Chemical Factors (including trace elements) as Etiological Mechanisms

Our plain-English summary of Chemical Factors (including trace elements) as Etiological Mechanisms, by J.S. Harington (1973).

The study

• Author: J.S. Harington
• Published: BIOLOGICAL EFFECTS OF ASBESTOS (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 8, PP. 304-311 (1973)
• 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 article was a review in which the author considered possible chemical and biological mechanisms by which asbestos causes lung fibrosis and cancer. It reported no new study of people or animals. Drawing on earlier laboratory, animal and epidemiological work, the author noted that short-term macrophage culture experiments had found chrysotile much more toxic to cells than crocidolite or amosite. Because most forms of asbestos cause fibrosis in man and animals, the author questioned whether that culture technique was adequate. Chrysotile was described as destroying red blood cells as strongly as silica powder, probably through magnesium. One chrysotile sample had been found to contain 5 mg nickel and 1 mg chromium per gram of fibre. Rat experiments by Wagner and Berry (published 1969) and Wagner and colleagues (unpublished) found no difference in mesothelioma numbers between untreated and oil-extracted asbestos. The author concluded that carcinogenic trace metals may contribute but seem unlikely to explain the whole effect, that organic matter seems passive or negligible, and that biochemical studies of asbestos as a carcinogen were almost completely lacking.

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• Design: Review and discussion of published and unpublished work on how asbestos causes fibrosis and cancer
• Who was studied: No study population of its own; the article reviewed cell culture, animal and epidemiological studies by others and by the author
• Exposure: Asbestos types including chrysotile, crocidolite, amosite, anthophyllite and tremolite; metals in the fibre structure and trace metal contaminants (such as chromium, lead and nickel); natural and contaminating oils and other organic matter
• Main results:
  • Cited macrophage culture experiments found that, over the short term, chrysotile seemed much more toxic to cells than other forms of asbestos
  • Cited studies found chrysotile as strong a haemolytic agent (destroyer of red blood cells) as silica powder
  • In cited work, the chelating agent EDTA and phosphate ions prevented red blood cell destruction by chrysotile, supporting the view that magnesium is the main reactant on the chrysotile surface
  • A cited study found a correlation between the haemolytic activity of different forms of asbestos and their magnesium to silicon ratio
  • In earlier work by the author (Harington, 1965), a single chrysotile sample contained 5 mg nickel per gram of fibre (0.5%) and 1 mg chromium per gram of fibre
  • Unpublished work by Wagner and colleagues found that the carcinogenicity of Canadian chrysotile samples was not related to their content of iron, chromium or nickel
  • In rat experiments by Wagner and Berry (published 1969) and by Wagner and colleagues (unpublished), UICC asbestos samples injected into the pleura, either untreated or with oils removed by hot benzene, produced no differences in numbers of mesotheliomas
  • Very low radioactive contents measured in crocidolite, amosite and chrysotile (Harington, 1965) were taken to indicate that radioactivity plays at most a very minor role
• The authors' conclusion: The author concluded that several mechanisms may be involved, that carcinogenic trace metals may contribute but seem unlikely to account for the entire effect, that organic matter seems to play a passive or negligible role, and that biochemical studies of asbestos as a carcinogen were almost completely lacking

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Macrophage, Chrysotile, Crocidolite, Amosite, Mesothelioma, Carcinogenic.

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