Myths and Facts About Radiation » The Unclouded Path

Radiation is one of the most misunderstood scientific concepts in the public. Comic books, urban legends, and chain emails have all contributed to public misconceptions about radiation. As a result, when most people hear “nuclear” or “radiation”, they immediately go into panic mode. So this post is going to clarify things and give you the facts about radiation.

What Is Radiation?

In scientific terms, radiation is the emission or transmission of energy through either empty space or some material. This energy can be in the form of waves or moving particles. Electromagnetic (EM) waves and byproducts from radioactive decay (or other nuclear reactions) are what most people associate with the word “radiation”. But you might not know that energy in the form of gravitational waves and sounds waves also count as forms of radiation. However, since electromagnetic waves and particle radiation are the most relevant to people, I’m just going to cover the facts about those kinds of radiation here.

Electromagnetic radiation consists of waves (also represented as photons) from any part of the electromagnetic spectrum. This includes radio waves, microwaves, infrared light, visible light, ultraviolet light, x-rays, and gamma rays. In essence, it’s just light with different wavelengths. The shorter the wavelength, the higher its frequency and energy.

Particle radiation consists of particles (ions or subatomic particles) moving at high speed. They’re usually produced by reactions involving the nuclei of atoms like radioactive decay. Examples include alpha particles (helium ions), beta particles (electrons or positrons), protons, and neutrons.

Ionizing and Non-Ionizing Radiation

The thing that makes some forms of radiation dangerous is the amount of energy it carries. So, scientists mark this distinction by classifying radiation as either ionizing or non-ionizing. Ionizing radiation contains enough energy in each photon or particle to knock electrons out of atoms (ionizing them), which effectively destroys whatever molecule they were a part of. This is the harmful “radiation” in colloquial language. Anything with more than 10 eV (electron volts) is considered ionizing radiation, though some prefer to use 33 eV (the energy needed to ionize water) as the benchmark for biology, since water makes up most of all life.

Small amounts of ionizing radiation are everywhere. Traces of uranium and thorium, both radioactive elements, are in soil and rocks. Both of them produce radon, a radioactive gas, as an intermediate byproduct in their decay processes. Radioactivity, in the form of radioactive potassium, is also present in many life forms. For example, bananas (which are good sources of potassium) are slightly radioactive. These natural sources of ionizing radiation account for roughly 60-80% of the total ionizing radiation you receive per year. The rest comes from man-made sources, mainly from medical imaging.

But, the vast majority of radiation that you come into contact with on a daily basis, like the heat from your food or the radio signals from Wi-Fi, is non-ionizing and harmless. However, even though it can’t ionize atoms, in some cases, non-ionizing radiation can build up enough energy in something to cause damage. For example, we all know how much damage the heat (mostly infrared) from fire can do. In addition, some of the electromagnetic radiation at the ultraviolet and upper visible light spectrum can excite certain molecules enough to cause harmful chemical reactions. An example is ultraviolet radiation causing skin damage.

Types of Harmful Radiation

As you now know, the reason that radiation is sometimes harmful is because at high enough energies, it’s essentially like a bunch of tiny bullets. When they hit atoms, they scatter a cascade of other particles which go on to interact with other atoms. So in terms of protection, you not only have to stop the radiation, but also the cascade effect it creates on impact. All this can damage cells, and with enough damage, problems like radiation burns, radiation sickness, and cancer can occur. Harmful radiation comes in several forms, all of which except the last one are ionizing.

Alpha Particles

An alpha particle consists of two protons and two neutrons. It’s essentially a helium atom that’s missing its two electrons, making it a positively charged helium ion. These particles are generally formed from the radioactive decay of heavy atoms like uranium. They can also form from ternary fission, a relatively rare type of nuclear reaction. But these particular alpha particles have a much higher energy.

Since alpha particles have a positive charge and relatively high mass they strongly interact with any matter in their path. This means that they don’t travel very far before they lose all their energy (comes to a stop). As a result, just a few centimeters of air or a sheet of paper can stop them. But if they do somehow get inside the body (by ingesting or inhaling radioactive material for example), they’re the most damaging form of ionizing radiation, since they knock a whole bunch of particles loose.

Beta Particles

A beta particle is just a high-speed electron or positron (antimatter form of an electron). Like alpha particles, beta particles are also mainly produced by radioactive decay. But, they have less energy than alpha particles.

