Data & Downloads
Every number on RadonGrade comes from the public datasets below, processed by scripts we publish with the site. This page lists each source (publisher, license, coverage, date) and offers the processed tables as CSV. Our compiled tables are released under CC BY 4.0 - cite "RadonGrade, radongrade.com" and the underlying source. Modeled values are predicted (model estimate); measured values are state-reported test results and are labeled with source and years.
Sources
| Dataset | Publisher | License / terms | Coverage | Retrieved |
|---|---|---|---|---|
| National Radon Exposure Model (ZIP-code averages; Li et al., PNAS 2024) | Harvard T.H. Chan / Emory | CC0 1.0 | 29,215 ZIPs, conterminous US, 2001-2021 | 2026-09-05 |
| EPA Map of Radon Zones (EPA 402/A-16/001 spreadsheet) | US EPA | Public domain (US government work) | 3,144 counties, 1993 classification | 2026-09-05 |
| Census ZCTA-county relationship files (2020 geography; 2010 population weights) | US Census Bureau | Public domain | National | 2026-09-05 |
| Home Radon Test Results by Zip Code (Idaho, measured) | Idaho Department of Health and Welfare, Indoor Environment / Radon Program | No license statement on the public feature service (publicly shared by the IDHW environmental-health account) | 44 counties, through 2019 (start year not stated by the source), 45,517 tests | 2026-09-05 |
| Minnesota radon test results by county (Minnesota, measured) | Minnesota Department of Health (MN Public Health Data Access) | Minnesota public data (Minn. Stat. ch. 13); no license statement on the portal | 87 counties, 2016-2025 | 2026-09-05 |
| Radon Test Results By County: Beginning 1987 (New York, measured) | New York State Department of Health, Bureau of Environmental Radiation Protection | No license field on the dataset; NYS Open Data terms of use (https://data.ny.gov/dataset/OPEN-NY-Terms-Of-Use/77gx-ii52) permit reuse with attribution | 58 counties, 1987-2025, 122,814 tests | 2026-09-05 |
| Radon Test Results September 1986 - Current Annual County Environmental Protection (Pennsylvania, measured) | Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection | Public Domain (as stated on data.pa.gov) | 67 counties, 1988-2026, 1,872,999 tests | 2026-09-05 |
| VT Data - Radon Tests by Town (Vermont, measured) | Vermont Department of Health, Environmental Public Health Tracking | Public Vermont Department of Health data; item terms are a disclaimer only ("No responsibility is assumed by the Vermont Department of Health ... All users must read and fully comprehend metadata prior to data use") | 14 counties, 1994-2025, 26,805 tests | 2026-09-05 |
| Wisconsin Indoor Radon Test Results (Wisconsin Radon Map Service, layer 3) (Wisconsin, measured) | Wisconsin Department of Health Services | No license statement on the public feature service; attribution "Wisconsin Department of Health Services, Bureau of Information Technology Services" per the item metadata | 72 counties, 1995-2016, 102,698 tests | 2026-09-05 |
Checked but not included: Tennessee (an earlier version of the state's ArcGIS layer states access requires Department of Health permission), Virginia (the dashboard's feature layer is not publicly readable), Colorado, Ohio, Iowa, Kentucky, Illinois, New Jersey, Maine, Montana and Utah (no county- or ZIP-level test export located on an open-data portal at the time of retrieval). We never estimate a state's measured results.
Downloads (CSV)
counties.csv - 3,143 rows
Predicted radon by US county (model estimate) with EPA zone
All 3,143 counties (50 states + DC). Predicted long-term mean indoor radon in pCi/L for basements and above-ground floors, 2010-population-weighted from the ZIPs whose primary county is that county (blank for 58 counties with no such ZIP), plus the 1993 EPA radon zone.
Columns: fips, state, county, epaZone, predBasementMean, predUpstairsMean, zipCount. Radon values in pCi/L; pct columns are percentages of tests.
zips.csv - 29,215 rows
Predicted radon by ZIP code (model estimate)
29,215 ZIP codes in the conterminous US with the model's predicted basement and upstairs means and the Census-assigned primary county.
