Radon concentrations and exposure levels in Hungarian caves

In addition to workers in uranium and coal mines, the staff of other underground workplaces, such as workers in caves, can be exposed to 222Rn and its progeny. In this study, radon and radon progeny concentrations were measured in four Hungarian caves. Two of them are used for speleotherapy, one is opened for tourist visits, and one is a reference cave used only for experimental purposes. Seasonal variation of radon levels, with summer maximums and winter minimums typical for cold karstic caves, were observed in all caves investigated. Non-regular diurnal variation of radon concentration was measured in the caves where indoor air was less isolated from the outdoor atmosphere. From the measured radon concentrations, cumulative WLM exposures, bronchial dose, an effective dose equivalent values were calculated for the staff, patients and visitors. The effective dose equivalent values for the cave personnel do not exceed the 20 mSv y-1 limit. The doses for visitors and patients were one or two magnitudes lower than that of the personnel.