Assessing the Uniformity of Plutonium Alpha Radiation Dose in Human Lung: The Mayak Experience

Radiation-induced lung cancer risk is currently estimated based on epidemiological data from populations exposed either to relatively uniform, low-LET radiation, or from uranium miners who inhaled radon and its progeny. Inhaled alpha-emitting radionuclides (e.g. Pu and Am) produce distinctive dose patterns that may not be adequately modelled at present. Thus the distribution of Pu is being measured in formalin-fixed autopsy lung tissue from former workers at the Mayak Production Association, and which is maintained in a tissue archive at SUBI. Lungs are sampled using contemporary stereological techniques and Pu particle activities and locations are determined using quantitative autoradiography and morphological identification of lung structures. To date >80% of Pu particles have been observed in parenchymal lung tissues with higher concentrations being found in scar tissue. Concentrations of Pu particles in conducting airways are uniformly low, thus indicating that long-term-retained Pu particles are non-uniformly distributed in human lung, mostly in the parenchyma.