What’s Actually In Your Tap Water? Over 300 Contaminants — And Most Filters Miss Them

Your tap water has been tested. And the results are not what most people expect. The Environmental Working Group — a US-based research organisation that analyses water quality data from utilities across the country — has detected over 300 contaminants in US tap water. Not three. Not thirty. Over three hundred.

According to Simply Younger’s review of the EWG data and peer-reviewed water quality research, most people assume their tap water is essentially clean. The full picture is considerably more complex — and considerably more relevant to how you feel on a daily basis.

PFAS: The Forever Chemicals

PFAS — per- and polyfluoroalkyl substances — are synthetic chemicals used in manufacturing since the 1940s, found in non-stick cookware, food packaging, waterproof clothing, and firefighting foam. They’re called forever chemicals because they don’t break down — not in the environment, not in your body. PFAS enter water supplies through industrial discharge and the use of firefighting foam at military bases and airports. Research has linked PFAS exposure to immune system disruption, thyroid disease, certain cancers, and hormonal interference. The EPA set enforceable limits for several PFAS compounds in 2024, but many variants remain unregulated.

Microplastics

Microplastics have been detected in tap water supplies globally. A 2018 study found microplastics in 83% of samples, with the United States recording some of the highest concentrations. Beyond their physical presence, microplastic particles act as vectors for other chemical contaminants — including endocrine disruptors and heavy metals — concentrating them and carrying them into the body. The presence of microplastics in human blood, lung tissue, and breast milk has been confirmed by peer-reviewed studies.

Chlorine Byproducts

When chlorine reacts with naturally occurring organic matter in water and ageing pipe infrastructure, it forms disinfection byproducts (DBPs) — primarily trihalomethanes (THMs) and haloacetic acids (HAAs). These are regulated at levels that reflect technical achievability rather than confirmed safety. Long-term exposure at elevated DBP levels has been associated with increased bladder cancer risk and adverse pregnancy outcomes in epidemiological research. The chlorine that makes your water safer from bacteria creates a different category of chemical exposure in the process.

Why Your Brita Filter Isn’t Enough

Standard activated carbon filters — Brita jugs and most basic tap attachments — are effective at improving taste and odour. They remove some chlorine, some sediment, and some heavy metals. But they are not designed to address PFAS, microplastics, or pharmaceutical residues. Estimates suggest standard filters address perhaps 5% of the full contaminant range in typical tap water. This isn’t a criticism of those products — they do what they’re designed to do. The issue is that most people assume a filter means their water is comprehensively clean. It doesn’t. Reverse osmosis systems offer substantially broader contaminant removal including PFAS reduction.

The Question You Should Be Asking

The useful question is not “is my tap water safe?” Safe and optimal are not the same thing. Water that meets regulatory standards can still contain dozens of unregulated compounds, legal contaminants at permitted levels, and chemicals whose long-term effects at low concentrations are genuinely not yet understood. The standards exist to prevent acute harm. They were not designed to optimise what you put into your body every day.

What You Can Do

• Read your annual water quality report. Every US water utility is required to publish one — it shows what’s tested and at what levels, though it won’t cover unregulated contaminants like many PFAS compounds.
• Understand what your filter actually removes. Check the NSF certification. NSF/ANSI 53 covers health-related contaminants. NSF/ANSI 58 covers reverse osmosis. If your filter has neither, it’s primarily a taste and odour device.
• Consider independent water testing. A home test kit or lab test gives you a clearer picture of what’s in your specific supply, particularly for PFAS, heavy metals, and nitrates.
• Think about the whole picture. Water quality is one variable in hydration. Cellular absorption, mineral balance, and timing matter as much as what’s in the glass.

Frequently Asked Questions

How many contaminants are in US tap water?

The Environmental Working Group has detected over 300 contaminants in US tap water. Many are legal under current EPA standards, but legal does not mean safe or optimal for long-term daily consumption.

What are PFAS and why are they dangerous?

PFAS (per- and polyfluoroalkyl substances) are synthetic chemicals used in manufacturing since the 1940s. They are called forever chemicals because they do not break down in the environment or the human body. Research links PFAS exposure to immune disruption, thyroid disease, hormonal interference, and certain cancers.

Does a Brita filter remove PFAS and microplastics?

Standard activated carbon filters like Brita are not designed to remove PFAS, microplastics, or pharmaceutical residues. They primarily improve taste and odour. Estimates suggest they address around 5% of the full contaminant range in typical tap water. Reverse osmosis systems offer significantly broader removal.

Are microplastics in tap water harmful?

Microplastics have been found in 83% of tap water samples tested globally. They have been detected in human blood, lung tissue, and breast milk. Beyond their physical presence, they act as carriers for chemical contaminants including endocrine disruptors and heavy metals. Long-term health effects are still being studied.

What is the best water filter for removing contaminants?

Reverse osmosis systems offer the broadest contaminant removal, including PFAS reduction. Look for NSF/ANSI 58 certification for reverse osmosis or NSF/ANSI 53 for health-related contaminant reduction. The right filter depends on what is actually in your specific water supply — start with your utility’s annual water quality report or an independent lab test.

How do chlorine byproducts get into tap water?

When chlorine reacts with naturally occurring organic matter in water or ageing pipe infrastructure, it forms disinfection byproducts (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). Long-term exposure has been linked in research to bladder cancer risk and adverse pregnancy outcomes.

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This article is for general informational purposes only and is not medical advice. If you have health concerns related to water quality, consult a qualified healthcare professional or environmental health specialist.