Radon concentrations in the Sudwala cave, South Africa

Abstract

AbstractThere has been a growing interest in the effect of radon gas on humans visiting caves. A radon survey was consequently done in the Sudwala tourist cave close to Nelspruit in the eastern part of South Africa to determine the radon exposure of tourists and guides. The Sudwala cave, which evolved in karst geology, is a popular tourist destination. Twenty-eight electret ion chambers were placed in various locations throughout the cave for a period of 24 h. Radon concentrations varied between a minimum of 255 Bq/m3 and a maximum of 1822 Bq/m3 with a geometric mean of 750 Bq/m3. The radon levels were found to be relatively stable up to 600 m from the entrance, after which they sharply increased. This suggests that different processes disperse radon in the initial and deeper parts of the cave. It was concluded that this is the result of natural cave ventilation which is caused by changes in ambient barometric pressure. Despite the measured level being higher than the World Health Organization (WHO)’s mitigation level of 200 Bq/m3, the occupational exposure is quite low due to the frequency and duration of a typical cave tour and therefore poses no risk to the tourists and tour guides.