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.
RE: Radioactive Potassium is in the Interior of the Cells of All Plants and Animals
George E. Smith says on February 16, 2011 at 1:43 pm:
K40 is a beta and gamma emitter, with a half life of 1.3 E+9 years. It is 0.0118% of natural Potassium, and emits an electron with 1.32 MeV energy. It can also capture an orbital electron and that is a 1.51 MeV event. The electron emission (beta decay is accompanied by a 1.46 MeV gamma.
The Beta electron is not likely to penetrate far into organs or cells; the gamma is a bit more of a problem
A human with a mass of 70 kg has 245 g of K of which 29 mg is the K-40 isotope. This mass of radioactive K produces ca 320,000 disintegrations per minute.
Ref: The Fire of Life” by Max Kleiber p 361.
The 1.32 mev beta particle could break ca 300,000 H-O bond (bond energy ca 4 ev) of water molecules to give a hydrogen radical and hydroxyl radical. The hydrogen radical could readily grab a hydrogen atom from an adjacent water molecule to produce another hydroxyl radical and a molecule of hydrogen gas. Thus ca 600,000
highly reactive hydroxyl radicals could be produce per minute and these could go on to attack the various organic molecules in cell such as DNA.
If the beta particle would happen to strike an organic molecule, it would be blown to bits. After ejection of the beta particle, the K-40 atom turns into a neutral argon atom which recoils with 2.8 mev of energy and which could possibly smash more organic molecules to bits.
I suspect that many spontaneous cancers in humans and mutations in plants and aminals may be due to radioactive K.
The concetration of K-40 in Pacific pink canned salmon (low salt type) is 400 ppb by wt. I’m not going to worry about a few ppb of any pesticide in salmon.
What would the greenies do if they learned of all food is contains substantial amounts of K-40. Hopefully they would stop eating and starve to death.
The push is originating from the WHO, which happens to be an UN “child” much like the IPCC.
But just wait. Sea salt is NaCl, sodium chloride. What replacement is that? More UN-grade science?
Leg said on February 17, 2011 at 12:30 am:
Under the Comment box you write in, are the usable HTML tags and attributes. Note the “code” option.
Nuclide__Half-life__Ci/gm____TBq/gm__1 Ci =
P-32_____14 day_____285,000__10545___3.5 ug
Po-210___138 day____4,490____166_____6 mg
C-14_____5730 yr____4.46_____0.165___6 g
Pu-239___24,400 yr__.0613____0.0023__435 g
U-238____4.5 E9 yr__3.3E-7___1.2E-8__6,600 lbs
That’s “code” like computer code. It uses a fixed-width font, all characters the same width. Space things out with underscores, as multiple spaces are auto-collapsed to a single space. Bracket the section with “code” above and “/code” below (using the left/right arrows of course). Then you can get as close to a readable table as possible.
However, unless you’re very good with character counting and very confident with your work, a Preview function is basically needed and desired to get the layout right with everything lined up and sufficient spacing for clarity. I used mine extensively for the reworking of your table above. If you want your own Preview function, you have to install it. WUWT is hosted on wordpress-dot-com, and such a function cannot be added to a wordpress-hosted blog site as wordpress-dot-com doesn’t offer one for sites as this. Thus to get Preview, you install CA Assistant, available here:
http://climateaudit.org/ca-assistant/
It also provides additional aides for nice HTML formatting. Caveat: Not all of the extra buttons are enabled on WUWT, just what’s listed as allowed under the Comment box. The non-enabled will look good on Preview but won’t be picked up when you Post Comment.
George E. Smith says: February 16, 2011 at 1:43 pm
Well I wouldn’t put a lot of stock in that use a truck load of bananas to hide your nuke in.
And just think of the gooey mess if it accidentally detonated.
Great thread.
Morton’s Lite Salt™ substitutes 50% potassium chloride for sodium chloride. I guess the slightly metallic taste is a radiation effect.
AnonyMoose says:
February 16, 2011 at 10:46 am
“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.”
Jim G above said:
“Potassium is a beta- (electron) emitter.”
OK So, beta-decay is the emission of an electron?
And that can turn C14 into nitrogen?
What’s wrong with this picture?
in aus in the 50s? they made some stunning apricot coloured glass ware…it is really pretty.
however it appears the sand they mined for it had a high radium content, all true product glows neon orange in a black light.
its now named “radium glass” and is very collectible, and also priced beyond the average!
From Josualdo on February 17, 2011 at 3:48 am:
Warning: Severe lack of knowledge of contents of sea water detected. Deploying relevant Wikipedia link:
http://en.wikipedia.org/wiki/Sea_salt
There are many distinctive “sea salts” of different colorations and textures, as known among cooking aficionados. And they can have them. Review the ion table at link. By concentrating on just the sodium in common table salt, reductions in sodium can be claimed by using “sea salt” where the sodium salt is partially displaced by other salts like calcium, magnesium, and potassium salt. Heck, you could make a soup with even greater salinity using “sea salt” instead of table salt, and still claim a sodium reduction.
