Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Stanislaus County, California
EPA puts Stanislaus County in Zone 3, its lowest radon zone, and only 27 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
23.0%
Tuolumne County
- Tuolumne
- 23.0%
- Alameda
- 6.7%
5 of 7 neighbours have 30+ tests, 2008 to 2017
Nearest county
14.9%
San Joaquin County, 30 miles
- San Joaquin
- 14.9%
- California
- 10.3%
Share at 4+ pCi/L, 74 tests, 2008 to 2017
Ground above low
50.9%
8.2 pts above California
- Stanislaus
- 50.9%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
27
Too few for a share
- Stanislaus
- 27
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Read a result for Stanislaus County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
The data
Stanislaus County, At a glance
Stanislaus County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Moderate across 51% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Stanislaus County, 2008 to 2017, laboratory
CDC holds 27 reported tests for Stanislaus County over the 2008 to 2017 laboratory totals, with a median of 1.4 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Stanislaus County beside the counties around it is how this page reads it.
What these figures count
Only 27 tests were reported to CDC for Stanislaus County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Stanislaus County, Compared
Stanislaus County radon figures, compared
Calculated by Radon411CDC's largest figure for Stanislaus County rests on 27 tests over the 2008 to 2017 laboratory totals, 3 of them at or above 4 pCi/L, so each test moves its share by 3.7 points and no rank or comparison is drawn from it. Results reached as high as 13.0 pCi/L, with a middle value of 1.4 pCi/L.
Of the counties bordering it, 5 have a figure over the 2008 to 2017 laboratory totals: Tuolumne County reported the largest share at or above 4 pCi/L, 23.0%, and Alameda County the smallest, 6.7%, with Calaveras County at 17.6%, San Joaquin County at 14.9% and Santa Clara County at 9.2% between. Farther out, Contra Costa County (57 miles away) at 8.8%, Amador County (64 miles away) at 27.8% and Sacramento County (64 miles away) at 7.7% have figures too. Pooled across 56 California counties, 10.3% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, El Dorado County reported the highest share (30.3%) and Sonoma County the lowest (0.8%). EPA's 1993 map puts Stanislaus County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 51% of the county's land moderate radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Stanislaus County, Geology
The ground under Stanislaus County
PredictedUSGS's geologic map splits Stanislaus County: 50.9% of its land is moderate radon potential and 49.1% low. The map puts 49.1% of Stanislaus County in the area it calls Great Valley and 28.6% in Southern Coast Ranges, 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 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Great Valley | Quaternary alluvial gravel, sand, silt, clay. | Low | 8 | 49.1% |
| Southern Coast Ranges | Metamorphosed marine sedimentary rocks, ultramafic rocks, Triasic metamorphic rocks, Mesozoic granitic rocks, and a series of fault-bounded linear basins in which Teriary marine and continental sedimentary rocks were deposited. | Moderate | 9 | 28.6% |
| Sierra Nevada | Northern Sierra Nevada is underlain primarily by Paleozoic and Mesozoic metamorphic rocks. Granitic rocks predominate in the southern Sierrra Nevada , with lesser Mesozoic metamorphic rocks. | Moderate | 9 | 22.2% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Stanislaus County beside the ground around it
Across California 0.1% of the land is rated high; none of Stanislaus County's is. Of the 7 counties that border it, 5 have more moderate-potential ground, Calaveras County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Stanislaus County, Local resources
Radon testing and mitigation in Stanislaus County
- California Indoor Radon ProgramCalifornia Indoor Radon Program, run by California Department of Public Health, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in California.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Discounted test kits can be purchased through our partner laboratory, Alpha Energy, for $14.95.
- Compare kits
- Professionals in California4 professionals are listed in California.
What California's program says
- Phone
- 1-800-745-7236
- Radonprogram@cdph.ca.gov
- Licensing of radon professionals
The Radon Program certifies all radon service providers operating in California.
What it means
Stanislaus County, Questions
Questions about radon in Stanislaus County
Are radon levels high in Stanislaus County?
