[vyoufinder]

Your statement reads as if the "boom" is over. Utah is gearing up for another uranium boom, from what I understand.


Steve

The big boom of the 80's is what I was referring to but yes, the fact that only recently it's become profitable to mine again. For years, people would joke about being rich because they owned mining claims... and now they're actually getting a few bucks for the ones who know they own them. Others, philantropists, are buying them for the sake of protecting the area, but as you might suspect, we'll need more of those and it only takes a few people to destroy an area for decades, centuries.. wait.. until beyond the scope of humanity? I guess the benefit is that some stockholders will gt even more insanely wealthy than they already are on the way, so we can all feel good about that.. Oh ya, and some poor schmuck will be able to feed his family for a few years before he dies miserably, leaving them a pension that will last a few years after he's gone.

[dConvert]

For anyone curious about alpha, beta, and gamma radiation, I had a Kodak Ektar and two 50mm Super Takumars that I tested with a geiger counter.

Kodak Instamatic Ektar lens: 50 mR/hr with no barrier.
Super Takumar lens: 500+ mR/hr with no barrier.
Super Takumar lens: 250 mR/hr with a plastic or aluminum rear cap barrier.
Super Takumar lens: 100 mR/hr with a lead barrier.

The ʻno barrierʻ readings are mostly alpha particles.
The ʻplastic or metal capʻ readings are mostly beta.
The ʻlead barrierʻ can only be gamma particles.

I donated two of the lesser lenses to our schoolʻs science department for chem and physics classes.

Surely the no barrier readings include the beta & gamma sources which on the numbers you give (ignoring the +) constitute half the counts. Likewise the readings with the cap would include gamma. Giving:
100 mR/hr Gamma
150 mR/Hr Beta
250+ mR/Hr Alpha


Using the whole body weighting factor that converts to (moving to SI units)
1mSv Gamma
1.5 mSv Beta
2.5+ mSv Alpha


Even totaled that's well below the 0.1Sv threshold for detectable chromosome change. Unless you like licking your lenses the Alpha can be ignored - the bodies outer layer of dead skin stops most of this.

[vyoufinder]

Wow! I have never seen any K-mount lens on the standard lists. The conventional word is that thoriated glass was illegal by the mid-1970s.


Steve

(...FWIW, I have a lens that is not on the standard lists, but which I suspect is radioactive...)

Thoriated glass was used and allowed up through the late 80's. My K mount 50mm 1:1.4 is radioactive. I also have an M 50mm 1:2 which was yellowed and cleared using UV light, so I'm pretty sure it is too (it's early, all metal version.)

https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1717/nureg-1717.pdf (see: 3-285)

There is definitely a risk. According to U.S. Nuclear Division's Office of Nuclear Regulatory research, the risk may even be "substantial."

[MarkJerling]

Thoriated glass was used and allowed up through the late 80's. My K mount 50mm 1:1.4 is radioactive. I also have an M 50mm 1:2 which was yellowed and cleared using UV light, so I'm pretty sure it is too (it's early, all metal version.)

https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1717/nureg-1717.pdf (see: 3-285)

There is definitely a risk. According to U.S. Nuclear Division's Office of Nuclear Regulatory research, the risk may even be "substantial."

So, looking at your source material, that states that, if you were to spend a thousand hours per year looking through your camera lens (that's 2.73 hours per day, every day of the year, or, 19.23 hours per week) you would be exposed to a total of 0.2 mSv/yr. That is the equivalent of about 5 or 6 intercontinental flights a year or 2 chest x-rays. One CT-scan is 20mSv, so you'd have to look through your lens for 10,000 hours (There's 8,760 hours in a year) to get the equivalent exposure as to one CT-scan.

If you were a normal user, and lets assume you have 5 or more lenses, one of which is radioactive, and lets assume you're not a commercial video camera operator, then lets assume you may spend, at most, 2 hours a day looking through your various lenses. Possibly therefore, you may look through your radioactive lens 0.4 hours per day. (24 minutes) That would give you 0.03 mSv/yr which is the same radiation you would receive if you flew from Seattle to Portland (a 55 minute flight) roughly 100 times a year.

