Chemical Technology June 2016

The effects of atomic radiation

The United Nations Scientific Committee on the Effects of Atomic Radiation undertook a broad review of the sources and effects of ionising radiation. The sessions of the Committee were attended by representatives of the World Health Organization and the International Atomic Energy Agency.

A lso represented were the International Commis- sion on Radiation Units and Measurements and the International Commission on Radiological Protection. New challenges as regards global levels of radiation exposure continue to arise and new biologi- cal information on the effects of radiation exposure is becoming available. Moreover, the potential risks from low-level radiation exposure, that is, exposure to radia- tion comparable with natural background radiation, are the cause of lively debate and controversy. The Com- mittee responded to those challenges and will do so further with new initiatives to be included in its future assessments of radiation sources, levels and effects. Governments and organisations throughout the world rely on the Committee’s evaluations of the sources and effects of radiation as the scientific basis for estimating radiation risk, establishing radiation protection and safety standards and regulating radiation sources. Within the United Nations system, those estimates are used by the International Atomic Energy Agency in discharging its statu- tory functions of establishing standards for the radiation protection of health and providing for their application. The Committee is proposing a renewed programme of work to fulfil its obligations to the General Assembly.

The effects of radiation exposure Radiation exposure can damage living cells, causing death in some of them and modifying others. Most organs and tissues of the body are not affected by the loss of even considerable numbers of cells. However, if the number lost is large enough, there will be observable harm to organs that may lead to death. Such harm occurs in individuals who are exposed to radiation in excess of a threshold level. Other radiation damage may also occur in cells that are not killed but modified. Such damage is usually repaired. If the repair is not perfect, the resulting modification will be transmitted to further cells and may eventually lead to cancer. If the cells modified are those transmitting hereditary information to the descendants of the exposed individual, hereditary disorders may arise. Radiation exposure has been associated withmost forms of leukaemia and with cancers of many organs, such as lung, breast and thyroid gland. However, a small addition of radiation exposure (eg, about the global average level of natural radiation exposure) would produce an exceedingly small increase in the chances of developing an attributable cancer. Moreover, radiation-induced cancer may manifest itself decades after the exposure and does not differ from cancers that arise spontaneously or are attributable to

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Chemical Technology • June 2016