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Radon Levels in Union County, New Jersey

EPA puts Union County in Zone 2, its middle radon zone, and most reported tests there come back low, though 5.1% of 6,111 (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

    5.1%

    4.6 pts below NJ

    Union
    5.1%
    New Jersey
    9.7%

    6,111 tests, 2022

  • Median result

    0.9pCi/L

    Below action level

    Union
    0.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    6,111

    9th of 21 by tests

    Union
    6,111
    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

    16 of 21

    Middle half

    Union
    5.1%
    Warren
    24.6%

    By share, of 21 with 30+ tests

Read a result for Union County

Starts at Union County's median, 0.9 pCi/L

0.9pCi/L

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

EPA’s reading of 0.9 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. Union County's median reported result, 2022.

Interpret this reading

The data

Union County, At a glance

Union County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Union 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: Low across 79% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Union County, 2022

Share of reported tests at or above 4 pCi/L, by year, Union County
Share of reported tests at or above 4 pCi/L, by year, Union County
YearShare of reported tests at or above 4 pCi/L
20147.6%
20157.3%
20167.0%
20176.1%
20186.4%
20196.2%
20207.3%
20215.2%
20225.1%

2022: 5.1%. Across these years the share ran from 5.1% to 7.6%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 6,111 tests reported to CDC for Union 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

Union County, Compared

Union County radon figures, compared

Calculated by Radon411

Union County reports fewer high tests than New Jersey overall. 5.1% of its 6,111 tests in 2022 were at or above 4 pCi/L. That is 4.6 points below the 9.7% pooled from 21 New Jersey counties.

Ordered from highest share down, it comes 16th 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%; Union County sits 18.8 points below it.

Next door, the shares run from 3.4% in Hudson County to 15.4% in Somerset County, with Essex County and Hudson County below Union County. The reported tests do not follow EPA's Zone 2 label for Union County (predicted average between 2 and 4 pCi/L): 5.1% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 0.9 pCi/L and half over it; the single highest reached 38.4 pCi/L. The rest split 80.2% under 2 pCi/L and 14.7% from 2 to 4 (New Jersey: 74.9% and 15.4%). Year by year, 2014 opened at 7.6% and 2022 closed at 5.1% (down 2.5 points), with 2014 the high at 7.6%.

The busiest year on file was 2021, with 8,264 tests reported; the quietest, 2014, had 4,886.

Share of reported tests at or above 4 pCi/L by year, Union County against New Jersey2014 to 2022, years with 30 or more tests: Union County 7.6% to 5.1%, the state's pooled share 9.7% in 2022.
Union CountyNew Jersey, pooled
Share of reported tests at or above 4 pCi/L by year, Union County against New Jersey: data table
YearTestsUnion County, at or above 4 pCi/LNew Jersey, pooled
20144,8867.6%12.8%
20155,5617.3%12.5%
20166,3367.0%12.5%
20176,9436.1%11.9%
20186,7706.4%11.0%
20196,8886.2%11.2%
20208,0887.3%11.7%
20218,2645.2%10.3%
20226,1115.1%9.7%
Union County against New Jersey, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Union County
Union County6,1115.1%0.9 pCi/LThis county
New Jersey, pooled21 counties, pooled108,9349.7%Not pooled+4.6 points
United States, pooled853 counties, pooled333,14023.9%Not pooled+18.8 points
Warren Countyhighest in the state2,81924.6%1.5 pCi/L+19.5 points
Cape May Countylowest in the state2460.0%0.3 pCi/L−5.1 points
Somerset County, NJborders it7,67915.4%1.2 pCi/L+10.3 points
Morris County, NJborders it10,93913.6%1.1 pCi/L+8.5 points
Middlesex County, NJborders it9,5947.3%0.8 pCi/L+2.2 points
Essex County, NJborders it8,3414.1%0.7 pCi/L−1.0 points
Hudson County, NJborders it2,6553.4%0.5 pCi/L−1.7 points
Where Union County's reported results fell, 2022, beside New Jersey and the United States
ResultUnion County testsUnion County shareNew Jersey shareU.S. shareAgainst New Jersey
Under 2 pCi/L4,90280.2%74.9%54.5%+5.3 points
2 to 4 pCi/L89914.7%15.4%21.7%−0.7 points
4 pCi/L and above3105.1%9.7%23.9%−4.6 points
Union 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
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
Hudson County18 of 212,6553.4%0.5 pCi/L
Atlantic County19 of 211,0472.1%0.3 pCi/L
Ocean County20 of 212,6041.8%0.5 pCi/L
Cape May County21 of 212460.0%0.3 pCi/L
Union County radon tests by year, against New Jersey's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNew Jersey, pooledChange from the row before
20226,1115.1%0.9 pCi/L38.4 pCi/L9.7%−0.1 points
20218,2645.2%0.9 pCi/L36.6 pCi/L10.3%−2.1 points
20208,0887.3%0.9 pCi/L62.0 pCi/L11.7%+1.1 points
20196,8886.2%1.1 pCi/L68.7 pCi/L11.2%−0.2 points
20186,7706.4%0.8 pCi/L80.3 pCi/L11.0%+0.3 points
20176,9436.1%0.9 pCi/L27.5 pCi/L11.9%−0.9 points
20166,3367.0%1.0 pCi/L67.2 pCi/L12.5%−0.3 points
20155,5617.3%1.0 pCi/L43.6 pCi/L12.5%−0.3 points
20144,8867.6%1.1 pCi/L40.1 pCi/L12.8%First on file

