Silicosis in Mica Mining in Bihar, India

Our plain-English summary of Silicosis in Mica Mining in Bihar, India, by S. Moskowitz (1954).

The study

• Author: S. Moskowitz
• Published: Monthly Review (New York Department of Labor) Volume 33 No6. June 1954
• Type of article: Trade 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, condensed by the author from a paper by Heimann and colleagues, reported on silicosis in mica mining in Bihar, India. It concerns silica dust, not asbestos. This installment gave only the engineering findings, not medical ones; the report was to continue in July 1954. Investigators visited nine typical mines, sampled dust in workers' breathing zones and estimated the hours each job spent on dusty tasks. Rock drillings had a median quartz content of 42%. Uncontrolled pneumatic drilling averaged 600 to 1000 million particles per cubic foot, depending on whether the rock was dry or moist. Wet drilling cut dustiness by over 99 percent. Estimated average daily exposure, in million particles per cubic foot, was 400 for pneumatic drillers without dust control, 200 with a dust trap, 3.5 with wet drilling, 45 for hand drillers and 15 for muckers. The author noted that no operation's average dust count was below the agreed limit, but judged wet drilling, done only four hours a day, safe from the dust hazard point of view and the only safe form of drilling.

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: Industrial hygiene field survey: dust sampling and estimates of exposure time, reported here as the engineering section of a combined engineering and medical study
• Who was studied: Workers in nine typical underground mica mines in Bihar, India, selected by the Inspector of Mines. The job groups were pneumatic drillers, hand drillers and scalers, and muckers.
• Exposure: Rock dust high in free silica (quartz) from mica-bearing pegmatite. The quartz content of rock drillings had a median of 42%. Dust was measured in workers' breathing zones with the midget impinger and reported in million particles per cubic foot of air (mppcf).
• Main results:
  • Uncontrolled pneumatic drilling gave average dust concentrations of 600 to 1000 million particles per cubic foot of air, depending on whether dry or moist rock was drilled.
  • Wet drilling reduced dustiness by over 99 percent.
  • Average daily dust exposure was 400 mppcf for pneumatic drillers using no dust control, 200 mppcf with a dust trap and 3.5 mppcf with wet drilling.
  • Average daily dust exposure was 45 mppcf for hand drillers and 15 mppcf for muckers.
• The authors' conclusion: The author noted that no mica mining operation had an average dust count below the generally agreed limit for average daily exposure. Because pneumatic wet drilling was done for only four hours a day, the author judged it safe from the point of view of the dust hazard and the only safe form of drilling. Muckers, who handle both dry and wet rock, were on average exposed above the safe level.
• Limitations the authors state:
  • The average composition of the pegmatite rock could not be determined, so random samples of drillings were analyzed instead.

Topics

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

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