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5.11 Air Resources

designated as Unclassified/attainment for the PM2.5 federal standard and Unclassified for
the PM2.5 State standard.

Carbon Monoxide (CO)
CO is a colorless and odorless gas which, in the urban environment, is associated primarily
with the incomplete combustion of fossil fuels in motor vehicles. CO combines with
hemoglobin in the bloodstream and reduces the amount of oxygen that can be circulated
through the body. High CO concentrations can lead to headaches, aggravation of
cardiovascular disease, and impairment of central nervous system functions. Carbon
monoxide concentrations can vary greatly over comparatively short distances. Relatively
high concentrations are typically found near crowded intersections; along heavily used
roadways carrying slow moving traffic; and at or near ground level. Even under the most
severe meteorological and traffic conditions, high CO concentrations are limited to locations
within a relatively short distance (i.e., up to 600 feet or 185 meters) of heavily traveled
roadways. Overall, CO emissions are decreasing as a result of the Federal Motor Vehicle
Control Program, which has mandated increasingly lower emission levels for vehicles
manufactured since 1973.

Currently, CO levels in the SoCAB and MDAB are in attainment for State and federal one-hour
and eight-hour standards.

Nitrogen Dioxide (NO2)

Nitrogen gas, normally relatively inert (unreactive), comprises about 80 percent of the air.
At high temperatures (i.e., in the combustion process) and under certain other conditions it
can combine with oxygen to form several different gaseous compounds collectively called
nitrogen oxides (NOx). NO is converted to NO2, a red-brown pungent gas, in the atmosphere.
Motor vehicle emissions are the main source of NOx in urban areas.

NO2 is toxic to various animals and to humans. Its toxicity relates to its ability to form nitric
acid with water in the eye, lung, mucus membrane, and skin. In animals, long-term exposure
to NOx increases susceptibility to respiratory infections lowering their resistance to such
diseases as pneumonia and influenza. Laboratory studies show susceptible humans, such as
asthmatics, exposed to high concentrations of NO2 can suffer lung irritation and, potentially,
lung damage. Epidemiological studies have also shown associations between NO2
concentrations and daily mortality from respiratory and cardiovascular causes and with
hospital admissions for respiratory conditions.

NOx is primarily a combination of NO and NO2. While the NAAQS and CAAQS only address
NO2, the total group of nitrogen oxides is of concern. NO and NO2 are both precursors in the
formation of O3 and PM2.5. Because of this and the fact that NO emissions largely convert to
NO2, NOx emissions are typically examined when assessing potential air quality impacts.
Currently, NO2 levels in the SoCAB and MDAB are in attainment for State and federal
standards.

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Draft EIR