Pulmonary Tumors In Mice Exposed To Asbestos Dust

Our plain-English summary of Pulmonary Tumors In Mice Exposed To Asbestos Dust, by K.M. Lynch, F.A. Mciver, J.R. Cain (1957).

The study

• Authors: K.M. Lynch, F.A. Mciver, J.R. Cain
• Published: Archives Of Industrial Health 15(3):207-214, March (1957)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 001632. The article is still under copyright, so we describe it here rather than post it.

In plain English

This was an animal experiment in mice. Hybrid mice, the offspring of Strain A males and Strain C females, were split at 2 months of age. Half were placed in cages exposed to a dust called Asbestos Floats 7-TF-2 and half were kept as controls. The authors described the dust as mostly inert granular serpentine rock, with chrysotile asbestos as the important material in its coarser part. The largest group, 127 mice exposed for 17 months and killed at 19 months, was compared with 222 control mice. Lung tumors, basically papillary adenomas, were found in 46% of dusted and 36% of control mice. The authors reported this difference as not statistically significant. Multiple lung tumors were found in 18% of dusted and 8% of control mice, a difference reported as statistically significant. No clear-cut proof of malignancy was found in any lung tumor. Asbestos bodies formed in almost every dusted mouse, but lung fibrosis did not occur. The authors concluded they could not prove asbestos caused cancer under these conditions. They noted that mice were probably poorly suited for this purpose.

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: inhalation of asbestos dust by mice, compared with unexposed control mice
• Who was studied: AC F1 hybrid mice (offspring of Strain A male and Strain C female mice). In all, 776 mice were examined after death. The largest exposed group was 127 mice killed at 19 months after 17 months of exposure, compared with 222 control mice.
• Exposure: Inhaled Asbestos Floats 7-TF-2 dust, described as mostly inert granular serpentine rock, with chrysotile asbestos the important material in the fraction not passing a 200-mesh screen. Dusting ran 8 to 12 hours a day, 5 days a week.
• Main results:
  • At 19 months, lung tumors were found on microscopic examination in 46% of dusted mice and 36% of control mice
  • The difference in overall lung tumor frequency between dusted and control mice was not statistically significant (7 chances in 100 that it was due to chance)
  • Multiple lung tumors were found in 18% of dusted mice and 8% of control mice
  • The authors reported the difference in multiple lung tumors between dusted and control mice as statistically significant
  • The tumors were basically papillary adenomas, and no clear-cut proof of malignancy was found in any lung tumor studied
  • Elongated asbestos bodies were found in the lungs of almost every dusted mouse
  • Lung fibrosis did not occur in the dusted mice
  • The authors regarded the higher rate of multiple tumors in dusted mice as a possible accentuation, by inhaled asbestos dust, of an existing tendency to develop lung tumors
• The authors' conclusion: The authors concluded that they were unable to demonstrate any proof that asbestos causes cancer under the conditions of this experiment. They recommended that future experiments use larger animals, probably monkeys.
• Limitations the authors state:
  • The authors stated that mice are probably poorly suited for this purpose
  • Mice did not develop lung fibrosis, which the authors suggested could be essential to the expected changes in the lining cells of the airways
  • The dust used was described as having little fibrous content

Topics

Medical terms in this study, explained in our Lexicon: Serpentine Group, Chrysotile, Asbestos Bodies, Fibrosis.

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