I stand corrected. If you scroll down to section 2.2 of the 'Standards and Guidelines for Tritium in Drinking Water ' you'll find the WHO calculations for deriving the guidelines.
http://nuclearsafety.gc.ca/eng/resource ... -water.cfmGL = (1x10^-4 Sv per year)/(730 L/year * 1.8x10^-11 Sv/Bq) = 7,610 Bq/L
The section also states "guidelines for radionuclides in drinking water have been derived based on a reference dose level (RDL) or effective dose of 0.1 mSv from one year’s consumption of drinking water. This represents 10 percent of the dose limit for members of the public, as recommended by the ICRP [ICRP, 1991a] and as adopted in the Basic Safety Standards of the International Atomic Energy Agency [IAEA, 1996] and the CNSC’s Radiation Protection Regulations."
So the calculated dose is based on 0.1mSv/y, not 1mSv/y as I stated earlier.
Section 3.3.2 shows Variation in RDL (or committed effective dose):
Australia:1 mSv per year=76,103 Bq/L [NHMRC, 2004]
Finland:0.5 mSv per year=30,000 Bq/L [STUK, 1993]
United States:0.04 mSv per year = 740 Bq/L (or 2,253 Bq/L, see variation 3.3.4)
I'm not justifying the numbers that faceless bureaucrats came up with all in the name of pubic safety, or attempting to defend nuclear power, I'm showing they haven't been increased.