Is radon high in Sioux City, Iowa?

High. Averaging the model's ZIP-code predictions across Sioux City (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 4.4 pCi/L - about 2.4× the US average of 1.8 and about 1.3× the Iowa average of 3.5. That is at or above the EPA action level of 4 pCi/L. Sioux City ranks 1 of 12 Iowa cities on this site.

Which Sioux City ZIP codes have the highest radon?

Predictions for the 9 modeled ZIP codes in Sioux City range from 3.1 to 5.5 pCi/L in the basement. 67% of them are predicted at or above 4 pCi/L and 100% at or above 2. That spread is why the ZIP table below matters more than the city-wide number.

Should I test for radon in Sioux City?

Yes, soon. With a predicted basement average of 4.4 pCi/L and ZIPs predicted as high as 5.5, a meaningful share of Sioux City homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.

What does EPA Radon Zone 1 mean for Sioux City?

Sioux City sits mainly in Woodbury County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.

Radon levels in Sioux City, Iowa

HighEPA Zone 1

Predicted long-term basement average of 4.4 pCi/L (model estimate) across the 9 modeled ZIP codes in Sioux City - about 2.4× the US average of 1.8, about 1.3× the Iowa average of 3.5. Ranked #1 of 12 Iowa cities on this site. Most of the city lies in Woodbury County (its ZIPs also reach into 1 other county).

Test Sioux City, IA now - and consider a continuous monitor

The model predicts a long-term basement average of 4.4 pCi/L here, at or above the EPA action level of 4. Homes in the same ZIP still vary widely, so a real test is the only way to know your number. A continuous digital monitor shows how your level swings with weather and season, which matters when you're near the action level.

Get a continuous radon monitor →Or start with a short-term test kit

Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.

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Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

4.4 ± 0.08

pCi/L predicted basement mean (model SD)

2.3 ± 0.08

pCi/L predicted upstairs (above-ground) mean

3.1-5.5

range of ZIP-level basement predictions in the city

67%

of Sioux City ZIPs predicted ≥ 4 pCi/L (100% ≥ 2)

What this means for Sioux City

The typical home in Sioux City is predicted to sit at or above the EPA action level of 4 pCi/L in the basement. A large share of houses here would qualify for mitigation if tested, and buyers routinely ask for radon tests in Iowa transactions.

The city figure is not a separate estimate: it is the mean of the model's ZIP-code predictions, weighted by the share of the city's land in each ZIP (Census 2020 ZCTA-to-place relationship file). The 1993 EPA zone (1) for Woodbury and the 2001-2021 model agree here.

Comparable Iowa cities: Des Moines (3.7), Council Bluffs (3.0), West Des Moines (3.0), Urbandale (2.9).

ZIP codes in Sioux City

ZIPs that overlap the city, largest share of its land first. Predicted basement and upstairs means are model estimates; ZIPs the model does not cover show a dash.

ZIP	Share of city	Basement	Upstairs	Grade
51106	25%	4.4 ± 0.06	2.4	High
51103	21%	4.5 ± 0.08	2.1	High
51108	14%	5.5 ± 0.07	2.8	High
51104	13%	4.2 ± 0.06	2.3	High
51111	10%	4.0 ± 0.07	2.0	Moderate
51105	10%	3.2 ± 0.13	1.8	Moderate
51109	3%	5.0 ± 0.08	2.3	High
51101	2%	3.1 ± 0.07	1.8	Moderate
51054	2%	5.1 ± 0.07	2.5	High

Testing help in Iowa

We link only state program pages we could verify, and Iowa's did not respond when we checked, so start from the EPA state radon contacts page. If a test comes back at 4 pCi/L or higher, mitigation typically costs $800-$2,500 installed; use EPA find-a-professional and read the mitigation guide.

Sioux City radon questions

Is radon high in Sioux City, Iowa?: High. Averaging the model's ZIP-code predictions across Sioux City (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 4.4 pCi/L - about 2.4× the US average of 1.8 and about 1.3× the Iowa average of 3.5. That is at or above the EPA action level of 4 pCi/L. Sioux City ranks 1 of 12 Iowa cities on this site.
Which Sioux City ZIP codes have the highest radon?: Predictions for the 9 modeled ZIP codes in Sioux City range from 3.1 to 5.5 pCi/L in the basement. 67% of them are predicted at or above 4 pCi/L and 100% at or above 2. That spread is why the ZIP table below matters more than the city-wide number.
Should I test for radon in Sioux City?: Yes, soon. With a predicted basement average of 4.4 pCi/L and ZIPs predicted as high as 5.5, a meaningful share of Sioux City homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.
What does EPA Radon Zone 1 mean for Sioux City?: Sioux City sits mainly in Woodbury County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.

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