The Facts about Light Bulbs and Mercury

Compact fluorescent lights (CFLs) use about a quarter of the electricity of traditional incandescent light bulbs, reducing energy costs for consumers.  By conserving electricity, CFLs also avoid some of the mercury emissions from power plants that burn coal. Burning coal is a far larger source of mercury in our environment and a far bigger risk to our health.  In fact, we’ve calculated that using a CFL results in less than half of the mercury emissions of using a 100 W incandescent light bulb.


However, CFLs themselves contain a small amount of mercury, which has led to some questions about whether they are safe to use. We’ve taken a close look at this issue, and we believe that CFLs are the right choice for those concerned about both their health and their energy bills.

The amount of mercury contained in a CFL is very small — a typical bulb today contains about 3mg.  To put that amount in perspective, there is up to five times that amount of mercury in the watch battery on your wrist; quite notably, between 60 to 200 times that amount of mercury in a single “silver” dental filling in people’s mouths, depending on the size of the filling; 100 to 200 times that amount in the old-style thermometers many people still have in their medicine cabinets; 200 times that amount per switch in the light switches of certain freezers; and about 500 times that amount in thermostats on the walls of people’s homes. (These are conservative estimates based on comparison to a bulb with 5 mg of mercury.) CFLs also use the same technology as the linear fluorescent tubes we have been using in our schools, offices and hospitals for over 50 years. Those tubes can contain up to 100 mg of mercury each.

Still, you may be concerned that a delicate glass bulb is different from the watch on your wrist: if a CFL breaks, some of the mercury inside can escape into your home.  Some news reports have raised concerns that broken CFLs could result in harmful air concentrations of mercury in the room where the bulb is broken, but  these reports are based on worst-case situations, assuming common sense measures (such as ventilating the room) are ignored.   If a bulb does break in your home, don’t panic.  The small amount emitted is unlikely to be harmful, and you can use simple cleanup procedures to further minimize any exposures.  Keep kids away from the breakage, open a window and carefully clean up the pieces and place them in a ziplock bag for proper disposal.  

While it is sensible to handle broken CFLs with care, by far the most important step people can take to reduce mercury exposure in their daily lives is to avoid eating fish contaminated with mercury. Eating fish is the main source of mercury exposure for Americans, and the form of mercury found in fish is more toxic than the form used in CFLs (or other household products).  While fish is part of a healthy diet, people should take care to choose the types of fish which contain the least amount of mercury, particularly if they are pregnant or nursing. NRDC’s website contains recommendations for choosing fish that contain the least amount of mercury. Visit for a printable shopping guide to safe fish.

About the Authors

Noah Long

Legal Director, Western Energy

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