Measuring EMPs in the lung what can be measured in the lung: Asbestiform minerals and cleavage fragments

Our plain-English summary of Measuring EMPs in the lung what can be measured in the lung: Asbestiform minerals and cleavage fragments, by V.L. Roggli (Toxicology and Applied Pharmacology, 2018).

The study

• Author: V.L. Roggli
• Journal: Toxicology and Applied Pharmacology
• Published: 2018;361:14-17
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos mineral fibers have been associated with the development of a variety of diseases in humans and experimental animals, including asbestosis, lung cancer, and mesothelioma. Asbestos includes several mineral types divided into two mineral groups, serpentine and amphibole forms. Chrysotile is the serpentine mineral classified as asbestos, whereas the amphiboles include amosite, crocidolite, tremolite, actinolite and anthophyllite. There are a number of mineral fibers that occur with asbestiform morphology and that have been associated with various asbestos-induced diseases. These include the Libby amphiboles (associated with a vermiculite mine northwest of Libby, MT), erionite (in Turkey and North America), fluoro-edenite (in Sicily), and perhaps balangeroite (in Italy). In addition, each of the asbestos minerals occurs in a non-fibrous form, and these may occur as cleavage fragments that satisfy the definition for a fiber, i.e., particles with an aspect ratio of at least 3:1 and roughly parallel sides. Cleavage fragments of non-asbestiform minerals have not been associated with asbestos-induced diseases nor are these minerals regulated by the Occupational Safety and Health Administration. Finally, there are a number of other mineral species which can occur in human lung samples that satisfy the definition for a fiber as given above. These similarly have not been associated with asbestos-induced diseases. All of these various minerals satisfying the definition for a fiber can be referred to as elongated mineral particles (EMP). It is the purpose of this presentation to discuss the role of scanning electron microscopy (SEM) equipped with an energy dispersive x-ray analyzer (EDXA) in the detection and classification of EMP in human lung samples.

Copyright © 2018 Elsevier Inc. All rights reserved.

In plain English

This article was a methods review, not a study of patients. It described how scanning electron microscopy with an energy dispersive x-ray analyzer (SEM/EDXA) is used to detect and classify 'elongated mineral particles' (EMP) in human lung tissue. It listed the types reported in lung samples: six asbestos minerals regulated as asbestos, asbestiform fibers not regulated as asbestos (such as erionite, fluoro-edenite and the Libby amphiboles), cleavage fragments, manmade fibers, and other particles such as talc and silica. The author's laboratory counted only fibers 5 µm or longer. In that laboratory's experience, very few amosite or crocidolite fibers were shorter than 10 µm, and nearly all were thinner than 1 µm. Many tremolite, actinolite and anthophyllite fibers were wider and not infrequently 5 to 10 µm long, which made them hard to tell apart from cleavage fragments. The author concluded that EMP types can usually be distinguished, with limitations, and recommended recording each such fiber's dimensions. Stated limitations included unstandardized methods, not knowing when a particle was deposited, contamination, and variation between sites in the lung.

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: Methods review (presentation) summarizing laboratory methodology and its difficulties and pitfalls; no new patient series or counts were reported
• Who was studied: Human lung tissue samples in general, including those analyzed in the author's laboratory; no number of samples, place or time period was given
• Exposure: Elongated mineral particles: asbestos (chrysotile, amosite, crocidolite, tremolite, actinolite, anthophyllite), non-regulated asbestiform fibers (erionite, fluoro-edenite, balangeroite, winchite, richterite), cleavage fragments, manmade fibers, and other particles such as talc, silica, titanium dioxide and metal oxides
• Main results:
  • The author's laboratory counted only fibers 5 µm or longer, on the stated basis that shorter fibers have not been convincingly shown to cause disease
  • In the author's laboratory experience with fibers 5 µm or longer, very few amosite or crocidolite fibers were shorter than 10 µm, and their diameter was nearly always under 1 µm
  • Many tremolite, actinolite or anthophyllite fibers tended to be wider than amosite or crocidolite and not infrequently were 5 to 10 µm long, so telling asbestiform fibers from cleavage fragments by shape and elemental composition alone remained problematic
  • For erionite, winchite, richterite, fluoro-edenite and balangeroite, telling them from asbestos was based on elemental composition and was usually straightforward
  • Fibrous glass was uncommonly identified in lung samples because it dissolves rapidly, while refractory ceramic fibers have been identified in human lung tissue samples
  • Identifying carbon nanotubes by SEM/EDXA was described as problematic because they are pure carbon
  • Other elongated particles routinely found by the author's laboratory included talc, silica, fibrous titanium dioxide, aluminum silicate, other silicates, endogenous calcium fibers, barium sulfate and metal oxides. The author stated there is little evidence these cause or contribute to human disease
• The authors' conclusion: The author concluded that analytical electron microscopy (TEM or SEM with EDXA) can identify and quantify elongated mineral particles in human tissue and can usually distinguish the different types, with limitations. The author recommended caution in classifying fibers shorter than 10 µm and wider than 1 µm, and recording the dimensions of each such fiber.
• Limitations the authors state:
  • Preparation methods for human tissue samples have not been standardized and are somewhat complex, so each laboratory needs its own control or reference population
  • Results from different laboratories are difficult to compare directly
  • It is not possible to tell when a particular particle was deposited in the lung
  • For particles that do not persist in the lung, such as fibrous glass or chrysotile asbestos, past dose is difficult to measure accurately from lung tissue
  • Samples can be contaminated, for example by particles released from glassware or from an outside source
  • Results can differ depending on which site in the lung is sampled
  • Laboratories have reported higher values with low temperature plasma ashing than with wet chemical digestion, and it is unclear whether ashing is more sensitive or breaks fibers apart

Topics

Medical terms in this study, explained in our Lexicon: Asbestiform, Cleavage Fragment, Mineral Fiber, Lung Cancer, Mesothelioma, Serpentine Group, Amphibole Group, Chrysotile.

Related studies

• Dimensions of elongated mineral particles: a study of more than 570 fibers from more than 90 cases with implications for pathogenicity and classification as asbestiform vs. cleavage fragments — V.L. Roggli, C.L. Green (2019)
• Comments on "Dimensions of elongated mineral particles with implications for pathogenicity and classification as asbestiform versus cleavage fragments" — M.M. Finkelstein (2019)
• Measurement of elongate mineral particles: What we should measure and how do we do it? — E.J. Chatfield (2018)
• Mechanistic in vitro studies: What they have told us about carcinogenic properties of elongated mineral particles (EMPs) — B.T. Mossman (2018)
• Identification and analysis of ambient EMPs — D.R. Van Orden (2018)
• Assessment of the pathogenic potential of asbestiform vs. nonasbestiform particulates (cleavage fragments) in in vitro (cell or organ culture) models and bioassays — B.T. Mossman (2008)

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