WATCH COLLECTING AND THE ISSUE OF RADIUM
For those who
don’t know me, in the real world I work in a hospital. Knowing that the
Hamilton Whitney watch I had recently purchased still had its original radium
dial and hands (to provide the ability to see the time in the dark -- although
long since burned out and, hence, dark brown), I took a trip down to the
radiology department to see whether or not the radium retained any level of radioactivity.
Big mistake!
The department
director took out the department’s Geiger Counter to take the readings. It
buzzed like crazy! In no uncertain terms she chastised me for wearing the
watch. A radiologist I know was walking nearby and heard her comments. He said
not to hold the watch near my groin -- to be polite -- or sleep with it on lest I raise my hand
near my brain!
The
information provided to me follows.
HERE IS THE
INFORMATION FROM THE GM {GEIGER-MARTIN} COUNTER SURVEY OF YOUR WATCH.
FACE OF
WATCH: 7mR/hr
BACK OF
WATCH: .4mR/hr
3 feet from
face of watch: .o4mR/hr
background
radiation exposure rate: .01 mR/hr
Total emitting
exposure from face of watch, at surface, for a 24 hr period:
168 mR/hr
The half life
of 226Ra is 1600 years. It is the
byproduct of 235Ur (235
Uranium) decay
series. Depending on where you
live in the U.S., the average
radiation
exposure to an individual from naturally occurring radioactivity
(ie: from the
ground) is approximately 100 mrem per year.
I sent this
information to the CDC (from its website) in the form of the following email.
Hello,
I collect
older watches and recently purchased a wristwatch from the 1930s that I had
tested with a Geiger counter because I was told it had a radium dial. The data
I received bears this out and follows below.
My question:
Is this watch safe to wear on a limited (i.e., less than 5 times/month)?
Thanks for
your anticipated help on this question.
The response I
received follows.
Dear Mr.
Berns,
We received
your e-mail request asking whether it is safe to wear a radium dial wristwatch
5 times a month. We would not
recommend you wearing the watch due to the additional radiation exposure it
will give you. Also, you should
check the bezel to see if it is cracked since the radon gas the watch produces
can escape through cracks and that would give you additional exposure from
breathing in the radon.
Radium decays into several radionuclides and so the material on
your watch is a combination of those. They emit alpha, beta, and gamma
radiation, and it is the beta and gamma that are being measured on the face and
the gamma that is being measured on the back. The alpha radiation cannot penetrate the case, so it does
not add to your exposure if the material is contained. If the bezel is cracked,
the radon gas you breath in also emits alpharadiation.
If you decide
to wear the watch anyway, you should limit your exposure time since the
radiation dose rate multiplied by the time gives the total radiation dose. For this reason, it is the total
wearing time and not the number of times worn that is important. Please do not sleep with the watch on
since placing it close to your face for many hours and days could give you a
large radiation dose. Storage
should be at good distance away and inside a sealed container as a double guard
against any radon gas that might leak out. If you decide to dispose of the watch, you may want to
contact your state health department since radium is regulated by the
individual states and not the federal government.
I might be ignorant but I’m not stupid! This was too much
information to ignore. I carefully shipped the dial and hands to a professional
watch restoration company and had all of the radium removed. I presume it was
done in compliance with all necessary safety precautions.