This is a common concern for irradiated gemstones — apart from diamonds, many other gems including sapphires and topazes are also treated with this method. In the United States, any laboratory that uses irradiation treatment must be specially licensed by the Nuclear Regulatory Commission. They use only approved methods and store their gems in a safe facility for a set amount of time, until the radiation levels decrease to a level well below that which is safe for handling. After this point, the gems can be released onto the jewelry market. The Nuclear Regulatory Commission has been regulating the use of irradiation treatments in gemstones for decades, and they have publicly said that they have never seen any evidence of these treatments being unsafe.