Survey of one-year average Rn levels in Pittsburgh area homes.

Radon concentrations averaged over 1 yr were measured in 169 homes selected without regard to factors known to influence Rn levels. The average level was 6.3 pCi/l in basements, 2.4 pCi/l on first floors, and 2.0 pCi/l on second floors; medians were considerably smaller, 2.6, 1.20, and 0.95 pCi/l, respectively. Distributions deviate considerably from log normal in having an excess of very large values and a deficiency of very low values. Levels in upper floors were somewhat lower where the basement was isolated by closed doors than where it was not. Drafty houses had lower Rn levels than less drafty ones. Houses exposed to wind had higher levels than those well sheltered from wind. There was little correlation between Rn concentration and age of the house, indicating that Rn exposures may not have changed appreciably during the past 50 yr; this is important for estimating risks of Rn-induced lung cancer. Houses with forced air heating systems seemed to have higher Rn levels in the upper floors than those with steam or hot water heat. No strong correlations were found between Rn levels and cooking with natural gas, or river vs well-water supplies.