Your Complete Guide to Radiation Exposure

Your Complete Guide to Radiation Exposure

by Matt Collins

Imagine a virus that can infect everything, not just humans or other animals.

Instead of spreading from person to person like a traditional virus, it can be carried by the wind for miles. It can infect trees, bushes, buildings, furniture—everything.

It can spread in seconds, leaving behind infections that last for decades or even centuries.

It’s hard to test for, difficult to contain, and practically impossible to get rid of. Depending on your level of exposure to the virus, you might die within days, months, or even years … and from a wide range of potential causes.

That’s how radiation works.

We used this metaphor in our 2022 Radioactive Survival Guide for Chernobyl, and we’re revisiting it today because we’re talking about the effects of radiation exposure and how you can avoid them. Keep in mind, that radiation exposure causes the majority of deaths in most nuclear incidents. When Hiroshima and Nagasaki were bombed, only half of the casualties resulted from the initial blast. The rest died from radiation exposure in the days, weeks, and months following the explosion.

Radiation is all around us in the natural world, yet most people are completely unaware of it. Humans react differently to different levels of radiation exposure, and individuals may exhibit only a handful of symptoms before needing urgent medical care. What’s more, most Americans live within 50 miles of an active nuclear reactor.

So today, we’re taking a deeper look at radiation, how it interacts with the human body, and what you can do to manage (or even prevent) the consequences of various kinds of exposure.

Let’s get started …


  • 01

    Radiation Exposure 101

  • 02

    Acute vs. Indirect Exposure

  • 03

    Initial/”Prodromal” Phase of Radiation Sickness

  • 04

    Manifest Illness Stage

  • 05

    Recovery or Death

  • 06

    5 Pieces of Functional Radiation Survival Gear

  • 07

    Dealing with Radioactive Threats

Radiation Exposure 101

The simplest definition for radiation is the emission of energy in either wave or particle form through space or material.

This definition applies to everything from radios, microwaves, and x-rays to sound and ultrasonic waves.

But the real concern is ionizing radiation—in which subatomic particles or electromagnetic waves have so much power they can rip electrons away from molecules, ionizing the molecules as a result (hence the name).

(Image courtesy of EPA)

Ionizing radiation is a part of the natural world, and it comes from both natural and cosmic sources to varying degrees. We’re exposed to minuscule amounts of radiation every day, and for the vast majority of folks, it has zero consequences. But in highly concentrated doses (from a nuclear meltdown or nuclear weapon, for example), ionizing radiation can tear through the human body at a molecular level with devastating consequences.

Currently, our best guide to the different levels of radiation exposure is from the XKCD webcomic by Randall Munroe.

In the table below (with its handwritten guide), Munroe details every level of exposure—many of which are from strange sources you might not expect.

Before we evaluate this table, it’s important to point out that 1 sievert is a MASSIVE amount of radiation. As little as 2 sieverts can be lethal, so exposure is often denominated in millisieverts (mSv). The sievert comes from the International System of Units (SI), whereas the traditional rem (roentgen equivalent man) measure does not. Roentgens or “rems” translate to sieverts at the rate of 100 to 1, or 10 mSv per rem.

Of course, all of this is rather confusing. Which is why Munroe’s table is so helpful …

For example, eating a banana is actually more dangerous than living next to a nuclear power plant. That’s because most power plants are tightly sealed, whereas the potassium in the banana is mildly radioactive (about 0.012% of its atoms disperse both beta and gamma radiation). Living next to a coal-fired power plant is even riskier in terms of radiation because the coal contains the trace elements thorium and uranium that are released into the air as the coal is burned.

Altitude is another factor in background radiation. Cities like Denver, Colorado, have higher background radiation levels simply because there’s less atmosphere between them and cosmic radiation sources. The effects are more pronounced the higher you go, with commercial airline flights exposing you to even more radiation.

But all of this exposure is still pretty trivial.

