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Answer to Question #6450 Submitted to "Ask the Experts"Category: Consumer Products — Watches, Clocks, and other Glow-in-the-Dark The following question was answered by an expert in the appropriate field: Q
I recently added a vintage watch to my collection. Below the 6 on the watch dial it is marked "T<25." I believe that this means that fewer than 25 millicuries of radioactive tritium was used on the hands and dial, but I'm not sure. Is this watch safe to wear on a daily basis or even at all? There appears to be no flaking and the crystal is intact.
A
The first question is, How old is the watch and does it actually contain tritium? Older watches may contain radioluminescent paints containing radium-226 or, in some cases, strontium-90. These more hazardous radionuclides were replaced by tritium a number of years back. Tritium, which occurs naturally in our environment, is a radioactive form of hydrogen that emits a very weak beta ray, sufficient to produce luminescence. Because the beta ray is so weak (that is, has little energy), tritium has very low radiotoxicity, and the beta ray would not penetrate the intact crystal of the watch. So the hazard from tritium would be negligible. So how can you rule out radium-226 or strontium-90? If you have access to a Geiger counter, these radionuclides will produce a reading external to the watch. If you do not have access to a Geiger counter, you might try calling your local state radiation control program or the radiation safety officer at a nearby university. If the watch contains tritium, wear it without worry.
Answer posted on May 10, 2007. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.
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