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    The Chemistry Of Light Bulbs—And Why CFLs Are Overrated
    By Enrico Uva | March 26th 2011 08:22 AM | 38 comments | Print | E-mail | Track Comments
    About Enrico

    I majored in chemistry, worked briefly in the food industry and at Fisheries and Oceans. I then obtained a degree in education. Since then I have...

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    Light bulbs rely not only on simple materials but on esoteric ions and compounds. And while we take their emissions, visible light, for granted, the inner workings of these deceivingly simple gadgets depend on the complex behavior of electrons.

    We’ll discuss four types of light bulbs:incandescent bulbs, halogens, fluorescent lights (including CFLs) and LEDs.

    A) INCANDESCENT BULBS

    The light bulb of the short-lived variety, is the traditional tungsten incandescent bulb. Inside the glass, electricity flows through a thin filament of the element tungsten (chemical symbol, W, for its old name wolfram).

    Because the wire is so thin, resistance is high, and it raises the temperature of the tungsten wire, so chosen because of its high melting point of 3410 oC. At the bulb’s temperature, which is about 1000o cooler, excited electrons that return to lower energy states release photons of a frequency that is visible to the human eye. The radiation is intense in the red to yellow regions but compared to daylight, the spectrum of an incandescent light bulb is very weak in the 400 to 500 nm region (blue). This would be nice to verify with a prism, and is the reason that plants don’t do as well if grown under such light. Although the heat is not sufficient to melt the tungsten it would certainly fry the heck out of it in an oxidizing atmosphere. Thus manufacturers replace oxygen with a mixture of the less reactive nitrogen and the noble gas argon. Note that a vacuum would not be a good solution because the tungsten would vaporize even more easily and dramatically shorten the bulb’s lifespan.

    Even within an argon-nitrogen atmosphere, however, the heat causes some of the tungsten to sublimate. Some of it returns to the wire as it bounces off the argon gas, but a good deal ends up on the glass. This is one of the reasons incandescent  bulbs tend to get darker with increased use. The glass suffers more abuse from plain old electrons which fly off the filament as if it were a cathode ray tube from a conventional television set. Such electrons cause tiny black spots to appear. These first caught Edison’s attention, but he had never time for further investigations; otherwise, as David Bodanis suggests, Edison may have discovered electrons before J.J. Thomson. To create a more diffuse light but perhaps in an attempt to camouflage all the future damage, manufacturers treat light bulb glass with hydrofluoric acid one of the few acids that can attack glass) which creates that familiar frosty look.


    B)HALOGENS

    Eventually the tungsten wire becomes so thin, that it snaps, breaking the circuit and sending you off to the hardware store. At one point someone got tired of the bulb’s short lifespan and  invented the halogen light bulb. This still uses tungsten but along with argon it includes a small amount a halogen gas, namely chlorine. The reactive gas combines with the tungsten vapour and deposits it again on the filament. In other words it recycles the tungsten, rather than letting it wastefully deposit on the glass. Of  course, it is very unlikely that the metal will be perfectly and evenly replaced all along the coiled filament. Weak spots eventually develop, and the coil still breaks, but it takes a lot longer, and halogen bulbs outlive their incandescent counterparts. The glass has to be able to withstand higher temperatures, so they use a purer form of silicon dioxide, one that unfortunately gets ruined by oils on our skin. If these bulbs are mishandled as such, the grease should be washed away with alcohol.

    C)FLUORESCENT BULBS

    To avoid wasting energy in the form of heat, fluorescent lights, ubiquitous in  schools and other institutions, operate by a totally different principle. They contain a small amount of
    mercury(Hg), which emits ultraviolet light when excited by electrical energy. The story
    cannot end there because ultraviolet(UV) is invisible to the human eye. The walls of the
    bulbs are coated with a phosphor, usually a halophosphate such as Ca5(PO4)3(F,Cl) with
    ions of Sb3+ and Mn2+ that absorb the UV radiation. The excited electrons then release visible
    light, compliments of fluorescence. In this form of luminescence, an excited electron
    returns from a specific molecular orbital to a lower one without inverting its spin. The
    resulting light has the bulk of its intense wavelengths in the yellow and blue regions. But
    relative to natural light, fluorescence is weak in the red regions. Plants will again remain
    "unhappy", unless you buy more expensive fluorescent lights which try to compensate for
    this weakness by substituting antimony and manganese ions in the phosphor with
    europium and terbium ions.

