Water Quality by State: A Regional Analysis
Understanding how water quality varies across the United States—regional trends, common contaminants, regulations, and state performance.
National Water Quality Research
Expert Reviewed
This content has been reviewed by Dr. Sarah Chen, PhD, Environmental Science Advisor, to ensure accuracy and alignment with current environmental science standards.
Last reviewed: February 2026
Understanding State-Level Water Quality
Water quality varies dramatically across the United States due to differences in source water, geology, industrial activity, agricultural practices, infrastructure age, state regulations, and enforcement. While federal EPA standards set a baseline, states can implement stricter regulations and invest more (or less) in water infrastructure.
Key Factors Affecting State Water Quality
- Source Water: Surface water (rivers, lakes) vs groundwater (wells, aquifers) have different contamination risks
- Geology: Natural arsenic, radon, radium, or uranium in certain regions
- Agricultural Activity: Nitrates and pesticides from farming
- Industrial Legacy: Historic contamination from manufacturing, mining
- Infrastructure Age: Lead service lines, aging treatment plants
- State Regulations: Some states enforce stricter limits than EPA
- Investment: State funding for treatment upgrades and system maintenance
- Population Density: Urban vs rural challenges
Important Context:
Even within a state, water quality can vary significantly between cities, towns, and rural areas. These state-level summaries represent general trends, not guarantees for specific locations. Always check your local water quality data.
Regional Water Quality Patterns
Northeast
States: ME, NH, VT, MA, RI, CT, NY, NJ, PA
Common Issues:
- Aging infrastructure and lead service lines (especially in older cities)
- Radon and arsenic in well water (particularly New England)
- Industrial legacy contamination (manufacturing, chemical plants)
- Disinfection byproducts from treating surface water
- PFAS contamination near military bases and airports
Strengths:
- Generally abundant freshwater sources
- Many states enforce stricter-than-EPA regulations
- Strong regulatory oversight and testing requirements
- Well-funded infrastructure improvement programs in some areas
Southeast
States: MD, DE, VA, WV, KY, NC, SC, TN, GA, FL, AL, MS, LA, AR
Common Issues:
- Agricultural runoff (nitrates, pesticides, especially in rural areas)
- Disinfection byproducts from treating warm surface water
- Industrial contamination (GenX chemicals in North Carolina, for example)
- Aging infrastructure in historic cities
- Bacteria and pathogens from inadequate sewage treatment
- Saltwater intrusion in coastal areas (Florida particularly affected)
Strengths:
- Generally high rainfall and surface water availability
- Some states (like North Carolina) have adopted stricter PFAS standards
- Growing investment in water infrastructure
Midwest
States: OH, MI, IN, IL, WI, MN, IA, MO, ND, SD, NE, KS
Common Issues:
- Agricultural contamination (nitrates, pesticides, herbicides) in rural areas
- Lead from aging infrastructure in industrial cities (Flint, Pittsburgh, etc.)
- Arsenic in groundwater (especially Great Plains states)
- Industrial legacy contamination
- PFAS near military bases
- Chromium-6 in some industrial areas
Strengths:
- Access to Great Lakes (world's largest freshwater source)
- Abundant groundwater in many areas
- Strong agricultural awareness of water quality issues
Southwest
States: TX, OK, NM, AZ, NV, UT, CO
Common Issues:
- Arsenic in groundwater (naturally occurring)
- Radium and uranium in certain geological areas
- Nitrates from agricultural and oil/gas operations
- Perchlorate from aerospace/defense industries
- PFAS near military bases (especially Colorado, New Mexico)
- Water scarcity and over-extraction of aquifers
- High total dissolved solids (mineral content)
Strengths:
- Modern infrastructure in fast-growing cities
- Advanced treatment in water-scarce areas (including some RO)
- Strong awareness of water conservation
West
States: CA, OR, WA, ID, MT, WY, AK, HI
Common Issues:
- Chromium-6 in California (industrial, natural sources)
- PFAS near military installations and airports
- Arsenic in groundwater (especially California Central Valley)
- Agricultural runoff (pesticides, nitrates) in farming regions
- Perchlorate from aerospace activities
- Wildfires affecting surface water quality
- Water scarcity driving reliance on groundwater
Strengths:
- California has strictest water quality standards in nation
- Strong environmental regulations and enforcement
- Significant investment in advanced treatment
- Robust testing and transparency requirements
States with Best Water Quality
Based on EPA compliance data, infrastructure investment, testing standards, and contamination levels, these states consistently rank among the best for drinking water quality:
Hawaii
Protected watersheds, modern infrastructure, minimal industrial activity, abundant rainfall. Volcanic filtration provides natural purification. Strict conservation and protection laws.
