Word on the street is that radiation levels you get never go down, as long as you live. Is that true? Why is it? So if I get a CT scan, I will get hit with say xxxx milirems or whatnot, and that will just add and add to my total radiation exposure?
But why does the radiation never go down over time? Why is it just worse and worse? Don’t these radioactive naughties the CT scans give us dissipate over time?
The radiation goes away instantly. The damage done by the radiation may or may not go away with time, depending on what sort of damage it was. The type of damage most often worried about is cancer, and most cancers don’t usually spontaneously go away. On the other hand, a sunburn will go away in a week or so.
Your “word on the street” is wrong.
When people say “radiation” they are generally referring to specific types of electromagnetic radiation. Electromagnetic radiation in general is a whole bunch of stuff. At the low frequency range you have long waves (useful for communication through polar ice but not much else), radio waves, microwaves (which are just higher frequency radio waves), infra-red light, visible light, ultraviolet light, x-rays, gamma rays, and cosmic rays. The lower frequencies are basically harmless. People generally don’t freak out if someone shines a flashlight on you, for example. People freak out over microwaves from cell phones and such, but they really don’t have any reason to. Radio waves aren’t any more harmful than visible light. Get a high enough power of radio waves and you’ll cook things (that’s how your microwave oven works), but if you get enough visible light on something you can cook it too, as kids with magnifying glasses have often demonstrated by frying ants.
At higher frequencies though, things change. Part way through the ultraviolet part of the spectrum, the electromagnetic radiation becomes “ionizing”, meaning that it can strip the electrons off of atoms and create ions. When people say “radiation” they generally mean ionizing radiation (x-rays, gamma rays…). This is the stuff that’s really bad for you, because it causes cell damage and cancers. Your body really doesn’t like having its molecules ripped apart and turned into ions.
Ionizing radiation is a lot like the lower frequency radiation though. When you turn off the flashlight, the visible light is gone. As soon as you remove the x-ray source, the radiation from it is gone too. Your “word on the street” seems to think that the “radiation” is some sort of solid, tangible thing that builds up in your body. It isn’t.
Your body can repair a certain amount of damage from radiation. It has to do it every day. Every day you walk out into sunlight, and the sunlight smashes into your skin and wreaks havoc on some of your molecules. Too much radiation though is going to kill your cells or cause lots of damage to the point where you’ll end up with some sort of cancer.
Obviously, if you get a whopping big dose of radiation all at once that can be very bad for you. Long term chronic exposure can be bad too. If you happen to be a radiation worker of some sort, national regulations don’t allow you to be exposed to more than 5,000 mrem per year. The safety regulations for us common folk are much lower, only 100 mrem per year. If you get x-rays and such they are going to total up your dosage, and try to keep it under 100 mrem per year. A typical x-ray is going to be about 10 or 20 mrem, so you don’t really want to go having bunches and bunches of x-rays done every year. But this stuff doesn’t accumulate in your body anywhere. Just because you had 5 x-rays last year doesn’t mean you can’t have any this year.
To put things in perspective, most of us get exposed to about 300 mrem per year from natural sources (sunlight, radon, the background radiation of the entire universe, etc).
Good explanation engineer_comp_geek.
All I can add to engineer_comp_geek’s explanation is that there’s no hard-and-fast line separating ionizing radiation from nonionizing, since some atoms and molecules are easier to ionize than others.
You need to find Rad Away power-ups to remove radiation poisoning.
To piggyback on the original question a bit:
Back in the early days of nuclear testing, there was a debate in the scientific community about whether a radiation “threshold” exists. Some scientists (many associated with the AEC) argued that exposure to radiation under a certain amount over a given length of time was more or less harmless. Other scientists maintained that there was no such thing as a safe dose, that any exposure increased your chance of cancer proportionally.
engineer_comp_geek’s explanation would seem to fall squarely in the threshold camp. Is this no longer a point of contention?
I think you are asking about the general concept of cumulative dose injury. In one sense all of the damaging radiation you’ve ever received increases your total risk of cancer (and early cell senescence, among other things). In another sense each subsequent dose of radiation you receive can be considered all on its own, and is independent of all prior exposures.
You might think of it this way: every damaging radiation dose is a game of Russian roulette with your cellular mechanisms (DNA in particular, but not exclusively). DNA is the factory for all the chemicals you need to stay alive and healthy. Suppose a given dose of damaging radiation has a one in a million chance of injuring your DNA in a way that it either cannot be repaired properly or that the repair process itself has a one in a million chance of working incorrectly. So if you get just one dose, hey; no biggie. If you get a thousand doses, you start to get nervous. A million doses? Pretty bad odds.
