North Dakota Cities Ranked by Indoor Radon Levels
Measured averages from Airthings devices across North Dakota, USA. Action level: 4 pCi/L — the threshold at which remediation is recommended.
Grafton has the highest measured indoor radon in North Dakota at 14.8 pCi/L, based on Airthings measurements across 14 cities.
Updated August 16, 2026
Highest city
14.8pCi/L
Grafton
North Dakota city average
5.7pCi/L
across 14 cities
Above action level
9/ 14
cities
| # | Location | Avg level | Monitors | vs action level |
|---|---|---|---|---|
| 1 | Grafton | 14.8 pCi/L | 7 | 3.7× over |
| 2 | Langdon | 12.5 pCi/L | 9 | 3.1× over |
| 3 | Park River | 6.9 pCi/L | 7 | 1.7× over |
| 4 | Casselton | 6.6 pCi/L | 8 | 1.6× over |
| 5 | Dickinson | 6.5 pCi/L | 14 | 1.6× over |
| 6 | Grand Forks | 4.9 pCi/L | 51 | 1.2× over |
| 7 | Fargo | 4.0 pCi/L | 67 | 1.0× over |
| 8 | Minot | 4.0 pCi/L | 25 | 1.0× over |
| 9 | West Fargo | 4.0 pCi/L | 55 | 1.0× over |
| ✓ Below EPA action level (4 pCi/L) | ||||
| 10 | Horace | 3.6 pCi/L | 45 | 0.9× under |
| 11 | Valley City | 3.3 pCi/L | 6 | 0.8× under |
| 12 | Mandan | 3.1 pCi/L | 9 | 0.8× under |
| 13 | Jamestown | 3.0 pCi/L | 7 | 0.8× under |
| 14 | Bismarck | 2.8 pCi/L | 40 | 0.7× under |