Mercury Emissions: The Global Context

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Controlling Power Plant Emissions

Mercury is a global problem that knows no national or continental boundaries. It can travel thousands of miles in the atmosphere before it is eventually deposited back to the earth in rainfall or in dry gaseous forms.

Types of Sources
Worldwide Distribution of Emissions
The U.S. in the Global Context
Related Information

Types of Sources

Natural sources of mercury—such as volcanic eruptions and emissions from the ocean—have been estimated to contribute about a third of current worldwide mercury air emissions, whereas anthropogenic (human-caused) emissions account for the remaining two-thirds. These estimates are highly uncertain. Much of the mercury circulating through today's environment is mercury that was released years ago, when mercury was commonly used in many industrial, commercial, and residential products and processes. Land and water surfaces can repeatedly re-emit mercury into the atmosphere after its initial release into the environment. The pie chart below shows that anthropogenic emissions are roughly split between these re-emitted emissions from previous human activity, and direct emissions from current human activity.

Pie chart showing that of total annual mercury emissions, about a third is generated by natural sources, a third is human-caused direct emissions, and a third is human-caused re-emitted emissions.
Source: Seingeur, 2004 and Mason and Sheu, 2002.

Worldwide Distribution of Emissions

Recent estimates, which are highly uncertain, of annual total global mercury emissions from all sources, natural and anthropogenic, are about 4,400 to 7,500 metric tons emitted per year. The world map and the pie chart below provide information about the worldwide distribution of mercury emissions.

World map showing distribution of emissions of mercury. Highest concentrations (5 to 22 metric tonnes per year) are shown on the east and west coasts of the United States, in southern Africa, in eastern Europe, and throughout China and Japan.
Source: United Nations Environment Programme Global Mercury Assessment, 2002, using J. Pacyna 1995 data, as presented by the Arctic Monitoring and Assessment Programme

Pie chart showing that 53% of mercury emissions originate in Asia; 18% originate in Africa; 11% originate in Europe; 9% originate in north America; 6% originate in Australia; and 4% originate in South America.
Source: Presentation by J. Pacyna and J. Munthe at mercury workshop in Brussels, March 29-30, 2004

The U.S. in the Global Context

U.S. anthropogenic mercury emissions are estimated to account for roughly three percent of the global total, and emissions from the U.S. power sector are estimated to account for about one percent of total global emissions. (United Nations Environment Programme (UNEP). Chemicals, Global Mercury Assessment, Geneva, 2002.).

EPA has estimated that about one third of U.S. emissions are deposited within the contiguous U.S. and the remainder enters the global cycle. Current estimates are that less than half of all mercury deposition within the U.S. comes from U.S. sources. However there are regional differences in these numbers. For example, U.S. sources represent a greater fraction of the total deposition in parts of the Northeast because of the direction of the prevailing winds.

Related Information

The Emissions Progress page presents information about progress in reducing mercury emissions in the U.S. from all human-caused sources.

The Controlling Power Plant Emissions: Decision Process and Chronology page describes the history of regulatory steps EPA has taken to reduce mercury emissions from power plants.