Explain xkcd: It's 'cause you're dumb.
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This is a chart listing various sources of radiation and the amount of dosage in sieverts (a unit of absorbed radiation) you would receive. There is an image of squares next to each radiation source, which act as a representation for an amount of sieverts. The blue squares represent .05 micro sieverts each, the green squares represent 20 micro sieverts each, the red squares represent 10 milli sieverts each, and the yellow squares represent 1 sievert each.

This was released shortly after, and due to, the Tohoku Earthquake and the beginning of the crisis at the Fukushima nuclear plant.

The first section, the blue section, shows small dosages of radiation compared to 1 to 800 blue squares. A much smaller version of the blue chart is shown in the green section to compare blue to green squares. The green section uses green squares in comparison to its radiation amounts, which are much larger than those listed on the blue section. The red section uses red squares to compare its much more powerful radiation sources. It has a smaller revision of the green chart to compare green to red squares. The yellow section compares yellow squares to a single source, the amount of radiation absorbed during ten minutes next to the Chernobyl reactor core after explosion and meltdown. It likewise features a small version of the red chart to compare yellow to red squares.

Randall points out the cell phones do not produce ionizing radiation, "unless it's a bananaphone". This is in reference to Bananaphone, a 1994 children's song by Raffi which, on the internet, saw its peak of memetic popularity in 2004. As noted in the blue chart, bananas give off less than a fraction of a micro-Sievert of radiation; thus, a phone that is also a banana would give off radiation.

Below the charts there is a conversion table comparing various squares to each other and their conversion rates. Below that is various web sources that have just the urls listed, not in any official citation like MLA or APA.

Randal explains at the bottom that this chart is merely a rough guideline, and may have errors. Indeed, his sources that he listed have many typos and some are broken links.

It is likely that this comic was the inspiration for the much larger and more complex 980: Money that came out later that year.


Title: Radiation Dose Chart
Subtitle: This is a chart of the ionization dose a person can absorb from various sources. The unit for absorbed dose is "sievert" (Sv), and measures the effect a dose of radiation will have on the cells of the body. One sievert (all at once) will make you sick, and too many more will kill you, but we safely absorb small amounts of natural radiation daily. Note: The same number of sieverts absorbed in a shorter time will generally cause more damage, but your cumulative long-term dose plays a big role in things like cancer risk.
Blue section:
1 blue square: Sleeping next to someone (0.05 μSv)
1.8 blue squares: Living within 50 miles of a nuclear power plant for a year (0.09 μSv)
2 blue squares: Eating one banana (0.1 μUsv)
6 blue squares: Living within 50 miles of a coal power plant for a year (0.3 μSv)
20 blue squares: Arm X-Ray (1 μSv)
25 blue squares: Extra dose from spending one day in an area with higher-than-average natural background radiation, such as the Colorado plateau (1.2 μSv)
100 blue squares: Dental x-ray (5 μSv)
200 blue squares: Background dose received by an average person over one normal day (10 μSv)
800 blue squares: Airplane flight from New York to LA (400 μSv)
Note under blue section: Using a cell phone (0 μSv)-a cell phone's transmitter does not produce ionizing radiation* and does not cause cancer.
  • Unless it's a bananaphone.
Green section:
1 green square: Chest x-ray (20 μSv)
1.5 green squares: EPA yearly release target for a nuclear power plant (30 μSv)
3 green squares: All the does in the blue chart combined (~60 μSv)
2 green squares: Extra dose to Tokyo in weeks following Fukushima accident (40 μSv
3.5 green squares: Living in a stone, brick, or concrete building for a year (70 μSv)
4 green squares: Average total dose from the Three Mile Island accident to someone living within 10 miles (80 μSv)
5 green squares: Approximate total dose received at Fukushima Town Hall over two weeks following accident (100 μSv)
12.5 green squares: EPA yearly release limit for a nuclear power plant (250 μSv)
19.5 green squares: Yearly dose from natural potassium in the body (390 μSv)
20 green squares: Mammogram (400 μSv)
50 green squares: EPA yearly limit on radiation exposure to a single member of the public (1 mSv=1,000 μSv)
50 green squares: Maximum external dose from Three Mile Island accident (1 mSv)
50 green squares: Typical dose over two weeks in Fukushima Exclusion Zone (1 mSv, but areas northwest saw far higher doses)
100 green squares: Head CT Scan (2 mSv)
200 green squares: Normal yearly background dose. About 85% is from natural sources. Nearly all the rest os from medical scans (~4 mSv)
300 green squares: Dose from spending an hour on the grounds at the Chernobyl plant in 2010 (6 mSv in one spot, but varies wildly)
350 green squares: Chest CT scan (7 mSv)
2,500 green squares: Maximum yearly dose permitted for US radiation workers (50 mSv)

