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Locations and reports

Radon in Sioux City, Iowa

Sioux City lies in 2 counties, in EPA Zone 1; 99.9% of it is in Woodbury County, where 69.2% of 3,541 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    69.2%

    10.7 pts above IA

    Woodbury
    69.2%
    Iowa
    58.5%

    Woodbury, 36th of 99 in IA, 2008 to 2017

  • Median result

    6.1pCi/L

    Action level reached

    Woodbury
    6.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of Woodbury's tests, 2008 to 2017

  • Highest county

    82.3%

    Plymouth

    Plymouth
    82.3%
    Woodbury
    69.2%

    2 counties, 2 with 30+ tests, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    Woodbury; Plymouth Zone 1

  • Tests reported

    3,541

    In Woodbury

    Woodbury
    3,541
    Plymouth
    1,405

    Reported to CDC before any fix, 2008 to 2017

Read a result for Sioux City

Starts at Woodbury County's median, 6.1 pCi/L

6.1pCi/L

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

EPA’s reading of 6.1 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. Woodbury County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Sioux City, What is published

What is published for Sioux City

Information:

Every figure for Sioux City is a county's

Radon data is published by county, not by city, and Sioux City reaches into 2 counties: Woodbury County and Plymouth 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.

Sioux City covers 58.5 square miles of land: 99.9% of it lies in Woodbury County and 0.1% in Plymouth County. About 86,356 people live there, 1,477 to the square mile.

Sioux City, Counties

Sioux City's counties, side by side

Measured

Each 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.

  • Woodbury County
    EPA zone
    Zone 1: Highest predicted potential
    At or above 4 pCi/L
    69.2%
    Median result
    6.1 pCi/L
    Tests reported
    3,541 tests
    Annual years on file
    None
  • Plymouth County
    EPA zone
    Zone 1: Highest predicted potential
    At or above 4 pCi/L
    82.3%
    Median result
    8.6 pCi/L
    Tests reported
    1,405 tests
    Annual years on file
    None
The counties Sioux City lies in, each with its own EPA zone and its own published CDC figures for 2008 to 2017, laboratory
CountyEPA zoneReported tests at or above 4 pCi/LMedian reported resultTests reportedAnnual years on file
Woodbury CountyZone 1: Highest predicted potential69.2%6.1 pCi/L3,541 testsNone
Plymouth CountyZone 1: Highest predicted potential82.3%8.6 pCi/L1,405 testsNone

Sioux City spans 2 counties, each with its own EPA zone and its own CDC figure: Woodbury County (Zone 1, 69.2% of 3,541 tests) and Plymouth County (Zone 1, 82.3% of 1,405 tests).

Woodbury County ranks 36th of 99 Iowa counties with 30 or more tests for that period, 10.7 points above the 58.5% pooled across Iowa's counties, 33.5 points above the national pool of 35.7%. Of the city's other county, Plymouth County reported 82.3%.

The counties nearest Sioux City with a CDC figure for 2008 to 2017, laboratory, measured from the middle of the city: Monona County (38 miles, 74.6% of 603 tests), Sioux County (42 miles, 84.2% of 1,982 tests) and Cherokee County (42 miles, 74.5% of 795 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 69.8% to 84.2%; the farthest of them, Harrison County, is 63 miles away at 69.8%.

The directory lists 4 businesses with an address in Sioux City, 2 for testing and 3 for mitigation. Iowa's other cities with a page of their own: Des Moines, Ames, Iowa City and Waterloo.

Against Iowa and its other counties

Radon test figures for the counties Sioux City lies in
CountyShare of Sioux CityTestsAt or above 4 pCi/LMedianIowa, pooledRank in the stateEPA zone
Woodbury County99.9%3,54169.2%6.1 pCi/L58.5%36 of 99Zone 1
Plymouth County0.1%1,40582.3%8.6 pCi/L58.5%2 of 99Zone 1

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 Sioux City

By distance from the middle of Sioux City; counties with 30 or more tests.

