Radiation

Cardiovascular Changes in Atherosclerotic ApoE-Deficient Mice Exposed to Co60 (γ) Radiation

Health Canada is responsible for the assessment of health risks associated with exposure to radiation. Exposure to radiation can occur from environmental or occupational sources, or due to use of radiation in medical procedures, and can result in a number of negative health effects including cardiovascular disease. However, the mechanism by which radiation can cause cardiovascular disease is unclear. In this study Health Canada, in collaboration with scientists from Chalk River laboratories and the University of Ottawa, sought to understand the mechanism by which radiation exposure may cause cardiovascular disease. Specifically, mice that had been genetically modified to increase their normal risk of developing cardiovascular disease, making them a model organism for studying cardiovascular risk factors, were exposed to radiation. Mice were allowed to recover from treatment for 3-6 months, after which they were screened for evidence of biological changes that might explain why radiation leads to toxicity in the heart. The results showed that mice previously exposed to radiation had increased number of reactive nitrogen species (RNS). RNS are molecules that contain nitrogen that can react with other molecules, potentially causing damage. In addition to the increased RNS, previously irradiated mice had increased levels of two proteins called endothelin 1 and endothelin 3. These proteins both function in causing constriction of blood vessels, so dysregulation could affect cardiovascular health. This study therefore increases our understanding of how radiation may lead to cardiovascular disease. Health Canada will be able to use the results of this study to better assess the health effects of radiation. Results of this research are published in PLoS One, 2013, 8(6), e65486. doi: 10.1371/journal.pone.0065486

Counting 241Am in the BfS Human Skull Phantom on Contact - Evaluation in the Human Monitoring Laboratory

Health Canada assesses the health risks of exposure to radiation in living and working environments, including situations where people become internally contaminated; for example, as a result of a workplace accident. In order to do this properly, it is necessary to develop very specialized measurement protocols as well as tools to accurately convert measured levels of radioactivity to radiation dose. This project identified better ways to measure and quantify americium-241 contamination in bone – specifically, the human skull. Health Canada will use the results of this study to improve its radiation exposure monitoring techniques.  This study is published in the Health Physics Journal, 2015, 108(3).

Managing Children during a Radiological or Nuclear Emergency – Canadian Perspectives

Health Canada manages the Federal Nuclear Emergency Plan and provides technical and operational advice on protecting workers and the public from being exposed to radiation following a radiological or nuclear (RN) emergency. Children have been identified as one of the most vulnerable populations during a response to an RN emergency; they are more sensitive to radiation health effects and suffer more significant psychological impacts than adults during an emergency. Health Canada, in collaboration with federal, provincial and municipal partners, developed a collection of recommendations on effective management of children during an RN emergency, covering all major aspects such as immediate on-site protective actions, monitoring and decontamination, medical management, and long-term follow-ups. These recommendations have been summarized as a paper, which is published in the Health Physics Journal, 2015, 109(1).

Evaluation of the Annual Canadian Biodosimetry Network Intercomparisons

Health Canada investigates the potential biological and health effects of ionizing radiation.  Biological dosimetry has been used for many years to estimate the dose of ionizing radiation received by an individual.  This information is critical to the medical community as it assists with effective and timely treatment regimens for potentially exposed individuals, or for identifying radiation workers who are near or have exceeded their limit for exposure.  In a mass casualty situation, where thousands of individuals could potentially be exposed to radiation, biodosimetry laboratory networks can help improve dose estimation throughput.  Canada has developed such a network and in order to maintain it in a state of readiness for emergency response, it is essential to conduct annual intercomparisons.  In this study Health Canada demonstrated, through 6 years of intercomparisons, that the Canadian biodosimetry network is capable of producing dose estimations over a variety of different assays quickly and accurately.  These findings provide confidence to the medical community, the public and government bodies that in the event of a nuclear accident, biodosimetry can be applied to manage and medically treat casualties to ensure the minimization of health risks.  Health Canada will use the results of this research to continue to improve their biological dosimetry services and provide advice to other biological dosimetry laboratories worldwide. The results of this research are published in the International Journal of Radiation Biology [May 2015; 91(5), 443-51].

Health Canada investigates radiation levels in food and the potential health effects resulting from food consumption.

Health Canada is responsible for promoting and protecting the health of Canadians by assessing and managing the risks posed by radiation exposure in living, working and recreational environments. Following the nuclear accident at Fukushima Daiichi in 2011, many Canadians were concerned about radioactive contamination from Japan, including radioactivity in food. This Health Canada study was intended to add some perspective to the assessed risk, which was very low, by measuring fish from the National Capital Region (NCR) and comparing levels of caesium contamination that could be attributed to Fukushima to levels of background radionuclides, which includes radioactivity from natural sources as well as from historic nuclear weapons testing.  While caesium-137 was measured in the samples, it was possible to determine that it was not from Fukushima because caesium-134, which is a tell-tale indicator of relatively recent emissions, was not detected. Caesium-137 from releases prior to 2011 was detected, as were many naturally occurring radionuclides. It can be concluded that the radiation dose received from both radioactive caesium and naturally occurring radionuclides as a result of eating these fish (such as bass, pike, catfish and walleye) is of no health concern. Furthermore, the contribution of caesium to the total dose is very small compared to the naturally occurring radionuclides, and there is no evidence that any of that caesium is due to the Fukushima accident. Results of this research are published in a letter to the editor in the

144:175-178 (2015).

