HSLL 5053 - Health Physics Society: Where Did This Come From? Lessons Learned from High-Routine Bioassay Investigations

Speaker - Eugene H. Carbaugh
Pacific Northwest National Laboratory

This PEP class provides actual case studies of high routing bioassay measurements addressing the investigation process, resolution, and lessons learned from each.High routine bioassay results can come from several sources, including normal statistical fluctuation of the measurement process, interference from non-occupational sources, and previous occupational intakes, as well as new intakes.A good internal dosimetry program will include an investigation process that addresses these alternatives and comes to a reasonable conclusion regarding which is most likely.A subtle nuance to these investigations is the possibility that a newly detected positive measurement might represent an old intake that has only now become detectable.This can result from the worker being placed on a different bioassay measurement protocol, a change in analytical sensitivity, unusual biokinetics associated with highly insoluble inhalations, or lack of a clear work history.As sites close down, the detailed dosimetry records of specific worker exposures are archived, becoming relatively inaccessible, with only summary dose information available.Likewise, the "tribal knowledge" of the site becomes lost or seriously diluted as long-term employees retire or move on.Therefore, it is incumbent upon the site performing a high bioassay result investigation to thoroughly address the possible alternatives or face the consequence of accepting responsibility for a new intake.The presenter has encountered all of the foregoing issues in the course of investigating high routine bioassay measurements at the US Department of Energy Hanford Site.The important lessons learned include, 1) have good measurement verification protocols, 2) confirm intakes by more than one bioassay measurement, 3) conduct interviews with workers concerning their specific circumstances and recollections, 4) have good retrievable site records for work history reviews, 5) exercise good professional judgment in putting the pieces together to form a conclusion, and 6) clearly communicate the conclusions to the worker, the employer, and the regulatory agency.