EPA Releases Fifth Round of Data from the Fifth Unregulated Contaminant Monitoring Rule (UCMR5)

EPA has released the fifth round of of data from the Fifth Unregulated Contaminant Monitoring Rule (UCMR5). While the UCMR5 monitoring is not yet completed (deadline of December 2025), the July 2024 UCMR5 Data Summary has some interesting results. For lithium, based on 32,343 samples from 6,520 public water systems (PWSs), 24.9% of PWSs (1,626 PWSs) had monitoring results greater than the reference concentration. In comparison, for 31,487 samples from 6,401 PWS, zero PWSs had PFBA results greater than the reference concentration and the same for PFHxA – zero PWSs with results greater than the reference concentration. Reference concentrations have not been developed for the other 21 unregulated PFAS, so no comparisons can be made.

For the regulated PFAS, 316 (9.1%) of PWSs had PFOS averages greater than the MCL, and 246 (7.1%) of PWSs had PFOA concentrations greater than the MCL, noting that there is likely some overlap, i.e., some systems have both PFOS and PFOA. Based on the UCMR5 data so far, 393 PWSs out of 3,463 (11%) had one or more averages greater than the MCLs.