0
USE ONLY
o
a
meters to deseribe lung deposition, retention, and clearance pre-
sented in the ICRP Task Group Report on Lung Dynamics, the average
dose to the lung can be calculated for recently deposited nuclides.
(Table 7)
Lung doses calculated for adults probably are also valid for
children because the relatively long equilibrium time and smaller
breathing volume offset the smaller mass of the lungs and possible
increase in radiosensitivity.
Plutonium translocates to other tissues such as bone and liver
following initial deposition in the lung.
The total lifetime
accumulated radiation dose to bone F liver is less than that received
by the lung.
Ingestion of plutonium is considered to be of much less importance
than inhalation mainly because of the small absorption from the gastrointestinal tract (0.003%).
Absorption of plutonium through unbroken
skin and skin exposure are negligible.
The number of particles comprising the contamination should also
be considered.
For example, an activity of 1 picocurie of
239 Pu
per
gram of soil, in which all the activity is on the surface, represents
ob
only about 4 one-micron diameter particles of *3?Pu0,,, or about 4 x 10
particles per square meter.
Thus, areas uniformly contaminated with
ea
hinges (2/