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.
From jojo on February 16, 2011 at 12:36 pm:
Ecological Tour to Chernobyl Nuclear Power Plant
http://www.tourkiev.com/chernobyltour/
Two and three day tours are available. Stay at Chernobyl’s hotel, visit the Chernobyl Museum, see all the local attractions. Fun for the whole family!
Take the tour, maybe you’ll get your answer there. Reasonable prices, a good boost for the local economy… What’s stopping you?
Speaking of common things that are radioactive brings to mind another product you can buy in most sporting goods stores.
Coleman Lantern Mantels for the old style gasoline fueled lanterns (and some propane models) are highly radioactive. The element that makes them glow a brilliant white when heated is thorium — yes that thorium.
They will absolutely light up a geiger counter. We used to use them a readily available check sources, as the emit a broad spectrum, and will verify that almost any type of radiation detector is working.
This is an example of common technology that has been around for over 100 years and most people have no clue. Thorium gas mantles, were developed in 1891 by an Austrian (Carl Auer von Welsbach).
In practical terms it is insignificant. Direct exposure of the Thorium mantel to a geiger counter will result in hundreds to thousands of counts per minute, but as used by the consumer, by their very nature they are used at a distance (exposure drops of a the square of the change in distance — inverse square law), and they are inherently used in a situation where you would not want to be very close.
A running fuel burning lantern is very very hot, so people stay back from them.
If you used such a lantern every weekend for a year your dose would be on the order of 0.3 – 0.6 millirem per year.
Here in Denver Colorado natural background radiation is about 2 mr/year depending on where you live. Just west of Denver in the Central City mining district pitchblend is found, and it is naturally radioactive (mined as a source of radium in the early 1900’s).
You can pickup rocks off the ground that would easily trip radiation sensors. As a result it was necessary for folks concerned about detecting radioactive shipments or illicit shipments of radioactive material to collect data regarding these natural radioactive regions, and major buildings that included such materials in their construction.
Fiesta ware is radioactive due to uranium which was commonly used for orange and yellow glazes in ceramics for many years. Older buildings with ceramic tiles with orange or yellow coloring are highly likely to have been made with glazes which contained uranium compounds to create their colored glazes.
This is one of the areas where our school systems are absolutely incompetent, as they do not teach students that radiation is perfectly normal and they are exposed to it every day of their lives. They only perpetuate this with the absurd assumption that health effects of radiation exposure are linear even at very low doses rather than understanding that detectable health effects are not statistically significant at low exposures, and as mentioned above low radiation doses seem to actually be beneficial.
Just like a sun burn, biological damage due to radiation exposure is a product or the rate of radiation, its duration, and what tissue is exposed.
Larry
Larry
My daily dose of bananas has become too extensive recently due to crops being flattened by cyclones. You know, the ones that some say are being caused by our CO2 emissions.
So our CO2 emissions are reducing my exposure to radiation. It’s all good. 😉
@ur momisugly Jeremy: me thinks that you got the NRC mixed up with DOE. However I don’t put a lot of faith in any large government agency or corporation as their internal morality depends mostly upon who’s in charge at the time and it is too easy too hide misdemeanors or worse because of the authority level.
Nothing wrong with Wikipedia depending on the subject and references. Sorry, but I like to look at opposing viewpoints from any sensible (determined from my experience of course) source and then draw my own conclusions, hopefully without emotion. Re a discussion I had once with a fellow about Reagan and what were his best accomplishments. Response, that he made Americans feel good about their country. I suggested that he research Reagan’s presidential stances and what actually took place under his administration, some of which actually set the course for the recent meltdown. All to no avail of course because of preformed opinions.
To me, a part of smart living is, where possible and without making life too dull, controlling risk to life and limb, and most people working for government agencies have mandatory basic safety training that should instill this attitude to some degree (and yet some still ride motorcycles in big city traffic).
So as far as radiation in food, there is not much that can be done to escape that or even the mercury contamination from coal fired power plants, even though these probably increase risk of cancers because some people are probably more genetically sensitive than others. 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. Others may do so at their own statistical peril of course.
