The main objective of this project is to improve capabilities for evaluating health risks to humans associated with inhaling plutonium (Pu). Two key DOE issues are being addressed: (1) the need to improve capabilities for evaluating plutonium dioxide (PuO 2 )-associated health risks for DOE workers involved in decommissioning/decontamination (D&D) activities; and (2) the need to improve capabilities for evaluating health risks for public exposures arising from residual PuO 2 in soil at

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... d (cleaned-up) DOE sites. The scientific goal of this project is to improve capabilities for assessing health risk distributions for DOE workers and the public associated with inhaling Pu. The focus of our work has been on DOE worker and public exposure scenarios related to the Rocky Flats Environmental Technology Site near Denver, Colorado, commonly called Rocky Flats. Research Progress and Implications This report summarizes work after 1 year of a renewed 3-year project. The project has focused on applying basic and applied science methodology to improve the following: (1) characterization of Pu/americium (Am) intake by inhalation; (2) subsequent organ radiation doses; and (3) the associated health risks. To achieve these improvements, more appropriate distributions relating to uncertainty/variability have replaced traditional but inappropriate point estimates.