Lesson Explainer: The Effects of Radiation on Living Organisms Science

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

Nuclear radiation can be harmful to living organisms.

There are different ways that nuclear radiation can harm organisms. When conceiving how nuclear radiation can harm living organisms, there are many factors to consider.

Some of the factors that need to be considered include the following:

  • the ways that damage can be done by nuclear radiation,
  • the parts of an organism that can be damaged by nuclear radiation,
  • and the amount of nuclear radiation an organism is exposed to.

Let us first consider the ways that damage can be done by nuclear radiation.

Nuclear radiation consists of particles (alpha and beta radiation) and electromagnetic waves (gamma radiation).

All these types of radiation can transfer energy from a decaying atomic nucleus to another object. The damage that can be done by nuclear radiation is due to this transfer of energy by the nuclear radiation.

When considering living organisms, it is useful to recall that such organisms are made of cells.

Cells from an animal are shown in the following figure.

The dashed line points out a single cell.

Characteristics of Squamous epithelial cell

The two main energy transfers to a cell due to nuclear radiation are the following:

  • thermal energy
  • and chemical energy.

The following table shows the two main ways that energy transfer to a cell by nuclear radiation can affect a cell and how this can then affect an organism made of cells.

Thermal Energy TransferChemical Energy Transfer
Effects on a CellIt causes energy dissipation.It causes chemical reactions.
Effects on an OrganismIt causes radiation burns.It causes radiation poisoning.
Description of EffectsIt has an effect similar to sunburn.
A radiation burn can also occur to parts of the body beneath the skin, not just to the skin.
Some chemical reactions can change the normal functioning of cells, similarly to the ways that poisons can affect cells.
Symptoms of radiation poisoning include the following:
blindness,
hair falling out,
internal bleeding,
and organ failure.

By introducing this table, we have started to consider the parts of an organism that can be affected by nuclear radiation.

A distinction is being made between the different parts of an organism, both on its outer surface and within that surface.

Nuclear radiation can transfer energy to any part of an organism that the radiation is absorbed by.

The following figure shows how nuclear radiation can be absorbed by different parts of the human body.

Some types of nuclear radiation cannot penetrate the skin and are absorbed by the skin.

Some types of nuclear radiation can penetrate the skin directly and so can be absorbed by internal organs.

A radioactive object emitting either type of radiation may be unintentionally swallowed or inhaled, allowing nuclear radiation to be absorbed inside the body.

Nuclear radiation that is absorbed by parts of an organism that contain vital organs (such as the lungs or the liver, for example) can damage these organs. The damage done to these organs can be fatal to an organism, leading to the death of the organism within days or hours.

Let us now look at an example concerning the dangers to health from nuclear radiation.

Example 1: Describing the Damage that Nuclear Radiation can Cause to Cells

Which of the following correctly describes the most severe effect on living cells that can result from them absorbing nuclear radiation?

  1. Cells are killed.
  2. Cells are damaged.
  3. Cells dissipate energy.

Answer

Energy transferred by nuclear radiation can be dissipated in a cell. This does not necessarily harm a cell if the amount of energy dissipated is very small.

Dissipation of a sufficiently great amount of energy can damage a cell, though, and even kill it. Killing a cell is the most severe effect on the cell that can occur.

Let us look at another such example.

Example 2: Describing the Dangers to Health from Nuclear Radiation

Which of the following statements correctly describes how a person’s life can be threatened by damage to cells of their body from absorbing nuclear radiation?

  1. If enough cells are damaged or killed in even one part of the body that is essential for life, a person can die.
  2. Cells must be damaged or killed throughout the entire body for a person to die.

Answer

There are parts in the human body that must function normally for a human to live. Such a vital body part can stop functioning normally if many of its cells are damaged or killed. It is not necessary for nuclear radiation to damage all of a person’s body for that person to die from the nuclear radiation damage.

We have seen the ways that nuclear radiation can do damage quickly. It is also possible for the damage done by nuclear radiation to have effects that are much more gradual. These effects are the results of damage to the nucleus of a cell.

The nucleus of a cell is a structure in the middle of a cell that contains the genes of the cell. A cell and its nucleus are shown in the following figure.

Damage to the main body of a cell contributes to radiation burns or radiation poisoning, possibly resulting in the death of the cell.

Damage to the nucleus of a cell that is not sufficient to kill the cell can result in damage to the genes of the cell. This can cause a mutation in the cell.

Damage to the genes of a cell may cause the cell to become a cancer cell. The cell may then generate other cancer cells.

Over a long time, this may lead to the development of a tumor in an organism. A tumor may eventually be fatal to the organism in which it develops.

If a cell that has damage to its genes is a germ cell, then offspring of the organism that grows from that germ cell may have mutations.

The following figure shows an animal that has a very obvious mutation due to the abnormal development of cells in some parts of its body.

a mutate cat

Many mutations are very harmful to offspring, meaning that they do not have a normal lifespan.

Let us now look at an example concerning the indirect dangers to health from nuclear radiation.

Example 3: Describing the Indirect Damage that Nuclear Radiation Can Cause

Nuclear radiation that damages a cell can produce mutations in the cell. Which of the following statements correctly describes the most severe possible effects on a person whose cells are mutated by nuclear radiation?

  1. The person develops fatal cancer.
  2. The person is temporarily sick until their body grows replacement cells.
  3. The person develops deformities.

Answer

Cells that mutate do not function normally. This can make a person temporarily sick.

Mutations of germ cells can result in deformities in offspring produced from these cells. This does not mean that a person that has cellular damage would themselves develop deformities, however.

A mutated cell can become a cancer cell. A cancer cell can reproduce to form a tumor that can be fatal. This is the most severe effect of cellular mutation.

We have now seen the harmful effects of the absorption of nuclear radiation on organisms.

Let us now consider how these harmful effects depend on the amount of radiation that an organism absorbs.

The damage done to a part of an organism by nuclear radiation is affected by the amount of nuclear radiation absorbed.

The amount of nuclear radiation absorbed is called the dose of nuclear radiation. The dose can be measured in the unit rem.

Let us now look at an example concerning the unit rem.

Example 4: Describing the Quantity Measured in the Unit Rem

Which of the following is measured by the unit rem?

  1. The nuclear radiation absorbed by a person
  2. The radioactivity of an object
  3. The intensity of nuclear radiation at a point

Answer

The unit rem does not measure how much nuclear radiation an object emits, so it does not measure the radioactivity of an object.

The unit rem does measure an amount of nuclear radiation, but it does not measure this at some arbitrary point. A dose of nuclear radiation absorbed by a person is measured in rem. This only applies to nuclear radiation that is absorbed, not nuclear radiation that is present somewhere but is not absorbed.

Increasing the rem value of a dose has two effects:

  • more severe radiation burns and radiation poisoning,
  • and a greater chance of cells becoming cancerous.

It is very important to understand that, for some kinds, the damage done by nuclear radiation to an organism does not fully heal over time.

Cells that are killed by nuclear radiation can be replaced by new, healthy cells. Cells that are damaged by nuclear radiation so that they do not function properly but are not killed can continue to harm the organism that they are part of.

Suppose that a person absorbs a dose of nuclear radiation of 1 rem.

The nuclear radiation damages the person’s cells in various ways. The person may not even notice this if the damage is only mild.

Weeks later, the person absorbs another dose of nuclear radiation of 1 rem.

The malfunctions of cells caused by damage done by the first dose that the person absorbed are still affecting the person when they absorb the second dose. The second dose adds the damage it does to the damage caused by the first dose.

Let us suppose that a dose of 1 rem is again absorbed weeks later. This dosing process continues for several years. There will have been many doses absorbed over these years.

It may be that the total damage due to all these doses is severe enough that the person now notices that they have symptoms of radiation poisoning, or of cancer.

Let us now look at an example concerning doses of nuclear radiation.

Example 5: Describing the Effect of Multiple Doses of Nuclear Radiation

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?

  1. The more days the technician works, the more harm they suffer from nuclear radiation.
  2. The dose that the technician receives is never large enough to harm them and so their health is unaffected.

Answer

It may well be the case that the dose absorbed by the technician in a single day is small. However, the damage done each day does not heal overnight. The damage done by nuclear radiation each day is added to the damage done the previous day.

The more days that the technician works, the greater the total damage done to their body by nuclear radiation.

Let us now summarize what has been learned in this explainer.

Key Points

  • Nuclear radiation can damage cells by transferring thermal and chemical energy to them.
  • Damage to cells by nuclear radiation can produce radiation burns and radiation poisoning.
  • The more energy transferred by nuclear radiation, the more severe the effects it has on an organism.
  • Severe radiation burns or poisoning of vital organs can be quickly fatal.
  • Damage to the nuclei or cells can cause mutations, including making cells into cancer cells.
  • Mutations to germ cells can cause offspring grown from these cells to be mutated.
  • Absorbed nuclear radiation doses can be measured in rem.
  • The damage done by absorbed radiation is cumulative.

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