54
PLUTONIUM
3. HEALTH EFFECTS
3.2.1.4 Neurological Effects
Possible associations between exposure to plutonium and mortality from brain or neurological diseases
have been examined in studies of workers at plutonium production and/or processing facilities in the
United States (Rocky Flats) (Wiggs et al. 1994) and the United Kingdom (Sellafield) (McGeoghegan et
al. 2003; Omar et al. 1999). These studies are summarized in Table 3-2 and study outcomes for mortality
are described in Section 3.2.1.1. Collectively, these studies have not found statistically significant
associations between mortality rates from diseases of the central or peripheral nervous
systems and
exposures to plutonium among workers at these facilities.
3.2.1.5 Reproductive Effects
Possible associations between exposure to plutonium and mortality from diseases of the genitourinary
tract and diseases of pregnancy have been examined in studies of workers at plutonium production and/or
processing facilities in the United States (Rocky Flats) (Wiggs et al. 1994) and the United Kingdom
(Sellafield) (McGeoghegan et al. 2003; Omar et al. 1999). These studies are summarized in Table 3-2
and study outcomes for mortality are described in Section 3.2.1.1. Collectively,
these studies have not
found statistically significant associations between mortality rates from genitourinary tract disease or
diseases of pregnancy and exposures to plutonium among workers at these facilities.
No studies were located regarding reproductive effects in animals following inhalation exposure to
plutonium compounds.
3.2.1.6 Developmental Effects
No studies were located regarding developmental effects in humans or animals following inhalation
exposure to plutonium compounds.
3.2.1.7 Cancer
Epidemiological Studies in Humans.
Possible associations between exposure to plutonium and
cancer
mortality and morbidity have been examined in studies of workers at the U.S. plutonium production
and/or processing facilities (Hanford, Los Alamos, Rocky Flats), as well as facilities in Russia (Mayak)
and the United Kingdom (e.g., Sellafield). The most recent findings from these studies are summarized in
Table 3-2. Compared to studies of U.K. and U.S. facilities, the Mayak cohorts had relatively high
55
PLUTONIUM
3. HEALTH EFFECTS
exposures to plutonium (i.e., mean body burdens ranging from 0.09 to 9.2 kBq,
with individual exposures
as high as 470 kBq (Krahenbuhl et al. 2005). Collectively, the Mayak studies provide evidence for an
association between cancer mortality and exposure to plutonium. Plutonium dose-response relationships
for lung cancer mortality have been corroborated in three Mayak studies (Gilbert et al. 2004; Jacob et al.
2005; Kreisheimer et al. 2003). Studies of U.K. and U.S. facilities have examined cohorts of workers
who had substantially lower estimated plutonium exposures and corresponding internal radiation doses
than the Mayak cohorts (e.g., Sellafield: body burdens ≤1 kBq in 97% of the assessed workers [Omar et
al. 1999]; Los Alamos: mean body burden 0.970 kBq, range: 0.05–3.18 kBq [Voelz et al. 1997]).
Although a significantly higher incidence of cancer mortality in certain groups of plutonium workers has
been found in some studies, higher cancer incidence and/or risks for tissues that received the
highest
plutonium radiation doses (i.e., lung, liver, bone) have not been found, making causal connections of
these outcomes to plutonium exposure more uncertain (Brown et al. 2004; Carpenter et al. 1998; Gilbert
et al. 1989b; McGeoghegan et al. 2003; Omar et al. 1999; Wing et al. 2004).
Mayak Production Association Workers.
Studies of mortality of plutonium workers at Russian facilities
are summarized in Table 3-2 (Gilbert et al. 2000, 2004; Jacob et al. 2005; Koshurnikova et al. 2000;
Kreisheimer et al. 2003; Sokolnikov et al. 2008). The total Mayak cohort includes approximately
22,000 workers; plutonium monitoring data exist on approximately 28% of subjects (Gilbert et al. 2004).
However, reliability of the monitoring data varies across subjects, which introduces
uncertainty into
stratification of the cohort by estimated plutonium body burden or internal radiation absorbed dose (i.e.,
Gy) or effective dose equivalents (i.e., Sv). These data yielded estimates of mean plutonium body
burdens in the full cohort that ranged from 0.9 to 9.2 kBq (Krahenbuhl et al. 2005). The mean body
burden, based on data considered to be the most reliable, was 9.2 kBq (range: 0–469 kBq, n=805). In an
earlier analysis of the Mayak
monitoring data, Gilbert et al. (2004) and Shilnikova et al. (2003) estimated
body burdens and lung radiation doses for various categories of employment (e.g., dates, jobs, work
conditions, monitoring and autopsy data) and exposure. The estimated job category mean body burdens
ranged from 0.45 to 17.8 kBq, and the corresponding internal absorbed doses to the lung ranged from
0.016 to 2.91 Gy. The corresponding effective dose equivalents are 0.32 and 58 Sv (assuming a radiation
weighting factor of 20 for -radiation). The mean body burden for the monitored fraction of the cohort
(n=6,193) was 1.84 kBq, and the corresponding internal lung absorbed dose was 0.24 Gy (Gilbert et al.
2004). Sokolnikov et al. (2008) applied recently improved individual dose estimates to 5,572 of the
Mayak workers with confirmed plutonium exposure and estimated that the mean
plutonium dose to the
lung was 0.19 Gy (0.14 Gy for males and 0.29 Gy for females).