EPA submitted the national-scale assessment for scientific peer review in 2001. The national-scale assessment is based on 1996 emissions data because emissions inventories from that year are the most complete and available to date. The 1996 data do not reflect pollution reductions that have taken effect since 1996, including those from federal, state and local regulations or from industry initiatives or facility closures. By identifying the air toxics that may pose the greatest risk in urban areas, this assessment will help regulatory agencies set priorities for collecting additional data to help assess risk. This national assessment was not designed to compare risks at local levels. The complete results of the technical analysis, as well as background and supporting information is posted at: http://www.epa.gov/ttn/atw/nata.