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Radon Levels in Nantucket County, Massachusetts

EPA puts Nantucket County in Zone 2, its middle radon zone, and most reported tests there come back low, though 5.0% of 40 (2008 to 2017, laboratory totals) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    5.0%

    18.8 pts below MA

    Nantucket
    5.0%
    MA
    23.8%

    40 tests, 2008 to 2017

  • Median result

    1.8pCi/L

    Below action level

    Nantucket
    1.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    40

    14th of 14 by tests

    Nantucket
    40
    Middlesex
    75,220

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in MA

    14 of 14

    Lowest quarter

    Nantucket
    5.0%
    Worcester
    33.5%

    By share, of 14 with 30+ tests

Read a result for Nantucket County

Starts at Nantucket County's median, 1.8 pCi/L

1.8pCi/L

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

EPA’s reading of 1.8 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Nantucket County's median reported result, 2008 to 2017.

Interpret this reading

The data

Nantucket County, At a glance

Nantucket County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Nantucket County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 85% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Nantucket County, 2008 to 2017, laboratory
Under 2 pCi/L: 57%2 to 4 pCi/L: 38%4 pCi/L and above: 5%

Of 40 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Nantucket County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L2357.5%
2 to 4 pCi/L1537.5%
4 pCi/L and above25.0%
What these figures count

These are the 40 tests reported to CDC for Nantucket 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

Nantucket County, Compared

Nantucket County radon figures, compared

Calculated by Radon411

Nantucket County reports fewer high tests than Massachusetts overall. 5.0% of its 40 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 18.8 points below the 23.8% pooled from 14 Massachusetts counties.

Ordered from highest share down, it comes 14th of 14 Massachusetts counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Nantucket County sits 30.7 points below it.

The reported tests do not follow EPA's Zone 2 label for Nantucket County (predicted average between 2 and 4 pCi/L): 5.0% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 1.8 pCi/L and half over it; the single highest reached 7.3 pCi/L. The rest split 57.5% under 2 pCi/L and 37.5% from 2 to 4 (Massachusetts: 49.6% and 26.6%).

CDC's ten-year totals for Nantucket County went from 22 tests (2005 to 2014) to 40 (2008 to 2017), the share going from 9.1% to 5.0%.

Nantucket County against Massachusetts, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Nantucket County
Nantucket County405.0%1.8 pCi/LThis county
Massachusetts, pooled14 counties, pooled234,15223.8%Not pooled+18.8 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+30.7 points
Worcester Countyhighest in the state46,44033.5%2.6 pCi/L+28.5 points
Suffolk Countylowest in the state8,52510.4%1.3 pCi/L+5.4 points
Where Nantucket County's reported results fell, 2008 to 2017, laboratory, beside Massachusetts and the United States
ResultNantucket County testsNantucket County shareMassachusetts shareU.S. shareAgainst Massachusetts
Under 2 pCi/L2357.5%49.6%39.6%+7.9 points
2 to 4 pCi/L1537.5%26.6%24.7%+10.9 points
4 pCi/L and above25.0%23.8%35.7%−18.8 points
Nantucket County ranked among the 14 Massachusetts counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Bristol County4 of 1413,35823.2%2.0 pCi/L
Franklin County5 of 1480222.3%1.6 pCi/L
Middlesex County6 of 1475,22022.0%1.9 pCi/L
Norfolk County7 of 1439,20521.2%1.8 pCi/L
Barnstable County8 of 146,52120.6%2.0 pCi/L
Hampshire County9 of 142,45718.8%1.5 pCi/L
Dukes County10 of 1431717.4%1.7 pCi/L
Plymouth County11 of 1416,32017.0%1.7 pCi/L
Hampden County12 of 143,45213.1%1.3 pCi/L
Suffolk County13 of 148,52510.4%1.3 pCi/L
Nantucket County14 of 14405.0%1.8 pCi/L
Nantucket County ten-year laboratory totals, against Massachusetts' pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMassachusetts, pooledChange from the row before
2008 to 2017405.0%1.8 pCi/L7.3 pCi/L23.8%Level
2007 to 2016405.0%1.8 pCi/L7.3 pCi/L23.6%−0.6 points
2006 to 2015365.6%1.8 pCi/L7.3 pCi/L23.4%−3.5 points
2005 to 2014229.1%2.0 pCi/L7.3 pCi/L23.0%First on file

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

Nantucket County, Geology

The ground under Nantucket County

Predicted

USGS's geologic map puts all of Nantucket County's mapped land in one class: moderate radon potential. 85.3% of it lies in the area the map calls Coastal Plain (Nantucket), to which USGS gives a radon index of 11, in the moderate band (9 to 11).

USGS's geologic areas under Nantucket County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Coastal Plain (Nantucket)Cretaceous and Tertiary coastal and marine sediments and Quaternary glacial outwash.Moderate1185.3%

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

Nantucket County beside the ground around it

Across Massachusetts 31.9% of the land is rated high; none of Nantucket County's is.

Share of land by USGS radon potential: Nantucket County and Massachusetts
AreaEPA zoneLow potentialModerate potentialHigh potential
Nantucket CountyZone 2None85.3%None
Massachusetts14 counties, pooled by land areaVaries8.7%57.9%31.9%

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

Local help

Nantucket County, Local resources

Radon testing and mitigation in Nantucket County

What Massachusetts's program says
Phone
(800) 723-6695
Email
DPHIAQ.radon@mass.gov

What it means

Nantucket County, Questions

Questions about radon in Nantucket County

Are radon levels high in Nantucket County?

Over the 2008 to 2017 laboratory totals, 5.0% of the radon tests reported to CDC for Nantucket County, Massachusetts were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. Of 14 Massachusetts counties with 30 or more tests for the same period, 13 reported a higher share; pooled, the state comes to 23.8%.

Which counties border Nantucket County?

No county is recorded as sharing a land boundary with Nantucket County.

Products

Nantucket County, Products

Testing a home in Nantucket County

In Nantucket County, 5.0% of 40 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 23.8% pooled across Massachusetts. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Nantucket County; a long-term test tells the year-round average.

Test kits and monitors3

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Best radon monitors for Nantucket County homes, compared

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Nantucket County, Bordering counties

Counties bordering Nantucket County

Calculated by Radon411

No bordering counties on file

Nantucket County has no county recorded as sharing a land boundary with it. Island and coastal county equivalents legitimately have none.

Nantucket County, Residents

Who lives in Nantucket County

The Census Bureau estimates 14,758 residents in Nantucket County for July 1, 2025, 518 more than in 2020 (+3.6%). That works out to 319 people per square mile of land. Reported testing is thin here: 40 tests over 2008 to 2017, or 2.7 for every 1,000 residents (2025 estimate), where Massachusetts as a whole comes to 32.7.

Census lists no incorporated place in Nantucket County: every home in it reads the county's figures.

Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Nantucket County, Homes

Homes in Nantucket County

Nantucket County is a place of houses on their own lots: 84% of its 12,449 homes are detached single-family houses, against 51% across Massachusetts. Much of Nantucket County is recent building: 21% of its homes have gone up since 2000 and the middle year built is 1983, against 1963 for Massachusetts. Owners live in 76% of the occupied homes (Massachusetts: 63%), so for most households a test and a fix are their own to order.

Homes in Nantucket County, Massachusetts, 2019 to 2023
HomesNantucket CountyMassachusetts
Housing units12,4493,014,657
Detached houses84%51%
In buildings of 5 or more2%22%
Mobile homesunder 1%1%
Built before 196024%47%
Built since 200021%14%
Middle year built19831963
Owner-occupied76%63%

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