The world is experiencing a nuclear renaissance and Canada is no exception, raising concerns of potential health and environmental hazards.
Canada’s fleet of aging nuclear power plants are being refurbished, medical isotope production is on the rise and long-term nuclear waste strategies are unfolding. In addition, the Government of Canada is promoting – and spending millions of dollars – to support the development of small nuclear reactors (SMRs) as part of a broader green energy policy.
In March, the Canadian Nuclear Safety Commission (CNSC) reviewed the design of GE Hitachi Nuclear Energy’s BWRX-300 SMR and “CNSC staff did not identify any fundamental barriers to licensing.” SMR pilot sites are well on their way to becoming a reality.
This raises the bar for governments, the nuclear industry and nuclear regulators not only to reassure but to demonstrate that the public is safe from long-term, and accidental, radiation exposure.
Radiation doses for those living next to Canadian nuclear power plants has been indirectly estimated based on the readings of radiation monitors and on environmental sampling of air, water, soil and vegetation. Radiation data is collected as part of CNSC’s regular monitoring program and through its Independent Monitoring Program.
But this information paints everyone with the same average radiation dose and does not tell what one’s specific dose is. Being able to measure radiation dose at the individual level is a powerful tool to inform, educate and reassure people about the risk of living next to a nuclear power plant.
It turns out that radiation causes stable chemical changes in tooth enamel, bones and fingernails that can be used to estimate lifelong radiation exposure (also called retrospective dose estimation). Unlike bones and fingernails that undergo continual turnover and remodelling, tooth enamel remains stable throughout life.
Tooth enamel is carbonated hydroxyapatite and radiation exposure results in cumulative production of molecules with unpaired electrons, that is, free radicals – namely CO2 – in tooth enamel. Free radical concentrations can be measured by electron paramagnetic resonance (EPR) spectroscopy that can be applied to extracted teeth or, hopefully soon, directly to the teeth still in your mouth.
ERP was first used to estimate radiation dose to human tissues in 1955. It has since been used to estimate doses after nuclear incidents such as in Japanese atomic bomb survivors, those living near or working in the former Soviet Mayak nuclear power plant that released large amounts of radioactive material into the environment, and among Chernobyl clean-up workers.
More recently, EPR has been used to assess radiation doses in individuals after nuclear accidents such as the 2012 incident in which a Peruvian worker was exposed to an unshielded portable radiation source while taking X-ray pictures to assess the quality of welding in metal pipes.
For the first time in Canadian history, researchers used EPR to measure lifelong radiation exposure in those living close to nuclear power plants.
In 2021, and for the first time in Canadian history, researchers used EPR to measure lifelong radiation exposure in residents living close to Canadian nuclear power plants.
The results were published in March in Health Physics by Lekhnath Ghimire and Edward Waller, a postdoctoral student and faculty member, respectively, at Ontario Tech University in Oshawa. Ghimire and Waller partnered with local dentists to collect teeth of permanent residents of Ontario’s Durham region, which has two operating nuclear power plants – Pickering and Darlington.
In 2021, after receiving ethics approval and informed consent, the scientists collected 64 extracted teeth from dental patients aged 16 to 69 years old and analyzed them using EPR spectroscopy.
Radiation dose is measured in Sieverts (Sv) and is usually reported in units of 0.001 Sv or mSv.
According to the authors, background radiation in Durham region is about 1.3 mSv per year and the EPR results found the average dose to residents to be about 2.0 mSv per year. They hypothesize that the difference between background and measured dose is a result of a combination of medical sources (X-ray, CT, nuclear medicine, radiation therapy) and the nuclear power plants.
CNSC estimates that the yearly radiation dose from these nuclear power plants in the public living close to them is about 0.001 mSv or less. This is 1,000 times less than the maximum public dose limit of 1 mSv. This would leave the bulk of non-background dose to medical sources, which is in keeping with increasing rates of medical imaging in Canada.
Communicating the risks of chronic low-dose radiation to the public is challenging. Radiation is invisible, exposure is involuntary, the risks at low doses are uncertain and large-scale nuclear accidents, such as Chernobyl and Fukushima, can create fear and dread.
Any strategy that can better close the gap between the public’s “risk perception” and “actual risk” should be strongly entertained by nuclear industries and regulators as well as by the Canadian government.
Health Canada’s Radiation Protection Bureau provides expertise in assessing radiation doses, especially after radiation incidents. Although EPR is not a tool Health Canada currently uses, the research by Ghimire and Waller demonstrates that EPR may be a valuable additional tool to assess radiation risks in the general population.
Future EPR surveys that take into account medical imaging would provide direct evidence of how much radiation individuals living around nuclear facilities are receiving.
Although this added information will not satisfy everyone, especially those who ideologically oppose “all things nuclear,” it may reassure many; reassurance and “buy in” are essential in preparing Canadians for our rapidly evolving nuclear renaissance.
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