However, in many cases use of CFLs will offset mercury that would otherwise be introduced into the environment from other sources. For example, coal contains mercury and this mercury is released into the environment when coal is burned to produce electricity. If the electricity used to operate your lamps is generated from coal, and you operate 100-watt incandescent lamps for 10,000 hours, the power generating plant will release between 40 mg and 70 mg of mercury into the environment, depending upon the type of coal being used. If instead of the 100-watt incandescent lamp, you use a 25-watt CFL, the power plant mercury emissions drop to between 10 and 18 mg over the same 10,000 hour period, again depending upon the type of coal used. Even when the 5 mg of mercury in the CFL is added to the environment at the end of the lamp's 10,000 hours life, the total mercury from using the CFL is far less than using the incandescent lamp. Mercury emissions will be lower for For lower power incandescent lamps and CFL replacements, but for any incandescent lamp of 40 watts or greater, there will be more mercury added to the environment by using an incandescent lamp than by using a CFL, assuming that the electricity used to operate both is generated by burning coal.
