This topic has been well discussed over the past year or so, catalyzed by an article from the UK about a high count coming from a collection of old radium pocket watches that were stored in a small, poorly ventilated space.
Fears about radiation exposure from vintage watches are largely overblown. For some perspective, I wrote this on the watchuseek forum several months ago:
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As this is an interesting "Topic du Jour", I'd like to dig a little deeper.
As luck would have it, I coincidentally bought my first radiation detector very recently, and have been testing various watches from my collection. One of the things that has quickly become clear is that there are radical differences between readings taken right on top of the crystal, and those taken in other locations. So, to use one example, I have an Eterna that is quite "hot". Below are the various results, taken with a high-quality Soeks detector, and using readings in μSv/h (i.e. microsieverts/hour). Note that microsieverts are 1000 smaller than millesieverts, so be careful not to confuse the two while pondering any related results. To be clear, the reading of 15.0 μSv/h (noted below) is equivalent to 0.015 mSv/h.
– directly above crystal = 15.0 μSv/h
– 4" above crystal = 2.90
– directly on the case back = 3.45
– adjacent to the watch = 0.60
So, while 15 μSv/h is a high reading, it is quite clear that even if one were to wear such a watch regularly, the actual accumulated dose would need to be calculated using a far lower level. That is not to say that it would necessarily be "safe", but I believe that it is important not to overreact to the readings taken directly from a dial, or just above the crystal, as no one would be that close to the crystal, or if they somehow were, it wouldn't be for any meaningful length of time.
What interests me the most is how one might calculate, with reasonable accuracy, what sort of dose prolonged exposure to such a watch would produce. For a bit of context, I am going to quote an apparent expert named Mark Foreman, who was responding to a Fukushima thread on another forum a few years ago. Although an event like that and wearing a vintage watch are obviously not closely analogous, I do think that he sheds some light on the topic with his response.
"I would say that 6.7 microSv is not a super nasty radiation field. But it is higher than the occupational limit for an area which the general public has free and easy access to.
If you were to spend 40 hours a week, 52 weeks a year in such a place you would get a 14 mSv dose which is legal for a radiation worker but is on the limit of what you can get in the UK without triggering an investigation of your exposure by the state. That occurs at 15 mSv per year.
In Sweden I think that if you go over 7 mSv in two months or some similar dose then you have to write a letter to SSM explaining what you have done, if you were to stay in this hot spot for two months your exposure would be well below this trigger dose.
At 14 mSv per year you would have to be a classified worker by UK law as you would get more than one third of the occupational limit (20 mSv) per year. This would require you to be placed under medical supervision and you would have to have regular blood tests.
On the other hand this dose is very unlikely to cause any illness unless you remained there a very long time, if you were to spend 20 years in such a hot spot you would clock up 280 mSv which would give you a one on 71 chance of inducing a cancer."
On the same thread, and still using 6.7 uVs/hr as a baseline, Frank Duncan (Chemist, retired, Radiation Safety Officer, retired, Class III Licensed Radiographer in Louisiana, retired) states:
"6.7 μSv/hr=0.77mR/hr so this is above background but well below anything dangerous. You will experience no ill effects from being in a radiation field this low. In the US, you are allowed up to 2mR/hr exposure."
Note that mR/hr is another type of measurement (milliroentgens per hour), but the point should be clear. So, using my Eterna example above, even the close proximity of the wrist to the case back would produce an exposure of roughly half the 6.7 μSv/h discussed by the experts. I therefore infer that even if worn regularly, a relatively "hot" vintage watch would produce only a minuscule cancer risk.
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Those interested can read the full thread here, as it addresses the related issue of radon gas, as well:
https://forums.watchuseek.com/f11/radium-study-well-dang-4735359.htmlClick to expand...