Mainichi Shinbun (in Japanese; 10:42PM JST 3/25/2011) reports:
Food Safety Commission of the Cabinet decided to raise the current provisional limits of radioactive materials allowed in foods and drinks and has directed Ministry of Health, Labor and Welfare to come up with the new safety numbers.
The current provisional limits were set on March 17 by Ministry of Health. They are based on the guidelines by Nuclear Safety Commission. The limit for radioactive iodine is 50 milli-sieverts per year from all foods and drinks, and the limit for cesium is 5 milli-sieverts per year.
Judging by the level of radioactive materials that has fallen on vegetables in Fukushima, the new provisional safety limit would be something like 1,500 milli-sieverts per year for radioactive iodine, and 300 milli-sieverts per year for cesium so that most of the vegetables would be "safely" consumed, and that the government wouldn't need to compensate the farmers as much.
I just can't wait to see the new numbers.
OH WAIT A MINUTE. Provisional? Decided on March 17? Does that mean the government didn't even have the level set for radioactive materials in foods and drinks before that date? Or they had had the level but they raised it on March 17?
30-Day free trial by following the link.
Tokyo Time
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1 comments:
There are two sets of guidelines from IAEA / WHO:
The first is the 'regular' limits, for long term consumption from the WHO. This limit is much lower than what's being quoted as the safe limit in the news; the targed is a total exposure equivalent of 0.1 mSv/year, and the guideline for Iodine-131 for example is 10 Bq / Kg.
http://www.who.int/water_sanitation_health/dwq/GDW9rev1and2.pdf
This document is also interesting because it gives the oral dose coefficients for the most common fission products, so you can do your own conversion of Bq / Kg to long-term dose equivalent in Sieverts.
The second is the set of guidelines that apply for 1 year in the case of "contamination after a nuclear or radiological emergency". It looks like the March 17 limits are based on these, though they appear to be higher than the IAEA / WHO standards; for example both IAEA and WHO specify 100 Bq/Kg for Iodine-131 in drinking water for both Infants and Adults:
WHO Standard (p 33-37): http://www.codexalimentarius.net/web/more_info.jsp?id_sta=17
IAEA Standard (p 9-13, Schedule for Intervention Levels and Action Levels in Emergency Exposure Situations): http://www-pub.iaea.org/MTCD/publications/PDF/ss-115-web/Pub996_web-5.pdf
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