Silver [tooth] fillings, commonly called dental amalgam, contribute mercury pollution to the environment. Recent developments suggest momentum is building against silver fillings based on environmental concerns: Norway, Denmark, Sweden, Japan and Finland have either banned dental amalgam or restricted its use within the last five years. Twelve states have mandatory dental amalgam reduction programs. About half the mercury entering municipal wastewater treatment plants, or about 3.7 tons annually, comes from dental amalgam waste. While treatment plants capture about 90 percent of amalgam, some mercury settles into sewage sludge that is deposited in landfills, incinerated, applied as fertilizer or flushed into waterways. Once in water, it can transform into methylmercury, a neurotoxin that builds up in fish, shellfish and animals that eat fish, including humans. Several studies have linked methylmercury to health and developmental problems, especially in pregnant women, fetuses, infants and children. High exposure to methylmercury has been linked to permanent damage in children's brains and nervous systems and to increased risk of kidney problems in adults. Research shows that the human body absorbs mercury vapor released from dental amalgam. Numerous studies raise concerns about mercury exposure from amalgam. In toxic doses, elemental mercury breathed in as vapor can cause symptoms including tremors, mood swings, neuromuscular changes and cognitive deficits.