    Next we come to the smaller version of type 3 bulbs, compact fluorescent bulbs(CFLs), which are overrated for three reasons:

    (1) Practically, the CFLs are not as bright as halogens and although they match the light intensity of incandescent bulbs, they take a while to reach their peak intensity.

    (2) They were not designed for cold climates, where the traditional bulb’s inefficiency is less of a drawback. The heat generation is actually desirable for about 9 months of the year in the northern states and Canada because it means the main heat source in the home does not have to work as hard.

    (3) It is ironic that something marketed as an environmental savior actually contains mercury. According to Environment Canada, the Hg content varies from 1 to 25 mg per bulb. There are about 115 million American households. If each household breaks 3 bulbs per year either by accident or indirectly by sending them to a landfill, then between 300 kg and 9000 kg of mercury (one significant figure) are added to the environment in the United States alone. The annual mercury emissions from all sources in the United States are estimated at 43 700 kg ( over 12000 kg from Alaska).

    D)LEDS

    To gain insight into how an LED (light emitting diode) bulb works we need to be reminded that a diode consists of two adjacent wafers of silicon doped with different impurities. The latter do not have the same valence number as silicon. If the impurity or "doping agent" is short of an electron(for example, boron), its wafer will receive an electron from the wafer with the opposite problem(example arsenic). Since electrons are stepping down from a higher energy level, photons are released. The energy gap is usually small and will only emit in the infrared, but it’s still useful if you want to use the remote control to turn off your daughter’s music channel.

    In LEDs silicon is not the primary material. Common combinations include GaAsxP1-x, GaxIn1-xP, AlxIn1-xP, AlxGayInzP, and GaxIn1-xN. To get visible light you need to get away from the classic boron-arsenic combo representing a valence of 3 and 5, respectively. If aluminum and gallium(each with a valence of 3) replace boron, one can create a red LED. If indium replaces aluminum, the transition energy increases, and blue light is released. The third primary color is created by replacing arsenic with another valence 5 element, phosphorus, and combining it with aluminum and gallium. A white color can result from combining all three recipes or by coating the bulb with a phosphor.

    Although there are still technical challenges ahead, LED lights will probably replace CFLs. But perhaps not to add too much arsenic to the environment, we should also use incandescent light or simply wait for sunrise to read science.

    References

    University Corporation for Atmospheric Research http://www.ucar.edu/news/releases/2007/nicc-table.shtml

    US Census http://www.census.gov/prod/1/pop/p25-1129.pdf

    Environment Canada http://www.ec.gc.ca/mercure-mercury/default.asp?lang=En&n=2486B388-1

    Efficiency of CFLs http://www.cbc.ca/news/canada/manitoba/story/2009/03/04/mb-light-bulbs.html

    US Department of Energy http://www1.eere.energy.gov/buildings/ssl/how.html

    http://science.howstuffworks.com/light-bulb2.htm

    Bodanis, David. Electric Universe. Crown. 2005

    Britannica. DVD edition. 2000       

    Haber Schaim and Al. PSSC Physics. Heath. 1971

    Comments

    Good stuff, here.

    Isn't one of the points of CFLs that they last way longer than incandescents, thereby reducing the number of bulbs needed/dropped/thrown away? Personal experience tells me CFLs don't live up to the long-lasting hype, so what's in the works to make them better in that area? And, are there substitutes for mercury that would lend themselves to light bulbs?

    The dirty secret about CFLs is that they only have a long lifetime if mounted with the base down (as in a table lamp). When mounted base up, the heat of the bulb adds to the self-heat of the electronics in the base increasing heat-related failures.

