Lead, Arsenic, PFAS, and Nitrates: The Most Common Water Contaminants Found in North American Homes (EPA Data)

Written by Craig "The Water Guy" Phillips

Lead corrodes from old pipes, arsenic seeps from geological deposits, PFAS migrate from industrial sites, and nitrates leach from fertilizers — and EPA data confirms these four contaminants appear in North American homes far more often than we'd expect. They don't just affect water quality; they affect our health in serious, lasting ways. Understanding where they come from, what they do to our bodies, and how to act is exactly what we'll cover next.

Key Takeaways

• Lead enters tap water through corroding pipes and solder, with older pre-1986 homes facing the highest exposure risk.
• Arsenic naturally erodes from geological deposits into groundwater, increasing cancer and cardiovascular risk at common concentration levels.
• PFAS migrate from industrial sites and firefighting foam into water supplies, accumulating in the body and resisting natural clearance.
• Nitrates leach from fertilizers and septic systems, causing infant oxygen deprivation and long-term cancer risk in adults.
• EPA limits for these contaminants reflect feasibility rather than pure safety thresholds, leaving gaps in cumulative exposure protection.

Where Lead, Arsenic, PFAS, & Nitrates Enter Your Home's Water

Most of us don't think twice about turning on the tap, but four contaminants—lead, arsenic, PFAS, and nitrates—can quietly work their way into home water through very different routes.

Lead typically corrodes off your own plumbing and service lines. Arsenic erodes from natural geological deposits into groundwater. PFAS migrate from industrial sites, firefighting foam, and wastewater into surface and groundwater supplies. Nitrates leach from fertilizers, manure, and septic systems into the same sources.

What makes this particularly important is that these pathways aren't mutually exclusive. A single household can face lead from its pipes, arsenic from regional geology, PFAS from upstream contamination, and nitrates from agricultural runoff—all simultaneously. Understanding each entry point is the first step toward addressing your actual exposure.

What These Four Contaminants Actually Do to Your Body

Knowing where contaminants enter our water is one thing—understanding what they're actually doing inside our bodies is another.

Lead accumulates permanently, quietly eroding children's cognitive development and adults' kidney function and blood pressure. Arsenic, even at concentrations common in North American groundwater, drives up cancer risk across multiple organs while damaging cardiovascular health.

PFAS concentrate in our blood, suppressing immune response, disrupting fetal development, and elevating cholesterol and cancer risk—effects that persist because our bodies can't clear these chemicals.

Nitrates threaten infants through oxygen deprivation and contribute to cancer risk and thyroid dysfunction in long-term adult exposure. What makes this especially concerning: these contaminants frequently co-occur, compounding each other's damage—and our regulatory standards don't always reflect the lower thresholds where harm begins.

Does Your Home Have a Higher Risk of Water Contamination?

While the health effects we've just covered are serious across the board, not every home carries the same level of risk—and identifying your specific risk factors can change what you do next.

Several factors quietly elevate your household's exposure:

• Older homes (pre-1986) likely contain lead solder or service lines—corrosion delivers lead directly into your glass.
• Private well users have zero EPA regulatory protection against arsenic, nitrates, or uranium—you're entirely responsible for your own testing.
• Proximity to agriculture, landfills, or industrial sites dramatically increases nitrate and PFAS likelihood, affecting millions who don't yet know it.

Groundwater-dependent systems also carry higher natural arsenic and uranium concentrations.

Understanding where you actually fall within these categories is the first real step toward protecting your household.

EPA Drinking Water Limits: and What the Rules Don't Cover

The EPA has set legal limits—called Maximum Contaminant Levels (MCLs)—for roughly 100 contaminants, and here's what those numbers actually mean for your tap: lead triggers corrective action at 15 µg/L, arsenic is capped at 10 µg/L, nitrate at 10 mg/L, and a newly finalized rule now sets MCLs for six PFAS compounds, including PFOA and PFOS at just 0.004 µg/L each.

But here's the critical gap: MCLs reflect what's technically and economically feasible—not purely what's safest. Of approximately 14,700 known PFAS, only six are regulated. Countless disinfection byproducts remain unmonitored.

Rules also ignore cumulative exposure—meaning concurrent arsenic and nitrate, or multiple PFAS together, aren't assessed as mixtures. And if you're on a private well or served by a small system, these protections may not even apply to you.

How to Test & Filter Your Home Tap Water

Once you know what might be lurking in your water, testing transforms that uncertainty into something actionable. Start by checking EPA or EWG databases using your ZIP code, or request your utility's Consumer Confidence Report. Private well users should go further—hire a state-certified lab, since PFAS require specialized methods most basic panels skip.

Testing transforms uncertainty into action—start with your ZIP code, your utility's report, or a certified lab.

When results reveal problems, your filter choice matters enormously:

• Lead detected? Install NSF/ANSI 53- or 58-certified point-of-use filters and replace cartridges on schedule.
• Arsenic or nitrates above benchmarks? Reverse osmosis reliably removes both; ion exchange handles nitrates at whole-house scale.
• PFAS present? Choose GAC filters with validated PFAS removal or reverse osmosis, then periodically retest treated water.

Testing without acting is just information. Acting without testing is just guessing.

Frequently Asked Questions

Are Home Water Contaminant Levels Required to Be Disclosed When Buying a House?

Disclosure laws vary by state and province, but they don't always require water quality testing. We recommend requesting a full water test before buying — it's the surest way to protect your family.

Can Contaminants Like PFAS Transfer Into Food Cooked With Tap Water?

Yes, PFAS can transfer into food we cook with tap water. When we boil, steam, or simmer with contaminated water, those persistent chemicals don't disappear—they're absorbed directly into our food.

Do Bottled Water Brands Contain the Same Contaminants Found in Tap Water?

Yes, bottled water can contain the same contaminants—including PFAS, arsenic, and nitrates. Unlike tap water, it's less regulated, meaning we're often paying more for water that's potentially no safer.

Are Renters Legally Entitled to Know About Their Building's Water Contamination History?

Yes, we're legally entitled to request our building's water quality reports. Landlords must provide Consumer Confidence Reports under the Safe Drinking Water Act, so let's use that leverage to uncover contamination risks before they affect our health.

How Do North American Contamination Levels Compare to Other Developed Countries?

We're not winning this race. North America's lead and PFAS levels often exceed EU standards, where stricter regulations push contaminants lower. Europe's precautionary approach means they're acting before harm is proven, while we're catching up.