Radon Levels & Zone Map in St. Louis County, MN
Direct Answer for basement and lowest-level tests: St. Louis County sits in the gray zone. The map helps, but your own reading matters more than the countywide signal.
Treat the map as a hint, not the answer
Zone 2 is the gray area. A real reading is what decides whether you retest, track, or price mitigation.
Gray-zone county signal. Some homes stay low, others cross the EPA line.
2.0-3.9 pCi/L usually means retest or track. 4.0+ is where EPA action and quote planning start to matter.
No reading: test first. Borderline results often need retest or long-term tracking.
Measured Radon Data
St. Louis County evidence before the next step
St. Louis County, MN has more than the EPA map: Minnesota Department of Health exposes 6,996 reported tests, 3.4 pCi/L county average, 2.1 pCi/L median, 27.0% of reported tests at or above 4.0 pCi/L, and 10.8 pCi/L high-end signal for 2010-2020.
Source window
2010-2020
Processed verdict
Elevated measured burden
High confidence - 100/100
Primary result
3.4 pCi/L
20th percentile in-state
4.0+ signal
27.0%
5th percentile in-state
High-end signal
10.8 pCi/L
25th percentile in-state
County-specific verdict
St. Louis County is elevated enough that map-reading should turn into a home test.
St. Louis County is a priority-test case because 3.4 pCi/L average, 2.1 pCi/L median, and 27.0% of reported tests at or above 4.0. In-state rank: 20th percentile for average, and 5th percentile for 4.0+ share. The county signal is strong enough to justify testing or retesting before cost decisions.
Real-estate use
Buyer or seller use: ask for a fresh lowest-level test before inspection deadlines, tie any 4.0+ result to a contractor quote, and do not negotiate from the county signal alone.
St. Louis County has enough measured elevation that buyers and owners should not stop at the county signal; confirm the home and price mitigation if the result crosses 4.0.
Choose Next StepElevated-intent answer
Are radon levels elevated in St. Louis County?
St. Louis County has enough measured elevation that the answer should not stop at the EPA zone. 27.0% of reported tests at or above 4.0 pCi/L, 3.4 pCi/L primary measured result, and 10.8 pCi/L high-end signal makes a first test or confirmatory retest the right next step before cost decisions.
Pick the situation that matches you
You should not need to read the whole guide before clicking one of these. Start with the lane that matches your current stage, then come back for the deeper reference only if you still need it.
Jump into a prefilled St. Louis County action plan based on the result you already have, instead of starting from a generic cost page.
I have not tested yet
Do not price mitigation blind. Get the first number, then decide whether you need monitoring, quotes, or nothing at all.
My result is 2.0-3.9
Usually retest or track first. If the reading keeps showing up, use the local action plan to decide whether pricing makes sense.
My result is 4.0+
This is the EPA action line. Use the local cost page before calling contractors so you know the likely scope, timing, and budget.
I am buying or selling
Turn the reading into a credit or repair number before negotiation starts. This is the faster path than arguing from a generic article.
Already tested once and just want to watch the number trend?
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County Evidence Snapshot
St. Louis County testing context
St. Louis County is a gray-zone county: the EPA map is useful context, but the local housing profile and your own home test decide the next step.
EPA map signal
Zone 2
County-level predicted indoor screening range, not a home-level test result.
Housing base
103,719
94th percentile among 87 MN counties with data.
Older housing share
28.9%
26th percentile in-state; older homes often need clearer test placement decisions.
Median home value
$192,900
Used as context for whether mitigation is a small maintenance item or a negotiation issue.
Measured Radon Data
Minnesota Department of Health Indoor Air Unit Radon Test Data
2010-2020
Average result
3.4 pCi/L
At or above 4.0
27.0%
95th percentile
10.8 pCi/L
Avg. tests/year
636.0
Minnesota county summaries are based on reported commercial and residential radon tests, mostly single-family homes, and exclude most continuous-monitor real-estate tests.
RadonVerdict Processed Verdict
Elevated measured burden
Primary result rank
20th percentile
3.4 pCi/L
4.0+ rank
5th percentile
27.0% at or above 4.0
High-end rank
25th percentile
10.8 pCi/L
Test volume rank
91st percentile
636.0 avg/year
How to use this county data
Data source
Official county measurements
Minnesota values combine reported commercial and residential tests, so the verdict favors distribution signals like 4.0+ share and high-end readings.
