This session will discuss a variety of impacts and hazard-associated manifestations of radon gas and other naturally occurring radioactive hazards. Radon is a health hazard: as well as being the second leading cause of lung cancer after tobacco smoking, radon-222 is also an accelerating factor in smoking-related lung cancer risk. In addition, there is evidence that under some circumstances, the shorter half-life isotope radon-220 (thoron) can also present a health hazard. As a health hazard, radon is chiefly associated with the built environment but, along with uranium and radium deposits, for example, there are wider aspects which include (ancient) mines and the health of mine-workers, caves and their dwellers (historical and modern) and visitors, and also archaeologists in a variety of caves - and excavators more generally.

Radon is also an indicator of other hazards and, indeed, radon gas might serve as an indicator of otherwise difficult to identify abandoned mine wastes and workings. There is also a variety of radon responses associated with natural hazards such as earthquakes and volcanic activity, and also with other geophysical processes, which have been reported in the literature.

This session will present a broad range of papers including methodological, technological and interpretative aspects, as well as case-study material.