In summary, to understand what is really being shown in the ozone movies you must take into account differences in ozone formation rates in different areas as well as transport by varying wind speeds and directions at all times of the day. Vehicles cause a greater percentage of air pollution in our area than in other parts of the country because the Sacramento region does not have a lot of heavy industry. Also, drivers in the Sacramento region travel an estimated 47-million vehicle miles every day, logging more miles per driver than in any other portion of the state. Therefore, the air reaching Sacramento contains very few ozone-forming materials. It is safe to exercise in the morning, because ozone does not usually reach unhealthy levels until the afternoon.
Morning is a good time for biking, walking, jogging, or other types of strenuous outdoor activities.
The reddish-brown haze that you often see hanging over the valley is oxides of nitrogen, better known as NOx. The air districts of the Sacramento region are therefore committed to developing programs to reduce NOx, because lower NOx levels will decrease ozone air pollution and improve visibility. Fine particles suspended in the air also contribute to reduced visibility. Fine particles consist mainly of soot and other by-products of combustion, particularly from automobile combustion. Chico is not located within this area and is, therefore, not depicted in the Ozone Movies.