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Indoor radon concentrations have been measured in Santana cave, the most frequented cave of PETAR (High Ribeira River Tourist State Park), situated southern of Sao Paulo State, Brazil. The measurements were carried out with CR-39 detectors installed in four of the most frequently visited galleries. Preliminary results from November 2009 to June 2010 show radon concentrations varying from 1.9 ± 0.1 to 8.4 ± 0.6 kBq m(-3). The total annual effective dose for all galleries was 3.32 mSv. The complete evaluation will be concluded by September 2010.

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Abstract. Radon ( 222 Rn) is the most important cause of exposure to mankind due to natural radioactivity. Radon exhalation depends not only on the 226 Ra concentration in the material, but also on other factors such as mineralogy of the region, size and density of grains and porosity of the material. As building materials are one of the major sources of environmental radon, the radiological implications of the use of materials with great content of uranium must be always assessed. In this work, radon exhalation from several undamaged granitic building materials used as ornamental rocks or coating tiles is determined using the "sealed-can technique" and CR-39 solid state nuclear track detectors (SSNTD). Preliminary results for radon concentrations showed values of the same order that literature values, in a range from 99 Bq.m −3 to 1100 Bq m −3 . Further, the methodology will be validated with standard sources of 222 Rn.

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Abstract. The levels of gross alpha and beta natural radioactivities in surface, underground and drinking waters consumed by the urban and rural population living in Lagoa Real Uranium Province of central south Bahia state, Brazil were determined in several samples collected from urban public supply of drinking water and, in the rural area, from dug and drilled wells and also from small dams and reservoirs supplied with rainfall. After pre-concentration, the samples were evaporated under an infrared lamp on an inox planchet and subsequently counted on a thin end-window low-background proportional counter, namely Berthold LB 770. Preliminary results show natural radiation levels varying from 0.02 ± 0.001 Bq/L to 0.80 ± 0.04 Bq/L for gross alpha activity and from 0.010 ± 0.006 to 3.0 ± 0.2 Bq/L for gross beta activity. Some values exceed the 2004 WHO recommendation levels that the screening levels for drinking water below which no further action is required are 0,5 Bq/litre for gross alpha activity and 1 Bq/litre for gross beta activity. However, as we are dealing with natural radiation in a well-known high background radiation area, more studies are needed.