Objective To explore the effect of delayed pre-job occupational health examination on occupational health surveillance by analyzing the results of pre-job occupational health examinations in radiation exposed workers. Methods A convenience sampling method was used to select 1 385 radiation workers as the research subjects in Guangdong Province in 2016 at a pre-job occupational health examination. Workers who did not engage in radiation work were selected as control group. Workers who engaged in radiation wo...