TOKYO — Most scientists who have been monitoring activity at the Fukushima Dai-ichi power plant say the current radioactive outflows do not pose a significant health risk beyond the surrounding prefecture and its waters — but a lack of data on some isotopes and an uncertain containment solution have those scientists less sure about the long-term risks.

Since the announcement of a 300-ton leak of radioactive water at the plant earlier this month, the Internet and social media have been abuzz with rumors that the leaks have contaminated water and rendered all seafood in the Pacific Ocean inedible, among other claims.

There are some studies suggesting that any radiation is harmful. If that is the case, there is nothing that can be done to avoid it entirely.

There is low-level radiation found in the air, soil and water throughout the planet. People absorb more of it on airplanes and during doctor’s visits. Bananas and anything else with the essential nutrient potassium contain a dash of unstable potassium isotope, which most scientists say is harmlessly excreted.

It is also true that some isotopes created by man-made endeavors pose a greater threat to human health than others.

The majority of Japanese and international scientists, who believe that tiny amounts of radioactivity in its most common forms do not pose a threat to most people, say the groundwater and seafood found outside of the affected area is safe to consume.

Tokyo posts daily ambient radiation readings and weekly, bilingual results of water testing from several groundwater. Radioactivity levels in the Tokyo water supply haven’t been deemed dangerous since the weeks following the March 11, 2011, earthquake and tsunami that spawned Fukushima’s problems, when testing briefly found Iodine-131 at unsafe levels for young children.

The U.S. military, which operates its own water systems on its bases in Japan — based on U.S. Environmental Protection Agency standards — says it has not found any elevated radionuclide levels in its drinking supplies.

Several bases in Japan include water confidence surveys on their public websites, though the surveys contain little testing information on the radioactive isotopes commonly found at the Fukushima site.

“More specifically to our installations, all of them conduct regular extensive testing as part of their normal procedures, just as we do at every military installation in the world,” Lt. Col. David Honchul, spokesman for U.S. Forces Japan, said in a statement to Stars and Stripes. “These routine requirements include testing for radionuclides. All the installations have tested within the last 15 months, and the drinking water remains completely safe.”

Since the partial nuclear meltdown at Fukushima, the Japanese government revised testing standards for seafood, which outside observers say appears to be working well.

The government allows cesium levels of up to 100 becquerels per kilogram of wet weight in seafood, a standard it lowered from 500 becquerels per kilogram in 2012. The figure is 12 times more strict than the U.S. cesium allowance in seafood.

“It’s hard to imagine that seafood [in Japan], which has been monitored properly and is in the market, is dangerous,” Minoru Takata, director of the Radiation Biology Center at Kyoto University, told Stars and Stripes.

A becquerel is a measurement of the decay of an isotope. While cesium is harmful to health, most scientists say levels in migratory fish diminish rapidly as they traverse the ocean.

Ken Buesseler, senior scientist at the Woods Hole Oceanographic Institution, concurred during a recent interview with Australia Broadcasting Corp.

Buesseler has examined the waters and marine life around Fukushima extensively, along with other international scientists. The teams found little radioactivity beyond Fukushima’s nearshore waters.

“What happens within even a few kilometers, you get 10 or 100 times less,” Buesseler said. “You go out several 100 kilometers offshore, the concentrations are lower.”

There are about 136,105,938,346,000,000,000 tons of water in the world’s oceans, half of which are in the Pacific, according to the National Oceanic and Atmospheric Administration.

Tepco estimates that 1,000 tons of groundwater flow into the area each day, 400 tons of which flow into the reactor buildings, according to a Wall Street Journal report.

Even assuming a rate of 1,000 tons of contaminated water rushing into the ocean for 800 days, radioactive outflows would make up 0.0000000000005 percent of the world’s oceans.

