Radiation Measurements 42 (2007) 1178 – 1180 www.elsevier.com/locate/radmeas Effect of chemical treatment on ESR dosimetry of cow teeth: Application to the samples from Southern Urals S. Toyoda a , ∗ , A. Romanyukha b , Y. Hino a , S. Itano a , H. Imata a , O. Tarasov c , M. Hoshi d a Department of Applied Physics, Okayama University of Science, Okayama, Japan b Department of Radiology, Uniformed Service University of the Health Sciences, Bethesda, MD, USA c Ozersk Technological Institute, Ozersk, Russia d Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan Abstract Chemical treatment with alkaline solution is used to extract enamel from teeth for retrospective ESR (EPR) dosimetry. It was confirmed in the present study that our condition of chemical treatment does not affect retrospective doses of cow teeth. The method was applied to 10 teeth collected in the South Ural region where the soil is contaminated with 90 Sr. As a result, no noticeable doses were detected so far. Significant variations of sensitivity of the radiation-induced ESR signal to radiation were found for different cow teeth, indicating that individual calibration is necessary. © 2007 Elsevier Ltd. All rights reserved. 1. Introduction The enamel of human teeth has been used for ESR (electron spin resonance) retrospective dosimetry as it has a very high sensitivity to radiation (IAEA, 2002). Examining the human teeth has the great advantage that the dose given to each individ- ual could be determined. In case if human teeth are not always available, teeth from animals could be used as an alternative to human teeth for retrospective dosimetry. There were a few stud- ies of ESR dose measurements of animal teeth (Serezhenkov et al., 1996; Klevezal et al., 1999; Toyoda et al., 2003) where it has been shown that they are as useful for dosimetry as human teeth. Cows are one of the animals living closely to humans, the teeth of which would represent the doses given to human as well as the environmental doses around the places in which humans are living. The first Russian industrial nuclear facility, Mayak, is located at the South Urals, Russia. In the initial period of operation of this facility, there were several events of the con- siderable radioactive releases into the environment (Alexakhin et al., 2001; Nikipelov et al., 1989) such as discharges of liquid ∗ Corresponding author. Tel.: +81 86 256 9608; fax: +81 86 256 9702. E-mail address: toyoda@dap.ous.ac.jp (S. Toyoda). 1350-4487/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2007.05.012 wastes into the Techa River (1949–1956), an explosion of the storage facility for high-level radioactive wastes (1957), and gaseous aerosol releases (1949–1957). We have already reported the results of imaging plate (Toyoda et al., 2006a), which visualizes the distribution of 90 Sr in cow teeth as had been observed in human teeth (Romanyukha et al., 2002). The concentrations of 90 Sr averaged in a cow tooth range up to 10 Bq/g where clear correlation was observed between the mean of the concentrations of 90 Sr in cow teeth averaged for the samples taken from the same soil contamina- tion level and the levels of 90 Sr in soil. It is then of interest to determine the radiation doses given to cow teeth in order to evaluate the present radiation environment which should include both internal and external radiation. Although mechanical separation has been adopted in some studies (Shiraishi et al., 2002), the method for chemical treat- ment with alkaline solutions has been well examined (Fattibene et al., 1998; Nakamura and Miyazawa, 1997; Romanyukha et al., 2001; Wieser et al., 2000) to extract enamel from human teeth as enamel has higher sensitivity than dentin. We have examined the best chemical conditions to treat the cow teeth and found that the best condition is different from that of human teeth and that NaOH or KOH of 20% for 5 h at 40 ◦ C makes the sensitivity of cow teeth comparable to that of human teeth (Toyoda et al., 2006b). However, it is necessary to test