Mercury Risk in CFLs: The Facts

The author of today’s post, John Balbus, M.D., is Chief Health Officer at Environmental Defense.

Compact Fluorescent Light BulbCompact fluorescent light bulbs (CFLs) use dramatically less energy than incandescent bulbs and reduce greenhouse gas emissions. But they also contain mercury – a dangerous toxin.

What if you drop a CFL and it breaks? How much trouble are you in?

Despite some alarming news reports, you don’t have much to worry about. If a CFL breaks, some of the mercury that’s contained in the bulb will evaporate into the air. How much? It’s hard to be certain, but one study [PDF] looking at long tubular fluorescent bulbs found that over a two week period, only 17 to 40 percent of the mercury in the bulb evaporated. The rest remained stuck in the bulb. Roughly one-third of the mercury that evaporated did so in the first eight hours after the breakage; the rest seeped out slowly over the remainder of the study period.

The amount of mercury in a CFL is very small, only 4-5 milligrams. This is almost one thousand times less than what was in mercury thermometers! So, let’s assume that what happens with CFLs is comparable to what happens with tubular fluorescents. If a bulb breaks, only 0.67 milligrams of mercury (one-third of 40 percent of 5 milligrams) might become airborne in the room during the first eight hours, and only a fraction of that would be breathed in. In short, the exposure from breaking a compact fluorescent bulb is in about the same range as the exposure from eating a can or two of tuna fish. (See our list of "Best and Worst Seafood Choices" for more on mercury in fish.)

The tiny amount of mercury you’re exposed to when breaking a CFL is extremely unlikely to cause any ill effects, noticeable or otherwise. But how do you minimize even this tiny amount of risk?

Remove children and pets from the room, and then clean up the broken bulb as quickly as possible. First, increase the ventilation in the room where the bulb broke by opening windows and doors. Then use index cards or other stiff paper to pick up the broken pieces of glass and any visible mercury. Don’t use your bare hands, and don’t use a vacuum cleaner because this can disperse the mercury more widely. Once you’ve gotten up the big pieces, use something sticky like duct tape to get up smaller pieces and dust. To be extra safe, stay out of the area for a few hours to let any remaining mercury disperse.

So what does mercury poisoning do to you, anyway? The symptoms are primarily neurological. A low level exposure (like if you broke a dozen CFLs in your house every day for a couple of weeks) would cause insidious symptoms – fatigue, memory problems, difficulty concentrating, and perhaps some mild clumsiness. Higher exposures could give tremors, and mood or emotional disturbances. But this is never going to happen from dropping one CFL!

Because they contain mercury, it’s best to recycle CFLs ( can tell you how), or bring them to your local Household Hazardous Waste (HHW) collection site. I’ve got five bulbs wrapped in bubble wrap in my basement, waiting for me to get a chance to take them to the county HHW site. But if you can’t do that, you should seal used bulbs in a plastic bag before placing them in your regular trash.

And if despite your best efforts the bulbs end up breaking in a landfill, using CFLs should still cause a net decrease in mercury in the environment. Why? Because they so dramatically reduce energy use, and coal-generated electricity releases much more mercury than a CFL ever could.

The phrase "contains mercury" sounds alarming, but there is very little risk in the tiny amount of mercury in CFLs, and the benefit to the environment of using them is huge. To learn more about switching to CFLs, visit our guide to making the switch.

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  1. KristinaMRichardson
    Posted October 7, 2007 at 11:08 pm | Permalink

    I found lots of useful information on CFLs including what to do if one breaks, how to dispose of them, and the difference between color temperatures at

  2. lees
    Posted March 13, 2008 at 6:54 pm | Permalink

    >>Because they so dramatically reduce energy use, and coal-generated electricity releases much more mercury than a CFL ever could.<<

    This, unfortunately, is where Mr. Balbus strays into “I-read-it-somewhere” territory.

