Health Risks of Ionizing Radiation: - Clark University

Figure 6-6 The effect of exposure age on the risk of cancer
mortality in Oak Ridge workers. The estimated % increase
per cSv is roughly the same as an estimate of ERR per Sv
at low doses. These data assume a 10-year lag time in the
development of cancer. Error bars show the standard error
of the estimate (based on Richardson and Wing 1999a).
Richardson and Wing (1999b) published another
analysis including all workers; estimated risks were
greater with the inclusion of all workers although
the greater diversity in the larger cohort increased
the uncertainty of the results. These results are at
odds with those of the atomic bomb survivors,
which generally show constant or declining risk
at increasing ages at exposure. In addition, a large
international pooled study of workers, discussed
below, did not detect such an effect (Cardis et al.
1995). At the same time, it is a plausible concept
mechanistically because cellular repair mechanisms
are known to become less efficient with age.
Rocketdyne. The Santa Susana Field Laboratory
in southern California has been the site of nuclear
activities under two companies that merged in 1984
(Atomics International and Rocketdyne, a division
of Boeing). Since the 1950s the area has been used
for various projects including rocket testing, the
development and testing of nuclear reactors, the
decladding of irradiated reactor fuel, and storage
of radioactive material. Health impacts on workers
Radiation Workers 77
have been studied by Hal Morgentstern, Beate Ritz,
and other researchers at UCLA (summarized by
Morgenstern and Ritz 2001 12 ).
Workers in this cohort have been exposed to
radiation externally, they have potentially taken
radionuclides into their bodies and been exposed
internally, and they have also been exposed to
chemical toxins. The UCLA study analyzed
each of these exposure pathways for risk. As in
other studies, the SMRs for this cohort were not
significantly elevated, although the leukemia SMR
was suggestive of an effect 13 . The authors attributed
these results to the healthy worker effect.
An analysis that grouped workers into dose
categories found associations between high doses
and mortality from leukemia/lymphoma, lung
cancer, cancers of the upper aerodigestive tract,
and all cancers 14 . Significant positive dose-response
Figure 6-7. Radiation-safety technicians check workers
for contamination before they exit a Rocky Flats
facility (Department of Energy, Office of Environmental
Management 1996).
12 Reports from this study have been published by Morgenstern et al. (1997) and Ritz et al. (1999a and 1999b).
13 The SMR for externally exposed workers was 1.60 (0.95-2.52); for internally monitored workers it was 1.46 (0.63-
2.88).
14 The highest category of external dose, 200 mSv or more, was significantly associated with mortality from all cancers
(RR 3.10, 1.13-8.48), lymphopoietic cancers (RR 15.7, 3.33-73.5) and lung cancer (RR 4.70, 1.05-21.0). The highest
category of internal dose (30 mSv or more) was also associated with mortality from all cancers (RR 2.56, 0.93-
7.09) and lymphopoietic cancer (RR 44.6, 5.64-353), but there were no lung cancer deaths in this category. The
highest category of internal dose was also associated with upper aerodigestive tract cancers including cancers of the
pharynx, esophagus, mouth, and stomach (RR 57.2, 8.17-401).