Mercury emissions, deposition, and releases into the environment explain only part of the spatial story of mercury pollution. Ecosystem sensitivity and food web relationships help further define the actual risks to human and ecosystem health.
Elemental mercury (Hg) is converted to a more toxic organic form of mercury through the process of methylation, which occurs with the help of bacteria found primarily in wet areas. Large variations in methylmercury (MeHg) concentrations may occur in different parts of the food web depending on the sensitivity of the ecosystem to mercury input.
Where methylmercury availability is elevated, fish and wildlife may exhibit harmful mercury concentrations and represent the places that will require the most attention by countries and global monitoring programs. The combination of these two factors—the risk of mercury contamination from multiple sources and ecosystem sensitivity to mercury methylation—represents a new approach to conducting a global mercury threat assessment (GMTA).
