Think green these days and the light bulb that comes on is increasingly a swirly CFL. Those compact fluorescent light bulbs are proven to save money and energy, but some researchers say they're no silver bullet. Beyond concerns about the amount of mercury in the bulbs, which require careful handling and disposal and can seep out of landfills, Dr. Magda Havas of Canada's Trent University points to some of their lesser-known side effects - ultraviolet radiation and radio frequency radiation that can cause health problems in electrically-sensitive people.

"Where they can't concentrate, they can't remember things, and so they have to take copious notes if they're at meetings where there are fluorescent light bulbs present, that type of thing."

It's called "foggy brain syndrome", according to Dr. Havas. She says people who react to CFLs also report migraines, skin rashes, body aches and pains.

Dr. Havas advises anyone who thinks they may be sensitive to CFLs to switch back to incandescent bulbs for a week to see if the symptoms are reduced.

Some researchers believe an alternative is LED lighting, also highly efficient, which could address the concerns with CFLs.

LEDs don't contain mercury, and have lower electromagnetic emissions, although current models can still affect many electrically-sensitive people if they produce what's called "dirty electricity" - created when high frequencies get onto wiring, which has some scientists concerned.

"These high frequency surges go on to the electrical wiring in your home, and so you don't even have to be in the same room with the compact fluorescent light bulb to be exposed to this, because the wires run throughout your home."

Robert Crane is with C. Crane Company, which developed the first bright LED light bulb approved by both the F-C-C and U-L, Underwriters Laboratories Inc., an independent product safety certification organization. Crane's bulbs save energy, are mercury-free and emit less radiation.

"In our tests here, we have fairly sensitive equipment and once you're two or three feet away from the light bulbs, it's very difficult to detect any radiation."

Crane predicts LEDs will be the preferred bulb ten years from now once the price comes down, design continues becoming more attractive and consumers catch on.

According to Camilla Rees, MBA, an independent health and technology advocate and researcher, LEDs like Crane & Co.'s GeoBulb, which does not produce dirty electricity, may be as good a choice for consumers today.

Rees reports that large lighting companies have been investing heavily in improving the quality of LEDs, long accused of poor lighting quality. She says Crane's GeoBulb is the best attempt yet at a LED bulb for a table lamp, although it still could use improvement to the color and warmth.

Today's LEDs are expensive, but when amortized over their useful life (as with compact fluorescent bulbs) they still come out far more economical than incandescent bulbs.