Your normal background radiation exposure, in the USA, averages 6.24 mSv per year. If you use your lens for 24 minutes every day, your annual exposure would increase by about 0.5%.
Put another way: If you have granite benches in your kitchen, your annual exposure will be somewhere between 0.005 to 0.18 mSv depending on the type of granite, if you spend 4 hours a day in the Kitchen. It could be argued that going outside and taking photos will be safer for you than spending time in your kitchen.

While there may be a risk, the risk is infinitesimally small and most certainly not "substantial".

---

Last edited by MarkJerling; 11-29-2017 at 03:33 AM.

[pathdoc]

It would make more sense financially if the taxpayers just paid the miners double what they would make mining to stay away.

If you put your money where your mouth is and be sure to exclude every benefit of radioactives from your life, that includes your smoke detectors.

I think we all agree about the importance of managing risk but society's current fixation on safety seems to be creating its own category of danger.

Not so much "safety" as "avoidance of all risk", but I agree completely.

[photoptimist]

If you put your money where your mouth is and be sure to exclude every benefit of radioactives from your life, that includes your smoke detectors.

Exactly!


Moreover, as "dangerous" as uranium & nuclear power seems, I'd wager that coal (mining, burning, and waste disposal) does far more short-term and long-term damage per unit of electrical energy than uranium.

[stevebrot]

Thoriated glass was used and allowed up through the late 80's. My K mount 50mm 1:1.4 is radioactive. I also have an M 50mm 1:2 which was yellowed and cleared using UV light, so I'm pretty sure it is too (it's early, all metal version.)

Per the earlier discussion on this thread, and published accounts on the Web including video, examples of the Pentax-K 50/1.4 have been demonstrated radioactive. These lenses were current product from 1975-1977. As for legality...I will have to do some more research. Whether it was force of law or change in acceptable manufacturing practice, thorium glass essentially disappeared from photographic lenses by the mid-1970s. Your Pentax-M might very well be the ultimate outlier, though I find it strange that Pentax would use exotic glass on what is a fairly pedestrian lens.

If you put your money where your mouth is and be sure to exclude every benefit of radioactives from your life, that includes your smoke detectors.

Exactly!

A bit of information might be helpful here. User vyoufinder lives in eastern Utah where there is a recognized health hazard due to windblown dust from uranium mine tailings. Many residents are quite vigilant about radiation as a result.

I don't have an environmental hazard other than radon on my crawlspace, but have had multiple X-ray procedures, including high resolution CT, in the last year. I too am fairly wary of additional exposure as of late.


Steve

[ZombieArmy]

Exactly!


Moreover, as "dangerous" as uranium & nuclear power seems, I'd wager that coal (mining, burning, and waste disposal) does far more short-term and long-term damage per unit of electrical energy than uranium.

You don't even have to wager, that's an absolute fact.

[vyoufinder]

So, looking at your source material, that states that, if you were to spend a thousand hours per year looking through your camera lens (that's 2.73 hours per day, every day of the year, or, 19.23 hours per week) you would be exposed to a total of 0.2 mSv/yr. That is the equivalent of about 5 or 6 intercontinental flights a year or 2 chest x-rays. One CT-scan is 20mSv, so you'd have to look through your lens for 10,000 hours (There's 8,760 hours in a year) to get the equivalent exposure as to one CT-scan.

If you were a normal user, and lets assume you have 5 or more lenses, one of which is radioactive, and lets assume you're not a commercial video camera operator, then lets assume you may spend, at most, 2 hours a day looking through your various lenses. Possibly therefore, you may look through your radioactive lens 0.4 hours per day. (24 minutes) That would give you 0.03 mSv/yr which is the same radiation you would receive if you flew from Seattle to Portland (a 55 minute flight) roughly 100 times a year.

Your normal background radiation exposure, in the USA, averages 6.24 mSv per year. If you use your lens for 24 minutes every day, your annual exposure would increase by about 0.5%.
Put another way: If you have granite benches in your kitchen, your annual exposure will be somewhere between 0.005 to 0.18 mSv depending on the type of granite, if you spend 4 hours a day in the Kitchen. It could be argued that going outside and taking photos will be safer for you than spending time in your kitchen.

