Local energy deposited for alpha particles emitted from inhaled radon daughters.

An analytical method has been developed to calculate the local energy deposited by alpha particles emitted from radon daughters deposited on the mucus surface in the lung airways. For the particular cases of 218Po (Ra A) and 214Bi (Ra C'), microdose spectra have been evaluated in test spheres of 1 micron diameter which were taken to lie within airways of diameters 18,000, 3,500 and 600 microns. In each case, the contributions of the near and far wall were computed separately. The average microdosimetric parameters yF and yD have also been calculated. For the two smaller airways, yF and yD values were found to be about 110 and 135 keV microns-1 for 218Po and about 87 and 107 keV microns-1 for 214Bi respectively. The corresponding values were about 10% higher for the largest airway.