Short, thin asbestos fibers contribute to the development of human malignant mesothelioma: pathological evidence

Our plain-English summary of Short, thin asbestos fibers contribute to the development of human malignant mesothelioma: pathological evidence, by Y. Suzuki, S.R. Yuen, R. Ashley (International Journal of Hygiene and Environmental Health, 2005).

The study

• Authors: Y. Suzuki, S.R. Yuen, R. Ashley
• Journal: International Journal of Hygiene and Environmental Health
• Published: 2005;208(3):201-10
• Type of article: Review
• Cited by: 89 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Based on animal studies, long and thin asbestos fibers (> or =8 microm in length and < or = 0.25 microm in width) have been postulated to be strongly carcinogenic inducing pleural malignant mesothelioma, while shorter, thicker fibers have been postulated to pose a lesser risk (Stanton hypothesis). The objective of this study is to test the validity of the Stanton hypothesis through direct pathologic analysis of human mesothelioma tissue. Digested bulk tissue samples, or ashed 25 microm thick sections, or both, were prepared from lung and mesothelial tissues taken from 168 cases of human malignant mesothelioma. In these tissues, 10,575 asbestos fibers (4820 in the lung and 5755 in mesothelial tissues (1259 in fibrotic serosa and 4496 in mesotheliomatous tissue)) were identified by high-resolution analytical electron microscopy. Dimensions of these asbestos fibers were measured in printed electron micrographs. Results were as follows: (1) long, thin asbestos fibers consistent with the Stanton hypothesis comprised only 2.3% of total fibers (247 / 10,575) in these tissues; (2) the majority (89.4%) of the fibers in the tissues examined were shorter than or equal to 5 microm in length (9454 of 10,575), and generally (92.7%) smaller than or equal to 0.25 microm in width (9808 of 10,575). (3) Among asbestos types detected in the lung and mesothelial tissues, chrysotile was the most common asbestos type to be categorized as short, thin asbestos fibers. (4) Compared with digestion technique of the bulk tissue, ashing technique of the tissue section was more effective to detect short, thin fibers. We conclude that contrary to the Stanton hypothesis, short, thin, asbestos fibers appear to contribute to the causation of human malignant mesothelioma. Such fibers were the predominant fiber type detected in lung and mesothelial tissues from human mesothelioma patients. These findings suggest that it is not prudent to take the position that short asbestos fibers convey little risk of disease.

In plain English

This study measured asbestos fibers in archived tissue from 168 people with malignant mesothelioma (156 pleural, 12 peritoneal). The samples had been sent to the first author for pathological review over 15 years. Using high-resolution analytical electron microscopy, the authors reanalyzed 10,575 asbestos fibers from lung, fibrotic serosa and tumor tissue that they had first described in a 2002 study. Only 247 of the 10,575 fibers (2.3%) fit the Stanton hypothesis dimensions of at least 8 micrometers long and no more than 0.25 micrometers wide. Most fibers were 5 micrometers or shorter (9454 of 10,575, 89.4%), and most were 0.25 micrometers or thinner (9808 of 10,575, 92.7%). Chrysotile accounted for 8541 of the fibers and was generally shorter and thinner than amosite, crocidolite, tremolite and anthophyllite. Ashed tissue sections showed a higher share of short fibers (95.2%) than digested bulk tissue (77.2%). The authors concluded that short, thin asbestos fibers appear to contribute to causing human malignant mesothelioma. They noted that they cannot tell when fibers were inhaled or deposited.

