New research has found that radiation from the 2011 Fukushima nuclear accident in Japan has reached more sites in the waters off the coast of North America.
The Woods Hole Oceanographic Institution has found the highest level of contamination at a monitoring site about 1,600 miles west of San Francisco, with the sample returned as being 50 per cent higher than other samples.
However the level of radiation is still 500 times lower than the U.S. government safety limit for drinking water. There is also no concern for boating or swimming within the Pacific Ocean.
On March 11, 2011, a magnitude-9 earthquake struck off the coast of Japan, triggering a tsunami, killing more than 10,000 people and leaving hundreds of thousands homeless.
The massive earthquake also damaged the Fukushima Dai-ichi nuclear power plant, causing three cooling systems to fail which resulted in partial meltdowns of some fuel rods. Contamination leaked out of the plant. That contamination has been carried along currents in the Pacific Ocean.
In 2012, Fukushima radiation was first detected 1,500 km off the coast of British Columbia.
Though the contamination is of concern, the levels are still eight to 10 fold less than when nuclear weapons were being tested in 1960s. And, according to Fukushima InFORM, a Canadian-based monitoring organization, the levels do not pose a risk to public health or the ecosystem.