Going bananas over radiation

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.

From Wikipedia:

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]

  1. ^ http://www.ehs.unr.edu/ehs/LinkClick.aspx?fileticket=EgZI00myQRM%3D&tabid=62&mid=615
  2. ^ Weston, Luke. (2007-07-25) banana dose « Physical Insights. Enochthered.wordpress.com. Retrieved on 2010-10-19.
  3. ^ CRC Handbook on Radiation Measurement and Protection, Vol 1 p. 620 Table A.3.7.12, CRC Press, 1978
  4. ^ Issue Brief: Radiological and Nuclear Detection Devices. Nti.org. Retrieved on 2010-10-19.
  5. ^ Radiation and Risk. Physics.isu.edu. Retrieved on 2010-10-19.
  6. ^ A Brief Review of the Accident at Three Mile Island
  7. ^ Radiation. Risks and Realities, US Environmental Protection Agency
  8. ^ [1][dead link]
  9. ^ Brazil Nuts. Orau.org. Retrieved on 2010-10-19.
  10. ^ Natural Radioactivity. Physics.isu.edu. Retrieved on 2010-10-19.
  11. ^ Bananas are radioactive—But they aren’t a good way to explain radiation exposure. Boing Boing. Retrieved on 2010-10-19.
  12. ^ Rahola, T; Suomela, M (1975). “On biological half-life of potassium in man”. Annals of clinical research 7 (2): 62–5. PMID 1181976.
  13. ^ Environmental Health-Risk Assessment for Tritium Releases at the NTLF at LBNL: Chapter 2. Lbl.gov. Retrieved on 2010-10-19.
  14. ^ Brazil Nuts. Orau.org. Retrieved on 2010-10-19.

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Brian D

Well no wonder I glow after eating a loaf of my wifes banana bread. And here I thought I was just fat and happy. LOL!


Very bad joke:
More people have died in Kennedy cars then died from radiation at three mile island….


I love it when nuclear physics and understandable analogies intersect.


Hahaha good stuff!
People are always amazed when I tell them that a nuclear power plant gets shut down when it leaks radiation equivalent to the amount a coal fired power plant puts out continuously…it puts the danger of nuclear in some much needed perspective…

John W.

This was a plot element on “NCIS LA” last night, and I snickered.
Color me chastised. 8^(


Thank goodness that the Australian bannana crop was wiped out by the recent cyclone (not really), humanity has been saved from lots of radiation. No if they could only do something about their AGW folks.

Phillip Bratby

Radiation hormesis is a well known effect and the benefits of living in a high background environment are well known. See for example about Ramsar in Iran (where the convention was signed) http://www.iaea.org/Publications/Magazines/Bulletin/Bull332/33205143638.pdf and http://www.probeinternational.org/Ramsar.pdf


don’t tell Michelle Obama, she’ll ban bananas …

Very apeeling.


Interesting timing of this article. You wrote “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]”
Last night, on “NCIS: Los Angeles”, the bad guys stole a nuclear weapon, and the NCIS crew was speculating that they may use a truck full of bananas to transport the weapon, thus making detection of the weapon harder. The thought was that the truck would be pulled over because it tripped the radiation sensors that had been deployed to look for the bomb, then the authorities would see all the bananas and let the truck go, not realizing there was a nuclear weapon underneath.


One excellent way of sequestering banana radiation is by putting sliced banana into a mixture of flour, sugar, water and oil and subjecting the blend to high heat for a short period of time. When made in large batches and put into kilogram-size wrapped parcels they can be shipped to many individuals for safe storage, reducing the risk of terrorist’s acquisition of large quantities of the resource.
Many studies have been done on this concept, and early studies resulted in the discovery of a replacement for expensive sandbags or concrete blocks for construction, affectionately called “fruitcake”. (unlike its impractical cousin “yellowcake”, “fruitcake” has an unlimited shelf life)

Dillon Allen

As a nuclear engineer who formerly worked for Uncle Sam and now works in the commercial nuclear industry, it is frustrating to hear the same “crowd” who is so slow to skepticism in all other relams jump off the skeptical cliff about nuclear power. We continuously present facts that show the power source is safe when operated properly only to be rebutted by “What about Three Mile Island or Chernobyl?” Bad joke above, but accurate point about the late Sen Kennedy’s auto woes vs the nuclear power industry.
The banana analogy, and the BED as a more specific measure, is a great way to get the point across. Discussing alphas, betas, and gammas, OH MY! just makes the uneducated eyes roll back. So thanks Anthony for spreading the word a little more.
Finally, if you are impressed by the dose from a banana, DO NOT eat off of old orange FiestaWare ceramic plates. The pigment (at least at one time) was made with some higher-than-natural percentage of uranium oxide. Those plates can easily alarm a geiger counter that has no issues with the background field. Not a huge deal in the scheme of things, but will certainly open the eyes of someone who doesn’t understand radiation is everywhere.

