Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in Jefferson County, New York
EPA puts Jefferson County in Zone 2, its middle radon zone, and only 5 radon tests from it are on file with CDC (2023). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
16.0%
8.5 pts below NY
- Jefferson
- 16.0%
- New York
- 24.5%
1,204 tests, 2008 to 2017
Median result
1.5pCi/L
Below action level
- Jefferson
- 1.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
1,204
22nd of 61 by tests
- Jefferson
- 1,204
- Erie
- 13,822
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in New York
43 of 61
Middle half
- Jefferson
- 16.0%
- Chemung
- 52.3%
By share, of 61 with 30+ tests
Read a result for Jefferson County
Starts at Jefferson County's median, 1.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.5 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Jefferson County's median reported result, 2008 to 2017.
The data
Jefferson County, At a glance
Jefferson County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Jefferson County is a
USGS geologic potential: Moderate across 93% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Jefferson County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 58.8% |
| 2015 | 30.0% |
| 2016 | 20.8% |
| 2017 | 23.5% |
| 2018 | 22.4% |
| 2019 | 25.0% |
| 2020 | 28.8% |
| 2021 | 0.0% |
| 2022 | 0.0% |
| 2023 | 40.0% |
2023: 40.0%. Across these years the share ran from 0.0% to 58.8%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 5 tests were reported to CDC for Jefferson County over 2023, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Jefferson County, Compared
Jefferson County radon figures, compared
Calculated by Radon411Jefferson County's 1,204 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.5 pCi/L and a maximum of 83.4 pCi/L, and 16.0% reached 4 pCi/L. New York as a whole (62 New York counties, pooled) comes to 24.5%: 8.5 points higher than here.
The newest figure, in 2023, counts only 5 tests (40.0% at or above 4 pCi/L), too few to compare, so this reading uses the 1,204-test figure.
Among its state's counties it ranks 43rd of 61 New York counties with 30 or more tests for the same period. Statewide for the same period, Chemung County reported the highest share (52.3%) and Bronx County the lowest (3.2%).
Below the action level, 724 tests (60.1%) came in under 2 pCi/L, against 51.7% statewide, and 287 tests (23.8%) fell between 2 and 4, against 23.7% statewide. The busiest year on file was 2017, with 68 tests reported; the quietest, 2022, had 3.
EPA's 1993 zone map puts Jefferson County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 93% of the county's land moderate radon potential.
Next door, the shares run from 13.2% in St. Lawrence County to 20.2% in Lewis County, with Oswego County and St. Lawrence County below Jefferson County. Over 5 years of annual figures the share rose 8.0 points, from 20.8% in 2016 to 28.8% in 2020; its peak was 28.8% in 2020.
CDC also counts 72 tests taken after mitigation in Jefferson County for the same period: tests in homes where a fix was already in.
Jefferson CountyNew York, pooled
| Year | Tests | Jefferson County, at or above 4 pCi/L | New York, pooled |
|---|---|---|---|
| 2016 | 53 | 20.8% | 20.4% |
| 2017 | 68 | 23.5% | 31.6% |
| 2018 | 58 | 22.4% | 26.9% |
| 2019 | 48 | 25.0% | 28.0% |
| 2020 | 52 | 28.8% | 22.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Jefferson County, State data
New York's own radon test data
MeasuredWhat New York's own agencies publish about radon tests in Jefferson County, with their period. These are not CDC's figures and are never added to them.
MeasuredState figures, not CDC's
What the New York State Department of Health reports for Jefferson County
Indoor air radon testing data (Environmental Public Health Tracker): short-term charcoal canister tests requested through the NYSDOH Radon Program, presented as five-year rolling averages. Period: 2015-2019. The publisher also lists 15 earlier periods.
Share at or above 4 pCi/L
24%
Average result
6.6 pCi/L
Tests behind these figures
48.4 tests a year on average
- Every figure is a five-year rolling average: the average result is the rolling average of each year's mean, and the test count is an average per year.
- The data only include tests requested through the NYSDOH Radon Program, and therefore may not capture all radon tests performed in a county.
- The data include both screening tests and post-mitigation tests, as it is not always possible to tell them apart.
- Radon testing by homeowners is optional in New York, so the values may not be representative of every home in the county.
- These figures describe tests reported to the New York State Department of Health in this area. They count a different set of tests than CDC's figures and are not a reading of any one home.
Measured: New York State Department of Health data, 2015-2019.
