Mercury is also known as quicksilver because it is a silver-colored liquid. It is a naturally occurring element that can cause serious environmental and health problems. There are several common sources of mercury in a household, including thermometers, fluorescent lights, button-cell batteries, barometers, thermostats, electrical switches, some blood pressure measuring devices, and in the lights commonly found in children's athletic sneakers (those that "light-up" with each step). These sources are poorly absorbed by the body, so accidental ingestion is a moderate toxicity level, but large amounts of inorganic forms/compounds such as these can lead to serious kidney damage.
Mercury is also present in organic forms, such as fish and other marine life, which when ingested at toxic levels or over a prolonged exposure period, can lead to irreversible brain damage, bone, joint, muscle, and organ failure.