Fukushima Radioactive Ocean Leak Biggest in History

As runoff of contaminated water continues to wash into the sea, the damage is not over.

Volunteers of a group from Hiroshima City work to remove radioactive substances from a fishing boat in Minamisoma, Fukushima Prefecture, October 24, 2011. (Photo: Kyodo/Reuters)

A six-time grantee of the National Geographic Expeditions Council, Jon writes about all things ocean.

It is difficult these days, when one disaster leads to the next, to keep track of statistics, whether it’s an earthquake or hurricane, wildfire or tsunami. The numbers of lives lost, buildings destroyed, homes flooded, etc., all tend to blur together.

In the nearly eight months since the 9.0 magnitude earthquake/tsunami rocked Japan in March, these are numbers we know for certain: Dead (15,813); injured (5,940); still missing (3,971).

But a more elusive if no less alarming stat was reported yesterday by the Institute for Radiological Protection and Nuclear Safety (IRSN): Based on figures gathered from a worldwide network of sensors, the leak of the Fukushima nuclear plant was the #1 single nuclear contamination of the ocean ever.

The threats to marine life and man will take a long time to accurately assess. Much of the most-dangerous caesium 137 that leaked into the Pacific is thought to have been diluted by ocean currents and pose “no discernible threat.” Yet at the same time it is said to be a “slow-decaying” element, taking 30 years to lose half of its radioactivity, so the potential for long-term harm is still strong.

Researchers at the Japanese government’s Meteorlogical Research Institute and Central Research Institute of Electric Power Industry suggest another long-term disaster in the making, one not limited to Japan. They describe how the radioactivity leaked into the ocean is likely to live in the northern Pacific currents for the next 20 to 30 years, eventually circulating back to the coastline.

How big was the leak into the ocean? Twice what Japanese authorities had previously estimated and twice the concentration that made its way into the ocean during all of the atmospheric nuclear testing done around the globe in the 1960s.

The biggest contributor was not a direct leak into the ocean from the damaged reactors but as part of the fresh water that was pumped into them in an effort to cool them down. Though 82 percent of the polluting radioactivity entered the sea before April 8, there is still daily leakage into the ocean due to the continued runoff of contaminated water from around the damaged nuclear plant. The study also found large quantities of iodine 131 in the water, though suggested it poses little concern in that its half-life is just eight days.

The report mimics studies done soon after the Gulf oil spill in 2010, when it suggests the “long-lasting impact” of the radioactivity on marine life will be limited while at the same time admitting that the big, deep-water fish at the top of the food chain and filter-feeding mollusks are the most at-risk.

Similar to the Gulf spill too, since this is the biggest such spill in history, no one has real-life experience at judging just how harmful it may be to the marine ecosystem over time.

...since this is the biggest such spill in history, no one has real-life experience at judging just how harmful it may be to the marine ecosystem over time.

Japanese residents are clearly concerned about both the radioactivity leaked into the land and sea and its government’s forthrightness about the potential harms. On land, radiation hotspots continue to be identified even as government officials say they do not pose health risks. Yet many of the contaminated areas on land will need to be stripped of all topsoil and be uninhabitable for decades.

The Fukushima plant itself, say government spokesmen, is stable; critics warn that is an optimistic view, that the continued melting of cores and cracks in containment structures make for lots of unknowns.

One thing the Japanese government will confirm is that the size of the contaminated area, on both land and sea, “may increase in the future.”

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