USA: EPA proposes UCMR 6 — monitoring of 30 unregulated drinking water contaminants in 2028–2030, including seven ultrashort organofluorine compounds by the new EPA Method 563; analyses only by EPA-approved laboratories
On 1 July 2026 the US Environmental Protection Agency (EPA) published in the Federal Register its proposed Sixth Unregulated Contaminant Monitoring Rule (UCMR 6). Water systems would collect occurrence data for 30 substances not covered by national primary drinking water regulations, and samples could be analysed only by EPA-approved laboratories; comments were accepted until 31 August 2026.
- Four groups, each tied to a method: seven ultrashort organofluorine compounds — PFPrS, PFEtS, PFPrA and PFMOAA (PFAS under the CCL 5 definition) plus TFMS, TFA and bistriflimide — by EPA Method 563 (LC-MS/MS); three pesticide metabolites by Method 540 (SPE LC-MS/MS); 13 semivolatile organic compounds by Method 525.3 (SPE GC-MS) and seven purgeable compounds by Method 524.3 Enhanced Sensitivity (purge-and-trap GC-MS). Samples would be collected from January 2028 to December 2030.
- Subject to appropriations, monitoring would cover all systems serving 3,300 or more people and a representative sample of smaller ones; EPA pays for testing at systems serving 10,000 or fewer people. EPA estimates the total annualised cost at USD 33.7 million (2025 dollars).
- A laboratory seeking approval submits initial demonstration of capability (IDC) data for each method, verifies performance at or below the minimum reporting levels (MRLs), provides its SOPs and passes an EPA proficiency test for every analyte in the method. The MRL is the lowest quantitation level achievable with 95% confidence by at least 75% of laboratories; it was set from LCMRL studies in at least three laboratories. EPA plans up to three PT studies before the final rule and at least two after it.
- According to EPA, Method 563 is easier and quicker to run than Methods 533 and 537.1 used in UCMR 5, because the sample is injected directly into the instrument with limited preparation — which reduces laboratory burden and increases the number of samples analysed per day. Microplastics were not included despite a petition from the governors of seven states, as no validated method with the required quality control exists; EPA continues to evaluate ASTM practices D8332-20 and D8333-20.