The use of gamma aeroradioactivity in regional indoor radon prediction: a case study from Fairfax County, Virginia, USA

Abstract

Measurement of indoor radon in homes of Fairfax County, Virginia in four seasons, with as many as 743 homes in a season, has shown that indoor radon potential may be predicted using aeroradioactivity maps. Homesites were located on a gross-count aerial gamma-ray intensity map, and indoor radon statistics for basement measurements were tallied according to aeroradioactivity range. For the winter season, the median indoor radon values showed a regular increase with increasing aeroradioactivity from 93 Bq m-3 in the aeroradioactivity range of 100-200 counts per second (CPS) up to 200 Bq cm-3 for homes in the >500 CPS range. Similarly, the percentage of homes with indoor radon values above 150 Bq m-3 also increased regularly from 20% to 83%. This regular increase occurs in other testing seasons as well, but with lower values. The results were good, even though ground permeability was not accounted for by this method, and the data suggest that a spectral survey could increase indoor radon predictability. Aerial gamma-ray mapping promises to be a simple, accurate and relatively inexpensive method for predicting the risk of indoor radon pollution.