RADON LEVELS IN PORTUGUESE THERMAL SPAS

Radon concentration measurements were performed in indoor air and in natural mineral waters in seventeen Portuguese thermal spas used for therapy, drinking and irrigation purposes. The gamma doses rates were also assessed in different workplaces of the considered thermal spas. The radon concentration was measured in water samples taken from different sampling points: boreholes, springs, inhalator chambers (ORL’s) and swimming pools, and in the indoor air of different treatment rooms: ORL’s, swimming pools, vapours areas and Vichy shower. Radon concentration in water ranged from 26 to 6949 Bq/L and in the indoor air ranged from 73 Bq/m3 to 3479 Bq/m3. The indoor gamma dose rates ranged from 0,148 μSv/h to 0,644 μSv/h and the annual dose rate was estimated ranging from 0,30 to 1,29 mSv/y, for 2000 working hours per year, which is far below the effective dose limit for workers (20 mSv/y). Nevertheless, the great contribution for the annual effective dose will result from radon inhalation which is not included in this estimation. The remedial action level for drinking water of 1000 Bq/L (2001/928/ EURATOM) was exceeded in 23% of the selected thermal spas and about 80% of the total measurements of the indoor radon concentration exceeded the previous reference level of 200 Bq/m3 for new buildings and about 63% exceeded the new reference level of 300 Bq/m3 as established in the Directive 2013/59/EURATOM for indoor radon concentration in workplaces. Therefore, as the recommended limits for radon concentration in water and in indoor air were exceeded, appropriate actions should be taken in order to reduce the hazard to health from radon indoors and the potential resulting occupational exposure.