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Research for New Regulation: UCMR5
Massachusetts Water Resources Authority

The US Environmental Protection Agency (EPA) periodically requires water systems across the country to conduct monitoring for substances that may be present in drinking water to help understand their national occurrence as part of the process of deciding whether to regulate them.  Under the Safe Drinking Water Act Amendments, EPA established the Unregulated Contaminant Monitoring Rule and is required once every five years to develop a list of up to 30 new contaminants that must be monitored during a three year period by public water systems that meet the criteria for sampling.  This monitoring is used by EPA to understand the frequency and level of occurrence of unregulated contaminants in the nation’s public water systems (PWSs).

EPA will collect and analyze data for all three years and from systems all across the country to develop an understanding of the occurrence, level and distribution of these substances in drinking water. That data, along with information on potential health effects and water treatment effectiveness will be used by EPA to determine if any new regulations are needed.

Return to UCMR Main Page

UCMR 5 (2023-2025)

The U.S. Environmental Protection Agency (EPA) issued the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) on December 27, 2021. Information on the contaminants to be monitored during 2023 through 2025 may be found here.

Under the Safe Drinking Water Act Amendments, EPA is required once every five years to develop a list of up to 30 new contaminants that must be monitored during a three year period by public water systems that meet the criteria for sampling. This process for determining the national occurrence of potential contaminants is conducted under EPA’s Unregulated Contaminant Monitoring Rule. For UCMR 5, EPA is requiring public water supplies to monitor 29 PFAS (per- and polyfluoroalkyl substances) and lithium. Additional information on PFAS may be found on EPA’s website here and information about MWRA’s current monitoring for PFAS can be found here.

PFAS are a group of synthetic chemicals used in a wide range of consumer products and industrial applications including: non-stick cookware, water-repellent clothing, stain resistant fabrics and carpets, cosmetics, firefighting foams, electroplating, and products that resist grease, water, and oil.

The Massachusetts DEP has issued a drinking water regulation for six of these PFAS compounds, and EPA has proposed a national regulation for an overlapping group of six PFAS.  MWRA easily meets both the Massachusetts and proposed federal standards.

See PFAS Testing in MWRA Drinking Water page for more information on the state and federal regulations and MWRA's test result page for information about MWRA’s test results.

Lithium is a naturally occurring metal that may concentrate in brine waters. Lithium is used in pharmaceuticals, and used in electrochemical cells, batteries, and in organic syntheses.

The 30 chemicals to be monitored are:

11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)

H,1H, 2H, 2H-perfluorodecane sulfonic acid (8:2FTS)

1H,1H, 2H, 2H-perfluorohexane sulfonic acid (4:2FTS)

1H,1H, 2H, 2H-perfluorooctane sulfonic acid (6:2FTS)

4,8-dioxa-3H-perfluorononanoic acid (ADONA)

9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid (9Cl-PF3ONS)

hexafluoropropylene oxide dimer acid (HFPO-DA)(GenX)

nonafluoro-3,6-dioxaheptanoic acid (NFDHA)

perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)

perfluoro-3-methoxypropanoic acid (PFMPA)

perfluoro-4-methoxybutanoic acid (PFMBA)

perfluorobutanesulfonic acid (PFBS)

perfluorobutanoic acid (PFBA)

perfluorodecanoic acid (PFDA)

perfluorododecanoic acid (PFDoA)

perfluoroheptanesulfonic acid (PFHpS)

perfluoroheptanoic acid (PFHpA)

perfluorohexanesulfonic acid (PFHxS)

perfluorohexanoic acid (PFHxA)

perfluorononanoic acid (PFNA)

perfluorooctanesulfonic acid (PFOS)

perfluorooctanoic acid (PFOA)

perfluoropentanesulfonic acid (PFPeS)

perfluoropentanoic acid (PFPeA)

perfluoroundecanoic acid (PFUnA)

N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)

N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)

perfluorotetradecanoic acid (PFTA)

perfluorotridecanoic acid (PFTrDA)



During 2023, MWRA will be sampling for the 30 UCMR chemicals in 12 fully supplied MWRA communities.

Quarter 1 Results:

  • None of the 29 PFAS compounds or lithium were detected in the first quarter of 2023 sampling.

Data will be periodically updated as results become available.

Quarter 2 Results:

  • Only one for the 30 compounds tested for was found at levels above EPA’s required method reporting levels.


Measurement Units

Running Average


1H,1H, 2H, 2H-perfluorooctane sulfonic acid (6:2FTS)

ppt (parts per trillion – ng/L)


ND – 6.2

This PFAS compound was detected at a quantifiable level in one of 12 samples taken during the second quarter sampling at a level slightly over the EPA required method reporting level (MRL) of 5 ppt. All other samples during both the first and second quarter were below the MRL and reported by EPA as zero. EPA did not develop a Health Based Reference Value for this compound, as no specific health data is available. No state or federal or international drinking water standards or health advisories exist for this compound. 

Updated July 14, 2023