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.
“don’t tell Michelle Obama, she’ll ban bananas …”
There is no doubt who wears the pants in the family.
What is amusing is that BANANA is an acroym for “build absolutely nothing anywhere near anything”. When people suggest going nuclear, the BANANA’s go, well, banana’s.
If the ironic symetry were any more perfect, I’d weep.
“The United States Bureau of Alcohol, Tobacco, and Firearms tests wine, gin, whisky, and vodka for radioactivity. If the product does not have sufficient radioactivity, it may not be legally sold in the United States.”
Just to make sure it isn’t synthesized from crude oil!
Re: nuclear power plants. Its not the radiation that they generate during operation but the (relatively low?) potential of mishaps and the especially acute problem of storage of long lived radioactive remains especially from decommission. Reviews of many of the mishaps reveal major cover ups of improper maintenance sometimes discovered only through the action of whistle blowers. I seem to recall that the Browns Ferry mishap was only one safety backup from a severe meltdown. I think that astute observation of that industry and the typical lack of trust of corporations in general (re the recent banking meltdown) is what probably makes most of the public nervous about nuclear reactors in general. It is also debatable if the standard design plants in use today would be economically viable without taxpayer subsidies for costs such as mishap insurance and waste disposal.
http://www.lutins.org/nukes.html
http://en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Power_Plant
http://www.iaea.org/Publications/Magazines/Bulletin/Bull314/31404684750.pdf
http://www.usatoday.com/news/nation/2005-11-01-weapons-ocean_x.htm
http://www.nrdc.org/nuclear/pnucpwr.asp
Gary Pearse says:
February 16, 2011 at 10:10 am
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 –
OH NO !
I spend hours a day at huge granite table, about 2 meters by 5 meters.
Ok it has a nice low expansion co-efficient ,but unfortunately it`s at er….ummm..just below waist height.
Does anyone know where i can buy a pair of lead lined undercrackers, suitable for girding ones plums;)
I’ll remember the banana comparison next time I try to convince one of my friends that nuclear power is the best way for the UK to head off energy supply problems. Even the ones open to my skeptical arguments about AGW doubt my view that the benefits of nuclear power today outweigh the risks, especially once Thorium is considered as a fuel source. Inevitably it comes down to the question why coal power stations won out over nuclear ones. Given the massive amounts of pollution the former used to produce, so goes the reasoning, the latter simply had to be massively worse to lose the competition.
Very interesting post, well worth going off task for…
@Dillion Allen
DO NOT eat off of old orange FiestaWare ceramic plates.
There was an article in The New Yorker many years ago about an artist who was working to come up with a suitable design for a marker to be placed over nuclear waste sites. He was struggling with the challenge of designing something that would be comprehensible to whoever is around to view it in 10,000 years or more. He wanted to include radioactive material in the design, but of course, it is not available on the market. So, he found a way to disintegrate the old red Fiestaware plates and extract the small amount of radioactive pigment they contain.
Stop monkeying around, Anthony! The anti-nuke crowd will alternately go bananas and ape$h!t over this news! };>)
Thanks for a most useful educational post!!!
Living in Europe which has lots of nuclear power stations and is busily extending their life, possibly beyond what is wise, the problem is not the potential leakage – I have two within “exposure risk from leaks” range near me – but from the waste. It is currently being stuffed into disused Salt Mines deep beneath us, and while the long half life waste is a relatively small amount and, I believe, is adequately protected and dealt with, the “low level” waste is a vast pile and not as well protected and stored.
Sadly, the morons of Greenpeace et al and the Campaign for Nuclear Disarmament failt o make a distinction between the two types. The vast majority of them also fail to realisethat radioactive radon gas, atural background radiation and cosmic rays – even before we get to the radioactive bananas sitting in the fruit bowl on the diningroom table, means we are all getting a daily dose of radiation we simply cannot avoid.
OK, now I’ll take Brazil nuts off my list of favourites. Bananas I can handle…
R John says:
February 16, 2011 at 10:52 am
No, I meant calcium, though Sr is the most potent of the bone adulterants.
48Ca alone is present in the average human at about 12 grams! That is 12,000 mg per person. In bone, assuming that isotopic preferential deposition does not occur, and bone is represented by Ca3(PO4)2, that is around 5,000 ppb!
With a half-life of 50 quintillion years this is serious stuff.
(Seriously, it is very stable, and all of these atoms may emit only a few betas in our lifetime.)
I was just being absurd, and showing how numbers can be confusing, maybe even frightening, to the average bear. Especially to the average Ph.D. professor.
My favorite radiation is that which radiates from the Sun. My second favorite radiation is the heat energy which radiates from a wood fire on a cold winter’s night. My least favorite radiation? The sounds waves which radiate from my wife’s mouth every time she discovers I’ve used the credit card again.
All this reminds me of a 2006 BBC Horizon documentary called “Nuclear Nightmares” (http://www.imdb.com/title/tt0828787/) which showed how the fear of low levels of radiation was irrational.
Chemists like me have our own analogies. During the review of an artficial sweetner someone complained that metabolytes of the product included a small amont of methanol, a toxic chemical. After several rounds with regulators another person pointed out that a 6 oz. Glass of orange juice contained 100x as much methanol, all natural and completely unregulated. The methanol issue was soon dropped.
