Asbestos fiber type in malignant mesothelioma: an analytical scanning electron microscopic study of 94 cases

Our plain-English summary of Asbestos fiber type in malignant mesothelioma: an analytical scanning electron microscopic study of 94 cases, by V.L. Roggli, P.C. Pratt, A.R. Brody (American Journal of Industrial Medicine, 1993).

The study

• Authors: V.L. Roggli, P.C. Pratt, A.R. Brody
• Journal: American Journal of Industrial Medicine
• Published: 1993;23(4):605-14
• Cited by: 45 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Although the association between asbestos exposure and malignant mesothelioma is indisputable, controversy continues regarding the relative contribution of the various types of asbestos fibers to the development of mesothelioma. We examined the types of asbestos fibers recovered from lung parenchyma in more than 90 cases of malignant mesothelioma from the United States, using an analytical scanning electron microscope. Almost half of the patients were former asbestos insulators or shipyard workers. The fibers were recovered from lung tissues obtained at autopsy or surgical resection by means of a sodium hypochlorite digestion procedure. Amosite asbestos was identified in 81% of the cases and accounted for 58% of all fibers 5 microns or greater in length. Tremolite/actinolite/anthophyllite were identified in 55% of the cases and accounted for 10% of all fiber types. Chrysotile was identified in 21% of the cases and accounted for 3% of fibers exceeding 5 microns in length. Crocidolite was found in 16% of the cases and accounted for 3% of fibers exceeding 5 microns in length. Nonasbestos mineral fibers (commonly found in the lungs of the general population) were observed in 71% of the cases and accounted for 25% of all fibers 5 microns or greater in length. The findings in this study are at odds with the assertion that crocidolite asbestos is responsible for most mesotheliomas in the United States.

In plain English

This study looked at which asbestos fiber types were in the lungs of 94 United States patients with malignant mesothelioma whose cases had been referred to the authors. Lung tissue taken at autopsy (75 cases) or surgery (19) was digested, and fibers 5 micrometers or longer were identified with an analytical scanning electron microscope. Tumors were pleural in 89 cases and peritoneal in 5, and 84 patients were men. An asbestos exposure history was found in 74 of the 94 (79%), including 24 insulators and 22 other shipyard workers. Amosite was found in 76 cases (81%) and made up 58% of the 1,512 fibers identified. The tremolite group (tremolite, anthophyllite, actinolite) was found in 55% of cases (10% of fibers), chrysotile in 21% (3%), and crocidolite in 16% (3%). Of the 15 cases with crocidolite, only one had a larger share of crocidolite than of amosite, chrysotile or tremolite-group fibers. Non-asbestos mineral fibers made up 25% of fibers. The authors noted their method probably undercounted long chrysotile fibers. They concluded their findings were at odds with the claim that crocidolite causes most United States mesotheliomas.

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. The authors analyzed the mineral fiber content of lung tissue by analytical scanning electron microscopy with energy dispersive x-ray analysis. There was no comparison group.
• Who was studied: 94 patients with malignant mesothelioma from the United States, referred from throughout the country. Median age was 60 years (range 31 to 89), and 84 were men. Tumors were pleural in 89 cases and peritoneal in 5. Lung tissue came from autopsy in 75 cases and surgical resection in 19.
• Exposure: Asbestos exposure history was found in 74 of the 94 cases (79%): 24 asbestos insulators, 22 shipyard workers other than insulators, 23 with other occupational asbestos exposure, and 5 household contacts of asbestos workers. Three others had possible exposure only from a building with asbestos-containing materials, 5 had no identifiable exposure, and information was unavailable for 12. Fibers studied were amosite, crocidolite, chrysotile, tremolite, actinolite, anthophyllite and non-asbestos mineral fibers, 5 micrometers or longer.
• Main results:
  • Amosite was the most common fiber type. It was identified in 76 of the 94 cases (81%).
  • Amosite made up 58% of all 1,512 fibers identified.
  • Tremolite, anthophyllite or actinolite fibers were identified in 52 cases (55%).
  • Tremolite-group fibers, mostly tremolite, made up 10% of all fibers.
  • Chrysotile fibers were detected in 20 cases (21%).
  • Crocidolite was identified in 15 of the 94 cases (16%).
  • Crocidolite and chrysotile each made up 3% of all fibers.
  • Of the 15 cases with crocidolite, only one had crocidolite making up a greater percentage of fibers than amosite, chrysotile or the tremolite-group fibers. The article does not compare crocidolite with non-asbestos mineral fibers in that case. That patient was an 82-year-old railroad worker who had insulated his own home in the 1940s.
  • In 5 cases (5%), amosite could not be reliably told apart from crocidolite.
  • Non-asbestos mineral fibers were identified in 67 cases (71%).
  • Non-asbestos mineral fibers made up 25% of all fibers.
• The authors' conclusion: The authors stated that, if fibers accumulating in the lung are the ones responsible for mesothelioma, their results indicate the order of importance of fiber types for mesothelioma in the United States is amosite, then tremolite, then chrysotile and crocidolite about equally. They concluded that their findings are at odds with the assertion that crocidolite asbestos is responsible for most mesotheliomas in the United States.
• Limitations the authors state:
  • The technique mainly detects fibers 0.2 micrometers or more in diameter, so thinner long fibers could have been missed. The authors judged this unlikely to affect their results or conclusions.
  • The authors considered it more likely that the analysis underestimated long chrysotile fibers.
  • Only fibers 5 micrometers or longer were counted, so the much larger number of short chrysotile fibers was not included.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Asbestos Exposure, Mesothelioma, Parenchyma, Insulator, Autopsy, Surgical Resection, Sodium Hypochlorite Digestion.

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