For decades, it was the secret behind the magic show of homemaking across the US. Applied to a pan, it could keep a fried egg from sticking to the surface. Soaked into a carpet, it could shrug off spills of red wine. Sprayed onto shoes and coats, it could keep the kids dry on a rainy day. But the most clandestine maneuver of perfluorooctanoic acid, or PFOA, was much less endearing: seeping into the blood and organs of hundreds of millions of people who used products containing the chemical. Read more.