Introduction
This fact sheet provides answers to questions frequently asked by private well owners about per- and polyfluoroalkyl substances (PFAS) in a private drinking water supply. A separate MassDEP fact sheet, “MassDEP Fact Sheet - PFAS in Drinking Water: Questions and Answers for Consumers”, describes the sources of PFAS compounds, health effects, and MassDEP recommendations to reduce consumer exposure.
What are PFAS?
PFAS are a group of man-made chemicals used in a variety of consumer products and industries throughout the world. Two PFAS chemicals, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), were extensively produced and are the most studied and regulated of these chemicals. Many other PFAS exist. These PFAS are contained in some firefighting foams used to extinguish oil and gas fires. They have also been used in a number of industrial processes, and to make carpets, clothing, fabrics for furniture, paper packaging for food, and other materials (e.g., cookware) that are resistant to water, grease, and stains. Because these chemicals have been used in many consumer products over the past 50 years, most people have been exposed to them.
What are the levels of concern for PFAS chemicals?
Massachusetts Drinking Water Standard
On October 2, 2020, MassDEP published its PFAS public drinking water standard of 20 nanograms per liter (ng/L) (or parts per trillion(ppt)) – individually or for the sum of the concentrations of six specific PFAS: perfluorooctane sulfonic acid (PFOS); perfluorooctanoic acid (PFOA); perfluorohexane sulfonic acid (PFHxS); perfluorononanoic acid (PFNA); perfluoroheptanoic acid (PFHpA), and perfluorodecanoic acid (PFDA). MassDEP abbreviates this set of six PFAS as “PFAS6.” This drinking water standard was set to be protective against adverse health effects for all people consuming the water based on an extensive assessment of the data available at the time. For information on the PFAS6 drinking water standard see: 310 CMR 22.00: The Massachusetts Drinking Water Regulations; and MassDEP’s technical support document Per- and Polyfluoroalkyl Substances (PFAS): An Updated Subgroup Approach to Groundwater and Drinking Water Values.
EPA Drinking Water Standards
On April 10, 2024 EPA announced National Primary Drinking Water regulations for six PFAS chemicals. EPA’s Maximum Contaminant Levels (MCLs) are:
- PFOA – 4.0 parts per trillion (ppt)
- PFOS – 4.0 ppt
- PFNA – 10 ppt
- PFHxS – 10 ppt
- HFPO-DA (commonly known as GenX Chemicals) – 10 ppt
- PFHxS, HFPO-DA, PFNA, and PFBS – 1.0 Hazard Index (HI) (unitless)
A Hazard Index accounts for the combined risk from mixtures of PFAS. For more information regarding the Hazard Index for PFAS and how to calculate it see: https://www.epa.gov/system/files/documents/2024-04/pfas-npdwr_fact-sheet_hazard-index_4.8.24.pdf and the Hazard Index Calculation Example provided below.
For more information on the EPA drinking water standards, see the following EPA webpage: https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas.
Note that the four PFAS chemicals PFOA, PFOS, PFNA, and PFHxS are regulated under both the EPA and current MassDEP drinking water standards. The MassDEP PFAS6 standard also includes the two PFAS chemicals PFHpA and PFDA. The EPA standards also includes the two PFAS chemicals HFPO-DA and PFBS.
PFAS Testing in Private Wells
MassDEP conducted free PFAS testing for a limited number of private wells, focusing on Massachusetts towns where 60% or more of residents are served by private wells. This Story Map presents the results to date.
How do PFAS get into private well water supplies?
While consumer products and food can be sources of exposure to PFAS, private drinking water can be a significant source of exposure at locations where these chemicals have contaminated water supplies. Such contamination is often localized and associated with a specific facility; for example, an airfield where PFAS were used for firefighting or a facility where these chemicals were produced or used.
Should I test my private well for PFAS?
MassDEP recommends that all private drinking water wells be tested for PFAS contamination, especially if your well is located within one to two miles of a known source of PFAS or of other water supplies where PFAS has been detected. Sources of PFAS may include airfields where certain firefighting foams were used in the past, firefighting training areas, certain manufacturing facilities, and some waste disposal sites. Your local health department may have information on historical or potential sources of PFAS, or other PFAS impacted water supplies, that may be in proximity to your private well. Because PFAS have been widely used in consumer products, it is possible that some septic systems and landfills may also be a source of PFAS in groundwater.
What is the Hazard Index and why is it used as a standard?
