Based on its review of the air quality criteria for oxides of sulfur and the primary national ambient air quality standard (NAAQS) for oxides of sulfur as measured by sulfur dioxide (SO<INF>2</INF>), EPA is revising the primary SO<INF>2</INF> NAAQS to provide requisite protection of public health with an adequate margin of safety. Specifically, EPA is establishing a new 1-hour SO<INF>2</INF> standard at a level of 75 parts per billion (ppb), based on the 3-year average of the annual 99th percentile of 1-hour daily maximum concentrations. The EPA is also revoking both the existing 24-hour and annual primary SO<INF>2</INF> standards.