Video Transcript
In this video, we will be discussing the dangers of ionizing radiation. Now, many of us might have some idea about this, often having a vague picture of a person in protective gear, walking around in a highly radioactive postapocalyptic world. But today, we’ll be learning some terms that help us to understand more thoroughly the dangers that we face when dealing with any amount of ionizing radiation. So let’s begin by recalling the ionizing radiation is any form of radiation that has enough energy, sufficient energy, to ionize any atoms or molecules it interacts with, in other words, to turn those atoms or molecules into ions. In other words, ionizing radiation has enough energy to rip electrons from atoms or molecules it happens to interact with.
So, for example, if we have this atom, then ionizing radiation coming in — in this case, we’ve drawn 𝛾 radiation — could interact with these electrons and cause some of these electrons to be knocked out of the atom. This way, what gets left behind is an ion, which is like an atom but has either a deficit or a surplus of electrons. And in this case, our ion has a deficit because it’s missing two electrons. And therefore the number of protons in the nucleus is not equal to the number of electrons surrounding the nucleus. This means that the ion now has a net or overall charge because once again the number of negative charges is no longer equal to the number of positive charges.
Now, when these atoms or molecules that are then turned into ions happen to be the atoms or molecules that make up living cells, such as the living cells in a human being, then these atoms or molecules becoming ionized can cause some terrible problems. For example, let’s imagine that this atom here that we’ve drawn already is one of the atoms that forms a human cell and has become ionized due to some interaction with some ionizing radiation. Well in that situation, because our ion is now positively charged due to the lack of electrons, this means that it will attract electrons from other atoms because electrons are negatively charged and the ion is positively charged.
And similarly, it will repel any other positively charged particles such as any other adjacent atoms that have been ionized due to the interaction with ionizing radiation. And therefore, we can see that this ion is highly likely to be moving out of position away from the place that it should be in, in order to form the cell of the human being that it’s a part of. And this can result in the cell being damaged or even dying in some cases. So on a large scale, the interaction of human cells with ionizing radiation can cause a lot of their cells to die. And sometimes if the ionizing radiation manages to find its way to the DNA of the cell, which is the genetic code held inside the cell, then this can lead to some form of genetic mutation which could cause some forms of cancer. So those are the dangers of ionizing radiation.
But here’s the thing, all of us are exposed to ionizing radiation all day, every day. Ionizing radiation can be found in the air that we breathe, the food that we eat, the rocks that make up the earth beneath our feet, and, in general, all around us. But this ionizing radiation that we’re exposed to is not due to some nuclear accident caused by human error. No, this ionizing radiation occurs mainly due to the small levels of radioactive isotopes, naturally occurring in the rocks that form the earth. For example, a lot of uranium can be found in these rocks, which is radioactive, and as well as this, its present in the air that we breathe as well. And the important thing here is that these radioactive substances are present in very small quantities. And the radiation that we’re exposed to from these sources, this very low level radiation, is known as background radiation.
Now there’s no need to worry. There isn’t enough background radiation apart from in a few rare places on Earth to cause us any real damage. We’re exposed to it all the time. And it’s a very low level radiation. And it’s not something that we need to be scared of. Now, more formally, we can define background radiation in the following way. We can say that background radiation is the low level radiation from the surrounding environment, which is not due to the deliberate introduction of radiation sources. So what do we mean by this? Well, first of all, we’ve already discussed that background radiation is low level in the sense that we are not exposed to a large amount of background radiation and its radiation from the surrounding environment. So we know that already.
But what we mean when we say that it’s not due to the deliberate introduction of radiation sources is that, in some places, we want to deliberately introduce radiation sources such as, for example, in a nuclear power plant. In places such as a nuclear power plant, we deliberately introduce radioactive substances in order to achieve some end goal. In the case of a nuclear power station, we’re trying to generate energy. However, background radiation is not caused by such deliberate introduction of radiation sources. In fact, the majority of it is caused by radioactive isotopes occurring naturally in our environment. In fact, if we look at this pie chart, which shows us all the different sources of background radiation, we can see that the majority of it, about 41.6% of background radiation, comes from radon gas that’s found in the air.
