Cottage Grove, Minnesota, has had a 3M factory in town since 1947. It makes everything from Post-It Notes and Scotch Tape to reflective road signs. In 2017, the city found out the state was lowering the acceptable level of PFAS, a chemical made and used at the factory, in its drinking water. Scientific studies show there could be serious health consequences for people exposed to it. And now dozens of U.S. cities are discovering PFAS is in their water too. This week on Decrypted, Bloomberg's Tiffany Kary and Pia Gadkari tell the story of how a Minnesota lawyer first learned of PFAS contamination, and discuss documents revealed through lawsuits that suggest 3M knew of certain risks for decades and never disclosed them. 3M says those documents have been taken out of context and that the chemical isn't a danger to public health.