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Mercury's Dangerous Flight

Landfills emitting highly toxic compound into the air, new study documents

MONDAY, Oct. 8, 2001 (HealthDayNews) -- Many landfills in the United States and around the world are acting as "bioreactors" that chemically alter mercury from household items like batteries and thermometers into a more toxic compound that's released into the air, says a new study.

The compound, called dimethyl mercury, could be a source of mercury in lakes, even in remote areas, that result in mercury-tainted fish.

"I think the most important thing was the discovery these landfills are not just generating dimethyl mercury in the landfill gas, but generating it in unexpectedly high concentrations," says the study's lead author, Steve E. Lindberg, a senior research scientist for the environmental sciences division at the Oak Ridge (Tenn.) National Laboratory.

In their study, Lindberg and fellow researchers measured gases in a landfill near Orlando, Fla., and found that levels of gaseous mercury were more than 1,000 times greater than levels found in normal air.

Dimethyl mercury is a kind of methyl mercury, a neurotoxin able to pass through the blood-brain barrier of humans and other animals. It can be passed to a child in the womb -- usually when the mother eats mercury-contaminated fish -- and can affect the development of the brain and nervous system.

The Washington, D.C.-based National Research Council estimates that each year more than 60,000 newborns may be at risk for health problems because exposure to methyl mercury while in the womb.

"The primary mercury exposure pathway to humans is through eating contaminated fish. These fish can live in lakes that are quite remote from major sources of mercury, because of its ability to be transported long distances in the atmosphere," Lindberg says.

"People have speculated in the past that mercury could be methylated in landfills, but there have never been any measurements made directly on the concentrations of gaseous forms of methyl mercury in the landfill gases," Lindberg adds.

The first hint that something might be going on was the discovery of elevated levels of methyl mercury in water vapor that was removed from the landfill gas -- called landfill gas condensate -- at a Florida site several years ago, Lindberg says.

"But no one has made the kind of measurements that we reported, because the technology just didn't exist until very recently," he adds.

The study was published in a recent issue of the journal Atmospheric Environment.

Mercury is added to landfills when you throw out everyday items like thermometers, batteries, electrical switches and fluorescent light bulbs. Aanaerobic bacteria decompose landfill wastes. These same bacteria convert the waste mercury from your household garbage into the highly toxic methyl mercury compounds.

Dimethyl mercury is destroyed at landfills that "flare" -- or burn -- their landfill gases or direct those gases to be used as fuel in electric power plants. But only half the landfills in the United States burn their landfill gases, and flaring is even less common in many parts of the world, Lindberg says.

Edward Swain, a research scientist at the Minnesota Pollution Control Agency, says Lindberg's study is the first documentation of the release of dimethyl mercury from landfills, even though it's something that has been strongly suspected for a long time.

Mercury is a danger for wildlife as well as humans. Swain says many species -- loons, kingfishers, otters, mink and osprey -- eat far more fish per bodyweight than humans.

The study provides a good reason to keep mercury out of landfills, he adds. And he notes many governments are trying to do that by getting people to properly dispose of mercury-containing items by bringing them to special collection areas or urging people not use products that contain mercury.

What to Do: For more information, go to this site about mercury contamination of food. And there's more about mercury-related guidelines and health threats from the National Research Council.

SOURCES: Interviews with Steve E. Lindberg, Ph.D., senior research scientist, environmental sciences division, Oak Ridge National Laboratory, Tenn.; Edward Swain, Ph.D., research scientist, Minnesota Pollution Control Agency, St. Paul; Atmospheric Environment journal, August 2001
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