Lesson Video: The Effects of Radiation on Living Organisms | Nagwa Lesson Video: The Effects of Radiation on Living Organisms | Nagwa

Lesson Video: The Effects of Radiation on Living Organisms Science

In this video, we will learn how to describe the dangers to the health of living organisms from nuclear radiation.


Video Transcript

In this video, we will learn how to describe the dangers to the health of living organisms from nuclear radiation. Before we get into these effects, let’s recall a bit about nuclear radiation.

All matter is made of atoms, and at the center of every atom is something called the nucleus. We’ve drawn it here as a ball, but we know the nucleus really is made up of particles called protons and neutrons. These smaller particles in the nucleus experience forces that pull them together and also that push them apart. When the pushing and pulling forces balance out, the nucleus is said to be stable. However, when there’s an imbalance of forces, that unstable nucleus becomes likely to emit nuclear radiation.

Nuclear radiation can consist either of particles or electromagnetic waves. In either case, this radiation transmits energy; that is, it carries energy from the decaying nucleus to wherever the radiation goes. That radiation might zoom off into space or be absorbed by the ground. But then it might also interact with a living organism. This means that atoms in that organism, either on its surface or in its interior, absorb the radiation. When atoms absorb radiation, they may well change. These changes can be passed on to what are called cells. All living organisms are made of cells.

We can picture cells as very small objects, usually too small to see by eye, with an irregular shape and a central region in the cell. This region contains what is called the cell’s DNA. A cell’s DNA is like an ordered list of instructions for reproducing the cell. When the atoms in a cell absorb nuclear radiation, there are several possible effects.

Since nuclear radiation transfers energy, it’s possible for the cell to be heated up. This may or may not be damaging to the cell. If the cell is heated only a small amount, it may be able to continue functioning normally. However, if there is enough heating, the cell may indeed be damaged. Damage to a cell means it’s no longer able to perform its normal job. When a cell’s DNA is damaged, this means the instructions for reproducing the cell are no longer correct. At this point, a couple different things can happen.

If the cell cannot reproduce itself, it will die out. On the other hand, if damaged DNA is still able to be reproduced, but perhaps incorrectly, this can lead to what is called a mutation. That’s when a cell or even an organism changes its form in some unintended way. Again, depending on just how the DNA in a cell may be damaged, a mutation may be passed on from one generation to another to another of cells. In extreme cases, mutations can lead to a change in form of an organism. Mutations are also the cause of all known cancers.

The energy transmitted to a cell that may lead to these effects comes in two categories. Radiation can directly transfer thermal energy to a cell, and indirectly, it can transfer chemical energy. So cell heating, cell damage, and cell death may be due to a combination of thermal and chemical energy transfer due to nuclear radiation. Now let’s say that this cell is part of a larger organism. Say that it’s one cell in a person’s body.

Nuclear radiation can affect an organism in ways different than the ways it affects a single cell. If enough cells in an organism are sufficiently heated, the organism overall may experience radiation burns. The effect of these burns is like a sunburn, but it can occur both on the outside and inner parts of an organism. Due to the transfer of chemical energy, an organism may also experience radiation poisoning. This can lead to symptoms including organ failure, internal bleeding, and blindness.

So the possible effects of radiation on an organism can be quite serious. Despite this, radiation has been found to be quite useful in some areas of medicine. For example, X-rays are one type of radiation, though not nuclear in origin, that help us understand the health of the body. Since radiation can be damaging but can also be useful for human health, the dose of this radiation in medical applications is carefully controlled. The dose amount tells how much radiation a person’s body absorbs. Radiation doses for people can be measured in a unit called the rem. An X-ray on a person’s wrist, for example, involves a dose of about 0.006 rem.

In general, the larger the dose, the greater the chance of that radiation negatively affecting a person’s body. But besides increasing the dose, there’s another way that nuclear radiation can be dangerous to human health. Even though the radiation dose of a single wrist X-ray, for example, is quite small and not generally dangerous, think of how this dose would change if the X-ray, instead of just lasting an instant of time, was left on continuously. That is, for minutes or even hours or days a person’s wrist was being X-rayed. Even though the amount of radiation absorbed by the person at any one moment is quite small, by extending their exposure time to the radiation, even that small dose can add up to have a damaging effect.

In general, there are two ways that radiation can be harmful or even fatal to a person. First, the person could absorb a large dose of radiation for a short amount of time. And second, if a small dose is applied but for a long time, that is, a long exposure time, because of the possible danger nuclear radiation poses to humans, the amount of radiation a person is exposed to on purpose, say, for medical reasons is carefully quantified and limited. Knowing all this, let’s look now at a few examples.

