Re: Radium on watch dials

[Chris Alston <alstonc@odrge.odr.georgetown.edu>]

Wayne

I think that, if I were to be concerned about something, it wouldn't be the 
radiation emitted by the watches, it would be the possibility of paint 
flaking off the dial, and eventually escaping the containment of the watch. 
To me, this would particularly be a concern if the watch were opened for 
repair. Does anyone on Radsafe think that it would be a poor idea, when 
working on such a watch, to wear light gloves, and perhaps use an 
impermeable, absorbent pad, of the kind readily avaiIable in drugstores 
(see the incontinence aisle). After work, the pad and gloves could then be 
folded up, and thrown away. As a long term storage issue, I also wonder 
what there might be in the way of radon emanations.

The indispensable book Environmental Radioactivity, by Eisenbud and Gesell, 
fourth edition (1997), page 318, gives a radium content, for men's watches, 
of 0.01 to 0.36 microcuries (uCi). So, if one had a hundred of them on 
hand, one could have a radioactive materials inventory of 1 to 36 uCi.

I'm not quite sure how to put this amount of radioactivity in proper 
perspective. But, e.g., people's yards have been excavated, and the spoils 
shipped off for burial in special disposal sites, because the top six (6) 
inches of soil contained average amounts of radium equivalent to, say, 
0.00001 uCi per gram (10 picocuries). Or, the owners of a laboratory, or 
industrial facility, where work had been done with radium, would be 
required to demonstrate (at least) that the physical plant was free of 
nonremovable (i.e., fixed, as, stuck to the floors or walls) contamination, 
to an average level of no more than 0.00005 uCi per 16 square inches.

On the other hand, ordinary Brazil nuts (which I love) naturally have an 
amount of radium equivalent to 0.0005 uCi per pound. This is another 
delectable datum from Eisenbud and Gesell, page 147 (though they are not 
responsible for my errors in converting units).

The bottom line is that I would treat the watches with some respect, most 
especially if they are to be repaired. Are those the sounds of a posse of 
Radsafers loading their weapons?

Cheers
cja

P.S. Eisenbud also states that the watches weren't sold after ~1968, in the 
USA, but that the National Council on Radiation Protection and Measurements 
(NCRP) estimated, in 1977, that ten million of them were still in use.


At 12:41 AM 2/2/01 -0600, you wrote:
>While I'm sure that most have ended up in landfills, many are radium
>dials are now accumulating in the hoards of watch collectors and are
>being handled on a regular basis by people who repair watches and
>clocks.  As you might guess, these people have a strong emotional and
>financial bias in believing these dials are perfectly harmless.  As a
>result, I am very skeptical of information that I hear from them.
>
>
>I have written up a web page with what I know on the subject at:
>
>http://www.midwestcs.com/elgin/help/luminous_dials.html
>
>As this web page is currently being read by maybe a half dozen people
>a day, I would really appreciate any comments that you may have.

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