    Incandescents radiate away the majority of the heat they generate. Because of this, existing light fixtures have poor heat dissipation. This is a problem for both CFLs and LEDs when used as a plug-in replacements for incandescent bulbs (some LED plug-in replacements have built in fans - not likely to increase their reliability).

    A CFL in a ceiling fixture with poor heat dissipation may have a lifetime little different from an incandescent.

    On/off cycling significantly diminishes CFL life.

    Not necessarily.
    I have three kitchen "track" fixtures, where the bulbs fit into a tin-can sized enclosures.
    The lights are switched on/off once, perhaps twice a day.
    So far the results are varied- some CFLs might last six months, some several years. I have not fastidiously kept track.
    But the average lifespan is certainly much longer than a tungsten bulb.
    It's pretty much luck of the draw. Don't ask me for the brand names- all I can say is that they are probably all made in China.
    I just buy them when a 3-pack or 6-pack of any brand is on sale at the local large mall store.
    But I DO know that the "SIX YEARS!" "12000 HOURS!" so called promises or guarantees are not worth their weight in Mercury. The retailer/manufacturer knows you aren't going to keep a $5 bill around for six years.

    Oh YEAH????
    Did anyone read this horror story about CFLs? THEY SHOULD BE BANNED!

    See CAT DIES FROM MERCURY! It's scary as all hell!

    Gerhard Adam
    Very funny
    Mundus vult decipi
    Good Stuff

    I personally believe that led lights are the future. They are energy-efficient and they last longer.

    Your argument is FLAWED in that it makes sense and politics and environmental activism is NOT about common sense!

    How does AK emit over 12000kg of Hg per year? Anyway different technologies are appropriate for different situations. In a clothes closet, incandescent bulbs are perfect; on for a minute or so, then off. In a kitchen where lights are on for hours at time (well in my house), CFLs in ceiling cans are great: 30-45 secs to warm up, then on for 3-6 hours at a time and much lower operating costs. It is rare to find one solution that is correct for all situations so use a mixture.

    UvaE
    Mostly from gold mines and milling, I imagine. The statistic is from University Corporation for Atmospheric Research http://www.ucar.edu/news/releases/2007/nicc-table.shtml
    Let me contribute to an excellent article.

    LED - are extremely energy efficient, convert juice to light, but as they age, their efficiency drops off significantly. Old LEDS look brown. This, and first cost, are being rigorously studied.

    Hg. - It is estimated that all the US coal fired plants emit about 25 tons, airborne, annually. The danger is created when the metal falls into water, where aquatic microorganisms ingest it and excrete methyl mercury, an known neurological toxin. Hence the intense pressure to regulate coal, which contains trace Hg. However this science parallels the discovery of black smokers, undersea volcanoes, which inject hot Hg directly into the sea. The mass estimates are inexact but one black smoker releases many tons of Hg per year directly into water, there are some 10,000 black smokers worldwide, and this process has been continuing since the earth was formed. Moreover, one vent, in one Latin American volcano, emits 7,000 tons of Hg per year. Yellow Stone alone may have 10,000 vents. Hg is a product of vulcanism.

    The wide spread fear that US coal combustion is poisoning our society can not sustain a mass balance review. Moreover the data correlations for methyl mercury toxicity from eating fish is quite weak. They, and we, came from the sea. The "danger" is largely a green myth. Ergo, use common sense when selecting your light bulb, or politician. Pick a bright one.

    Bonny Bonobo alias Brat
    Moreover the data correlations for methyl mercury toxicity from eating fish is quite weak. They, and we, came from the sea. The "danger" is largely a green myth
    Try telling that to the hundreds of Japanese people suffering from Minamata disease or mercury toxicity from eating methyl mercury polluted fish from their bay. For years they were studied by scientists who believed that they had a genetic predisposition to a form of Motor Neurone Disease (MND) until the real cause of mercury poisoning was discovered.

