Radiation Chart

There’s a lot of discussion of radiation from the Fukushima plants, along with comparisons to Three Mile Island and Chernobyl. Radiation levels are often described as “<X> times the normal level” or “<Y>% over the legal limit,” which can be pretty confusing.

Ellen, a friend of mine who’s a student at Reed and Senior Reactor Operator at the Reed Research Reactor, has been spending the last few days answering questions about radiation dosage virtually nonstop (I’ve actually seen her interrupt them with “brb, reactor”). She suggested a chart might help put different amounts of radiation into perspective, and so with her help, I put one together. She also made one of her own; it has fewer colors, but contains more information about what radiation exposure consists of and how it affects the body.

I’m not an expert in radiation and I’m sure I’ve got a lot of mistakes in here, but there’s so much wild misinformation out there that I figured a broad comparison of different types of dosages might be good anyway. I don’t include too much about the Fukushima reactor because the situation seems to be changing by the hour, but I hope the chart provides some helpful context.

(Click to view full)

Note that there are different types of ionizing radiation; the “sievert” unit quantifies the degree to which each type (gamma rays, alpha particles, etc) affects the body. You can learn more from my sources list. If you’re looking for expert updates on the nuclear situation, try the MIT NSE Hub. Ellen’s page on radiation is here.

Lastly, remember that while there’s a lot of focus on possible worst-case scenarios involving the nuclear plants, the tsunami was an actual disaster that’s already killed thousands. Hundreds of thousands more, including my best friend from college, are in shelters with limited access to basic supplies and almost no ability to contact the outside world. If you’re not sure how to help, Google’s Japan Crisis Resource page is a good place to start.

Edit: For people who asked about Japanese translations or other types of reprinting: you may republish this image anywhere without any sort of restriction; I place it in the public domain. I just suggest that you make sure to include a clear translation of the disclaimer that the author is not an expert, and that anyone potentially affected by Fukushima should always defer to the directives of regional health authorities.

809 replies on “Radiation Chart”

  1. “safety” … reactor safety, not security, damn! It’s the same word in German

    Also: The 3D versions of your comics rock! Totally worth it!


  2. @Euonymous

    I think you’ve made the same mistake as I. The chart is not ‘scientific’. Scientific means criticism would be addressed or rebutted, not suppressed.

    Instead the chart is a one-panel comic that like all comics tells a story. The story this panel sells was read and treated as reality by George Monbiot at the Guardian:


    The problem of treating comics as reality is that fiction is a poor basis for policy and that’s what makes this comic a disservice.


  3. @Bob Kearns

    Since I am not censored at the moment … this is the gist of what was censored yesterday.

    The Guardian article I mention above has a world-wide audience, so indeed the chart has widely mislead.

    Please consider the testimony of those living near Three Mile Island in 1979 to evaluate whether the purported 80 uSv “average exposure” reported in the chart reflects the radiation hazards experienced by neighbors of TMI.


    (Be sure to read the Bill Peters story. It looks to me like lethal levels of radiation wafted over the Peters’ property over the course of a few days. At least it was lethal to a dog, cats and a lot of birds. Had the Peters family not evacuated, I suspect it would have been lethal to them too.)

    The illusion being sold — and read by Monbiot and now his readers as meaningful — is that an average of radiation levels over a geographic area is an indicator of health risks. Fallout and the path of emissions from a plant are distributed very unevenly, so all that taking an average does is hide the intensity of the hot spots. This is one case where an average is meaningless and reporting an average is deceptive.


    The chart’s pretty much launched and has accomplished its mission, so I’m sure to our mutual relief, I’m signing off.


  4. @überRegenbogen
    “Ionising radiation is by no means the only carcinogenic force out there. Electromagnetic radiation certainly does have adverse effects on animal tissue (the usually ½ to 2 kilowatt emissions of microwave ovens being an obvious extreme example), even if non-carcinogenic (which, afaik, has yet to be determined conclusively).”

    Microwave ovens cause cancer? I thought they just heated things up. Cancer happens when atoms in DNA are ionized, causing changes in the genetic code, right? Not just when they are heated. Microwaves heat. Ionizing radiation ionizes. What am I missing here?

    The screed you link to is very similar to various “testimonies” I’ve read for religions, perpetual motion machines, quack doctors, and alien abductions. This all happened in the middle of the Cold War. Didn’t any of those people own a Geiger counter? Let’s hear some measurements. Or, in modern parlance: pics or it didn’t happen.

    “The illusion being sold — and read by Monbiot and now his readers as meaningful — is that an average of radiation levels over a geographic area is an indicator of health risks.”

    It’s only an illusion if high concentrations happen to coincide with large population centers more than chance would predict. Otherwise, an average plus the LNT model should give a pretty accurate estimate of cancer deaths in the area.

    Maybe the hysteria would subside if we could just hand out a Geiger counter to every neighborhood in the US (or industrialized world). This wouldn’t be very expensive per capita, and would show exactly how much danger we’re really in, if any.


