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Radon Levels in Washington County, Texas

EPA puts Washington County in Zone 3, its lowest radon zone. 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

  • Highest bordering

    0.0%

    Brazos County

    Brazos
    0.0%

    1 of 7 neighbours have 30+ tests, 2007 to 2016

  • Nearest county

    0.0%

    Brazos County, 31 miles

    Brazos
    0.0%
    Texas
    10.4%

    Share at 4+ pCi/L, 49 tests, 2007 to 2016

  • Ground above low

    None

    27.3 pts below Texas

    Washington
    0.0%
    Texas
    27.3%

    Share of land USGS rates moderate or high potential

  • Tests reported

    0

    None published

    2008 to 2017, laboratory

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

Read a result for Washington County

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.

Interpret this readingWhat a fix costs

The data

Washington County, At a glance

Washington County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Washington County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Low across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Washington County, 2008 to 2017, laboratory

Tests reported to CDC, often from homes being sold or suspected of a problem: the area, not this house.

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

How to read these figures

Washington County, Compared

Washington County radon figures, compared

Calculated by Radon411

No CDC figure names Washington County, in any year or ten-year total; over the 2007 to 2016 laboratory totals, the agency's counts reach 140 Texas counties without it. Pooled across 140 Texas counties, 10.4% of reported tests reached that level; across every county in the country with a figure, 35.8%.

Brazos County, the one bordering county with a figure over the 2007 to 2016 laboratory totals, reported 0.0% of its tests at or above 4 pCi/L. Farther out, Montgomery County (54 miles away) at 7.1%, Fort Bend County (61 miles away) at 3.4% and Harris County (65 miles away) at 3.1% have figures too. Statewide for the same period, Randall County reported the highest share (71.4%) and Nueces County the lowest (0.0%).

EPA's 1993 map puts Washington County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 100% of the county's land low radon potential.

Texas, the United States and the counties around Washington County, 2007 to 2016, laboratory
AreaTestsAt or above 4 pCi/LMedian
Texas, pooled140 counties, pooled4,54810.4%Not pooled
United States, pooled2,666 counties, pooled1,939,02535.8%Not pooled
Randall Countyhighest in the state8471.4%6.2 pCi/L
Nueces Countylowest in the state450.0%0.6 pCi/L
Fayette County, TXborders it60.0%0.1 pCi/L
Brazos County, TXborders it490.0%0.2 pCi/L
Austin County, TXborders it20.0%0.1 pCi/L
Waller County, TXborders it70.0%0.1 pCi/L
Grimes County, TXborders it10.0%0.1 pCi/L
The nearest Texas counties to Washington County with 30 or more tests, 2007 to 2016, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Brazos County31 mi490.0%0.2 pCi/L
Montgomery County54 mi857.1%0.6 pCi/L
Fort Bend County61 mi1173.4%0.2 pCi/L
Harris County65 mi7753.1%0.2 pCi/L
Williamson County77 mi982.0%0.7 pCi/L
Travis County83 mi4089.3%0.8 pCi/L
Bell County86 mi3514.3%1.1 pCi/L
Brazoria County91 mi326.3%0.3 pCi/L

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

Washington County, Geology

The ground under Washington County

Predicted

USGS's geologic map puts all of Washington County's mapped land in one class: low radon potential. The map puts 88.1% of Washington County in the area it calls Coastal Plain and 11.9% in East Texas Province. USGS gives the first a radon index of 7 and the second 6, both in the low band (5 to 8).

USGS's geologic areas under Washington County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Coastal PlainCretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite.Low788.1%
East Texas ProvinceCretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite.Low611.9%

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

Washington County beside the ground around it

Across Texas 0.5% of the land is rated high; none of Washington County's is. None of the 7 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: Washington County, the 7 counties bordering it and Texas
AreaEPA zoneLow potentialModerate potentialHigh potential
Washington CountyZone 3100%NoneNone
Burleson CountyZone 3100%NoneNone
Austin CountyZone 3100%NoneNone
Lee CountyZone 3100%NoneNone
Brazos CountyZone 3100%NoneNone
Waller CountyZone 3100%NoneNone
Grimes CountyZone 3100%NoneNone
Fayette CountyZone 3100%NoneNone
Texas254 counties, pooled by land areaVaries72.4%26.8%0.5%

The map rates the ground, not the air in any home.

Local help

Washington County, Local resources

Radon testing and mitigation in Washington County

What Texas's program says
Licensing of radon professionals
There are no radon certification requirements for the State of Texas at this time, but the National Radon Proficiency Program lists radon testers and mitigators within Texas that have passed a rigorous national certification program.

What it means

Washington County, Questions

Questions about radon in Washington County

Are radon levels high in Washington County?

Over the 2008 to 2017 laboratory totals, CDC published only a count for Washington County, Texas, with no share of tests at or above 4 pCi/L and no median. Brazos County, the one bordering county with a figure over the 2007 to 2016 laboratory totals, reported 0.0% of its tests at or above 4 pCi/L.

Which counties border Washington County?

Washington County borders 7 counties: Burleson County, Austin County, Lee County, Brazos County, Waller County, Grimes County and Fayette County.

Products

Washington County, Products

Testing a home in Washington County

No CDC figure names Washington County; the nearest county with one, Brazos County (31 miles away), reported 0.0% of its tests at or above 4 pCi/L over the 2007 to 2016 laboratory totals, the only reading nearby until a test of this home. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Washington County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Washington County homes, compared

Explore

Washington County, Bordering counties

Counties bordering Washington County

Calculated by Radon411

Washington County, Cities and towns

Cities and towns in Washington County

Washington County is growing: the Census Bureau puts it at 38,288 residents on July 1, 2025, up 7.0% from 35,791 in 2020. That works out to 63 people per square mile of land. Brenham alone is home to 19,957 of them, 52.1% of the total. Together its 2 incorporated places hold 52.9% of those residents; the other 47.1% live outside any of them. CDC publishes no radon test count for Washington County; across Texas its counts for 2008 to 2017 come to 0.1 tests for every 1,000 residents (2025 estimate).

From Brenham to Burton, CDC publishes no figure by town: each reads Washington County's.

The cities and towns in Washington County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Brenham19,957+15.0%52.1%
Burton288−2.4%0.8%

2 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).

Washington County, Homes

Homes in Washington County

Of Washington County's 17,371 homes, 74% are detached houses, against 65% across Texas; 11% are mobile homes. Half of its homes were built before 1990, close to Texas' 1990: 14% date from before 1960 and 35% from 2000 or later. 73% of occupied homes are lived in by their owner (Texas: 63%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Washington County, Texas, 2019 to 2023
HomesWashington CountyTexas
Housing units17,37111,890,808
Detached houses74%65%
In buildings of 5 or more7%21%
Mobile homes11%7%
Built before 196014%13%
Built since 200035%37%
Middle year built19901990
Owner-occupied73%63%

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