Radon in residences: influences of geological and housing characteristics

222Rn is a radioactive gas emitted during the decay of 238U. 222Rn is a recognized lung carcinogen in humans and a common indoor air contaminant. This paper describes the results of research undertaken in 894 residences of the Province of Quebec (Canada), in which one of the objectives was to evaluate the influence of geological and housing characteristics on 222Rn levels. After a random selection of homes, 222Rn concentrations were measured with alpha track detectors in the basement and the main bedroom during two consecutive 6-mo periods. Geological subsoil characteristics were determined from various sources (e.g., geological maps, databanks on uranium sampling in lake and stream sediments), and housing characteristics were documented with a questionnaire. Statistical variance analysis of data indicates that geological factors only explain 5% and 4.5% of the variations in 222Rn concentrations, respectively, in the basement and on the first floor. When variables relative to housing characteristics are added, the analysis explains only 18% and 15% of the variations in 222Rn concentrations in the basement and on the first floor. These results illustrate the difficulties in predicting 222Rn concentrations in homes.