Many people do not realize that "silver" amalgam fillings are 50% mercury. A large filling may contain as much mercury as a thermometer. Mercury vaporizes easily at room temperature, and in this state is odorless, colorless, and tasteless. Inhaled mercury vapor is readily absorbed into the bloodstream. The World Health Organization has concluded that dental fillings contribute more mercury to a person's body than all other sources of mercury combined. Mercury is a powerful poison. Published research demonstrates that mercury is more toxic than lead, cadmium, or arsenic. No amount of exposure to mercury vapor can be considered harmless, especially considering its cumulative effect.