Locations and reports
Radon in Austin, Texas
Austin lies in 4 counties, in EPA Zone 3; 92.6% of it is in Travis County, where 9.2% of 426 reported tests (2008 to 2017, laboratory totals) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so the only way to know your home's level is to test it.
Data checked By Radon411Methodology
Share at 4+ pCi/L
9.2%
1.0 pts below TX
- Travis
- 9.2%
- Texas
- 10.2%
Travis, 7th of 22 in TX, 2008 to 2017
Median result
0.9pCi/L
Below action level
- Travis
- 0.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of Travis's tests, 2008 to 2017
Highest county
9.2%
Travis
- Travis
- 9.2%
- Williamson
- 1.9%
4 counties, 2 with 30+ tests, 2008 to 2017
EPA radon zone
Zone 3
Low potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
Travis; Williamson Zone 3, Hays Zone 3, Bastrop Zone 3
Tests reported
426
In Travis
- Travis
- 426
- Williamson
- 103
Reported to CDC before any fix, 2008 to 2017
Read a result for Austin
Starts at Travis County's median, 0.9 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.9 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Travis County's median reported result, 2008 to 2017.
The data
Austin, What is published
What is published for Austin
Every figure for Austin is a county's
Radon data is published by county, not by city, and Austin reaches into 4 counties: Travis County, Williamson County, Hays County and Bastrop County. Each has its own EPA zone and its own CDC test figures, set side by side below and each labelled with its county. Only a test tells you about one home.
Austin covers 320 square miles of land across 3 counties: 92.6% in Travis County, 6.4% in Williamson County and 1.0% in Hays County. About 1,002,632 people live there, 3,134 to the square mile.
Austin, Counties
Austin's counties, side by side
MeasuredEach county's own EPA zone and its own published CDC figures for 2008 to 2017, laboratory, the newest period any of them has. A county without a figure for that period is shown without one, never with a figure from another year.
- Travis County
- EPA zone
- Zone 3: Lower predicted potential
- At or above 4 pCi/L
- 9.2%
- Median result
- 0.9 pCi/L
- Tests reported
- 426 tests
- Annual years on file
- None
- Williamson County
- EPA zone
- Zone 3: Lower predicted potential
- At or above 4 pCi/L
- 1.9%
- Median result
- 0.7 pCi/L
- Tests reported
- 103 tests
- Annual years on file
- None
- Hays County
- EPA zone
- Zone 3: Lower predicted potential
- At or above 4 pCi/L
- 17.4%
- Median result
- 0.5 pCi/L
- Tests reported
- 23 tests
- Annual years on file
- None
- Bastrop County
- EPA zone
- Zone 3: Lower predicted potential
- At or above 4 pCi/L
- 61.5%
- Median result
- 6.5 pCi/L
- Tests reported
- 13 tests
- Annual years on file
- None
| County | EPA zone | Reported tests at or above 4 pCi/L | Median reported result | Tests reported | Annual years on file |
|---|---|---|---|---|---|
| Travis County | Zone 3: Lower predicted potential | 9.2% | 0.9 pCi/L | 426 tests | None |
| Williamson County | Zone 3: Lower predicted potential | 1.9% | 0.7 pCi/L | 103 tests | None |
| Hays County | Zone 3: Lower predicted potential | 17.4% | 0.5 pCi/L | 23 tests | None |
| Bastrop County | Zone 3: Lower predicted potential | 61.5% | 6.5 pCi/L | 13 tests | None |
Austin spans 4 counties, each with its own EPA zone and its own CDC figure: Travis County (Zone 3, 9.2% of 426 tests), Williamson County (Zone 3, 1.9% of 103 tests), Hays County (Zone 3, 17.4% of 23 tests) and Bastrop County (Zone 3, 61.5% of 13 tests).
Travis County ranks 7th of 22 Texas counties with 30 or more tests for that period, 1.0 points below the 10.2% pooled across Texas's counties, 26.5 points below the national pool of 35.7%. Of the city's other counties, Williamson County reported 1.9%, Hays County reported 17.4% and Bastrop County reported 61.5%.
The counties nearest Austin with a CDC figure for 2008 to 2017, laboratory, measured from the middle of the city: Bell County (53 miles, 16.7% of 30 tests), Bexar County (75 miles, 6.5% of 201 tests) and Brazos County (90 miles, 0.0% of 47 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 0.0% to 23.3%; the farthest of them, Brazoria County, is 158 miles away at 6.3%.
No business in the directory gives Austin as its address; the Texas list covers it. Texas's other cities with a page of their own: Houston and San Antonio.
