US rainwater contains new and phased out PFAS

Rainwater collected in the Ohio-Indiana region contains both new and phased-out per- and polyfluoroalkyl substances (PFAS), according to research presented Monday at the American Chemical Society Spring 2021 meeting in the Division of Environmental Chemistry. College of Wooster chemist Jennifer A. Faust explained that these persistent pollutants are transported in the atmosphere and can be deposited far from the source via precipitation. Her group wanted to know how much variation there was in rainwater PFAS levels within a region. This information can lead researchers back to point sources of the chemicals.

Faust’s team used mass spectrometry to detect 17 kinds of PFAS in rainwater collected in summer 2019 at 7 urban, suburban, and rural sites. “We saw PFAS everywhere,” she said, at concentrations of 50-850 ng/L. The team was surprised that long- and short-chain PFAS were equally present in rainwater. “We expected lower concentrations of long-chain PFAS because they are less volatile and water soluble,” she said, but these compounds’ widespread use may explain the unexpectedly high levels.

Rainwater samples also contained high levels of perfluorooctanoic acid (PFOA), which is no longer made in the US. The continued presence of PFOA is likely explained by its ability to persist in the environment over the long term. What’s more, Faust said, they also found high levels of PFOA’s relatively new replacement, hexafluoropropylene oxide dimer acid (HFPO-DA).

Faust said that the PFAS profiles at the different sites suggested local point sources had a strong influence on rainwater concentrations. Her team is now performing isomeric fingerprinting in the hopes of tracing some of the PFAS they measured back to sources in the region.