I'm very surprised that radiation workers are allowed half the dose which is directly linked to cancer. Especially because you get that dose in two years, imagine how much you get over a 40 year career.
Generally kept lower than that. Exceeding the human exposure threshold for a worker amounts to an international nuclear incident. Literally. Must be reported and the IAEA will do a full investigation and eventually assign it an International Nuclear Event Scale number. (7 = Chernobyl. 2 = Worker dropped a small vial of tritium gas and breathed it in.)