Radon levels and tap water records by ZIP code

Enter a ZIP code to see radon levels by ZIP code the way EPA maps them, through the radon zone of the county the ZIP sits in, along with the public water systems registered there. A zone is a prediction for an area; only a test measures your home.

Check radon levels by ZIP code

Radon

1,073

counties in EPA's highest zone, home to 89 million people

PFAS

of 11 city systems had PFOA or PFOS above 4 ng/L

Violations

city systems with a health violation since 2016

Coverage

3,144

counties in all 50 states and DC

Is my tap water safe? Start with your city

Water quality by ZIP code depends on which system pipes water to the address, and a ZIP can be split between several. The city reports below follow each city's main system through its EPA file: violations, lead sampling, PFAS testing and where the water comes from.

New YorkNew York Los AngelesCalifornia ChicagoIllinois HoustonTexas PhoenixArizona PhiladelphiaPennsylvania San AntonioTexas San DiegoCalifornia DallasTexas JacksonvilleFlorida Las VegasNevada

All 11 city water reports

Radon map by state

Each state page lists every county with its EPA zone, along with the state's own radon program where we have checked it. The national radon map compares them.

Where these numbers come from

Every figure traces to a public federal dataset: EPA's Safe Drinking Water Act records, EPA's nationwide PFAS testing (UCMR 5), EPA's county radon zones and Census population estimates, last refreshed October 2026. We don't sell filters, tests or services. Read the methodology.