Personal monitoring of Po-218 and Po-214 radionuclide deposition onto individuals under normal environmental exposure conditions

Personal dosemeters have been utilized to monitor the deposition of the radon decay products Po-218 and Po-214 to individuals under normal environmental exposure conditions. Each detector consists of TASTRAK alpha-sensitive plastic incorporated into an ordinary working wristwatch. Subsequent analysis provides energy discrimination of the detected alpha-particle decays, and allows events from the individual radon decay products Po-218 and Po-214, attached to the detector surface, to be uniquely identified. Assuming similar deposition onto skin and detector surfaces, the activity per unit area of deposited radionuclides can be determined for exposed skin. Forty-one personal dosemeters were issued to volunteers selected through the hospital medical physics departments at Reading, Northampton, Exeter and Plymouth. Each volunteer was also issued with a personal radon dosemeter to determine their individual radon exposure. The volunteers wore the two dosemeters simultaneously and continuously for a period of around one month. Correlations were observed between the radon exposure of the individual and the activity per unit area of Po-218 and Po-214 on the detector surface. From these correlations it can be estimated that at the UK average radon exposure of 20 Bq m(-3), the number of decays/cm(2)/year on continuously exposed skin surface is between 3500 and 28 000 for Po-218, and between 7000 and 21 000 for Po-214. These results can be combined with theoretical modelling of the dose distribution in the skin to yield the alpha-particle radiation dose to any identified target cells.