People are stockpiling special pills to guard against radioactive fallout - but here's what you actually need in a nuclear survival kit

• Sales of potassium iodide or KI pills, which are often marketed as protecting the body from radioactive fallout, are soaring.
• But radiation health experts say the pills aren't really helpful in the aftermath of a nuclear attack.
• The pills account for a fraction of a percent of the radiation emitted by fallout.
• It's more important for survival kits to include water, food, a radio, flashlight, and other basic necessities to last a few days.

Hopefully it won't be the tweet that launched 1,000 ships - or nuclear weapons.

"North Korean Leader Kim Jong Un just stated that the 'Nuclear Button is on his desk at all times,'" President Donald Trump tweeted on January 2. "Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!"

Many people are concerned that statement was belligerent enough to back the US into war.

Shortly after Trump posted the statement, which received about 700,000 interactions, store managers across the country noticed a spike in sales of potassium iodide (or KI) pills, which are often advertised as able to block radiation from nuclear fallout.

For example, Troy Jones - who runs the website www.nukepills.com - told NPR that he saw demand for the pills soar.

"On Jan. 2, I basically got in a month's supply of potassium iodide and I sold out in 48 hours," he said.

In two days, Jones said he sent out about 140,000 doses of the drug, whereas he normally would have shipped about 8,400. Some local pharmacies have seen a similar rise in sales.

But the pill is far from a protect-all against a nuclear attack. In fact, radiation health experts say it's pretty much the last thing people need in a nuclear-blast survival kit - especially with the type of strike North Korea might be capable of.

Why potassium iodide pills are probably a waste of money

North Korea is working feverishly to miniaturize the nuclear devices it has detonated and perfect an intercontinental ballistic missile to deliver them thousands of miles away.

ICBM-launched warheads are likely to explode high above a city, leading to relatively little radioactive fallout.

Instead, the US government says fallout is a greater concern in the event of a terrorist's nuclear detonation, which would be close to the ground. That's because fallout is formed and spread when dirt and debris get sucked up by a nuclear blast, irradiated to dangerous levels, pushed into the atmosphere, and sprinkled over great distances.

One of the products in fallout is radioactive iodine. Iodine is absorbed and used by the thyroid gland in the neck, so radioactive forms can concentrate there and promote cancer. KI pills - which cost anywhere from a few cents to more than a dollar per pill online - can block that absorption.

However, radioactive iodine represents a tiny percentage of the elements that the human body would be exposed to in the event of a nuclear disaster.

"Most people seem to think of the potassium iodide, or KI, pills as some type of anti-radiation drug. They are not," Brooke Buddemeier, a health physicist and expert on radiation at Lawrence Livermore National Laboratory, previously told Business Insider. "They are for preventing the uptake of radioiodine, which is one radionuclide out of thousands of radionuclides that are out there."

Buddemeier estimated that radioiodine is just 0.2% of the overall exposure you may face outdoors, and said the pills are more helpful for addressing longer-term concerns about food-supply contamination. In the case of a nuclear blast, he said, "the most important thing is sheltering in place."

The best thing you can do is stay put

If you're lucky enough to survive the searing flash of light, crushing shockwaves, and incendiary fireball that is a nuclear explosion, your next item of concern is fallout.

Sheltering inside a robust structure for at least 12 to 24 hours is a key way to survive that threat, Buddemeier said, since fallout can easily out-speed vehicles as it gets blown around by high-speed winds in the upper atmosphere.

Buddemeier is a fan of the mantra "go in, stay in, tune in."

"Get inside ... and get to the center of that building," he said. "If you happen to have access to below-ground areas, getting below ground is great."

Soil is a great shield from radiation, Buddemeier says, so ducking into a home with a basement would be better than going into a place without.

Besides cars, the poorest shelters are made of wood, plaster, and other materials that don't shield against much radiation - about 20% of houses fall into this category. Better shelters, such as schools and offices, are made of bricks or concrete and have few or no windows.

Prepare an emergency kit with these items instead

Buddemeier recommends visiting Ready.gov to see a complete list of what to do in various emergency scenarios, including a nuclear blast, and what to include in a full emergency kit.

It's smart to prepare a family plan and assemble a few emergency kits, which you can stash at home, work, and in your vehicles.

"This isn't just for the nuclear holocaust event," Buddemeier said. "This is for general emergency preparedness and making sure that you and your family can be safe in an emergency."

The first item to include is a radio, he said - ideally a hand-cranked type with a USB charging port that can power other devices.

A radio is important for receiving emergency broadcasts and instructions. It's one of the simplest ways to figure out where dangerous fallout has landed, when you can leave your shelter, and where the safest routes to exit a fallout zone are.

"If you have a cellphone, that'll work too," Buddemeier said, though he prefers a radio because "sometimes the cell towers may be affected," by power outages, crushing demand, or an invisible yet powerful effect of nuclear weapons called electromagnetic pulse. (The effect can disable electronics, though a ground detonation would mostly confine EMP to the blast damage zone, where you'd have much bigger problems.)

Second, Buddemeier says, you'll want water - ideally 1 gallon per person per day, according to Ready.gov. In addition to drinking it, you may need it to rinse off radioactive fallout after removing your clothes, since this can drastically reduce your radiation exposure.

Third, Buddemeier said, "I would probably grab a breakfast bar or two to stave off the hunger a little bit." Fourth, he says, is any essential medications or treatments you might need.

If one of your kits isn't handy in the event of an explosion, Buddemeier recommends trying to grab a few of these items - as long as that process doesn't delay taking shelter by more than a couple of minutes. The first minutes and hours after a blast are when radioactive fallout exposure risk is the greatest - especially outdoors.

FEMA recommends each of your emergency kits have these essential items in a portable bag:

1. Water: 1 gallon of water per person per day for at least three days, for drinking and sanitation.
2. Food: at least a three-day supply of nonperishable food.
3. Battery-powered or hand-crank radio and a NOAA Weather Radio with tone alert and extra batteries for both.
4. Flashlight and extra batteries.
5. First-aid kit.
6. Whistle to signal for help.
7. Dust mask to help filter contaminated air, and plastic sheeting and duct tape to shelter in place.
8. Moist towelettes, garbage bags, and plastic ties for personal sanitation.
9. Wrench or pliers to turn off utilities.
10. Can opener for food (if kit contains canned food).
11. Local maps.

If you have the space, the need, and the foresight, FEMA also recommends beefing up your basic kits with these items:

1. Prescription medications and glasses.
2. Infant formula and diapers.
3. Pet food and extra water for your pet.
4. Important family documents, such as copies of insurance policies, identification, and bank-account records in a waterproof, portable container.
5. Cash or traveler's checks and change.
6. Emergency reference material such as a first-aid book or information from Ready.gov.
7. Sleeping bag or warm blanket for each person. Consider additional bedding if you live in a cold-weather climate.
8. Complete change of clothing, including a long-sleeved shirt, long pants, and sturdy shoes. Consider additional clothing if you live in a cold-weather climate.
9. Household chlorine bleach and medicine dropper: When diluted nine parts water to one part bleach, bleach can be used as a disinfectant. Or in an emergency, you can use it to treat water by using 16 drops of regular household liquid bleach per gallon of water. Do not use scented or color-safe bleaches, or those with added cleaners.
10. Fire extinguisher.
11. Matches in a waterproof container.
12. Feminine supplies and personal-hygiene items.
13. Mess kits, paper cups, plates and plastic utensils, and paper towels.
14. Paper and pencil.
15. Books, games, puzzles, or other activities for children.

You can access more information about how to prepare for a variety of emergency scenarios at FEMA.

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