On July 1, 2026, EPA announced the proposed scope and analyte list for the Unregulated Contaminant Monitoring Rule (UCMR) 6, with sampling scheduled for 2028 to 2030. Once again, PFAS have made the list with the focus on “ultrashort organofluorine compounds”. While some of these organofluorine compounds are not considered PFAS under some technical definitions, they are commonly referred to as ultrashort-chain PFAS.
The seven (7) ultrashort-chain PFAS on the proposed sampling list include trifluoroacetic acid (TFA), perfluoropropanoic acid (PFPrA), and bistriflimide (TFSI). The full list of UMCR6 analytes can be found on the EPA online summary.
The proposed monitoring program for UCMR6 includes the same expanded list of water systems as compared to UCMR5, recently completed between 2023-2025, which included all small water systems serving customers of more than 3,300. The expanded sampling scope started under UCMR5 includes a much larger percentage of “Small PWSs” or smaller public water systems (community and non-transient non-community water systems) serving customers between 3,300 and 10,000 where prior UCMR sampling programs, such as UCMR4, only sampled 800 randomly selected systems serving less than 10,000 customers. Although UCMR6 does note that the expanded list of systems is subject to available funding. The result of the expanded list of systems monitored results in an increase from approximately 5,000 systems sampled for UCMR4 to more than 10,000 systems sampled for UCMR5 and the larger number is again proposed for UCMR6.
As discussed in the Federal Register publication of the regulatory action, the selected PFAS, namely TFA, TFMS, and TSMI were on the Contaminant Candidate List (CCL) 5 but were not selected for UCMR5. EPA states that available data indicate that the ultrashort-chain PFAS are persistent in the environment, have health concerns, are “highly mobile”, and are commonly used in industry. Also, EPA states the EPA Method 563 is now available to better analyze for ultrashort-chain PFAS. The combination of their environmental aspects, use, and a validated method to quantify these PFAS are the rationale used by EPA to include ultrashort-chain PFAS on the UCMR6 analyte list.
Some other notable items with respect to the proposed UMCR6 scope include the following:
- The remaining 23 constituents on the list consist of 3 pesticide metabolites, 7 volatile organic compounds (VOCs), and 13 semi-volatile organic compounds (SVOCs).
- Two compounds previously monitored during the UCMR program are proposed for UMCR6: 1,2,3-Trichloropropane (1,2,3-TCP) and Chlorpyrifos. EPA describes 1,2,3-TCP as a “likely carcinogenic man-made compound” used as a solvent and cleaning agent and describes Chlorpyrifos/Chlorpyrifos Oxon as an organophosphate pesticide and its metabolite classified as neurotoxins. 1,2,3-TCP is being included since prior UCMR monitoring resulted in minimum reporting limits above health-based criteria and a recent EPA analytical method can now provide lower reporting limits. For Chlorpyrifos, while it had low occurrence data in UCMR4, its metabolite is understood to potentially form during PWS chlorination processes making it more likely to be present. Therefore, EPA selected both compounds for UCMR6.
- Notably absent from the UCMR6 list are microplastics, which have received significant attention in regulatory circles recently including a Governor’s Petition from 7 states to further research microplastics. EPA noted the absence of a standard, validated method and the unlikelihood that one could be developed prior to the start of the monitoring program as its rationale for not including microplastics.
In addition to the information in the Federal Register, EPA provides summaries and explanation of key UCMR 6 items on the EPA website.
Public comments are open until August 31, 2026, and can be sent via the Federal eRulemaking Portal: https://www.regulations.gov/ .
