What is a CFL? It is a Compact Fluorescent Light bulb. It is a new breed of low energy consumption, high lumen (light) output screw-in type light bulb, similar to the tungsten filament conventional bulbs most of us have grown up with.
There are a lot of urban legends and complaints after these bulbs have made their debut that they have dangerous amounts of mercury that can contaminate our surroundings if broken.
A little history first: These bulbs have been around for around ten years now. Early bulbs were a little less efficient, slow to turn on, and had a strange white glow that some people weren't used to. They also didn't last as long as expected. Within the last few years, they have been getting better performance. They would come on a good bit quicker, the color temperature was closer to what we were/are used to, they last longer, are more efficient, and in some cases smaller globe size. Typical bulbs have an electronic switching supply contained in the base of the bulb.
Some caveats were: the overall size would make it hard to place into some light fixtures; they would not start if used outside in cold weather; not dimmable like conventional bulbs (some special ones do dim but they are expensive); they are fragile; ideally they should be used upright; they would overheat and fail if placed in a small globe fixture with little ventilation; the cost is almost eight times the price of a conventional bulb.
New technology is slowly addressing these problems.
What has happened is there has been an outcry by some environmentalists and politicians that these CFL's cause serious mercury contamination. What I find interesting is when I ask an opponent of these CFL's, when did they become a problem? Did they know when they were first used?
In reality, CFL's are no more dangerous than typical fluorescent tube type bulbs that have been around for more than fifty years. In fact, most homes use standard tube or coil type fluorescent bulbs in garages, kitchens, workshops, commercial offices grocery stores, industrial complexes, etc.
They have even more mercury than a typical CFL. In fact, if you take a four foot tube and tip it to one end, you can usually see a small ball of mercury rolling around inside. We have been disposing millions of these bulbs in dumps and landfills for years and no one has ever complained. Sure, there should be a special containment area or bin in a community trash dumpster to recycle these tubes or CFL's but I haven't seen one yet.
Study the following link:
http://sound.westhost.com/articles/incandescent.htm