Yet for each of those individual radiation doses, you only had a one in a million chance of crapping out from it. The idea of cumulative radiation injury is not so much that the prior individual dose injury was critical; it’s the idea that from a statistical perspective, the total chance that radiation gun wins the Russian roulette game is the sum of all the previous shots plus the current trigger pull. And it might just be a single given dose that’s the one which picked off the DNA just so for a critical cell patrolling against cancer.
It’s not quite as simple as that, but that’s the basic idea. Radiation injury is cumulative also in the same way that lobbing little grenades into a very large factory is cumulative. The radiation–the grenade–doesn’t stick around but the damage might not get repaired perfectly back to a like-new whole. Or you might only knock out the main system with one grenade and it might be years before you pick off both of the two back-up systems. etc.
Finally, there is a concept of threshold dose for creating any injury at all, but we don’t know what it is. Say you are trying to kill me with a cork pop gun. It’s probably possible but it might take a while. If you only have a kid’s toy shooting really soft nerf balls, it might never happen. A .22 could kill me in a single lucky dose. A bazooka would be fatal almost always. So a million nerf balls which equal the energy of a single .45 caliber might be a safer “cumulative dose” of damaging energy. But those kinds of fine points are a bit too tricky to add up, and we know that most radiation we’re using in medical studies is at least strong enough to do some damage. It therefore makes sense to talk about “cumulative dose” with an assumption that every individual dose crosses the threshold.
There is also the possibility of a hormesis (sub-threshold exposure actually being beneficial by stimulating the repair systems). The Master is skeptical, but reports that the jury is still out.
I thought the Master kind of missed an opportunity there. IMO he should have point out that if at low levels you can’t tell whether radiation is either bad or maybe even GOOD for you, it certainly can’t be very bad.
And it could be that without natural background radiation the rate of cancers would drop 50% and people would live to be 120.
You dont think the statistiscians correct/account for the background radiation?
And thats STILL irrelvant because you aint getting rid of background radiation pretty much by definition.
Statisticians can determine background rates for cancer, but how do you split that up by cause? There’s radiation, as we’re discussing, but there’s also a lot of inherent sloppiness in our biochemistry. There’s lots of natural chemicals, inevitable products of our metabolism, that can cause DNA damage. Plus there’s simple errors in DNA replication, or chemical carcinogens in our environment, or any of a host of things that muck things up and lead to cancer. As much as cancer researchers can dissect the causes of cancer, they can’t really specify how much each influence contributes to the background cancer rate.
But yeah, you can’t avoid background radiation. There’s some tiny fraction of radioactive isotopes in just about everything: food, water, air, environment, and by extension even in our own bodies.
So would it be possible for people to adapt to higher and higher levels of background radiation over time? I remember ereading several 1950’s SF stories where this had happened.
The other thing to consider is that it usually requires several mutations for a cell to become cancerous. So if one of your cell lines gets a mutation which knocks out one cancer-preventing gene, and that cell line spreads through your body, then it is much more likely for later mutations to lead to cancer, because you’ve got lots of the at-risk cells in your body.
Cancer is really a form of natural selection that occurs in your own body. Normal cells get told to stop growing, or die, and they do. Any cell that mutates to ignore the signals to die or not grow will spread.
One other possibility is that “the street” is referring to ingesting some sort of radioactive substance. Such a substance, and you naturally have some in you right now, bombards your innards with high energy particles that can cause damage. This effect is cumulative, i.e. the more in your body and the longer it is in there, the greater the risk that the substance will cause a problem.
I think there are two things going on. Electromagnetic radiation has both frequency (‘color’) and intensity (‘brightness’). engineer_comp_geek did a great job of explaining that some frequencies of E-M radiation (X-Rays, etc) are ionizing and can cause cancer, while other frequencies (light, radio) are non-ionizing and not directly harmful in the sense of ‘radiation’.
What ‘threshold’ usually means in terms of radiation damage is whether, for a frequency that’s definitely ionizing, there’s an intensity below which there’s no damage. And the general scientific consensus is that data is tough to get on very low radiation exposures, but a linear model (half the radiation is half the chance to get cancer) is consistent with what we know about how radiation damages cells, fits the data as well as any other model, and is simpler than any other model. So that’s what scientists go with right now. In particular, there’s no strong repeatable evidence of a threshold below which radiation is helpful; certainly not enough to adopt a different model at this point.
There is evidence that sunburns cause some slight but permanent and cumulative damage.
There’ more than evidence, it’s indispustable fact. In fact any sun exposure causes such permanent damage, you don’t need to burn. However sun damage and sunburn are not the same thing. Sunburn does indeed go away within days.
1950’s sci-fi is probably the absolute worst source for scientific knowledge, ever.