Overview of Occupational Radon Exposure — Past, Present and Future

All soils and rocks contain natural levels of uranium-238 and its decay product, radium-226 which is the parent of radon-222 (radon). Since radon is a noble gas, some portion of the radon produced through the decay of radium-226 will escape from the soil or rocks where it is formed and migrate through pore space in soil or fractures in rock, either as a gas or dissolved in water, and subsequently may enter mines or underground workplaces. Epidemiology studies of underground miners, and more recently residential radon, have demonstrated that exposure to radon and its progeny can cause lung cancer. This paper discusses how the regulation of workers exposure to radon in mines and the exposures of miners to radon and progeny (radon) have changed since the widespread recognition of radon as a health hazard in the 1950's. Radon levels in non-mine workplaces is also discussed. (author)