House Resources Committee Chairman Richard W. Pombo (R-CA) and Energy and Mineral Resources Subcommittee Chairman Jim Gibbons (R-NV) released on February 16 an exhaustive paper on the science of mercury and the environment, Mercury in Perspective: Fact and Fiction About the Debate Over Mercury.
The paper is a comprehensive synopsis of the peer-reviewed research regarding the debate over regulating mercury. Said Pombo in an accompanying news release, “We have simply highlighted, in documented fashion, the most important bodies of evidence on this subject. It is clear that research must be continued, and it is very clear that the current knowledge does not support the rhetorical campaigns of special interest groups.”
Below is the second in a series of articles that reproduces, in condensed form, the Pombo-Gibbons report.
III. U.S. Emissions: The U.S. Has Aggressively Reduced the Risk of Exposure
The U.S. designated mercury a hazardous pollutant in 1971 and a toxic pollutant in 1973. Since these designations, the use of mercury for industrial and medical purposes in the U.S. has declined by more than 80 percent. Anthropogenic emissions of mercury in the U.S. ha[ve] declined by 40 percent (97 tons) between 1990 and 1996 due to the closure of domestic mercury mines in 1991 and pollution controls for mercury emissions from medical, municipal, and hazardous waste incineration. In addition, air pollution controls on coal-fired power plants also reduced mercury.
The significant reduction of these emissions has left power plants as the largest remaining industry-specific source of anthropogenic mercury emissions in the U.S. Even so, mercury emissions from power plants have declined by more than 38 percent between 1995 and 1999. This reduction resulted from the installation of pollution controls designed to address other types of air emissions.
Former EPA Administrator [Carol] Browner announced on December 14, 2000–two days after Bush v. Gore was settled by the U.S. Supreme Court–that the [Environmental Protection Agency (EPA)] would issue a rule by December 2003 to regulate mercury emissions from power plants.
In EPA’s “Notice of Regulatory Finding,” Browner described the uncertainties between power plant emissions of mercury and methylmercury concentrations in fish: “It is acknowledged that there are uncertainties regarding the extent of the risks due to electric utility mercury emissions. For example, there is no quantification of how much of the methylmercury in fish consumed by the U.S. population is due to electric utility emissions relative to other mercury sources (e.g., natural and other anthropogenic sources).”
Despite these continued and uncertain findings related to mercury emissions, Browner still went forward with implementing new regulations in the waning hours of the Clinton Administration. The Bush Administration will regulate emissions for the first time ever.
IV. Further Reducing Mercury Emissions: A Look at the Technology
Mercury emissions from power plants were reduced by 38 percent from 1995 through 1999 as a result of pollution control technologies put in place to reduce sulfur dioxide, nitrogen oxides, and particulate matter. Additional reductions should be achieved as more controls are put in place to meet new standards for this group of emissions under the Clean Air Act (CAA). However, at present it is not technically possible to reduce mercury emissions from coal power generation by 70-90 percent, nor is the technology required to meet these proposed reductions expected to be available within the next several years.
According to the [Department of Energy (DOE)], ” there is no commercially available technology that can consistently and cost-effectively capture mercury from coal-based power plants.”
During a briefing hosted by the National Wildlife Federation for congressional staff on January 31, 2005, the Institute of Clean Air Companies (ICAC) stated that a cap and trade approach would allow the industry and themselves more flexibility in achieving significant reductions in mercury emissions from all power plants. In fact, they stated the flexibility of the cap and trade approach would probably bring more reductions more quickly than a Maximum Achievable Control Technology (MACT) standard.
There are several conditions that create technical challenges for reducing the less than 1 percent of global mercury that U.S. power plants produce. First, there are different types of coal. The concentrations of mercury found in coal are very minute and can vary within a given mine and even within a given seam or bed of coal. These differences and variations result in significant variability in power plant operations and emissions.
Additionally, there are differences in the power plants themselves, including how the boilers are configured and how they are operated. These factors alone present challenges for developing a single technology to address mercury emissions. This is also why a cap and trade approach to reduction makes good sense and good public policy. U.S. utilities would be able to implement control technologies that will yield the best results for their individual plants.
Reducing the less than 1 percent of total mercury emissions consistently and effectively has not yet been proven for the range of fuels and power plants in the U.S., nor have the costs and potential impacts on plant operations been determined. However, the electric utility industry, in partnership with the federal government, has ongoing research programs in place to identify sound mercury control technologies that are effective and consistent.
Several potential technologies are currently in advanced research and development phases. These demonstration projects are projected to be completed and evaluated for their effectiveness within the next two to three years.
Issuing an inflexible MACT rule without a commercially available and cost-effective technology that has been proven reliable is irresponsible and would force the premature closure of some coal-fired plants and/or encourage fuel switching. Either scenario exacerbates our existing energy problems, aggravating the natural gas supply crisis and laying the groundwork for more price spikes for natural gas and electricity.
V. The Truth About Mercury, Power Plants, and Fish
Atmospheric deposition of mercury and other sources of mercury in the environment that enter water bodies can be converted to methylmercury, an organic mercury compound. It is this form of mercury that is found in trace levels in some fish and thought to be harmful to humans if consumed in large enough quantities. Methylation, the process by which atmospheric mercury is converted to methylmercury, is very complex and is dependent on many different factors. It occurs more often in fresh water and wetland areas than in saltwater. This is important since most fish consumed in the U.S. are ocean-dwelling species.
