ESTIMATION OF THE DOSE OF RADON PROGENY TO THE PERIPHERAL LUNG AND THE EFFECT OF EXPOSURE TO RADON PROGENY ON THE ALVEOLAR MACROPHAGE

Groups of rats were exposed to radon progeny attached to a vector aero sol of cigarette smoke particles in a closed-loop exposure system. The total exposures ranged from 70 to 1020 WLM over a 3-5-h period. Alveo lar macrophages were lavaged from exposed and control rats (exposed to the vector aerosol alone). There were no differences between phagocyt ic capabilities of the macrophages lavaged from the controls and any g roup of exposed rats. The increases in the numbers of binucleated/mult inucleated and micronucleated macrophages were enumerated using cytolo gical preparations of lavaged alveolar macrophages after exposure comp ared to the numbers in the control rats. The peak response in numbers of binucleated/multinucleated and micronucleated macrophages occurred at 21 days after exposure, beyond which the numbers decreased. This pe ak response showed a significant exposure-dependent relationship. The number of micronuclei provided a sensitive indicator of exposure. The lowest exposure level used (70 WLM) resulted in a significant differen ce in the number of micronucleated macrophages between control and exp osed rats. The alpha-particle dose to the peripheral lung was estimate d by comparing formation of micronuclei in cultured macrophages expose d to alpha particles from Pu-238 (where the dose was known) to micronu clei in lavaged macrophages from animals exposed to radon progeny (whe re the exposure concentration was known, but the dose was not known). The dose estimated in this way for the peripheral lung was 9.8 +/- 1.2 mGy/WLM. This value is three to five times higher than predicted from mathematical models currently available.