Now, this radon gas is radioactive. And it’s actually formed as a by-product of the uranium that’s found in the rocks underneath the earth’s surface. Let’s remember, the uranium that’s found underneath the Earth’s surface is radioactive itself, and so it decays. And one of the products of this decay is radon gas, which is also radioactive. And so 41.6% of all background radiation is due to this radon gas. We can also see that a large contributor to background radiation is medical sources coming in at 19.8%. An example of one such medical source is when 𝛾-rays are sent into certain parts of the human body in order to kill cancer cells. All the sources of background radiation are the ground and buildings because, remember, buildings are built from materials found on Earth, obviously. But then those materials also contain some traces of radioactive isotopes.
And another source is cosmic rays. That’s, radiation coming from outer space. And finally, our food and water is slightly radioactive, too. So that’s an overview of background radiation, the low-level radiation that’s present basically everywhere. But remember, we mentioned earlier that background radiation is not caused by the deliberate introduction of radiation sources. Well, let’s now think about the opposite. Let’s now think about a scenario where we are deliberately introducing a radiation source. Let’s imagine that we’ve literally got a lump of radioactive material, not just the small amounts found in the environment, but literally an isolated lump. In other words, the whole of this block is radioactive and it, therefore, emits some sort of ionizing radiation, whether that’s 𝛼 radiation, 𝛽 radiation, or 𝛾 radiation.
In day to day life, many people actually have to deal with such radioactive materials. We’ve already mentioned people working at a nuclear power station. They most commonly have to work with the uranium, which is radioactive because uranium is what’s most commonly used as fuel in a nuclear power station. Another rather surprising example of somebody that has to deal with radioactive materials is food hygiene of food production workers because in many countries, there are very strict regulations that ensure that the food that anybody eats is actually safe to eat. And one way to do this is to expose the food that’s going to be sold to customers to ionizing radiation.
This might sound surprising, but the reason that we do this is that ionizing radiation can kill any bacteria or other microorganisms living in the fruit and veg in the very same way that ionizing radiation can kill human cells as we discussed earlier. Except this time, the use of ionizing radiation is positive for us. Because this way, if we manage to kill microorganisms living on food, then the people who eventually end up eating the food are much less likely to get ill from eating that food, for example, from developing food poisoning. So the way that the ionizing radiation works is that it passes straight through the food, killing microorganisms on the way. And then it doesn’t remain in the food. In other words, once the food is no longer exposed to a radioactive material, the food itself is no longer radioactive and it’s safe to eat.
So in this case, exposure of the food to radiation is a good thing for us. However, that’s assuming everything is done correctly. Let’s instead imagine that the food production worker who is working on irradiating the food accidentally touches the radioactive material, whether that be with a glove or with their own hand, or with anything else for that matter. So here’s the hand accidentally touching the radioactive material. And then they end up touching the food, obviously not drawn to scale. But the point is that they could accidentally transfer some radioactive substances onto or into the food itself. And this is a very bad thing indeed, because when this happens, the radioactive substance transferred to the food is still radioactive and is going to be emitting ionizing radiation.
And remember, the food is meant for people to eat. And people could accidentally eat this food that has some amount of radioactive substance on it. This means that they would end up ingesting some radioactive substance and that radioactive substance would release ionizing radiation inside their body. Now, once ionizing radiation gets inside the body, it can wreak a lot of havoc. It’s not good at all. And therefore, the transfer of radioactive substances onto things such as food is a highly dangerous thing. And there are very stringent procedures that food workers have to go through to ensure that that doesn’t happen. However, the actual process of accidentally transferring radioactive substances on the surface of, or inside, objects where we do not want any radioactive substances to be is known as contamination or, more specifically, radioactive contamination.
And it’s important to know that simply exposing food or other objects to radiation is not equivalent to contamination because, as we said earlier, in some cases we do want to expose objects to ionizing radiation. But it is contamination if radioactive material itself, stuff that itself is radioactive, gets on to the surface of, or inside, an object where we do not want any radioactive substances to be. And so we can technically define contamination as the undesired presence of radioactive substances on the surface of, or within, other substances, in other words, putting radioactive substances where we do not want them to be.
