Detection of Contaminated Properties with Indoor Radon Levels within Local Natural Variation


R. H. Stager, R. Moridi


Soils on some residential properties within the City of Toronto were contaminated with radium as a result of radium-recovery operation. An extensive characterization program comprising surficial gamma radiation surveys, soil sampling and indoor radon measurements was conducted in support of the identification and remediation of radium-contaminated properties in the surrounding area. The two objectives of the indoor radon measurement program were to assess potential health risks from radon decay product (RDP) and to identify radium contamination not otherwise identified during surficial gamma radiation surveys and soil sample analysis on the properties. Radon levels were measured using E-PERMs. Radon decay product concentrations were measured using home and school radon monitors. Duplicate measurements of indoor radon and RDP concentrations were collected in more than 500 residences in the investigation area on a two-week campaign basis and about 100 control residences were measured in six consecutive two-month periods over a one-year time period. The seasonal patterns in radon and RDP concentration were investigated as well as the equilibrium fractions in these homes. The highest radon and RDP concentrations were present during the late summer and early fall. There were significant variations in radon levels between control neighborhoods with some neighborhoods having higher radon concentrations than in residences on contaminated properties. Statistical modeling approaches were implemented to improve the sensitivity for identifying contaminated properties with indoor radon levels within the range of radon levels in the control residences.


This abstract was presented at the 35th Annual Midyear Meeting, "Decommissioning and Environmental Restoration", Poster Session, 2/17/2002 - 2/20/2002, held in Orlando, FL.

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