When it comes to air pollution and ozone, trees have gotten a bad rap lately, according to a horticulturist with the Texas Agricultural Extension Service. Industry spokesmen have suggested that trees, particularly pine trees, produce chemicals that act as precursors to ozone production.
Ozone is an unstable chemical.
A typical Texas hardwood species, beech for example, forms a considerable amount of leaf surface in a small area. Baker also cites a 1991 USDA Forest Service study that found a healthy tree with a 30-inch trunk may remove 1.1 pounds of ozone per year and two pounds of other pollutants including sulfur dioxide and nitrogen dioxide. He noted that, strictly speaking, it's the oils and other chemicals coating the rough surfaces that are responsible for the breakdown. There's also considerable evidence that trees contribute only a small percentage of the total ozone in any given area. Part of Sloan's responsibility is to monitor six air pollutants, including ozone.