PFOA and PFOS are two of the most widely studied PFAS. One or each of these two PFAS was measured
at or above EPA’s minimum reporting level (MRL), and therefore above EPA’s Health Advisory (HA)
levels, in the first sampling event for 7.8-8.5% of PWSs with results to date.

The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5): Data Summary, July 2023 (epa.gov)