Per- and polyfluoroalkyl chemicals, known commonly as PFAS, could take over 40 years to flush out of contaminated groundwater in North Carolina's Cumberland and Bladen counties, according to a new study from North Carolina State University. The study used a novel combination of data on PFAS, groundwater age-dating tracers, and groundwater flux to forecast PFAS concentrations in groundwater discharging to tributaries of the Cape Fear River in North Carolina.

These results suggest it could take decades for natural groundwater flow to flush out groundwater PFAS still present from the ‘high emission years,’ roughly the period between 1980 and 2019. And this could be an underestimate; the time scale could be longer if PFAS is diffusing into and out of low-permeability zones (clay layers and lenses) below the water table.