PFAS in Well Water

The short answer

PFAS (per- and polyfluoroalkyl substances) are a group of manufactured chemicals that EPA says have been used in industry and consumer products since the 1940s^[2]. There are thousands of them. Many break down very slowly and can build up in people, animals and the environment over time, which is why Pennsylvania's Department of Environmental Protection says they are called "forever chemicals." EPA lists private drinking water wells among the places PFAS can be found.

This page covers the five PFAS that EPA's 2024 rule gave individual federal drinking water limits: PFOA, PFOS, PFHxS, PFNA and HFPO-DA (often called GenX). Three facts frame a well owner's result:

• The federal limits are final but not yet in force. EPA set them in 2024. The limit for PFOA is 4.0 ng/L (effective Apr 26, 2029)^[1] and the limit for PFOS is 4.0 ng/L (effective Apr 26, 2029)^[1]. EPA has since proposed changes, covered below.
• Michigan and Pennsylvania limits are in force for public water. Michigan's limit for PFOA, for example, is 8 ng/L^[13], and Pennsylvania's is 14 ng/L^[14]. Michigan's limits are being challenged in court, so we compare a result with them as a health guideline, as explained below.
• None of these limits covers a private well. EPA says the quality of drinking water from private domestic wells is not regulated by the federal government under the Safe Drinking Water Act, nor by most state governments.

So no one tests your well for PFAS unless you do. EPA's advice is to use a state-certified laboratory that uses EPA-developed testing methods. Our PFAS water test guide explains who should test and how to take a sample without contaminating it. If the lab doesn't detect PFAS, no treatment is needed based on that result.

PFAS levels and what to do

The table below lists every benchmark we track for these five PFAS: EPA's 2024 limits and health goals, and the Michigan and Pennsylvania state limits. The values come from our versioned benchmark data, which records each source and the date we last checked its status. Our guide on how to read your lab report explains the units and terms you will see on it.

Federal limits: on the books, not yet in force

EPA announced its final PFAS drinking water rule on April 10, 2024^[1]. It set enforceable maximum contaminant levels (MCLs) and non-enforceable health goals (MCLGs). The health goal for PFOA is 0 ng/L^[1] and for PFOS 0 ng/L^[1]. The table lists the limits and health goals for PFHxS, PFNA and HFPO-DA as well.

The rule also set a Hazard Index limit for mixtures of two or more of PFHxS, PFNA, HFPO-DA and PFBS. Our table compares each PFAS with its own limits only and does not calculate a Hazard Index.

The limits do not bind water systems yet. EPA says public water systems have five years, to 2029^[1], to put in solutions if their monitoring shows levels above the MCLs. That is why our table marks the federal limit rows as not yet in force.

On May 18, 2026^[1], EPA announced two proposed rules. One keeps the PFOA and PFOS limits but lets water systems ask for two more years, to 2031^[1], to comply. The other would rescind the limits for PFHxS, PFNA and HFPO-DA, and the Hazard Index for mixtures of those three plus PFBS. A proposal is not a final rule, so the table still shows the 2024 values. The status box below shows what applies as of its date.

Michigan and Pennsylvania

Michigan set limits for seven PFAS in Rule 325.10604g of its drinking water rules. EGLE says the rules took effect on August 3, 2020^[6], for community and nontransient noncommunity water supplies. Five are the PFAS on this page: PFOA 8 ng/L^[13], PFOS 16 ng/L^[13], PFHxS 51 ng/L^[13], PFNA 6 ng/L^[13] and HFPO-DA 370 ng/L^[13]. Michigan's list also includes PFBS and PFHxA, two PFAS we don't track, so this page gives no values for them.

3M has challenged these rules in court. The Court of Claims held them invalid but stayed its ruling until appeals are exhausted, the Court of Appeals affirmed, and the case is before the Michigan Supreme Court^[12]. The limits stay in force while the case continues. Until it is settled, we compare a Michigan result with them as a health guideline rather than a settled legal limit.

Pennsylvania regulates two PFAS. Its rule, published in the Pennsylvania Bulletin on January 14, 2023^[11], sets limits of 14 ng/L^[14] for PFOA and 18 ng/L^[14] for PFOS for public water systems.

What the limits mean for a private well

Both states judge a public supply's compliance by a running annual average of its sample results. Neither rule covers your well. Pennsylvania's Environmental Quality Board wrote that it does not have the authority to regulate private water sources. Michigan says private residential wells are not regulated under the Safe Drinking Water Act, but that it uses the MCLs, along with other factors, when it evaluates private well results. For a well owner, the limits are the benchmarks to compare a lab result with, not rules your well must meet.

Health effects of PFAS

EPA says current peer-reviewed studies have shown that exposure to certain levels of PFAS may lead to:

• reproductive effects, such as decreased fertility or high blood pressure in pregnant women;
• developmental effects or delays in children, including low birth weight, accelerated puberty, bone variations or behavioral changes;
• a higher risk of some cancers, including prostate, kidney and testicular cancers;
• a reduced ability of the immune system to fight infections, including a reduced response to vaccines;
• interference with the body's natural hormones;
• higher cholesterol levels or risk of obesity.

