I’ve been receiving questions from concerned friends and family about how radiation from the Fukushima Dai-ichi nuclear power plant is affecting the marine environment and human seafood consumption. As ocean lovers, I’m sure you’re equally concerned. After reading different scientific articles and speaking with experts, I found that there are local impacts from radiation to humans and marine life around Fukushima – but impacts from radiation on the rest of the Pacific Ocean are not expected to be harmful to human consumers and marine animals.

Human tragedy and nuclear power plant meltdown

The Tōhoku earthquake and tsunami in Japan in March 2011 was a human tragedy, killing at least 15,550 people and displacing more than 130,000 people. Economic losses caused by the magnitude-9.0 earthquake and the resulting tsunami in Japan came to $210 billion, making it the costliest natural catastrophe of all time. This event also triggered the Fukushima Dai-ichi nuclear power plant meltdown, creating a radiation scare around the world. The plant released radiation from:

• atmospheric deposition due to the meltdown during mid-March 2011;
• direct discharge from the plant;
• river runoff; and
• contaminated underground water flow.

The latter three sources are now small and continuous sources of input. These pathways introduced mostly iodine-131, cesium-137 and cesium-134 but also low levels of tellurium, uranium and strontium to the area surrounding the power plant.

Local radiation impacts: fishery closures, leaking storage tanks, elevated cancer rates

Radiation from the plant is impacting the area near the disaster. In local coastal waters and bottom sediments near Fukushima, cesium levels for certain marine life, such as bottom-dwelling fish, have been above the Japanese government’s limits for seafood and have prompted local fishery closures and nearby countries to ban importing fish caught near Fukushima. Direct exposure to leaking nuclear waste storage tanks is causing health problems among plant workers. The power plant meltdown also likely caused higher rates of certain cancers – which will unfold in the years to come – in local residents.

Distant radiation impacts: no harm likely to marine animals and human consumers of seafood

The implications for the larger Pacific Ocean, however, will be much less deleterious. In the Pacific Ocean, currents, eddies and other physical ocean dynamics dilute radiation from Fukushima, making these concentrations much lower in the ocean with distance and time. While the overall concentration of radionuclides will increase in the Pacific Ocean from pre-Fukushima levels, the increased levels will not likely be enough to be harmful to marine animals and human consumers outside the local area.

For example, migratory Pacific bluefin tuna, traveling from Japan to California, had elevated radiation levels of cesium-134 in 2012, a year after the Fukushima accident, but these levels were below safety guidelines for public health and less than half those from 2011.

To understand health risks, scientists also calculated that the additional dose from Fukushima radionuclides to humans consuming tainted Pacific bluefin tuna in the United States was 0.9 and 4.7 μSv for average consumers and subsistence fishermen, respectively. Such radiation doses are comparable to, or less than, the dose all humans routinely obtain from naturally occurring radionuclides in many food items, medical treatments or air travel. (From a sustainable seafood perspective, Monterey Bay Aquarium Seafood Watch recommends avoiding bluefin tuna since they are being caught faster than they can reproduce.) With more scientific research, we can better understand how radioactivity from Fukushima will affect marine life and the food chain.

Dr. Ken Buesseler, senior scientist at Woods Hole Oceanographic Institution, has been studying the spread and impacts of radiation from Fukushima into the Pacific Ocean. He has an analogy to help understand the movement of Fukushima-derived radiation as it enters the ocean:

“The spread of cesium once it enters the ocean can be understood by the analogy of mixing cream into coffee. At first, they are separate and distinguishable, but just as we start to stir the cream forms long, narrow filaments or streaks in the water. The streaks became longer and narrower as they moved off shore, where diffusive processes began to homogenize and dilute the radionuclides. In the ocean, diffusion is helped along by ocean eddies, squirts, and jets that broaden, mix, and continue to dilute the cesium as it travels across the ocean. With distance and time, radionuclide concentrations become much lower in the ocean, something that our measurements confirm.”

For more information regarding the Fukushima nuclear power plant and radiation, check out Woods Hole Oceanographic Institution’s special series on Fukushima. For more information on sustainable seafood choices, visit Monterey Bay Aquarium Seafood Watch.