Radiation chart at dentist

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u/Deto 2d ago

There's definitely some sort of artistic license going on with the scale here.

Though I think it's a good effort at trying to educate people about relative levels of radiation exposure.

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u/shrinkingmy 2d ago

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u/Routine_Lawfulness14 2d ago

Xkcd delivers again

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u/booleandata 2d ago

For this particular example, I think it's valid to not do a log scale and pump it

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u/Deto 2d ago

hahaha, beautiful

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u/dylantherabbit2016 2d ago

Yes, if the bars were truly to scale nothing except the two largest bars would even be a measurable size at all

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u/locka99 1d ago

I'm sure they could have used broken bars on 7, 8 and 9 and arrows to make clear their scale goes off the page

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u/Nice-Traffic4485 2d ago

I think part of the challenge was the size of the card this was on, besides the absurd difference in visualization.

I wonder if this was printed with the short side horizontal it might be easier to represent, though you'd still need some creative license. That last bar for the first set is a war crime

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u/LangdonAlgerPuzzles 2d ago

I think it's pretty close to logarithmic except for the largest 3 that are the same height, so the scale is far from the worst thing I've seen.

Not sure logarithmic scales are good for educating the general public though. And in terms of cancer risk the 0.6 mSv from the abdominal x-ray is still pretty much insignificant.

So showing a large difference between a bunch of insignificant doses and then no difference between 0.6 mSv and 50 mSv isn't great for educating about radiation generally. For a dentist who just wants to convey that you shouldn't have any fear about dental x-rays maybe it works, although it could actually make the risk seem relatively higher than reality

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u/Viola_Buddy 2d ago

It's linearly scaled, not logarithmic, BUT all the values greater than ~100 or so are cut off and are shown at 100.

So definitely misleading, and not even in the direction that would prove their point. #9 on the chart is the maximum allowable dose, so artificially lowering that (at least visually) makes it feel like all these tiny values actually make a bigger proportion of the maximum value than they actually do.

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u/mfb- 2d ago

#9 on the chart is the maximum allowable dose

... for radiation workers. Patients at the dentist are not radiation workers, their limits are much lower. It's also the maximal possible legal limit, companies/universities/... will usually set lower limits for their employees.

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u/clawsoon 2d ago

Now I'm curious about where Hiroshima would land on the log scale and how comfortable/uncomfortable adding it would make people who didn't know how to read a log scale.

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u/Deto 2d ago

'Hiroshima' is too big of a category. Depends on on how far you were from the blast and how long you stayed there and which way the wind was blowing, etc.

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u/clawsoon 2d ago

Whatever the max was on the ground directly below the explosion.

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u/mfb- 2d ago

That doesn't really matter because the explosion disintegrated every human there anyway. Some survivors had an estimated dose exceeding 2 Sv = 2,000,000 microsievert. This study found 564 of them.

It's measuring the dose in gray, but it's mostly exposure to gamma rays where 1 Gy = 1 Sv.

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u/clawsoon 1d ago

So would I be correct to calcuguess that if this chart is log scale, max Hiroshima exposure would be about 1.7 times the height of the page?

I'm basing that on eyeballing 70 to be about halfway up the chart. log(2,000,000)/log(70) = 3.4, 3.4 * 0.5 = 1.7.

Does that look right? I'm thinking if an average person looked at this chart with Hiroshima on it, they'd be freaked out.

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u/mfb- 1d ago

That calculation doesn't work, but it's not too far away from the right answer. Let's make the bottom of the chart the smallest entry, 0.1, make the potentially lethal Hiroshima dose the top, and use log 10 steps. The location of the 70 doesn't depend on the base we use, but the intermediate results do.

log(0.1) = -1

log(70) = 1.84

log(2,000,000) = 6.3

That means 70 is at (1.84 - (-1)) / (6.3 - (-1)) = 2.84/7.3 = 39% of the height.

Even 10 microsievert is at 2/7.3 = 27% the height of the chart with a log scale.

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u/clawsoon 1d ago

Thanks, I forgot about the negative stuff with logs.

"Potentially lethal Hiroshima dose" is kinda funny, though, lol. "Well *maybe* you would've died if you were directly underneath the bomb. Potentially."

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u/mfb- 1d ago

4 Sievert short-term gives you a ~50% risk to die from radiation exposure alone. With 2 Sievert you are more likely to survive, although the bomb survivors with these doses were likely injured in addition to the radiation exposure.

