Instant radioactive death?

Probably not…from what little I understand it’s fine, but a second opinion from someone amongst the Teeming Millions who’s knowledgeable about such things could set my mind at rest.

A pal bought me a bunch of radioactive marbles that have a trace of uranium in 'em (because they fluoresce like green Kryptonite does and I collect fluroescent minerals).

But the level of “It’s RADIATION! WE’RE ALL GONNA DIE!” in our society has apparently worked on me too and I’d like some reassurance that I’m not gonna wake up glowing green or something (the fact that my sister-in-law just died of cancer isn’t helping either).

Anyway, apparently these things “will register on a CDV-700 Geiger Counter though with low reading. Depending on what type of counter and probe you have they should register right around 100 CPM or .2mR approximately.” (and I’ve got either 10 or 12 of 'em), which, best as I can figure, isn’t as dangerous as the fact that I live in the Rocky Mountains which, having granite in 'em are mildly radioactive too. Besides, they were able to be shipped through the mail, and presumably the post office would have a hissy fit if someone tried to mail radioactive waste, right?

So…reassure me. No big deal, or is it time to get the lead foil and call the hazmat teams?


I think you’ll make it, Fenris.

The NRC yearly limit for skin exposure is 50,000 mR for adult radiation workers.

As to your title, a lethal dose of radiation will of course vary depending on type of radiation and where on the body it is absorbed. A whole body dose of 300-600 rems will do the job in under 30 days.

Oops, wasn’t quite done.

This site has some interesting dose comparisons.

I guess your marbles don’t qualify as radiological WMD after all then.

Radiation level sounds safe enough, but I would try to avoid spending a lot of time in close proximity. Don’t store it under your bed or in your desk drawer.

IIRC, Uranium is an alpha emitter so ingesting or inhaling bits of the rock may be very dangerous. Never grind, polish or machine them, and try not to break them. If one breaks, dispose of all the small pieces properly.

mR (or mili-rem) is a mesure of how big a “dose” of radiation has been absorbed by the body. By itself it can only describe the dose from a single event, so it’s often incorporated into a mesurement called a dose rate which is the dose that would be aquired over a period of time, which makes me wonder if the .2mR you quote isn’t really supposed to be .2mR per some unit of time, like an hour/day/month/year.

Also, it’s important to know what distance the dose rate was determined at: was it a contact dose, with the geiger probe touching the marbles? Taken at 5cm? 30cm? Radiation operates by the inverse square law: a .2mR dose at 5 cm becomes a .05mR dose at 10 cm, and a .0025mR dose at 20 cm.

Having established those disclaimers, how bad is a .2mR dose? For the US, the average annual dose from background radiation, airline travel, medical radiography and so forth is 360mR per year. If you figure that the .2mR is per hour, taken at contact, you’d have to keep the marble in your pocket 24 hours a day, 75 days straight, just to match the average dose you’re likely to get this year.

Does this make you feel safer?

Well, as you said, the marbles are about .2mR. A cross country airplane trip will expose you to about 4mR. Background radiation, from just sitting around, exposes you to about 200-300mR a year. Because Denver is so high up, living there exposes you to another 50mR a year. Here’s a list of some more things that will expose you to radiation, and how much they will.

Because uranium is a radioactive element, we automatically think of it as dangerous, but you can find it around the home, in glass, in glazing for china, in dentures, and, in reality, especially in the amounts you’re talking about, isn’t dangerous. Now, if you were a uranium miner, I’d tell you to be careful…

Sure, it’s safe, as the women that worked for the Radium Dial Company all know.

That’s just a poem, but here detail the ongoing efforts to remediate contamination in Ottowa, Illinois, the site of the radium dial factories. If you search the web, I’m sure you’ll be able to find detailed horror stories of what this exposure cost the workers and their families.

Yes, we may all live in close proximity to natural radioactive decay. However, you have just added another source to your immediate environment. While it may not be enough to ever give you “radiation sickness” it may be enough to work minute changes in your genes - or your wife’s genes - or your children’s genes.

The “glow” from radioactive materials IS radioactive decay - an active expulsion of gamma rays, among others (I’m no expert). When my grandmother was suffering from cancer back in the 30’s, the accepted “radiation treatment” was to strap a piece of radium to the body over the affected area (the strap being lead-lined, of course. The result, as in my grandmother’s case, was usually a hole burned through the body, along with a healthy dose of radiation sickness.

While the radioactivity of the type of material used for “treatment” is probably far greater than the material you own, I still wouldn’t want to sleep with it. Nor would I want it constantly pulsing it’s eerie green glow in my vicinity. Call me paranoid, but…

The dose from your marbles is an additional dose. It doesn’t replace the dose from the world you live in. Cumulative radiation dosage does correlate with lots of bad stuff.

How are you going to be using the marbles?