@Dave Andrews says:
February 16, 2011 at 1:49 pm “…Its even worse. A 70kg man contains about 4.26kBq of Potassium 40 equivalent to 115,135 picocuries. Its obviously very important to make women aware of the potential radioactive risks associated with lovemaking with their partners :-)…” Well, you’ve just given those Swedish trollops suing WikiLeaks dude (Assange?) for whatever a sure win and probable death penalty in Sweden!
If you think your granite countertop is radioactive, and don’t have a scintillation counter or Geiger counter handy, find a Polaroid camera film, tape it to the counter top for a couple of days, then pull off the cover. Voila, you’ll see the location of every little speck of uraninite (U) or monazite (Th) and maybe even the potassium-bearing minerals (feldspars) showing up as bright spots. Their radioactivity exposes the film.
@Dave Andrews says:
February 16, 2011 at 1:49 pm “…Its even worse. A 70kg man contains about 4.26kBq of Potassium 40 equivalent to 115,135 picocuries. Its obviously very important to make women aware of the potential radioactive risks associated with lovemaking with their partners :-)….” Whoa, you’ve given those trollops in Sweden suing Assange (WikiLeaks dude) a conviction and probably a death sentence (buhbye, dude!).
If you think your granite countertop is radioactive and you don’t have a scintillation counter or Geiger counter handy, get a piece of polaroid film (unopened frame) and tape it to the counter. After a couple of days, pull it up, peel the covering, and Voila! there will be a bright spot wherever there’s a bit of uraninite or monazite (and maybe some feldspars, residence of potassium). Their radioactivity exposes the film.
BFL – Well, we all have our superstitions, don’t we? I guess this one is yours.
Your “statistics” is the same kind of madness (i.e., bad math and incorrect assumptions) that lead people to play the lottery.
For example, your “statistics” about the TMI accident are limited to what you can regurgitate from Wikipedia. Meanwhile, those of us who are actually familiar with the epidemiological literature know that you can’t cite one credible paper that has found, with any certainty, any adverse health effects due to radiation from that accident.
Radiation
[youtube=http://www.youtube.com/watch?v=3VKzqAefBVY&w=480&h=390]
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?
Perhaps apes eating bananas was the trigger for the mutation that makes us humans.
Another “former nuclear worker” (Engineering type) here, with plenty of radiation health physics experience, to give a few examples of ex-nuclear-poweris (the Latin term) radiation exposure:
1. 400 miliRem per year of cosmic. (700 mR in Denver, 2500 mR if you are a commercial pilot, and roughly 4000 mR if you are a flight attendent.)
2. CAT Scan (1) = 1.8 R
3. Chest Xray = 100 mR
4. GI Track/fluoroscope = 30R to 70R, (or 30,000 to 70,000 milliRem)
5. EB Cancer treatment, about 20 to 30 R whole body, with 900 to 1200 R to the tumor. (Why it is effective!)
Other radiation sources:
A. Household Radon exposure – Jimmy Carter’s recommendation of tightening houses to 1/6 of an air exchange per hour would have increased the radon exposure such that the concomittant dose across the United States would have been equivalent to a Cherynoble accident once every 6 months…
B. Coleman lamp mantles: Made with Thorium nitrate (now Yerbittium, not nearly as bright…mantles made in China and Pakistan still have good old Th !!!)
C. “Salt Substitute” or Potasium Chloride, really raises the GM Counter nicely. Used to use this on Nuclear power talks given for a former employer. Got a LOT of attention when people realized they were EATING this…
D. Cigarettes ! Polonium 210, in the Phosphate fertilizer used to grow commercial tobacco. 1 pack per day = whole body dose of 5R per year. Lung dose of 15R per year, could be actual cause of lung cancers, not the tars and cyclic aromatic hydrocarbons usually blamed!
E. Mozanite Sands in Brazil: One stretch of beach, a few hundred miles long…gives you an Alpha dose of 1R per hour (that’s primarily SKIN, as alpha doesn’t penetrate) if you are lying on it. Great part about that is you can get a “tan” on both sides of your body at the same time!
Now let’s talk about “high level nuclear waste”. If ALL the high level waste from commercial Nuclear plants in the USA were put in one place, it would not completely cover the football field at any stadium, and it would barely reach 70′ high.