While I would like to blame UN Science for that, it’s actually more like PR Science. ☺
In the late 1970s I wore a wrist watch that had belonged to my grandfather. One day during a high-school science class the teacher produced a geiger counter. I remembered reading somewhere that old watches used to have radium in the luminous paint. Sure enough, the watch was radioactive.
It just came to me that Harry Chapin had a song about a truckload of bananas called “30,000 Pounds of Bananas”. Based on a true story, a truck carrying 30,000 lbs of bananas crashes after the driver fails to shift to low gear on a steep descent. That’s one big radioactive mess to clean up.
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.
Many years ago a group in the UK issued a report showing the occurrence of certain types of cancers near “military establishments” due to the increased levels of radiation in the local area. There followed all the usual brouhaha over the control of radioactive materials in the military etc etc.
The sites were not revealed till later when it turned out they were all mediaeval or older and the radiation was from the rocks on and from which they were made.
James.
Here is another fact that makes me crazy: opponents of irradiating food have succeeded in terrorizing enough of the public so that it isn’t a routine procedure, thus leading to thousands of cases of food poisoning and not a few deaths, all of which are preventable.
High energy radiation in space can be explained by the presence of electric currents in plasma, so for cosmology electrical banana is bound to be the very next phase.
“However, I would NOT live next door to a Nuclear Power plant as I would not personally accept the increased risk based upon their history of incidents.”
Good lord, you’re innumerate.
“It just came to me that Harry Chapin had a song about a truckload of bananas called “30,000 Pounds of Bananas”. Based on a true story, a truck carrying 30,000 lbs of bananas crashes after the driver fails to shift to low gear on a steep descent. That’s one big radioactive mess to clean up.”
As the EPA has claimed authority over spilled milk (due to the oil content and their authority over oil spills), perhaps the NRC needs to take authority over banana spills?!
Chris says:
February 16, 2011 at 7:38 pm
Ric Werme says:
“Once radon decays, it emit two more alphas and betas very quickly, hangs out at 210 Pb for a while (22.3 year half life) and that emits an alpha and two betas before stopping for good at 206Pb.”
Forgive my ignorance, but how can something emit an alpha and still remain the same element?
It cant, alpha decay means the nucleus loses 2 protons and 2 neutrons, thus atomic number goes down by 2.
Also Rick’s description of Pb-210 decay was a shorthand, Pb-210 decays by beta (22.3 yr half ilf) to Bi-210, which promptly decays by beta (t1/2 5 days) to Po-210, this is the alpha emitter of Alexander Litvinenko fame, which decays with the 138 day t1/2 by alpha decay to Pb-206 which is stable, the end of the U-238 series.
Po-210 was the radiotoxin of choice for the Russians since (a) it is the only alpha emitter with purely soft tissue biodistribution (not a boneseeker) thus the most radiotoxic, and also a remarkably pure alpha emission with negligible x-ray / gamma emission, thus no external detection by geiger counter.
Physics for all. I took what I thought was an easy ace science elective called Energy and the Envriornment when younger and greener. All kids and greenies are know-it-alls and the physics instructor was pro-nuke recently after TMI. So grateful for that class – not just for giving me the ability to begin to understand the nature, benefits and limits of various energy sources, but to dissect the public “witch” of the moment.
Radon and bananas and granite – Oh My!! And radioctivity in all other sorts of household sources. We may laugh now, but there is a drastic solution for every unjustified fear. Explaining dosages /exposures just doesn’t capture the attention like a scare does. And once scared, the explanation can cause more fear. Try telling someone scared of germs that they’re everywhere and that they are certainly breathing some in whenever they go in a kitchen or a restroom.
@Rob Crawford — don’t give them any ideas.
Oh, I see. Thanks a bunch. PR science it is! Indeed most of it ends up being NaCl anyway, displacement here and there (and sodium sulphate, that’s a funny one).
bfl,
My summary of the TMI health studies:
.
A little more reading for the interested, Three Mile Island Accident Health Effects. This is really interesting reading if you go through the whole article in Wikipedia. The initial Government report determined that nothing much happened health wise. Either fear factor, class action law suit piling on or hyper awareness caused residents to report more health problems which started another health study. That study showed an ~ 0.14 % +/- 0.07% increase in all cancer cases which is barely statistically significant. A study in 2008 found that thyroid cancer rates in the county of the reactor were 1/3 the rate of neighboring counties. Like the low level radiation dosages may have acted like a thyroid cancer vaccine. Pretty fascinating stuff but health statistics are not in my job description.
BFL: most of your 1:16 post has been dealt with by others. I do find it amusing that you’re quoting CCNR, a website and antinuclear group run by a high school math teacher with no expertise whatsoever in any field of nuclear science, nuclear engineering or radiation health physics. Your claims however about health effects from TMI are bogus. These claims were all tested in court in the 1990s. None were found to have any substance whatsoever.
Slacko says: “OK So, beta-decay is the emission of an electron?
And that can turn C14 into nitrogen?
What’s wrong with this picture?”