Even spending an hour near Chernobyl will only expose you to 1.5x the average background dose. Not even as much as a chest CT scan!

In fact, the first effects of radiation exposure only tend to happen around 10 rem (100 mSv).

Everyone is affected differently, but once you reach about 40 rem (400 mSv), you will almost certainly experience the full spectrum of radiation sickness symptoms. At five times that level (200 rem, 2 sieverts), medical attention is necessary for survival. That’s just 2 sieverts. Once you reach 10, it’s only a matter of time until one’s death.

For a bit of perspective—10 minutes next to the Chernobyl core? That’s 50 Sieverts.

Again, everyone reacts differently to radiation exposure. The very nature of ionizing radiation is as devastating as it is unpredictable. But the LD50-30, which is the lethal dose for 50% of a given population within 30 days, is 4 sieverts. Experts believe that medical care is crucial at this stage, but there’s little they can do for those who’ve been exposed to 8 sieverts or more.

For context, consider the Radium Girls of the 1920s.

These young women were factory workers who painted radium onto wristwatches that were then sold to the US military. Back then, radium was used for its luminescent properties. That way, men working in the dark could still read the time on their watch.

At the time, no one realized how dangerous this was. Of course, the Radium Girls had no idea and were assured by their factory foreman that the paint was perfectly safe. They were trained to use their lips to straighten the thin paintbrush every few minutes—essentially ingesting poisonous radium paint every day, all day long. Some girls went even further and painted their nails with the radium.

By 1923, the first of the dial painters had died. The damage from the radiation was so bad that her jaw fell away from her skull before she died. By the following year, a dozen more girls had died, and more than 50 were sick at the plant. Just a few years later, the inventor of radium paint, Dr. Sabin Arnold von Sochocky, died due to radium poisoning in his hands.

This eventually became headline news, with a large settlement and a new occupational disease labor law added to the books. But radium paint continued to be used until the 1970s.

Acute vs. Indirect Exposure

Background radiation is a natural part of our everyday world, but aside from cases like the Radium Girls, most acute exposure is from nuclear power sources or atomic weapons. Both use highly refined isotopes of radioactive elements to achieve their desired outcomes.

Radioactivity isn’t the end goal in either case but an ever-present byproduct. The detonation of nuclear weapons instantly exposes massive areas to extremely high levels of radiation. By some estimates, nearly half of those killed in the Hiroshima bombing died in a matter of days because of massive radiation exposure.

Nuclear meltdowns are no less concerning.

Whereas the “Little Boy” bomb dropped on Hiroshima carried just 64 kilograms of uranium, the #4 reactor at Chernobyl contained 100–150 fuel assemblies with 100 kg of uranium each. That’s hundreds of times that in a nuclear bomb—and instead of being expended all at once, it’s still partially intact.

Beyond the fuel, there are other radioactive byproducts to worry about in a nuclear meltdown. The wastewater at both Fukushima and Chernobyl became a serious factor in the wake of both disasters. Remember, radiation is like a virus that can spread from practically any object or individual to anything else at any time. And depending on the concentration, things can stay irradiated for years or even decades.

Following the meltdown at Chernobyl, firefighters rushed in to put out the blaze. Unknowingly, these men were exposed to massive doses of radiation and had to be rushed to the hospital afterward. Their clothes were removed and taken to the hospital’s basement to avoid exposing the staff or other patients to radiation. The clothes remained in that basement even after Pripyat was evacuated. Just recently, nearly four decades after the disaster, the clothing was tested … and was still emitting massive amounts of radiation.

Fortunately, there are only two significant radioactive exposure threats …

Acute exposure is infrequent, but it’s also the cause of the most severe cases of radiation sickness. Acute exposure happens when an individual is exposed to radioactive isotopes like plutonium, enriched uranium, or radioactive elements like those in the Radium Girls’ paint or the Curies’ experiments. Most cases have involved unshielded/unstable reactors or the aftermath of a nuclear explosion. Acute exposure should be avoided at all costs since a lethal dose of radiation can accumulate in hours, if not minutes.

