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RADON411
$5

County radon report

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Data

Data sources

Every source behind Radon411's numbers and guides, by name, grouped by what it feeds: predicted maps, measured test results, the figures we calculate, the guidance and the directory.

Updated October 2, 2026

At a glance

Where the numbers come from

Radon411 keeps three kinds of number apart, and every source below feeds exactly one of them, or the guides and the directory.

2
Predicted maps: what an area is expected to have, never a measurement
7 of 7
Measured datasets loaded: tests that were actually carried out
88
Publications behind the guides, from 25 publishers

Predicted

Predicted: maps of expected radon

A classification for a whole area, produced from geology and past measurements. It says nothing certain about any one home.

  • U.S. Environmental Protection Agency

    EPA Map of Radon Zones

    On Radon411
    The EPA zone on every county and state report, and the county map
    Covers
    All U.S. counties
    Licence
    U.S. Government Work, public domain; redistribute with attribution to EPA.

    Updated September 25, 2026

  • U.S. Geological Survey

    USGS Geologic Radon Potential Map of the United States (2025)

    On Radon411
    The geologic radon potential on county reports, as the share of each county in each class
    Covers
    United States: conterminous states, Alaska and Hawaii (three layers)
    Licence
    CC0 1.0 Universal, public domain dedication; no restriction on redistribution.

    Updated September 25, 2026

Measured

Measured: radon tests that were carried out

Results reported to a public health agency, shown at the geography the agency published them for. A state's figures are never mixed with CDC's.

Measured datasets
PublisherDatasetCoversDate
Centers for Disease Control and PreventionCDC Environmental Public Health Tracking, Radon TestingStates and counties that report to CDC EPHT radon testing measuresUpdated September 25, 2026
Colorado Department of Public Health and Environment (CDPHE), Colorado Environmental Public Health TrackingRadon data (county results)CO: county; 2005 to 2025, evaluated across all years availableUpdated October 1, 2026
Michigan Department of Environment, Great Lakes, and Energy (EGLE), Indoor Radon ProgramMichigan Indoor Radon ResultsMI: zip; approximately the preceding 10 years, refreshed at least quarterlyUpdated October 1, 2026
Minnesota Department of Health (MDH), Minnesota Environmental Public Health TrackingRadon Testing (MN Public Health Data Access Portal)MN: county, state; 2016 to 2025Updated October 2, 2026
Nevada Bureau of Mines and Geology and University of Nevada Cooperative Extension (Nevada Radon Education Program)Radon averages by ZIP code (NBMG Hazards: Radon_Average)NV: zip; 1989 through 2015Updated October 2, 2026
New York State Department of Health, Bureau of Environmental Radiation ProtectionIndoor air radon testing data (Environmental Public Health Tracker)NY: county, state; five-year periods from 2000-2004 to 2015-2019Updated October 2, 2026
Pennsylvania Department of Environmental Protection (DEP), Bureau of Radiation ProtectionRadon Test Data by Zip CodePA: zip; not stated in DEP's reportUpdated October 2, 2026

Where a state reports fewer than five tests for a place, Radon411 shows the count but not the figures. Every state dataset's terms of reuse were checked before it was used; the licences are in the last section.

Calculated

Calculated: what Radon411 works out

Figures Radon411 derives from published data, each labelled as calculated, with its method on the methodology page. These are the places and populations it works from.

  • U.S. Census Bureau

    Cartographic boundary files, through the us-atlas package

    On Radon411
    Every state and county, its boundary and code; the neighbours and map points Radon411 works out from them
    Covers
    56 states and territories, 3,231 counties
    Licence
    U.S. government work, public domain; the us-atlas packaging is under the ISC licence

    Updated October 2, 2026

  • U.S. Census Bureau

    Census 2020 ZCTA to County Relationship File

    On Radon411
    Which county a ZIP code area falls in
    Covers
    All 2020 ZCTAs and the 2020 counties they overlap
    Licence
    U.S. Government Work, public domain; redistribute with attribution to the U.S. Census Bureau.

    Updated September 25, 2026

  • U.S. Census Bureau

    Census 2020 Place Reference Codes (incorporated places)

    On Radon411
    The cities and towns that have their own report
    Covers
    Incorporated places in the 2020 place reference file, 50 states, DC and Puerto Rico where listed
    Licence
    U.S. Government Work, public domain; redistribute with attribution to the U.S. Census Bureau.

    Updated September 25, 2026

  • U.S. Census Bureau

    Census Population Estimates Program, county and state totals

    On Radon411
    State and county population on reports
    Covers
    50 states, the District of Columbia and their counties (Puerto Rico is published separately)
    Licence
    U.S. Government Work, public domain; redistribute with attribution to the U.S. Census Bureau.

