Follow-up of Could the entire world have been destroyed by the existing nuclear arsenal in 1962?

  • Is it safe to grow food on land that was hit by nuclear bombs? Or will such food kill/fatally sicken anyone that eats it?
  • If the food is lethal, how long would it take for land to become arable again?

Expect that bombs are not only detonated in the air, but also on the ground to hit bunkers.

I know that Pripyat and Chernobyl is now flourishing with all sorts of plants, but I wonder if that is safe for eating and whether it would be different if the cause was a nuclear explosion that would have wiped out most plants in its blast, so that it would first have to regrow?

Most radiation from a nuclear explosion is gone in a matter of days, but the protagonist stays in their bunker for about 6 months after which they emerge to scavenge the world because the bunker is running out of supplies. Would it be possible for the player to discover farms growing crops that are perfectly edible?

I consider it "safe" when people don't die within a year as a direct result from eating it. Only an increased risk of cancer I will consider "safe".

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    $\begingroup$ You need a good definition of safe vs non-safe. For example, today we'd stop people eating crops if they were 10 times more radioactive than background; but in a post-nuclear environment, you wouldn't care about an increased risk of certain cancers because 'dying from starvation' would be a more pressing worry. $\endgroup$ – Andrew Dodds May 15 '17 at 7:32
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    $\begingroup$ There's a very very big difference between what we would consider safe and what actually poses a threat to the survival of humanity. If eating contaminated food kills one person in a thousand every year, it would be a public health calamity by contemporary developed-world standards, but would barely affect the total human population. $\endgroup$ – Mike Scott May 15 '17 at 10:41
  • $\begingroup$ If you tell us how many bombs and what kind of bombs someone might be able to give you an answer, but the answer will most likely be either "yes" or "they are dead anyways". I think this is an interesting question if you modify it. What kinds of food are edible after how much contamination, what kinds are not? I can tell you that people didn't care at Hiroshima and Chernobyl was during the European atomic war paranoia and people overreacted by a lot $\endgroup$ – Raditz_35 May 15 '17 at 14:46
  • $\begingroup$ "Safe" as in not dying within a year from eating it. Only increased risk of cancer is "safe". $\endgroup$ – Quwin May 15 '17 at 15:00
  • $\begingroup$ @Raditz_35 I actually had a bit of background information on this question about the level of destruction although it was edited out, probably because it was in the same paragraph as me telling it was for a game. The northern hemisphere has been destroyed in a nuclear war using the existing nuclear arsenal in 1962. Southern hemisphere is mostly untouched. $\endgroup$ – Quwin May 15 '17 at 15:11

Scrape off the top layer, grow the right kind of crops

Fallout is essentially dust. It is not something that infuses everything and cannot be gotten rid of. You need to remove the top layer of soil a — and with that the contamination — and from then on the ground is fine to use.

Also it helps if you grow the right kind of crops. In some the contamination will be spread evenly through the edible parts, in others — such as stone fruits — the contamination tends to be concentrated to the seed while the flesh is all fine.

Much information about this can found from the Chernobyl Recovery and Rehabilitation Programme

As far as water is concerned, the constant runoff and replenishment will quickly dilute the contamination in water. Especially streams and rivers of fresh water will be a safe source to use for drinking and irrigation.

Also, as was concluded in other answers: there is a huge difference between peacetime concerns for radiation and a situation like that which you are describing. You can easily increase your yearly dose of radiation to 250 - 500 mSv, which is an increase of about 10 000% compared to present day conditions, without any acute ill effects, only increasing your probability of some cancers by a few percent.

