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Radon Levels in Cumberland County, Maine

EPA puts Cumberland County in Zone 1, its highest radon zone, and high results are common there: 43.5% of the 4,076 radon tests reported to CDC (2008 to 2017, laboratory totals) came back 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    43.5%

    5.9 pts above ME

    Cumberland
    43.5%
    Maine
    37.6%

    4,076 tests, 2008 to 2017

  • Median result

    3.2pCi/L

    Below action level

    Cumberland
    3.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    4,076

    Most tested in Maine

    Cumberland
    4,076

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Maine

    4 of 16

    Top quarter

    Cumberland
    43.5%
    York
    48.4%

    By share, of 16 with 30+ tests

Read a result for Cumberland County

Starts at Cumberland County's median, 3.2 pCi/L

3.2pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 3.2 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Cumberland County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Cumberland County, At a glance

Cumberland County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Cumberland County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

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 Cumberland County, 2008 to 2017, laboratory

Reported results by concentration band, Cumberland County, 2008 to 2017, laboratory
Under 2 pCi/L: 34%2 to 4 pCi/L: 22%4 pCi/L and above: 44%

Of 4,076 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Cumberland County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1,38834.1%
2 to 4 pCi/L91422.4%
4 pCi/L and above1,77443.5%
What these figures count

These are the 4,076 tests reported to CDC for Cumberland 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).

How to read these figures

Cumberland County, Compared

Cumberland County radon figures, compared

Calculated by Radon411

In Cumberland County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (1,774 of 4,076) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 7.8 points higher. Across 16 Maine counties pooled together, 37.6% of tests reached that level, so Cumberland County runs 5.9 points above its state.

Of 4 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 30.0% (Sagadahoc County) to 48.4% (York County). By share, Cumberland County is 4th of 16 Maine counties with 30 or more tests for the same period.

Half the tests came in under 3.2 pCi/L and half over it; the single highest reached 466.0 pCi/L. Below the action level, 1,388 tests (34.1%) came in under 2 pCi/L, against 41.4% statewide, and 914 tests (22.4%) fell between 2 and 4, against 21.0% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 43.5% share point the same way here. USGS geology rates 85% of the county's land high radon potential. CDC also counts 36 tests taken after mitigation in Cumberland County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Cumberland County went from 3,094 tests (2005 to 2014) to 4,076 (2008 to 2017), the share going from 43.9% to 43.5%.

Cumberland County against Maine, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Cumberland County
Cumberland County4,07643.5%3.2 pCi/LThis county
Maine, pooled16 counties, pooled11,82537.6%Not pooled−5.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−7.8 points
Piscataquis Countyhighest in the state4447.7%3.5 pCi/L+4.2 points
Penobscot Countylowest in the state1,49116.4%0.8 pCi/L−27.1 points
York County, MEborders it1,38948.4%3.7 pCi/L+4.9 points
Oxford County, MEborders it39243.1%3.3 pCi/L−0.4 points
Androscoggin County, MEborders it1,49736.9%2.8 pCi/L−6.6 points
Sagadahoc County, MEborders it28330.0%2.1 pCi/L−13.5 points
Where Cumberland County's reported results fell, 2008 to 2017, laboratory, beside Maine and the United States
ResultCumberland County testsCumberland County shareMaine shareU.S. shareAgainst Maine
Under 2 pCi/L1,38834.1%41.4%39.6%−7.3 points
2 to 4 pCi/L91422.4%21.0%24.7%+1.4 points
4 pCi/L and above1,77443.5%37.6%35.7%+5.9 points
Cumberland County ranked among the 16 Maine counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
York County1 of 161,38948.4%3.7 pCi/L
Piscataquis County2 of 164447.7%3.5 pCi/L
Aroostook County3 of 1660845.1%3.5 pCi/L
Cumberland County4 of 164,07643.5%3.2 pCi/L
Oxford County5 of 1639243.1%3.3 pCi/L
Hancock County6 of 1632739.1%2.6 pCi/L
Androscoggin County7 of 161,49736.9%2.8 pCi/L
Lincoln County8 of 1624635.8%2.5 pCi/L
Waldo County9 of 1620932.1%2.3 pCi/L
Kennebec County10 of 1669630.3%2.1 pCi/L
Sagadahoc County11 of 1628330.0%2.1 pCi/L
Cumberland County ten-year laboratory totals, against Maine's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMaine, pooledChange from the row before
2008 to 20174,07643.5%3.2 pCi/L466.0 pCi/L37.6%−0.8 points
2007 to 20163,86444.3%3.3 pCi/L466.0 pCi/L37.6%Level
2006 to 20153,54544.3%3.3 pCi/L466.0 pCi/L37.6%+0.4 points
2005 to 20143,09443.9%3.3 pCi/L466.0 pCi/L36.6%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Cumberland County, Geology

