Mercury can assume many forms and, through interactions with the environment, can be transformed into a variety of structures. The most commonly known forms of mercury include: Elemental Mercury, divalent mercury (mercuric chloride) and methyl mercury.
It is thought that stack emissions of mercury commonly consist of both elemental mercury and divalent mercury (U.S. EPA, HHRAP, 2001). Divalent mercury further evolves through a process called methylation when it comes into contact with the surrounding environment. The following sections are derived from the U.S. EPA-OSW, Human Health Risk Assessment Protocol.