Dust particles in lung sections. Some notes on methods of their visualization

Our plain-English summary of Dust particles in lung sections. Some notes on methods of their visualization, by P. Gross, E.B. Tolker (Archives of Environmental Health, 1966).

The study

• Authors: P. Gross, E.B. Tolker
• Journal: Archives of Environmental Health
• Published: 1966;12(2):213-6
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

In plain English

This 1966 article was a short methods note, not a study of disease. While studying how rat lungs cleared inhaled antimony trioxide, the authors found that darkly staining tissue made dust hard to see in stained sections. They described examining cleared, unstained lung sections under a microscope with dark-field lighting, which made opaque dust glow against a dark background and showed its overall amount and distribution. Examples included rat lungs exposed to antimony trioxide or metallic aluminum. Another example was a field from an asbestotic lung in which two asbestos bodies, easily missed in the stained section, stood out clearly. Coarser asbestos fibers could also be seen this way. Formaldehyde precipitate and hemosiderin also glowed, but could be removed. Silica and silicates could not be seen with this method, and the authors considered microincineration still the best method for them. In rats injected with quartz dust, the authors could not see any of the dust with polarized light either.

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 methods note describing a microscopy technique (dark-field examination of unstained lung sections), illustrated with rat experiments and a section of asbestotic lung
• Who was studied: Lung sections from rats exposed to dusts in the laboratory, plus a field from an asbestotic lung. The article does not say whose lung it was or how many sections were examined.
• Exposure: Rats exposed to antimony trioxide dust (1,230 mg/m3 for 12 hours in an inhalation chamber), intratracheal metallic aluminum powder, and intratracheal quartz dust (30 mg). Other dusts examined included lignite, coal, carbon black, silicon carbide, iron oxide and aluminum oxide. Asbestos bodies and fibers were examined in an asbestotic lung; the fiber type is not stated.
• Main results:
  • Dark-field examination of unstained sections gave an overall picture of the amount and distribution of dust, which was hard to obtain from stained sections.
  • In the asbestotic lung, two asbestos bodies that could easily be missed in the stained section were clearly visible under dark-field lighting. The method had been useful for finding asbestos bodies otherwise missed in routinely stained sections.
  • Coarser asbestos fibers could also be visualized with the dark-field method.
  • Several dusts were well demonstrated with the method, including silicon carbide, iron oxide, metallic aluminum and aluminum oxide. Lignite dust glowed differently from coal dust.
  • Hemosiderin and formaldehyde precipitate also glowed under dark-field lighting. Hemosiderin glow was removed by soaking in 5% oxalic acid for three hours, and formaldehyde precipitate by treatment with dilute ammonia.
  • In rats injected intratracheally with 30 mg quartz dust, none of the dust could be seen with crossed Polaroid films (polarized light).
• The authors' conclusion: The authors concluded that asbestos bodies and coarse asbestos fibers are readily visualized with dark-field illumination in cleared, unstained sections. They also concluded that silica and silicates cannot be visualized this way, and that microincineration remains the best method for those dusts.
• Limitations the authors state:
  • Silica and silicates cannot be visualized with the dark-field method.
  • Stained sections are generally not suitable for dark-field examination, because stains make tissues glow.
  • Microincineration, the alternative method, is not suitable for combustible dusts or dusts soluble in hydrochloric acid, and it destroys the section.

Related studies

• Fibrous dust particles and ferruginous bodies. Methods for quantitating them and some results from the lungs of city dwellers — P. Gross, J. Tuma, et al. (1970)
• An electron microscopy study of the effect of asbestos dust on the lung — J.M. Davis (1963)
• Sample preparation method for visualization of nanoparticulate captured on mixed cellulose ester filter media by enhanced darkfield microscopy and hyperspectral imaging — N.M. Neu-Baker, A.C. Eastlake, et al. (2019)
• Patterns of histopathological change determined by the point counting method and its application for the hazard assessment of respirable dust — A. Ogami, Y. Morimoto, et al. (2004)
• A comparison of historic asbestos measurements using a thermal precipitator with the membrane filter-phase contrast microscopy method — G. Burdett (1998)
• Some biological properties of respirable iron ore dust — D. Keast, N.P. Sheppard, et al. (1987)

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