Radon and progeny in the city of São Paulo—Brazil

Abstract

Results of indoor radon and progeny concentration measurements carried out during the winter of 2003 in dwellings in the city of São Paulo—Brazil are presented. A random sample of 70 residences was prepared all over the city. Monitoring was carried out using the time-integrated passive detector technique, using bare cellulose nitrate (LR115—type II) solid state nuclear track detector (SSNTD) as alpha particle detector placed in one of the bedrooms of the house. Total alpha emission concentration, related to alpha emissions of radon and progeny, was evaluated, considering the influence of the plate-out effect near the detector surface. The results show large variation of total alpha emission concentration and an arithmetic mean of 147 Bq / m 3 . A log-normal fitting produced good agreement with the data distribution. Some dwellings show values of total emission concentration similar to other places in the world, where the weather conditions are more rigorous and winter temperatures are lower than in São Paulo. During the exposition period, the lowest mean daily temperature in the city was 10 ∘ C . The correlation of the alpha emission concentrations with some residence characteristics showed that good ventilation, floor covering of wood or carpet and bedrooms in a higher floor result in lower geometric values of the alpha concentration. Nevertheless, none of the characteristics alone is responsible for the higher or lower radon and progeny concentrations.