Arsenic in Well Water: Understanding, Testing, and Treatment
September 25, 2026
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by
Raul Grimaldo
EPA PFAS drinking water regulations currently maintain enforceable limits of 4.0 parts per trillion for PFOA and PFOS in public drinking water systems. EPA proposed additional regulatory changes in May 2026, but those changes have not yet been finalized. Homeowners concerned about PFAS should start by reviewing local water data or testing their water, then choose filtration specifically designed and certified for PFAS reduction.
EPA PFAS drinking water regulations have put greater attention on a group of chemicals often called “forever chemicals.” PFAS, or per- and polyfluoroalkyl substances, have been used for decades in consumer products and industrial applications because of their resistance to heat, oil, grease, and water.
Those same properties also allow many PFAS to persist in the environment. When PFAS reach groundwater or surface water used for drinking supplies, they can become a concern for communities and individual households.
The regulatory landscape has also changed quickly. EPA finalized the first national drinking water standards for several PFAS in 2024, then proposed significant revisions in 2026. Understanding what is final, what is proposed, and what homeowners can do now is essential for making informed water treatment decisions.
PFAS are a large group of synthetic chemicals that have been used in manufacturing and consumer products since the mid-20th century.
They have appeared in products such as stain-resistant materials, water-resistant fabrics, food packaging, certain industrial processes, and some firefighting foams. Manufacturing sites, airports, military facilities, landfills, and other locations associated with PFAS use can become potential sources of environmental contamination.
PFAS are sometimes called “forever chemicals” because many are highly persistent. They can move through soil and water and may remain in the environment for long periods.
Not every community has the same PFAS exposure risk. Local industrial history, groundwater movement, source water, waste sites, and other regional conditions can all influence whether PFAS are detected in a drinking water supply.
EPA’s current federal drinking water regulations establish Maximum Contaminant Levels of 4.0 parts per trillion for both PFOA and PFOS.
A Maximum Contaminant Level, or MCL, is an enforceable standard that applies to regulated public water systems. EPA finalized its first national PFAS drinking water regulation in April 2024.
The 2024 rule also included limits for PFHxS, PFNA, and HFPO-DA, commonly known as GenX chemicals, along with a Hazard Index approach for certain mixtures containing PFHxS, PFNA, HFPO-DA, and PFBS.
However, EPA’s approach to several of those additional standards is now under reconsideration. That makes it especially important to distinguish the regulations that remain in effect from changes that have only been proposed.
EPA proposed changes to the PFAS drinking water regulations in May 2026, but those proposed changes are not final as of August 2026.
One proposal would maintain the 4.0-ppt limits for PFOA and PFOS while creating a process that could allow qualifying public water systems additional time, potentially until 2031, to meet those enforceable limits.
A separate proposal would rescind the federal drinking water regulations and regulatory determinations for PFHxS, PFNA, HFPO-DA, and the Hazard Index mixture involving those three PFAS and PFBS.
The public comment periods for these proposals closed in July 2026. Until EPA completes the rulemaking process, homeowners should avoid interpreting the proposals as finalized regulatory changes.
Research has associated exposure to certain PFAS with a range of potential health effects, although risks vary depending on the specific chemical, exposure level, duration, and individual factors.
Studies have examined possible associations involving immune function, cholesterol, liver effects, thyroid function, reproductive and developmental effects, cardiovascular concerns, and certain cancers.
This does not mean every person exposed to PFAS will experience a health problem. PFAS include thousands of different compounds, and researchers continue to study their behavior and potential effects.
The purpose of drinking water standards is to reduce exposure through a source people may consume every day. For homeowners, the practical response is to determine whether PFAS have been detected in their water and take appropriate action based on reliable test results.
PFAS can enter drinking water when releases into soil, groundwater, rivers, lakes, or other source waters eventually reach public water supplies or private wells.
Potential sources can include industrial sites, locations where PFAS-containing firefighting foam was used, manufacturing operations, landfills, and areas affected by waste or runoff.
Whether these sources create a drinking water concern depends on local conditions. A home located near a potential PFAS source does not automatically have contaminated water, and PFAS cannot be reliably identified by taste, smell, or appearance.
That is why local monitoring information and laboratory testing are more useful than assumptions based on geography alone.
