Thirty unregulated contaminants are proposed for new monitoring requirements in the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6). The Safe Drinking Water Act (SDWA) requires the U.S. Environmental Protection Agency (USEPA) to issue a list of unregulated contaminants to be monitored by public water systems once every five years under the UCMR.
PROPOSED UCMR 6
By gathering nationwide data on contaminants, USEPA learns more about their occurrence, concentrations, and potential risk to public health. The proposed UCMR 6 contains 30 chemicals, including four PFAS. Microplastics were expected by some in the water industry to be listed on the UCMR 6. However, the USEPA did not include microplastics in its proposed list, most likely since a standard method of testing remains to be developed. Once the rule is finalized, USEPA will collect and release data on the chemicals from sampled public water systems.
PROPOSED UCMR 6 LIST
7 Purgeable Organic Compounds using USEPA Method 524.3 Enhanced Sensitivity (Purge-and-trap (P&T) capillary column gas chromatography/mass spectrometry (GC/MS)) (USEPA, 2026e)
- 1,2,4-Trimethylbenzene
- 1,2,3-Trichloropropane (1,2,3-TCP)
- 1,1,2,2-Tetrachloroethane
- Total 1,3-Dichloropropene (cis- & trans-)
- Naphthalene
- Hexachlorobutadiene
- 1,1,1,2-Tetrachloroethane
13 Semivolatile Organic Compounds using EPA Method 525.3 (Solid phase extraction (SPE) capillary column gas chromatography/mass spectrometry (GC/MS)) (USEPA, 2012a)
- Phorate
- Chlorothalonil
- Dichlorvos (DDVP)
- Metribuzin
- N,N-Diethyl-m-toluamide (DEET)
- Pyrene
- Trifluralin
- Isophorone
- 2,4-Dinitrotoluene
- 2,6-Dinitrotoluene
- Tetrachlorvinphos (Stirofos)
- Anthracene
- Fluorene
3 Pesticide Metabolites using EPA Method 540 (Solid phase extraction (SPE) liquid chromatography/tandem mass spectrometry (LC/MS/MS)) (USEPA, 2013a)
- Chlorpyrifos oxon
- Phorate sulfone
- Phorate sulfoxide
7 Ultrashort Organofluorine Compounds using EPA Method 563 (Liquid chromatography/tandem mass spectrometry (LC/MS/MS)) (USEPA, 2026f)
- Perfluoropropanesulfonic acid (PFPrS)*
- Perfluoropropanoic acid (PFPrA)*
- Perfluoroethanesulfonic acid (PFEtS)*
- Perfluoro-2-methoxyacetic acid (PFMOAA)*
- Trifluoromethanesulfonic acid (TFMS)
- Bistriflimide (TFSI)
- Trifluoroacetic acid (TFA)
*Identified as a PFAS in accordance with definition used in USEPA Contaminant Candidate List 5.
Public Webinars & Comment Period
USEPA will host two identical public webinars on August 11, 2026, and August 12, 2026. Register for the webinars on the USEPA website here.
Public comments on the proposed UCMR 6 will be accepted through August 31, 2026, on the Federal Register. For more information about the current and previous UCMR cycles, visit the USEPA UCMR website.