Studies on the portion of mercury emissions from power plants that were deposited locally on land or water–approximately 2 tons annually from the nation’s 1,100 power plants–showed that 97 percent of the mercury was trapped in sediments, 3 percent remained in the water, and only a very small amount, 0.03 percent, was converted to methylmercury.
Methylmercury enters the food chain through microorganisms eaten by fish and other aquatic life. Thereafter, it may bioaccumulate up the food chain, which explains why some larger species of fish and marine mammals can have increased levels of methylmercury. The average concentrations of methylmercury for the top-ten types of seafood consumed in the U.S. range from non-detectable to 0.358 parts per million (ppm), which is still below FDA’s action level of 1.0 ppm methylmercury. As noted, human exposure to mercury is generally from the organic compound, methylmercury, and occurs indirectly through the consumption of fish.
On rare occasions, such as direct poisoning events that occurred in Japan and Iraq, human exposure to extremely high concentrations of methylmercury can cause neurological problems and death.
During the 1950s, 111 people from Minamata City, Japan died or experienced neurological disorders from eating fish contaminated with very high concentrations of methylmercury, up to 40 parts per million (ppm). In this case, an industrial facility was releasing manufactured methylmercury directly into Minamata Bay. A second incidence in 1965 occurred in Niigata, Japan, where 120 people were similarly poisoned.
Two incidents in Iraq occurred in the 1970s. They were caused by the consumption of seed grain that had been treated with methylmercury, which was used as a fungicide (methylmercury is not used as a fungicide in the U.S.). The grain was to be planted, not eaten; however, the grain had not been distributed early enough in the growing season to be planted. Thousands of Iraqis were hospitalized and 459 died.
The direct poisoning events in Japan and Iraq were very serious and alerted governments and the medical community to the adverse impacts of human exposure to high concentrations of methylmercury. However, these were direct poisoning events from manufactured methylmercury that was introduced into consumed food by industrial processes and eaten in large doses, not through accumulation in aquatic environments. The most current peer-reviewed science does not support conclusions that the U.S. population is at risk from the trace amounts of mercury found in fish.
VI. Putting it into Perspective
Should we be concerned? Is there a link between the mercury released from U.S. power plants and the complex transformation process that produces methylmercury?
As a result of all the media coverage and environmental campaigning, many Americans are unaware that there has been a significant decrease in U.S. mercury emissions and instead are led to believe that U.S. emissions are on the rise and will increase in the future. Still others wonder whether the overall increase in global mercury emissions and deposition means that Americans will be exposed to higher concentrations of methylmercury in fish. Recently published and ongoing scientific research can provide some insight to this question.
A Princeton University study, funded by EPA, compared mercury analysis of recently caught Pacific tuna with similar tuna that had been caught in the 1970s. Princeton found that mercury levels in the tuna had not changed over time. The concluding statement in the paper reads as follows:
“The bare fact that the concentrations of Hg [methylmercury] in tuna were identical in 1971 and 1998 either reflects a remarkable coincidence or indicates that, regardless of mechanisms, these concentrations are not responding to atmospheric pollution.”
Hair samples from eight 550-year-old Alaskan mummies had concentrations of methylmercury higher than Alaska’s modern population (i.e., a group of pregnant women). The methylmercury concentrations in hair collected from the mummies ranged from 1.2 ppm to 4.6 ppm. The mean methylmercury concentration in today’s Alaska population is 0.6 ppm.
Analyses of lakebed sediments deposited over the past 11,000 years in Minnesota’s Elk Lake show that anthropogenic (man-released) emissions have not been significant or exceptional. Average mercury levels in the lakebed sediments today are 140 parts per billion (ppb). Mercury levels in the sediment have been higher on seven different occasions due to natural causes with the highest being 350 ppb about 8,000 years ago.
Concentrations of mercury, lead, and persistent organic pollutants in the umbilical cord blood of Inuit infants born in Nunavik, Quebec decreased between 1994 and 2001. Inuit inhabitants of Nunavik consume great quantities of marine food and are therefore exposed to high doses of food chain contaminants. A significant reduction of lead and mercury concentrations was found, amounting to more than an 8 percent decrease per year.
A twelve-year longitudinal study conducted in the Seychelles Islands reported no negative effects from dietary exposure to methylmercury through regular fish consumption. The Seychelles population consumes an average of 12 fish meals a week and has hair methylmercury concentrations approximately ten times higher than the U.S. population.
A new study that compared the rates of atmospheric mercury deposition to amounts of mercury contained in Illinois and other U.S. soils found that: “The amounts of Hg [mercury] in these soils are too great to be attributed mainly to anthropogenic atmospheric Hg deposition.” The results of this study should not be surprising. As the authors point out in their paper, when mercury pollution became a “popular concern” in the 1970s “the common presumption that the principle [sic] source of Hg in the environment is anthropogenic” was widely criticized in the scientific literature.
The findings of these studies bring into question several claims made by environmental organizations. Most importantly, the claim that atmospheric deposition of mercury from power plants or other anthropogenic sources is directly related to methylmercury levels in fish. [sentence fragment in original] Since there isn’t any current, peer-reviewed science which supports that notion, advocating for a MACT mercury emissions rule seems misguided.
For more information …
The full text of the Pombo/Gibbons paper on the science of mercury and the environment, Mercury in Perspective: Fact and Fiction About the Debate Over Mercury, is available online at http://resourcescommittee.house.gov/Press/reports/mercury_in_perspective.pdf.