When contaminants may have the same (or similar) adverse health effects, you may be concerned about the potential additive effects of having several of these chemicals in your drinking water, even if each individually meets its allowable level. The Hazard Index is a tool used to evaluate the potential for such a cumulative impact and takes into account the levels of the contaminants and their potency or strength. EPA has identified an allowable level, a Health-Based Water Concentration (HBWC) for each of the following four PFAS: PFHxS: 10 ppt, GenX (HFPO-DA): 10 ppt, PFNA: 10 ppt, and PFBS: 2000 ppt. The first three are equal in strength or potency while PFBS is 200 times less potent than the others.
In order to evaluate the potential additive effect of having these multiple contaminants in drinking water, you add the numbers generated by dividing the level (concentration from the laboratory results) of each of the above four PFAS by its corresponding strength or potency which is indicated by the HBWC value. The result you get is the Hazard Index. Hazard Index values above 1 mean that the cumulative level of all four PFAS, adjusted for their strength, exceeds EPA’s standard for public water supplies. See the EPA Fact Sheet Understanding the Final PFAS National Primary Drinking Water Regulation Hazard Index Maximum Contaminant Level for additional information regarding the Hazard Index at: https://www.epa.gov/system/files/documents/2024-04/pfas-npdwr_fact-sheet_hazard-index_4.8.24.pdf and the following example calculation.
Example of a Hazard Index calculation:
If a drinking water supply contains PFHxS at 3 ppt; GenX at 6 ppt; PFNA at 7 ppt; and, PFBS at 200 ppt the Hazard Index would be calculated as follows.
Hazard Index = (3 ppt/10 ppt) + (6 ppt/10 ppt) + (7 ppt/10 ppt) + (200 ppt/2,000 ppt)
Hazard Index = 0.3 + 0.6 + 0.7 + 0.1
Hazard Index = 1.7
In this case, the Hazard Index exceeds the new EPA standard for the mixture of these contaminants even though the concentration of each of these contaminants is below its corresponding Health-Based Water Concentration listed above.
How can I test my well water for PFAS?
- Currently, there are three U.S. EPA testing methodologies for testing drinking water for PFAS. Laboratories will analyze drinking water for PFAS using either USEPA Method 537, 537.1, or 533. These methods test for multiple PFAS compounds, including the PFAS compounds that are part of the current MassDEP and EPA Drinking Water Standards. Please note that Method 533 is not yet approved for public water supply testing in Massachusetts Several laboratories have been approved by the EPA to use Method 533 for UCMR5 testing and are able to provide useful data for private wells.
- Use the Online Searchable Laboratory Certification Listing (Search for Analyte = PFAS and Matrix = Potable (Drinking Water) to find laboratories that have been certified by MassDEP to test for PFAS in public drinking water supplies. Laboratories approved by EPA to use Method 533 can be found at https://www.epa.gov/dwucmr/list-laboratories-approved-epa-third-and-fourth-unregulated-contaminant-monitoring-rule-ucmr.
- When collecting the sample, to avoid contaminating it we encourage you to carefully follow the PFAS sample collection procedures or those provided by the laboratory that will be doing the analysis.
How often should I test my well water for PFAS?
If after initial testing no PFAS is detected, continue testing for PFAS at least once every 10 years or on a schedule recommended by your local public health agency. Contact your local Board of Health for any local testing requirements for private wells.
If I Have PFAS in My Well Water What Can I Do?
The options include the use of alternative sources of water that have been verified to meet the PFAS drinking water standards for cooking, drinking, and ice making, or the installation and use of a treatment system to remove PFAS from the well water. A common alternative source of water would be the use of bottled water. Additional information on bottled water and water treatment options are provided in the answers to some of the following questions in this document.
Can I use bottled water if I have concerns about PFAS in my private well water?
If PFAS has been detected in your private well and you are a consumer in one of the groups considered most sensitive to PFAS (pregnant women, nursing mothers, and infants) you can minimize your exposure by using bottled water that has been tested for PFAS for drinking, making infant formula, and cooking of foods that absorb water.
The Massachusetts Department of Public Health (MDPH) Food Protection Program publishes a list of companies licensed to sell or distribute bottled water or carbonated non-alcoholic beverages in Massachusetts. The list includes bottling company weblinks to enable searches for products sold in Massachusetts. Licenses are renewed annually, and the MDPH list will be updated quarterly.
The MDPH list includes only bottlers licensed by MDPH after they provided test results which show that their bottled water or beverages comply with drinking water standards for PFAS and other contaminants established by:
- The Massachusetts Department of Environmental Protection,
- The US Environmental Protection Agency, and
- The US Food and Drug Administration.
