This report presents the results of ambient air monitoring conducted as part of the 1997 Urban Air Toxics Monitoring Program (UATMP)--a program designed to characterize the magnitude and composition of potentially toxic air pollution in, or near, urban locations. The 1997 UATMP included 12 monitoring stations that collected 24-hour air samples, typically on a biweekly basis. These samples were analyzed for concentrations of 47 volatile organic compounds (VOC) and 16 carbonyls. Overall, nearly 28,000 ambient air concentrations were measured during the 1997 UATMP. This summary report uses various graphical, numercial, and statistical analyses to put this vast amount of ambient air monitoring data into perspective. This report is divided into sections that review the specific air quality trends for individual monitoring stations. Each section of this report presents a succinct, yet thorough, overview of the monitoring data collected at a particular site. Each section analyzes and interprets air quality trends for nine compounds (all nitriles and oxygenated compounds) that were not measured during previous UATMPs, including methyl tert-butyl ether--a compound that has received much attention lately due to its use as a fuel additive in may parts of the country. Finally, to assess annual variations in air quality, each section describes how levels of air pollution have changed since the 1994 UATMP. Each section concludes by highlighting the most notable trends for the particular monitoring station.

"EPA-454/R-99-036." "January 1999." "EPA Contract No. 68-D3-0095."