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Q Compact fluorescent lightbulbs, or CFLs, save energy, but they also contain mercury. Should I use them?

A CFLs do contain a very small amount of mercury. About 4 milligrams are sealed inside each bulb. For comparison, there are about 25 milligrams of mercury bound up in a watch battery and as much as 2 grams encapsulated in a home thermostat. But consider this: A 27-watt CFL lights up a room as well as a 100-watt incandescent bulb but uses only one-fourth the energy. This is where mercury comes in again: More than half of all electricity generated in the United States comes from coal-fired power plants, a huge source of mercury pollution. Over a CFL's 10,000-hour life span, the mercury within the bulb, plus the mercury emitted by power plants supplying electricity to the bulb, adds up to about 8 milligrams. An incandescent has a life span of just 1,000 hours, or one-tenth the lifespan of a CFL. To equal one CFL, you would have to burn 10 incandescents, emitting about 17.6 milligrams of mercury. By the time CFLs burn out, little mercury remains. But don't throw the bulb in the trash; it might end up at the incinerator. Ask about disposal at your local Household Hazardous Waste collection site. NRDC is working to establish CFL recycling programs. Visit the government's EnergyStar website for more information.

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Illustration: Mark Matcho

OnEarth. Spring 2005
Copyright 2005 by the Natural Resources Defense Council