Carcinogenicity of fibrous glaucophane: How should we fill the data gaps?

Our plain-English summary of Carcinogenicity of fibrous glaucophane: How should we fill the data gaps?, by A.G. Wylie, A.A. Korchevskiy (Current Research in Toxicology, 2021).

The study

• Authors: A.G. Wylie, A.A. Korchevskiy
• Journal: Current Research in Toxicology
• Published: 2021;2:202-203
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

•The modeled glaucophane mesothelioma potency is 0.0085 % vs. 0.5 % for riebeckite.•Lung cancer potency of glaucophane is 0.36 % vs. 4.82 % for Australian crocidolite.•The fibrosity index of glaucophane (0.77) is typical for non-asbestiform amphiboles.

© 2021 The Author(s).

In plain English

This was a letter to the editor, not a new study of cancer in exposed people. The authors responded to a 2021 paper by Gualtieri on fibrous glaucophane, an amphibole mineral present at the Calaveras Dam construction site in California. No studies of cancer in people exposed to glaucophane were available. The authors applied mathematical models they had built from fiber sizes and cancer data in other groups. They used size measurements of 27,650 airborne glaucophane particles collected just outside the construction area. Only about 54% of the particles were longer than 5 µm. Their models estimated a mesothelioma potency of 0.0085% for glaucophane, against about 0.5% for crocidolite. They estimated a lung cancer potency of 0.36% for glaucophane, against 4.82% for Australian crocidolite. Another model gave 0.013 to 0.017%, about 35 times lower than crocidolite but about 10 times higher than chrysotile. These were model estimates, not observed cancer rates. The authors concluded that their models place glaucophane in a low carcinogenicity category. They added that further toxicological and especially epidemiological studies would be needed.

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: Letter to the editor responding to another author's paper. It presents model-based calculations applied to existing particle size data and reports no new observations of cancer in people.
• Who was studied: Airborne glaucophane particles from aerosol samples collected downwind and just outside the Calaveras Dam construction area in California (data from B. Erskine); 27,650 particles were sized. No human population was studied.
• Exposure: Fibrous glaucophane, an amphibole mineral; compared with crocidolite (including Australian riebeckite/crocidolite) and chrysotile
• Main results:
  • For the Calaveras Dam glaucophane, the thin-fiber parameter EMPA was 1.2 and EMPB was 7.01%, compared with 46.7% and 71.1% for Australian riebeckite (crocidolite)
  • Width-based (power law) models gave a mesothelioma potency of 0.0085% for glaucophane, against approximately 0.5% estimated for different varieties of crocidolite
  • The Calaveras Dam glaucophane sample had a mean particle length of 6.94 µm, but only about 54% of particles were longer than 5 µm
  • Length-and-width models estimated the mesothelioma potency of the Calaveras Dam glaucophane as negative (non-existent) and its lung cancer potency as 0.36%, against 0.52% for mesothelioma and 4.82% for lung cancer for Australian crocidolite
  • A 2019 model based on chemical composition and dimensions gave a mesothelioma potency for glaucophane of 0.013 to 0.017%, approximately 35 times lower than for crocidolite
  • By that estimate, the Calaveras Dam glaucophane had a mesothelioma potency higher than chrysotile by a factor of 10
  • Raising the aspect ratio to match the more fibrous San Anselmo sample (median 18, against 5.4 for the Calaveras Dam sample) still gave a mesothelioma potency of around 0.2%, which the authors described as significantly lower than for crocidolite
  • The fibrosity index of glaucophane was 0.77. For comparison, nonasbestiform cummingtonite-grunerite from the Homestake gold mine had an average of 0.81 and Transvaal commercial grunerite had 0.17. The index is usually higher for nonasbestiform particles.
  • When Gualtieri's FPTI index values were compared with published mesothelioma potency in the corresponding worker cohorts, the correlation was not statistically significant (log-log R2 = 0.682, P = 0.2; untransformed R2 = 0.003, P = 0.92)
• The authors' conclusion: The authors concluded that models based on epidemiological data place this glaucophane in a low carcinogenicity category. They said further toxicological and especially epidemiological studies would be needed, and that filling data gaps without considering epidemiological information did not seem like a good idea.
• Limitations the authors state:
  • No epidemiological observations on cancer among workers or populations exposed to glaucophane were available
  • The authors stated that further toxicological and especially epidemiological studies would be needed to fully assess the carcinogenicity of California glaucophane

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Riebeckite, Lung Cancer, Crocidolite, Non-Asbestiform, Amphibole Group.

Related studies

• In vitro toxicity of fibrous glaucophane — A.F. Gualtieri, A. Zoboli, et al. (2021)
• Characterization and assessment of the potential toxicity/pathogenicity of fibrous glaucophane — D. Di Giuseppe, M. Harper, et al. (2019)
• Carcinogenicity of fibrous glass: pleural response in the rat in relation to fiber dimension — M.F. Stanton, M. Laynard, et al. (1977)
• Toxicity and carcinogenicity mechanisms of fibrous antigorite — V. Cardile, L. Lombardo, et al. (2007)
• Natural fibrous zeolites and their carcinogenicity-a review — K.R. Spurny (1983)
• Fibrous minerals in the lungs of mesothelioma patients: comparison between data on SEM, TEM, and personal interview information — T. Tuomi (1992)

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