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Maryland Radon Map and Levels by County

Maryland's counties span all three EPA radon zones. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    23.9%

    11.8 pts below U.S.

    Maryland
    23.9%
    U.S.
    35.7%

    47,941 tests across 24 counties, 2008 to 2017

  • Rank among states

    30 of 47

    Middle of the states

    Maryland
    23.9%
    North Dakota
    59.3%

    By share, every state pooled the same way, 2008 to 2017

  • Counties in EPA Zone 1

    8 of 24

    Some at highest potential

    Zone 1
    8
    Zone 2
    9

    Most counties sit in Zone 2; Zone 1 is the highest potential

  • Highest county

    56.0%

    Washington County

    Washington
    56.0%
    Wicomico
    0.0%

    Counties with 30+ tests, 2008 to 2017

Read a result for Maryland

Starts at EPA's action level

4.0pCi/L

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

EPA’s reading of 4.0 pCi/L

At or above 4 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 at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. 23.9% of Maryland's reported tests reached 4 pCi/L, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Maryland, At a glance

Maryland at a glance

Predicted: EPA radon zone

24 of 24 counties classified

EPA classifies counties, not states. Of the 24 counties in Maryland with a zone, 8 are in Zone 1, 9 in Zone 2 and 7 in Zone 3.

  • Zone 1: Highest predicted potentialgreater than 4 pCi/L8 of 24 counties · 33.3%
  • Zone 2: Moderate predicted potential2 to 4 pCi/L9 of 24 counties · 37.5%
  • Zone 3: Lower predicted potentialless than 2 pCi/L7 of 24 counties · 29.2%

An EPA radon zone predicts a whole county. It is not intended to determine whether any individual home should be tested: homes with elevated levels occur in all three zones, and EPA recommends testing every home regardless of zone.

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

CDC test figures, county by county

CDC publishes Maryland's radon test figures by county: 24 of its 24 counties have one. Each one's share is in the county list.

How to read these figures

Maryland, Compared

Maryland radon figures, compared

Calculated by Radon411
Maryland, 2008 to 2017, laboratory
23.9%
of 47,941 tests at or above 4 pCi/L, pooled
Against the U.S.
−11.8points
35.7% pooled
Rank among the states
30 of 47
1 is the highest share
Counties with 30 or more tests
19
Highest
56.0%
Washington County
Lowest
0.0%
Wicomico County

About 2 in 10 of the 47,941 tests reported for Maryland over the 2008 to 2017 laboratory totals came back at or above 4 pCi/L (23.9%, 24 counties pooled). That is 30th of 47 states with county figures for the period; New York (24.5%) above it and Massachusetts (23.8%) below.

By band, 2 counties at 50% or more, 5 counties at 30% to 50%, 10 counties at 15% to 30%, 1 county at 5% to 15%, 1 county at under 5%. Its 19 counties with 30 or more tests run from 0.0% in Wicomico County to 56.0% in Washington County; in 2 of them half or more of the reported tests reached 4 pCi/L.

EPA's 1993 map puts 8 of its 24 classified counties in Zone 1; against that, 23.9% of the tests reported since reached 4 pCi/L. The national pool for the same period is 35.7%, so Maryland runs 11.8 points below the country.

Across its 4 overlapping ten-year totals, the share went from 24.6% (2005 to 2014) to 23.9% (2008 to 2017), within 2 points, with 2006 to 2015 the highest at 24.9%.

