Answer to Question #5304 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 work in a warehouse that recently started carrying light bulbs which contain ¹⁴⁷Pm. The exact writing on the package says: "0.33 Micro-Ci ¹⁴⁷Pm." Do these light bulbs pose any danger to the employees who handle them? What if an entire pallet of these bulbs were dropped, resulting in several broken units? We have no Material Safety Data Sheet (MSDS) data on this material. I am a little curious, and a little worried.

The light bulbs that you refer to are most likely "Compact Fluorescent" bulbs. These light bulbs may contain the radioactive material promethium-147 (¹⁴⁷Pm) in a "sealed glow (starter) switch." The amount of ¹⁴⁷Pm in each bulb can be 0.33 microcuries (the same as 330 nanocuries or nanoCi). Such light bulbs also contain mercury metal-vapor and phosphor powder, which are hazardous materials. An example of an MSDS for such light bulbs is at Compact Fluorescent Light Bulb MSDS.

When ¹⁴⁷Pm gives off its radiation, 100 percent of the time it emits a low-energy beta particle (a fast moving electron) that can easily be stopped by the glass or plastic used to make the light bulb. Promethium-147 also gives off a low-energy gamma ray 0.003 percent of the time (or three times in every 100,000 decays). This means that you will never notice any additional radiation from even hundreds of these light bulbs.

If an entire pallet of these bulbs were dropped, resulting in several broken units, the broken glass and mercury vapor are the only health hazards of note, as discussed in the MSDS above.

As a point of interest, the Nuclear Regulatory Commission (in 10 CFR 30.15) states that any individual can own and wear a timepiece with 100 microcuries of ¹⁴⁷Pm per watch or own and use 200 microcuries of ¹⁴⁷Pm per any other timepiece, with no undue risk. The radiation dose to a homeowner with a clock containing 200 microCi of ¹⁴⁷Pm (600 times the 0.33 microCi) might be 0.004 millirem per year. The average person in the United States gets 365 millirem from natural sources of radiation (e.g., radon) and medical radiation exposure each and every year. More information on ¹⁴⁷Pm can be found at Radioluminescent Paint, by Paul Frame, Oak Ridge Associated Universities.

Lastly, there are no MSDS sheets for radioactive material, except for some chemical compounds of naturally occurring radioactive material like uranium, thorium, and radium.

John P. Hageman, MS, CHP

Answer posted on March 22, 2006. 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.