Deposition of 214Pb and nuclear aberrations in the respiratory tract of rats after exposure to radon progeny under different aerosol conditions

Abstract

The aim of this work was to relate 214Pb deposition within the respiratory tract of the rat to aerosol characteristics during exposure to radon and its progeny. Two different exposure conditions were studied: static, without air recirculation with a low unattached fraction of radon progeny ( fp≈10%); and dynamic, with continuous air recirculation ( fp>80%). Deposition was estimated by measuring 214Pb retention in nasopharynx and lungs at the end of a 3-h exposure using gamma spectrometry. The deposition of 214Pb in the pulmonary region was the same in the two exposure conditions. By contrast, nasopharynx deposition was 5 times higher under dynamic than under static exposure. The dose delivered to the deep lung was estimated by micronuclei scoring in alveolar macrophages extracted by pulmonary lavage. For a similar cumulative dose delivered under static or dynamic conditions, a similar micronuclei index was measured, 1.22% ± 0.26 and 1.47% ± 0.42, respectively, 8 d after exposure. These results suggest that the unattached fraction did not influence radon progeny deposition and the resulting delivered dose in the deep lung of the rat.