Variable spacial and seasonal hazards of airborne radon

The concentrations of indoor radon in the basements of homes located in northern Virginia average about 1.4 times the first-floor radon concentration. Basement indoor radon concentrations exhibit seasonal variations which can be related to home use patterns of the occupants. Little indoor radon difference was seen between homes that have concrete block basement walls and poured concrete basement walls, but homes that use oil or gas furnaces for heating have a 25% lower indoor radon than homes that use electrical heating systems. Particular geological units seem to be associated with elevated indoor radon concentrations, and several units are associated with indoor radon concentrations that exceed 4 pCi l(-1) (the U.S. Environmental Agency ''Action Level'') in more than 40% of the homes. Comparative studies between indoor radon and total-gamma aeroradioactivity show that aeroradioactivity can be accurately used to estimate community radon hazards. (C) 1997 Elsevier Science Ltd.