Health Risks of Ionizing Radiation: - Clark University

myeloid leukemia) was significantly associated
with dose as was mortality from multiple
myeloma 9 . Wilkinson and Dreyer (1991) pooled
the leukemia mortality results of seven worker
studies. These authors found a significant risk
among workers with doses of 0.01-0.05 Sv
(Rate ratio 2.1, 90% CI 1.4-3.3).
• Leukemia among nuclear weapons test
veterans. Veterans who were involved with
nuclear weapons testing were typically exposed
to low doses of radiation 10 . Muirhead et al. (2003)
did not detect any significant dose-response
trends in a subgroup of UK veterans with dose
information, but this is not surprising given the
low numbers of cases 11 . UK veterans followed
through 1983 showed increased mortality from
leukemia (RR 3.45, 90% CI 1.50-8.37) and
multiple myeloma (6 deaths among participants
and zero deaths among controls); total cancer
mortality was not different from controls (RR
0.96, 90% CI 0.86-1.08). A purely low-dose
cohort was studied by Caldwell et al. (1983);
these were veterans of one test (Smoky, 1957)
who had a mean dose of 0.005 Sv and a maximum
dose of 0.1 Sv. Among these veterans there was
a significant excess of leukemia, registered as
either incidence or mortality (incidence RR
2.5, 1.2-4.6), and total cancer mortality was not
different from expected (incidence RR 0.95,
0.78-1.14).
• Medical exposures and leukemia. Studies of
diagnostic x-rays are of limited utility because
they typically lack dose estimates. In one study
that did estimate doses there was evidence of
a chronic myeloid leukemia risk at low doses
(Preston-Martin et al. 1989). Out of 130 cases
and 130 matched controls 80% had estimated
cumulative bone marrow doses less than 0.02
Gy. The maximum dose in this group would have
Discussion 169
been received by one patient who had 22 back
x-rays; at 247-749 mrad per exam this would be
a cumulative dose of 0.05-0.16 Gy. This group
showed a significant dose-response relationship
with an estimated ERR of 30/Gy. When analysis
was restricted to the period within 6-10 years of
diagnosis the ERR estimate was 76/Gy and the
OR for the 0.01-0.02 Gy exposure group was
significantly positive (3.1, p