While there may be a risk, the risk is infinitesimally small and most certainly not "substantial".

"Substantial" was a word I quoted from the report. It's not my opinion, though I agree. What you need to keep in mind is that radioactive effects are bad when the levels of exposure accumulate. In other words, the more you are exposed, the more you are at risk. I don't walk through metal detectors at airports for the reasons you listed. A person can easily pass through 5 or 6 xrays on a long international series of connecting flights. I feel I get exposed to enough radiation without them and have spent decades doing photography. I hope to do decades more.. When you add it all up, radioactive lenses might be an issue for someone like me, which is not to say the same is true of you or anyone else. I think people should make up their own minds based on the actual research and what is known about radioactivity and its effects on health.

[MarkJerling]

"Substantial" was a word I quoted from the report. It's not my opinion, though I agree. What you need to keep in mind is that radioactive effects are bad when the levels of exposure accumulate. In other words, the more you are exposed, the more you are at risk. I don't walk through metal detectors at airports for the reasons you listed. A person can easily pass through 5 or 6 xrays on a long international series of connecting flights. I feel I get exposed to enough radiation without them and have spent decades doing photography. I hope to do decades more.. When you add it all up, radioactive lenses might be an issue for someone like me, which is not to say the same is true of you or anyone else. I think people should make up their own minds based on the actual research and what is known about radioactivity and its effects on health.

There's no point scaremongering about these lenses. While I agree that radiation should be avoided, where possible, the simple reality is that regular and normal use of a lens containing Thorium glass elements is an exceedingly low risk.

Some more examples as to low levels of radiation we get from everyday activities:

• Sleeping next to another person = 0.02 mSv/y

• One backscatter wave scan at an airport = 0.001 mSv for about 5 seconds of full body exposure

• Eating one banana per day for a year = 0.036 mSv/yr

• Cooking with natural gas = 10 mSv/yr

• Living in a brick house compared with a wood-frame house = 0.1 mSv/yr

Sleeping next to someone is therefore nearly as dangerous than the likely exposure you'll get from your Takumar lens. Also, stay away from bananas! And don't cook with gas.

[photoptimist]

"Substantial" was a word I quoted from the report. It's not my opinion, though I agree. What you need to keep in mind is that radioactive effects are bad when the levels of exposure accumulate. In other words, the more you are exposed, the more you are at risk. I don't walk through metal detectors at airports for the reasons you listed. A person can easily pass through 5 or 6 xrays on a long international series of connecting flights. I feel I get exposed to enough radiation without them and have spent decades doing photography. I hope to do decades more.. When you add it all up, radioactive lenses might be an issue for someone like me, which is not to say the same is true of you or anyone else. I think people should make up their own minds based on the actual research and what is known about radioactivity and its effects on health.

Fortunately, you've got the math wrong on incremental exposure vs. incremental danger. Each additional exposure to radiation (from another day living at altitude, eating a banana, a day of cooking with gas, using a hot Takumar for an hour, etc.) adds a tiny amount to the risk of cancer regardless of the already accumulated exposure.

Thus radioactive lenses are not an issue for "someone like you." Your increased chance of getting cancer from another hour of use of a hot Takumar is no greater (and no less) than if you were someone who had avoided all forms of excess environmental radiation all your life.

That said, everyone makes their own life choices about high altitude living, brick houses, bananas, etc. Maybe living in Moab is worth a lot of extra radiation to you but using a hot Takumar is not even the tiny amount of added exposure (1 hr of lens use ≈ 1 banana).

[vyoufinder]

Fortunately, you've got the math wrong on incremental exposure vs. incremental danger. Each additional exposure to radiation (from another day living at altitude, eating a banana, a day of cooking with gas, using a hot Takumar for an hour, etc.) adds a tiny amount to the risk of cancer regardless of the already accumulated exposure.

Thus radioactive lenses are not an issue for "someone like you." Your increased chance of getting cancer from another hour of use of a hot Takumar is no greater (and no less) than if you were someone who had avoided all forms of excess environmental radiation all your life.

