About Radon by ZIP
Radon by ZIP turns the EPA Map of Radon Zones into a fast ZIP and county lookup, and pairs it with plain-language guides on testing and fixing radon.
Why we built it
EPA estimates radon causes about 21,000 lung cancer deaths a year in the United States, making it the second leading cause of lung cancer and the leading cause among people who have never smoked. Yet EPA’s zone map is a county-level PDF and spreadsheet from 1993, and most people search by ZIP code. We join the two with Census Bureau data so anyone can see their county’s zone in seconds.
Just as important, we repeat EPA’s own caution everywhere the zone appears: the map is not a substitute for a test. A Zone 3 county can have homes well above the action level, and a Zone 1 county can have homes with very little radon. The lookup is a nudge to test, not a verdict.
Where the data comes from
County zones come from EPA’s text version of the Map of Radon Zones (the downloadable JSON/XLS on EPA’s site). ZIP codes are matched to counties using the U.S. Census Bureau’s 2020 ZCTA-to-county relationship file; when a ZIP spans more than one county, we list each county and the share of the ZIP’s land area in it. A handful of counties created or renamed after 1993, and Virginia’s independent cities, are not listed separately on EPA’s map; for those we show the zone of the county they were part of or sit within, and label it clearly.
Who writes it
Radon by ZIP is written and maintained by a small editorial team at an independent web publisher. We are not lawyers, engineers, doctors, or government officials, and we do not claim to be. What we do is read the primary sources (statutes, agency guidance, university extension publications, and official court and health-department pages), turn them into plain steps, and link every claim back to where it came from.
How the site is paid for
The site is free to use and is supported by display advertising from Google. Advertisers do not choose or review our topics, and ads never change what a guide says. Read our editorial standards for how we pick sources, correct mistakes, and keep ads separate from content.
Tell us what we got wrong
Rules change and local details vary. If you spot an error or an out-of-date figure, please send us a note with a link to the source. We read every correction and date-stamp the fix.
Photo and video credits
Home page background video (aerial view of a suburban home) by Jaxon Matthew Willis on Pexels, used under the Pexels license.