The effect of sunlight and UV lamps on EPR signal in nails

Agnieszka Marciniak,Anita Prawdzik-Dampc,Bartłomiej Ciesielski,Mirosław Sawczak,Małgorzata Juniewicz

doi:10.1007/s00411-019-00777-2

Abstract

The effects of illumination of nail clippings by direct sunlight, UV lamps and fluorescent bulbs on native and radiation-induced 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/m2), 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.

Highlights

Recent studies suggest applicability of electron paramagnetic resonance (EPR) signals generated by ionizing radiation in nails for radiation dosimetry (Trompier et al 2014a; Reyes et al 2012; Sholom and McKeever 2016; Marciniak and Ciesielski 2016; Marciniak et al 2018)
Non-invasive sampling, and easy and quick sample preparation, the dosimetry in nails potentially can provide a fast determination of radiation dose, provided problems resulting from the instability of the radiation-induced signal (RIS) and from
EPR signals measured in nail clippings can originate from native paramagnetic centers present in the nails’ substance and from radicals induced by physical factors exerted on the nails: mechanical stress, e.g., caused by cutting the clippings, or ionizing radiation

Summary

Introduction

Recent studies suggest applicability of electron paramagnetic resonance (EPR) signals generated by ionizing radiation in nails for radiation dosimetry (Trompier et al 2014a; Reyes et al 2012; Sholom and McKeever 2016; Marciniak and Ciesielski 2016; Marciniak et al 2018). EPR signals measured in nail clippings can originate from native paramagnetic centers present in the nails’ substance (the intrinsic background, the BKG spectral component) and from radicals induced by physical factors exerted on the nails: mechanical stress, e.g., caused by cutting the clippings (mechanically induced signal, the MIS spectral component), or ionizing radiation (radiation-induced signal, the RIS spectral component). Radiation and Environmental Biophysics (2019) 58:287–293 et al (2015) and Sholom and McKeever (2017) show that illumination of nails by light can induce EPR signals overlapping with the background and radiation-induced signals This is an additional, serious confounding factor in potential EPR dosimetry in nails, which is based on reliable measurements of the RIS component used to determine the radiation dose

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Conclusion