Mercury is a natural element, but it is also a toxic pollutant that could have devastating effects on wildlife and human health, as well as the economic vitality and way of life of our coastal communities, if humanity cannot adopt stringent measures to curb mercury use and emissions. Mercury has been used in a great variety of industrial, commercial, and pharmaceutical applications, despite knowledge of its toxic effects. Thermometers, switches, fluorescent lamps, batteries, and dental fillings are just a few of the products that may contain mercury. Major emission sources include metal processing, fossil fuel combustion, municipal waste and sludge incineration, oil refining, crematoria, and landfills. Though mercury is released from natural sources, scientists estimate that over two-thirds of global mercury emissions are from human sources.

Most mercury reaches ecosystems through atmospheric deposition, and the remainder is deposited directly to land or water. Mercury is usually emitted in its elemental or inorganic forms, either as vapor or particles, which have relatively low toxicity at low doses. Once it reaches water, however, inorganic mercury can be converted to organic mercury, primarily methylmercury, by microorganisms. Methylmercury is highly toxic, and it bioaccumulates in aquatic food webs. Microorganisms can assimilate mercury directly from the water or sediment, and this mercury is passed to successively higher levels of the food web. In top-level consumers, such as piscivorous fish, birds, or mammals, methlymercury can be millions of times more concentrated than in the surrounding water.

Mercury is a problem in the northeastern US and eastern Canada. Mercury deposition is high in this region compared to many other parts of North America, partly because the prevailing winds carry airborne mercury from more industrialized areas of the continent. Remote mountain lakes in interior New England have mercury levels comparable to lakes near cities, suggesting that atmospheric deposition from distant sources is a significant mercury source. Mercury pollution in our region may be exacerbated by the acidic nature of our waterbodies and by elevated tropospheric ozone levels. Fish and wildlife in the northeastern U.S. and eastern Canada have some of the highest levels of methylmercury measured on the entire continent.

Mercury is having adverse effects on wildlife, especially those that consume large amounts of freshwater or marine fish or invertebrates, including otters, seals, dolphins, whales, polar bears, eagles, ospreys, loons, and cormorants, just to name a few. There is scientific evidence that common loon populations in areas of the Gulf of Maine region are unsustainable due to the effects of elevated mercury levels on reproduction and behavior.

People who consume large amounts of fish containing mercury may put themselves, their children, or their unborn fetuses at risk. The primary effects of mercury on both wildlife and humans are on reproduction and development of the central nervous system. Mercury can be transferred directly to a developing fetus from the mother across the placenta. Known effects include damage to the central nervous system, endocrine system, immune system, and chromosomes, causing abnormalities that lead to behavioral deficits, impaired fertility, or death. Mercury may also impair hearing, speech, vision, and gait; cause involuntary muscle movement; corrode skin and mucous membranes; and cause chewing and swallowing to become more difficult.

States and provinces throughout North America have issues strongly worded fish consumption advisories in response to mercury levels in game fish. In the U.S., more than 2250 fish consumption advisories have been issued by over 40 states because of mercury, primarily in freshwater habitats. There are a growing number of consumption advisories for coastal waters. All New England states have statewide consumption advisories for freshwater fish, as do the provinces of Nova Scotia and New Brunswick.

Until recently, fish consumption advisories were issued primarily for freshwater fish, and had few economic ramifications because freshwater fishing is traditionally recreational and many anglers practice catch-and-release fishing. However, consumption advisories do have cultural ramifications, especially with regard to how we view, use, and enjoy our freshwater resources. Families that rely on fishing for subsistence, and traditionally have enjoyed bass or perch filets for the family throughout the fishing season, are now being advised to consider health risks.

Recently, mercury has become much more contentious because the area of concern has expanded to include saltwater fisheries, which are traditionally commercial fisheries that form the economic base for Atlantic coastal communities. Fish consumption advisories for marine fish may threaten the livelihood of many people and communities throughout the Gulf of Maine. Yet the scientific evidence is compelling: the body burden of mercury in some commercially-important marine fish—such as tuna, swordfish, shark, striped bass, and bluefish—are at high enough levels to prompt health agencies to issue consumption advisories.

Clearly, mercury is an important issue in the Gulf of Maine. The Gulf of Maine Council is actively involved in research, monitoring, and education about mercury. The Gulfwatch program measures mercury and other contaminants in blue mussels (Mytilus edulis) to understand spatial and temporal trends in contamination in Gulf of Maine coastal areas. Gulfwatch found that in 50 of 56 sampling sites, mercury concentrations were much higher than the national average (exceeded the National Status & Trends "Mussel Watch" median + 1 standard deviation).

Mercury is one of three priority contaminants in the Council's Action Plan 2001-2006, with several objectives for mercury research, monitoring, and education. Other agencies and organizations are also making outstanding contributions to our understanding and management of the mercury problem. At the forefront are the New England Governors and Eastern Canadian Premiers (NEG-ECP), which adopted a Mercury Action Plan in 1998 and have since been working to implement the plan. Other agencies and organizations are included in the list of resources.