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 St. Lawrence County, New York
EPA puts St. Lawrence 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
0.4%
22.3 pts below NY
- St. Lawrence
- 0.4%
- New York
- 22.7%
275 tests, 2020
Median result
0.5pCi/L
Below action level
- St. Lawrence
- 0.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2020
Tests reported
275
Most tested in New York
- St. Lawrence
- 275
Reported to CDC before any fix, 2020
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
21 of 21
Lowest quarter
- St. Lawrence
- 0.4%
- Cortland
- 64.0%
By share, of 21 with 30+ tests
Read a result for St. Lawrence County
Starts at St. Lawrence County's median, 0.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.5 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. St. Lawrence County's median reported result, 2020.
The data
St. Lawrence County, At a glance
St. Lawrence County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
St. Lawrence County is a
USGS geologic potential: Moderate across 59% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for St. Lawrence County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 8.3% |
| 2015 | 16.7% |
| 2016 | 25.0% |
| 2017 | 22.2% |
| 2018 | 0.0% |
| 2019 | 0.0% |
| 2020 | 0.4% |
| 2021 | 0.0% |
| 2023 | 0.0% |
2023: 0.0%. Across these years the share ran from 0.0% to 25.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 5 tests were reported to CDC for St. Lawrence 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).
St. Lawrence County, Compared
St. Lawrence County radon figures, compared
Calculated by Radon411Only 1 of 275 radon tests reported for St. Lawrence County in 2020 reached 4 pCi/L (0.4%). The median result, 0.5 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 4.5 pCi/L.
The newest figure, in 2023, counts only 5 tests (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 275-test figure.
Across 60 New York counties pooled together, 22.7% of tests reached that level, so St. Lawrence County runs 22.3 points below its state. Against the national pool of 25.5%, the gap is 25.1 points lower. Its place in the state: 21st of 21 New York counties with 30 or more tests for the same period.
The reported tests do not follow EPA's Zone 2 label for St. Lawrence County (predicted average between 2 and 4 pCi/L): 0.4% of them reached 4 pCi/L, fewer than that label suggests. Jefferson County, the one bordering county with a figure for the same period, reported 28.8%.
Below the action level, 271 tests (98.5%) came in under 2 pCi/L, against 59.1% statewide, and 3 tests (1.1%) fell between 2 and 4, against 18.1% statewide. USGS geology rates 59% of the county's land moderate radon potential.
The busiest year on file was 2020, with 275 tests reported; the quietest, 2021, had 2.
Pooled shares: Radon411's sum of CDC's county counts for one period.
St. Lawrence County, State data
New York's own radon test data
MeasuredWhat New York's own agencies publish about radon tests in St. Lawrence 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 St. Lawrence 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
13.6%
Average result
2.9 pCi/L
Tests behind these figures
9.2 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.
St. Lawrence County, Geology
The ground under St. Lawrence County
PredictedUSGS's geologic map splits St. Lawrence County: 58.8% of its land is moderate radon potential and 38.9% low. The map puts 38.9% of St. Lawrence County in the area it calls Adirondacks and 32.5% in St. Lawrence Champlain-Lowlands, with one smaller area beside them. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Adirondacks | Anorthosite and charnockitic gneisses. | Low | 8 | 38.9% |
| St. Lawrence Champlain-Lowlands | Cambrian-Ordovician sedimentary rocks (conglomerates and sandstones). | Moderate | 10 | 32.5% |
| Northwest Lowlands | Glacial gravel deposits, marble, quartzite, felsic to mafic gneiss. | Moderate | 11 | 26.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Lawrence County beside the ground around it
Across New York 48.9% of the land is rated high; none of St. Lawrence County's is. Of the 5 counties that border it, 1 has more high-potential ground, Herkimer County the most at 6.0%.
The map rates the ground, not the air in any home.
Local help
St. Lawrence County, Local resources
Radon testing and mitigation in St. Lawrence 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
St. Lawrence County, Questions
Questions about radon in St. Lawrence County
Are radon levels high in St. Lawrence County?
In 2023, 0.0% of the radon tests reported to CDC for St. Lawrence County, New York were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.6 pCi/L. Of 21 New York counties with 30 or more tests for the same period, 20 reported a higher share; pooled, the state comes to 22.7%.
Which counties border St. Lawrence County?
St. Lawrence County borders 5 counties: Franklin County, Jefferson County, Lewis County, Hamilton County and Herkimer County.
Products
St. Lawrence County, Products
Testing a home in St. Lawrence County
In St. Lawrence County, 0.4% of 275 tests reported to CDC in 2020 reached 4 pCi/L, against 22.7% pooled across New York. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in St. Lawrence 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
Monitor
RM-65 rechargeable radon detector with a color screen and alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
St. Lawrence County, Bordering counties
Counties bordering St. Lawrence County
Calculated by Radon411- Radon levels in Herkimer CountyEPA zone 3
77.8%at or above 4 pCi/L
Median 7.8 pCi/L · 9 tests · 77.4 points above St. Lawrence County
- Radon levels in Lewis CountyEPA zone 2
66.7%at or above 4 pCi/L
Median 4.6 pCi/L · 9 tests · 66.3 points above St. Lawrence County
- Radon levels in Jefferson CountyEPA zone 2
28.8%at or above 4 pCi/L
Median 2.2 pCi/L · 52 tests · 28.4 points above St. Lawrence County
- Radon levels in Franklin CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.6 pCi/L · 2 tests · 0.4 points below St. Lawrence County
- Radon levels in Hamilton CountyEPA zone 3
No CDC figure for 2020; its page reads it against its own neighbours.
St. Lawrence County, Cities and towns
Cities and towns in St. Lawrence County
About 105,488 people live in St. Lawrence County by the Census Bureau's estimate for July 1, 2025, 2,694 fewer than in 2020 (−2.5%). That works out to 39 people per square mile of land. No town dominates: Massena, the largest, has 9,898 residents, 9.4% of the total. Testing is reported here more often than across the state: CDC's 275 reported tests for 2020 come to 2.6 for every 1,000 residents (2025 estimate), against 0.1 for New York.
From Massena to Morristown, CDC publishes no figure by town: each reads St. Lawrence County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Massena | 9,898 | −3.5% | 9.4% |
| Ogdensburg | 9,123 | −7.6% | 8.6% |
| Potsdam | 8,019 | −5.6% | 7.6% |
| Canton | 6,894 | −4.9% | 6.5% |
| Gouverneur | 3,560 | −1.8% | 3.4% |
| Norwood | 1,521 | −3.2% | 1.4% |
| Waddington | 925 | +0.1% | 0.9% |
| Heuvelton | 706 | −1.5% | 0.7% |
| Rensselaer Falls | 318 | Level | 0.3% |
| Hammond | 281 | −1.4% | 0.3% |
| Richville | 257 | −3.4% | 0.2% |
- Morristown
12 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).
St. Lawrence County, Homes
Homes in St. Lawrence County
Of St. Lawrence County's 51,884 homes, 71% are detached houses, against 41% across New York; 10% are mobile homes. Half of its homes were built before 1964, close to New York's 1958: 47% date from before 1960 and 12% from 2000 or later. 72% 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 | St. Lawrence County | New York |
|---|---|---|
| Housing units | 51,884 | 8,539,536 |
| Detached houses | 71% | 41% |
| In buildings of 5 or more | 9% | 34% |
| Mobile homes | 10% | 2% |
| Built before 1960 | 47% | 53% |
| Built since 2000 | 12% | 12% |
| Middle year built | 1964 | 1958 |
| Owner-occupied | 72% | 54% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.