Electron Paramagnetic Resonance Measurements of Lifetime Doses in Teeth of Durham Region Residents, Ontario

Abstract

The Canadian Nuclear Safety Commission (CNSC) and Ontario Power Generation (OPG) determined the total dose contribution of nuclear power plants in Durham Region populations by analyzing environmental samples from the surrounding areas of both nuclear generating stations (Pickering and Darlington). However, the total doses from the various sources were unknown in Durham Region populations, Ontario. Electron paramagnetic resonance (EPR) dosimetry with tooth enamel has been successfully established as an effective tool for gamma dose assessment for chronic and acute exposures in individuals, groups, or populations to reconstruct the absorbed dose down to 30 mGy. This study collected the extracted teeth from people of different ages in Durham Region, Ontario, and analyzed them using the x-band continuous wave (CW) EPR spectrometer. The total dose rate from the natural and anthropogenic sources was 1.9721 mSv y−1. The anthropogenic dose rate from the various sources was 0.6341 mSv y−1, about 47.39% of the natural background dose (1.338 mSv y−1) in Durham Region, Ontario. The combined anthropogenic doses from these sources were lower than the local background dose in Durham Region and lower than the regulatory annual effective dose limit of 1 mSv y−1 in Canada. Based on these data, this study concluded that the anthropogenic dose contribution was lower than the regulatory limit to the local populations.

Electron Paramagnetic Resonance (EPR) Biodosimetry with Human Teeth: A Crucial Technique for Acute and Chronic Exposure Assessment

“…Tooth enamel is the only human tissue capable of recording radiation doses throughout life and measuring doses ranging from low to high using EPR spectrometers. The minimum detection limit found in tooth enamel using EPR dosimetry (X-band), as per the literature, is <100 mGy (down to 30 mGy) (Ghimire and Waller 2023;Hayes et al 1998;Shishkina et al 2016). However, the actual detection limit depends on how experiments are conducted.…”

“…These studies have indicated the necessity for EPR tooth enamel dosimetry standardization to improve dose calibration. To this end, increasing measurement accuracy and reproducibility can be accomplished by removing impurities (dentin) from the tooth enamel using chemical and mechanical methods, employing highly sensitive EPR resonators, and using background subtraction, among other techniques (Ghimire and Waller 2023). Most importantly, unlike many modern instruments, EPR spectrometers are designed and built within a tradition primarily for use by specialists and are not intended to be foolproof.…”

“…To date, different studies (Ghimire and Waller 2023;Hayes et al 1998;Shishkina et al 2016;Egersdorfer et al 1996;Wieser et al 2006Wieser et al , 2008Fattibene et al 2011;Haskell et al 1999Haskell et al , 1997 have been conducted to develop methods further and measure low doses in enamel. These studies revealed that due to long radiation stability and low detection limit, EPR tooth enamel dosimetry is one of the most vital tools for determining the low dose exposures to the local population and environment from various sources (Ghimire and Waller 2023;Romanyukha et al 2000;Ainsbury et al 2011).…”

“…To date, different studies (Ghimire and Waller 2023;Hayes et al 1998;Shishkina et al 2016;Egersdorfer et al 1996;Wieser et al 2006Wieser et al , 2008Fattibene et al 2011;Haskell et al 1999Haskell et al , 1997 have been conducted to develop methods further and measure low doses in enamel. These studies revealed that due to long radiation stability and low detection limit, EPR tooth enamel dosimetry is one of the most vital tools for determining the low dose exposures to the local population and environment from various sources (Ghimire and Waller 2023;Romanyukha et al 2000;Ainsbury et al 2011). Among many different types of EPR bands, EPR dosimetry with tooth enamel has been using the X-band CW EPR for the assessment of absorbed doses from ionizing radiation; however, the X-band has a lower signal-to-noise ratio (SNR) in a dose below 0.5 Gy, lower sensitivity, and requires a large sample size (i.e., ~100 mg enamel) for radiation dose estimation (De et al 2013;Romanyukha et al 2007).…”

A Perspective from Ontario Tech University Industrial Research Chairs on 20 Years of Capacity Building in Health Physics and Radiation Science

“…The equipment used is a Bruker EMXmicro X-Band EPR spectrometer. The technique has been used to measure physical doses near CANDU NPPs using tooth samples obtained from local dentists (Ghimire and Waller 2023a) and also yielded numerous approaches to improve sensitivity and decrease the lower limit of detection (Ghimire and Waller 2023b, c, d). Low dose non-human biota studies have been conducted on a variety of shelled aquatic species near and of interest to nuclear facilities in Canada (Gough et al 2022).…”