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 Monterey County, California
EPA puts Monterey County in Zone 2, its middle radon zone, and most reported tests there come back low, though 14.9% of 87 (2008 to 2017, laboratory totals) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
14.9%
4.6 pts above CA
- Monterey
- 14.9%
- California
- 10.3%
87 tests, 2008 to 2017
Median result
0.8pCi/L
Below action level
- Monterey
- 0.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
87
22nd of 33 by tests
- Monterey
- 87
- Los Angeles
- 2,363
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 California
10 of 33
Middle half
- Monterey
- 14.9%
- El Dorado
- 30.3%
By share, of 33 with 30+ tests
Read a result for Monterey County
Starts at Monterey County's median, 0.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.8 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. Monterey County's median reported result, 2008 to 2017.
The data
Monterey County, At a glance
Monterey County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Monterey County is a
USGS geologic potential: Moderate across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Monterey County, 2008 to 2017, laboratory
Under 2 pCi/L: 77%2 to 4 pCi/L: 8%4 pCi/L and above: 15%
Of 87 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 67 | 77.0% |
| 2 to 4 pCi/L | 7 | 8.0% |
| 4 pCi/L and above | 13 | 14.9% |
What these figures count
These are the 87 tests reported to CDC for Monterey County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Monterey County, Compared
Monterey County radon figures, compared
Calculated by Radon41114.9% of its 87 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 4.6 points above the 10.3% pooled from 56 California counties.
Ordered from highest share down, it comes 10th of 33 California counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Monterey County sits 20.8 points below it.
Next door, the shares run from 11.0% in Fresno County to 21.9% in Santa Cruz County, with San Luis Obispo County and Fresno County below Monterey County. Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 14.9% share point the same way here.
Half the tests came in under 0.8 pCi/L and half over it; the single highest reached 20.3 pCi/L. The rest split 77.0% under 2 pCi/L and 8.0% from 2 to 4 (California: 76.8% and 12.9%).
CDC's ten-year totals for Monterey County went from 211 tests (2005 to 2014) to 87 (2008 to 2017), the share going from 11.8% to 14.9%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Monterey County, Geology
The ground under Monterey County
PredictedUSGS's geologic map puts all of Monterey County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Southern Coast Ranges, to which USGS gives a radon index of 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| 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 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Monterey County beside the ground around it
Across California 0.1% of the land is rated high; none of Monterey County's is. Of the 5 counties that border it, none has as large a share of moderate-potential ground; San Benito County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Monterey County, Local resources
Radon testing and mitigation in Monterey 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
Monterey County, Questions
Questions about radon in Monterey County
Are radon levels high in Monterey County?
Over the 2008 to 2017 laboratory totals, 14.9% of the radon tests reported to CDC for Monterey County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.8 pCi/L. Of 33 California counties with 30 or more tests for the same period, 9 reported a higher share; pooled, the state comes to 10.3%.
Which counties border Monterey County?
Monterey County borders 5 counties: San Benito County, Santa Cruz County, San Luis Obispo County, Kings County and Fresno County.
Products
Monterey County, Products
Testing a home in Monterey County
In Monterey County, 14.9% of 87 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 10.3% pooled across California. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Monterey 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
Hello Radon C battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Monterey County, Bordering counties
Counties bordering Monterey County
Calculated by Radon411- Radon levels in Santa Cruz CountyEPA zone 2
21.9%at or above 4 pCi/L
Median 1.2 pCi/L · 105 tests · 7.0 points above Monterey County
- Radon levels in San Luis Obispo CountyEPA zone 2
12.5%at or above 4 pCi/L
Median 1.0 pCi/L · 80 tests · 2.4 points below Monterey County
- Radon levels in Fresno CountyEPA zone 2
11.0%at or above 4 pCi/L
Median 1.5 pCi/L · 100 tests · 3.9 points below Monterey County
- Radon levels in San Benito CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 0.7 pCi/L · 19 tests · 14.9 points below Monterey County
- Radon levels in Kings CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.7 pCi/L · 2 tests · 14.9 points below Monterey County
Monterey County, Cities and towns
Cities and towns in Monterey County
About 433,729 people live in Monterey County by the Census Bureau's estimate for July 1, 2025, 6,764 fewer than in 2020 (−1.5%). That works out to 132 people per square mile of land. Its largest town, Salinas, has 159,134 residents, 36.7% of the total. Together its 12 incorporated places hold 76.6% of those residents; the other 23.4% live outside any of them. CDC's 87 reported tests for 2008 to 2017 work out to 0.2 per 1,000 residents (2025 estimate), close to California's 0.2.
From Salinas to Sand City, CDC publishes no figure by town: each reads Monterey County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Salinas | 159,134 | −2.6% | 36.7% |
| Seaside | 31,636 | −2.1% | 7.3% |
| Monterey | 28,953 | −4.1% | 6.7% |
| Soledad | 26,357 | −1.3% | 6.1% |
| Marina | 23,256 | +4.0% | 5.4% |
| Greenfield | 21,138 | +11.5% | 4.9% |
| Pacific Grove | 14,659 | −2.9% | 3.4% |
| King City | 14,002 | +4.8% | 3.2% |
| Gonzales | 8,313 | −3.5% | 1.9% |
| Carmel-by-the-Sea | 3,105 | −3.5% | 0.7% |
| Del Rey Oaks | 1,536 | −2.9% | 0.4% |
| Sand City | 323 | −0.3% | Under 0.1% |
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).
Monterey County, Homes
Homes in Monterey County
Of Monterey County's 144,659 homes, 63% are detached houses, against 57% across California; 17% are in buildings of five or more homes. Half of its homes were built before 1975, close to California's 1976: 27% date from before 1960 and 15% from 2000 or later. 52% 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 | Monterey County | California |
|---|---|---|
| Housing units | 144,659 | 14,532,683 |
| Detached houses | 63% | 57% |
| In buildings of 5 or more | 17% | 24% |
| Mobile homes | 4% | 4% |
| Built before 1960 | 27% | 27% |
| Built since 2000 | 15% | 18% |
| Middle year built | 1975 | 1976 |
| Owner-occupied | 52% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.