So I am reading a book called "Voices from Chernobyl" where witnesses, nuclear plant workers, firefighters and other persons involved in the 1986 accident give testimony of their experiences.

The very first chapter goes along the lines of the wife of a firefighter that was dispatched for duty on the very day of the incident. He suffered acute radiation and was hospitalized. His wife remain with him throughout the last days before he died. One thing it was mentioned in the book very clearly is how nurses constantly tried to warn his wife not to touch him, hug him or even share objects with him.

In this article, it is mentioned that a person who was exposed to radiation should not be a danger for others once his clothes have been disposed.

So, my question is, I am getting confused between the two readings. Is a person who has been exposed to a big dose of radiation a danger for other people? Why?

  • $\begingroup$ Things like sweat can carry radioactive elements to the surface of the skin. Plus the victim is emitting radiation, and even a little distance helps. $\endgroup$ – Jon Custer Aug 10 at 12:29
  • $\begingroup$ @TAR86: thank you for that link. I shamelessly included it into my answer :-) $\endgroup$ – cbeleites unhappy with SX Aug 10 at 13:32
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    $\begingroup$ With all due respect to Svetlana Alexievich for her writing skills and moral standing, she's no expert in nuclear physics, so not all details are necessarily accurate. $\endgroup$ – Ivan Neretin Aug 10 at 15:42
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    $\begingroup$ The question reminds a bit to HBO's mini series «Chernobyl» (en.wikipedia.org/wiki/Chernobyl_(miniseries)), and in particular of the snippet around 2:30 min here: youtube.com/watch?v=EV6G1GpTxjE. A counter balance to the series: youtube.com/watch?v=m1GEPsSVpZY. $\endgroup$ – Buttonwood Aug 10 at 16:24
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    $\begingroup$ @IvanNeretin and even if she were, I understand that the book is a (literarily edited) collection of interviews/monologues/witness reports. This limits severely what can be done against misunderstandings that the witnesses have and express in the interviews. However, a reader of the book needs to be aware of this. $\endgroup$ – cbeleites unhappy with SX Aug 11 at 6:32

Summary: there is not necessarily a contradiction between the two.

  • Radiation is not contagious, and
  • a person who has been exposed to ionizing radiation is not dangerous to other people once they are not contaminated with radioactive material any more, but
  • while they are still contaminated with radioactive material, they may pose a danger (highest danger is to themselves, though).
  • In any case, other people are dangerous to someone who suffers radiation illness (infection risk).


  • Thinking radiation contagious is (still!) a fairly widespread mistake, and
  • I'd think misunderstanding the purpose of the instructions (she being dangerous for her husband rather than the other way round) quite likely in a highly stressful situations such as the husband dying. I.e., I wouldn't expect her to spend time then on double-checking whether she correctly understood the reason behind the instructions and ask, "Sorry, sister, is this because he's dangerous to me or because I'm dangerous to him?".

Thus, it should not be surprising to meet any such misconceptions in such a book. Nor would I be surprised if readers misunderstand the book this way even in case the firefighter's wife is and was perfectly aware that her husband did not pose a radiation danger to her. I'm writing the remainder of this answer mostly assuming that the mistake is in the book rather than on OP's side.

There are basically only two possibilities clear a misunderstanding that happened back then in a book of witness reports: the witness saying "nowadays I know I was dangerous to him, not he to me. But back then I didn't know that."
or the editor putting a footnote explaining the misunderstanding and that it was widespread at the time.

Ionizing radiation and contamination with radioactive substances

Radiation is not contagious in the sense that the firefighter's exposure to ionizing radiation did make him radiate himself. That being said,

But: chemical contamination, including radioactive substances, can be transferred from one body to another, and they can be incorporated and accumulated where they cause much damage.
(I also wouldn't call that contagious, since the total amount of radioactive material does not increase, but if you consider, say, crystal violet or methylene blue contagious "since if you touch someone, the ones touched by them will be violet/blue", then you can also call the radioactive substances contagious)
However, any radioactive substance contamination that is transferred to a practically relevant amount by touching can also be washed off - and that is the first thing to do for decontamination besides taking off potentially contaminated clothes. Any injury that means that the area cannot be thoroughly washed can also not be touched (for reason of the injury).

Thirdly, during the decay of such radioactive material, other substances form, which may be far more difficult to get rid of (see radon example below). Here, one may say that one can "catch" a contamination that one doesn't easily get rid off again. However, any such conamination would not be transferred from the firefighter to his wife.

