Per- and polyfluoroalkyl substances – PFAS – are made up of a chain of carbon atoms, surrounded by fluorine atoms.

The carbon-fluorine bond is one of the strongest in nature. This made PFAS super-slippery, and great for uses such as grease and water resistance. But it also means natural processes that break down many other compounds: heat, radiation, humidity, dilution – don’t really work on PFAS compounds.

A piece of steel rusting -- a natural oxidation process in the presence of moisture. PFAS compounds, however, strongly resist such natural chemical changes and breakdowns.