Radon and PFAS: only 13 labs on official state lists are certified to test water for radon

Bacteria is the test nearly every list certifies: 35 of the 45 lists name it outright, and 42 of the 45 do so at least at the group level. Radon in water is the opposite. We counted, contaminant by contaminant, how many labs the official state drinking-water certification lists actually certify. Of the 2,294 distinct labs on the 45 state and territory lists on this site, 1,882 are certified for bacteria. Only 13 are certified for radon in water.

The numbers: radon and PFAS against the everyday tests

EPA's private-well page is blunt about who is in charge: "Private well owners are responsible for delivering safe drinking water to their households." A well owner who wants a result they can rely on is usually pointed to a state-certified lab. The question is which tests those labs are certified for. Here is the count for seven tests, nationally, at the strictest level: the state list names the analyte or the method.

A lab counts once nationally, however many state lists name it. "Group" means the list certifies a broader category that may include the test, such as an inorganic-chemistry or radiochemistry group, without naming it. For PFAS the gap to bacteria is smaller but still wide: about 14.6 bacteria-certified labs for every PFAS-certified lab.

Why so few labs are certified for radon in water

Drinking-water lab certification was built around compliance testing under federal rules. EPA's own description: "Certified laboratories use approved methods to analyze drinking water compliance samples from public water systems (PWSs)." To hold a certification, labs must "successfully analyze proficiency testing (PT) samples at least annually for each method and analyte for which they desire certification." So certification is granted test by test, and the program centers on the tests public water systems are required to run.

Radon in drinking water has never had that requirement. EPA proposed a radon rule in 1999: "The proposed MCL is 300 picoCuries per liter (pCi/L) and the proposed AMCL is 4,000 pCi/L," and it would have covered "all community water systems (CWSs) that use ground water or mixed ground and surface water." EPA's current page for that rulemaking (RIN 2040-AA94, last updated June 9, 2026) still says: "Publication Date for Final Rule: A Final Rule has not published yet." With no final federal standard, public water systems have no federal radon compliance samples to send, and so no federal radon test for a state program to certify labs against. That is the most likely reason so many state lists name no radon-in-water certification: only 11 of the 45 lists certify any lab for it by name.

It is also why "not on the list" is not the same as "no lab can test it." Vermont's list certifies no lab for radon in water at the level we count, yet the Vermont Department of Health says you can "order a radon in water test kit for $25 from the Health Department Laboratory, or use another certified drinking water lab to test for radon." Wisconsin's list on this site is its bacteria list only, and the Wisconsin DNR tells owners that "Test kits for radon in water can be found by visiting Wisconsin Radon Information Centers or the Wisconsin State Laboratory of Hygiene." Labs can and do run the test. Vermont's list has no radon line to record it on, and the Wisconsin list we use covers bacteria only.

Radon is a gas, which adds a second constraint. EPA gives its half-life as 3.8 days. A radon sample is a race against decay, so the lab's collection and shipping instructions matter more than for a metal or nitrate sample. Our guide to collecting a well water sample sets out how state labs want radon vials filled and how fast they must arrive.

Radon in water, state by state

These are the 11 state lists that certify at least one lab for radon in water, with the number of those labs located in the state:

Most of these lists certify the same small pool of out-of-state labs, which is how 11 lists can share only 13 labs between them. Across the 42 lists we compare, 39 (93%) have no in-state lab certified for radon in water. Among the 33 lists with per-lab chemistry detail it is 30 (91%), or 29 (88%) if group certifications count: Connecticut's list certifies some in-state labs for a group that may include radon.

PFAS: a federal rule, but uneven in-state certification

PFAS are in a different position from radon. EPA did finalize a rule. Its PFAS page (last updated May 18, 2026) says "EPA established legally enforceable levels, called Maximum Contaminant Levels (MCLs), for six PFAS in drinking water," with PFOA and PFOS at 4.0 parts per trillion. Under the final rule, public water systems "have three years to complete initial monitoring (by 2027)" and "five years (by 2029) to implement solutions." That rule is now partly in question. On May 18, 2026, EPA proposed two rules: one "upholds the NPDWR for PFOA and PFOS" while giving systems an option to "request two additional years - to 2031" to comply, and another would "rescind drinking water regulations for PFHxS, PFNA, HFPO-DA (commonly known as GenX), and the Hazard Index mixture of these three PFAS plus PFBS." EPA's pages for the rescission proposal and the compliance extension proposal (both last updated October 8, 2026) each say the comment period "closed on July 20, 2026." As of November 4, 2026, both are proposals, not final rules, and the 2024 limits are the ones on EPA's page. None of these limits applies to private wells; EPA's private-well PFAS page says "the EPA does not regulate or provide recommended standards for private wells."

