# Appalling levels of radioativity at Fukushima!

According to the survey, 1.13 becquerels of caesium-134 per litre of urine were found in an eight-year-old girl – the highest reading for that isotope. The highest reading for caesium-137 – 1.30 becquerels – came from a seven-year-old boy, Kyodo news agency said.

Given that no one\’s rushed these kids into a lead lined ICU bed I assume that these aren\’t in fact very high levels.

And I\’ll also admit that I get very lost in these various radiation measurements. Rads, rems, becquerels, sieverts, there\’re grays and joules as well aren\’t there?

So, could one of you more mathematically inclined readers do me a favour and convert this into the banana equivalnet dose?

Since a typical banana contains about half a gram of potassium,[6] it will have an activity of roughly 15 Bq.

## 18 thoughts on “Appalling levels of radioativity at Fukushima!”

1. I learned this stuff in millirems, and when I looked at it again years later the bastards had changed it all without consulting me.

2. By the by, I am a victim. I started my desensitisation-to-radioactivity programme by eating bananas and Brazil nuts, only to find that I have somehow become allergic to Brazils. It’s a protein problem, apparently.

3. Further bying: this protein problem isn’t mentioned in the Wikipedia entry – I found out about it in Jim Watson’s book on DNA.

4. Surely,

If 1 BED = 15 Bq,
0.09 BED = 1.30 Bq

Rads, rems, becquerels, sieverts, there’re grays and joules as well aren’t there?

Measuring different things.

5. The Becquerel is the decay rate metric for radioactivity. 1.3Bq means 1.3 decays per second.

This doesn’t correspond directly to the biological effects (measured in Sieverts) because that depends on the nature of the emission (alpha, beta, or gamma), the location at which the emission occurs (alpha outside the body irrelevant – inside the body devastating, beta slightly worse outside, gamma more or less irrelevant), and the emission energy (can vary considerably between isotopes emitting the same type of particle).

Anyways, 1.3Bq, I’m astonished they managed to detect that above background. My guess is they mass-specced urine samples and calculated the Bq per unit volume of urine based on the number of atoms of Cs134 detected.

Off the top of my head, this is an absolutely trivial quantity and noteworthy only because the only possible source is human nuclear activity.

6. Of course talking about 1.3 “Becquerels” is just woo. It sounds far more scary than using conventional units that people are actually familiar with.

The conversion to familiar units yields:
2.7 x10^-14 grams.

Which still looks scary to the average journalist or other typical innumerate.

Does anyone feel like converting that into a Systeme Internationale des Unites Populaires number? What’s the mass equivalent for the “N football pitches”, ” N empire state buildings” and so on?

7. What’s that in Olympic Sized Swimming Pools, or Football Pitches?

8. JamesV @7,

I’d say a bag of sugar is a Systeme Internationale des Unites Populaires unit, but even a grain of sugar is too many orders of magnitude heavier to understand. Perhaps a comparable mass to a Escherichia coli bacterium?
http://en.wikipedia.org/wiki/Escherichia_coli

Oh wait, no-one likes E.Coli, do they?

OK, ‘a 1000th of an average human cell’…

9. 1 Becquerel = 1 nuclear disintegration per second

From Jacob Shapiro, Radiation Protection, 2nd. ed., (Harvard University Press, Cambridge MA, 1981), as quoted in Harvard Natural Sciences Lecture Demonstrations, Radiation and Radioactive Decay

“There are 1.2 radioactive atoms of 40K for every 10,000 nonradioactive atoms of potassium. There is of the order of 140 g of potassium in an adult who weighs 70 kg, and 0.0169 g consists of the 40K isotope. This amount of 40K disintegrates at the rate of 266,000 atoms per minute.”

266,000 disintegrations per minute = 4,430 Becquerel.

So in the highest case, the boy with 1.3 Bq per litre of urine, that amount is about 0.03% of an adult’s natural level of radioactive potassium.

Next question: are 40K and 137Cs equally harmful?

137Cs gives mostly gamma rays with an energy of 662 keV. 20K gives mostly beta particles with a maximum energy of 1.33 MeV (1330 kEV), with abour 10% as 11.46 MeV gamma rays. So, your nice natural 40K is more energetic and so more harmful in its decay than nasty manmade 137Cs.

Interesting fact: Bordeaux wine from the early 60s, the time of big nuclear tests, may have over 1 Bq/litre of 137 CS, comparable to the Japanese levels that are given so much prominence. See http://www.cenbg.in2p3.fr/heberge/DDV/Wine_dating2.pdf

10. How many Waleses are in a War and Peace?

11. There are a couple of Waleses in Canada at the mo.

Sorry.

12. Yeah, but that potassium is natural. Innit?

To be completely fair to the woo merchants we’d also need to look at the pharmacokinetics of cesium – basically how much is in the body and how long it stays there. Excreted (urine) levels might not be that informative, but no one is likely to volunteer for brain, testicle, and so on biopsies for the stuff.

13. James V: biological half-life of caesium is about 70 days. See
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/biohalf.html#c2

That’s rather more than double the half-life of potassium. Caesium is in the same periodic table group as potassium and sodium, but it’s heavier, which may account for the longer half-life in the body. Like K and Na it’s very soluble and doesn’t accumulate in bone: soft tissue concentrations are unlikely to be enormously higher than urine levels (depends on how much the boy had been drinking, I suppose)

14. I still think we should all avoid drinking wee wee to be on the safe side. I know it’s a grinding hardship, but I propose we should all just drink whisky for the foreseeable future.
You can’t be too careful…..

15. Dunno about that. Better stick to whiskey. Malt is manufactured in the highly radioactive conditions of the highlands.

16. Does anyone feel like converting that into a Systeme Internationale des Unites Populaires number?

Yes: slightly more than a Fanny’s Hair but less than a Gnat’s Bollock.