Jefferson County, Geology
The ground under Jefferson County
PredictedUSGS's geologic map puts all of Jefferson County's mapped land in one class: moderate radon potential. The map puts 73.6% of Jefferson County in the area it calls Erie-Ontario Lowland and 14.4% in Northwest Lowlands, with 2 smaller areas beside them. USGS gives the first a radon index of 9 and the second 11, both in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Erie-Ontario Lowland | Limestone, dolomite, shale, sandstone, and salt deposits. | Moderate | 9 | 73.6% |
| Northwest Lowlands | Glacial gravel deposits, marble, quartzite, felsic to mafic gneiss. | Moderate | 11 | 14.4% |
| Tug Hill Plateau | Limestone, dolomite, chert. | Moderate | 9 | 3.1% |
| St. Lawrence Champlain-Lowlands | Cambrian-Ordovician sedimentary rocks (conglomerates and sandstones). | Moderate | 10 | 2.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Jefferson County beside the ground around it
Across New York 48.9% of the land is rated high; none of Jefferson County's is. Of the 3 counties that border it, 1 has more moderate-potential ground, Oswego County the most at 99.5%.
The map rates the ground, not the air in any home.
Local help
Jefferson County, Local resources
Radon testing and mitigation in Jefferson County
- Radon ProgramRadon Program, run by New York State Department of Health, does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in New York.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Providing patients with information about how low-cost test kits may be obtained from the Radon Program.
- Compare kits
- Professionals in New York88 professionals are listed in New York.
What New York's program says
- Phone
- 518-402-7556
- radon@health.ny.gov
- Licensing of radon professionals
NYS does not certify or license radon testers.
What it means
Jefferson County, Questions
Questions about radon in Jefferson County
Are radon levels high in Jefferson County?
In 2023, 40.0% of the radon tests reported to CDC for Jefferson County, New York were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.4 pCi/L. Of 61 New York counties with 30 or more tests for the same period, 42 reported a higher share; pooled, the state comes to 24.5%.
Which counties border Jefferson County?
Jefferson County borders 3 counties: Lewis County, Oswego County and St. Lawrence County.
Products
Jefferson County, Products
Testing a home in Jefferson County
In Jefferson County, 16.0% of 1,204 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 24.5% pooled across New York. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Jefferson County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
MonitorAranet
Radon Plus battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Approved
- Battery
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Jefferson County, Bordering counties
Counties bordering Jefferson County
Calculated by Radon411- Radon levels in Lewis CountyEPA zone 2
20.2%at or above 4 pCi/L
Median 1.4 pCi/L · 109 tests · 4.2 points above Jefferson County
- Radon levels in Oswego CountyEPA zone 2
15.2%at or above 4 pCi/L
Median 1.4 pCi/L · 778 tests · 0.8 points below Jefferson County
- Radon levels in St. Lawrence CountyEPA zone 2
13.2%at or above 4 pCi/L
Median 1.2 pCi/L · 151 tests · 2.8 points below Jefferson County
Jefferson County, Cities and towns
Cities and towns in Jefferson County
About 111,540 people live in Jefferson County by the Census Bureau's estimate for July 1, 2025, 4,535 fewer than in 2020 (−3.9%). That works out to 88 people per square mile of land. Its largest town, Watertown, has 23,517 residents, 21.1% of the total. Together its 20 incorporated places hold 38.2% of those residents; the other 61.8% live outside any of them. Testing is reported here more often than across the state: CDC's 1,204 reported tests for 2008 to 2017 come to 10.8 for every 1,000 residents (2025 estimate), against 4.9 for New York.
From Watertown to Ellisburg, CDC publishes no figure by town: each reads Jefferson County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Watertown | 23,517 | −4.2% | 21.1% |
| Carthage | 3,196 | −3.7% | 2.9% |
| West Carthage | 1,721 | −2.6% | 1.5% |
| Clayton | 1,656 | −4.5% | 1.5% |
| Adams | 1,636 | −2.9% | 1.5% |
| Sackets Harbor | 1,337 | −2.7% | 1.2% |
| Black River | 1,208 | −4.2% | 1.1% |
| Philadelphia | 1,125 | −4.3% | 1.0% |
| Dexter | 989 | −2.0% | 0.9% |
| Alexandria Bay | 922 | −2.7% | 0.8% |
| Brownville | 911 | −2.8% | 0.8% |
| Theresa | 727 | −4.3% | 0.7% |
- Cape Vincent
- Evans Mills
- Chaumont
- Antwerp
- Glen Park
- Mannsville
- Deferiet
- Ellisburg
20 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).
Jefferson County, Homes
Homes in Jefferson County
Of Jefferson County's 61,721 homes, 56% are detached houses, against 41% across New York; 11% are mobile homes. Much of Jefferson County is recent building: 19% of its homes have gone up since 2000 and the middle year built is 1972, against 1958 for New York. 54% of occupied homes are lived in by their owner (New York: 54%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Jefferson County | New York |
|---|---|---|
| Housing units | 61,721 | 8,539,536 |
| Detached houses | 56% | 41% |
| In buildings of 5 or more | 10% | 34% |
| Mobile homes | 11% | 2% |
| Built before 1960 | 41% | 53% |
| Built since 2000 | 19% | 12% |
| Middle year built | 1972 | 1958 |
| Owner-occupied | 54% | 54% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.