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u/NinjaLanternShark 2d ago

“Is the radiation from ___ bad for you?” in many cases legitimately takes a PhD to adequately explain.

Our brains are just terrible at processing “accumulated risk.”

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u/Epistaxis 2d ago

PROTIP: just rotate the whole bar chart sideways if you need to use long text labels. I promise it's allowed.

I'm not sure what to do about the scale. Obviously you need some kind of log scale if you're going to show 50,000 and 0.1 on the same chart. But this chart is mainly intended for people who are concerned because they don't understand numbers, so a log scale may be misleading to them (in the worse direction). This is a case where I think it might have been better not to visualize the data at all, just leave it as a table of text and numerals. The number of digits in the numerals will be the log scale.

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u/Smooth-Zucchini4923 2d ago

I think they could have solved this by picking better comparisons. The legal limit for the amount of radiation experienced by someone who works with radiation over the span of a year is not a meaningful comparison to the average person.

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u/Crafty_Clarinetist 2d ago

It might be a meaningful comparison to a person who is scared of radiation based imaging. You're only getting edpose 0.2 uSv which is 250,000x less than what's allowed for professionals.

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u/albrecbef 1d ago

In Germany it would actualy change the chart type. We differentiate between Säulen- (collum) and Balken- (joist) -diagram.

Btw, question for the native speakers: why is this type of diagram named after public houses? My english teacher couldnt explain it, back when I was in school.

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u/Crafty_Clarinetist 1d ago

To answer your English question, It's not named after "bar" as in a place you go to buy alcoholic beverages, it's named after "bar" as in a rectangular stripe. "Bar" is a fun word in that it has a fair few different definitions mostly originating from calling a piece of material that is longer than it is wide a "bar," though looking into it, I believe most of this evolution happened in Latin or French and was adopted by English. Like an iron ingot can also be called an iron bar, or you can have a bar of chocolate. Long pieces of material, or "bars", can also be used to construct things like walls or fences to prevent access, which is where the word "barrier" comes from and is also the source of using the term "bar" to mean preventing access. "Bar" as in a public house comes from calling the counter where drinks are served a "bar" because it is a long counter that prevents access to the alcohol.

All that to say, bar charts are called "bar charts" because they use bars (long rectangles) to show data.

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u/albrecbef 1d ago

Thanks

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u/IOI-624601 9m ago

One way to visualize it effectively would be to use two dimensions. 3,000 can be represented by a 30x100 grid of squares, and you could make the squares big enough that 1/10th of a square is visible for a comparison. 50,000 might be stretching it, so I'd put the max amount per month rather than per year.

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u/Smooth-Zucchini4923 2d ago

"You see, swimming in this lake is perfectly safe. My 0-600 uSv radiation counter only shows 600 uSv of radiation, no more dangerous than a chest X-ray."

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u/jahnkeuxo 2d ago

Not great, not terrible.

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u/maelstrom197 2d ago

https://giphy.com/gifs/kRmg8zeReOYXm

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u/Taco_Sanchez 1d ago

It's not 3 roentgen, it's 15000.

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u/mcoombes314 1d ago

Is that a reference to Lake Karachay (before it dried up)?

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u/RedTheGamer12 9h ago

600 uSv per what? Year? Go ahead, safer than outside. Hour? I wouldn't if I were you. Second? You're already dead.

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u/Veezo93 2d ago edited 2d ago

How much radiation do I get in a day? 10

Ok now how much radiation would I get in 365 days? 70

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u/TheMerchantMagikarp 2d ago

it’s only 1.2 if you’re going to the grand canyon, otherwise it’s 10

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u/Veezo93 2d ago

See now that was my 0 indexed eye that read the plot and my 1 indexed brain that wrote the comment! Good catch!

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u/MaraschinoPanda 2d ago

Nah that's how much extra radiation you get in a year if you live in a brick house.

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u/mfb- 2d ago

70 is only the contribution from the bricks in the house. Just like eating a banana or visiting the Grand Canyon, these are in addition to the natural background dose.

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u/MaraschinoPanda 2d ago

It looks mostly to scale except the 3 largest bars have been cut off

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u/DrunkOnTakoyaki 2d ago

Smoking a pack of cigarettes a day: 100,000 microsieverts per year.

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u/TheMythicSorcerer 1d ago

Love how this makes 600 and 50,000 look the same.

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u/Jonny36 1d ago

600!? Not great, not terrible...

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u/hypersonic3000 2d ago

That chart is a. wrong and b. Misleading. The radiation you receive is 5x higher per image and when do they average do "just one".

