Report on The Pulmonary Response to Brake-Dust A Preliminary Investigation

Our plain-English summary of Report on The Pulmonary Response to Brake-Dust A Preliminary Investigation, by P. Gross (1968).

The study

• Author: P. Gross
• Published: Industrial Hygiene Foundation of America INC. (1968)
• Type of article: Report
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This report described a preliminary animal experiment on lung responses to brake-drum dust. Brake-drum dust, said to be iron-free, was suspended in water and injected into the windpipes of laboratory animals. For a four-day comparison, quartz, chrysotile, aluminum silicate and silicon carbide were also injected. For the longer-term study, 10 rats and 12 hamsters received brake-drum dust: hamsters 10.5 mg in total, rats 21 mg. After four days, brake-drum dust caused swelling of air-sac lining cells and clusters of dust-filled scavenger cells. This resembled the reaction to aluminum silicate and silicon carbide, and was unlike the inflammation in rats given quartz or chrysotile. Hamster lungs at 7 1/2 months were nearly normal, though lung washings showed scattered ferruginous bodies. The authors questioned whether to call these asbestos bodies and concluded they were indistinguishable from them. At 12 months there was no collagen build-up in air-sac walls. The authors concluded the response suggested the dust is biologically "inert." They noted that the dust's share of the asbestos derivative was unknown, so the dose might have been inadequate. They advised a larger, longer study.

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: Preliminary animal experiment (intratracheal injection of dust into rats and hamsters, with lungs examined by microscope)
• Who was studied: Rats and hamsters. For the longer-term study, 10 rats and 12 hamsters were injected; three hamsters were killed at 7 1/2 months and the rest at 12 months. A separate acute group, killed after four days, also received comparison dusts. The number of animals in that group cannot be read in the text.
• Exposure: Brake-drum dust (less than 1 gm, said to be free of iron), suspended in water at 3.5 mg per ml and given by intratracheal injection. In the longer-term study, hamsters received three injections totalling 10.5 mg and rats six injections totalling 21 mg. The acute comparison dusts were quartz, chrysotile, aluminum silicate and silicon carbide.
• Main results:
  • Four days after injection of brake-drum dust, the cells lining the air sacs had multiplied and swollen, and dust-filled macrophages had gathered in the air sacs. There was only slight proliferation of argyrophilic (reticulin) fibers.
  • The four-day reaction to brake-drum dust was very similar to that in rats given aluminum silicate or silicon carbide. It contrasted with the reaction in rats given quartz or chrysotile, in which air spaces were filled with inflammatory tissue.
  • In hamsters killed at 7 1/2 months, the lungs were nearly normal apart from widely scattered small clusters of macrophages.
  • Smears of lung washings from these hamsters showed scattered bodies, many of them segmented, which the results section called asbestos bodies. In their comment, the authors questioned whether these ferruginous bodies should be called asbestos bodies.
  • At 12 months (rats and hamsters), the only significant lesions were accumulations of dust-filled macrophages in widely scattered clusters of air sacs. There was no collagenization of air-sac walls and no obliteration of air-sac spaces.
  • In rats, despite a six-fold greater dose, the amount of air-sac involvement at one year was not greater than that seen four days after a single 3.5 mg dose. A similar finding was reported in hamsters.
  • In their conclusions, the authors stated that brake-drum dust can produce ferruginous bodies in hamster lungs that are indistinguishable from asbestos bodies.
• The authors' conclusion: The authors concluded that brake-drum dust evoked a pulmonary response in rats and hamsters which suggests that the dust is biologically "inert."
• Limitations the authors state:
  • The authors stated that it was not known what percentage of the brake-drum dust consisted of the asbestos derivative. They acknowledged that the dust's apparent "inertness" could be due to inadequate dosage.
  • The authors stated that the study should be repeated with more animals and larger doses, letting the animals live out their lives.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Silicate, Inflammation, Ferruginous Bodies, Asbestos Bodies, Collagen.

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