Skip to content
RADON411

Locations and reports

Radon Levels in Marion County, Florida

EPA puts Marion County in Zone 2, its middle radon zone, and high results are common there: 44.5% of the 182 radon tests reported to CDC (2023) came back 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    44.5%

    26.0 pts above FL

    Marion
    44.5%
    Florida
    18.5%

    182 tests, 2023

  • Median result

    3.6pCi/L

    Below action level

    Marion
    3.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    182

    16th of 30 by tests

    Marion
    182
    Broward
    2,165

    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 Florida

    1 of 30

    Top quarter

    Marion
    44.5%
    Marion
    44.5%

    By share, of 30 with 30+ tests

Read a result for Marion County

Starts at Marion County's median, 3.6 pCi/L

3.6pCi/L

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

EPA’s reading of 3.6 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Marion County's median reported result, 2023.

Interpret this readingWhat a fix costs

The data

Marion County, At a glance

Marion County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Marion 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: Low across 69% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Marion County, 2023

Share of reported tests at or above 4 pCi/L, by year, Marion County
Share of reported tests at or above 4 pCi/L, by year, Marion County
YearShare of reported tests at or above 4 pCi/L
201450.9%
201554.7%
201644.3%
201745.8%
201831.4%
201925.9%
202043.5%
202135.8%
202231.9%
202344.5%

2023: 44.5%. Across these years the share ran from 25.9% to 54.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 182 tests reported to CDC for Marion 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

Marion County, Compared

Marion County radon figures, compared

Calculated by Radon411

In Marion County, about 4 in 10 reported tests in 2023 (81 of 182) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 11.1 points higher. Across 49 Florida counties pooled together, 18.5% of tests reached that level, so Marion County runs 26.0 points above its state.

Of 3 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 0.0% (Lake County) to 21.4% (Alachua County). By share, Marion County is 1st of 30 Florida counties with 30 or more tests for the same period.

Year by year, 2014 opened at 50.9% and 2023 closed at 44.5% (down 6.4 points), with 2015 the high at 54.7%. Half the tests came in under 3.6 pCi/L and half over it; the single highest reached 165.3 pCi/L. Below the action level, 33 tests (18.1%) came in under 2 pCi/L, against 57.3% statewide, and 68 tests (37.4%) fell between 2 and 4, against 24.2% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 44.5% share point the same way here. USGS geology rates 69% of the county's land low radon potential. CDC also counts 103 tests taken after mitigation in Marion County for the same period: tests in homes where a fix was already in.

The busiest year on file was 2022, with 546 tests reported; the quietest, 2017, had 83.

Share of reported tests at or above 4 pCi/L by year, Marion County against Florida2014 to 2023, years with 30 or more tests: Marion County 50.9% to 44.5%, the state's pooled share 18.5% in 2023.
Marion CountyFlorida, pooled
Share of reported tests at or above 4 pCi/L by year, Marion County against Florida: data table
YearTestsMarion County, at or above 4 pCi/LFlorida, pooled
201422050.9%25.7%
201525854.7%26.5%
201648544.3%24.3%
20178345.8%21.7%
201811831.4%23.5%
201913525.9%29.6%
202014743.5%23.2%
202130235.8%15.4%
202254631.9%22.8%
202318244.5%18.5%
Marion County against Florida, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Marion County
Marion County18244.5%3.6 pCi/LThis county
Florida, pooled49 counties, pooled16,58918.5%Not pooled−26.0 points
United States, pooled642 counties, pooled128,74033.4%Not pooled−11.1 points
Palm Beach Countyhighest in the state1,52640.1%3.0 pCi/L−4.4 points
Clay Countylowest in the state360.0%1.0 pCi/L−44.5 points
Citrus County, FLborders it333.3%3.4 pCi/L−11.2 points
Alachua County, FLborders it65921.4%2.4 pCi/L−23.1 points
Volusia County, FLborders it1631.2%0.6 pCi/L−43.3 points
Sumter County, FLborders it120.0%0.9 pCi/L−44.5 points
Lake County, FLborders it1590.0%0.6 pCi/L−44.5 points
Levy County, FLborders it110.0%1.7 pCi/L−44.5 points
Putnam County, FLborders it100.0%0.9 pCi/L−44.5 points
Where Marion County's reported results fell, 2023, beside Florida and the United States
ResultMarion County testsMarion County shareFlorida shareU.S. shareAgainst Florida
Under 2 pCi/L3318.1%57.3%41.4%−39.2 points
2 to 4 pCi/L6837.4%24.2%25.2%+13.2 points
4 pCi/L and above8144.5%18.5%33.4%+26.0 points
Marion County ranked among the 30 Florida counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Marion County1 of 3018244.5%3.6 pCi/L
Palm Beach County2 of 301,52640.1%3.0 pCi/L
Miami-Dade County3 of 301,91939.6%2.8 pCi/L
Charlotte County4 of 309131.9%2.9 pCi/L
Collier County5 of 301,60722.7%2.3 pCi/L
Alachua County6 of 3065921.4%2.4 pCi/L
Lee County7 of 301,22420.3%2.2 pCi/L
Leon County8 of 301,19619.1%1.8 pCi/L
Gadsden County9 of 309614.6%1.3 pCi/L
Sarasota County10 of 3049612.3%1.6 pCi/L
Polk County11 of 3013611.0%1.1 pCi/L
Marion County radon tests by year, against Florida's pooled share
YearTestsAt or above 4 pCi/LMedianHighestFlorida, pooledChange from the row before
202318244.5%3.6 pCi/L165.3 pCi/L18.5%+12.6 points
202254631.9%2.8 pCi/L39.2 pCi/L22.8%−3.9 points
202130235.8%2.7 pCi/L52.4 pCi/L15.4%−7.7 points
202014743.5%2.8 pCi/L77.0 pCi/L23.2%+17.6 points
201913525.9%2.4 pCi/L27.0 pCi/L29.6%−5.5 points
201811831.4%3.0 pCi/L25.9 pCi/L23.5%−14.4 points
20178345.8%3.7 pCi/L93.2 pCi/L21.7%+1.5 points
201648544.3%3.5 pCi/L128.6 pCi/L24.3%−10.4 points
201525854.7%4.4 pCi/L33.0 pCi/L26.5%+3.8 points
201422050.9%4.0 pCi/L85.0 pCi/L25.7%First on file

