Radon levels in Maryland

Verified county-level radon indicators are available for 24 Maryland counties. Select a county for its source period and sample details.

High results are most common in Washington County (56%) and least common in Wicomico County (0%)Share of tests at or above 4 pCi/L by county · Radon test results from laboratories, 2008–2017 · 24 of 24 counties have data
Allegany County: 36% of tests at or above 4 pCi/L · 286 testsAnne Arundel County: 17% of tests at or above 4 pCi/L · 4,088 testsBaltimore County: 19% of tests at or above 4 pCi/L · 7,706 testsCalvert County: 30% of tests at or above 4 pCi/L · 1,205 testsCaroline County: 0% of tests at or above 4 pCi/L · 12 testsCarroll County: 42% of tests at or above 4 pCi/L · 3,334 testsCecil County: 25% of tests at or above 4 pCi/L · 1,071 testsCharles County: 24% of tests at or above 4 pCi/L · 477 testsDorchester County: 17% of tests at or above 4 pCi/L · 6 testsFrederick County: 28% of tests at or above 4 pCi/L · 3,933 testsGarrett County: 37% of tests at or above 4 pCi/L · 187 testsHarford County: 23% of tests at or above 4 pCi/L · 5,283 testsHoward County: 31% of tests at or above 4 pCi/L · 4,549 testsKent County: 53% of tests at or above 4 pCi/L · 57 testsMontgomery County: 18% of tests at or above 4 pCi/L · 10,969 testsPrince George's County: 19% of tests at or above 4 pCi/L · 1,603 testsQueen Anne's County: 17% of tests at or above 4 pCi/L · 65 testsSt. Mary's County: 21% of tests at or above 4 pCi/L · 636 testsSomerset County: 0% of tests at or above 4 pCi/L · 2 testsTalbot County: 8% of tests at or above 4 pCi/L · 26 testsWashington County: 56% of tests at or above 4 pCi/L · 1,259 testsWicomico County: 0% of tests at or above 4 pCi/L · 32 testsWorcester County: 0% of tests at or above 4 pCi/L · 7 testsBaltimore city: 8% of tests at or above 4 pCi/L · 1,148 tests
  • Under 10%
  • 10–20%
  • 20–30%
  • 30–40%
  • 40% or more
  • No data

Counties

CountyTests% ≥ 4 pCi/LMedian (pCi/L)EPA zone (1993)Source
Allegany County28636%2.7Zone 2Radon test results from laboratories through 2017
Anne Arundel County4,08817%1.4Zone 2Radon test results from laboratories through 2017
Baltimore County7,70619%1.4Zone 1Radon test results from laboratories through 2017
Baltimore city1,1488%0.8Zone 2Radon test results from laboratories through 2017
Calvert County1,20530%2.0Zone 1Radon test results from laboratories through 2017
Caroline County120%0.8Zone 3Radon test results from laboratories through 2017
Carroll County3,33442%2.8Zone 1Radon test results from laboratories through 2017
Cecil County1,07125%1.9Zone 2Radon test results from laboratories through 2017
Charles County47724%1.8Zone 2Radon test results from laboratories through 2017
Dorchester County617%1.6Zone 3Radon test results from laboratories through 2017
Frederick County3,93328%1.5Zone 1Radon test results from laboratories through 2017
Garrett County18737%3.0Zone 2Radon test results from laboratories through 2017
Harford County5,28323%1.7Zone 1Radon test results from laboratories through 2017
Howard County4,54931%2.0Zone 1Radon test results from laboratories through 2017
Kent County5753%4.4Zone 3Radon test results from laboratories through 2017
Montgomery County10,96918%1.3Zone 1Radon test results from laboratories through 2017
Prince George's County1,60319%1.4Zone 2Radon test results from laboratories through 2017
Queen Anne's County6517%1.3Zone 3Radon test results from laboratories through 2017
Somerset County20%0.3Zone 3Radon test results from laboratories through 2017
St. Mary's County63621%1.8Zone 2Radon test results from laboratories through 2017
Talbot County268%1.1Zone 3Radon test results from laboratories through 2017
Washington County1,25956%5.2Zone 1Radon test results from laboratories through 2017
Wicomico County320%0.9Zone 3Radon test results from laboratories through 2017
Worcester County70%0.6Zone 3Radon test results from laboratories through 2017

Test your home

County figures show how often tests come back high, not the level in your home. Only a test tells you that: see how to test for radon.

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