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Radon Levels in Hillsborough County, Florida

EPA puts Hillsborough County in Zone 2, its middle radon zone, and most reported tests there come back low, though 7.5% of 984 (2023) reached 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

    7.5%

    11.0 pts below FL

    Hillsborough
    7.5%
    Florida
    18.5%

    984 tests, 2023

  • Median result

    0.9pCi/L

    Below action level

    Hillsborough
    0.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    984

    8th of 30 by tests

    Hillsborough
    984
    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

    15 of 30

    Middle half

    Hillsborough
    7.5%
    Marion
    44.5%

    By share, of 30 with 30+ tests

Read a result for Hillsborough County

Starts at Hillsborough County's median, 0.9 pCi/L

0.9pCi/L

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

EPA’s reading of 0.9 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. Hillsborough County's median reported result, 2023.

Interpret this reading

The data

Hillsborough County, At a glance

Hillsborough County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Hillsborough 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 56% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Hillsborough County, 2023

Share of reported tests at or above 4 pCi/L, by year, Hillsborough County
Share of reported tests at or above 4 pCi/L, by year, Hillsborough County
YearShare of reported tests at or above 4 pCi/L
201414.8%
20158.1%
201610.3%
201713.8%
201816.2%
20196.0%
20207.6%
20214.8%
202217.6%
20237.5%

2023: 7.5%. Across these years the share ran from 4.8% to 17.6%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 984 tests reported to CDC for Hillsborough 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

Hillsborough County, Compared

Hillsborough County radon figures, compared

Calculated by Radon411

Hillsborough County reports fewer high tests than Florida overall. 7.5% of its 984 tests in 2023 were at or above 4 pCi/L. That is 11.0 points below the 18.5% pooled from 49 Florida counties.

Ordered from highest share down, it comes 15th of 30 Florida counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 33.4%; Hillsborough County sits 25.9 points below it.

Next door, the shares run from 0.6% in Pasco County to 11.0% in Manatee County, with Pinellas County and Pasco County below Hillsborough County. The reported tests do not follow EPA's Zone 2 label for Hillsborough County (predicted average between 2 and 4 pCi/L): 7.5% of them reached 4 pCi/L, fewer than that label suggests.

Half the tests came in under 0.9 pCi/L and half over it; the single highest reached 48.2 pCi/L. The rest split 82.8% under 2 pCi/L and 9.7% from 2 to 4 (Florida: 57.3% and 24.2%). Year by year, 2014 opened at 14.8% and 2023 closed at 7.5% (down 7.3 points), with 2022 the high at 17.6%.

The busiest year on file was 2022, with 2,205 tests reported; the quietest, 2016, had 507.

Share of reported tests at or above 4 pCi/L by year, Hillsborough County against Florida2014 to 2023, years with 30 or more tests: Hillsborough County 14.8% to 7.5%, the state's pooled share 18.5% in 2023.
Hillsborough CountyFlorida, pooled
Share of reported tests at or above 4 pCi/L by year, Hillsborough County against Florida: data table
YearTestsHillsborough County, at or above 4 pCi/LFlorida, pooled
20141,08214.8%25.7%
20157088.1%26.5%
201650710.3%24.3%
201767913.8%21.7%
201899816.2%23.5%
20196486.0%29.6%
20207007.6%23.2%
20216674.8%15.4%
20222,20517.6%22.8%
20239847.5%18.5%
Hillsborough County against Florida, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Hillsborough County
Hillsborough County9847.5%0.9 pCi/LThis county
Florida, pooled49 counties, pooled16,58918.5%Not pooled+11.0 points
United States, pooled642 counties, pooled128,74033.4%Not pooled+25.9 points
Marion Countyhighest in the state18244.5%3.6 pCi/L+37.0 points
Clay Countylowest in the state360.0%1.0 pCi/L−7.5 points
Manatee County, FLborders it26311.0%1.5 pCi/L+3.5 points
Polk County, FLborders it13611.0%1.1 pCi/L+3.5 points
Pinellas County, FLborders it5595.9%1.2 pCi/L−1.6 points
Pasco County, FLborders it1640.6%0.8 pCi/L−6.9 points
Where Hillsborough County's reported results fell, 2023, beside Florida and the United States
ResultHillsborough County testsHillsborough County shareFlorida shareU.S. shareAgainst Florida
Under 2 pCi/L81582.8%57.3%41.4%+25.5 points
2 to 4 pCi/L959.7%24.2%25.2%−14.5 points
4 pCi/L and above747.5%18.5%33.4%−11.0 points
Hillsborough 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
Sarasota County10 of 3049612.3%1.6 pCi/L
Polk County11 of 3013611.0%1.1 pCi/L
Manatee County12 of 3026311.0%1.5 pCi/L
Orange County13 of 301,1079.5%0.9 pCi/L
Broward County14 of 302,1659.4%1.7 pCi/L
Hillsborough County15 of 309847.5%0.9 pCi/L
Duval County16 of 307926.2%0.4 pCi/L
Pinellas County17 of 305595.9%1.2 pCi/L
Wakulla County18 of 30313.2%0.8 pCi/L
Seminole County19 of 301901.6%0.6 pCi/L
Osceola County20 of 30701.4%1.2 pCi/L
Hillsborough County radon tests by year, against Florida's pooled share
YearTestsAt or above 4 pCi/LMedianHighestFlorida, pooledChange from the row before
20239847.5%0.9 pCi/L48.2 pCi/L18.5%−10.1 points
20222,20517.6%1.1 pCi/L32.3 pCi/L22.8%+12.8 points
20216674.8%0.9 pCi/L24.1 pCi/L15.4%−2.8 points
20207007.6%0.8 pCi/L118.7 pCi/L23.2%+1.6 points
20196486.0%1.0 pCi/L17.9 pCi/L29.6%−10.2 points
201899816.2%1.7 pCi/L23.9 pCi/L23.5%+2.4 points
201767913.8%1.1 pCi/L38.5 pCi/L21.7%+3.5 points
201650710.3%0.8 pCi/L14.5 pCi/L24.3%+2.2 points
20157088.1%1.0 pCi/L24.3 pCi/L26.5%−6.7 points
20141,08214.8%1.1 pCi/L31.3 pCi/L25.7%First on file

