So long as you don’t wind up with a piece of the alpha-emitter inside you (ex. by eating it, breathing it, introduction via a wound) they are radiologically harmless. Alpha particles are highly charged and comparatively heavy since they have two protons and two neutrons. That mass and charge means that they make a lot of collisions and dump a ton of energy along a short track… VERY short, like the diameter of an individual cell even. Devastating if they are doing that in living tissue due to massive energy deposition all concentrated in a particular area, but on the outside the layers of your skin will adequately protect you. Or, as memes of old have put it:
They are of more concern as like an airborne gas or dusty contamination since you may not be aware if you are breathing them in or accidentally eating traces after touching a innocuous looking dusty surface and not washing your hands before lunch.
A little thought exercise they tell you when you study radiation: if you were to hypothetically have four equivalent activity sources that emitted alpha, beta, gamma and neutron radiation, and you have only four methods of either putting one in your pocket, throwing it in the trash, eating it, or holding it in your hand, which emitter do you match to which method?
Alpha is fine to hold in your hand since your skin will block the alpha particles; you want to avoid eating it because that would really mess you up. Beta has a bit more penetration so you don’t want to have it in your hand but the pocket is relatively fine. Neutron radiation is very penetrating except for moderators similar in mass to neutrons like the hydrogen atoms in water which the neutrons collide with and dump a ton of energy on; unfortunately you are made up of a lot of excellent moderating material where those neutrons would dump a lot of energy in you so you don’t want those anywhere near you and it’s best to throw that source away. Gammas are also highly penetrating so they don’t care that much about small differences like being in your hand or pocket but through having basically no mass and no charge they aren’t particularly likely to interact with you either so all else being equal they’re the safest of the emitters to have inside you if that’s a forced option.
The idea is that it gets mostly blocked by the combo of the layers of clothes and skin so that kind of optimizes you not absorbing dose for that contrived scenario. If you swap beta with alpha then the beta will be doing more damage because it can penetrate the skin while the alpha is still entirely blocked. If you swap the beta with the gamma then the beta will be depositing basically all of the energy inside you and the gamma will not really be shielded at all from being in the pocket so that’s also more dose. If you have the neutron source swapped with the beta then although the beta is no longer a problem the neutrons will be penetrating you and moderating throughout your body which is bad. So beta in the pocket is the optimized option for that scenario even if it’s not necessarily where you would want to keep it in real life… similarly don’t actually go around eating gamma sources lol.
Wait, I thought neutrinos were the ones that were electromagnetically neutral and thus didn’t interact with anything (that’s why they’re so penetrative, they just ignore the electron shells).
Neutrinos are indeed tremendously penetrating precisely due to very little mass and no charge, many are constantly streaming through the entire world and you at any given moment. They are also way less likely to interact with matter than gamma rays. Since they very rarely do much of anything (you have to build ridiculous facilities to have a chance of detecting their uncommon interactions) they are not really considered as ionizing radiation.
Neutrons have much more mass but are still electrically neutral. Most materials have much more mass than a neutron so they bounce off and barely lose any energy in their collisions, sort of like when you throw a ping pong ball at a wall, which keeps them as highly penetrating in many materials. They only appreciably slow down when they collide with atoms similar in mass to them like the hydrogens in water, think like how a billiard ball will hit another and dump almost all of its energy into the similarly sized ball. So materials like water and concrete are good shielding for neutrons but lead not so much.
Erm, actually, neutrinos aren’t massless. The Super-Kamiokande experiment has observed neutrinos to oscillate between electron-muon-tau lepton family numbers (or flavors), which means that they experience time and necessarily travel slower than the speed of light, which implies that they have a nonzero rest mass. This discovery changed the Standard Model and resulted in a Nobel prize.
they aren’t particularly likely to interact with you either so all else being equal they’re the safest of the emitters to have inside you
First time I’ve heard of this. Care to give a source?
(edit) By the way, actinium-225, a strong alpha emitter, is being used as cancer medication. Capsules are implanted near inoperable tumors and function like radiation therapy.
