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 percent 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 percent 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 percent. 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 percent 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 percent, 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.
