Nevada Applied Ecology Group model for estimating plutonium transport and dose to man

A Standard Man is assumed to live in and obtain most of his food from a plutonium-contaminated area at the Nevada Test Site (NTS). A plutonium transport model, based on the results of other Nevada Applied Ecology Group plutonium studies, is used to estimate potential chronic rates of 239Pu inhalation and ingestion as functions of the average concentration of 239Pu (C/sub s/ = pCi/g) in the surface soil (0 to 5 cm depth) of the reference area. Assuming the transport system to be in steady state, the estimated inhalation and ingestion rates (pCi/day) are 0.002 C/sub s/, respectively. A dose estimation model based on parameters values recommended in publications of the International Commission on Radiological Protection is used to estimate organ burdens, accumulated doses, and dose commitments as functions of exposure time. Estimated doses (rems) due to chronic inhalation and ingestion of 239Pu for 50 years at the rates indicated above are: thoracic lymph nodes, 0.610 C/sub s/; lungs, 0.026 C/sub s/; bone, 0.014 C/sub s/; liver, 0.009 C/sub s/; kidney, 0.003 C/sub s/; total body, 0.0007 C/sub s/; and gastrointestinal tract (lower large intestine), 0.0002 C/sub s/. Inhalation accounts for 100 percent of the estimated dose to lungs and thoracic lymph nodes and for about 95 percent of the estimated dose to bone, liver, kidney, and total body. Ingestion accounts for > 99 percent of the dose to the gastrointestinal tract. According to ICRP recommendations for individual members of the public, the dose rate to the lungs after 50 years' exposure should not exceed 1.5 rems/year. The plutonium transport and dose estimation model described in the report indicate that the average concentration of 239Pu in the surface (0 to 5 cm) soils of contaminated areas at NTS which could result in a maximum dose rate of 1.5 rems/year to the lungs is approximately 2.8 nCi/g or about 140 μCi/m2 for soils weighing 1.0 g/cm3