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The energy-saving compact fluorecent lamps (CFLs) contain some amount of mercury. If they break, it might be released. I've heard claims that they are really dangerous, and claims that the amount of mercury is completely harmless.

So how dangerous are they, do I need to call a Hazmat team when I break one?

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+1 I've heard contradicting claims on this one as well :) – David Hedlund Mar 1 '11 at 21:40
What about the effects of getting cut by a broken CFL bulb and getting mercury traces injected into your body that way? I just saw a safety bulletin showing a fellows foot after he stepped on a broken CFL bulb... it was disgusting, and he apparently spent something like 2 weeks in the ICU over it as well. – user5275 Nov 14 '11 at 11:32

5 Answers 5

up vote 26 down vote accepted

According to the WHMIS documents (French only) provided by the Commission de la santé et de la sécurité du travail (CSST), you're under no immediate danger.

Here's the relevant passage, translated from French:

Exposure to vapors: Mercury has no scent. As such, we can only detect its presence with instruments. At ambient temperature (20°C), mercury possesses a saturation concentration of 1.6 ppm (13 mg/m³), which is 160 times the occupational exposure limit (0,003 ppm or 0,025 mg/m³). As a result, in the event of a leak or spill in a room, a significant quantity of mercury evaporates and the OEL is easily surpassed. However, in practice, the IDLH (1,2 ppm or 10 mg/m³) is never surpassed, even if it is really near of the saturation concentration.

Put in simpler terms, at ambient temperature, a concentration which would be dangerous to be exposed to for a long period of time is easily reached. However, the concentration at which your health is immediately threatened is rarely reached. There's no reason to panic or to put on an Hazmat suit.

If you break a CFL, just follow the EPA's recommendations on how to clean up a broken CFL:

  • Open the window.
  • Carefully collect the debris.
  • Avoid dermal contact with the broken bulb.
  • Clean the surface thoroughly.
  • Don't keep the debris inside.
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Definitely don't panic. But those specific procedures are more rigorous than those for 90% of the chemicals I use in my house, so I'm not sure I'd consider that perfectly OK and harmless. – Russell Steen Mar 4 '11 at 22:12
@Russell: It's not harmless, by any measure, but the vapors are not immediately dangerous. Take the right precautions and clean it quickly, and you'll be fine. – Borror0 Mar 4 '11 at 22:20
definitely in agreement with you there :), still gave you the +1 – Russell Steen Mar 4 '11 at 22:21
It's also worth noting that even if you DO break a CFL, you're releasing LESS mercury into the atmosphere than you do by using an incandescent bulb in a region that is mostly coal-powered (e.g. most of the US) -… - if you properly recycle your bulbs, a CFL releases no mercury in to the atmosphere, but producing the power to run a bulb does, and an incandescent bulb needs a whole lot more power. – Erik Harris Aug 17 '11 at 0:53

CFLs contain about 4mg of mercury --

The OSHA OK level for mercury is 0.1mg/m3 --

The California limit is 0.05mg/m3 --

Obviously many questions can result from this. Are the legal limits reasonable or too strict? How much does it vary per bulb? In a given space, when a bulb violently shatters, how much mercury of the 4mg particulates over what area?

Let's assume a standard US 8x10x10 room in meters (roughly 2.5x3x3). That's at most 27m3. So 4/27m3 = 0.14mg/m3. That's clearly in excess of the OSHA and CA limits. However, the mercury would not instantly disperse uniformly throughout the room. So while you'd get probably 0 exposure far from it, you'd get more at the distance you'd have to be to say... clean it up.

Note this too from the EPA Clean up guide. Have everyone leave the area, and turn off your AC/Heating. "Dangerous" is a funny term, because it is subjectively defined. We'd consider most chemicals that require those procedures dangerous. Indeed, those standards are typically ones you'd see for chemicals cleaners which require a licences to possess and use.

In addition there is paper --

It basically says that most people will be okay, because the safety regulations are only meant to be used over a long time frame. It doesn't seem to address the fact that one can presume that more than one bulb would break in your house in a lifetime, or the environmental buildup in a house after many years of CFLs with the occasional breakage.

You're also not going to get a perfect clean up every time. Imagine being 30 years from now. You have houses for sale that have had CFLs break periodically or 30 years. Maybe the homeowners cleaned them, maybe they didn't. We're now looking at having a mercury testing done as part of home inspections to buy houses (as seven or eight broken bulbs in the same area would certainly exceed "safe" levels if not cleaned properly). As you can see here, mercury that is not disposed of properly does build up over time.

Also very pertinent is "How dangerous are CFLs compared to other lighting sources?".

