Sometime in the early 1970s a serious problem was reportedly noticed at a uranium mine in Europe. It seems that the miners were contracting lung cancer at a rate 50 times higher than normal. A study of some sort was apparently conducted and it was concluded that the cancer was being caused by radon.

No information appears to be available regarding the location of the mine, who may have conducted the study, or what methods were employed in arriving at the conclusion presented. What is obvious, however, is that this was the beginning of the worldwide indictment of radon as a public health hazard. Many of the reports that have been published regarding the radon hazard nebulously refer to the “European uranium mine.”
http://proliberty.com/observer/20020205.htm