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Radon
in California Homes:
Current State of Knowledge
in California
Radon
Survey
Statewide study of residential
radon concentrations was carried out by the California
Department of Health Services (CDHS) in 1988-89. The
survey was a statewide effort to determine the extent of indoor
radon exposure in representative California homes and to
identify areas of the State where residences may have elevated
radon concentrations.
In this study, radon monitors were
placed in 310 residences. Measurements were carried out
for a full year to obtain an accurate estimate of exposure
unbiased by short-term fluctuations in radon levels because of
weather conditions or changes in ventilation. The survey
determined the proportion of homes exceeding the action level of
4 picocuries per liter (pCi/L) of air recommended by the U. S.
EPA. Homes with long-term concentrations measured at or
above the action level are recommended for radon reduction.
The U.S. EPA action level is largely based on current mitigation
technologies. It is recognized that radon exposures below 4 pCi/L
still contribute to the risk of lung cancer.
The statewide survey showed that about
0.8% (approximately 100,000) of California homes are expected to
have annual average radon levels exceeding the U.S. EPA action
level. These results confirmed the magnitude of high radon
homes found in earlier limited studies and another statewide
radon survey by CDHS and U.S.EPA using short-term monitors.
The geometric mean (GM) for long-term radon concentrations in
the state was 0.85 pCi/L.
Selected
Regions
The results also were analyzed by
dividing the state into six geographic regions. The
highest level was measured in the Sierra Nevada region (from
Placer south to Mariposa, as well as Alpine, Mono, Inyo
counties), which was significantly higher than other areas
(GM=2.2 pCi/L). The limited data for this region in the
statewide survey indicated 11-45% of homes are above the U.S.
EPA action level. The Fresno-Ventura region (Madera,
Fresno, Kings, Tulare, Kern, Santa Barbara, Ventura counties)
had the next highest level (GM=1.3 pCi/L).
In 1991, a focused survey of residential radon levels was
carried out in 862 residences of Ventura and northwestern Los
Angeles. It determined 1-14% of homes in this region had
long-term radon exposure above the U.S. EPA action level.
Currently, CDHS is conducting a survey of residential radon
levels in 1,000 homes in the Sierra Nevada region, with
preliminary results expected in early 2001.
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Related
Publications
Journal
Articles:
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The Distribution of Lifetime
Cumulative Exposures to Radon for California Residents,
Liu KS, Chang YL, Hayward SB, Gadgil AJ and Nero AJ, 1993,
Journal of Exposure Analysis and Environmental Epidemiology.
3:165-179.
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Annual Average Radon Concentrations
in California Residences,
Liu KS, Hayward SB, Girman JR, Moed BA and Huang FY, 1991,
J. Air and Waste Mgmt. Assoc. 41:1207-1212.
Reports:
Survey
of Indoor Radon Concentrations in California Elementary Schools,
report by Zhou J, Liu KS, and
Waldman J, May 1998
Report by CA Department of Health Services, Indoor Air Quality
Section, Berkeley, CA. Survey of
Residential Radon Levels in Ventura County and Northwestern Los
Angeles County,
Liu K-S, Chang Y-L, Hayward SB,
1991.
Report by CA Department of Health Services, Indoor Air Quality
Section, Berkeley, CA. Survey of
Residential Indoor and Outdoor Radon Concentrations in
California,
Liu K-S, Hayward SB, Girman JR, et
al., 1990.
Report by CA Department of Health Services, Indoor Air Quality
Section, Berkeley, CA.
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