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RankingsMarylandHighest radon potential

Counties with the Highest Radon Potential in Maryland

The top 23 of 23 Maryland counties on GIS Map, ranked by EPA radon zone, where zone 1 carries the highest predicted indoor radon potential and zone 3 the lowest.

#CountyEPA radon zone
1Caroline County
3
2Dorchester County
3
3Kent County
3
4Queen Anne's County
3
5Talbot County
3
6Wicomico County
3
7Worcester County
3
8Allegany County
2
9Anne Arundel County
2
10Baltimore County
2
11Cecil County
2
12Charles County
2
13Garrett County
2
14Prince George's County
2
15Somerset County
2
16St. Mary's County
2
17Calvert County
1
18Carroll County
1
19Frederick County
1
20Harford County
1
21Howard County
1
22Montgomery County
1
23Washington County
1

Source: EPA Map of Radon Zones (September 2025). All counties with data are ranked. Estimates carry margins of error.

Citing this page: GIS Map, “Counties with the Highest Radon Potential in Maryland”, https://gismap.land/rankings/maryland/highest-radon-counties. Figures from EPA Map of Radon Zones (September 2025).

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