I will never again eat peanut butter toast and a banana before flying. You get everything searched. Trust me. I know.
At an airport, not that long ago…
After a fruitless trip through my luggage (pun intended), a pat down down and whatever she could think of the frustrated security agent looked up and said “Did you eat breakfast?” “Uh-huh” I said. She looked me straight in the eye and said “Peanut butter and bananas?.. Or are you smuggling?” I replied: “Peanut butter toast and a banana.” She told me to “Get lost!” and yelled her supervisor over and gave him a lecture about “crappy detectors”.
True. I swear!
The latest one was “Did you polish this jewelry while you were gone?” at the end of the search. Another sin apparently… That one set off the chemical sniffers and unfortunately it was quiet and they were bored so I got about 15 minutes worth of pat down and bags checking…

Alan S. Blue

Along the lines of advancing nuclear power, I’ve been thinking about a potential change.
A fair chunk of getting permission for a nuclear site resides in the extensive geological survey and environmental impact assessment. And the budget for the lawsuits involving every detail overlooked in those studies.
Put the actual core building on a barge. Put the ’emergency shutdown’ cooling on the barge as well.
The mammoth cooling towers are for the outer loop. And thus not part of ’emergency cooling’. Nor are they dealing with radiologically active material.
The major threat to a nuclear site – earthquakes – is pretty much relegated to a side issue at that point. Yes, it can damage the stuff that isn’t on the barge. But it essentially can not cause a radiological leak. The fact that the actual core ends up with a sizable moat and is thus also more difficult for a truck bomb or protestor to even reach is a bonus.


Your neighbour should move to Cornwall (UK).


Another interesting fact…
A person living within 50 miles of a nuclear plant receives less radiation from it in a year than you get from eating one banana.
from a highly recommended read
Power to Save the World: The Truth About Nuclear Energy by Gwyneth Cravens

Myron Mesecke

Hey Mister tally-man, tally me bananas.
Geiger counter click and me wan’ go home.


They actually mentioned this last night on the TV show “NCIS Los Angeles.” It was suggested that someone smuggling a nuclear weapon could hide it in a truck full of bananas.

Dave Wendt

For God’s sake don’t let Michelle Obama see this!

The voice of Kraftwerk’s “Radioactivity – is in the air for you and me” suddenly appeared in my head. http://www.youtube.com/watch?v=kXD6Gtinvbc

Jim G

An important note to remember though:
Not all radiation is equivalent.
Potassium is a beta- (electron) emitter.
Cobalt 60, will give off a b- and/or gamma.
Radon, found in bricks, will give off an alpha (helium) particle.
As for protection, clothing will stop alpha, unless you ingest it, your dead skin layer will stop beta.
gamma and neutron are considered whole body doses, because it will interact anywhere in the body.
Alphas and neutrons will cause more damage than betas or gammas.
After an element experiences decay, it loses mass and usually becomes another element.

George Steiner

Mr. Watts you have something against scientific notation.
REPLY: Huh? Lots of WUWT articles contain scientific notation. What’s your gripe here? – Anthony

richard verney

“Low-dose radiation has been shown to enhance biological responses for immune systems, enzymatic repair, physiological functions, and the removal of cellular damage, including prevention and removal of cancers and other diseases.”
– 21st Century Science and Technology Magazine
See http://radiationhormesis.com/tag/natural-immune-system/


In the high mountains of Colorado, radiation exceeds three times the average in the USA, because of radon and granitic elements.
Colorado natives have much longer life spans, compared to the USA mean.
Causality or correlation?


So wait. 40 Tbls of peanut butter increases my risk of death?
*sigh* I’ll miss you, Favorite Midnight Snack…


Another fun fact about bananas – they have five sides. Useless trivia, I know.
I do like to tell people about bananas and the “banana-equivalent dose” whenever they start to rant about how evil radiation is, etc., etc.

