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Radon Levels in Middlesex County, New Jersey

EPA puts Middlesex County in Zone 2, its middle radon zone, and most reported tests there come back low, though 7.3% of 9,594 (2022) reached 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

    7.3%

    2.4 pts below NJ

    Middlesex
    7.3%
    New Jersey
    9.7%

    9,594 tests, 2022

  • Median result

    0.8pCi/L

    Below action level

    Middlesex
    0.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    9,594

    4th of 21 by tests

    Middlesex
    9,594
    Bergen
    11,440

    Reported to CDC before any fix, 2022

  • 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 New Jersey

    12 of 21

    Middle half

    Middlesex
    7.3%
    Warren
    24.6%

    By share, of 21 with 30+ tests

Read a result for Middlesex County

Starts at Middlesex County's median, 0.8 pCi/L

0.8pCi/L

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

EPA’s reading of 0.8 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. Middlesex County's median reported result, 2022.

Interpret this reading

The data

Middlesex County, At a glance

Middlesex County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Middlesex 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 63% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Middlesex County, 2022

Share of reported tests at or above 4 pCi/L, by year, Middlesex County
Share of reported tests at or above 4 pCi/L, by year, Middlesex County
YearShare of reported tests at or above 4 pCi/L
201410.2%
201510.7%
20169.5%
20179.4%
20188.1%
20198.7%
20209.2%
20218.0%
20227.3%

2022: 7.3%. Across these years the share ran from 7.3% to 10.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 9,594 tests reported to CDC for Middlesex County over 2022, 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: 2022. Measured data period: 2014 to 2022 (every CDC figure on file).

How to read these figures

Middlesex County, Compared

Middlesex County radon figures, compared

Calculated by Radon411

Middlesex County reports fewer high tests than New Jersey overall. 7.3% of its 9,594 tests in 2022 were at or above 4 pCi/L. That is 2.4 points below the 9.7% pooled from 21 New Jersey counties.

Ordered from highest share down, it comes 12th of 21 New Jersey counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 23.9%; Middlesex County sits 16.6 points below it.

Next door, the shares run from 5.1% in Union County to 15.4% in Somerset County, with Union County below Middlesex County. The reported tests do not follow EPA's Zone 2 label for Middlesex County (predicted average between 2 and 4 pCi/L): 7.3% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 0.8 pCi/L and half over it; the single highest reached 62.0 pCi/L. The rest split 78.8% under 2 pCi/L and 13.9% from 2 to 4 (New Jersey: 74.9% and 15.4%). Year by year, 2014 opened at 10.2% and 2022 closed at 7.3% (down 2.9 points), with 2015 the high at 10.7%.

The busiest year on file was 2020, with 10,933 tests reported; the quietest, 2014, had 7,489.

Share of reported tests at or above 4 pCi/L by year, Middlesex County against New Jersey2014 to 2022, years with 30 or more tests: Middlesex County 10.2% to 7.3%, the state's pooled share 9.7% in 2022.
Middlesex CountyNew Jersey, pooled
Share of reported tests at or above 4 pCi/L by year, Middlesex County against New Jersey: data table
YearTestsMiddlesex County, at or above 4 pCi/LNew Jersey, pooled
20147,48910.2%12.8%
20158,61010.7%12.5%
20168,7099.5%12.5%
20179,4539.4%11.9%
20189,6618.1%11.0%
20199,5378.7%11.2%
202010,9339.2%11.7%
202110,5298.0%10.3%
20229,5947.3%9.7%
Middlesex County against New Jersey, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Middlesex County
Middlesex County9,5947.3%0.8 pCi/LThis county
New Jersey, pooled21 counties, pooled108,9349.7%Not pooled+2.4 points
United States, pooled853 counties, pooled333,14023.9%Not pooled+16.6 points
Warren Countyhighest in the state2,81924.6%1.5 pCi/L+17.3 points
Cape May Countylowest in the state2460.0%0.3 pCi/L−7.3 points
Somerset County, NJborders it7,67915.4%1.2 pCi/L+8.1 points
Mercer County, NJborders it6,37010.6%0.9 pCi/L+3.3 points
Monmouth County, NJborders it9,7459.8%0.7 pCi/L+2.5 points
Union County, NJborders it6,1115.1%0.9 pCi/L−2.2 points
Where Middlesex County's reported results fell, 2022, beside New Jersey and the United States
ResultMiddlesex County testsMiddlesex County shareNew Jersey shareU.S. shareAgainst New Jersey
Under 2 pCi/L7,56378.8%74.9%54.5%+3.9 points
2 to 4 pCi/L1,33113.9%15.4%21.7%−1.5 points
4 pCi/L and above7007.3%9.7%23.9%−2.4 points
Middlesex County ranked among the 21 New Jersey counties with 30 or more tests, by share at or above 4 pCi/L, 2022
CountyRankTestsAt or above 4 pCi/LMedian
Salem County7 of 2145410.8%1.1 pCi/L
Mercer County8 of 216,37010.6%0.9 pCi/L
Monmouth County9 of 219,7459.8%0.7 pCi/L
Cumberland County10 of 217528.6%0.9 pCi/L
Passaic County11 of 214,8257.5%0.8 pCi/L
Middlesex County12 of 219,5947.3%0.8 pCi/L
Camden County13 of 216,7616.7%0.9 pCi/L
Burlington County14 of 215,3556.2%0.9 pCi/L
Bergen County15 of 2111,4406.1%1.0 pCi/L
Union County16 of 216,1115.1%0.9 pCi/L
Essex County17 of 218,3414.1%0.7 pCi/L
Middlesex County radon tests by year, against New Jersey's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNew Jersey, pooledChange from the row before
20229,5947.3%0.8 pCi/L62.0 pCi/L9.7%−0.7 points
202110,5298.0%0.9 pCi/L147.7 pCi/L10.3%−1.2 points
202010,9339.2%0.9 pCi/L80.4 pCi/L11.7%+0.5 points
20199,5378.7%1.1 pCi/L47.6 pCi/L11.2%+0.6 points
20189,6618.1%0.9 pCi/L54.1 pCi/L11.0%−1.3 points
20179,4539.4%1.0 pCi/L101.4 pCi/L11.9%−0.1 points
20168,7099.5%1.1 pCi/L52.8 pCi/L12.5%−1.2 points
20158,61010.7%1.0 pCi/L40.3 pCi/L12.5%+0.5 points
20147,48910.2%1.0 pCi/L49.3 pCi/L12.8%First on file

