A user over on Home Improvement asked How to deal with broken compact fluorescent (and its mecury) without breaking the bank? with emphasis on the mercury which such lamps contain.

I had a vague recollection of something I'd heard a few years ago and a quick search led to me leaving a comment:

Gloves to avoid getting a cut are a good idea as the phospor-containing coating on the inside of the glass can stop blood from clotting: The dangers from phosphor-coated glass of broken CFL bulbs.

Another user pointed out:

this is the first I've read about the anti-clotting effect of phosphors, and I can't find an independent source. Do you know of one?

So I went looking for more information and it seems that all articles I can find on the Internet mentioning the danger of the phosphor coating have wording derived from The Fluorescent Lighting System, which states:

The biggest immediate injury threat from a broken lamp is from the phosphor-coated glass. If cut with fluorescent lamp glass, any phosphor that gets into the wound is likely to prevent blood clotting and will interfere with healing.

I have contacted the author of that article to ask if they can supply a reference for that information.

An article in Scientific American mentions only the mercury and not the phosphors: Are Compact Fluorescent Lightbulbs Dangerous? I would have thought that SA would mention a problem with the phosphors if there was one.

There is anecdotal evidence at Cut by a broken CFL that it isn't that harmful (in the bleeding sense), and contributor retiredsparktech there suggests that it was arsenic-containing phospors which were to blame

So, are, or at any time were, the phosphors in fluorescent lamps anticoagulant, and if so would it be to a dangerous extent?

  • 3
    Your question is kind of muddled; you are forgetting to add the critical bit to any question of the sort "Is substance X dangerous?", and that is "At what doses are substance X dangerous?". Ever since Paracelsus we know that "The dose makes the poison". So in your particular case your question becomes: "Can a person be subjected to substances from a broken low energy light, to such a dose that it becomes an acute hazard to their health?".
    – user32299
    Jan 8, 2018 at 14:04
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    @MichaelKarnerfors: It is more specific that that. Can a person be subjected to phosphor from a broken low energy light, to such a dose that it acts as an anticoagulant, causing an (even mild) hazard? This in on top of the physical hazards due to sharp glass fragments and due to mercury.
    – Oddthinking
    Jan 8, 2018 at 14:09
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    Low energy lights are not coated by "phosphor". They are coated by several phosphor compounds. Several are needed because each compound usually gives only one colour of light. Googling for phosphor and clotting, the only thing I can find is that phosphor is beneficial for blood clotting, and a necessary substance for clotting to take place. Regarding phosophor compounds used in low energy lights, I find nothing. Also I think that this is not a notable claim since the site that is referred to make the claim does not even exist any more.
    – user32299
    Jan 8, 2018 at 14:31
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    @MichaelKarnerfors The site nemesis.lonestar.org/reference/electricity/fluorescent/… works for me. For "phosphor and clotting", did the article refer to phospors or phosphorus? The two are not the same. Jan 8, 2018 at 14:42
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    Note that phosphor is a generic term for "compound that emits light" and it's the used term for the stuff that coats some lamps (or CRT tubes). It's not phosphorous or a phosphorous compound. In fact phosphorous is (confusingly) not used in phosphor. Reference: chemistry.stackexchange.com/questions/81915/…
    – Sklivvz
    Jan 8, 2018 at 17:18

2 Answers 2


Not in any way that would make it dangerous.

Warfarin and Coumarin, two pharmaeutical compounds that are used for their severe anticoagulant effects, are fluorescent - Warfarin having a peak emission of ~370nm when excited with 320nm light, so not exactly ideal for CFL lighting, additionally, both are organic compounds and as such would not be used in a high-UV environment, like the inside of a CFL, for any length of time. Mineral is the way to go there.

The fluorescent Warfarin is an anticoagulant that is widely known as a rodent poison. Another well known rodent poison was Thallium sulfate (usually just called 'Thallium') - Thallium (not sulfate) also used to be part of CFL phosphors before it got replaced by more benign alternatives... so this might be a source of the myth.

Also, in very old (pre-1950s) fluorescent lamps, Beryllium was present, which is rather nasty, and was credited with adding insult to injury in cuts from lamp-shards. The reports of wounds 'refusing to heal' (for two months!) might also have gotten garbled to 'refuse to stop bleeding'

This 2011 study on glass-fragment removal has a CFL-victim, but reports no special treatment/circumstances.

A pamphlet on work safety from 2008 actually mentions a problem with clotting for cuts by CFL through the phosphor, but does not provide any references for that. It could very well be from the same disinformation source as the 'grassroots campaign' against energy saving lamps that is one of the links in the Q (same timeframe)

A site on lighting mentions it can lead to clotting.

Modern Fluorecent lights contain a mixture of many rare earth metals (REE) because they all phosphoresce vigorously in UV (the red phosphors Y2O3:Eu3+ (YOX), the green phosphors LaPO4:Ce3+,Tb3+ (LAP), (Gd,Mg)B5O12:Ce3+,Tb3+ (CBT), (Ce,Tb)MgAl11O19 (CAT) and the blue phosphors BaMgAl10O17:Eu2+)- looking at the MSDS or toxicity studies on this we see that their salts are often anticoagulant. Still, e.g. Cerium will show (systemic!) anticoagulant effects after injecting 100mg/kg (not like, lethal, just experimentally noticeable). Fluorescent tubes are coated with about 0.7mg/cm² of phosphor, of which a 27% are REE, so about 0.08mg/cm².

Danger from the anticoagulant properties of CFL shards can be ruled out. Having REE particles in higher dosage in/on your body for an extended period of time may be inadvisable, but more along the lines of a rash and bad wound healing.

