On the tuna (NPR):

Yes, radiation in seafood seems scary. But here's the catch (if you pardon the expression). Tuna, like every other food on the planet, already contains naturally occurring radiation. It has potassium-40 and polonium-210. It always has and it always will. In addition, seafood in general contains a trace of cesium-137 left over from nuclear weapons testing in the 1950s and 1960s.

So the question is, how much more radiation did these particular tuna fish contain? The answer is: A trivial amount. In fact, radiation from the cesium is 30 times less than the radiation that's already in the fish naturally in the form of potassium-40, according to the research paper. And the natural polonium-210 packs a radiation dose 200 times larger than the dose from the cesium.

Really, the result is a testament to how well scientists can now measure tiny amounts of radiation. And of course it's a remarkable lesson in how wildlife can be traced using accidental "tags" instead of using the labor-intensive plastic ones.

If you are still worried about the cesium from Fukushima, Robert Emery at the University of Texas Health Science Center at Houston says you'd need to eat 2.5 to 4 tons of tuna in a year to get a dose of cesium-137 that exceeds health limits. That's a lot of sushi.

and from Nature on direct effects of Fukushima radiation on people:

The large population involved could mean that the eventual number of radiation-induced cancers among the public will actually be higher than among workers, even though the risk to each individual civilian is tiny, says David Brenner, a radiologist at Columbia University in New York city. But he doubts a direct link will ever be definitively made. Under normal circumstances, "40% of everybody will get cancer", he says. "It doesn't seem to me that it's possible to do an epidemiological study that will see an increased risk." Still, it may be valuable to conduct studies to reassure the population that they are not being misled, he adds.

A far greater health risk may come from the psychological stress created by the earthquake, tsunami and nuclear disaster. After Chernobyl, evacuees were more likely to experience post-traumatic stress disorder (PTSD) than the population as a whole, according to Evelyn Bromet, a psychiatric epidemiologist at the State University of New York, Stony Brook. The risk may be even greater at Fukushima. "I've never seen PTSD questionnaires like this," she says of a survey being conducted by Fukushima Medical University. People are "utterly fearful and deeply angry. There's nobody that they trust any more for information."

~ Becky in Tucson