While doing some research on Thorium, I came across this interesting little fact that I wasn’t familiar with, so I thought I’d pass it along. Many people fear radiation, sometimes the fear is irrational, based on the erroneous concept that we live in a “radiation free lifestyle”. I’ll never forget one time when I showed my geiger counter to a neighbor who was shocked when it started clicking. She was horrified to learn that cosmic rays were in fact zipping right through her body right that very second. I didn’t have the heart to tell her about neutrinos.
But, along the same lines, this little factoid might drive some people “bananas” when they read it. But, it illustrates a fact of life: radiation is everywhere.
A banana equivalent dose is a concept occasionally used by nuclear power proponents[1][2] to place in scale the dangers of radiation by comparing exposures to the radiation generated by a common banana.
Many foods are naturally radioactive, and bananas are particularly so, due to the radioactive potassium-40 they contain. The banana equivalent dose is the radiation exposure received by eating a single banana. Radiation leaks from nuclear plants are often measured in extraordinarily small units (the picocurie, a millionth of a millionth of a curie, is typical). By comparing the exposure from these events to a banana equivalent dose, a more intuitive assessment of the actual risk can sometimes be obtained.
The average radiologic profile of bananas is 3520 picocuries per kg, or roughly 520 picocuries per 150g banana.[3] The equivalent dose for 365 bananas (one per day for a year) is 3.6 millirems (36 μSv).
Bananas are radioactive enough to regularly cause false alarms on radiation sensors used to detect possible illegal smuggling of nuclear material at US ports.[4]
Another way to consider the concept is by comparing the risk from radiation-induced cancer to that from cancer from other sources. For instance, a radiation exposure of 10 mrems (10,000,000,000 picorems) increases your risk of death by about one in one million—the same risk as eating 40 tablespoons of peanut butter, or of smoking 1.4 cigarettes.[5]
After the Three Mile Island nuclear accident, the NRC detected radioactive iodine in local milk at levels of 20 picocuries/liter,[6] a dose much less than one would receive from ingesting a single banana. Thus a 12 fl oz glass of the slightly radioactive milk would have about 1/75th BED (banana equivalent dose).
Nearly all foods are slightly radioactive. All food sources combined expose a person to around 40 millirems per year on average, or more than 10% of the total dose from all natural and man-made sources.[7]
Some other foods that have above-average levels are potatoes, kidney beans, nuts, and sunflower seeds.[8] Among the most naturally radioactive food known are brazil nuts, with activity levels that can exceed 12,000 picocuries per kg.[9][10]
It has been suggested[11] that since the body homeostatically regulates the amount of potassium it contains, bananas do not cause a higher dose. However, the body takes time to remove excess potassium, time during which a dose is accumulating. In fact, the biological half-life of potassium is longer than it is for tritium,[12][13] a radioactive material sometimes leaked or intentionally vented in small quantities by nuclear plants. Also, bananas cause radiation exposure even when not ingested; for instance, standing next to a crate of bananas causes a measurable dose. Finally, the banana equivalent dose concept is about the prevalence of radiation sources in our food and environment, not about bananas specifically. Some foods (brazil nuts for example) are radioactive because of radium or other isotopes that the body does not keep under homeostatic regulation.[14]
- ^ http://www.ehs.unr.edu/ehs/LinkClick.aspx?fileticket=EgZI00myQRM%3D&tabid=62&mid=615
- ^ Weston, Luke. (2007-07-25) banana dose « Physical Insights. Enochthered.wordpress.com. Retrieved on 2010-10-19.
- ^ CRC Handbook on Radiation Measurement and Protection, Vol 1 p. 620 Table A.3.7.12, CRC Press, 1978
- ^ Issue Brief: Radiological and Nuclear Detection Devices. Nti.org. Retrieved on 2010-10-19.
- ^ Radiation and Risk. Physics.isu.edu. Retrieved on 2010-10-19.
- ^ A Brief Review of the Accident at Three Mile Island
- ^ Radiation. Risks and Realities, US Environmental Protection Agency
- ^ [1][dead link]
- ^ Brazil Nuts. Orau.org. Retrieved on 2010-10-19.
