Higher levels of Fukushima radiation detected off West Coast

Higher levels of radiation from Japan’s 2011 Fukushima nuclear accident are showing up in the ocean off the west coast of North America, scientists from the Woods Hole Oceanographic Institution reported Thursday.

And an increased number of sampling sites are showing signs of contamination.

The new findings are important for two reasons, said Ken Buesseler, the Woods Hole scientist who was the first to begin monitoring radiation in the Pacific after the accident.

“First, despite the fact that the levels of contamination off our shores remain well below government-established safety limits for human health or to marine life, the changing values underscore the need to more closely monitor contamination levels across the Pacific,” Buesseler said. “Second, these long-lived radioisotopes will serve as markers for years to come for scientists studying ocean currents and mixing in coastal and offshore waters.”

Buesseler launched a crowdfunded, citizen-science sea sampling effort in January 2014, and the National Science Foundation has funded his research.

In October 2014, Buesseler reported that a sample taken about 745 miles west of Vancouver, British Columbia, tested positive for cesium-134, the so-called fingerprint of Fukushima because it can only have come from the plant.

The sample also showed higher-than-background levels of cesium-137, another Fukushima isotope that already is present in the world’s oceans because of nuclear testing in the 1950s and 1960s.

In November 2014, Buesseler reported that Fukushima radiation had been identified in 10 offshore samples, including one 100 miles off the coast of Eureka, California.

In April of 2015, Buesseler’s team announced it had  found Fukushima radiation in a sample of seawater taken from a dock on Vancouver Island, B.C., marking the first time it was recorded on West Coast shores.

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This year, Buesseler has added about 110 new sample results to 135 already on the project’s web site.

They include the highest detected level to date, from a sample collected about 1,600 miles west of San Francisco.

The level of radioactive cesium isotopes in the sample, 11 becquerels per cubic meter of seawater (about 264 gallons), is 50 percent higher than other samples collected along the West Coast so far, but still is 500 times lower than U.S. government safety limits for drinking water, and well below limits of concern for direct exposure while swimming, boating, or other recreational activities, WHOI said in a news release.

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Since June 2011, the Oregon Health Authority’s Public Health Division has taken quarterly samples of sand and water at Oregon beaches to test for radiation, although it does not test for cesium-134, the Fukushima fingerprint. Instead, the state tests for cesium-137 and iodine-131.

None of the sea water samples taken through August 2015 exceeded the minimum amount that can be distinguished from background levels using the state’s equipment.

November results have not yet been reported.

Buesseler will present his latest findings on the spread of Fukushima radiation on Dec. 14 at the American Geophysical Union conference in San Francisco.

tloew@statesmanjournal.com, (503) 399-6779 or follow at Twitter.com/Tracy_Loew