EPA adds that research is still under way to learn how different levels of different PFAS lead to these effects, especially low levels over long periods and especially in children.

Who may be exposed more. EPA says pregnant and breastfeeding women drink more water per pound of body weight than the average person, so they may have higher exposure if PFAS are in their drinking water. Children drink more water, eat more food and breathe more air per pound of body weight than adults. Infant formula made with water that contains PFAS can expose babies too. EPA says that, based on current science, the benefits of breastfeeding appear to outweigh the risks for infants exposed to PFAS in breast milk, and that mothers should talk with their doctors.

Drinking water is one source among several. EPA says surveys by the Centers for Disease Control and Prevention show most people in the United States have been exposed to some PFAS, and that most known exposures are relatively low. Food, packaging, household dust and some jobs add to the total.

A water test measures PFAS in your water, not in anyone's body. If you have health concerns, talk to a health professional and bring your lab report. In Michigan, you can call the state health department's Environmental Health Hotline to review your water test results with a toxicologist.

Where PFAS in well water come from

EPA lists the places PFAS are found. Several of them can reach groundwater and the wells that draw from it:

• Firefighting foam. Foams used to put out flammable liquid fires, in training and emergencies at airports, military bases, shipyards, fire training sites, chemical plants and refineries.
• Waste sites. Soil and water at or near landfills, disposal sites and hazardous waste sites.
• Factories that make or use PFAS. EPA names chrome plating, electronics and some textile and paper makers.
• Biosolids. Fertilizer from wastewater treatment plants, used on farmland, can affect ground and surface water.

Pennsylvania DEP says PFAS readily dissolve in water, are mobile and are highly persistent in the environment. Michigan's PFAS team says that once PFAS are in the environment they may enter surface water, groundwater and drinking water wells.

What makes one well more at risk than another. When Michigan investigates a known or suspected PFAS source, its project team looks at the direction groundwater flows, how deep nearby wells are, how close each well is to the site, and the soil the well sits in. Sand, it notes, does not protect a well from contamination as well as clay does. If Michigan's team decides wells near a site need testing, EGLE mails the owners a letter offering to test the well for free.

You can't judge your own risk from a map alone. If a landfill, airport, military base, plant or farm that spreads biosolids is nearby, ask your state environmental or health agency whether PFAS have been found in your area. EPA points well owners to the same agencies for advice.

When to test and retest for PFAS

PFAS are measured in parts per trillion, amounts so small that Michigan warns even the smallest cross-contamination during sampling could cause a false positive. Plan a test, or a retest, in these situations:

• When you have never tested. EPA's routine yearly well tests (total coliform bacteria, nitrates, total dissolved solids and pH) don't include PFAS, so you have to ask for it.
• When a possible source is nearby, or your state tells you your home is near a PFAS investigation.
• Before a baby drinks the water, or when someone in your home is pregnant or breastfeeding, given EPA's point that these groups may have higher exposure.
• To confirm a detection. If PFAS were found near or above a limit in the table, retest with a state-certified lab before you decide on treatment.
• After you install a filter. Test the filtered water to see that it works. EPA warns that not replacing a filter on the maker's schedule can increase your exposure.

If a careful sample showed no PFAS and nothing near your well has changed, keep the report so you can compare future results. You can build a test plan that covers PFAS and your well's other tests, and our well water testing guide explains the yearly well check.

How to lower PFAS in your water

Start with a confirmed result from a state-certified lab. What you do next depends on what it shows, and "no treatment needed" is a real outcome.

If PFAS were not detected, no treatment is needed based on that result. EPA says that if PFAS have not been measured in your water, or were measured below federal limits, a filter may not be useful to you.

If PFAS were detected, EPA suggests contacting your state environmental or health agency for its advice. If you remain concerned, EPA says to consider another water source for drinking, cooking, brushing teeth and making baby formula while you decide on a fix.

If you choose a filter, EPA and Michigan describe these options in summary:

• Granular activated carbon. EPA says carbon filters trap chemicals as water passes through. Michigan adds that carbon gives more water flow than reverse osmosis and leaves minerals in the water.
• Reverse osmosis. EPA says it forces water through a very thin barrier that separates chemicals from the water. Michigan notes it also lowers more contaminants, removes minerals and uses about three times^[7] as much water as it treats.
• Ion exchange resins. EPA describes tiny beads that attract and hold the contaminants.

Look for certification to NSF/ANSI 53 or NSF/ANSI 58 for PFAS reduction on the package, as both EPA and Michigan advise. EPA cautions that, as of April 2024, filter certifications did not yet show that a filter removes PFAS down to EPA's new limits. Filters only work if you maintain them, so follow the maker's schedule for cartridges and membranes. Then retest the treated water with a certified lab.

In Michigan, if the state health department (MDHHS) or your local health department has contacted you recommending a filter for your private well, Michigan says one will be provided at no cost, with replacement cartridges. Ask your local health department.