Perand polyfluoroalkyl substances (PFAS) are a group comprising thousands of synthetic chemicals that are extensively used in society, including certain hydrofluorocarbon (HFC) and hydrofluoroolefin (HFO) refrigerants. They all contain carbon-fluorine bonds, so they resist degradation during use and also when released into the environment. Most PFAS are also easily transported in the environment, and can be found at great distances from the source of their release. Contamination of water and soil by PFAS has been observed frequently.