Radon in Maine
About 4 in 10 homes tested in Maine were at or above the EPA action level of 4 pCi/L.
- Below 2 pCi/L: 40%
- 2 to 4 pCi/L: 22%
- 4 pCi/L or more: 38%
The EPA puts 12 of Maine's 16 counties in Zone 1, its highest radon category, 4 in Zone 2 and 0 in Zone 3.
Every county in Maine
Sorted by the share of homes tested at or above 4 pCi/L. Select a county for local details and costs.
| County | Homes tested | At or above 4 | Median | EPA zone |
|---|---|---|---|---|
| York County | 48% | 3.7 pCi/L | 1 | |
| Piscataquis County | 48% | 3.5 pCi/L | 1 | |
| Aroostook County | 45% | 3.5 pCi/L | 1 | |
| Cumberland County | 44% | 3.2 pCi/L | 1 | |
| Oxford County | 43% | 3.3 pCi/L | 1 | |
| Hancock County | 39% | 2.6 pCi/L | 1 | |
| Androscoggin County | 37% | 2.8 pCi/L | 1 | |
| Lincoln County | 36% | 2.5 pCi/L | 1 | |
| Waldo County | 32% | 2.3 pCi/L | 2 | |
| Kennebec County | 30% | 2.1 pCi/L | 1 | |
| Sagadahoc County | 30% | 2.1 pCi/L | 2 | |
| Knox County | 30% | 2.3 pCi/L | 2 | |
| Washington County | 30% | 1.6 pCi/L | 2 | |
| Franklin County | 29% | 1.8 pCi/L | 1 | |
| Somerset County | 19% | 1.5 pCi/L | 1 | |
| Penobscot County | 16% | 0.8 pCi/L | 1 |
"–" means fewer than 20 tests or no lab data, too few for a reliable figure.
Sources
- EPA Map of Radon Zones (public domain).
- CDC Environmental Public Health Tracking Network, radon tests from labs, 2008–2017. Pre-mitigation tests only.
Last updated October 2026. How we calculate these numbers.