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Visible light falls within the electromagnetic spectrum.
Michael Duva/Getty ImagesEssential Insights
- Radiation refers to the release and propagation of energy through electromagnetic waves or particles.
- It can be categorized into ionizing and nonionizing types, with ionizing radiation possessing sufficient energy to potentially harm cells and DNA.
- Radiation originates from natural sources like cosmic rays and radioactive materials, as well as artificial sources such as X-ray equipment and nuclear reactors.
Mention the term "radiation" to three individuals, and you’re likely to receive three distinct responses. Your aunt might share how radiation helped eliminate her cancer. Your neighbor could recall the "duck and cover" drills from his youth. Meanwhile, your comic-enthusiast friend might elaborate on how gamma rays transformed Bruce Banner into The Hulk. Radiation exists in numerous forms and surrounds us constantly. While it can be hazardous at times, it isn’t always harmful.
Radiation is both a natural phenomenon and a product of human innovation. Daily, our bodies encounter natural radiation from sources like soil, underground gases, and cosmic rays emitted by the sun and outer space. Additionally, we are exposed to radiation from modern inventions such as medical treatments, televisions, cell phones, and microwave ovens. The danger of radiation depends on its intensity, type, and duration of exposure.
Many attribute the discovery of radiation to Marie Curie, alongside her husband and research collaborator, Pierre. While this is partially accurate, Curie’s groundbreaking achievement was the discovery of the element radium in 1898, earning her the distinction of being the first woman to win a Nobel Prize. However, in 1895, scientist Wilhelm Röntgen first identified X-rays and the concept of radioactivity (a term later coined by Curie, derived from the Latin word for "ray"). Following Röntgen’s breakthrough, French scientist Henri Becquerel sought to uncover the source of X-rays and discovered that uranium emitted a potent "ray." Curie’s doctoral research built on Becquerel’s findings, leading to her discovery of radium [source: Vaught].
Radiation is energy that moves either as waves (electromagnetic radiation) or as high-velocity particles (particulate radiation). Particulate radiation occurs when an unstable (or radioactive) atom breaks down. Conversely, electromagnetic (EM) radiation has no mass and propagates in wave forms. EM radiation spans a wide range of energy levels, collectively known as the electromagnetic spectrum. This spectrum includes two primary types of radiation: ionizing and non-ionizing.
Feeling a bit overwhelmed? Don’t worry—we’ll break it all down in detail over the next few pages.
Ironically, the very discovery that immortalized Marie Curie in history also led to her demise. In the late 1890s, both Marie and her husband Pierre began experiencing various health issues. Marie developed cataracts, a known side effect of radiation exposure, and ultimately died from anemia caused by radiation damage to her bone marrow.
The Electromagnetic Spectrum
Sunlight's ultraviolet rays are a type of radiation.
DAJ/Getty ImagesElectromagnetic (EM) radiation consists of photons that travel in wave-like patterns. The photon is the fundamental unit of all EM radiation. But what exactly is a photon? It’s a packet of energy—essentially light—that is always in motion. Interestingly, the energy level of a photon determines whether it behaves like a wave or a particle, a phenomenon known as wave-particle duality. Low-energy photons, such as those in radio waves, act like waves, while high-energy photons, like X-rays, behave more like particles. For more on photons, check out How Fluorescent Lamps Work.
EM radiation has the unique ability to travel through a vacuum, unlike other wave types such as sound, which require a medium to propagate. All EM radiation forms are part of the electromagneticspectrum, organized from the lowest energy and longest wavelengths to the highest energy and shortest wavelengths. Higher energy levels correlate with stronger and potentially more hazardous radiation. The distinction between a radio wave and a gamma ray lies solely in the photon energy levels [source: NASA]. Below is an overview of the electromagnetic spectrum.
Radio: Radio waves possess the longest wavelengths in the electromagnetic spectrum, sometimes as long as a football field. They are invisible to the human eye but deliver music to radios, transmit audio and video to televisions, and relay signals to cell phones. While shorter than traditional radio waves, cell phone waves are longer than microwaves.
Microwaves: Invisible to the eye, microwaves are commonly used to heat food rapidly. They are also employed in telecommunications satellites to transmit voice signals over phones. Microwaves can penetrate haze, clouds, and smoke, making them ideal for information transmission. Some microwaves are utilized in radar systems, such as the Doppler radar used in weather forecasting. The universe itself emits faint cosmic microwave background radiation, which scientists link to the Big Bang Theory.
Infrared: Infrared radiation sits between the visible and invisible sections of the EM spectrum. It is used in remote controls to change channels and is felt as heat from the sun. Infrared photography can capture temperature variations, and certain animals, like snakes, can detect infrared radiation, enabling them to locate warm-blooded prey even in complete darkness.
