By Margaret Henderson
Efforts of the California Department of Public Health (CDPH) Indoor Radon Program, through an interagency agreement with the California Department of Conservation and California Geological Survey (CGS), have resulted in the development of the 2015 radon potential zone map for Orange County. A 113 page, comprehensive report documents the map’s development. Radon potential maps developed by CGS for the CDPH-Indoor Radon Program show areas where, based on geologic conditions, radon concentrations in homes are predicted to exceed 4 pCi/L, the EPA recommended action level.
The report summarizes testing results from November 2007 to May 2008 by zip code, test results and percent of homes where results exceeded 4 pCi/L. During that period, the CDPH Indoor Radon Program conducted a survey, soliciting 40,000 Orange County homeowners via mail, inviting them to participate. Responding to the offer of free detectors, 2.8% or 1136 homes were tested using short-term radon detectors. The results ranged from 0.5 pCi/L (minimum detection level) to 22 pCi/L. (In January 2010, a high result of 25.6 pCi/L was determined and due to its significance, it was included in the test data summary.)
Radon potentials zones were identified using after analysis of radon test data, soils and radionuclide information of the geologic areas. When considered with 2010 U.S. Census data, these estimates were developed:
- an estimated 106,727 people in Orange County live in residences with indoor-air radon concentrations likely to equal or exceed 4.0 pCi/L;
- an estimated 5,410 people live in homes that will likely test 10 pCi/L or more; and
- about 3,113 people are estimated to live in homes that will likely test at 20 pCi/L or higher. (Churchill 2015)
While the zones give potential indications for radon levels, the CDPH Indoor Radon Program encourages testing all homes for radon.
The most recently published map and report, covering Orange County is available on the website ftp://ftp.consrv.ca.gov/pub/dmg/pubs/sr/SR_232/SR232_Orange_Radon_Final.pdf
Source: Special Report 232 - Radon Potential In Orange County, California by Ronald K. Churchill, Ph.D. , 2015
For information about radon and health issues, testing and remediation see
http://www.cdph.ca.gov/healthinfo/environhealth/Pages/Radon.aspx
United States