Unfortunately, PM and ozone levels in most urban areas of California frequently exceed the ambient air quality standards. ARB and local air districts operate regulatory programs under state and federal requirements to reduce airborne levels of these pollutants to the ambient air quality standards. ARB is sponsoring a major 10-year study of the effects of air pollution on children's health. Toxic Air Contaminants California also regulates the emissions of other pollutants, known as toxic air contaminants, which may pose a present or potential hazard to human health or contribute to an increase in deaths or serious illnesses. More than 200 chemicals are currently listed as toxic air contaminants in California.
Motor vehicles are a major source of certain toxic air contaminants.
For example, benzene is a fundamental component of gasoline and diesel fuel, and it is present in vehicle exhaust. Benzene is known to cause cancer in humans. Many toxic air contaminants are formed from the combustion of other chemicals and are present in industrial emissions. Other toxic contaminants have numerous sources. Formaldehyde, which can inflame the airways and is also suspected of causing cancer, is found in motor vehicle exhaust and industrial emissions as well as in furniture and carpeting products.