[The radon risk in Lombardy].

We investigated the geographical distribution of lung cancer mortality rates in some Italian regions, Lombardy and Emilia-Romagna in particular, where the investigation was mainly focused on the risk related to the presence of radon inside dwelling-houses. We referred to the death certificates provided by the Central Institute of Statistics (ISTAT) relative to the years 1980-1988 to calculate the relevant mortality rates. Mortality rates appear higher in some northern than in southern regions and in the islands and also (> a factor of 10) in the male than in the female population; the mortality rates in the male population exhibit a linear correlation with past cigarette smoking. The death rates in the male population (age range: 35-64 years) in northern Italy average 100 events/100,000 inhabitants, but several local health centers in Lombardy at the foot of the Alpine range, north of the Po River, have mortality rates over 50% higher than estimated rates. We considered radon exposure in Lombardy dwelling-houses. The Alps are rich in granite rocks, with 50-150 Bq/kg uranium concentrations, which produce the sediments, sands and gravels making the ground of the Lombardy plain. A recent survey of indoor radon exposure levels showed average values around 100 Bq/m3. The National Academy of Sciences (Washington, DC) has presented a formula to calculate the relative risk of lung cancer related to radon exposure during a lifetime. When this model was applied to excess events in Lombardy, acceptable agreement was found with the assumption that excess deaths are ascribable to higher radon exposure levels. We also compared Lombardy with Emilia-Romagna where the sediments and soil in the plain come from the Apennine range where calcareous rocks have low uranium content. Radon exposure levels in Emilia-Romagna were around 50 Bq/m3 and the radon risk factor in this region is therefore not particularly significant.