Indirect exposure through irradiated fallout is far more common. The nuclear meltdown at Chernobyl involved a massive explosion that volatilized massive amounts of radioactive waste—transforming heavy metals into an extremely fine powder that floated on the wind for hundreds of miles. Tens, if not hundreds of thousands (maybe millions), were exposed to radioactive fallout after the meltdown, and the vast majority had no idea at the time.

Acute radiation exposure tends to result in acute radiation syndrome (ARS), which we discuss in greater detail below. ARS is the type of radiation sickness you most often see in films and television. But indirect exposure (and any lower-level dose, for that matter) won’t result in ARS. Instead, experts calculate what are called “excess deaths.”

(Image courtesy of Health Jade)

Much like a life insurance adjuster calculates mortality rates, these experts estimate the expected mortality of a given population versus a similar population that has been exposed to some level of radiation. Radiation exposure is closely linked to a higher incidence of cancer. Even though 1 in 4 humans develop cancer anyway, even small doses of radiation can increase the risk. It’s estimated that for each additional rem of exposure, 200 per million more will die from cancer-related causes.

While that might not sound like much, some folks in St. Louis would ardently disagree.

For decades now, people in 90 municipalities in the area have experienced higher-than-average levels of life-threatening illnesses—from brain tumors, appendix cancer, and leukemia to lupus and congenital disabilities. They’ve been called the “poison children of Coldwater Creek.” As residents began to connect on Facebook in 2011, they recognized the pattern. They linked it to the Department of Energy’s Mallinckrodt facility. That’s where the uranium for America’s first nuclear weapons was processed and produced.

While the facility was top secret during World War Two, it’s been making headlines recently for the 250,000 barrels of toxic waste that were dumped in pits and have been exposed to the elements—even splashed off the trucks driving them to the dump sites.

Now, the area is a massive cancer cluster with hundreds of cases.

Even though none of these people were exposed to anything as dangerous as a nuclear blast or an exposed reactor, they’re suffering lifelong consequences from toxic waste that’s roughly 80 years old. Such indirect exposure results in smaller doses of radiation that in the long-term, can be just as devastating as a much larger dose in the short term.

Understanding Acute Radiation Syndrome

Acute radiation syndrome (ARS) is the medical term for radiation sickness, which results from acute exposure to very high radiation levels. The total amount absorbed by your body is referred to as your radiation dose.

An individual is only at risk of ARS if their exposure meets the following criteria:

  • Their radiation dose was very high.

  • Most of their body was exposed to radiation.

  • The radiation penetrated internal organs.

  • The radiation dose was received in a very short period.

Each radiation dose is different, and each individual reactsto exposure differently. Two individuals exposed to similar conditions with similar levels of protection and radiation may ultimately have different outcomes.

For example, three men called the “Divers of Chernobyl” waded through waist-deep radioactive water just days after the reactor meltdown on May 4, 1986. They volunteered to expose themselves to tremendous amounts of radiation to reach the valves for the reactor’s bubbler pools. They were successful, and all three went on to live long and happy lives without any consequences from their exposure. Two are still alive today.

Meanwhile, many firefighters who tried to contain the initial blaze at the Chernobyl plant perished within days after their exposure.

As the essential organs are highly sensitive to radioactive damage, ARS tends to manifest in three syndromes with increasingly deadly consequences.

Bone marrow syndrome is common for those exposed to lower radiation doses. With this type of ARS, the radiation destroys the marrow in your bones, leading to higher rates of infection, hemorrhaging, and death.

(Image courtesy of Cancer Help Essential Health)

Gastrointestinal syndrome occurs when an individual’s radiation dose exceeds 10 Sv (1,000 rems). Survival is extremely unlikely because this involves massive damage to the gastrointestinal tract (in addition to bone marrow). Dehydration, electrolyte imbalance, and death usually occur within two weeks.

