Investigations are ongoing to archive historical data useful for specific exposure scenarios, to refine and improve existing dosimetric techniques, and to develop new strategies for retrospective dose estimation. There are five major components of the present investigations.
One major component involves archiving of unique historical data. Dose reconstruction relies on historical data relevant to the population exposed, however, historical data is usually sparse and often insufficient in quantity and quality.
Three recent examples of historical datasets archived by the Radiation Epidemiology Branch (REB) that are unavailable elsewhere include:
A second component uses measurements of trace elements as surrogates of radioactive isotopes including: stable iodine in soil from Kazakhstan to estimate the degree of iodine deficiency and in vegetation consumed by dairy animals; cesium, iodine, and strontium to estimate the efficiency of transfer from vegetation to animal milk; and the concentration of naturally occurring Radium-226 (226Ra) in human thyroid glands for developing a more accurate biokinetic model of 226Ra in the human body.
A third component uses radioactivity measurements in soil to confirm model assumptions about levels of radionuclides in fallout.
A fourth approach uses historical meteorological data (early 1950s-present) on wind and precipitation to estimate fallout dispersion over the entire globe. Presently, REB dosimetrists are exploring the utility of using the HYSPLIT model developed by the National Atmospheric and Oceanic Administration to reconstruct trajectories of fallout and deposition as a function of particle size and rainfall conditions following U.S. nuclear tests conducted in the Marshall Islands between 1946 and 1958.
A fifth approach uses biodosimetric techniques to validate historical dose levels, including the following: