Longer-term temporal trends in PFAS concentrations in Midwestern landfill leachate

It is well documented that per- and polyfluoroalkyl substances (PFAS) are routinely detected in leachate from municipal solid waste (MSW) landfills. PFAS-containing products are ubiquitous in society and in end-of-life discarded materials. While considerable data have been generated in recent years for PFAS concentrations in landfill leachate, little published information exists concerning longer-term trends in leachate concentrations. In this study, we examine a ten-year dataset for three MSW landfills located in the upper Midwestern United States where leachate PFAS testing has been performed on a quarterly basis. The significance of these data are considered in light of phase-out initiatives implemented in the US manufacturing companies for longer-chain PFAS including perfluorooctanoic acid (PFOA), perfluorooctane sulphonate (PFOS) and perfluorononanoic acid (PFNA). Findings from this study indicate that the average concentration of longer-chain PFOA in the three landfills decreased from 2400 to 1900 ng/L and the average PFOS concentrations decreased from 1000 to 370 ng/L. This may be indicative of reduced domestic production and use of these compounds. The phase-out of long-chain PFAS has also led to the introduction of shorter-chain replacement compounds such as perfluorobutanoic acid, perfluorobutane sulphonate and perfluorohexanoic acid, and this paper also examines long-term trends in leachate concentrations of these compounds.