Rhode Island
High EPA compliance, strong infrastructure investment, abundant freshwater sources, comprehensive testing. Small size enables better oversight.
Massachusetts
Excellent compliance rates, strong state regulations, significant infrastructure investment, robust testing requirements. Advanced treatment systems.
Connecticut
High compliance, well-maintained infrastructure, strict state standards, comprehensive monitoring. Strong environmental protections.
Minnesota
Abundant freshwater (10,000+ lakes), high compliance rates, strong investment in infrastructure, excellent testing protocols. Environmental consciousness.
Vermont
Pristine source water, strong environmental regulations, minimal industrial activity, high compliance. Small population limits stress on systems.
New Hampshire
High-quality source water, strong testing requirements, good infrastructure. Some concerns with PFAS near Pease Air Force Base, but state responded aggressively.
Oregon
Excellent surface water sources (Bull Run, protected watershed), modern treatment, strong environmental regulations, high compliance.
What these states do well: Consistent EPA compliance (> 95%), infrastructure investment, comprehensive testing beyond minimum requirements, stricter-than-federal standards, transparent reporting, and strong environmental protections.
States with Significant Water Quality Challenges
These states face persistent challenges with aging infrastructure, contamination, compliance, or limited resources:
Texas
Issues: Widespread arsenic and radium in groundwater, nitrates from agriculture and oil/gas, aging infrastructure in rural areas, water scarcity. Large geographic size makes oversight difficult. High number of small systems with violations.
California
Issues: Chromium-6 widespread (natural and industrial), arsenic in Central Valley groundwater, agricultural contamination (pesticides, nitrates), PFAS near military bases. Despite strictest regulations, scale and diversity of contamination sources create challenges. Rural communities particularly affected.
Arizona
Issues: Arsenic in groundwater, perchlorate from defense industries, nitrates, water scarcity forcing reliance on contaminated aquifers. Rural areas struggle with compliance.
Oklahoma
Issues: Arsenic, radium, nitrates, aging infrastructure, limited state funding, high rates of small system violations. Oil and gas activity impacts water quality.
Ohio
Issues: Aging infrastructure in industrial cities, lead service lines, agricultural runoff, algal blooms from phosphorus (Lake Erie), legacy industrial contamination.
Pennsylvania
Issues: Lead in Pittsburgh and Philadelphia, coal mining legacy (acid mine drainage), fracking impacts, aging infrastructure. Some rural areas have severe contamination.
New Mexico
Issues: Arsenic, uranium, radium, nitrates, PFAS near military bases (especially Cannon and Holloman), perchlorate, limited water resources.
Mississippi
Issues: Aging infrastructure, limited funding, high violation rates in small systems, agricultural contamination. Jackson water crisis (2022) highlighted systemic problems.
Common challenges: Underfunded infrastructure, natural geological contamination (arsenic, radon, radium), agricultural impacts, legacy industrial pollution, rural water system compliance issues, limited state resources for oversight and enforcement.
State-Specific Regulations: Going Beyond EPA Standards
Some states enforce stricter standards than federal EPA requirements, providing extra protection to residents:
California
Stricter Standards For:
- Chromium-6: 10 ppb (EPA has no specific Cr-6 limit)
- PFAS: Lower notification levels than EPA
- Perchlorate: 6 ppb (EPA has no enforceable standard)
- 1,2,3-TCP: 5 ppt (pesticide, EPA has no standard)
California's Office of Environmental Health Hazard Assessment (OEHHA) sets Public Health Goals (PHGs) often stricter than EPA.
Massachusetts
Stricter Standards For:
- PFAS (PFOA + PFOS + 4 others): 20 ppt combined (much stricter than EPA's 4 ppt individual)
- Perchlorate: 2 ppb
- Lead: Lowered action level trigger, more aggressive testing
North Carolina
Stricter Standards For:
- GenX and related PFAS: 70 ppt (state-specific response to Chemours contamination)
- PFOA: 70 ppt (stricter than EPA)
New Jersey
Stricter Standards For:
- PFOA: 14 ppt (now superseded by EPA but was first in nation)
- PFOS: 13 ppt (also pioneering standard)
- PFNA: 13 ppt
- Multiple other PFAS compounds
Michigan
Stricter Standards For:
- PFAS: 6-8 ppt for various compounds (post-Flint reforms)
- Lead: More stringent action level and response requirements
Why this matters: If you live in a state with stricter standards, your water is held to higher safety thresholds. However, enforcement and funding for compliance vary.
