National Radon Survey in Canada, Annex V

Between 1978 and 1980, Health Canada carried out a national survey of 13 500 dwellings in 18 cities across Canada. The radon measurements made were all short term using instantaneous grab sampling. The survey predicted that approximately 5% of Canadians were living in dwellings with radon concentrations above 200 Bq/m³. The survey also identified a number of areas where the radon concentrations indoors were higher than in other areas. In the late 1980s, a large study of radon concentrations indoors was undertaken in the Winnipeg area. The radon measurements were all long term and were made using passive integrating track etch detectors. Some smaller targeted studies were also carried out in other regions. In 1988, Canada established a national radon 'guideline'1 of 800 Bq/m³. This was based on the scientific information available at the time. In 2007, with new information available and following a public consultation, the national radon 'guideline' level was reduced to 200 Bq/m³.