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Lead and Phosphors in CRTs

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    erewen started this thread.
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    Lead and Phosphors in CRTs

    Having had responsibilities for safety issues in a previous career, the ongoing discussion about safety of broken CRTs has caused me to do a bit more research into the matter. I wanted to throw my 2 cents into the mix, since I hate junk science.

    Lead is bound within the glass and has very low solubility. Unless inhaled or ingested, it is not a safety hazard. I guess if you are inhaling or ingesting glass of ANY sort, you may have more immediate problems than lead contamination. Broken glass, rather than lead, is obviously the primary safety factor. Common sense safety equipment includes eye protection and leather gloves.



    The ashy coating on the inside of CRTs are the phosphors. The following information on "phosphor" was taken from Wikipedia:

    ......

    Cathode ray tubes

    Cathode ray tubes produce signal-generated light patterns in a (typically) round or rectangular format. Bulky CRTs were used in the black-and-white household television ("TV") sets that became popular in the 1950s, as well as first-generation, tube-based color TVs, and most earlier computer monitors. CRTs have also been widely used in scientific and engineering instrumentation, such as oscilloscopes, usually with a single phosphor color, typically green.

    White (in black-and-white): The mix of zinc cadmium sulfide and zinc sulfide silver, the ZnS:Ag+(Zn,Cd)S:Ag is the white P4 phosphor used in black and white television CRTs.

    Red: Yttrium oxide-sulfide activated with europium is used as the red phosphor in color CRTs. The development of color TVs took a long time due to the long search for a red phosphor. The first red emitting rare earth phosphor, YVO4,Eu3, was introduced by Levine and Palilla as a primary color in television in 1964. In single crystal form, it was used as an excellent polarizer and laser material.

    Yellow: When mixed with cadmium sulfide, the resulting zinc cadmium sulfide (Zn,Cd)S:Ag, provides strong yellow light.

    Green: Combination of zinc sulfide with copper, the P31 phosphor or ZnS:Cu, provides green light peaking at 531 nm, with long glow.

    Blue: Combination of zinc sulfide with few ppm of silver, the ZnS:Ag, when excited by electrons, provides strong blue glow with maximum at 450 nm, with short afterglow with 200 nanosecond duration. It is known as the P22B phosphor. This material, zinc sulfide silver, is still one of the most efficient phosphors in cathode ray tubes. It is used as a blue phosphor in color CRTs.

    .......

    Looking through the MSDSs for these compounds, inhalation and possibly skin irritation are the primary health concerns. When disturbed, the phosphors are easily airborne and practices that minimize health hazards of dust are applicable. Ventilation, is key. Respiratory masks are helpful. A low tech application of soapy water with a misting bottle can help manage levels of airborne particulates.


    As always, local, state, and federal regulations should be the first consideration in your handling and disposal of CRTs.

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