7 March 2014, 06:14

Fukushima radiation monitoring: is the worst over?

Fukushima radiation monitoring: is the worst over?

"Since 2011 we were off the coast trying to assess some of the levels of different radio nuclides, the contaminants coming from Fukushima and then their fate in the ocean The worst has passed in terms of the immediate dozes," Ken Buessler, Scientist at Woods Hole Oceanographic Institution and Director of the Center for Marine and Environmental Radioactivity. 

Mr. Buessler has launched a crowd funded project to assess ocean contamination from the Fukushima Daiichi event.

As I understand, you are doing a research project off the coast of Japan. What are you looking for exactly?

Since 2011, as early as June we were off the coast trying to assess some of the levels of different radio nuclides, the contaminants coming from Fukushima and then their fate in the ocean – which ones move with the currents, which ones end on the seafloor and how much accumulates in the food chain.

What are the current research results? What have you found?

Well, certainly, the levels have decreased. I mean, we were amongst some of the first with our Japanese colleagues to say that there were still continued leaks on that site that we should be concerned about. But the worst reactions were in the early weeks to months after March 11 in 2011. A lot of the isotopes of concern with a longish half-life – cesium 137 and 134 – would be transported by those ocean currents into the Pacific. So, lower concentrations are further away you get from Japan.

So, if I understood you correctly, the worst has passed.

The worst has passed in terms of the immediate dozes. There were things like iodine 131 that has an 8-day half-life and of very much concern on land for things like thyroid cancer. But once those immediate short-lived decay products are gone, then you have these longer-lived isotopes and cesium became of concern because it was also accumulated in fish and caused the closure of fisheries in coastal Japan, the coastal waters near those reactor sites.

Has the sea life really been affected heavily by this radiation?

We are talking about closing fisheries because of the consumption of contaminants and internalizing them in our bodies. We are not talking about the health of the marina organisms. Now, at its peak, in early April, we were concerned there could have been reproductive mortality of marine life. That is when cesium was in… we are going to have to use some units here – becquerels – how many decays per second of cesium in a cubic meter of seawater. Those numbers were in tens of millions. They dropped down to the 1000-10,000 range pretty quickly. At that point it is safe to be on those waters or in those waters swimming, but perhaps not to eat the seafood. And that is kind of where it is lingering today, in the 100-1000 Bq per cubic meter range near Japan of cesium isotopes.

You mentioned that we could be swimming there, what about drinking the water itself? Would that affect our health?

The drinking water standard in Japan is about 10,000 in those same units. And so, again, we are talking about relatively low levels today, that the concern is not as much from our direct exposure in the ocean, but internalizing it and getting those, say, through seafood and other sources.

Using your studies, how much time will it take to recover from this contamination, if it is possible to recover at all?

That’s a good question. So, for the oceans –we are talking about currents. Those ocean currents mix the isotopes that are in the water across the Pacific. It is about 5,000 miles to the west coast of North America. And we just saw it in the sea, the front edge of that plum on the west coast, again, the concentrations are much lower than at the source. These things will be deluded along the way moving at the speed of ocean currents. That is where most of the radioactivity ends up. A fraction is in there by order and then they decay and die in the seafloor. A much smaller amount, but that’s more persistent, that is going to remain for decades near Japan until those isotopes decay.

If I understood your correctly, you are suggesting that the worst has passed in Japan, but now the radioactive plum is actually slowly migrating towards the west coast of America.

Correct! This we saw with debris, if you remember, a year plus ago. Debris moves with currents and it’s blown by the wind – a soccer ball and other trash on the surface. The currents themselves take a little longer to show up. And those follow the pathways that we know something about, but it is very hard to predict exactly what the concentrations will be on the west coast. By all predictions they will not be of human health concern on our coast of North America.

I’ve covered a lot of stories on this and I have to say that you are the most positive reporter that I’ve had. Thank you for joining us on the show.

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