  • X-rays/γ-rays: these are ionizing electromagnetic rays, i.e. high energy photons. They cause damage when being absorbed, either by directly damaging some biomolecule or by forming OH⋅ radicals/ROS which in turn cause further damage.
    The radicals in themselves are nothing very special - they occur all the time as side products of our energy metabolism and we have powerful mechanisms to cope with them. Part of radiation illness is that these mechanisms are overwhelmed.

    So, after exposure to X- or γ-rays, we have radicals inside the body, but no "foreign" nuclei, and no body surface contamination. I.e. nothing that became radioactive because of the exposure to high energy photons.

  • A somewhat different example related to Chernobyl and Fukushima would be incorporation of radioactive $\ce{^{131}I}$ in the thyroid gland. In particular, if someone with iodine deficiency incorporates iodine, pretty much all of it will end up in the thyroid gland. If that available iodine is $\ce{^{131}I}$, their thyroid gland will subsequently be exposed to large radiation doses. This incorporated radioactivity does include γ radiation of which a part leaves their body.

    $\ce{^{131}I}$ is administered in radiotherapy in doses where the patients are e.g. kept in hospital for approximately 2 days (at least here in Germany) so as to not contaminate the wastewater with the radioactive $\ce{^{131}I}$ they excrete in their urine. Such patients are also advised to avoid close contact for e.g. a week after treatment in order to not cause accidental exposure to others, in particular children and pregnant women.. Such radiotherapy treatements use dosages in the 100 - 400 Gy range to the thyroid. And the guidelines are of course with a safety margin. A quick search for $\ce{^{131}I}$ radiation doeses to the thyroid in Ukrainian children after Chernobyl got me to Brenner et al: I‐131 Dose Response for Incident Thyroid Cancers in Ukraine Related to the Chornobyl Accident. The largst dose category is > 3.0 Gy, and a diagram has a point a bit below 5 Gy, so 1 - 2 orders of magnitude below the radiotherapy doses.
    My conclusion from this is that even in case the firefighter got a $\ce{^{131}I}$ dose to kill off his thyroid, the wife giving the dying husband several close goodbye hugs 10 - 14 days after the exposure would be unlikely to pose a significant threat to her health due to radiation from his thyroid (and under the particular circumstances, the $\ce{^{131}I}$ she ingested after the accident would be a far more important concern for her health).

    Again, I would not describe this as "contagious" - but your word use may vary.

  • In this guest post to cancer letter, R. P. Gale discusses some of his experiences as an MD at the famous hospital 6 (the Soviet Russian radiation clinic) treating the radiation illness patients from Chernobyl with at particular view to the HBO series.

    Another error was to portray the victims as being dangerously radioactive. Most radiation contamination was superficial and relatively easily managed by routine procedures. This is entirely different than the Goiania accident, where the victims ate 137-cesium and we had to isolate them from most medical personnel.

    Lastly, there is the dangerous representation that, because one of the victims was radioactive, his pregnant wife endangered her unborn child by entering his hospital room. First, as discussed, none of the victims were radioactive—their exposures were almost exclusively external, not internal. More importantly, risk to a fetus from an exposure like this is infinitesimally small.

Valid Reasons for not allowing the wife close to the husband that have nothing to do with radiation being "contagious".

  • Radiation illness: the bone marrow is rather radiation sensitive, and leukopenia (too low leukocyte counts, a type of immune suppression) are a typical part of radiation illness.
    A radiation illness patient is thus at a very high risk from infections.

  • Radiation illness often comes with burns (the skin is most exposed, and for α and β radiation, almost all damage happens in the skin). Already "normal" severe burns are doubly difficult in terms of infections: the skin damage means that the normal protective barrier against microorganisms is broken down in those areas, and in addition there is a severe immune suppression (after initial inflammatory response). Infections cause half of the deaths after severe burns

Both are very valid safety reasons, just for the firefighter rather than for his wife's safety. Saying that the wife can go close to the firefighter would amount to saying "He's anyways going to die within the next days - it doesn't matter whether he catches an additional sepsis."