Beta particles have a charge, so they strongly interact with any matter in their path. But since they’re a lot smaller than alpha particles, they can travel farther before losing all their energy. As a result, they need more matter to stop them (in this case, 1 m of air or a thin plate of aluminum). When they interact with matter, they can create x-rays and other electrons.

High-Energy Photons

Photons from the upper ultraviolet, x-ray, and gamma ray part of the EM spectrum are the ones with enough energy to ionize atoms. These are produced by reactions involving atomic nuclei (radioactive decay or matter-antimatter annihilation) or by energized electrons and other charged particles.

Since photons don’t have a charge or mass, they don’t interact with matter that easily. So, these high-energy photons can travel through matter for much longer distances than alpha and beta particles. As a result, it takes much more stuff to stop them. In fact, you typically need a high-density material like lead or depleted uranium to do it (or the Earth’s atmosphere). When one of these photons hits an electron, it gets absorbed and splits its energy between that electron and a newly created photon. The electron flies off with enough energy that it becomes a beta particle, which goes on to interact with other atoms. If the new photon still has enough energy, it can continue to cause more ionization reactions.

High-Energy Neutrons

These high-speed neutrons are the products of a number of nuclear reactions, including nuclear fusion, nuclear fission, and radioactive decay. But they’re unstable when not bound to the nucleus of an atom, lasting slightly under 15 minutes on average.

Neutrons don’t have a charge, so they can travel farther through matter than alpha and beta particles. But depending on the kind of matter, they can either travel longer or shorter distances than high-energy photons. In contrast with those photons, they tend to get stopped more easily by materials with low atomic number (like hydrogen and water). When they hit matter, they either scatter a bunch of particles like protons (which then ionize other atoms) or they get absorbed into an atom’s nucleus which creates a radioactive isotope that decays (and produces byproducts that ionize other atoms).

Cosmic Rays

Cosmic rays aren’t a particular type of radiation. Instead it’s a blanket term for very high energy particles that come from reactions outside Earth. Roughly 99% of them are ions, about 1% are single electrons, and a tiny fraction is antimatter. Of the ions, about 90% of them are protons (hydrogen ions), 9% are alpha particles, and the rest are the nuclei of heavier atoms.

These particles have way higher energy than anything found on Earth outside of particle accelerators. The ones with the highest energy that we’ve found so far are about 40 million times more energetic than anything the Large Hadron Collider (currently the world’s most powerful particle accelerator) can produce. To put that into perspective, that’s an atom that packs as much punch as a 100 km/h baseball. You may have heard that astronauts need strong radiation shielding when they’re in space. It’s because of cosmic rays. But for people on Earth, they’re not really a concern because the Earth’s atmosphere stops them from reaching the surface.

Non-Ionizing EM Radiation

The non-ionizing EM radiation you usually encounter is relatively harmless since it’s low energy. But as mentioned before, certain kinds can still cause damage even though it doesn’t have enough energy to ionize atoms. The lower end of ultraviolet and some visible light can cause chemical reactions. While some of these are beneficial like photosynthesis, others can cause damage, like reactions that produce free radicals.

EM radiation even lower on the EM spectrum can also cause a buildup of heat energy, which can obviously damage things. If enough heat energy builds up, it can even ionize atoms. But this requires many photon interactions instead of just one in the case of ionizing radiation.

Uses of Radiation

Radiation has many practical uses in modern technology. Here are some major ones:

Many medical techniques use radiation to see inside your body. For example, x-ray imaging and CT (computed tomography) scans both use x-rays. Radioactive isotopes can also be used as a “marker” that shows where a certain substance in the body is going. For instance, PET (positron emission tomography) scans typically use a short-lived radioactive isotope carried by sugar to see what parts of the body are the most metabolically active.
Radiation is also used to treat cancer (radiation therapy). To do this, doctors aim precise, shaped beams of either x-rays or gamma rays from multiple angles, all intersecting at the tumor. This ensures that only the tumor gets a focused dose of radiation while none of the surrounding tissue gets dangerous amounts. The radiation either destroys the tumor cells or stops their ability to divide and spread. To further reduce the chance of harm to the surrounding tissue, doctors space the treatments over several days or even weeks.
Cooking food uses EM radiation. All kinds of cooking techniques use infrared energy in the form of heat to cook food. Your microwave oven is another example. It uses microwave radiation to heat up the water molecules in food.
Modern communication relies on many types of EM radiation. Radio communications, lasers, and fiber-optics all use various EM waves.
Radiation can disinfect food and medical instruments. This process is called irradiation and typically uses ultraviolet (mainly for surfaces and liquids) or electron beams/x-rays/gamma rays (for foods). It’s a completely safe and efficient way to sterilize stuff.
One of the more widely-known uses is nuclear power. It works by moving fuel rods (rods of enriched uranium or plutonium) close enough together so that the neutrons resulting from nuclear fission reactions keep starting other fission reactions (a chain reaction). Control rods absorb excess neutrons to keep the reactions under control. All this produces lots of heat, which is used to boil water and turn steam turbines (which generate electricity). That “smoke” you see from those huge cooling towers at nuclear power plants is just water vapor created by waste heat, not radioactive pollution.
Radiocarbon dating relies on measuring levels of radioactive carbon with known half-lives (the amount of time it takes for half of the material to decay). Once scientists know the amount, they can infer how long ago something died.

