The U.S. EPA has concluded that mercury is not a necessary ingredient in a number of consumer products, and subsequently developed a searchable database of products that contain mercury and possible non-mercury alternatives.
Mercury is a commonly known ingredient in many thermometers and thermostats, but it's also found in batteries, fluorescent lamps and the switches in cars and electronics. It can be used as a corrosion inhibitor along with other heavy metals like lead.
Mercury poses both a health concern and an environmental concern. Because it is colorless and odorless, it is hard to clean up. If a mercury-containing product breaks, it can damage the kidneys and nervous system if inhaled. If these products break in a landfill, the mercury can contaminate soil and groundwater. For this reason, recycling is the prescribed solution for any products containing mercury.