Understanding Radon in Michigan
1 IN 4
Michigan homes is expected to have elevated radon
83 COUNTIES
have found elevated radon levels
RADON
is the second-leading cause of lung cancer in the United States
4.0 pCi/L
is the EPA level at which mitigation is recommended
WHAT IS RADON?
Radon begins in the ground beneath us.
Radon forms naturally when uranium and radium in soil and rock break down. It is radioactive, but because it is a gas, it can move through the soil and enter buildings.
Radon exists in outdoor air at low concentrations. The concern begins when it enters an enclosed building and accumulates to higher levels. The national average is approximately 0.4 pCi/L outdoors and 1.3 pCi/L inside homes, although individual homes can test much higher.
Uranium in soil → Radium → Radon gas → Home
A basement does not cause radon.
Basements and lower levels are simply closer to the soil and are often where radon concentrations are highest.
How does radon enter a home?
Your home can draw soil gas inside.
Common entry points include:
-
Cracks in concrete floors and foundation walls
-
Construction joints
-
Sump pits
-
Gaps around pipes and utility penetrations
-
Openings around drains
-
Crawlspaces
-
Hollow block walls
-
Well water in certain circumstances
EPA says radon can enter through cracks, construction joints, gaps around service pipes, wall cavities, water supplies, and other openings connected to the ground. It can affect new or old homes, sealed or drafty homes, and homes with or without basements.
The danger comes from long-term exposure
health risks
Why is radon a health risk?
When radon gas breaks down, it produces radioactive particles. When inhaled, those particles can become trapped in the lungs and damage lung tissue over time. That damage can eventually contribute to lung cancer.
Radon exposure generally does not cause immediate symptoms. Lung cancer may develop many years after exposure, which is why testing and prevention are important even when everyone in the home feels healthy.
-
Radon is the second-leading cause of lung cancer after cigarette smoking.
-
It is the leading cause of lung cancer among people who have never smoked, according to EPA estimates.
-
EPA estimates that radon contributes to approximately 21,000 lung cancer deaths each year in the United States.
-
Smoking and radon exposure together create a substantially greater risk than either exposure alone.
Researchers are continuing to study radon’s wider health effects
The established health effect of residential radon exposure is lung cancer. New research is also examining whether radon may be associated with other cancers.
A 2026 prospective cohort study published in JAMA Network Open followed 127,547 postmenopausal women. Women whose baseline residences were located in areas estimated to have radon above 4 pCi/L had a statistically higher risk of ovarian cancer than women in lower-radon areas. The adjusted hazard ratio was 1.31, corresponding to a 31% higher relative hazard in the study’s high-radon group. Ovarian cancer mortality was also higher in that group. The study does not yet establish radon as a cause of ovarian cancer. It does, however, add to the reasons scientists and public-health organizations continue to study and reduce long-term residential radon exposure.
Radon is not limited to one part of Michigan
Why radon matters in Michigan
Michigan EGLE reports:
-
Elevated radon has been found in all 83 counties.
-
Approximately one in four Michigan homes has elevated radon.
-
One home’s result cannot predict the result next door.
-
Home age, foundation type, and apparent draftiness cannot determine whether a home has elevated levels.
-
The state’s county map is based on more than 200,000 homeowner tests.
EGLE also maintains a ZIP-code-level map of first-time tests that includes minimum and maximum results, average values, total tests, and the percentage of tests above 2 and 4 pCi/L. EGLE specifically warns that regional data should not be used to decide whether an individual home needs testing.
Your ZIP code can show regional patterns. It cannot tell you the radon level inside your home.
High risk does not always mean strong protections
The Indoor Environments Association’s 2026 Michigan Radon Report Card identifies several policy gaps:
-
Michigan does not require a radon credential statewide.
-
No statewide radon professional standards are listed as being in effect.
-
Homebuyer protection is limited to disclosure of known conditions.
-
School radon testing is not required statewide.
-
Radon systems are required in new one- and two-family homes in applicable EPA Zone 1 counties through IRC Appendix F.
Radon is not only a homeowner issue
-
Homeowners
-
Renters
-
Homebuyers and sellers
-
Children and school employees
-
Child care providers
-
Office and commercial building occupants
-
People who spend significant time in basements
-
Current and former smokers
Radon can accumulate in homes, schools, offices, child care settings, and other buildings. Lower occupied levels frequently deserve particular attention because they are closest to the ground.
Testing is the only way to know.
know your radon level
01
Test
Place or schedule a test
02
MEASURE
Measure the lowest occupied level
03
REVIEW
Review your average radon result
When to test
-
Your home has never been tested.
-
The previous result is unknown.
-
You are buying or selling a home.
-
You are finishing or beginning to use a basement.
-
You have renovated the home or altered the HVAC system.
-
You have installed a mitigation system and need verification.
-
It has been approximately two years since your previous test.
EGLE recommends testing every two years because foundations and building conditions can change. EPA also recommends considering a new test when a previous test is more than two years old, after renovations, or when living patterns move to a lower level.
CDC states that there is no known safe level of radon and advises keeping exposure as low as practical. EPA recommends mitigation at 4.0 pCi/L or higher. AARST’s report card notes that professional standards also advise considering mitigation between 2.0 and 4.0 pCi/L.
Low exposure
Below 2.0 pCi/L
Lower exposure, but not zero risk. Retest periodically.
Mild exposure
2.0–3.9 pCi/L
Consider steps to reduce the level and continue monitoring.
Dangerous exposure
4.0 pCi/L or higher
EPA recommends installing a radon-reduction system
Elevated radon can be reduced
Most residential systems use active soil depressurization. A fan creates negative pressure beneath the slab or crawlspace membrane, captures radon before it enters the occupied space, and vents it safely above the roofline.
After installation, the building should be tested again to verify that the system is working. EPA says even very high radon levels can generally be reduced using a properly designed reduction system.
Myth vs Fact
Fact: New and old homes can both have elevated levels.
Fact: Slab-on-grade and crawlspace homes can also be affected.
Fact: Results can vary substantially from one lot or house to another.
Fact: There are typically no short-term warning signs.
Fact: Ventilation may temporarily change the level, but it is not a reliable permanent mitigation strategy.
Fact: Maps describe regional patterns; only a test measures your home. These points are directly supported by Michigan EGLE, CDC, and EPA guidance.
You do not have to guess about the air in your home
take action
Radon is common, invisible, and potentially dangerous—but it is also measurable and manageable. A properly conducted test gives you the information needed to make a confident decision.
Trusted Resources
Michigan EGLE Indoor Radon Program
Michigan Radon Results Map
CDC Radon Toolkit
EPA Radon Guidance
JAMA Network Open ovarian-cancer study
Indoor Environments Association Michigan Report Card
All Michigan Mitigation Blog