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.
xkcd 
woah, go ellen! how weird to see someone i know referenced on your blog, randall.
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For this, I love you even more.
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That chart is a great idea, the amount of media induced hysteria about the plant is becoming truly tedious and is obscuring the greater disaster.
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tl;dr
I’ll make it simplier and just go back to panicing about radiation.
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How many bananas would you have to eat in a day to die of radiation poisoning ?
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@Christ
According to the data in this chart and assuming you could eat any quantity of bananas withing a short period of time and without sustaining ill effects other than those caused by the radiation, you would have to eat 160,000 to be certain, but 40,000 might do it.
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Double checking my work fail.
I used the wrong value for one banana and left of three zeros from the result.
It’s really 20 million at the low end and 80 million to be certain.
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now we need a plot of the radiation released from fukushima using these units
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The third to last line stole the http:// from the second line.
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In response to the banana question, if you introduced that amount of potassium into your system in a short amount of time, you’d die from heart failure before the radiation could get you.
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Are you sure this is right, If i have learned anything from playing video games its that 1000 rads will kill you dead, now your saying 800 rads is enough?
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To The lone wanderer (nice name btw):
The Rad has been in disuse for a long time, since it was “replaced” with the Gray unit which measures absorbed radiation more accurately. The lethal dose of radiation measured in Rads could vary wildly between 200 and 1000. Fallout just picked the maximum as the instadeath number 😛
Sieverts (the unit used in the chart) are used to measure absorbed radiation in humans, grays are used to measure absorbed radiation in anything.
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The Wikipedia article states eating one banana is 0.0001 mSv while sleeping next to a human for 8 hours is 0.0005 mSv. Is this an error on the Wiki page or on the chart, or just my misunderstanding?
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@hilllie: So sleeping next to a human for 8 hours is equivalent to eating 5 bananas?
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Now make a chart of deaths per terawatt-year for all the different power sources. I get wind power being 4x more deadly than nuclear.
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hey does anyone know where cell phone use or microwaves are relative to these
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>The Wikipedia article states eating one banana is 0.0001 mSv while >sleeping next to a human for 8 hours is 0.0005 mSv. Is this an error on >the Wiki page or on the chart, or just my misunderstanding?
Well, that’s exactly what the chart says. What’s the problem?
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Anyone want to make this same chart with interactive zoom?
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So how many sleeping humans would I need to eat to equal 8 hours of living among the bananas?
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Cudder: Cell phone use is below the blue section… see the little white square? White.. because its 0 sV. Doesn’t cause ionising radiation!
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what if you work at a freeze drying plant processing bananas ?! all that water evaporation must be lethal 😀
lol, just imagine the affects of whey protein… either the dairy worker gets it, or bodybuilders will share some more traits with the hulk 🙂
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@nicolagiacobbe: Note that 1μSv = 0.001mSv. One banana is 0.1μSv (or 0.0001 mSv)
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Very nice. It would be great if you made this available as a poster in the store as well, I’d love to add this to my wall of science posters at work.
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There’s only once source for the value of 0.1 µSv given in the Wikipedia article, a PDF by the University of Nevada Reno Environmental Health & Safety. They don’t give this as a rate like 0.X µSv/hour, and they don’t show how they computed the value in sieverts/rads, so it’s not clear whether they calculated this over the time the potassium is in the body (about 24 hours before it’s excreted), or over the lifetime of the radioactivity of the potassium-40 (a half-life of about 1.25 billion years, or a mean lifetime of about 1.80 billion years). It seems possible that this number is off by a factor of 657 billion.
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So 5 x Chest+Abdomen+Pelvis CT scans would put me at about 9 red dots. Hooray, I’ve still got 16 left to use on emergency lifesaving work! 🙂
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Nice to see someone with a forum attempt to explain this to people. NBC Nightly News journalists say things like “We have lot of radiation on our shoes” and it makes my skin crawl. Your friend’s website was very nice, too; but I think she forgot one prevention technique that goes hand in hand with shielding: filtering. It’s important to make sure you don’t get anything highly radioactive inside your body. I work with xray and alpha sources and the main fear in my lab is not standing too close or too long in front of a source, but of eating a candy bar in the lab.
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@hillie Randall used microsieverts in his chart, whereas the wikipedia article used milisieverts. I milisievert is 1,000 times more than a microsievert. I think that is where you misunderstood. The two articles are saying the same thing but the scale is different by 1,000.
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Love it! Puts me in mind of an old youtube clip:
Ring ring ring ring ring ring ring….banana-phone!
(Don’t answer it, you’ll get cancer)
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What does it the yearly release for a power plant mean when measured in sieverts? That would have to be a dose measured over a particular subtended solid angle, no? If the dose up to 50 miles from a plant is 0.09 uSv, and the human body is ~ m^2 in cross section, then the 4pi dosage released would be kSv. Is dosage not calculated so?
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Excellent chart, but as a medical physicist, I have one issue with it. Partial body doses (ie hand x-ray, chest ct, mammography) should not be compared with total body doses (ie occupational exposure limits, airplane flights). In fact, occupational limits for total body versus, say, extremities are not the same.