Dropping it in the subduction zone trench in the Bahaj, would send it to the center of the Earth in 100,000 years..where it would mix with the magma and never be noticed.
Simple, straightforward, and YES we live in a very radioactive enviroment. Ask Dr. Svensmark how that changes CLIMATE!
Max
It doesn’t, but his intention was to indicate that once the initial radon atom decay occurs (which may be delayed for some period of time since it has a 3.8 day half life), the subsequent daughter products follow a relatively rapid series of decays, followed by some longer decay times from pb210 on down the decay chain.
Imprecise wording perhaps, but the intent was clear that the reference was to the progression of the decay chain starting with radon.
http://www.ead.anl.gov/pub/doc/natural-decay-series.pdf
Larry
I skipped most of the comments, but if no one has mentioned salt substitute yet, I will. Salt substitute is mostly KCl which is similar chemically to NaCl or regular salt. It tastes similar and can be bought at most grocery stores. I used to use it as a radioactive check source for my gamma spectrometer. It is pretty toasty if you get close to a bottle with a geiger counter.
From Max Hugoson on February 16, 2011 at 7:58 pm:
Note the recent push with foods to reduce sodium intake, by replacing common sodium chloride with “sea salt.” And I keep thinking of all the assorted minerals that are dissolved in the sea, that end up in “sea salt” after removing the water from the “sea soup” (which contains numerous waste products from aquatic life), of which there are substances that virtually No One would willingly consume if they could avoid it. Like uranium, and just about every radioactive isotope on this planet…
Holy cow! I learned something new today. And my mother used to tell me to eat bananas, because they had lots of potassium that was good for me. I wonder what she would have said if she found out that potassium was radioactive. But this post relates an obvious truth: from my computer screen to bananas, radiation is EVERYWHERE! So don’t worry about it. Unless you get way too much of it.
The equipment used to measure radioactive stuff is soooo sensitive, however when
needle moves, and/or speaker squawked it must be bad, bad BAD.
Conflict bananas….worser than conflict diamonds.
Ditching nukes in banana shipments ^ crap… Unknown known, so far.
The following line is great…
“I didn’t have the heart to tell her about neutrinos.”
Me I have low tact, how about the massive dose passengers receive in an aircraft ride. Wonder if she has a passport?
Fred Finn traveled at 60,000 feet looks ok.
http://heritageconcorde.com/?page_id=4541
To bad we didn’t freak out like France did in the 70’s. We have 80% of our electric power produced by Nuclear Power TODAY. Oh wait….
Taught this stuff for 25 years.
Imagine 1 carbon-14 atom. It will only emit radiation once – more on this below. There is a 50-50 chance this one atom will emit its radiation in a 5500 year period (half-life). So what is that one atom doing the rest of the time? Nothing. Acting like carbon, smelling like carbon and going out on dates like carbon wants to do. One day it will emit its radiation, then never emit radiation again. Statisticians and rad professionals leave me alone on this next bit, as it is presented to make it understandable. So you need at least 10,000 carbon-14 atoms to get 1 disintegration per year. 10, ooo x 365 x 24 x 60 x 60 atoms to get 1 disintegration per second (1 Bq). That is 3 E11 C-14 atoms to get 1 Bq. The longer the half-life, the more atoms it takes to get any significant disintegrations. See the table below.
Back to the one C-14 atom. It has too many neutrons in the nucleus. It is not comfortable with that fact. Imagine buttons on a too tight shirt. One day one of those neutrons (buttons) pops and emits an electron (beta particle is the correct term but a beta particle is an electron). The electron has a lot of energy like a bullet from a gun. And like a bullet, it will lose that energy as it interacts with the environment, but cause changes and maybe damage as it loses the energy. Eventually it becomes a free electron just hanging around until some big boy picks it up.
Meanwhile, what happened to the C-14 atom? Well the neutron that emitted the electron, instantaneously becomes a proton. That atom now has 7 protons and 7 neutrons. It is now a N-14 atom. N-14 is not radioactive. How many times did the one C-14 atom emit radiation? Once and only once.
