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).