New research shows that rainwater in most locations on Earth contains levels of chemicals that “greatly exceed” safety levels. These synthetic substances called PFAS are used in non-stick pans, fire-fighting foam and water-repellent clothes. Scientists fear PFAS may pose health risks including cancer, though research has so far been inconclusive. They have been growing increasingly concerned about the proliferation of PFAS in recent years. PFAS stands for poly- and perfluoroalkyl substances. There are around 4,500 of these fluorine-based compounds and they are found in almost every dwelling on Earth in hundreds of everyday products including food packaging, non-stick cookware, rain gear, adhesives, paper and paints. Safety concerns about the presence of these long-lasting substances in drinking water have also been raised.