Like your friend, my co-workers and I have been answering more questions than usual lately. On the point mentioned above, your chart could leave people misinformed. I would anticipate the questions like “why is it okay for mammography to deliver three times the annual non-occupational limit?”
Aside from that, though, kudos!!!
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Also, Andy, without looking at the regs, I would assume it is referring to dose to the theoretical Maximally Exposed Individual, which must be calculated for any site study.
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Ok. Thanks for the response. Concerning your first comment, Elizabeth, why is it okay for mammography to deliver three times the annual non-occupational limit? I would think that total-body doses would be more relaxed than partial-body doses, because the same amount of dosage is received in higher concentration on one part of the body.
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A few people have responded to hilllie’s question, basically saying that the chart and the Wikipedia article agree, and the differing scales are causing confusion. But, that’s not true. Hilllie is correct. The Wikipedia says that sleeping next to someone is equal to five bananas. Randall’s chart says that sleeping next to someone is equal to one half of a banana.
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I love how the commenters have latched onto the “sleeping next to a human” and the banana radiation levels. Thanks, everyone, I absolutely did need the laughs this evening.
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@Andy: 1 Gy is 1 J deposited _per 1 kg of body_. Thus, partial body dose deposits less energy than full-body dose of the same value, so it can’t be more harmful.
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@Daneil:
Thanks for the comment about ingestion; I’ve updated that paragraph accordingly. I didn’t think of that so much because it’s just *obvious* to me at this point that you don’t eat lunch in the same room we count samples in (as frustrating as that is when you want to watch your count, but are hungry).
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Andy, there are two principles at work, here.
Physics:
Perhaps the most important thing to realize about radiation dose, is that it is energy deposited *per unit mass.*
To illustrate: There’s a trick question on our board exams that goes something like this,
“If the dose from one 0.5 cm CT slice is 15 mSv, what is the dose from an axial CT with 20 slices?”
The answer is still 15 mSv, provided the CT slices do not overlap.
Obviously if you get 20 slices you’ve received more radiation than if you get just one slice, but you have not, in fact, received a higher radiation dose. So, for a mammography, the 3 mSv are received by the breast tissue only. Getting 3 mSv to the whole body would not “dilute” the dose. Now, the difference between an organ dose and a whole body dose are covered below.
Biology:
Any complex biological system, including the human body, has parts that are more radiation sensitive than others. Our most sensitive part is bone marrow, followed by the lining of the intestine. (Cells that reproduce quickly and are less differentiated are more radiosensitive, as a general rule.) The central nervous system and muscle, on the other hand, are much less radiosensitive.
Since different systems respond differently to the same dose, comparing even the same doses in one organ to a different organ, or to the same total body dose does not make sense! Because of this, there exist tissue weighting factors, published by the ICRU, that are used to convert an organ dose into an effective total body dose equivalent for purposes of comparison. For example, if someone’s liver received 2 mSv, and if the weighting factor for liver is 0.06, then it introduces them to the same risk as a total body dose of 0.12 mSv.
In the case of a mammography, a 3 mSv dose to breast, multiplied by the appropriate tissue weighting factor to give the effective total body dose equivalent, is indeed less than the annual member-of-public dose limit. In the case of procedures that are not (like a radiation therapy course) the benefits, of course, outweigh the risks.
I hope this answers your question.
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*Unless it’s a banafone. lol
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Or, you could just read Robert’s answer. He’s much more concise.
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thanks, this is really helpful in understanding the radiation risks! nice work 🙂
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You are getting some sweet re-postage and linkage over at Starts With A Bang on Monday!
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Actually, this chart just tells the effects of GAMMA radiation. This tells us very little about ALPHA particles, the radiation that people get inside of their bodies and which caused most of the deaths and disease from Chernobyl. Radiation is accumulative over time, so alpha particles in the body, even if low radiation, will cause accumulative tissue damage over time.
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Just a minor nitpick. As much as I find the hysteria about nonionizing radiation ridiculous, I don’t think it’s safe to say that EM from cell phones or any other source is incapable of causing cancer. For years people dismissed the notion that lower-frequency radiation could have biological effects on the grounds that there was no known mechanism for non-ionizing radiation to affect biological processes, which is IMO a dangerously arrogant position to take, at least for anyone with a functioning pair of eyes and/or skin capable of feeling a temperature gradient.
As it turns out, there is research supporting the ability of low-frequency EM and magnetic fields to affect biological processes via several mechanisms, e.g., modulation of enzyme kinetics, ephaptic coupling, suppression of melatonin secretion, etc. It’s a bit of a stretch but I suppose it’s plausible any of these could adversely impact recovery processes in such a way to increase the risk of cancer or other disease.
On the other hand, until there’s statistical evidence of a higher rate of cancer among cell phone users, I think it’s safe to say there’s no reason to believe it either.
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Thank you! I love this chart.
Among the many moments of happiness your comics have afforded me, one of my favourites is “Duty Calls”…whenever I feel like my brain will explode from the internet stupidity I sometimes come across, I think of it.
Living 150km west of Tokyo, I’ve spent too much time this morning arguing with the more frustrating posts on a news-site about radiation and the general situation here (most of it coming from people who aren’t even here). I had to stop…and came here for a little happiness & sanity again. This chart was a pleasant surprise.
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