Mark Horstman travels to Fukushima Prefecture in Japan to investigate where the radioactive fallout has travelled since the Daichi nuclear power plant accident over three years ago.
This was the profile of a recent ABC Catalyst documentary investigation on the aftermath of the Fukushima nuclear event. You can watch the 17 min report here.
An open letter to the ABC about Catalyst’s latest Fukushima piece
Geoff Russell, August 2014
Can anybody imagine ABC’s Alan Kohler without his graphs?
Can anybody imagine him leaving the units of measurements off his axes? Instead of ‘$’s, ‘percent’s or something similarly meaningful, what if he started labelling his X or Y axis as ‘wiggles’ or ‘puds’. I’d reckon the ABC would get more than a few complaints.
So why can Catalyst’s Mark Horstman cite radiation units, which are about as meaningful as ‘wiggles’ to most of the population, without explaining what they mean? Isn’t explaining stuff what science communication is all about?
Horstman recently presented a Radiation fallout Catalyst story about the long term radiation impacts of the 2011 Fukushima nuclear meltdowns. He opens with a statment about forest areas having a radiation count of 7 micro Sieverts per hour (uSv/hr).
Horstman could have explained what 7 uSv/hr means. I’m sure he knows. But the closest we got to any kind of information about this level was his claim that 5 uSv/hr was “50 times the maximum dose rate considered safe for the general public”. Without information about how risk changes as the dose changes, this is vacuous at best and misleading at worst. Taking a teaspoon of wine a day may be safe, but what about half a glass a day? That’s 50 times more than a teaspoon, but does it matter? Does raising a safe dose by 50 times make it low risk, high risk, deadly, or perhaps even make it beneficial? Maybe 50 times safe is still just safe.
And Horstman didn’t even get the numbers right. Let’s go through it slowly. Horstman could have got the Catalyst graphics team to do a nice little image. I’ll rely on words.
First, let’s convert the hourly rate to an annual rate so we can compare it to normal background radiation, which averages about 2.4 milli Sieverts per year (mSv/year). Background radiation varies from place to place but usually ranges from 1 mSv/year to around 7 mSv/year. If you were to lay on one of Brazil’s black monazite beaches 24×7, you could get a hefty 800 mSv/year. So 5 micro Sieverts per hour (uSv/hour) is 5 x 24 x 365 = 43800 uSv/year and since there are 1000 micro Sieverts per milli Sievert, this is 43.8 mSv/year. Divide this by the global average background level of 2.4 mSv/year and you get 18.25. So 5 uSv/hour is 18 times the global average background radiation level. Is Horstman telling us that the global average background level is dangerous? If he is, he’s simply wrong. How wrong? The background level of radiation in Finland is 7 mSv/year, much higher than in the UK where it’s below 2 mSv/year, but the cancer rate in Finland is actually a little lower than the cancer rate in the UK. So it seems reasonable to regard the Finnish background radiation rate as safe. Then since 5 uSv/hour is about 6 times higher than the Finnish background rate, I’d say it’s only 6 times higher than a safe rate.
But Horstman’s arithmetic mistakes are a minor matter. Whether it’s 6 times or 50 times greater than something that’s safe doesn’t tell us anything at all about how safe it is.
Is there any evidence that a level of radiation 18 times the global average is dangerous? Not that I know of. But there is certainly quite good evidence that it is harmless.
After the Fukushima meltdowns, researchers at MIT subjected mice to levels of radiation 400 times higher than the global average of 2.4 mSv/year for 6 months and found no effects. They estimated that this level of radiation caused about 12 extra pieces of DNA damage per cell per day in the DNA of the mice but pointed out that this is on top of the 10,000 pieces of normal damage which have nothing to do with radiation. Pedants will point out that background radiation will cause the occasional piece of damage. As far as the MIT researchers could tell, all the additional damage was repaired. We are talking about 1/10th of one percent extra damage here and that’s at a much, much higher radiation exposure rate than anything mentioned in Horstman’s story.
But mice aren’t people. Indeed. They get about twice as much cancer in their brief lifespan as we get in three score and ten. Which makes mice very poor predictors of what might cause cancer in people but pretty good predictors of what won’t.
But Horstman didn’t just muck up the math and not explain its significance, he also glossed over some significant details in inferring that people or animals could actually be subjected to the full force of this mildly elevated exposures.
One of Horstman’s interviewees tells us that “almost all” of the radiation in the streams is bound to clay and unavailable to the food chain. Furthermore, people living in an area generally spend considerable periods in buildings and vehicles and have little contact with the areas having the highest levels. So nobody will actually get the full 5 or 7 uSv/hr for all that many hours per year. The fact that Horstman didn’t take this into account when he was misleading people with talk about the dose being “50 times” a safe dose made it doubly misleading.
But I’m waiting for Catalyst to do a story about the health impacts of the Fukushima evacuation. When faced with a decision about whether to evacuate because of a chemical spill, radiation leak, flood or fire, it’s crucial to compare the risks due to an evacuation with the risks of staying in place.
Regular readers of BNC may recall the following details from previous posts of mine, but they are worth repeating for new readers and they are directly relevant to Horstman’s Catalyst piece.
After the meltdowns, people were evacuated from areas within a 20km radius of the reactors … and a few areas outside that. This is because of contamination … as Horstman states in his story. But does that make the evacuation justified? Or was it a supreme act of folly? Horstman doesn’t seem to care about this question. But it’s a real question. People have died and had their lives greatly disrupted. For what? Presumably to protect them from cancer due to radioactive contamination.
Suppose that instead of being evacuated to other parts of Japan, people were relocated to Australia. How would their cancer risk change and how does that change compare with the possible risks associated with no evacuation?
The cancer rate in Japan is about 200 per 100,000 per annum (age standardised to the world population). In Australia it’s 50 percent higher and the new arrivals would gradually adopt Australian lifestyle habits and their cancer rate would rise and approach that of Australians. So while there might be the occasional extra cancer in the next 30 years from radiation if people had not been evacuated, moving 100,000 people to Sydney and having them adopt an Aussie diet and lifestyle would have produced roughly 100 extra new cancers every year in that group.
Is there any evidence at all that residing in the Fukushima exclusion zone will raise cancer risk by that rate of about 50 percent? None at all. Is there any evidence that staying in the Fukushima exclusion zone was more dangerous than the hurried evacuation which killed people directly and shattered so many lives? None that I’ve ever seen, and I’ve been looking!
The available evidence (see for example Lancet study) is clear that the Fukushima evacuation (and clean-up) was and continues to be one of the biggest screw-ups by any Government in recent times.