A new national assessment of drinking water quality suggests that as many as one in three Americans may be exposed to at least one contaminant in their tap water that exceeds modern health-based guidelines. The finding, drawn from a combination of U.S. Geological Survey (USGS) monitoring, EPA violation records, and state-level reports, highlights the scale of the challenge facing the country’s aging water infrastructure.

The assessment does not mean that all U.S. tap water is unsafe. Instead, it shows how common it has become for certain contaminants—such as PFAS, lead, nitrates, arsenic, and disinfection byproducts—to appear at levels that exceed health advisory thresholds or state limits in many regions.

A Patchwork of Quality Across the United States

Unlike many countries with national, centralized water systems, America’s drinking water network is highly decentralized, consisting of more than 148,000 public water systems—many of them small, rural, or operating with limited resources.
This patchwork structure means water quality varies significantly from one community to another.

Larger metropolitan utilities typically have robust testing and modern treatment systems. Smaller towns, however, may rely on older infrastructure or have difficulty funding upgrades. This uneven landscape contributes to disparities in contaminant exposure.

PFAS: A Growing National Concern

Among the contaminants identified, PFAS (“forever chemicals”) remain one of the leading concerns. In 2024, USGS researchers reported that nearly half of U.S. tap water samples contained measurable levels of at least one PFAS compound. While not all detections exceed regulatory limits, the widespread presence underscores the challenge utilities face.

The EPA’s new national drinking water standards for PFOA and PFOS—set at 4 parts per trillion—mean that many water systems are now required to take action where levels exceed the new legal limit. These standards are among the strictest ever set for drinking water contaminants in the US.

While some states, including Michigan, New Jersey, and Massachusetts, have already implemented PFAS testing and filtration requirements, many regions are still at early stages of compliance.

Lead Still Persists in Older Infrastructure

Lead contamination remains a recurring issue in cities and towns with older homes and outdated service lines.
According to EPA estimates, the United States still has around 9 million lead service lines in operation.
Lead typically enters drinking water after treatment—through corrosion in home plumbing, rather than from the treatment plant itself.

Even low levels can be harmful to children. For this reason, many states are ramping up service line replacement programs, though progress varies greatly across the country.

Disinfection Byproducts: A Common but Overlooked Issue

Another category highlighted in the assessment is disinfection byproducts (DBPs)—chemicals that can form when disinfectants like chlorine react with natural organic matter in the water.
While DBPs are regulated under the EPA’s Stage 2 Disinfection Byproducts Rule, many small systems struggle to consistently maintain levels below the regulatory limits.

DBPs are most commonly elevated in systems that use surface water sources, such as lakes and rivers, especially during warm months or periods of heavy rainfall.

Nitrates and Arsenic in Rural Systems

Rural communities that rely on groundwater face different challenges.
Nitrate contamination—often linked to agricultural runoff—is a persistent issue in farming regions, particularly across the Midwest and California’s Central Valley.

Arsenic, a naturally occurring contaminant, is also prevalent in parts of the Southwest and Northeast.
In some cases, arsenic levels exceed the EPA’s 10 µg/L limit, requiring additional filtration or blending.

The “One in Three” Figure: What It Actually Means

The “one in three Americans” estimate reflects exposure to any contaminant that exceeds a health-based guideline—not all contaminants at once.
These guidelines come from sources such as:

• EPA enforceable Maximum Contaminant Levels
• EPA Health Advisory Levels
• State environmental health limits
• USGS monitoring thresholds

Most water systems deliver water that meets federal safety standards. However, health-based guidelines can be more stringent than enforceable limits, meaning a system may be legally compliant but still score poorly under more protective standards.

Why Some Communities Are Hit Harder Than Others

Many of the communities most affected by elevated contaminants share similar characteristics:

• Older infrastructure with aging pipes
• Small water systems with limited budgets
• High reliance on groundwater
• Agricultural regions with runoff exposure
• Historic industrial activity that left soil and water contamination
• Rapidly growing cities where infrastructure upgrades lag behind population growth

For example, some rural counties in the Midwest face persistent nitrate challenges linked to fertilizer use, while older Northeastern cities manage risks associated with lead plumbing and legacy pipes.

Meanwhile, Western states that depend heavily on groundwater face different patterns—including arsenic and uranium in naturally occurring aquifers.

This diversity of challenges means no single solution can address all contamination issues. Water systems must tailor upgrades, filtration, and public communication strategies to local conditions.

What Utilities Are Doing to Improve Safety

Across the country, water utilities continue to:

• Upgrade treatment processes
• Add granular activated carbon (GAC) or reverse osmosis systems to remove PFAS
• Replace aging service lines, including lead and galvanized steel
• Implement real-time monitoring systems
• Improve corrosion control programs
• Increase public reporting and transparency

Many states are also investing in infrastructure improvements through federal funding allocated under the Bipartisan Infrastructure Law and EPA State Revolving Funds. These programs help smaller systems access modern filtration and monitoring technology that would otherwise be cost-prohibitive.

