DEVELOPMENT OF A SENSITIVE RADON IN BREATH ANALYZER FOR EXPOSURE ASSESSMENT TO URANIUM ORE CONSTITUENTS

Currently only imprecise metrics, such proximity to mines, are available to assign lifetime exposure to uranium ore constituents. This limits confidence in epidemiology of health effects. We seek to develop a radon in breath analyzer sensitive enough to measure radon in the breath of people exposed to radium in uranium ore. Radon is exhaled from decaying radium stored in the bones.

The system is in development and consists of two SS U traps cooled to liquid nitrogen temperatures, a glass water trap, a CO2 absorber, various vacuum gauges, a flow meter, a vacuum pump, and Pylon 610A scintillation cells. The interior surface of the SS traps was maximized to increase trapping efficiency by filling the trap volume with fine brass wool.

In typical experiments radon gas at 0.1 pCi/l or less is drawn through the system at 2 to 3 lpm for 10 to 15 minutes. The intake valve is then closed and the system evacuated to remove trapped oxygen. The traps are warmed and any radon present moved to a 610A Lucas cell for later analysis .

The overall processing time, assuming 10-15 minutes to collect a 40-liter breath sample, and 20 minutes to trap and transfer the sample to a 610A Lucas cell is about 35 minutes. The 610A Lucas cell then analyzed by taking a 15-minute count after a delay of 3-4 hours.

With typical 610A Lucas cell background counts of less than 0.1 cpm, trapping and transfer efficiencies of 65%, we have achieved sensitivities in the range of 0.001 to 0.0005 pCi/l radon. Work continues on reducing the background of the Lucas cells, on increasing the overall trapping efficiency of the system, and on a method for the collection and storage of breath samples.

If this instrument proves to be feasible in the field, future epidemiology studies can assign historical exposure individuals with chronic exposure to uranium with much greater accuracy. The instrument may also be useful for screening people for clinical purposes to assess their health risk from deposited radium.