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Radon Levels in St. Louis County, Minnesota

EPA puts St. Louis County in Zone 2, its middle radon zone, and 20.2% of its 496 reported radon tests (2023) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    20.2%

    14.4 pts below MN

    St. Louis
    20.2%
    Minnesota
    34.6%

    496 tests, 2023

  • Median result

    1.7pCi/L

    Below action level

    St. Louis
    1.7 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    496

    9th of 62 by tests

    St. Louis
    496
    Hennepin
    6,545

    Reported to CDC before any fix, 2023

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Minnesota

    59 of 62

    Lowest quarter

    St. Louis
    20.2%
    Renville
    75.7%

    By share, of 62 with 30+ tests

Read a result for St. Louis County

Starts at St. Louis County's median, 1.7 pCi/L

1.7pCi/L

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

EPA’s reading of 1.7 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. St. Louis County's median reported result, 2023.

Interpret this reading

The data

St. Louis County, At a glance

St. Louis County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

St. Louis County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for St. Louis County, 2023

Share of reported tests at or above 4 pCi/L, by year, St. Louis County
Share of reported tests at or above 4 pCi/L, by year, St. Louis County
YearShare of reported tests at or above 4 pCi/L
201424.8%
201527.6%
201623.6%
201727.4%
201824.5%
201931.1%
202023.2%
202126.3%
202230.2%
202320.2%

2023: 20.2%. Across these years the share ran from 20.2% to 31.1%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 496 tests reported to CDC for St. Louis County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

St. Louis County, Compared

St. Louis County radon figures, compared

Calculated by Radon411

St. Louis County's 496 reported tests in 2023 had a middle value of 1.7 pCi/L and a maximum of 33.0 pCi/L, and 20.2% reached 4 pCi/L. Minnesota as a whole (86 Minnesota counties, pooled) comes to 34.6%: 14.4 points higher than here.

Among its state's counties it ranks 59th of 62 Minnesota counties with 30 or more tests for the same period. Statewide for the same period, Renville County reported the highest share (75.7%) and Lake County the lowest (3.8%).

Below the action level, 274 tests (55.2%) came in under 2 pCi/L, against 36.6% statewide, and 122 tests (24.6%) fell between 2 and 4, against 28.9% statewide. The busiest year on file was 2016, with 1,507 tests reported; the quietest, 2019, had 425.

EPA's 1993 zone map puts St. Louis County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.

Next door, the shares run from 3.8% in Lake County to 41.9% in Carlton County, with Douglas County, WI and Lake County below St. Louis County. Over 10 years of annual figures the share fell 4.6 points, from 24.8% in 2014 to 20.2% in 2023; its peak was 31.1% in 2019.

