Massachusetts Radon Levels
3Zone 1 (High)
10Zone 2 (Moderate)
1Zone 3 (Low)
21% of counties in Massachusetts are classified as EPA Zone 1 (highest radon potential), meaning predicted average indoor radon levels exceed 4 pCi/L — the EPA action level. The EPA recommends that all homes be tested for radon, regardless of zone classification.
| County | EPA Zone | Risk Level |
|---|---|---|
| Barnstable County | Zone 2 | Moderate Potential |
| Berkshire County | Zone 2 | Moderate Potential |
| Bristol County | Zone 2 | Moderate Potential |
| Dukes County | Zone 2 | Moderate Potential |
| Essex County | Zone 1 | Highest Potential |
| Franklin County | Zone 2 | Moderate Potential |
| Hampden County | Zone 2 | Moderate Potential |
| Hampshire County | Zone 2 | Moderate Potential |
| Middlesex County | Zone 1 | Highest Potential |
| Nantucket County | Zone 2 | Moderate Potential |
| Norfolk County | Zone 2 | Moderate Potential |
| Plymouth County | Zone 2 | Moderate Potential |
| Suffolk County | Zone 3 | Lowest Potential |
| Worcester County | Zone 1 | Highest Potential |