New approaches to respiratory tract dosimetry modeling for inhaled radionuclides

Respiratory tract dosimetry models for inhaled radioactivity are currently being reviewed and revised by a task group of the U.S. National Council on Radiation Protection. Revised models are likely to place increased emphasis on the nasal and tracheobronchial airways because studies with laboratory animals and people have shown cancers in these regions to be associated with inhaled radioactivity or other toxic substances. A morphometric model of the tracheobronchial airways describing a typical airway path for the respiratory tract and a clearance model based upon mucus flow velocity in conducting airways are also being evaluated. This combination of models appears to offer the greatest flexibility for dosimetry calculations applicable to people of different body size and health status. Doses to all epithelial cells lining the conducting airways will be calculated, instead of focusing exclusively on basal cells. (author)