Dr. Tsubokura's Radiation Lecture Vol.48

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

95. Standards intended to limit radioactive substances in food are different in Japan and overseas

Internal radiation exposure is caused mainly by the ingestion of radioactive substances in food. To prevent the overconsumption of food contaminated with radioactive substances, a reference value has been established.

In Japan, the reference value for radioactive cesium is 100 Becquerels/kilogram, but this value varies among countries worldwide. For example, in the EU, the reference value is 1250 Becquerels/kilogram. The codex committee, a committee established by the United Nations and the World Health Organization, and the United States consider 1,000 and 1,200 Becquerels/kilogram a universal reference value for radioactive cesium.

Some people may be surprised to learn that other countries’ reference values are much looser than Japan’s. However, these values are established based on the same principle and have the same purpose: to keep total internal radiation contamination, both from radioactive cesium and other radioactive substances, such as strontium, below 1 millisievert/year.

In other countries, reference values are calculated based on the assumption that 10% of all circulating food is contaminated, whereas in Japan, 50% of food is assumed to be contaminated. Because of this, Japan’s reference values are different.

96. Reference values ensure food safety for all age groups

Internal radiation exposure is caused mainly by the ingestion of radioactive substances in food. To prevent the overconsumption of food contaminated with radioactive substances, the reference value for radioactive cesium has been established as 100 Becquerels/kilogram.

This reference value was created to ensure food safety for all age groups. Let’s compare the impact of ingested radioactive substances on 3-year-old children and 15-year-old teenagers. If they consume the same amount of radioactive substances, 3-year-olds will experience more significant health impacts. In contrast, 15-year-olds are larger than their counterparts and are expected to eat more food.

Therefore, a proper reference value cannot be established based on the simple assumption that the younger a child is, the larger the health effects of food contamination. The reference value for radioactive cesium per one kilogram of food is designed to ensure food safety for 3-year-olds, who are more susceptible to radiation, as well as 15-year-olds, who are expected to eat more.

The reference value is established to maintain the level of total annual radiation exposure to below 1 millisievert for diverse types of people, including infants; elementary, middle, and high school students; adult men and women; and pregnant women, by accounting for radiation sensitivity and total daily food intake.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on October 30th and November 6th 2016 was reproduced for MRIC Global under the author's permission.