Urban vs Rural Water Quality
Within states, water quality challenges differ dramatically between urban and rural areas:
Urban Areas
Advantages:
- Large, well-funded water systems
- Advanced treatment technologies
- Professional operation and maintenance
- Regular testing and monitoring
- Economies of scale
Challenges:
- Aging infrastructure in historic cities (lead service lines)
- Legacy industrial contamination
- Extensive distribution systems where contamination can occur
- Higher population density strains systems
- Disinfection byproducts from treating poor-quality source water
Rural Areas
Advantages:
- Often cleaner source water
- Less industrial contamination
- Simpler distribution systems
Challenges:
- Small systems lack funding and technical expertise
- Higher violation rates for small community systems
- Limited treatment capabilities
- Agricultural contamination (nitrates, pesticides)
- Many homes on private wells (no regulation)
- Difficulty attracting certified operators
- Higher per-capita infrastructure costs
Bottom line: Urban areas have better infrastructure and treatment but often face lead and industrial legacy issues. Rural areas may have cleaner source water but lack resources for proper treatment and testing. Private wells in rural areas are completely unregulated.
How to Check Your State's Water Quality
Official State Resources
- State Environmental/Health Department
Every state has a drinking water program. Search "[Your State] drinking water quality" to find the official website with statewide data and reports. - EPA SDWIS Database
The Safe Drinking Water Information System tracks all violations and testing nationwide. Search by state, county, or water system. - State-Specific Water Quality Reports
Many states publish annual reports on overall water quality, emerging issues, and compliance rates. - Local Utility CCR (Consumer Confidence Report)
Your water utility must publish an annual report. This is the most relevant data for YOUR tap water.
Third-Party Resources
- EWG Tap Water Database: Compiles EPA data with user-friendly interface
- US Water Grade: Our database with searchable city-specific water quality data
- Natural Resources Defense Council (NRDC): Publishes state water quality assessments
What to Look For
- Compliance rates (percentage of systems meeting standards)
- Common contaminants detected in your state
- Violation trends (improving or worsening)
- State-specific standards beyond EPA requirements
- Infrastructure investment plans
- Emerging contaminant concerns (PFAS monitoring, for example)
Frequently Asked Questions
Which state has the worst water quality?
No single state is "worst" uniformly—it depends on the metric. Texas has high rates of arsenic and radium violations. California faces widespread chromium-6. Pennsylvania struggles with lead in major cities. States with significant rural populations often have more small-system violations.
Does living in a "best water quality" state guarantee my water is safe?
No. State-level rankings reflect averages and trends. Even in top-ranked states, individual cities or neighborhoods can have serious contamination. Always check your local water utility's reports and consider home testing.
Are state regulations better than EPA standards?
Some states enforce stricter limits than EPA (California, Massachusetts, New Jersey), providing extra protection. However, stronger regulations don't guarantee better enforcement or compliance. Some states with strong rules still have infrastructure challenges.
How do I find my state's specific water quality standards?
Search "[Your State] drinking water standards" or visit your state environmental/health department website. Most states publish tables comparing their standards to EPA standards.
Why do some states have naturally occurring contaminants?
Geology varies by region. Arsenic occurs naturally in Western and New England groundwater. Radon is common in areas with granite bedrock. Radium occurs in certain sedimentary rocks. States can't eliminate natural contamination but must treat it.
Do wealthier states have better water quality?
Generally, yes—infrastructure investment matters. However, wealth doesn't guarantee good water. California is wealthy but faces massive contamination challenges due to industrial history and agriculture. Some less wealthy states with cleaner source water and smaller populations rank highly.
Should I move to a state with better water quality?
Water quality is just one factor in quality of life. Instead of moving, invest in water testing and filtration for your current home. Even "bad water quality" states have many communities with excellent water, and vice versa.
How often do state rankings change?
Rankings shift slowly based on multi-year trends in compliance, violations, and investment. Major events (like Flint) can accelerate changes. Check updated data every few years rather than relying on old rankings.