Recycling a CFL – Do Not Throw Compact Fluorescent Lamps Away! Why all the fuss? CFL's contain about 5 milligrams of a neurotoxin called MERCURY...the amount of mercury in one CFL "is enough to contaminate up to 6,000 gallons of water beyond safe drinking levels."...read more!
http://homerepair.about.com/od/electricalrepair/ss/CFL_recycling.htm