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Scientists have been urging the Japanese government to slowly release tritium-contaminated water from the Fukushima accident into the Pacific Ocean over about a ten-year period. The water is stored on-site in 900 or so large tanks. All of the other radioactive elements have been removed from the water by chemical treatment.

Although not intuitive, this is a very good idea.

Tritium is the mildly radioactive isotope of hydrogen that has two neutrons and one proton, with radioactivity so low that no environmental or human problems have ever come from it, even though it is a common radioactive element in the environment. Tritium is formed naturally by atmospheric processes as well as in nuclear weapons testing and in nuclear power plants.

Tritium is assumed to be carcinogenic to humans at extremely high levels, although that claim is only hypothetical since adverse health effects from tritium have never appeared in humans or in the environment. Only laboratory studies on mice at extremely high levels have shown any adverse health effects and they were not fatal, even after ingesting 37,000,000 Bq/L.

Putting this water into the ocean is without doubt the best way to get rid of it. Concentrating it and containerizing it actually causes more of a potential hazard to people and the environment. And is really expensive.

Unfortunately, the idea of releasing radioactivity of any sort makes most people cringe. But that’s the problem, only the perception of tritium is bad, not the reality. And in our new world of anti-science, such a wrong idea might rule over what is the right thing to do, wasting precious resources and time.

The scientific reality is tritium emits an incredibly weak beta particle that is easily stopped by our dead skin layer. It only goes a quarter inch in air. Even ingestion of tritium doesn’t do anything unless it’s at very high concentrations that can only be maintained in the laboratory.

The health risks of tritium-contaminated water are so low that all countries of the world have no idea what regulatory limits to put on it.

Using Becquerel per liter as the concentration unit (a Bq is a disintegration of a single nucleus per second), the United States has set 740 Bq/L for drinking water, but Canada has 7,000 Bq/L as its limit. Switzerland set 10,000 Bq/L, and Australia a whopping 76,103 Bq/L.

But these limits were just taken out of thin air. They are not health-based. They were chosen because they were easy to achieve.

Meaning none of these levels, or a hundred times these levels, are harmful. Even though more tritium has been formed in the last 60 years than all other radionuclides combined, there has never been a correlation of tritium with cancer or any other health effects in humans.

Why is this the case?

Hydrogen is a really small atom and easily gets through microscopic pores, even biological membranes and cell walls. Tritium (still hydrogen just heavier) can be found in water molecules (since water is two hydrogen atoms and one oxygen atom) and in organic materials which are mainly hydrogen and carbon.

In fact, because tritium is three times heavier than normal hydrogen, tritium tends to replace normal hydrogen in water molecules, rapidly diluting any tritium in our bodies and in the environment.

Our bodies are mostly hydrogen, and that is mostly in water. So while tritium’s radioactive half-life is 12.3 years, its biological half-life in our bodies is only 10 days. Therefore, ingestion of this weak emitter doesn’t have the same effect as most other ingested radionuclides.

It’s also difficult for the extremely low-energy beta from tritium to get through the water, cell walls and other materials in between the radionuclide and any DNA. The energy in the slow-moving beta from tritium mostly gets dispersed within the electron clouds of other molecules through inelastic collisions and the Bremsstrahlung effect. This turns the kinetic energy of the beta emission into electromagnetic non-ionizing energy.

In the end, it’s really difficult to get a large radiation dose from tritium, unlike any other radionuclide. It exits the body and is diluted too quickly.

Even more important, there’s more tritium in the atmosphere from natural processes and left over from old bomb testing, than ever has been, or will be, released from commercial reactors. Cosmic rays produce four million curies worth of tritium every year (150,000,000,000,000,000 Bq) in the upper atmosphere, much of which rains out into surface waters that we end up drinking.

Presently, however, the biggest source of tritium is from old above ground nuclear bomb tests that caused a peak in atmospheric tritium in 1963.

These amounts of tritium from other sources are millions of times greater than what would be slowly released from these tanks at Fukushima. Since there’s been no health or environmental effects from any of these larger sources, it’s hard to get excited about dumping such a tiny amount from Fukushima into the ocean.

Besides, there are 16,280,000,000,000,000,000,000 Bq of potassium-40, rubidium-87 and many more radionuclides already in the world’s oceans. So the fish are swimming in plenty of natural radioactive material.

The biological half-life of tritium in fish and marine life is even shorter than in humans, less than 2 days and the dilution in seawater would be too rapid for any significant dose to get back to any people.

Opposite to many other radionuclides, the physical and chemical properties of tritium means it does not concentrate up the food change, it dilutes up the food chain. So while Japanese fishermen fear this strategy of release from a public relations perspective, their fish will still test negative with respect to food radiation limits and their packaged fish sold at market would still carry the official ‘safe’ stickers.

So it all comes down to perception and fear. We as scientists can give you the answers, but you can ignore them if you want, especially since non-scientists make these decisions anyway.

This particular problem with Fukushima is really important because Japan needs to restart most of their reactors that were shut down after the earthquake in 2011. They were not affected by the quake or the tsunami that followed, and wouldn’t be by future ones, and are critical to addressing global warming, not to mention the country’s economic doldrums.

All climate scientists agree that continuing and expanding nuclear power is essential to stemming the worst of global warming. Japan was once at the forefront in the fight against global warming but their carbon emissions have skyrocketed since the output from their nuclear plants were replaced by fossil fuels.

Although some reactors are being restarted – just this week the Governor of Japan’s Fukui Prefecture approved the restart of units 3 and 4 at their Ohi nuclear power plant – the number has been small. Nineteen of 42 operable reactors have applied for restart, but only five have actually restarted.

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