The ground under Cumberland County

Predicted

Most of the ground under Cumberland County is one class on USGS's geologic map: 85.5% of its land is high radon potential, with 10.1% low. The map puts 85.5% of Cumberland County in the area it calls Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal Province and 10.1% in Coastal Province. USGS gives the first a radon index of 14, in the high band (12 to 17), and the second 8, in the low band (5 to 8).

USGS's geologic areas under Cumberland County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal ProvinceGranite and high grade metamorphic rocks.High1485.5%
Coastal ProvinceGlacial lake clay and marine clay.Low810.1%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Cumberland County beside the ground around it

Cumberland County has more high-potential ground than Maine as a whole: 85.5% of its land against 24.5%. Of the 4 counties that border it, 1 has more high-potential ground, York County the most at 99.1%.

Share of land by USGS radon potential: Cumberland County, the 4 counties bordering it and Maine
AreaEPA zoneLow potentialModerate potentialHigh potential
Cumberland CountyZone 110.1%None85.5%
Androscoggin CountyZone 132.3%None67.7%
Sagadahoc CountyZone 275.4%None10.5%
York CountyZone 1None0.1%99.1%
Oxford CountyZone 1None14.9%85.1%
Maine16 counties, pooled by land areaVaries35.9%38.3%24.5%

The map rates the ground, not the air in any home.

Local help

Cumberland County, Local resources

Radon testing and mitigation in Cumberland County

What Maine's program says
Phone
207-287-5676
Email
radon.dhhs@maine.gov
Licensing of radon professionals
Under Maine law, only the owner or occupant of a residence or someone registered with the state to provide these services, may test for radon, install and/or advise on the installation of a radon reduction (mitigation) system.

What it means

Cumberland County, Questions

Questions about radon in Cumberland County

Are radon levels high in Cumberland County?

Over the 2008 to 2017 laboratory totals, 43.5% of the radon tests reported to CDC for Cumberland County, Maine were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.2 pCi/L. Of 16 Maine counties with 30 or more tests for the same period, 3 reported a higher share; pooled, the state comes to 37.6%.

Which counties border Cumberland County?

Cumberland County borders 4 counties: Androscoggin County, Sagadahoc County, York County and Oxford County.

Products

Cumberland County, Products

Testing a home in Cumberland County

In Cumberland County, 43.5% of 4,076 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 37.6% pooled across Maine. In Zone 1 the year-round level in Cumberland 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

Cumberland County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Cumberland County

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Cumberland County, Bordering counties

Counties bordering Cumberland County

Calculated by Radon411

Cumberland County, Cities and towns

Cities and towns in Cumberland County

The Census Bureau estimates 317,222 residents in Cumberland County for July 1, 2025, 13,634 more than in 2020 (+4.5%). That works out to 379 people per square mile of land. Its largest town, Portland, has 69,911 residents, 22.0% of the total. Together its 3 incorporated places hold 37.4% of those residents; the other 62.6% live outside any of them. Testing is reported here more often than across the state: CDC's 4,076 reported tests for 2008 to 2017 come to 12.8 for every 1,000 residents (2025 estimate), against 8.4 for Maine.

From Portland to Westbrook, CDC publishes no figure by town: each reads Cumberland County's.

The cities and towns in Cumberland County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Portland69,911+2.1%22.0%
South Portland27,007+1.6%8.5%
Westbrook21,565+5.5%6.8%

3 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).

Cumberland County, Homes

Homes in Cumberland County

Of Cumberland County's 151,519 homes, 64% are detached houses, against 70% across Maine; 14% are in buildings of five or more homes. Half of its homes were built before 1975, close to Maine's 1976: 36% date from before 1960 and 20% from 2000 or later. 70% of occupied homes are lived in by their owner (Maine: 74%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Cumberland County, Maine, 2019 to 2023
HomesCumberland CountyMaine
Housing units151,519746,552
Detached houses64%70%
In buildings of 5 or more14%9%
Mobile homes4%8%
Built before 196036%35%
Built since 200020%20%
Middle year built19751976
Owner-occupied70%74%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.