The radiological impact of mining in a Th-rich Norwegian area.

The radiological impact of former mining activities in the Fen area in southern Norway has been assessed. The area is known to have enhanced concentrations of Th. A recent epidemiological study suggested a significant increment of lung cancer among the former miners, and the doses to the miners have been assessed. The main contributor to the effective dose equivalent in one of the mines was inhaled 220Rn progeny. Water in drilled wells and in nearby lakes has been analysed for 220Rn and Ra. Uranium and Th analyses were performed on mine and lake water. The mining activity does not seem to have contaminated drinking water significantly. The tailings from Nb production has enriched Ra and Th concentrations. The tailings and the possible use of waste rock from the mining are probably the most important environmental results of the mining activities.