At a certain commercial nuclear facility “tribal knowledge” stated that the blue glow was due to Bremsstrahlung effect, as opposed to Cerenkov radiation. I do not question Cecil’s explanation, as I sometimes found that there was a prevalence of tribal knowledge amongst those that had no vested interest in accuracy. However, it was definitely not due to blue boron.
OK in order to understand the short term vs. long term effects of ionizing radiation, a little lesson on terminology is in order. So, here goes.
Sometimes you here terms like dose or dose rate, REM, RAD, or Roentgens. Let’s start with RAD. A RAD is roughly the amount of any type of radiation equivalent to 100 ergs in 1 cubic centimeter of dry air. A Roentgen is 1 RAD of gamma radiation. A REM (Roentgen equivalent man) is that amount of any type of radiation which causes the amount of BIOLOGICAL damage equivalent to depositing 100 ergs of gamma radiation in 1 gram of soft body tissue. RAD and REM can be equated by using a “quality factor”. For gammas the Q factor is 1. So, 100 RAD is equal to 100 REM. For alphas the Q factor is 20. So 100 RAD of alpha radiation is equivalent to 2000 REM.
Dose is the amount of total radiation received in REM. Dose rate of course is the rate at which you received the dose. An average chest X-ray will give you about 0.1 rem (100 mrem), watching T.V. for a year will net you about 1 mrem, and an average day at the beach (in Hawaii) will give you around 20 mrem.
Long term cancer risks goes as follows: In any random sample of 100,000 people, 1600 will die of cancer. If you expose those 100,000 people to 1 rem of radiation (instantaneous) then 1601 people will die of cancer.
Short term effects are dependant on how much. of course. Up to 25 REM, no effect. 25 -50 rem, small changes in the blood, nausea. 50-100, vomiting and blood dammage leading to various problems. 100-500 rem, all the things you think about radiation, hair loss, teeth loss, vomiting, etc. 50% will die. over 500 is almost certain death. over 1000 rem is instantaneous death.
Anyway I hope that helps.
“If you stick your finger in a pie, whatever is in the pie will be on your finger, and whatever is on your finger will be in the pie…unless you wear a rubber glove”----some demented old lady
All right, so it’s taken me a while to get back to you. My question was a trick question, actually, since I already know the answer – I was just hoping for a bit more detail, like the best substances to use next time I go in for X-Rays so I can really play havoc with the techs. In case you’re wondering, I am a physicist, and I have worked with medical imaging. We were building a portable gamma camera, and testing it on people walking out of Dr’s offices after being imaged. Turned out we could see their fingers with our neat little camera – which ONLY imaged high-energy photons (I wrote the software which filtered out lower energies, and our machine didn’t register betas or alphas) So technically, if you injected someone with a nonlethal dosage of a gamma-emitting radioactive substance, and painted them with a substance which fluoresced when exposed to that wavelength, they WOULD glow. You wouldn’t be able to perceive the glow unless you were in a cave at midnight during the dark of the moon, and possibly not even then, but tiny amounts of visible light would be emitted.
“. . . and all places are alike to me.”
–R. Kipling
WELLLL…we like ourselves don’t we Kat?
Just out of curiosity; did you image people who were not recently exposed to see if they also, in fact, had glowing fingers? I’m sure you must have. Also, how high is high energy? Both Potassium and Calcium have naturally occuring radioactive isotopes that emit relatively high energy gammas. Which is why, if you eat bannanas or drink a lot of milk before being internally monitored, you will have a higher whole body count than someone who abstains from ingesting them. Also KCl salt substitutes are so radioactive that they are banned on U.S. submarines. Is it possible that your supersensitive imaging thingamajiggy is sensing these gammas from the hands because thay are not attenuated by a lot of tissue.
Just a thought.
“If you stick your finger in a pie, whatever is in the pie will be on your finger, and whatever is on your finger will be in the pie…unless you wear a rubber glove”----some demented old lady
Back to the topic of radium paint in wristwatches.
