Radionuclides
Radon in U.S. tap water
28 public water systems across 9 U.S. states report Radon in their annual Consumer Confidence Report. None currently sit at or above the federal limit.
What it is
A naturally occurring radioactive gas that can dissolve into groundwater.
Why it's regulated
No enforceable federal limit in drinking water yet; inhalation of released radon raises lung-cancer risk.
Within the federal limit (5)
| Water system | Measured |
|---|---|
| Beverly Hills-city, Water Dept. — Beverly Hills, Ca, CA 2021 annual report | Not detected pCi/L |
| Lewisville, TX 2024 annual report | Not detected pCi/L |
| Three Valleys MWD — Claremont, Ca, CA 2023 annual report | Not detected pCi/L |
| West Jordan, UT 2024 annual report | Not detected pCi/L |
| West Valley City, UT 2024 annual report | Not detected pCi/L |
Frequently asked
+What is Radon?
A naturally occurring radioactive gas that can dissolve into groundwater. No enforceable federal limit in drinking water yet; inhalation of released radon raises lung-cancer risk.
+Does Radon have a federal limit in drinking water?
Radon does not have an enforceable federal MCL. Utilities still report any measured levels in their annual Consumer Confidence Report.
+How many U.S. water systems have Radon over the federal limit?
Zero of the 28 public water systems in The Water Map dataset currently report Radon at or above its federal limit.
+How can I check if Radon is in my city's tap water?
Search your city on The Water Map (https://www.thewatermap.com/) or browse the list on this page. Every U.S. public water utility is required to publish an annual Consumer Confidence Report that lists every contaminant it measured, including Radon.