Are high ambient ozone concentrations found only in heavily urbanized areas?
Many people mistakenly believe that tropospheric ozone concentrations are high only in major urban areas, but high ambient ozone concentrations can and do occur anywhere. Ozone formation is not limited to big cities like Los Angeles, Houston, Atlanta, and New York City. It is also formed in smaller cities like Raleigh, NC and Cincinnati, OH, and it is transported hundreds of miles downwind from where it is created to affect ambient air quality in other urban and rural areas. Where ozone is formed, peak concentrations usually occur during afternoon hours, when sunlight is the most intense. However, areas downwind of major sources of VOC and NOx may experience ozone peaks in the afternoon and evening, after wind has carried ozone and its VOC and NOx precursors many miles from their sources. Thus, high ozone concentrations can occur in remote areas and at various times of day, including during the early evening or night.
