Mercury concentrations in the environment are currently two to four times the levels of pre-industrial times. Mercury exists naturally in the environment. But it is also released by human actions such as coal burning, smelting base metals, waste incineration, small-scale gold mining and collecting water in reservoirs.

Mercury is a risk particularly when it enters aquatic environments, where it converts to its most toxic form (methylmercury) and enters the food web. Humans and wildlife are exposed to methylmercury by eating foods from freshwater and marine environments.

Mercury compounds are more concentrated in fish and wildlife predators feeding high in the food web. Effects of mercury exposure include lower reproductive rates, adverse changes in hormone and immune systems, changes in brain chemistry, and behavioural and visual abnormalities. The need to reduce mercury in the environment is widespread and requires international action.

Science is fuelling world-wide cooperation through increased understanding of the urgent need for protection from detrimental exposure.

Seeking Solutions through S&T

Generally, Canadians are exposed to methylmercury by eating fish or certain northern country foods such as marine mammals. Environment Canada’s long-term analyses show increasing concentrations in some fish-eating wildlife over the past 30 years. Common loons and river otters from the interior of Nova Scotia have among the highest tissue concentrations reported for these species. In Kejimkujik National Park, 92 percent of adult loons have mercury concentrations in their blood that pose a high risk of impairing reproduction.

Scientists are monitoring and modelling mercury’s global atmospheric movements and deposition in combination with interdisciplinary analyses of water, sediment and wildlife exposure. Extensive examination of feathers, blood and eggs of common loons reveals a west-to-east pattern of increased mercury exposure – with regional variation – that roughly matches the pattern of atmospheric deposition.

The Canadian Atmospheric Mercury Measurement Network (CAMNet) measures airborne mercury from sites near urban areas, in rural areas, and in one remote location in the high Arctic. A major analysis of data from the network between 1995 and 2005 showed only a slight decline in most of Canada:

– areas near the urban centres of Toronto and Montreal declined by 15 percent;

– rural eastern Canada decreased up to 7 percent; and

– the high Arctic had no change.

Computer modelling demonstrates how airborne industrial mercury moves around the world through the atmosphere. In recent decades, Europe’s emissions have decreased. Asia’s have increased and significantly contribute to mercury deposition in North America, including the Arctic.

Mercury is a major concern in the Arctic, where prevailing winds move in a circular pattern and draw air pollutants from much of the Northern Hemisphere. In addition, the polar sunrise, which follows months of winter darkness, may have photochemical effects that cause mercury to fall back to the earth in a strongly reactive form. The fate of that mercury has not been established. However, it is entering a fragile ecosystem currently undergoing unprecedented changes including warming temperatures that may influence conversion to methylmercury.

Mercury in the Remote Arctic

Ivory Gulls are a rare marine bird breeding at remote sites in the high Arctic such as Seymour Island (Nunavut). They are in serious decline and are protected under the Species at Risk Act. Ecological knowledge acquired from northern residents through interviews corresponds with scientific surveys that show an 80 percent decline since the early 1980s.

Environment Canada’s seabird egg archives at the National Wildlife Research Centre (Ottawa) were analyzed and revealed high mercury concentrations over the past three decades. This may be an important stressor on the population. Mercury is easily passed to eggs and nearly 100 percent of the transferred mercury is toxic to the unborn young.

Overall, about 120 tonnes of mercury are deposited in Canada each year. About half is from anthropogenic (human) sources and half is in the form of revolatilized mercury from the oceans and land. Up to 19 percent of mercury from human sources that is deposited in Canada comes from Asia, 11 percent from the United States, four percent from Europe, and 3.5 percent from Russia.

Transforming Knowledge into Action

Who can use these results?

Environment Canada’s understanding of trends in mercury deposition and effects of exposure in wildlife provides the scientific basis for Canada’s domestic and international decisions on mercury reduction. Managing mercury is a complex business due to its volatile nature and ability to travel long distances in the atmosphere.

