Millions of pounds of toxic chemicals are being dumped into the region's main source for drinking water, according to a report published by Environment America.
The report shows the health of the nation's rivers, streams and lakes is at risk due to the pollution.
And it's all legal.
The environmental advocacy group's Illinois chapter said the public should be outraged.
"The need to protect the lake is clear and pressing," said Lisa Nikodem of Environment Illinois Research & Education Center.
Polluters dumped more than 8 million pounds of toxic chemicals in the Great Lakes watershed in 2012, and the bulk of the pollution came from industries in Wisconsin, Indiana and Michigan, according to the report.
The study is based on data reported by polluting facilities to the Environmental Protection Agency's Toxics Release Inventory for 2012, the most recent data available.
"The lake is extremely important for Illinois' economy and the health of its people," said State Rep. Robyn Gabel (D-18th District). "We need to continue to protect the Lake Michigan so it can continue to be a resource for all of us."
The report also showed facilities dumped 6 million pounds of toxic chemicals into rivers and streams in Illinois. This ranks Illinois as the 13th worst state in the nation for direct toxic discharges into waterways.
A Tyson fresh meats facility in Hillsdale was the biggest polluter in the state, according to Environment Illinois. The environmental group said the facility dumped 2.5 million pounds of toxic pollution from slaughtered animals into waterways.
However, a spokesperson for Tyson said the company complies with the Clean Water Act and operates waste water treatment facilities as required by law.
Environment Illinois said the solution for the nation's toxic pollution problem is for polluters to use less toxic chemicals, and for the Clean Water Act to be strengthened.
"Due to a couple of bad Supreme Court decisions in cases brought by big polluters, we now have loopholes and ambiguities in the Clean Water Act, so we're working to restore it to its original intention," Nikodem said.
An organic farmer who depends on clean water for her crops and animals said clean water is just as important to a farmer as the ingredients in a recipe are to a chef.
"If our dairy cow was given polluted water it would affect her milk and it's gonna end up on your breakfast table," said Shannon Konczal, owner of Justafew Acres in Herscher.
The report comes as the EPA is considering a new rule that would restore Clean Water Act protections to thousands of waterways in Illinois and across the nation.