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.