About Mercury

In the environment, mercury can migrate between various media, such as air, soil and water. Conceptually, movements of mercury between these different environmental "compartments" are commonly known as "fluxes", and the quantities of mercury in the various compartments are often referred to as "pools". These fluxes and pools are studied in order to help assess the global mercury budget. Quantifying human versus natural mercury fluxes can be challenging because mercury deposited from anthropogenic releases can be re-emitted from land and water, undergo long-range transport in the atmosphere, be re-deposited elsewhere, and so on. This process of emission and re-emission is the reason why animals and peoples in remote areas with no local mercury releases, such as in the Arctic, may have elevated mercury levels.

Mercury exists as a gas and in a range of organic (carbon containing) and inorganic (not containing carbon) forms that vary in toxicity and persistence in living organisms. In the environment, mercury is transformed through complex biogeochemicalinteractions that affect environmental and biological forms and concentrations. Some mercury compounds are more easily absorbed by living organisms than elemental mercury itself. When atmospheric mercury falls to earth, it may be altered by bacterial or chemical action into an organic form known as methylmercury.

Methylmercury is much more toxic than the original metal molecules that drifted in the air, and has the ability to migrate through cell membranes and "bioaccumulate" in living tissue. Bioaccumulation is the process by which a substance builds up in a living organism from the surrounding air or water, or through the consumption of contaminated food. Bioaccumulation will vary for different species and will depend on emission sources as well as local factors like water chemistry and temperature. In the following figure, the concept of accumulated methylmercury is illustrated by the red dots, however the dots are not to scale.

(If the concentration of methylmercury in lake water is considered to have an absolute value of 1, then approximate bioaccumulation factors for microorganisms like phytoplankton are 10⁵; for macroorganisms like zooplankton and planktivores are 10⁶ ; and for piscivores like fish, birds and humans are 10⁷.)

The bioaccumulation of methylmercury in natural ecosystems is an environmental concern because it inflicts increasing levels of harm on species higher up the food chain. This occurs through a process known as "biomagnification", whereby persistent substances like methylmercury will increase in concentration from microorganisms, to fish, to fish eating predators like otters and loons, and to humans. Elevated methylmercury levels may lead to the decline of affected wildlife populations and may affect human health when people consume significant quantities of fish or other contaminated foods. The most infamous case of this impact occured in Minimata, Japan, where local residents consumed fish with toxic levels of methylmercury originating from an industrial sewer discharge, leading to the deaths of more than 1000 people. This type of exposure has now come to be known as Minamata disease.

Sources of Mercury

Since industrialization, the amount of mercury found in the environment has increased by a factor of 2 to 4, largely because of human activities. Mercury has always been emitted from natural sources such as volcanic eruptions, the weathering of soils and rocks and vaporization from the oceans; however, scientists believe that more than half of the mercury in the environment today is from anthropogenic sources. Canadian anthropogenic emissions of mercury to the atmosphere in 2000 are estimated to have been approximately 8 tonnes, while the U.S.A. and global emissions were approximately 120 and 2200 tonnes respectively during 1995. In addition to industrial releases, mercury can be found in thermometers, dental fillings, fluorescent light bulbs, and other consumer products.

Managing Mercury

The challenge for governments is to ensure that the levels of mercury in the environment do not exceed the concentrations which we would expect from natural processes. As the dangers of mercury and its compounds become more apparent, governments are working with concerned citizens, industries and environmental organizations to examine a range of mercury management tools. In Canada, mercury is managed by federal legislation and guidelines, various programs and researchgroups, and through participation in international initiatives. Provincial and territorial governments have also established tools for reducing the impact of mercury pollution. Several Canada-wide standardshave been endorsed by Environment Ministers from provinces, territories, and the federal government to ensure that efforts are consistent across the country. Educational programs are being created to answer the question, "what can I do?" in order to inform people of appropriate reduction measures that can be used in the home, cars, schools and the workplace.

In addition to providing information on the topics outlined above, this website provides a selection of resources for visitors, including an extensive list of links, fish consumption advisories, steps for cleaning up small mercury spills, information about mercury disposal, and a glossary of terms related to mercury.