This is part of our ongoing collection of radiation safety limits and standards around the world.

EPA drinking water limits by nuclide

US EPA Limits of Radioactive Isotopes:

EPA has established a maximum contaminant level of 4 millirem per year for beta particle and photon radioactivity from man-made radionuclide’s in drinking water.

Iodine-131 = 3piC/L (0.11 Bq/L)
Cesium-137 = 200 picocuries per liter (7.41 Bq/L)
Stronium-90 = 8 picocuries per liter. (0.30 Bq/L)
Technetium-99 = 900 picocuries per liter (33.3 Bq/L)
Tritium = 20,000 picocuries per liter (741 Bq/L)
Uranium-238 = 30 µg/L (micrograms/liter)
Iodine-129 = 3 picocuries per liter (0.11 Bq/L)
Milk = 170 Bq/kg (of iodine-131)

FDA has set a Derived Intervention Level (DIL) for Iodine-131 of 170 Bq/kg in foods prepared for consumption.

*All except Iodine-131 found here: http://www.ecy.wa.gov/programs/nwp/gwcontaminants.htm
Iodine-131 and milk/food max statistic found here:
http://www.mass.gov/Eeohhs2/docs/dph/environmental/radiationcontrol/rad_rainwater_i131_fed_faq.pdf

Canada Radioactive Isotopes, Maximum Limits (MAC):

Iodine-131 = 6 Bq/L
Cesium-137 = 10 Bq/L
Strontium-90 = 5 Bq/L
Tritium = 7000 Bq/L
uranium1 = 0.02 mg/L
Radium-226 = 0.5 Bq/L

**This list is fairly old and may be changed

Not sure what country or group set these standards, may be Japan, EU or US

http://newsletter.sgs.com/eNewsletterPro/uploadedimages/000006/SGS-Safeguards-06211-Radiation-Contamination-Found-in-Imported-Food-from-Japan-EN-11.pdf

Iodine-131
Water and Milk = 300 Bq/kg
Vegetables = 2000 Bq/kg (veggies except tubers and root veggies)

Cesium-137
Water and Milk = 200 Bq/kg
Vegetables, Grain, Meat, Eggs, Fish = 500 Bq/kg

Uranium
Infant foods = 20 Bq/kg
Water and Milk = 20 Bq/kg
Vegetables, Grain, Meat, Eggs, Fish = 100 Bq/kg

Plutonium and elements (Total radioactive concentration of 238Pu,239Pu, 240PU, 241Am,242Cm, 243Cm, 244Cm)
Infant food = 1 Bq/kg
Water and Milk = 1 Bq/kg
Vegetables, Grain, Meat, Eggs, Fish = 10Bq/kg

Derived Intervention Levels for consumption or export
Iodine-131 = 170 Bq/kg
Cesium-137 = 1200 Bq/kg (also Cesium-134)
Plutonium = 2 Bq/kg (includes Plutonium-238 + Plutonium-239 + Americium-241)
Stronium-90 = 160 Bq/kg
Ruthenium-103 &106 = (C3 / 6800) + (C6 / 450) < 1

EU standards for Cesium

Cesium-137 & 134
Milk = 370 Bq/kg
Infant food = 370 Bq/kg
Other food products = 600 Bq/kg

source: http://ec.europa.eu/energy/nuclear/radioprotection/doc/legislation/90737_en.pdf

***These were Japan’s levels listed before the accident****

Japan current threshold amounts:

I-131 = 300 Bq/kg
Cs-134/137 = 200 Bq/kg

NOTE: 1 Becquerel = 27 picoCuries