Large-particle inhalation dose conversion factors (where derivable) are used to high-side estimates of internal dose, despite the apparent dominance of the ingestion pathway. For some radionuclides, the original deposition of inhaled particles in the nasopharyngeal region affords a significantly greater absorption into the body than occurs in the GI tract. A minor contribution to GI tract doses is depleted through this pathway, but lung dose is greatly increased. complete with either pathway. For iodine, absorption is essentially Thus, the iodine-dominated thyroid dose is insensitive to the mix of ingestion and large-particle inhalation contributions to the total activity intake (so long as these occur at about the same time). Moreover, the use of the calculated I-131 intake to normalize the radionuclide inventory is independent of this mix. Dose calculations are made for intake at 9 hours after detonation. In the early portion of significant fallout deposition, this high-sides organ doses by including greater activities of fast-decaying radionuclides. The large-particle dose conversion: factors used in the calculation are listed in Reference 21. 4.4 ORGAN-SPECIFIC DOSE COMMITMENTS The 50-year dose commitment to organ j, Dis resulting from the intake of a mixture of radionuclides is given by D == U2i, DCF:j 1 Qi, the amount of intake of radionuclide i, is determined from the radionuclide inventory as normalized by the I-131 activity intake developed from the urinalysis data. The dose conversion factor, pcr, for organ j due to the intake of radionuclide i is as discussed previously. 22