The Environmental Protection Agency recommends reverse osmosis water treatment to remove radioactive isotopes that emit beta-particle radiation. But iodine-131, a beta emitter, is typically present in water as a dissolved gas, and reverse osmosis is known to be ineffective at capturing gases.
A combination of technologies, however, may remove most or all of the iodine-131 that finds its way into tap water, all available in consumer products for home water treatment.
First, the standard disclaimers: Every government agency involved in radiation monitoring—the EPA, FDA, USDA, NRC, CDC, etc.—has stressed that the radiation now reaching the United States has been found at levels thousands of times lower than standards of health concern. When it found iodine-131 in drinking water samples from Boise, Idaho and Richland, Washington this weekend, the EPA declared:
An infant would have to drink almost 7,000 liters of this water to receive a radiation dose equivalent to a day’s worth of the natural background radiation exposure we experience continuously from natural sources of radioactivity in our environment.”