The U.S. Environmental Protection Agency said it increased the level of monitoring of milk, precipitation, drinking water and other possible exposure routes because of fallout from Japan's nuclear reactors.
Japanese reactors were devastated by the March 11 earthquake and subsequent tsunami.
The EPA said it found levels of radioactive iodine in samples from Spokane, Wash., but those levels were 5,000 times lower than what would prompt a federal intervention.
"Iodine-131 has a very short half-life of approximately eight days and the level detected in milk and milk products is therefore expected to drop relatively quickly," the EPA added in a statement.
U.S. lawmakers are calling for a review of nuclear safety regulations in the wake of the Japanese disaster.
"The lesson is that we need to think carefully about whether our country has properly estimated the threats to our nuclear facilities and designed the facilities to endure them," said U.S. Sen. Dianne Feinstein, D-Calif., chairwoman of the Senate Appropriations Subcommittee on Energy and Water, in a statement. "An independent review of the design basis for all U.S. plants should be a priority."