Visible: This is the sole portion of the electromagnetic spectrum visible to the human eye. The varying wavelengths within this range are perceived as the colors of the rainbow. The sun is a natural emitter of visible light. When observing an object, our eyes detect the color of light it reflects, while all other colors are absorbed.
Ultraviolet: Ultraviolet (UV) rays are responsible for causing sunburns. While humans cannot see UV rays, certain insects can. The ozone layer in our atmosphere filters out most UV rays. However, with the depletion of the ozone layer due to chlorofluorocarbons (CFCs), UV exposure is on the rise, increasing risks such as skin cancer [source: EPA].
Gamma rays: Gamma rays possess the highest energy and shortest wavelengths in the electromagnetic spectrum. They are produced by nuclear explosions and radioactive atoms. These rays can destroy living cells, a property harnessed by medical professionals to target and eliminate cancer cells. In space, gamma ray bursts occur daily, though their exact origins remain unknown.
Continue reading to explore the distinctions between non-ionizing and ionizing radiation.
Today, we recognize the dangers of excessive X-ray exposure, and both technicians and patients wear protective gear. However, from the 1930s to the 1950s, shoe stores used X-ray machines to fit shoes. While no customer injuries were reported, employees faced significant risks. One shoe model experienced severe complications from X-ray overexposure, ultimately leading to the amputation of her leg [source: Frame].
Non-ionizing Radiation
A microwave drum tower illuminated at dusk in Baltimore, Md.
Greg Pease/Getty ImagesRadiation is categorized into two primary types: non-ionizing and ionizing. On the electromagnetic (EM) spectrum, this division occurs between infrared and ultraviolet. Delving deeper, ionizing radiation manifests in three main forms: alpha particles, beta particles, and gamma rays. We’ll explore these radiation types in greater detail later in this article.
Non-ionizing radiation refers to lower-energy radiation that lacks the energy required to ionize atoms or molecules. It occupies the lower end of the electromagnetic spectrum. Sources of non-ionizing radiation include power lines, microwaves, radio waves, infrared radiation, visible light, and lasers. While generally considered less harmful than ionizing radiation, prolonged exposure to non-ionizing radiation can still pose health risks. Let’s examine some examples of non-ionizing radiation and the associated safety concerns.
Extremely low frequency (ELF) radiation is emitted by power lines and electrical wiring. Concerns have been raised about the health effects of prolonged exposure to magnetic fields near power lines, though this remains a contentious topic. While ELF radiation is ubiquitous in daily life, the risk of harmful exposure depends on the intensity of the ELF source, as well as the proximity and duration of exposure. Research on ELF radiation primarily investigates its potential links to cancer and reproductive issues. While no conclusive evidence ties ELF radiation to illness, some studies suggest preliminary associations [source: WHO].
Radio frequency (RF) and microwave (MV) radiation are primarily emitted by devices such as radios, televisions, microwave ovens, and cell phones. Both RF and MV waves can disrupt medical devices like pacemakers, hearing aids, and defibrillators, necessitating precautionary measures. In recent years, concerns about cell phone radiation have gained significant attention. While no definitive link between cell phone use and health problems has been established, the potential risks remain. The key factor is exposure level. High levels of RF exposure can heat body tissues, potentially causing skin or eye damage and increasing body temperature. Experts often recommend using headsets or hands-free devices for prolonged cell phone use [source: FCC]. For more details, refer to our article How Cell Phone Radiation Works.
Infrared radiation (IR) is absorbed by our skin and eyes as heat. Excessive exposure to IR can lead to burns and discomfort. Ultraviolet (UV) radiation is particularly concerning because its effects are not immediately noticeable. However, consequences like sunburns or more severe conditions can develop rapidly. Prolonged UV exposure increases the risk of skin cancer, cataracts, and weakened immunity [source: EPA]. Besides sunlight, UV sources include black lights and welding equipment.
Lasers emit IR, visible, and UV radiation, posing significant risks to the eyes and skin. Individuals working with lasers must wear protective gear to shield their eyes, hands, and arms.
Continue reading to explore the effects of high-energy ionizing radiation.
In the 1920s, a watch company utilized radium, a newly discovered element, to create glow-in-the-dark watches. Thousands of young women worked in the factory, meticulously painting watch dials by hand. To achieve finer brush strokes, the workers would lick the brushes. Occasionally, to alleviate monotony, they painted their teeth and lips, then turned off the lights to see the glow. Despite regular radioactivity tests conducted by management, the workers were never informed of the results. In 1938, Catherine Donahue, one of the workers, sued the company to access her test results. She won a settlement but passed away the same year. Many other radium girls also died over the years, but no conclusive link was proven, and the company avoided accountability [source: Irvine].
Ionizing Radiation
X-ray image of a young boy's torso.
