Mercury is a naturally occurring element that is a silver-colored liquid at room temperature. It is sometimes referred to as a "heavy metal". Historically, mercury has been valued for its ability to:
- Conduct electricity;
- Measure pressure and temperature;
- Form alloys with almost all other metals.
Because of these diverse properties, mercury has been used in a large number of household, commercial, medical and industrial applications, including:
- Medical instruments and equipment, such as blood pressure, gauges, thermometers and x-ray machines;
- Fluorescent lights;
- Electrical switches and relays used in certain devices and equipment, such as lighting, thermostats, pumps, space heaters and computers;
- Dental amalgam.
While mercury use in the United States has declined, the U. S. Environmental Protection Agency estimates that manufacturers use 500 - 600 metric tons of mercury annually as part of their production processes or to create products that rely on mercury's chemical and physical properties.