Case-control study of lung cancer in civilian employees at the Portsmouth Naval Shipyard, Kittery, Maine

Our plain-English summary of Case-control study of lung cancer in civilian employees at the Portsmouth Naval Shipyard, Kittery, Maine, by R.A. Rinsky, J.M. Melius, R.W. Hornung, et al (American Journal of Epidemiology, 1988).

The study

• Authors: R.A. Rinsky, J.M. Melius, R.W. Hornung, R.D. Zumwalde, R.J. Waxweiler, P.J. Landrigan, P.J. Bierbaum, W.E. Murray
• Journal: American Journal of Epidemiology
• Published: 1988;127(1):55-64
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000262).

Abstract

Case-control analysis of deaths due to lung cancer (International Classification of Diseases, Eighth Revision, code 162) among persons who worked at the Portsmouth Naval Shipyard, Kittery, Maine, between 1952 and 1977 found elevated odds ratios for exposures to ionizing radiation, asbestos, and welding byproducts. The radiation-related excess was statistically significant in persons with cumulative lifetime exposures of 1.0-4.999 rem. When asbestos and welding histories were combined into a single risk factor, odds ratios for the combined exposure were significantly elevated for two of three duration-of-exposure categories examined. Further analysis of data on radiation exposure, controlling for exposures to asbestos and welding, found reductions in initial estimates of radiation risk at all levels of radiation exposure. This reduction suggests that radiation workers were more heavily exposed to asbestos and/or welding fumes than were other workers and that those exposures confounded the observed association between radiation and lung cancer. Analysis of mortality by time since first exposure to radiation revealed no pattern of progressive increase as latency increased. By contrast, odds ratios for asbestos/welding increased with latency. Data on cigarette smoking and socioeconomic status were not available. The results of this study do not preclude a possible association between radiation exposure at the Portsmouth Naval Shipyard and excess mortality from lung cancer. However, they provide no evidence in support of such a relation.

In plain English

This case-control study examined lung cancer deaths among white male workers at the Portsmouth Naval Shipyard, Kittery, Maine, between January 1, 1952 and August 15, 1977. The authors compared 405 lung cancer deaths with 1,215 matched controls. Radiation came from recorded doses, and asbestos and welding exposure from how shops and jobs were classified. Before adjusting for asbestos and welding, men with 1.00 to 4.999 rem lifetime radiation had a statistically significant odds ratio of 1.81 (95% confidence interval 1.05 to 3.12) versus men with no radiation history. Pipe Shop workers had significantly raised odds ratios, reaching 1.99 (1.10 to 3.58) for at least 10 years there. For ever working in a job classified as having asbestos or welding exposure, the odds ratio was 1.43 (1.12 to 1.81). After adjusting for asbestos and welding, no radiation odds ratio was statistically significant. The authors concluded that asbestos and/or welding by-products appeared largely responsible for the excess risk. They had no smoking histories and could not separate asbestos effects from welding effects. Exposure classifications rested on sparse industrial hygiene data.

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: Case-control study (cases and matched controls drawn from an earlier shipyard cohort), analysed from death certificates and coded work histories
• Who was studied: White male civilian workers at the Portsmouth Naval Shipyard, Kittery, Maine, who worked there at any time from January 1, 1952 to August 15, 1977: 405 lung cancer deaths (cases) and 1,215 controls (three per case), matched on date of birth, date of first employment and duration of employment
• Exposure: Ionizing radiation (gamma radiation, mainly from cobalt 60, and x-radiation from radiographic examination of welds), measured by dosimeters and recorded as cumulative lifetime dose in rem. Asbestos and welding by-products were assessed by classifying shops and jobs as 'probable' or 'potential' exposure. The article does not name asbestos fiber types.
• Main results:
  • For cases compared with controls, ever having a radiation history gave an odds ratio of 1.23 (95% CI 0.91-1.67), which was not statistically significant
  • Before adjusting for asbestos and welding, workers with cumulative lifetime radiation exposure of 1.00-4.999 rem, compared with those with no radiation history, had a statistically significant odds ratio of 1.81 (95% CI 1.05-3.12)
  • Before adjustment, workers with cumulative lifetime radiation exposure of 5.00 rem or greater had an odds ratio of 1.37 (95% CI 0.68-2.78), which was not statistically significant
  • Jobs with probable asbestos exposure: ever exposed odds ratio 1.24 (95% CI 0.92-1.68); minimum 5 years 1.53 (0.99-2.36); minimum 10 years 1.61 (0.94-2.75). None was statistically significant, though the odds ratios rose with duration.
  • Shop 56 (Pipe Shop), where almost all employees were classified as having probable or potential asbestos exposure: odds ratios were significantly elevated at 1.43 (95% CI 1.03-2.00) for ever working there, 1.83 (1.14-2.95) for at least 5 years, and 1.99 (1.10-3.58) for at least 10 years
  • Jobs with probable or potential welding exposure: ever worked in such a job gave an odds ratio of 1.46 (95% CI 1.17-1.83). For Shop 26 (Welding Shop), the odds ratios of 1.13, 1.16 and 0.83 were not statistically significant.
  • Jobs classified as having any asbestos or welding exposure (combined category): ever exposed odds ratio 1.43 (95% CI 1.12-1.81); minimum 5 years 1.50 (1.11-2.04); minimum 10 years 1.38 (0.97-1.98)
  • After controlling for asbestos/welding exposure, all radiation odds ratios were not statistically significant, including 1.68 (95% CI 0.97-2.91) for 1.00-4.999 rem. The asbestos/welding odds ratio with radiation in the model was significant, at 1.41 (95% CI 1.10-1.81).
  • When exposures were lagged 5, 10, 15 and 20 years before death, no radiation odds ratio was significant at any dose or lag period
• The authors' conclusion: The authors concluded that the hypothesis that radiation accounted for the excess lung cancer deaths could not be substantiated. In their view, exposures to asbestos and/or welding by-products appeared largely responsible for the excess risk and confounded the radiation association.
• Limitations the authors state:
  • Asbestos and welding exposure designations were largely subjective, based on sparse industrial hygiene data, so misclassification was possible
  • The effects of welding could not be separated from those of asbestos because most exposed persons had both
  • No smoking histories were available
  • Controls were not selected from workers alive at the time each case died, which may have introduced error
  • Statistical power was low for small excess risks: 56 per cent to detect a relative risk of 1.3 and 31 per cent for 1.2
  • Radiation exposure had existed at the shipyard for fewer years than asbestos and welding exposure, so results could change with more latency

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Shipyards and maritime work.

Medical terms in this study, explained in our Lexicon: Case-Control Study, Lung Cancer, Odds Ratio, Latency.

Related studies

• A nested case-control study of lung cancer risk and ionizing radiation exposure at the portsmouth naval shipyard — J.H. Yiin, S.R. Silver, et al. (2007)
• Asbestos exposure control at Puget Sound Naval Shipyard — R.R. Beckett (1976)
• Radiographic search for asbestos-related disease in a naval shipyard — J.S. Felton (1979)
• A visual historical review of exposure to asbestos at puget sound naval shipyard (1962-1972) — D.M. Hollins, D.J. Paustenbach, et al. (2009)
• Experience with asbestos disease and its control in Great Britain's naval dockyards — P.G. Harries (1976)
• Incidence of lung cancer among shipyard welders investigated for siderosis — T.E. Danielsen, S. Lang rd, et al. (1998)

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