Health Risks of Ionizing Radiation: - Clark University

Figure 5-2. Military observers shield their faces from the
Teapot Test in 1955 (http://www.aracnet.com/~pdxavets/).
of blood and lymph cancers including leukemia.
Darby et al. (1988, 1993) and Muirhead et al. (2003)
conducted a cohort follow-up of 20,000 British test
veterans through 1998 and found that the leukemia
mortality rate, while not much greater than the
national rate, was significantly higher than in a
control population (servicemen not participating in
the tests). For the follow up through 25 years the
relative risk (RR) was 3.38 (90% CI 1.45-8.25). 2
New Zealand servicemen also participated in the
same tests as the British servicemen and were also
found to have increased leukemia mortality (RR 5.6;
90% CI 1.0-41.7; Pearce et al. 1990, 1997). 3
Several studies of U.S. servicemen have also
found evidence of increased leukemia. Caldwell et
al. (1983) followed 3,217 participants in the 1957
test “Smoky” through 1979 and found an increase
Nuclear Weapons Testing 59
in both leukemia incidence (RR 2.50; 1.20-4.60)
and leukemia mortality (RR 2.58; 1.11-5.09). The
same authors, looking at the same cohort, also
found four cases of polycythemia vera, another
type of blood neoplasm, when 0.2 cases would be
expected in this population based on national rates
(Caldwell et al. 1984). This translates into a relative
risk of 20.2 (5.5-51.7). Dalager et al. (2000) found
statistically significant increases in mortality from
lymphopoietic cancers (RR 3.72; 1.28-10.83) and
all-cause mortality (RR 1.22; 1.04-1.44) when
comparing U.S. test veterans with high doses (> 50
mSv) to veterans with “minimal” doses.
The leukemia association is less clear in some
other studies of U.S. veterans. Johnson et al. (1997)
studied the mortality of approximately 40,000
participants in Operation Crossroads, a 1946 test
series at the Bikini atoll. Leukemia mortality was not
significantly elevated (RR 1.02; 0.75-1.39) although
all-cause mortality was (RR 1.05; 1.02-1.07). 4
Watanabe et al. (1995) also found a nonsignificant
increase in leukemia mortality among the 1,094
personnel exposed to more than 1 cGy of gamma
radiation during the 1958 test series “Hardtack I”
(RR 1.73; 0.39-7.56). This study looked at a total of
8,554 veterans and also found significant increases
in total cancer mortality (RR 1.42; 1.03-1.96) and
liver cancer mortality (RR 6.42; 1.17-3.53).
5.2 Semipalatinsk Test Site downwinders
There were 118 atmospheric tests at the
Semipalatinsk Test Site between 1949 and 1963,
and over 300 underground tests through 1989, some
of them releasing radioactive material when they
broke the surface (vented). 95% of the collective
dose received by nearby residents is thought to
have come from four tests in 1949, 1951, 1953 and
1956. In 1994 Zaridze et al. published a paper that
examined the relationship between childhood cancer
incidence and distance from the test site. They began
2 For the extended follow-up (through 1998) the RR for non-CLL leukemia mortality was significant but lower (1.83,
90% CI 1.15, 2.93). Leukemia incidence risks were similar to those of mortality (Muirhead et al. 2003).
3 In this cohort the RR of leukemia incidence was the same as the RR of leukemia mortality. There was also a significant
excess of all hematologic cancers, with a RR of 1.9 (0.8-4.3) for incidence and 3.8 (1.4-10.8) for mortality (Pearce
et al. 1997).
4 The subgroup of Operation Crossroads participants having an Engineering and Hull specialty showed a
leukemia risk that was close to statistical significance (RR 1.51; 0.94-2.44) (Johnson et al. 1997).