What the numbers show
Fuller county picture
This is the most useful setup: county average, 4.0+ share, high-end readings, and 6,996 reported tests/properties can be read together instead of relying on one number.
Nearby comparison
Nearby comparison: Closest counties by share of tests at or above 4.0 pCi/L: Lake County (25.4%) is just lower, and Kittson County (27.1%) is just higher.
How this helps
Use this to decide whether the county signal is strong enough to justify testing or retesting before cost decisions.
What the data says
St. Louis County, MN is measurement-backed for 2010-2020. The measured average is 3.4 pCi/L, and 27.0% of reported results are at or above 4.0 pCi/L. The high-end signal reaches 10.8 pCi/L.
St. Louis County, MN sits at the 20th percentile for measured average, 5th percentile for 4.0+ share, 25th percentile for high-end readings, and 91st percentile for test volume among 87 measured counties in the state. Closest counties by county average: Pine County (3.4 pCi/L) is just lower, and Washington County (3.4 pCi/L) is just higher.
What to do with it
St. Louis County has enough measured elevation that buyers and owners should not stop at the county signal; confirm the home and price mitigation if the result crosses 4.0.
Retest trigger: a 2.0-3.9 pCi/L home result should be confirmed here because 3.4 pCi/L average, 2.1 pCi/L median, and 27.0% of reported tests at or above 4.0 keeps the county from being a dismiss-it signal.
High confidence (100/100) from Minnesota Department of Health based on about 6,996 reported tests/properties plus comparable county-level measurement fields.
No reading yet
No reading yet: run a short-term test now, then confirm or price mitigation quickly if the result is elevated.
2.0-3.9 result
2.0-3.9 pCi/L: retest or track longer-term rather than dismissing the result, because the county distribution has meaningful elevated readings.
4.0+ result
4.0+ pCi/L: use the result for mitigation quotes, repair scope, or seller-credit negotiation; the county signal is no longer the deciding input.
Source hierarchy: Minnesota Department of Health is used for this county, with EPA zone and Census housing data kept as supporting context. Minnesota values combine reported commercial and residential tests, so the verdict favors distribution signals like 4.0+ share and high-end readings.
Direct Answer
What radon risk level should homeowners assume in St. Louis County?
St. Louis County is currently categorized as EPA Zone 2 (Moderate Risk). Test all lived-in levels and confirm with follow-up testing if elevated.
| Evidence | Value |
|---|---|
| Area | St. Louis County, MN |
| EPA Zone | Zone 2 |
| Primary Recommendation | Perform direct radon testing in the lowest livable level |
Your Radon Reading
Enter your home's measured level; the starting value is only a planning example until you have your own result.
Elevated - Consider Action
Your reading is below the US EPA action level (4.0 pCi/L), but this range still warrants follow-up testing. The World Health Organization uses 2.7 pCi/L as a tighter reference point.
If this was just a one-time snapshot, confirm it with another test or with longer tracking. If this level persists, planning mitigation is reasonable, especially for homes with frequent basement use, children, or pending real-estate transactions. Scroll down to see your estimated cost.
Understanding Radon Levels: Complete Reference
Below 2.0 pCi/L - Lower Concern, Keep Testing
Below both the EPA (4.0) and WHO (2.7) action reference levels. This usually means mitigation is not the next immediate step after a confirmed result. The average outdoor radon level is approximately 0.4 pCi/L, and there is no known risk-free indoor level. Periodic testing is still recommended because levels can change over time due to seasonal variations, changes in home ventilation, or foundation settling.
-4.0
2.0 - 4.0 pCi/L - Elevated, Consider Action
Exceeds the World Health Organization's reference level of 2.7 pCi/L but falls below the US EPA action threshold. The EPA states that homeowners should "consider fixing" homes in this range, especially if the home has a basement used as living space, if children are present, or in connection with a real estate transaction. Practical next step: run a confirmatory long-term test, then compare mitigation quotes if levels remain elevated.
-8.0
4.0 - 8.0 pCi/L - Action Recommended
Exceeds the EPA action level of 4.0 pCi/L. The EPA and Surgeon General strongly recommend mitigation within a few months. At this level, prioritize confirmatory testing and contractor planning. Standard sub-slab depressurization systems typically reduce indoor levels by 80-99%.