Against Texas and its other counties
Shares of tests people chose to run and report, by county (2008 to 2017, laboratory); the state's is its counties' counts added up, calculated by Radon411. Only a test measures a home.
The counties around Austin
By distance from the middle of Austin; counties with 30 or more tests.
The median reported pre-mitigation result for 2008 to 2017, laboratory was 0.9 pCi/L in Travis County, 0.7 pCi/L in Williamson County, 0.5 pCi/L in Hays County and 6.5 pCi/L in Bastrop County.
Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2008 to 2017, laboratory.
Austin, Geology
The ground under Austin
PredictedUSGS's geologic map splits Austin: 66.3% of its land is low radon potential and 33.7% moderate. The map puts 36.2% of Austin in the area it calls East Texas Province and 33.7% in Cretaceous Gulfian series, with 2 smaller areas beside them. USGS gives the first a radon index of 6, in the low band (5 to 8), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| East Texas Province | Cretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite. | Low | 6 | 36.2% |
| Cretaceous Gulfian series | Cretaceous sandstone, shale, limestone, siltstone. | Moderate | 10 | 33.7% |
| Central Texas/Gulf Coast Plain | Cretaceous through Quaternary marine sandstone, shale, chalk, limestone, siltstone, clay, and lignite. | Low | 7 | 17.0% |
| Southern High Plains and Plateaus | Paleozoic and Mesozoic sandstone, limestone, shale. | Low | 7 | 13.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Austin beside its counties and Texas
Austin sits on more moderate-potential ground than Travis County as a whole: 33.7% of the city against 13.5% of the county. Across Texas 0.5% of the land is rated high; none of Austin's is.
The map rates the ground, not the air in any home.
Austin, Homes
Homes in Austin
Austin has 466,428 homes, and many share a building: 42% are in buildings of five or more, 44% are detached houses, against 52% across Travis County. Half of its homes were built before 1993, close to Travis County's 1997: 8% date from before 1960 and 40% from 2000 or later. Most occupied homes here are rented: owners live in 44% (Travis County: 53%). A tenant can run a test; a fix is the landlord's to make.
| Homes | Austin | Travis County | Texas |
|---|---|---|---|
| Housing units | 466,428 | 594,638 | 11,890,808 |
| Detached houses | 44% | 52% | 65% |
| In buildings of 5 or more | 42% | 34% | 21% |
| Mobile homes | 1% | 3% | 7% |
| Built before 1960 | 8% | 7% | 13% |
| Built since 2000 | 40% | 45% | 37% |
| Middle year built | 1993 | 1997 | 1990 |
| Owner-occupied | 44% | 53% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.
Local help
Austin, Local resources
Local resources for Austin
Who to ask in Texas: its radon program, test kits and professionals.
- Texas Radon GroupRun by Texas Tech University.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The Texas Radon Group offers free radon test kits for Texas individuals who qualify.
- Compare kits
- Professionals in TexasRadon testers and mitigators in Texas, each with how its listing was checked.
The program's own words on licensing are on the Texas page.
What it means
Austin, Questions
Questions about radon in Austin
What radon zone is Austin in?
All 4 counties Austin reaches into (Travis County, Williamson County, Hays County and Bastrop County) are in Zone 3, the map's lowest class: a predicted county average under 2 pCi/L. EPA zones counties, not cities, so that is the zone for every part of Austin.
What are radon levels in Austin?
Only 9.2% of 426 tests from Travis County for 2008 to 2017 (laboratory totals) reached 4 pCi/L, so reported levels around Austin run low. The median reported result was 0.9 pCi/L. Low is not none. Williamson County reported 1.9% of 103 tests, Hays County reported 17.4% of 23 tests and Bastrop County reported 61.5% of 13 tests; the counties are kept apart.
Should I test my home in Austin?
Yes, even here. 39 of 426 tests reported from Travis County were at or above 4 pCi/L. That is about what Texas as a whole reports (10.2%), and ranks Travis County 7th of the 22 Texas counties with 30 or more tests. Those homes were found by testing, not by the county's low share. How to test a home.
What ground is Austin built on, as far as radon goes?
36.2% of Austin sits on what USGS's map calls "East Texas Province", rated low for radon potential, radon index 6; another 33.7% is "Cretaceous Gulfian series", rated moderate for radon potential, radon index 10. 2 smaller areas make up the rest. So the ground changes within Austin itself.
Is radon higher in the counties around Austin?
Some are and some are not. Against Travis County's 9.2%, 2 of the 8 nearest counties with a figure report more and 6 less, from Brazos County (0.0%, 90 miles off) to McLennan County (23.3%, 92 miles off).
The answers use the published figures of Travis County, Williamson County, Hays County and Bastrop County, the counties Austin lies in.
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