For the most part, ozone forms from the interaction of nitrogen oxides emitted from motor vehicles, power plants, and industrial facilities and volatile organic compounds from spray painting, refueling of vehicles, road paving, and numerous other activities. Sunlight provides the catalyst for this reaction. Large urban areas have a higher levels of ozone formed due to greater amounts of smog associated with the aggregation of people and air pollution-producing activities. Due to its hot arid climate, its geological features, and the large number of people, the Los Angeles metro area is consistently plagued with higher ozone levels than the rest of the nation. EPA's National Air Quality and Emissions Trend Report for 1993.
Ozone is a strong irritant of the mucus membranes, especially the respiratory tract.
It causes constriction of the airways which makes breathing difficult and produces coughing, wheezing, and shortness of breath. Ozone can also be involved in the development of asthma. Lastly, it increases the vulnerability of the lungs to infection. Those particularly susceptible to adverse effects from exposure to ozone include young children, the elderly, and people with asthma, chronic bronchitis, or emphysema. However, adverse effects are not confirmed to this sensitive population.