- ^ Natural Radioactivity. Physics.isu.edu. Retrieved on 2010-10-19.
- ^ Bananas are radioactive—But they aren’t a good way to explain radiation exposure. Boing Boing. Retrieved on 2010-10-19.
- ^ Rahola, T; Suomela, M (1975). “On biological half-life of potassium in man”. Annals of clinical research 7 (2): 62–5. PMID 1181976.
- ^ Environmental Health-Risk Assessment for Tritium Releases at the NTLF at LBNL: Chapter 2. Lbl.gov. Retrieved on 2010-10-19.
- ^ Brazil Nuts. Orau.org. Retrieved on 2010-10-19.
Hi Leg (and Mods.)
Thanks for spotting the “deliberate” mistake! (It was after midnight, my time.)
My (admittedly LONG) explanation overlapped a number of different posts with good comments. The delay in moderation didn’t help (NOT, please NOT a complaint to the Mods. who do an excellent job but the unavoidable delay means that a lot can happen between comments).
I worked in a civil nuclear power plant as an industrial chemist and all of this sits well with the Radiochemistry I learnt and re-learnt during my education and my career. I am a strong believer that I you cannot explain something, you don’t understand it
Let’s not forget the oh so common radioactive exit signs. 🙂
http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/fs-tritium.html
Russ says:
February 17, 2011 at 6:41 am
Interesting twist on our being bathed in radiation. My only quarrel with the post is the application of a linear, no-threshold (LNT) to cancer risk from radiation exposure. The 2 NCRP members that were on my doctoral committee didn’t agree with that concept at low doses.
Agree strongly, the LNT theory of carcinogenesis is very much in the same category of politically driven pseudoscience as CAGW (carbon-dioxide anthropogenic greenhouse warming). It is deeply reductionist and inductive, built primarily on mathematical / computer modelling, is false, and exists to serve a political objective.
In the very lowest dose range of ionising radiation, there is more evidence for a slightly health positive effect of radiation than of any carcinogenic (or any other such as mutaenic) risk. You cant extrapolate from the petri-dish to the organism any more than you can from a computer model to the global climate.
The LNT theory of carcinogenesis for low dose radiation would be difficult to prove because of other factors at those levels. But cells are complex and sensitive to DNA damage. If the organism is lucky, an overly damaged cell will die by apoptosis or other programmed cell death with no further damage done. If not, then possibly a tumor or cancer will arise from one or more cells run a muck. There are many, many known and proven carcinogens from simple physical irritation to chemical and radiation. Therefore it just appears logical to me that based on the mechanisms of cell DNA damage involved that one should not go out of the way to cause that damage. This includes smoking, playing with asbestos, benzene, radium, the sensor in a smoke detector, or getting unnecessary X-rays/CAT scans. Of course there are exposures that can’t be entirely avoided, food aflatoxins (although it wouldn’t hurt to eat less peanut butter and corn), mercury from coal ash or large fish, breathing the portion of gasoline vapors that contain benzene, and radioactive compounds in food.
Sometimes a paycheck requires that one be exposed to some radiation or other hazards such as those people in the nuclear arms industry. But this is the reason the technicians go away from the X-ray machine in a dentist or doctors office as there is no benefit/reward to the excess exposure and the harm can be catastrophic.
I reiterate, that unlike AGW which can, if it exists, be adapted to, the consequences of loose thinking about hazardous substances, including radiation, can be quite lethal in the long run depending literally on your luck.
Boris G.;
Perhaps the reason the radiation benefit study hasn’t received much publicity is indicated by scanning the list of co-authors: it is considered sort of ‘Wu, Wu’.
😉
And it shows many of the commenters here are still in the grips of reflex rad fear. The real point of this posting is that avoiding radiation is an exercise in foolish futility in all but exceptional cases.
P.S. re my above, the phlogiston comment is a kind of demonstration: “In the very lowest dose range of ionising radiation, there is more evidence for a slightly health positive effect of radiation than of any carcinogenic (or any other such as muta[g]enic) risk.”
