Climatide

High levels of radioactive iodine have been detected in seawater near the crippled Fukushima Dai-ichi power plant in Japan.

Since the very beginning of the nuclear crisis in Japan, it’s been clear that some portion of the radioactive material released into the atmosphere would make its way into the ocean as fallout. But there’s new evidence that radioactive elements are leaking directly into the Pacific Ocean around the Fukushima Dai-ichi power plant. Numerous media outlets are reporting that, in the past few days, radioactive iodine has been found in seawater just north of the plant at levels 1,150 times the legal limit, nearly ten times levels detected a week ago. Radioactive iodine levels in the ocean just south of the plan were found to be more than 1,850 times the legal limit. It’s still unclear what this leakage indicates in terms of damage to the nuclear reactors.

Radioactive iodine impacts

Radioactive iodine is an immediate concern for human health because it accumulates in the thymus and can increase the risk of cancer, particularly in individuals exposed at a young age. That’s why there’s so much attention being devoted to tracking contamination of spinach, milk, and drinking water supplies in Japan. However, at this point, there seems to be broad agreement among experts that the iodine released from Fukushima Dai-ichi does not pose a major threat to people outside of Japan or to marine life. Here’s why:

• Iodine-131 (the official name for radioactive iodine) decays fairly quickly; it has a half-life of just 8 days, meaning that half of the radioactivity is gone after eight days. Even for large releases, radioactive iodine levels would be expected to fall to background levels within a matter of weeks to a few months.
• As iodine-131 is whisked around the globe on atmospheric air currents, it quickly becomes diluted. While low levels of radioactivity from Fukushima Dai-ichi have been detected in air and rainwater around the U.S. (even here in Massachusetts), the E.P.A. stresses that levels are thousands of times below even conservative levels of concern.
• That’s even truer in the ocean. Oceanographer Ken Buesseler of Woods Hole Oceanographic Institution says that radioactive material would quickly become mixed throughout the top 300 feet of the ocean, then carried around the Pacific Ocean on currents. Buesseler says that, even after Chernobyl, the Black Sea remained safe for both swimming and seafood consumption, and there were no noteworthy impacts on marine life.
• The U.S. Food and Drug Administration has said that it is monitoring seafood, milk, and produce imported from Japan, but doesn’t expect contamination problems. Besides, the fishing fleet and shipping infrastructure in northeastern Japan was devastated by the earthquake and tsunami, severely limiting the availability of food products from the affected region.
• One possible exception would be seaweed from the area immediately around the crippled plant. Seaweed contains high levels of iodine, so could concentrate the radioactive iodine. Again, this is a relatively short-term concern, primarily in Japan.

Radioactive cesium and plutonium

Of course, Iodine-131 is not the only radioactive material being released from the reactors at Fukushima Dai-ichi. Radioactive cesium-137 has been found in seawater near the plant, albeit at much lower levels than radioactive iodine. Cesium-137 is much longer-lived than iodine-131; it’s half-life is 30 years, so it could be around for hundreds of years, making it the greater threat to marine life. However, at this point, levels of cesium-137 in seawater around Fukushima are similar to levels seen in the Black Sea after Chernobyl where (as I mentioned above) scientists saw no serious impacts on marine life.

Questions about plutonium are also surfacing. Traces of plutonium have been found in soil samples around the nuclear power plant, and the contamination appears to have originated from the current crisis. Plutonium has a half-life of more than 24,000 years and is very dangerous if inhaled or ingested, but its radioactivity can’t penetrate skin or clothes and the levels found in the soil samples were too low to pose a human health risk. But Hidehiko Nishiyama, an official from Japan’s nuclear safety agency, has been quoted as saying that “While it’s not at a level harmful to human health, I am not optimistic. This means the containment mechanism is being breached, so I think the situation is worrisome.”

The Take-Home

Obviously, this crisis is far from over. Normal operations have not been restored (or, alternatively, permanent containment solutions implemented) and new contamination is being discovered almost daily. Still, at this point, it appears that the environmental and human health impacts of the Fukushima Dai-ichi nuclear crisis will likely be limited to the surrounding area in Japan with by far the heaviest burden falling on plant operators.