Nearest counties to Sioux City with 30 or more tests
CountyDistanceTestsAt or above 4 pCi/LMedian
Monona County38 mi60374.6%7.0 pCi/L
Sioux County42 mi1,98284.2%10.7 pCi/L
Cherokee County42 mi79574.5%7.6 pCi/L
Ida County45 mi39971.7%7.4 pCi/L
O'Brien County56 mi65281.7%8.9 pCi/L
Crawford County61 mi37374.8%7.0 pCi/L
Lyon County62 mi23777.6%8.3 pCi/L
Harrison County63 mi36769.8%6.2 pCi/L

The median reported pre-mitigation result for 2008 to 2017, laboratory was 6.1 pCi/L in Woodbury County and 8.6 pCi/L in Plymouth County.

Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2008 to 2017, laboratory.

Sioux City, Geology

The ground under Sioux City

Predicted

USGS's geologic map puts all of Sioux City's mapped land in one class: high radon potential. 99.0% of it lies in the area the map calls Loess-Covered Drift Plains, to which USGS gives a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Sioux City
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1399.0%
Pre-Wisconsin glacial depositsLoess-mantled glacial drift.High131.0%

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

Sioux City beside its counties and Iowa

All of Sioux City, like all of Woodbury County, is rated high. On high-potential ground Sioux City is close to Iowa as a whole: 100% of its land against 98.8%.

Share of land by USGS radon potential: Sioux City, the counties it lies in and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Sioux CityBy countyNoneNone100%
Woodbury CountyZone 1NoneNone100%
Plymouth CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Sioux City, Homes

Homes in Sioux City

Of Sioux City's 34,901 homes, 71% are detached houses, against 73% across Woodbury County; 16% are in buildings of five or more homes. Half of its homes were built before 1956, close to Woodbury County's 1958: 57% date from before 1960 and 8% from 2000 or later. 65% of occupied homes are lived in by their owner (Woodbury County: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Sioux City, Woodbury County, Iowa, 2019 to 2023
HomesSioux CityWoodbury CountyIowa
Housing units34,90143,1211,427,175
Detached houses71%73%72%
In buildings of 5 or more16%14%14%
Mobile homes4%4%3%
Built before 196057%53%39%
Built since 20008%11%21%
Middle year built195619581971
Owner-occupied65%68%72%

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

Local help

Sioux City, Professionals

Radon professionals listed in Sioux City

Businesses whose listed city is Sioux City, from the state registries and listings in the Radon411 directory, with the same business and certification status the directory shows.

4 listings with Sioux City as the city. See radon mitigation and testing in Sioux City, or all radon professionals in Iowa.

Sioux City, Local resources

Local resources for Sioux City

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

The program's own words on licensing and disclosure are on the Iowa page.

What it means

Sioux City, Questions

Questions about radon in Sioux City

What radon zone is Sioux City in?

Both counties Sioux City reaches into (Woodbury County and Plymouth County) are in Zone 1, the map's highest class: a predicted county average above 4 pCi/L. EPA zones counties, not cities, so that is the zone for every part of Sioux City.

What are radon levels in Sioux City?

69.2% of the 3,541 tests reported from Woodbury County for 2008 to 2017 (laboratory totals) were at or above 4 pCi/L, the level at which EPA says to fix a home: high results are ordinary around Sioux City. The median reported result was 6.1 pCi/L. Plymouth County reported 82.3% of 1,405 tests; the counties are kept apart.

Should I test my home in Sioux City?

Yes. About 2,450 of the 3,541 tests reported from Woodbury County were at or above 4 pCi/L. That is above Iowa's pooled 58.5%, and ranks Woodbury County 36th of the 99 Iowa counties with 30 or more tests. No map says which homes those are. How to test a home.

What ground is Sioux City built on, as far as radon goes?

USGS's geologic map puts all of Sioux City on one named area, "Loess-Covered Drift Plains", rated high for radon potential, radon index 13.

Is radon higher in the counties around Sioux City?

Yes, in every direction measured. Each of the 8 nearest counties with a figure reports a larger share of high tests than Woodbury County's 69.2%; the highest is Sioux County (84.2%, 42 miles off).

Who tests for or fixes radon in Sioux City?

Radon411's directory has 4 businesses with an address in Sioux City, 2 listed for testing and 3 for mitigation. Every entry names the public list it was taken from. Radon professionals in Sioux City.

The answers use the published figures of Woodbury County and Plymouth County, the counties Sioux City lies in.

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