Throughout its eight years in power, the Bush administration stubbornly opposed U.S. involvement in any international treaty that would control mercury pollution. Mercury, most of which is generated by coal-fueled power plants, settles in the oceans and is absorbed by fish that are then eaten by humans. Mercury can cause developmental problems in children. While he was a senator, Barack Obama sponsored legislation that would require toxic mercury to be stored in the United States rather than allow it to be exported to countries where regulation was looser. Now that he is president, Obama has moved quickly to join with the international community to limit the creation of more mercury pollution.