Abstract
Electron paramagnetic resonance (EPR) signals generated by ionizing radiation in touch-screen glasses have been reported as useful for personal dosimetry in people accidently exposed to ionizing radiation. This article describes the effect of light exposure on EPR spectra of various glasses obtained from mobile phones. This effect can lead to significant inaccuracy of the radiation doses reconstructed by EPR. The EPR signals from samples unexposed and exposed to X-rays and/or to natural and artificial light were numerically separated into three model spectra: those due to background (BG), radiation-induced signal (RIS), and light-induced signal (LIS). Although prolonged exposures of mobile phones to UV light are rather implausible, the article indicates errors underestimating the actual radiation doses in dose reconstruction in glasses exposed to UV light even for low fluences equivalent to several minutes of sunshine, if one neglects the effects of light in applied dosimetric procedures. About 5 min of exposure to sunlight or to light from common UV lamps reduced the intensity of the dosimetric spectral components by 20–60% as compared to non-illuminated samples. This effect strongly limits the achievable accuracy of retrospective dosimetry using EPR in glasses from mobile phones, unless their exposure to light containing a UV component can be excluded or the light-induced reduction in intensity of the RIS can be quantitatively estimated. A method for determination of a correction factor accounting for the perturbing light effects is proposed on basis of the determined relation between the dosimetric signal and intensity of the light-induced signal.
Highlights
Electron paramagnetic resonance (EPR) signals have been observed in different types of commercial glasses after their exposure to ionising radiation (Engin et al 2006; Teixeira et al 2008)
The samples, each about 90–180 mg in total mass, were obtained from different types of glasses taken from touch screens of mobile phones: Gorilla Glass, the type which was used in the intercomparison study reported by Fattibene et al 2014; screen glass from iPhone 6S; mineral glass from Sony Xperia L, model C2105; and protective screen, a tempered glass used commonly as additional protective cover of the original screen with a thickness of 0.3 mm thickness, and a ninth level of hardness according to the Mohs’ scale
The present study showed that in all four types of examined glasses, exposures to light including a UV component caused significant fading of the dosimetric signal (RIS), which was determined by decomposition of EPR spectra into two separate spectra: background and radiation-induced components
Summary
Electron paramagnetic resonance (EPR) signals have been observed in different types of commercial glasses (window glass, windscreen glass, watch glass, glass used for cathode ray tubes, and glass kitchenware) after their exposure to ionising radiation (Engin et al 2006; Teixeira et al 2008). Radiation and Environmental Biophysics (2020) 59:539–552 of the intensity of the dosimetric EPR signals, causing errors in dose reconstruction. One of such potential factors is light, both natural and artificial, which is permanently present in human’s environment and has a potential for generation of free radicals. No changes in EPR signal were observed in comparison to samples kept in dark for the both types of samples—irradiated and not irradiated. During an interlaboratory comparison study of retrospective dosimetry using smart phone touch screen glass carried on in 2013, the participants were recommended to expose the irradiated samples to daylight for at least 5 days, to speed up the fading of any unstable EPR signal components (Fattibene et al 2014). The origin of this component and the mechanism and kinetics of its decay after illumination as well as its effect on dosimetry were not described in details
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