Proposed revision of the ICRP model for inhaled mercury vapor

A critical review of the literature on the biokinetics of inhaled mercury vapor was performed as part of an accident analysis for the Spallation Neutron Source to be built at Oak Ridge National Laboratory. It was concluded that current models for inhaled mercury vapor do not accurately describe the distribution or residence time of mercury deposited in the respiratory tract. This paper proposes a model that is more consistent with collective information on the fate of inhaled mercury vapor in laboratory animals and human subjects. Compared with the model currently recommended by the International Commission on Radiological Protection (ICRP), the proposed model predicts lower deposition in the bronchi and bronchioles, greater deposition in the alveolar-interstitial region, and a different pattern of absorption to blood. The proposed model yields substantially reduced estimates of lung dose and effective dose for most radioisotopes of mercury inhaled as mercury vapor.