European Nuclear Society:
The effective dose for members of the public must not exceed 1 mSv/year.

On May 24, 2011, Japan raised the  exposure rate from 1 millisievert to 20 millisieverts per year (ABC)

In the United States safe limits have been “relaxed” under  President Obama’s administration. For drinking water, “the new EPA guide refers to International Atomic Energy Agency guidelines that suggest intervention is not necessary until drinking water is contaminated with radioactive iodine 131 at a concentration of 81,000 picocuries per liter. This is 27,000 times less stringent than the (current) EPA rule of 3 picocuries per liter.” (Forbes)  President Obama’s action of raising radiation levels follows President Bush’s action which created huge hikes in what was considered allowable amounts of radiation indrinking water, air, and soil.  (PEER)

MIT explanation of basic conversions:

1 gray (Gy) = 100 rad
1 rad = 10 milligray (mGy)
1 sievert (Sv) = 1,000 millisieverts (mSv) = 1,000,000 microsieverts (μSv)
1 sievert = 100 rem
1 becquerel (Bq) = 1 count per second (cps)
1 curie = 37,000,000,000 becquerel = 37 Gigabecquerels (GBq)

For x-rays and gamma rays, 1 rad = 1 rem = 10 mSv
For neutrons, 1 rad = 5 to 20 rem (depending on energy level) = 50-200 mSv
For alpha radiation (helium-4 nuclei), 1 rad = 20 rem = 200 mSv