    R. L. Hails have you read the instructions for clearing up just one small CFL light bulb if it breaks in your house? Here are just a few, they all involve evacuating the room and using duct tape to pick up the mercury powder and broken glass, as well as throwing out all materials that have come into contact with the mercury powder including carpets. I think you are right, CFLs are a 'green myth'.

    Millions of these CFL lightbulbs are breaking all over the world in offices, schools, shops and homes and many people have no idea how toxic they are or how to clean them up safely. The incidence of MND is also increasing in Australia, where incandescent bulbs have been prohibited from sale for over a year now, CFLs have taken their place in most households and establishments. MND symptoms are almost identical to mercury poisoning symptoms.

    Here are just a few guidelines about clearing up broken CFLs from different sources :-
    http://www.ehow.com/how_7950613_clean-broken-fluorescent-comp-light.html
    http://www.epa.gov/cfl/cflcleanup-detailed.html
    http://en.wikipedia.org/wiki/Compact_fluorescent_lamp#Broken_and_discarded_lamps
    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    Neven
    It's too bad they don't use depleted uranium in CFLs. This could be recycled to bullets and anti-tank missiles!
    Aitch
    I'm assuming you had politician targets in mind, Neven .....?

    Perhaps a burning laser is a good recycling project with similar usefulness....?

    http://showsyouhow.blogspot.com/2007/12/diy-dvd-burner-laser-pointer-pro...

    tongue  firmly in cheek, of course....

    Aitch
    My use for two 100 watt incadescent bulbs on a reostat cannot be replaced by these currly florescents - I use them to keep my home brew warm so it will ferment in the wintertime! I have two 5-gallon cauldrons with the two 100 watt bulbs between them covered by an inverted corregated cardboard box to contain the heat from the bulbs. A lab thermometer sticks throught the cardboard to tell me if I should turn the bulbs up or down. No more incadescent bulbs = no more home brew in the winter:(

    Hank
    And for the younger crowd, no more EZ-Bake Ovens.
    Aitch
    Home Brewer
    Simply replace your standard incandescent lamps with Halogen lamps, they'll still work on a dimmer.....and they aren't due to be phased out until 2016.....in Europe, at any rate

    Aitch
    seba
    Regarding the article:
    1) You have a typo CFC->CFL.
    2) Heating from electricity can be less efficient than other methods, so it might be better that it doesn't emit so much heat.
    3) If coal plants are the source of energy, then a lot of mercury is emitted by generation of energy, so CFLs might be more enviromental in such case.
    4) The problem with halogen lamps is also that they let UV out, but with UV filters (normal glass) they emit less than normal ones. Also the new doped glass ones are brighter and fix this problem.
    5) Grease on glass of halogen lamps forms local hotspots afaik, because of harder heat dissipation.
    6) I don't think chlorine is used much in halogen lamps. Iodine and bromine is mainly used. Read this:
    http://www.sylvania.com/ConsumerProducts/AutomotiveLighting/Products/Halogen/HowHalogenWorks.htm
    7) Halogens work at a higher temp. therefore a better light spectrum. That's a big plus.

    Regarding comments:
    Elemental mercury is mostly toxic only by inhalation, but not so much as anorganic (ionic) form of it or organo-mercuric compounds which are highly toxic.
    Bonny Bonobo alias Brat
    Regarding comments:
    Elemental mercury is mostly toxic only by inhalation, but not so much as anorganic (ionic) form of it or organo-mercuric compounds which are highly toxic.
    Sebastian, a broken CFL potentially gives off dangerous levels of mercury in the air which is why most of the government and non-government websites on 'how to clear up a broken CFL' always recommend evacuating the room for 15 minutes, to let the mercury powder in the air settle.

    They normally also recommend that whoever clears up the broken CFL lightbulb wears a mask and gloves and doesn't use a bagless vacuum cleaner, which if used can be turn into a mercury generating machine for the rest of its working life. How many people do you think know this, even though increasing numbers of people have these CFLs in their houses, offices, shops and schools  around the world?

