Study finds it could take over 40 years to flush PFAS out of groundwater

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.