study aims to provide such a comparison, investigating, as well, differences in asbestos lung burden with sex and time trends.

Methods: Asbestos lung content has been assessed on formalin-fixed lung fragments using scanning electron microscopy coupled with energy dispersion spectroscopy (SEM-EDS) on individuals deceased from MM (cases) and healthy subjects without any lung disease who died from violent causes (controls) between 2005 and 2023.

Results: Asbestos and asbestos bodies (ABs) were found, respectively, in 73.7% and 43.2% of cases and in 28 and 22% of controls; in MM cases the most represented asbestos types were crocidolite and amosite, whereas in controls it was tremolite-actinolite asbestos. The concentration of both asbestos fibers and ABs was statistically significantly higher in MM cases compared to controls. The mean asbestos fibers width was also significantly higher in cases than controls. Males and females with MM showed similar asbestos and ABs concentrations, but females had higher concentrations of chrysotile, and significantly lower fibers width compared to males. Time trends show that MM lung asbestos concentrations decreased starting in 2011.

Discussion: The results suggest a correlation between asbestos burden in lungs and MM risk. The different concentration of chrysotile, as well as the different width of asbestos fibers in MM males and females might reflect a sex difference in response of the lung microenvironment to inhaled asbestos. Finally, this study provides the first pathological evidence of the effect of the ban of asbestos use, demonstrating a significant decrease of asbestos lung content after 2011.

© 2023. The Author(s).

In plain English

This case-control study from Pavia University, northern Italy, measured asbestos in lung tissue taken at autopsy. It compared 95 people who died of malignant mesothelioma (93 pleural, 2 peritoneal) with 50 controls. Cases lived mostly around Broni, where an asbestos-cement factory used chrysotile and amphiboles. Controls were people over 40 who died of traumatic causes, without known asbestos exposure or lung disease, living elsewhere. Asbestos fibers were found in 73.7% of cases and 28% of controls. Mean asbestos concentration was 79705.59 fibers per gram of dry lung in cases versus 3187.74 in controls, a significant difference. Most asbestos in cases was amosite and crocidolite; in controls, tremolite/actinolite asbestos. Fibers were wider in controls than in cases. Among cases, men and women had similar total concentrations, but women had more chrysotile. In mesothelioma cases, lung asbestos levels fell significantly after 2011 overall and in men; women had lower levels throughout, falling slightly after 2012. The authors concluded that concentrations were significantly lower in controls, always below 100000 fibers per gram. They called the decline the first pathological evidence of the asbestos ban's effect.

