PFAS (per- and polyfluoroalkyl substances) are man-made chemical compounds. They’re not a natural part of our ecosystem: scientists developed them to make products water-, grease- and dirt-repellent. Today, they’re a common component of everyday items like certain kinds of rain coats, food packaging, some cosmetics, textiles and various types of non-stick pans.
It takes an incredibly long time for PFAS to be broken down, with some probably only disappearing after a thousand years. Almost all PFAS that were ever released into the environment still linger on our planet to this day.