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    $\begingroup$ 1) Then you also do not have a plow, a harrow and/or a cultivator. At worst: use a shovel. 2) Again: same problem. This stuff does not move around to any noticeable degree. It is fallout, not some liquid or a contagious plague. I mean... any amount of land that you wish to cultivate you must also be able to scrape a layer of top soil off of. If you cannot do the one you also cannot do the other. You are complicating this needlessly. 3) In a pile on a piece of land you are not using for cultivating. This is not something you need to be particular about. Just dump it some place else. $\endgroup$ – MichaelK May 15 '17 at 13:07
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    $\begingroup$ Read the question for cryin' out loud... we are not talking about restoring the agricultural industry to its former glory, most so because it is not needed: people are dead by the billions. And in any case the point is moot: if you can farm one acre of land you can damned well first scrape a layer of top soil off that very same acre too! Sure, if you would try to remediate every acre of farm land, then that is a huge task in absolute terms. But so is farming on that same amount of land. So stop... just stop. You are being silly now. $\endgroup$ – MichaelK May 15 '17 at 13:38
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    $\begingroup$ So in conclusion: for every unit of area of farmland you wish to farm.... you can remediate that area unit of farmland too, by removing the upper most layer of soil if needed (fallout is never uniformly distributed). $\endgroup$ – MichaelK May 15 '17 at 13:39
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    $\begingroup$ No I am not. Radioactive fallout is not magic. Land remediation after fallout is not some extraordinarily difficult process. It is well known and easy: stick a dosimeter at the soil and measure the intensity of the radiation. If it is too high, remove the top layer and try again. And since we are talking about a post-apocalyptic scenario where are are facing a food shortage we are not particular about it. I am sorry but this whole trope where people try to make radiation to be this inescapable black plague that cannot be avoided or remedied, is just plain stupid. I hate it, with a passion. $\endgroup$ – MichaelK May 15 '17 at 13:49
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    $\begingroup$ @RonJohn We're talking about a post-apocalyptic world. Most of the people are dead - you need just a fraction of the original food production, while at least for the first few seasons you get all the yield-improving bonuses we have available. A single farmer could still feed hundreds for quite a while. Want to survive? Get a shovel and help. Even with just your own muscles, you'll be able to clear enough land to survive. $\endgroup$ – Luaan May 15 '17 at 13:59

With radiation everything is always a trade off. You can have something which is very radioactive, but short-lived, or something that lasts millennia but is not very radioactive. Same for dissemination: you can have a small area heavily contaminated, or little background contamination on a very large area. You can't have both.

An airburst nuke would blow out a lot of surface, but produces little radiation, and very short lived. The plutonium of the bomb itself isn't very radiactive - it's far more poisonous than radioactive - and it will be spread in homeopathic amounts in a very big area. Hiroshima is a very big and beautiful city today (been there), and it's radioactive levels aren't anything extraordinay - in fact, lower than many other cities of the world.

An antibunker nuke would volatilize large quantities of dirt, concrete, steel and many other things, heavily irradiated, and blow it into the atmosphere. Since I know of no bunker made of cobalt, most of the irradiated isotopes created by the explosion will be either short-lived, or mildly radioactive. If they are blown to fall down on a large area, the quantities won't be significative, if they fall very much in the same place of the explosion, the dangerous zone will be quite small. As I said, you can't have both.

In short, you can have some very dangerous zones to grow vegetables, for a very long time, as long as they are small - and probably, quite easily detectable. If you want the whole globe to be irradiated... well, it already is, but the amount of extra radiation caused by all those bombs won't raise the background radiation level by more than a few decimal points.

EDIT: As per @Murphy suggestion, I'll clarify some aspects about alpha/beta/gamma emitters. The issue about cobalt-made bunkers is because radiation from a nuke could turn standard Co-59 into nasty Co-60, which is a very strong gamma emitter, with a relatively long life of little more than 5 years. That's really dangerous stuff. However, most of the byproducts of an underground nuke are going to be short (days) or medium (less than 5 years) alpha or beta emitters. Alpha radiation is mainly harmless unless ingested, but extremely dangerous if it's inside the body. However, in all of these cases, concentration is the key.

