The use of human hair as biodosimeter S. Tepe Çam a,n , M. Polat b , N. Seyhan c a Turkish Atomic Energy Authority, Sarayköy Nuclear Research and Training Center, Saray, Ankara 06983, Turkey b Physics Engineering Department, Hacettepe University, Beytepe, 06800 Ankara, Turkey c Gazi University Faculty of Medicine Biophysics Department, Beşevler, Ankara 06500, Turkey HIGHLIGHTS  Applied electron spin resonance spectroscopy to human hair used in biodosimetry.  Showed the limitations of hair samples using as a biological dosimeter.  Provided more systematic information on radiation-induced radicals in hair.  Found at least 3 different contributions in the RIS. That is the major finding of this work. article info Article history: Received 1 April 2014 Received in revised form 26 August 2014 Accepted 28 August 2014 Available online 8 September 2014 Keywords: Ionizing radiation Biologic dosimeter Hair Electron spin resonance abstract The potential use of human hair samples as biologic dosimeter was investigated by electron spin resonance (ESR) spectroscopy. The hair samples were obtained from female volunteers and classified according to the color, age and whether they are natural or dyed. Natural black, brown, red, blonde and dyed black hair samples were irradiated at low doses (5–50 Gy) and high doses (75–750 Gy) by gamma source giving the dose rate of 0.25 Gy/s in The Sarayköy Establishment of Turkish Atomic Energy Authority. While the peak heights and g-values (2.0021–2.0023) determined from recorded spectra of hair were color dependent, the peak-to-peak line widths were varied according to natural or dyed hair (ΔH pp : 0.522–0.744 mT). In all samples, the linear dose–response curves at low doses saturated after 300 Gy. In black hair samples taken from different individuals, differences in the structure of the spectrum and signal intensities were not observed. The EPR signal intensities of samples stored at room temperature for 22 days fell to their half-values in 44 h in black hair, 41 h in blonde and brown hairs, 35 h in dyed black hair and in 17 h in red hair. The activation energies of samples annealed at high temperatures for different periods of time were correlated well with those obtained in the literature. In conclusion, hair samples can be used as a biological dosimeter considering the limitations showed in this study. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Application of ionizing radiation in many different fields is constantly increasing, including the use for energy and medical purposes, so it becomes very important to monitor people exposed to radiation. In case exposed people do not wear a personal dosimeter, a rapid and accurate method to meet the needs for effective and efficient triage after a large-scale radiation exposure event is required. But in this case, it is needed to be able to assess doses about 1 Gy, whereas in the case of an accident, doses can locally reach several Gy up to tens of Gy. Therefore, this paper describes the potential use of human hair as a physically-based biodosimetry method that uses electron paramagnetic resonance spectroscopy (EPR) for a large scale radiological/nuclear event. The usefulness of this method has been reported several times in the case of serious accidents (Clairand et al., 2006; Schauer et al., 1993, 1996; Desrosiers, 1991). In the EPR technique, depending on the material, a single measurement can take between some minutes up to a few hours. The readout is non-destructive, allowing for repeated measurements on the same sample. The EPR signal intensity is directly proportional to the amount of free radicals specifically generated by ionizing radiation. But in case of a sample that has fast radical decay after irradiation (Müller and Streffer, 1991), the EPR method should be applied immediately. The biolo- gical tissues that have been proposed for EPR dosimetry should have some criteria such as ubiquity, noninvasiveness and ease of sample collection, presence of a post-irradiation EPR signal, negli- gible background signal, linearity of dose–response relationship, Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/apradiso Applied Radiation and Isotopes http://dx.doi.org/10.1016/j.apradiso.2014.08.021 0969-8043/& 2014 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ90 312 8101711; fax: þ90 312 8154307. E-mail address: stepe06@gmail.com (S. Tepe Çam). Applied Radiation and Isotopes 94 (2014) 272–281