Executive summary -- I. Why is mercury pollution a problem in the Great Lakes region? -- II . What risks does mercury pollution pose in the Great Lakes region? -- III. Where are mercury levels highest in the Great Lakes region? -- IV. How is mercury contamination changing over time in the Great Lakes region? -- V. What are the key mercury policy connections in the Great Lakes region and beyond? Mercury pollution is a local, regional, and global environmental problem that adversely affects ecosystems worldwide. As the world's largest freshwater system, the Great Lakes are a unique and extraordinary natural resource providing drinking water, food, recreation, employment, and transportation to more than 35 million people. Mercury has been released into the air and waterways of the Great Lakes region since the early to mid-1800s from human activities such as fossil fuel combustion, waste incineration, metal smelting, chlorine production, mining, and discharges of mercury in wastewater. The widespread loading of mercury into the Great Lakes environment is responsible for mercury-related fish consumption advisories in the eight Great Lakes states and the province of Ontario. Past and present inputs of mercury pollution have created a substantial recovery challenge for the Great Lakes region.