out of a post-apocalyptic horror film.

And it often is.

It's been portrayed in movies and television for more than 50 years.

And those portrayals vary a lot.

I mean, the fate-worse-than-death described

in 1959's On the Beach is very different

than the 'based on a true story' version

depicted in the 2019 miniseries Chernobyl.

But if there's one thing pretty much all

these portrayals have in common, it's that

they get radiation sickness wrong—at least somewhat.

Like, people don't just start oozing blood

out of their legs, and you can't get the

illness from hugging a hospitalized loved one.

To start off, technically, radiation sickness

is called Acute Radiation Syndrome or ARS.

And it's not one thing, but rather, a bunch

of different syndromes that result from being

exposed to large doses of ionizing radiation.

That's the kind of radiation that carries

enough energy to knock electrons off of atoms.

And it's a problem for your cells,

because all that energy can break chemical bonds and

therefore mess with essential molecules like DNA.

Your cells have ways of fixing broken molecules,

of course, especially breaks to DNA.

But they aren't perfect, so ionizing radiation

often leads to mutations.

And let's be clear: cells don't become better from these mutations.

The more radiation-induced mutations

a cell has, the more likely it is that it will die or become cancerous.

So although radiation can change your DNA,

it isn't going to turn you into a walking,

roaring, city destroyer a la Godzilla,

or give you superpowers.

I'd hope that radiation myth was pretty

obvious, but not all of them are so easy to spot.

For example, let's say a person walks into

the exact wrong room and is exposed to a lot of radiation.

And by a lot, I mean enough that this person

gets more than 0.7 grays of radiation exposure

from spending five minutes in that room.

A gray is a measure of how much energy is absorbed

by an object or person per kilogram of weight.

And though it might not sound like much,

0.7 grays is a lot.

For comparison, when you get a chest x-ray,

you absorb about 0.0001 grays, and a full-on

CT scan exposes you to just 0.01 grays.

So, yeah, 0.7 grays is a lot of radiation,

and this person has just been exposed to it.

What happens next?

Based on Hollywood, you might think their

skin will instantly blister or they'll start

bleeding from everywhere.

But that's not how radiation sickness works.

They might have no symptoms for a while.

Depending on the exposure, it could take minutes

to hours before they enter what's called

the prodromal stage of ARS.

At this point, they might feel nauseous or vomit,

or have a fever, headache, or diarrhea.

Symptoms like these can happen on and off for a few days.

And we're not entirely sure why that happens.

The best explanation we have is that radiation

somehow activates cells in the gastrointestinal

tract to release the neurotransmitter serotonin,

and that triggers the brain's vomit center.

A similar thing can happen when people get chemotherapy.

What's weird about ARS, though, is that

after this period of queasiness, people often feel a lot better.

This is what's known as the latent stage.

And as the name implies, during this phase,

it might not seem like there's a lot going on.

A person who's been exposed can feel generally

healthy… but they're not.

Oddly enough, this is the stage where cells are actually dying.

You see, the cells that die from radiation

generally don't die right away.

DNA damage mostly becomes a problem when cells

go to divide and realize they can'ｔ, because

the DNA has breaks in it or

the coding sequence is wrong.

So the length of the latent period

partially depends on where the

radiation damage occurred

and how often the affected cells divide.

That's why, when symptoms start to show

up, they often appear in places like the intestines,

bone marrow, or skin, because those tissues

contain cells that divide the most often.

Of course, how long the latent period lasts also depends

how strong the dose of radiation was.

Higher doses over a shorter period of time

mean more damage, faster.

Now, the latent period might sound similar

to the incubation period of other illnesses

where a person doesn't show symptoms,

but they can transmit the disease to someone else.

But, unlike TV shows would have you think,

people with ARS aren't dangerously radioactive.

Their radiation sickness isn't contagious.

You could, say, sit by the bedside of your

dying partner for days or even weeks, and

you wouldn't develop ARS yourself.

Now, it is possible for a person to be emitting

dangerous amounts of radiation right after

they've left the exposure site, because

radioactive material can stick to their skin and clothes.

But once those clothes are removed and

their skin is thoroughly washed, the danger is gone—

even if there's still radioactive material inside them.

If they inhaled or swallowed bits of ash,

for example, they might have stuff emitting

ionizing radiation inside their body.

But, even though any radioactive material

inside them will continue to give off radiation

until it fully decays, that radiation is lost so quickly to nearby cells that the person

doesn't pose a danger to others.

Basically, it's just hurting them.

So, technically, you could go ahead and hug a loved one who's been hospitalized with ARS.

But it might not be a good idea to do that—for their sake.

You see, the radiation may have killed off a lot of the stem cells in bone marrow that make white blood cells.

And those white blood cells are the immune system's army, so without them, the immune

system is weakened and the person is vulnerable to infection.

Plus, damage done to other tissues — like connective tissue and blood vessels — can

eventually cut off the bone marrow's blood supply.

And without blood, the bone marrow keeps dying even after the radiation threat has passed.

Eventually, the body can't compensate for the cell damage anymore.

And that that point, the person enters the manifest illness stage.

This stage lasts anywhere from a few hours to several months, and looks different depending

on the kinds of tissues that were damaged.

Some forms of radiation syndrome show up in the skin, which can get dry, red, or itchy,

or in severe cases can start to blister.

Basically, it's the same idea as a sunburn—though, potentially, a lot worse.

Other forms, triggered by smaller doses of radiation, mostly affect the bone marrow,

resulting in internal bleeding, a drop in white blood cells, and anemia.

But if a person is exposed to more than 10 grays of radiation, advanced phases can also

have gastrointestinal effects, like severe diarrhea, vomiting, or becoming unable to

absorb the nutrients in food.

And if the exposure was more than 50 grays, the patient could move really quickly through

all the earlier stages to reach the manifest illness stage in a matter of hours.

And in cases like these, damage occurs to the central nervous and cardiovascular systems,

resulting in convulsions or comas.

And… there isn't really any chance of survival.

But, the good news is, in most of those lower-dose scenarios, a person can recover—especially

if they receive prompt treatment.

Though, there is no silver bullet.

Hollywood seems to think all you have to do to survive a nearby nuclear disaster is pop some iodine tablets.

Don't get me wrong, iodine tablets are great.

And it's true these pills are recommended as soon radiation exposure is suspected.

But they're not a cure-all.

In fact, they don't so much treat ARS as prevent the person from absorbing too much

radiation in their thyroid—that walnut-sized, H-shaped organ in your neck.

See, the thyroid's job is to take iodine and use it to make thyroid hormones, which

help regulate your metabolism, among other things.

Most of the time, that's totally fine.

But if you've been in a fallout zone, you might have radioactive forms of iodine in

your body—like iodine 131, which is one of the radioactive elements made in a nuclear reactor.

And if a bunch of that gets into your thyroid, it can cause a lot of DNA damage and even

lead to thyroid cancer.

Iodine pills contain potassium iodide, a stable form of iodine.

The hope is that your thyroid absorbs it instead of the radioactive stuff.

And for that reason, they do help—but they only really protect the thyroid, because it's

the body part that sucks up most of the iodine in your body.

And they don't help your body deal with any other radioactive elements.

Plus, they don't actually do anything to the radioactive material.

And if a person has radioactive stuff inside them—what doctors call internal contamination—getting

rid of it will help minimize the total damage done, so that's an important part of treating ARS patients.

Radioactive elements do eventually stop emitting radiation on their own, of course.