Since food standards are rumored to being adjusted (see my blogpost ‘Radiation Levels: Acceptability Standards for radioactive food being adjusted in US and EU‘ from April 7, 2011), here’s an overview of (pre-adjusted) radiation guidelines for air, water and food, taken from the Canadian Nuclear Safety Commission‘s website (April 9, 2011):
Noteworthy, I find, is that “normal” is infinitely higher than ‘natural’: for instance, Cs-137 and Sr-90 are solely manmade (only through nuclear fission) and did not occur in nature prior to the first nuclear bomb test in New Mexico on July 16, 1945.
On a side-note, this was followed by the Nuclear War against Mother Earth (1945 – present…), which started with the bombing of Hiroshima and Nagasaki, about which I highly recommend this incredible documentary: http://www.youtube.com/watch?v=x9lwvImJqT0 ; and followed by over 2,000 nuclear tests, as shown powerfully in this video artwork by Isao Hashimoto: http://www.youtube.com/watch?v=I9lquok4Pdk
–> the above table shows concentration in Becquerel per square meter of air, which (according to the formula used) would lead to an additional dose of 100 µSv/year. See ‘Radiation Units‘ and ‘Exposure Health Effects‘ for additional help interpreting this.
–> The below table show maximum allowable concentrations (in Bq/kg) for milk, food and drinking water. Noteworthy I find is that the allowable dose of I-131 in drinking water is 5 times more strict in Canada than in Japan, while for Cs137 and I-131 in food it is half as strict.
SOURCE for tables (+ text to explain them!): http://www.cnsc-ccsn.gc.ca/eng/mediacentre/updates/march-28-2011-japan-earthquake-safe-concentrations-of-radionuclides-air-water.cfm
(screenshot images taken April 9, 2011)