Design and interpretation of large surveys for indoor exposure to radon daughters

The Canadian experience in carrying out large surveys for indoor exposure to radon daughters is reviewed. These surveys have been carried out for a number of distinct purposes e.g. to establish geographic variation and to explore the extent of man made contamination. Four studies are described with special attention to the constraints, which lead to design modifications presenting problems in interpretation. There is a discussion of both continent wide statistical sampling systems and intense regional monitoring where every house is sampled. Factors affecting the interpretation of the surveys are discussed and an attempt is made to relate collected information to human dose. (author)