"Contagious" radiation as wrong but possibly valid concern after the Chernobyl accident

So from a scientific point of view radiation is not "contagious". Nevertheless, there is a still widespread, though mistaken fear of this. Personally, here and now I count this pretty much in the tin foil hat corner. But OTOH, in the situation in the Ukraine(ian SSR) immediately after the accident I think it a more understandable concern since the possibilities to check whether this concern is valid or not were severely limited. Not only for the general population, but even for the medical staff. In such a situation, it is a valid decision to err on the side of caution.

In addition: How much did the hospital staff know about what actually had happened and what the firefighter had actually been exposed to?
With those activities to hush up the Chernobyl incident, the hospital staff may have been unsure about what else that firefighter had been exposed to besides high doses of radiation.

Remaining contamination with radioactive material (including incorporated material) can be measured comparatively easily. However, I have no idea whether such instruments were available at the hospitals, say, in Kiev, to measure remaining contamination of their patients: a) the available instruements may have been needed more urgently at the site of the power plant and b) also political coniderations/hushing up may have been standing against that. I'd expect the Moskow hospital to have all kinds of instruments (but that may be my predjudice)

* I'm pretty sure that a non-negligible fraction of the population here in Germany would express that fear if you ask them. Including medical staff, and even after Chernobyl and Fukushima.

If you want an example: have a look at this post (in German) about radiation treatment for food on a web site by the offical consumer protection organizations

 Werden Lebensmittel mit ionisierenden Strahlen behandelt, wird die Strahlenmenge genau dosiert. Die Energiemenge ist so gering, dass die Lebensmittel nicht radioaktiv werden und sich nur leicht erwärmen.

My translation and my emphasis:

When food is treated with ionizing radiation, the amount of radiation is accurately dosed. The energs is so small that the food does not become radioactive and only heats up slightly.

While it is of course true that the food does not become radioactive, that sentence IMHO does insinuate that this could [easily] be the case with higher doses. And one comment (out of a total of 14) clearly indictates that the writer thinks radiated potatoes will radiate themselves.

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  • $\begingroup$ While some of the comments about whether the firefighers not being radioactive might be true, it is clear that the authorities at the time though they were (hence the precautions). Unless we have definitive measurements we can't be sure. Moreover, they were exposed to extraordinary amounts of material from an exploded nuclear core without any proper protection so general observations from other incidents might well not apply here. $\endgroup$ – matt_black Aug 10 at 14:51
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    $\begingroup$ In addition to HBO's series «Chernobyl», because one accent of your answer is about the medication «at least here in Germany», you might be interested to know the Swiss precautions for those in vicinity (50 km) of the (now former) nuclear power plants on Swiss terain. Every 10 yr each inhabitant gets his / her blister of KI by mail: iodtabletten.ch/de/home (German), iodtabletten.ch/fr/home (French). Looking westwards, vigilance is kept (old Fessenheim, or Superphenix) and the many still running plants (en.wikipedia.org/wiki/Nuclear_power_in_France). $\endgroup$ – Buttonwood Aug 10 at 16:18
  • $\begingroup$ Another problem here is that the instructions to the Firefighter's wife were very clearly not for his protection alone. The authorities clearly thought the firefighters were a risk to others (they might have been wrong, but they didn't bury them in lead-lined coffins for no reason). Theoretical arguments are not relevant to what they did at the time and are probably not relevant anyway given the extreme nature of the exposure they were subjected to. $\endgroup$ – matt_black Aug 11 at 12:36
  • $\begingroup$ It's worth noting that it's not just misguided fear and lack of information - after all, while the opinion of the survivors can be mistaken, it's all based on the fact that the child of Ludmila Ignatenko did die four days after being born after being diagnosed with cirrhosis of the liver and congenital heart disease. The only question is whether it is related to some radiation damage during the hospital visit, or perhaps solely to the exposure Ludmila had before leaving the area of Chernobyl. $\endgroup$ – Peteris Aug 11 at 13:52

Radiation isn't "contagious" unless you are heavily contaminated and can cause damage to others

The firefighters in Chernobyl attended the fire before anyone fully appreciated just how bad the accident was. The core was exposed and lumps of the extremely radioactive graphite moderator were spread around the area where they worked (the series had one scene where a fireman picked up a graphite lump for a short period and suffered extreme radiation burns just a short time later). The firefighters were not wearing protective clothing suitable for protecting them from radiation or from the radioactive particles scattered around the site. Their clothes were heavily contaminated–so much so that they are still a hazard today (they are still in the abandoned hospital's basement). But, since the clothes were not designed to protect the firefighters from bodily contamination, their removal does not mean the firefighters' bodies were radiation free.