Up to 100mG/y, with a 97% reduction of cancer incidence, is hardly “the very lowest dose range” with “a slightly health positive effect”. It’s strong moderate exposure, with overwhelmingly positive health effect.
A banana a day hardly makes a dent! Even a dozen a day wouldn’t be enough.
🙂
@ur momisugly Brian H.
You might be interested in this:
http://www.phyast.pitt.edu/~blc/LNT-06 fig.rtf
Which would indicate that low or even moderate levels of radiation MAY reduce cancer risk through a proposed increased immune function by stress resulting from radiation damaged cells perhaps similar to “Coley’s Toxins”.
http://en.wikipedia.org/wiki/William_Bradley_Coley
However, I would (personally) think it more logical to produce this stress through exercise or to increase cell repair efficiency with herbal supplements/vitamins rather than whacking cells with atomic bullets or bacterial poisons and hoping the immune system kicks in enough to kill cancer cells too.
Interestingly many commenter’s will argue for ignoring controllable exposure to radiation or even for intentional exposure but I have found few people to date that will try the following even though it appears to have a dramatic affect on some immune system diseases:
http://en.wikipedia.org/wiki/Helminthic_therapy
I guess radiation is psychologically less repugnant than worms.
Brian H says:
February 19, 2011 at 2:56 pm
P.S. re my above, the phlogiston comment is a kind of demonstration: “In the very lowest dose range of ionising radiation, there is more evidence for a slightly health positive effect of radiation than of any carcinogenic (or any other such as muta[g]enic) risk.”
Up to 100mG/y, with a 97% reduction of cancer incidence, is hardly “the very lowest dose range” with “a slightly health positive effect”. It’s strong moderate exposure, with overwhelmingly positive health effect.
A banana a day hardly makes a dent! Even a dozen a day wouldn’t be enough.
🙂
Thanks for correcting my typo – or mutation – of mutagenic!
Yes indeed I rather understated the case for hormesis (I’m British so understatement is probably genetic) – but a few minutes on PubMed central will produce many papers showing consistently increased longevity, stimulated immune function and decreased tumour incidence from ionising irradiation of mice and other organisms. It appears – as BFL mentions – that low dose irradiation induces a surge of immune response, due to cell damage, heat shock proteins etc, and this “surge” enhances the continual activity of the immune system in mopping up precancerous cells. So the net result is actually tumour suppression. This would be unquestioned orthodoxy if it were not so politically inconvenient.
Here’s a paper I just found on PubMed (took about 10 seconds) (mice+immune+Gy):
Int J Radiat Biol. 2011 Feb;87(2):202-12. Epub 2010 Nov 10.
Anti-neoplastic and immunostimulatory effects of low-dose X-ray fractions in mice.
Nowosielska EM, Cheda A, Wrembel-Wargocka J, Janiak MK.
Department of Radiobiology & Radiation Protection, Military Institute of Hygiene & Epidemiology, Warsaw, Poland.
Abstract
Purpose: The exploration of immune mechanisms of the tumour-inhibitory effect of exposures to low-level fractions of X-rays. Materials and methods: BALB/c mice were exposed to whole-body daily irradiations with 0.01, 0.02, or 0.1 Gy X-rays per day for 5 days/week for two weeks. Then, mice were intravenously injected with L1 tumour cells, killed 14 days later, and neoplastic colonies were counted in the lungs. Natural killer (NK) cell-enriched splenocytes and activated peritoneal macrophages (Mϕ) were collected and cytotoxic activities of these cells against susceptible tumour targets were assayed. Concanamycin A (CMA) and antibody against the ligand for the Fas receptor (FasL) were used to inhibit the NK cell-mediated cytotoxicity. Production of nitric oxide (NO) was quantified using the Griess reagent. Secretion of interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-12 (IL-12), and tumour necrosis factor-α (TNF-α) was measured using the enzyme-linked immunosorbent assays. Results: All the exposures to X-rays significantly reduced the number of the induced tumour colonies and enhanced cytotoxic properties of the NK cell-enriched splenocytes and activated Mϕ. Conclusion: Suppression of the growth of pulmonary tumour colonies by irradiations of mice with low-dose fractions of X-rays may result from stimulation of anti-tumour reactions mediated by NK cells and/or cytotoxic macrophages.
