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Radon Levels in Aroostook County, Maine

EPA puts Aroostook County in Zone 1, its highest radon zone, and high results are common there: 45.1% of the 608 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

    45.1%

    7.5 pts above ME

    Aroostook
    45.1%
    Maine
    37.6%

    608 tests, 2008 to 2017

  • Median result

    3.5pCi/L

    Below action level

    Aroostook
    3.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    608

    6th of 16 by tests

    Aroostook
    608
    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

    3 of 16

    Top quarter

    Aroostook
    45.1%
    York
    48.4%

    By share, of 16 with 30+ tests

Read a result for Aroostook County

Starts at Aroostook County's median, 3.5 pCi/L

3.5pCi/L

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

EPA’s reading of 3.5 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. Aroostook County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Aroostook County, At a glance

Aroostook County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Aroostook 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: Low across 64% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Aroostook County, 2008 to 2017, laboratory

Reported results by concentration band, Aroostook County, 2008 to 2017, laboratory
Under 2 pCi/L: 36%2 to 4 pCi/L: 19%4 pCi/L and above: 45%

Of 608 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Aroostook County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L22136.3%
2 to 4 pCi/L11318.6%
4 pCi/L and above27445.1%
What these figures count

These are the 608 tests reported to CDC for Aroostook 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

Aroostook County, Compared

Aroostook County radon figures, compared

Calculated by Radon411

In Aroostook County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (274 of 608) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 9.4 points higher. Across 16 Maine counties pooled together, 37.6% of tests reached that level, so Aroostook County runs 7.5 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 16.4% (Penobscot County) to 47.7% (Piscataquis County). By share, Aroostook County is 3rd of 16 Maine counties with 30 or more tests for the same period.

Half the tests came in under 3.5 pCi/L and half over it; the single highest reached 124.3 pCi/L. Below the action level, 221 tests (36.3%) came in under 2 pCi/L, against 41.4% statewide, and 113 tests (18.6%) fell between 2 and 4, against 21.0% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 45.1% share point the same way here. USGS geology rates 64% of the county's land low radon potential.

CDC's ten-year totals for Aroostook County went from 430 tests (2005 to 2014) to 608 (2008 to 2017), the share going from 41.6% to 45.1%.

Aroostook County against Maine, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Aroostook County
Aroostook County60845.1%3.5 pCi/LThis county
Maine, pooled16 counties, pooled11,82537.6%Not pooled−7.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−9.4 points
York Countyhighest in the state1,38948.4%3.7 pCi/L+3.3 points
Franklin Countylowest in the state14129.1%1.8 pCi/L−16.0 points
Piscataquis County, MEborders it4447.7%3.5 pCi/L+2.6 points
Washington County, MEborders it5429.6%1.6 pCi/L−15.5 points
Somerset County, MEborders it8518.8%1.5 pCi/L−26.3 points
Penobscot County, MEborders it1,49116.4%0.8 pCi/L−28.7 points
Where Aroostook County's reported results fell, 2008 to 2017, laboratory, beside Maine and the United States
ResultAroostook County testsAroostook County shareMaine shareU.S. shareAgainst Maine
Under 2 pCi/L22136.3%41.4%39.6%−5.1 points
2 to 4 pCi/L11318.6%21.0%24.7%−2.4 points
4 pCi/L and above27445.1%37.6%35.7%+7.5 points
Aroostook 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
Aroostook County ten-year laboratory totals, against Maine's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMaine, pooledChange from the row before
2008 to 201760845.1%3.5 pCi/L124.3 pCi/L37.6%+0.9 points
2007 to 201656144.2%3.5 pCi/L124.3 pCi/L37.6%+0.5 points
2006 to 201551743.7%3.4 pCi/L124.3 pCi/L37.6%+2.1 points
2005 to 201443041.6%3.1 pCi/L124.3 pCi/L36.6%First on file

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

Aroostook County, Geology

The ground under Aroostook County

Predicted

USGS's geologic map splits Aroostook County: 63.8% of its land is low radon potential and 10.4% high and 25.7% moderate. The map puts 63.8% of Aroostook County in the area it calls Northern Maine Lowlands and 20.7% in Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal Province, with 2 smaller areas beside them. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 11, in the moderate band (9 to 11).

USGS's geologic areas under Aroostook County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern Maine LowlandsClastic and carbonate sedimentary rocks.Low863.8%
Moose River Lowlands/Central Maine Lowlands/Central Maine Highlands/Coastal ProvinceHeterogeneous metamorphic and igneous rocks.Moderate1120.7%
Northern Maine LowlandsMetasedimentary, predominantly carbonate, rocks.High1210.4%
Northern Maine LowlandsHeterogeneous metamorphic and igneous rocks.Moderate115.0%

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

Aroostook County beside the ground around it

Maine as a whole has more high-potential ground than Aroostook County: 24.5% of its land, against 10.4% here. Of the 4 counties that border it, 1 has more high-potential ground, Washington County the most at 19.3%.

Share of land by USGS radon potential: Aroostook County, the 4 counties bordering it and Maine
AreaEPA zoneLow potentialModerate potentialHigh potential
Aroostook CountyZone 163.8%25.7%10.4%
Piscataquis CountyZone 152.5%37.3%10.2%
Penobscot CountyZone 129.7%66.2%4.0%
Washington CountyZone 230.8%45.5%19.3%
Somerset CountyZone 145.6%52.3%2.1%
Maine16 counties, pooled by land areaVaries35.9%38.3%24.5%

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

Local help

Aroostook County, Local resources

Radon testing and mitigation in Aroostook 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

Aroostook County, Questions

Questions about radon in Aroostook County

Are radon levels high in Aroostook County?

Over the 2008 to 2017 laboratory totals, 45.1% of the radon tests reported to CDC for Aroostook County, Maine were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.5 pCi/L. Of 16 Maine counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 37.6%.

Which counties border Aroostook County?

Aroostook County borders 4 counties: Piscataquis County, Penobscot County, Washington County and Somerset County.

Products

Aroostook County, Products

Testing a home in Aroostook County

In Aroostook County, 45.1% of 608 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 Aroostook 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

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

Explore

Aroostook County, Bordering counties

Counties bordering Aroostook County

Calculated by Radon411

Aroostook County, Cities and towns

Cities and towns in Aroostook County

About 66,609 people live in Aroostook County by the Census Bureau's estimate for July 1, 2025, 442 fewer than in 2020 (−0.7%). Spread over its land, that is 10.0 people to the square mile. No town dominates: Presque Isle, the largest, has 8,694 residents, 13.1% of the total. Together its 2 incorporated places hold 24.0% of those residents; the other 76.0% live outside any of them. CDC's 608 reported tests for 2008 to 2017 work out to 9.1 per 1,000 residents (2025 estimate), close to Maine's 8.4.

From Presque Isle to Caribou, CDC publishes no figure by town: each reads Aroostook County's.

The cities and towns in Aroostook County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Presque Isle8,694−0.9%13.1%
Caribou7,321−1.1%11.0%

2 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).

Aroostook County, Homes

Homes in Aroostook County

Of Aroostook County's 38,444 homes, 74% are detached houses, against 70% across Maine; 9% are mobile homes. Half of its homes were built before 1971, close to Maine's 1976: 39% date from before 1960 and 14% from 2000 or later. 74% 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 Aroostook County, Maine, 2019 to 2023
HomesAroostook CountyMaine
Housing units38,444746,552
Detached houses74%70%
In buildings of 5 or more7%9%
Mobile homes9%8%
Built before 196039%35%
Built since 200014%20%
Middle year built19711976
Owner-occupied74%74%

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