Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Worcester County, Massachusetts
EPA puts Worcester County in Zone 1, its highest radon zone, and 33.5% of its 46,440 reported radon tests (2008 to 2017, laboratory totals) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
33.5%
9.7 pts above MA
- Worcester
- 33.5%
- MA
- 23.8%
46,440 tests, 2008 to 2017
Median result
2.6pCi/L
Below action level
- Worcester
- 2.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
46,440
2nd of 14 by tests
- Worcester
- 46,440
- Middlesex
- 75,220
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in MA
1 of 14
Top quarter
- Worcester
- 33.5%
- Worcester
- 33.5%
By share, of 14 with 30+ tests
Read a result for Worcester County
Starts at Worcester County's median, 2.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.6 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Worcester County's median reported result, 2008 to 2017.
The data
Worcester County, At a glance
Worcester County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Worcester County in
USGS geologic potential: High across 85% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Worcester County, 2008 to 2017, laboratory
Under 2 pCi/L: 40%2 to 4 pCi/L: 27%4 pCi/L and above: 33%
Of 46,440 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 18,500 | 39.8% |
| 2 to 4 pCi/L | 12,363 | 26.6% |
| 4 pCi/L and above | 15,577 | 33.5% |
What these figures count
These are the 46,440 tests reported to CDC for Worcester County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Worcester County, Compared
Worcester County radon figures, compared
Calculated by Radon411In Worcester County, about 3 in 10 reported tests over the 2008 to 2017 laboratory totals (15,577 of 46,440) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 2.2 points lower. Across 14 Massachusetts counties pooled together, 23.8% of tests reached that level, so Worcester County runs 9.7 points above its state.
Of 10 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 8 a smaller one; the spread is 13.1% (Hampden County) to 34.4% (Hillsborough County, NH). By share, Worcester County is 1st of 14 Massachusetts counties with 30 or more tests for the same period.
Half the tests came in under 2.6 pCi/L and half over it; the single highest reached 426.0 pCi/L. Below the action level, 18,500 tests (39.8%) came in under 2 pCi/L, against 49.6% statewide, and 12,363 tests (26.6%) fell between 2 and 4, against 26.6% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 33.5% share point the same way here. USGS geology rates 85% of the county's land high radon potential. CDC also counts 152 tests taken after mitigation in Worcester County for the same period: tests in homes where a fix was already in.
CDC's ten-year totals for Worcester County went from 46,435 tests (2005 to 2014) to 46,440 (2008 to 2017), the share going from 32.4% to 33.5%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Worcester County, Geology
The ground under Worcester County
PredictedMost of the ground under Worcester County is one class on USGS's geologic map: 85.4% of its land is high radon potential, with 14.6% moderate. The map puts 59.3% of Worcester County in the area it calls Merrimack Belt and 25.4% in Nashoba and Rhode Island Terranes, with 2 smaller areas beside them. USGS gives the first a radon index of 14 and the second 13, both in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Merrimack Belt | Granitic plutons, metasedimentary rocks (phyllites, carbonaceous slates and schists). | High | 14 | 59.3% |
| Nashoba and Rhode Island Terranes | Granitic plutonic rocks and metamorphic rocks. | High | 13 | 25.4% |
| Gneissic Domes | Domes of mafic gneiss surrounded by younger schists and amphobilites, intruded by granite, and overlain by sandy and gravelly to clayey glacial till. | Moderate | 10 | 14.5% |
| Avalonian Terrane | Gneiss, granite gneiss, granite, felsic metavolcanic rocks. | High | 12 | 0.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Worcester County beside the ground around it
Worcester County has more high-potential ground than Massachusetts as a whole: 85.4% of its land against 31.9%. Of the 10 counties that border it, none has as large a share of high-potential ground; Middlesex County comes nearest at 82.6%.
The map rates the ground, not the air in any home.
Local help
Worcester County, Local resources
Radon testing and mitigation in Worcester County
- Radon UnitRadon Unit, run by Department of Public Health, answers questions about testing, mitigation and the rules in Massachusetts.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Massachusetts5 professionals are listed in Massachusetts.
What Massachusetts's program says
- Phone
- (800) 723-6695
- DPHIAQ.radon@mass.gov
What it means
Worcester County, Questions
Questions about radon in Worcester County
Are radon levels high in Worcester County?
Over the 2008 to 2017 laboratory totals, 33.5% of the radon tests reported to CDC for Worcester County, Massachusetts were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.6 pCi/L. Of 14 Massachusetts counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 23.8%.