  5. I think the best part about radiation is how it makes me feel warm and fuzzy on the outside. . . and the inside.


  6. @ViviWannabe, if you nave 1 pound of I131 and it has a half life of 8 days, than after 8 days you have 0.5 lbs of I131, not the zero that you seem to be implying….. moreover, you need to consider decay chains….. I don’t know anything about I131 except that you are oversimplifying things…..


  7. @ Isaac:
    I131 emits a beta particle and becomes Xe131, which is stable (according to wikipedia). This means that after emmision of Iodine into the atmosphere stops, radiation will decay at least exponentially with a half life of 8 days. In realtity, it will be faster, because the stuff is at the same time spreading in the atmosphere and being thinned.
    That’s only the Iodine part, of course…


  8. Aside from other obvious sad things, the Fukushima disaster has dramatically highlighted the rampant innumeracy in the U.S., including, surprisingly, among some XKCD fans, not to mention the appalling news media (quite shocking and pathetic; when I heard Bill Nye on CNN say that nuclear fission produces hydrogen, that Fukushima used cesium as a moderator, etc., I just blanched).

    So I applaud XKCD for trying to address this important and urgent social issue with a graphic method that the poor innumerate victims of a bad educational system bombarded by brain-dead news media “pundits” can at least potentially understand in a non-mathematical way. If only they would apply their minds, even slightly. Even if they have to use “banana units” (which, given how things work, will likely have the unintended consequence of destroying banana sales).

    I also think people should cut @ViviWannabe a little slack on the I131 issue. Yes, if you read what she wrote one way then you might think that she implied that I131, of any amount, would decay to safe levels in about 8 days. But it seems painfully obvious to me that the actual error she made involved her not explicitly stating that after 8 days or so of travel, anything from Japan would have half as much I131 and therefore would wind up even more safe than the levels permitted by the Japanese government. She, like I once did, probably generously assumed that all XKCD fans knew how half-lives worked (yes, a big mistake, in retrospect).

    And this all makes me even more depressed: if a vocal amount of XKCD fans, a group that I always considered well above-average in terms of numeracy, don’t understand such remarkably simple issues, then I really fear for the future of human race. And not because of nuclear power.


  9. @Isaac: I crunched the numbers on I-131 decay and how long it takes before all of it is gone. You can view the results here.

    In short: within about 3 years, there won’t be a single atom of I-131 left. All of it will have decayed to stable Xenon.

    Already since the accident began, there is approximately only 1/8 left.
    In 3 months, the levels of I-131 will be one in 64 billion of what it is today.

    But, yes, there are other substances to worry about… Cs-137 being the most troublesome one.


  10. The average person’s background dose is 10uSv/day, while the EPA yearly limit is 1mSv/year. So the “average person” gets 3.6x the EPA limit (?).


  11. The EPA limit is for the *additional* dose an average person allowed to receive in a year above the normal background radiation.


  12. I’ve heard it passing that raised radiation levels had been detect a while back but it really really hard to find any actually data on what kind of raditions(they had too many lasers on and the reporter was a lieing SOB) or any actual units(per time). For those of use who do understand a little of the physics its not very reasuring when people say things like its aproximately .5mSvs of raditions or what ever cause at least I think “is that the grand total? how can you possibly know that at this point” but this chart is pritty cool. But if you could happen across a comparsison of say…. something like “the levels on the west coast rose by 2.4 bananas” that would be pritty sweet


  13. Thank you for this informative post. I have been in Tokyo since March 11th and I have always been on the lookout for clear explanations I can pass on to those without a scientific background who have let fear take over.
    Numbers have been used by medias without any clear explanation about what they really mean.
    I very much appreciate your perspective about who the real victims are, right now. So far as I can see, most of those who have been in Tokyo during the crisis focused their talks on the plight of the refugees, not on the small inconveniences we have to endure in Tokyo.


  14. Hey. Anyone know how to make this type of chart once you have the data? What program was used?


  15. Someone liked your radiation chart as it seems – And that someone is the “GRS”. That’s the department for “reactor safety” of the german ministry for environmental protection. Impressive, they took the interesting sidenotes out of the chart (they have no clue about the radiation levels of sleeping next to someone obviously) but otherwise publish pretty much the same chart:

    Click to access Natuerliche_und_kuenstliche_Strahlenexposition.pdf



  16. I don’t understand the difference between the “Extra dose from one day in an average town near the Fukushima plant (~3.5 microSv)…” and the “One-day dose (~3.6 mSv) at two sites 50 km NW of Fukushima”.

    What is the meaning of “near” if the one-day dose at 50 km is 1000 times the first one ?



  17. Wow. Well and awesomely done chart. It’s never about the data, it’s about understanding the data, in layhuman’s terms.

    Unfortunately the terms layhumans understand seems to drop in relation to Moore’s law, so that chart’d get you the Nobel Prize for Smartness in about 30 years.


