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Radon Levels in Morris County, New Jersey

EPA puts Morris County in Zone 1, its highest radon zone, and most reported tests there come back low, though 13.6% of 10,939 (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

    13.6%

    3.9 pts above NJ

    Morris
    13.6%
    New Jersey
    9.7%

    10,939 tests, 2022

  • Median result

    1.1pCi/L

    Below action level

    Morris
    1.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    10,939

    2nd of 21 by tests

    Morris
    10,939
    Bergen
    11,440

    Reported to CDC before any fix, 2022

  • 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 New Jersey

    5 of 21

    Top quarter

    Morris
    13.6%
    Warren
    24.6%

    By share, of 21 with 30+ tests

Read a result for Morris County

Starts at Morris County's median, 1.1 pCi/L

1.1pCi/L

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

EPA’s reading of 1.1 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. Morris County's median reported result, 2022.

Interpret this reading

The data

Morris County, At a glance

Morris County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Morris 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 78% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Morris County, 2022

Share of reported tests at or above 4 pCi/L, by year, Morris County
Share of reported tests at or above 4 pCi/L, by year, Morris County
YearShare of reported tests at or above 4 pCi/L
201417.5%
201517.5%
201617.8%
201716.4%
201815.7%
201915.6%
202015.4%
202114.5%
202213.6%

2022: 13.6%. Across these years the share ran from 13.6% to 17.8%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 10,939 tests reported to CDC for Morris 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

Morris County, Compared

Morris County radon figures, compared

Calculated by Radon411

13.6% of its 10,939 tests in 2022 were at or above 4 pCi/L. That is 3.9 points above the 9.7% pooled from 21 New Jersey counties.

Ordered from highest share down, it comes 5th 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%; Morris County sits 10.3 points below it.

Next door, the shares run from 4.1% in Essex County to 24.6% in Warren County, with Passaic County, Union County and Essex County below Morris County. The reported tests do not follow EPA's Zone 1 label for Morris County (predicted average above 4 pCi/L): 13.6% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 1.1 pCi/L and half over it; the single highest reached 308.3 pCi/L. The rest split 67.9% under 2 pCi/L and 18.5% from 2 to 4 (New Jersey: 74.9% and 15.4%). Year by year, 2014 opened at 17.5% and 2022 closed at 13.6% (down 3.9 points), with 2016 the high at 17.8%.

The busiest year on file was 2021, with 13,320 tests reported; the quietest, 2014, had 9,295.

Share of reported tests at or above 4 pCi/L by year, Morris County against New Jersey2014 to 2022, years with 30 or more tests: Morris County 17.5% to 13.6%, the state's pooled share 9.7% in 2022.
Morris CountyNew Jersey, pooled
Share of reported tests at or above 4 pCi/L by year, Morris County against New Jersey: data table
YearTestsMorris County, at or above 4 pCi/LNew Jersey, pooled
20149,29517.5%12.8%
20159,60717.5%12.5%
201610,33017.8%12.5%
201710,73216.4%11.9%
201810,74315.7%11.0%
201911,06515.6%11.2%
202012,53915.4%11.7%
202113,32014.5%10.3%
202210,93913.6%9.7%
Morris County against New Jersey, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Morris County
Morris County10,93913.6%1.1 pCi/LThis county
New Jersey, pooled21 counties, pooled108,9349.7%Not pooled−3.9 points
United States, pooled853 counties, pooled333,14023.9%Not pooled+10.3 points
Gloucester Countyhighest in the state3,33312.2%1.1 pCi/L−1.4 points
Cape May Countylowest in the state2460.0%0.3 pCi/L−13.6 points
Warren County, NJborders it2,81924.6%1.5 pCi/L+11.0 points
Sussex County, NJborders it4,11622.3%1.5 pCi/L+8.7 points
Hunterdon County, NJborders it3,74821.1%1.4 pCi/L+7.5 points
Somerset County, NJborders it7,67915.4%1.2 pCi/L+1.8 points
Passaic County, NJborders it4,8257.5%0.8 pCi/L−6.1 points
Union County, NJborders it6,1115.1%0.9 pCi/L−8.5 points
Essex County, NJborders it8,3414.1%0.7 pCi/L−9.5 points
Where Morris County's reported results fell, 2022, beside New Jersey and the United States
ResultMorris County testsMorris County shareNew Jersey shareU.S. shareAgainst New Jersey
Under 2 pCi/L7,42767.9%74.9%54.5%−7.0 points
2 to 4 pCi/L2,02318.5%15.4%21.7%+3.1 points
4 pCi/L and above1,48913.6%9.7%23.9%+3.9 points
Morris 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
Warren County1 of 212,81924.6%1.5 pCi/L
Sussex County2 of 214,11622.3%1.5 pCi/L
Hunterdon County3 of 213,74821.1%1.4 pCi/L
Somerset County4 of 217,67915.4%1.2 pCi/L
Morris County5 of 2110,93913.6%1.1 pCi/L
Gloucester County6 of 213,33312.2%1.1 pCi/L
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
Morris County radon tests by year, against New Jersey's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNew Jersey, pooledChange from the row before
202210,93913.6%1.1 pCi/L308.3 pCi/L9.7%−0.9 points
202113,32014.5%1.2 pCi/L139.1 pCi/L10.3%−0.9 points
202012,53915.4%1.3 pCi/L276.1 pCi/L11.7%−0.2 points
201911,06515.6%1.3 pCi/L148.4 pCi/L11.2%−0.1 points
201810,74315.7%1.3 pCi/L169.5 pCi/L11.0%−0.7 points
201710,73216.4%1.4 pCi/L273.3 pCi/L11.9%−1.4 points
201610,33017.8%1.5 pCi/L330.4 pCi/L12.5%+0.3 points
20159,60717.5%1.4 pCi/L247.0 pCi/L12.5%Level
20149,29517.5%1.4 pCi/L352.9 pCi/L12.8%First on file