What This Means for Households

For most households, tap water is still safe to drink under EPA regulations.
However, the report’s findings help illustrate why:

• Local conditions matter
• Infrastructure age matters
• Source water quality matters
• Testing frequency matters

Families who want a clearer picture of their local water quality can review their city’s annual Consumer Confidence Report (CCR) or explore independent summaries.

CleanAirAndWater.net provides simple, plain-English breakdowns of 2025 water quality reports for cities and states across the United States, including:

• PFAS detections
• Lead and copper sampling results
• Disinfection byproduct trends
• Source water descriptions
• Utility-reported upgrades and changes

You can browse your local system from our Water Directory to understand how your community’s water compares to national trends.

Home Filtration: A Personal Choice for Extra Protection

For households wanting an additional layer of protection, point-of-use filters certified under NSF/ANSI standards—especially NSF-53, NSF-401, and NSF-58—can reduce contaminants such as:

• Lead
• PFAS
• Arsenic
• Nitrates
• Disinfection byproducts

These systems do not replace public treatment.
Instead, they offer peace of mind, especially in regions with older infrastructure, frequent boil notices, or elevated PFAS detections.

As always, filtration is a personal choice, not a requirement. Customers should review certification standards and manufacturer documentation to ensure a system meets their needs.

A National Wake-Up Call for 2025

The “one in three” figure serves as a reminder that even in a highly regulated country, drinking water safety is an ongoing effort—one shaped by infrastructure, environment, and local investment.

The United States has made significant progress over the last several decades, yet new contaminants, aging pipes, and changing environmental conditions continue to test the resilience of water systems.

Public health regulators and utilities agree on one key point: transparency and regular testing are essential.
With new EPA rules for PFAS taking effect, increased funding for service line replacement, and stronger focus on rural groundwater safety, 2025 is expected to be a year of meaningful change.

For residents, staying informed—through CCR reports, local updates, and independent summaries—remains one of the best tools for understanding what’s in their water and how it’s being managed.

Sources & Notes

1. USGS National Tap Water PFAS Study (2023–2024)
https://www.usgs.gov/news/national-news-release/usgs-finds-pfas-nearly-half-sampled-us-tap-water
(Shows PFAS detected in nearly half of U.S. tap water.)

2. EPA PFAS National Primary Drinking Water Regulation (Final Rule 2024)
https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas
(Confirms new legal limits including 4 ppt for PFOA and PFOS.)

3. EPA Lead Service Line Estimates (2023 Report)
https://www.epa.gov/ground-water-and-drinking-water/lead-service-line-inventory
(Approximately 9 million lead service lines still in use.)

4. EPA Drinking Water Infrastructure Needs Survey (DWINSA)
https://www.epa.gov/dwsrf/2023-drinking-water-infrastructure-needs-survey-and-assessment
(148,000+ public water systems across the U.S.)

5. CDC Lead in Drinking Water – Health Effects & Sources
https://www.cdc.gov/lead/prevention/water.htm
(Lead enters water mainly through corrosion in plumbing.)

6. EPA Stage 2 Disinfection Byproducts Rule (DBPR)
https://www.epa.gov/dwreginfo/stage-2-disinfectants-and-disinfection-byproducts-rule
(Regulates THMs and HAA5; small systems often struggle during warm seasons.)

7. USGS – Geosmin & 2-MIB Taste-and-Odor Compounds
https://www.usgs.gov/mission-areas/water-resources/science/taste-and-odor-compounds
(Covers why warm water and algae cause musty/earthy tastes.)

8. USGS – Nitrate Contamination in Agricultural Regions
https://www.usgs.gov/mission-areas/water-resources/science/nitrate-and-nitrite-groundwater
(Explains nitrate issues in Midwest and Central Valley.)

9. EPA Arsenic in Drinking Water
https://www.epa.gov/ground-water-and-drinking-water/arsenic-drinking-water
(Arsenic MCL = 10 µg/L; detections common in Western states.)

10. AWWA – Source Water Blending & Treatment Adjustments
https://www.awwa.org/Resources-Tools/Resource-Topics/Source-Water-Protection
(How utilities blend water sources and adjust disinfection.)

11. EPA Climate Impacts on Water Sources
https://www.epa.gov/climate-indicators/climate-change-indicators-water
(Warming lakes, runoff variability, storm patterns.)

12. State Consumer Confidence Reports (CCRs) Directory
https://www.epa.gov/ccr
(Local utility reports used for examples of taste changes, DBPs, seasonal shifts.)