Limitation of exposure to natural radioactivity in Canada

The jurisdictional responsibility for natural radioactivity in Canada is divided between the federal and provincial governments. The desire for uniform standards has resulted in the formation of a scientific group to advise governments concerning the desirability of standards for exposure to natural radioactivity. The various types of exposure are reviewed with emphasis on naturally occurring radon in homes. The scientific Committee could not agree either philosophically or practically on the control level for radon in homes. To resolve this impasse, it undertook a calculation designed to illustrate for Canada, the potential cancers saved each year compared to the actual lung cancer rate, with an estimate of the cost for each limit derived. A second calculation reviewed the cost of modifying the building code and estimated the long term effect by comparing avoided cancers and cost. The calculations are based on cross-Canada surveys, intensive long term investigation of smaller groups of homes and national housing statistics. The results are discussed and serve to illustrate development of the proposed policy.