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Fast and precise retrospective dosimetry is crucial in making decisions about medical procedures and safety measures in radiation accidents. Electron paramagnetic resonance (EPR) spectroscopy has a potential as one of available biodosimetry methods for use in victims of such incidents. In this study, authors present the findings on EPR dosimetry in fingernails. Authors describe changes of EPR signals in unirradiated and irradiated nails in time after cutting and the effect of water on the mechanically induced and radiation-induced EPR signals measured ex vivo in the fingernails. The effect of dose on amplitude of the EPR signal was measured in nails that were soaked for 10 min in water after their irradiation. The obtained dose-response curves, which reflect changes in concentration of the radiation-induced RIS5 radicals, reach their maximum for doses of 40-60 Gy.

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The effects of illumination of nail clippings by direct sunlight, UV lamps and fluorescent bulbs on native and radiationinduced electron paramagnetic resonance (EPR) signals in nails are presented. It is shown that a few minutes of exposure of the nail clippings to light including a UV component (sunlight and UV lamps) generates a strong EPR signal similar to the other EPR signals observable in nails: native background (BKG), mechanically induced (MIS) or radiation-induced (RIS). This effect was observed in clippings exposed and unexposed to ionizing radiation prior to the light illuminations. An exposure of the clippings to fluorescent light without a UV component generated, within the examined range of the light fluences (up to 240 kJ/m 2), an EPR signal with considerably lower yield than UV light. The light-induced signal (LIS) decayed after 10 min of water treatment of the samples. In contrast, it was still observable 3 months after illumination in samples stored in air at room temperature, and 3 weeks in frozen samples, respectively. It is concluded that the LIS can considerably affect assessment of the dosimetric RIS components in irradiated nails, and of the background signals in unirradiated nails, thus contributing to errors in EPR dosimetry in nails.