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    $\begingroup$ Plutonium is not very toxic. It is like lead, which means you should not eat it, but it is not some super-toxin as some like to make it out. Also plutonium salts are extremely stable and are not taken up by the body. $\endgroup$ – MichaelK May 15 '17 at 8:38
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    $\begingroup$ Caveat: metallic plutonium isn't all that toxic, but Plutonium oxide is extremely toxic. And plutonium oxidises very easily, so plutonium dust readily turns into plutonium oxide. $\endgroup$ – jwenting May 15 '17 at 10:01
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    $\begingroup$ Although if it's only "spread in homeopathic amounts", radiation will only be effective in placebo amounts. $\endgroup$ – Reuben Mallaby May 15 '17 at 11:46
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    $\begingroup$ I'm gonna build my bunkers out of cobalt just to mess with the people who nuke them. $\endgroup$ – Michael May 15 '17 at 14:04
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    $\begingroup$ @MauganRa Surviving is overrated! $\endgroup$ – Michael May 15 '17 at 19:57



The first thing that is obvious from the table is how much higher the values are for strontium-90 than other isotopes. This shows how dangerous Sr-90 is, how pervasive it is in the environment. This isotope, which causes bone cancer and leukemia, concentrates in bones and bone marrow. Note that 8 times as much collects in wheat, versus corn and rice. Also 33 times as much Sr-90 is absorbed into alfalfa than cesium-137. Alfalfa is fed to dairy cows. Trying to gauge the safety of milk and dairy products by cesium alone is misleading.

Iodine-129 is also very high in alfalfa (20 times the ratio of Cs-137). We can see that the highest risk in milk is in Sr-90 and I-129 (which causes thyroid cancer). These two isotopes are also found in grasses, which is the food source for beef cattle.

Note that the ratio of plutonium-239 is very low. The main risk for exposure to Pu-239 is in air and drinking water. Plutonium binds tightly to clay soil. But note americium-241 has a much higher ratio. Pu-241 decays to Am-241 with a half-life of 14 years. Americium is a bone seeker like strontium and plutonium."

I don't know about vegetables, but we'd all be pretty screwed for at least six 14 year generation (dying from bone cancer and leukemia).

EDIT: existing stores of food (everything from cans to still-standing granaries that hadn't been ravaged by rodents) would not be affected by nuclear radiation.

Plant absorption of radionucleotides

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    $\begingroup$ It's curious that they say "Trying to gauge the safety of milk and dairy products by cesium alone is misleading", because back in the era of outdoor nuclear testing the level of strontium in milk was a popular concern. My father remembers that my grandmother would check the newspaper each day to see the strontium level, and a letter to the editor of a scientific journal comments on public misapprehension of the risk due to strontium in milk. $\endgroup$ – Peter Taylor May 15 '17 at 6:26
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    $\begingroup$ I remember Sr-90 fears from back in the 1970s, too. However, fearful worrywarts can't just be fearful of the same old isotopes, decade after decade. They need new things to worry about, and Cs-137 is what they've latched onto. $\endgroup$ – RonJohn May 15 '17 at 6:34
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    $\begingroup$ While is true that Sr-90 and Cs-137 are known carcinogens, the thing is that they are much less powerful carcinogen than smoking, for example. We all know that radiation causes cancer, but many other things cause cancer, and chemical sources (such asbestos) are much more dangerous than radioactive ones. A world filled with Sr-90 and Cs-137 is way healthier than one filled with cigarrettes and car exhaustion gases. $\endgroup$ – Rekesoft May 15 '17 at 7:16
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    $\begingroup$ I wouldn't call it "screwed". Would not eating be better? Hardly. There'd be health issues, greatly diminished lifetime expectations, but it's still vastly better than starving, and not enough to kill humanity off (that is, it doesn't kill you before you can produce a healthy offspring). It's all about priorities, and a nuclear apocalypse tends to change those... :) Before refridgeration, the most common cancer was stomach cancer - which of the two would be more dangerous and prevalent in a post-apocalyptic society? Not rhetorical question, I really don't know :P $\endgroup$ – Luaan May 15 '17 at 13:37
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    $\begingroup$ @Rekesoft: the dose makes the poison. Sr-90 and Cs-137 in high enough levels are probably much worse than smoking. $\endgroup$ – Peter Shor May 15 '17 at 14:03

"Safe" is always relative. Nothing in this life is completely safe.

