Ionising radiation affects people by depositing energy in body tissue, which can cause cell damage or cell death. In some cases there may be no effect. In other cases, the cell may survive but become abnormal, either temporarily or permanently, or an abnormal cell may become malignant. Large doses of radiation can cause extensive cellular damage and result in death. With smaller doses, the person or specific irradiated organ(s) may survive, but the cells will be damaged, increasing the chance of cancer. The extent of the damage depends upon the total amount of energy absorbed by body tissue (absorbed dose), the time period and dose rate of exposure and the particular organ(s) exposed.
Evidence of injury from low or moderate doses of radiation may not show up for months or even years. For leukaemia, the minimum time period between the radiation exposure and the appearance of disease (latency period) is 2 years. For solid tumours, the latency period is more than 5 years. The types of effects and their probability of occurrence can depend on whether the exposure occurs over a large part of a person’s lifespan (chronic) or during a very short portion of the lifespan (acute).
Ionising radiation is a source of risk for humans but it has to be used for the benefit of the community.