Midland County

Chuck Lichon, R.S., M.P.H.

As new coal plant proposals expand across our country, our state, and more specifically within our local community, issues such as mercury, fine particulate matter, and other concerns become "front page news." However, are mercury emissions a real, or perceived concern for area residents?

If you look at elemental mercury, which is the type emitted from coal plants, it needs to be assessed globally. Most of human exposure is attributed to natural and human sources that exist outside the United States. An extremely small amount of mercury exists naturally in coal and oil, and when burned, mercury is released to the atmosphere. It has been estimated that approximately 40 percent of the total mercury emissions released annually in the U.S., comes from electric power generation. The remaining sources include municipal and medical solid waste incineration, mining, pulp and paper milling, and cement manufacturing.

Natural sources of mercury include volcanoes, soil and oceans. If you include these natural sources, manufacturing in the U.S. now contributes only about 10% of the total. And, to put this in a global perspective, U.S. electric generation plants contribute about 1 percent of the total mercury emissions to air. Asia can be held accountable for almost half of the total emissions due to human activities, much of which eventually falls on U.S. soil.

According to the Environmental Protection Agency, "the same amount of mercury has existed on the planet since the earth was formed" (Mercury Study Report to Congress, 1997). It cycles in various forms through the environment, undergoing complex chemical and physical changes along the way.

EPA indicates that almost all people have at least trace amounts of methylmercury in their tissues, reflecting methyl mercury's widespread presence in the environment and people's exposure through the consumption of fish, shellfish and marine animals.

Studies have shown that mercury concentrations in fish vary depending on size, with herring containing about 0.01part per million and shark more than 1 part per million, for example. Large, predatory fish contain more methyl mercury than smaller fish species due to accumulation effects at each increasing stage of the food chain. Anglers consume more locally caught fish than most people with concurrently higher methyl mercury exposures than average if those fish are contaminated. Only about half of U.S. residents report eating fish at all, and those that do eat fish consume almost entirely ocean fish. More than 75 percent of the fish consumed in the United States is imported.

But methymercury, the type that we are mostly concerned with from a health standpoint, is not what is emitted from power plants. Methymercury is transformed by microorganisms from elemental mercury.

Because mercury in the atmosphere can originate from global, regional, and local sources, the extent to which an individual source contributes locally or even regionally is highly disputed.

EPA further states that whether an exposure to the various forms of mercury will harm a person's health depends on a number of factors, giving the fact that the methy mercury form is more toxic than elemental mercury, the dose a person receives, tha age of a person, the duration of exposure, the route of exposure (e.g., inhalation, ingestion) and the heatlh of the person exposed.

Many studies have been researched on the various forms of mercury, including methy mercury and whether the source in ocean fish is due to be a result of human or natural activities. Space does not allow for extensive review or detail here, nor is it needed, however here is a summery of a couple of the more popular and well known examples that are used to compare methy mercury in fish and overall elemental mercury levels in the atmosphere: a study compared 1971 and 1998 methyl mercury concentrations in tuna caught near Hawaii resulting in no differences, although the level of mercury in the atmosphere has almost tripled since 1971 (due to non-U.S. human activities).

Similarly, no differences were seen in the mercury concentrations of museum tuna specimens caught between 1878 and 1909 and tuna caught in 1972. Another study of fish reported no obvious increasing trend for mercury levels in the tissue of striped bass caught off three widely dispersed locations throughout the San Francisco Bay area between 1970 and 2000 despite increases in environmental levels during that period.

While the goals of the 2005 Clean Air Mercury Rule may constitute good public policy, whether the mandated reductions in emissions ultimately will have an impact on fish contamination, human exposure, and public health is far less certain.

As in any study, content of the study need to be peer reviewed by credible scientists. There are scores of websites, media articles, and other exposures to mercury and mercury health effects. The health effects of methyl mercury at certain levels are indisputable and must be adhered to; however mercury related emissions as a result of human activity, and their relations to overall effects to the environment are in great disagreement.

The evidence suggests that reducing power plant mercury emissions may have little impact on most U.S. exposure to methyl mercury on a national scale. But it could, for example, impact exposure to fishing enthusiasts such as in the eastern states where anglers frequently consume freshwater fish caught near coal-fired power plants. In these areas, coal chemistry, emission characteristics, atmospheric characteristics, mercury deposition, and water chemistry are consistent with a relationship between mercury emissions and uptake by fish.

If mercury hot spots prove to be important contributors to risk in some locations, local concentration-based limits on mercury emissions should be explored so that specific plants can be targeted where needed, not as a generic regulation for all areas of the country.

According to a report by the Northeast States for Coordinated Air Use Management, a non-profit association of state air quality regulators, "Given the global nature of the problem, a significant reduction in U.S. power sector mercury will be insufficient by itself to adequately address mercury contamination of fish and the resulting adverse health impacts."

Although our current coal technology is not perfect (what is), it is far superior to the old existing technology in reducing mercury and other emissions. Unless we move on with new practical and economical energy sources, the old will continue to discharge mercury, nitrogen oxide, sulfur dioxide and other emissions that otherwise could be significantly reduced.

And until the mercury problem is addressed globally, pregnant women and children should follow the advice of EPA and the Food and Drug Administration and limit their consumption of high-mercury-containing fish while maintaining the health benefits of fish consumption by eating a variety of other fish.