So, you have this nice looking bit of land that happens to be radioactive.

Given a choice between eating the food from there and other food, you would choose other food.

However, given a choice between that food and NO food, you would choose radioactive food.

So, you eat what is available, you might get cancer many years from now but at least you aren't starving today.

In the same manner, people are still evacuated from Bikini and Chernobyl because they can. If they had too they could move back and live there. They would have a slightly increased risk of cancer, but life is full or risks anyway. Smoking is still more risky.

The limit comes when people die faster than childbirth replaces them. But this limit is very high. A mere nuclear war won't come close. (In long term effects, that is. People caught a bit too close to the initial blast would have problems)


It is not safe to eat plants grown on Bikini even to this day, so the legal residents remain displaced and the atoll has no permanent inhabitants.

The lasting culprit is Caesium-137.

So the answer is no, if the weapons are anything like the ones tested there.

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    $\begingroup$ Define "not safe". Humans tend to be very paranoid on setting the limits on radiation. For that reason for instance Sweden has butchered and discarded over 200 000 reindeer after Chernobyl (a big loss to the indigenous Sami people that live off of the reindeer farming), probably for nothing. So there is a huge difference between "not safe" (as in: "it will cause you ill health") and "does not meet regulation ceilings". Also Bikini is unique in that many weapons were detonated in a very concentrated area, and among them many surface bursts, which makes contamination a much greater issue $\endgroup$ – MichaelK May 15 '17 at 9:06
  • $\begingroup$ And more burst in the lagoon, seriously contaminating the ground water supply. $\endgroup$ – jwenting May 15 '17 at 10:05
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    $\begingroup$ The animals near Chernobyl are thriving, despite the radioactivity, because humans aren't killing them anymore. Low-level radioactivity doesn't kill you right away. It waits years or decades, and then gives you cancer. Having some percentage of your population die young from cancer is much better than starving to death. $\endgroup$ – Peter Shor May 15 '17 at 13:53
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    $\begingroup$ ... unless all the children die before they reach puberty, but Bikini is a long way away from that threshold; some islanders moved back to Bikini, lived there a decade, and were moved away not because they were dying, but because researchers found too much radioactive caesium in their bodies. So Bikini levels of radioactivity don't seem to be unsurvivably lethal. $\endgroup$ – Peter Shor May 15 '17 at 13:58

Its hard to answer concisely, since there would be great local variations, depending on where in the world your protagonists bunker is located, if the country was a direct belingerent in the war and many other factors.

In the scenario where the first six month are spent inside a bunker, you can at least assume that the most volatile and thus most radiactive isotopes (e.g. Iodine 131, see here for example https://en.wikipedia.org/wiki/Chernobyl_disaster#/media/File:AirDoseChernobylVector.svg) have decayed sufficiently to the point where they no longer contribute the majority of radiation.

Most radioactive particles would have settled to the ground/have been washed out by rain after six month. This suggests a scenario where contamination in the air is minor compared to radiation from topsoil and/or incorporation by food/water.

While groundbursts are considered very dirty, the majority will be deposited within a few hundred miles in the downwind direction. While such plumes can contaminate significant areas (e.g. https://en.wikipedia.org/wiki/Nuclear_weapons_testing#/media/File:Bravo_fallout2.png), there would still remain some areas not directly affected, except in the most densely populated/hardest hit areas.

