Radiation hazards

Hazards from radiation may arise from external sources of radiation or from radioactive materials taken into the body. The effects depend on the dose, the duration of exposure, and the organs exposed. With some forms of radiation, damage occurs when the radiation dose exceeds a certain limit, usually 1 sievert (Sv) (see radiation unit). This damage may include radiation dermatitis, cataracts, organ failure (which may occur many years later), or radiation sickness. For other types of radiation damage, the risk that damage will occur increases with increasing doses of radiation. Cancer caused by radiation-induced mutation is the major example of this type of damage. Radioactive leaks from nuclear reactors can cause a rise in mutation rates, which may lead to an increase in cancers, such as leukaemias; to birth defects; and to hereditary diseases. Cancer usually develops years after exposure. Radiation damage can be controlled by limiting exposure. People exposed to radiation at work have their exposure closely monitored to ensure that it does not exceed safe limits. People of reproductive age or younger should have their reproductive organs shielded when having X-rays or radiotherapy. There is no evidence of radiation hazards with visual display units (VDUs).