Red section:
4 red squares: Approximate total dose at one station at the north-west station of the Fukushima exclusion zone (40 mSv)
5 red squares: Radiation worker one-year dose limit (50 mSv)
7.5 red squares: All doses in green chart combined (~75 mSv)
10 red squares: Lowest one-year dose clearly linked to increased cancer risk (100 mSv)
18 red squares: Dose received by two Fukushima plant workers (~180 mSv)
40 red squares: Dose causing symptoms of radiation poisoning if received in a short time (400 mSv, but it varies)
200 red squares: severe radiation poisoning, in some cases fatal (2000 mSv, 2 Sv)
400 red squares: Usually fatal radiation poisoning. Survival occassionally possible with prompt treatment (4 Sv)
800 red squares: Fatal dose, even with treatment (8 Sv)
Smaller section within red section:
EPA guidelines for emergency situations, provided to ensure quick decision-making:
10 red squares: Dose limit for emergency workers protecting valuable property (100 mSv)
25 red squares: Dose limit for emergency workers in lifesaving operations (250 mSv)
Yellow section:
50 yellow squares: Ten minutes next to the Chernobyl reactor core after explosion and meltdown (50 Sv)
Conversion charts:
1 blue square equals (0.05 μSv)
400 blue squares equal 1 green square (20 μSv)
500 green squares equal 1 red square (10 mSv)
100 red squares equal 1 yellow square (1 Sv)
Chart by Randal Munroe, with help from Ellen, Senior Reactor Operator at the Reed Research Reactor, who suggested the idea and provided a lot of the sources. I'm sure I've added in lots of mistakes; it's for general education only. If you're basing radiation safety procedures on an internet PNG image and things go wrong, you have no one to blame but yourself.
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There are some errors/problems in the sources Randal listed on the image:
-left an http out on the beginning of the 2nd source
-source 3 and 4 are inl-oversight, not inl_oversight
-source 7 isn't available any more due to the restructure of their site, but it might have been fine when randal made it
-source 11 should be fact-sheets, not fzact-sheets
-source 12 is a 404 (and the double underscore seems a bit strange), and I can't find the original page
-the last source seems to be a dead domain

Kirdneh (talk) 21:47, 26 December 2014 (UTC)

It's probably important to note that this was released shortly after, and due to, the Tohoku Earthquake and the beginning of the crisis at the Fukushima nuclear plant. 07:45, 19 January 2015 (UTC)

Does anyone else have the problem where the previous link at the top leads to "comic -1," a nonexistent page, the next link leads to comic 1, the comic is number "#," and the article is titled "Radiation" instead of "(comic number): Radiation?" 14:13, 2 February 2015 (UTC)

There is no "comic number" because this was a blog post, not one of the numbered comics. 04:50, 3 February 2015 (UTC)

I can't seem to scale the image properly. It remains pixelated.--Forrest (talk)15:51, 25 August 2015 (UTC)

Interestingly enough, i found a poster of this in my highschool science lab. Whiskey07 (talk) 10:44, 26 August 2015 (UTC)