That said, everyone makes their own life choices about high altitude living, brick houses, bananas, etc. Maybe living in Moab is worth a lot of extra radiation to you but using a hot Takumar is not even the tiny amount of added exposure (1 hr of lens use ≈ 1 banana).

What math? I don't remember doing any math.. I simply quoted what the U.S. Nuclear Regulatory Commission Office of regulatory Research published. Actual numbers published, however:

A serious outdoor photographer is assumed to spend 30 days/yr in the field (average
photographers-10 days/yr) and to carry a camera next to the body for 6 hours per day during
that time. This exposure time should be conservative for most photographers. Based on the
assumed exposure time and the absorbed dose rate, the annual EDE would be 0.02 mSv
(2 mrem). For an average photographer the EDE would be 0.007 mSv (0.7 mrem)
The dose estimate obtained above results from an unknown amount, in weight percent, of
thorium in a lens. If photographic lenses are optically similar to the lenses for television
cameras discussed previously, then a lens may contain about 10% by weight of thorium,
i.e., one-third of the limit on thorium content of 30% by weight allowed under this exemption,
which agrees with the estimate obtained in Section 3.19.3.1. Thus, the annual EDE to an
individual photographer corresponding to the maximum allowable thorium content in a lens
would be about 0.06 mSv (6 mrem).

Now... Carrying 8 lenses, and each higher than example used in estimate, plus sleeping roughly a meter away from them too? Now you can do some math if you like.

[Alex645]

....and as we discuss this, tomorrow Hawaii will be having it's first state-wide nuclear attack warning sirens since the end of the Cold War, as I reduce my diet of fish from increased mercury and evidence of the effects of the Fukushima Nuclear Power plant disaster.

For the first time since the end of the Cold War, Hawaii will test nuclear sirens - CNN

As a teacher, we are told in the event of an attack, we should expect to shelter-in-place for 48 hours. Reminds me of Kennedy/Khrushchev/Cuba when I was in kindergarten in San Diego and we had dog tags and nuke attack drills...but I digress.....

[photoptimist]

What math? I don't remember doing any math.. I simply quoted what the U.S. Nuclear Regulatory Commission Office of regulatory Research published. Actual numbers published, however:

A serious outdoor photographer is assumed to spend 30 days/yr in the field (average
photographers-10 days/yr) and to carry a camera next to the body for 6 hours per day during
that time. This exposure time should be conservative for most photographers. Based on the
assumed exposure time and the absorbed dose rate, the annual EDE would be 0.02 mSv
(2 mrem). For an average photographer the EDE would be 0.007 mSv (0.7 mrem)
The dose estimate obtained above results from an unknown amount, in weight percent, of
thorium in a lens. If photographic lenses are optically similar to the lenses for television
cameras discussed previously, then a lens may contain about 10% by weight of thorium,
i.e., one-third of the limit on thorium content of 30% by weight allowed under this exemption,
which agrees with the estimate obtained in Section 3.19.3.1. Thus, the annual EDE to an
individual photographer corresponding to the maximum allowable thorium content in a lens
would be about 0.06 mSv (6 mrem).

Now... Carrying 8 lenses, and each higher than example used in estimate, plus sleeping roughly a meter away from them too? Now you can do some math if you like.

Interesting.

Sleeping a meter away drops the exposure by probably a factor of 100. Also if you really carried 8 hot lenses if that is even possible, you'd get much less than 8X the dose. Radiation is not like a gas, it's more like a lightbulb. If one lens is behind another lens, you would be significantly shielded.

Anyway, if that is their definition of "substantial" risk, then each extra week one lives at altitude also brings "substantial" risk.

It's obviously a very personal choice of what activities are worth the extra radiation but it helps to understand the numerical magnitudes so that one does not overly fear a minor risk whilst ignoring the truly larger one.

[MarkJerling]

Now... Carrying 8 lenses, and each higher than example used in estimate, plus sleeping roughly a meter away from them too? Now you can do some math if you like.

Radiation drops off in terms of the inverse-square law, so 8 lenses would, if you slept next to them all year round, give you roughly 0.00024 mSv/y. Far safer therefore than sleeping next to a person.
In fact, you'd have to surround yourself with around 600-700 of these lenses to get the same radiation as sleeping next to one person.

I like math.