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Radon Levels in New Castle County, Delaware

Zone 2Moderate predicted potential451 square miles · 7 bordering counties

What this means for you

  • Your area: EPA rates New Castle County Zone 2, the middle of its three radon zones. That is a prediction for the whole county, and homes with elevated levels occur in all three zones.
  • Local tests: Of 10,247 radon tests reported to CDC for New Castle County (2008 to 2017), 17.0% were at or above 4 pCi/L, EPA's action level.
  • Your home: The only way to know your home’s level is to test it.

pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.

Over the 2008 to 2017 laboratory totals, 17.0% of the radon tests reported to CDC for New Castle County, Delaware came back at or above the EPA action level of 4 pCi/L, and the median result was 1.8 pCi/L. EPA's Map of Radon Zones places the county in Zone 2, moderate predicted potential. Radon levels vary from home to home, so only a test measures the level in yours.

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

EPA predicts an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³) across the county as a whole.

This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.

USGS geologic potential: Moderate across 64% of the county's land area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for New Castle County, 2008 to 2017, laboratory

Tests reported
10,247
At or above 4 pCi/L
17.0%
Median result
1.8 pCi/L
Reported results by concentration band, New Castle County, 2008 to 2017, laboratory
Under 2 pCi/L: 54%2 to 4 pCi/L: 29%4 pCi/L and above: 17%

Of 10,247 pre-mitigation tests reported to CDC, not homes in this area. CDC publishes the share in each band, not a count per band, so the per-band counts in the table are calculated by Radon411 and rounded to add up to the published total.

Reported results by concentration band, New Castle County, 2008 to 2017, laboratory: data table
Result bandTests Calculated by Radon411Share Measured
Under 2 pCi/L5,55454.2%
2 to 4 pCi/L2,95128.8%
4 pCi/L and above1,74217.0%

Distribution of tested buildings, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

New Castle County, In figures

New Castle County in figures

What the published data says about New Castle County, in words. A zone and a share of tests describe an area, never the level in any one home.

    • Predicted

      Predicted

      EPA places New Castle County in Zone 2, moderate predicted potential, as it does 0 other counties of Delaware's 3.

      Of the 7 bordering counties, EPA places Chester County and Delaware County in Zone 1, Cecil County, Gloucester County and Salem County in Zone 2 and Kent County and Kent County in Zone 3.

  • Reported tests

    Measured

    CDC publishes no annual figure for New Castle County; its figure is a laboratory total for 2008 to 2017: 17.0% of 10,247 reported tests were at or above 4 pCi/L.

  • Local record

    Delaware's radon program is the Delaware Division of Public Health Radon Office, run by Delaware Division of Public Health; its contacts are under Local resources.

    The county's largest incorporated places are Wilmington, Newark and Middletown; the figures here cover them as part of the county.

New Castle County, Comparison

How New Castle County compares

Measured

New Castle County's own published CDC figures beside those of the counties that border it, for the same period.

Share of reported tests at or above 4 pCi/L

Measured

2008 to 2017, laboratory, highest first. Each county’s own published CDC figure.

  1. Kent CountyMD57 tests52.6%
  2. Chester CountyPA12,912 tests29.3%
  3. Cecil CountyMD1,071 tests24.9%
  4. Delaware CountyPA9,005 tests21.0%
  5. New Castle CountyThis page10,247 tests17.0%
  6. Kent CountyDE1,516 tests16.9%

Median reported result

Measured

2008 to 2017, laboratory, highest first. Each county’s own published CDC figure.

  1. Kent CountyMD57 tests4.4 pCi/L
  2. Chester CountyPA12,912 tests2.2 pCi/L
  3. Cecil CountyMD1,071 tests1.9 pCi/L
  4. Delaware CountyPA9,005 tests1.9 pCi/L
  5. New Castle CountyThis page10,247 tests1.8 pCi/L
  6. Kent CountyDE1,516 tests1.6 pCi/L

Each figure is that county’s own published CDC figure for 2008 to 2017, laboratory, counting radon tests reported to CDC, not homes. New Castle County is this page. Nothing is averaged or combined across counties. The test count beside each county is CDC’s published number of pre-mitigation tests behind its figures. Figures from few tests can swing widely from year to year. No published CDC figure for 2008 to 2017, laboratory: Salem County, NJ; Gloucester County, NJ. Every Delaware county’s own figure is in the Delaware county table.

