The short version: you should be able to drink the water and still "protect your precious bodily fluids."
I received some information from an acquaintance who works for Atomic Energy Canada Limited, which I summarize below. It's his word and AECL's (which has had minor incidents of its own), not mine, and I did not ask for his permission to put his name on anything, so I cannot supply it or references. You should be able to corroborate all of this from credible online sources if you need to. Take it for what it is worth.
- there is a natural base level of radioactive iodine and cesium in all drinking water, the later from weapons testing
- iodine has a half-life of 8 days; in 40 days it has all decayed
- the Japanese legislated limit is 300 Becquerel/kg
- the current level of iodine in Tokyo water would give you 0.5% of 1.33% of the radiation in a chest X-ray if you drank only that water every day for a year
- Canadian and Japanese limits are based on recommendations of the ICRP (International Committee for Radiation Protection)
- both use more conservative doses than the base recommendation, Japan being more conservative than Canada
- drinking water at the allowable limit would expose you to about 4mRem total in a year
- this is an insignificant amount of dose when compared to dental or chest x-rays (as much as 300 mRem per x-ray)
- the dose received by individuals through natural radiation is about 300mRem per year
- the legal limit for Nuclear Energy Workers in Canada is 5 Rem/year or 5000mRem/year
I am just the messenger, and a liberal arts graduate, so do not bother questioning me about the facts or the math. Thanks.