Myths About Radiation

Now that you have a much clearer view of the facts about radiation, some of the myths floating around should seem pretty ridiculous. Here are some that you might have come across:

Radiation will mutate you or give you superpowers. It’s a staple of movies and comic books. But radiation just damages stuff. If you receive too much radiation, too many of your cells die or get damaged, and you may suffer organ failure or even death. If the genetic information in your cells gets damaged, they may malfunction and become cancerous. Now, while genetic information damage won’t “mutate” a grown organism, if it happens when an organism is in the earliest stages of development, it could lead to defects later on.
Any amount of radiation is harmful. As you’ve read, most radiation you come across isn’t harmful. In addition, your cells can take some of the damage from harmful radiation and still repair themselves. In other words, your organs and tissues have a tolerance level that depends on the type of tissue, the type of radiation, the length of exposure, and various individual differences. As with all substances, the “poison” is in the dose.
Irradiated food is dangerous. Some people stay away from irradiated food because they think it’s radioactive. But all you’re doing to food when you irradiate it is essentially shining high-energy light at it to kill all the bacteria and other harmful organisms. It doesn’t make it radioactive because you aren’t adding any radioactive substances to the food. For example, does getting an x-ray make you radioactive? No, it doesn’t.
Radiation therapy will make you radioactive. This is false for the same reason as the irradiation myth above. The key to remember is that these two are examples of exposure (you received radiation), not contamination (you got stuff that’s radioactive on or in you). Exposure won’t make you radioactive, but contamination will.
Nuclear power plants give off dangerous amounts of harmful radiation. A properly-built nuclear power plant has plenty of shielding in the form of water, concrete, and lead. In fact, you might get more radiation from coal power plants because coal contains trace amounts of radioactive elements, and they don’t have shielding. Also, the amount of harmful radiation from either power plant is tiny compared to the amount you get from natural background radiation (about 10000 times less).
Microwaving water changes it into a harmful substance. This myth came from an experiment that supposedly showed that water heated in a microwave oven killed plants. But, as you now know, microwaves are non-ionizing, so they can’t do anything except heat stuff up. And that’s all the microwaves from your microwave oven do.
Cell phones can give you cancer. This claim has been floating around the internet for a while. Cell phones use low-energy radio waves, which are non-ionizing. So the most it can do is heat stuff up. But the energy in cell phone signals is way too weak to do any damage. Numerous studies have tried to find strong evidence that radio waves from cell phones could cause damage through means other than heating, but they couldn’t find it.
Getting an x-ray can cause nausea and vomiting. These are signs of radiation sickness. But imaging x-ray machines don’t produce enough radiation to cause it.
There’s nothing you can do to stop harmful radiation. Well, as you’ve read, plenty of materials can stop harmful radiation. And if for some reason, you were contaminated with radioactive dust, you could just wash it off or throw whatever was contaminated away.
There are “cures” for radiation. No medicine or food will “stop” radiation. What this claim is probably referring to are medicines that stop the body from taking in radioactive substances, make your body excrete them faster, or help your body repair damage. For example, potassium iodide gives the thyroid gland plenty of regular iodine so it won’t take up radioactive iodine from the environment. But it only works against this particular substance, so if you aren’t exposed to it, it’s useless.
You can’t survive a nuclear blast or the radioactive fallout that ensues. If you’re close to the blast, then yeah the intense heat would definitely kill or severely burn you. But in areas further away, it’s possible to survive the fallout relatively unharmed by staying inside a sturdy structure (preferably underground) until some time has passed. This is because the radioactive dust decays pretty quickly, on the order of a few days. Staying inside will limit the radiation you receive until it’s safe to come out.