Gary Pearse

Get your elbows off the table (granite countertop). One of the best kept secrets for many decades up to recently was the radioactivity of granite building stone – notably the red and pink varieties which are high in potassium feldspar and mica. Some contain uranium that would be economic ores at approximately $100/lb for U3O8 (Indian Red from India I seem to recall was one of the high level ones). Working in a granite quarry one gets a full measure of the radioactivity. The Canadian Precambrian Shield has alternating volacanic and granite belts, the latter making up perhaps 75% of the area – all radioactive to a measurable degree. Even a spoonful of soil has all 92 elements in it so lets keep our cool – we must be in equilibrium with all this stuff around us. The link is for Czech building materials but applies for the whole world.
“All building materials that originate from minerals always contain a certain amount of radionuclides. These are mainly potassium, uranium, thorium and the radionuclides that are created as their radioactive decay chains. Of these, the most significant is radium (Ra-226). The Ra-226 presence in building materials causes exposure to persons living in dwellings – either by inhalation of radon daughters that decay from radium and release from the building material to indoor air, or by hard gamma radiation that releases from the building material as a consequence of the radioactive decay of the natural radionuclides to be present.”

Many years back Blaine County in Idaho, home to Ketchum and Sun Valley and hundreds of idle rich declared itself a Nuclear Free Zone.
We wondered how that worked out at the hospital and other medical centers among several location for potential radiation sources.

Gras Albert

Next time you are outside on a clear night look up…
Nuclear energy is the single most common naturally occurring phenomena in our universe

What amount of radiation does your body get from the potassium it contains and from others you live with? We ought to become hermits, but only after ensuring our cave is not carved out of potassium-rich granite, sandstone or shale.


As a nuclear power plant worker, it always amazes me just how little people understand the concepts and actual exposure levels resulting from the plants. The sailors working on the flight decks of Aircraft Carriers routinely receive significantly higher doses from cosmic radiation and shine from the jets than the folks working in the nuclear reactor plant below deck.


The human body is a system. It regulates itself. It has mechanisms to repair damage done by radiation. There is controversy about whether these mechanisms respond (increase in activity) when a person is exposed to radiation. It is possible that we live in a world with too little radiation. Sounds similar to CO2.


I particularly like the comparison between the ‘radioactive’ milk after TMI and bananas. Unless my arithmetic is off, you’d have to drink about seven gallons of the milk to get the same dose as you would from eating one average banana. …or if you made a banana shake with that milk, less than 1.5% of the total dose you’d get would come from the milk.

Gary Pearse

gcb says:
February 16, 2011 at 10:05 am
“Another fun fact about bananas – they have five sides. Useless trivia, I know.”
I believe you would enjoy doing the old trick with a banana where you stick a needle into one of the ridges of the banana and swing the needle back and forth to slice the banana before peeling – my grandkids think I’m majic.


Thanks Anthony for a well articulated note of radiation common sense.
For non-Americans some unit translation:
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).
1 curie = 3.7 E+10 becquerels (Bq). One Bq is one disintegration per second.
So 1 picoCurie (pCi) = 0.037 Bq. (One disintergration per 27 seconds.)
So a banana contains 520 pCi or 19 Bq.
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]
This is the orthodoxy, but the risk of cancer from 10 mrems (100 uSv) is zero. There is a threshold of in the 10-100 mSv (mSv, not uSv) below which radiation causes zero cancer risk and probably slight health benefit.


Some beta-emitting isotopes are more dangerous to be considered than others, if eaten. Some calcium isotopes are strong beta emitters, accumulate in bone, and have long half lives, so they sit and emit. A by-product of some of these (called a decay product) is an alpha-emitter. This radiation be a good or a bad thing, as mentioned, depending on one’s immunity. Sulfur 35 is actually dangerous, since it accumulates in important tissues, especially gonads.

Truth is, that looking at volcano belching chlorine and fluor-rich smoke is “amazing”, while the steam coming off the cooling tower is “dangerous pollution”. Or three molecules of CO2 per 10,000 other molecules from 1750 are natural, but the fourth is again a “dangerous pollution”.
Now understand how even almost harmless dirty bomb will make havoc in a modern society. Radiation, run!!


Elvis was fond of banana and peanut butter sandwiches. He was doomed, even without the drug abuse.

