Skip to content
RADON411

Locations and reports

Radon Levels in Brazoria County, Texas

EPA puts Brazoria County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 6.3% of 32 (2008 to 2017, laboratory totals) reached 4 pCi/L. 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

  • Share at 4+ pCi/L

    6.3%

    3.9 pts below TX

    Brazoria
    6.3%
    Texas
    10.2%

    32 tests, 2008 to 2017

  • Median result

    0.3pCi/L

    Below action level

    Brazoria
    0.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    32

    20th of 22 by tests

    Brazoria
    32
    Harris
    733

    Reported to CDC before any fix, 2008 to 2017

  • 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

  • Rank in Texas

    12 of 22

    Middle half

    Brazoria
    6.3%
    Randall
    69.0%

    By share, of 22 with 30+ tests

Read a result for Brazoria County

Starts at Brazoria County's median, 0.3 pCi/L

0.3pCi/L

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

EPA’s reading of 0.3 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Brazoria County's median reported result, 2008 to 2017.

Interpret this reading

The data

Brazoria County, At a glance

Brazoria County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Brazoria 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 98% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Brazoria County, 2008 to 2017, laboratory
Under 2 pCi/L: 88%2 to 4 pCi/L: 6%4 pCi/L and above: 6%

Of 32 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Brazoria County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L2887.5%
2 to 4 pCi/L26.3%
4 pCi/L and above26.3%
What these figures count

These are the 32 tests reported to CDC for Brazoria County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, 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

Brazoria County, Compared

Brazoria County radon figures, compared

Calculated by Radon411

Brazoria County reports fewer high tests than Texas overall. 6.3% of its 32 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 3.9 points below the 10.2% pooled from 138 Texas counties.

Ordered from highest share down, it comes 12th of 22 Texas counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Brazoria County sits 29.4 points below it.

Next door, the shares run from 0.0% in Galveston County to 2.9% in Harris County, with Harris County, Fort Bend County and Galveston County below Brazoria County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 6.3% share point the same way here.

Half the tests came in under 0.3 pCi/L and half over it; the single highest reached 4.4 pCi/L. The rest split 87.5% under 2 pCi/L and 6.3% from 2 to 4 (Texas: 80.3% and 9.6%).

CDC's ten-year totals for Brazoria County went from 35 tests (2005 to 2014) to 32 (2008 to 2017), the share going from 5.7% to 6.3%.

Brazoria County against Texas, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Brazoria County
Brazoria County326.3%0.3 pCi/LThis county
Texas, pooled138 counties, pooled4,61510.2%Not pooled+3.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+29.4 points
Randall Countyhighest in the state8769.0%6.1 pCi/L+62.7 points
Nueces Countylowest in the state430.0%0.6 pCi/L−6.3 points
Matagorda County, TXborders it633.3%0.1 pCi/L+27.0 points
Harris County, TXborders it7332.9%0.4 pCi/L−3.4 points
Fort Bend County, TXborders it1052.9%0.2 pCi/L−3.4 points
Wharton County, TXborders it90.0%0.5 pCi/L−6.3 points
Galveston County, TXborders it730.0%0.2 pCi/L−6.3 points
Where Brazoria County's reported results fell, 2008 to 2017, laboratory, beside Texas and the United States
ResultBrazoria County testsBrazoria County shareTexas shareU.S. shareAgainst Texas
Under 2 pCi/L2887.5%80.3%39.6%+7.2 points
2 to 4 pCi/L26.3%9.6%24.7%−3.3 points
4 pCi/L and above26.3%10.2%35.7%−3.9 points
Brazoria County ranked among the 22 Texas counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Travis County7 of 224269.2%0.9 pCi/L
Dallas County8 of 227288.4%0.9 pCi/L
Collin County9 of 222897.6%1.0 pCi/L
Denton County10 of 221926.8%0.9 pCi/L
Bexar County11 of 222016.5%0.6 pCi/L
Brazoria County12 of 22326.3%0.3 pCi/L
Smith County13 of 22525.8%0.8 pCi/L
Montgomery County14 of 221883.2%0.8 pCi/L
Harris County15 of 227332.9%0.4 pCi/L
Fort Bend County16 of 221052.9%0.2 pCi/L
Williamson County17 of 221031.9%0.7 pCi/L
Brazoria County ten-year laboratory totals, against Texas' pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestTexas, pooledChange from the row before
2008 to 2017326.3%0.3 pCi/L4.4 pCi/L10.2%Level
2007 to 2016326.3%0.3 pCi/L4.4 pCi/L10.4%+0.9 points
2006 to 2015375.4%0.2 pCi/L4.4 pCi/L11.0%−0.3 points
2005 to 2014355.7%0.2 pCi/L4.4 pCi/L10.6%First on file