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

Marion County, Geology

The ground under Marion County

Predicted

USGS's geologic map splits Marion County: 68.6% of its land is low radon potential and 31.4% moderate. The map puts 68.6% of Marion County in the area it calls Gulf/Atlantic Lowland and Central Highland and 31.4% in Highland Anomalous areas. USGS gives the first a radon index of 6, in the low band (5 to 8), and the second 11, in the moderate band (9 to 11).

USGS's geologic areas under Marion County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Gulf/Atlantic Lowland and Central Highlandsand, silt, clay, gravelLow668.6%
Highland Anomalous areasPhosphate deposits.Moderate1131.4%

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

Marion County beside the ground around it

Marion County has more moderate-potential ground than Florida as a whole: 31.4% of its land against 7.1%. Of the 7 counties that border it, 2 have more moderate-potential ground, Citrus County the most at 50.4%.

Share of land by USGS radon potential: Marion County, the 7 counties bordering it and Florida
AreaEPA zoneLow potentialModerate potentialHigh potential
Marion CountyZone 268.6%31.4%None
Putnam CountyZone 3100%NoneNone
Lake CountyZone 3100%NoneNone
Alachua CountyZone 252.7%47.3%None
Citrus CountyZone 240.7%50.4%None
Sumter CountyZone 380.6%19.4%None
Levy CountyZone 384.6%12.3%None
Volusia CountyZone 398.3%NoneNone
Florida67 counties, pooled by land areaVaries89.7%7.1%None

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

Local help

Marion County, Local resources

Radon testing and mitigation in Marion County

Listed radon businesses with an address in Marion County:

Listed radon professionals by town: Ocala

What Florida's program says
Phone
850-245-4288
Email
PHtoxicology@FLhealth.gov
Licensing of radon professionals
Florida Statutes require the certification of businesses and individuals providing radon services or any other radon related activity.

What it means

Marion County, Questions

Questions about radon in Marion County

Are radon levels high in Marion County?

In 2023, 44.5% of the radon tests reported to CDC for Marion County, Florida were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.6 pCi/L. Of 30 Florida counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 18.5%.

Which counties border Marion County?

Marion County borders 7 counties: Putnam County, Lake County, Alachua County, Citrus County, Sumter County, Levy County and Volusia County.

Products

Marion County, Products

Testing a home in Marion County

In Marion County, 44.5% of 182 tests reported to CDC in 2023 reached 4 pCi/L, against 18.5% pooled across Florida. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Marion County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Marion County homes, compared

Explore

Marion County, Bordering counties

Counties bordering Marion County

Calculated by Radon411

Marion County, Cities and towns

Cities and towns in Marion County

Marion County is growing: the Census Bureau puts it at 442,660 residents on July 1, 2025, up 17.3% from 377,432 in 2020. That works out to 279 people per square mile of land. No town dominates: Ocala, the largest, has 71,753 residents, 16.2% of the total. Together its 5 incorporated places hold 18.4% of those residents; the other 81.6% live outside any of them. Reported testing is thin here: 182 tests over 2023, or 0.4 for every 1,000 residents (2025 estimate), where Florida as a whole comes to 0.7.

From Ocala to Reddick, CDC publishes no figure by town: each reads Marion County's.

The cities and towns in Marion County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Ocala71,753+12.3%16.2%
Belleview6,512+17.6%1.5%
Dunnellon2,056+5.8%0.5%
McIntosh551+17.5%0.1%
Reddick535+18.4%0.1%

5 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).

Marion County, Homes

Homes in Marion County

Of Marion County's 183,453 homes, 67% are detached houses, against 55% across Florida; 19% are mobile homes. Half of its homes were built before 1992, close to Florida's 1988: 5% date from before 1960 and 35% from 2000 or later. Owners live in 77% of the occupied homes (Florida: 67%), so for most households a test and a fix are their own to order.

Homes in Marion County, Florida, 2019 to 2023
HomesMarion CountyFlorida
Housing units183,45310,082,356
Detached houses67%55%
In buildings of 5 or more6%25%
Mobile homes19%8%
Built before 19605%10%
Built since 200035%30%
Middle year built19921988
Owner-occupied77%67%

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