Sources of mercury

Natural sources of mercury

Natural levels of mercury exist in soil, air, and water around the world.

The most common geological deposits of mercury are cinnabar, a mercury sulfide mineral that can be composed of up to 86% mercury. Mercury is naturally present in raw materials such as coal, crude oil and other fossil fuels. It is also present in some minerals such as limestone, and in some metal ores that contain other metals such as zinc, copper and gold.

Various natural processes, including volcanic eruptions, weathering of rocks, and undersea vents can release mercury from the Earth's crust into water bodies, soils, and the atmosphere. Natural sources account for roughly 60% of the mercury deposited in Canada each year. 

Mercury travels around the planet in complex ways over decades. In its elemental form (its pure form), mercury evaporates easily and can enter the mercury cycle or be transported long distances by global wind currents.  As mercury enters the environment, it can be stored in vegetation, water bodies and soils. Mercury can be released to the environment through the decomposition of vegetation, forest fires, emission from water bodies, particles in air from sea salt spray, and leaching from soils into water.   

In addition, mercury deposited from natural and human-made sources can be re-emitted by natural processes and then end up in the atmosphere again. Scientists are still working to determine what impact climate change will have on the global movement and cycling of mercury.

Mercury sources from human activities

Because elemental mercury evaporates, it can move easily through the air and end up thousands of kilometres away from where it was first released. This makes it a global concern.

Mercury can enter the environment through human activities such as the burning of coal, the extraction of metals from ore, the manufacturing of cement, and the use and disposal of products containing mercury, such as fluorescent lights and some types of batteries. In certain regions of the world, small-scale gold mining processes using mercury are also a significant source of mercury pollution. Emissions from human activities account for 40% of mercury deposited in Canada each year, and 97% of these emissions come from other countries.

Between 2007 and 2017, Canadian industrial emissions of mercury to air decreased by 61%. This is the result of the closure of some industrial operations, the use of new emission control technologies, and increased use of best management practices. In 2017, the Canadian industrial sectors that released the largest amounts of mercury to air were iron and steel industries (24%), coal-fired electrical power generation (19%) and the cement and concrete industry (11%). 

During the same decade, Canadian industrial releases of mercury to water declined by 66%. In 2017, the Canadian industrial sectors that contributed the most to national releases of mercury to water were pulp and paper manufacturing (16%), non-ferrous smelting and refining (10%), and mining and rock quarrying (6%). The largest source of releases to water was from sewage treatment and waste management facilities, representing 68% of the total. These facilities do not generate mercury, but they do capture, as solid waste, most of the mercury generated upstream from industrial sectors or from the use or disposal of products containing mercury, and release any remaining amounts to water.

Managing and reducing mercury

The challenge for governments is to ensure that the levels of mercury in the environment do not exceed the concentrations expected from natural sources. Many countries and jurisdictions have implemented laws, regulations, policies, initiatives and agreements designed to lessen the threat of mercury. Proper disposal of mercury-containing products may also contribute to reduce mercury pollution into the environment.

In Canada, mercury is managed by federal legislation and guidelines, various programs and research groups, and through participation in international initiatives. Provincial and territorial governments have also established tools for reducing the impact of mercury pollution.

For more information on what the Government of Canada is doing to reduce the impacts of mercury, visit the Toxic Substances List page for mercury.

Visit the following page for information on mercury-containing products.  Information on proper disposal of mercury-containing products is available on the following pages for: 

• Lamps
• Batteries (see the “Electronic and electronic equipment” category)
• Other products such as thermostats (see the “Mercury containing products” category)