Sami Sarkis/Getty ImagesLike non-ionizing radiation, ionizing radiation consists of energy in the form of particles or waves. However, ionizing radiation possesses such high energy that it can disrupt chemical bonds, effectively ionizing atoms it interacts with. At lower energy levels, it may remove a few electrons, while at higher levels, it can obliterate an atom's nucleus. This capability allows ionizing radiation to damage DNA when it passes through bodily tissues. This is why gamma rays, for instance, are effective in destroying cancer cells during radiation therapy.
Ionizing radiation is emitted by radioactive substances, high-voltage equipment, nuclear reactions, and stars. It exists both naturally and as a result of human activity. Radon, a radioactive element found underground, is a natural source of ionizing radiation. X-rays, on the other hand, are a prime example of man-made ionizing radiation.
The three primary forms of ionizing radiation we’ll explore are alpha particles, beta particles, and gamma rays.
Particulate radiation consists of fast-moving, tiny particles that possess both energy and mass. This type of radiation is emitted when unstable atoms decay, producing alpha and beta particles. For instance, radioactive elements like uranium, radium, and polonium release alpha particles during decay. These particles, composed of protons and neutrons, are relatively large and can only travel short distances—they can even be blocked by a sheet of paper or human skin. However, alpha particles pose significant risks if inhaled or ingested, as they can irradiate internal tissues.
Beta particles, in contrast, are high-speed electrons capable of traveling farther and penetrating deeper than alpha particles. While clothing or materials like aluminum can block or reduce their impact, some beta particles have sufficient energy to penetrate the skin, potentially causing burns. Similar to alpha particles, beta particles are highly dangerous if inhaled or ingested.
Gamma rays, a form of electromagnetic radiation, also emit ionizing radiation due to their high energy levels. They often accompany alpha and beta particles but are far more penetrating. Stopping gamma rays requires several inches of lead or even a few feet of concrete. These rays pose a whole-body radiation risk, as tissues absorb some of their energy as they pass through. Gamma rays occur naturally in minerals like potassium-40, though the radioactive isotope is present in minimal amounts and potassium remains essential for health [source: HPS].
X-rays are similar to gamma rays but differ in their origin. While gamma rays originate from within an atom’s nucleus, X-rays result from changes in an atom’s electron structure and are typically machine-generated. X-rays are less penetrating than gamma rays and can be blocked by a few millimeters of lead, which is why patients wear lead aprons during medical X-ray procedures.
Excessive exposure to ionizing radiation can lead to genetic mutations, resulting in birth defects, an increased risk of cancer, burns, or radiation sickness [source: NLM].
Feeling overwhelmed by this information? Let’s dive into the topic of radiation exposure on the next page.
Radiation exposure has long fascinated comic book creators, likely because it can alter DNA, opening the door to mutations and extraordinary abilities. Here’s a glimpse of some iconic characters shaped by radioactivity: Spider-Man, The Hulk, Radioactive Man (naturally), Sun Boy, Sandman, Godzilla, Graviton, X-ray, Rampage, Doctor Phosphorous, Doctor Manhattan, Flux, and Ion. With countless more in existence and countless others yet to be imagined, the possibilities are endless [source: Comic Vine].
Radiation Exposure
Radiation is omnipresent, a natural part of our environment since Earth’s formation. It exists in the air, soil, water, and even within our bodies. This phenomenon is known as natural background radiation, and it poses no harm to us.
Radiation impacts the body by transferring energy to tissues, potentially causing cell damage. In some cases, this may have no noticeable effect. In others, it can lead to abnormal cell growth, which may become malignant. The outcome depends on the intensity and duration of exposure. In rare instances of extreme radiation exposure over a short period, death can occur within days or hours, a condition known as acute exposure. Conversely, chronic exposure involves repeated, low-dose radiation over an extended period, with potential delays before health effects manifest. The most reliable data on radiation risks come from atomic bomb survivors in Japan and individuals regularly exposed to radiation through work or medical treatments.
Radiation exposure is measured in millirem (mrem), with higher doses measured in millisieverts (mSv), where 1 mSv equals 100 mrem. In the U.S., the average annual radiation dose is approximately 360 mrem, with over 80% originating from natural background radiation [source: DOE]. However, external factors significantly influence this average. Geographic location and lifestyle play a role; for example, residents of the Pacific Northwest typically receive about 240 mrem annually from natural and artificial sources, while those in the Northeast may receive up to 1700 mrem, largely due to radon in rocks and soil. Is 1700 mrem safe? Check the sidebar for details.
Wondering what to do if you’re exposed to radiation? Find out on the next page.
This chart focuses on ionizing radiation. Among non-ionizing radiation types, only ultraviolet rays are known to cause cancer.
- 10,000 mSv (1,000,000 mrem) as a short-term, whole-body dose can cause immediate illness and death within weeks.