The are basically six factors that need to be accounted for when determining the hazard of a radioactive material. I have presented two above: half-life and quantity (number of atoms). Because of its relatively long half-life, if I put five atoms of C-14 in your body, chances are high that none of them will emit radiation in your lifetime.
Test question: From the info I’ve given above, roughly how many atoms of U-238, which has a 4.5 billion year half-life, do you need to get 1 disintegration per second (1 Bq)? Radiation professionals are not allowed to respond! Bonus points for converting to gm.
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
Note it takes very little mass of a short half-life nuclide to equal a Curie (3.7E10 Bq). If all the other factors I haven’t discussed are equal, then pound for pound a short half-life nuclide can be much more dangerous. If anyone wants, I can continue and try to simply explain the other four factors.
Yeah I wrote a letter to the editor of my local paper several months ago about this, regarding the campaign they are colluding in to shut down the Vermont Yankee reactor over some tritium leaks, and explaining that the local lefty food co-op’s fruit section is a bigger radiation threat. They refused to publish, no big surprise.
Wow . . .
Just read the entire thread and I have learned stuff I never knew. Thanks everybody.
Edit note to Anthony: typoz —
“reasearch” = research
“Among the most naturally radioactive food known are” = foods
______
The “lifespan” effects may be incorrect in sign:
Taipei radiation study
(My emphasis)
🙂
Moderator: I accidentally double clicked my first post and it did not like that. If it got through, please delete this post.
Taught this stuff for 25 years. Many antinuclear folks make a big deal out of half-life, so I would like to address it here. Incidentally, substitute salt (KCl) has less chance of self-absorption and makes a great demonstration tool for Potassium-40 in our environment. Buy it at the grocery store when you buy your bananas.
Imagine a single Carbon-14 atom and its nucleus of 6 protons, 8 neutrons. There are too many neutrons in the nucleus, and the atom is uncomfortable – imagine straining buttons on a too tight shirt. One day one of the neutrons pops. A tiny bit of the neutron flies off into space. This tiny bit is an electron (aka a beta particle for you professionals). The electron has a lot of energy like a bullet from a gun. And like a bullet, it will lose its energy as it interacts with the environment – eventually coming to rest. The energy it imparts will cause changes in the environment that may or may not be harmful. For example, the electron may break the hydrogen bond on a water molecule that is nearby. If the free hydrogen gets back together with the hydroxyl molecule, then no harm.
Meanwhile what happened to the C-14 atom? Well the neutron that “popped” instantaneously becomes a proton. The nucleus now has 7 protons and 7 neutrons! It just became a N-14 atom. N-14 is not radioactive. How many times did the atom emit radiation? Just once and only once. All radioactive atoms emit their radiation only once. Some, like C-14, immediately become a non-radioactive atom. Some like Uranium-238 change to an atom that is radioactive and someday will also emit its radiation.
Okay, our single C-14 atom will only emit its radiation once. When will it emit the radiation? We don’t know. Our atom has a 50-50 chance of emitting its radiation in a 5,500 year period. What is the atom doing the rest of the time until it “pops”. Nothing. It is acting like carbon, smelling like carbon, and going out on dates like carbon likes to do. No radiation emissions until the fateful day that it becomes a N-14 atom.
(Radiation pros leave me alone on this next bit as I know I really simplify it.)
How many C-14 atoms does it take to make 1 disintegration per second (1 bq)? It would take roughly 10,000 atoms to get 1 disintegration per year. 10,000 x 365 x 24 x 60 x 60 = 3E11 atoms. If I were to put five atoms of this relatively long half-life C-14 in your body, odds are that none of them would emit their radiation during your lifetime.
I’ve presented two of the six factors that determine the hazard of a radioactive material: half-life and quantity (# of atoms). Presuming all other factors are equal, when the quantity is very small and the half-life is large, the risk is essentially zero. A short half-life nucleide can be more dangerous depending on the other factors.
The following table gives you a clue as to the relationship of quantity and half-life plays out. A Curie (Ci) and a TerraBequrerel (TBq) are measures of the relative hazard. I handle a Ci or TBq very carefully.
