**GAO-02-988T**                      Published: Jul 30, 2002. Publicly Released: Jul 30, 2002.                  

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## Highlights

Despite regulations limiting emissions and improved vehicle and fuel technologies, the air in many cities and towns still does not meet air quality standards. Vehicle emissions contain substances, including carbon monoxide, nitrogen oxides, and volatile organic compounds, that degrade air quality and threaten public health and the environment. Vehicles emissions account for about one third to one-half of these pollutants. Epidemiological and other studies have consistently found that breathing emissions containing these compounds contributes to respiratory and other health problems. Vehicle emissions also harm vegetation and cause crop damage. Provisions in the clean air and surface transportation laws have encouraged transportation planners to look for ways to curb harmful emissions, but predominantly in areas that already suffer pollution problems. The Clean Air Act requires planners to demonstrate that their plans and programs will not worsen air quality, but only in areas with current or prior air quality problems. Congress and federal agencies have opportunities to provide more help to transportation planners and communities considering the environmental impacts of their transportation and land use decisions.

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## Topics

Natural Resources and Environment

Air pollutionAir qualityEnvironmental monitoringHealth hazardsMotor vehiclesVolatile organic compoundsLand useOzonePollutionTransportation