  • Thank you for your research. Yes, that pamphlet doesn't seem to provide any references, other than the Philips one which I can't track down, even from just the filename in www.nam.lighting.philips.com/us/ecatalog/msds/s08-93005.pdf, and that site "has been excluded from the Wayback Machine." A couple of other Philips MSDS docs A, B make no mention of any danger from their phosphors. (Although the radioisotope Kr85 may be present.) Jul 5, 2023 at 16:05
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    This seems to veer around to hit a lot of issues that aren't addressing the question. Warfarin being fluorescent has no relevance. Speculation at the cause of the myth should be referenced. That no-one in South Africa was cut by fluorescent bulbs doesn't mean fluorescent bulbs aren't dangerous if someone is cut by them. The pamphlet specifically mentions phosphor which you seem to have overlooked as an agent.
    – Oddthinking
    Jul 5, 2023 at 17:06
  • @Oddthinking you are right about the utter meaninglessness of the SA paper in regards to the Q. I got carried away. Deleted it.
    – bukwyrm
    Jul 5, 2023 at 20:23
  • If you cut yourself on shards of glass, that is the immediate danger but also one that is easy to avoid. The total amount of exposure to the phosphor is likely to be extremely low with a cut (unless you brew up the shards and inject yourself with the liquor). The risk, compared to the damage of any cut is likely unmeasurably small.
    – matt_black
    Jul 5, 2023 at 20:38
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    It is also worth noting that some of the references (eg designlife-cycle.com/fluorescent-lights-lifecycle) that claim safety worries about phosphors clearly confuse phosphor with phosphorus which deeply undermines their concerns (and might be one source for the myths).
    – matt_black
    Jul 7, 2023 at 9:10

Material Safety Data Sheets (MSDS) document the known health/exposure risks of hazardous substances. They are legally required to be provided by manufacturers in some circumstances.

We can look at the MSDS documents for CFL lights.

Starting with the one that makes the clearest, strongest statements:

  • ProLume® Eco-Shield® Fluorescent Lamps MSDS

    It explains what the phosphor is, and how much is present:

    The ProLume Eco-Shield product line uses two different phosphor systems. One phosphor system (halophosphate) uses calcium chloro-fluoro-phosphate, with small amounts (less than 1- 2% by weight the phosphor) of antimony and manganese, both of which are tightly bound in the phosphor matrix. The second phosphor system (SP/SPX) uses a mixture of rare earth elements such as lanthanum, and yttrium as either an oxide or as a phosphate, along with a barium/aluminum oxide. These phosphors produce better lamp efficiency and color rendition. The phosphor components may vary slightly depending on the color of the lamp (cool white, warm white, etc.). Normally a 1.5 inch diameter (T12) fluorescent lamp has approximately 1 - 1.25 grams of the phosphor per foot of lamp, resulting in about 4 - 5 grams of the phosphor coating it’s inside length. A 1 inch diameter (T8) lamp has approximately 1.5 - 2 g phosphor coating per lamp.

    It them goes on to talk about health concerns:

    Except for small modifications, the halophosphor is essentially the same material that has been in use in fluorescent lamps for over fifty years. No significant adverse effects, either by ingestion, inhalation, skin contact, or eye implant, were found in a five-year animal study of the original phosphor by the Industrial Hygiene Foundation of the Mellon Institute. Also, there have been no significant adverse effects on humans by any of these routes during the many years of its manufacture or use. The phosphor is somewhat similar to the inert mineral apatites (calcium phosphate-fluorides) which occur in nature. Antimony, manganese, yttrium and barium compounds are characterized by OSHA as hazardous chemicals, as are most inorganic compounds. However, due to their insolubility, relatively low toxicity and small amount present in the phosphor and the lamp, these materials do not present a significant hazard in the event of breakage of the lamp.

    My search for a reference to the original animal study turned up nothing. This is a weakness in this answer.

    I do note that they never use the term "compact" or CFL. I found them sold at Walmart and they are labelled as CFL there, and certainly look compact.


    Again, it talks about the presence of phosphor:

    Phosphor – (nuisance dust) phosphate mix using manganese, rare earth elements such as lanthanum, and yttrium as either an oxide or as a phosphate, along with a barium/aluminum oxide all are tightly bound in the phosphor matrix. These phosphors produce better lamp efficiency and color rendition. The phosphor components may vary slightly depending on the color of the lamp. Some lamps may contain a thin coating of tin oxide inside the glass.

    Under Health Concerns it explains:

    There have been no significant adverse effects on humans by ingestion, inhalation, skin contact, or eye contact. Antimony, manganese, yttrium and tin compounds are characterized by OSHA as hazardous chemicals, however, due to their insolubility, relatively low toxicity and small amount present in the phosphor and lamp, these materials do not present a significant hazard in the event of breakage of the lamp.

  • Philip;s CFL MSDS similarly says there are no "important symptoms and effects" to be concerned about.

  • FEIT Electric's CFL MSDS says:

    Phosphor dust is considered to be physiologically inert and as such, has an OSHA exposure limit of 15 mg/cubic meter for total dust and 5 mg/cubic meter for respirable dust.

    For cuts, it suggests:

    Perform normal first aid procedures

In summary, the manufacturer's legally-required descriptions of the dangers of CFL tubes covers a number of threats (including mercury), but do not mention anti-coagulant properties, and consider the phosphor safe for skin contact in the amounts present.

  • The toxicity mentioned in these MSDS only covers cases that would not be relevant in case of laceration or impalement - "ingestion, inhalation, skin contact, or eye implant" would all not neccessarily uncover influence on the coagulation. I concur though that the MSDS would contain mention of such dangers if they were known.
    – bukwyrm
    Jul 6, 2023 at 21:12

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