33 regulated contaminants with no certified filter claim

By Andrew Bates, FounderPublished 2026-09-10Updated 2026-09-11

No. Crossing EPA's 94 regulated contaminant entries against NSF's 101 selectable reduction claims leaves 33 with no claim of that name — including haloacetic acids, GenX, uranium and most regulated pesticides. A claim not existing is not the same as nothing treating it.

Every roster page ends the same way. This is the inverse.

Each claim-based page on this site answers “which products hold this claim”. A question none of them asks is whether the claim exists at all.

So: EPA’s regulated contaminant tables, against NSF’s complete list of selectable reduction claims, both read on 2026-09-10.

	Entries
EPA regulated contaminant entries	94
With an NSF reduction claim of that name	61
With no NSF claim of that name	33

Where the gaps are

Group	Gaps
Organic chemicals	19
Microorganisms	4
Inorganic chemicals	4
Disinfection byproducts	3
Radionuclides	3

Three of those deserve attention because they are contaminants people are actively shopping for.

HAA5 — an enforceable limit with nothing to shop for

The five haloacetic acids are one of two regulated byproduct groups, capped at 0.060 mg/L, and they appear on every annual water quality report alongside trihalomethanes.

Trihalomethanes has a claim, held by 153 models. Haloacetic acids has none.

→ Filters certified for trihalomethanes

Three NSF claims sound close and are not the same group. Tribromoacetic acid is not one of the five EPA regulates — those are monochloroacetic, dichloroacetic, trichloroacetic, bromoacetic and dibromoacetic acid. Haloacetonitriles and haloketones are separate compound families.

So a household reading both byproduct figures off its report can shop against one and not the other.

→ Disinfection byproducts: both figures, and what they mean

PFAS — one compound is genuinely uncovered, and it is not the one you expect

EPA’s regulation covers PFOA, PFOS, PFHxS, PFNA and HFPO-DA individually, plus a Hazard Index combining four of them.

NSF offers named claims for PFOA and PFOS only — so on claim names alone, four EPA entries look uncovered.

They are not. NSF defines its Total PFAS claim in the listing footnotes, and the definition names the compounds:

Total PFAS includes perfluoroheptanoic (PFHpA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), perfluorobutanesulfonic acid (PFBS), perfluorodecanoic acid (PFDA)

PFHxS, PFNA and PFBS are in there. So the real gap is a single compound: HFPO-DA, the one EPA calls GenX, which appears in no NSF claim by name and is not among the seven in the bundle.

Two caveats hold. A product must actually hold the Total PFAS claim for the bundle to apply, and 49 models did. And EPA has stated that current certification standards do not yet indicate a filter will reduce PFAS to its limits, so appearing in a definition is not evidence of meeting the regulation.

→ Filters certified for PFAS, and the three separate claims

Organic chemicals — 19 of the 33

The biggest of the five groups, and mostly pesticides and industrial compounds: acrylamide, benzo(a)pyrene, dalapon, dichloromethane, the two di(2-ethylhexyl) compounds, dioxin, diquat, endothall, epichlorohydrin, glyphosate, oxamyl, picloram and vinyl chloride among them.

Several have a partial route. NSF’s VOC reduction claim is a bundle covering a defined list of compounds, so a product holding it may address some of these without any of them being named individually.

→ What a VOC claim covers

What the absence means, and what it does not

This is the part that matters most, and it cuts against the alarming reading.

A missing claim is a missing verification, not a missing technology. EPA maps contaminants to treatment types — distillation, reverse osmosis, ion exchange, adsorptive media — independently of whether NSF offers a claim. Reverse osmosis reaches a great deal of this list.

Distillation is invisible here entirely. NSF offers no selectable reduction claims under NSF/ANSI 62, its distillation standard, so no distiller appears in any claim search — not on this page and not on any roster on this site.

Microorganisms have a separate route. NSF/ANSI 55 certifies ultraviolet systems for Disinfection Performance Class A or B rather than naming organisms, which is why coliforms, viruses, Legionella and heterotrophic plate count show as gaps while a certification path exists.

