Rain and water in ponds and lakes slowly seeps into the soil, moving through minute cracks to refill underground aquifers. Per- and polyfluoroalkyl substances (PFAS), often described as forever chemicals, can tag along into groundwater that's later removed for drinking. Researchers analyzed water from over 100 wells in Denmark for one particularly persistent PFAS: trifluoroacetate. They report steadily increasing levels of the forever chemical in recent decades.