In 2022, the MDPH conducted a pilot surveillance program on PFAS in bottled water sold in Massachusetts. All bottled water test results met the MassDEP PFAS6 MCL and the US EPA's announced MCLs.
Information from MDPH regarding bottled water, including contact information, can be found here.
Can I use a Point of Use (POU) or a Point of Entry (POE) water treatment device to remove PFAS?
Point of Use (POU) water treatment devices treat the water at one fixture in a home, such as a kitchen faucet. Point of Entry (POE) water treatment devices treat all of the water for the main water line serving a whole house.
- Yes. You may use a POU or POE treatment device to remove PFAS. However, before installing any treatment device for drinking water, you should get your water tested, because the type of treatment device you select will depend on the level of specific PFAS in the water. You should also test your water after the treatment device is installed to verify that it is removing PFAS to levels less than both the MassDEP and EPA drinking water standards.
- Ingestion of water with elevated PFAS is the main health concern, rather than other uses such as showering or use of the water for laundry. Therefore, installing a POU treatment device for drinking or food preparation in the kitchen, e.g., under a kitchen sink, may be a good option and location for a treatment device.
Point of Use (POU) and Point of Entry (POE) treatment devices are not specifically designed to meet the Massachusetts’ or Federal drinking water standards for PFAS. Any treatment device you use should be certified to meet “NSF/ANSI 53” or “NSF/ANSI 58” standards. It's important to note that the current certification standards for PFAS filters (as of April 2024) do not yet indicate that a filter will remove PFAS down to the levels EPA has now set for a drinking water standard. EPA is working with standard-setting bodies to update their filter certifications to match EPA’s new requirements. If you chose to install a treatment device, you should check to see if the manufacturer has independently verifiable PFAS monitoring results demonstrating that the device can reduce PFAS below the MassDEP and EPA drinking water standards.
Additional Resources
What types of POU and POE treatment systems are available to treat for PFAS?
There are several treatment technologies that are capable of removing PFAS from drinking water, including granulated activated carbon (GAC), ion-exchange resin, and reverse-osmosis (RO). It is recommended that you evaluate the pros and cons for each type of treatment device to determine what is best for you.
- GAC treatment devices trap the PFAS inside the filter so that the PFAS is not discharged back into the environment. GAC has proven effective in removing PFAS contaminants, particularly the longer chain PFAS.
- Ion-exchange treatment devices also trap the PFAS inside the filter and are effective in removing PFAS.
- Maintaining GAC or ion-exchange treatment devices. These treatment devices must be maintained by replacing the filters periodically in accordance with the manufacturer’s instructions. Some manufacturers will recycle spent filter cartridges. Check the website of the manufacturer for recycling locations and disposal options.
- RO treatment devices remove and then discharge the PFAS in a concentrated wastewater stream.
- Discharge of the RO wastewater stream must comply with local and state requirements and may be costly; as such, cost may be a significant concern in determining which treatment device you choose.
- Options for discharging a PFAS wastewater stream depend on where the private well is, and include municipal sewer system, an onsite Title 5 septic system, or an installed Underground Injection Control (UIC) dry well.
- All wastewater disposal options will ultimately result in some treated wastewater reaching the ambient groundwater or surface water. As such, MassDEP does not recommend RO treatment as your primary treatment option if your wastewater disposal method is to a UIC dry well.
Studies on the Effectiveness of POU and POE Treatment Devices on PFAS Removal
These studies show the effectiveness of different water filters at reducing PFAS from drinking water. MassDEP will add to this list as more studies become available.
- For MassDEP information on home water treatment devices see https://www.mass.gov/info-details/home-water-treatment-devices-point-of-entry-and-point-of-use-drinking-water-treatment
- A North Carolina study analyzed effectiveness of multiple (73) POU and POE units and found they “exhibited variable PFAS removal”: https://pubs.acs.org/doi/pdf/10.1021/acs.estlett.0c00004 Individual results are found in the supporting information Table S9: https://pubs.acs.org/doi/suppl/10.1021/acs.estlett.0c00004/suppl_file/ez0c00004_si_001.pdf
- A North Carolina Study analyzed ability of activated carbon block POUs certified to meet NSF P473 (replaced by NSF/ANSI 53 or 58) to reduce PFAS using a readily commercially available POU (AO-MF-ADV, A.O. Smith) as the test device. Results are in Section 4.1 https://awwa.onlinelibrary.wiley.com/doi/10.1002/aws2.1262
- MassDEP and its partner UMass Amherst evaluated the effectiveness of commercially available POU devices to remove PFAS from contaminated drinking water in Massachusetts. The report can be downloaded here: MassDEP, UMass Amherst Per- and Polyfluoroalkyl Substances (PFAS) Point-of-Use Treatment System Study Final Report
Can wastewater containing PFAS from RO treatment systems go to a Title 5 septic or UIC dry well?
