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/