So read the 33 as “no product can be certified and listed for this by name”, which is a real constraint on a buyer and not a verdict on treatment.

The decision framework

1. Check whether your contaminant has a claim before shopping

If it does, the listing settles it per model.

→ Which claims exist at all, and how populated each is

If it does not, no amount of product comparison will produce a certified answer, and that is worth knowing in the first five minutes rather than after a purchase.

2. Fall back to the technology mapping

EPA names treatment types per contaminant. That is weaker than a certified claim — it describes a category, not a tested model — and it is what remains when no claim exists.

3. Ask the supplier the two questions

Which accredited body certified this, and for which claim. If the answer names a contaminant with no claim, the assertion is not something any listing can support.

→ How to read an NSF listing, footnotes included

4. Treat reverse osmosis as the broad instrument

Under NSF/ANSI 58 only TDS reduction is required and everything else is optional, so an RO system is not automatically certified for anything in particular — but it is the technology EPA maps to the widest range of this list.

The decision path

Your contaminant	Claim exists?	What to do
Lead, cyst, TTHM, nitrate, fluoride	Yes	Search the claim, check the model
Haloacetic acids	No	No certified option; utility-side control
PFOA or PFOS	Yes, by name	60 models each
PFHxS, PFNA, GenX	No claim of that name	Total PFAS claim is the nearest
A regulated pesticide	Usually no	Check whether VOC bundle covers it
Uranium or alpha/beta particles	No	Technology mapping, not certification
Coliforms, viruses, Legionella	No reduction claim	NSF/ANSI 55 disinfection classes

Choose a certified product if

Your contaminant has a claim. That is 61 of 94 EPA entries, including most of what households actually test for.

Choose on technology mapping if

Your contaminant is among the 33. EPA’s treatment-type mapping is the next reference, and reverse osmosis or distillation will often be the answer even though neither can be certified for it by name.

Choose to ask rather than buy if

A product claims one of the 33 by name. No listing can support that, and the question of which body certified it is the right one before paying.

Mistakes that cost the most money

Assuming a claim exists because the contaminant is regulated. A third of EPA’s regulated entries have none.

Reading a missing claim as “nothing removes it”. It means nothing is certified for it by name, which is a different statement.

Accepting a marketing claim for one of the 33. There is no listing to check it against, which is precisely why it can be printed.

Assuming a TTHM claim covers haloacetic acids. Different group, no claim, and the similar-sounding NSF claims are other compound families.

Assuming a total PFAS claim covers the four unnamed PFAS. NSF does not enumerate what it covers, and EPA has said certification does not yet demonstrate reduction to its limits.

Ruling out distillation because it never appears in certified lists. It cannot appear; there are no claims under its standard.

Three situations, and what changes

Your report shows HAA5 above TTHM. The shopping question has no certified answer for HAA5. What remains is the utility-side control — the Operational Evaluation Level and the report that follows it — rather than a product.

You are buying for PFAS after the 2024 rule. PFOA and PFOS are named and searchable. The other four entries are not, so a product addressing them specifically cannot be verified in NSF’s listing today.

A salesperson names a contaminant from the list of 33. Ask which body and which claim. The honest answer will be that no such claim exists, and what happens next tells you what kind of supplier you are dealing with.

The objections worth answering

“This makes certification look useless.” The opposite: 61 of 94 entries have a claim, including nearly everything a household tests for. Knowing which third is uncovered is what makes the other two-thirds worth relying on.

“Reverse osmosis removes almost all of these anyway.” Quite possibly, and EPA’s technology mapping supports that for many. The point is that you cannot verify it per model, which is the whole function of a listing.

“You have only checked NSF.” Correct, and stated. WQA and IAPMO certify to the same NSF/ANSI standards and publish separate listings, and their claim taxonomies were not compared here.

“These figures will move.” They will. NSF dates its listings and asks readers to confirm status at source, and EPA revises its regulations — the 2024 PFAS rule is why four of these gaps exist at all.

Who this is for

Anyone who has looked for a certified filter for a specific contaminant and found nothing, and anyone evaluating a product claim that no listing seems to support.

