Fears that ocean currents might carry Fukushima radiation across the Pacific Ocean to contaminate the coast of North America continue to be founded, even four and a half years since the onset of the disaster. New research out of the Woods Hole Oceanographic Institution shows not only that Fukushima radiation is still percolating along the U.S. West Coast, but that current levels are at the highest ever recorded.

In fact, readings from waters about 1,600 miles west of San Francisco represent the highest of all, where radioactive cesium isotopes were a significant 50 percent higher than any other samples collected along the West Coast.

While this is alarming, it's not yet reason to stop consuming seafood caught off the coast, said researchers. The radioactive materials are still more than 500 times lower than U.S. government safety limits for drinking water, and concentrations are too low to worry about swimming or boating.

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“These new data are important for two reasons,” said Ken Buesseler, director of the Woods Hole Center for Marine and Environmental Radioactivity. “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. 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.”

Though better contained today, the Fukushima plant continues to leak radioactive material into the ocean. Concentrations off the coast of Japan are 10 to 100 times higher than those off the U.S. coast.

“Levels today off Japan are thousands of times lower than during the peak releases in 2011. That said, finding values that are still elevated off Fukushima confirms that there is continued release from the plant,” explained Buesseler.