Mortality from Leukemia and Cancer in Shipyard Nuclear Workers

Our plain-English summary of Mortality from Leukemia and Cancer in Shipyard Nuclear Workers, by T. Najarian, T. Colton (1978).

The study

• Authors: T. Najarian, T. Colton
• Published: Lancet, May 13th 1978
• 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 preliminary communication examined deaths among former workers at the Portsmouth Naval Shipyard, where nuclear submarines are repaired and refuelled. The authors reviewed 1959-77 death certificates from New Hampshire, Maine and Massachusetts and found 1722 deaths of former shipyard workers. Interviewers reached next of kin for 592 of them. 146 men were classed as nuclear workers because relatives said they worked with radiation or wore a radiation badge. Deaths under age 80 were compared with the proportions of cancer deaths expected from 1973 U.S. White male figures. Among nuclear workers, 6 leukaemia deaths were observed, which the authors described as six times the proportional leukaemia mortality expected, and the observed/expected ratio for all cancers was 1.78. Among non-nuclear workers there was no statistically significant increase. The authors noted that only deaths were analysed, with no information on the workforce at risk, length of work or doses received. They named asbestos, with smoking and solvents, only as a possible factor that might have interacted with radiation; the article gives no asbestos exposure data. They concluded the finding did not prove a risk but should prompt more thorough cohort studies.

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: Proportionate mortality study based on death certificates and next-of-kin telephone interviews, with expected deaths calculated by indirect age adjustment to U.S. White male proportional mortality (preliminary communication)
• Who was studied: 1722 deaths in 1959-77 among former Portsmouth Naval Shipyard workers, identified from death certificates in New Hampshire, Maine and Massachusetts. Next of kin were contacted for 592: 146 were classed as nuclear workers and 446 as non-nuclear workers. The non-nuclear group fell to 379 when the analysis was restricted to deaths under age 80. Nearly all were White males.
• Exposure: Occupational radiation exposure during nuclear submarine repair and refuelling, classified from next of kin's answers about working with radiation or wearing a radiation badge. Information from 50 past or present nuclear workers suggested lifetime doses of less than 10 rem. Asbestos is mentioned only in the discussion as a possible interacting factor.
• Main results:
  • Among the 146 former nuclear workers, 6 leukaemia deaths were observed; the scanned expected count and observed/expected ratio have damaged decimal points
  • The authors described the nuclear workers as having six times the proportional leukaemia mortality, and twice the proportional mortality for all cancers, expected for U.S. White males of the same age groups
  • Among nuclear workers, the observed/expected ratio for all cancer deaths was 1.78
  • Among non-nuclear workers, there was no statistically significant increase in proportional mortality from leukaemia or from all cancers; the increase in cancer deaths was only 10% (p greater than 0.05)
  • Among nuclear workers, the excess of cancer deaths was most distinct at ages 60-69 (p less than 0.00001); increases in other age groups were not statistically significant
  • Next of kin were contacted slightly more often for cancer deaths (39%) than for non-cancer deaths (35%); the authors said this difference was not significant
• The authors' conclusion: The authors concluded that the increased proportional mortality from cancer and leukaemia at probably low occupational radiation levels, while not proving a risk, ought to prompt more careful and thorough cohort studies of workers in naval yards where nuclear-powered vessels are serviced.
• Limitations the authors state:
  • Only deaths were analysed; there was no information on the total population at risk
  • There was no information on how long the men worked at the shipyard, how long nuclear workers were exposed to radiation, or how much radiation they received
  • The information supplied by next of kin may have contained systematic error or bias
  • Other factors, including asbestos, smoking and industrial solvents, may have interacted with radiation

Topics

Medical terms in this study, explained in our Lexicon: Death Certificate, Asbestos Exposure.

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