Which counties border Worcester County?
Worcester County borders 10 counties: Franklin County, MA, Middlesex County, MA, Hampden County, MA, Hampshire County, MA, Windham County, CT, Providence County, RI, Norfolk County, MA, Hillsborough County, NH, Cheshire County, NH and Tolland County, CT.
Products
Worcester County, Products
Testing a home in Worcester County
In Worcester County, 33.5% of 46,440 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 23.8% pooled across Massachusetts. In Zone 1 the year-round level in Worcester County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
MonitorAEGTEST
HOUND-1011 rechargeable radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Worcester County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Worcester County
Explore
Worcester County, Bordering counties
Counties bordering Worcester County
Calculated by Radon411- Radon levels in Hillsborough County, NHEPA zone 2
34.4%at or above 4 pCi/L
Median 2.5 pCi/L · 5,528 tests · 0.9 points above Worcester County
- Radon levels in Windham County, CTEPA zone 2
33.7%at or above 4 pCi/L
Median 2.6 pCi/L · 1,340 tests · 0.2 points above Worcester County
- Radon levels in Tolland County, CTEPA zone 2
26.8%at or above 4 pCi/L
Median 2.2 pCi/L · 1,316 tests · 6.7 points below Worcester County
- Radon levels in Franklin County, MAEPA zone 2
22.3%at or above 4 pCi/L
Median 1.6 pCi/L · 802 tests · 11.2 points below Worcester County
- Radon levels in Middlesex County, MAEPA zone 1
22.0%at or above 4 pCi/L
Median 1.9 pCi/L · 75,220 tests · 11.5 points below Worcester County
- Radon levels in Norfolk County, MAEPA zone 2
21.2%at or above 4 pCi/L
Median 1.8 pCi/L · 39,205 tests · 12.3 points below Worcester County
- Radon levels in Cheshire County, NHEPA zone 2
20.4%at or above 4 pCi/L
Median 1.8 pCi/L · 952 tests · 13.1 points below Worcester County
- Radon levels in Hampshire County, MAEPA zone 2
18.8%at or above 4 pCi/L
Median 1.5 pCi/L · 2,457 tests · 14.7 points below Worcester County
- Radon levels in Providence County, RIEPA zone 2
16.8%at or above 4 pCi/L
Median 1.6 pCi/L · 17,655 tests · 16.7 points below Worcester County
- Radon levels in Hampden County, MAEPA zone 2
13.1%at or above 4 pCi/L
Median 1.3 pCi/L · 3,452 tests · 20.4 points below Worcester County
Worcester County, Cities and towns
Cities and towns in Worcester County
The Census Bureau estimates 888,502 residents in Worcester County for July 1, 2025, 31,474 more than in 2020 (+3.7%). That works out to 588 people per square mile of land. Its largest town, Worcester, has 213,862 residents, 24.1% of the total. Together its 5 incorporated places hold 38.2% of those residents; the other 61.8% live outside any of them. Testing is reported here more often than across the state: CDC's 46,440 reported tests for 2008 to 2017 come to 52.3 for every 1,000 residents (2025 estimate), against 32.7 for Massachusetts.
From Worcester to Southbridge Town, CDC publishes no figure by town: each reads Worcester County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Worcester | 213,862 | +5.6% | 24.1% |
| Leominster | 44,194 | +1.0% | 5.0% |
| Fitchburg | 42,136 | +1.2% | 4.7% |
| Gardner | 21,483 | +1.3% | 2.4% |
| Southbridge Town | 18,105 | +2.3% | 2.0% |
5 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Worcester County, Homes
Homes in Worcester County
Of Worcester County's 353,405 homes, 57% are detached houses, against 51% across Massachusetts; 17% are in buildings of five or more homes. Half of its homes were built before 1966, close to Massachusetts' 1963: 45% date from before 1960 and 14% from 2000 or later. 66% of occupied homes are lived in by their owner (Massachusetts: 63%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Worcester County | Massachusetts |
|---|---|---|
| Housing units | 353,405 | 3,014,657 |
| Detached houses | 57% | 51% |
| In buildings of 5 or more | 17% | 22% |
| Mobile homes | 1% | 1% |
| Built before 1960 | 45% | 47% |
| Built since 2000 | 14% | 14% |
| Middle year built | 1966 | 1963 |
| Owner-occupied | 66% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.