管理提醒： 本帖被 chenshuuu 执行加亮操作(2010-12-27)
Because they last a long time, generate little heat, and contain no mercury, light-emitting diodes (LEDs) seem like an ideal environmentally friendly light source. But a new study by researchers at the University of California's Davis and Irvine campuses finds that by California standards, the all LEDs used in products such as Christmas lights, traffic signals, and remote controls should be classified as hazardous waste (Environ. Sci. Technol., DOI: 10.1021/es101052q).
Davis materials engineer Julie Schoenung and her colleagues subjected nine colors and intensities of 5mm pin-type LEDs to leachability tests that the federal and California environmental protection agencies use to determine if a product is hazardous. The researchers pulverized the LEDs and mixed them with acids to represent the chemical conditions that the LEDs would encounter in a landfill. Using mass spectrometry, they measured how much of various metals escaped into the acid.
Only one LED, the low-intensity red one, failed the federal test involving acetic acid: It leached an unacceptable level of lead. But eight out of nine of the diodes registered high levels of copper, lead, nickel, or silver using the more-rigorous California standards involving nitric acid. The researchers also detected metals from the semiconductor portion of the LEDs such as gallium and indium, which have no established regulatory threshold limits.
"These products have things in them you shouldn't be disposing of," says Schoenung. "Companies should try to either design out these toxic components or design their products for recovery and recyclability."
Megan Schwarzmann, a doctor and public health researcher with the Center for Green Chemistry at the University of California, Berkeley, says that the new findings don't indicate a danger to consumers during product use. But she says the study emphasizes the need to consider a product's full life cycle. "This study highlights a classic case of 'risk shifting'," she says. "LEDs chosen for their energy efficiency and lack of mercury introduce new hazards."
