Fiber carcinogenesis: epidemiologic observations and the Stanton hypothesis

Our plain-English summary of Fiber carcinogenesis: epidemiologic observations and the Stanton hypothesis, by J.S. Harington (Journal of the National Cancer Institute, 1981).

The study

• Author: J.S. Harington
• Journal: Journal of the National Cancer Institute
• Published: 1981;67(5):977-89
• Type of article: Review
• Read it: PubMed

In plain English

This guest editorial was a narrative review, not a new study. The author reviewed evidence on the Stanton hypothesis: that durable fibers, asbestos among them, cause cancer mainly through size and shape rather than chemistry. In rat experiments placing fibers directly on the pleura, mesothelioma correlated best with fibers under 1.5 μm in diameter and longer than 8 μm. The author described unpublished measurements by Timbrell. At the Paakkila anthophyllite mine in Finland, where no mesotheliomas were reported, 1% of airborne fibers were finer than 0.1 μm. At the Whitekloof crocidolite mine in South Africa's northwestern Cape the estimate was 60%. These figures suggested a critical diameter far below Stanton's. The editorial also recounted mesothelioma outbreaks among people exposed to crocidolite in South Africa and to erionite-type zeolite fibers in Turkish villages. The author noted that the inoculation experiments were artificial and limited to rats. The author concluded that the hypothesis was plausible for rat mesothelioma and that, allied with aerodynamic data on fiber deposition in the lung, no reason was apparent not to extend it to humans.

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: Guest editorial (narrative review) of animal experiments and epidemiologic observations on fiber carcinogenesis and the Stanton hypothesis; no new data collected by the author
• Who was studied: No study population of its own. The editorial reviewed rat (and some mouse) experiments by Wagner, Stanton, Pott and others. It also reviewed human observations from South Africa (northwestern Cape crocidolite area and northeastern Transvaal), the Paakkila anthophyllite mine in Finland, and the villages of Karain and Tuzköy and other parts of central Anatolia in Turkey.
• Exposure: Durable fibers of defined dimensions. These included asbestos (crocidolite, chrysotile, amosite, anthophyllite, tremolite), fibrous glass, aluminum oxide and other man-made fibers, and the zeolite erionite.
• Main results:
  • In the reviewed Stanton rat experiments using intrapleural application, the optimum correlation with mesothelioma was for fibers less than 1.5 μm in diameter and greater than 8 μm in length.
  • In the reviewed Wagner rat inoculation experiments, finer fibers produced more mesotheliomas.
  • The author reported that up to 14 fibrous materials were known to produce malignant tumors after implantation in the pleural or peritoneal cavities of animals.
  • In unpublished data from Timbrell described by the author, 1% of airborne fibers at the Paakkila anthophyllite mine (Finland, no reported mesotheliomas) were less than 0.1 μm in diameter. At the Whitekloof crocidolite mine (northwestern Cape, positive for mesothelioma) an estimated 60% were.
  • From these data the author suggested that a length of 8 μm is too high a threshold for fiber carcinogenicity.
  • In the reviewed South African observations, by 1959 domestic or occupational asbestos exposure had been found in 32 of 33 patients with histologically confirmed pleural mesothelioma.
  • In the reviewed Turkish report by Baris et al., 35 cases of pleural mesothelioma (over 40% of all deaths) occurred in Karain, a village of about 700 people, between 1970 and 1976.
  • In Karain and Tuzköy, where asbestos does not occur, fibers in the local tuff were identified as erionite-type zeolite fibers.
  • In a preliminary mouse experiment by Suzuki described by the author, intraperitoneal erionite produced 6 malignant peritoneal tumors (4 consistent with mesothelioma) in 10 mice. Mordenite had produced no malignant tumors so far.
• The authors' conclusion: The author concluded that the Stanton hypothesis is plausible for mesotheliomas and related malignant pleural tumors in rats. The author also stated that, allied with aerodynamic considerations, no reason is apparent why it should not be extended to humans.
• Limitations the authors state:
  • Intrapleural inoculation with massive fiber amounts is artificial, and direct application to humans would be unwise.
  • The hypothesis makes no judgment about lung cancer or asbestosis, about other animals, or about humans.
  • Precise information on how the Stanton fibers were prepared is not available.
  • Submicroscopic fibers, not visible by light microscopy, are present in all samples and are not counted.
  • Data on lung cancer and other cancers in the Turkish villages are limited.

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: Carcinogenesis, Stanton Hypothesis.

Related studies

• Characterization of mineral population by index particle: implication for the Stanton hypothesis — A.G. Wylie, R.L. Virta, et al. (1987)
• Studies of carcinogenesis of asbestos fibers and their natural oils — J.S. Harington, F.J. Roe (1965)
• Tests for effect of asbestos on benzo[a]pyrene carcinogenesis in the respiratory tract — L. Miller, W.E. Smith, et al. (1965)
• Man-made vitreous fibers and workers' health. An overview of the epidemiologic evidence — R. Saracci, L. Simonato (1982)
• Cell proliferation and carcinogenesis may share a common basis of permeable plasma membrane clusters — J.A. Beech (1992)
• Beyond Stanton and Pott hypothesis; carbon nanotubes-induced malignant mesothelioma as a disease of gene loss — G.J. Yoshida (2019)

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