Retired Engineer

Nostalgia: So my old C-D radiation survey meter is not the only one left? From the days of fallout shelters and “What to do in case of Nuclear attack” movies? Mine doesn’t click, only has a meter. If it moves off zero, say goodbye.
Teller said something about getting more radiation from two women than from a nuclear power plant, so sleep with only one at a time.
I think Chernoble killed more folks than TK’s car, so the bad joke may be obsolete.

kerry rodgers

Run your counter down any pre-stressed concrete surface and listen to it hum. Used to do it when I was teaching first year geology to demonstrate the levels of radiation in the world around us. The teaching laboratory walls were alive with the sound of radiation. In fact most concretes will do it but pre-stressed is nice and high in potassium – as is the crust of our planet.
And when it comes to high natural levels of radiation that population of Niue have been living with it for hundreds of generations. The limestone of the island is replete with both uranium and thorium. There is not a mutant in sight among the animals or plants either on land or in the Pacific.


“There are about 1,200 beta particles per second produced by the decay of 14C. However, a 14C atom is in the genetic information of about half the cells, while potassium is not a component of DNA. The decay of a 14C atom inside DNA in one person happens about 50 times per second, changing a carbon atom to one of nitrogen.”


Jeff says: “don’t tell Michelle Obama, she’ll ban bananas …”
Don’t tell Obama, either–He’ll want to regulate food by Federal fiat. Oh, wait…

Back in my commercial nuclear power days, we would periodically get whole body scans to determine if we had exposure. One woman came up very (VERY) high in K-40. There was quite a bit of excitement surrounding whole thing until it was recognized she ate two bananas with her lunch….daily.

Robert M. Marshall

Back in the ’80’s Psychology Today had a feature articla on common fears compared to the actual risk the feared phenominon represented. Everything from carcinogens in peanut butter (near the top risks) to Nuclear Power Plant emissions. Car travel vs. Air travel vs walking around a city block. The lowest risk, represented in the average days the risk shortened ones life-span, was living next door to a nuclear power plant.
Toronto, Ontario has a science museum with a few articles in a glass box. The items included a red glazed plate, a brick, a cement block, and a pound of dirt from the perimeter of the Three Mile Island Unit 2 containment building. There was a geiger counter, much like the one pictured above, for masuring relative radiactive emissions. Nothing from the dirt, but I have to admit, I’ve decided not to buy any red fiesta ware.

Dr. Dave

I never knew that bananas are beta emitters. I don’t know, but I’ve been told you can shield plutonium (an alpha emitter) with a sheet of notebook paper. On the other hand colbolt60 can shine gamma radiation right through your very soul. I live in the Rocky mountains at 7,000 ft above sea level. We’ve got lots of granite around. I don’t even think about my radiation exposure but I’m quite sure it’s higher than most of the US population. In fact, I was told when I first moved here that the road was paved with uranium mine tailings.
A lot of folks would be shocked by the natural radiation that is emitted by the planet’s oceans (not to mention the mercury!). Radiation is ubiquitous. Ironically about your only escape is to spend 6 months aboard a submerged nuclear powered submarine. These guys have extremely low radiation exposure.

R John

bubbagyro – The only beta emitters for Ca are Ca-46 (0.004% abundance) and Ca-48 (0.187%). They are not a significant source of radiation. Perhaps you meant Sr-90, which is a byproduct of nuclear fission. Tons of were emitted in the Chernobyl accident and since Sr and Ca are in the same group, one will replace the other in bone structures. Sr-90 has a half-life of 28.8 years and is a principle cause for bone cancer to those exposed to it.

JB Williamson

A pal of mine arrived in JFK from LHR a few years back and set all the alarms off. Even after a strip search they still couldn’t work it out. Finally they let him offer an explanation, which was that he had been to hospital a day or so previously to have a barium meal, related to an ongoing medical investigation.
All the more embarrassing as he was the skipper of the flight!
Makes you think!
I had never heard the banana explanation before – nice one Anthony.

Murray Duffin

I read a few years ago that people who live in slightly elevated radiation environments (natural background radiation) are healthier and less prone to ailments like cancer. One city mentioned was Aberdeen Scotland, where the homes are largely built grom local grey granite that has a low level of radioactivity. The article suggested that American concern with low levels of radon may be misplaced.


Denver has 3x the normal radiation exposure due to its proximity to the mountains. Yet cancer rates are lower there than on average. Who would have thought? Current theory alleges that the cellular DNA repair mechanisms are used more which allows for less errors to accumulate before repair, yielding more intact DNA.