Beyond mining in general, radon is a particular problem in the mining of uranium; significant excess lung cancer deaths have been identified in epidemiological studies of uranium miners and other hard-rock miners employed in the 1940s and 1950s.[32][33][34] Residues from processing of uranium ore can also be a source of radon. Radon resulting from the high radium content in uncovered dumps and tailing ponds can be easily released into the atmosphere.[35] Modern mining techniques, including better ventilation for underground mines, routine radiation monitoring as well as technologies like in-situ leaching have helped decrease the incidence of radon exposure among miners in subsequent decades.