    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    Aitch
    Sadly, Helen, many websites advocating the change-over to CFLs, do NOT give the warnings about broken bulbs, often merely stating that the mercury content is about 5 mg and will fit on the tip of a ballpoint pen!

    example

    http://www.which.co.uk/environment-and-saving-energy/energy/guides/energ...

    Only the energy saving is being pushed, not the disadvantages/dangers

    Aitch
    Bonny Bonobo alias Brat
    Actually Henry it does mention in passing the need to evacuate the room for 15 minutes in the 'unlikely event' (they've got to be joking, these CFLs are breaking all the time) that a bulb should get broken but it doesn't mention any of the other hazards of clearing up broken CFLs.

    How can that website have a page entitled 'Energy saving light bulbs - your concerns - Problems with energy saving light bulbs' and not even mention the hazards of incorrectly clearing up a broken CFL in a building? I must say I didn't even realise that there were all these other problems with CFLs too. It is difficult to understand how Compact Fluorescent Bulbs are still being promoted as a safe green alternative, without proper testing having been done for these other problems as well? Has the world gone mad? Here are a few excerpts from your link:-
    We address your questions on possible health impacts and disposal of energy-saving lamps and whether energy-saving light bulbs live up to their light output and lifetime claims.

    Do energy-saving light bulbs cause cancer? A low energy lightbulb will not cause skin cancer. The Health Protection Agency (HPA) issued a warning in October 2008 about some energy-saving light bulbs emitting higher levels of UV radiation than guidelines suggest is safe. It suggests, as a precaution, that spiral and tube-type energy-saving light bulbs shouldn’t be used for more than one hour a day when people are less than 30cm away from the bulb – for example, on a desk lamp. Instead, consumers should switch to globe-style bulbs, or move the lamp further away.

    Do energy-saving bulbs cause migraines? Some migraine support groups, such as the Migraine Action Association, have raised this as a concern. The Department of Health has said in response: 'The Department is aware of concern from migraine support groups that the use of some energy-saving light bulbs could potentially affect migraine sufferers. We are continuing to work with clinicians and support groups regarding the nature and extent of any reported health effects, and bring influence to bear where appropriate.

    'Can energy-saving light bulbs trigger epilepsy? The charity Epilepsy Action has some anecdotal reports from members who believe ill-effects such as headaches and dizziness have been caused by energy-saving light bulbs. It has said: 'Epilepsy Action is not aware of any evidence that low-energy light bulbs can directly trigger epileptic seizures in people with photosensitive epilepsy. However, we have been contacted by a number of people with epilepsy who believe that energy-saving light bulbs have impacted on their condition. 'We are not able to quantify how many people with epilepsy are affected by these bulbs or say definitively how energy-saving light bulbs may affect people with epilepsy. We are asking the government to confirm that ordinary light bulbs will still be available for people with epilepsy, should they have concerns about the use of energy-efficient light bulbs and their epilepsy. We will continue to monitor the situation.

    'Do energy-saving light bulbs cause radio-interference? Any radio interference is only likely if your radio aerial is placed very close to an energy-saving light bulb – on a bedside table close to a bedside lamp, for example. Over short distances, energy-saving light bulbs can cause radio interference (a buzz) on medium wave (MW) and long wave (LW) reception.

    How can I dispose of used energy-saving light bulbs?The Weee logo mercury content in an average Compact Fluorescent Lamp (CFL) is no more than 5 milligrams – and would fit on the tip of a ballpoint pen – but it's still a hazardous material. So used energy saving light bulbs are included in the Weee recycling scheme and you need to recycle them rather than putting them in the bin. Find your nearest recycling point for Compact Fluorescent Lamps (CFLs) by entering your postcode into the Recycle Now website. Facilities accepting ‘fluorescent/gas discharge lamps’ should be able to accept used CFLs for recycling. Ikea offers recycling points in its stores and accepts all energy-saving light bulbs for recycling.A number of Sainsbury’s stores have CFL (and battery) recycling points – type your postcode into the Recolight website to find those nearest to you.Currys has a similar scheme in place – check whether CFL recycling available at your local store before taking in your used bulb. In the unlikely event that you should break a CFL, the government recommends leaving the room and ventilating it for 15 minutes until the mercury contained in the light bulb has dispersed.