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

Morris County, Geology

The ground under Morris County

Predicted

Most of the ground under Morris County is one class on USGS's geologic map: 78.2% of its land is high radon potential, with 21.8% low. The map puts 62.1% of Morris County in the area it calls Highlands and 21.8% in Northern Piedmont, with 2 smaller areas beside them. USGS gives the first a radon index of 15, in the high band (12 to 17), and the second 8, in the low band (5 to 8).

USGS's geologic areas under Morris County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
HighlandsGlacial deposits, granite, pegmatites, and gneiss.High1562.1%
Northern PiedmontSandstone, conglomerate, basalt, and shale.Low821.8%
Green Pond OutlierConglomerate, sandstone, shale, glacial depositsHigh158.2%
Southern PiedmontBlack shale, sandstone and siltstone.High148.0%

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

Morris County beside the ground around it

Morris County has more high-potential ground than New Jersey as a whole: 78.2% of its land against 29.8%. Of the 7 counties that border it, 4 have more high-potential ground, Hunterdon County the most at 100%.

Share of land by USGS radon potential: Morris County, the 7 counties bordering it and New Jersey
AreaEPA zoneLow potentialModerate potentialHigh potential
Morris CountyZone 121.8%None78.2%
Essex CountyZone 299.4%NoneNone
Passaic CountyZone 235.7%None64.3%
Sussex CountyZone 1None19.4%80.6%
Warren CountyZone 1None4.6%95.4%
Somerset CountyZone 1NoneNone100%
Union CountyZone 279.1%None19.5%
Hunterdon CountyZone 1NoneNone100%
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

Morris County, Local resources

Radon testing and mitigation in Morris 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

Morris County, Questions

Questions about radon in Morris County

Are radon levels high in Morris County?

In 2022, 13.6% of the radon tests reported to CDC for Morris County, New Jersey were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.1 pCi/L. Of 21 New Jersey counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 9.7%.

Which counties border Morris County?

Morris County borders 7 counties: Essex County, Passaic County, Sussex County, Warren County, Somerset County, Union County and Hunterdon County.

Products

Morris County, Products

Testing a home in Morris County

In Morris County, 13.6% of 10,939 tests reported to CDC in 2022 reached 4 pCi/L, against 9.7% pooled across New Jersey. In Zone 1 the year-round level in Morris 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

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

Explore

Morris County, Bordering counties

Counties bordering Morris County

Calculated by Radon411

Morris County, Cities and towns

Cities and towns in Morris County

The Census Bureau estimates 524,251 residents in Morris County for July 1, 2025, 16,040 more than in 2020 (+3.2%). Packed into its land, that is 1,137 people per square mile. No town dominates: Morristown, the largest, has 20,750 residents, 4.0% of the total. Together its 19 incorporated places hold 31.8% of those residents; the other 68.2% live outside any of them. Testing is reported here more often than across the state: CDC's 10,939 reported tests for 2022 come to 20.9 for every 1,000 residents (2025 estimate), against 11.4 for New Jersey.

From Morristown to Victory Gardens, CDC publishes no figure by town: each reads Morris County's.

The 12 largest cities and towns in Morris County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Morristown20,750+3.2%4.0%
Dover18,919+2.8%3.6%
Madison16,607−1.8%3.2%
Florham Park14,456+14.8%2.8%
Lincoln Park10,950+1.0%2.1%
Kinnelon10,138+1.7%1.9%
Chatham10,027+9.3%1.9%
Boonton8,920+1.4%1.7%
Butler8,184+2.2%1.6%
Wharton7,618+5.1%1.5%
Rockaway6,631+1.1%1.3%
Morris Plains6,586+7.5%1.3%
  • Mount Arlington
  • Mendham
  • Mountain Lakes
  • Riverdale
  • Netcong
  • Chester
  • Victory Gardens

19 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).

Morris County, Homes

Homes in Morris County

Of Morris County's 198,611 homes, 65% are detached houses, against 53% across New Jersey; 19% are in buildings of five or more homes. Half of its homes were built before 1971, close to New Jersey's 1969: 33% date from before 1960 and 13% from 2000 or later. 74% 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 Morris County, New Jersey, 2019 to 2023
HomesMorris CountyNew Jersey
Housing units198,6113,775,842
Detached houses65%53%
In buildings of 5 or more19%22%
Mobile homesunder 1%1%
Built before 196033%38%
Built since 200013%15%
Middle year built19711969
Owner-occupied74%64%

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