Asbestos in Relation to Tumors of the Respiratory Tract

Our plain-English summary of Asbestos in Relation to Tumors of the Respiratory Tract, by W.E. Smith (1965).

The study

• Author: W.E. Smith
• Published: Reprinted form Lung Tumors in Animals. Proceedings of the Third Quadrennial International Conference on Cancer held at the University of Perugia, Italy. June 24-29, 1965
• Type of article: Conference paper
• 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 1965 conference paper by W. E. Smith summarized the author's group's animal experiments on asbestos and respiratory tract tumors, and reported new results. In earlier hamster tests, a single 25 mg injection of asbestos into the pleural space (around the lungs) produced pleural mesotheliomas with amosite and a "harsh" chrysotile, but not a "soft" chrysotile. The earliest tumor was in a hamster that died 244 days after injection. In an earlier test, respiratory tract tumors appeared in 5 of 19 hamsters (26%) given benzo(a)pyrene with amosite and 8 of 27 (29%) given benzo(a)pyrene alone. The author called these yields closely comparable. As new information, a transplanted hamster mesothelioma was sensitive to the drug cyclophosphamide (Cytoxan), even when treatment started after the tumors had grown. No tumors had yet been found in rats given repeated windpipe injections of asbestos, though frequent lung infections complicated the rat findings. In hamsters, such injections produced asbestosis with extensive growth of cells lining the air sacs, often resembling a cancer called adenocarcinoma, but no spread of these cells had been found.

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: Conference paper summarizing the author's research group's animal experiments (hamsters and rats) and reporting new results since earlier publications
• Who was studied: Hamsters (pleural and intratracheal injection tests, and a transplantable mesothelioma) and 234 rats in intratracheal tests, with rat controls
• Exposure: Amosite, a harsh and a soft variety of chrysotile, and crocidolite, given by injection into the pleural space (25 mg single injection in hamsters) or by repeated intratracheal injection; some hamsters also received benzo(a)pyrene with or without asbestos
• Main results:
  • Pleural mesotheliomas were found in hamsters after intrapleural injection of amosite and of a harsh variety of chrysotile (earlier reported work)
  • No tumors were found in hamsters after intrapleural injection of a soft variety of chrysotile
  • No tumors were found in a preliminary series of hamsters given repeated intratracheal injections of amosite, harsh chrysotile or soft chrysotile (earlier reported work)
  • The earliest tumor in the hamster intrapleural tests was in a hamster that died 244 days after injection
  • In an earlier reported test, respiratory tract tumors were found in 5 of 19 hamsters (26%) given benzo(a)pyrene with amosite
  • In the same test, respiratory tract tumors were found in 8 of 27 hamsters (29%) given benzo(a)pyrene without amosite; the author described the yields as closely comparable
  • New: the sensitivity of a transplantable hamster mesothelioma to cyclophosphamide (Cytoxan) was confirmed in a test where treatment did not begin until the transplanted tumors had grown
  • New: no tumors had been found in rats treated by intratracheal injection with any of the asbestos varieties tested
  • In one untreated control rat, a lobe of the lung was entirely replaced by a large sarcoma
  • Repeated intratracheal injections of asbestos in hamsters produced asbestosis, with extensive proliferation of alveolar lining cells frequently simulating adenocarcinomas, but no metastases of such cells had been found
• The authors' conclusion: The author summarized that a single massive intrapleural dose of amosite or harsh, but not soft, chrysotile produced mesotheliomas in hamsters. In the author's summary, repeated intratracheal injections in hamsters produced asbestosis and alveolar lining-cell proliferation frequently simulating adenocarcinomas, with no metastases found. No pulmonary tumors had so far been found in rats given amosite, soft chrysotile or crocidolite.
• Limitations the authors state:
  • Pathology findings in rats were complicated by frequent evidence of pulmonary infections

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Amosite, Chrysotile, Mesothelioma, Adenocarcinoma.

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