Global geological occurrence and character of the carcinogenic zeolite mineral, erionite: A review

Our plain-English summary of Global geological occurrence and character of the carcinogenic zeolite mineral, erionite: A review, by J.P. Patel, M.S. Brook, M. Kah, et al (Frontiers in Chemistry, 2022).

The study

• Authors: J.P. Patel, M.S. Brook, M. Kah, A. Hamilton
• Journal: Frontiers in Chemistry
• Published: 2022;10:1066565
• Type of article: Review
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

As with the six regulated asbestos minerals (chrysotile, amosite, crocidolite, anthophyllite, tremolite, and actinolite), the zeolite mineral, erionite, can exhibit a fibrous morphology. When fibrous erionite is aerosolized and inhaled, it has been linked to cases of lung cancers, such as malignant mesothelioma. Importantly, fibrous erionite appears to be more carcinogenic than the six regulated asbestos minerals. The first health issues regarding erionite exposure were reported in Cappadocia (Turkey), and more recently, occupational exposure issues have emerged in the United States. Erionite is now classified as a Group 1 carcinogen. Thus, identifying the geological occurrence of erionite is a prudent step in determining possible exposure pathways, but a global review of the geological occurrence of erionite is currently lacking. Here, we provide a review of the >100 global locations where erionite has been reported, including: 1) geological setting of host rocks; 2) paragenetic sequence of erionite formation, including associated zeolite minerals; 3) fiber morphological properties and erionite mineral series (i.e., Ca, K, Na); and 4) a brief overview of the techniques that have been used to identify and characterize erionite. Accordingly, erionite has been found to commonly occur within two major rock types: felsic and mafic. Within felsic rocks (in particular, tuffaceous layers within lacustrine paleoenvironments), erionite is disseminated through the layer as a cementing matrix. In contrast, within mafic (i.e., basaltic) rocks, erionite is typically found within vesicles. Nevertheless, aside from detailed studies in Italy and the United States, there is a paucity of specific information on erionite geological provenance or fiber morphology. The latter issue is a significant drawback given its impact on erionite toxicity. Future erionite studies should aim to provide more detailed information, including variables such as rock type and lithological properties, quantitative geochemistry, and fiber morphology.

Copyright © 2022 Patel, Brook, Kah and Hamilton.

In plain English

This was a review, not a new laboratory or health study. The authors gathered published reports of erionite, a natural zeolite mineral that can form fibers. Earlier studies, which the authors cite, have linked erionite to malignant mesothelioma. They found reports of erionite at 139 locations in 26 countries. Of these, 95 described the basic shape of the mineral, 37 reported fiber size, and 38 gave its chemical makeup in any detail. Erionite was most often reported in rocks from the Miocene epoch (23 to 5.3 million years ago). In silica-rich (felsic) rocks such as tuff, it was usually spread through the body of the rock. In basalt and other mafic rocks, it was usually found in small cavities called vesicles. Using World Health Organization fiber-size criteria, the authors judged that erionite could potentially be a hazard in at least 15 of the reported locations. The authors concluded that all three types of erionite (calcium, potassium and sodium) can potentially be inhalable. They cautioned that the fiber-size data were limited and that much published information was fragmentary.

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: Review of published literature on where erionite occurs geologically and how it has been characterized
• Who was studied: Published reports of erionite from 139 locations in 26 countries worldwide (rock and mineral occurrences, not people)
• Exposure: Erionite, a zeolite mineral that can be fibrous, in its three compositional forms: erionite-Ca, erionite-Na and erionite-K
• Main results:
  • Of the 139 locations, 95 reports described the basic shape of the erionite and only 37 reported fiber size
  • Of the 139 locations, only 38 reported the chemical composition of the erionite in any detail
  • In felsic rocks (tuff) erionite was usually found within the rock matrix; in mafic rocks (basalt) it was found in vesicles
  • Most erionite worldwide was reported from rocks formed during the Miocene epoch (23 to 5.3 million years ago)
  • The authors identified six characteristic geological settings in which erionite forms
  • The zeolites most commonly reported alongside erionite were clinoptilolite, chabazite, phillipsite, analcime and mordenite
  • Most reported erionite fiber diameters were under 1 micrometre, regardless of erionite type
  • Applying WHO size guidelines (length 5 micrometres or more, diameter under 3 micrometres, length-to-diameter ratio of at least 3 to 1), erionite could potentially be a hazard in at least 15 of the reported locations
  • Within the limited fiber-size data, erionite-K may be the type most likely to have an inhalable size and shape
  • X-ray diffraction was the method most often used in the literature to identify erionite, followed by scanning electron microscopy and electron microprobe analysis
  • The authors questioned an earlier study's use of a ternary diagram to conclude that North Dakota and Old Sarihidir (Turkey) erionite were chemically similar
• The authors' conclusion: The authors concluded that, from the morphological data reported, all three end-member types of erionite (Ca, K, Na) can potentially be inhalable. They also concluded that cryogenic TEM-EDS combined with ICP-MS has been shown to have the potential to be the most accurate way to identify erionite.
• Limitations the authors state:
  • The information compiled from the published studies was fragmentary, because most studies did not focus on geology
  • The fiber-size dataset was limited and should be treated with caution
  • Some studies reported the diameter of fiber bundles rather than single fibrils, which may hinder comparisons between sites
  • Reported fiber lengths may be affected by fibers breaking during sample collection and preparation
  • Most publications did not specify host rock composition, so many rocks had to be classed as undifferentiated volcanics
  • The exact timing or duration of erionite formation within host rocks is unknown in most cases

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Zeolite, erionite, Asbestos, Chrysotile, Amosite, Crocidolite, Anthophyllite.

Related studies

• Geological occurrence, mineralogical characterization, and risk assessment of potentially carcinogenic erionite in Italy — M. Giordani, M. Mattioli, et al. (2017)
• Erionite series minerals: mineralogical and carcinogenic properties — A.U. Dogan, M. Dogan, et al. (2008)
• Occurrence, behaviour, and human exposure pathways and health risks of toxic geogenic contaminants in serpentinitic ultramafic geological environments (SUGEs): A medical geology perspective — W. Gwenzi (2020)
• CT findings in malignant pleural mesothelioma related to nonoccupational exposure to asbestos and fibrous zeolite (erionite) — C. Erzen, M. Eryilmaz, et al. (1991)
• Detection of Erionite and Other Zeolite Fibers in Soil by the Fluidized Bed Preparation Methodology — D. Berry, J. Januch, et al. (2019)
• Geologic occurrences of erionite in the United States: an emerging national public health concern for respiratory disease — B.S. Van Gosen, T.A. Blitz, et al. (2013)

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