Long Chain Per/Polyfluoroalkyl Acids (C8 and Above)

Abstract

Abstract This chapter is about a series of per‐ and polyfluoroalkyl substances (PFAS) that can also be described as “long‐chain” perfluoroalkyl acids (PFAAs). The overall structure of PFAAs is a lengthy carbon chain with fluorine atoms substituting for hydrogen atoms and either a carboxylic or sulfonate head group. PFAAs are unusually chemically stable, water and oil resistant, and useful for many industrial applications, such as in the formation of polymers. In biological systems, these chemicals are generally well‐absorbed, resistant to metabolism, but also have the unusual property of widely different elimination kinetics among and within mammalian species. The range of estimated elimination half‐lives in humans for the perfluorooctanoic acid (PFOA), for example, is quite large ranging from one‐half to as much as 14 years, although a recent estimate from an international collaboration places this value closer to 1 year. The available literature on PFAAs is voluminous. This chapter will not attempt to review all this literature. Rather human studies will be emphasized, but since these studies nearly always suggest associations between PFAA exposure and health outcomes, this will be followed by studies in experimental animals that give insights into the human evidence. Afterward, a summary of attempts to estimate potential human risk by various international agencies will be described. What will become obvious, however, is that the overall uncertainty in the database of these chemicals has led to widely divergent risk assessment positions that need to be resolved. Risk management decisions on this class of chemistries are seen to be premature without such scientific resolution.