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-control study of lung samples from forensic autopsies held in a university archive, analysed by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS)
• Who was studied: 95 people who died of malignant mesothelioma and had a forensic autopsy at Pavia University between 2005 and 2018. Most lived in or around Broni (Pavia Province, northern Italy). Of the cases, 93 (97.9%) had pleural and 2 had peritoneal mesothelioma. The 50 controls were otherwise healthy people over 40 who died of traumatic causes between 2001 and 2023. They had no history of cancer or respiratory disease, no known asbestos exposure, and lived outside Broni and other known asbestos-exposure areas.
• Exposure: Most cases lived near the Fibronit asbestos-cement factory in Broni, active 1932 to 1993. The factory used a mixture of chrysotile and amphiboles: mainly crocidolite, with small amounts of amosite. Among cases, exposure was reported as occupational in 38.9%, household in 17.9% and anthropogenic environmental in 42.1%. One case had no history of exposure. Lung samples of 0.25 g from the lower right lobe were analysed. Only fibers longer than 5 µm, thinner than 3 µm, and at least three times as long as wide were counted.
• Main results:
  • Asbestos fibers were identified in 73.7% of mesothelioma cases and 28% of controls. Asbestos bodies were found in 43.2% of cases and 22% of controls.
  • Mean asbestos concentration was 79705.59 fibers per gram of dry weight (SD 240333.83) in cases and 3187.74 (SD 7582.45) in controls (p = 0.0025; p = 0.0002 adjusted for age and sex). Mean asbestos body concentration was 74670.71 in cases and 2013.54 in controls (adjusted p = 0.0137).
  • Amosite and tremolite/actinolite asbestos concentrations were significantly higher in cases than controls. Differences for the other asbestos types did not reach statistical significance. Of all asbestos found in cases, 40.58% was crocidolite and 48.33% amosite. In controls, 72.7% was tremolite/actinolite asbestos.
  • In 26.3% of mesothelioma cases, no asbestos was found in the lung sample. Most cases had concentrations below 100000 fibers per gram of dry weight. All controls were below that value.
  • Fiber length did not differ significantly between groups. Fibers were significantly wider in controls (mean 0.96 µm) than in cases (mean 0.68 µm), with p = 0.0070.
  • Among cases, men (49) and women (46) did not differ significantly in total asbestos or asbestos body concentration after adjustment for age and type of exposure. Chrysotile was significantly more frequent in women (mean 895.85 versus 0 fibers per gram; adjusted p = 0.0187). Fiber width tended to be greater in men (0.80 versus 0.60 µm), but this did not reach statistical significance after adjustment (p = 0.0763).
  • In mesothelioma cases, lung asbestos concentrations decreased significantly after 2011, both overall and in men. Women had lower levels across all years and only a slight decrease after 2012.
• The authors' conclusion: The authors concluded that asbestos concentration was significantly lower in controls than in mesothelioma cases, and always below 100000 fibers per gram of dry weight in controls. They wrote that the difference supports the hypothesis that asbestos concentration can influence mesothelioma risk. They suggested that women's higher chrysotile levels and thinner fibers might reflect a different lung response. They described the post-2011 decline as the first pathological evidence of the effect of the asbestos ban, which in Italy dates from 1992.
• Limitations the authors state:
  • Only fibers longer than 5 µm, thinner than 3 µm, and at least three times as long as wide were counted. Some authors have linked shorter, lower-aspect-ratio fibers to mesothelioma.
  • Asbestos bodies were counted by SEM-EDS on the same small sample, not the usual method, so their concentration may be underestimated.
  • Only one lung site (lower right lobe) was sampled, and asbestos content can vary considerably between lung areas.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Lung cancer, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Attribution, Asbestos Exposure, Scanning Electron Microscopy (SEM), Asbestos Bodies, Crocidolite, Amosite, Tremolite.

Related studies

• Asbestos burden in lungs of non-occupationally exposed women from Broni (Pavia, Italy): a postmortem SEM-EDS study — S.D. Visonà, S. Capella, et al. (2023)
• Inorganic Fiber Lung Burden in Subjects with Occupational and/or Anthropogenic Environmental Asbestos Exposure in Broni (Pavia, Northern Italy): An SEM-EDS Study on Autoptic Samples — S.D. Visonà, S. Capella, et al. (2021)
• Asbestos Burden in Lungs of Subjects Deceased From Mesothelioma Who Lived in Proximity to an Asbestos Factory: A Topographic Post-Mortem SEM-EDS Study — S.D. Visonà, M. Untalan, et al. (2025)
• Reply to Mirabelli et al. Is Mesothelioma Unrelated to the Lung Asbestos Burden? Comment on "Visonà et al. Inorganic Fiber Lung Burden in Subjects with Occupational and/or Anthropogenic Environmental Asbestos Exposure in Broni (Pavia, Northern Italy): An SEM-EDS Study on Autoptic Samples. Int. J. Environ. Res. Public Health 2021, 18, 2053" — S.D. Visonà, S. Capella, et al. (2021)
• Evaluation of Deposition and Clearance of Asbestos (Detected by SEM-EDS) in Lungs of Deceased Subjects Environmentally and/or Occupationally Exposed in Broni (Pavia, Northern Italy) — S.D. Visonà, S. Capella, et al. (2021)
• Fiber burden and patterns of asbestos-related disease in chrysotile miners and millers — A. Churg, J.L. Wright, et al. (1993)

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