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i KLE®IVFELDER Bright People.Bight Solutions. Both the State of California and the federal government have established ambient air quality standards for criteria air pollutants. The ambient air quality standards define clean air; the primary standards are established to protect the health of even the most sensitive individuals in our communities. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. In addition to the criteria pollutants, the California Air Resources Board also identifies other air pollutants as toxic air contaminants (TACs), which are defined below. The SJVAB is designated a non-attainment area for ozone. Ozone is not emitted directly into the air, but is formed by a photochemical reaction in the atmosphere. Ozone precursors, which include reactive organic gases (ROG) and nitrogen oxides (NOx), react in the atmosphere in the presence of sunlight to form ozone. Because photochemical reaction rates depend on the intensity of ultraviolet light and air temperature, ozone is primarily a summer air pollution problem. Ozone is a respiratory irritant and an oxidant that increases susceptibility to respiratory infections and can cause substantial damage to vegetation and other materials. The SJVAB is also designated a non-attainment area for respirable particulate matter, because concentrations of these pollutants sometimes exceed the ambient air quality standards. Health concerns associated with suspended particulate matter focus on those particles small enough to reach the lungs when inhaled. Few particles larger than ■ 10 microns in diameter reach the lungs. Consequently, both the federal and state air quality standards for particulate matter apply to particulate matter 10 microns or less in diameter (PM10) as well as to particles less than 2.5 microns in diameter (PM2.5), which are carried deeper into the lungs. PM conditions in San Joaquin County are a result of a mix of rural and urban sources, including agricultural activities, industrial emissions, dust suspended by vehicle traffic, and secondary aerosols formed by reactions in the atmosphere. Carbon monoxide (CO) is managed as a local pollutant of concern; localized areas subject to high levels of traffic congestion may be subject to carbon monoxide levels in excess of ambient air quality standards. Motor vehicles are the predominant source of CO emissions in most areas. High CO levels develop primarily during winter when periods of light winds combine with the formation of ground level temperature inversions (typically from the evening through early morning). These conditions result in reduced dispersion of vehicle emissions. Motor vehicles also exhibit increased CO emission rates at low air temperatures. High CO concentrations occur in areas of limited geographic size, sometimes referred to as "hot spots." TACs are defined by California Health and Safety Code Section 39655 as "air pollutant(s) which may cause or contribute to an increase in mortality or in serious illness, or which may pose a present or potential hazard to human health." Air toxics include diesel particulate emissions from trucks, railroads, shipping and stationary diesel combustion sources; diesel particulate was identified as a TAC under the State 121339/ST011 R226 3-15 October 14, 2011 Copyright 2011 Kleinfelder