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When a CFL bulb breaks, it emits mercury that far exceeds federal standards, the DEP found.

For tips about handling and recycling fluorescent bulbs,click here.

To read the DEP report, click here.

Compact fluorescent light bulbs that get broken release mercury that can be more difficult to clean up than consumers and government agencies have thought, says a new report from the Maine Department of Environmental Protection.

The DEP spent months breaking bulbs in a laboratory and experimenting with cleanup strategies before issuing its report on Monday. It also posted new cleanup advice and precautions about the spiral bulbs, and advised consumers for the first time that the popular, energy-efficient lights may not the best choice for some parts of the home, including children's bedrooms and playrooms.

The results from what is believed to be the first research of its kind nationwide are being reviewed by other states and by federal officials, who may update their own advisories about the mercury in fluorescent bulbs.

DEP officials said the results won't change the state's policy of promoting the bulbs as a way to save energy and reduce global-warming pollution.

"We are still very much in support of CFL use," said Stacy Ladner, an environmental specialist with the DEP and one of three staff researchers who did the study. "Hopefully, people will think about where they put them" and how they clean up any bulbs that break.

Mercury is a toxin that affects the nervous system and can harm brain development in young children and fetuses.

A compact fluorescent bulb contains only about 5 milligrams of mercury, enough to fit on the tip of a ball-point pen. An old-fashioned mercury thermometer, by comparison, contains about 100 times that amount.

But if a bulb breaks, the small amount of mercury can create high levels of vapor in the air, the study showed.

The mercury-vapor standard in federal and state safety guidelines is 300 nanograms per cubic meter of air. Broken bulbs created levels that often exceeded that standard and sometimes exceeded 25,000 or even 50,000 nanograms per cubic meter for short periods of time, according to the study.

The safety standard is based on long-term exposure for adults in industrial settings. No one knows what is a safe level of short-term exposure for children or fetuses, or exactly how dangerous a broken bulb might be, said Deborah Rice, a toxicologist with the Maine Center for Disease Control and Prevention.

"How much of a risk is posed by breaking one bulb, I think, is really unclear," Rice said. "We don't really know. The only thing we can advise is, clean up as well as you can and recognize when you vacuum a month later, you'll stir up mercury again."

Rice said the Maine study broke new ground because no one had studied the risks that way.

For example, federal and state agencies have long recommended that the pieces of broken fluorescent bulbs be sealed in plastic bags. The DEP researchers found that mercury migrates through the plastic, so the agency now says the residue should be sealed in a glass jar.

"They've come up with what we think are pretty common-sense guidelines," said Denis Bergeron of Efficiency Maine, the state agency that offers rebates to promote sales of the fluorescent bulbs.

Bergeron said people have come to accept the bulbs despite the fact that they contain small amounts of mercury and must be recycled carefully.

"They are safe. Glass contains mercury completely well, and if people recycle, they'll provide huge environmental benefits," he said.

Efficiency Maine has set up collection sites for burned out bulbs at more than 300 retailers around the state. Broken bulbs must be taken to trash transfer stations for disposal.

Scott McFarland, manager of the Riverside Recycling Center in Portland, said residents bring in two or more broken fluorescent bulbs a week. Some drop off the pieces in sealed plastic bags, while many simply hand over the stem of the bulb with whatever glass is still attached.

"It's like any of that stuff, you've got to learn...