Maryland ranked among 47 states by pooled share of tests at or above 4 pCi/L, 2008 to 2017, laboratory
StateRankCountiesTestsAt or above 4 pCi/L
Connecticut25 of 47825,57226.5%
Washington26 of 47398,20125.5%
Oregon27 of 473423,95125.4%
Georgia28 of 4712930,15224.8%
New York29 of 476297,14524.5%
Maryland30 of 472447,94123.9%
Massachusetts31 of 4714234,15223.8%
Rhode Island32 of 47537,87423.8%
Arkansas33 of 475866823.2%
Nevada34 of 471610,93022.8%
Florida35 of 476253,79422.7%
Maryland's highest and lowest counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/L
Washington County1 of 191,25956.0%
Kent County2 of 195752.6%
Carroll County3 of 193,33441.9%
Garrett County4 of 1918737.4%
Allegany County5 of 1928635.7%
Howard County6 of 194,54930.8%
Calvert County7 of 191,20530.2%
Frederick County8 of 193,93328.1%
Cecil County9 of 191,07124.9%
Charles County10 of 1947724.1%
Wicomico County19 of 19320.0%
Baltimore city18 of 191,1487.9%
Queen Anne's County17 of 196516.9%
Anne Arundel County16 of 194,08817.4%
Montgomery County15 of 1910,96918.0%
Maryland's counties with 30 or more tests, by their own share at or above 4 pCi/L, 2008 to 2017, laboratory
ShareCountiesTheir testsFor example
50% or more21,316Washington County, Kent County
30% to 50%59,561Carroll County, Garrett County, Allegany County
15% to 30%1035,831Frederick County, Cecil County, Charles County
5% to 15%11,148Baltimore city
Under 5%132Wicomico County
Maryland ten-year laboratory totals, pooled, against the United States
PeriodCountiesTestsAt or above 4 pCi/LUnited StatesChange from the row before
2008 to 20172447,94123.9%35.7%−0.5 points
2007 to 20162444,23224.4%35.8%−0.5 points
2006 to 20152438,86624.9%36.3%+0.3 points
2005 to 20142435,12224.6%36.0%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period. CDC publishes no state or national figure.

Maryland, Counties

Maryland counties by EPA zone

Predicted

The map of Maryland, then its 24 counties zone by zone, each with its reported share at or above 4 pCi/L and a report of its own.

Maryland radon map by county: EPA radon zones. Map of Maryland's 24 counties shaded by EPA radon zone: Zone 1 in red-orange, Zone 2 in amber, Zone 3 in pale sand. 8 in Zone 1, 9 in Zone 2, 7 in Zone 3.
Maryland radon map by countyEPA radon zones for Maryland's counties: 8 counties in Zone 1, 9 counties in Zone 2, 7 counties in Zone 3.A prediction for each county, not a reading of any home; elevated homes occur in all three zones.

The 12 highest in Maryland, 2008 to 2017

Zone 1: highest predicted potential8

Local help

Maryland, Local resources

Local resources in Maryland

Who to ask in Maryland: its radon program, test kits and professionals.

What Maryland's program says
Phone
1-866-703-3266

What it means

Maryland, Questions

Questions about radon in Maryland

Is radon a problem in Maryland?

Maryland has 24 counties on EPA's Map of Radon Zones: Zone 1, the highest predicted potential, for 8; Zone 2 for 9; Zone 3 for 7. Pooled from 24 counties, 23.9% of the 47,941 radon tests reported to CDC over the 2008 to 2017 laboratory totals were at or above 4 pCi/L, 30th of 47 states.

Who does radon mitigation in Maryland?

Radon411's Maryland directory lists 5 radon businesses for testing, mitigation or both, each with the licensing list it was read from.

Which Maryland counties are in EPA radon Zone 1?

8 counties are in Zone 1: Baltimore County, Calvert County, Carroll County, Frederick County, Harford County, Howard County, Montgomery County, Washington County.

Which Maryland counties have the highest radon?

By the share of reported tests at or above 4 pCi/L, 2008 to 2017, laboratory: Washington County 56.0% (1,259 tests), Kent County 52.6% (57 tests), Carroll County 41.9% (3,334 tests), Garrett County 37.4% (187 tests), Allegany County 35.7% (286 tests).

Which EPA region is Maryland in?

Maryland is in EPA Region 3: Mid-Atlantic.

Products

Maryland, Products

Testing a home in Maryland

23.9% of the 47,941 tests reported to CDC for Maryland over the 2008 to 2017 laboratory totals reached 4 pCi/L: a short-term kit (2 to 90 days) gives a first answer in days, a long-term test the year-round average. A short-term kit (2 to 90 days) is the quick first check for a home in Maryland; a long-term test tells the year-round average.

Test kits and monitors3

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Best radon monitors for Maryland homes, compared

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