Specific bloodabsorption parameters for ²³⁹puo₂ and ²³⁸puo₂ nanoparticles and impacts on bioassay interpretation

Specific absorption parameters for ²³⁹puo₂ and ²³⁸puo₂ have been determined based on available biokinetic data from studies in rodents, and the impacts of these parameters on bioassay interpretation and dosimetry after inhalation of nanoPuO2 materials have been evaluated. Calculations of activities after an acute intake of nanoparticles of ²³⁹puo₂ and ²³⁸puo₂ are compared with the corresponding calculations using standard default absorption parameters using the International Commission on Radiological Protection (ICRP) 66 respiratory tract model. Committed effective doses are also evaluated and compared. In this case, it was found that interpretation of bioassay measurements with the assumption that the biokinetic behaviour of PuO2 nanoparticles is the same as that of micrometre-sized particles can result in an overprediction of the committed effective dose by two orders of magnitude. Although in this case the use of the default assumptions (5 mm AMAD, Type S) for assessing dose following inhalation exposure to airborne PuO₂ nanoparticles appears to be conservative, the evaluation of situations involving PuO₂ nanoparticles that may have different particle size and solubility properties should prudently follow the ICRP recommendation to obtain and use additional, material-specific information whenever possible.