Radium occurs in ground water due to the radioactive decay of Uranium in geologic formation. Also, Radon gas can dissolve and accumulate in underground water sources, such as wells, and in the air in your home. There is a health risk if the Radium level exceeds 20 pecocuries per liter (pCi/L). Some people who drink water containing Radium 226 or 228 in excess of EPA’s standard over many years may have an increased risk of getting cancer.