    The figure often cited (the EPA, more than one coal industry group, and various researchers) for coal plant mercury pollution is .0234 milligrams/kWh of *coal* generated power ( Coal contributes slightly over 50% of our energy needs in the US. The burden nationwide, on average, is then .0117 mg/kWh.Yes, you may burn 80% or 90% coal in your light bulbs, but as a nation, the .0117 number is the one to use when evaluating widespread adoption. This means a 22W CFL (about equivalent to a 100W incandescent in light emission) with a rated life of 6000 hours will, on average, represent about 1.5mg of mercury emissions from a coal plant in its rated lifetime. A 100W incandescent will represent an emission of about 7mg in the same time period. At the end of that life, the CFL will put around 4mg (perhaps much higher in some brands and lower in others) plus 1.5mg into the environment. We can argue all day about which form of mercury is worse, but first lets look at the myth that CFL’s use less mercury.

    To produce purified mercury in a CFL, the extraction process releases about .4mg for every milligram produced into the waterways, atmosphere, and soil as waste. This is a well-established worldwide average that includes many processes, both crude and hi-tech. This means that the 4mg in the CFL actually represents 5.6mg of mercury that enters our environment. Adding the coal energy contribution means the CFL’s account for 7.1mg versus 7mg for incandescents.

    Add to this the Lawrence Livermore Laboratories study that concluded that the average CFL life is reduced by 50% where they are turned on and off every hour and the mercury contribution goes up to a whopping 13.6mg or so. The reduction in incandescent life for the same use model (20%) does not affect its mercury consumption and it remains at 7mg or so. The same study concluded that a 30 minute use model reduced the CFL life by 85%…which would mean CFL’s would use ..gulp.. 38.8mg of mercury by the time the rated life of the CFL was reached…compared to the 7mg used by the incandescents.

    These are real numbers. CFL’s can offer significant energy savings in general. However, the thrust of a lot of pro-CFL articles in addressing mercury emissions is completely unfettered by reality by claiming less mercury pollution is generated through CFL adoption. CFL’s will use a lot more mercury than incandescents, period. How unhealthy that mercury is is a valid debate, however.

  3. patdecat
    Posted July 6, 2008 at 11:51 am | Permalink

    Compact fluorescents bulbs, now that is a “GREAT IDEA” …. Hum now the last time I looked at a pack of Compact Fluorescent bulbs I noticed two things; 1. Made in China and 2. Contains mercury (please dispose of in accordance to local laws) .

    Kind of interesting that when you Global Warming Alarmists are in favor of something you will bend over backwards to excuse and play down and ill effects of what you are pimping. Say can any of you tell me what China is using to light their homes? It would be interesting to find out that the Chinese might be using the old fashion bulb while they flood our nation and then our landfills with tons of mercury. As a side have any of you ever considered that maybe running Atomic power plants might not have as many problems as you once thought.

  4. Posted July 9, 2008 at 1:37 pm | Permalink

    > Say can any of you tell me what China is using to light their homes?

    The Chinese are using compact fluorescents. In fact, they have agreed to phase out incandescent bulbs entirely – they figure it will take about 10 years. They are the first developing nation to make this commitment:

  5. patdecat
    Posted July 10, 2008 at 12:42 pm | Permalink

    Well I guess if the Chinese are using mercury filled bulbs then the bulbs got to be all good because we all know how well they treat their people and care about the environment. Fact is mercury is still toxic to a humans just as asbestos is toxic and there were many applications were asbestos was used where it was completely contained. If we use the bend over backward reasoning for why it is safe to use CFL then we should mandate that all homes install asbestos siding because as long as you do not damage the siding then the asbestos is completely harmless.

    Good for the Chinese ,gosh darn it, they have a much less polluted country then the US. Why the way some of the blame America first and always crowd tend make one think that China is cleanest nation on the earth and that they can do no wrong when it comes to pollution as a matter of fact the only nation that contributes to the junk science of Climate change is the US.

  6. sarah
    Posted January 14, 2009 at 1:26 pm | Permalink

    Great blog. Great comments. True that the CFLs contain small amounts of mercury, but when everyone starts to dispose of these and they hit our landfills and aquifers that’s where the problems are going to start. We have a solution to the disposal of CFLs and fluorescent tube lighting. We have a machine that crushes and safely extracts the mercury.

    It is called the E-Lampinator.

    Check out our website.

  7. Posted January 12, 2010 at 2:54 am | Permalink

    I agree with everything you posted in this entry, I’m a loyal reader so please keep updating so often!