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Mercury in Compact Fluorescent Lamps Spurs Superfund Research

By Melissa Fabiano
July 2008

Fluorescent Light Bulb
Compact fluorescent lamps offer consumers a chance to save on electricity costs. However, the bulbs' mercury content means that it is also important to dispose of them responsibly and to avoid exposure to vapor from broken lamps. (Photo courtesy of Steve McCaw)

The Superfund Basic Research Program (SBRP) laboratory of Robert Hurt, Ph.D., director of the Institute for Molecular and Nanoscale Innovation at Brown University, is studying mercury vapor release from broken and spent compact fluorescent lamps (CFLs). A member of the Hurt Lab at Brown, senior Natalie Johnson, is the lead author on a new study reporting the lab's latest findings, titled "Mercury Vapor Release from Broken Compact Fluorescent Lamps and In Situ Capture by New Nanomaterial Sorbents" (in press, Environmental Science and Technology).

The research team found that breakage of a CFL produces mercury vapor concentrations that can exceed the limit of 0.2 microgram per cubic-meter in air for continual habitation by children recommended by the Centers for Disease Control and Prevention (CDC) Agency for Toxic Substances and Disease Registry( Exit NIEHS Website. The lab also noted that mercury vapor release is greatest at breakage and then decays by the hour. Within a four-day period following breakage, vapor release is greatly reduced but continues at a significant rate.

The study grew out of Johnson's undergraduate award-winning poster displayed in the environmental section of the American Institute of Chemical Engineers' National Meeting in Salt Lake City in November 2007. The poster presented results of an SBRP-funded, independent project titled, "The Characterization and Capture of Mercury Released from Broken Fluorescent Bulbs."

Johnson and colleagues in the Hurt Lab tested vapor release and capture using nanoscale sorbents, including sulfur, selenium, copper, nickel, zinc, silver, and tungsten disulfide. The adsorption capacities of these elements and compounds varied over a range of more than seven orders of magnitude, from zinc micropowder to unstabilized nano-selenium, depending on sorbent chemistry and particle size.

The research was driven by two important questions in regard to managing mercury in CFLs:

  1. What are the implications of direct consumer or worker exposure to mercury vapor from fractured or crushed CFLs?
  2. How much mercury is released into the environment at the end of a CFL life?

Johnson and Hurt focused their research on these CFL impacts because of the expected market growth for energy efficient products, and the ways in which CFLs may affect lifestyles following expiration.

The researchers experimented with sorbents of different chemistry and particle size on mercury vapors. They were surprised to find that a few of the common sorbents, such as powdered sulfur or zinc, require enormous amounts of material - greater than 10 kilograms - to treat vapor release for a single CFL, while small quantities of sorbents (for instance, nano-silver and sulfur-impregnated activated carbon forms) have capacities that require less than 1 gram of sorbent to capture the vapor.

Thus far, Hurt and Johnson have found that when comparing low-temperature mercury vapor sorbents, the most effective is a type of nano-selenium that is capable of capturing CFL vapors at a level of less than 10 milligrams. By using this sorbent, mercury vapor release was reduced by 99 percent compared to an untreated bulb. If a broken CFL was stored in a sealed space with the 10 milligrams of the unstable nano-selenium for 24 hours, nearly complete suppression of mercury vapor could be achieved.

Hurt served as corresponding author on the study. Co-authors from the Hurt Lab included students Shawn Manchester, also a poster award winner( Exit NIEHS Website, and Love Sarin, along with Senior Research Engineers Indrek Kulaots, Ph.D., and Yuming Gao.

Hurt's lab continues to study methods to improve mercury vapor capture at the time of fracture and vapor release, and vapor stabilization at ambient temperatures by identifying and evaluating high-efficiency sorbents, with a focus on nanosynthesis. With the projected market increase of CFLs, the motivation and support for the development of methods to manage consumer exposure to mercury and its environmental release (upon breakage or disposal) increases with each day, month, and year.

Could "Going Green" Give Consumers More than They Expected?

"Going green" is today's catch-phrase, and American's are becoming aware that even the simplest changes in lifestyle can impact an individual's personal ecological footprint. The number one economically feasible change people can make is investing in compact florescent lamps (CFLs) to replace incandescent light bulbs, but scientists wonder whether CFLs may also harm the environment and how those potential effects could be remediated.

Current studies show that consumers using the newest bulb innovations are reducing their energy use by 75%. These CFLs also pack in more "light" years compared to the incandescent bulbs, increasing the lifetime of bulbs by ten-fold.

Federal legislation calls for phasing out the old-fashioned bulb by 2012. Should this occur, it is essential for researchers to find solutions for effectively disposing of or recycling spent CFLs because of their mercury content. Environmentalists agree that more work must be done on bulb recycling programs. Some retailers will accept expired CFLs, and the Environmental Protection Agency( Exit NIEHS Website and Earth911( Exit NIEHS Website have sites where consumers can search for other recycling programs near their homes.

Mercury toxicity and lethality is old news; its detrimental effects have been apparent since the 1930s. Today's CFLs underscore mercury's volatile vapor form, which is still a significant health concern - ventilation reduces but does not eliminate this toxicant. Mercury vapor inhalation can cause significant neural damage in developing fetuses and children.

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