Study Shows Fear of Mercury ‘Hot Spots’ Unfounded

Published August 1, 2004

Faced with scientific consensus that current levels of exposure to mercury pose little or no threat to human health, some environmental activist groups have taken to claiming mercury “hot spots” immediately surrounding power plants have been overlooked in scientific studies. Two new studies, however, show such fears are also unfounded.

Ohio River “Hot Spot” Meets EPA Standards

In a study concluded this spring, the Ohio River Valley Sanitation Commission (ORSANCO), the interstate agency responsible for developing Ohio River water quality standards, reported on mercury levels in the Ohio River. Anti-mercury activists have alleged the Ohio River Valley may be the most concentrated “hot spot” for environmental mercury because 49 power-generating facilities are located on the Ohio River.

According to ORSANCO, tests for water quality in the valley show the Ohio River is not “impaired” for mercury, a designation that would require fish consumption advisories and similar actions. Applying Environmental Protection Agency (EPA) mercury standards, which are among the world’s toughest, ORSANCO determined the Ohio River as a whole contains safe mercury levels and meets EPA standards.

Noted Rob Reash, a senior environmental analyst with American Electric Power, “We believe the action taken by ORSANCO verifies the position that AEP has made concerning mercury ‘hot spots’–there are a wide variety of sources of mercury (global, regional, local, wastewater sources) to a given waterbody, and that the probability of local ‘hot spots’ is extremely negligible.

“The hot spot concern would be valid only if all of the mercury that accumulates in an area around a power plant originates exclusively (or predominantly from) that facility,” Reash continued. “This assumption is quite erroneous, and ignores the well-documented facts of mercury chemistry and transport, and the contribution of global sources to mercury that is deposited in the United States (which is significant).”

Analysis Confirms Superiority of Cap-and-Trade

In a separate study, scientists at the Electric Power Research Institute (EPRI) have concluded that the Bush administration’s cap-and-trade approach to regulating mercury emissions provides the most effective means of reducing industrial mercury emissions and any alleged hot spots of increased deposition.

EPRI, an independent, nonprofit center for public interest energy and environmental research, documented its findings June 16 in comments submitted to EPA. The report described results from extensive, state-of-the-art computer models simulating deposition of mercury released from every coal-fired plant in the United States and from all other mercury emission sources in the U.S. and throughout the world.

The analysis compared results from three different scenarios: a Base Case that simulated current conditions and two regulatory approaches proposed by EPA. The Bush administration supports EPA’s proposed cap-and-trade approach, while some activist groups support EPA’s proposed one-size-fits-all Maximum Achievable Control Technology (MACT).

While both EPA proposals would reduce mercury emissions, computer models showed the cap-and-trade approach would be more effective. Said Leonard Levin, technical leader in air toxics at EPRI, “We found that the Cap and Trade proposal would produce larger and more widespread reductions in mercury deposition than the MACT proposal, particularly in regions with the highest deposition right now. The Cap and Trade rule would drop mercury deposition across the U.S. by an average of 7 percent versus a 5 percent drop under the MACT rule.”

The study determined that cap-and-trade mercury reductions would be far less costly than reductions achieved through the MACT proposal. The 7 percent reduction in mercury through cap-and-trade regulation would cost $2 billion, while the 5 percent reduction achieved through MACT would cost $10 billion.

Other Sources More Significant

More than half the mercury in the Earth and its environment comes from natural sources, while man-made sources produce the rest. According to the Center for Science and Public Policy, U.S. power plants account for only 1 percent of global environmental mercury.

Although both of EPA’s proposed rules target power plants, EPRI’s research showed that in most areas of the United States, sources other than power plants dominate mercury deposition. According to EPRI’s findings, the highest levels of anthropogenic mercury disposition are produced by sources such as waste incinerators.

According to EPRI’s Levin, “Locations dominated by mercury from other sources, such as incinerators, would see only small changes in mercury deposition [under EPA’s proposed rules]. These sources are still relatively large emitters, even though they have already been subject to regulation.”

Levin says much of the mercury deposited in the United States appears to have originated in Asia, which releases roughly half of the global human-origin mercury emitted. This is then carried eastward across the Pacific by prevailing global wind patterns.

The study noted reductions in mercury deposition under the proposed EPA rules would vary by location, with the greatest reductions in some of the mid-Atlantic and southeastern states, because the proposed rules incorporate greater incentives for power plants in those regions to install mercury controls. Those power plants typically burn bituminous coal, which emits a relatively higher proportion of divalent mercury–the chemical form most easily captured by the control technologies likely to be employed. Because it is more cost-effective to reduce mercury emissions at those plants, they are more likely to install controls and therefore will have a greater relative impact on reducing mercury emissions and deposition.

Health Risk Is Small, Uncertain

Another study included in EPRI’s comments to EPA assessed how the two proposed rules would affect exposure to mercury among women of childbearing age. The analysis showed exposure to mercury would fall by only 0.5 percent on average across the United States under either a MACT or cap-and-trade rule. Even in states where freshwater fish consumption is more prevalent, such as Indiana and West Virginia, the change would be less than a 7 percent drop for women with the highest blood levels of mercury.

Activist group representatives attending a June 15 panel discussion sponsored by Resources for the Future responded to the findings by arguing that stricter MACT standards than those considered by EPA might make up the difference between the 7 percent mercury reductions forecast under cap-and-trade and the mere 5 percent reductions forecast under MACT. They did not identify a means by which to lower the significantly greater costs of implementing MACT.

Other observers cite scientific evidence disputing the need for stricter mercury regulations.

“Let’s put the EPA’s numbers into perspective,” said food and health expert Sandy Szwarc of Tech Central Station. “The Center for Disease Control’s 1999 National Health and Nutrition Examination Survey (NHANES 1999) of American women found no measurements of blood or hair values over the EPA’s benchmark dose. All women were well under the lowest levels the EPA even theorized might risk detrimental effects to their babies.”

It has “become sort of an urban legend” that current environmental mercury levels pose a threat to human health, added Dr. James Heimbach, former U.S. Department of Agriculture associate administrator of Human Nutrition Information Services. According to Heimbach, current environmental mercury levels pose no threat to even the most vulnerable people in society: newborn infants. “They [American women] simply are not exposed to levels of methylmercury that would place newborn children at risk,” Heimbach stated.

James M. Taylor is managing editor of Environment & Climate News. His email address is [email protected].

For more information …

The minutes of the 174th annual meeting of the Ohio River Valley Sanitation Commission, at which the agency’s mercury level report was issued, are available online at

Comments submitted to EPA by the Electric Power Research Institute on June 16 are available online at