About those radiation charts: Cesium 137 was never in natural "background radiation"

There was no "background radiation" that included cesium-137 before nuclear testing and nuclear accidents such as Chernobyl.

There are, of course, naturally occurring radioactive materials.

But lumping all types of radiation together is misleading like comparing apples to oranges.

As the National Research Council's Committee to Assess the Scientific Information for the Radiation Exposure Screening and Education Program explains:

Radioactivity generates radiation by emitting particles. Radioactive materials outside the the body are called external emitters, and radioactive materials located within the body are called internal emitters.

Internal emitters are much more dangerous than external emitters. Specifically, one is only exposed to radiation as long as he or she is near the external emitter.

For example, when you get an x-ray, an external emitter is turned on for an instant, and then switched back off.

But internal emitters steadily and continuously emit radiation for as long as the particle remains radioactive and are much more dangerous.

http://www.counterpunch.org/takashi03222011.html

Hirose Takashi:

All of the information media are at fault here I think. They are saying stupid things like, why, we are exposed to radiation all the time in our daily life, we get radiation from outer space. But that’s one millisievert per year. A year has 365 days, a day has 24 hours; multiply 365 by 24, you get 8760. Multiply the 400 millisieverts by that, you get 3,500,000 the normal dose. You call that safe? And what media have reported this? None. They compare it to a CT scan, which is over in an instant; that has nothing to do with it. The reason radioactivity can be measured is that radioactive material is escaping. What is dangerous is when that material enters your body and irradiates it from inside. These industry-mouthpiece scholars come on TV and what to they say? They say as you move away the radiation is reduced in inverse ratio to the square of the distance. I want to say the reverse. Internal irradiation happens when radioactive material is ingested into the body. What happens? Say there is a nuclear particle one meter away from you. You breathe it in, it sticks inside your body; the distance between you and it is now at the micron level. One meter is 1000 millimeters, one micron is one thousandth of a millimeter. That’s a thousand times a thousand: a thousand squared. That’s the real meaning of “inverse ratio of the square of the distance.” Radiation exposure is increased by a factor of a trillion. Inhaling even the tiniest particle, that’s the danger.

This one has some effort and study at least behind it.

Or power and energy. People confusing these will remain confused, but that's the goal, isn't it.

and the public unfortunately will learn those numbers by the time this disaster plays out.

intensity (say, 1 mSv/h) by the number of hours you are exposed, to get a dose. With internal emitters, that time is until you get rid of the emitters or until you die.

not here if we're lucky.

At that point I'll want to see the feel good charts of yesteryear!

http://www.boingboing.net/2010/08/27/bananas-are-radioact.html


-- snip
Meggitt worked for the United Kingdom Atomic Energy Authority and its later commercial offshoots for 25 years. He says there's an enormous variation in the risks associated with swallowing the same amount of different radioactive materials—and even some difference between the same dose, of the same material, but in different chemical forms.

It all depends on two factors:
1)The physical characteristics of the radioactivity—i.e, What's its half-life? Is the radiation emitted alpha, beta or gamma?
2) The way the the radioactivity travels around and is taken up by the body—i.e., How much is absorbed by the blood stream? What tissues does this specific isotope tend to accumulate in?

The Potassium-40 in bananas is a particularly poor model isotope to use, Meggitt says, because the potassium content of our bodies seems to be under homeostatic control. When you eat a banana, your body's level of Potassium-40 doesn't increase. You just get rid of some excess Potassium-40. The net dose of a banana is zero.

And that's the difference between a useful educational tool and propaganda. (And I say this as somebody who is emphatically not against nuclear energy.) Bananas aren't really going to give anyone "a more realistic assessment of actual risk", they're just going to further distort the picture.

Being near bricks (even living in a brick house) isn't much of an issue. Inhaling brick dust can be.

"the potassium content of our bodies seems to be under homeostatic control. When you eat a banana, your body's level of Potassium-40 doesn't increase. You just get rid of some excess Potassium-40. The net dose of a banana is zero."

Wrong.

Your body doesn't know the difference between radioactive K and non-radioactive K. As such, you can not "get rid of some excess Potassium-40". You can get rid of some excess K, radioactive or not. In addition, one could argue that the K already in your body is somewhat depleted of it's radioactivity - it's already decayed. Bringing in new K may replace the old K, 'refreshing' it's radioactivity.

Either way, the radioactivity from bananas is still negligible. They can be a useful tool in helping to educate about how much radioactivity is really dangerous. Although you often see such people respond by stopping eating bananas and removing the granite countertops from their house.

I am not intending to reduce my banana consumption.

one of the bad critters, cesium or something!

Total additional dose from eating a banana, after figuring length of time excess potassium-40 is in your system, closeness of potassium to organs and cells, and biological harm caused by potassium-40's particular profile of radiation types, apparently comes to about 1/1,000 of a microsievert (0.001 uSv) (see stuff from Wikipedia below).