(Image courtesy of Glutathione Reporter)

Cardiovascular/central nervous system syndrome usually occurs with a dose greater than 50 Sv (5,000 rems). Death occurs within three days. This form of ARS usually involves the complete collapse of the circulatory system.

While radiation doses and ARS types may vary, the timing of symptoms is relatively uniform. ARS progresses in four primary phases with distinct symptoms, durations and fatality rates.

(Image courtesy of MDPI)

Initial/”Prodromal” Phase of Radiation Sickness

The clock starts ticking immediately upon exposure to 1 sievert (Sv) or more, with the initial phase lasting anywhere up to 48 hours.

A common symptom during this initial phase is nausea and vomiting. The higher the radiation dose, the sooner an individual is likely to begin vomiting. If vomiting starts within an hour of initial exposure, long-term survival is unlikely. With bone marrow ARS, the symptoms begin within 1–2 days.

At higher radiation doses, other symptoms may appear in the first few hours—including diarrhea, headaches, fatigue, weakness, hypotension, fever, and nausea. The face may begin to take on a reddish color. At extremely high doses, radiation can cause an individual to lose consciousness within hours.

With GI ARS, initial symptoms typically start within hours, whereas those with cardiovascular ARS start experiencing symptoms within minutes.

Regardless of when the symptoms start, many cases are so severe that the individual is effectively immobilized. Thus, if you’re knowingly exposed to radiation, you should seek shelter and safety as soon as possible.

Incubation/Latent Phase

Following the initial symptoms, ARS seemingly subsides for up to three weeks after exposure. Individuals may show no specific symptoms and may seem to have recovered. Many individuals won’t even need hospitalization during this phase, and since it can last for several weeks, it’s easy to think the worst is over.

In reality, the worst has just begun. During this latent phase, radiation attacks the body’s vital organs. Over time, the damage accumulates—preventing the processes necessary to sustain life.

Once again, the duration of this stage depends on the type of ARS. For bone marrow syndrome, the latent phase may last anywhere from 1 to 6 weeks. For GI syndrome, it lasts less than a week. And for cardiovascular syndrome, it’s usually just a matter of hours.

Manifest Illness Stage

Once the symptoms of serious illness become apparent, most of the damage is done.

Those with bone marrow syndrome will suffer symptoms like fever, malaise, and anorexia. Blood cell counts will typically drop for weeks since the marrow is no longer replenishing the blood cells. The immune system suffers due to the reduced blood cell count, and the patient, as a result, can become immunocompromised.

With good medical care, individuals can survive for months with advanced bone marrow ARS. If death occurs, the immediate cause is typically hemorrhaging or infection. So doctors treat infections as soon as possible, keep bleeding to a minimum, and infuse platelets and factors to stimulate bone marrow growth.

(Image courtesy of Medscape Reference)

With GI syndrome, individuals also experience severe diarrhea and dehydration. Typically, death occurs within two weeks of exposure. Radiation doses over 10 Sv (1,000 rems) are generally lethal. In addition to treating bone marrow ARS, doctors will work diligently to maintain the patient’s electrolytes and hydration.

Those suffering from cardiovascular/CNS syndrome experience symptoms much sooner. Within 5 to 6 hours of exposure, they will experience watery diarrhea, convulsions, and coma. Recovery is not expected, and death usually occurs within three days.

In this stage, another symptom of ARS is skin damage, ranging from reddish swelling to what looks like sunburn and even large chunks of skin separating from subcutaneous tissue and sloughing off.

Recovery or Death

Most individuals suffering from bone marrow ARS will recover within a few weeks to two years. Bone marrow cells gradually begin to repopulate, elevating blood cell counts and restoring the immune system’s ability to ward off infections. During this time, patients must stay under observation by their physician in a safe environment.

