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S, Environmental Analysis
<br />AIR QUALITY
<br />quantified and {prioritized by the air quality maEnagement district or air pollution control district. High priority
<br />facilities are required to perform a health risk assessment and, if specific thresholds are exceeded, are required
<br />to communicate the results to the public in the form of notices and public meetings.
<br />Since the last update to the TAC list in December 1999, GARB has designated 244 compounds as TAs
<br />(GARB 1999). Additionally, GARB has implemented control measures for a number of compounds that pose
<br />high risks and show potential for effective control. The majority of the estimated health risks from TA Cs can
<br />be attributed to relatively few compounds, the most important being particulate matter from diesel - fueled
<br />engines.
<br />In 1998, CAR B identified particulate emissions from die el4ueIed engines (diesel P I ) as a TA . Previously,
<br />the individual chemical compounds in the diesel exhaust were considered as TAs. Almost all diesel exhaust
<br />particle mass is 10 microns or less in diameter. Because of their extremely small size, these particles can be
<br />inhaled and eventually trapped in the bronchial and alveolar regions of the lung.
<br />In 2009r the B CAQ MD conducted a study on ambient concentrations of TA Cs and estimated the potential
<br />health risks from air toxics. The results showed that the overall risk for excess cancer from a lifetime
<br />exposure to ambient levels of air tonics was about 1 ,490 in a mil Iion. The largest contributor to this risk was
<br />diesel exhaust, accounting for 71 percent of the air tonics risk. In 2093, the SAIID conducted its third
<br />update to their study on ambient concentrations of TACs and estimated the potential health risks from air
<br />tonics. The results shoved that the overall risk for excess cancer from a lifetime exposure to ambient levels of
<br />air tonics was about 1,206 in a million. The largest contributor to this risk was diesel exhaust, accounting for
<br />approximately 34 percent of the air tonics risk (SCAQMD 2008).
<br />Greenhouse Gases and Climate Change
<br />Climate charge can be due to natural variability or human activities. The climate system is interactive,
<br />consisting of five major components: the atmosphere, the hydrosphere (ocean, rivers, and lakes, the
<br />cryos phere (sea ice, ice sheets, and glaciers), the land surface, and the biosphere (flora and fauna) . The
<br />atmosphere is the most unstable and rapidly changing part of the system. It is composed of 78,1 percent
<br />nitrogen N2), 29.9 percent oxygen (02), and 0.93 percent argon (Ar). These gases have only limited
<br />interaction with the Incoming solar radiation and do not interact with infrared (long -wave) radiation emitted by
<br />the Earth. However, there are a number of trace gases, such as carbon dioxide (CO2), methane (H', nitrous
<br />oxide (N20), and ozone (03), that absorb and emit infrared radiation and therefore have an affect on the
<br />Earth's climate. These are greenhouse gases HG , and while they comprise less than 0.1 percent of the
<br />total volume mixing ratio in dry air, they play an essential role in influencing the Earth's climate I PCC 2901).
<br />In California and western forth Am erica, 1 observations in the climate have showed a trend toward warmer
<br />winter and spring temperatures, a smaller fraction of precipitation is falling as snow instead of rain,
<br />0 there is a decrease in the amount of spring snow accumulation in the lower and middle elevation
<br />mountain zones, 4 there is an advance snowmelt of 5 to 30 days earlier in the springs, and 5 there is a
<br />similar shift (5 to 39 days earlier) in the timing of spring flower blooms (COAT 2096, According to the
<br />California CI imate Action Team (CAT), even if actions could be taken to im medi ate Iy curtail climate change
<br />emissions, the potency of emissions that have already built up, their long atmospheric lifetimes (see Table
<br />5.2-1), and the inertia of the Earth's climate system could produce as much as 0.6°C 1.1 °F of additional
<br />warming. Consequently, some impacts from climate change are now unavoidable.
<br />CAT and the California Environmental Protection Agency (Cal /EPA) use the results from the recent analysis
<br />of g lob l climate change impacts for California underthree I PCC scenarios; louver emissions (131) , medium -
<br />9
<br />hi h ern is ions (A , and high emissions Al F1 ; each is associated with an increasing rise in akve rag e global
<br />a1r a enl incoln and Santa 'lar ancoln Intersection Mo a; ice onj City of Santa Aria a Page .1-5
<br />Supplement to the Santa Ana Second Main Track Project EIS
<br />Resolution No. 2009 -034
<br />Page 55 of 130
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