The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Health Risks from Exposure to Low Levels of Ionizing Radiation: Beir VII Phase 2
Studies of occupationally exposed persons have been reviewed in BEIR V (NRC 1990) and in more detail in UNSCEAR (2000b). Because of the large number of studies of radiation workers, they are not described exhaustively in this chapter, which focuses mainly on the most informative studies for the current BEIR VII evaluation (i.e., studies in which the sample size is sufficiently large and the historical individual dosimetric information is sufficiently complete for radiation risk estimation). As in the other review chapters in this report, studies were judged to be informative for the purpose of radiation risk estimation if (1) the study design was adequate and no major bias could be identified (see Chapter 5 concerning informative study designs and limitations); (2) individual quantitative estimates of radiation dose to the organ of interest were available for study subjects; (3) if so, the details of the dose reconstruction or estimation approach were evaluated; and (4) a quantitative estimate of disease risk in relation to radiation dose—in the form of an excess relative risk (ERR) or excess absolute risk (EAR) per gray—was provided. The data and confidence intervals are those given in the cited papers.
NUCLEAR INDUSTRY WORKERS
A direct assessment of the carcinogenic effects of protracted, generally low-level radiation exposure can be made from studies of cancer risk among workers in the nuclear industry, many of whom have been exposed to above-background levels of ionizing radiation over several decades and whose exposures have been monitored through the use of personal dosimeters. Throughout this report, the term “nuclear industry” will be used to refer to facilities engaged in the production of nuclear power, the manufacture of nuclear weapons, the enrichment and reprocessing of nuclear fuel, or reactor research. Uranium mining is not included.
Many studies of mortality—and, in some instances, cancer incidence—among nuclear industry workers have been carried out over the past 20 years. Published studies have covered workers in Canada, Finland, France, India, Japan, Russia, Spain, the United Kingdom, and the United States. Most have been cohort studies. The main studies in which mortality or morbidity has been examined by level of individual radiation dose are listed in Table 8-1. The characteristics of the cohorts and results are summarized briefly in Table 8-2. A number of published studies are not described in Table 8-2, for the following reasons:
The studies of Mayak workers in the former USSR are described in the next section of this chapter. Many of these workers received mixed exposures to low- and high-LET (linear energy transfer) ionizing radiation, including considerable doses from internal contamination with plutonium-239.
Studies of nuclear industry workers in which analyses were not reported in relation to individual external dose estimates are not discussed further in this chapter. These are studies of the employees of the U.S. Department of Energy (DOE) facilities of Linde (Dupree and others 1987), Oak Ridge Y-12 plant (workers employed between 1943 and 1947; Polednak and Frome 1981), Pantex (Acquavella and others 1985), Savannah River (Cragle and others 1988), and United Nuclear Corporation (Hadjimichael and others 1983); studies of mortality of nuclear industry workers in Slovakia (Gulis 2003) and at the French Atomic Energy Commission (Telle-Lamberton and others, 2004); and the proportional mortality studies of workers in nuclear installations in India (Nambi and Soman 1990; Nambi and others 1991, 1992).
Nested case-control studies of specific cancers in the cohort studies including melanoma (Austin and Reynolds 1997; Moore and others 1997); leukemia (Stern and others 1986); prostate cancer (Rooney and others 1993); and lung cancer (Rinsky and others 1988; Petersen and others 1990) are not included.
Studies of combined cohorts comprising many of the workers included in individual studies have been carried out in the United Kingdom and the United States, as well as studies of all workers included in the national dose registries in Canada, Japan, and the United Kingdom. In the USA, combined analyses of the data on workers from Hanford, Rocky Flats, and Oak Ridge National Laboratory (ORNL) have been reported by Gilbert and collaborators (1989, 1993a). The latest analysis included 35,933 workers, followed until the end of 1986 (Gilbert and others 1993a). A study of workers employed in one of 15 commercial nuclear power facilities was also conducted (Howe and others 2004). The study included 53,698 workers followed up for mortality from 1979 to 1997.
The British study of the National Registry of Radiation Workers (NRRW; Kendall and others 1992a, 1992b; Little and others 1993; Muirhead and others 1999) includes 124,743 monitored workers in the above-mentioned U.K. cohorts as well as employees of Nuclear Electric, the Defense Radiological Protection Service, and a number of other nuclear facilities. The latest publication covers follow-up for mortality until the end of December 1992. Combined analyses of three U.K. nuclear industry workforces (the Atomic Energy Authority [AEA], Atomic Weapons Establishment [AWE] and Sellafield) with follow-up extended to the end of 1988 have also been carried out (Carpenter and others 1994, 1998).
In Canada, the study of the National Dose Registry (NDR) covered 206,620 workers in the industrial, medical, and dental fields, as well as nuclear power, followed for mortality through 1987 (Ashmore and others 1998) and cancer incidence through 1988 (Sont and others 2001). About 25% of these were nuclear industry workers, but detailed results were not presented for this group. The average dose of the entire cohort is low (6.6 mSv). The average length of follow-