Ask TreeHugger: Is Mercury From a Broken CFL Dangerous?

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Question: I have been in the process of converting to an all CFL household only to find out by trial and error (and some googling) that CFL's fail very quickly in track lighting and recessed fixtures. In my online searches I have stumbled upon some real horror stories about people who have broken the bulbs in their homes which has resulted in thousands of dollars worth of cleanup to remove the mercury.

I did read in the past the post about the quality of various manufacturers, but do you have any information on "best practices" for use and safety/disposal/mercury contamination topics? As far as the mercury information goes - I am not looking for a debate about how much mercury ends up in the environment from other sources.... I just want to know if my kids are going to get mercury poisoning if a bulb breaks in their rooms. Real scientific responses only please.

Response: There has recently been some concern over the possibility that broken CFLs can be an important source of exposures to mercury, a toxic metal and a key component of compact fluorescent lightbulbs (CFLs). Although mercury is a toxic pollutant, mercury exposures from broken CFLs are not likely to harm you and your family. This is due to several factors, including the amount and duration of your exposures and the specific type of mercury that you are exposed to. Mercury in CFLs are present as elemental (or metallic) mercury. Once spilled, you can be exposed to elemental mercury by touching it, after which it can be eaten and/or absorbed through your skin. More importantly for health, you can also be exposed to mercury through the air, as elemental mercury vaporizes readily (essentially becomes a gas) and can thus be inhaled into your lungs. Breathing elemental mercury into your lungs is generally more dangerous than if you ate the mercury or absorbed it through your skin. Once inhaled, the mercury vapor can damage the central nervous system, kidneys, and liver.

These toxic effects are why any mercury spill should be handled carefully, including one that results from a CFL breaking. Having said this, careful handling does not mean that expensive or complicated clean-up of the spill is needed or that you should be worried about you or your family's health, if a CFL were to break in your home.

This is because CFLs contain relatively small amounts of mercury -- EPA estimates this amount to be 4-5 milligrams (mg) in a typical CFL. A spill of this amount of mercury is not likely to present any excess risk to you or your family. A quick back-of-the-envelope calculation shows why. [Note: This example is meant only as a quick and dirty example. It is not intended to represent every case nor every situation.] For example, we could imagine the following scenario:

A CFL containing 5 mg of mercury breaks in your child’s bedroom that has a volume of about 25 m3 (which corresponds to a medium sized bedroom). The entire 5 mg of mercury vaporizes immediately (an unlikely occurrence), resulting in an airborne mercury concentration in this room of 0.2 mg/m3. This concentration will decrease with time, as air in the room leaves and is replaced by air from outside or from a different room. As a result, concentrations of mercury in the room will likely approach zero after about an hour or so.

Under these relatively conservative assumptions, this level and duration of mercury exposure is not likely to be dangerous, as it is lower than the US Occupational Safety and Health Administration (OSHA) standard of 0.05 mg/m3 of metallic mercury vapor averaged over eight hours. [To equate these values, we could estimate the average indoor airborne mercury concentration for 8 hours, beginning post-spill at an estimated starting value of 0.2 mg/m3 and decreasing from there. If one assumes the the air exchanges completely in one hour (a fairly standard assumption), then the 8-hour average concentration would be 0.025 mg/m3.]

Even though mercury from the broken CFL is not likely to be dangerous, it would be wise to take extra precautions to minimize mercury exposures. The US EPA publishes guidelines about the specific steps that you should take to clean up mercury in the event that a CFL breaks in your home. Briefly, EPA recommends that (1) you immediately open windows to reduce mercury concentrations inside your home; (2) you do not touch the spilled mercury; (3) you clean up the broken CFL glass carefully and immediately (but not with your hands or a vacuum cleaner), and (4) you wipe the affected area with a paper towel to remove all glass fragments and mercury. EPA further recommends that you place the paper towel and glass fragments in a sealed plastic bag and bring the sealed bag to your local Household Hazardous Waste (HHW) Collection Site.

Helen Suh MacIntosh is a professor in environmental health at Harvard University and studies how pollution behaves in the environment and how it affects people's health. Please keep in mind that her answers are just her interpretation of available information and should not be taken as the only viewpoint or solution to a problem. Use this column at your own risk. Having said this, please feel free to post any of your environmental health questions to (please use a descriptive email subject line and mention if you want to remain anonymous or not).