Compact florescent lightbulbs (CFL's) have been heralded as a great way to save energy and materials. They last up to 10 times longer than incandescent bulbs, don't emit waste heat, and use about 2/3 less electricity than incandescents. However, they do contain mercury, an element that can be dangerous. Currently there is no good way of recycling these bulbs, so how do you decide which is worse? Well, it turns out there are only about 4 mg of mercury in one CFL (compared to 25 mg in your watch battery). Also, burning coal to create electricity releases mercury into the air, so using a more efficient lightbulb reduces mercury in that respect. Reducing the amount of coal burned in a power plant will also reduce emissions of sulphur oxide and carbon dioxide. So use CFLs and save some money and energy, and when they burn out just make sure to bring them to a hazardous waste facility.