Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes

Our plain-English summary of Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes, by Y. Grosse, D. Loomis, K.Z. Guyton, et al (The Lancet. Oncology, 2014).

The study

• Authors: Y. Grosse, D. Loomis, K.Z. Guyton, B. Lauby-Secretan, F. El Ghissassi, V. Bouvard, L. Benbrahim-Tallaa, N. Guha, C. Scoccianti, H. Mattock, K. Straif, International Agency for Research on Cancer Monograph Working Group
• Journal: The Lancet. Oncology
• Published: 2014;15(13):1427-1428
• Type of article: News
• Cited by: 209 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

This news report summarised the evaluations made in October 2014 by 21 experts from ten countries who met at the International Agency for Research on Cancer (IARC) in Lyon, France, to assess the carcinogenicity of fluoro-edenite, silicon carbide (SiC) fibres and whiskers, and carbon nanotubes (CNTs). The assessments were to be published as Volume 111 of the IARC Monographs. Fluoro-edenite, which can occur as asbestiform fibres, was identified near the Etna volcano at Biancavilla, Italy. There, surveillance studies reported excess mesothelioma that was similar in men and women and most prominent in young adults, and most cases had no history of occupational asbestos exposure. Fibrous fluoro-edenite was classified as carcinogenic to humans (Group 1). Occupational exposures in the Acheson process were classified as Group 1 because of lung cancer in Canadian and Norwegian worker cohorts. Fibrous SiC was classified as possibly carcinogenic (Group 2B) because its effects were difficult to separate from those of cristobalite. SiC whiskers, produced as asbestos substitutes, caused mesotheliomas in rats. In a decision that was not unanimous, they were classified as probably carcinogenic (Group 2A) because they resemble asbestos and erionite fibres. No human cancer data were available for CNTs. MWCNT-7, which caused mesotheliomas in rats and mice, was classified as possibly carcinogenic (Group 2B). Single-walled CNTs and other multi-walled CNTs were not classifiable (Group 3).

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This is a short news report, not an original study. It summarised an October 2014 meeting where 21 experts from ten countries at the International Agency for Research on Cancer (IARC) reviewed cancer evidence on fluoro-edenite, silicon carbide (SiC) fibres and whiskers, and carbon nanotubes. Fluoro-edenite, found near the Etna volcano at Biancavilla, Italy, can occur as asbestiform fibres. Surveillance studies there reported excess mesothelioma, similar in men and women. The group classified fluoro-edenite fibrous amphibole as carcinogenic to humans (Group 1) for mesothelioma. Occupational exposures in the Acheson process for making SiC were placed in Group 1 for lung cancer. Fibrous SiC itself was placed only in Group 2B (possibly carcinogenic), because its effects were hard to separate from cristobalite. SiC whiskers, made as asbestos substitutes, were rated probably carcinogenic (Group 2A). The basis was animal evidence and their resemblance to asbestos, and the decision was not unanimous. MWCNT-7, one type of multi-walled carbon nanotube, was rated Group 2B. Single-walled nanotubes, and multi-walled nanotubes other than MWCNT-7, were placed in Group 3 (not classifiable). No human cancer data were available for nanotubes or SiC whiskers.

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: News report of an IARC Monographs expert Working Group evaluation (a review of published human, animal and mechanistic evidence), not an original study
• Who was studied: Published evidence reviewed by the Working Group in October 2014. It included surveillance studies of the regional population of Biancavilla, Italy, two cohorts of Acheson process workers (Canada and Norway), and studies in rats, mice and cultured cells.
• Exposure: Fluoro-edenite fibres, which can be asbestiform, from local quarry products used in unpaved roads and building materials in Biancavilla. Also silicon carbide fibres (by-products of the Acheson process), SiC whiskers (made as asbestos substitutes), and single-walled and multi-walled carbon nanotubes.
• Main results:
  • In Biancavilla, the mesothelioma excess was similar in men and women and most prominent in young adults. The report says this suggests an environmental rather than occupational cause.
  • Most of the Biancavilla mesothelioma cases had no history of occupational asbestos exposure.
  • Fluoro-edenite fibrous amphibole was classified Group 1 (carcinogenic to humans), based on sufficient evidence in humans that it causes mesothelioma.
  • Occupational exposures associated with the Acheson process were classified Group 1, based on sufficient evidence in humans that they cause lung cancer.
  • Fibrous SiC was classified Group 2B (possibly carcinogenic to humans), based on limited evidence in humans for lung cancer.
  • SiC whiskers were classified Group 2A (probably carcinogenic to humans), and the decision was not unanimous. The basis was mesotheliomas in rat studies and physical properties resembling asbestos and erionite.
  • MWCNT-7 caused peritoneal mesotheliomas in male and female rats in one intraperitoneal injection study.
  • MWCNT-7 was classified Group 2B. Single-walled nanotubes, and multi-walled nanotubes other than MWCNT-7, were placed in Group 3 (not classifiable).
• The authors' conclusion: The Working Group classified fluoro-edenite fibrous amphibole and Acheson process occupational exposures as Group 1. It placed SiC whiskers in Group 2A, fibrous SiC and MWCNT-7 in Group 2B, and single-walled nanotubes and other multi-walled nanotubes in Group 3.
• Limitations the authors state:
  • In the Norwegian SiC worker cohort, the exposure-response relationship was somewhat weakened after adjusting for cristobalite exposure.
  • Exposures to SiC fibres and cristobalite were correlated, making their separate effects difficult to disentangle.
  • No data on cancer in humans exposed to SiC whiskers were available.
  • No human cancer data on carbon nanotubes were available to the Working Group.
  • Measurement of occupational exposure to nanotubes is limited, and consumer exposure was not quantified.
  • A majority did not consider the mechanistic evidence strong for any specific nanotube. Lack of coherent evidence across nanotube types prevented generalising to other types.

Topics

Medical terms in this study, explained in our Lexicon: fluoro-edenite, IARC, Asbestiform, Biancavilla, Mesothelioma, Asbestos Exposure, Carcinogenic, Occupational Exposure.

Related studies

• The toxicity, in vitro, of silicon carbide whiskers — G.L. Vaughan, J. Jordan, et al. (1991)
• The carcinogenicity of WHO fibers of silicon carbide: SiC whiskers compared to cleavage fragments of granular SiC — K. Rödelsperger, B. Brückel (2006)
• Histopathological changes in rat lung following intratracheal instillation of silicon carbide whiskers and potassium octatitanate whiskers — A. Ogami, Y. Morimoto, et al. (2007)
• Pulmonary response, in vivo, to silicon carbide whiskers — G.L. Vaughan, S.A. Trently, et al. (1993)
• In vitro activity of silicon carbide whiskers in comparison to other industrial fibers using four cell culture systems — N.F. Johnson, M.D. Hoover, et al. (1992)
• Pulmonary effects and biopersistence of deposited silicon carbide whisker after 1-year inhalation in rats — I. Akiyama, A. Ogami, et al. (2007)

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