Image PFAS (per- and polyfluoroalkyl substances) are a large class of thousands of industrial chemicals that are recognised by many prominent scientists and agencies as toxicants. Extreme persistence is the defining characteristic of this class of compounds, but they can also be highly mobile, bio-accumulative and hazardous. Many of the most-studied PFAS persist in human tissue for years, with serum half-lives ranging from several years to decades. PFAS cross the placenta, are detected in cord serum, and are transmitted to newborns and infants via contaminated breast milk. PFAS are linked to serious health impacts even at low levels of exposure. They can affect reproductive health and birthweight and are linked to thyroid disease and asthma.