The federal government combines legislation and guidelines for industry with research and reduction programs. The Canadian Council of Ministers of the Environment has endorsed several Canada-wide Standards to reduce industrial releases, such as emissions standards for coal-fired electric power generation plants. Other guidelines include a Risk Management Strategy for Mercury Containing Products and Municipal Actions Guidance on the Canadian Environmental Protection Act Registry.

Canada contributes to mercury assessments and policy development internationally, including the United Nations Environment Programme (UNEP) and the Arctic Council. Canada also invests in research to improve global understanding of mercury’s behaviour and effects on ecosystems, and to build on socio-economic analyses and predictive computer modelling of land-use impacts.

Benefits to Canadians

Canada has reduced domestic mercury emissions by 90 percent since the 1970s. If international mercury deposition comes down, there will be benefits for healthy aquatic ecosystems that support local and global biodiversity. These healthy ecosystems will support commercial and recreational fishing for generations. And the people who live along shorelines and near reservoirs, and those who eat fish, will be protected from exposure.

For more information:

Environment Canada’s Mercury Website (Environment Canada’s comprehensive hub on mercury in the environment)

Mercury: Your Health and the Environment (Health Canada’s Mercury Issues Task Group 2004)

Mercury in the Environment: A Primer (Part of Pollution Probe’s Primer Series, funded in part by Environment Canada)

Mercury Management: Federal Legislation and Guidelines including Canada-wide Standards (Environment Canada’s website on laws and regulatory programs)

Intercontinental Atmospheric Transport of Anthropogenic Pollutants to the Arctic Network (International Polar Year research project on atmospheric contaminants)

Northern Contaminants Program (Indian and Northern Affairs Canada links to non-technical and scientific reports for this program and for the Arctic Monitoring and Assessment Programme)

Scientific papers

Braune, B.M. 2007. Temporal trends of organochlorines and mercury in seabird eggs from the Canadian Arctic, 1975 to 2003. Environmental Pollution 148(2): 599-613.

Braune, B.M., M.L. Mallory and H.G. Gilchrist. 2006. Elevated mercury levels in a declining population of ivory gulls in the Canadian Arctic. Marine Pollution Bulletin 52(8): 978-982.

Burgess, N.M. and M. Meyer. 2008. Methylmercury exposure associated with reduced productivity in common loons. Ecotoxicology 17(2): 83-91.

Scheuhammer, A.M., M.W. Meyer, M.B. Sandheinrich and M.W. Murray. 2007. Effects of environmental methylmercury on the health of wild birds, mammals, and fish. Ambio 36: 12-19.

• This paper was identified by Thomson Reuters Essential Science Indicators as one of the most-cited papers in its discipline (Environment/Ecology) published during the past two years. Read the Science Watch Q&A with Tony Scheuhammer.

Scheuhammer, A.M. and M.B. Sandheinrich. 2008. Recent advances in the toxicology of methylmercury in wildlife. Ecotoxicology 17(2): 67-68.

Scheuhammer, A.M., N. Basu, N.M. Burgess, J.E. Elliott, G.D. Campbell, M. Wayland, L. Champoux and J. Rodrigue. 2008. Relationships among mercury, selenium, and neurochemical parameters in common loons (Gavia immer) and bald eagles (Haliaeetus leucocephalus). Ecotoxicology 17(2): 93-101.

Steffen, A., T. Douglas, M. Amyot, P. Ariya, K. Aspmo, T. Berg, J. Bottenheim, S. Brooks, F. Cobbett, A. Dastoor, A. Dommergue, R. Ebinghaus, C. Ferrari, K. Gardfeldt, M.E. Goodsite, D. Lean, A.J. Poulain, C. Scherz, H. Skov, J. Sommar and C. Temme. 2008. A synthesis of atmospheric mercury depletion event chemistry in the atmosphere and snow. Atmospheric Chemistry and Physics 8: 1445–1482.

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© Her Majesty the Queen in Right of Canada, represented by the Minister of Environment, 2008.
Catalogue No. En164-15/9-2008E; ISBN 978-1-100-10518-5