Unusual Cancer Mortality Among a Group of Underground Metal Miners

Our plain-English summary of Unusual Cancer Mortality Among a Group of Underground Metal Miners, by J.K. Wagoner, R.W. Miller, F.E. Lundin, et al (1963).

The study

• Authors: J.K. Wagoner, R.W. Miller, F.E. Lundin, Jr, J.F. Fraumeni, Jr, M.E. Haij
• Published: The New England Journal of Medicine 269(6):284-289 August (1963)
• 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 1963 study looked at deaths among long-term underground metal miners in the United States. Each had completed at least 15 years underground, and follow-up ran through December 31, 1959. Deaths were compared with those expected in the white male population of the same states. The miners had higher overall mortality. Respiratory and heart disease deaths exceeded expectation. A further excess was largely due to pneumoconiosis, but expected pneumoconiosis deaths could not be calculated. The standardized mortality ratio for respiratory tuberculosis was 808 for both cohorts combined. Respiratory cancer was about threefold higher than expected, with significant excesses in both foreign-born and native-born miners. Cancers of other organ systems were also significantly raised when the two cohorts were combined. The ore contained silica, arsenic and iron among other elements, and chromium and asbestos were not detected. The authors concluded that the respiratory cancer excess was not attributable to age, smoking, nativity, urbanization, socioeconomic status, heredity, diagnostic accuracy or silicosis. They judged that radiation alone seemed unlikely to account for it, and that a carcinogen in the mine air appeared likely. Smoking histories were not collected.

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: Mortality study of two cohorts of miners. Deaths were compared with expected deaths calculated from the general white male population of the same states, using a modified life-table method.
• Who was studied: White male underground metal miners in the United States who had completed at least their fifteenth year of underground mining, followed for deaths through December 31, 1959. Cohort 1 had completed 15 years before January 1, 1937; cohort 2 completed them from January 1, 1937 to December 31, 1948. Records of about 75,000 employees were reviewed. The number of miners included is not legible in the scanned text.
• Exposure: Fifteen or more years of underground metal mining. The ore contained silica, sulfur, iron, copper, zinc, manganese, lead, arsenic, calcium, fluorine, antimony and silver. Nickel was present only as a trace, and chromium and asbestos were not detected in the deposits. Radon in the mines in 1958 was 10 to 80 micromicrocuries per liter, and earlier levels were estimated at possibly five to ten times higher.
• Main results:
  • The miners had higher total mortality than the general white male population of the region.
  • Cancer of the respiratory system among the miners was increased about threefold.
  • The respiratory cancer excess was significant in both foreign-born miners (standardized mortality ratio 241) and native-born miners (standardized mortality ratio 317).
  • For both cohorts combined, the standardized mortality ratio for respiratory tuberculosis was 808.
  • In cohort 1, the excesses of respiratory diseases and of diseases of the heart were each statistically significant at the 1 per cent level.
  • In cohort 1, the excess in 'all other causes' was largely attributable to pneumoconiosis (31 cases as printed). Expected numbers of pneumoconiosis deaths could not be calculated.
  • In cohort 2, the excess of cancers of the digestive system was statistically significant.
  • Cancers of systems other than the digestive and respiratory systems were not significantly raised in either cohort alone, but were significant at the 5 per cent level with the cohorts combined.
  • Of the miners' respiratory cancer deaths, 49 per cent were verified by pathological examination and 24 per cent by X-ray. These percentages were similar to those for a sample of people in the same counties.
• The authors' conclusion: The authors concluded that the respiratory cancer excess was not attributable to age, smoking, nativity, urbanization, socioeconomic status, heredity, diagnostic accuracy or silicosis. They judged it unlikely that radiation alone accounted for it, and considered a carcinogen in the mine air likely. They added that no single factor was clearly implicated.
• Limitations the authors state:
  • Smoking histories were not obtained.
  • Some deaths may have been missed. Men whose status was unknown were assumed to be alive at the end of 1959.
  • Data were not available to exclude air pollution from smelters or other industries in the communities as a cause.
  • Radiation levels during the miners' earlier work were unknown.
  • Expected deaths from pneumoconiosis could not be calculated because published population data did not list this disease separately.

Topics

Medical terms in this study, explained in our Lexicon: Pneumoconiosis, standardized mortality ratio (SMR), Silicosis.

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