Health Risks of Ionizing Radiation: - Clark University

7
MAYAK WORKERS
7.1 Introduction
The cohort of Mayak workers is distinctly different
from other worker cohorts in that the average
exposures of these workers were much higher and
women made up a greater fraction of the workforce.
For this reason we have devoted a separate section to
this cohort. Mayak has also made a profound impact
on the communities along the Techa River; this is
discussed in Section 12.
Mayak (the Mayak Production Association), in
the southern Urals region of Chelyabinsk, was the
first nuclear complex in the Soviet Union. The plant
included a nuclear reactor, a plutonium production
facility, and a radiochemical fuel separation facility.
Radiation exposures during the first few years of
operation were quite high, with average annual
external doses of roughly 0.5 Gy. Exposures declined
following a 20-fold reduction in the maximum daily
permissible dose in 1952 (Koshurnikova et al. 1999),
but were still relatively high- the mean lifetime
dose received by Mayak workers averaged 0.8 Gy,
roughly an order of magnitude higher than mean
lifetime doses in most worker cohorts (see Section
6). In addition to external radiation these workers
were exposed to plutonium. Inhaled plutonium
is deposited most heavily in the lungs, and of the
plutonium that migrates to the rest of the body about
50% is deposited in the skeleton (Koshurnikova et
al. 2000). Deposited plutonium remains in the body
for a long time resulting in chronic exposure to alpha
particles; the mean alpha lung dose in this cohort
was 0.2 Gy. Exposure profiles varied by facility as
shown in Table 1.
7.2 Health effects
Two approaches to this cohort have been pursued
by different teams of scientists from Chelyabinsk
and their colleagues- case-control studies of lung
cancer (Tokarskaya et al. 1995, 1997, 2002) and
cohort studies of total mortality and various causes
of death. These studies have been reviewed by the
United Nations Scientific Committee on the Effects
of Atomic Radiation (UNSCEAR 1994, 2000), by
the Radiological Assessments Corporation for an
analysis of plutonium risks around Rocky Flats
Plant (RAC 2000), and recently by Harrison and
Muirhead for a comparison of risks from external
and internal radiation (2003). A comprehensive
cohort study of mortality in all 21,557 Mayak
workers was presented in 2003 (Shilnikova et al.).
The most apparent health effects in Mayak workers
have been the cancers associated with plutonium-
lung, liver, and bone cancer and leukemia.
Lung cancer. Tokarskaya et al. (1995) found
that lung cancer was associated with plutonium
exposures, gamma exposures, and smoking. No
dose-response analysis was performed for gamma
exposures but the plutonium dose-response curve
that they generated was nonlinear with a threshold
at 0.8 Gy 1 . In 2002 Tokarskaya et al. used an
1 Issues with this dose-response analysis were raised by Jan Beyea (1998); he noted that case-control studies are
not able to distinguish between non-linear dose-response relationships and differences in exposure distributions
between cases and controls.
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