Introduction

Chemical Integrity: The example of Mercury

The chemical integrity of the Great Lakes is dynamic. The waters of the Great Lakes are continuously changing through the addition, interaction, and loss of both natural and man-made substances. Natural geophysical processes change these substances' spatial and temporal distribution within the Great Lakes system. While much is known, considerable uncertainty remains concerning the chemical integrity of the Great Lakes and the impacts of various chemicals, and combinations of chemicals, on the basin's human and other inhabitants.

Mercury, a persistent bioaccumulative toxic metal, provides an excellent example of the challenges inherent in understanding impacts on the chemical integrity of the Great Lakes. It occurs widely in nature, both in concentrated form in cinnabar (ore) and in small amounts in fossil fuels such as coal. Humans have used mercury for over 3,000 years in medicine and industry. ¹ The Commission's Great Lakes Water Quality Board in 1985 identified mercury as one of a "dirty dozen" chemical substances for virtual elimination under the Great Lakes Water Quality Agreement. The governments included this list in the 1987 Agreement in Annex 11: Persistent Toxic Substances. In keeping with this annex the United States and Canada developed a binational strategy for eliminating releases of 12 toxic substances, ² including mercury that provides a framework to achieve specific actions from 1997-2006. ³