Quantitative assessment of asbestos fibers in some normal and pathological extra-abdominal tissues-a scoping review

Our plain-English summary of Quantitative assessment of asbestos fibers in some normal and pathological extra-abdominal tissues-a scoping review, by F. Graziosi, P. Caffaro, M. Bonetti, et al (Journal of Occupational Medicine and Toxicology, 2023).

The study

• Authors: F. Graziosi, P. Caffaro, M. Bonetti, F. Roccuzzo, S. Rota, P. Boffetta, Y.A. Caraballo-Arias, C. Zunarelli, N. Danilevskaia, F.S. Violante
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2023;18(1):24
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Asbestos is a mineral present in nature and it has been used for years in numerous settings. Asbestos enters the bloodstream and lymphatic system mainly through breathing.

Objectives: Studies with asbestos fiber's quantification in human tissues are scarce except for the lung. This article summarizes asbestos studies in some extra-abdominal tissues.

Methods: A scoping review of articles that quantified asbestos fibers in extra-abdominal tissues (lymph nodes, pharynx, larynx, trachea, heart) by electron microscopy (Scanning-SEM or Transmission-TEM) was performed.

Results: The 10 studies selected comprised 52 cases, out of whom 108 samples were analyzed. Mostly samples were lymph node tissues (102), followed by larynx (3) and myocardium (3). No studies were found that determined the presence of asbestos in the pharynx or trachea. The concentration of asbestos fibers detected in the lymph nodes was from 0.003 million fibers per gram of dry tissue (mfgdt) up to 7400 mfgdt, in the larynx the range was from 0.5 mfgdt up to 3.6 mfgdt, in myocardium no asbestos fibers were detected.

Discussion: The studies included were heterogeneous in terms of case and sample characteristics and analytical techniques. As subjects exposed to asbestos are often positive for fibers in thoracic lymph nodes, we suggest that whenever a human tissue sample is analyzed for asbestos presence, the relevant draining lymph node should be concomitantly studied.

© 2023. The Author(s).

In plain English

This article was a scoping review, a structured survey of published studies, not new research. The authors sought studies counting asbestos fibers by electron microscopy in the pharynx, larynx, trachea, heart and thoracic lymph nodes. They found 10 studies, all case series from 1979 to 2014, covering 52 people and 108 tissue samples. No study meeting the review's criteria had measured the pharynx or trachea. Asbestos fibers, mostly amphiboles, were found in 88 of 102 lymph node samples. Concentrations ranged from 0.003 to 7400 million fibers per gram of dry tissue; the highest was in an asbestos sprayer. In one study of 21 people not occupationally exposed, 13 of 21 lymph node samples contained amphiboles. In another study, larynx samples from two occupationally exposed patients contained 0.5 to 3.6 million fibers per gram of dry tissue. No asbestos fibers were found in three heart muscle samples. The authors said the studies were too varied in cases, microscopes and counting methods for formal comparison. They suggested also studying the draining lymph node whenever tissue is tested for asbestos.

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: Scoping review of published studies (all of them case series) that measured asbestos fibers in extra-abdominal tissues by electron microscopy
• Who was studied: 10 published studies covering 52 subjects and 108 tissue samples from the larynx, myocardium and thoracic lymph nodes
• Exposure: Asbestos fibers (amphiboles and chrysotile) in tissues of people with occupational and/or non-occupational exposure, as measured by electron microscopy
• Main results:
  • No study meeting the review's inclusion criteria measured asbestos in the pharynx or trachea.
  • Lymph nodes: asbestos fibers, mostly amphiboles, were found in 88 of 102 samples.
  • Lymph node concentrations ranged from 0.003 to 7400 million fibers per gram of dry tissue. The highest value was found in an asbestos sprayer.
  • In one included study of 21 non-occupationally exposed people, amphibole fibers were found in 13 of 21 peritracheal lymph node samples (Table 3 lists 13 with and 8 without). The concentrations were 0.11 to 1.7 million fibers per gram of dry tissue.
  • Larynx: in one included study, two samples from two occupationally exposed patients both contained asbestos, at 0.5 to 3.6 million fibers per gram of dry tissue.
  • Myocardium (heart muscle): no asbestos fibers were found in the three samples, which all came from one included study.
• The authors' conclusion: The authors suggested that whenever a human tissue sample is analyzed for asbestos, the relevant draining lymph node should also be studied at the same time.
• Limitations the authors state:
  • Only 10 studies were found. They were very heterogeneous in cases and samples, which did not allow a formal comparison of results.
  • The studies used different microscopes with different resolving power.
  • Fiber counting procedures, including fiber length cut-offs, varied widely between studies.
  • There were few data for each tissue type, so asbestos-related cases could not be compared with the general population.

Topics

Medical terms in this study, explained in our Lexicon: Fibers Per Gram.

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