Adverse health effects of per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are a class of anthropogenic chemicals with wide industrial and consumer applications that have been in use for the past seven decades. These commercial compounds consist of a variety of precursors that can be terminally degraded to perfluoroalkyl acids (PFAA), which are composed of a fully fluorinated carbon backbone of various chain lengths (~4-14), and a functional group primarily of sulfonate or carboxylate, or to a lesser extent, phosphonate/phosphinate. In recent years, the 8-carbon PFAA (perfluorooctane sulfonate, PFOS and perfluorooctanoate, PFOA) have been withdrawn from production in U.S., and alternatives of diverse chemical structures have emerged in their place. The carbon backbone of many of these replacements contains an ether linkage(s) and is partially fluorinated, with the usual sulfonate or carboxylate functional head (polyfluoroalkyl substances). PFAS are stable, non-reactive chemicals, and their hydrophobic and oleophobic properties render them ideal surfactants for commercial uses. However, their stability also makes them practically non-degradable and persistent in the environment. They are globally distributed, and detectable in all environmental media, humans and wildlife. During the past two decades, intense scrutiny of these chemicals has revealed properties of toxicity in laboratory animals, and to a lesser extent in wildlife. Epidemiological surveys also reported associations between PFAS exposure and some adverse health outcomes, particularly among populations where chemical contamination has been detected. In the past few years, various regulatory bodies worldwide have begun to conduct human health risk assessment of PFAS exposure (primarily through drinking water and food intake), and some advisory values became available. This presentation will provide a brief overview of the current understanding of PFAS toxicology and associated issues. (author)