A proposal would set a cap, and allow emissions trading by industry.
The latest fight over environmental pollution in the United States focuses on mercury, a highly toxic substance that's dangerous to wildlife and humans.
Under a court agreement, the Environmental Protection Agency issued regulations Tuesday sure to generate controversy, particularly since a new study focusing on the Northeast warns that mercury levels are higher than earlier thought. Adding to the political tension here, the new mercury regulations - like the Bush administration's general approach to reducing air pollution - include a cap-and-trade program that allows some power plants to buy and sell mercury pollution credits.
It's an approach favored by coal-burning utilities and other industries who oppose what officials call "traditional command-and-control approaches." But environmentalists say it delays the kind of protection provided under the Clean Air Act of 1990.
Mercury, a highly toxic substance that can poison wildlife and cause brain and nervous system damage in children and fetuses, is a difficult issue for several reasons. Unlike some other air pollutants, such as carbon dioxide, mercury tends to concentrate in dangerous "hot spots." So merely reducing overall levels leaves some areas vulnerable. Also, 40 percent or more of the mercury polluting the US comes from abroad - mainly coal-burning power plants in places like China.
The border issue works the other way as well: Ten percent of mercury in the Canadian environment comes from the US - as much as 38 percent in the Great Lakes region, home to more than 9 million Canadians. Canadian officials have expressed concern that both cap-and-trade as well as the tougher measures some say are called for in the Clean Air Act "fall short of the emissions reductions that are achievable with current and emerging control technologies."
Mercury is the only metal that is in liquid form at room temperature, which means that it evaporates easily and thus spreads throughout the environment. It tends to concentrate in fish, birds, and other wildlife. Among the largest emitters of mercury pollution: coal-fired power plants, factories that produce chlorine, and automobile scrap yards. About 115 tons of mercury is emitted in the US each year, 48 tons of which come from power plants.
According to the Natural Resources Defense Council, a research and advocacy group, mercury pollution in the US has contaminated 12 million acres of lakes, estuaries, and wetlands (30 percent of the total), and 473,000 miles of streams, rivers, and coasts.