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Outdoor CO levels are a fairly reliable indicator of potential indoor CO levels. CO is not chemically reactive and is poorly soluble in water. Thus, it is not adsorbed onto surfaces or otherwise removed from outdoor air entering a building through open doorways, open windows, or building ventilation systems. During late 1980 and early 1981, the Air Resources Board (ARB), California California Department of Transportation (Caltrans), and the Sacramento County Air Pollution Control District (APCD) conducted a special CO study at three intersections in the Sacramento area (Macaluso 1981). One of the conclusions of the study was that episodes of high CO levels at all three locations occurred most often during late afternoon to nighttime hours. Since the p.m. peak hour is the our of highest traffic volumes in the City of Lodi, the air quality analysis in this Background Report focuses on the afternoon/nighttime period. Data from previous studies suggest that CO problems occur primarily in the vicinity of major traffic arteries having significant amounts of commercial development. The presence of significant commercial development is an important contributing factor for two reasons. Parking lots for such developments represent a localized source of emissions which augments the CO emissions from vehicles traffic on adjacent roadways. Additionally, vehicles leaving major parking lots are likely to be in a "cold start" operating mode, resulting in higher CO emission rates than is typical for "through' traffic on major roadways. Meteorological conditions are also a significant factor affecting the development of CO problems. High CO levels develop primarily during the winter months when periods of light winds or calm conditions combine with the formation of ground level temperature inversions (typically in the evening through early morning period). These conditions result in reduced dispersion of vehicle emissions, allowing CO problems to develop and persist during hours when traffic volumes are declining from peak levels. Motor vehicles also exhibit increased CO emission rates at low air temperatures. CO levels are a public health concern because CO combines readily with hemoglobin and thus reduces the amount of oxygen transported in the blood stream. Relatively low concentrations of CO can significantly affect the amount of oxygen in the blood stream since CO binds to hemoglobin 220 to 245 times more strongly than does oxygen. Both the cardiovascular system and the central nervous system can be affected when 2.5 to 4.0 percent of the hemoglobin in the blood stream is bound to CO rather than to oxygen. State and federal ambient air quality standards for CO have been set at levels intended to keep CO from combining with more than 1.S percent of the blood's hemoglobin (U.S. Environmental Protection Agency 1978, California Air Resources board 1982). Estimated Existing Conditions Pollutant Concentrations Ozone is a regional pollutant which results form cumulative regional development. Therefore, an air quality analysis was not performed for existing conditions. The air quality monitoring data presented in Table 13-1 describes existing ozone concentrations in the study area. 17