Share of reported tests at or above 4 pCi/L by year, St. Louis County against Minnesota2014 to 2023, years with 30 or more tests: St. Louis County 24.8% to 20.2%, the state's pooled share 34.6% in 2023.
St. Louis CountyMinnesota, pooled
Share of reported tests at or above 4 pCi/L by year, St. Louis County against Minnesota: data table
YearTestsSt. Louis County, at or above 4 pCi/LMinnesota, pooled
20141,43324.8%42.9%
20151,49827.6%43.6%
20161,50723.6%37.0%
20171,21727.4%38.2%
201875424.5%38.3%
201942531.1%36.1%
202067323.2%31.8%
202171126.3%33.1%
202249430.2%31.6%
202349620.2%34.6%
St. Louis County against Minnesota, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from St. Louis County
St. Louis County49620.2%1.7 pCi/LThis county
Minnesota, pooled86 counties, pooled22,44934.6%Not pooled+14.4 points
United States, pooled642 counties, pooled128,74033.4%Not pooled+13.2 points
Renville Countyhighest in the state3775.7%6.3 pCi/L+55.5 points
Cook Countylowest in the state3212.5%1.8 pCi/L−7.7 points
Koochiching County, MNborders it450.0%2.9 pCi/L+29.8 points
Carlton County, MNborders it10541.9%3.1 pCi/L+21.7 points
Aitkin County, MNborders it3138.7%3.1 pCi/L+18.5 points
Itasca County, MNborders it13726.3%1.9 pCi/L+6.1 points
Douglas County, WIborders it449.1%1.5 pCi/L−11.1 points
Lake County, MNborders it783.8%1.3 pCi/L−16.4 points
Where St. Louis County's reported results fell, 2023, beside Minnesota and the United States
ResultSt. Louis County testsSt. Louis County shareMinnesota shareU.S. shareAgainst Minnesota
Under 2 pCi/L27455.2%36.6%41.4%+18.6 points
2 to 4 pCi/L12224.6%28.9%25.2%−4.3 points
4 pCi/L and above10020.2%34.6%33.4%−14.4 points
St. Louis County ranked among the 62 Minnesota counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Cass County52 of 6210625.5%2.3 pCi/L
Todd County53 of 626323.8%2.0 pCi/L
Ramsey County54 of 622,21323.5%2.2 pCi/L
Benton County55 of 624323.3%2.2 pCi/L
Isanti County56 of 626622.7%2.0 pCi/L
Sherburne County57 of 6235121.7%1.8 pCi/L
Washington County58 of 621,51821.3%1.9 pCi/L
St. Louis County59 of 6249620.2%1.7 pCi/L
Anoka County60 of 6288019.3%1.9 pCi/L
Cook County61 of 623212.5%1.8 pCi/L
Lake County62 of 62783.8%1.3 pCi/L
St. Louis County radon tests by year, against Minnesota's pooled share
YearTestsAt or above 4 pCi/LMedianHighestMinnesota, pooledChange from the row before
202349620.2%1.7 pCi/L33.0 pCi/L34.6%−10.0 points
202249430.2%2.4 pCi/L79.0 pCi/L31.6%+3.9 points
202171126.3%2.2 pCi/L415.7 pCi/L33.1%+3.1 points
202067323.2%1.9 pCi/L39.2 pCi/L31.8%−7.9 points
201942531.1%2.6 pCi/L32.3 pCi/L36.1%+6.6 points
201875424.5%2.1 pCi/L51.8 pCi/L38.3%−2.9 points
20171,21727.4%2.1 pCi/L67.6 pCi/L38.2%+3.8 points
20161,50723.6%1.9 pCi/L138.9 pCi/L37.0%−4.0 points
20151,49827.6%2.3 pCi/L130.1 pCi/L43.6%+2.8 points
20141,43324.8%2.0 pCi/L75.1 pCi/L42.9%First on file

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

St. Louis County, State data

Minnesota's own radon test data

Measured

What Minnesota's own agencies publish about radon tests in St. Louis County, with their period. These are not CDC's figures and are never added to them.

MeasuredState figures, not CDC's

What the Minnesota Department of Health reports for St. Louis County

Radon Testing (MN Public Health Data Access Portal): home radon tests reported voluntarily by private laboratories and licensed radon measurement professionals, counted by property. Period: 2016-2025.

Share with one or more tests at or above 4 pCi/L

26.6%

1,602 properties tested with one or more tests at or above 4 pCi/L

Median result

2.2 pCi/L

Average result

3.3 pCi/L

Tests behind these figures

602 properties tested a year on average

  • MDH says these data do not include all of the radon tests conducted in Minnesota.
  • Post-mitigation tests are excluded from the averages and the median; the percentages use each property's highest test.
  • Each home is unique and can have very different results than a neighbor's home; the only way to know is to test.
  • These figures describe tests reported to the Minnesota Department of Health in this area. They count a different set of tests than CDC's figures and are not a reading of any one home.

Measured: Minnesota Department of Health data, 2016-2025.

St. Louis County, Geology

The ground under St. Louis County

Predicted

USGS's geologic map puts all of St. Louis County's mapped land in one class: moderate radon potential. The map puts 56.0% of St. Louis County in the area it calls Superior Upland/Central Lowland-Western Lake Section and 43.9% in Lake Agassiz Plain/Central Lowland-Western Lake Section. USGS gives both a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under St. Louis County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Superior Upland/Central Lowland-Western Lake SectionGlacial deposits derived primarily from volcanic rock.Moderate1056.0%
Lake Agassiz Plain/Central Lowland-Western Lake SectionSilty and clayey glacial deposits and lake deposits.Moderate1043.9%

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

St. Louis County beside the ground around it

Across Minnesota 61.1% of the land is rated high; none of St. Louis County's is. Of the 6 counties that border it, 4 have more moderate-potential ground, Itasca County the most at 100%.