  18. Today April 12 the Japanese atomic agency has reclassified the accident. Up to now about ten percent of the radioactive material set free in Chernobyl has been set free in Fukushima. Shouldn’t you update the corresponding numbers in your figure?


  19. Actually, the EPA limit would be that PLUS the average person’s dose, wouldn’t it?


  20. I’m gonna print this and put it on a wall at my office. Is really impressive what you’ve done with the information. As many have said here before, this is something that the common people can understand… or at least try 😛


  21. @ein pythaogaeer: The reclassification reflects new analysis of the total amount of airborne radioactivity released. Most of that radioactivity was released in the early part of the crisis, during the hydrogen explosions. The chart is based on doses that people would get, which in turn was based mostly on direct radiation measurements at various places inside and outside the evacuation zone.

    It’s a common misunderstanding that the reclassification means the accident has gotten worse–it has not, there was just initially more radiation released than was thought. However, since people were evacuated quickly, it doesn’t mean that more people got higher doses than originally thought. Furthermore, the isotope of greatest concern, I-131, has decayed by now to less than 1/16 of its initial activity. (This is because I-131 has an eight-day half-life). The dose rates in the evacuation zone and on the reactor site have been decreasing steadily.

    I hope this helps people understand the meaning of the reclassified INES level a bit better.


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  23. All radiation is not the same. Radiation from natural sources are known as beneficial, while what industry “creates” (plutonium) thru nuclear power plants is extremely toxic.


  24. Randall,
    I love this chart. I especially liked the comparison of normal operational emission of coal v. nuclear. I found your chart while searching for better free porn.

    I have been unable to locate information to support an interesting thing I heard in a lecture years ago: total cumulative release from all nuclear power plants including chernobyl and 3mile assdents (sic) is far less than total cumulative release from all coal burning plants, ever. Maybe something for xkcd.com/radiation/v2. I wonder if Fuku will tip the scale?

    (I apologize for the remainder of this post in advance.)

    And, I just must disagree wholeheartedly with what “Matt Colburn says: April 21, 2011 at 10:39 am, “… radiation from natural sources are known as **beneficial**, while what industry “creates” … is toxic.”

    I can see that you have a point to make but, … in this case:

    Natural ≠ Beneficial and Industrial ≠ Toxic.

    (In case of unicode failure those should be not-equal signs.)

    While I am certain to stick my foot in fully here …

    I contend that the application as well as the levels of duration, intensity, distance, and protection predicate benefit v. toxicity where nature v. industry do not at all in any way do any such thing ever even a little bit.

    Cases to think about:

    Naturally-occurring Radon gas buildup in/under a dwelling causing illness to dwellers. Dwellings are bad.

    Naturally-occurring Radium or some such thing decayed from Uranium in the water supply of a small town and a larger city I have lived in. Yep, it was on my water report! Testing authority said lovely, safe water according to EPA and, it tastes great. Hmmm.

    Naturally-occurring, solar-radiation effects, both good and bad, upon unprotected people, also, both good and bad. (The Sun, responsible for life, health, illness, and death is the biggest damn “Natural” nuclear reactor and omni-directional transmitter of every wavelength of energy in the neighborhood! Only 1 AU away!)

    Naturally-occurring cosmic radiation effect upon unprotected astronauts and, I gather, mostly indirectly upon us surface dwellers due to fallout from upper atmospheric process which mostly protects us from the direct rays. Somewhere in between for high flying airline passengers.

    Safety-industry-created smoke and carbon monoxide sensors with alarms for saving lives. (Teensy little bits of plutonium or the like in these sensors might eventually have adverse effects upon you if swallowed but, …)

    Medical-industry-created radiation for flow tracing, imaging, and irradiation of cancer to make us live a little longer.

    War-industry-created nuclear weapons to make our evil enemies not live any longer. Hey! It could be a good thing! … OK, … it’s bad. But they could be used to blow up a deadly ass-troid like in that movie! No, the other movie.

    Power-industry-created nuclear plants, sans earthquake/tsunami/equipment failures/operational fuckups, providing power for our microwave ovens. OK, bad!

    Power-industry-created coal-burning plants providing wonderful power while slowly layering the planet with low-level radioactive waste, even after scrubbing the exhaust! A polished turd is still a turd.

    Food-industry-created irradiation for longer term preservation of foodstuffs so a few of us can lament our demise in caves and shelters a little longer while the nuclear winter rages on and the planet dies around us and the cockroaches laugh.

    Archaeological-industry-created carbon dating techniques for future generations, if any, to determine in which century we really fucked it bad.

    Natural radiation all good? Industrial radiation all bad? Nope!

    So, Matt, you can see that beneficial v. toxic do not directly correlate to nature v. industry when thinking about ionizing radiation. I take away a different message completely: Without natural rad we wouldn’t exist. Industry rad has surely complicated things for us all. Either one is a mixed bag of both beneficial and toxic effects. Radiation, natural or man made, is a necessary but tricky bitch. Always be careful.


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