Infants and children can be more at risk than adults of developing some cancers when exposed to radiation, for example from nuclear accidents, a U.N. scientific report said on Friday.

Children were found to be more sensitive than adults for the development of 25 percent of tumor types including leukemia, and thyroid, brain and breast cancer, it said.

“The risk can be significantly higher, depending on circumstances,” the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) added in a statement.

UNSCEAR said it began working on the report in 2011, the same year as Japan’s Fukushima nuclear accident, although the world’s worst such disaster in 25 years was not mentioned in the statement. The committee said in May that cancer rates were not expected to rise after the Fukushima accident.

Studies into the 1986 accident at Chernobyl in Ukraine have, however, linked thyroid cancer to radioactive iodine. The thyroid is the most exposed organ as radioactive iodine concentrates there. Children are deemed especially vulnerable.

Friday’s report, presented to the U.N. General Assembly, said children and adults should be considered separately following exposure in order to predict risk more accurately.

“Because of their anatomical and physiological differences, radiation exposure has a different impact on children compared with adults,” Fred Mettler, chair of an UNSCEAR expert group on the issue, said. “It is not recommended to use the same generalizations used for adults when considering the risks and effects of radiation exposure during childhood,” he added.

Children are generally assessed along with adults in epidemiological studies, the U.N. committee said.

UNSCEAR said it had reviewed 23 cancer types, some of which were “highly relevant for evaluating the radiological consequences” of nuclear accidents and of some medical procedures.

For about 15 percent of cancer types such as colon, children were found to have the same radiation sensitivity as adults, and for 10 percent of cancer types, such as those affecting the lungs, children were less sensitive than adults, it said.

“Data were too weak to reach any conclusions for 20 percent of cancers,” UNSCEAR said. “There was a weak or non-existent link between exposure and risk at any age for 30 per cent of cancers.”

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(Reuters)