Validation of freeze-drier/plasma asher method for analysis of asbestos in the lung tissue

Our plain-English summary of Validation of freeze-drier/plasma asher method for analysis of asbestos in the lung tissue, by A.B. Somigliana (Frontiers in Chemistry, 2025).

The study

• Author: A.B. Somigliana
• Journal: Frontiers in Chemistry
• Published: 2025;13:1581910
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: The analysis of asbestos fibers in lung tissue is complex due to both the biological matrix and the analyte. Lung tissue preparation techniques for asbestos burden analysis require the removal of organic matter to make the inorganic mineral components visible. The method's validation is challenging due to the analyte's inherent variability. This study outlines a procedure for validating an asbestos fiber analysis method in lung tissue.

Methods: At the Electron Microscopy Laboratory of ARPA Lombardia, a method using a plasma asher for freeze-dried lung tissue digestion was developed. The analysis is carried out with a scanning electron microscope equipped with an energy-dispersive x-ray spectrometer. Problems associated with interferences, instrument calibration and resolution, analytical sensitivity, recovery were described in detail. The trueness and precision of the analytical method were evaluated using certified reference materials in accordance with ISO 33403:2024 standard.

Results And Conclusion: The developed method underwent a rigorous validation process to ensure metrological traceability of the results. Using validated analytical methods with consistent counting rules ensures comparability of data across laboratories while guaranteeing traceable results.

Copyright © 2025 Somigliana.

In plain English

This brief research report from ARPA Lombardia's Electron Microscopy Laboratory in Milan, Italy, described and validated a method for counting asbestos fibers in human lung tissue. Lung samples were freeze-dried, 100 mg of dry tissue was burned in an oxygen plasma asher, and the ash was filtered and examined by scanning electron microscopy with x-ray analysis. Asbestos fibers longer than 1 μm were counted. Asbestos-free lung tissue was spiked with chrysotile, amosite and crocidolite. In it, the preparation did not significantly alter fiber appearance or x-ray spectra, and fibrils about 30 nm wide were visible. Two certified reference lung materials were each analyzed eight times, one containing amosite plus crocidolite and one containing anthophyllite. Their measured means (49.6 and 5.8 million fibers per gram of dry tissue) were not significantly different from the certified values (49.0 and 5.1). No lung tissue reference material certified for chrysotile was available, so this precision and trueness check could not be done for chrysotile. The author concluded that validated methods with consistent counting rules ensure comparable data across laboratories and traceable results. The laboratory gained ISO 17025 accreditation for the method.

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: Laboratory analytical method development and validation study (brief research report)
• Who was studied: No group of people was studied. The method was tested at the Electron Microscopy Laboratory of ARPA Lombardia, Milan, Italy, on two things: a sample of asbestos-free lung tissue spiked with asbestos, and two certified reference materials of freeze-dried lung tissue (BCR-665 and BCR-666), analyzed eight times.
• Exposure: The spiked lung tissue contained chrysotile, amosite and crocidolite (commercial asbestos NIST 1866b). The reference materials contained amphibole asbestos (amosite plus crocidolite) in BCR-665 and anthophyllite in BCR-666. Asbestos fibers longer than 1 μm were counted at 12,000 times magnification.
• Main results:
  • At 12,000 times magnification, the microscope could see and identify fibrils as small as about 30 nm in diameter.
  • In the spiked lung tissue, the preparation method did not significantly alter the morphology or x-ray spectra of the asbestos fibers, compared with fibers that had not been processed.
  • BCR-665 (amosite plus crocidolite): measured mean 49.6 million fibers per gram of dry tissue, against a certified value of 49.0. BCR-666 (anthophyllite): measured mean 5.8, against a certified value of 5.1. Both means came from 8 measurements. For both materials, the measured means were not significantly different from the certified values.
  • There was no evidence that the method's precision differed from what the counting (Poisson) uncertainty would predict. The precision test values were 1.15 for BCR-665 and 1.56 for BCR-666, both below the table value of 2.01.
  • The Poisson counting component was the main source of uncertainty. When 50 fibers are counted, the extended Poisson uncertainty is 28%, which the author found close to the roughly 30% uncertainty given for the reference materials.
  • The analytical sensitivity should be at least 0.1 million fibers per gram of dry tissue. The working range runs from 0 to about 300 million fibers per gram of dry tissue, and can be extended by using a filter with less lung tissue on it.
• The authors' conclusion: The author concluded that the method went through a validation process to ensure metrological traceability. The author also concluded that validated methods with consistent counting rules ensure comparable data across laboratories and traceable results. The work led to ISO 17025 accreditation of the laboratory for the method.
• Limitations the authors state:
  • No lung tissue reference material certified for chrysotile content was available, so precision and trueness could not be assessed in the same way for chrysotile. The author states that the recovery assessments on chrysotile reasonably allow the method to be used for it.
  • Recovery could only be assessed indirectly, by checking that the preparation does not change fiber composition or morphology. The author explains that spiking lung tissue with a known, controlled amount of asbestos is impractical.
  • Only fibers longer than 1 μm were counted, because the two available reference materials are certified only for amphibole fibers longer than 1 μm.

Topics

Medical terms in this study, explained in our Lexicon: Tissue Digestion, Analytical Sensitivity.

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