Which of the following correctly describes the most severe effect on living cells that can result from them absorbing nuclear radiation? (A) Cells dissipate energy. (B) Cells are damaged. (C) Cells are killed.

When radiation is emitted by a nucleus, it may be absorbed by the atoms in a cell that help make up a living organism. A cell has various parts; we haven’t drawn them here. But the point is that practically nuclear radiation can transfer energy to a cell. The radiation may directly transfer thermal energy and indirectly transfer chemical energy. If a cell is heated through thermal energy, the cell may simply dissipate that energy through cooling with no negative effects.

So we see then that option (A) cells dissipating energy is one result of them absorbing nuclear radiation. But it’s a very minor one. Recall we’re looking to identify the most severe effect on a living cell. A cell may also be damaged by absorbing nuclear radiation; for example, it may heat up enough so that the cell no longer functions properly. It’s still possible, though, for a damaged cell to reproduce itself. Depending on the type of cell damage sustained, this reproduction may not be accurate, but still in this case, the cell remains alive.

Option (C), however, describes an outcome where a cell has absorbed enough nuclear radiation that the energy transferred to it results in cell death. A dead cell, of course, can’t reproduce itself. So a cell being killed is the most severe effect on that cell that can result from an absorbing nuclear radiation.

Let’s look now at another exercise.

Which of the following is measured by the unit rem? (A) The radioactivity of an object, (B) the nuclear radiation absorbed by a person, (C) the intensity of nuclear radiation at a point.

Let’s think about these three answer options in the context of a person being exposed to nuclear radiation. For a person to be exposed to radiation, first, there needs to be some object, say, this one here, that emits radiation. So let’s say this object is indeed giving off nuclear radiation and that a person is exposed to it. While some of this radiation may pass right through the person, some may also be absorbed. When this happens, there is a transfer of energy to the atoms in the person’s body that absorbed the radiation.

The unit rem is designed to indicate just how large of a dose of radiation is absorbed. If the unit rem described the radio activity of an object, then in our sketch we wouldn’t need to involve a person. We would just consider this part of the diagram. But this unit does have to do with how a person experiences, that is, absorbs, radiation. We won’t choose answer option (A).

Considering option (C), this claims that the unit rem has to do with the intensity of nuclear radiation at a point. Once again, this definition has nothing to do with how much radiation a person absorbs. If option (C) was correct, we could pick a point in space, say, this point here, and use the unit rem to indicate the intensity of nuclear radiation at that point. However, the unit rem is used for medical purposes. It’s designed to help safeguard people from being overexposed to nuclear radiation.

The unit rem gives a quantitative measure of the amount of nuclear radiation absorbed by a person. Notice that this does not include any nuclear radiation that the person will be exposed to but that they don’t absorb. This points to the fact that the unit rem is designed to support human health and safety.

Let’s look now at one last example.

A technician in a nuclear waste storage facility receives a very small radiation dose every day that they work. Which of the following statements correctly describes the effect this has on their health? (A) The more days the technician works, the more harm they suffer from nuclear radiation. (B) The dose that the technician receives is never large enough to harm them, and so their health is unaffected.

We have here a scenario where a nuclear technician receives a very small dose of radiation every day that this person goes to work. Because this daily dose is so small, receiving it on any given day is unlikely to lead to a negative health effect. But the thing is, the technician is exposed to this very small dose day after day after day. Damage caused to the body by nuclear radiation is cumulative. This means that every time a person is exposed to nuclear radiation, it adds to the likelihood that they will be harmed.

By way of analogy, consider a person who gets a sunburn. Getting burned by the sun once is painful but likely won’t have any negative long-term health effects. However, if a person gets a sunburn day after day, after week, after month, after year, those small bits of daily damage to the skin will add up. In the long term, the likelihood of this person developing skin cancer increases.

A similar principle applies for our nuclear technician. The more days the technician works, the more cumulative harm they suffer from nuclear radiation. A solution, of course, is for the technician to stop going to work. But that’s something they can work out with their supervisor.

Let’s finish our lesson now by summarizing a few key points. In this video, we saw that nuclear radiation may affect cells by heating them, damaging them, or even destroying them. We learned further that when the DNA of a cell is damaged, this may result in a mutation. A mutation in a cell or a gene or an organism can be passed on to later generations. This may lead to a cancer or another abnormality in an organism. On the other hand, nuclear radiation may affect organisms by radiation burns or radiation poisoning.

Because radiation can be harmful to organisms while also having applications in medicine, a unit called the rem was developed to measure the radiation dose absorbed by a person. And as a final point, nuclear radiation can be harmful or even fatal to a person if a large dose is received over a short time or a small dose is received continuously over a long time. This is a summary of the effects of radiation on living organisms.

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