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Pacific Currents Likely to Take Fukushima Radiation to U.S. West Coast in Five Years

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This visualization shows the Kuroshio Current's ocean surface movements between 2005 and 2007. The current south of Japan is a major factor in dispersal of contaminated water from Fukushima Daiichi. Image courtesy of NASA Goddard Space Flight Center/Flickr.

In five to six years, highly diluted radioactive water from the crippled Fukushima Daiichi nuclear plant in Japan could arrive on the Pacific shoreline in the United States, a new study concluded.

The model developed by German oceanographers and the U.S. National Oceanic and Atmospheric Administration’s Pacific Marine Environment Laboratory traced the probable pathway of contaminated water from site of disaster triggered by the devastating March 11, 2011 earthquake and tsunami.

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In the scenario the researchers modeled, although the level of radioactivity in the water when it reaches North America could be twice what it was before Fukushima, it would still be less than the levels allowed in drinking water, one of the scientists told Environmental Research Web.

But in an interview with National Geographic, the lead researcher stressed there are many uncertainties.

“Based on the assumptions we made and the lack in knowledge about the real total released amount of radioactive materials, I am not able to assess whether the concentrations on the West Coast of the U.S. will be harmful or not,” said Erik Behrens, of the Helmholtz Centre for Ocean Research in Kiel, Germany. “It can not be excluded that even small radioactive doses can have a harmful effect.”

The team simulated the movement of a tracer that was continuously injected into Japanese coastal waters over a period of 54 days. Then, the researchers used global ocean circulation models to see how it would spread — and dilute — in the Pacific Ocean over the course of 10 years.

The study was published this month in the journal Environmental Research Letters.

Behrens says there are “large uncertainties” about the amount of radioactive material that was released in to the Pacific from Fukushima, making it difficult to know what impact it might have. “Even today, radioactive material from Fukushima is released into the ocean, which is not taken into account in our model simulation, but affecting present radioactive concentrations.”

The study also didn’t account for biological effects like adhesion to sinking particles or the accumulation processes in the food chain, Behrens said.

He was struck by the speed at which the tracer was stirred by the Kuroshio Current, which flows past Japan in a northeasterly direction.

“I was surprised about the fast initial spreading of the tracer in the energetic Kuroshio regime and the small-scale resolved ocean currents contributing to the ongoing tracer spreading,” he said.

“Within one year it will have spread over the entire western half of the North Pacific and in five years we predict it will reach the U.S. West Coast,” study co-author Claus Böning told Environmental Research Web.

The model is one of several recent studies on Fukushima’s potential impact on the U.S. coastline.

Last month, the Statesman Journal reported that two new studies by California scientists had found that radioactive elements from Fukushima had been discovered in marine life on the Pacific coast — one study uncovered the elements in kelp, and the other in Bluefin tuna.

While the amounts were too insignificant to pose a health problem for humans, they raised questions about the accumulation of radiation in ocean life.

Meanwhile, the Seattle Times reports that while experts expect to see debris from the Japanese tsunami washing up on the Northwestern shores of the U.S. over the next few months, they don’t anticipate radioactivity in the materials being a problem.

“Wind, rain and salt spray has been pounding that material for more than a year,” Kathryn Higley, head of the Department of Nuclear Engineering & Radiation Health Physics at Oregon State University, told the Seattle paper. “Anything that was on there is going to have washed off to extremely low, if not undetectable levels.”

 The Washington state Department of Health has scanned some items that have washed up, like plastic bottles and at least one boat, and has done laboratory testing on fish. They haven’t found high levels of radiation.

There are sure to be more studies to come as we wait to see what might turn up on the West Coast from Fukushima.

(Related:”Japan’s Nuclear Refugees” and “One Year After Fukushima, Japan Faces Shortages of Energy, Trust”)