If I had to rank them, safest to worst I'd go

  • LEDs (hard plastic, won't shatter)
  • Incandescents (may cut, but won't poison you)
  • CFLs (wont' kill you, but handle with care)
  • Candles & Lamps (burning house down = bad)
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Not a good answer. Mercury cannot continually evaporate because the bulb is not an infinite source, and it can be presumed that air circulates in and out of a residence, so the mercury residue from prior spills should be unmeasurably low, and the basic premises of the answer are wrong. – user1770 Aug 31 '11 at 19:12
@jprete -- The basic premises of the answer are fact, ie - that that amount of mercury in a bulb exceeds the OSHA and California standards. The speculation is presented as such. – Russell Steen Aug 31 '11 at 21:21
@jprete -- I also added a link to the Oregon DEQ, which clearly states that improperly disposal of mercury does lead to a build up over time. So my statement that mercury is likely to build up with each bulb breakage is accurate (if you have verifiable sources otherwise, please post them) – Russell Steen Aug 31 '11 at 21:29
The basic premise of your answer is that multiple breakages over the lifespan of a house result in concentrations that are unsafe. Since the mercury air concentration from one bulb results from evaporation into the air, and since that air eventually circulates out of the house, multiple breakages will only slightly contribute to mercury levels in the house, so the multiple-breakage issue is a red herring. Many more breakages might cause an environmental hazard over a house's lifetime - say, 100 years - but you are not establishing what that rate might be. – user1770 Aug 31 '11 at 21:57
@jprete, unless you can provide references (countering the DEQ link provided) in place of rhetoric, i see no reason to discuss further. I went to the effort to research my answer, I recommend you do the same (and please provide an answer as well). – Russell Steen Sep 1 '11 at 2:52

Wasn't sure on this one myself, so I did some research.

I've come across this explanation, which sounds similar to what was my understanding before, so it's true by confirmation bias:

Exposure to broken CFLs can pose a health risk, especially to a fetus or young child. But don't panic. Open a window, shut off central A/C or forced-air heating, and clear the room for at least 15 minutes as the Environmental Protection Agency recommends. Read "What to Do If a Compact Fluorescent Lightbulb Breaks" for more details. And be sure to keep CFLs out of lamps that could easily tip, especially in rooms used often by children or pregnant women. *

The don't panic, open a window part, especially, seems very plausible.

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"so it's true by confirmation bias" <3 – Borror0 Mar 1 '11 at 21:55
"Don't panic." Wise words indeed. – Scott Mitchell Mar 1 '11 at 22:19
@Scott: So what's the problem with panic? :) – Mike Dunlavey Nov 14 '11 at 18:16

It is important for consumers to realize that CFLs and fluorescent bulbs do contain mercury and require special handling. The mercury vapor can be detrimental to handlers' health—from those involved with handling new bulbs to people involved with storing, packaging and shipping used lamps. Mercury vapor, which can be absorbed through the skin or inhaled, can cause neurological damage, and when it gets into water, it can enter the food chain through fish. Read more about the dangers of mercury exposure here:

If a bulb is broken or burns out, it should be properly cleaned up and recycled—it should not be disposed of in landfills. To reduce the risk for mercury vapor exposure, CFLs and fluorescent lamps should be safely handled, stored and transported to recycling facilities in a package that is proven to effectively contain hazardous mercury vapor. Find out more about how to minimize environmental risks and safely package CFLs here:

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Realistically there is little to worry about from the mercury in a broken CFL

Using the same sources as Russell Steen's post above, I conclude there is little to worry about.

First many CFLs have a lot less than 4mg of mercury. Then only about 10% of the mercury is released when a bulb breaks (the rest is adsorbed onto the surfaces in the bulb and will go away with the broken glass). AS the source says:

Most mercury vapor inside fluorescent light bulbs becomes bound to the inside of the light bulb as it is used. EPA estimates that the rest of the mercury within a CFL – about 11 percent – is released into air or water when it is sent to a landfill, assuming the light bulb is broken

Then you need to take into account the circulation of air in the room. His original calculations assume no air turnover and that all the mercury is released. Under more realistic assumptions the peak concentration in a room will be 0.4mg/27 cubic meters or about 0.015 mg/m3 or substantially less than even the strict Californian standards from occupational exposure (i.e. how much you could be exposed to every day). Even this small level will decline rapidly as fresh air circulates through the room. So the worst case seems to involve lower than occupation standard exposure for a limited period.

As to worries about accumulation, there shouldn't be any. It is mercury vapour and will be swept away with the circulation of air in the room/house. Breaking a mercury thermometer and releasing liquid mercury is much worse (for a start there might be 500mg of mercury and it will stick around for a while releasing vapour which may well build up to a dangerous level if the ventilation is not good). UK sources suggest, though, that even this is not a worry as long as it is handled sensibly

If you break a mercury thermometer or light bulb, some liquid mercury may spill out, but probably very little. Liquid mercury can separate into small beads, which can roll some distance away. You may also be exposed to mercury vapour. However, this small amount of mercury is extremely unlikely to cause problems for your health.

A health protection agency source also offers reassurance:

Exposure to airborne mercury vapour at concentrations near 0.05 milligrams per cubic metre (mg m-3) may result in an onset of mild to moderate symptoms...The concentrations described above of mercury in air are 1000 to 40000 times greater than that which could be produced from the quantities of mercury released from a broken domestic fever thermometer in a room.

Since the amounts released from a CFL bulb are 500-1000 times smaller than this, the immediate risks are probably very small. Moreover all the mercury in a CFL is vapour so there is no liquid mercury to hang around once the air has circulated.

Really high levels of mercury vapour have occasionally been observed in domestic premises but only because large volumes of liquid mercury have been dealt with badly (like by trying to use a vacuum cleaner which splits the blobs into smaller blobs and disperses them over a wider and warmer area over which air is flowing quickly leading to a drastic increase in the evaporation rate).

Chemists often work safely with large volumes of mercury, but are careful to clean up spills and to keep good ventilation to keep the vapour levels low. But there is so little mercury in CFLs that they don't count as a significant hazard.

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Wouldn't mind knowing why the downvote. I like to improve. – matt_black Oct 5 '11 at 22:04
I didn't downvote you, but maybe is it because you started off by saying you used the same sources as Russel Steen? – ChrisR Nov 14 '11 at 22:38

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