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Old Mar 12, 2007, 3:45 AM   #1
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I just learned that my smc Pentax 50mm f/1.4 may be one of those lenses that may have the radioactive element thorium in it (probably explains the yellowing I see in the lens). This has me thinking, what will happen if I include this lens with my kit bag if I go to the airport? I love this lens, but I don't want to be banned from flying or marked as some national security threat (lord knows what that could do to my job search efforts).

Has anyone had problems brining the old Takumar primes with thorium to the airport?

This whole radioactive lens deal has me shaken up; I had the rear of the lens about 6 from my eye at one point. I may just part with this lens altogether and try looking for the smc Pentax-M version of this prime, which supposedly doesn't use the radioactive element anymore.
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Old Mar 12, 2007, 4:55 PM   #2
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Thorium is an emitter of Alpha radiation. As such it is not dangerous, unless ingested. Close contact with the material is not dangerous, as human skin provides a sufficient barrier to the radiation. Since the alpha particles are stopped so easily, it is highly unlikely that any radiation detector in use in any airport could possibly detect the presence of thorium in this lens. Keep in mind that radioactive isotopes are used in a myriad of consumer products. Tritium is used in watches to make the hands glow in the dark, and, to the best of my knowledge, has never caused any deaths, or caused anyone to be added to the no-fly list.

Bottom line: If it makes you uncomfortable, sell it. If you keep it, it is safe to fly with, and does not pose a health risk (unless you take it apart and eat it).

Chris
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Old Mar 12, 2007, 5:01 PM   #3
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silverstone wrote:
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Thorium is an emitter of Alpha radiation. As such it is not dangerous, unless ingested. Close contact with the material is not dangerous, as human skin provides a sufficient barrier to the radiation. Since the alpha particles are stopped so easily, it is highly unlikely that any radiation detector in use in any airport could possibly detect the presence of thorium in this lens. Keep in mind that radioactive isotopes are used in a myriad of consumer products. Tritium is used in watches to make the hands glow in the dark, and, to the best of my knowledge, has never caused any deaths, or caused anyone to be added to the no-fly list.

Bottom line: If it makes you uncomfortable, sell it. If you keep it, it is safe to fly with, and does not pose a health risk (unless you take it apart and eat it).

Chris
Just don't mention the word "radiation" when going through security:-)

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Old Mar 15, 2007, 12:52 AM   #4
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my mother was treated with radioactive iodine for her hyperthyroid a month ago.

during the treatment, she was not allowed any close/prolonged human contact as the levels of radiation emitting from her could prove to be dangerous. also, she would be able to set off said radiation detectors at airports.

during the treatment, i still did have some contact with her although not recommended, and i was probably exposed to more radioactive emissions then your lens would give off, but it is still not enough to cause any harm.

for those wondering, my mother has fully recovered and is perfectly fine. and no, she did not glow... or gain the ability to fly.

-b
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Old Mar 16, 2007, 2:41 PM   #5
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You have to love modern medicine. Apparently they now have to make you glow in the dark like the hand on a watch before they can make you better. Was she siwss movement?

Glad she is better.

Why would this radio active stuff be needed in a lens? What did it do?

Thanks,

Robert
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Old Mar 16, 2007, 2:55 PM   #6
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silverstone wrote:
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Tritium is used in watches to make the hands glow in the dark, and, to the best of my knowledge, has never caused any deaths, or caused anyone to be added to the no-fly list.
you're correct about tritium but before it they used radium. women were hired to paint it on the watches by hand and they would bring the brush to a point using their mouths and saliva. many died from cancer because of it.

roy
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