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

Middlesex County, Geology

The ground under Middlesex County

Predicted

USGS's geologic map splits Middlesex County: 63.3% of its land is moderate radon potential and 26.1% high and 9.1% low. The map puts 63.3% of Middlesex County in the area it calls Inner Coastal Plain and 26.1% in Southern Piedmont, with one smaller area beside them. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Middlesex County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Inner Coastal PlainCretaceous-Lower Tertiary gravel, sand, silt, clay.Moderate1063.3%
Southern PiedmontBlack shale, sandstone and siltstone.High1426.1%
Northern PiedmontSandstone, conglomerate, basalt, and shale.Low89.1%

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

Middlesex County beside the ground around it

On high-potential ground Middlesex County is close to New Jersey as a whole: 26.1% of its land against 29.8%. Of the 5 counties that border it, 2 have more high-potential ground, Somerset County the most at 100%.

Share of land by USGS radon potential: Middlesex County, the 5 counties bordering it and New Jersey
AreaEPA zoneLow potentialModerate potentialHigh potential
Middlesex CountyZone 29.1%63.3%26.1%
Monmouth CountyZone 160.3%36.5%None
Somerset CountyZone 1NoneNone100%
Richmond County, NYZone 392.4%0.2%None
Union CountyZone 279.1%None19.5%
Mercer CountyZone 1None49.5%50.5%
New Jersey21 counties, pooled by land areaVaries53.8%13.8%29.8%

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

Local help

Middlesex County, Local resources

Radon testing and mitigation in Middlesex County

What New Jersey's program says
Phone
800-648-0394
Licensing of radon professionals
By law, all businesses and professionals conducting radon testing and mitigation in New Jersey must be certified by the DEP.
Disclosure when a home is sold or rented
Under the law, the seller must provide the buyer, at the time the contract of sale is entered into, with a copy of the results of the radon test and evidence of any mitigation or treatment.

What it means

Middlesex County, Questions

Questions about radon in Middlesex County

Are radon levels high in Middlesex County?

In 2022, 7.3% of the radon tests reported to CDC for Middlesex County, New Jersey were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.8 pCi/L. Of 21 New Jersey counties with 30 or more tests for the same period, 11 reported a higher share; pooled, the state comes to 9.7%.

Which counties border Middlesex County?

Middlesex County borders 5 counties: Monmouth County, NJ, Somerset County, NJ, Richmond County, NY, Union County, NJ and Mercer County, NJ.

Products

Middlesex County, Products

Testing a home in Middlesex County

In Middlesex County, 7.3% of 9,594 tests reported to CDC in 2022 reached 4 pCi/L, against 9.7% pooled across New Jersey. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Middlesex County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Middlesex County homes, compared

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Middlesex County, Bordering counties

Counties bordering Middlesex County

Calculated by Radon411

Middlesex County, Cities and towns

Cities and towns in Middlesex County

The Census Bureau estimates 883,335 residents in Middlesex County for July 1, 2025, 22,087 more than in 2020 (+2.6%). Packed into its land, that is 2,857 people per square mile. No town dominates: New Brunswick, the largest, has 57,133 residents, 6.5% of the total. Together its 15 incorporated places hold 35.7% of those residents; the other 64.3% live outside any of them. CDC's 9,594 reported tests for 2022 work out to 10.9 per 1,000 residents (2025 estimate), close to New Jersey's 11.4.

From New Brunswick to Helmetta, CDC publishes no figure by town: each reads Middlesex County's.

The 12 largest cities and towns in Middlesex County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
New Brunswick57,133+3.3%6.5%
Perth Amboy56,739+2.5%6.4%
Sayreville46,787+3.4%5.3%
Carteret25,781+1.9%2.9%
South Plainfield24,891+2.5%2.8%
South River16,262+1.2%1.8%
Metuchen15,363+2.1%1.7%
Highland Park15,259+1.5%1.7%
Middlesex14,740+1.0%1.7%
South Amboy10,403+11.4%1.2%
Dunellen8,337+9.5%0.9%
Spotswood8,236+1.4%0.9%
  • Milltown
  • Jamesburg
  • Helmetta

15 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).

Middlesex County, Homes

Homes in Middlesex County

Fewer than six in ten of Middlesex County's 316,633 homes are detached houses (53%, against 53% across New Jersey); the rest are attached, in shared buildings or mobile. Half of its homes were built before 1973, close to New Jersey's 1969: 32% date from before 1960 and 16% from 2000 or later. 63% of occupied homes are lived in by their owner (New Jersey: 64%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Middlesex County, New Jersey, 2019 to 2023
HomesMiddlesex CountyNew Jersey
Housing units316,6333,775,842
Detached houses53%53%
In buildings of 5 or more24%22%
Mobile homes1%1%
Built before 196032%38%
Built since 200016%15%
Middle year built19731969
Owner-occupied63%64%

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