Public records, one place
What's the risk where you live?
Radon potential for every county, plus PFAS, lead and violation records for the water systems serving 10 US cities. All from EPA's own data, updated October 2026.
Check your ZIP code
Radon
1,073
counties in EPA's highest zone, home to 89 million people
PFAS
2
of 10 cities had PFOA or PFOS above EPA's 4 ng/L limit
Violations
4
city water systems with a health violation since 2016
Coverage
3,144
counties in all 50 states and DC
Largest cities
New York, NYTap water: PFAS, lead, violationsLos Angeles, CATap water: PFAS, lead, violationsChicago, ILTap water: PFAS, lead, violationsHouston, TXTap water: PFAS, lead, violationsPhoenix, AZTap water: PFAS, lead, violationsPhiladelphia, PATap water: PFAS, lead, violationsSan Antonio, TXTap water: PFAS, lead, violationsSan Diego, CATap water: PFAS, lead, violationsDallas, TXTap water: PFAS, lead, violationsJacksonville, FLTap water: PFAS, lead, violations
Radon and water by state
Where these numbers come from
Every figure on this site 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. We don't sell filters, tests or services, so nothing here is written to make you buy one. Read the methodology.