Air Hygiene in the Mining Industry

Our plain-English summary of Air Hygiene in the Mining Industry, by L.U. Gardner (1940).

The study

• Author: L.U. Gardner
• Published: Mining Congress Journal January Issue (1940)
• Type of article: Journal article
• 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 is a written commentary on silica dust and silicosis in mining, by the Director of the Saranac Laboratory. It does not mention asbestos. The author described what was then accepted: free silica, usually quartz or flint, was the main cause of lung disease, and smaller particles caused faster tissue reaction. The tentative maximum permissible limit was 5 million particles per cubic foot of air. The author cautioned that this standard might not apply to all exposures and might have to be revised as experience accumulated. In ordinary mining, silicosis had never appeared in less than three or four years, and ten or twenty years of exposure was more commonly reported. The author stated that prevention remained the only reliable means of combating silicosis. Experiments on aluminum were reviewed. At the Saranac Laboratory, animals given aluminum hydroxide were completely protected for a year and more. In the author's opinion, aluminum had not been investigated enough to replace better known methods of prevention, and it was not expected to cure existing scarring. The author concluded that essential details were still lacking, including individual susceptibility and permissible limits for dust mixtures.

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: Commentary / narrative overview addressed to a mining audience (not an original study)
• Who was studied: No study population. The article discusses miners and silica-exposed workers in general and describes animal experiments, including those at the Saranac Laboratory.
• Exposure: Free silica dust, usually quartz or flint, in mining. Aluminum and aluminum hydroxide were discussed as possible inhibitors. No asbestos exposure is discussed.
• Main results:
  • The tentative maximum permissible limit was 5 million particles per cubic foot of air. The author said this standard might not apply to all exposures and might have to be revised as experience accumulated.
  • In ordinary mining, silicosis had never appeared in less than three or four years, and exposures of ten or twenty years were more commonly reported. Under extraordinary conditions of very fine, very pure silica dust, disease could develop within two years.
  • In Saranac Laboratory experiments, animals given aluminum hydroxide were completely protected for a year and more.
  • Experiments with Barre granite, which is known to cause silicosis in humans, failed to produce fibrosis within 22 months. This was despite doses containing 100 times the quartz needed to cause fibrosis in pure form.
• The authors' conclusion: The author stated that prevention remained the only reliable means of combating silicosis. In the author's view, aluminum had not been investigated enough to warrant use in place of better known methods, though it probably did little harm as an addition to them. The author also said essential details were still lacking.
• Limitations the authors state:
  • The author noted that no experiment had fully evaluated the influence of time on aluminum's protective effect.

Topics

Medical terms in this study, explained in our Lexicon: Silicosis, Saranac Laboratory, Million Particles per Cubic Foot (mppcf).

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