Gross alpha and beta activities in surface, underground and drinking waters of a high natural radioactivity region of central south Bahia state, Brazil

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