According to the EPA's ENERGY STAR® Compact Fluorescent Light Bulbs (CFLs) and Mercury FAQ Sheet, CFLs contain an average of 5 milligrams of mercury—about the amount that would cover the tip of a ballpoint pen. How does this compare to, say, the amount in the thermometer your family used when you were growing up? It would take approximately 100 CFLs to equal the 500 milligrams of mercury found in an old-fashioned thermometer. Most people don't have anywhere near that many light fixtures in their homes.
However, CFLs are similar to other hazardous household items (paint, batteries, thermostats, etc.) and should be handled with care. Your best bet is to use common sense when installing and replacing them. Always screw and unscrew the lamp by its base (not the glass), and never forcefully twist the CFL into a light socket. And if you do break a CFL in your home, make sure to follow the clean-up steps outlined in the PDF linked above.
Another tip is to go green all the way: Don't throw old CFLs away—recycle them! If you aren't sure what's available in your area, check out www.lamprecycle.org, www.earth911.org or call 1-877-EARTH911 for local disposal options. And, in addition to having adorable furniture and tasty meatballs, IKEA stores also take back used CFLs.
In the end, the environmental benefits of CFLs far out weight any hazard or inconvenience they may cause you. They last longer, don't give off any heat and use about 75% less electricity than regular light bulbs. Besides, if you are concerned about mercury, you can check out this list of 5 Ways To Stay Safe From Mercury.
Forty percent of the mercury being released into our environment comes from coal-fired power plants. That means 13.6 milligrams of mercury is released in generating the power needed to light an incandescent bulb, whereas you only result in 3.3 milligrams to run CFLs.
If you need more information, check out a few other helpful articles on the subject:
National Geographic News - Fluorescent Lights' Mercury Poses Dim Threat
GE Lighting - Compact Fluorescent Light Bulb FAQ
Snopes.com - CFLs Urban Legend Reference Page
