Mapping the fraction of dwellings exceeding radon level thresholds in the Lazio region, central Italy.

The risks arising from exposure to radon in buildings call for the planning of actions to reduce indoor radon levels. Maps of the fraction of dwellings above a threshold make it possible to identify areas where actions can be concentrated to optimize resources. The grid square method was applied to data collected in the radon survey carried out in the Lazio region, located in central Italy, to estimate the fractions of dwellings with radon concentrations above 100, 200 and 300 Bq m-3. Spatial correlation between radon measurements was used to improve the estimates. Depending on the threshold, selecting areas where >10% of dwellings are above, the territory covered varies from about 100% to about 20% of the entire region.