Showing them to friends now and then, and other than that, leave them in a desk drawer? Well, get a metal box for them, what the heck. Probably no big deal, anyway. Square of the distance, and all, pick a drawer you don’t sit next to.

Keep them in your pants pocket all the time? Hmmmm. Naah, probably a bad idea.

Children? Well, I figure the increase in dose over a lifetime is twice as dangerous for a person not half way through a normal lifespan. Me, I wouldn’t let my kid play with them hardly at all. In fact, only enough to avoid the “forbidden object” taint that would make them steal the little suckers from my desk and eat them.

By the way, don’t eat them.


Granite used in building construction is probably worse for you, in aggragate, than those marbles will ever be. Imagine how many granite buildings you enter in a day (probably mainly relevant if you live in a city with a lot of old construction or an old subway system).

Orange Fiestaware or old dentures (search the archives) might be slightly more dangerous, but even those relics of the Innocent Era are mainly harmless. Radium-dial watches, another Hot Topic :D, were mainly harmful to those who made them (they licked their paintbrushes, fer chrissakes). I think older TV sets were badly shielded as well, but I’m not so sure about that.

The point is, radiation is a minor threat and mainly inescapable anyway. Your marbles are within epsilon of being totally cold, anyway, but even if they emitted ten times their current level they’d still be harmless.

And just a nitpick: uranium and other materials undergoing radioactive decay do not glow on their own. When found in their natural state, they are often acompanied by trace ammounts of naturally phosphorescent material that glow when interacting with the charged particles released by the decay.

And just another number to add perspective to this debate: the Polonium-210 found in cigaretes can lead to a 8000mR per year addition to your annual dose if you have a 2 pack a day habit.

How about handling spent depleted uranium ammunition? Or is that an animal for a whole 'nother thread?

DU has a fairly low “specific activity” (number of disintigrations per unit time per unit mass) so consequently, it also has a fairly low dose rate. I don’t know exact numbers, though.

The Free Enterprise, MT, Radon Health Mine

Yep. Go down to a mine full of radon, a radioactive noble gas, for your health. Some people say it’s a cure-all, especially for things like chronic pain.

If those boobs can stay in a hot zone and come out with all their teeth, you have nothing to worry about.

Thought about it a little more, and I’d ballpark it at somewhere less than 1mR/hr, but that’s just an educated guess.

Just don’t carry them in your front pants pockets and play with them at the same time …
The marbles, Fenris!!!


Given the low activity of the those marbles, the biggest danger to eating them would probably be to your kidneys. Uranimum is chemically toxic as well as radioactive, and the chemical toxicity remains even when it’s depleted uranimum.

The real point here is don’t carry them about your person all the time, don’t suck on them like a gumball, and fer gawd’s sake don’t swallow them!

When you and your friends aren’t admiring them keep them in substantial box (lead if you can get it) and store them in areas without a lot of human or animal traffic. Don’t allow children to play with them.

Don’t worry so much.

Thanks, everyone, for the info! A few points:

  1. I was like 99.9 % certain that they weren’t instant radioactive death, but…I just wanted to be sure.

  2. They don’t glow on their own, you have to use shortwave ultraviolet light to get them to light up like a neon sign and that’s absolutely no indication of danger: I’ve got some specimens of Franklinite that light up just about as much and Franklinite (Zinc Iron Manganese Oxide) and is as safe as it gets.

  3. I’m pretty sure it’s .2mR/hour. The guy my friend bought ‘em from doesn’t say so, but I looked on eBay and someone else selling th’ things say “Radioactivity on these is @ 250 CPM per Marble (@ .04 mR/Hr depending on counter and probe type).” so it’s safe to assume he was using /hr too. The photos on eBay has shows the giger counter’s microphone-looking-dealie about ohh…say 1 inch at most from the stack of marbles.

  4. I’d intended to keep 'em on a shelf in the living room with some fluoresent rocks. The shelf is at least 2-4 feet from the nearest chair. (Assuming they weren’t instant radioactive death. :smiley: )

  5. I have no intention of A)eating them, B) grinding them into powder and snorting them, C) putting them in my pocket (with or without fondling :wink: D) using them as ben-wa balls .



If you want reassurance on this, there’s a very active collecting circuit for uranium glass (a.k.a. vaseline glass) in far larger forms than a few marbles. See, for instance, Vaseline Glass Collectors Inc. or the Japan Uranium Glass Collectors Club . The general view among collectors is that the stuff is fine as long as youre not planning to grind it up and breathe it, or have long-term skin contact. I have quite a lot of it about, but as Triskadecamus says, it mostly sits in its cupboard and only comes out occasionally for me to bore guests by demonstrating the fluorescence.

Here’s the Master’s column Derleth referred to: Is uranium added to false teeth to give them a natural glow?