15
PLUTONIUM
2. RELEVANCE TO PUBLIC HEALTH
between mortality rates
for liver disease, other than cancer, and exposures to plutonium among workers at
these facilities.
Elevated serum liver enzymes (indicative of adverse liver effects),were the most consistent indicators of
non-neoplastic liver effects in dogs exposed to aerosols of
238
PuO
2
and
239
Pu(NO
3
)
4
at levels resulting in
mean initial lung burdens ≥0.36 and ≥0.19 kBq/kg, respectively. No consistent changes in serum liver
enzymes were seen in
239
PuO
2
-exposed dogs. Although elevated liver enzymes may serve as indicators of
hepatotoxicity, clinical signs of liver dysfunction (i.e., ascites, icterus clotting disorders) were not
observed in the
238
PuO
2
-exposed dogs.
Musculoskeletal Effects.
Possible associations between exposure to plutonium and mortality from
bone disease (e.g., bone cancer) and other musculoskeletal diseases have
been examined in studies of
workers at 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).
Collectively, these studies
have not found significant associations between mortality rates for bone or musculoskeletal disease, other
than cancer, and exposures to plutonium among workers at these facilities. Radiation osteodystrophy,
observed in dogs with high intakes of plutonium, would be expected in humans following
intake of large
amounts of plutonium.
Radiation osteodystrophy, characterized by peritrabecular fibrosis, osteosclerosis, and osteoporosis, was
observed on necropsy in dogs exposed to
238
PuO
2
. The incidence and severity was dose-related and was
seen at mean initial lung burdens as low as 1.17 kBq/kg; necrotic osteoblasts and empty lacunae near
endosteal surfaces were observed at relatively high initial lung burdens. Although osteodystrophy in
238
PuO
2
exposed dogs was often
associated with bone tumors, it also occurred in the absence of bone
tumors. Radiation osteodystrophy has also been reported in dogs that inhaled
239
Pu(NO
3
)
4
.
Immunological Effects.
Possible associations between exposure to plutonium and mortality from
immunological or lymphoreticular diseases have been examined in studies of workers at plutonium
production and/or processing facilities in the United States (Rocky Flats) and the United Kingdom
(Sellafield). Collectively, these studies have not found statistically significant associations between
mortality rates from diseases of the immunological or lymphoreticular systems and exposures to
plutonium among workers at these facilities.
16
PLUTONIUM
2. RELEVANCE TO PUBLIC HEALTH
Histopathologic lesions of lymph nodes, particularly tracheobronchial lymph nodes, have been observed
following exposure of dogs to aerosols of
238
PuO
2
,
239
PuO
2
, or
239
Pu(NO
3
)
4
. Fibrosis and loss of lung-
associated and mediastinal lymph nodes were observed
in dogs exposed to
238
PuO
2
at levels resulting in
mean initial lung burdens ≥10 kBq/kg. Severity of non-neoplastic lesions was dose-related, progressing
from lymphoid atrophy of medullary cords to significant lymph node atrophy with hypocellular scar
tissue replacing lymphoid tissue. Similar dose-related atrophy and fibrosis of lung-associated,
mediastinal, sternal, and hepatic lymph nodes were observed in dogs exposed to
239
PuO
2
. Sclerotic lymph
nodes were observed in the groups of
239
Pu(NO
3
)
4
-exposed dogs with
mean initial lung burdens
≥5.91 kBq/kg, but lymph node lesions in these dogs were considered less severe than those observed in
238
PuO
s
- or
239
PuO
2
-exposed dogs.
Results of studies on immunological function indicate that inhalation exposure to
239
PuO
2
impairs T-cell
response to antigens, as indicated by decreased response to antigen. A study detected accelerated aging of
the T-cell response to mitogenic stimulation in dogs that had been exposed to
239
PuO
2
10 years earlier.
Other reports of
239
PuO
2
-induced effects from plutonium exposure include decreases in pulmonary
alveolar macrophages in mice and depressed antibody-forming cells in hamsters.
Cardiovascular Effects.
Possible associations between exposure to
plutonium and cardiovascular
disease have been examined in studies of workers at production and/or processing facilities in the United
Kingdom (Sellafield). One study compared mortality rates between plutonium workers and other
radiation workers within a cohort of Sellafield workers and found the mortality rate ratios were
significantly elevated for cerebrovascular disease (1.27, p<0.05) in a cohort of Sellafield workers. The
cumulative internal uptakes of plutonium in the cohort were estimated to range from 0 to 12 kBq, with
approximately 75% of the cohort having cumulative uptakes ≤250 Bq. Another study compared mortality
rates between plutonium workers and other radiation workers within a cohort of Sellafield workers and
found that morality rate ratios for plutonium workers were significantly elevated for deaths from
circulatory disease (2.18, p<0.05) and ischemic heart disease (4.46, p<0.01).
No significant changes in cardiovascular function were seen in dogs exposed to
239
PuO
2
at initial lung
burdens up to and including those resulting in radiation pneumonitis; observed
right ventricular
hypertrophy was most likely a compensatory response to decreased respiratory function.
Gastrointestinal Effects.
Gastrointestinal effects were observed in rats following oral administration
of
238
Pu/kg (as plutonium citrate) by gavage. Effects included mild hypertrophy of the crypts of the small