    Updated September 25, 2026

  • U.S. Census Bureau

    Census Population Estimates Program, incorporated place totals

    On Radon411
    City population on city reports
    Covers
    Incorporated places in the 50 states and the District of Columbia
    Licence
    U.S. Government Work, public domain; redistribute with attribution to the U.S. Census Bureau.

    Updated September 25, 2026

Guidance

Guidance: what the guides and answers are written from

Every fact in a guide or answer is checked against the publication's own words before it is published. Open a publisher to see its publications and when each was last checked.

  • U.S. Environmental Protection Agency

    The action level, the testing and fixing advice, and the guides built on them

    Checked September 25, 2026

  • Kansas State University

    Background for the guides

    Checked September 25, 2026

EPA43 publications · checked September 28, 2026

CDC10 publications · checked September 28, 2026

Minnesota Department of Health5 publications · checked September 28, 2026

Iowa HHS3 publications · checked September 28, 2026

PubChem (NIH)3 publications · checked September 28, 2026

National Cancer Institute2 publications · checked September 28, 2026

New Jersey Department of Environmental Protection2 publications

Pennsylvania Department of Environmental Protection2 publications · checked September 28, 2026

Wisconsin Department of Health Services2 publications

AARST1 publication · checked September 28, 2026

ATSDR (CDC)1 publication · checked September 28, 2026

HHS1 publication · checked September 28, 2026

HUD Archives1 publication · checked September 28, 2026

IARC1 publication · checked September 28, 2026

Idaho Department of Health and Welfare1 publication

Illinois Emergency Management Agency and Office of Homeland Security1 publication

Mississippi State Department of Health1 publication

Missouri Department of Health and Senior Services1 publication

Nebraska DHHS1 publication · checked September 28, 2026

NIEHS (NIH)1 publication · checked September 28, 2026

North Carolina Division of Public Health1 publication

Utah DEQ1 publication

Virginia Department of Health1 publication

Washington State Department of Health1 publication

WHO1 publication · checked September 28, 2026

Directory

The directory and the state program cards

Professionals are listed from the lists their state licenses them on, and checked against the national certification bodies. Neither pays to be named here.

  • Radon411, compiled from individual state agency pages

    The state radon program card on every state and county report

    Checked September 25, 2026

  • National Radon Proficiency Program (a program of AARST)

    Checking a listed professional's NRPP certification before it is marked verified

    Checked September 25, 2026

  • National Radon Safety Board

    Checking a listed professional's NRSB certification before it is marked verified

    Checked September 25, 2026

  • Various state environmental and health agencies

    The state radon program card, checked against each state's own page

    Checked September 25, 2026

  • Illinois Emergency Management Agency (IEMA)

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • Iowa Department of Health and Human Services, Bureau of Radiological Health

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • Minnesota Department of Health

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • New Jersey Department of Environmental Protection

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • Kentucky Board of Radon Safety

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • Nebraska Department of Health and Human Services, Radon Program

    The professionals that state licenses, in the directory

    Checked September 25, 2026

  • Florida Department of Health, Radon Program

    The professionals that state licenses, in the directory

    Checked September 25, 2026

Licences

Attributions a licence requires

Most of what Radon411 uses is public domain. These are the sources whose licence asks for a credit or a notice, given here in the licence's own terms.

Radon averages by ZIP code (NBMG Hazards: Radon_Average)

Credit
Nevada Bureau of Mines and Geology, University of Nevada, Reno
Licence
Creative Commons Attribution 4.0 International (CC BY 4.0), creativecommons.org/licenses/by/4.0/
Notice
© Copyright 2010 The University of Nevada, Reno. The data are supplied as-is: the Nevada Bureau of Mines and Geology, the University of Nevada, Reno and the Nevada System of Higher Education make no warranties of any kind. The material: gisweb.unr.edu/nbmg/rest/services/Hazards/Radon_Average/MapServer
Changes
Radon411 rounds each average to one decimal place for display.
Why it is here
CC BY 4.0, section 3(a)(1)(C): “indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License”.

us-atlas, the packaging of the Census boundary files the maps are drawn from

Credit
Michael Bostock
Licence
ISC licence
Notice
Copyright 2013-2019 Michael Bostock. Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
Why it is here
ISC licence: “provided that the above copyright notice and this permission notice appear in all copies”.

The EPA, CDC and Census Bureau material is a U.S. government work and the USGS map is dedicated to the public domain under CC0; each is named in its group above.

Our images

Reusing our images

The figures, charts and maps Radon411 makes are free to reuse under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.

What you may do

You may copy, share and adapt them, for any purpose, commercial included, as long as you credit us.

The credit line

RADON411, linked to the page the image came from: for example, “Image: RADON411”, with RADON411 linking to the guide or state report where you found it.

The facts in each image come from the public agencies named in its source line. Photographs on the site that we did not take keep their own licences, given on the about page.

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Where to go from here