Delaware has 3 counties, with 0 classified as EPA Zone 1 (highest risk). With an average radon level of 6.08 pCi/L, Delaware state testing data reveals significantly elevated risks across multiple counties. Testing is highly recommended.
Delaware is the second smallest state in terms of size, and the sixth least populous. Of course, it also happens to be the sixth most densely populated state in the country.
The ZIP code areas in the state with the highest percentages of radon over the EPA action level are Middletown (27%) and Odessa (22%). The ZIP code areas with the highest percentages between 15%-20% over the action level are Townsend (17%), Arden (17%), Hockessin (17%), and Talleyville (15%). It would appear that all of these areas have some form of granitic rocks above or below the ground surface.
Explore radon data organized by metro region, including average levels, hotspot cities, and local mitigation professionals.
Cities with the most user-submitted radon test data, ranked by number of submissions.
| City | Avg User Radon Level | Submissions |
|---|---|---|
| Middletown | 7.43 pCi/L | 7 |
| Wilmington | 5.50 pCi/L | 4 |
| Lewes | 6.00 pCi/L | 1 |
| New Castle | 4.00 pCi/L | 1 |
| Newark | No submissions | 0 |
All 3 Delaware counties with their EPA radon zone classification and user-submitted average radon levels.
Browse radon data for individual cities across Delaware. Each city page includes user-submitted radon levels, local contractors, and mitigation resources.