From The Denver Post (Bruce Finley):
The radioactive isotope iodine-131 was detected at 0.17 picocuries per liter in Denver on March 30. EPA officials posted the results late Friday. The EPA has not set a specific drinking water contaminant standard for iodine-131. However, iodine-131 is a beta emitter, and the EPA has set a limit for total beta emitters equivalent to 3 picocuries per liter of iodine-131. “We understand that people get concerned when we talk about radiation, but it’s important to understand how these low levels compare to the radiation we experience from natural sources every day,” EPA spokesman Rich Mylott said in a prepared e-mail statement.
“To put this drinking water sample into context, an infant would have to drink nearly 7,000 liters of this water to receive a radiation dose equal to just one day’s worth of natural background exposure. That’s exposure we all experience every day from natural sources, such as the sun and rocks and gases in the earth’s crust.”