Per- and Polyfluoroalkyl Substances (PFAS) -Information for Public Water Systems

Beginning in 2013, the United States Environmental Protection Agency (EPA) required that all public water systems (PWSs) serving more than 10,000 individuals test for six PFAS compounds.  Connecticut’s large PWSs conducted multiple rounds of testing from 2013 to 2015 and did not detect PFAS in the water from their sources of supply.  These sources of supply provide drinking water for over 2.4 million daily customers in CT.    During 2018 in collaboration with the CT DPH, PWSs conducted risk assessments to determine potential areas where PFAS contamination could be present. Improving technologies and laboratory techniques allow for the detection of PFAS at lower concentrations, therefore the CT DPH requested follow-up sampling by PWSs to determine if PFAS are present in the water systems near those areas.  On July 8, 2019, Governor Ned Lamont asked the Commissioners of the Department of Public Health and the Department of Energy and Environmental Protection to lead an Interagency Task Force that included representatives from a broad variety of state agencies to address PFAS in Connecticut. The Task Force developed a PFAS Action Plan and delivered this plan to Governor Lamont on November 1, 2019.  This Action Plan contains a comprehensive strategy to:
  1. Minimize human health risk for Connecticut residents,
  2. Minimize future releases of PFAS to the environment, and
  3. Identify, assess, and clean up historic releases of PFAS to the environment.
The DPH is currently working with our Agency partners to implement the recommendations in the PFAS Action Plan. The CT DPH has derived individual health-based drinking water Action Levels for 10 PFAS. Action Levels are guidelines for drinking water that are protective of public health and also feasible based upon analytical detection and treatment technology. This means that an Action Level concentration can be detected in drinking water by certified laboratories and that treatment systems are available to remove the contaminant(s) to a concentration that is below the Action Level. The 10 PFAS for which CT has developed Action Levels have enough toxicological data available to support development of health-based Action Levels. These PFAS include the most widely studied PFAS that have also been detected in human blood more frequently and at higher concentrations than other PFAS. CT DPH established Action Levels for four PFAS (PFOA, PFOS, PFNA, PFHxS) in June 2022 and for another six PFAS (GenX, PFHxA, PFBS, PFBA, 6:2 Cl-PFESA, 8:2 Cl-PFESA) in June 2023. The current Action Levels are listed in the Table below:



CT Drinking Water Action Level

(nanograms per liter; ng/L)^


6:2 chloropolyfluoroether sulfonic acid (6:2 Cl-PFESA, 9Cl-PF3ONS,*

F-53B major)



8:2 chloropolyfluoroether sulfonic acid (8:2 Cl-PFESA, 11Cl-PF3OUdS,**

F-53B minor)



Perfluorooctane sulfonic acid (PFOS)



Perfluorononanoic acid (PFNA)



Perfluorooctanoic acid (PFOA)



Hexafluoropropylene oxide dimer acid (HFPO-DA; GenX)



Perfluorohexane sulfonic acid (PFHxS)



Perfluorohexanoic acid (PFHxA)



Perfluorobutane sulfonic acid (PFBS)



Perfluorobutanoic acid (PFBA)


* EPA Methods 533 & 537.1 use9Cl-PF3ONS (9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid) for this PFAS.

** EPA Methods 533 & 537.1 use11Cl-PF3OUdS (11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid) for this PFAS.

CT DPH develops its drinking water Action Levels by considering health impacts to the most sensitive and most exposed populations across all stages of human development. These PFAS Action Levels are based on the most sensitive, human-relevant effects seen in laboratory animals exposed to PFOS (immune effects); PFNA, PFOA, PFHxA (developmental effects); PFHxS, PFBS, PFBA (thyroid effects); or GenX, 6:2 Cl-PFESA (liver effects). The data are insufficient for 8:2 Cl-PFESA so its Action Level is based on toxicity data for 6:2 Cl-PFESA. The chemical-specific approach reflects the evolving scientific evidence on the toxicity of PFAS and is more protective of public health than the summed approach used previously in CT. Also, the resulting individual Action Levels are within the range of drinking water guidance and standards most recently derived by the federal Agency for Toxic Substances and Disease Registry (ATSDR) and by other states, including most of CT’s neighboring states. Please refer to the DPH’s Per- and Polyfluoroalkyl Substances Webpage for further information. DPH encourages all public water systems to test for PFAS. Please see Circular Letters 2022-272022-30 and 2023-23.

Recommended Actions for Public Water Systems that have tested for PFAS

Steps to Assess Contamination

If water sampling results confirm that drinking water contains PFAS concentrations greater than the Action Levels, water systems should quickly undertake additional sampling to assess the level, scope, and localized source of contamination to inform next steps.  Public Water systems should also contact the CT DPH Emerging Contaminants Unit at (860) 509-7356 or email to .

Steps to Inform

Drinking water systems should promptly provide consumers with information about the levels of PFAS in their drinking water. This notice should include specific information on the risks to fetuses during pregnancy and to infants (breastfed and formula-fed) from exposure to drinking water with a PFAS concentration above Action Levels. In addition, the notification should include actions the public water system is taking and identify options that consumers may consider reducing risk such as seeking an alternative drinking water source, or in the case of parents of formula-fed infants, using formula that does not require adding water. Templates for use by public water systems can be found on the DWS Public Notification Rule page.

Steps to Limit Exposure

A number of options are available to drinking water systems to lower concentrations of PFAS in their drinking water supply. In some cases, drinking water systems can reduce concentrations of PFAS by closing contaminated wells.

Alternatively, public water systems can treat source water with activated carbon, ion exchange systems or high-pressure membrane systems (e.g., reverse osmosis) to remove certain PFAS from drinking water. These treatment systems are currently used by some public water systems to mitigate other contaminants but should be carefully designed and maintained to ensure that they are effective for treating the target PFAS. In some communities, entities have provided bottled water to consumers while steps to reduce or remove PFAS from drinking water or to establish a new water supply are being completed.

We can be exposed to PFAS not only through drinking PFAS contaminated water, but also through pathways such as: eating foods packaged in PFAS containing materials; using consumer products such as non-stick cookware, stain resistant carpeting, and water repellant clothing; and eating fish contaminated with PFAS. For more information on the health effects of PFAS and answers to frequently asked questions, please refer to the DPH’s PFAS webpage.

Basic Information

Circular Letters  


Treatment Options Available

For further inquiries:

Questions about drinking water from Public Supplies and treatment options: DPH Drinking Water Section: 860-509-7333

Questions on drinking water from Private Wells and treatment options:
DPH Private Well Program, 860-509-8401.

Questions about PFAS Health Effects:
DPH Environmental & Occupational Health Assessment Program, (860) 509-7740

Questions on PFAS Sources:
DEEP Remediation Division, 860-424-3061