FAIRBANKS -- Radiation released into the Pacific Ocean by the Fukushima nuclear accident is expected to raise the amount of cesium-137 in those waters close to levels last seen during the Cold War.
Cesium-137, a manmade byproduct of nuclear fission with a half-life of 30 years, has been gradually disappearing from the Pacific following the end of atmospheric tests in the 1950s and 1960s. Douglas Dasher, a researcher at the University of Alaska Fairbanks, said the modeling of the accident shows that ocean currents will carry low levels of the radioactivity to the West Coast and Alaska in the months and years ahead.
"The concern has been that we have these models indicating the potential for levels to increase," he said. However, it "still would not indicate an immediate health problem," with levels many times smaller than the guidelines used by the U.S. Food and Drug Administration for drinking water and food.
One big unknown is how the continued release of cesium-137 will impact the ocean waters over the long run and whether the Japanese will be able to stabilize the site.
Dasher said researchers don't believe that the levels will pose a threat to human health, but there is no sampling data and no plan for detailed monitoring. He said the lack of ongoing research and data collection is a serious concern, given the scale of the accident.
"It's one of the largest releases that's ever occurred into the marine environment. It's occurred in a shorter period of time than anything has occurred before. For better or worse, it's a sort of testing program to test the models, to test the knowledge of radionuclide effects on the environment," he said.
"We really need to sample to understand this, we really need to look at what's happening out there in the ecosystem," he said.
A recent study published in Deep-Sea Research 1 said cesium-137 is expected to reach the West Coast and Northwest Coast this year or next. That study projected levels of 10-to-30 becquerels per cubic meter, which are units of radioactivity. The model persisting for up to six years.
The study said that after the plume reaches North America, it will split into two branches. "One branch flows northward to feed the Alaska Current," the researchers said.
Radiation transported through the atmosphere reached North America within days, in contrast to the years it takes radiation in the ocean to cover the same distance.
In late October, the New York Times reported that the emissions from the damaged plant are such that oceanographer Michio Aoyama believes that "radioactive cesium 137 may now be leaking into the Pacific at a rate of about 30 billion becquerels per day, or about three times as high as last year. He estimates that strontium 90 may be entering the Pacific at a similar rate."