It names no recommended product and is a map of where verification exists.

What to settle first

Does a claim for my contaminant exist at all?

Sixty-one times out of 94 the answer is yes and the listing takes over. The other 33 times, knowing it early saves the search.

→ Which claims exist at all, and how populated each is → How to read an NSF listing, footnotes included → City water treatment, and the three gaps a utility cannot close → The VOC bundle: broad, printed in full, and it does not reach the gaps → Arsenic: a claim exists, and only for one of the two species → Manganese: health guidance, no federal limit, and no claim to search → Radium and uranium: three of four regulated radionuclides have no claim → EPA names a technology for many of these; certification is a separate question → Unregulated contaminants: the candidate list and the monitoring rule → Microcystin: unregulated, and certified anyway → Radon: a certified claim for a contaminant with no limit → Legionella: regulated, unmeasured, and uncertified → Distillation, which reaches some of these and certifies against none → The inverse case: unregulated contaminants with large certified fields → Coliform and E. coli: regulated, measured, and uncertifiable

The bottom line

Sixty-one of EPA's 94 regulated contaminant entries have an NSF reduction claim you can shop for. Thirty-three do not, and the gaps are not obscure: haloacetic acids carry an enforceable limit and appear on every annual report, and GenX appears in no NSF claim at all. Treat a missing claim as a missing verification rather than a missing technology — reverse osmosis and distillation reach many of these — and ask a supplier which body certified their product and for which claim before believing a label.

Who this is not for

This compares names in two documents. A contaminant with no claim of that name may still be removed by reverse osmosis or distillation — the absence means no product can be certified and listed for it, not that nothing works. NSF offers no selectable claims under NSF/ANSI 62, so distillation cannot appear in any claim search. Microorganisms are certified through disinfection performance classes rather than by contaminant. NSF listings only.

Questions

Is there a certified filter for every regulated contaminant?

No. Crossing EPA's 94 regulated contaminant entries against NSF's 101 selectable reduction claims on 2026-09-10 leaves 33 with no claim of that name, across organic chemicals, microorganisms, inorganic chemicals, disinfection byproducts and radionuclides.

Why is there no filter certified for haloacetic acids?

NSF offers no reduction claim of that name. The nearest-sounding claims are not the same group: tribromoacetic acid is not one of the five haloacetic acids EPA regulates, and haloacetonitriles and haloketones are separate compound families.

Are all the PFAS EPA regulates covered by certification?

Almost. NSF names PFOA and PFOS as claims, and its Total PFAS claim definition additionally names PFHxS, PFNA and PFBS. HFPO-DA, the compound EPA calls GenX, appears in no NSF claim by name and is not in the bundle, making it the one regulated PFAS with no coverage.

Does no claim mean no filter will remove it?

No. It means no product can be certified and listed for that contaminant by name. Reverse osmosis and distillation remove many of these, and EPA maps several to those technologies; what is missing is the verification, not the treatment.

Why do distillers never appear in certified filter lists?

Because NSF offers no selectable reduction claims under NSF/ANSI 62, its distillation standard, while it does offer them under standards 42, 44, 53, 55, 58, 177 and 401. Any list built by searching claims therefore cannot return a distillation system, whatever that system removes.

How are bacteria and viruses certified then?

Through a different route. NSF/ANSI 55 certifies ultraviolet systems for Disinfection Performance Class A or Class B rather than naming organisms, so coliforms, viruses and Legionella have no reduction claim while a certification path still exists.

What should I do if my contaminant has no claim?

Ask the supplier which accredited body certified their product and for which claim, and treat any unlisted assertion as unverified. EPA's technology mapping is the other reference point, since it names treatment types rather than certified products.

Which group has the most gaps?

Organic chemicals, with 19 of the 33. They include most regulated pesticides and industrial compounds — glyphosate, diquat, endothall, dioxin, vinyl chloride and epichlorohydrin among them. Microorganisms and inorganic chemicals follow with four each.

