The Environmental Protection Agency issued a separate warning Friday warning the same women to avoid fish caught in freshwater. 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. The EPA's warning stems from a report this past summer from the National Academy of Sciences that said the greatest threat from mercury and waterways is to pregnant women and women who may become pregnant, nursing mothers and young children who eat fish. They say those at risk should limit their consumption to one, six-ounce meal per week. Mercury is a naturally occurring element that is present throughout the environment and in plants and animals.
Most mercury pollution is released into the air.
It falls either into water or onto land where it is washed into the water. Bacteria in the water cause chemical changes that turn it into the toxic form of methylmercury. Methylmercury accumulates in fish and because larger fish eat the smaller fish they usually have higher amounts. The EPA said it is working with the states to reduce mercury levels, but it will take years. For more Health news, myCNN will bring you news from the areas and subjects you select.