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

Hillsborough County, Geology

The ground under Hillsborough County

Predicted

USGS's geologic map splits Hillsborough County: 56.1% of its land is low radon potential and 41.4% moderate. The map puts 56.1% of Hillsborough County in the area it calls Gulf/Atlantic Lowland and Central Highland and 41.4% 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 Hillsborough County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Gulf/Atlantic Lowland and Central Highlandsand, silt, clay, gravelLow656.1%
Highland Anomalous areasPhosphate deposits.Moderate1141.4%

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

Hillsborough County beside the ground around it

Hillsborough County has more moderate-potential ground than Florida as a whole: 41.4% of its land against 7.1%. Of the 5 counties that border it, none has as large a share of moderate-potential ground; Polk County comes nearest at 33.7%.

Share of land by USGS radon potential: Hillsborough County, the 5 counties bordering it and Florida
AreaEPA zoneLow potentialModerate potentialHigh potential
Hillsborough CountyZone 256.1%41.4%None
Pinellas CountyZone 384.1%NoneNone
Pasco CountyZone 376.2%23.0%None
Polk CountyZone 266.3%33.7%None
Manatee CountyZone 386.6%6.9%None
Hardee CountyZone 374.3%25.7%None
Florida67 counties, pooled by land areaVaries89.7%7.1%None

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

Local help

Hillsborough County, Local resources

Radon testing and mitigation in Hillsborough County

Listed radon businesses with an address in Hillsborough County:

Listed radon professionals by town: Tampa

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

Hillsborough County, Questions

Questions about radon in Hillsborough County

Are radon levels high in Hillsborough County?

In 2023, 7.5% of the radon tests reported to CDC for Hillsborough County, Florida were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of 30 Florida counties with 30 or more tests for the same period, 14 reported a higher share; pooled, the state comes to 18.5%.

Which counties border Hillsborough County?

Hillsborough County borders 5 counties: Pinellas County, Pasco County, Polk County, Manatee County and Hardee County.

Products

Hillsborough County, Products

Testing a home in Hillsborough County

In Hillsborough County, 7.5% of 984 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 Hillsborough County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Hillsborough County homes, compared

Explore

Hillsborough County, Bordering counties

Counties bordering Hillsborough County

Calculated by Radon411

Hillsborough County, Cities and towns

Cities and towns in Hillsborough County

Hillsborough County is growing: the Census Bureau puts it at 1,574,115 residents on July 1, 2025, up 7.4% from 1,466,246 in 2020. Packed into its land, that is 1,540 people per square mile. Its largest town, Tampa, has 413,554 residents, 26.3% of the total. Together its 3 incorporated places hold 30.8% of those residents; the other 69.2% live outside any of them. CDC's 984 reported tests for 2023 work out to 0.6 per 1,000 residents (2025 estimate), close to Florida's 0.7.

From Tampa to Temple Terrace, CDC publishes no figure by town: each reads Hillsborough County's.

The cities and towns in Hillsborough County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Tampa413,554+6.4%26.3%
Plant City44,118+10.9%2.8%
Temple Terrace27,075+1.4%1.7%

3 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).

Hillsborough County, Homes

Homes in Hillsborough County

Of Hillsborough County's 618,220 homes, 57% are detached houses, against 55% across Florida; 23% are in buildings of five or more homes. Half of its homes were built before 1990, close to Florida's 1988: 11% date from before 1960 and 36% from 2000 or later. 61% of occupied homes are lived in by their owner (Florida: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Hillsborough County, Florida, 2019 to 2023
HomesHillsborough CountyFlorida
Housing units618,22010,082,356
Detached houses57%55%
In buildings of 5 or more23%25%
Mobile homes7%8%
Built before 196011%10%
Built since 200036%30%
Middle year built19901988
Owner-occupied61%67%

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