Development of a Sensitive Radon in Breath Analyzer for Exposure Assessment to Uranium Ore Constituents

Abstract

Currently only imprecise metrics are available to assign lifetime exposure to uranium ore constituents, such as living in proximity to sources of exposure. The purpose of this project is to develop a radon in breath analyzer sensitive enough to measure radon in the breath of people exposed to uranium ore. Radon is exhaled from decaying radium stored in the bones. We are exploring the use of traditional Lucas cells as the radon detection method. To date, background levels in the range of 0.02 to 0.05 CPM have been achieved through careful choice of the ZnS(Ag) scintillator, the method of deposition and an optimized detector operating point. We are also using liquid nitrogen to collect and focus small amounts of radon from large volumes of breath (50 L). To do this, radon samples are passed through a processing system consisting of a CO2 trap, a water trap employing dry ice/acetone, and a liquid nitrogen trap where the radon is collected. To date, approximately 75% of the radon in the initial sample is collected and transferred to the Lucas cell for analysis. Assuming a breath sample of liters (10 minutes breathing for a measurement), a 75% collection and transfer efficiency to the Lucas cell, and a background level of 0.02 to 0.05 CPM in the Lucas cell, the projected sensitivity of the instrument will be 0.00005 to 0.0005 pCi/l. This level of sensitivity was targeted to provide exposure assessment for people exposed to lower levels than historical underground uranium miners. If this instrument has necessary detection limit and is feasible in the field, future epidemiology studies can assign historical exposure with much greater accuracy. The instrument may also be useful for screening people for clinical purposes to assess their health risk.