    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    Aitch
    hmmm....dispersed into your vacuum cleaner, most likely, ....without adequate warning!!

    keep plugging Helen, people might read it!

    Aitch
    Could you tell me what the average recycling facility does with all this "recovered" mercury?
    More to the point: HOW do they recover this ball-point pen tip amount of mercury? With tweezers?
    I'll give you a $100 for every teaspoon of mercury recovered.
    I'd like to see some pictures, or better yet, some videos of the high-tech recovery process.
    And so the mercury in the broken bulbs "disperses"? Where? Does it hop on a bus and go away never to be seen again?
    "disperses" is a weasel word, much like "sequestration" is, with reference to CO2
    Always challenge people who mumble these words, and who then blithely move the topic on. But I digress.
    I could go on and on here regarding some of this "scientific" discussion, but there is just too much to debunk.

    BTW, could I mail you some of my broken (amalgam) tooth fillings? Oh I forgot- this hazardous waste is not permitted to be mailed. Let's hope the remaining ones stay in my mouth, at least until...
    hmnn. this may indeed be an environmental time-bomb!

    seba
    One lamp contains up to (but not more) than 5 mg of elemental mercury (according to RoHS), most contain around 2 mg.
    The concentration is dangerous only if you would break one CFL fairly regurarly and then inhale all of it as for acute effects you need 1.1 - 44 mg/m3 of mercury (source).
    If you have a room of 3 m * 2 m with a 2.5 m height, that's 15 m3, with 2 mg of mercury you get a concentration of 0.13 mg/m3. That's 10 times lower than the lowest concentration for acute effects.
    So well yes opening a window and/or door to the outside is recommended, but you don't need to panic, evacuate or call HAZMAT.

    Wearing gloves is not needed for the mercury itself, skin absorption is very low. I would recommend thick gloves to not be cut by glass. Some phosphors inside are probably toxic as well.

    I think the greatest source of mercury exposure for the public is from public "old CFL lamp garbage bins". Almost all CFLs get broken there.

    BTW LEDs could be an enviromental issue as well, they contain arsenic for example.
    Bonny Bonobo alias Brat
    Sebastian, you might be interested in this CFL lamp study by the Maine Department of Environment Protection, here are some excerpts from the executive summary :-
    Forty five (45) experimental trials where compact fluorescent lamps (CFLs) were broken in asmall/ moderate sized room were conducted in May through September of 2007...Broken lamps were either not cleaned up, cleaned up using Maine Department of Environmental Protection (DEP) pre-study cleanup guidance, vacuumed, or cleaned up using variations of the pre-study cleanup guidance.

    The mercury concentrations at the five foot height (adult breathing zone) and one foot height (infant/toddler breathing zone) above the study room floor were continuously monitored. The most notable finding of the study was how variable the results can be depending on the type of lamp, level of ventilation and cleanup method...as a result of this study, the cleanup guidance was modified to include:

    • Leaving the area/room and waiting 15 minutes after breakage before returning to begin cleaning up (mercury levels in the air will have fallen from their highest levels by then);
    • Using a glass container, metal screw top lid with a seal, such as a canning jar, to contain the lamp pieces, powder, and cleanup materials;
    • Immediately removing the lamp breakage from the home once containerized, especially if the homeowner did not have a glass container with a good seal;
    • Continue ventilating the room for several hours;
    • Suggesting that homeowners consider removal of the area of carpet where the breakage occurred as a precaution, particularly in homes with infants, small children or pregnant women;
    • If carpet is not removed, the homeowner should consider ventilating the room during vacuuming for the next several vacuuming events;
    • Suggesting that homeowners consider not utilizing fluorescent lamps in situations where they could easily be broken, in bedrooms used by infants, small children, or pregnant women, or over carpets in rooms frequented by infants, small children and pregnant women;