Multi-Parameter Dose Estimations in Radiation Biodosimetry Using the Automated Cytokinesis-Block Micronucleus Assay with Imaging Flow Cytometry

Health Canada provides technical expertise to determine the health effects posed by exposure to radiation in the case of a nuclear emergency. Health Canada conducts research on how to more efficiently and effectively co-ordinate triage during a nuclear event. One of the analytical procedures that can be used for assessing radiation damage is the cytokinesis-block micronucleus (CBMN) assay. The CBMN assay measures the frequency of micronuclei in binucleated white blood cells and correlates this to a dose estimate. Typically, the CBMN assay has been a microscope-based assay, but in this study, with the use of a relatively new technology known as the imaging flow cytometer, the assay has been adapted to an imaging-flow-based method. This adapted method allows for the processing of a greater number of samples in a shorter amount of time for application in mass casualty events. Research results are published in the journal Cytometry Part A, 85(10):883-93.

A Report on Radioactivity Measurements of Fish Samples from the West Coast of Canada

Health Canada investigates the potential health effects to the Canadian population from natural and technological sources of environmental radioactivity. The Fukushima-Daiichi nuclear accident in 2011 resulted in significant and ongoing releases of radioactive contaminants, especially the long-lived radioactive caesium-137 (137Cs), into the Pacific Ocean. This raised public concerns about the safety of consuming west coast seafood. After the Fukushima-Daiichi nuclear accident, many studies have shown that radioactive caesium levels in fish caught outside of Japan were below experimental detection limits. These findings are summarised in the document, Preliminary Dose Estimation from the Nuclear Accident after the 2011 Great East Japan Earthquake and Tsunami prepared by the World Health Organization. To complement these findings from a Canadian perspective, more than 60 fish samples (adult salmon and groundfish) harvested from the Canadian west coast by Fisheries and Oceans Canada in 2013 were provided to Health Canada for radiological analysis. None of the fish samples analyzed in this study contained any detectable levels of 134Cs and 137Cs under the given experimental setting, with an average detection limit of about 2 Bq/kg. Using a conservative worst-case scenario where all fish samples would contain 137Cs exactly at the detection limit level and 134Cs at half of the detection limit level (to account for much shorter half-life of 134Cs), the resulting radiation dose from potential exposure to assumed 134Cs and 137Cs contamination would be a very small fraction of the annual dose from exposure to natural background radiation in Canada. Therefore, fish, such as salmon and groundfish, from Canadian west coast are of no radiological health concern. Health Canada will use the results of this research to help inform future risk assessments. The results of this research are published in the journal of Radiation Protection Dosimetry, (2014), pp. 1-6 (doi:10.1093/rpd/ncu150).

Analysis of Chromosome Damage for Biodosimetry Using Imaging Flow Cytometry

As the lead department responsible for coordinating the federal response to a nuclear emergency, Health Canada provides technical and operational advice on the health effects posed by exposure to radiation, and conducts ongoing research to identify more efficient methods for emergency response to protect the public. The Dicentric Chromosome Assay, which looks for chromosomes that have inappropriately fused as a result of radiation damage, is the gold standard method for estimating the amount of ionizing radiation that a person has been exposed to. Traditionally, this assay has been performed by manually counting cells imaged through a microscope. In this study, Health Canada made use of a new technology, called imaging flow cytometry, to develop a new technique that allows for a quicker assessment and triage of people who may have been exposed to radiation during a nuclear emergency.  The advantage of using an imaging flow cytometer is that it allows images of cells to be automatically captured as they are counted by the machine, and it also sorts the cell images based on size, shape and DNA content. This information is then used to determine how much radiation an individual has been exposed to. By making it faster and easier to accurately determine how much radiation exposure large numbers of people have been exposed to, the findings demonstrate that this technology has the potential to improve the efficiency and effectiveness of emergency responses in the event of radiation exposure. Health Canada will use the results of this study to inform emergency procedures related to radiological and nuclear events. Research results are published in the journal Mutation Research - Genetic Toxicology and Environmental Mutagenesis (April 2013).