Reminds me of Jr. High School in the Fifties. One of my teachers became the county radiation civil service person. We learned to identify just about anything from the clicks it caused on the geiger counter.
Linear extrapolation of radiation risks is not appropriate. If X dose will cause a 50% cancer risk increase , a .1X dose will not cause a 5% risk increase, and a .02X dose will not cause a 1% increase. In fact low dose radiation risks are wildly exaggerated by linear techniques. I suspect linear extrapolation of cigarette risks are also wrong, but in the case of radiation they are known to be not only wrong in size but in direction.
The phenomena is known as radiation hormesis and is actually fairly well established. For the tyical American an increase in radiation exposure by a factor of 2-5 would in fact lower your cancer risk.
Bananas are primarily gamma emitters. So even your lead lined undies won’t do much.
The potassium-40 emission referred to should be a 1.46 MeV gamma ray.
As for some types of radiation being more harmful… that is what the rem unit was for. I don’t think there is any hard rule for this, an alpha particle dose in the lungs can be more harmful than a high energy gamma ray dose externally.
BFL says:
February 16, 2011 at 11:21 am
Nuclear waste disposal is a political, not a scientific problem. We can just dump them in a stable salt mine or into the Marianas trench with each encased in concrete and glass. End of problem. Remember that Ur is an element that is present in the ground and in ground water already. We don’t manufacture it. We collect it and concentrate it. The logical solution is to redilute it back where it came from—even better, my preference, the deep oceans, where it can slowly be redissolved over a few millennia, never exceeding background levels as it dissolves..
[Oh, wait: isn’t that how to make Godzilla!] LOL
Is that a banana in your pocket or are you just trying to set off my geiger counter?
http://nvl.nist.gov/pub/nistpubs/jres/105/2/j52hob.pdf
Radioactivity Measurements on Glazed Ceramic Surfaces
Thomas G. Hobbs, NIST, 2000
Small file (72KB), and worth reading just for the descriptions of some of the samples. That may have been the most incidentally humorous peer-reviewed scientific paper I have ever read, outside of (C)AGW research.
So where does this dose compare to the TSA backscatter machines.
I hear way to much whining about radiation that equates to an extra 2 minutes at cruising altitude and wanted to see how many banana equivalents the scans were.
Juraj V. says:
February 16, 2011 at 10:35 am
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!!
Jason says:
February 16, 2011 at 11:10 am
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.
Low level radiation up to about 100 mGy stimulate the immune system, partly from activity of heat shock proteins and other pathways, resulting in decreased – not increased – cancer mortality.
Cancer deaths and mortality from low level radiation do not rest on experimental evidence but are in exactly the same category as CO2 global warming – a construct of computer modeling based on unfounded assumptions. Pure fiction.
On that theme, coal fired power stations release more radioactivity into the environment than nuclear power plants, due to natural radioactivity in coal.
Juraj V. says:
February 16, 2011 at 10:35 am
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!!
On that theme, coal fired power stations release more radioactivity into the environment than nuclear stations, due to the radioactive content of coal.
BFL: “…discovered only through the action of whistle blowers…”
Drivel. All reportable incidents must be reported to the national nuclear regulator within the time limit specified, which is usually minutes or hours depending upon the nature of it.
“…only one safety backup from a severe meltdown…”
More drivel. This was an insulation fire unrelated to the reactor’s operating or shutdown systems. The plant’s shutdown systems were not impaired. What was impaired were government certification processes that approved an insulating material which was not fireproof.
“..taxpayer subsidies for costs such as mishap insurance and waste disposal…”
The mythmaking just never stops. All nuclear liability legislation has been tested by court challenges, and all court decisions have found that limited, sole liability does not constitute an economic benefit to the utility. With respect to waste disposal, there is no subsidy. Utilities have been paying disposal funds for decades and have now successfully sued the US federal government for its failure to deliver what has already been paid for.
BFL says:
“It is also debatable if the standard design plants in use today would be economically viable without taxpayer subsidies for costs such as mishap insurance and waste disposal.”
No it’s not. Taxpayers do not subsidize disposal of spent nuclear fuel from nuclear power plants.
bubbagyro says:
February 16, 2011 at 11:51 am
R John says:
February 16, 2011 at 10:52 am
No, I meant calcium, though Sr is the most potent of the bone adulterants.
In your first post you mentioned alpha emitters. You must have been meaning Ra (224 or 226). 226Ra is in the natural 238U decay series, 2600y half life (224Ra has a few days half life and was once used medicinally).
90Sr indeed is the most radiotoxic of the bone-seekers. Due to the longer range beta emission irradiation from marrow endocortical and trabecular surfaces, the entire haemopoietic marrow cavities are irradiated, including the hematic stem cells in the centers of the marrow sinuses. Thus both leukemia is caused (hits to the central stem cells) and osteosarcoma (hits to the bone lining cells). Ra226 by contrast emits alphas with 20-30 micron range which only irradiate the bone lining cells, causing osteosarcoma, but no leukemia since the marrow cavities are not traversed.
Hormesis is uncertain, so I’ll continue to like bananas because they have no bones.