This, I think, is the key to understanding how cautious the hospitals were at letting outsiders near the firefighters. They were radioactive because of their extensive exposure to dust and radiation from the reactor core. As far as I can remember, the series didn't show any radiation measurements on the firefighters but it strongly implied they were still "hot" and that staying near them was hazardous for others.

So it isn't so much that radiation is "contagious", it is just that, in this circumstance, the firefighters were themselves quite radioactive. Less radioactive than their clothes, but still radioactive enough to be dangerous.

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  • $\begingroup$ Do you have a source to how radioactive the firefighters (i.e. the contaminations that stuck to them after washing) were? I was looking for some, but only found various not-so-trustworthy looking sites they had to be buried in special coffins - ranging from leaden coffin to being wrapped twice in zinc foil [!?] in wooden coffins, and to whether a big concrete block was needed [but not sufficient] to protect the graveyard visitors. In contast, a post (see quotation in my answer) by one of the MDs helping to treat the patients claims that there wasn't much of a problem in that respect. $\endgroup$ – cbeleites unhappy with SX Aug 10 at 14:41
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    $\begingroup$ I don't have a reliable source. But the thinking at the time that the firefighters needed to be buried in sealed, lead-covered coffins is accurate. The Chernobyl series shows this and it did happen. So, fairly clearly, the authorities at the time thought they were dangerously radioactive. Hence the precautions. $\endgroup$ – matt_black Aug 10 at 14:45
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    $\begingroup$ @matt_black it does not and did not to be opinion based - it's trivial to put a dosimeter next to a patient or a corpse and verify if it's radioactive or not. It may be tricky to find evidence of whether and how it was done, and how radioactive (if any) the corpses were, but I'd presume that the local officials would not go out of the way and order a concrete-covered burial unless the corpses were actually still radioactive. $\endgroup$ – Peteris Aug 11 at 13:58
  • $\begingroup$ I forgot to mention that this woman was pregnant and she lost her newly born after just a few hours of giving birth. Both the book and the series seem to imply it was because she had been with her husband going against the recomendations of dtaying away from her husband. Itis exolained that the baby was born wirh a damaged liver due to the exposure and that saved his mother's life. How can that be explained? $\endgroup$ – Matias Barrios Aug 12 at 12:37
  • $\begingroup$ @Peteris "Trivial" to put a dosimeter next to a patient or a corpse... If you have a dosimeter, as well as the knowledge to use it and interpret its readings with confidence... not so trivial, considering the time (pre-internet). $\endgroup$ – DevSolar Aug 12 at 21:20

Radiation and radioactivity are often mixed up. A matter like uranium can be radioactive. It means that it contains atoms that can emit radiations made of particules that travel away with great speed in the surroundings. These radiations may snatch electrons in the surroundings, which cause serious troubles in the target. But at the end of their path, they disappear as matter or are transformed into ordinary electrons, or harmless helium atoms. So there is no radioactive material in the target.

A radioactive matter is like an army. Its soldiers are dangerous, because they can fire and shoot bullets that may kill a victim. But after the shot, the bullet is not dangerous any more. After the shot, the soldier is still dangerous, as he may shoot again, but the bullet and victim are not dangerous.

Radiation is not "contagious". Radioactivity may be considered as "contagious" : radioactive substances may be transmitted from place to place, like an army that can move.

A person who had touched a radioactive substance like uranium, may have absorbed some uranium atoms through the skin. This person becomes radioactive and then emits radiations. Apparently the Chernobyl firefighter has been irradiated when fighting the accident. He was touched by the radiation and became a victim of his duty during his job. But, bad luck, he had also the opportunity of touching some uranium from the exploding power station. And then, this uranium will stay on or in his body, and will emit radiation later on in the future. This person becomes radioactive, not because of the radiation he has received during his job, but because of the uranium that entered his body when he touched a piece made of uranium in the rubble of the power station. That is why nobody should touch him, because if this uranium is glued on the skin, it may be transmitted to somebody else.

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  • $\begingroup$ If substantial amounts of the contaminant can be transfered by touch (e.g. [sweaty] skin to other person's skin), they can also be washed off. Off the patient in the first place, and the wife should also wash e.g. her hands before and after holding his hand. $\endgroup$ – cbeleites unhappy with SX Aug 10 at 13:30

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