McLean Tap Water and PFAS: What the 2029 Limit Means

7.4 parts per trillion. That is how much PFOA the EPA's latest monitoring found in the water that reaches McLean, and it is the number most worth understanding in this year's data.

McLean's tap water meets every federal legal limit that applies to it today, and the EPA has no violations on file for its supplier. But in 2024 the EPA set a new limit for PFOA and PFOS, and that limit becomes enforceable in 2029. This explainer covers where McLean stands against it, what it means for a household now, and how the rest of the report looks.

The two PFAS readings that stand out

McLean is served by Fairfax Water, listed on the EPA's record as the Fairfax County Water Authority. It serves about 1,121,613 people across Fairfax County, Fairfax City and Falls Church City through 281,686 connections, drawing from the Potomac River and the Occoquan Reservoir.

The EPA's most recent PFAS monitoring round (UCMR5, 2023 to 2025) found 8 PFAS compounds in this supply. Two of them matter most:

PFAS	Found	EWG standard	Over by
PFOA	7.4 ppt	0.09 ppt	82×
PFOS	5.7 ppt	0.3 ppt	19×

EWG links PFOA to harm to the immune system, harm to fetal growth and child development, and increased cholesterol. It links PFOS to cardiovascular harm and harm to fetal growth.

The other compounds in the report were below EWG's standards and have no federal limit: PFPeA (21.5 ppt), PFBA (17.6 ppt), PFHxA (17.1 ppt), PFBS (8.1 ppt) and PFHpA (5.6 ppt).

What the EPA's 2024 rule actually says

The federal limit for PFOA and PFOS is 4 ppt each. The EPA set it in 2024, and it becomes enforceable in 2029.

Two details keep this in perspective:

• It is not enforceable yet. Until 2029, these readings cannot be a violation of that limit.
• Compliance is judged on a running annual average, not on a single sample. One reading above 4 ppt is not, on its own, how the rule measures a system.

Still, both single readings sit above the line the EPA itself drew. That is a different situation from most contaminants on a typical report, where the only gap is between a legal limit and EWG's stricter guideline. Here, the federal number and the measured number are close enough to compare directly.

What this means for a McLean household

Practically, nothing about your water changed overnight. It is the same water it was last year, and it is legal to drink.

What changed is the yardstick. Fairfax Water's treatment includes coagulation, flocculation, rapid sand filtration, powdered activated carbon, chloramine disinfection and fluoridation. That process makes water safe to distribute, but it is not designed to remove PFAS. So how the system's annual average compares with 4 ppt by 2029 is the utility's question to answer.

For you, the more useful question is personal. Some households would rather act before the 2029 deadline, and others are comfortable with legal compliance. Both are reasonable positions, and the numbers above are what you need to choose.

The rest of the report, briefly

PFAS is the headline, but EWG's analysis of Fairfax Water data flags a few other items above its health guidelines. All are within federal legal limits.

• Disinfection byproducts. Total trihalomethanes were reported at up to 75.9 ppb and haloacetic acids (HAA5) at up to 54.1 ppb. EWG lists each at 300 times its guideline (0.15 ppb and 0.1 ppb). These are the highest readings, not typical ones, and they form when the disinfectant reacts with natural organic matter, continuing in the pipes after treatment. EWG links TTHMs to cancer and fetal development effects, and HAA5 to cancer.
• Chromium-6. An average of 0.10 ppb of chromium-6, 5 times EWG's 0.02 ppb guideline. EWG links it to stomach cancer.
• Lead. The 90th percentile lead result is 1.2 ppb, well under the EPA action level of 10 ppb (lowered from 15 ppb, in force November 2027) and 6 times EWG's 0.2 ppb standard. The system uses chloramines, which are more corrosive to old plumbing, so an older McLean home's tap can differ from that figure.

Why the two kinds of numbers differ: EPA limits weigh treatment cost and feasibility, while EWG's standards are, in its words, "based only on protecting health and does not consider technical feasibility or the cost of water treatment." This article uses EWG's February 2025 standards.

Your options now, and in 2029

Now. Start with data from your own faucet. A free water test from Sanavia is mailed anywhere in the U.S., or done in person in Northern Virginia. If you decide to filter, carbon pitchers mainly help with taste and odor, and what they do for PFAS varies by product, so read the manufacturer's test data. Under-sink reverse osmosis is a common way to reduce dissolved contaminants at the tap.

Our Sanavia Hydra is a tankless under-sink reverse osmosis system. In independent accredited lab testing of an Arlington, VA home's tap water, total trihalomethanes fell from 58 ppb to 2.79 ppb after the Hydra, a 95% reduction. See the lab report. That was one home's water, so treat it as a reference point.

Between now and 2029. Watch for Fairfax Water's annual reports and how its PFOA and PFOS averages compare with 4 ppt.

In 2029. The limit becomes enforceable, and the system will be judged on its running annual average.

For every compound in one place, read the full McLean, VA water quality report.