Sources — 15 claims

Crosswalk of EPA National Primary Drinking Water Regulations against the NSF reduction-claim taxonomy (both captured 2026-09-10)
Crossing EPA 94 regulated contaminant entries against NSF 101 selectable reduction claims on 2026-09-10 leaves 33 regulated contaminants with no NSF reduction claim of that name: 19 organic chemicals, 4 microorganisms, 4 inorganic chemicals, 3 disinfection byproducts and 3 radionuclides. (captured 2026-09-10)
Limits: The absence of a claim by name is not evidence that no product treats the contaminant. Reverse osmosis and distillation remove many of these; NSF offers no named claim to certify them against. NSF offers no claims at all under its distillation standard, so distillation is invisible to this crosswalk, and microorganisms are certified through NSF/ANSI 55 disinfection performance classes rather than by contaminant.
Crosswalk of EPA National Primary Drinking Water Regulations against the NSF reduction-claim taxonomy (both captured 2026-09-10)
EPA regulates PFOA, PFOS, PFHxS, PFNA and HFPO-DA individually plus a Hazard Index, while NSF offers named reduction claims for PFOA and PFOS only. Three of the remaining EPA compounds — PFHxS, PFNA and PFBS — are named inside NSF Total PFAS bundle claim, leaving HFPO-DA, which EPA calls GenX, as the only regulated PFAS absent from NSF claims entirely. (captured 2026-09-10)
Limits: Coverage by name, not by performance. EPA has stated that current certification standards do not yet indicate a filter will reduce PFAS to its limits, so appearing in a bundle definition is not evidence a product meets the regulation. This claim was first written before the Total PFAS bundle definition was located in NSF listing footnotes, and originally said four EPA compounds had no claim of that name; that was true on its stated basis and misleading, and it has been corrected.
Crosswalk of EPA National Primary Drinking Water Regulations against the NSF reduction-claim taxonomy (both captured 2026-09-10)
The five haloacetic acids EPA regulates as HAA5 have no NSF reduction claim of that name, and the nearest-sounding NSF claims are not that group: tribromoacetic acid is not one of the five, and haloacetonitriles and haloketones are separate compound families. (captured 2026-09-10)
Limits: A statement about claim names, not about performance. A product reducing trihalomethanes may well reduce haloacetic acids; there is no claim under which that could be certified and listed.
NSF Official Listings — Drinking Water Treatment Units, NSF/ANSI 53 Total PFAS reduction claim listing footnotes (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF defines its Total PFAS reduction claim in the listing footnotes as including seven compounds: perfluoroheptanoic acid (PFHpA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorobutanesulfonic acid (PFBS) and perfluorodecanoic acid (PFDA). (captured 2026-09-10)
Limits: A list of compounds the claim covers, not a reduction level or a treated concentration. HFPO-DA, the compound EPA calls GenX, is not among the seven. EPA has separately stated that current certification standards do not yet indicate a filter will reduce PFAS to its limits.
NSF Official Listings — Drinking Water Treatment Units, NSF/ANSI 53 Total PFAS reduction claim listing footnotes (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
Of the PFAS compounds EPA regulates, PFOA and PFOS have named NSF claims, and PFHxS, PFNA and PFBS appear inside the Total PFAS bundle; HFPO-DA, which EPA calls GenX, appears in no NSF claim by name or within the bundle. (captured 2026-09-10)
Limits: Coverage by name in a claim definition, not evidence of performance against EPA limits. A product must still hold the Total PFAS claim for the bundle to apply to it, and 49 models held it on the capture date.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim search form (captured 2026-09-10)
NSF lists NSF/ANSI 62 as Drinking Water Distillation Systems but offers no selectable reduction claims under it in its listing search, which offers claims only under standards 42, 44, 53, 55, 58, 177 and 401. (captured 2026-09-10)
Limits: A property of how NSF indexes claims, not of distillation. Any roster built by searching reduction claims therefore cannot surface a distillation system, so the absence of distillers from such a roster is an artefact of the method and says nothing about what a distiller removes.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim search (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF offers seven selectable reduction claims under NSF/ANSI 42: bacteriostatic effects, chloramine reduction, chlorine reduction, Filter First, nominal particulate reduction, taste and odor reduction, and zinc reduction. (captured 2026-09-10)