Most of the Iodine-131 has a half-life of only eight days, while much of the cesium has settled on the sea bottom near the plant, according to surveys conducted by Woods Hole and other international scientists. Local fish harvested from the region since the 2011 disaster are not allowed to be sold for local consumption. Instead, catches are sent to nearby laboratories where the radiation levels are tested.

But those radiations levels in fish are not being seen elsewhere: Buesseler also told ABC Australia radio that while a bluefin tuna containing cesium had been reported off the coast of Santiago, Chile, the levels were non-threatening and much lower than fish found near Fukushima.

The most recently discovered leaks at Fukushima Dai-ichi “will not cause immediate health damage,” Takata added. “The bigger problem is how they can contain the leakage in the future.”

Here’s the bad news

The radioactive outflows aren’t under control, according to the plant’s operator, and plans are now being discussed to create a permafrost wall in an effort contain the leaks.

Meanwhile, recently identified concentrations of the strontium-90 isotope at the site may eventually pose danger to seafood on some scale, if future data finds it accumulating in the ocean, according to Buesseler and others.

The initial 300-ton leak from a container identified earlier this month by Fukushima operator Tokyo Electric Power Co., commonly known as Tepco, was only the tip of the problem.

There are roughly 1,000 of these tanks holding about 335,000 tons of contaminated water — and Tepco thinks the container seals may be faulty, according to a New York Times report.

But leaky tanks aren’t even the biggest problem. That distinction goes to gravity.

The former nuclear power plant is now a disturbingly efficient contaminated water generator. Every day, hundreds of tons of groundwater flow downhill into the plant’s contaminated vessels and unsealed basements, then leak into the ocean.

Scientists have known this for a long time, Buesseler told several media outlets — it just took Tepco this long to admit it.

The Japanese government is finally divesting Tepco of its authority, officials said recently.

“We’ve allowed Tokyo Electric to deal with the contaminated water situation on its own, and they’ve essentially turned it into a game of ‘Whack-a-Mole,’ ” Trade Minister Toshimitsu Motegi told reporters Sept. 26 in Fukushima, according to Bloomberg News. “From now on, the government will move to the forefront.”

On Tuesday, Japan announced it would spend 47 billion yen ($472 million) on containment, of which, 32 billion yen would be spent constructing a nearly mile-long permafrost wall, a trade ministry official confirmed with Stars and Stripes.

Ground freezing is an old technology and it was used successfully to contain radioactive waste by U.S. contractors working with Oak Ridge National Laboratory in the 1990s.

However, Japanese officials have conceded that the technology has never been maintained on such a large scale.

While Japan works on a solution, scientists say concentrations of some relatively ignored isotopes now deserve much closer watch.

Strontium-90, which has a half-life of 29 years, has been reported near the reactors on land in recent months, though what little data there is on the isotope hasn’t shown it much beyond the site.

It was found in very low levels on land last year. Unlike some of the other isotopes released, strontium accumulates like calcium in bones and stays there, Buesseler said. It also transfers easily to from fish to humans. Buesseler and other researchers remain concerned about its potential spread into the ocean.

On Friday, Japan’s Nuclear Regulation Authority will convene a panel to study the effect of strontium, tritium and other isotopes on marine life.

Among the 106,183 people who still live in temporary housing areas on the outskirts of the Fukushima exclusion zone and beyond, it’s hard to find anyone surprised by the recent news of leaks. Many stopped believing anything the government or Tepco said years ago. In a temporary housing block in Minamisoma, nearly everyone has been drinking bottled water for years, despite reports that the groundwater was safe.

Hiromi Matsumoto, who has lived in temporary housing since June 2011, said any decontamination done on land could be upended if the plant can’t be contained.

“I want to be hopeful,” Matsumoto told Stars and Stripes in a phone interview. “But when I have high expectations and nothing happens, it’s greatly disappointing. So, I don’t want to have high expectations.”

Stars and Stripes reporter Hana Kusumoto contributed to this report.

slavin.erik@stripes.comTwitter: @eslavin_stripes

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