CalEnviroscreen Version 1.1 - OEHHA - State of California

CalEnviroScreen 1.1
and lungs, including lung irritation, exacerbation of existing respiratory
disease, and cardiovascular effects. The US EPA has set a new standard
for ambient PM2.5 concentration of 12 µg/m 3 , down from 15 µg/m 3 .
According to EPA’s projections, by the year 2020 only 7 counties
nationwide will have PM2.5 concentrations that exceed this standard. All
are in California (US EPA, 2012b).
In children, researchers associated high ambient levels of PM2.5 in
Southern California with adverse effects on lung development
(Gauderman et al., 2004). Another study in California found an
association between components of PM2.5 and increased hospitalizations
for several childhood respiratory diseases (Ostro et al., 2009). In adults,
studies have demonstrated relationships between daily mortality and
PM2.5 (Ostro et al. 2006), increased hospital admissions for respiratory
and cardiovascular diseases (Dominici et al. 2006), premature death
after long-term exposure, and decreased lung function and pulmonary
inflammation due to short term exposures (Pope, 2009). Exposure to PM
during pregnancy has also been associated with low birth weight and
premature birth (Bell et al. 2007; Morello-Frosch et al., 2010).
An additional source of PM2.5 in California is wildfires. Fires are not
uncommon during dry seasons, particularly in Southern California and the
Central Valley. Smoke particles fall almost entirely within the size range
of PM2.5. Although the long term risks from exposure to smoke during a
wildfire are relatively low, sensitive populations are more likely to
experience severe symptoms, both acute and chronic (Lipsett et al. 2008).
During the wildfires that spread throughout the state in June 2008,
PM2.5 concentrations at a site in the northeast San Joaquin Valley were
far above air quality standards and approximately ten times more toxic
than normal ambient PM (Wegesser et al. 2009).
Method o PM2.5 annual mean monitoring data for was extracted all monitoring
sites in California from CARB’s air monitoring network database for
the years 2007-2009.
o Monitors that reported fewer than 75% of the expected number of
observations, based on scheduled sampling frequency, were
dropped from the analysis.
o For all measurements in the time period, the quarterly mean
concentrations were estimated at the geographic center of the ZIP
code using a geostatistical method that incorporates the monitoring
data from nearby monitors (ordinary kriging).
o Annual means were then computed for each year by averaging the
quarterly estimates and then averaging those over the three year
period.
o ZIP codes were ordered by the PM2.5 concentration values and
assigned a percentile based on the statewide distribution of values.
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