Limits: The claims selectable in NSF’s own search on the capture date. It bounds what a product certified to NSF/ANSI 42 alone can be claiming, and says nothing about how well any product performs a claim it does hold.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim search (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF/ANSI 53 lists PFOA reduction, PFOS reduction and total PFAS reduction as three separate selectable claims. (captured 2026-09-10)
Limits: Three separate claims, so a product certified for PFOA is not thereby certified for PFOS or for total PFAS. It does not state what total PFAS covers or to what level.
NSF — NSF/ANSI 58: Reverse Osmosis Drinking Water Treatment Systems (page dated 2025-12-18)
Under NSF/ANSI 58, TDS reduction is the only required claim. Every other claim, including arsenic, nitrate/nitrite, lead and cyst reduction, is optional. (captured 2026-09-10)
Limits: This is the sharpest form of "claims vary by product": a system certified to NSF/ANSI 58 is verified for TDS reduction and nothing else unless the individual claim is listed for that model.
NSF — NSF/ANSI 42, 53 and 401: Filtration Systems Standards (page dated 2025-12-16)
Under NSF/ANSI 42 and NSF/ANSI 53, certification claims vary by product; certification to the standard does not mean a product carries every claim available under it. (captured 2026-09-09)
Limits: NSF does not print 'claims vary by product' under NSF/ANSI 401. See certification-nsf-0008 for the 401 position, which rests on weaker source language.
EPA Office of Research and Development — Identifying Drinking Water Filters Certified to Reduce PFAS
EPA states that as of April 2024 the current certification standards for PFAS filters do not yet indicate that a filter will remove PFAS down to the levels EPA has set as a drinking water standard. (captured 2026-09-10)
Limits: This does not say certified filters fail. It says certification was written against older reduction targets, so a PFAS-certified filter is not evidence of reaching 4.0 ppt. EPA says it is working with standards bodies to update them, so the position may change.
NSF Official Listings — Drinking Water Treatment Units (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF Official Listings mark some entries "Conforms to the material requirements only", meaning the product appears under a standard without any contaminant reduction performance claim having been certified. (captured 2026-09-10)
Limits: The footnote states what was evaluated, not what the product does. It does not say the product performs badly, only that performance was not the basis of this listing. A separate listing for the same model can carry performance claims.
EPA — National Primary Drinking Water Regulations
EPA sets a Maximum Contaminant Level of 0.080 mg/L for total trihalomethanes and 0.060 mg/L for the five haloacetic acids, both byproducts of drinking water disinfection. (captured 2026-09-10)
Limits: These are enforceable health-based limits for public water systems, measured as system-wide running averages rather than at an individual tap.
EPA — Comprehensive Disinfectants and Disinfection Byproducts Rules (Stage 1 and Stage 2): Quick Reference Guide, EPA 816-F-10-080, August 2010
EPA lists the total trihalomethanes group as chloroform, bromodichloromethane, dibromochloromethane and bromoform, and the five haloacetic acids as monochloroacetic, dichloroacetic, trichloroacetic, bromoacetic and dibromoacetic acid. (captured 2026-09-10)
Limits: Composition only. The per-compound MCLG column of EPA’s Table 2 did not survive text extraction from the PDF and is deliberately not recorded here; the enforceable limits are the group totals in contaminant-epadis-0002.
EPA Office of Water — Home Water Treatment Facts / Filtration Facts (published November 2005)
EPA maps contaminants to home treatment technologies: Giardia and Cryptosporidium to distillation, reverse osmosis, absolute one micron filters, ultraviolet light and cyst-certified filters; bacteria and viruses to distillation, reverse osmosis, ultraviolet light and disinfection; arsenic to adsorptive media; lead to distillation, reverse osmosis and some carbon filters; nitrates to distillation, reverse osmosis or ion exchange; and radon to activated carbon and aeration. (captured 2026-09-10)
Limits: Technology classes, not product endorsements, from a 2005 EPA sheet. "Some carbon filters" for lead is EPA’s own hedge and should be read as requiring a certified lead claim on the specific model.