- 1,000 to 10,000 mSv (100,000 to 1,000,000 mrem) in a short-term dose leads to severe radiation sickness with a high risk of fatality.
- 1,000 mSv (100,000 mrem) in a short-term dose causes immediate radiation sickness but is unlikely to be fatal.
- Short-term doses exceeding 1000 mSv (100,000 mrem) over time significantly increase the risk of future cancer.
- Doses above 100 mSv (10,000 mrem) increase the likelihood of cancer, rather than the severity of illness.
- 50 mSv (5,000 mrem) is considered the lowest dose at which cancer may develop in adults and is the maximum annual occupational exposure limit.
- 20 mSv/yr (2,000 mrem) averaged over five years is the limit for radiological workers, including nuclear industry employees, miners, and hospital staff (who are closely monitored).
- 10-12 mSv (1,000-1,200 mrem) in one dose is equivalent to a full-body CT scan.
- 3 mSv/yr (300 mrem) is the typical natural background radiation in North America, including nearly 2 mSv/yr from radon.
- 2 mSv/yr (200 mrem) is the average natural background radiation, including 0.7 mSv/yr from radon, close to the minimum dose received globally.
- 0.3-0.6 mSv/yr (30-60 mrem) is the typical range from artificial sources, primarily medical procedures like bone density scans, dental X-rays, chest X-rays, and bone X-rays.
- 0.01-0.03 mSv (1-3 mrem) is the typical radiation dose from a single coast-to-coast flight. Frequent flyers (100,000 to 450,000 miles annually) may receive 1 to 6 mSv (100-600 mrem) per year.
[sources: World Nuclear Association and Health.com]
What to Do If You're Exposed to Radiation
A nuclear power plant accident has the potential to release dangerous radiation into the atmosphere.
Pete Turner/Getty ImagesMany films and novels exploit the dangers of radiation, such as nuclear disasters and bomb threats, to create suspense and fear. But what’s fact and what’s fiction? While it’s unlikely that zombies will emerge and dominate the world (we hope), radiation poisoning and sickness are real possibilities. Radiation can enter the environment through various means—accidents at nuclear power plants, atomic bomb detonations, accidental releases from medical or industrial equipment, nuclear weapons testing, or acts of terrorism like dirty bombs. When discussing radiation exposure here, we’re primarily referring to the rare but catastrophic release of radiation on a large scale.
Every community has a radiation disaster response plan. Local authorities are trained in emergency preparedness and will provide guidance in the event of such a crisis. During a radiation emergency, the Centers for Disease Control and Prevention (CDC) may advise staying indoors rather than evacuating. This is because the walls of your home can shield you from some harmful radiation. The safest area in your home is typically a room with few or no windows, such as a basement or bathroom.
If your job involves working with radiation or radioactive materials, there are strict regulations on permissible exposure levels. Depending on your industry, additional precautions such as safety gear, masks, gloves, and lead-lined aprons are required to minimize risk.
During a radiation emergency, the first step is to determine if you’ve been contaminated. Contamination occurs when radioactive materials are present on or inside your body. It can spread rapidly—external contaminants can be shed as you move, and bodily fluids can release internal contaminants. The CDC advises the following steps to minimize contamination:
- Leave the affected area immediately.
- Remove your outer layer of clothing.
- Seal the clothing in a plastic bag or place it away from others.
- Thoroughly wash all exposed skin.
- Seek medical attention if internal contamination is suspected.
[source: CDC]
If exposed to radiation, medical professionals can assess you for radiation sickness or poisoning by evaluating symptoms, conducting blood tests, or using a Geiger counter to detect radioactive particles. Treatment varies based on exposure severity. Decontamination is the initial step and may suffice. Annual blood tests might be recommended to monitor for delayed symptoms.
Certain medications can alleviate symptoms of radiation exposure. For instance, potassium iodide tablets are often taken during nuclear emergencies to prevent radioactive iodine from accumulating in the thyroid. However, these tablets do not protect against direct radiation exposure or other radioactive particles. Prussian blue, a dye, binds to radioactive elements like cesium and thallium, accelerating their elimination from the body and reducing radiation absorption. Diethylenetriamine pentaacetic acid (DTPA) binds to metals in radioactive elements such as plutonium, americium, and curium, allowing them to be excreted in urine and minimizing radiation absorption.
To learn more about radiation, explore the links provided on the next page.
Before retreating to a fallout shelter, keep in mind that certain types of radiation can be beneficial. For instance, ultraviolet (UV) radiation is crucial for the body to produce Vitamin D. Moderate sunlight exposure is actually healthy, but don’t discard your sunscreen just yet. Experts recommend just five to 15 minutes of sunlight, three times a week, to maintain adequate Vitamin D levels.
