Mercury's Toxic Emissions And How to Reduce Them
by John W. Anderson
Mercury is a dangerous pollutant, and environmental policy is moving to reduce the amount of it that drifts into the food chain. But the next steps are entangled in a fierce political debate over how far to go, how fast to do it and, especially, what approach to use.
The most prolific source of mercury pollution in the United States is smoke from coal burned to generate electricity. Some of these emissions are deposited in lakes, streams and oceans where they accumulate in the tissues of fish --- and then of humans who eat the fish.
By 2001, 41 states had issued some 2259 advisories for mercury contamination in a wide variety of fish species. Last March the federal Food and Drug Administration and the Environmental Protection Agency jointly warned women of child-bearing age and young children not to eat albacore tuna more than once a week. They should not eat swordfish, king mackerel, shark or tilefish at all, the agencies said, because of high levels of mercury.
Even health advisories, the least coercive of interventions, carry an economic cost. One key question is whether the health benefits outweigh those costs. Researchers at RFF recently examined this issue for a hypothetical advisory by the State of Maryland to limit consumption of striped bass from the Chesapeake Bay because of mercury contamination.
Although much of the public would be unaware of the advisory or would ignore it, the researchers found that the cost to consumers would run to millions of dollars a year with an additional but smaller burden on the commercial fishing industry. But a conservative estimate of the economic value of the health benefits, they concluded, would be more than half again as great as the costs. ("The Benefits and Costs of Fish Consumption Advisories for Mercury ," by Paul Jakus, Meghan McGuinness and Alan J. Krupnick, October 2002, RFF Discussion Paper 02-55 | Abstract)
In a global assessment of mercury pollution, a study for the UN Environment Program in 2002 described the process: "Once released, mercury persists in the environment where it circulates between air, water, sediments, soil and biota in various forms. Current emissions add to the global pool --- mercury that is continuously mobilized, deposited on land and water, and remobilized." The form that the mercury takes --- its "speciation" --- matters importantly to the distance that it travels and its ultimate transfer to living organisms. Different types of coal and other emissions sources have different speciation, making the issue to tracking pollution even more complex.
Regulation of mercury emissions encounters several difficulties. One is the tendency of these emissions to stay aloft for long periods, which means that the winds carry them across national boundaries.
The UNEP study estimated that worldwide in 1995 the emissions resulting from human activity, from the sources it was able to count, came to roughly 2200 metric tons a year. About one-tenth of that came from North America. Half came from Asia.
Only about 50 per cent of the mercury deposited in the United States comes from American sources, the EPA estimates. Paulette Middleton of Panorama Pathways, in a study done for Environmental Defense, puts the ratio even lower, at 30 per cent. That limits, in some parts of the country, the effectiveness of national regulation. But in other regions, particularly along the East Coast, the proportion of mercury deposition from local sources can range as high as 80 per cent. Tight restrictions on incinerators that went into effect in the 1990s have sharply reduced deposition in Florida and, in turn, reduced the concentrations of mercury found in fish and wading birds there, Middleton reports.
At present the only major source of mercury emissions that remains unregulated in the United States is coal-fired power generation, which contributes about 40 per cent of the country's total. In 1999 that was about 48 tons.
Several bills are now before Congress to reduce emissions of several pollutants by the electric utility industry. They include mercury for the first time, and they show great differences in approach. (See RFF's "Making Sense of Proposed Multipollutant Regulations and Legislation," at www.rff.org/multipollutant.)
The Bush administration's Clear Skies bill sets emissions targets for mercury of 34 tons by 2010 and 15 tons by 2018. But the bill contains an early credit program and a safety valve, a provision allowing generators to exceed those limits if the cost goes above a certain level.
In an analysis published in May, the federal Energy Information Administration found that the utilities' actual emissions would exceed both targets, first because of the early credits and in the longer term because the safety valve would be triggered. The utilities' mercury emissions would come to 40 tons in 2010, or six tons over the target, and 29 tons in 2025, or 14 tons over the target, according to the EIA's projections.
A Democratic alternative sponsored by Sen. Thomas Carper of Delaware contains no safety valve. It would set limits of 24 tons in 2009 and 10 tons in 2013.
Sen. James M. Jeffords (Independent, Vermont) has taken a more restrictive position. His bill would limit the electric utilities' mercury emissions to 5 tons by 2009.
Beyond the dispute over limits and timetables, the bills vary in the methods they would use to achieve them. Both the administration bill and the Carper bill would employ cap-and-trade programs, encouraging economic efficiency by allowing utilities to trade emissions permits among themselves to ensure that the reductions are made where the costs of compliance are lowest. Jeffords would not allow trading.
But all the bills concerning air pollution appear to be deadlocked at least until after the coming presidential election. Meanwhile the administration is pursuing by regulation some of the goals that it cannot achieve by legislation. The EPA is under a court order to produce by March 2005 a rule limiting mercury emissions from power plants.
Last December the EPA published, for discussion, a proposed rule --- or, more accurately, two alternative proposed rules. (See RFF"s "EPA Proposed Mercury Rule: A Supplement to the RFF Legislative Comparison Table," in Making Sense of Proposed Multipollutant Regulations and Legislation at www.rff.org/multipollutant.)
The first, which the administration prefers, is a cap-and-trade program under which the emissions target would be 15 tons a year by the time it is fully implemented in 2018 --- the same target as its Clear Skies bill's. Like the Clear Skies bill the rule also contains early reduction credits and a safety valve, implying that, as under the bill, the target will not be met.
As its second choice, the administration proposes to require the installation of "maximum achievable control technology" (MACT) on every power plant. That, it says, would reduce mercury emissions from the present 48 tons to about 34 tons by 2008.
The administration argues that cap-and-trade will result in much lower emissions over the long term, at lower cost, than MACT. But a number of environmental advocacy organizations are fighting cap-and-trade. Among other reasons, they point out that trading leaves open the possibility that while the national total emission falls, certain areas --- "hot spots" --- will continue to suffer high mercury loads.
In response, two RFF scholars published an appeal to the environmentalists not to confuse cap-and-trade, a highly effective tool, with the relatively lenient cap that the administration has proposed. There are ways to prevent hot spots from appearing, they note, such as a minimum requirement for every plant, or an opt-out provision for states with unusually vulnerable ecosystems. But they emphasize that cap-and-trade, used properly, is a highly efficient methods for achieving emissions reductions at the lowest possible cost. ("A Mercurial Reaction to Mercury?" a Web Feature by Dallas Burtraw and Alan J. Krupnick, Dec. 12, 2003.)
However it turns out, the EPA's rule is not likely to end American concerns about mercury pollution. UNEP's report found the pattern of deposition to be global.
Some countries, the report acknowledged, have taken action to reduce emissions. "However," it added, "due to long-range transport, even nations with minimal mercury releases, and other areas remote from industrial activity, may be adversely affected. For example, high mercury levels are observed in the Arctic, far from the sources of any significant releases."
Mercury contamination appears to be the kind of environmental threat that, like climate change or the shrinking of the ozone layer, must eventually be addressed through international action.