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5.0 Environmental Analysis 5.5 Air Quality <br />Avion Project SEIR <br />Page 5.5-6 <br />a. Ozone <br />Ozone is the primary component of smog. Ozone is not directly emitted into the air but is formed <br />through complex chemical reactions between precursor emissions of nitrogen oxides (NOX) and <br />reactive organic gases (ROG) (a.k.a. volatile organic compounds [VOC] or reactive organic <br />compounds) in the presence of sunlight. The adverse health effects associated with exposure to <br />ozone pertain primarily to the respiratory system. Scientific evidence indicates that ambient levels of <br />ozone affect not only sensitive receptors, such as asthma sufferers and children, but healthy adults <br />as well. Exposure to ozone has been found to significantly alter lung functions by increasing <br />respiratory rates and pulmonary resistance, decreasing tidal volumes (the amount of air inhaled and <br />exhaled), and impairing respiratory mechanics. Symptomatic responses include throat dryness, <br />chest tightness, headache, and nausea. About half of smog-forming emissions come from <br />automobiles. <br />b. Carbon Monoxide <br />Carbon monoxide is a colorless, odorless gas that is formed when carbon in fuel is not burned <br />completely. It is a component of motor vehicle exhaust, which contributes about 56 percent of all CO <br />emissions nationwide. CO enters the bloodstream through the lungs by combining with hemoglobin, <br />which normally supplies oxygen to the cells. However, CO combines with hemoglobin much more <br />readily than oxygen does, resulting in a drastic reduction in the amount of oxygen available to the <br />cells. Adverse health effects associated with exposure to CO concentrations include such symptoms <br />as dizziness, headaches, and fatigue (U.S. EPA 2017a). <br />Small-scale, localized concentrations of CO above the NAAQS and CAAQS may occur at intersections <br />with stagnation points such as those that occur on major highways and heavily traveled and <br />congested roadways. Localized high concentrations of CO are referred to as “CO hotspots” and are a <br />concern at congested intersections, where automobile engines burn fuel less efficiently and their <br />exhaust contains more CO. <br />c. Nitrogen Dioxide <br />Nitrogen dioxide is a brownish, highly reactive gas that is present in all urban environments. The <br />major human-made sources of NO2 are combustion devices, such as boilers, gas turbines, and <br />mobile and stationary reciprocating internal combustion engines. Inhalation is the most common <br />route of exposure to NO2. Because NO2 has relatively low solubility in water, the principal site of <br />toxicity is in the lower respiratory tract. The severity of the adverse health effects depends primarily <br />on the concentration inhaled rather than the duration of exposure. An individual may experience a <br />variety of acute symptoms, including coughing, difficulty with breathing, vomiting, headache, and <br />eye irritation during or shortly after exposure. After a period of approximately 4 to 12 hours, an <br />exposed individual may experience chemical pneumonitis or pulmonary edema with breathing <br />abnormalities, cough, cyanosis, chest pain, and rapid heartbeat.