JAPAN | Gov’t panel advises keeping lifetime radiation exposure in check

Posted on July 27, 2011

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JAPAN | MAINICHI | 27 July 2011

One-year-old Himari, center, held by her mother Tomomi Sato, left, undergoes a radiation screening test at the welfare office in Oyama, Fukushima Prefecture, on May 24, 2011. (Mainichi)

TOKYO (Kyodo) — A government food safety panel recommended on Tuesday that safeguard measures be taken to ensure that cumulative radiation exposure during a person’s lifetime not exceed 100 millisieverts, a benchmark beyond which the risk of cancer increases.

The Food Safety Commission’s conclusion paves the way for the health ministry to consider revising its provisional limits for radioactive nuclides in food, set in the wake of the Fukushima Daiichi nuclear power plant crisis based on annual internal exposure levels and which do not take into consideration amounts absorbed through external exposure or lifetime accumulated amounts.

The commission also urged the government and the public to note that children may be more vulnerable to radiation than adults, indicating the possibility of more discussions on lowering allowable levels for children.

The current government limits are set at the same levels for adults and children for the majority of foodstuffs, with a few exceptions such as for water and milk which specify lower figures for infants.

The panel’s decisions Tuesday were reached after analyzing research conducted in Japan and abroad on the health impact of radiation exposure, participants said.

Research on survivors of the 1945 atomic bombings in Hiroshima and Nagasaki showed that exposure levels above 100 millisieverts were associated with increased risk of developing cancer.

Almost none of the studies were conducted solely on internal exposure from food consumption, prompting the panel set the yardstick from the viewpoint of lifetime cumulative levels, including external exposure.

The 100 millisieverts yardstick does not include an average annual dose of 1.5 millisieverts of radiation from the natural environment in Japan, as well as exposure during medical procedures such as X-ray examinations.

The commission also discussed acceptable limits for the ingestion of individual isotopes, such as radioactive cesium and iodine, but did not reach a conclusion due to the lack of research data.

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