Brought to you by my "Fact-A-Day" desk calendar

"What is the world’s largest repository of fresh water?

The Great Lakes, remembered by the mnemonic “homes” – Huron, Ontario, Michigan, Erie and Superior – contains almost 20% of the world’s supply of fresh water, and nearly 90% of the supply in the United States."
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Which lake is the most "fresh", i.e. less polluted?  My guess is Huron.
Most polluted?  Maybe Michigan.
I'm too lazy to go hunt it up right now.  Does anyone know?