Prediction of 222Rn from topography in Pennsylvania.

The relationships of Rn levels in basements and first floors of homes to topographic location in a northeastern ridge and valley section of Pennsylvania were investigated. Topographic variables relating to elevation and slope were quantified and related to house Rn levels using both conventional and classification and regression tree (CART) analyses. The original interest was in using topographic correlates to estimate missing values in epidemiologic studies. In this area, Rn levels are usefully predicted by relative and absolute elevations and nearness to hills and ridges. Three- to fourfold differences in geometric mean Rn levels can be obtained for categories representing significant portions of the population of houses. The relationship of first-floor to basement Rn levels was found to be curvilinear and modestly affected by topography.