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
As the half-life increases, it takes a lot more mass (# of atoms) to give a Ci or TBq worth of radiation.
One critical factor in determining the hazard of a radionuclide is its chemical form. The uranium used in a powerplant is in a chemical form that if you swallow it, likely you will poop out greater than 99% within 3 days. However if this is ground into an aerosol with a low AMD number (<10) and you breath it in, then about 10 – 20 % will lodge in the lung with eventual transport to other parts of the body. If our body likes the chemical form, it will be taken up. If not, then we poop, pee and or otherwise excrete the material fairly quickly. Some other contributors mentioned nuclides that are analogous to chemicals which our bodies like. Radium and Cesium are a couple of those. I might swallow a source of radium encapsulated in plastic that I wouldn't worry two hoots about, but I handle radium salts very, very carefully.
Other factors are the type of radiation, the energy of the radiation, how it gets deposited, and whether or not it decays to another radionuclide
I see the table in the previous post looks lousy. How do you do a good table posting to a site like this?
What I find surprising is the huge amount of misinformation that exists about radiation. I find that not a single patient who’s refused to get a chest xray because of “dangers of radiation” knows about K40. These same patients will have no qualms about flying to Australia where they receive more radiation during their flights than during the chest xray!
The most devastating study debunking the no-threshold assumption was published in spring 2004 in the Journal of American Physicians and Surgeons. It documented the effect of accidental contamination of structural steel with Co-60 which was used to construct apartment buildings. (link: http://www.jpands.org/vol9no1/chen.pdf). The expectation was increased deaths from cancer whereas the exact opposite occurred: 242 deaths were expected based on age standardized cancer mortality and 7 were observed.
What I find most surprising is the minimal amount of publicity this has received with the only article referencing it in the MSM being a recent article in the Financial Post which was given in a previous comment. I’ve printed out a copy of the JAPS article to give to my radiationphobic patients who sometimes will be ready to spend $1500 to get an MRI rather than an xray.
Thanks for the info regarding the CT scan/lung cancer link Rational Debate; another piece of information I can give to the radiationphobic. Perhaps I should shock them with some of the pottery I painted years ago (when I had time for such diversions) using Uranium oxide to make a nice yellow underglaze paint. When I get around to buying a geiger counter will see how radioactive those ceramic pieces are.
There are some excellent comments regarding radiation risk. To add to them…
There is a huge controversy in the radiation world regarding low dose radiation. With thousands of studies demonstrating low doses can have a beneficial effect, then it rapidly becomes a moral and ethical question of whether or not we should limit or try to eliminate low dose radiation. For example, if a low dose gives one susceptible individual a cancer, but prevents hundreds of thousands from getting a cancer (research seems to indicate this is possible), where should the limits be set? In other words, if we set the limits extremely low, like we do now, you might get a cancer but that one susceptible person may not. It is a huge dilemna and has large impact on the costs of protecting the public from radiation. The present day limits are set based on the precautionary principle. However, if low doses are good for us, then this precautionary principle may harm more than it helps.
The 10 mRem equals so much risk concept is a scientific joke. It is derived, based on precautionary principle, from high dose radiation effects. There are no (none, zip, nada) studies that show low dose radiation has any deletorius effect on our life spans. Yes, there are lots of sttudies showing deletorius effects at the atomic and cellular level, but too often overlooked is the amazing ability of our cells and organs to repair the deletorius effects (which exercises the repair mechanisms). Compared to other things, low dose radiation is very weak in causing harm at the microscopic level. Our bodies have been handling low dose radiation ever since we were mudpuppies. Without the small assault of low dose radiation, would those repair mechanisms wither? Research seems to indicate this is so. Bernard Cohen at the U of Pittsburgh has demonstrated that the level of Radon that the EPA considers hazardous (4 – 20 pCi/l) seems to be better for us than getting less than 4 pCi/l. Go figure, but no one has been able to refute his work, and more than a few have tried.
Don’t forget, that background radiation is the reason we are here in the first place. Without it the mutation rate in DNA would be much less and evolution would either have been much slower or not occurring at all.
I love bananas! But that’s because I’m a chimp, really.