And as we’ve seen already, eating contaminated food can be very dangerous, drinking contaminated water can be very dangerous, not just for humans but for wildlife as well. And so there are many situations where we need to be very careful to avoid radioactive contamination. But anyway, so now that we’ve looked at what background radiation is, as well as what radioactive contamination is, let’s get some practice by attempting an example question.
Which of the following statements is the correct definition of background radiation? A) Background radiation is any electrically neutral radiation. B) Background radiation is low-level radiation from the surrounding environment, which is not due to the deliberate introduction of radiation sources. C) Background radiation is any low-energy electromagnetic radiation. D) Background radiation is any radiation from sources that have a half-life of less than one minute.
Okay, so to answer this question, let’s start by recalling that background radiation is low-level radiation that’s present everywhere on Earth. The amount of background radiation does vary from place to place. But in general, it’s very low level, and for that reason it’s not really harmful to humans. It occurs mainly due to naturally occurring radioactive substances found in the rocks beneath the earth and in the air around us. But there are some man-made causes to it as well.
For example, if we look at this pie chart, which shows us the percentages of background radiation produced by different sources, then we can see that the majority of it, 41.6% of all background radiation, is due to radon gas found in the air. And this radon gas is naturally occurring, but the next largest source is medical sources at 19.8%, for example, when radioactive isotopes are used to treat cancer. But the point is that all of these sources are not deliberate introductions of radioactive substances to the local environment. They’re either naturally occurring or a by-product of something man-made. And as well as this, as we mentioned earlier, background radiation is very low-level. And that there isn’t a lot of it and certainly not enough to cause any serious damage to humans.
So based on this description, let’s go through the options one by one and see which option fits best. Starting with option A, which says that background radiation is any electrically neutral radiation. Well, we know that this is not true because background radiation can be any kind of ionizing radiation, which includes 𝛼, 𝛽, and 𝛾 radiation. Now, 𝛾 radiation is electrically neutral because it’s an electromagnetic wave. But 𝛼 radiation and 𝛽 radiation are not electrically neutral, and they do form some parts of background radiation. Therefore, option A is not the answer that we’re looking for.
Moving on to option B then. This one says that background radiation is low-level radiation from the surrounding environment, which is not due to the deliberate introduction of radiation sources. And this description does match what we said earlier about background radiation. Therefore, it looks like option B is the answer that we’re looking for.
Quickly looking at option C and D, starting with option C. This one says that background radiation is any low-energy electromagnetic radiation. But this is not true either, because like we said earlier background radiation can include 𝛼, 𝛽, and 𝛾 radiation. And 𝛼 and 𝛽 radiation is not electromagnetic radiation. In fact, an 𝛼 particle is the same thing as the nucleus of a helium atom. And a 𝛽 particle, or at least a 𝛽 minus particle, is an electron. And both of these are not low-energy electromagnetic radiation. And finally, even though 𝛾-rays are electromagnetic radiation, they most certainly are not low-energy electromagnetic radiation. In fact, they’re very high energy electromagnetic radiation. And hence option C is not what we’re looking for, either.
Finally, looking at option D, this one says that background radiation is any radiation from sources that have a half-life of less than one minute. Now, let’s recall that half-life is the amount of time taken for the activity, the radioactivity, of a particular sample of radioactive material to fall to half its initial value. In other words, if a substance has a half-life of less than one minute, then it takes less than one minute for half of that radioactive substance to have decayed away.
But then, if this were the case, then all of the radioactive isotopes causing background radiation would decay away very quickly and we’d have background radiation for a few minutes. But then it would disappear in a very short time scale. And this certainly does not happen. Background radiation is present constantly. Therefore, the answer to our question is that background radiation is a low-level radiation from the surrounding environment, which is not due to the deliberate introduction of radiation sources.
Okay, so now that we’ve looked at an example question, let’s summarize what we’ve talked about in this lesson. In this video we saw firstly, that background radiation is low-level radiation from the surrounding environment, which is not due to the deliberate introduction of radiation sources. And secondly, we saw that radioactive contamination is the undesirable presence of radioactive substances on the surface of, or within, other substances.
