Assessment of effective doses from radon levels for tour guides at several galleries of Santana Cave, Southern Brazil, with CR-39 detectors: preliminary results.

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.

222Rn and 212Pb exposures at a Brazilian spa.

Termas de Araxá spa is located in Araxá, State of Minas Gerais. In this region, several minerals rich in uranium and thorium are found. The mineral waters and mud from Termas de Araxá spa have been used for therapeutic and recreation purposes. In this study, the committed effective dose was evaluated for workers and patients at Araxá spa due to (222)Rn and (212)Pb inhalation. Radon measurements were carried out through the passive method with solid state nuclear track detectors (Makrofol E) over a period of 21 months, with results varying from 258 +/- 20 to 1634 +/- 111 Bq m(-3). The (212)Pb air concentration was assessed through the modified Kusnetz's method, the results varying from 0.3 +/- 0.1 to 2.1 +/- 0.2 Bq m(-3). Doses received by the spa workers are below 20 mSv.y(-1), suggested by ICRP 60 as an annual effective dose limit for occupational exposure. The radiation doses for the patients are below the mean annual effective dose due to natural sources estimated to be 2.4 mSv.y(-1).

Dosimetric assessment from 212Pb inhalation at a thorium purification plant.

At the Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, Brazil, there is a facility (thorium purification plant) where materials with high thorium concentrations are manipulated. In order to estimate afterwards the lung cancer risk for the workers, the thoron daughter (212Pb) levels were assessed and the committed effective and lung committed equivalent doses for workers in place. A total of 28 air filter samples were measured by total alpha counting through the modified Kusnetz method, to determine the 212Pb concentraion. The committed effective dose and lung committed equivalent dose due to 212Pb inhalation were derived from compartmental analysis following the ICRP 66 lung compartmental model, and ICRP 67 lead metabolic model.