For information only - not an official document

7 April 2011

Backgrounder on UNSCEAR Reports: Radiation Exposures in Accidents and Effects on Non-human Biota

VIENNA, 6 April (UN Information Service) - The use of ionizing radiation in medical diagnosis and treatment appears to be the most common cause of injury from accidents involving overexposure to radiation, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) says in a report released today.

The Committee reviewed 32 reported accidents since 1945 involving 46 deaths and 623 injuries. "It is likely that some deaths and many injuries in the medical use of radiation have not been reported," the report said.

The report lists the accidents reported worldwide since 1945 that resulted in acute health effects or had potential for significant off-site exposures, but excludes malicious acts. In all some 203 accidents were reported, at nuclear facilities, involving industry, from exposure to orphan sources (abandoned, lost or stolen radioactive sources) and from medical use.

"Serious radiation accidents have been rare occurrences. Much information has been published about these accidents, but information about some less serious accidents remains unreported in the literature," the report said. "Human error, carelessness, failure to follow procedures and safety guidelines, defective equipment or defective repair, inadequate training, loss of control and source abandonment, and other conditions have led to accidents in the past 60 years, and will probably lead to accidents in the future."

In a compilation of accidents over more than 60 years (1945-2007) the report states:

• There have been 35 serious radiation accidents reported at nuclear facilities.

• Seven of these caused off-site releases of radioactive materials with potential for significant population exposures.

• Of the 35 reported accidents, 24 were in facilities related to nuclear weapons research, development and production, and the reprocessing of nuclear fuel for weapons programmes

• Other accidents occurred in power reactor research, development and operation, and in the reprocessing of nuclear fuel.

• Excluding the 1986 accident at Chernobyl, 32 deaths are known to have occurred due to radiation exposure and 61 workers suffered radiation injuries requiring medical care. The incidence of accidents in these facilities has fallen.

• Most of the deaths and injuries occurred in the early years of nuclear weapons development.

• Only one criticality accident, (involving a nuclear chain reaction) with the death of two workers, has occurred in the past 20 years.

• Eighty accidents were reported at other industrial facilities utilizing radiation sources, accelerators and X-ray devices. Nine deaths were reported in these accidents, and 120 workers were injured, with their hands being a common site of injury. Serious injuries frequently led to amputations. Acute radiation syndrome developed in some injured workers, and multiple amputations were needed in some cases.

• Thirty-four reported accidents have been attributed to lost, stolen or abandoned sources (orphan sources) since 1960. The accidents resulted in the deaths of 42 members of the public, including children. In addition, acute radiation syndrome, serious local injuries, internal contamination or psychological problems necessitated medical care for hundreds of persons.

• The number of reported accidents involving orphan sources has increased in the past 20 years. Six accidents were associated with abandoned medical therapy units.

• The report also states that the extensive worldwide civilian transport of radioactive materials has not resulted in any human injuries related to radiation exposure.

• A limited number of spacecraft containing radioactive material have burned up on re-entry into the earth's atmosphere or have crashed, resulting in significant releases of radioactive material to the environment. However, there is no documented evidence of anyone sustaining injury from these events.

The findings are contained in the first of three scientific annexes to be released as part of the second volume of supporting evidence underpinning the Committee's 2008 report to the General Assembly. Its publication had suffered delay.

In February UNSCEAR published an advance copy of the second annex to the report, an updated assessment about health effects due to the Chernobyl accident. It reported more than 6,000 cases of thyroid cancer so far, 15 of which had been fatal, among people exposed as children or adolescents in Belarus, Ukraine and the four most affected regions in the Russian Federation, a substantial fraction of which were associated with radiation exposure. The report also reconfirmed that radiation doses to the public from the 1986 accident were relatively low and most residents "need not live in fear of serious health consequences".

The third of the three annexes to the 2008 report, also released today, addresses the effects of ionizing radiation on animals and plants. It contains new information based on follow-up observations in the area surrounding the site of the Chernobyl accident. The Committee confirmed that reproductive changes were a more sensitive indicator of radiation effects than mortality, and that mammals were the most sensitive of all animal organisms. But the Committee concluded that overall there was no evidence to support changing the conclusions of its 1996 UNSCEAR report on the dose rates below which detrimental effects at the population level were unlikely.


The mandate of UNSCEAR, established in 1955, is to undertake broad reviews of the sources of ionizing radiation and the effects on human health and the environment. Its assessments provide a scientific foundation for United Nations agencies and governments to formulate standards and programmes for protection against ionizing radiation.

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For more information please contact:

Peter Rickwood
Telephone: (+43-) 664 248 9680

The report can be downloaded from the UNSCEAR website: