The Basics of Radiation: Understanding Types and Risks

Radiation is a topic that often evokes strong reactions and emotions.

On one hand, it is an essential tool in many areas of modern life, from medical imaging and cancer treatment to telecommunications and energy production.

On the other hand, radiation exposure can also cause serious harm, long-term health risks, and incidents like the Fukushima and Chernobyl nuclear disasters have highlighted its dangers in the public consciousness.

Understanding the basics of radiation, including what it is, the different types, and, at the same time, the benefits associated with it, is crucial for making informed decisions and staying safe.

Radiation Origins

Radiation occurs when energy is emitted by a source, then travels through a medium, such as air, until it is absorbed by matter. Can be described as being one of two basic types: non-ionizing and ionizing radiation.

Understanding the origin and the sources is important for assessing the potential risks of exposure, and in forming radiation protection policies and guidelines.

Non-Ionizing Radiation

It refers to types of electromagnetic radiation that do not have enough energy to ionize atoms or molecules, and thus do not have the ability to damage DNA or cells directly.

Some examples include:

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet light.

They are commonly used in a variety of applications, such as in telecommunications, microwave ovens, and in medical imaging and treatment.

Origin of Non-Ionizing Radiation

It is a type of electromagnetic radiation, which is a form of energy that travels in waves and is characterized by its wavelength and frequency.

Natural sources include:

  • The sun (which emits, among others, ultraviolet, visible light, and infrared)
  • Lightning (which emits visible light and electromagnetic waves)
  • The earth’s magnetic field.

Artificial sources include:

  • Radio and television transmitters
  • Cell phones
  • Microwaves.

The scientific understanding of non-ionizing radiation and its effects on living organisms is a complex and ongoing field of research.

Some studies have suggested that exposure to certain types of non-ionizing radiation, such as ultraviolet light or radiofrequency radiation, may be associated with certain health risks, while other studies have found no clear evidence of harm in some cases.

The Effects of Non-Ionizing Radiation

They can vary depending on the type and intensity and duration of exposure. Some potential effects include:

1- Thermal effects

Some types, such as microwaves and infrared radiation, can cause heating of the body’s tissues. This can be beneficial in some medical applications, such as in physical therapy, but can also be harmful if the exposure is too intense or prolonged.

2- Photochemical effects

Ultraviolet radiation can cause chemical changes in the body’s tissues, leading to skin cancer and other skin damage.

3- Neurological effects

Long-term exposure to high levels, such as radiofrequency radiation, has been linked to an increased risk of neurological effects such as headaches and fatigue.

4- Effects on the eyes

Exposure to high levels can cause cataracts, retinal damage, and other eye-related problems.

Overall, non-ionizing radiation is considered to be less harmful than ionizing radiation, which has the ability to directly damage DNA and cells. However, prolonged exposure can still have negative effects on human health.

Ionizing Radiation

It is made up of high-energy particles or waves that can strip electrons from atoms, ionizing them. In living tissues, the electrical ions produced by radiation can affect normal biological processes.

The common types of ionizing radiation include:

1- X-rays/Gamma rays

They are electromagnetic radiation similar to light, and radio waves, but with much higher energies. Gamma rays, depending on their energy, can pass right through the human body, but can be stopped by thick walls of concrete or lead.

2- Alpha particles (radiation)

They are heavy, positively charged particles emitted by atoms of elements such as uranium and radium, consisting of two protons and two neutrons (formed as 4He nucleus). ِIt can be stopped completely by a sheet of paper or by the thin surface layer of our skin (epidermis).

However, if alpha-emitting materials are taken into the body by breathing, eating, or drinking, they can expose internal tissues directly and may, therefore, cause severe biological damage

3- Beta particles (radiation)

They consist of electrons (or positrons), are more penetrating than alpha particles, and can pass through 1-2 centimeters of water. In general, a sheet of aluminum a few millimeters thick will stop beta radiation.

4- Neutrons

They are uncharged particles and do not produce ionization directly. But, their interaction with the atoms of matter can give rise to alpha, beta, gamma, or X-rays which then produce ionization. Neutrons are penetrating and can be stopped only by thick masses of concrete, water, or paraffin.

Ionizing radiation is powerful and can be harmful to living tissue, but it is also used in a variety of applications, such as medical imaging and cancer treatment.

Origin of Ionizing Radiation

Certain types of unstable atoms that emit high-energy particles or waves to become more stable produce ionizing radiation. These atoms are said to be radioactive, and an excess of energy or mass within their atomic nuclei causes their instability. Typical sources are:

1- Natural sources

It can be found naturally in the environment, such as from the ground and from certain types of rocks and minerals.

Some elements, such as uranium and radon, are naturally radioactive and emit ionizing radiation as they decay. Cosmic radiation from outer space is also a natural source.

2- Artificial sources

Ionizing radiation can also be produced artificially, through the use of nuclear reactions or other technologies.

For example, X-rays are produced by high-energy electrons “hitting” a metal target. Another example is radioactive isotopes that can be produced in a laboratory by bombarding certain elements with high-energy particles.

Ionizing radiation is used in a variety of applications, including medical imaging, cancer treatment, and industrial processing. However, it must be handled with care because of the risks it poses to living tissue.

Natural Radiation

The ionizing radiation that is present naturally in the environment includes both cosmic radiation and environmental radioactivity from naturally occurring radioactive materials (radionuclides of the uranium and thorium decay chains together with radioactive potassium) from the earth’s crust, etc.

In general, exposure to natural radiation is the largest source of exposure for most people, and it varies depending on location (specifically local elevation, atmospheric conditions, the Earth’s magnetic field, soil composition, etc.) and lifestyle factors.

Also, background radiation originates from other sources, such as man-made medical X-rays, the fallout from nuclear weapons testing and nuclear accidents, etc.

Background Radiation

There are several sources contributing to background radiation, including:

  1. Cosmic radiation
  2. Terrestrial radiation
  3. Endogenous radiation
  4. Artificial radiation

These are the main sources, but there can be variations in intensity and location. The levels of radiation from these sources can vary depending on factors such as altitude, location, and the concentration of naturally occurring radioactive elements in the environment.

1- Cosmic Radiation

It refers to high-energy particles and electromagnetic radiation that enter Earth’s atmosphere but originate from outside the Earth’s atmosphere.

Some particles make it to the ground, while others interact with the atmosphere to create different types of secondary radiation.

Mainly, it consists of photons,  high-energy protons and other atomic nuclei, which come from our Sun or outside of the solar system. It is present all around the Earth and can penetrate the atmosphere, reaching the surface of the Earth.

It is made up of a variety of subatomic particles or wave energy particles, including:

  • Protons,
  • Mesons, electrons, neutrons, heavier ions,
  • Gamma rays,
  • X-rays.

Cosmic radiation can have both beneficial and detrimental effects on the Earth’s atmosphere and climate. On one hand, it can play a role in the formation of clouds and the modulation of the Earth’s climate. On the other hand, it can also pose a hazard to human health and electronic equipment.

Its study is important for understanding the history of the universe, the origins of life on Earth, and the properties of matter and energy at their most extreme.

It also has practical applications, such as in:

  • The detection of underground minerals
  • The design of radiation-hardened electronics for use in space.

Origin of Cosmic Radiation

  1. The Sun: It produces a steady stream of high-energy particles known as solar wind, and occasional bursts of more intense radiation known as solar flares.
  2. Supernovae: These are the explosive deaths of stars that can produce intense bursts of high-energy particles.
  3. Cosmic Rays: Cosmic rays are high-energy protons and atomic nuclei that are believed to be produced by supernova explosions and other energetic events in the universe.
  4. Cosmic background radiation: It is the thermal radiation left over from the big bang.

There may be other sources that are still being studied and understood by scientists.

Solar radiation in terms of solar power

Efforts should be made to understand the difference between the terms solar cosmic radiation and solar radiation. While cosmic radiation discussed above can originate from the Sun, when mentioning solar radiation or, more frequently, solar power then it is implying the energy emitted by the sun in the form of electromagnetic waves, including:

  • Visible light
  • Ultraviolet (UV) radiation
  • Infrared (IR) radiation.

The sun is a massive ball of hot, glowing gas that generates energy through nuclear fusion, a process in which atomic nuclei are fused together to form heavier elements.

The energy generated by nuclear fusion in the sun’s core is in the form of heat and light, which is then radiated outward through the sun’s atmosphere. This energy travels through space in the form of electromagnetic waves, which make up the solar radiation that reaches the earth.

The sun is the primary source of energy for life on Earth, and solar radiation plays a vital role in the planet’s climate and weather. It drives the water cycle, powers photosynthesis in plants, and is the ultimate source of energy.

While solar radiation is beneficial in many ways, excessive exposure to certain types, such as UV, can have harmful effects on human health, such as sunburn, skin cancer and cataracts.

2- Terrestrial radiation

It refers to the ionizing radiation that originates from the earth’s surface and its immediate environment. It includes gamma rays and X-rays that are emitted naturally by the Earth’s crust.

Origin of Terrestrial Radiation

The terrestrial sources vary significantly from place to place. These are categorized into building materials and soil surfaces. Exposure to terrestrial radiation can come from:

a. Radon gas

It is a naturally occurring radioactive noble gas element that is found in soil and rock. As all building materials mostly constitute rock and soil; these two raw materials include a number of natural radioactive isotopes such as 232Th and 238U decay series.

As it is gaseous under standard conditions, it can seep into buildings and become concentrated, leading to potential inhalation and exposure for inhabitants.

b. Terrestrial gamma rays

They are a type of ionizing radiation that is emitted by certain types of rock and minerals, such as granite and potassium-rich (40K isotope-containing) clay.

Most of the terrestrial background radiation is due to potassium and elements of the uranium series (238U to 206Pb), thorium series (232Th to 209Pb), and actinium series (235U to 207Pb). Each of these series consists of many α, β, and γ (alpha, beta, and gamma) emitters.

Exposure to terrestrial radiation can occur through various pathways, including inhalation, ingestion, and direct skin contact with radioactive materiel.

The levels of radiation exposure are generally low and are considered to be within safe limits. However, exposure to high levels (in some geographical locations) can increase the risk of cancer and other health problems.

While it can have potential health effects after exposure to terrestrial radiation, most people are exposed to relatively low levels in their everyday lives, and the risks are generally considered to be small.

Additionally, there are ways to reduce exposure by testing and mitigating radon levels in homes and buildings.

3- Endogenous Radiation

It originates from within the body and is also called internal radiation. It is emitted by naturally occurring radioactive materials that are present in the human body, such as potassium-40 and carbon-14.

Origin of endogenous radiation

Internal radiation can come from, among others, following sources:

  1. Natural sources: The human body contains small amounts of naturally occurring radioactive materials such as potassium-40, which is present in the body’s cells and tissues.
  2. Artificial sources: Some medical treatments and procedures, such as nuclear medicine, use radioactive materials that are introduced into the body to diagnose or treat certain conditions.
  3. Ingestion: Trace amounts of radioactive minerals are naturally found in the contents of food and drinking water. For instance, vegetables are typically cultivated in soil and ground water which contains radioactive minerals. Once ingested, these minerals result in internal exposure to natural radiation.

The effects of internal radiation depend on the level of exposure and the specific radioactive material involved. In general, it is not harmful to human health as it is at quite low levels.

However, high exposure levels can cause a range of health effects, including cancer and other diseases, birth defects, and other genetic mutations. Additionally, exposure to high internal radiation levels can cause symptoms such as nausea, vomiting, and fatigue.

4- Artificial Radiation

It refers to types of electromagnetic radiation created by human-made sources, as opposed to natural sources. Also, it can be either ionizing or non-ionizing.

Some examples include:

  • Radio and television broadcasts
  • Cell phone transmissions
  • X-rays
  • Radiation emitted by certain types of industrial equipment.

Origin of Artificial Radiation

Some sources, such as X-ray machines and nuclear power plants, can produce ionizing radiation, which has enough energy to remove tightly bound electrons from atoms and potentially cause damage to living tissue.

Other sources, such as radio and television transmitters, produce non-ionizing radiation, which does not have enough energy to cause this type of damage.

Here is a list of some common sources:

  1. Medical devices: X-ray machines, CT scanners, and other medical imaging equipment produce ionizing radiation.
  2. Nuclear power plants: These facilities generate electricity by harnessing the energy released during nuclear reactions.
  3. Industrial processes: Some industrial processes, such as welding and the use of certain chemicals.
  4. Telecommunications: Radio and television transmitters, cell phone towers, and other telecommunications equipment emit radio waves.
  5. Consumer products: Microwave ovens, some types of light bulbs, and other consumer products.
  6. Military uses: They include electromagnetic (impulse) weapons, radiological weapons, (thermo)nuclear weapons, radars, and sonars.

Medical devices and nuclear power plants produce ionizing radiation. However, industrial processes, telecommunications, and consumer products mostly emit non-ionizing radiation.

The Effects of Ionizing Radiation

It can have a variety of harmful effects on living tissue, including DNA damage and cell death. The severity of these effects depends on the amount of radiation exposure an individual receives, the type of ionizing radiation and the length of time the person is exposed to it.

Based on the site of interaction, the radiation-cellular interactions may be termed as either direct or indirect:

Direct action occurs when an ionizing particle interacts with and is absorbed by a macromolecule in a cell (DNA, RNA, protein, enzymes, etc.). These macromolecules become abnormal structures, which initiate the events that lead to biological changes.

Indirect action involves the absorption of ionizing radiation in the medium in which the molecules are suspended. The molecule, which most commonly mediates this action, is water. Through a complex set of reactions, the ionized water molecules form free radicals that can cause damage to macromolecules.

Stochastic Radiation Damage

It’s the harmful effects of ionizing radiation that occur at low to moderate doses and are generally unpredictable and inconsistent. These effects are often referred to as “non-threshold” effects because they can occur even at very low doses and are not generally associated with a specific threshold.

Some examples of stochastic radiation damage include:

1- Cancer

Exposure to ionizing radiation has been linked to an increased risk of cancer, as it can damage DNA and other genetic material in cells, leading to mutations that can cause cells to grow and divide abnormally.

The risk of cancer increases with the increase in dose received, but it is not possible to predict with certainty which exposed individuals will develop cancer.

2- Genetic mutations

It can also damage DNA in sperm and eggs, leading to genetic mutations in offspring. These mutations can be passed down to future generations and may lead to genetic disorders or other health problems.

The risk of stochastic damage increases with the radiation dosage received, but it is not possible to predict with certainty which individuals will be affected. Therefore, it is generally recommended to minimize exposure as much as possible to reduce the risk of these effects.

Deterministic Radiation Damage

It’s the harmful effects of ionizing radiation that occur at high doses and are generally predictable and consistent. These effects are often referred to as “threshold” effects because they only occur when the dose exceeds a certain threshold.

Some examples of deterministic radiation damage include:

1- Acute radiation syndrome (ARS)

A condition that can occur after exposure to a high dose of ionizing radiation over a short period of time. Symptoms of ARS include nausea, vomiting, diarrhea, and skin irritation, and in severe cases, it can lead to organ damage and death.

2- Cataracts

Prolonged exposure can increase the risk of cataracts, a condition in which the lens of the eye becomes cloudy, causing vision problems.

3- Fertility problems

High doses can damage the reproductive organs and reduce fertility in both men and women.

4- Growth and developmental abnormalities

Fetuses and young children are particularly sensitive to the effects of ionizing radiation, and exposure can cause growth and developmental abnormalities.

Generally, deterministic damage is only seen at very high doses of radiation. Most people do not experience these effects unless they are exposed to much higher levels than typical background levels.

Radiation Dose

The biological effects of ionizing radiation vary with the type and energy. A measure of the risk of biological harm is the dose that the tissues receive. The unit of absorbed radiation dose is the Sievert (Sv).

Since one Sievert is a large quantity, the doses normally encountered are expressed in milli-Sievert (mSv) or micro Sievert (µSv) which are one-thousandth or one-millionth of a Sievert. For example, one chest X-ray will give about 0.2 mSv of radiation dose.

On average, our exposure due to all-natural sources amounts to about 2.4 mSv a year – though this figure can vary, depending on the geographical location by several hundred percent.

Radioactive Protection

Over the years, as more was learned, scientists became increasingly concerned about the potentially damaging effects of exposure to large doses of radiation. The need to regulate its exposure prompted the formation of a number of expert bodies to consider what needed to be done.

In 1928, an independent non-governmental body of experts in the field, the International X-ray and Radium Protection Committee was established. It later was renamed the International Commission on Radiological Protection (ICRP). Its purpose is to establish basic principles for, and issue recommendations on, radiation protection.

These principles and recommendations form the basis for national regulations governing the exposure of workers and members of the public. The International Atomic Energy Agency (IAEA) into its Basic Safety Standards also has incorporated them for Radiation Protection published jointly with the World Health Organization (WHO), International Labour Organization (ILO), and the OECD Nuclear Energy Agency (NEA). These standards are used worldwide to ensure the safety and protection of radiation workers and the public.

Basic approaches to protection are consistent all over the world. The ICRP recommends that any exposure above the natural background radiation should be kept as low as reasonably achievable (ALARA), but below the individual dose limit. Basically, it is achieved either by reducing the exposure time and/or (increasing the) distancing from the radioactive source and/or by shielding from radiation.

The individual dose limit for workers with radioactive materials averaged over 5 years is 100 mSv, and for members of the public, is (one) 1 mSv per year.

These dose limits have been established based on a prudent approach by assuming that there is no threshold dose below which there would be no effect. It means that any additional dose will cause a proportional increase in the chance of a health effect. This relationship has not yet been established in the low dose range where the dose limits have been set.

Radioactive Contamination

It refers to the presence of radioactive substances on the skin, the surface of an object, food, clothes, or in the environment, etc. Contamination can be either external or internal.

Internal Contamination

Internal contamination refers to the presence of radioactive material inside the body. This can occur through:

  • Inhalation
  • Ingestion
  • Absorption through the skin.

Internal contamination is more dangerous than external contamination because the radioactive material can continue to expose the body to radiation from the inside and may cause internal injury.

Samples of body fluids or tissues can be collected and analyzed to determine if a person has been internally contaminated with radioactive material.

Treatment of Internal Contamination

It may involve the use of medications to remove the radioactive material from the body. Depending on the type and amount of radioactive material, treatment may include supportive care to manage any symptoms or complications that may arise as a result of the internal contamination.

External contamination

It’s the presence of radioactive material on the surface of an object or in the environment, on the skin, etc., but not inside the body. This type of contamination can occur in a variety of settings/incidents, including:

  • Nuclear power plants
  • Research laboratories
  • Hospitals
  • Use of radiological/nuclear weapons.

Decontamination of External Contamination

To decontaminate a surface or object that has been contaminated with radioactive material, the main goal is the safe removal of the radioactive material from the contaminated surface. So, it may be necessary to use (specialized) decontamination methods such as:

  • Washing with soapy water
  • Washing with a special chemical solution (containing detergents, complexing agents, etc.)
  • Wiping off with a cloth, or dusting off the clothes
  • etc.

It is crucial to follow proper procedures and guidelines when decontaminating an object to ensure that the contamination is properly removed (and collected) and that the decontamination process does not create additional hazards.

Hotzone Solutions Role in Raising Awareness about Radiation Safety

Hotzone Solutions provides a group of Radiation safety and response training programs to:

  • Emergency management agencies
  • Emergency medical services
  • Fire service
  • Health care
  • Governmental administrative
  • Law enforcement
  • Public health
  • Public safety communications
  • Public workers who deal with Radioactive materials.

Our mission is to strengthen them with the knowledge and skills necessary to safely handle radioactive materials and respond to radiation-related emergencies. These programs can be offered by a variety of organizations, including government agencies, hospitals, and universities.

Some of the capabilities that may be provided as part of a radiation safety and response-training program include:

Basic radiation safety principles

Training on the fundamentals of radiation safety, including the types and properties of radiation, the units of measurement used to quantify radiation, and the effects of radiation on living organisms.

Handling and storage of radioactive materials

Training on the proper techniques for handling and storing radioactive materials, including the use of personal protective equipment and the appropriate containers for storing different types of radioactive materials.

Detection and measurement of radiation

Training on the use of radiation detection and measurement instruments, including survey meters, dose rate meters, and contamination monitors.

Overall, Hotzone Solutions’ radiation safety and response training programs are essential for ensuring the safe handling and use of radioactive materials and for preparing individuals to respond effectively to radiation emergencies.


  1. “Introduction to Radiological Physics and Radiation Dosimetry” by Frank Herbert Attix
  2. “Radiation Protection in Medical Radiography” by Mary Alice Statkiewicz Sherer
  3. “Radiological Control for Conventional Weapons Destruction” by Robert E. Long
  4. “Radiation and Scattering of Waves” by Leung Tsang, Jin Au Kong, Kung-Hau Ding
  5. “Radiation Detection and Measurement” by Glenn F. Knoll
  6. “Radiation and Health” by Ernest J. Sternglass
  7. International Atomic Energy Agency Publications

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