Molecular model of GenX, the ammonium salt of hexafluoropropylene oxide (HFPO) dimer acid. This is a synthetic short-chain organofluorine molecule that is used in non-stick coatings, food packaging and fire-fighting foams. It was developed as a replacement for Teflon and similar chemicals that were shown to be persistent organic pollutants and to be toxic to humans and wildlife. However, GenX has since been detected in water and plants around factories and its toxicity is being investigated. Atoms are represented as spheres and are colour-coded: carbon (grey), fluorine (green), oxygen (red), hydrogen (white) and nitrogen (blue).