This report provides an overview of the prototype chemical fate and human exposure model developed to support Japan's National Life Cycle Assessment (LCA) initiative for toxicological impacts.  The model facilitates calculation of damage-based characterization factors for toxicological effects (time-integrated impact associated with a unit mass of a chemical or particulate matter emitted into the environment) in Japan.  Toxicological potency and severity measures are considered elsewhere.  The model outputs include change in concentrations in environmental media per unit mass emission and dose fractions (time-integrated mass resulting in exposure to a defined population divided by mass released) for humans associated with chemical emissions into the environment.  Multimedia chemical fate, multi-pathway human exposure and multiple classes of chemicals (organics, speciating, metals, gases and priority pollutants) are taken into account.  Preliminary results are presented for 40 chemicals using the prototype and a comparison is made with the predictions of existing models/field data for 68 chemicals.