Assessing occupational mercury exposures during the on-site processing of spent fluorescent lamps.* A fluorescent lamp usually consists of a sealed glass tube coated with a powdered phosphor A rare earth material used to coat the inside face of a CRT. When struck by an electron beam, the phosphor emits a visible light for a few milliseconds. In color displays, red, green and blue phosphor dots are grouped as a cluster. See screen burn. material. * The tube is filled at low pressure with argon argon (är`gŏn) [Gr.,=inert], gaseous chemical element; symbol Ar; at. no. 18; at. wt. 39.948; m.p. −189.2°C;; b.p. −185.7°C;; density 1.784 grams per liter at STP; valence 0. gas and mercury vapor. * At either end, tungsten coils coated with an electron-emitting material form electrodes. * When voltage is applied, electrons pass through the tube, striking the argon atoms and releasing more electrons. * These electrons strike the mercury atoms, causing the orbital electrons to move to an excited state. * Upon relaxation, the mercury atoms emit ultraviolet light Ultraviolet light A portion of the light spectrum not visible to the eye. Two bands of the UV spectrum, UVA and UVB, are used to treat psoriasis and other skin diseases. . * The UV light strikes the phosphor, causing it to fluoresce fluo·resce intr.v. fluo·resced, fluo·resc·ing, fluo·resc·es To undergo, produce, or show fluorescence. [Back-formation from fluorescence. and produce visible light. * When fluorescent lamps are discarded or recycled, and subsequently broken, mercury may be released into an occupational setting or the surrounding environment. * U.S. EPA EPA eicosapentaenoic acid. EPA abbr. eicosapentaenoic acid EPA, n.pr See acid, eicosapentaenoic. EPA, n. added used mercury-containing lamps to the list of "universal wastes" in 1999. * Used lamps designated as universal waste must be shipped to an authorized facility for disposal or treatment such as recycling. * One of U.S. EPA's goals was to make it easier and more cost-effective for handlers to recycle used lamps. * On-site crushing of lamps into 55-gallon drums prior to shipment to a recycling facility can reduce volume and transportation costs. * As a result, many generators of used lamps have implemented comprehensive fluorescent-lamp recycling programs. * There are, however, occupational-safety issues to be considered. * U.S. EPA's toxicity characteristic leachate leach·ate n. A product or solution formed by leaching, especially a solution containing contaminants picked up through the leaching of soil. procedure (TCLP TCLP Toxicity Characteristic Leaching Procedure (US EPA) TCLP total concentrate leachate procedure TCLP Type Classification Limited Procurement TCLP Type Classification Limited Production ) value for mercury is 0.2 mg/L. * Modern lamps with green markings contain reduced mercury at levels below the TCLP value. * They do not have to be managed as universal wastes. * The TCLP value was not, however, derived for the purposes of controlling possible occupational exposures. * A controlled series of lamp-processing operations was monitored for mercury exposure levels. * The processing operations included lamp handling, lamp crushing, and drum closure operations. * OSHA OSHA n. Occupational Safety and Health Administration, a branch of the US Department of Labor responsible for establishing and enforcing safety and health standards in the workplace. exposure levels were exceeded even when half of the lamps processed were of the "low-mercury-content" variety. * Of particular note were differences between results from enclosed settings and outdoor settings. * Although individual fluorescent lamps contain only a small amount of mercury, the potential for mercury overexposures still exists, depending on the number of lamps processed and the subsequent concentrations of residues prior to recycling. |
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