Due to a focused research effort in the United States there have been remarkable advancements in the past 35 years related to the understanding of the photochemical ozone problem. However, despite these efforts, appilcation of ozone related controls in the United States have had disappointing results. Much of the uncertainty related to determining the impact of control programs on ozone levels can be ascribed to an incomplete information base on volatile organic compound (VOC) emission levels and species and to inadequate information on ambient VOC concentrations and trends. IN recent years it has become apparent that anthropogenic VOC emission inventories underestimate actual emissions, with the underestimation potentially most significant on high temperature days, ambient VOC/nitrogen oxide (NOx) ratios are higher than emission derived ratios, biogenic emissions can be important in rural ozone formation but emission estimates are very uncertain, ambient VOC trends estimated from emission changes can be grossly in error, and photochemical model outputs are quite sensitive to chemical mechanism and VOC species mixtures.
Dann, T.. 1989. Speciation and Reactivity of Volatile Organic Compounds in Ambient Air Samples and Emission Inventories. Environment Canada