Has anyone ever shown that these watches caused any significant harm to the wearer? I’m familiar with the theory that it was harmful to the factory workers, but it seems to me that they would likely be harmless to the wearer. Radium gives off alpha particles, right? Alpha particles wouldn’t be able to penetrate the watch glass to harm anyone.
I’ve always figured that the reason radium paint was outlawed was because of irrational fear of radiation in any quantity under any conditions, rather than any real health risk.
Sue, you’re correct that alpha particles would be stopped by the watch glass. But radium also emits gamma rays, which would easily penetrate the glass.
Despite that, I don’t think that radium watches were discontinued because of harm to people wearing them; it was the problems of manufacturing. The radioactivity from a single watch dial is trivial, but if you worked in a factory producing the things, the doses would add up.
We know more about radiation today than we did then, so if there were a demand for radium watch dials now, we could probably produce them safely. But why bother with the radioactive stuff at all? An Indiglo™ light is brighter and isn’t remotely hazardous.
I thought I would check out this site, because I really enjoyed Cecils last article. In any case, I wanted to add a few things…
To TheDude…nice job, you handled most of my corrections.
The blue glow is in fact due to Cerenkov radiation, to whomever asked.
Lethal dose would depend on several factors. 500 rem would kill about 50% of those exposed within a month. 700 rem would kill almost everyone inside of a month. 5000 rem would probably result in instant death.
No, the watches wouldn’t expose you to very much radiation at all. The people who painted the dials were injesting the material. Radium is a bone seeking…so goodbye jaw bones, etc. Not sure what the exposure is to one of these while wearing it, but it would probably be comparable to what dose you give yourself. Yes, that is right…all of you are radioactive!!!
Also, being 100 yards from the bomb blast, those individuals would have died from the heat blast or the force of the explosion, but not the radiation.
Oops…forgot one other thing. Bremsstrahlung is the german word for “braking radiation”. This occurs when electrons decelerate inside of a material (thus releasing x-rays). Trust me…it is cerenkov radiation that you ‘see’.
This is a bit off the topic, but I would like to know how important it is to wear sunglasses with so-called UV protection.
UV light is composed of short-wavelength, high frequency photons, but these should still be largely absorbed by ordinary glass or plastic. They get scattered very easily (being far beyond the blue end of the spectrum), I think.
Is there empirical evidence that there is special protection needed for the eyes, once they are shielded by a 3mm wall of glass or plastic? What, exactly, is UV protection, anyway?
The state of non-bliss implies some knowledge.
My Dear Mr. Mollusk –
Must be nice to know barely enough to bring up irrelevant details when you can’t understand the facts.
But I see I must explain. The device was calibrated to a known radioactive source – which source depended on which isotope we were looking for. I’m hoping you comprehend spectrometry, and that gamma-emitting radioactive isotopes emit those gammas in wavelengths specific to the isotope? When you have good enough spectral resolution, you can narrow the energy band in which you record events to only cover the peak of the isotope you’re seeking. If you calibrate a device to a known source, you can make absolutely certain that you’re only looking at the peak from that isotope, and the S-to-N ratio is relatively low. I do hope I don’t need to explain the scientific method to you, too? I try so hard not to be patronizing, but it seems some people demand it. . . .
“. . . and all places are alike to me.”
–R. Kipling
UV radiation causes cataracts. How important that is depends on whether you mind going blind or not. From what I remember, glass has no UV protection and only some plastics do. This was from Consumer Reports and they recommended getting shades that claimed UV protection.
Those who can’t hear the music, think the dancer is mad.