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

Brazoria County, Geology

The ground under Brazoria County

Predicted

USGS's geologic map puts all of Brazoria County's mapped land in one class: low radon potential. 98.0% of it lies in the area the map calls Coastal Plain, to which USGS gives a radon index of 7, in the low band (5 to 8).

USGS's geologic areas under Brazoria County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Coastal PlainCretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite.Low798.0%

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

Brazoria County beside the ground around it

Across Texas 0.5% of the land is rated high; none of Brazoria County's is. None of the 5 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: Brazoria County, the 5 counties bordering it and Texas
AreaEPA zoneLow potentialModerate potentialHigh potential
Brazoria CountyZone 398.0%NoneNone
Fort Bend CountyZone 3100%NoneNone
Galveston CountyZone 384.4%NoneNone
Matagorda CountyZone 384.5%NoneNone
Harris CountyZone 3100%NoneNone
Wharton 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

Brazoria County, Local resources

Radon testing and mitigation in Brazoria 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

Brazoria County, Questions

Questions about radon in Brazoria County

Are radon levels high in Brazoria County?

Over the 2008 to 2017 laboratory totals, 6.3% of the radon tests reported to CDC for Brazoria County, Texas were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.3 pCi/L. Of 22 Texas counties with 30 or more tests for the same period, 11 reported a higher share; pooled, the state comes to 10.2%.

Which counties border Brazoria County?

Brazoria County borders 5 counties: Fort Bend County, Galveston County, Matagorda County, Harris County and Wharton County.

Products

Brazoria County, Products

Testing a home in Brazoria County

In Brazoria County, 6.3% of 32 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.2% pooled across Texas. 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 Brazoria County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Brazoria County homes, compared

Explore

Brazoria County, Bordering counties

Counties bordering Brazoria County

Calculated by Radon411

Brazoria County, Cities and towns

Cities and towns in Brazoria County

Brazoria County is growing: the Census Bureau puts it at 419,080 residents on July 1, 2025, up 12.2% from 373,490 in 2020. That works out to 307 people per square mile of land. Pearland, the largest place on its list (129,930 residents in all), extends beyond Brazoria County, so no share of the total is worked out for it. Reported testing is thin here: 32 tests over 2008 to 2017, or 0.1 for every 1,000 residents (2025 estimate), where Texas as a whole comes to 0.1.

From Pearland to Hillcrest, CDC publishes no figure by town: each reads Brazoria County's.

The 12 largest cities and towns in Brazoria County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Pearlandextends beyond Brazoria County129,930+1.7%Counted whole
Alvin30,115+11.4%7.2%
Lake Jackson27,803−1.2%6.6%
Angleton21,295+9.7%5.1%
Manvel20,699+104.2%4.9%
Iowa Colony20,503+139.8%4.9%
Clute10,821+1.7%2.6%
Freeport10,508−1.7%2.5%
Richwood4,777Level1.1%
West Columbia3,636+0.1%0.9%
Sweeny3,594−0.7%0.9%
Brazoria2,882+0.6%0.7%
  • Jones Creek
  • Danbury
  • Brookside Village
  • Oyster Creek
  • Holiday Lakes
  • Bailey's Prairie
  • Surfside Beach
  • Liverpool
  • Sandy Point
  • Bonney
  • Quintana
  • Hillcrest

24 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 Brazoria County is counted whole, so it has no share.

Brazoria County, Homes

Homes in Brazoria County

Of Brazoria County's 146,587 homes, 73% are detached houses, against 65% across Texas; 14% are in buildings of five or more homes. Half of its homes were built before 1995, close to Texas' 1990: 8% date from before 1960 and 43% from 2000 or later. 74% 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 Brazoria County, Texas, 2019 to 2023
HomesBrazoria CountyTexas
Housing units146,58711,890,808
Detached houses73%65%
In buildings of 5 or more14%21%
Mobile homes9%7%
Built before 19608%13%
Built since 200043%37%
Middle year built19951990
Owner-occupied74%63%

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