Columns: zip, state, countyFips, predBasementMean, predUpstairsMean. Radon values in pCi/L; pct columns are percentages of tests.
measured-id.csv - 44 rows
Measured radon test results by county, Idaho (through 2019 (start year not stated by the source))
44 counties. IDHW publishes tests (N), mean pCi/L and the number of tests above 3.9 pCi/L for 272 ZIP codes, "updated through 2019". We assign each ZIP to its primary county with the Census 2020 ZCTA-county relationship file, sum counts and take the test-weighted mean of ZIP means. ">3.9" equals ">= 4.0" for results reported to one decimal.
Columns: fips, state, county, tests, testsPerYear, mean, median, pctAbove4, pctAbove2, basementMean, upperMean, yearsCovered, source. Radon values in pCi/L; pct columns are percentages of tests. Blank cells mean the source does not publish that measure.
measured-mn.csv - 87 rows
Measured radon test results by county, Minnesota (2016-2025)
87 counties. MDH publishes county arithmetic mean, median, 95th percentile, % of tests at or above 4 and 2 pCi/L, and the average annual number of properties tested. Used as published.
Columns: fips, state, county, tests, testsPerYear, mean, median, pctAbove4, pctAbove2, basementMean, upperMean, yearsCovered, source. Radon values in pCi/L; pct columns are percentages of tests. Blank cells mean the source does not publish that measure.
measured-ny.csv - 58 rows
Measured radon test results by county, New York (1987-2025)
58 counties. NYSDOH publishes one row per county per test location (Basement, 1st Floor) with homes tested, average pCi/L and counts of results < 4, 4-20 and >= 20. We add the two locations: tests = homes tested, mean = test-weighted mean of the two averages, % >= 4 from the counts. Results are from the state program's own short-term charcoal kits (NYSDOH notes 30,000-40,000 other tests a year are not included). 59 of 62 counties are present in the source.
Columns: fips, state, county, tests, testsPerYear, mean, median, pctAbove4, pctAbove2, basementMean, upperMean, yearsCovered, source. Radon values in pCi/L; pct columns are percentages of tests. Blank cells mean the source does not publish that measure.
measured-pa.csv - 67 rows
Measured radon test results by county, Pennsylvania (1988-2026)
67 counties. PA DEP publishes every individual test reported by certified testers (2.80 million rows, 616 MB). We kept Residential tests with a numeric result, then computed per-county count, arithmetic mean, median, % >= 4 and % >= 2 pCi/L across all floors, plus the basement-only mean. Not de-duplicated by address, so repeat and post-mitigation tests are included as the state publishes them.
Columns: fips, state, county, tests, testsPerYear, mean, median, pctAbove4, pctAbove2, basementMean, upperMean, yearsCovered, source. Radon values in pCi/L; pct columns are percentages of tests. Blank cells mean the source does not publish that measure.
measured-vt.csv - 14 rows
Measured radon test results by county, Vermont (1994-2025)
14 counties. VDH geocodes every residential test (long-term program tests 1994-2025 plus VDH Laboratory tests 2020-2025), keeps the highest result per address, and publishes residences tested and residences >= 4.0 pCi/L by town. We sum towns to counties. "tests" therefore means tested residences, and no mean or median is published.
Columns: fips, state, county, tests, testsPerYear, mean, median, pctAbove4, pctAbove2, basementMean, upperMean, yearsCovered, source. Radon values in pCi/L; pct columns are percentages of tests. Blank cells mean the source does not publish that measure.
measured-wi.csv - 72 rows
Measured radon test results by county, Wisconsin (1995-2016)
72 counties. 102,698 indoor tests aggregated by DHS to ZIP code (count, mean, median, tests >= 4 and >= 2). Each ZIP carries a county FIPS in the file; we sum counts per county and take the test-weighted mean of ZIP means. County medians cannot be derived and are left blank.
Columns: fips, state, county, tests, testsPerYear, mean, median, pctAbove4, pctAbove2, basementMean, upperMean, yearsCovered, source. Radon values in pCi/L; pct columns are percentages of tests. Blank cells mean the source does not publish that measure.
How to cite
"RadonGrade (2026). Predicted and measured radon levels by US county and ZIP code. radongrade.com/data/. Predicted values from Li et al., National Radon Exposure Model (CC0); measured values from the state agencies listed above." For the method behind every figure see the methodology.