This dataset provides the results obtained by Health Canada’s Radiological Monitoring Network (CRMN) for airborne radioactivity content at monitoring stations across Canada. More information about the CRMN network can be found here.

The results provided are activity concentration, uncertainty and the minimum detectable concentration for the naturally occurring radionuclides, beryllium-7 (⁷Be) and lead-210 (²¹⁰Pb), and the anthropogenic (originating from human activity) radionuclides, cesium-134 (¹³⁴Cs), cesium-137 (¹³⁷Cs), and iodine-131 (¹³¹I). The data comes from the analysis of particulates accumulated in filter media, drawn by high-volume air samplers fixed in the field. Such data is typically dominated by natural radionuclides, such as ⁷Be and ²¹⁰Pb. ⁷Be is a natural cosmogenic radionuclide that is produced in the upper atmosphere when cosmic rays bombard oxygen and nitrogen. ²¹⁰Pb is also a natural radioisotope that results from the decay of uranium (²³⁸U) naturally present in the ground. An important intermediate step of uranium decay is radon. Radon is a naturally occurring radioactive gas that moves through the soil and becomes diluted when mixed with outdoor air. Radon represents close to 50% of radioactivity exposure for most Canadians because it can accumulate in indoor environments, sometimes to high levels. ²¹⁰Pb is present in the CRMN air filters because radon eventually decays to ²¹⁰Pb, with several intermediate steps. More information about Health Canada’s National Radon Program can be found here.

For all our stations, the airborne radioactivity data shows a small increase in the activity concentration of ¹³⁴Cs, ¹³⁷Cs and ¹³¹I measured between March and May of 2011, attributable to the nuclear accident at the Fukushima-Daiichi Nuclear Power Station. It is important to note that, even at their respective peaks, the measured activity concentrations of ¹³⁴Cs, ¹³⁷Cs and ¹³¹I represent only a small fraction of typical background exposure from natural sources of radiation. Occasionally, other small increases in activity concentration of anthropogenic radionuclides are observed. Spikes in ¹³⁷Cs activity are often associated with forest fires, which can lead to the re-suspension of ¹³⁷Cs already present in the environment, most likely from atmospheric nuclear testing in the 1960’s. Detection of small amounts of ¹³¹I is commonly associated with its medical use by hospitals.