Share of land by USGS radon potential: St. Louis County, the 6 counties bordering it and Minnesota
AreaEPA zoneLow potentialModerate potentialHigh potential
St. Louis CountyZone 2None99.9%None
Lake CountyZone 2None99.9%None
Itasca CountyZone 2None100%None
Carlton CountyZone 2None100%None
Koochiching CountyZone 2None99.9%None
Douglas County, WIZone 2None99.5%None
Aitkin CountyZone 2None100%None
Minnesota87 counties, pooled by land areaVariesNone38.9%61.1%

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

Local help

St. Louis County, Local resources

Radon testing and mitigation in St. Louis County

Listed radon businesses with an address in St. Louis County:

Listed radon professionals by town: Duluth, Hibbing, Proctor

What Minnesota's program says
Phone
651-201-4601
Email
health.indoorair@state.mn.us
Licensing of radon professionals
The Radon Licensing Act requires anyone who performs a radon test or radon mitigation, in a building they do not own or lease, must be licensed by MDH.
Disclosure when a home is sold or rented
The Minnesota Radon Awareness Act requires specific disclosure and education be provided to potential home buyers during residential real estate transactions in Minnesota.

What it means

St. Louis County, Questions

Questions about radon in St. Louis County

Are radon levels high in St. Louis County?

In 2023, 20.2% of the radon tests reported to CDC for St. Louis County, Minnesota were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.7 pCi/L. Of 62 Minnesota counties with 30 or more tests for the same period, 58 reported a higher share; pooled, the state comes to 34.6%.

Which counties border St. Louis County?

St. Louis County borders 6 counties: Lake County, MN, Itasca County, MN, Carlton County, MN, Koochiching County, MN, Douglas County, WI and Aitkin County, MN.

Products

St. Louis County, Products

Testing a home in St. Louis County

In St. Louis County, 20.2% of 496 tests reported to CDC in 2023 reached 4 pCi/L, against 34.6% pooled across Minnesota. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in St. Louis County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for St. Louis County homes, compared

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St. Louis County, Bordering counties

Counties bordering St. Louis County

Calculated by Radon411

St. Louis County, Cities and towns

Cities and towns in St. Louis County

St. Louis County's population has barely moved since 2020: 200,518 residents on July 1, 2025 against 200,067 then, by the Census Bureau's estimates. That works out to 32 people per square mile of land. Its largest town, Duluth, has 88,330 residents, 44.1% of the total. Together its 27 incorporated places hold 77.2% of those residents; the other 22.8% live outside any of them. Reported testing is thin here: 496 tests over 2023, or 2.5 for every 1,000 residents (2025 estimate), where Minnesota as a whole comes to 3.9.

From Duluth to Leonidas, CDC publishes no figure by town: each reads St. Louis County's.

The 12 largest cities and towns in St. Louis County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Duluth88,330+1.7%44.1%
Hibbing15,823−2.2%7.9%
Hermantown10,110+0.6%5.0%
Virginia8,187−2.6%4.1%
Chisholm4,625−2.9%2.3%
Rice Lake4,169+1.5%2.1%
Eveleth3,381−3.0%1.7%
Ely3,231−0.9%1.6%
Proctor3,054−1.9%1.5%
Mountain Iron2,835−1.3%1.4%
Hoyt Lakes1,978−1.8%1.0%
Gilbert1,644−2.6%0.8%
  • Aurora
  • Babbitt
  • Biwabik
  • Buhl
  • Cook
  • Floodwood
  • Tower
  • Orr
  • Winton
  • Kinney
  • Meadowlands
  • Brookston
  • Iron Junction
  • McKinley
  • Leonidas

27 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

St. Louis County, Homes

Homes in St. Louis County

Of St. Louis County's 103,924 homes, 74% are detached houses, against 66% across Minnesota; 13% are in buildings of five or more homes. The homes are older than Minnesota's as a whole: half were built before 1962 (1978 for Minnesota), and 48% date from before 1960. 72% of occupied homes are lived in by their owner (Minnesota: 72%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in St. Louis County, Minnesota, 2019 to 2023
HomesSt. Louis CountyMinnesota
Housing units103,9242,519,538
Detached houses74%66%
In buildings of 5 or more13%19%
Mobile homes4%3%
Built before 196048%29%
Built since 200014%22%
Middle year built19621978
Owner-occupied72%72%

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