CDC publishes this figure only for counties here, so there is no state or national number to compare New Castle County, Delaware with.

New Castle County, Bordering counties

Counties bordering New Castle County

Calculated by Radon411

New Castle County, Local resources

Local resources in Delaware

Who to ask in Delaware: the state's radon program, test kits and professionals.

Delaware Division of Public Health Radon Office

Delaware Division of Public Health

Delaware’s radon program answers questions about testing, mitigation and the rules where you live.

Phone
1-800-464-HELP
Visit the program's page(opens in a new tab)

Test kits

The program says: Delaware Residents click HERE for your free radon test kit.

Radon professionals

25 professionals are listed in Delaware.

Professionals in Delaware

New Castle County, Cities and towns

Cities and towns in New Castle County

The radon figures on this page are for New Castle County as a whole. They do not differ by city or town.

  • Wilmington
  • Newark
  • Middletown
  • Smyrna (part)
  • Elsmere
  • New Castle
  • Clayton (part)
  • Townsend
  • Delaware City
  • Bellefonte
  • Newport
  • Arden
  • Odessa
  • Ardentown
  • Ardencroft

15 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county.

New Castle County, Questions

Questions about radon in New Castle County

Common questions8 questions, answered from the figures above

Who does radon mitigation in New Castle County?

No listed mitigator names New Castle County as a service area yet; the Delaware directory lists 25 companies. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional. Your state radon program is the place to check whether Delaware requires one.

How radon mitigation worksWhat mitigation costsMitigators in Delaware

Are radon levels high in New Castle County?

In 2017, 17.0% of the radon tests reported to CDC for New Castle County, Delaware were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. That is a share of reported tests, not of homes. EPA places New Castle County in Zone 2, moderate predicted potential, a predicted average indoor screening level 2 to 4 pCi/L. Homes with elevated levels occur in all three zones, so the figures describe the area, not your house. Testing is the only way to know the radon level in a specific building.

What a radon level meansRadon in Delaware

How do I get a radon test in New Castle County?

EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. No certified tester listed on Radon411 names New Castle County as a service area yet. The Delaware radon program is the place to ask about certified testers and any test kit offer it runs.

How to test a homeTest kits comparedFree and low-cost kits by stateDelaware radon program

What EPA radon zone is New Castle County in?

EPA places New Castle County, Delaware in Zone 2, which EPA describes as moderate predicted potential for the area. A zone is a prediction for the whole county and never determines whether a particular home should be tested. EPA recommends testing every home regardless of zone.

Should I test my home in New Castle County?

Yes. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. How to test a home.

When is the best time of year to test?

EPA says short-term tests stay in the home from 2 to 90 days and that all radon tests should run a minimum of 48 hours; long-term tests stay more than 90 days. EPA's guides do not name a best season: they say radon levels tend to vary from day to day and season to season, so a long-term test is more likely than a short-term test to tell you the year-round average.

What does it cost to test?

EPA's Citizen's Guide calls testing easy and inexpensive, and EPA's Home Buyer's and Seller's Guide says passive short-term and long-term devices are generally inexpensive, while active devices may cost more. No national average price is published for this, so Radon411 does not give one. What testing costs.

Which counties border New Castle County?

New Castle County borders 7 counties, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.

What these figures mean if you own, buy, sell or rent

The reported-test figures on this page describe New Castle County, Delaware in 2017. They describe tests other people carried out in other buildings, and none of them measures yours.

  • If you own your home

    Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.

    How to test a home
  • If you are buying

    Ask for past results and any system's post-mitigation test, and test during the sale.

    Buying a house: radon guide
  • If you are selling

    Testing before you list puts the timing in your hands; disclosure rules differ by state.

    Selling a house: radon guide
  • If you rent, or rent out a home

    A tenant can test; a fix is the owner's to make, and duties differ by state.

    Radon in rental homes

How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.

New Castle County, Products

Testing and mitigation products

Whatever the figures for New Castle County show, only a test tells you about one home.

New Castle County / Next steps

What to do next

Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.