Learn about mercury

Properties of mercury

Mercury is a naturally occurring element found in the Earth’s crust. Mercury is a heavy metal, which means it has a high density and can be toxic in low concentrations.

Mercury travels through air, water and soil. This substance exists in the environment in different forms: elemental, inorganic and organic.

Elemental mercury

Elemental mercury (its pure form) is silver in colour and is the only metal that is a liquid at room temperature.It can combine with other metals such as tin, copper, gold and silver to form mercury alloys known as amalgams. Elemental mercury is very volatile and can vapourize to produce a colourless, odourless gas.  In its gaseous form, mercury can stay in the air for months and can travel long distances.

Inorganic mercury compounds

Inorganic mercury compounds occur when elemental mercury combines with elements such as sulfur, chlorine or oxygen to form mercury salts. Cinnabar is a mercury sulfide mineral that contains up to 86% mercury and is the most common form of mercury in nature.

Organic mercury compounds

Organic mercury compounds occur when elemental mercury combines with carbon and hydrogen. In the environment, particularly lakes, waterways and wetlands, mercury can be converted to a highly toxic, organic compound called methylmercury. Living organisms absorb methylmercury about six times more easily than inorganic mercury, as the substance can migrate through cells that normally block toxins. Methylmercury builds up in the tissues of living organisms and becomes more concentrated in the food chain as larger predators eat smaller prey. Humans are most often exposed to this form of mercury, primarily through consumption of fish and other seafood.

Because mercury is an element, it will never disappear from the environment, but its form and availability to living organisms may change over time.

For more scientific information on mercury, see the Canadian Mercury Science Assessment.

For more information on the movement of mercury through the atmosphere and ecosystems, consult the Mercury Cycle page.