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: Pathological tissue fiber-burden analysis of archived samples from mesothelioma cases. It is an additional analysis of the same 10,575 fibers the authors first reported in a 2002 preliminary study. There was no comparison group.
• Who was studied: Lung and mesothelial tissues (autopsy or biopsy samples) from 168 cases of human malignant mesothelioma: 164 males and 4 females; 156 pleural and 12 peritoneal. The samples were sent to the principal author for pathological review over a 15-year period and archived at the Mount Sinai School of Medicine, New York. Calendar years are not given.
• Exposure: Patients had diverse occupations, including asbestos insulators, pipe fitters, electricians, shipyard workers, US Navy servicemen, sheet metal workers, power plant workers, boiler men, brake lining mechanics, fire fighters, and family members of asbestos workers. The fiber types identified in tissue were amosite, chrysotile, crocidolite, tremolite and anthophyllite. No exposure doses are given.
• Main results:
  • Across all tissues, 247 of 10,575 asbestos fibers (2.3%) fit the Stanton dimensions (8 micrometers or longer and 0.25 micrometers or thinner).
  • The proportion of fibers fitting the Stanton dimensions, by fiber type: crocidolite 20.7%, amosite 10.5%, tremolite 6.2%, chrysotile 0.2%, anthophyllite 0%.
  • 9454 of 10,575 fibers (89.4%) were 5 micrometers or shorter in length. Only 10.6% were 5 micrometers or longer.
  • 9808 of 10,575 fibers (92.7%) were 0.25 micrometers or less in width.
  • Chrysotile fibers (8541 in total) were generally shorter and thinner than the other types. 8521 of 8541 chrysotile fibers (99.8%) were 0.25 micrometers or less in width, and 83 of 8541 (1.0%) were 5 micrometers or longer.
  • In mesotheliomatous (tumor) tissue, 11 of 4496 fibers (0.2%) fit the Stanton dimensions. In fibrotic serosa (plaque), 9 of 1259 (0.6%) did, and in lung, 227 of 4820 (4.7%).
  • Ashed tissue sections showed a higher proportion of short fibers (95.2%, 6,811 of 7153) than digested bulk tissue (77.2%, 2643 of 3422). They also showed more thin fibers (96.4% versus 85.1%) and fewer fibers fitting the Stanton dimensions (1.1% versus 4.9%).
  • Negative control samples prepared without tissue were free of asbestos fibers. From this, the authors concluded that the chrysotile in the tissues came from inhaled dust, not from contaminated water, air or paraffin.
• The authors' conclusion: The authors concluded that, contrary to the Stanton hypothesis, short, thin asbestos fibers appear to contribute to the causation of human malignant mesothelioma, because such fibers were the majority found in lung and mesothelial tissues of mesothelioma patients. They also stated that it is not prudent to take the position that short asbestos fibers convey little risk of disease.
• Limitations the authors state:
  • The authors stated that no technique can determine when the fibers were inhaled or when they were deposited in the tissues, so the fibers that directly took part in causing the tumor cannot be specified.
  • The authors noted that no epidemiological studies have been reported of human populations exposed only to short asbestos fibers.
  • The authors acknowledged that long, thick chrysotile fibers tend to break into short, thin fibers in the lung after inhalation. They argued, however, that it is unlikely all the short, thin chrysotile fibers they found arose this way.
  • Selected area electron diffraction was used only in a limited number of cases.

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: Mesothelioma, Carcinogenic, Stanton Hypothesis, Chrysotile, Causation.

Related studies

• Long and short fiber amosite asbestos alters at a different extent the redox metabolism in human lung epithelial cells — C. Riganti, E. Aldieri, et al. (2003)
• Quantification of the pathological response and fate in the lung and pleura of chrysotile in combination with fine particles compared to amosite-asbestos following short-term inhalation exposure — D.M. Bernstein, R.A. Rogers, et al. (2011)
• Persistence of long, thin chrysotile asbestos fibers in the lungs of rats — P.G. Coin, V.L. Roggli, et al. (1994)
• Short-term inhalation and in vitro tests as predictors of fiber pathogenicity — R.T. Cullen, B.G. Miller, et al. (1997)
• Cytotoxicity of a short-fiber chrysotile asbestos for human alveolar macrophages: preliminary observations — H. Yeager, D.A. Russo, et al. (1983)
• A comparative study on the hemolytic action of short asbestos fibers on human, rat, and sheep erythrocytes — J.P. Pelé, R. Calvert (1983)

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