Q: What's the danger?A: Radioactive iodine, from food or the air, can build up in the thyroid, leading to thyroid cancer years later. Young children and pregnant women are at greatest risk. Thyroid cancer is one of the least fatal cancers if treated promptly. Radioactive cesium can build up throughout the body, is harder to eliminate and high levels are thought to be a risk for various other cancers. But it takes quite high exposure to harm, says Mettler: In contaminated villages around Chernobyl, thyroid cancer was documented. But if there was an increase in any other cancer, it was too small to detect, he says.
Q: In what foods in Japan have these radioactive elements been found?A: Iodine has been found mostly in milk and spinach, but also in chrysanthemum greens, leeks and a few other foods. Cesium also has been found in some vegetables. Levels found so far range from trace amounts to milk with iodine levels five times the acceptable limit, and in spinach, iodine levels 27 times the ceiling. Officials soon will test seafood.
Q: If you ate that, what would it mean?A: You'd have to eat 2 pounds of the most contaminated spinach to absorb about as much radiation as you'd get from a CT scan of the head, says Dr. Clifford Chao, radiologist-in-chief at New York-Presbyterian Hospital. People who drank milk with the highest measured levels of iodine for two weeks would absorb less than a year's worth of natural background radiation, according to a report from British environmental radiation group, Mike Thorne and Associates Ltd. But infants would absorb more than adults.
Every day, hundreds of tons of fish and seaweed are bought and sold at Tokyo's seafood markets. The markets are still bustling, but prices have fallen sharply amid concerns that some products might be contaminated with radioactive material leaking from Japan's troubled Fukushima Dai-ichi nuclear plant. How likely is that?
NPR posed the question to Masashi Kusakabe, director of the Nakaminato Laboratory for Marine Radioecology not far from Tokyo. The research center is devoted to figuring out precisely what happens to radioactive material that gets into the ocean.Kusakabe says what's been getting into the Pacific Ocean near Fukushima is mostly radioactive iodine. It dissolves in water, and experiments have shown that the iodine tends to concentrate in algae. Then it gets even more concentrated as it works its way up the food chain.
Kusakabe says that might sound bad, "but the iodine we're talking about now is iodine -131, which has a very short half-life at eight days."
Every eight days, half of the iodine goes away. So after a few weeks, there's not much iodine-131 left in a fish.
Kusakabe says radioactive cesium is a lot worse: Its half-life is measured in decades, not days. But so far, much less cesium has gotten into the ocean at Fukushima.
So the Japanese fish most likely to become contaminated are the ones that spend their entire lives right near the Fukushima power plant. And the government isn't letting fishing vessels anywhere near the place.
But what about the ocean-going fish that show up on sashimi platters — fish like salmon and tuna? Might they be contaminated by radioactive material from the power plant?
"I don't think so," he says, "because tuna move everywhere. They travel, you know, maybe hundreds of kilometers, so they never stay there."
A tuna might swim by the Fukushima plant. But it wouldn't hang around long enough to become seriously contaminated.
Kusakabe says the biggest threat to the Japanese fishing industry right now isn't radiation. It's fear."Most people now think, 'Oh, it's very dangerous to eat fish in Japan or fish around this coast.' But I think it's very safe. So now is your chance to eat fish, because it's cheap," he says.
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