Radioxenon Detections in the CTBT International Monitoring System Likely Related to the Announced Nuclear Test in North Korea on February 12, 2013

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) seeks to eliminate all testing of nuclear explosions globally using an International Monitoring System (IMS) of environmental sensors and stations to verify treaty compliance. Canada, through Health Canada, is responsible for the assessment of radiological data from the IMS in preparation for verification of this treaty when it enters into force. At 02:58 UTC, on February 12, 2013, the Democratic People’s Republic of Korea (DPRK) conducted its third announced nuclear test, the explosion registering on seismic stations belonging to the International Monitoring System (IMS). Although seismic stations are normally used to monitor earthquake tremors, IMS seismic stations are dedicated to detecting tremors from large explosions in order to verify the CTBT. This began a two month intensive review of data from IMS radioactivity monitoring stations for direct evidence of emission of radioactive contaminants, the best evidence to establish the nuclear nature of seismically observed explosions. Finally, observations of two radioactive forms of a gas called xenon, 133Xe and 131mXe, were made in April 2013 at IMS measurement stations in Japan and Russia. The amounts and ratios of the observed xenon contaminants were compared with expected values from the North Korean test and from normal environmental background as well as analyzed using atmospheric transport models. Thus, an international team of verification scientists, including Health Canada scientists, was able to convincingly identify the 2013 DPRK test as the likely origin of these contaminants. The approaches and techniques developed in this technical assessment will be incorporated into treaty verification operations. Results of this work are published in the Journal of Environmental Radioactivity 128 (2014) 47-63.

Source Term Estimation of Radioxenon Released from the Fukushima Dai-ichi Nuclear Reactors Using Measured Air Concentrations and Atmospheric Transport Modeling

Health Canada is the lead department responsible for coordinating the federal scientific and technical activities required to plan, prepare and respond to a peacetime nuclear emergency affecting Canada or Canadians abroad. These responsibilities are outlined in the Federal Nuclear Emergency Plan (FNEP). One of the challenges in the assessment of nuclear accidents is determining the quantity of radioactive emissions released to the environment. This study was focused on the development of a technique to assess the quantity of radioactive emissions using gas (air) samples from multiple distant (greater than 1000 km) sampling sites. The data from this study came from the International Monitoring System (IMS) that was designed to detect radioactive releases from nuclear explosions in order to enforce the Comprehensive Nuclear-Test-Ban Treaty. This monitoring network was also used to estimate the radioactive gas emissions from the Fukushima Dai-ichi Nuclear Power Plant accident of March, 2011. Data from several sampling locations of the IMS were interpreted with atmospheric transport models to give the amount and timing of releases of a radioactive gas, 133Xe, from the damaged nuclear facility. Fifty-seven atmospheric concentration measurements of 133Xe from March 18 to March 23, 2011 were used to estimate the total amount of this gas released to the atmosphere. The analysis suggested 92% of the total 133Xe contained in the 3 reactors prior to their damage was released to the atmosphere over a period of 3 days. This work demonstrated a successful approach using multiple monitoring sites to accurately reconstruct the emissions from a reactor site using only long-range (greater than 1000 km distant from accident site) measurements. The estimates from this study are consistent with those from the International Atomic Energy Agency (IAEA) and these methods will be incorporated into Health Canada's radioactivity monitoring operations for use during other release events to provide timely and accurate estimates. This research is published in the Journal of Environmental Radioactivity (Volume 127, January 2014, Pages 127–132).

A Gamma-Gamma Coincidence/Anticoincidence Spectrometer for Low-Level Cosmogenic 22Na/7Be Activity Ratio Measurement

Health Canada contributes to the International Monitoring System designed in order to enforce the Comprehensive Nuclear Test Ban Treaty (CTBT). In order to verify whether a source of radioactive gas, such as radioxenon (133Xe), is emitted from a nuclear explosion overseas versus background from local medical isotope production, it is necessary to use atmospheric transport models that incorporate measurements of air current flow. Air current flow can be determined by measuring the ratio of 22Na to 7Be, two radionuclides that come from cosmic sources. The ratio of 7Be to 22Na indicates how much air movement has occurred and thus helps to determine the likely source of 133Xe. Unfortunately, given their usually low atmospheric concentrations within the environment, it is often difficult to detect these radionuclides using standard measurement techniques. To improve low-level environmental radioactivity measurement of 7Be and22Na, this Health Canada study was aimed at developing a novel gamma-gamma coincidence/anticoincidence spectrometer. The spectrometer consists of two scintillation detectors that cause a light-reaction when they come in contact with an ionizing radiation source, and digital data processing software and hardware. The spectrometer design allows more selective 22Na measurement and significant background reduction, which provides a more sensitive way to quantify trace amounts of 22Na with detection limit of 3 mBq. The use of this type of acquisition technique enabled simultaneous determination of 22Na and 7Be activity concentration with a single measurement by coincidence and anticoincidence mode respectively. The study confirms the feasibility of this approach. Comparison of analytical results obtained with an older single HPGe detector spectrometer and this new detector indicates that gamma-gamma coincidence counting mode improves capabilities for detecting 22Na by one order of magnitude. The innovative technology will improve Health Canada’s ability to quantify, communicate and minimise radiation exposure and related risks to Canadians. Results of this research have been published in the Journal of Environmental Radioactivity, 2014, Vol. 130, 1-6.