Death may still result for some individuals with exposure levels as low as 1.2 Sv (120 rems), with increased lethality for doses in the 5–6 Sv range.

Other forms of ARS are generally fatal. Those with radiation doses as low as 6 Sv can still be fatal. For those who survive, lifelong consequences include elevated cancer risk, infertility, persistent health problems, and more. Symptoms can manifest months or decades later—seemingly unconnected to the initial radiation exposure.

It’s all the more confusing because, again, not everyone reacts the same way to radiation exposure. Some individuals will show symptoms of GI ARS at just 60% of what’s considered to be a minimal dose. These individuals might seem more susceptible to radiation sickness, but they’re far more likely to survive.

This brings us back to the simplest solution for managing your radiation exposure …

Avoid exposure in the first place, at all costs.

5 Pieces of Functional Radiation Survival Gear

To protect yourself from direct exposure to radiation and fallout, you need to ensure you’re not ingesting or making any direct contact with radioactive materials. That means full-body CBRN gear and a respirator with the appropriate filters.

Here are five critical pieces of personal protective equipment you want to have on hand if you’re worried about radiation exposure.

Geiger-2 Portable Dosimeter: Radiation exposure can lead to potentially incurable consequences—so your best first step is to avoid radiation at all costs with something like the Geiger-2 Portable Dosimeter.

Unlike the dosimeters you’ve probably seen in the movies or on television, the Geiger-2 isn’t an analog gauge. It’s a fully-digital device with a 1.1-inch LED screen and an easy-to-use operating system. It’s almost as small as a ballpoint pen and can easily fit in a pocket or pack. If you’re ever concerned—or even just curious—you can activate the Geiger-2 and get a nearly instant reading of background radiation.

Using the simple two-button interface, you can track your accumulated exposure over weeks. You can also set customizable exposure limits—the unit’s integrated alarm will let you know when you’ve reached your programmed limit.

Instead of using disposable batteries, the Geiger-2 has an integrated LiPo battery that can be recharged in just two hours to provide up to 30 days of regular use. A solar panel on the rear of the unit can help boost its charge when you’re out in the field.

Since it uses the same Geiger Muller tube as standard military detectors, we’re comfortable recommending the Geiger-2 as a must-have inclusion for any CBRN bug-out bag.

Thyrosafe Tablets: We simply can’t recommend these enough. At just over $20, this potentially life-saving CBRN precaution is an outstanding deal as far as we’re concerned.

The isotope iodine-131 is a common byproduct of nuclear power plants, explosions, and meltdowns. When humans are exposed to I-131, it accumulates in the body’s thyroid gland and emits 90% of its energy as damaging beta radiation. Even limited exposure to I-131 can lead to thyroid cancer and death.

Our Thyrosafe tablets flood your system with stable potassium iodide, providing far more than the recommended daily allowance. As a result, your thyroid becomes functionally incapable of absorbing any more, so it can’t absorb damaging I-131.

Each dose provides 24 hours of protection, buying you crucial time to get away from the disaster site and make your way to safety. It’s produced by Recipharm in Sweden and has a 7-year shelf life. It’s easy, cheap, and effective protection that (once again) belongs in your kit.

CM-7M Gas Mask: When confronted with major radioactive threats nearby, gas masks and other full-face respirators are essential.

They protect the soft tissue of your eyes, nose, and mouth and filter radioactive particulates out of the air you breathe. To avoid getting ARS, you mustn’t ingest any radioactive particulates or fallout. That’s where your CM-7M Gas Mask comes in.

Made from butyl rubber with a six-point adjustable head harness, the CM-7M is a heavy-duty solution trusted by military and police worldwide. It’s also packed with essential features that make the mask more usable and practical for various situations. There’s an integrated hydration system for easy drinking and a speech diaphragm for communicating while wearing your mask. You can mount your filter on either side depending on whether you’re left- or right-handed, and it’s compatible with accessories like the MIRA Safety Gas Mask Microphone.