Because the rule exists, PFAS methods do appear on many lists: 34 lists certify at least one lab for PFAS, and 129 distinct labs hold a PFAS certification somewhere. But a list can certify plenty of labs and still have none in the state. Virginia's list certifies 20 labs for PFAS, 0 of them located in Virginia.

Among the 33 lists with per-lab chemistry detail, 13 (39%) certify no in-state lab for PFAS. Counting group certifications, it is 11 (33%): New Mexico and Idaho each have in-state labs certified at the group level only. Across all 42 compared lists, including those with little chemistry detail, the figure is 20 (48%), but that larger number partly reflects lists that do not say which chemistry tests each lab holds.

Where the first column is above zero, the state's own list certifies out-of-state PFAS labs, and a mail-in sample is the expected route. Where it is zero, the list as we have it names no PFAS certification at the level we count; ask the state drinking-water or lab-certification program which labs it accepts for PFAS. New York's and Kentucky's lists on this site are PFAS-only lists, so they appear in the chart but not in the state-share figures.

The tests in between: uranium, VOCs, asbestos and nitrate

Radon and PFAS are the extremes, but they are not the only tests where many states have no in-state certified lab. This chart counts, for each test, the detailed lists with no in-state lab certified for it:

Because the share depends on which lists you count, here is every version side by side. The first two columns use all 42 compared lists, the last two only the 33 with per-lab chemistry detail.

The group column matters most for the common tests. Some lists record bacteria or nitrate only inside a broader group. For bacteria, Missouri's and New Mexico's lists certify their in-state labs at the group level, so the detailed-list count drops to 0 once groups count. For nitrate, Connecticut, Tennessee and Vermont certify it only as part of an inorganic-chemistry group on the lists we use, so their certified-level nitrate count is zero (Connecticut 0, Tennessee 0, Vermont 0) although their lists do include labs at the group level. For nitrate comparisons, use the group column. Vermont's group-level nitrate labs are all outside Vermont, so Vermont stays in the group-level count of 4 lists, with Hawaii, New Mexico and South Dakota.

Uranium shows the same pattern on a smaller scale: 11 of the detailed lists (33%) have no in-state lab certified for it. Where three or more labs on a state's list carry the test at any certification level, including group, we publish a state page for it, such as uranium testing in California or Colorado. Background is on our uranium in well water page.

What a well owner can do

A missing in-state lab is a logistics problem, not a dead end. Your state's own list often certifies labs in other states for exactly these tests, which means it expects samples to travel. Radon is the time-sensitive one because it decays, so the shipping plan matters more than the distance.

1. Start with your state's own list. Your state page shows every lab on the official list, including out-of-state labs it certifies. The finder filters by test: radon, PFAS, or any test.
2. Ask your state program. EPA's private-well PFAS page suggests you contact your state environmental or health agency "to obtain a list of state-certified laboratories using EPA-developed testing methods in drinking water." The same call works for radon: some state labs test radon in water even though the list we use has no radon line, as Vermont's and Wisconsin's pages show.
3. Use a certified lab in another state by mail. Ask the lab for its kit and instructions before you collect. Ask which state certifies it for the test and whether it accepts samples from homeowners.
4. Collect and ship exactly as the lab says. Ask how quickly a radon sample must reach the lab and follow its filling instructions to the letter; PFAS and the other tests each come with their own container and instructions. See how to collect a well water sample.
5. Read the result in context. Our radon in well water and PFAS in well water pages explain the numbers and the state guidelines. If radon is high, radon in water mitigation covers the treatment options and the retest.

Labs on state lists certified for radon in water that a state marks as taking outside samples. Of the 13 radon-certified labs, 9 carry a mark on at least one state list saying they accept samples from outside customers. The mark does not always come from the state that certifies the lab for radon, and the marks mean different things (see the last column). This is a listing from official data, not a recommendation, and none of these marks guarantees a lab will take a household sample: call first.

