Following Hurricane Katrina (Katrina) EPA evaluated air quality to determine whether the storm damage in Louisiana and Mississippi and subsequent cleanup efforts caused air quality in the affected areas to (1) exceed screening levels and (2) change in comparison to monitored air quality prior to the storm. Ambient air quality monitoring sites were established throughout the impacted area to collect samples beginning in October 2005. Measurements of over 80 pollutants, including metals, volatile organic compounds (VOCs), carbonyl compounds, particulate matter (PM), ozone, and polycyclic aromatic hydrocarbons (PAHs) were made. Sites were operated in the New Orleans and Gulfport/Pascagoula, Mississippi, areas; not all sites measured all pollutants. This document reports on air quality data collected from October 2005 through September 2006, the first year after the hurricane. In partnership with other federal, state and local agencies, EPA monitored air quality in as many locations as possible, given limited resources. Locations included heavily populated areas, near roadways, near waste sites and in locations of remediation. EPA's goal was to provide adequate protection to the general population. The purpose of this report is to describe air quality levels across the region.