This final action provides rules and guidance on the Clean Air Act (CAA) requirements for State and Tribal plans to implement the 1997 fine particle (PM<INF>2.5</INF>) national ambient air quality standards (NAAQS). Fine particles and precursor pollutants are emitted by a wide range of sources, including power plants, cars, trucks, industrial sources, and other burning or combustion-related activities. Health effects that have been associated with exposure to PM<INF>2.5</INF> include premature death, aggravation of heart and lung disease, and asthma attacks. Those particularly sensitive to PM<INF>2.5</INF> exposure include older adults, people with heart and lung disease, and children. Air quality designations became effective on April 5, 2005 for 39 areas (with a total population of 90 million) that were not attaining the 1997 PM<INF>2.5</INF> standards. By April 5, 2008, each State having a nonattainment area must submit to EPA an attainment demonstration and adopted regulations ensuring that the area will attain the standards as expeditiously as practicable, but no later than 2015. This rule and preamble describe the requirements that States and Tribes must meet in their implementation plans for attainment of the 1997 fine particle NAAQS. (Note that this rule does not include final PM<INF>2.5</INF> requirements for the new source review (NSR) program; the final NSR rule will be issued at a later date.)