Radon in California

Radon has been found in every county of the State. Radon Potential Maps are used to speculate where high levels of radon might be found. These maps WILL NOT tell you how much radon is in your home or any other location. The ONLY way to know if radon is present is to test.    

The Indoor Radon Abatement Act of 1988 directed the U.S. Environmental Protection Agency (USEPA) to identify areas of the United States that have the potential to produce elevated levels of radon.  US EPA, along with U.S. Geological Survey (USGS) and the Association of American State Geologists, produced a series of maps and documents (EPA's Map of Radon Zones, CALIFORNIA 402-R-93-025).  The full report is available upon request--contact CDPH's Radon Program.

California's Indoor Radon Program, along with California Geological Survey, is developing detailed radon potential maps for counties of the State. The maps of Radon Zones identify areas of each state that have the highest potential for elevated indoor radon levels (greater than 4 pCi/L) (EPA United States Radon Map). 

Radon Potential Maps and Reports

The maps were designed to assist national, State and local governments and organizations to target their radon program activities and resources and should not be used to determine radon levels of a given area or house within a particular county. We have completed the following maps to date: 

·      Special Report 238 - Radon Potential in Western Tulare County, California
Download Report (9.16 MB PDF); Download Western Tulare County Map (2.17 MB PDF)

·      Special Report 232 - Radon Potential in Orange County, California
Download Report (3.7 MB PDF); Download Orange County Map (6.8 MB PDF)

·      Special Report 226 - Radon Potential in San Mateo County, California
Download Report (2.7 MB PDF); Download San Mateo County Map (1.79 MB PDF)

·         Special Report 224 - Radon Potential in the Palos Verdes Area, California
Download Report (2.7 MB PDF);  Download Palos Verdes Area Map (1.4 MB PDF)

·         Special Report 216 - Radon Potential in Santa Cruz County, California
Download Report (2.2 MB PDF);  Download Santa Cruz County Map (3.8 MB PDF)

·         Special Report 211 - Radon Potential in the Lake Tahoe Area, California
Download Report (2.3 MB PDF);  Download Lake Tahoe Map (12 MB PDF)

·         Special Report 208 - Radon Potential in San Luis Obispo County, California
Download Report (1.9 MB PDF);  Download Eastern San Luis Obispo Map (5.3 MB PDF);  Download Western San Luis Obispo Map (5.8 MB PDF)

·         Special Report 201 - Radon Potential in Monterey County, California
Download Report (1.8 MB PDF);  Download Eastern Monterey Map (1.5 MB PDF);  Download Western Monterey Map (2.7 MB PDF)

·         Special Report 194 - Radon Potential in Ventura County, California. 
Download Report (1.8 MB PDF);  Download Map (3.0 MB PDF)

·        Special Report 182 - Radon Potential in Southern Los Angeles County, California.
Download Report (19 MB PDF);  Download Map (5.6 MB PDF)

·         Radon Zone Map for Santa Barbara County
Download Map (851 KB PDF)

​Radon Program