Is Cary, NC Tap Water Contaminated, According to EWG?

Triangle Waterworks · informational guide

Direct answer: No — "contaminated" overstates it. EWG's Tap Water Database flags 13 substances in Cary's water above its own stricter, non-regulatory health guidelines, which is real data, not an error. But Cary's 2025 Consumer Confidence Report shows the same water fully compliant with every legal EPA limit. Both are true because EWG and EPA measure against two different bars — and a carbon filtration stage addresses what's detectable either way.

If you've pulled up Cary on EWG's Tap Water Database, you've likely seen contaminants listed at what looks like an alarming multiple of a guideline — hundreds of times over, in some cases. That number is accurate as far as it goes. What it doesn't tell you on its own is that EWG's guidelines were built to be far stricter than the legal standard EPA enforces, so a large multiple over an EWG guideline is a completely different statement than a violation of a legal limit. Here's how to read both numbers correctly.

What Does EWG's Tap Water Database Actually Say About Cary's Water?

EWG's compiled dataset for Cary shows HAA9 (a nine-compound haloacetic acid sum) at 27.5 ppb, TTHM at 38.2 ppb, PFOA at 2.86 ppt, and PFOS at 3.79 ppt, with 13 contaminants total listed above EWG's health guidelines. Those figures are real and worth taking seriously — they're just not the same kind of number as a legal violation.

EWG's guidelines are set at a level the organization considers protective against the most sensitive possible health outcome, often with a wide margin below where EPA sets its own enforceable limit. That's a deliberate design choice on EWG's part, not a flaw in the data — it's simply a stricter bar than the one utilities are legally required to meet.

Is an EWG Guideline the Same Thing as an EPA Legal Limit?

No, and this is the single most important distinction in reading a Cary EWG entry correctly. An EPA Maximum Contaminant Level (MCL) is an enforceable legal ceiling — a utility that exceeds it is in violation and has to act. An EWG guideline is a voluntary, non-regulatory health benchmark EWG sets independently, often well below the MCL, reflecting the level EWG considers ideal rather than the level the law requires.

A contaminant can sit comfortably under its EPA limit and still land far above its EWG guideline at the same time, because the two numbers were never meant to describe the same thing. "Above the EWG guideline" and "fully compliant with EPA" can both be accurate statements about the identical glass of water.

What Does Cary's Own 2025 Water Quality Report Show?

Cary's 2025 Consumer Confidence Report — the town's own annual compliance document — reports TTHM at 37 ppb, ranging 17 to 43, against an EPA limit of 80 ppb. It reports HAA5 (the five-compound haloacetic acid sum that actually carries an EPA limit) at 17 ppb, ranging 9 to 17, against a limit of 60 ppb. PFOA averaged 1.3 ppt in Cary's 2025 testing. Every one of those figures is compliant, with no MCL violation reported.

Cary's CCR is available directly from the town at carync.gov/waterreport.

Why Do the EWG Numbers and Cary's 2025 Report Look Different?

Two honest reasons, and neither one means either source got it wrong. First, EWG's dataset is older than Cary's current 2025 CCR — the two documents reflect different testing years, so some drift between them is expected the same way any two readings taken years apart would differ. Second, EWG and Cary aren't always measuring the identical compound set the same way, particularly on haloacetic acids, which brings us to the next point.

Is HAA9 the Same Thing as HAA5, and Is It Federally Regulated?

No, and this distinction matters more than it looks. HAA5 is the five-compound sum EPA actually regulates, with a 60 ppb Maximum Contaminant Level. HAA9 is EWG's own broader nine-compound sum, used because EWG considers it a more complete health picture — but it carries no EPA limit of its own. There is no legal ceiling for HAA9 to be "compliant" or "non-compliant" against, because none exists.

That means a HAA9 figure like Cary's 27.5 ppb is a genuine, useful data point — it should never be described as "compliant with EPA limits," because EPA never set a limit for that specific nine-compound measurement. Cary's own regulated figure is HAA5, reported separately at 17 ppb, well under its 60 ppb limit.

What Health Effects Is the EPA Actually Regulating Against?

