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Radon Levels in Grayson County, Texas

EPA puts Grayson County in Zone 3, its lowest radon zone, and only 20 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). 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

    7.7%

    Collin County

    Collin
    7.7%
    Denton
    7.2%

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

  • Nearest county

    7.7%

    Collin County, 31 miles

    Collin
    7.7%
    Texas
    10.4%

    Share at 4+ pCi/L, 284 tests, 2007 to 2016

  • Ground above low

    85.4%

    58.1 pts above Texas

    Grayson
    85.4%
    Texas
    27.3%

    Share of land USGS rates moderate or high potential

  • Tests reported

    20

    Too few for a share

    Grayson
    20
    Needed
    30

    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 Grayson 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

Grayson County, At a glance

Grayson County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Grayson 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: Moderate across 85% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

CDC holds 20 reported tests for Grayson County over the 2008 to 2017 laboratory totals, with a median of 1.1 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Grayson County beside the counties around it is how this page reads it.

What these figures count

Only 20 tests were reported to CDC for Grayson County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor 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

Grayson County, Compared

Grayson County radon figures, compared

Calculated by Radon411

CDC's largest figure for Grayson County rests on 20 tests over the 2008 to 2017 laboratory totals, 1 of them at or above 4 pCi/L, so each test moves its share by 5.0 points and no rank or comparison is drawn from it. Results reached as high as 4.3 pCi/L, with a middle value of 1.1 pCi/L.

Of the counties bordering it, 2 have a figure over the 2007 to 2016 laboratory totals: Collin County reported the largest share at or above 4 pCi/L, 7.7%, and Denton County the smallest, 7.2%. Farther out, Dallas County (60 miles away) at 8.7%, Tarrant County (69 miles away) at 10.6% and Smith County (119 miles away) at 9.1% have figures too. Pooled across 140 Texas counties, 10.4% of reported tests reached that level; across every county in the country with a figure, 35.8%.

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 Grayson County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 85% of the county's land moderate radon potential.

Texas, the United States and the counties around Grayson 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
Collin County, TXborders it2847.7%1.0 pCi/L
Denton County, TXborders it1817.2%0.9 pCi/L
Bryan County, OKborders it10.0%0.6 pCi/L
Fannin County, TXborders it10.0%0.9 pCi/L
The nearest Texas counties to Grayson County with 30 or more tests, 2007 to 2016, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Collin County31 mi2847.7%1.0 pCi/L
Denton County39 mi1817.2%0.9 pCi/L
Dallas County60 mi6998.7%1.0 pCi/L
Tarrant County69 mi31210.6%0.9 pCi/L
Smith County119 mi339.1%0.8 pCi/L
McLennan County146 mi4117.1%1.0 pCi/L
Bell County184 mi3514.3%1.1 pCi/L
Brazos County206 mi490.0%0.2 pCi/L
Grayson County ten-year laboratory totals, against Texas' pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestTexas, pooledChange from the row before
2008 to 2017205.0%1.1 pCi/L4.3 pCi/L10.2%Level
2007 to 2016205.0%1.1 pCi/L4.3 pCi/L10.4%−1.7 points
2006 to 2015156.7%1.1 pCi/L4.3 pCi/L11.0%Level
2005 to 2014156.7%1.1 pCi/L4.3 pCi/L10.6%First on file

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

Grayson County, Geology

The ground under Grayson County

Predicted

Most of the ground under Grayson County is one class on USGS's geologic map: 85.4% of its land is moderate radon potential, with 14.6% low. The map puts 85.4% of Grayson County in the area it calls Cretaceous Gulfian series and 14.4% in Central Texas/Gulf Coast Plain. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 7, in the low band (5 to 8).

USGS's geologic areas under Grayson County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Cretaceous Gulfian seriesCretaceous sandstone, shale, limestone, siltstone.Moderate1085.4%
Central Texas/Gulf Coast PlainCretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite.Low714.4%

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

Grayson County beside the ground around it

Across Texas 0.5% of the land is rated high; none of Grayson County's is. Of the 7 counties that border it, none has as large a share of moderate-potential ground; Fannin County comes nearest at 82.5%.

Share of land by USGS radon potential: Grayson County, the 7 counties bordering it and Texas
AreaEPA zoneLow potentialModerate potentialHigh potential
Grayson CountyZone 314.6%85.4%None
Collin CountyZone 340.7%59.3%None
Marshall County, OKZone 3100%NoneNone
Fannin CountyZone 317.5%82.5%None
Cooke CountyZone 375.6%24.4%None
Denton CountyZone 349.0%51.0%None
Bryan County, OKZone 345.8%54.3%None
Love County, OKZone 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

Grayson County, Local resources

Radon testing and mitigation in Grayson 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

Grayson County, Questions

Questions about radon in Grayson County

Are radon levels high in Grayson County?

Over the 2008 to 2017 laboratory totals, 5.0% of the radon tests reported to CDC for Grayson County, Texas were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.1 pCi/L. Of the counties bordering it, 2 have a figure over the 2007 to 2016 laboratory totals: Collin County reported the largest share at or above 4 pCi/L, 7.7%, and Denton County the smallest, 7.2%.

Which counties border Grayson County?

Grayson County borders 7 counties: Collin County, TX, Marshall County, OK, Fannin County, TX, Cooke County, TX, Denton County, TX, Bryan County, OK and Love County, OK.

Products

Grayson County, Products

Testing a home in Grayson County

No CDC figure names Grayson County; the nearest county with one, Collin County (31 miles away), reported 7.7% 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 Grayson County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Grayson County homes, compared

Explore

Grayson County, Bordering counties

Counties bordering Grayson County

Calculated by Radon411

Grayson County, Cities and towns

Cities and towns in Grayson County

Grayson County is growing: the Census Bureau puts it at 153,613 residents on July 1, 2025, up 12.8% from 136,157 in 2020. That works out to 165 people per square mile of land. Its largest town, Sherman, has 52,417 residents, 34.1% of the total. CDC's 20 reported tests for 2008 to 2017 work out to 0.1 per 1,000 residents (2025 estimate), close to Texas' 0.1.

From Sherman to Dorchester, CDC publishes no figure by town: each reads Grayson County's.

The 12 largest cities and towns in Grayson County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Sherman52,417+19.2%34.1%
Denison26,822+9.2%17.5%
Pilot Pointextends beyond Grayson County8,052+82.2%Counted whole
Van Alstyneextends beyond Grayson County8,012+79.6%Counted whole
Whitesboro4,188+2.5%2.7%
Howe3,686+1.9%2.4%
Pottsboro2,767+11.1%1.8%
Gunter2,574+24.0%1.7%
Collinsville2,076+10.7%1.4%
Whitewrightextends beyond Grayson County1,749+1.0%Counted whole
Bells1,525+0.3%1.0%
Tioga1,302+12.1%0.8%
  • Southmayd
  • Tom Bean
  • Trenton (part)
  • Knollwood
  • Sadler
  • Dorchester

18 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Grayson County is counted whole, so it has no share.

Grayson County, Homes

Homes in Grayson County

Of Grayson County's 60,366 homes, 71% are detached houses, against 65% across Texas; 11% are in buildings of five or more homes. Half of its homes were built before 1984, close to Texas' 1990: 20% date from before 1960 and 29% from 2000 or later. 67% 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 Grayson County, Texas, 2019 to 2023
HomesGrayson CountyTexas
Housing units60,36611,890,808
Detached houses71%65%
In buildings of 5 or more11%21%
Mobile homes10%7%
Built before 196020%13%
Built since 200029%37%
Middle year built19841990
Owner-occupied67%63%

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