Anthracosilicosis

Our plain-English summary of Anthracosilicosis, by R.T. Johnstone (1948).

The study

• Author: R.T. Johnstone
• Published: OCCUPATIONAL MEDICINE AND INDUSTRIAL HYGIENE, ST. LOUIS: C.V. MOSBY, PP. 361-367 (1948)
• Type of article: Book excerpt
• Our copy: from Johns-Manville's own medical library.

In plain English

This is a textbook chapter on anthracosilicosis, a lung disease of hard-coal miners in eastern Pennsylvania. It does not concern asbestos. The author mainly summarized a United States Public Health Service survey (Bulletin 221, 1938) that examined 2,711 anthracite mining employees, along with disabled former miners. Workers were grouped by the share of free silica in the dust they breathed. As the chapter reported, about 23 per cent of all employees had anthracosilicosis. Outside rock work, fewer than 2 per cent developed it with less than fifteen years of employment. Among men employed over twenty-five years in dust with less than 5 per cent free silica, prevalence rose with dust concentration. It went from 7 per cent in the lowest band, which started at 50,000,000 particles per cubic foot, to 89 per cent at 300,000,000 or more. About 10 per cent of regular miners and 13 per cent of rock workers had moderate or marked impairment, compared with under 2 per cent of controls. The chapter stated that the links between dust exposure and bodily changes left little doubt about the dust's role in causing disease.

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: Textbook chapter (secondary summary), mainly restating the findings of a U.S. Public Health Service survey of anthracite miners. It also gives a general description of symptoms, pathology and X-ray findings.
• Who was studied: In the summarized survey: 2,711 anthracite coal-mining employees (about 96 per cent of the payroll of three anthracite companies studied) in eastern Pennsylvania, plus disabled former miners hospitalized for observation and a smaller group in a state tuberculosis sanitarium
• Exposure: Dust in anthracite coal mining, measured as particles per cubic foot of air. Workers were grouped by the proportion of free silica (quartz) in the dust: less than 5 per cent, about 13 per cent, and about 35 per cent for rock workers. Asbestos was not studied.
• Main results:
  • Anthracosilicosis was found in about 23 per cent of the entire group of employees
  • Among all except rock workers, less than 2 per cent developed anthracosilicosis when employment lasted less than fifteen years, regardless of dust concentration
  • Among men employed more than twenty-five years in dust with less than 5 per cent free silica, prevalence was 7 per cent at 50,000,000 to 99,000,000 particles per cubic foot, 51 per cent at 100,000,000 to 199,000,000, 71 per cent at 200,000,000 to 299,000,000, and 89 per cent at 300,000,000 or more
  • Among men exposed to dust that was about 35 per cent free silica, prevalence ranged from 10 per cent (under 200,000,000 particles per cubic foot, under fifteen years) to 92 per cent (over twenty-five years above 200,000,000 particles, including more than two or three years of rock work)
  • Employment in air with less than 50,000,000 dust particles per cubic foot produced a negligible number of cases when the quartz content of the dust was less than 5 per cent. Where silica content was about 13 per cent, a safe limit appeared to be 10,000,000 to 15,000,000 particles per cubic foot.
  • After twenty years' service including more than two or three years of rock work, 47 per cent of rock workers showed evidence of pulmonary tuberculosis
  • Pulmonary infection (tuberculous or nontuberculous) was found in 92 per cent of workers with more advanced anthracosilicosis. The printed figure for early-stage cases appears to be 58 per cent.
  • Only 6 per cent of the control group had nontuberculous respiratory disease, compared with about 20 per cent of nontuberculous workers in all other groups combined
  • Moderate or marked physical impairment affected less than 2 per cent of the control group, about 10 per cent of regular miners and approximately 13 per cent of rock workers
  • Mortality from respiratory diseases was much greater among anthracite workers than in the general adult male population. The data indicated that underground work without dust did not predispose to fatal respiratory disease.
• The authors' conclusion: The chapter stated that the correlations between dust exposure and evidence of bodily changes left little doubt as to the etiological significance of the dust. Similar correlations were found between silica exposure and the extent of lung changes.

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