EPA's National Primary Drinking Water Regulations table lists the potential health effects for long-term exposure above the legal limit. For TTHMs: "Liver, kidney or central nervous system problems; increased risk of cancer." For HAA5: "Increased risk of cancer."

Those effects describe long-term exposure above the MCL, not a description of Cary's current, compliant water. "Legally compliant" is a ceiling EPA set at its own risk tolerance — a level the agency judged acceptable, not a guarantee that zero risk exists below it. These are the exact compounds and exact effects EPA had in mind when it drew that line, which is a stronger reason to filter them out at the tap than to treat compliance alone as the end of the conversation.

So Is Cary Water Actually Safe to Drink?

By EPA's legal standard, yes — Cary's 2025 CCR shows full compliance with no MCL violations. By EWG's stricter, non-regulatory benchmark, 13 measured substances sit above what EWG considers ideal. Neither statement contradicts the other, and neither source is wrong; they're answering different questions with different rulers. See the fuller breakdown of what's actually in Cary's water for the full contaminant picture beyond DBPs and PFAS.

What Actually Removes These Contaminants From Cary Tap Water?

Activated carbon handles the disinfection byproducts driving most of the EWG numbers — TTHM and the haloacetic acid family, both listed and unlisted compounds included. Trihalomethanes form as a byproduct of disinfecting your water, and haloacetic acids form the same way — carbon filtration removes both classes rather than relying on staying under whichever limit applies. PFAS specifically needs carbon certified to NSF/ANSI 53 or P473, or reverse osmosis certified to NSF/ANSI 58 — a standard carbon block isn't automatically rated for it.

That's the case for a whole-home system that pairs softening resin for Cary's hardness with a certified carbon stage for everything else, rather than treating "compliant" as the finish line. See what Cary's water actually needs from a softener and carbon system together, and read the full Triangle-wide explainer on TTHM and HAA5 disinfection byproducts for how the two compound classes form and what removes them.

Frequently Asked Questions

I looked up my address on EWG and saw a contaminant listed at hundreds of times the guideline — should I panic? No, but it's worth understanding what that multiple actually means. EWG sets its guidelines far below the legal EPA limit on purpose, so a large multiple over an EWG number is a statement about a strict voluntary benchmark, not proof of a legal violation — Cary's own 2025 report shows the same compounds compliant with every enforceable limit.

I'm about to move to Cary and the EWG rating worried me — is the water actually unsafe? Cary's 2025 Consumer Confidence Report shows full compliance with EPA's legal limits, with no violations reported. The EWG numbers you saw reflect a stricter, non-regulatory benchmark from an older dataset — both are accurate, they're just measuring against different bars, and either way a carbon-equipped system addresses what's detectable.

Why does EWG show HAA9 instead of the regulated HAA5 number? EWG uses a broader nine-compound sum because it considers that a more complete health picture, but no EPA limit exists for that specific nine-compound measurement. Cary's regulated figure is HAA5, reported separately at 17 ppb against a 60 ppb limit.

Does this mean EWG got the numbers wrong? No — EWG's figures are a legitimate, verified dataset; they're simply older than Cary's current 2025 report and measured against EWG's own stricter benchmark rather than EPA's legal one. Neither source contradicts the other once you know which bar each one is using.

If Cary is legally compliant, why would I still need to filter my water? Because "compliant" describes a legal ceiling, not a promise of zero detectable substances — TTHM, haloacetic acids, and trace PFAS are all still measurably present in compliant water. A carbon-equipped system removes them rather than relying on staying under whichever limit applies.

What's the fastest way to know what's actually in my specific tap, not just the town average? A free water analysis at your address, since both EWG's database and Cary's CCR report system-wide figures rather than a reading from your exact home. That test is what a properly sized all-in-one softening-and-carbon system gets built around.

See What's in Your Own Cary Tap

EWG's database and Cary's CCR both describe the system average — a free water analysis tells you what's actually coming out of your specific faucet. Take the 60-second water quiz to see what a Cary home typically needs, or book a free water analysis to get a number tied to your own address.

Sources

• EWG Tap Water Database — Cary, NC
• Town of Cary — 2025 Water Quality Report
• EPA — National Primary Drinking Water Regulations