Retrospective assessment of human exposures to low dose ionizing radiation using Electron Paramagnetic Resonance (EPR) dosimetry with tooth enamel
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This study collected the extracted teeth from people of different ages in the Durham region and analyzed them using the X-band CW EPR spectroscopy. The total dose rate from the natural and anthropogenic sources was 1.9721 mSv/year. The anthropogenic dose rate from the various sources was 0.6341 mSv/year, about 47.39% of the natural background dose (1.338 mSv/year) in Durham Region, Ontario. The combined anthropogenic doses from these sources were lower than the local background dose in Durham Region, Ontario, and lower than the regulatory annual effective dose limit of 1 mSv/year in Canada. These data demonstrated that the background doses to the public are lower than the regulatory limit. There is a minimal risk to the public from the anthropogenic doses in Durham Region populations. The dose contribution of the nuclear generating stations is small in Durham Region, Ontario. So, the excess anthropogenic doses could be from diagnostic radiology, nuclear medicines, radiation therapy, and other industrial uses of radiation or radioactive materials, but further study would be needed for conclusions about this region's situation. At the same time, there are more chances of providing deciduous teeth for the low dose (10 - 100 mGy) reconstruction in the actual radiation accidents or chronic exposures. To this end, this study used the dose spiking technique in alanine, where a low dose down to 20 mGy was measured with reasonable precision and accuracy. The same method was used in deciduous teeth for measuring low doses, which was challenging to measure precisely using the conventional EPR methods. The measurement accuracy and reproducibility in the deciduous teeth enamel were significantly higher in that dose range than the conventional methods. Thus, this method can solve the measurement problems associated with low doses and is helpful for retrospective and accident dosimetry. Finally, this study concluded that the total anthropogenic doses in the teeth of Durham Region residents were lower than the regulatory limits. The dose spiking technique can be used to measure low doses in tooth enamel for retrospective and accident dosimetry.