In the more heavily developed areas of those counties, the unhealthy levels were found in 65 percent of the water supplies tested, the paper said.
Radium is a known cause of nasal and bone cancers.
It is an issue that warrants public health attention. It is of direct concern for individual well owners. The study says the radium, which occurs naturally, can seep into the water supply because of pollution from fertilizer from residential and agriculture use. The USGS report was released last month but was not made public.