Asbestos and Zeolites: from A to Z via a Common Ion

Our plain-English summary of Asbestos and Zeolites: from A to Z via a Common Ion, by G. Reid, S. Klebe, N. van Zandwijk, et al (Chemical Research in Toxicology, 2021).

The study

• Authors: G. Reid, S. Klebe, N. van Zandwijk, A.M. George
• Journal: Chemical Research in Toxicology
• Published: 2021;34(4):936-951
• Type of article: Review
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos and zeolites are silicate-based minerals, linked inextricably via paradoxical similarities and differences which have emanated from different geological epochs. Both have been employed in the service of humanity through millennia: asbestos, for its "inextinguishable" quality of being an insulator against heat and fire; zeolite, a "boiling stone" with its volcanic and marine sedimentary rock origins, for its propensity to adsorb water and remove metals and toxins. Serious adverse health effects observed in asbestos miners as long ago as the 1st Century AD did not halt the rising popularity of asbestos. As the miracle material of the 1900s, asbestos production and consumption exploded, culminating in its ubiquity in ships, vehicles, homes, commercial buildings, and over 3000 different industrial and household products. Through the 1940s and 1950s, epidemiological studies concluded that asbestos was a likely cause of asbestosis, lung cancer, and malignant mesothelioma, and it is now banned in many but far from all countries. The long latency between exposure to asbestos and the occurrence of cancer has obscured the deadly consequences of asbestos exposure for centuries. Even today, a considerable part of the world population is insufficiently aware of the dangers of asbestos, and millions of tons of this carcinogen continue to be mined and used worldwide. Zeolites, both natural and synthetic, are microporous aluminosilicate minerals commonly used in a myriad of processes, in the petrochemical industry, in domestic appliances and cleaning agents, as commercial adsorbents and exchangers for toxins and pollutants, and as catalysts. Zeolites are found in agriculture, veterinary science, and human health. More recently, new materials such as carbon nanotubes are being employed in materials requiring durability and thermal and electrical conductivity, yet nanotubes are now joining the ranks of more established particulates such as asbestos and silica, in causing human disease. In this review, we compare and contrast the similarities and differences of these two groups of silicate minerals and their waxing and waning use in the employ of humanity.

In plain English

This article was a review, not a new study. The authors compared asbestos and zeolites, both silicate minerals, using published cell, animal and human research. They described the main difference as iron. Asbestos is laden with iron while zeolite is iron-free. Chrysotile typically contains 2 to 6% iron, and crocidolite and amosite up to 28%. The authors cited multiple studies suggesting iron in or on asbestos fibers is a key "catalyst" for asbestos toxicity. The zeolite erionite was the noted exception: the review described a mesothelioma epidemic in Cappadocia, Turkey, that caused 50% of all deaths in three small villages. The review also described an earlier pilot study by Fan and colleagues, three of whom wrote this review, in a transgenic mouse model of mesothelioma. By the end of the 30-week trial, all 13 mice injected with crocidolite alone reached humane end points, compared with 7 of 29 given crocidolite plus the zeolite clinoptilolite. The authors concluded zeolites appear benign or far less injurious than asbestos, except erionite. They said more thorough studies of zeolites in humans are warranted.

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: Narrative review
• Who was studied: No study population of its own. The review covered published cell culture, animal and human studies of asbestos and zeolites.
• Exposure: Asbestos fibers (chrysotile, crocidolite, amosite and other amphiboles) compared with natural and synthetic zeolites (including clinoptilolite and erionite). The review emphasized differences in iron content. Carbon nanotubes were also discussed briefly.
• Main results:
  • The authors described iron as the chief chemical difference between the two mineral groups: asbestos contains iron and zeolite does not.
  • Citing other studies, the authors stated that iron in or on asbestos fibers appears to be a key factor in asbestos toxicity.
  • The zeolite erionite was described as the exception. A mesothelioma epidemic in Cappadocia, Turkey, caused 50% of all deaths in three small villages.
  • Erionite has been classified by IARC as a Group 1 human carcinogen.
  • In the cited Fan et al. pilot study, mice in a transgenic mouse model were injected with crocidolite, with or without clinoptilolite, and monitored for 30 weeks.
  • By the end of that 30-week trial, all 13 mice injected with crocidolite alone had reached humane end points. Only 7 of 29 mice given crocidolite plus clinoptilolite had reached a similar stage of disease.
  • The cited Fan et al. 2019 mouse study was co-authored by three of this review's authors (van Zandwijk, Reid and George).
  • Citing other studies, the review stated that breathing in carbon nanotubes can cause inflammation, fibrosis and fibrotic granulomas similar to those seen with asbestos exposure.
• The authors' conclusion: The authors concluded that zeolites appear benign, or at least far less injurious to human health than asbestos, with the exception of erionite, which may induce cancer.
• Limitations the authors state:
  • Studies from one research group claiming that zeolites act against toxins and cancer have not been reproduced by other groups.
  • The authors called their summary of asbestos toxicity in cells and animals patchy.
  • The zeolite toxicology studies reviewed were constrained by giving zeolite in the diet.
  • The authors stated that more thorough toxicological studies of zeolites in humans are needed.
  • The review was restricted to articles judged scientifically rigorous and deliberately left out 'alternative medicine' claims.

Topics

Medical terms in this study, explained in our Lexicon: Zeolite, Silicate, Insulator, Lung Cancer, Malignant Mesothelioma, Latency, Asbestos Exposure.

Related studies

• Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates — E. Fach, W.J. Waldman, et al. (2002)
• In vitro interaction of zeolite fibers with individual cells (macrophages NR8383): measurement of intracellular oxidative burst — B.D. Hogg, P.K. Dutta, et al. (1996)
• Peculiarities of the clastogenic properties of chrysotile-asbestos fibers and zeolite particles — A.D. Durnev, N.O. Daugel-Dauge, et al. (1993)
• Zeolites ameliorate asbestos toxicity in a transgenic model of malignant mesothelioma — X. Fan, C. McLaughlin, et al. (2019)
• Malignant mesothelioma induced by asbestos and zeolite in the mouse peritoneal cavity — Y. Suzuki, N. Kohyama (1984)
• CT findings in malignant pleural mesothelioma related to nonoccupational exposure to asbestos and fibrous zeolite (erionite) — C. Erzen, M. Eryilmaz, et al. (1991)

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