This is potentially very good news: the EPA, in response to a lawsuit, has agreed to set limits on mercury pollution from coal-fired power plants. Many other emission sources are already subject to mercury regulations. I am not sure why power plants were originally exempted from them since coal-based power is the single biggest source of airborne mercury. Perhaps the coal industry's lobbyists were exceptionally persuasive. Here is why mercury pollution is important:
Controlling mercury is significant because the pollutant enters the food chain and ends up in fish. Children, including those who were exposed to mercury before birth, are especially at risk of developmental and learning disabilities. Adults also can experience health problems from eating too much contaminated fish.
Although the EPA has issued guidelines about eating fish, it hasn't required power plants to reduce toxic emissions. The Clinton administration, before leaving office, declared that plants should be subject to controls under the Clean Air Act, but the Bush administration reversed that decision. Instead, it set up a cap-and-trade system, which imposed limits on emissions and established a system to trade pollution allowances.
In February 2008, however, a federal appeals court overturned that approach and ordered the EPA to regulate toxic air pollutants from power plants. Then the American Nurses Association and environmental groups sued to compel the EPA to issue the regulations.
Reducing mercury pollution should also benefit birds, and not just ones that eat fish. Some previous studies have found mercury (and its more toxic byproduct methylmercury) in Wood Thrushes and other songbirds. Similar to the way that humans ingest mercury via contaminated fish, songbirds ingest mercury via invertebrates.
Unfortunately we have to wait a little longer for the rules to take effect. The EPA plans to issue the new mercury regulations by 2011. Most likely companies will have a grace period to install scrubbers so those regulations may not take effect until 2015 or so. Still, this should mean big improvements in air quality and food safety.