The U. S. Environmental Protection Agency (USEPA) regulates the concentration of radioactivity in public drinking water systems (i.e., those that are publicly- or privately-owned, serve at least 25 people or 15 service connections for at least 60 days per year). To protect public health, the USEPA has established maximum contaminant levels (MCLS) for several types of radioactive contaminants in drinking water (40 CFR 141). For combined radium (i.e., Ra-226/228) the MCL is five (5) picocuries per liter. For gross alpha activity, the MCL is 15 picocuries per liter. For uranium, it is 30 micrograms per liter.
For beta emitters, the MCL is a concentration which produces an annual radiation dose of four (4) millirem effective dose equivalent in one year (65 FR 76708). The MCLs are calculated assuming a two (2) liter per day water intake using the 168-hour maximum permissible concentration (MPC) listed in a 1963-vintage NBS Handbook that used a “critical organ” philosophy (i.e., NBS Handbook 69).
The following is a listing of the derived concentrations of beta and photon emitters in drinking water, units of picocuries per liter (pCi/l) that yields an effective dose equivalent of four (4) millirem based upon the NBS Handbook 69 factors. If multiple radionuclides are present, compliance should be demonstrated using the “unity rule”.
Antimony
Arsenic
Barium
Berkelium
Beryllium
Bismuth
Bromine
Cadmium
Calcium
Carbon
Cerium
Chlorine
Cobalt
Cromium
Cesium
Copper
Dysprosium
Erbium
Europium
Fluorine
Iron
Gallium
Gadolinium
Germanium
Gold
Hafnium
Holmium
Hydrogen
Indium
Iridium
Potassium
Iodine
Lanthanum
Lutetium
Manganese
Mercury
Molybdenum
Neodymium
Neptunium
Nickle
Niobium
Osmium
Phosphorus
Protactinium
Palladium
Promethium
Praseodymium
Platinum
Plutonium
Rubidium
Rhenium
Rhodium
Ruthineum
Sulfur
Samarium
Scandium
Selenium
Silicon
Silver
Sodium
Strontium
Tantalum
Terbium
Technetium
Tellurium
Thallium
Thulium
Tin
Tungsten
Vanadium
Yttrium
Ytterbium
Zinc
Zirconium