Panic! Dropped and Broke Thorium Lens

The day has arrived where I accidentally dropped and broke a thorated lens. I have encountered and repaired a few of them, though I understand it is rarely risky as long as you don't drop or eat them. Well, today I accidentally knocked a box of lens parts off the shelf and SHATTERED the thorated element.

I wore mask and gloves when cleaning it up, and used a wet paper towel. Did I deal with this correctly? Should I be worried about thorium dust I may have breathed in as it broke?

Probably have a million other things to worry about. Here in the US lead poisoning, either in the water or in hunting season
Seriously it's not something I would be overly concerned about. You did the right thing in taking precautions.

CámaraLiberada said:

Should I be worried about thorium dust I may have breathed in as it broke?

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Nope. Nothing to worry about.

Sorry about the lens though!

You've handled it as correctly as is possible for an amateur. The level of radioactivity in thoriated lens elements was very low when they were new, though it tends to climb very slowly over time (thorium has decay products that are more active than the parent isotopes); still, the only significant hazard even from dust and fragments of a shattered element are if you get them inside your body, where the alpha particle emissions are a known carcinogen. If you live in a radon zone and have a basement, you're at much higher risk from just living in your house than from cleaning up that broken lens element.

The thorium salt or oxide itself is dissolved into the glass, so it would have been glass dust you'd have inhaled if anything, and that's very unlikely; particles from shattering glass are much too coarse to float in the air (this is a hazard if you're grinding or polishing the lens element, but not for cleaning up a broken piece).

Donald Qualls said:

You've handled it as correctly as is possible for an amateur. The level of radioactivity in thoriated lens elements was very low when they were new, though it tends to climb very slowly over time (thorium has decay products that are more active than the parent isotopes); still, the only significant hazard even from dust and fragments of a shattered element are if you get them inside your body, where the alpha particle emissions are a known carcinogen. If you live in a radon zone and have a basement, you're at much higher risk from just living in your house than from cleaning up that broken lens element.

The thorium salt or oxide itself is dissolved into the glass, so it would have been glass dust you'd have inhaled if anything, and that's very unlikely; particles from shattering glass are much too coarse to float in the air (this is a hazard if you're grinding or polishing the lens element, but not for cleaning up a broken piece).

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Good answer thanks! I don't live in a Radon area, though I still worry about that too.

Did you call your local hazmat to dispose of the glass?

CámaraLiberada said:

Good answer thanks! I don't live in a Radon area, though I still worry about that too.

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Don't ever fly in a plane then. The background radiation there is way more than a radioactive lens.

beemermark said:

Did you call your local hazmat to dispose of the glass?

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I'm not a nuclear materials expert, but I don't recall thoriated glass requiring hazmat disposal. The thorium and its decay products are bound in the glass, and the total amount of radioactivity is quite small -- less than what's in a Californium-based smoke detector, if I've understood correctly.

I'd be much more concerned (given the relative numbers in use) with compact fluorescent light bulbs going into landfills, since the mercury from those isn't captive the way the thorium and products are in even a shattered lens.

The problem with these types of radiation emitters is if you ingest them. Outside your body they are not strong enough to be an issue. Alpha particles from thorium are absorbed in the first few layers of skin. The daughter products emit betas and gammas, but I don't think the daughter products are strong enough to be an issue unless you had it actually in your body. See the links below on how the possession of a thoriated lens is exempt from controls on radioactive products, but the manufacture is not.

This is why comparisons to the background radiation in an airplane are not totally helpful. You can't ingest the background radiation. I agree that just having a thoriated lens around is not hazardous, but I also agree with wearing a mask to clean it up, just in case.

Old farts will remember Coleman lantern mantles, which also used to have thorium. Again, safe to possess, but don't lick it. I don't know about disposal requirements. You could just box it up and take it to the hazmat facility, not call them to come clean it up.

Merely shattering glass from one impact will not generate enough dust to be a problem. You would have to deliberately crush it, or grind the lens. Presumably a major reason companies stopped using thorium oxide in lenses is all the radioactive dust that would be generated in manufacturing.

https://www.orau.org/health-physics.../products-containing-thorium/camera-lens.html

https://www.epa.gov/radiation/radionuclide-basics-thorium

reddesert said:

Presumably a major reason companies stopped using thorium oxide in lenses is all the radioactive dust that would be generated in manufacturing.

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And yet thoriated tungsten rods are still made and sold for TIG welding -- where the welding itself vaporizes tiny amounts of thorium (oxide) and sharpening the rods both produces radioactive dust and collects it in the sharpening machine. Thorium mantles were discontinued decades ago, as were thoriated lenses -- but thoriated tungsten rods are still manufactured and sold, despite the fact they aren't necessary for TIG welding (they make the arc slightly easier to start and maintain, and compensating for this makes the welding machine a little more expensive).

Donald Qualls said:

Thorium mantles were discontinued decades ago

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Do the mantles sold today use a different element?

koraks said:

Do the mantles sold today use a different element?

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There may be some Chinese imports that still contain thorium salts, but according to Google all the common ones (including the ones Coleman sells) have switched to yttrium (along with cerium that was always there alongside the thorium). The claim is they last longer than the thoriated mantles (while producing half a stop less light), but are no more radioactive than untreated silk. My recent experience is that at least the cheaper mantles are hard to get burned to the ash bulb that makes the light without getting holes (bought a lantern at a yard sale this past summer) -- but I might just be out of practice; I last owned a gas lantern in the early 1980s.

Thanks; I was just wondering. I still have one of those lanterns and some of the mantles I bought 20+ years ago. Pretty sure those are still the old thorium ones. I liked that lamp; it was nice. Good memories.

reddesert said:

The problem with these types of radiation emitters is if you ingest them.

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Now you tell me!

pentaxuser

You have nothing to worry about. Enjoy the repaired lens.

Sirius Glass said:

Enjoy the repaired lens.

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Maybe it's a good idea to read post #1 again.

Good thing you were careful and clearned up the glass. It sounds very unlikely you have inhaled any dust. I wouldn't worry.

Beside alfa and beta particles thoriated glass will also emit more dangerous radiation; gamma particles from it's decay products and, I believe, X-ray through bremsstrahlung. The gamma radiation will increase over a number of decades until it drops again.

I can measure 6μSv/h from one of my favourite lenses. If I carried it around in my pocket at all times the dose I recieved would be larger than the allowed annual dose for a radiation worker in the US. And I would get a significantly increased lifetime risk of cancer.

So the lens lives in a lead bag. Probably overkill, but an easy precaution. It comes out every now and then and makes fine photos, though,

Thanks for all of the great answers. I guess I just won't worry too much about it then.