All CFCs have a little mercury that can pollute landfills if the bulb is broken. There are a few "low mercury" varieties, which I guess means even less mercury than the little bit the bulbs hold regularly. They still need special treatment, though. If you buy at IKEA, they have a take-back program, or if you don't live near an IKEA, then you can find a special recycling program in your area at
www.earth911.org or
www.lamprecycle.org.