Mercury

Mercury is a heavy metal. Natural mercury derives from the weathering of mercury-bearing rocks, volcano's and hydrothermal vents. Important anthropogenic sources are paper and lumber industries, antifouling paints, pesticides and pharmaceutical and other industries. In the Northern hemisphere these anthropogenic sources have largely been eliminated since the 1980's.

Mercury has been the only contaminant (apart from pathogens) that certainly has been responsible for human deaths.. In anoxic sediments inorganic mercury is transformed in the more toxic methylmercury.