The chernobyl desaster was much worse than a single bomb test in terms of radioactivity released, still the death zone is relatively small, and the area where plants died completely was even smaller. Note that the affected areas are spread very unevenly: https://en.wikipedia.org/wiki/Chernobyl_disaster#/media/File:Chernobyl_radiation_map_1996.svg

Assuming an arsenal of ~2000 warheads, which are presumably mostly in the 10-100kt range, there should be plenty of zones left that are only affected by the fraction of fallout that has spread globally (or barely at all on the southern hemisphere).

Lastly, edible food can be grown in chernobyls worst affected zones. The main problem is to select crops that do not readily take in the radioisotopes that contaminate the topsoil. And of course even carefully selected crops have to be constantly tested - its has been done on research scale.

So in summary, there would be areas where crops would be "safe" (as in acceptably low contamination) for consumption. Its another question if your protagonist would be able to find and identify such areas though. Plants may appear perfectly healthy and may still be contaminated enough to kill you within a few month or less. A common geiger counter would probably be not sensitive enough towards the lower end to identify "safe" food. Something a little more sensitive would be needed.


Not sure scraping off the top soil will remediate the issue:

  1. in a nuclear war, most of the nuclear power plants are likely to meltdown or release large amounts of radiation from spent fuel pools.
  2. Wind and rain will continue to diffuse contaminated dust for years. Even if you use non-contaminated soil it becomes contaminated over time just from airborne dust and rainfall
  3. In addition to radioactive contamination, destroyed cities are likely to burn for many months, if not years. After 9/11 the Trade Center buildings continue to smoke for more than a month even with firecrew pouring water into the wreckage.
  4. During heavy rains water is likely to wash contaminents from nearby land that wasn't prepared. Perhaps if you scrape land on top of hill since water will flow away.

My thoughts on how to grow food safely:

  1. Use greenhouses to isolate your food crops from the contaminated environment.

  2. You need to use deep ground water to have a process to decontaminate rainwater. The only process I can find is to use an ozone water treatment to convert soluble contaminates into non-soluble contaminates so they can be effectively filtered out. Only a very high pressure reverse osmosis system can remove soluble contaminates.

  3. Protect fruit/nut tree prior to the nuclear war with a non water permeable barrier and with a irrigation system below to provide water.

  4. pile up top soil prior to the nuclear war and protect using a non water permeable barrier. This way you have a source of non-contaminated top-soil. Use raised beds with the non-contaminated soil so any runoff water from heavy rain does not contaminate it. Use crop cover hoops to help protect the raised beds from getting contaminated from rainfall and dust.

  • $\begingroup$ ad 1. Not really. We have really good Q&A about nuclear power plants and they do not tend to melt down when unattended. Direct hit is another matter, of course. $\endgroup$ – Mołot Jan 10 at 9:49
  • $\begingroup$ @Mołot, that depends on period of construction, some older ones will melt down when they lose power, newer ones won't. $\endgroup$ – Separatrix Jan 10 at 11:12
  • $\begingroup$ Issue I see is that during a nuclear war it will be chaotic. First events will be NEMPs that probably will take out most electronics & control systems with huge power surges While the control rods may drop automatically its not going to be enough if the circulation pumps fail to continue to run. Most US plants are of older designs and do not support the ability to passively cool. $\endgroup$ – Guy Tech Jan 11 at 18:36
  • $\begingroup$ FYI: NRC Publication estimate 15 meltdowns in the CONUS during a nuclear war: osti.gov/servlets/purl/6593812 $\endgroup$ – Guy Tech Jan 11 at 18:49

I believe that in a highly irradiated area, growing crops and subsequently eating those crops could be very dangerous. That dirt's irradiated man, so is that water, and those crops will be too.
This article might help a bit and if not, it's an interesting read regardless: https://phys.org/news/2015-03-crops-radiation-contaminated-soil.html

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    $\begingroup$ This answer misses the second question... if it is too dangerous to eat food grown on the land, how long until the land is healed? $\endgroup$ – SRM May 15 '17 at 4:21

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