    Mercury concentration in the study room air often exceeds the Maine Ambient Air Guideline(MAAG) of 300 nanograms per cubic meter (ng/m3) for some period of time, with short excursions over 25,000 ng/m3, sometimes over 50,000 ng/m3, and possibly over 100,000 ng/m3from the breakage of a single compact fluorescent lamp. A short period of venting can, in most cases, significantly reduce the mercury air concentrations after breakage. Concentrations can  sometimes rebound when rooms are no longer vented, particularly with certain types of lamps and during/after vacuuming. Mercury readings at the one foot height tend to be greater than at the five foot height in non vacuumed situations.
    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    seba
    Yes, that's what I calculated in the previous comment: 100 000 ng/m3 = 0.1 mg/m3, so in real life it seems that is even lower than that.

    Anyway, I haven't said that the methods of cleaning up aren't effective. My point is that even with 0.1 mg/m3 in an acute exposure (a few [<10] times per year) probably won't cause any effects and for 2 exposures per year (once per 6 months) won't cause any effect at all. The half-life1 of mercury is not enormously long, but 3 to 6 months if I recall correctly, so you would need to be quite clumsy to actually get any symptom.
    Children are of course more prone to get the symptoms as they are lighter, closer to the ground and have a developing brain.

    1 Half-life in the sense how much time you need to halve the concentration of mercury in your body.
    Bonny Bonobo alias Brat
    My point is that even with 0.1 mg/m3 in an acute exposure (a few [<10] times per year) probably won't cause any effects and for 2 exposures per year (once per 6 months) won't cause any effect at all.
    Not maybe for the average healthy adult living in a relatively unpolluted environment. Sebastian, you do realize that most people are already being exposed to cumulative and sometimes dangerous levels of mercury on a daily basis in many other different ways? Surely by adding mercury in 'green' CFL light bulbs into nearly every room of every electrically powered building in the world, makes it more likely that they will occasionally be broken accidentally and become the straw that breaks the camel's back, especially for children, pregnant women and their developing babies?

    Mercury and many of its chemical compounds, especially organomercury compounds are readily absorbed through direct contact with bare, or in some cases (such as dimethylmercury) insufficiently protected skin, though according to Wikipedia fish consumption is probably the main source of mercury poisoning in people.

    Although fish consumption is the primary source of mercury, plants and livestock also contain mercury due to bioaccumulation of mercury from soil, water and atmosphere, and due to biomagnification by ingesting other mercury-containing organisms. Exposure to mercury also occurs from breathing contaminated air, eating foods which have acquired mercury residues during processing, mercury amalgam dental restorations, and from improper use or disposal of mercury and mercury-containing objects, after spills of elemental mercury and the improper disposal of fluorescent lamps in land-fill and now in homes, shops and workplaces.

    Coal plants emit about half of the atmospheric mercury, volcanoes the remainder. Two-thirds of human-generated mercury comes from coal combustion. Other human-generated sources are gold production, non-ferrous metal production, cement production, waste disposal, human crematoria, caustic soda production, pig iron and steel production, mercury production (mostly for batteries), and biomass burning. Mercury is also commonly used in chemical laboratories, hospitals, dental clinics, and facilities involved in the production of items such as fluorescent light bulbs, batteries, and explosives.


    The U.S. government tested fish in 291 streams around America for mercury contamination. They found mercury in every fish tested, even in fish of isolated rural waterways. Twenty five percent of the fish tested had mercury levels above the safety levels determined by the U.S. Environmental Protection Agency for people who eat fish regularly. I hate to think how high the mercury levels are in fish in many other developing and industrialized countries of the world.

    All around the world people are accidentally breaking CFLs and/or not disposing of the released mercury properly. Babies and toddlers are potentially playing on mercury contaminated carpets and floors in shops, houses, hospitals and schools and pregnant women are accidentally inhaling mercury in quantities that can potentially adversely affect their developing embryos. Why are we adding this additional risk of mercury containing CFL lightbulbs by the millions
    into our own buildings in an already increasingly polluted environment and world?


