I agree Radon gas is an issue. I remember that I once got an e-mail of someone working at an environmental agency in Norway. He wanted some help on an issue with determining a statistical relationship between soil / rock types and measured Radon levels in houses. Now I'm neither an expert on statistics or radioactivity, but I had developed a highly automated tool in a much used Geographical Information System (the GIS program ArcView by ESRI, the "Microsoft" of the GIS IT world) that allowed you to interpolate measurements like that. That's why he came to me.
Originally Posted by Mark Layne
Anyway, back to your remark: Although the measurements showed no immediate concerns with moderate usage of 4 hours / week, a cumulative exposure of an unprotected Ektar lens 24 hours a day, 365 days a year at close proximity, WILL cross the 1000 microSV safety zone as determined by law.
It's probably not without reason many of these old lenses show a brownish radiation damage to the lens, as described by Michael Briggs here:
So, all in all, I would keep it stored safely when not in use...
And don't store all your films next to it!
Originally Posted by Marco B
I have an old Minolta 28mm f2.5 MC W. Rokkor SI lens that apparently was manufactured with rare earth elements (lanthanum & thorium). The glass has yellowed and I've read (in the following link) that exposing the lens to UV light can help remove that. I haven't tried to remove the yellowing, but, this is simply a fantastic lens with b&w film. One of my favorites.
There is some interesting info here regarding radioactive Kodak lenses, among others: http://www.camerapedia.org/wiki/Radioactive .
Marco, I agree with you on th erelative "dangers2 of Aero-Ektar use and fondling.
But I would be extremely sceptical about interpolating anything to do with the bedrock of Norway. I've worked here as a geologist for 25 years, and there are daily surprises! I think Statens Strålevern might need a little bit more geological competence in their numbers - if the oil boom ends, I'll send them a note.
-- Ole Tjugen, Luddite Elitist
I wouldn't worry at all about this level of radiation. To quote from the Health Physics Society position statement on radiation:
"There is substantial and convincing scientific evidence for health risks following high-dose
exposures. However, below 0.05–0.10 sV (which includes occupational and environmental
exposures), risks of health effects are either too small to be observed or are nonexistent."
The measured dosage you listed is 0.00027 sieverts.
Don't forget that the existing regulations which limit exposure aren't the levels at which the danger starts. They are the values where danger starts divided by some very very large fudge factor! In your case, the Netherlands government chose a fudge factor (safety factor) of 50x.
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There are fudge factors, and then there are safety factors...
Basically, there are three different kinds of effects of radioactivity: Acute, accumulated, and genetic. Or "somatic, teratogenic and genetic", depending on which report you read.
All that says is that there is a certain dose which is very likely to make you sick, which has unfortunately been determined rather precisely through the nuclear bombs of Hirosima and Nagasaki, and the firefighters of Chernobyl.
Then there is a lower dose which will eventually make you sick, as in increasing the risk of cancer at a future time.
Then there's the dose that might might make your children sick, or their children again, or...
As I wrote we have a fair idea of the acute dose. But 60-odd years is far too short a time to have any idea about the "safe" dose levels for the other effects - only that there might be one.
Interestingly there is a study that seems to indicate there might actually be a minimum safe exposure too, which makes people receiving at least some radiation healthier than those who live an extremely "screened" life.
-- Ole Tjugen, Luddite Elitist
I had my Aero Ektar checked by the nuclear medicine department at the local hospital and got similar results. Just for curiousity they also tested the lens in the home made box I constructed and it blocked all measurable radiation and so that is what I store it in.
What is it? A 6"x6" x6" cardboard postal carton lined with pieces of "Wonderboard" a cement impregnated fiberglass backing left over from when I installed a tile floor in the kid's bathroom.
With all the radiation detectors all over the highways (Albuquerque has a bunch on interstate 25) I would want to put it in a box with a lot of lead when using it out in the field. Otherwise a bunch of goons in black with machine guns will stop your car. Some people who have had heart imaging done have been pulled over, it's mildly radioactive for a number of days. If their heart was giving them trouble they really had a heart attack after being pushed to the ground and machine guns held at their heads.
Very interesting thread. Doctors are now telling us to get 15-20 minutes of direct sun per day to help with Vitamin D levels to prevent certain cancers. And of course every individual has different tolerances to radiation. Last year the local paper ran a story about a judge well in his 70's. Before law school this guy was famous for having been in the most above ground atom bomb tests in the 50's and early '60s! His reason for volunteering was "It was the closest army base to Las Vegas!". This guy has no ill health effects. The docs ought to study him top to bottom.
Hell. The sun, other cosmic rays, and the various Earthborne types of decay radiation are downright unhealthy compared to that lens!
As a nuke mechanic on subs, I got less exposure when submerged than I did as a civilian driving to work every day in Southern California and living in a 100-year-old house.
Your average Joe or Josephine gets about 300mRem per year from various sources. I think the most exposure I ever got while aboard was not even 40mREM in a year, and this year included a reactor shutdown and a good deal of work in the Rx compartment itself. That is considered well within limits for the Navy, but still relatively high, due to the work in close proximity to the Rx itself. Most of our exposure is from betas that come from the decay of Co-60 that gets lodged in low points in the system or around junctions, pumps, valves, etc. That C-60 is created when the stable Co-59 is impacted by a particle ejected into the primary coolant from the fuel itself. The Co-59 gets into the coolant due to wear. (Valve seats, etc.) So, as you can see, it takes a lot to cause the primary source of exposure for us. Much more than it takes to just get hit directly by sunlight.
Last edited by 2F/2F; 07-26-2008 at 11:35 PM. Click to view previous post history.
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