Historic bioassay surveillance data are often employed by dosimetrists and epidemiologists to reconstruct the extent of occupationally-received past exposures to one or more internally deposited radionuclide contaminants. Before these early data can be employed in an interpretive manner, however, two questions must be answered; 1) how technically accurate are the measurements, and 2) to what extent are they representative of past exposure events? In this study we have: 1) determined the extent to which validity can be attached to the archival surveillance bioassay data; 2) provided an algorithm for their transformation to a more accurate state when discrepancies were found to exist in the older assay techniques; 3) defined a program for calculating error terms which would be attached to each of the individual bioassay values once the data had been transformed; and, 4) examined the collection protocol for its relevance to the interpretation of the associated bioassay data, as a means of estimating the time-course and magnitude of the exposure(s).

To accomplish these aims, the approach taken was represented as part of two major categories; 1) analytical accuracy and precision; and 2) biological considerations. In the first category, it was necessary to statistically propagate the uncertainties associated with each of the procedural steps (e.g., chemical and plating recoveries, detection efficiency, etc.) as well as to consider all those factors that make up the statistical counting error (e.g., background variability, sample-size, counting-time, etc.). In addition, other sources of uncertainty such as the specificity of the analysis for the contaminant in question, and individual plating problems resulting in unwarranted alpha particle absorption, was defined quantitatively. All of these considerations become particularly important when no tracer isotope had been employed (as frequently encountered in early analytical procedures). The second category that was considered, i.e., biological aspects, includes factors such as the time and frequency of the bioassay sample collection (important, for example, to that extent defined by the magnitude of the "retention" parameter viz. effective half-life) as well as other time-related collection factors that relate to the exposure scenario. Attempts at quantifying this second category necessarily invokes knowledge of the metabolic disposition (along with the uncertainties attached to the magnitude of each of the metabolic parameters) of the considered contaminant.