Beagle dogs exposed to (PuO2)-Pu-238 aerosols (136 dogs, 13-22 per gro
up, mean initial lung depositions of 0.0, 0.13, 0.68, 3.1, 13, 52 and
210 kBq) were observed throughout life to determine tissues at risk an
d dose-effect relationships. The pulmonary retention of Pu-238 was rep
resented by the sum of two exponentially decreasing components of the
initial lung deposition; about 84% cleared with a 174-day half-time; t
he half-time of the remainder was 908 days. The average percentages of
final body burden found in lung, skeleton, liver and thoracic lymph n
odes in the 30 longest-surviving dogs (mean survival 14 years) were 1,
46, 42 and 6%, respectively. Of 116 beagles exposed to plutonium, 34
(29%) developed bone tumors, 31 (27%) developed lung tumors, and 8 (7%
) developed liver tumors. Although lungs accumulated a higher average
radiation dose than skeleton, more deaths were due to bone tumors than
to lung tumors. Deterministic effects included radiation pneumonitis,
osteodystrophy, hepatic nodular hyperplasia, lymphopenia, neutropenia
and sclerosing tracheobronchial lymphadenitis. Hypoadrenocorticism wa
s also observed in a few dogs. Increased serum alanine aminotransferas
e, indicative of liver damage, was observed in groups with greater tha
n or equal to 3.1 kBq initial lung deposition. Estimates of cumulative
tissue dose in a human exposed to airborne (PuO2)-Pu-238 for 50 years
at a rate of one annual limit on intake each year were derived based
on a comparison of the data on metabolism for humans and beagles. The
50-year dose estimates for humans are an order of magnitude lower than
doses at which increased incidence of neoplasia was observed in these
dogs, whereas the projected doses to humans from 50-year exposure at
the annual limit of intake are of similar magnitude to those at which
deterministic effects were seen in the beagles. (C) 1997 by Radiation
Research Society.