Radon levels in Massachusetts: Low
The model predicts a population-weighted basement average of 1.8 pCi/L across Massachusetts's 14 counties - close to the US average of 1.8 pCi/L. Above-ground floors average 1.1 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
3 / 14
EPA Zone 1 counties (21%)
10 / 1
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
0.4%
of ZIP codes predicted ≥ 4 pCi/L
Massachusetts counties by predicted radon
Sorted highest to lowest predicted basement average. 14 counties.
| County | Predicted basement | Upstairs | Grade | EPA zone | ZIPs |
|---|---|---|---|---|---|
| Worcester County | 2.5 pCi/L | 1.4 | Moderate | EPA Zone 1 | 78 |
| Essex County | 2.0 pCi/L | 1.4 | Low | EPA Zone 1 | 41 |
| Barnstable County | 2.0 pCi/L | 1.1 | Low | EPA Zone 2 | 38 |
| Dukes County | 1.9 pCi/L | 1.1 | Low | EPA Zone 2 | 7 |
| Middlesex County | 1.8 pCi/L | 1.2 | Low | EPA Zone 1 | 80 |
| Plymouth County | 1.8 pCi/L | 1.0 | Low | EPA Zone 2 | 30 |
| Bristol County | 1.8 pCi/L | 0.9 | Low | EPA Zone 2 | 33 |
| Norfolk County | 1.8 pCi/L | 1.0 | Low | EPA Zone 2 | 39 |
| Berkshire County | 1.7 pCi/L | 1.1 | Low | EPA Zone 2 | 26 |
| Franklin County | 1.6 pCi/L | 0.9 | Low | EPA Zone 2 | 26 |
| Hampshire County | 1.6 pCi/L | 0.8 | Low | EPA Zone 2 | 24 |
| Nantucket County | 1.6 pCi/L | 1.1 | Low | EPA Zone 2 | 1 |
| Hampden County | 1.3 pCi/L | 0.7 | Low | EPA Zone 2 | 35 |
| Suffolk County | 1.2 pCi/L | 0.6 | Low | EPA Zone 3 | 27 |
Massachusetts radon questions
- Is radon high in Massachusetts?
- Massachusetts's population-weighted predicted basement average is 1.8 pCi/L, close to the US average of 1.8. 0 of its 14 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 1 are in the 2-4 "consider fixing" range and 13 are below 2. 0.4% of Massachusetts ZIP codes are predicted at 4 or higher.
- Which Massachusetts county has the highest radon?
- Worcester County has the highest predicted basement average in Massachusetts at 2.5 pCi/L (EPA Zone 1). The lowest is Suffolk County at 1.2 pCi/L. These are modeled area averages; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Massachusetts?
- 3 of Massachusetts's 14 counties (21%) are EPA Zone 1 (highest potential), 10 are Zone 2 and 1 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Massachusetts?
- Yes. Even though Massachusetts's predicted average is below 2 pCi/L, the EPA recommends every home be tested - radon varies house to house, and 34.8% of Massachusetts ZIP codes are still predicted at 2 pCi/L or higher.
Massachusetts radon program
Many states offer free or discounted test kits and keep lists of certified mitigators. Find the Massachusetts radon office through the EPA state radon contacts page. Then read how to test and what mitigation costs.