Re: Radium on watch dials

["Otto G. Raabe" <ograabe@ucdavis.edu>]

February 2, 2001
Davis, CA

Dear Wayne:

Collectors of old watches need to be aware that they should avoid ingestion
of paint that may be flaking off the watches. The paint dust could
contaminate the collection and be passed from hand to mouth. Good
cleanliness in handling the collection is important, but swipes need to be
taken and evaluated with a radiation detector to determine if serious
contamination exists. 

Radon gas emitted from the watches is probably not a major problem in a
relatively well ventilated area, but the radon levels in confined spaces
could be significantly elevated and they should be measured to ensure that
they are less than 10 pCi/L.  Of course this depends on how many watches
are in the collection. 

Another issue is the penetrating beta-gamma radiation emitted from the
radium dials. A survey should be taken of the collection to see if the
radiation levels around it are within acceptable limits. It is reasonable
to avoid putting a collection in a location where people tend to spend much
time, such as in a sitting or dining room. But radiation measurements
should be made to ascertain what the level are where people can be exposed.
The amount of time spent near the collection is a key factor determining
the extent of the radiation exposure.

A local university radiation safety officer would probably help you free of
charge to evaluate whether your collection is seriously contaminated or
poses a radon or radiation problem, and can help with the clean-up or
suggest corrective action if necessary. 

As with all radiation issues, safety is a matter of dose. One watch is
probably not a serious problem, but a collection of 100 radium watches
definitely requires some special concern. 

Radiation measurements are needed to determine if a collection is safe,
meaning, within acceptable annual dose limits. Without these measurements
it is not possible to be sure whether a collection would be deemed to be safe.

Otto
	*****************************************************
	Prof. Otto G. Raabe, Ph.D., CHP
	Institute of Toxicology & Environmental Health (ITEH)
	(Street Address: Bldg. 3792, Old Davis Road)
	University of California, Davis, CA 95616
	E-Mail: ograabe@ucdavis.edu
	Phone:(530) 752-7754, FAX:(530) 758-6140
	*****************************************************
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