Nuclear or radiation emergency: what to do and when to take iodine tablets
What to do in the first hours after a nuclear accident: get inside, stay inside, stay tuned. How to decontaminate, which food and water are safe, and what potassium iodide tablets do, who they're for and when to take them.
In short
- The basic rule: get inside a building, stay inside for at least 24 hours and follow official information.
- If you were outside, take off your outer layer of clothing and bag it: that can remove up to 90% of contamination. Then wash.
- Iodine tablets protect only the thyroid, and only from radioactive iodine. Take them only when officials tell you to, never in advance.
- Never use iodine tincture, antiseptics or iodized salt as a substitute. They don't work or are dangerous.
There are more than 400 nuclear power reactors around the world, and the war in Ukraine put the Zaporizhzhia plant in the headlines for months. In 2022, iodine tablets sold out in pharmacies across Europe within days. A serious nuclear accident is very unlikely, but it’s one of the few scenarios where what you do in the first hour matters enormously. And the rules are few and easy to remember.
What kind of emergency it could be
- An accident at a nuclear power plant: radioactive material, including radioactive iodine, is released into the air and can be carried long distances by the wind. Officials announce the affected areas and what to do.
- A “dirty bomb”: ordinary explosives mixed with radioactive material. The main danger is the blast; contamination is usually local.
- A nuclear explosion: the most serious and least likely scenario. The rules below still apply, plus protection from the blast.
In every case, the basic response is the same.
Get inside, stay inside, stay tuned
This is the rule used by the CDC and civil protection agencies in most countries.
1. Get inside. If you’re outside or in a car, get into a solid building as fast as you can, ideally brick or concrete. Cars give poor protection.
2. Stay inside. Go to the basement or the middle of the building, as far as possible from the roof and outer walls, where radioactive particles settle. Close windows and doors, and switch off air conditioning, fans and any system that draws in outside air. Stay inside for at least 24 hours unless officials say otherwise: radioactivity drops quickly in the first hours and days.
3. Stay tuned. Follow phone alerts, radio and TV. A battery or hand-crank radio is essential if the power goes out. If phone lines are busy, send texts instead of calling.
If your children are at school or relatives are in a hospital or care home, don’t go to get them. Those facilities have their own shelter plans, and the trip would expose all of you.
Nuclear explosion: the first seconds
If you see an unusual blinding flash, don’t look at it. Lie face down behind anything that offers protection and cover your head. The blast wave can arrive seconds later. Then get into the most solid building nearby, ideally within 10 minutes, before fallout starts to arrive, and stay there for at least 24 hours.
If you were outside: decontamination
- Take off your outer layer of clothing, before going indoors if possible. Put it in a plastic bag, seal it and leave it away from people and pets. This can remove up to 90% of radioactive material.
- Wash with soap and water, ideally in the shower. Wash your hair with shampoo but no conditioner, which can bind particles to hair. Don’t scrub your skin raw.
- If you can’t shower, wash at a sink or wipe down with a damp cloth, especially hands, face and hair.
- Put on clean clothes that were kept in a closet or drawer.
- Wash pets that were outside too.
Water and food
- Bottled water and sealed packaged food kept indoors are safe. Wipe the packaging before you open it.
- Don’t eat garden vegetables, drink milk from animals kept outdoors or use well water until officials say it’s safe.
- A water supply and non-perishable food for a few days let you stay indoors as long as needed.
Iodine tablets (potassium iodide, KI)
The most discussed and least understood part of a nuclear emergency.
What they do: an accident at a power plant can release radioactive iodine. If inhaled or swallowed, it builds up in the thyroid and raises the risk of thyroid cancer, especially in children. Potassium iodide fills the thyroid with stable iodine so the radioactive kind isn’t absorbed.
What they don’t do: they don’t protect you from other radioactive substances or from external radiation. They are not a “radiation antidote” and don’t help against a dirty bomb that contains no radioactive iodine.
When to take them: only when officials explicitly tell people in your area to. They work best taken shortly before exposure or within the first few hours after. One dose protects for about 24 hours. The dose depends on age and is set by officials and the package leaflet, not by websites.
Who needs them most: babies, children, teenagers, and pregnant or breastfeeding women. For adults over 40 the benefit is small and the risk of side effects is higher.
Who should ask a doctor first: people with thyroid disease, a known iodine allergy, or certain rare skin and blood vessel conditions. Your doctor can tell you whether tablets are right for you.
What not to do:
- Don’t take tablets “just in case” before an official announcement.
- Don’t take more than the recommended dose: it doesn’t protect better and can cause harm.
- Never swallow iodine tincture, povidone-iodine or other iodine antiseptics instead. They are poisonous if swallowed.
- Don’t rely on iodized salt: it contains far too little iodine to protect the thyroid.
Where to get them depends on where you live. In the US, potassium iodide is sold over the counter and some states supply it to residents near nuclear plants. In the UK and many EU countries, tablets are pre-distributed to households near nuclear sites. If you keep tablets at home, store them in the original box with the leaflet, somewhere everyone knows, and check the expiry date.
What to have ready
- A battery or hand-crank radio
- Water and food for at least 3 days
- Large plastic bags for contaminated clothing
- Duct tape and plastic sheeting to seal a room if told to
- Soap, shampoo and towels
- A few days of daily medication
- Iodine tablets, if your doctor or authority has provided them
Most of this is already in your home emergency supplies. If you have them, you’re ready for this scenario too.
Frequently asked questions
Should I take iodine tablets now, just in case?
No. The FDA warns that taking potassium iodide without reason, or in larger doses than recommended, gives no extra protection and can cause serious harm. Take tablets only when public health or emergency officials explicitly tell people in your area to do so.
Who needs potassium iodide most?
Babies, children, teenagers, and pregnant or breastfeeding women: their thyroids absorb the most radioactive iodine. For adults over 40 the benefit is small, and the FDA recommends tablets for them only at very high exposures.
Where can I get iodine tablets?
It depends on the country. In the US, potassium iodide is sold over the counter and some states supply it to people living near nuclear plants. In the UK and many EU countries, tablets are pre-distributed to households near nuclear sites and stockpiled for wider use. In Romania, people up to 40 have been able to get them free with a prescription from their family doctor. Check with your doctor or national health authority.
Can I drink tap water after a nuclear accident?
Bottled water and sealed packaged food kept indoors are safe: wipe the packaging before opening. For tap water and garden produce, wait for official guidance; authorities measure contamination and announce what is safe.
Sources and further reading
Preper is for general education and does not replace instructions from your local authorities or advice from a doctor. In an emergency, call your local emergency number.