So why the CM-7M over the CM-6M in this case?

Well, the CM-7M is available in three sizes. And while one size fits most (if not all, in your family’s case), we’ve found that some users need a different size for optimal protection. Mask fit is crucial—if your mask doesn’t seal tightly around your face and pass a negative pressure test, you shouldn’t wear it.

In addition to giving you more size options, the CM-7M is also ideal for use with pistols and rifles—which can be an important factor, depending on your situation.

NBC-77 SOF / P3 Filters: We recommend the NBC-77 SOF filter because it’s almost always the correct answer.

(Image courtesy of Blue Line Syndicate Group)

On the civilian market, the NBC-77 SOF is the closest thing to a true super filter. It provides practical protection from a wide range of threats, including all known CBRN agents. It has an unrivaled 20-year shelf life (most filters only last 5–7 years) and comes in individually sealed and wrapped packages for easy storage and use.

Two key features help this filter stand out in terms of radiation protection. First, it has the all-important Reactor rating; a filter with this rating is necessary to protect the body from radioactive iodine (the I-131 mentioned above). And second, it has a P3 rating—the highest standard for particle protection. P3 filters can protect you from a wide range of inhaled fallout and biological threats.

So when it comes to radiation protection, your best choice is a Reactor-rated P3 mask (like the NBC-77 SOF). If none are available, a standard P3 Filter will provide substantial protection.

Full-Body Protection: Since it’s crucial to avoid direct contact with radioactive fallout, you’ll want to ensure that you’re wearing a complete protective kit—starting with a hazmat suit like the MIRA Safety HAZ-SUIT. It’s designed to be reusable and is available in various sizes for each member of your family. Entirely impermeable to CBRN threats with a practically unlimited shelf life, this is an excellent option for every member of your party.

(Image courtesy of Blue Line Syndicate Group)

Other options include the M4 CBRN Poncho, which can be worn with a hazmat suit for added protection from fallout and other threats.

(Image courtesy of Blue Line Syndicate Group)

Once you’re suited up, you’ll need protective gloves like our HAZ-GLOVES. Made from the same butyl rubber as our gas masks, these gloves provide more than twice the protection offered by military alternatives. Kappler ChemTape can then be used to seal the junctions between gloves, boots, and suits.

(Image courtesy of Blue Line Syndicate Group)

Together, these components can provide practical protection from radioactive threats and fallout. Still, you must limit your exposure to radioactive hazards. If you’re exposed, do NOT remove your suit before completing a full decontamination. Radioactive material may be on the outer surface of your suit, so removing it too soon could expose you to the threat you’re wearing it to avoid.

Dealing with Radioactive Threats

As you’ve read, radioactive exposure poses various health threats to individuals.

Low-level exposure occurs every day from things as simple as eating a banana. But if levels rise substantially above typical background rates, the risk of cancer and other health issues begins to increase. At the lowest relevant levels, radiation exposure can lead to a 1 in 500 chance that you’ll develop cancer in any given year. Once radiation reaches the levels experienced by those in St. Louis, the health consequences are unavoidable.

The higher the dose, the more personal the problem of radioactive exposure becomes. Once someone develops acute radiation syndrome, they have already taken in 20 times the maximum annual dose allowed for any radiation worker anywhere in the world. By that point, the statistical risk of developing cancer pales in comparison to the reality of your body’s various systems shutting down in weeks, if not days. When exposed to high doses, you’ll become non-responsive and pass out in a matter of minutes.

The best solution, as with any CBRN threat, is simple: Avoid radiation at all costs. Immediately evacuate an area with extremely high concentrations of radiation, and don’t stay too long in an area associated with a cancer cluster, toxic waste, or other potential radioactive threats. Stockpile key gear, like P3 Reactor filters, gas masks, and hazmat suits. But first and foremost, do your best to avoid the situation entirely. And don’t forget to take your Thyrosafe pills.