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State overview
Radon in Maryland
Of Maryland's 24 counties and county equivalents, EPA places 8 in Zone 1, 9 in Zone 2, 7 in Zone 3. Zones are county-wide predictions; testing is the only way to know your home's level.
Radon in the news
Maryland stories
- Experts warn radon causes cancer. Why hasn’t Maryland acted?Baltimore Sun · 2026-05-27
Headlines link to the original publishers via Google News. Updated 2026-10-27.
All 24 counties
| County | EPA zone |
|---|---|
| Allegany County | Zone 2 |
| Anne Arundel County | Zone 2 |
| Baltimore County | Zone 1 |
| Baltimore city | Zone 2 |
| Calvert County | Zone 1 |
| Caroline County | Zone 3 |
| Carroll County | Zone 1 |
| Cecil County | Zone 2 |
| Charles County | Zone 2 |
| Dorchester County | Zone 3 |
| Frederick County | Zone 1 |
| Garrett County | Zone 2 |
| Harford County | Zone 1 |
| Howard County | Zone 1 |
| Kent County | Zone 3 |
| Montgomery County | Zone 1 |
| Prince George's County | Zone 2 |
| Queen Anne's County | Zone 3 |
| Somerset County | Zone 2 |
| St. Mary's County | Zone 2 |
| Talbot County | Zone 3 |
| Washington County | Zone 1 |
| Wicomico County | Zone 3 |
| Worcester County | Zone 3 |
Source: EPA radon zones spreadsheet (EPA 402/A-16/001).