Environmental Engineering Reference
In-Depth Information
fallout radionuclide with other studies points out the dificulties in deriving reasonable estimates of
air concentrations based on sampling site location.
22.10 EXPOSURE ESTIMATION OF U, TH, AND PU
The measurements of U, Th, and Pu in TSP show the vast differences in concentrations with
geographical location. To generalize the inhalation estimate of these radionuclides, Th (1 Bq m
−3
of
air) are adopted, and for Pu, a single location, New York, is selected for a 23 year period from 1963
to 1985. The estimations are for the adult male with a daily breathing rate of 22.2 m
−3
of air. The total
exposure to U and Th for a 23 year period is 186 mBq for each or 372 mBq for U and Th. The exposure
estimate based on New York Pu measurements from samples collected in the latitude with the highest
fallout air concentration is 802 mBq or a factor of >2.2 than the sum of the U and Th exposures.
These estimates are made only for illustrative purposes and are not representative of speciic
geographical areas or particular time periods, except for Pu. The ANL TSP measurements for the
calendar year 2001 yield air concentrations of 0.15 µBq U m
−3
, 0.04 µBq Th m
−3
, and 0.01 Pu µBq
m
−3
. The sum of U and Th annual exposures at site for 2001 is a factor of 15 greater than the Pu
exposure.
As noted earlier, all three environmental aerosols are refractory and, thus, only very slowly
transferred from the alveolar region of the lung to the bloodstream. Some of the deposited aerosol is
sequestered for long periods of time in the pulmonary lymph nodes, in effect reducing the systemic
body burden.
The alpha-dosimetric consequences from the inhalation of these environmental aerosols are
minor compared to the dose from radon progeny.
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