Methylmercury contamination of fish warrants worldwide public warning

That is one of the key findings comprising "The Madison Declaration on Mercury Pollution" published March 8  in a special issue of the international science journal Ambio. Published by the Royal Swedish Academy of Sciences, Ambio is widely recognized as an important international forum for debate on scientific, social, economic and cultural issues affecting the human environment.

"Exposure during pregnacy will affect children's development later on in life," said Donna Mergler, an environmental health professor at the Université du Québec à Montréal, who contributed to the report. The exposure to mercury in the womb does not cause sickness as does exposure from major mercury disasters, but it does lead to a shift in children's intellectual capacities, said Mergler. Some children may have learning difficulties and fewer will be super bright.

Developed at the Eighth International Conference on Mercury as a Global Pollutant last August in Madison, Wis., the declaration is a synopsis of the latest scientific knowledge about the danger posed by mercury pollution. It presents 33 principal findings from five synthesis papers prepared by the world's leading mercury scientists and published in the same issue of Ambio. The declaration and supporting papers summarize what is currently known about the sources and movement of mercury in the atmosphere, the socioeconomic and health effects of mercury pollution on human populations, and its effects on the world's fisheries and wildlife.

Five other major findings in the declaration were:

• On average, three times more mercury is falling from the sky today than before the Industrial Revolution 200 years ago as a result of the increasing use of mercury and industrial emissions.
• The uncontrolled use of mercury in small-scale gold mining is contaminating thousands of sites around the world, posing long-term health risks to an estimated 50 million inhabitants of mining regions. These activities alone contribute more than 10 percent of the mercury in Earth's atmosphere attributable to human activities today.
• Little is known about the behavior of mercury in marine ecosystems and methylmercury in marine fish, the ingestion of which is the primary way most people at all levels of society worldwide are exposed to this highly toxic form of mercury.
• Methylmercury exposure now constitutes a public health problem in most regions of the world.
• Methylmercury levels in fish-eating birds and mammals in some parts of the world are reaching toxic levels, which may lead to population declines in these species and possibly in fish populations as well.

"The policy implications of these findings are clear," said James Wiener, a Wisconsin Distinguished Professor at the University of Wisconsin-La Crosse who served as technical chair for last summer's conference. "The declaration and detailed analyses presented in the five supporting papers clearly show that effective national and international policies are needed to combat this global problem."


Wiener said the Madison Declaration summarizes a year-long effort by many of the world's leading mercury scientists, assembled into four expert panels, to review and synthesize the major mercury science findings. Every member of all four scientific panels endorsed the declaration, he said. Wiener added that all 1,150 participants at the conference were invited to express their confidence in the experts' findings, and the vast majority of those who did so agreed with the experts' conclusions.

Other major findings in the declaration include:

• Increased mercury emissions from developing countries over the last 30 years have offset decreased emissions from developed nations.
• There is now solid scientific evidence of methylmercury's toxic health effects, particularly to the human fetus.
• New evidence indicates that methylmercury exposure may increase the risk of cardiovascular disease, particularly in adult men.
• Increasing mercury concentrations are now being found in a number of fish-eating wildlife species in remote areas of the planet.
• The actual socioeconomic costs of mercury pollution are probably much greater than estimated because existing economic analyses don't consider mercury's impacts on ecosystems and wildlife.
• The concentration of methylmercury in fish in freshwater and coastal ecosystems can be expected to decline with reduced mercury inputs; however, the rate of decline is expected to vary among water bodies, depending on the characteristics of a particular ecosystem.

Besides Wiener, conference organizers included James Hurley of the University of Wisconsin-Madison Sea Grant Institute, David Krabbenhoft of the U.S. Geological Survey and Christopher L. Babiarz of the UW-Madison Water Science & Engineering Laboratory. Wisconsin Sea Grant, USGS and UW-La Crosse were among the major sponsors of the 2006 conference.

Note: This story has been adapted from a news release issued by University of Wisconsin-Madison.


The original publication

Donna Mergler, Henry A. Anderson, Laurie Hing Man Chan, Kathryn R. Mahaffey, Michael Murray, Mineshi Sakamoto, Alan H. Stern, Methylmercury Exposure and Health Effects in Humans: A Worldwide Concern, Ambio, 36/1 (2007) 3-11. DOI: 10.1579/0044-7447(2007)36[3:MEAHEI]2.0.CO;2


Related publications

D. Mozaffarian, E.B. Rimm, Fish intake, contaminants, and human health: evaluating the risks and the benefits, J. Am. Med. Assoc., 296/15 (2007) 1885-99. DOI: 10.1001/jama.296.15.1885

BUND (Report, in German): Quecksilber - Globale  Belastung und Gefährdung kindlicher Fähigkeiten, BUND, February 2007

Anna L. Choi, Philippe Grandjean, Methylmercury exposure and health effects in humans, Environ. Chem. , 5/2 (2008) 112-120. DOI: 10.1071/EN08014


Link page: All about mercury

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last time modified: March 9, 2024