First, in the case of a small dose, it can't cause harm. In some cases, cells will not die, but become abnormal cells, some are temporary, some are permanent, and those abnormal cells will even develop into cancer cells. Under low dose irradiation, the human body or some irradiated organs can survive, but the incidence of cancer is greatly increased.
Second, a large dose of radiation will cause a large area of cell death. The damage range depends on the size of irradiation source, irradiation time and irradiated tissue.
Third, the damage caused by low-dose or moderate-dose radiation can not be revealed in a few months or even a year. For example, leukemia caused by radiation, the incubation period from radiation to onset is two years. The incubation period of tumor is five years. Pathological changes and incidence of diseases after irradiation depend on the type of irradiation (chronic irradiation, acute irradiation). However, not all the causes after irradiation are caused by irradiation. At the same time, there is no obvious difference between radiation carcinogenesis and human genetic damage. Among them, chronic radiation is long-term intermittent exposure to low-level radiation environment.
Fourth, the effects of chronic radiation can only be detected after a period of time. This influence includes: DNA variation; Induce cancer; Benign tumor; Cataract; Skin cancer; Congenital defects, etc. Acute radiation is a large dose of radiation in a short time. Large doses of radiation are generally caused by radiation accidents or special medical procedures. In most cases, large doses of acute radiation will cause immediate and chronic injuries. For the human body, large doses can cause acute radiation sickness, such as massive hemorrhage, bacterial infection, anemia, endocrine disorders and so on. Late effects may lead to cataracts, cancer, DNA variation, etc. And extreme doses can lead to death in a short time.
5. It is possible (extremely low probability) that the gene after irradiation will mutate, and the inheritance will cause genetic effects to future generations.