The large, coal-fired power plants that emit the bulk of Iowa's air pollution are no longer required to measure emissions of mercury - one of the most toxic chemicals they produce - following the withdrawal of a federal rule last year.
Environmental groups say they are counting on state and federal regulators to put a new monitoring standard in place quickly, but state officials say it could take until at least August before a new standard is brought before the Iowa Environmental Protection Commission for discussion and approval.
At issue is the ability to better measure the mercury infiltrating the state's waterways, which experts say is notoriously difficult. Mercury, a potent neurotoxin that can also damage the kidneys and lungs, is typically ingested by people when they eat contaminated fish. "We really don't know how much is falling into our lakes and water supplies," said Neila Seaman, director of the Iowa chapter of the Sierra Club. "I'm hopeful that's going to be changed."
Large quantities of mercury are released in the coal-burning process, but the element can also be produced by natural events such as forest fires. The Union of Concerned Scientists, based in Cambridge, Mass., has said that less than one teaspoon is enough to contaminate all the fish in a small lake.
The Iowa Department of Natural Resources has said that fish in Iowa are generally safe to eat, but it has advised that pregnant women, children and other sensitive groups eat no more than one serving per week of large predator fish, such as walleye and bass. Northwest Iowa, including vacation hot spots such as the Iowa Great Lakes, had among the state's highest mercury concentrations in 2007, according to studies by the government-sponsored National Atmospheric Deposition Program.
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