Radon in Massachusetts
Radon in Massachusetts varies from house to house, so the county figures below describe areas, not homes. EPA places 3 of the state's 14 counties in Zone 1, its highest band of predicted indoor radon, where about 47% of residents live; 1 is in Zone 3. On the water side, EPA has recorded health-based violations at 0 of the state's 528 community water systems since 2016.
What Massachusetts's radon program offers
The state radon unit no longer gives free kits to the general public and points residents to discounted kits sold by Kansas State University. Radon line: (800) 723-6695.
Since 2015, new one- and two-family homes and townhouses built in Worcester, Essex and Middlesex Counties must include a passive radon system under the Massachusetts Building Code.
The Department of Public Health recommends radon testing in all schools and child care facilities.
The Department of Public Health advises that anyone hired to test for or fix radon in a home hold national certification from AARST/NRPP or NRSB.
Read on Massachusetts Department of Public Health, Bureau of Climate and Environmental Health, Division of Healthy Homes and Childhood Lead Poisoning Prevention pages, checked 2026-10-29: state radon program.
Radon in Massachusetts by county
The Massachusetts radon map below groups counties by EPA zone; zones predict Massachusetts radon levels from geology and past surveys and are not home measurements. The largest county, Middlesex County (1,668,956 residents), is in Zone 1.
| County | Residents | Water systems | Violations since 2016 | Unresolved |
|---|---|---|---|---|
| Essex County | 823,938 | 39 | 0 | 0 |
| Middlesex County | 1,668,956 | 98 | 0 | 0 |
| Worcester County | 881,248 | 110 | 0 | 0 |
| County | Residents | Water systems | Violations since 2016 | Unresolved |
|---|---|---|---|---|
| Barnstable County | 232,570 | 30 | 0 | 0 |
| Berkshire County | 128,726 | 41 | 0 | 0 |
| Bristol County | 588,593 | 29 | 0 | 0 |
| Dukes County | 21,061 | 7 | 0 | 0 |
| Franklin County | 70,871 | 26 | 0 | 0 |
| Hampden County | 464,151 | 29 | 0 | 0 |
| Hampshire County | 165,399 | 28 | 0 | 0 |
| Nantucket County | 14,670 | 2 | 0 | 0 |
| Norfolk County | 740,754 | 39 | 0 | 0 |
| Plymouth County | 542,090 | 45 | 0 | 0 |
| County | Residents | Water systems | Violations since 2016 | Unresolved |
|---|---|---|---|---|
| Suffolk County | 793,144 | 5 | 0 | 0 |
Massachusetts tap water: violations and PFAS
Massachusetts has 528 active community water systems serving about 10,829,918 people. Since January 2016, EPA has recorded at least one health-based violation at 0 of them (0% of the people served).
EPA tested 261 Massachusetts systems for PFAS between 2023 and 2025. 106 had a PFOA or PFOS result above the 4 ng/L limit that applies from 2029; the highest was Raynham Center Water District at 92 ng/L.
Records: EPA Map of Radon Zones, EPA ECHO drinking water data (2026Q3), EPA UCMR 5, Massachusetts Department of Public Health, Bureau of Climate and Environmental Health, Division of Healthy Homes and Childhood Lead Poisoning Prevention, US Census Bureau Vintage 2024. How zones and violations are counted: methodology · all states.