The US Environmental Protection Agency (EPA) has not established drinking water standards specifically for Polonium 210 (Po-210). However, the maximum contaminant level (MCL) for alpha radioactivity in drinking water is 15 pCi/L. The maximum contaminant level is the concentration of a contaminant that EPA considers protective of public health if someone lived to be 70 years old and drank 2 liters of water per day. Maximum contaminant levels are regulatory concentrations.
Po-210 is a radioactive material that occurs in nature at very low levels. Po-210 results from the natural radioactive decay of uranium, which is commonly found in Sierra Nevada granites. Po-210 emits alpha particles, which makes it decay to form a stable isotope of lead. The alpha particles carry high amounts of energy which can damage or destroy genetic material in cells inside the body. Po-210 is considered to be one of the most hazardous radioactive materials known, but it must be breathed in or eaten to exert its toxic effects. Your skin or a piece of paper is enough to stop the radiation emitted by Po-210.
EPA regulates the following radionuclides in drinking water: (Adjusted) Gross Alpha Emitters, Beta Particle and Photon (gamma) Radioactivity, Radium 226 and Radium 228 (Combined) and Uranium. EPA Method 912.0 is applicable to the determination of polonium-210 in drinking water samples. The method detection limit is defined by the regulations as 0.1 pCi/L based on an instrumental alpha particle background of 0.1count/minute and 100-minute counting period. For more information on the method, please visit here.