RADON IN OUTDOOR AIR IN NEVADA

Measurements of radon at 50 sites with varying geology indicate that o utdoor air in Nevada is comparable to that measured nationwide by Hopp er et al. (1991). The statewide median of 15 Bq m-3 (0.4 pCi L-1) is e ssentially the same as the nationwide median. The range is considerabl e: from 2.6-52 Bq m-3 (0.07-1.40 pCi L-1). Variations in these measure ments can generally be correlated with different concentrations of rad on in soils and uranium and its progeny in rocks. Silica-rich igneous rocks (rhyolites and granites) appear to be the main sources of high l evels of radon in outdoor air in Nevada. Concentrations of radon in ou tdoor air generally correlate with levels of radon in soil gas. Measur ements taken from heights of 0.5, 1.0, and 2.0 m above the ground sugg est that radon in outdoor air reflects the local geology throughout th is range of heights. Towns for which >20% of the homes have indoor-air radon concentrations >48 Bq m-3 (4 pCi L-1) generally have relatively high soil-gas radon, relatively high outdoor-air radon, or both.