BTW IJRB is a high profile international radiation biology journal, I was fortunate to publish in it a few times myself (look for Salmon PL).
BFL says:
February 19, 2011 at 5:45 pm
No relation to BNFL I’m guessing 🙂 ?
re: REPLY: get your own blog and you can talk about Chernobyl all you want, this thread is about Potassium-40 in bananas. – Anthony
Now, now, Anthony. He wants to talk Chernobyl, let him
Point out that that is what happens when socialism runs the plants. The design was by the man who curried the most favour in the party, the techs were those that were not politically suspect
What happened at Chernobyl would not have in an American reactor, let alone a Canadian Candu reactor.
Watermelons (green on the outside, red all the way to the core) are not interested in your interests, they are interested only on their historical inevitability.
@BFL;
I chased after this cite for a bit, it resolves (allegedly) to a paper in an issue of Bulletin of the Atomic Scientists, well known as a completely objective and non-political organization…
Sadly, the article apparently can’t be found even on their site.
So, what I’d like to know is what raw numbers the cited “28%” and “54%” increases actually represent? If you’d had four deaths in 1978 and five in 1979, you’d have a 25% increase right there. Also nothing close to a statistically relevant number.
Any chance we can have a “Update: ….” to this article relating to the Japanese reactor leaks.. specifically a reasonable guess at the number of bananas the people within the 20km evacuation zone might have encountered?
So what’s the half-life of a banana? Not much more than a week I’d guess.
The Fukushima 50 were exposed to >1,000,000 BED
The peak radiation at Fukushima was >4,000,000 BED/hour
People outside of the immediate area <100 BED
Earlier this year, I read that Pakistan is increasing its nuclear arsenal from 100 bombs to 200. This is a country that has rolling blackouts as a matter of course. So I thought, that is idiotic – they have an intention to use those bombs. So I went on Amazon and bought 25 courses of potassium iodide. Then I found the mother lode. Nasco in Wisconsin sell 500 gram bottles of potassium iodide for about $50. So I bought a kilo – enough for 720 people. It works out at about $0.02 per person.
Historically, the progression in scientific/technological innovations by man progresses from the large and clumsy to the small and more refined. Some of this comes naturally via many iterations through trial and error, and some comes from new insight gained from increased understanding of a phenomenon.
The day may come when we can harness nuclear energy on a small scale without the complication of highly radioactive waste. (A few scientists have postulated the transmutation of elements in biological systems; however this is regarded as fringe science similar to cold fusion.)
There is certainly a fear of radiation in the general public, but is that fear misplaced I think what is happening in Japan shows it is not.
There are a number of different scales for radiation levels and yes Bananas do emit radiation as do things like florescent paint and CRT monitors. In a reactor with it safety systems intact you would expect find little radiation, that is what safety measures are for. As do the tracers used in CAT scans
But levels last Thursday at the main problem site in Japan went considerable above safety limits and bananas as a scale
Your banana is 0.1 μSv, but on that same scale normal background radiation is
2.4 millisievert (mSv) per year on the same scale as your banana that is 2400 μSv (a lot of bananas)
What are the levels at the worst reactor in Japan, the peak on Friday was 20 millisievert (mSv) per HOUR or 20,000 μSv, multiply that number by 10 (as your banana is only 0.1 μSv) to get the number of bananas you would have to eat to get the equivalent dose of radiation.
A Handy radiation cross calculator
http://hptech.org/nuclear/convert/sievert.html
1 banana = 1microsievert
Highest radiation level = 400,000 microsieverts/hour
x 24 hours a day, 365 days a year.
Assuming an average banana weighs 120 grams – then:
0.12 x 3504000000 = 420480000 kg or 420480 metric tonnes of bananas.
Or approximately the weight of one of one of the biggest ships in the world, in bananas.
Someone should check my working, but I think that’s right.
“Great is the power of steady misrepresentation, but the history of scienc