Over the 2008 to 2017 laboratory totals, 11.1% of the radon tests reported to CDC for Stanislaus County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.4 pCi/L. Of the counties bordering it, 5 have a figure over the 2008 to 2017 laboratory totals: Tuolumne County reported the largest share at or above 4 pCi/L, 23.0%, and Alameda County the smallest, 6.7%, with Calaveras County at 17.6%, San Joaquin County at 14.9% and Santa Clara County at 9.2% between.
Which counties border Stanislaus County?
Stanislaus County borders 7 counties: San Joaquin County, Merced County, Calaveras County, Santa Clara County, Alameda County, Mariposa County and Tuolumne County.
Products
Stanislaus County, Products
Testing a home in Stanislaus County
No CDC figure names Stanislaus County; the nearest county with one, San Joaquin County (30 miles away), reported 14.9% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Stanislaus County.
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
MonitorAEGTEST
HOUND-3786 rechargeable radon monitor with a 3.5-inch color screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
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
Stanislaus County, Bordering counties
Counties bordering Stanislaus County
Calculated by Radon411- Radon levels in Tuolumne CountyEPA zone 2
23.0%at or above 4 pCi/L
Median 1.4 pCi/L · 74 tests
- Radon levels in Calaveras CountyEPA zone 2
17.6%at or above 4 pCi/L
Median 1.7 pCi/L · 34 tests
- Radon levels in Mariposa CountyEPA zone 2
16.7%at or above 4 pCi/L
Median 1.3 pCi/L · 6 tests
- Radon levels in San Joaquin CountyEPA zone 3
14.9%at or above 4 pCi/L
Median 1.4 pCi/L · 74 tests
- Radon levels in Santa Clara CountyEPA zone 2
9.2%at or above 4 pCi/L
Median 0.9 pCi/L · 793 tests
- Radon levels in Alameda CountyEPA zone 2
6.7%at or above 4 pCi/L
Median 0.7 pCi/L · 478 tests
- Radon levels in Merced CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 2.1 pCi/L · 5 tests
Stanislaus County, Cities and towns
Cities and towns in Stanislaus County
The Census Bureau estimates 557,719 residents in Stanislaus County for July 1, 2025, 4,017 more than in 2020 (+0.7%). That works out to 373 people per square mile of land. Its largest town, Modesto, has 219,652 residents, 39.4% of the total. Together its 9 incorporated places hold 80.3% of those residents; the other 19.7% live outside any of them. Reported testing is thin here: 27 tests over 2008 to 2017, or under 0.1 for every 1,000 residents (2025 estimate), where California as a whole comes to 0.2.
From Modesto to Hughson, CDC publishes no figure by town: each reads Stanislaus County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Modesto | 219,652 | +0.4% | 39.4% |
| Turlock | 72,864 | +0.2% | 13.1% |
| Ceres | 48,982 | −1.5% | 8.8% |
| Patterson | 26,587 | +11.6% | 4.8% |
| Riverbank | 26,557 | +6.5% | 4.8% |
| Oakdale | 23,246 | +0.2% | 4.2% |
| Newman | 12,453 | +0.5% | 2.2% |
| Waterford | 9,258 | +1.4% | 1.7% |
| Hughson | 8,051 | +7.5% | 1.4% |
9 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).
Stanislaus County, Homes
Homes in Stanislaus County
Stanislaus County is a place of houses on their own lots: 76% of its 184,240 homes are detached single-family houses, against 57% across California. Half of its homes were built before 1981, close to California's 1976: 20% date from before 1960 and 21% from 2000 or later. 61% of occupied homes are lived in by their owner (California: 56%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Stanislaus County | California |
|---|---|---|
| Housing units | 184,240 | 14,532,683 |
| Detached houses | 76% | 57% |
| In buildings of 5 or more | 10% | 24% |
| Mobile homes | 4% | 4% |
| Built before 1960 | 20% | 27% |
| Built since 2000 | 21% | 18% |
| Middle year built | 1981 | 1976 |
| Owner-occupied | 61% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.