摘要：Objectives. We examined the relationship between radiation and excess deaths from mesothelioma among deceased nuclear workers who were part of the US Transuranium and Uranium Registries. Methods. We performed univariate analysis with SAS Version 9.1 software. We conducted proportionate mortality ratio (PMR) and proportionate cancer mortality ratio (PCMR) analyses using the National Institute for Occupational Safety and Health Life Table Analysis System with the referent group being all deaths in the United States. Results. We found a PMR of 62.40 ( P < .05) and a PCMR of 46.92 ( P < .05) for mesothelioma. PMRs for the 4 cumulative external radiation dose quartiles were 61.83, 57.43, 74.46, and 83.31. PCMRs were 36.16, 47.07, 51.35, and 67.73. The PMR and PCMR for trachea, bronchus, and lung cancer were not significantly elevated. Conclusions. The relationship between cumulative external radiation dose and the PMR and PCMR for mesothelioma suggests that external radiation at nuclear facilities is associated with an increased risk of mesothelioma. The lack of a significantly elevated PMR and PCMR for trachea, bronchus, and lung cancer suggests that asbestos did not confound this relationship. Mesothelioma is a rare disease that accounts for approximately 0.10% of all deaths per year in the United States. 1 The age-adjusted incidence is approximately 2.1 per 100 000 among men and about 0.4 per 100 000 among women in the United States for the period 2000–2005. 2 Price and Ware 1 estimated that approximately 2400 new cases of mesothelioma were diagnosed in the United States in 2008. The risk factor most commonly associated with an increased risk of mesothelioma is asbestos. Smoking has not been identified as a risk factor for mesothelioma; neither does the combination of smoking and mesothelioma increase the risk of mesothelioma. 3,4 Spirtas et al. 5 estimated that among men, the attributable risk of asbestos for pleural mesothelioma and peritoneal mesothelioma was 88% and 58%, respectively. Among women, the attributable risk from asbestos for both sites combined (pleural and peritoneal) was only 23%. 5 Peto et al. 6 reported that among men the attributable risk from asbestos was 86%; among women, the attributable risk was only 38%. A variety of other agents including radiation, minerals, chemicals, viruses, and chronic inflammation have been implicated as causes of mesothelioma. 7–10 Ionizing radiation, such as x-rays, gamma rays, and alpha and beta particles, from both acute and long-term, low-level exposure is known to be associated with an increased risk of a variety of cancers. Exposure to radiation can cause mutations in the DNA and mutations can also occur during the body’s attempt to repair damaged DNA. Such mutations can lead to cancer. 11 Metz-Flamant et al. 12 reported that 15 of 17 studies of nuclear workers found an elevated risk of malignant pleural mesothelioma; all 17 studies provided exposure information. Eight studies reported that mesothelioma risks were higher for radiation-exposed workers than for other workers. 12 The authors claimed, however, that only 1 of 12 studies found a significant exposure–response relationship for cumulative external radiation dose but noted that with 1 exception, each study had few mesothelioma deaths. 12 Because of the lack of exposure–response and because asbestos could not be ruled out as a confounding agent, the authors concluded that studies of nuclear workers have not demonstrated an association between ionizing radiation exposure and malignant pleural mesothelioma. 12 Gold and Kathren 13 reported an excess of mesothelioma deaths in the US Transuranium and Uranium Registries (USTUR). The USTUR, currently in its 44th year of operation, maintains whole and partial-body donations acquired postmortem from volunteer donors, most of whom worked at US Department of Energy nuclear facilities. These registrants worked with, and typically had a documented accidental intake of, 1 or more alpha-emitting radionuclides (e.g., uranium, plutonium, and americium). Intakes varied from background levels to substantial intakes. USTUR donors typically worked at government sites where plutonium, americium, or uranium were processed (e.g., Hanford, Rocky Flats, Los Alamos, Savannah River, Fernald, and Mound). 14 We examined the possible association of the excess of mesothelioma deaths in the USTUR with radiation exposure.
