Worldwide bioassay data resources for plutonium/americium internal dosimetry studies

Full text: Biokinetic models are the scientific underpinning of internal dosimetry. These models describe how materials of interest taken into the body by various routes (for example inhalation) are transported through the body, allowing the modelling of bioassay measurements and the estimation of radiation dose. The International Commission on Radiation Protection (ICRP) publishes biokinetic models for use in internal dosimetry. These models represent the consensus judgement of a committee of experts, based on human and animal data. Nonetheless, it is important to validate biokinetic models using directly applicable data, in a scientifically transparent manner, especially for internal dosimetry research purposes (as opposed to radiation protection), as in epidemiology studies. Two major goals would be to determine individual variations of model parameters for the purpose of assessing this source of uncertainty in internal dose calculations, and to determine values of workplace specific parameters (such as particle solubility in lung fluids) for different representative workplaces. Furthermore, data on the observed frequency of intakes under various conditions can be used in the interpretation of bioassay data. All of the above may be couched in the terminology of Bayesian statistical analysis and amount to the determination of the Bayesian prior probability distributions needed in a Bayesian interpretation of bioassay data. The authors have direct knowledge of several significant databases of plutonium/americium bioassay data (including autopsy data). The purpose of this paper is to acquaint the worldwide community with these resources and to invite others who may know of other such databases to participate with us in a publication that would document the content, form, and the procedures for seeking access to these databases. These databases represent a tremendous scientific resource in this field. Examples of databases known to the authors include: the Sellafield plutonium bioassay database, consisting of some 400,000 bioassay measurements, the Los Alamos plutonium/americium database, consisting of some 200,000 bioassay measurements, and the US transuranic Registry (USTUR), consisting of about 400 autopsy cases. Each of these databases has a particular structure, based on the perspectives of the database creators. One of the goals of our publication would be to describe these structures, explaining the rational, and possibly generalizing them as a proposed basis for future internal dosimetry databases. If the format and content of databases can be standardized, this would greatly increase the prospects of using combined databases to improve plutonium/americium dosimetry methodology and hence dose/risk estimates. (author)