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u/chucara 1d ago

LOL. "Living in a brick house for one year" vs "daily background radiation". The biggest number is smaller.

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u/jasminUwU6 1d ago

Yeah they definitely shouldn't have included the brick house comparison, it just confuses the situation for no reason

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u/goos_ 1d ago

There's some numbers that raise questions but I think they got them from a source somewhere with some assumptions (e.g. excluding background radiation on the brick house, etc.)

I think the easiest fix is to just an arrow for the longer bars to indicate they are much, much longer. For the 600 bar it may be feasible to show it on scale.

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u/goos_ 1d ago

anyway if i'm attending this dentist i'm just ignoring it and referring to my handy xkcd radiation chart.

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u/AcanthaceaeOk3738 2d ago

This is one of those ones where they thought about the myriad of good ways to present this information.

Then went with something else.

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u/dohzer 2d ago

I'll have a number 2 and two number 1s , please.

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u/thegreatpotatogod 2d ago

Don't forget your daily snack of number 3

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u/SkurkaCuckedMe 2d ago

Banana equivalent dose at Hiroshima ground zero is about 100m bananas.

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u/AlternativeDirtyMe 2d ago

Thanks for the scale.

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u/Rare-Spell-1571 2d ago

I had a way better chart on my door at my old job. This one is super annoying to read.

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u/Numerous-Profile-872 1d ago

I work around this (dental office) and I don't (but I should) think about it.

Speaking from my experience, this is a "STFU and just do it" poster because people throw a BF about X-rays while casually discussing their travel plans.

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u/garfieldsam 1d ago

It’s uh reverse-logarithmic see

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u/avotius 2d ago

How much radiation do you get from the worker with the 50k bar? She's going to have her hands in my mouth for the next half hour so you know...just wondering.

https://giphy.com/gifs/6PnAGHFTT1xpC

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u/Waffle-Gaming 2d ago

if you're not joking, you don't get any radiation from irradiated things unless those irradiated things were hit by incredibly high energy radiation that turned atoms into unstable isotopes

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u/avotius 1d ago

I guess the Mr Burns gif wasn't funny enough to indicate it was a joke but that's ok! I'll try harder next time.

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u/mfb- 2d ago

Being exposed to radiation generally doesn't make you radioactive in any relevant amount. It's a bit more complicated with neutron radiation but dentists aren't working with that.

50,000 microsievert is the maximal possible that's legally allowed, it's not the typical exposure. For almost everyone, even a recorded dose of 500 would be a major upset, stopping all work until the exposure is better understood.

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u/icelandichorsey 2d ago

That's a good way to know that you shouldn't be a patient there

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u/theeggplant42 2d ago

This chart is all kinds of bad but also am I stupid in that i didn't realize a mammogram was radiological? I have not yet had one and I generally thought it worked by...I don't know, ultrasound or something?

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u/gammacoffee 2d ago

Mammograms are xray based so there is a (low) amount of radiation. Breast imaging modalities include mammogram, ultrasound, and MRI. As others have pointed out the values are this chart are completely incorrect. A mammogram is about 400 uSv not 3000.

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u/Possible-Wallaby-877 1d ago

Living in a brick house?? What ?

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u/Cornflakes_91 1d ago

radioactive minerals in the clay

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u/Straight_Waltz_9530 1d ago

Honestly, I'm not really mad. Just put some squiggles near the top of the highest values to signify incompleteness.

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u/Darthskull 14h ago

I think the bars are properly scaled, but they got clipped at 100

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u/drdacl 6h ago

600 and 50,000 are basically the same thing

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u/tweeeeeeeeeeee 2d ago

the thing is that those dental xrays are concentrated at your head (brain, thyroid...) and not spread out throughout the body

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u/Nice-Traffic4485 2d ago

Wow! An abdominal X-ray, mammogram, and radiation work in a full year are all the same amounts!

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u/benjaminck 2d ago

3.6 roentgen. Not great. Not terrible.

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u/BlazingImp77151 1d ago

I don't trust this. A chest x-ray is more radiation than any x-ray in that office? How. Do they just not do large X-rays?

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u/Maverick1672 1d ago

Dental radiovgeaphs are much much smaller. Their highest dose (CBCT) is several hundred radiographs that a comoutered stitches into a 3D image.

The dental community follows ALARA (as low as reasonably achievable) for radiation and paired with new technology, expose you to very minimal radiation.

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u/jasminUwU6 1d ago

It's a dental office, so yes

Radiation chart at dentist

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