Above 8.0 pCi/L - Urgent Action Required
At these levels, the EPA recommends expedited mitigation - ideally within weeks, not months. Occupants should minimize time in lower-level rooms until the system is installed. Use a certified mitigator and request priority scheduling to shorten high-exposure time. Many mitigators offer priority scheduling for homes above 8.0 pCi/L.
Why Radon is Worth Monitoring in St. Louis County
St. Louis County falls in EPA Zone 2, where the predicted indoor screening range is between 2.0 and 4.0 pCi/L. Even when the countywide map signal sits below the EPA action level, geological variability means that some individual homes will still test above 4.0 pCi/L.
The soil composition in this area typically includes a mix of sedimentary formations that can contain moderate uranium deposits. Homes with basement or crawlspace foundations are particularly susceptible, as they provide more pathways for soil gas entry.
The World Health Organization recommends action at 2.7 pCi/L - well below the US EPA threshold. If you have children, spend significant time in below-grade rooms, or are buying/selling a home, testing is essential even in a Zone 2 area.
Radon & Health: What the Science Says
lung cancer
from radon
4.0 pCi/L
Radon is a Class A carcinogen - the same classification as asbestos and tobacco smoke. The National Academy of Sciences estimates that radon causes approximately 21,000 lung cancer deaths annually in the United States, making it the leading environmental cause of cancer death.
Unlike smoking, radon exposure is involuntary and often invisible. There is no safe level of radon - risk increases linearly with exposure. The good news: radon mitigation systems are highly effective, typically reducing indoor levels by 80-99% within hours of activation.
Source: US Environmental Protection Agency, "A Citizen's Guide to Radon" (EPA 402/K-12/002). National Academy of Sciences, Biological Effects of Ionizing Radiation (BEIR VI) Report, 1999.
Step 1: Test Your Home
Testing is the only way to know your home's radon level. Zone data tells you the regional risk, but your home could be significantly higher or lower than the countywide pattern. For most homeowners, the right first purchase is a low-cost short-term test kit.
A digital monitor is a better fit after your first result, for seasonal re-checks, or to keep tracking levels after mitigation.
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Already Know Your Level?
If your test shows 4.0 pCi/L or higher, get an itemized cost estimate specific to St. Louis County - including regional labor rates and permit requirements.
Get Mitigation Cost Estimate ->MN Radon Regulations
Minnesota requires radon disclosure at the time of sale. The Minnesota Department of Health provides extensive radon resources for homebuyers and sellers.
Minnesota requires radon mitigation professionals to be licensed by the Minnesota Department of Health.
How to Test for Radon in St. Louis County
Buy a Test Kit
Purchase a short-term charcoal test kit online or from a local hardware store. Cost: $15-$30. Place it in the lowest livable level of your home.
Wait 2-7 Days
Keep doors and windows closed (except normal entry/exit) during the test period. Avoid running whole-house fans. Mail the kit to the lab provided.
Read Your Results
If results are below 4.0 pCi/L, re-test every 2 years or use a monitor for ongoing tracking. If above 4.0, use our cost calculator to see mitigation options.
Related Radon Resources for St. Louis County
Explore Other MN Counties
Official State Resource
Minnesota radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure rule tracked
Minnesota requires radon disclosure at the time of sale. The Minnesota Department of Health provides extensive radon resources for homebuyers and sellers.
State licensing required
Minnesota requires radon mitigation professionals to be licensed by the Minnesota Department of Health.
Sources & Methodology
Radon zone classifications for St. Louis County are sourced from the EPA's Map of Radon Zones, which uses geological surveys, indoor radon measurements, and soil permeability data to assign each county a risk tier.
Disclaimer: Zone data represents county-level screening ranges and cannot predict the radon level in any specific home. Testing is the only reliable method to determine your home's radon concentration. This content is for informational purposes and is not medical advice.
Content review: Source-level retrieval dates
Editorial and Data Transparency
- Author
- RadonVerdict Data Team (Public Data and Cost Modeling)
- Content Review
- Source-level dates shown below
- Data Retrieved At
- 2026-02-24
Primary Sources
- EPA Map of Radon Zones (retrieved 2026-02-21)
- EPA A Citizen's Guide to Radon (retrieved 2026-05-05)
- CDC Environmental Public Health Tracking - Radon Testing (retrieved 2026-05-05)
- Minnesota Department of Health Indoor Air Unit Radon Test Data (retrieved 2026-05-05)
- Official MN radon program
- US Census Bureau, 2018-2022 American Community Survey 5-Year Estimates (retrieved 2026-02-24)