Malignant mesothelioma and occupational exposure to asbestos: a clinicopathological correlation of 1445 cases

Our plain-English summary of Malignant mesothelioma and occupational exposure to asbestos: a clinicopathological correlation of 1445 cases, by V.L. Roggli, A. Sharma, K.J. Butnor, et al (Ultrastructural Pathology, 2002).

The study

• Authors: V.L. Roggli, A. Sharma, K.J. Butnor, T. Sporn, R.T. Vollmer
• Journal: Ultrastructural Pathology
• Published: 2002;26(2):55-65
• Cited by: 137 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos exposure is indisputably associated with development of mesothelioma. However, relatively few studies have evaluated the type of occupational exposure in correlation with asbestos fiber content and type. This study reports findings in 1445 cases of mesothelioma with known exposure history; 268 of these also had fiber burden analysis. The 1445 cases of mesothelioma were subclassified into 23 predominant occupational or exposure categories. Asbestos body counts per gram of wet lung tissue were determined by light microscopy. Asbestos fiber content and type were determined by scanning electron microscopy and energy dispersive x-ray analysis. Results were compared with a control group of 19 lung tissue samples. Ninety-four percent of the cases occurred among 19 exposure categories. Median asbestos body counts and levels of commercial and noncommercial amphibole fibers showed elevated levels for each of these 19 categories. Chrysotile fibers were detectable in 36 of 268 cases. All but 2 of these also had above-background levels of commercial amphiboles. When compared to commercial amphiboles, the median values for noncommercial amphibole fibers were higher in 4 of the 19 exposure groups. Most mesotheliomas in the United States fall into a limited number of exposure categories. Although a predominant occupation was ascertained for each of these cases, there was a substantial overlap in exposure types. All but 1 of the occupational categories analyzed had above-background levels of commercial amphiboles. Commercial amphiboles are responsible for most of the mesothelioma cases observed in the United States.

In plain English

The authors reviewed 1445 mesothelioma cases (1322 men, 123 women) with known exposure information, drawn from one author's consultation files at Duke University and the Durham Veterans Administration in North Carolina. The tumor began in the pleura in 1309 cases and the peritoneum in 136. Cases were sorted into 23 exposure categories. Nineteen of them accounted for 94% of cases, with shipbuilding the largest industry and pipefitter the largest occupation. Fiber analysis of lung tissue from 268 cases was compared with 19 controls with no history of asbestos exposure and no evidence of asbestos-related disease. Commercial amphiboles (mostly amosite, some crocidolite) were the main fiber type in most categories. Noncommercial amphiboles (mostly tremolite) predominated in automotive brake repair workers, household contacts, building occupants and environmental cases. Chrysotile was detected in 36 of 268 cases. Pleural plaques were present in 608 of 778 informative cases (78%), and asbestosis in 135 of 577 (23%). The authors concluded that commercial amphiboles are responsible for most mesothelioma cases in the United States. They noted that over 90% of cases were medicolegal and might not be representative.

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: review of a pathologist's consultation files, with lung fiber burden analysis in a subset compared with control lungs from people with no history of asbestos exposure
• Who was studied: 1445 histologically confirmed mesothelioma cases (1322 men, 123 women; median age 67, range 17 to 94). The tumor was pleural in 1309 and peritoneal in 136. Of these, 268 had lung fiber analysis. Controls were 19 lung samples with no history of asbestos exposure and no evidence of asbestos-related disease. Dates of the cases are not stated.
• Exposure: 23 exposure categories: 12 industries, 7 occupations and 4 nonoccupational groups. Lung asbestos bodies were counted by light microscopy, and fibers were typed by scanning electron microscopy with x-ray analysis. Amosite and crocidolite were grouped as commercial amphiboles; tremolite, anthophyllite and actinolite as noncommercial amphiboles; chrysotile was counted separately.
• Main results:
  • 19 exposure categories (12 industries, 6 occupations, 1 nonoccupational exposure) accounted for 94% of the 1445 cases.
  • The industry with the most cases was shipbuilding (289 cases), followed by U.S. Navy, construction and insulation. The occupation with the most cases was pipefitter (187).
  • Commercial amphiboles (mostly amosite with some crocidolite) were the predominant fiber type in every category except automotive brake repair workers, household contacts, building occupants and environmental exposures. In those four, noncommercial amphiboles (mostly tremolite) predominated.
  • Chrysotile was detectable in 36 of 268 cases with fiber analysis. All but 2 of these also had above-background commercial amphiboles. Chrysotile was not detected at all in 7 categories.
  • Pleural plaques were present in 608 of 778 cases with information (78%). Asbestosis was present in 135 of 577 cases with information (23%).
  • Those with nonindustrial exposure (household contacts, building occupants, other) had the highest relative hazard, 2.19, meaning mesothelioma at an earlier age. Insulation workers also had a higher hazard (1.33). Pipefitters (0.66) and railroad workers (0.52) had lower hazards.
  • The highest share of peritoneal mesotheliomas was among insulators and asbestos manufacturing plant workers, where the pleural-to-peritoneal ratio was about 2:1.
  • Asbestosis began to become prevalent when the commercial amphibole burden exceeded 22 000 fibers per gram of tissue. At that level, 64% of cases already had plaques.
  • In automotive brake repair workers, the median asbestos body count was within the laboratory's normal range. Where tissue asbestos was elevated, excess commercial amphiboles (mostly amosite) were found.
• The authors' conclusion: The authors concluded that commercial amphiboles are responsible for most of the mesothelioma cases observed in the United States.
• Limitations the authors state:
  • More than 90% of the cases were medicolegal, so they may not represent U.S. mesothelioma cases generally. The authors compared their categories with the Australian registry and found them similar.
  • Many patients worked in more than one exposure category, so assignment to a single predominant category was approximate.
  • The analysis did not distinguish intermittent from continuous exposure.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Occupational Exposure, Asbestos Exposure, Mesothelioma, Exposure History, Fiber Burden Analysis, Asbestos Body Formation, Scanning Electron Microscopy (SEM).

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