Answer to Question #8650 Submitted to "Ask the Experts"

I was a little alarmed by the information about older watches in the fact sheet on radioactive materials in consumer products (http://hps.org/documents/consumerproducts.pdf). I have a pendant that is the inside of an old watch. You see a small (about 2 cm diameter) silver disk with two cogs that you can move. It was explained to me when I bought it that the inside of old watches was meant to represent the heavens—the  larger golden cog was the sun, the smaller silver one was the moon, and when you held it up to the light, you saw little pinpricks for stars and ruby ones for planets. I have had this piece of jewelry since about 1995. I have handled it many times, as have many others, including kids. I'm wondering if I have to be concerned about this piece and about anything else it may have touched.

If I understand the fact sheet correctly, the radioactive material is in what may reflect light—the face or the hands—which would mean that what my pendant is made of is unlikely to be dangerous. However, I just want to make sure.

In any case, as long as the watch is intact, the material is not touched, and (especially) the material is not ingested, you are safe. Again, for more specific analysis you should contact experts in radiation measurement; appropriate contacts would be your local university, hospital radiation safety officer, or health department, where they should be able to assist you.

I am attaching several URLs from several organizations, some of which provide additional links, which may be helpful:

The U.S. Environmental Protection Agency has an excellent and informative site.

The U.S. Nuclear Regulatory Commission has a publication (NUREG-1717) that discusses such products.

An interesting site is the Oak Ridge Associated Universities website, which discusses jewelry in more detail.

And finally, I will refer you to our own Health Physics Society site, which has many similar questions related to watches. Simply search on "watches."