Swann's Fly Tying and Fly Fishing Outfitters
presents information about Mercury contamination of fish

February 8, 2008 - A federal appeals court today struck down the Bush Administration's Evironmental Protection Agency policy that would let coal-fired power plants trade the right to emit mercury. Mercury is a neurotoxin that contaminates waterways, accumulates in fish, and has been linked to nervous system and brain damage, particularly in young children. Environmentalists and public health advocates have been pushing for rules that would require every coal plant to have to reduce its emissions of mercury, but in 2005 the Bush administration put forth a CAP and TRADE system that would let dirtier plants buy the right to pollute from cleaner ones. The federal appeals court stated that the EPA violated the Clean Air Act in 2005 when it exempted power plants from adhering to the emissions controls set forth in the Clean Air Act. The court ruling means that big coal-burning utilities like Atlanta-based Southern Company and American Electric Power of Columbus, Ohio will have to install expensive mercury-reduction equipment at more of their power plants rather than rely on an industry-wide trading program. This ruling came in response to a lawsuit filed by 14 states and public health groups. The cap-and-trade approach is widely touted as a good way to tackle greenhouse-gas emissions because green house gases affect the atmosphere as a whole. In contrast, mercury pollution produces severe local effects, so communities near plants with high mercury emissions would get the short end of the stick in a cap and trade system

Facts about mercury:

Highly toxic to the nervous system
Persistent in the environment
Bioaccumulates (higher concentrations in tissues of aquatic plants and animals than in water)
Biomagnifies (higher concentrations at increasingly higher levels in the food chain)
Numerous chemical forms in air, water, sediment, and biota
Responsible for nearly 80 percent of U.S. fish-consumption advisories

For the most part, Florida's freshwater fish are considered safe to eat. The most common health advisory issued in Florida by the Department of Health for freshwater fish deals with mercury. For a pdf (Acrobat) copy of the "2003 Florida Fish Consumption Advisories," click here.

Freshwater fish from contaminated waters have been shown to have particularly high levels of methylmercury, posing potential risks for recreational anglers and people who regularly fish for food.

A report by the National Academy of Sciences (NAS, Toxicological Effects of Methylmercury July 2000) confirms that methylmercury is a potent toxin and concludes that the babies of women who consume large amounts of fish when pregnant are at greater risk for changes in their nervous system that can affect their ability to learn.

Some entities are working to reduce mercury pollution in the environment, but because methylmercury is very persistent, it may be many many years before methylmercury levels in fish and the environment are reduced.

While it is true that the primary danger from methylmercury in fish is to the developing nervous system of the unborn child, it is prudent for nursing mothers and young children not to eat these fish as well.

The Centers for Disease Control and Prevention estimate that 4.9 million women of childbearing age in the U.S. — that's 8 percent — have unsafe levels of mercury in their blood. The people hit hardest will be new-born infants — every year over 630,000 infants are born with levels of mercury in their blood so high they can cause brain damage.

The toxic effects of mercury depend on its chemical form and the route of exposure. At dietary mercury concentrations that are typical of parts of the Everglades, the behavior of juvenile great egrets can be affected. Studies with mallards, great egrets, and other aquatic birds have shown that protective enzymes are less effective following exposure to mercury.

Methylmercury (CH3Hg) is the form most toxic to humans and other fish and wildlife. It affects the immune system, alters genetic replication and the functioning of enzymatic systems, and damages the nervous system, which affects coordination and the senses. Methylmercury is particularly damaging to developing embryos, which are five to ten times more sensitive than adults. Exposure to methylmercury is usually by ingestion, and it is absorbed more readily and excreted more slowly than other forms of mercury.

Elemental mercury (Hg) the form commonly found in thermometers causes tremors, gingivitis, and excitability when vapors are inhaled over a long period of time. Although it is less toxic than methylmercury, elemental mercury may be found in higher concentrations in environments such as gold mine sites, where it was used to extract gold from ore. If elemental mercury is ingested, it is absorbed relatively slowly and may pass through the digestive system without causing significant damage.

Ingestion of other forms of mercury, such as the salt HgCl2, which damages the gastrointestinal tract and causes kidney failure, is unlikely from environmental sources.

Although scientists from USGS and elsewhere are beginning to unravel the complex interactions between mercury and the environment, a lack of information on the sources, behavior, and effects of mercury in the environment has impeded identification of effective management responses to the Nation's growing mercury problem.