    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    LOL! Yes and I bet youbelieve in the "science" of homeopthy also. Where does .000001mg of elemental mercury fit in their grand scheme of things?

    Bonny Bonobo alias Brat
    No, I don't believe in the science of homeopathy but I do take EPA Government health warnings on how to clean up a broken CFL bulb seriously, see http://www.epa.gov/cfl/cflcleanup-detailed.html Also, I can't be bothered to find it now, but there is a study somewhere that showed that the levels of mercury in CFLs can vary considerably between 1 and 25 mg and often the amount of mercury that CFLs contain is higher than they are labelled as being. The CFLs that were fitted for free in my parents house by the council were 12 mg per bulb and several were broken during installation as they did not easily fit into the slanted ceiling light sockets, which is also quite a common problem I believe.
    My latest forum article 'Australian Researchers Discover Potential Blue Green Algae Cause & Treatment of Motor Neuron Disease (MND)&(ALS)' Parkinsons's and Alzheimer's can be found at http://www.science20.com/forums/medicine
    "which if used can be turn into a mercury generating machine for the rest of its working life"
    What are you- an Alchemist? Can I use these vacuum cleaners to get free mercury forever? (it's a valuable metal!)

    I've broken a couple of these things, not to mention those ABSOLUTELY LETHAL 40" tubes in my basement and workplace.
    Could you offer us some advice on where to find the hazmat teams to clean up this toxic waste in my living room? How many months or (shudder) weeks do I have left?
    I generally eschew vacuum cleaners, preferring instead the hi-tech dustpan and small broom.

    UvaE
    Thx for pointing out the typo. It's been corrected. http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.... Although it's a bit dated, it reveals that all three: iodine, chlorine and bromine have been used.
    Sorry- the typos still haven't been corrected.
    CFL's (sic) should be CFLs.
    See my other posts here.
    And STOP USING apostrophes COMPLETELY until you have been fully grounded in their usage.

    Percy - brain-damaged

    UvaE
    Typos corrected.
    This was exactly what me and my new chapter was looking for, this will really help us out. Thanks!

    You seem to be implying that LEDs are silicon based using different dopants. This is not how LEDs work at all. Silicon is an indirect semiconductor meaning optical transitions are highly unlikely leading to extremely low efficiencies.

    Visible LEDs are built around III/V binary, ternary and quaternary compounds such as InGaN or AlInGaAs. A p-n junction is used to inject electrons but dopants for III/V materials are typicaly Si and Mg. Emission wavelength is not controled by doping but by control of the alloy composition inside the thin active layers between this p-n junction.

    For example - highly efficient blue emitting LEDs are made using GaN p-n junction, inbetween these thick layers the active region consists of thin (~2-3nm) layers of undoped InGaN. The composition of the InGaN is chosen to be ~20% In 80% Ga giving a band gap corresponding to blue light, this bandgap is lower than that of the p-n junction meaning electrons get traped until they loose energy and emit a photon, all emission comes from this thin active region.

    it is possible to use multipul LEDs such as red green blue, but due to limitations in efficiency at green and red wavelengths (using different materials systems such as AlGaAs and InP) this by far the minority of white LEDs.
    The most common >95% tchnique uses highly efficient blue emitting GaN/InGaN LEDs coupled to yellow emitting phosphors to give a tunable white spectrum.

    So currently white LEDs are remarkably free of toxic materials, even the As containing red LEDs never contain free As and don't pose any environmental issue after manufacture.

    UvaE
    You seem to be implying that LEDs are silicon based using different dopants.
    I wasn't, but I made some changes, so that it's not misinterpreted.
    even the aresenic-containing red LEDs never contain free As and don't pose any environmental issue after manufacture.
    I hope you're right, but do you have references that could verify your claim that it remains bonded?
    UvaE
    Cleanup instructions (for CFLs) can be found here at the Environmental Protection Agency Site :