What the marks say, in each state's words: Oregon's accreditation search marks labs "accepting public samples," which the Oregon Health Authority explains as labs that "can accept samples from anyone." Vermont highlights labs that accept private samples, and MassDEP's list asks "Offers services to residential customers?" Oklahoma's DEQ points to a "Commercial Sample" column "to view laboratories accepting private samples." Washington's label is "Accepts Commercial/Public Samples," Colorado's is "Accepts Outside Samples," and Louisiana's and California's refer to commercial samples, which is broader than homeowner. Each lab page lists the marks and their sources.

Method

Labs. We used every lab on the 45 official state and territory drinking-water lab lists on this site (data version 2026-11-03). One lab is one WaterListed lab page: where a list has several rows for the same business, they count once. That gives 2,294 distinct labs.

Certification levels. A lab is certified for a test when the state list names the analyte or method (for example Radon-222). It is certified at the group level when the list certifies a broader group that may include the test, some or all of it. Entries marked partial or subcontracted count in neither total. All headline figures use the certified level; the group versions are given alongside.

Per state. A state's count uses only that state's own rows: what its list says. A lab is in-state when its address on the list is in that state. A lab on Michigan's list located in Indiana counts for Michigan's total, not its in-state count.

Nationally. A lab counts once if any state list certifies it for the test.

Two denominators. State shares come in two versions. The wider one uses the 42 lists left after dropping New York, Kentucky and Alaska, whose lists on this site are partial (New York's covers only labs in its PFAS rebate program, Kentucky's only PFAS-certified labs, Alaska's only microbiology). The narrower one, marked "detailed," also drops lists that carry little per-lab chemistry detail: Wisconsin (bacteria list only), Minnesota (bacteria, nitrate, arsenic, lead and manganese only), Maine (marks only PFAS and bacteria), Massachusetts (broad categories only), Georgia and Alabama (chemistry lists do not say which tests each lab holds; PFAS has its own list), Montana (categories only), Puerto Rico (groups mapped only for bacteria) and Mississippi (bare categories). That leaves 33 lists. A zero on a low-detail list means "not stated," not "none," so the detailed figure is the fairer one for chemistry.

Radon labs taking outside samples. Labs with a certified Radon-222 entry on any state list and a homeowner or outside-sample mark on any state list, not necessarily the same one.

Limits

• "Not on a list" does not mean "no lab can run it." These are counts of certifications printed on official lists. Many states do not certify radon in water at all, most likely because EPA has no final radon drinking-water standard. Vermont's and Wisconsin's state-run testing shows that labs run the test anyway. A zero is about the list, not about what labs can do.
• Lists differ in scope and detail. Some lists record only some tests or only categories (see the two denominators above). Every share is therefore given for both 42 and 33 lists. Quote the one that fits, and say which.
• Group certifications hide some tests. Connecticut, Tennessee and Vermont record nitrate only inside an inorganic group, so their certified-level nitrate count is zero. Use the group figures for nitrate and bacteria.
• In-state is about the address, not distance. A lab just over a state line may be closer than one in the same state. Out-of-state labs on your own state's list are certified by your state.
• Certified does not mean it takes your sample. Many certified labs serve utilities. Where a state publishes a homeowner or outside-sample mark, we show it, and those marks mean different things in different states.
• Lists have different dates. Each state page shows the version of its list we use; for example, Pennsylvania's list on this site comes from reports printed in June 2024. Certifications change.
• Only the lists on this site are counted. States without a list here (for example New Jersey) are not in the figures, so the national counts are counts of labs on these 45 lists, not of every lab in the country.

For how close the nearest certified lab is to where well users live, see our companion study on well water testing deserts.

Getting the data

Behind this page are three tables:

• By state: for each of the 45 lists, labs certified and certified-or-group, in total and in-state, for all seven tests, plus partial and subcontracted counts and the low-detail flag.
• National: distinct labs per test.
• Radon labs taking outside samples: names, cities, the states that certify and mark each lab, the wording of each mark and the WaterListed page. No phone numbers.

We do not publish them as downloads. Journalists and researchers can request the data here: say who you are, where the work will appear and which data you need, and we will reply.

Questions people ask