Fears of radiation contamination have led the U.S. Food and Drug Administration to ban imports of milk products, fruit and vegetables from the four areas near Japan's Fukushima Daiichi nuclear plant, which was wracked by the massive March 11 earthquake and tsunami. Plus, local authorities are warning mothers in Tokyo not to use tap water to mix infant formulas as radioactive iodine levels had exceeded safe limits for babies.

The FDA said all food from the Fukushima, Ibaraki, Tochigi and Gunma prefectures coming to the United States that didn't fall under the banned list would be diverted for extra screening. Japan has already blocked shipments of raw milk and spinach from these regions after discovering radioactive iodine levels were five times higher than normal in some dairy and produce.

Officials in Tokyo are also cautioning against using tap water in infant formulas. As of Wednesday morning, levels of iodine-131 in Tokyo's water rose to 210 becquerels per kilogram, the Financial Times reported. While this is twice the recommended limit for babies, at 100, it's well shy of the limit for adults, at 300.

But officials are also cautioning against panic, saying consuming the water is only unsafe if done so over a long period of time. "Even if you drink this water for one year, it will not affect people's health," said Chief Cabinet Secretary Yukio Edano, according to the Christian Science Monitor.

Fears over the radiation leaks have prompted some unusual buying sprees. In California, worries that plumes of ionizing radiation blasting off the stricken reactors will reach the West Coast reportedly have led to a run on potassium iodide pills and kelp supplements. (The pills are often given to potential radiation exposure victims to prevent the body from absorbing radioactive iodine, which can lead to thyroid cancer years down the road.) And Reuters reports that in South Korea anxious shoppers are buying up Japanese-made diapers, apparently preferred to the local variety, as some Korean mothers fret they won't be on sale for much longer. Some packages were selling online for $133.30, Reuters said.

Meanwhile, on its website, the Environmental Protection Agency said it detected "minuscule levels of an isotope that is also consistent with the Japanese nuclear incident" in Hawaii on Tuesday, but that they were "far below any level of concern for human health."

The EPA said radiation doses generated from natural sources, such as rocks and the sun, are "100,000 times higher than what we have detected coming from Japan."

"For example," the agency went on, "the levels we're seeing coming from Japan are 100,000 times lower than what you get from taking a roundtrip international flight."

As radiation and accompanying fears travel the globe, the human and financial toll of the 9.0 earthquake and resulting tsunami is being assessed. According to recent estimates, the disaster has caused nearly $300 billion in damages, with almost 25,000 dead or missing.

Randall Munroe, creator of the web comic xkcd, has a nice, sanity-promoting chart explaining the relative risks of radiation here: http://xkcd.com/radiation/

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