Answer to Question #1796 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:

I collect stainless steel watches. As steel is produced, many different elements are added, such as vanadium or hafnium. In doing so, does it increase the overall radioactive makeup of the steel? In your opinion, would wearing a stainless steel watch for 18 hours a day pose any greater risk than normal background radiation?

Although you are correct in indicating that there could be many additives to the steel that is used for watch production, the only radioactivity that may exist would be due to the use of radioactive materials to illuminate the watch face itself. The use and production of watches have changed dramatically since World War II, when ²²⁶Ra used to be incorporated into timepieces, compasses, and other products like gauges and instrument dials to illuminate dials. With the development of the nuclear industry over the years, today the most common artificially produced radionuclides are tritium (hydrogen-3 [³H]) and promethium-147 (¹⁴⁷Pm). The average annual exposure from wearing a watch containing either ³H or ¹⁴⁷Pm is estimated to be between 0.04 and 1 millirem per year (source: NCRP Report 95, "Radiation Exposure of the U.S. Population from Consumer Products and Miscellaneous Sources"), which is far below the annual average exposure from background radiation of about 300 millirem per year.

Cynthia Jones, PhD
Senior Advisor for Materials
U.S. NRC

Answer posted on April 17, 2002. 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.