Higher radiation levels from Japan's 2011 Fukushima disaster have been detected off the coast of North American shores though scientists stress that the doses weren't high enough to pose any health risks.

(Robyn Beck/Getty Images)

Heightened measurements of radiation from the Fukushima nuclear disaster have been detected off the shores of North America, according to a by theWoods Hole Oceanographic Institution.

Multiple sites near the coast showed contamination from the nuclear accident in March 2011, indicating that that there was a continued release from the plant; however, the detectable levels of radioactive cesium isotopes were still deemed to be safe for human and marine health by the scientists conducting the study.

"So far the levels that we see are not at levels that would have a noticeable negative impact to marine life or humans,"observed Jay Cullen, marine chemistry professor at the University of Victoria’s School of Earth and Ocean Sciences. "It would be like if you dumped a big barrel of dye into a river; if you're standing down stream, you will see that contamination show up as a pulse, and see it pass by you."

Isotopes are still going into the ocean, Cullen said, with peak contamination levels expected in the next 6 to 12 months.

WHOI marine radiochemistKen Buesseler, who collected the data through a citizen science monitoring program called Our Radioactive Ocean, has that the doses of cesium detected were so low that you could swim in the ocean on the West Coast for six hours a day for a thousand years and get exposure much less than a single dental X-ray.

"That is not to say the dose is zero, but it is very small," Buesseler told weather.com. "... while I am concerned, and levels are increasing, what we measure on our side of the Pacific is small compared to off [the coast of] Japan and on land in Japan where health concerns are greater."

This infographic shows the location of seawater samples reviewed at the Woods Hole Oceanographic Institution. The white dots represent cesium-137, while cesium-134, seen in the yellow/orange dots, is an "indicator of contamination from Fukushima."

(Jessica Drysdale, Woods Hole Oceanographic Institution)

U.S. Nuclear Regulatory Commission spokesman Scott Burnell also said there was no need for Americans to worry.

"As the WHOI release correctly notes, the levels detected are 'more than 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,'" Burnell said. "The radioactive material is dispersed so widely across the Pacific that it is difficult to detect. That being said, both federal and state agencies test food to ensure Fukushima contamination does not affect public health in the United States."

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Despite the assurances of scientists and government officials, Kevin Kamps, a radioactive waste watchdog at the nonprofit Beyond Nuclear, an anti-nuclear advocacy group, is still concerned that the radiation levels in the ocean will have a negative impact on human health.

"I take exception to the notion that 'low-dose radiation' is somehow harmless," Kamps said.

Robert Peter Gale, a medical researcher who helped coordinate relief efforts after the Chernobyl disasterand co-author of the book Radiation: What It Is, What You Need to Know,told weather.com that while he agreed that any radiation should generally be avoided, the oceans are already radioactive to begin with. With the ocean diluting radiation's impact, the magnitude of the risk of harm from the Fukushima radiation was negligible, he said.

"The scientific consensus and operating procedure is to make the assumption that any level of radiation has the [potential] to cause cancer, but we have to distinguish that from 'what's the level of risk of harm?'" Gale explained. "I agree that any exposure has the potential to do harm; any level is potentially dangerous. But now when you put this all together, is the cesium that's in the ocean dangerous for those who go swimming? No. The level of risk is extremely small."

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