Homeowners should review available public water testing information or use appropriate laboratory testing to determine whether PFAS are present.
If you receive municipal water, start with your water utility. Public water systems may have PFAS monitoring information available through local reports, utility websites, state agencies, or federal monitoring databases.
Private well owners are responsible for their own water quality. Because PFAS testing involves extremely low concentrations, specialized laboratory analysis is typically more appropriate than relying on a basic home water test.
A test result provides an important starting point because PFAS treatment should not be selected solely because these chemicals are receiving national attention. If PFAS have not been detected, another water quality issue may deserve greater attention.
Reverse osmosis can substantially reduce many PFAS when the system is properly designed, installed, and maintained.
RO works by forcing water through a semipermeable membrane. The membrane separates many dissolved substances from the treated drinking water, making reverse osmosis a commonly considered option for targeted PFAS reduction at a kitchen sink or other point of use.
Performance still varies. Membrane condition, incoming water chemistry, system design, pressure, maintenance, and the particular PFAS compounds present can influence results.
Homeowners should look for independently certified systems with a PFAS reduction claim rather than assuming every reverse osmosis system provides identical protection.
Granular activated carbon can reduce certain PFAS by adsorbing them onto the carbon media as water passes through the treatment system.
Activated carbon has been widely studied for PFAS treatment, but performance depends on factors including carbon type, bed depth, water flow, organic matter, contact time, and which PFAS are present.
Some longer-chain PFAS, including PFOA and PFOS, have historically been easier for granular activated carbon to capture than certain shorter-chain compounds.
This makes system design and maintenance especially important. Once filtration media approaches the end of its useful capacity, performance can decline. Filters should be replaced according to appropriate service schedules rather than being left in place indefinitely.
The best PFAS treatment depends on the contaminants identified, their concentrations, your water chemistry, and whether you need point-of-use or whole-home treatment.
| Technology | Role in PFAS Treatment |
|---|---|
| Reverse Osmosis | Can substantially reduce many PFAS in drinking water. |
| Granular Activated Carbon | Can adsorb certain PFAS when properly sized and maintained. |
| Ion Exchange | Specialized resins can capture many PFAS under appropriate conditions. |
| Sediment Filtration | Not designed as a primary treatment for dissolved PFAS. |
| Water Softener | Designed primarily for hardness and should not be treated as a standard PFAS solution. |
Certification also matters. Home drinking water filters with PFAS reduction claims may be certified under standards such as NSF/ANSI 53 or NSF/ANSI 58, depending on the technology and claim.
Even certification does not eliminate the need for maintenance. Cartridges, carbon media, membranes, and other treatment components have limited service lives.
Homeowners concerned about PFAS should confirm their water quality first, then choose certified treatment based on the results.
This approach keeps the decision focused on your water instead of fear or assumptions. PFAS are an important water quality concern, but treatment should still be targeted to actual conditions.
PFAS concerns can vary significantly by water source and location. Municipal treatment practices, nearby industrial activity, groundwater conditions, historical firefighting foam use, landfills, and private well characteristics can all influence local risk.
Shark Filtration helps homeowners evaluate water treatment options based on their actual water conditions. Depending on testing results, that may include point-of-use reverse osmosis, activated carbon filtration, specialized media, or a broader treatment strategy designed around multiple water quality concerns.
Professional guidance can also help determine whether treating drinking water at a specific faucet is sufficient or whether a larger point-of-entry system should be considered. The goal is not simply to install more filtration. It is to use the right treatment technology in the right place.
PFAS drinking water regulations continue to evolve, but the most useful approach for homeowners remains straightforward: understand your water before choosing treatment.
EPA currently maintains enforceable 4.0-ppt limits for PFOA and PFOS, while significant regulatory changes proposed in 2026 remain under consideration. Homeowners should therefore rely on current regulatory information rather than headlines that may blur the difference between a proposal and a final rule.
If PFAS are detected in your water, technologies such as reverse osmosis, granular activated carbon, and specialized ion exchange can provide meaningful reduction when they are correctly designed and maintained. No filter should be assumed to address PFAS simply because it is marketed as a general water filtration system.
Testing, certification, proper system selection, and ongoing maintenance provide a more reliable path forward. Shark Filtration can help homeowners evaluate those factors and choose treatment based on actual water quality needs.
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