Other person handled a source on it but one way to think of it is like x-rays. Gamma rays are more much more energetic x-rays basically. X-rays are used in imaging becuase they easily pass through less dense materials like your flesh but not as much in dense materials like say bone. The difference in the distribution of x-rays that passed through your body to get to the other side can be used to make an image showing those differences in density. The higher the energy of the light in this part of the spectrum increases the penetration (not necessarily the case for light in general but at this end of the pool yes), more penetration means less of a percentage of the energy is deposited along the path so more makes it through. Though, even a fraction of high energies deposited can still be bad for you if enough is shining on you. But anyway human tissue is mostly not dense and gamma rays are best attentuated by dense materials like a lead blanket or something so gamma rays coming from the inside can escape you. If you swallow beta or alpha the size and charge of the particle makes it much harder to escape you so virtually all of their energy would be deposited inside you. And neutrons are well moderated by the materials your body is composed of so they will also dump a ton of energy in your body. Alpha and neutron radiation get multipliers for the biological effect of the energy they deposit that reflect them having a much worse impact on you than beta and gamma.
Alpha emitters have medical applications in the body if well-targeted and immediately adjacent or inside of something you want destroyed. For instance boron neutron capture therapy was developed which entails providing B-10 in a compound that is selectively taken up by tumors but ideally NOT by healthy tissue. They then shine a particular energy spectrum of neutrons that will penetrate to the level the cancer is in and the neutrons are captured by the boron isotope (which is very very good at capturing neutrons). The resulting nucleus is not stable and releases an alpha particle, ideally causing massive local damage to the cancerous cell while the short range spares healthy cells.
First generation for that treatment when it was devised many decades back botched it though and wound up killing patients even faster (though it was introduced on people with brain cancers that were basically a death sentence anyway which I guess is where people were willing to try anything). The boron containing compound didn’t target the tumor as selectively as hoped for so a lot wound up in healthy tissues, the neutron energy was too low so the neutrons didn’t penetrate to the necessary depth to destroy the tumors deep in the skull but did cause a lot of damage to healthy scalp tissue, etc.
That said it underwent a lot of refinement later that made it a much more effective treatment.
I think it is true that gamma rays can go right through you without hitting you. Not sure what the absorption rate is, but considering 5cm of concrete only absorbs half of a given gamma radiation source, it’s likely pretty low.
This paper seems to imply that the half-value of human flesh is around 10cm under 10MeV, but up to 40cm at 100MeV:
So I guess the gamma radiation from a gamma emitter in your stomach would be around 25-75% absorbed, depending on your diameter and the emitter. Not great, but still not 100% absorbed like the other sources, at least.
So long as you don’t wind up with a piece of the alpha-emitter inside you (ex. by eating it, breathing it, introduction via a wound) they are radiologically harmless. Alpha particles are highly charged and comparatively heavy since they have two protons and two neutrons. That mass and charge means that they make a lot of collisions and dump a ton of energy along a short track… VERY short, like the diameter of an individual cell even. Devastating if they are doing that in living tissue due to massive energy deposition all concentrated in a particular area, but on the outside the layers of your skin will adequately protect you. Or, as memes of old have put it:
They are of more concern as like an airborne gas or dusty contamination since you may not be aware if you are breathing them in or accidentally eating traces after touching a innocuous looking dusty surface and not washing your hands before lunch.
A little thought exercise they tell you when you study radiation: if you were to hypothetically have four equivalent activity sources that emitted alpha, beta, gamma and neutron radiation, and you have only four methods of either putting one in your pocket, throwing it in the trash, eating it, or holding it in your hand, which emitter do you match to which method?
Alpha is fine to hold in your hand since your skin will block the alpha particles; you want to avoid eating it because that would really mess you up. Beta has a bit more penetration so you don’t want to have it in your hand but the pocket is relatively fine. Neutron radiation is very penetrating except for moderators similar in mass to neutrons like the hydrogen atoms in water which the neutrons collide with and dump a ton of energy on; unfortunately you are made up of a lot of excellent moderating material where those neutrons would dump a lot of energy in you so you don’t want those anywhere near you and it’s best to throw that source away. Gammas are also highly penetrating so they don’t care that much about small differences like being in your hand or pocket but through having basically no mass and no charge they aren’t particularly likely to interact with you either so all else being equal they’re the safest of the emitters to have inside you if that’s a forced option.
Wouldn’t you want the beta in your hand so that your body mass proximity is lower? (and avoiding proximity to your “T storage”)
The idea is that it gets mostly blocked by the combo of the layers of clothes and skin so that kind of optimizes you not absorbing dose for that contrived scenario. If you swap beta with alpha then the beta will be doing more damage because it can penetrate the skin while the alpha is still entirely blocked. If you swap the beta with the gamma then the beta will be depositing basically all of the energy inside you and the gamma will not really be shielded at all from being in the pocket so that’s also more dose. If you have the neutron source swapped with the beta then although the beta is no longer a problem the neutrons will be penetrating you and moderating throughout your body which is bad. So beta in the pocket is the optimized option for that scenario even if it’s not necessarily where you would want to keep it in real life… similarly don’t actually go around eating gamma sources lol.
