Atmospheric deposition, a process that transfers pollutants, including NOx, SO2, and mercury, from the air to the earth's surface, can significantly impair the quality of the nation's waters. The EPA can potentially address atmospheric deposition through the Clean Water Act (CWA) and the Clean Air Act (CAA), but concerns have been raised about its ability to do so. This book examines the EPA's efforts to address atmospheric deposition of pollutants that impair water bodies, with a focus on the extent to which atmospheric deposition of NOx, SO2, and mercury contribute to the impairment of the nation's waters and identification of the key sources of these pollutants. Also discussed are the regulatory tools that the EPA uses under the CWA and CAA to address the effects and challenges of atmospheric deposition.