That's the formal recommendation of the experts on the government's Food Safety Commission.
External radiation is not counted in this number, as opposed to their draft plan in July which did include external radiation, and it is in addition to the natural radiation exposure (by which is meant pre-Fukushima natural).
The experts on the Commission didn't rule on the radiation limit for children, leaving the decision to the Ministry of Health and Labor as if the top-school career bureaucrats in the Ministry would know better.
Yomiuri and other MSMs are spinning it as "tightening" the existing provisional safety limits on food.
From Yomiuri Shinbun (10/27/2011):
The Food Safety Commission under the Cabinet Office has been deliberating on the health effect of internal radiation exposure from the radioactive materials in food. On October 27, it submitted its recommendation to set the upper limit on lifetime cumulative radiation from food at 100 millisieverts.
On receiving the recommendation, the Ministry of Health and Labor will start setting the detailed guidelines for each food items. They are expected to be stricter than the provisional safety limits set right after the Fukushima I Nuclear Plant accident. The Radiation Commission under the Ministry of Education will review the guidelines to be set by the Ministry of Health and Labor, and the new safety limits will be formally decided.
According to the draft of the recommendation in July, the Food Safety Commission was aiming at setting "100 millisieverts lifetime limit" that would include the external radiation exposure from the nuclides in the air. However, based on the opinions from the general public, the Commission decided that the effect of external radiation exposure was small and focused only on internal radiation exposure from food.
If we suppose one's lifetime is 100 years, then 1 millisievert per year would be the maximum. The current provisional safety limit assumes the upper limit of 5 millisievert per year with radioactive cesium alone. So the new regulations will inevitably be stricter than the current provisional safety limits.
In addition, the Commission pointed out that children "are more susceptible to the effect of radiation", but it didn't cite any specific number for children. The Commission explained that it would be up to the Ministry of Health and Labor and other agencies to discuss" whether the effect on children should be reflected in the new safety limits.
Oh boy. So many holes in the article.
First, I suspect it is a rude awakening for many Japanese to know that the current provisional safety limits for radioactive materials in food presuppose very high internal radiation level already. The Yomiuri article correctly says 5 millisieverts per year from radioactive cesium alone. The provisional safety limit for radioactive iodine, though now it's almost irrelevant, is 2,000 becquerels/kg, and that presupposes 2 millisieverts per year internal radiation. From cesium and iodine alone, the provisional safety limits on food assume 7 millisievert per year internal radiation.
(The reason why the radioactive iodine limit is set lower than that for radioactive cesium is because radioactive iodine all goes to thyroid gland and gets accumulated in the organ.)
I am surprised that Yomiuri even mentioned the 5 millisieverts per year limit from cesium exposure alone. I suspect it is the first time ever for the paper.
Second, the article says the Commission decided to exclude external radiation from the "100 millisieverts" number because of the public opinion. Which "public" opinion are they talking about? Mothers and fathers with children? I doubt it. If anything, the general public (at least those who doesn't believe radiation is good for them) would want to include external radiation so that the overall radiation limit is set, rather than just for food.
Third, and most importantly, if the proposed lifetime limit of 100 millisieverts is only for internal radiation from FOOD, then the overall internal radiation could be much higher. Why? Because, pre-Fukushima, the natural internal radiation from food in Japan was only 0.41 millisievert per year (mostly from K-40), or 28% of total natural radiation exposure per year of 1.45 millisievert (average). Of internal radiation exposure, inhaling radon is 0.45 millisievert per year in Japan, as opposed to the world average of 1.2 millisievert per year.
Now, these so-called experts in the government commission are saying the internal radiation from food can be 1 millisievert per year (assuming the life of 100 years), in addition to the natural internal radiation from food (K-40) which is 0.41 millisievert per year. Then, you will have to add internal exposure from inhaling the radioactive materials IN ADDITION TO radon which is 0.45 millisievert per year.
Winter in the Pacific Ocean side of east Japan is dry, particularly in Kanto. North wind kicks up dust, and radioactive materials in the dust will be kicked up. The Tokyo metropolitan government will be burning away the radioactive debris from Iwate Prefecture (Miyagi's to follow) into the wintry sky. So-called "decontamination" efforts all over east Japan will add more radioactive particles in the air for people to breathe in.
Don't be fooled by this 100-millisievert lifetime number. It's bogus.
For your information, the comparison of natural radiation exposure levels (the world vs Japan), from the Nuclear Safety Research Association Handbook on treating acute radiation injury (original in Japanese; my translation of labels). Japan has (or had) markedly lower radon inhalation than the world average, and much lower external radiation from the ground and from cosmic ray. It makes it all up by overusing the medical X-rays and CT scans, and even the Nuclear Safety Research Association who issued the following table says Japan tends to use too many X-rays and scans and that the medical professionals should make effort not to overuse them.
|Type of exposure ||World average |
（UN Science Commission）
|Japan average |
|Natural radiation ||From ground |
Ingestion (K-40, etc)
|Artificial radiation ||Medical ||World average ||Industrial nations ||Japan|
|Medical X-ray, CT |
Nuclear medicine diagnostics