Risk of Lung Cancer and Leukemia from Exposure to Ionizing Radiation and Potential Confounders among Workers at the Portsmouth Naval Shipyard

Abstract

Significantly elevated lung cancer deaths and statistically significantly positive linear trends between leukemia mortality and radiation exposure were reported in a previous analysis of Portsmouth Naval Shipyard workers. The purpose of this study was to conduct a modeling-based analysis that incorporates previously unanalyzed confounders in exploring the exposure-response relationship between cumulative external ionizing radiation exposure and mortality from these cancers among radiation-monitored workers in this cohort. The main analyses were carried out with Poisson regression fitted with maximum likelihood in linear excess relative risk models. Sensitivity analyses varying model components and using other regression models were conducted. The positive association between lung cancer risk and ionizing radiation observed previously was no longer present after adjusting for socioeconomic status (smoking surrogate) and welding fume and asbestos exposures. Excesses of leukemia were found to be positively, though not significantly, associated with external ionizing radiation, with or without including potential confounders. The estimated excess relative risk was 10.88% (95% CI -0.90%, 38.77%) per 10 mSv of radiation exposure, which was within the ranges of risk estimates in previous epidemiological studies (-4.1 to 19.0%). These results are limited by many factors and are subject to uncertainties of the exposure and confounder estimates.

Risk of Chronic Myeloid and Acute Leukemia Mortality after Exposure to Ionizing Radiation among Workers at Four U.S. Nuclear Weapons Facilities and a Nuclear Naval Shipyard

“…This study also adjusted for exposure to benzene, which was not feasible in the 15-country study. Recent estimates of radiation-associated risk within the PNS cohort (8,25) are somewhat higher than those observed in this study but are consistent with the rate ratio modification by facility shown in Table 5.…”

“…Current cigarette smokers were defined as workers who were smoking cigarettes as of their cutoff date or workers who quit smoking 5 or fewer years prior to their cutoff date. For the 54% of workers with insufficient smoking history information, smoking status was imputed based on the socioeconomic status associated with the first job title (25), refined to reflect average smoking histories for a given job from survey data collected in the 1950s to 1980s (26). These assignments were validated using the relation between job titles and smoking history information for workers with complete information.…”

A meta-analysis of leukaemia risk from protracted exposure to low-dose gamma radiation

“…The risk estimate for this study (within this meta-analysis) is benzene-adjusted. Other worker-based studies, particularly those based on more recent employment, have found little evidence of potential benzene exposures, as this substance was never used or has been phased out of many workplaces 29 40. Unlike solid cancers, leukaemia is advantageous for meta-analysis because it is not strongly associated with lifestyle factors, although there is some evidence of a moderate association (RR=1.4–2.0) between smoking and some leukaemias 57–59.…”

An updated historical cohort mortality study of workers exposed to asbestos in a refitting shipyard, 1947–2007

“…Epidemiological studies among shipyard workers have been performed in many countries (Kolonel et al 1985;Krstev et al 2007;Nicholson et al 1980;Puntoni et al 2001;Yiin et al 2005), and health problems caused by asbestos exposure have been reported.…”