The discharge of wastewater from an RO treatment system to a Title 5 septic system is prohibited under MassDEP Title 5 regulations (310 CMR 15.000).
For other RO wastewater discharge options the answer depends upon the type of RO treatment system; and the concentration of the PFAS in the water.
- Prior to installing a RO treatment device, you may estimate the concentration of PFAS6 that will be in your RO wastewater and compare it with the PFAS6 drinking water standard:
- You will need the following information: a) the total amount of PFAS6 chemicals in your untreated water from your laboratory results, and b) the percentage of water entering your RO device that will be discharged as wastewater.
- If specific PFAS6 removal efficiencies are not available from the manufacturer of the RO device, you should assume that all of the PFAS6 is being concentrated into the wastewater, to avoid underestimating the wastewater concentration.
- If specification sheets for the RO devices do not provide information on the percent of water entering the device that is discharged as wastewater, you may assume 80%.
- You may use the following equation for estimating the concentration of PFAS6 or other individual PFAS chemical with an EPA drinking water standard in the wastewater from the RO device (the following example is specific to the MassDEP drinking water standard for PFAS6):
[concentration of PFAS6 in your well water] X [100% / % of water entering the device that is discharged as wastewater]
Example: If the concentration of PFAS6 chemicals in your untreated well water equals 10 ppt and 80% of the water entering the RO filter is discharged as wastewater, then the above equation results in:
10 ppt PFAS6 X [100% / 80%] = 12.5 ppt PFAS6 - If your RO device is more efficient than the example above and discharges less than 80% of the water entering it, then the calculation will show a higher concentration of PFAS6 in the wastewater.
- Note that the EPA drinking water standards for five of the six PFAS chemicals that they regulate are significantly less than the MassDEP PFAS6 standard of 20 ppt.
- If PFAS6 concentration in the wastewater stream from the RO device exceeds MassDEP PFAS6 drinking water standard, you may not discharge to a UIC dry well. Note: If the water entering your RO for treatment has a PFAS6 concentration exceeding the drinking water standard, then the PFAS in your RO wastewater will also exceed the drinking water standard.
- If PFAS6 concentration in the wastewater stream from the RO device is less than the drinking water standard and the estimated or tested PFAS concentrations in the wastewater are also below the drinking water standard, then on-site and other options for discharging the wastewater may be considered under the conditions mentioned in the following table.
| Municipal Waste Water System Allowed? | UIC/Dry Well Allowed? | Title 5 Septic System Allowed? |
Yes, but be advised that discharges other than sanitary waste to municipal sewer systems may require sewer authority approval. Check with your local sewer authority. If you are serviced by a private sewer system, check with your treatment plant operator about discharging RO wastewater. | Yes, but only if the PFAS concentrations in the wastewater also remain below the drinking water standard. In accordance with 310 CMR 27.00, discharge to a dry well may be considered. The discharge to a dry well requires the submittal of a MassDEP Underground Injection Control (UIC) registration application with the exception of properties that are only used for a one unit residence. UIC application information is located at https://www.mass.gov/underground-injection-control-uic For questions on UIC, contact program.director-dwp@mass.gov: Subject UIC | No. In accordance with 310 CMR 15.000, discharge to a Title 5 system is not allowed. |
Who can I contact for more information on PFAS in drinking water?
Private well owners or users should contact their local board of health or town government for information regarding groundwater quality issues in the area. For any additional PFAS drinking water inquires, contact the MassDEP Drinking Water Program at: Program.director-dwp@mass.gov, Subject: PFAS.
Where can I get more information on PFAS?
For health-related questions/contact:
Environmental Toxicology Program
Bureau of Environmental Health, MDPH
250 Washington Street
7th Floor
Boston, MA 02108
Phone: 617-624-5757
Fax: 617-624-5777
TTY: 617-624-5286
The Centers for Disease Control and Prevention’s webpage on PFAS
CDC’s fact sheet on PFAS and Breastfeeding
USEPA Fact Sheet: Reducing PFAS in Your Drinking Water with a Home Filter