Ozone (O3) - formed from the fusion of sunlight and heat with nitrogen oxides (NOx) and volatile organic compounds (VOC) and causes tissue damage and causes the lungs to become more sensitive to other irritants and ambient levels of O3 cause respiratory problems in non- asthmatic, healthy individuals, as even low concentrations of the matter in the air decreases lung function. O3 has also been shown to cause decreased lung capacity by 15 to 20 percent and during summer months has even been the cause of 10 to 20 percent of respiratory-related hospitalizations in the northeastern U.S.
Carbon monoxide (CO) - a colorless, odorless, poisonous gas. According to the EPA, 77 percent of CO in the air comes from vehicles and other "transportation sources”. A product of incompletely burned carbon in fuels, CO poses serious threats to the cardiovascular system and impairs the body's ability to effectively deliver oxygen to tissues and organs. Exposure to CO can cause impaired vision and manual dexterity.
Nitrogen dioxide (NO2 ) - a lung tissue irritant that causes bronchitis and pneumonia as well as other respiratory infections (EPA, "Criteria Pollutants"). A compound found in all urban atmospheres, NO2 is a necessary component in conjunction with VOCs to form O3.
Particulate matter (PM) - one of the primary components of air pollution is able to penetrate the deepest recesses of the lungs and cause disease, carcinogenesis and premature death. Children and elderly are particularly susceptible to PM's effects. PM10 and PM2.5 (less than 10 and 2.5 microns) are the most dangerous as far as vehicle emissions are concerned. Some of the illnesses attributed to PM include bronchitis, asthma and decreased lung function.
Lead (Pb) - exposure to high concentrations of lead include seizures, mental retardation, and other behavioral disorders and even lower doses of Pb can lead to damage of the nervous system, according to the EPA. Though lead is a serious threat, it is no longer as prominent a concern from vehicle emissions as it was in the 1980s. In 1985, over twenty thousand tons of air-borne lead came from vehicle emissions. However, thanks to improved EPA regulation of lead content in gasoline that number had dropped to only 4,900 tons in 1993 (with the help of widespread use of unleaded gasoline).