Leg response: Nothing wrong with the picture at all. It’s what happens. Read my posts previous to yours. C-14 has 6 protons and 8 neutrons in its nucleus. Upon decay, one of the neutrons ejects mass in the form of an electron(beta particle). That neutron instantaneously becomes a proton. The conversion of a neutron to a proton now causes the nucleus to have 7 protons and 7 neutrons which is N-14. N-14 is not radioactive. Like any radioactive atom, this C-14 atom emitted radiation once and only once.
Neutrons, protons and electrons have mass. If you look at the mass difference between a proton and a neutron, you will see it is almost the mass of an electron. The mass of a proton and an electron together equal the mass of a neutron (there is a teeny fractional difference not worth mentioning unless you want me to get into atomic physics a lot deeper).
Sometimes a proton captures an electron and becomes a neutron. When this happens, there is typically an emission of gamma energy. I-125 does this. At the instant of decay (gamma emission) the I-125 atom becomes a Te-125 atom. This atom will no longer emit radiation. Decay mechanisms usually involve Einstein’s formula which says mass is energy and energy is mass as there is some conversion of mass to energy or vice-versa.
If you have a pile of C-14 and put a radiation detector on it, you will see fewer and fewer clicks occurring as time passes because each click of the meter means a C-14 atom has become N-14. Hence there are fewer C-14 atoms as time goes on.
Further to the query from Chris 7:38 pm:
“Once radon decays, it emit two more alphas and betas very quickly, hangs out at 210 Pb for a while (22.3 year half life) and that emits an alpha and two betas before stopping for good at 206Pb.
Forgive my ignorance, but how can something emit an alpha and still remain the same element?”
I’m not sure if anyone has given a good enough answer to an excellent question from Chris: perhaps I can try…
The nucleus of an atom contains both protons (positively charged) and neutrons (no charge). Which element an atom belongs to is determined SOLELY by the number of protons alone.
Thus, hydrogen has 1 proton. Most of the hydrogen in the universe has no extra neutron.
Hydrogen with 1 proton (always) but also with one neutron is called Deuterium and is stable.
Hydrogen with 1 proton (always – that defines hydrogen) and 2 neutrons is Tritium and is radioactive, emitting a beta particle i.e an electron.
The nucleus does not contain free electrons. It only contains protons and neutrons. In Tritium (and all other beta emitters) the elctron comes from the breakdown of a neutron (neutral) to an electron (negative) and a proton (positive). Charge is conserved and the proton stays in the nucleus. Thus, the nucleus (which used to have only 1 proton and 3 neutrons) now contains 2 protons and 2 neutrons. Any atom containing 2 protons is, by definition, Helium. Helium (with 2 protons) and 2 neutrons is stable and the most common form of Helium (often referred to as He-4 for the 2 + 2 particles in the nucleus). [Helim also exists in nature as He-3 with 2 protons by definition but only 1 neutron.]
To recap. Beta decay changes a neutron into a proton and hence changes to the element with an Atomic Number (number of protons) that is one greater than before.
An alpha particle is a He-4 nucleus (i.e. without any electrons). Thus, emitting an alpha particle lowers the atomic number by 2 and reduces the number of nucleons (protons + neutrons) by a total of 4.
Thus, Pb-210 has 82 protons and 210-82 = 128 neutrons.
Its decay goes through a series of stage:
1) Loss of 1 beta particle thus changing a neutron into a proton. The nucleus now has 83 protons and is Bismuth. The number of nucleons stays the same – 210. Thus, Bi-210 is formed.
2) Bi-210 now undergoes the loss of another beta particle from the conversion of another neutron to a proton. Protons now number 84 which is Polonium. Thus, we now have Po-210.
3) Po-210 now looses an alpha particle – 2 protons and 2 neutrons. The number of protons drops by 2 from 84 (Po) to 82 (our old friend, lead Pb). The total number of nucleons lost is 4 so this is Pb-206.
So. Loss of 2 beta particles and one alpha (in any order although the order I’ve given is correct for Pb-210) takes you back to the element you first thought of but 4 nucleons lighter.
I’ll try again if anyone doesn’t follow this! (Assuming anyone wants me to!!)
The key is that the element present is determined totally by the number of protons.
Pb-210 to Bi-210 beta – increases protons by 1.
Bi-210 to Po-210 beta – increases protons by a further 1.
Po-210 to Pb-210 alpha – REDUCES the number of protons by 2 and nucleons by 4.
IN EFFECT, four neutrons have been lost – 2 converted to protons + 2 lost in the alpha particle.
Alan Bates: great explanation but one oops…
instead of “Po-210 to Pb-210 alpha – REDUCES the number of protons by 2 and nucleons by 4. ” it should be “Po-210 to Pb-206 alpha – REDUCES the number of protons by 2 and nucleons by 4.” So Pb-206 not Pb-210. Of course Pb-206 is non-radioactive.
We should get together and collaborate on these explanations of how radiation works. I like your style.
I’ve always found it similarly amusing that smoke detectors contain radiation sources (americium, I believe). This page:
http://www.epa.gov/rpdweb00/sources/smoke_alarm.html
gives the activity of a smoke detector as several microcuries. I wonder how many of the people who wet their pants over the radioactive iodine from Three Mile Island have since voluntarily purchased and installed much more substantial sources of radiation in their homes.