There were many scare-tactic articles and television shows that persuaded us to second-guess the fillings in our mouths as harmful to our health. Clinical studies have proven these claims as false; many of the most vocal persons with symptoms (and blamed the symptoms on their fillings) had no increased levels of mercury in their systems.
You can read more about this controversy here: http://www.ncahf.org/pp/amalgampp.html
And below is the ADA (American Dental Association) position statement, with additional organizations listed:
"While questions have arisen about the safety of dental amalgam relating to its mercury content, the major U.S. and international scientific and health bodies, including the National Institutes of Health, the U.S. Public Health Service, the Centers for Disease Control and Prevention, the Food and Drug Administration and the World Health Organization, among others have been satisfied that dental amalgam is a safe, reliable and effective restorative material."