For comparison, dose (in terms of biological harm) from a chest x-ray is quoted by various sources anywhere from 35 to 100 microSieverts, as far as I can find.

So, roughly speaking, eating 35,000 bananas a year would be expected to give similar harm to the body as 1 chest x-ray per year. But, considering 35,000 bananas a year is like 100 bananas a day, you would probably die from overeating after the first day.

On the other hand, the dose from eating an amount of Iodine-131 with an equal amount of Curies as a banana would be quite different, I think, since Iodine concentrates in the thyroid and may not be easily eliminated. Unfortunately, I haven't found a similar calculation for expected dosage from ingesting a given amount of Iodine-131. Perhaps some of the numerous radiation experts that seem to have appeared on this site could assist with that.

It's also important to consider that these effects don't necessarily 'scale'. If dose A is 100 times dose B, for the same time period, it does not necessarily follow that dose A causes 100 times the harm of dose B (might be more, might be less, it's complicated); in addition, the same dose over a long period of time will likely have a different effect than that dose received over a very short period of time.

From wiki http://en.wikipedia.org/wiki/Banana_equivalent_dose :
======
The major natural cause of radioactivity in biomass is potassium. One in ten thousand potassium atoms (0.0117%) is an unstable isotope, potassium-40 (abbreviated 40K). This isotope has a half-life of about a billion years (4×1016 s). Therefore, out of a gram of potassium about 30 atoms disintegrate per second, or in other words the activity of potassium is 30 Bq g-1.<12> Each decay event releases an average of 1.3MeV of energy, so each gram of potassium continuously radiates ~10-11 watts of power.<13>

An average banana contains about half a gram of potassium.<14> Therefore if a typical person (70kg) is exposed to all of the radiation coming from one banana then the dose they will be absorbing is of order 10-13 watts per kg (or gray per second). Since 40K decay emits an electron or positron, the weighting factor of 1 is used to quantify the basic biological effect; the equivalent dose rate is of order 0.0001 μSv per hour.

A person's body maintains potassium under homeostasis, at a fairly constant level.<15> Therefore, eating an extra banana will not cause more potassium to be assimilate into the body than would otherwise have occurred. Instead it will cause the body to excrete potassium more quickly. Because the half-life of 40K is so long compared to biological time-scales and because the ratio in food is the same as that in the body, the isotopic ratio will stay the same. Therefore, eating a banana will only cause a temporary increase in the quantity of radioisotope enclosed by the body. For example, if excess potassium atoms consumed from one banana were estimated to take an average of 8 hours to be excreted from the body, the total additional dose of radiation would be around 0.001 μSv.
======

But I see a lot of stuff that seems to be equating radioactive materials (matter) with "radiation" (energy).

My point below was that at the energy levels we are talking about (high as compared to the amount of space involved) the distinction between "matter" and "energy" isn't exactly easy to make.

Radiation can be protons, electrons, or photons; generally the protons and electrons are called matter and the photons are called energy, but again at the sizes and energies we're talking about it's kind of a distinction without a difference.

It's a beta (electron) emitter, but so are a ton of other things.

It decays to IIRC Barium, which is a mild gamma (photon) emitter.

The worry with Cesium is not that it's particularly radioactive, but that it's exceptionally reactive, and will bond with almost anything, so it's hard to get rid of.

Thanks for continuing to humor me :hi:

If you swallow or inhale it, it's likely to bond to tissue and stay in your body for a long time.

So the fact that the radiation it produces is not terribly strong compared to environmental radiation sources can be misleading, because unlike those sources cesium will stay inside you for a long time. He's also saying that there isn't radioactive cesium in the environment naturally, so you shouldn't compare it to radiation sources that we evolved to cope with (I'm not persuaded on that count, but I'm doing my best to speak for him here).

Thanks for taking the time :)

Thanks...

http://www.physics.isu.edu/radinf/natural.htm



My understanding is that natural reactors can't occur today. The radioactive elements found in nature are decays from the original creation, and more decay has occurred in the 2 billion years since Oklo was active.

Really fascinating. Especially since it appears that the natural reactor bred its own plutonium.

In a much more detailed account, I read that one site studied appeared to have a natural flux. Fission would occur, would build up heat, burn off steam, accumulate poisoners like xenon and stop. Then it would cool and water would leach back in, and the cycle would start again. They estimated around a 3 hour cycle.

That's what I thought of when I read about very weak neutron "beam" detected from the 13th through the 16th 1.5 km off the Daiichi site. Because it flickered. I wondered if that wasn't due to activity in the spent fuel pond on 4 or 3.

Unlike certain crappy, meaningless panic-inspiring, mouth-breathing OP's I have seen from you on the issue.

It's good to see you were inspired to do some studying.

It's the unclarity, stupid.

And thanks for proving my statement that radiation is not a monolithic thing to be true.


NO ONE ever said, Cesium 137 is harmless and NO ONE ever said it occurs in nature.