The effect of asbestos, and of asbestos and aluminium, on the lungs of rabbits

Our plain-English summary of The effect of asbestos, and of asbestos and aluminium, on the lungs of rabbits, by E.J. King, J.W. Clegg, V.M. Rae (Thorax, 1946).

The study

• Authors: E.J. King, J.W. Clegg, V.M. Rae
• Journal: Thorax
• Published: 1946;1(3):188-97
• Cited by: 44 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002845).

In plain English

This was an animal experiment carried out in London. The authors tested whether short-fibre asbestos does less damage to rabbit lungs than long-fibre asbestos, and whether fine metallic aluminium powder suppresses any harmful effect. Rabbits were given 100 mg of Rhodesian asbestos in saline once a month through a rubber tube passed into the windpipe. The article does not name the asbestos fibre type beyond calling it Rhodesian asbestos. Group 1 (12 rabbits) received fibres about 15 microns long. Group 2 (12 animals) received the same plus 2 mg of aluminium per dose. Group 3 (7 animals) received fibres 2.5 microns long, and Group 4 (9 animals) received the short fibres plus aluminium. In Group 1, a few animals died at 2 to 3 months and others lived as long as 19 months. All groups showed a foreign-body reaction in the lungs. Long fibres produced nodules that the authors compared with the experimental silicotic nodule. Short fibres produced widespread thickening of the alveolar walls. Aluminium increased and prolonged the foreign-body reaction and gave no benefit in any group. The authors concluded that their experiments suggest asbestos retained in the lung leads ultimately to fibrosis.

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: animal experiment (repeated intratracheal dosing of rabbits, with microscopic examination of the lungs)
• Who was studied: Fully grown rabbits in four groups: 12 given long-fibre asbestos, 12 given long-fibre asbestos plus aluminium, 7 given short-fibre asbestos, 9 given short-fibre asbestos plus aluminium. Work was done at the British Postgraduate Medical School and the Brompton Hospital, London. In Group 1, a few animals died at 2 to 3 months and others lived as long as 19 months; Group 2 was described as comparable in numbers and survival.
• Exposure: 100 mg of Rhodesian asbestos in 4 ml of saline, given into the trachea once a month. Fibres were cut to about 15 microns (long fibre) or 2.5 microns (short fibre). Two groups also received 2 mg of metallic aluminium powder per 100 mg of asbestos.
• Main results:
  • All four groups showed a foreign-body reaction in the lungs.
  • Long-fibre groups developed a nodular reticulinosis, which the authors described as comparable with the experimental silicotic nodule.
  • Short-fibre group (Group 3): the increase in reticulin was mainly in the alveolar walls, giving a fairly widespread thickening of the alveolar wall.
  • Adding aluminium increased and prolonged the foreign-body giant-cell reaction, and the authors reported it gave no benefit in any group.
  • In the long-fibre group, the frequency of a black pigment increased with survival time. The authors wrote that this pigment is presumably comparable with the asbestos body seen in human asbestosis.
• The authors' conclusion: The authors concluded that the experiments suggest asbestos retained in the lung excites a connective-tissue response ultimately leading to fibrosis. In their view, where the lesion forms depends on fibre size, and metallic aluminium appeared to be entirely without benefit.
• Limitations the authors state:
  • It was not possible to make a powder in which all fibres were 15 microns long, because fibres broke during cutting. The authors reported that well over 80 per cent were close to that length.
  • The authors noted that their results differed from Gardner's inhalation experiments. They suggested this may be because they placed a known weight of asbestos directly into the trachea, so more asbestos may have reached the lung than in animals that only breathed dusty air.

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