The use of mercury in products such as fluorescent and most high intensity discharge (HID) lamps is crucial to achieve desired light output and lamp life. In fact, this mercury enables lamps to operate more efficiently than incandescent and halogen lamps. Energy-efficient light sources greatly reduce the amount of solid waste that enters the waste stream, since these lamps last longer than incandescent or halogen lamps and require fewer replacements. In addition, use of energy-efficient lamps reduces the need for power generation , thereby reducing emissions from power plants that burn fossil fuel to generate needed electricity.
Ironically, while mercury use in lamps increases their efficiency, it also prevents the release of much higher amounts of mercury and other air pollutants from being emitted from power plants.
According to the National Electrical Manufacturers Association (NEMA)," the average mercury-conatining lamp manufactured in 1990 contained 43 mg of mercury. In 2003, that level was 11.4 mg of mercury. If manufacturers had used 43 milligrams of mercury in each of the 650 million lamps manufactured in 2003, those lamps would have contained 31 tons of mercury rather than 7 tons."
Mercury is found in many rocks including coal. When coal is burned, mercury is released into the environment. Coal-burning power plants, which account for a little over 50% of US electricity generation, are the largest human-caused source of mercury emissions to the air in the United States, accounting for about 40 percent of all domestic mercury emissions.
Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish. Fish and shellfish are the main sources of methylmercury exposure to humans. Methylmercury builds up more in some types of fish and shellfish than others.The levels of methylmercury in fish and shellfish depend on what they eat, how long they live and how high they are in the food chain.
Mercury does not get into the air directly from an operating lamp. It may bind with the glass or the phosphors or other coatings, but it stays in the lamp. Even when lamps are manufactured, mercury is contained by manufacturing processes or captured by filters. This leaves only one opportunity for direct mercury release from lamps into the air—breakage at the end of the lamp’s life.
This occurs when lamps are thrown into dumpsters or garbage trucks, typically prior to disposal. Because the amount of mercury content in an individual lamp is so low, breaking a small number of lamps does not present a health threat to workers. The improper disposal of large numbers of lamps, however, adds to the global reservoir of mercury. Burning hazardous wastes, or incineration of disposed materials can also release mercury into the environment.