In 1922, Radium Dial opened a factory in my hometown of Ottawa, Illinois. They paid up to $17.50/week to local high school girls (a pretty big paycheck at the time: the average pay back then was about $5/wk) and taught them how to paint clock faces with radium in order to make the numbers glow inn the dark. In order to do this, they dipped the brush in the paint and then rolled the tip on the end of their tongues to make a fine point. The plant closed in 1968, but re-opened across town as “Luminous Processes”. My spouse has an in-law who worked there until it was closed in 1977, and this in-law’s fingernails literally glowed in the dark for years after working there; in order to see this phenomenon you would have to be in a very dark place, such as a closet or a windowless bathroom with the lights off, but one could definitely see the glow. For further investigation I recommend the documentary “Radium City”, Produced by Carole Langer and featured on the Discovery Channel some years back.
There are two clock chime tunes, though, “Westminister” and, um, maybe “Big Ben”? Both are structured as four quarters, with first just the one part played at ?:15, then two parts played at ?:30, etc. until the whole tune gets played on the hour before the chime counting the hour.
Our family actually had a chiming clock which would play either one depending on the position of a switch, is how I know.
I thought “Westminster” refered to Big Ben. Big Ben is located in a tower of the Parliment Building. Across the street is the Abbey. I don’t recall ever hearing more than one clock strike the hour, there.
Hence the “um.”
All right, time for some research. According to the Klockit home page, www.klockit.com, there are three popular melodies : Westminster (= “Big Ben”,) Whittington and St. Michael’s.
I remember our clock having a choice between “Westminster” and something else, but neither of those other two . . .
. . . ring a bell.
-j
[We know more about radiation today than we did then, so if there were a demand for radium watch dials now, we could probably produce them safely. But why bother with the radioactive stuff at all? An Indiglo™ light is brighter and isn’t remotely hazardous]
Indiglo may be heaven sent however, the “old” technology of using radioactive paints to make watches and other objects (night sights for firearms) glow is still in use. The radioactive (mildly so but still dangerous see: http://drambuie.lanl.gov/~esh12/inkret/DAh3.htm) is tritium.
I knew a watchmaker next door who’s hands shook like crazy. I don’t know how he ever worked on watches. He said that the radium in the old watch hands is what caused it.
It might be just a little, but when you work with it day after day eventually it has a profound effect.
Even seeing the new glow necklaces makes me nervous.
I don’t have any citations for this and I can’t even remember where I heard it, but I recall the lyrics to the bell song being “Hail to the bells/ we bow our heads/ We thank the Lord/ our daily bread.”
Everything you said is correct (other than about radium decay--I don't know to confirm or deny.) However, you missed one type of radiation: neutron. It's the worst one--for a given energy it does far more damage to the human body. Also, unlike the other forms, it's liable to make whatever it hits radioactive.
Fortunately, natural decay sequences normally don't include neutrons. However, you do sometimes see them from the byproducts of fission.
Also, to clarify something: Externally, alpha and beta emitters pose basically no risk. Very few beta particles make it deep enough through the skin to affect tissue that remains--most all will be absorbed in the skin layers that will soon be shed. The real danger from such isotopes is when they get inside your body. Then you aren't shielded from their harmful effects. From some older data I've read about this: It's only in the upper part of the 100-500 range that kills 50%--and that's assuming no treatment. At that level, the radiation kills the bone marrow. If enough of it dies and you don't get treatment, you die. However, even if it all dies, treatment is still possible--bone marrow transplant. You'll be in for several quite unpleasant weeks and might die anyway, but you've got a fair chance. If it kills, it kills in like a month.
Beyond this level is disruption of the digestive system. This is in the 1000 rem range. Death occurs in 48 hours, there is no treatment last I knew. (Such cases are exceedingly rare--even if someone had an idea of how to treat it, they wouldn't have gotten a case to work on.) Finally, at a few thousand rem there is central nervous system disruption. Kills in 24 hours, unconcious in a few minutes. These are also exceedingly rare. The only case I heard of the guy lived long enough to run out from the building--even at that level it's not instantaneous.
Obviously, the higher the dose the faster it would do it's harm. However, it's a realm with very little data--the only cases I've heard of came from unintended criticalities while processing nuclear materials.