Wait, I thought neutrinos were the ones that were electromagnetically neutral and thus didn’t interact with anything (that’s why they’re so penetrative, they just ignore the electron shells).
Neutrinos are indeed tremendously penetrating precisely due to very little mass and no charge, many are constantly streaming through the entire world and you at any given moment. They are also way less likely to interact with matter than gamma rays. Since they very rarely do much of anything (you have to build ridiculous facilities to have a chance of detecting their uncommon interactions) they are not really considered as ionizing radiation.
Neutrons have much more mass but are still electrically neutral. Most materials have much more mass than a neutron so they bounce off and barely lose any energy in their collisions, sort of like when you throw a ping pong ball at a wall, which keeps them as highly penetrating in many materials. They only appreciably slow down when they collide with atoms similar in mass to them like the hydrogens in water, think like how a billiard ball will hit another and dump almost all of its energy into the similarly sized ball. So materials like water and concrete are good shielding for neutrons but lead not so much.
neutrons =/= neutrinos
Oh whoops, I misread the chart.
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Erm, actually, neutrinos aren’t massless. The Super-Kamiokande experiment has observed neutrinos to oscillate between electron-muon-tau lepton family numbers (or flavors), which means that they experience time and necessarily travel slower than the speed of light, which implies that they have a nonzero rest mass. This discovery changed the Standard Model and resulted in a Nobel prize.
deleted by creator
First time I’ve heard of this. Care to give a source?
(edit) By the way, actinium-225, a strong alpha emitter, is being used as cancer medication. Capsules are implanted near inoperable tumors and function like radiation therapy.
Other person handled a source on it but one way to think of it is like x-rays. Gamma rays are more much more energetic x-rays basically. X-rays are used in imaging becuase they easily pass through less dense materials like your flesh but not as much in dense materials like say bone. The difference in the distribution of x-rays that passed through your body to get to the other side can be used to make an image showing those differences in density. The higher the energy of the light in this part of the spectrum increases the penetration (not necessarily the case for light in general but at this end of the pool yes), more penetration means less of a percentage of the energy is deposited along the path so more makes it through. Though, even a fraction of high energies deposited can still be bad for you if enough is shining on you. But anyway human tissue is mostly not dense and gamma rays are best attentuated by dense materials like a lead blanket or something so gamma rays coming from the inside can escape you. If you swallow beta or alpha the size and charge of the particle makes it much harder to escape you so virtually all of their energy would be deposited inside you. And neutrons are well moderated by the materials your body is composed of so they will also dump a ton of energy in your body. Alpha and neutron radiation get multipliers for the biological effect of the energy they deposit that reflect them having a much worse impact on you than beta and gamma.
Alpha emitters have medical applications in the body if well-targeted and immediately adjacent or inside of something you want destroyed. For instance boron neutron capture therapy was developed which entails providing B-10 in a compound that is selectively taken up by tumors but ideally NOT by healthy tissue. They then shine a particular energy spectrum of neutrons that will penetrate to the level the cancer is in and the neutrons are captured by the boron isotope (which is very very good at capturing neutrons). The resulting nucleus is not stable and releases an alpha particle, ideally causing massive local damage to the cancerous cell while the short range spares healthy cells.
First generation for that treatment when it was devised many decades back botched it though and wound up killing patients even faster (though it was introduced on people with brain cancers that were basically a death sentence anyway which I guess is where people were willing to try anything). The boron containing compound didn’t target the tumor as selectively as hoped for so a lot wound up in healthy tissues, the neutron energy was too low so the neutrons didn’t penetrate to the necessary depth to destroy the tumors deep in the skull but did cause a lot of damage to healthy scalp tissue, etc.
That said it underwent a lot of refinement later that made it a much more effective treatment.
I think it is true that gamma rays can go right through you without hitting you. Not sure what the absorption rate is, but considering 5cm of concrete only absorbs half of a given gamma radiation source, it’s likely pretty low.
This paper seems to imply that the half-value of human flesh is around 10cm under 10MeV, but up to 40cm at 100MeV:
https://www.researchgate.net/publication/345815027_Investigation_of_Gamma-Ray_Attenuation_Coefficients_for_Some_Different_Tissues
So I guess the gamma radiation from a gamma emitter in your stomach would be around 25-75% absorbed, depending on your diameter and the emitter. Not great, but still not 100% absorbed like the other sources, at least.