Congratulations! You've been doing your part to slow down global warming by switching to the new energy-efficient compact fluorescent lights (CFLs) - those swirly bulbs that claim to use up to 75 percent less energy than incandescent light bulbs and last up to 10 times longer, according to the United States Department of Energy.

But before you smugly pat yourself on the back, answer this: What do you do with them when they burn out?

Don't put them with your regular recyclables, says Tim Basta, co-owner of stjoegreen, a St. Joseph curbside recycling company. Although customers regularly try to leave them in the recycling bins, he says his company can't take them because the bulbs are considered a hazardous waste.

"I was kind of shocked to be honest," Mr. Basta says about when he first learned of the situation. "They are supposed to be the greatest invention since sliced bread and then there's mercury in it."

Mercury is a highly toxic heavy metal that, when put into landfills, will leach into the ground water and contaminate streams, rivers, lakes and drinking water. According to the HTR-Group, a government-certified resource recovery facility in Kaiser, Mo., 1/70th of a teaspoon of mercury can contaminate a 25-acre lake to the point that the fish in it are unsafe to eat for 50 years. Although one CFL only contains a tiny amount of mercy (an average of 4 milligrams, according to the EPA), small amounts add up and are a hazard if not disposed of properly.

DISPOSE

One option is to take your CFLs to a hazardous waste collection site. The city of St. Joseph household hazardous waste program is held twice a year, once in the spring and once in the fall, says Public Works Director Bill Woody. You also can take your batteries, paint and other hazardous waste at the same time. The dates are not yet scheduled for this year, but it's always on a Saturday from 9 a.m. to 3 p.m., and the city advertises the date several weeks ahead of time. It's free, however, it is only open to St. Joseph resident property owners.

It is legal to throw the bulbs in your regular trash, says Mark Conner, public information specialist with the Missouri Department of Natural Resources Hazardous Waste Program. If you do, the department recommends putting the bulb in a zipper-type plastic bag before disposal. The Environmental Protection Agency suggests two bags. Although it is legal, he says the department recommends recycling them instead. But it must be a recycling facility that handles bulbs with mercury.

RECYCLE

Probably the easiest and best thing to do is to take your bulbs to Home Depot. All stores recently began accepting them for recycling at no charge as part of the Eco Options program. Simply bring unbroken bulbs to the service desk at any Home Depot. They'll take your batteries, too.

The city of St. Joseph also will recycle them if you bring them to the landfill (not the recycling center). The cost is 50 cents per bulb (which is at cost for the city to recycle them), and anyone can bring them in. They also take other types of fluorescents for a fee. Call the landfill at 253-9764 for more information.

If you break one, the Missouri Department of Natural Resources has a seven-step process to follow (www.dnr.mo.gov and click on Fluorescent Bulbs in the directory). Essentially, you should evacuate and ventilate the room for 15 minutes before cleaning it up. Then wear disposable gloves to pick up the broken pieces and put them in a glass jar with a metal lid or a zipper-type plastic bag. Clean the area with a wet paper towel and put the towel and the gloves in the container. Do not use a vacuum because it will spread the mercury vapor and dust throughout the room. The site also suggests that consumers may want to avoid using CFL's in bedrooms or carpeted areas frequented by infants, small children or pregnant women.

Lifestyles reporter Sylvia Anderson may be reached at sylviaanderson@npgco.com