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

Union County, Geology

The ground under Union County

Predicted

Most of the ground under Union County is one class on USGS's geologic map: 79.1% of its land is low radon potential, with 19.5% high. The map puts 79.1% of Union County in the area it calls Northern Piedmont and 19.5% in Southern Piedmont. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Union County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern PiedmontSandstone, conglomerate, basalt, and shale.Low879.1%
Southern PiedmontBlack shale, sandstone and siltstone.High1419.5%

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

Union County beside the ground around it

New Jersey as a whole has more high-potential ground than Union County: 29.8% of its land, against 19.5% here. Of the 6 counties that border it, 3 have more high-potential ground, Somerset County the most at 100%.

Share of land by USGS radon potential: Union County, the 6 counties bordering it and New Jersey
AreaEPA zoneLow potentialModerate potentialHigh potential
Union CountyZone 279.1%None19.5%
Essex CountyZone 299.4%NoneNone
Richmond County, NYZone 392.4%0.2%None
Hudson CountyZone 288.6%0.1%None
Middlesex CountyZone 29.1%63.3%26.1%
Somerset CountyZone 1NoneNone100%
Morris CountyZone 121.8%None78.2%
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

Union County, Local resources

Radon testing and mitigation in Union 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

Union County, Questions

Questions about radon in Union County

Are radon levels high in Union County?

In 2022, 5.1% of the radon tests reported to CDC for Union County, New Jersey were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of 21 New Jersey counties with 30 or more tests for the same period, 15 reported a higher share; pooled, the state comes to 9.7%.

Which counties border Union County?

Union County borders 6 counties: Essex County, NJ, Richmond County, NY, Hudson County, NJ, Middlesex County, NJ, Somerset County, NJ and Morris County, NJ.

Products

Union County, Products

Testing a home in Union County

In Union County, 5.1% of 6,111 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 Union County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Union County homes, compared

Explore

Union County, Bordering counties

Counties bordering Union County

Calculated by Radon411

Union County, Cities and towns

Cities and towns in Union County

The Census Bureau estimates 601,863 residents in Union County for July 1, 2025, 28,381 more than in 2020 (+4.9%). Packed into its land, that is 5,857 people per square mile. Its largest town, Elizabeth, has 141,675 residents, 23.5% of the total. Together its 13 incorporated places hold 68.8% of those residents; the other 31.2% live outside any of them. CDC's 6,111 reported tests for 2022 work out to 10.2 per 1,000 residents (2025 estimate), close to New Jersey's 11.4.

From Elizabeth to Garwood, CDC publishes no figure by town: each reads Union County's.

The 12 largest cities and towns in Union County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Elizabeth141,675+3.7%23.5%
Plainfield57,141+5.2%9.5%
Linden45,752+5.1%7.6%
Westfield32,595+5.5%5.4%
Rahway31,010+4.5%5.2%
Summit23,314+3.0%3.9%
Roselle23,261+2.9%3.9%
Roselle Park15,603+11.5%2.6%
New Providence14,092+2.6%2.3%
Kenilworth8,602+2.5%1.4%
Fanwood8,035+3.8%1.3%
Mountainside7,346+4.8%1.2%
  • Garwood

13 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).

Union County, Homes

Homes in Union County

Fewer than six in ten of Union County's 211,269 homes are detached houses (50%, against 53% across New Jersey); the rest are attached, in shared buildings or mobile. The homes are older than New Jersey's as a whole: half were built before 1956 (1969 for New Jersey), and 59% date from before 1960. 58% 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 Union County, New Jersey, 2019 to 2023
HomesUnion CountyNew Jersey
Housing units211,2693,775,842
Detached houses50%53%
In buildings of 5 or more20%22%
Mobile homesunder 1%1%
Built before 196059%38%
Built since 200011%15%
Middle year built19561969
Owner-occupied58%64%

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